Method for producing fibers

Abstract

The present invention relates to a method for producing fibers, which includes a step of preparing a spinning dope containing a dope solvent, lignin dissolved in the dope solvent, and a carbon nanomaterial dispersed in the dope solvent, wherein the dope solvent contains an ionic liquid and optionally further contains water; and a step of extruding the spinning dope into a coagulation liquid to obtain one or more fibers.

Description

Technical Field

[0001] The present invention relates to a method for producing fibers, comprising the steps of preparing a spinning dope comprising a dope solvent, lignin dissolved in the dope solvent, and carbon nanomaterials dispersed in the dope solvent, wherein the dope solvent comprises an ionic liquid and optionally further comprises water; and extruding the spinning dope into a coagulation bath to obtain one or more fibers.

Background Art

[0002] Carbon fiber (CF) is a robust material that can be used to produce carbon fiber reinforced composite materials, which are desirable lightweight building materials. Carbon fibers are produced by pyrolysis of precursor fibers made from polyacrylonitrile (PAN) and mesophase petroleum pitch. However, these two main precursors are derived from petroleum and are therefore non-renewable. For PAN, the use of toxic spinning solvents such as DMF and the generation of toxic by-products such as HCN during carbonization raise additional environmental and health concerns. The high costs associated with precursor production and the energy-intensive high-temperature treatment also limit the use of carbon fiber composites to high-end markets and are obstacles to rapid market growth.

[0003] Lignin is an easily accessible biopolymer with a high carbon content and thus has the potential to be a lower-cost and renewable alternative precursor. Lignin is attractive due to its sustainable origin, low cost, and relatively high fiber yield after carbonization. More than 70 million tons of lignin are extracted annually during paper and pulp production. Commercial lignin-based carbon fibers could support the economy of the developing renewable chemical industry by providing additional revenue to wood processing biorefineries that currently burn most of the lignin to generate heat and electricity rather than producing value-added products.

[0004] Many studies on the production of lignin fibers have focused on melt spinning at approximately 200 °C, often using copolymers. The process is attractive as it avoids solvents, but it is difficult to control the thermal behavior of lignin to obtain suitable melt behavior, and the oxidative stabilization is slow to maintain the fiber shape.

[0005] Wet (coagulation) spinning of pure unmodified lignin has not been demonstrated, probably due to its low average molar weight. Wet spinning may be made possible by blending lignin with another fiber-forming polymer, such as cellulose. Solvents reported to date for wet spinning include DMSO (Foellmer, M. et al., Wet-Spinning and Carbonization of Lignin-Polyvinyl Alcohol Precursor Fibers. Advanced Sustainable Systems 2019; Lu, C. et al., ACS Sustainable Chemistry and Engineering 2017, 5(4), 2949 - 2959).

[0006] In addition, the ionic liquid (IL) 1-ethyl-3-methylimidazolium acetate, [Emim][OAc], has been used with pure water as a coagulation bath to form precursor lignin / cellulose fibers (Bengtsson, A. et al., Holzforschung 2018, 72(12), 1007 - 1016; Vincent, S. et al., ACS Sustainable Chemistry and Engineering 2018, 6(5), 5903 - 5910). The ionic liquid 1,5-diazabicyclo[4.3.0]non-5-enium acetate [DBNH][OAc] has also been used to produce carbon fibers derived from 50 / 50% kraft lignin / cellulose precursor fibers (Ma, Y. et al., ChemSusChem 2015, 8(23), 4030 - 4039). However, these methods require expensive ILs that must be rigorously dried to dissolve cellulose, which is a challenge for commercialization. SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

[0007] Therefore, there is a need for a new method for producing lignin fibers that enables the use of non-toxic and low-cost solvents. It is also desirable to produce lignin fibers having an improved graphite structure and a higher carbon yield.

Means for Solving the Problems

[0008] In a first aspect, a method for producing fibers, comprising the steps of preparing a spinning dope comprising a dopant solvent, lignin dissolved in the dopant solvent, and a carbon nanomaterial, wherein the dopant solvent comprises an ionic liquid and optionally water; and extruding the spinning dope into a coagulation bath to obtain one or more fibers, is provided herein.

[0009] In a second aspect, fibers obtainable by the method of the first aspect are provided herein.

[0010] In a third aspect, a spinning dope comprising a dopant solvent, lignin, and a carbon nanomaterial, wherein the dopant solvent comprises an ionic liquid and optionally water, is provided herein. The spinning dope may be as described with respect to the first aspect.

[0011] In a fourth aspect, a dispersion comprising carbon nanotubes and [DMBA][HSO4] is provided herein.

[0012] Embodiments of the present disclosure will now be described with reference to the drawings, which are merely exemplary.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0014] In a first aspect, a method for producing fibers, comprising the step of preparing a spinning dope comprising a dope solvent, lignin dissolved in the dope solvent, and a carbon nanomaterial, wherein the dope solvent comprises an ionic liquid and optionally water; and the step of extruding the spinning dope into a coagulation bath to obtain one or more fibers, is provided herein.

[0015] Fibers produced by this method may also be referred to as lignin fibers. The fibers comprise lignin and a carbon nanomaterial. The fibers can be used, for example, as precursor fibers for producing carbon fibers or as raw materials for other fiber-based materials.

[0016] The dope solvent is a solvent in which lignin can be dissolved. Preferably, the dope solvent is a solvent in which cellulose has lower solubility than lignin. More preferably, the dope solvent does not dissolve cellulose.

[0017] The spinning dope preferably contains a cellulose loading rate of 10% or less based on the mass of the spinning dope excluding the mass of cellulose, lignin and carbon nanomaterials (i.e., w / w%). Preferably, the cellulose loading rate is 5% or less, 2% or less or 1% or less. The spinning dope preferably contains substantially no cellulose. Undissolved cellulose can be removed, for example, by filtration.

[0018] The dope solvent may have a water content of 0 to 30% by weight, 0 to 20% by weight, 0 to 10% by weight or 0 to 5% by weight. The dope solvent may have a water content of at least 1% by weight, at least 2% by weight or at least 3% by weight. The water content of the dope solvent is calculated based on the mass of water present relative to the total mass of the dope solvent (i.e., w / w%). The dope solvent may further contain ethanol. The dope solvent may contain 0 to 20% by weight of ethanol, for example 1 to 20% by weight of ethanol, preferably 5 to 15% by weight of ethanol, calculated relative to the total mass of the dope solvent (i.e., w / w%).

[0019] When the dope solvent contains ethanol, the ionic liquid:ethanol mass ratio may be 3:1 to 15:1, preferably 5:1 to 12:1.

[0020] Lignin may be present in the spinning dope at a loading rate of at least 5% by weight, preferably at least 10% by weight, based on the mass of the spinning dope excluding the mass of lignin and carbon nanomaterials. Lignin may preferably be present at a loading rate of 10 to 50% by weight, 10 to 40% by weight, 10 to 30% by weight based on the mass of the spinning dope excluding the mass of lignin and carbon nanomaterials. Lignin may be, for example, hardwood lignin, softwood lignin, grass lignin or other lignin (e.g., genetically modified lignin). Lignin may be hardwood lignin. Lignin may be ionoSolv lignin or kraft lignin, such as LignoBoost lignin.

[0021] The carbon nanomaterial may be present in the spinning dope at a loading rate of at least 0.001 wt%, at least 0.01 wt%, or at least 0.1 wt% based on the mass of the spinning dope excluding the mass of the lignin and the carbon nanomaterial. The carbon nanomaterial may be present at a loading rate of 0.001 to 10 wt%, 0.001 to 8 wt%, 0.01 to 8 wt%, 0.1 to 5 wt%, 0.1 to 1 wt%, or 0.3 to 0.7 wt% based on the mass of the spinning dope excluding the mass of the lignin and the carbon nanomaterial. The carbon nanomaterial may be present at a loading rate of about 0.5% based on the mass of the spinning dope excluding the mass of the lignin and the carbon nanomaterial.

[0022] The weight ratio of lignin to carbon nanomaterial in the spinning dope may be 5:1 to 10000:1, preferably 5:1 to 5000:1, more preferably 10:1 to 1000:1, and still more preferably 20:1 to 200:1.

[0023] The spinning dope may have a water content of 0 to 30 wt%, 0 to 20 wt%, 0 to 15 wt%, 0 to 10 wt%, or 0 to 5 wt%. The dope solvent may have a water content of at least 1 wt%, at least 2 wt%, or at least 3 wt% calculated based on the mass of water present relative to the mass of the spinning dope excluding the mass of the lignin and the carbon nanomaterial.

[0024] The carbon nanomaterial may include carbon nanotubes, carbon nanoribbons, graphene nanoplatelets, or combinations thereof. Preferably, the carbon nanomaterial includes carbon nanotubes. Preferably, the carbon nanotubes are single-walled carbon nanotubes (SWCNT).

[0025] The carbon nanomaterial may be dispersed in the dope solvent.

[0026] The ionic liquid may be any ionic liquid described herein. Preferably, the ionic liquid has a cation and C 1~20 alkyl sulfate ([alkylSO4] -)、C 1~20 Alkyl sulfonate ([alkyl SO3] - )、Hydrogen sulfate ([HSO4] - )、Hydrogen sulfite ([HSO3] - )、Dihydrogen phosphate ([H2PO4] - )、Hydrogen phosphate ([HPO4] 2- )、Chloride (Cl - )、Bromide (Br - )、Trifluoromethanesulfonate ([OTf] - )、Formate ([HCOO] - ) and Acetate ([MeCO2] - ) contains an anion selected from. Preferably, the anion is [HSO4] - and [HCOO] - selected from.

[0027] The cation may be an aprotic cation or a protic cation, preferably a protic cation. The cation may contain a nitrogen-containing heterocyclic moiety or a cation of formula I

[0028]

Chemical formula

[0029] [wherein, A 1 ~A 4 are each independently H, aliphatic, C 3~6 carbocyclic ring, C 6~10 aryl, alkylaryl, and heteroaryl selected from].

[0030] The ionic liquid may be an [alkylammonium][HSO4] or [alkylammonium][HCOO] ionic liquid.

[0031] The ionic liquid may be N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4]), 1-butylimidazolium hydrogen sulfate ([HBim][HSO4]), triethylammonium hydrogen sulfate ([TEA][HSO4]), N-methylbutylammonium hydrogen sulfate ([MBA][HSO4]), 1-methylimidazolium formate ([HMim][HCOO]), N,N-dimethylbutylammonium formate ([DMBA][HCOO]), or a mixture thereof. Preferably, the ionic liquid is [DMBA][HSO4].

[0032] The ionic liquid may be [DMBA][HSO4]. [DMBA][HSO4] has certain suitability in the extraction of lignin from lignocellulosic biomass fractions, while having a lower melting point (and thus viscosity) and an estimated production cost of approximately $1 / kg (similar to [TEA][HSO4]) compared to other ionic liquids containing hydrogen sulfate anions. Therefore, the production cost is lower than that of many ionic liquids and also lower than DMSO. Furthermore, ammonium-based hydrogen sulfate ILs may be recyclable.

[0033] In the method described herein, the fibers are formed using wet (coagulation) spinning. This involves extruding a spinning dope into a coagulation liquid to form the fibers. The coagulation liquid may be contained within a coagulation bath. The coagulation liquid may include water, preferably deionized (DI) water. The coagulation liquid may consist essentially of water. Alternatively, the coagulation liquid may include water and an ionic liquid. The ionic liquid may be any ionic liquid as described herein, preferably the same ionic liquid that is present in the dope solvent. The ionic liquid may be present in the coagulation liquid at 60 wt% or less, 30 wt% or less, or 15 wt% or less, preferably 1 - 60 wt%, 1 - 30 wt% or 1 - 15 wt%, more preferably 5 - 10 wt% (based on the total mass of the coagulation liquid). In a further alternative, the coagulation liquid includes water and sodium sulfate (Na2SO4). For example, the coagulation bath may contain an aqueous sodium sulfate solution at a concentration of 0.5 - 1.5 M, preferably about 1 M.

[0034] The fibers can be extruded using any suitable wet spinning process, for example using a continuous spinning line. The fibers can be extruded into a rotating bath.

[0035] The spinning dope can be a) dissolving lignin in a dope solvent to obtain a lignin solution; and b) combining the lignin solution with a carbon nanomaterial; and c) dispersing the carbon nanomaterial in the dope solvent to obtain a spinning dope by a process including.

[0036] The dispersing step can be carried out by shear. For example, shear can be carried out using a pestle and mortar, a shear mixer, such as a Banbury mixer, a two-roll mill, a three-roll mill, a centrifugal mixer, a bead mill, a Silverson mixer, or a jet mill to obtain a dispersion of the carbon nanomaterial.

[0037] The dissolution of lignin can be carried out at a temperature of 10°C to 200°C, preferably 10°C to 100°C, more preferably 20°C to 100°C, 20°C to 60°C, or 20°C to 30°C.

[0038] The spinning dope can be prepared by a process comprising the steps of preparing a lignin solution and combining the lignin solution with a carbon nanomaterial. The lignin solution may be aged before combining it with the carbon nanomaterial. As used herein, “aging” of the lignin solution refers to the period from after the lignin solution is prepared until before it is combined with the carbon nanomaterial. During aging, the lignin solution can be maintained at room temperature or heated to a temperature of at least 30°C, at least 60°C, for example up to 150°C. Aging can be carried out for at least 2 minutes, at least 5 minutes, at least 30 minutes, at least 1 hour, at least 1 day, at least 5 days, or at least 10 days. The lignin solution can be prepared by: (a) contacting a lignocellulosic biomass containing lignin and cellulose with a composition containing an ionic liquid and optionally water to dissolve the lignin and produce a cellulose pulp; (b) separating the cellulose pulp to obtain a liquor containing the ionic liquid, water, and lignin; and (c) optionally adjusting the amount of the ionic liquid and / or water in the liquor to obtain the lignin solution. The ionic liquid is the same ionic liquid as that present in the dope solvent. The liquor produced in step b) can be concentrated before step c). The step of preparing the spinning dope may include shearing after combining the lignin solution with the carbon nanomaterial to obtain the spinning dope. For example, using a pestle and mortar, a shear mixer such as a Banbury mixer, a two-roll mill, a three-roll mill, a centrifugal mixer, a bead mill, a Silverson mixer, or a jet mill to perform shearing can obtain a dispersion of the carbon nanomaterial.

[0039] The composition containing the ionic liquid and water (also referred to as the ionic liquid / water composition) mentioned in step (a) may contain a water content of 2 to 40% by weight, for example, a water content of 5 to 40% by weight, preferably a water content of 5 to 10% by weight. The water content mentioned in step (a) is calculated based on the mass of water present relative to the total mass of the ionic liquid / water composition. The ionic liquid / water composition may consist essentially of an ionic liquid and water. The biomass loading rate in step (a) may be, for example, 10 to 50% or 20 to 50%, for example, 30 to 40% relative to the mass of the ionic liquid / water composition. Steps (a) to (c) enable lignin extraction, formation of a spinning dope, and fiber formation without the need for another step to isolate and / or dry the lignin. This may be referred to as an integrated spinning process. This approach has the potential to reduce the cost of precursor fiber production by avoiding lignin precipitation, drying, and redissolution steps.

[0040] The lignocellulosic biomass contacted with the composition in step a) can be heated to a temperature of at least 70 °C, preferably 100 to 180 °C, more preferably 120 to 170 °C. For example, the lignocellulosic biomass contacted with the composition can be heated to 120 to 150 °C. The heating can be carried out for 1 minute to 22 hours, 10 minutes to 20 hours, 10 minutes to 10 hours, 15 minutes to 8 hours, or 30 minutes to 8 hours.

[0041] The biomass is contacted with the composition and subjected to mechanical treatment, such as stirring or vortexing, to assist in the dissolution of lignin and the production of cellulose pulp. The mechanical treatment can be carried out before heating. Ethanol can be added to the mixture resulting from step a) before the separation of the cellulose pulp. The separation of the cellulose pulp can be carried out using filtration, such as vacuum filtration. The biomass can be subjected to mechanical treatment before being contacted with the composition.

[0042] The integrated spinning process results in the dissolution of lignin from lignocellulosic biomass in a dope solvent, while avoiding the dissolution of cellulose. Other components of lignocellulosic biomass, such as hemicellulose, may dissolve.

[0043] The spinning dope may contain additional solutes, which may be lignocellulosic biomass components, such as hemicellulose, or hemicellulose degradation products, such as furfural.

[0044] The method may further include drying one or more fibers under mechanical tension.

[0045] The method may further include heating one or more fibers in air at 150 - 300 °C. This step can be performed to thermally stabilize one or more fibers.

[0046] The method may further include carbonizing one or more fibers to obtain carbon fibers. Carbonization may include heating one or more fibers to 800 - 3000 °C, preferably 1200 - 1800 °C, in an inert atmosphere. For example, carbonization can be performed under nitrogen or argon, preferably nitrogen. Carbonization can be carried out using fibers under tension.

[0047] The spinning dope may have a viscosity of 0.3 - 300,000, such as 0.3 - 100,000 or 0.3 - 2500 Pa·s, at zero shear (when measured at the spinning temperature). The zero - shear - rate viscosity can be measured using an AR 2000ex rheometer having a cone - and - plate geometry (cone angle 2°, plate diameter 20 mm and gap 53 μm) at a low shear rate of 3.00×10 -6 ~30 s -1 The spinning temperature, when referred to herein, may refer to 25 °C.

[0048] In a second aspect, fibers obtainable by the method of the first aspect are provided herein.

[0049] In a third aspect, a spinning dope comprising a dope solvent, lignin, and a carbon nanomaterial, wherein the dope solvent comprises an ionic liquid and optionally water, is provided herein. The spinning dope may be as described with respect to the first aspect.

[0050] In a fourth aspect, a dispersion comprising carbon nanotubes and [DMBA][HSO4] is provided herein. The dispersion may be a dispersion of carbon nanotubes in any dope solvent as described herein, and the ionic liquid is [DMBA][HSO4]. Thus, the dope solvent may comprise water and optionally ethanol at any concentration as described herein. The carbon nanotubes may be present at a loading rate of at least 0.001 wt%, at least 0.01 wt%, or at least 0.1 wt%. The carbon nanotubes may be present at a loading rate of 0.001 - 10 wt%, 0.001 - 8 wt%, 0.01 - 8 wt%, 0.1 - 5 wt%, 0.1 - 1 wt%, or 0.3 - 0.7 wt%. The carbon nanomaterial may be present at a loading rate of about 0.5 wt%. The carbon nanotubes may be single-walled carbon nanotubes. Ionic liquid The ionic liquids referred to herein may be, for example, ionic liquids as described in WO2012080702, WO2014140643, or WO2017085516, which are incorporated herein by reference.

[0051] As used herein, "ionic liquid" refers to ionized species (i.e., cations and anions). Ionic liquids typically have a melting point of less than about 100°C. Any of the anions listed below can be used in combination with any of the cations listed below to produce an ionic liquid for use in the present invention.

[0052] The ionic liquid may contain one of the listed anions, or a mixture thereof.

[0053] The anion is C 1~20 alkyl sulfate ([alkyl SO4] - ), C 1~20 alkyl sulfonate ([alkyl SO3] - ), hydrogen sulfate ([HSO4] - ), hydrogen sulfite ([HSO3] - ), dihydrogen phosphate ([H2PO4] - ), hydrogen phosphate ([HPO4] 2- ), chloride (Cl - ), bromide (Br - ), trifluoromethanesulfonate ([OTf] - ), formate ([HCOO] - ) and acetate ([MeCO2] - ) and may be selected from. For example, the anion is [MeSO4] - , [HSO4] - 、 [MeSO3] - , Cl - , [HCOO] - and [MeCO2] - and may be selected from, for example, chloride Cl - and hydrogen sulfate [HSO4] - or [MeSO4] - , [HSO4] - 、 [MeSO3] - , and [MeCO2] - and may be selected from. Preferably the anion is selected from [HSO4] - and [HCOO] - . The ionic liquid may contain one of the listed anions, or a mixture thereof. The ionic liquid may contain any one of the cations identified herein, or a mixture thereof.

[0054] The cation is preferably a protonic cation. That is, the cation is a cation that can donate a proton (H + ).

[0055] The cation may be an ammonium or phosphonium derivative. These cations have the general formula

[0056]

Chemical formula

[0057] wherein [In the formula, X is N or P; A 1 ~A 4 are each independently selected from H, aliphatic, C 3~6 carbocyclic, C 6~10 aryl, alkylaryl, and heteroaryl. The aliphatic may be substituted with one or more -OH].

[0058] In one embodiment, the cation is an ammonium ion, a derivative thereof, or a mixture thereof. The cation may be of the formula

[0059]

Chemical formula

[0060] wherein [In the formula, A 1 ~A 4 are each independently selected from H, aliphatic, C 3~6 carbocyclic, C 6~10 aryl, alkylaryl, and heteroaryl, and the aliphatic may be substituted with one or more -OH]. Preferably, at least one of A 1 ~A 4 is H. Preferably, at least one of A 1 ~A 4is independently selected from H and aliphatic. In one embodiment, A 1 ~A 4 at least one of which is H, and the remaining three are each independently aliphatic. In another method, A 1 ~A 4 two of which are each H, and the remaining two are each independently aliphatic. In another method, A 1 ~A 4 at least one of which is aliphatic, and the remaining three are all H. Preferably, the cation is not ammonium (NH4 + ). That is, A 1 ~A 4 at least one of which is not H. The aliphatic may be alkyl, preferably C 1~6 alkyl, which may be substituted with one or more -OH groups. In some embodiments, the aliphatic is unsubstituted.

[0061] In one embodiment, the cation is alkylammonium or a mixture thereof (i.e., A 1 ~A 4 is independently selected from H or alkyl, and A 1 ~A 4The cation in the above formula, at least one of which is not H. Preferably, this is a protonated alkylammonium, but aprotic alkylammonium can also be used. Optionally, one or more of the alkyl groups may be substituted with -OH to form an alkanolammonium, which may also be referred to as an alcoholammonium. For example, the cation may be choline. As used herein, "alkylammonium" includes trialkylammonium, dialkylammonium, monoalkylammonium, and alcoholammonium including trialkanolammonium, dialkanolammonium and monoalkanolammonium. Trialkylammonium includes trimethylammonium, triethylammonium, and triethanolammonium. Examples of dialkylammonium include diethylammonium, diisopropylammonium, and diethanolammonium. Monoalkylammonium includes methylammonium, ethylammonium, and monoethanolammonium. The ionic liquid may preferably be an [alkylammonium][HSO4] or [alkylammonium][HCOO] ionic liquid.

[0062] In one embodiment, the alkylammonium cation is selected from triethylammonium, diethylammonium, dimethylethylammonium, diethylmethylammonium, dimethylbutylammonium, diethanolammonium and choline. The alkylammonium cation can be selected from triethylammonium, diethylammonium, dimethylethylammonium, diethylmethylammonium, and dimethylbutylammonium, diethanolammonium. In another embodiment, the alkylammonium cation is selected from dimethylbutylammonium, triethylammonium and methylbutylammonium.

[0063] The cation can also contain a nitrogen-containing heterocyclic moiety, which, as used herein, refers to a monocyclic or bicyclic ring system containing one nitrogen atom and optionally one or more additional heteroatoms selected from N, S, and O. The ring system contains 5 to 9 members, preferably 5 or 6 members, for a monocyclic group, and 9 or 10 members for a bicyclic group. The ring can be aromatic, partially saturated or saturated, and thus includes both "heteroalicyclic" groups meaning non-aromatic heterocycles and "heteroaryl" groups meaning aromatic heterocycles. The cation is

[0064] [Chemical formula]

[0065] selected from [wherein R 1 and R 2 are independently C 1~6 alkyl or C 1~6 alkoxyalkyl groups, and R 3 , R 4 , R 5 , R 6 , R 7 , R 8 and R 9 , when present, are independently H, C 1~6 alkyl, C 1~6 alkoxyalkyl groups, or C 2~6 alkyloxy groups]. Preferably, R 1 and R 2 are C 1~4 alkyl, one of which is methyl, and R 3 to R 9 (R 3 , R 4 , R 5 , R 6 , R 7 , R 8 and R 9 ), when present, are H. In one embodiment, the cation ring is imidazolium or pyridinium.

[0066] In one embodiment, the cation may be an imidazolium-based cation or a mixture thereof, particularly a protonated imidazolium-based cation. In one embodiment, the imidazolium-based cation may be 1-butyl-3-methylimidazolium [BMim] + 、1-ethyl-3-methylimidazolium [EMim] + 、1-methylimidazolium [HMim] + 、1-butylimidazolium [HBim] + and mixtures thereof. For example, the imidazolium-based cation may be selected from 1-butyl-3-methylimidazolium [BMim] + 、1-methylimidazolium [HMim] + 、1-butylimidazolium [HBim] + and mixtures thereof, for example, 1-methylimidazolium [HMim] + 、1-butylimidazolium [HBim] + and mixtures thereof. In one embodiment, the imidazolium-based cation is selected from 1-butyl-3-methylimidazolium [BMim] + 、1-butylimidazolium [HBim] + and mixtures thereof.

[0067] In some embodiments, the cation includes protonated alkylammonium, protonated methylimidazolium, protonated pyridinium, aprotic tetraalkylammonium, and aprotic dialkylimidazolium ions.

[0068] The ionic liquid may preferably be N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4]), 1-butylimidazolium hydrogen sulfate ([HBim][HSO4]), triethylammonium hydrogen sulfate ([TEA][HSO4]), N-methylbutylammonium hydrogen sulfate ([MBA][HSO4]), 1-methylimidazolium formate ([HMim][HCOO]), N,N-dimethylbutylammonium formate ([DMBA][HCOO]), or a mixture thereof.

[0069] In one embodiment, the ionic liquid is not 1-ethyl-3-methylimidazolium acetate [EMim][OAc].

[0070] In another embodiment, the ionic liquid is selected from triethylammonium hydrogen sulfate ([TEA][HSO4]), N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4]), diethylammonium hydrogen sulfate ([DEA][HSO4]), N,N-dimethylethylammonium hydrogen sulfate ([DMEA][HSO4]), diethanolammonium chloride [DEtOHA]Cl, 1-methylimidazolium hydrogen chloride [HMim]Cl, 1-ethyl-3-methylimidazolium chloride [EMim]Cl, and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [EMim][OTf].

[0071] In another embodiment, the ionic liquid is selected from 1-butyl-3-methylimidazolium methyl sulfate [BMim][MeSO4], 1-butyl-3-methylimidazolium hydrogen sulfate [BMim][HSO4], 1-butyl-3-methylimidazolium methanesulfonate [BMim][MeSO3], 1-butylimidazolium hydrogen sulfate ([HBim][HSO4]), and 1-ethyl-3-methylimidazolium acetate [EMim][MeCO2].

[0072] Preferred ionic liquids are [alkylammonium][HSO4] ionic liquids, such as N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4]), triethylammonium hydrogen sulfate ([TEA][HSO4]), N-methylbutylammonium hydrogen sulfate ([MBA][HSO4]), diethylammonium hydrogen sulfate [DEA][HSO4], N,N-dimethylethylammonium hydrogen sulfate ([DMEA][HSO4]), and ethylammonium hydrogen sulfate [ethylNH3][HSO4].

[0073] The dope solvent referred to herein contains an ionic liquid and optionally water. For use in the methods disclosed herein, an ionic liquid is provided such that the dope solvent can dissolve lignin. Preferably, cellulose has lower solubility in the dope solvent than lignin. More preferably, the dope solvent does not dissolve cellulose.

[0074] An ionic liquid, which is optionally a mixture with water, can be used to separate lignin and cellulose, for example, when preparing a spinning dope in an integrated spinning process, in the treatment of lignocellulosic biomass. Since the ionic liquid can dissolve the lignin in the biomass but not the cellulose, this treatment results in a cellulose pulp and a lignin solution. Thus, most of the cellulose, for example at least 70%, preferably at least 80% (weight % based on the oven-dry weight of the biomass), remains solid. The cellulose pulp can be easily removed mechanically from the lignin solution, for example, by filtration. Other components such as hemicellulose can also dissolve in the ionic liquid.

[0075] When the ionic liquid is present as a mixture with water, this may be represented as x% / water y% where the percentage is the mass of the component relative to the total mass of the mixture (i.e., w / w%). For example, [DMBA][HSO4] 95% / water 5% refers to a mixture of [DMBA][HSO4] and water in which [DMBA][HSO4] is present at 95% (w / w) (95% by weight) and water is present at 5% (w / w) (5% by weight).

[0076] Ionic liquids can be prepared by methods known to those skilled in the art or can be obtained commercially. For example, protonated ammonium-based ILs can be prepared in a one-step synthesis from simple alkylamines such as triethylamine and sulfuric acid, as described, for example, in George et al., (2015) "Design of low-cost ionic liquids for lignocellulosic biomass treatment" Green Chemistry 17:1728 - 1731.

[0077] In ionic liquids, typically, the cations and anions are present in equimolar amounts. However, the ionic liquid may contain an excess of base, preferably a protonated base. As used herein, "base" refers to the base from which the cation is derived, such as an amine / imidazole. The ionic liquid may contain a 10% molar excess of base, for example, a 4 - 8%, 5 - 7.5% excess of base. The ionic liquid may contain a 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% molar excess of base.

[0078] In another embodiment, the dope solvent further contains an acid in a 0.01 - 20% molar excess, preferably a 1 - 5% molar excess, as a percentage with respect to the IL. The acid can be selected from any known strong acid, such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, hydroiodic acid, perchloric acid and hydrobromic acid. Preferably the acid is sulfuric acid or hydrochloric acid or phosphoric acid. More preferably, the acid is the same acid used to synthesize the protonated IL.

[0079] It should be appreciated that the features described through this disclosure may exist in any combination, with necessary modifications. For example, whenever a discussion of the components of a spinning dope or the component loading rates is provided, these components may exist in any combination, and the loading rates may exist in any combination.

[0080] All publications, published patent documents, and patent applications cited herein are hereby incorporated by reference to the same extent as if each individual publication, published patent document, and patent application were specifically and individually indicated to be incorporated by reference.

[0081] Definitions To make the present invention more readily understood, some terms are first defined below. Additional definitions for the following terms and other terms are described throughout this specification.

[0082] As used herein, the singular forms "a", "an", and "the" include the plural forms as well, unless the context clearly dictates otherwise. The use of the singular form includes the plural form unless specifically stated otherwise. Whenever the term "comprising" is referred to herein, this may also refer to "consisting essentially of" and "consisting of". For example, a dope solvent comprising an ionic liquid, water, and optionally ethanol may also be a dope solvent consisting essentially of an ionic liquid, water, and optionally ethanol.

[0083] As referred to herein, a "dope solvent" is a solvent in which lignin can dissolve. The dope solvent may include a mixture of solvents. The dope solvent includes an ionic liquid and optionally water. This may also include additional solvents, such as ethanol. All solvents present in the spinning dope may constitute the dope solvent (i.e., the spinning dope does not contain any solvent other than the dope solvent). The dope solvent may consist essentially of an ionic liquid, water, and optionally ethanol. Preferably, the dope solvent does not dissolve cellulose.

[0084] Various components are described as being present in the spinning dope at a certain percentage loading rate. The loading rate is the mass loading rate, which can be referred to as loading % or loading weight %. Usually, the loading rate is described with respect to the mass of the spinning dope excluding the mass of lignin and carbon nanomaterials. The loading rate calculation for the spinning dope component (i.e., lignin or carbon nanomaterial) is: (Component mass / Mass of the spinning dope excluding the mass of lignin and carbon nanomaterials) × 100 is. In embodiments where the spinning dope consists essentially of a dope solvent (water, ionic liquid and optionally ethanol), lignin and carbon nanomaterials, the loading rate calculation is: (Mass of the component / Dope solvent) × 100 is. As described herein, in some embodiments, the spinning dope may contain additional solutes. In such embodiments, the loading rate calculation is: (Mass of the component / Dope solvent + Additional solutes) × 100 is.

[0085] As used herein, a "coagulating liquid" is a liquid into which the spinning dope can be extruded. Extrusion of the spinning dope into the coagulating liquid results in fiber formation.

[0086] Nanomaterials can be defined as materials having an outer dimension of at least one of 100 nm or less. Carbon nanomaterials include, but are not limited to, carbon nanotubes, graphene nanoribbons, graphene nanoplatelets and graphene nanoflakes. Carbon nanotubes can be single-walled carbon nanotubes or multi-walled carbon nanotubes. The use of carbon nanomaterials in the fiber production methods described herein can provide improved rheology for spinning, improved precursor fiber strength for handling, improved graphite microstructure after conversion (in some cases, conversion at lower temperatures), and direct strengthening of the final carbon fiber.

[0087] As used herein, the term "lignocellulosic biomass" refers to living or dead biomass and can include any cellulosic or lignocellulosic material, including materials containing cellulose, and optionally further includes hemicellulose, lignin, starch, oligosaccharides and / or monosaccharides, biopolymers, natural derivatives of biopolymers, mixtures thereof, and degradation products. This can also include additional components, such as proteins and / or lipids. The biomass may be derived from a single source or may include mixtures derived from more than one source. Some specific examples of biomass include, but are not limited to, bioenergy crops, agricultural residues, municipal solid waste, industrial solid waste, sludge from papermaking, yard waste, wood and forestry waste. Additional examples of biomass include, but are not limited to, corn kernels, corn cobs, crop residues such as corn husks, corn stover, grasses including Miscanthus X giganteus, wheat, wheat straw, hay, rice straw, switchgrass, paper scraps, sugarcane bagasse, sorghum, soybeans, components obtained from the grinding of grains, trees (e.g., pine), branches, roots, leaves, wood chips, wood pulp, sawdust, shrubs and bushes, vegetables, fruits, flowers, animal manure, multi-component feeds, and crustacean biomass (i.e., chitinous biomass). It may be preferable to process the biomass before use in the methods of the present invention. For example, the biomass can be mechanically processed, e.g., ground or crushed.

[0088] As referred to herein, "aging" of the spinning dope refers to the period from after the spinning dope is prepared until before the dope is extruded. During aging, the dope can be maintained at room temperature or heated. During aging, the dope can be mixed. Aging can be carried out for at least 5 minutes, at least 30 minutes, e.g., up to 72 or 48 hours.

[0089] Room temperature, when referred to in this specification, may refer to 25°C.

[0090] As used herein, the term "aliphatic" refers to straight-chain or branched-chain hydrocarbons that are either fully saturated or contain one or more unsaturated units. Thus, aliphatic may preferably be an alkyl, alkenyl or alkynyl having 1 to 12 carbon atoms, preferably up to 6 carbon atoms, or more preferably up to 4 carbon atoms. Aliphatic can have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms.

[0091] As used herein, the term "alkyl" typically refers to a straight-chain or branched alkyl group or moiety containing 1 to 20 carbon atoms, such as 11, 12, 13, 14, 15, 16, 17, 18, or 19 carbon atoms. Preferably, the alkyl group or moiety contains 1 to 10 carbon atoms, i.e., 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms, for example, C 1~4 alkyl or C 1~6 alkyl group or moiety, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl and t-butyl, n-pentyl, methylbutyl, dimethylpropyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,3-dimethylbutyl, and 2,2-dimethylbutyl.

[0092] As used herein, the term "carbocyclic" refers to a saturated or partially unsaturated cyclic group having 3 to 6 ring carbon atoms, i.e., 3, 4, 5, or 6 carbon atoms. The carbocyclic is preferably a "cycloalkyl", which, as used herein, refers to a fully saturated hydrocarbon cyclic group. Preferably, the cycloalkyl group is a C3-C6 cycloalkyl group.

[0093] As used in this specification, "C 6~10The term "aryl group" means an aryl group composed of 6, 7, 8, 9 or 10 carbon atoms, and includes fused ring groups such as monocyclic ring groups, or bicyclic ring groups and the like. Specifically, "C 6~10 Examples of "aryl groups" include phenyl groups, indenyl groups, naphthyl groups or azulene groups and the like. It should be noted that fused rings such as indane and tetrahydronaphthalene are also included in the aryl group.

[0094] As used herein, the term "alkylaryl" refers to an alkyl group as defined below, substituted with an aryl as defined above. The alkyl component of an "alkylaryl" group may be substituted with any one or more of the substituents listed above for aliphatic groups, and the aryl or heteroaryl component of an "alkylaryl" or "alkylheteroaryl" group may be substituted with any one or more of the substituents listed above for aryl, and carbocyclic groups. Preferably, the alkylaryl is benzyl.

[0095] As used herein, the term "heteroaryl" refers to a monocyclic or bicyclic aromatic ring system having 5 to 10 ring atoms, i.e., 5, 6, 7, 8, 9, or 10 ring atoms, and at least one ring atom is a heteroatom selected from O, N or S.

[0096] The aliphatic, aryl, heteroaryl, or carbocyclic groups referred to herein may be unsubstituted or substituted with one or more substituents independently selected from the group consisting of halo, C 1~6 alkyl, -NH2, -NO2, -SO3H, -OH, alkoxy, -COOH, or -CN.

[0097] As used herein, the term "halogen atom" or "halo" means a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like, preferably a fluorine atom or a chlorine atom, more preferably a fluorine atom.

[0098] "C 2~6 alkoxy" refers to an alkyl group bonded to an oxygen that is also bonded to the cation ring, where the C 1~6 is as defined above. "C 2~6 alkoxyalkyl group" refers to an alkyl containing an ether group of the general formula X-O-Y, where X and Y are each independently C 1~5 alkyl and the total number of carbon atoms is between 2 and 6, for example 2, 3, 4, 5, or 6.

[0099] As used herein, the term "alkenyl" refers to a straight-chain or branched alkenyl group or moiety containing from 2 to 20 carbon atoms, such as 11, 12, 13, 14, 15, 16, 17, 18, or 19 carbon atoms. Preferably, the alkenyl group or moiety contains from 2 to 10 carbon atoms, i.e., 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms, and examples thereof include C 2~4 alkenyl or C 2~6 alkenyl group or moiety, such as ethenyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl, and 5-hexenyl.

[0100] As used herein, the term "alkynyl" refers to a straight-chain or branched alkynyl group or moiety containing from 2 to 20 carbon atoms, such as 11, 12, 13, 14, 15, 16, 17, 18, or 19 carbon atoms. Preferably, the alkynyl group or moiety contains from 2 to 10 carbon atoms, i.e., 2, 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms, and examples thereof include C 2~4 alkynyl or C 2~6An alkynyl group or moiety, such as ethynyl, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 3-butynyl, 1-pentynyl, 2-pentynyl, 3-pentynyl, 4-pentynyl, 1-hexynyl, 2-hexynyl, 3-hexynyl, 4-hexynyl, and 5-hexynyl.

[0101] This disclosure provides aspects and embodiments as presented in the following clauses: 1. A method for producing fibers, comprising: preparing a spinning dope comprising a dope solvent, lignin dissolved in the dope solvent, and carbon nanomaterials, wherein the dope solvent comprises an ionic liquid and optionally water; extruding the spinning dope into a coagulation bath to obtain one or more fibers. A method comprising the above steps. 2. The method according to clause 1, wherein the water content in the dope solvent is at least 0 to 30 wt%. 3. The method according to clause 1 or 2, wherein the water content in the dope solvent is 0 to 20 wt%. 4. The method according to any one of the preceding clauses, wherein the water content in the dope solvent is 0 to 15 wt%. 5. The method according to any one of the preceding clauses, wherein the water content in the dope solvent is 0 to 10 wt%. 6. The method according to any one of the preceding clauses, wherein the water content in the dope solvent is 0 to 5 wt%. 7. The method according to any one of the preceding clauses, wherein the dope solvent comprises at least 1 wt% water. 8. The method according to any one of the preceding clauses, wherein the dope solvent comprises at least 2 wt% water. 9. The method according to any one of the preceding clauses, wherein the dope solvent comprises at least 3 wt% water. 10. The method according to any one of the preceding clauses, wherein the lignin is present at a loading rate of at least 5 wt% based on the total mass of the spinning dope excluding the mass of the lignin and the carbon nanomaterials. 11. The method according to clause 10, wherein the lignin is present at a loading rate of at least 10 wt%. 12. The method according to clause 11, wherein lignin is present at a loading rate of at least 10 to 50% by weight. 13. The method according to clause 12, wherein lignin is present at a loading rate of at least 10 to 40% by weight. 14. The method according to clause 13, wherein lignin is present at a loading rate of at least 10 to 30% by weight. 15. The method according to any one of the preceding clauses, wherein the carbon nanomaterial is present at a loading rate of at least 0.001% by weight based on the weight of the spinning dope excluding the weights of the lignin and the carbon nanomaterial. 16. The method according to clause 15, wherein the carbon nanomaterial is present at a loading rate of at least 0.01% by weight. 17. The method according to clause 16, wherein the carbon nanomaterial is present at a loading rate of at least 00.1% by weight. 18. The method according to clause 17, wherein the carbon nanomaterial is present at a loading rate of 0.001 to 10% by weight. 19. The method according to clause 18, wherein the carbon nanomaterial is present at a loading rate of 0.001 to 8% by weight. 20. The method according to clause 19, wherein the carbon nanomaterial is present at a loading rate of 0.01 to 8% by weight. 21. The method according to clause 20, wherein the carbon nanomaterial is present at a loading rate of 0.1 to 5% by weight. 22. The method according to clause 21, wherein the carbon nanomaterial is present at a loading rate of 0.1 to 1% by weight. 23. The method according to clause 22, wherein the carbon nanomaterial is present at a loading rate of 0.3 to 0.7% by weight. 24. The method according to any one of the preceding clauses, wherein the weight ratio of lignin to carbon nanomaterial in the spinning dope is 5:1 to 10000:1. 25. The method according to any one of the preceding clauses, wherein the weight ratio of lignin to carbon nanomaterial in the spinning dope is 5:1 to 5000:1. 26. The method according to any one of the preceding clauses, wherein the weight ratio of lignin to carbon nanomaterial in the spinning dope is 10:1 to 1000:1. 27. The method according to any one of the preceding clauses, wherein the weight ratio of lignin to carbon nanomaterial in the spinning dope is 20:1 to 200:1. 28. The method according to any one of the preceding clauses, wherein the carbon nanomaterial is dispersed in a dope solvent. 29. The method according to any one of the preceding clauses, wherein the carbon nanomaterial includes carbon nanotubes, carbon nanoribbons, graphene nanoplatelets, or a combination thereof. 30. The method according to clause 29, wherein the carbon nanomaterial includes carbon nanotubes. 31. The method according to clause 30, wherein the carbon nanotubes are single-walled carbon nanotubes (SWCNT). 32. The ionic liquid includes a cation and an anion, and the anion is C 1~20 alkyl sulfate ([alkylSO4] - ), C 1~20 alkyl sulfonate ([alkylSO3] - ), hydrogen sulfate ([HSO4] - ), hydrogen sulfite ([HSO3] - ), dihydrogen phosphate ([H2PO4] - ), hydrogen phosphate ([HPO4] 2- ), chloride (Cl - ), bromide (Br - ), trifluoromethanesulfonate ([OTf] - ), formate ([HCOO] - ), and acetate ([MeCO2] - ), and is selected from the methods according to any one of the preceding clauses. 33. The method according to clause 32, wherein the anion is selected from [HSO4] - and [HCOO] - . 34. The method according to any one of the preceding clauses, wherein the ionic liquid includes a cation and an anion, and the cation is a protic cation. 35. The ionic liquid includes a cation and an anion, and the cation contains a nitrogen-containing heterocyclic moiety, or the cation is a cation of formula I

[0102] [Chemical formula]

[0103] [wherein, A 1 ~A 4 are each independently H, aliphatic, C 3~6 carbocyclic ring, C 6~10 aryl, alkylaryl, and heteroaryl, respectively] The method according to any of the preceding clauses. 36. The method according to any of the preceding clauses, wherein the ionic liquid is an [alkylammonium][HSO4] or [alkylammonium][HCOO] ionic liquid. 37. The ionic liquid is triethylammonium hydrogen sulfate [TEA][HSO4], N,N-dimethylbutylammonium hydrogen sulfate [DMBA][HSO4], diethylammonium hydrogen sulfate [DEA][HSO4], N,N-dimethylethylammonium hydrogen sulfate ([DMEA][HSO4]), diethanolammonium chloride [DEtOHA]Cl, 1-methylimidazolium hydrogen chloride [HMim]Cl, 1-ethyl-3-methylimidazolium chloride [EMim]Cl, and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [EMim][OTf], 1-butylimidazolium hydrogen sulfate ([HBim][HSO4]), methylbutylammonium hydrogen sulfate ([MBA][HSO4]), 1-methylimidazolium formate ([HMim][HCOO]), N,N-dimethylbutylammonium formate ([DMBA][HCOO]), N,N-dimethylethylammonium hydrogen sulfate ([DMEA][HSO4]), 1-butyl-3-methylimidazolium hydrogen sulfate [BMim][HSO4], or N-dimethylbutylammonium acetate ([DMBA][OAc]), or a mixture thereof. The method according to any of the preceding clauses. 38. The method according to any of the preceding clauses, wherein the ionic liquid is N,N-dimethylethylammonium hydrogen sulfate ([DMEA][HSO4]), N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4]), 1-butylimidazolium hydrogen sulfate ([HBim][HSO4]), triethylammonium hydrogen sulfate ([TEA][HSO4]), methylbutylammonium hydrogen sulfate ([MBA][HSO4]), 1-methylimidazolium formate ([HMim][HCOO]), N,N-dimethylbutylammonium formate ([DMBA][HCOO]), 1-methylimidazolium hydrogen chloride [HMim]Cl, N,N-dimethylbutylammonium chloride [DMBA]Cl, 1-butyl-3-methylimidazolium hydrogen sulfate [BMim][HSO4], or N-dimethylbutylammonium acetate ([DMBA][OAc]), or a mixture thereof. 39. The method according to any of the preceding clauses, wherein the ionic liquid is N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4]), 1-butylimidazolium hydrogen sulfate ([HBim][HSO4]), triethylammonium hydrogen sulfate ([TEA][HSO4]), methylbutylammonium hydrogen sulfate ([MBA][HSO4]), 1-methylimidazolium formate ([HMim][HCOO]), N,N-dimethylbutylammonium formate ([DMBA][HCOO]), 1-methylimidazolium hydrogen chloride [HMim]Cl, N,N-dimethylbutylammonium chloride [DMBA]Cl, 1-butyl-3-methylimidazolium hydrogen sulfate [BMIM][HSO4], or N-dimethylbutylammonium acetate ([DMBA][OAc]), or a mixture thereof. 40. The method according to any preceding clause, wherein the ionic liquid is N,N-dimethylbutylammonium hydrogen sulfate ([DMBA][HSO4]), 1-butylimidazolium hydrogen sulfate ([HBim][HSO4]), triethylammonium hydrogen sulfate ([TEA][HSO4]), methylbutylammonium hydrogen sulfate ([MBA][HSO4]), 1-methylimidazolium formate ([HMim][HCOO]), or N,N-dimethylbutylammonium formate ([DMBA][HCOO]), or a mixture thereof. 41. The method according to any preceding clause, wherein the ionic liquid is [DMBA]Cl, [DMBA][HSO4], [BMim][HSO4], [MBA][HSO4] or [HBim][HSO4], or a mixture thereof. 42. The method according to any preceding clause, wherein the ionic liquid is [DMBA][HSO4]. 43. The method according to any preceding clause, wherein the dope solvent further contains ethanol. 44. The method according to clause 43, wherein ethanol is present at 1 to 20% by weight of the dope solvent based on the total weight of the dope solvent. 45. The method according to clause 44, wherein ethanol is present at 5 to 15% by weight. 46. The method according to any of clauses 43 to 45, wherein the mass ratio of ionic liquid:ethanol is 3:1 to 15:1. 47. The method according to any of clauses 43 to 46, wherein the mass ratio of ionic liquid:ethanol is 5:1 to 12:1. 48. The method according to any preceding clause, wherein the spinning dope has a water content of at least 5% by weight, calculated based on the mass of water present relative to the mass of the spinning dope excluding the masses of lignin and carbon nanomaterials. 49. The method according to any preceding clause, wherein the spinning dope has a water content of 5 to 40% by weight, calculated based on the mass of water present relative to the mass of the spinning dope excluding the masses of lignin and carbon nanomaterials. 50. The method according to any of the preceding clauses, wherein the spinning dope has a water content of 10 to 40% by weight, calculated based on the mass of water present relative to the mass of the spinning dope excluding the masses of lignin and the carbon nanomaterial. 51. The method according to any of the preceding clauses, wherein the spinning dope has a water content of 20 to 40% by weight, calculated based on the mass of water present relative to the mass of the spinning dope excluding the masses of lignin and the carbon nanomaterial. 52. The method according to any of the preceding clauses, wherein the coagulating liquid contains water. 53. The method according to any of the preceding clauses, wherein the coagulating liquid contains water and an ionic liquid, and the ionic liquid is present at 60% by weight or less based on the total mass of the coagulating liquid. 54. The method according to any of the preceding clauses, wherein the coagulating liquid contains water and an ionic liquid, and the ionic liquid is present at 30% by weight or less based on the total mass of the coagulating liquid. 55. The method according to any of the preceding clauses, wherein the coagulating liquid contains water and an ionic liquid, and the ionic liquid is present at 15% by weight or less based on the total mass of the coagulating liquid. 56. The method according to any of the preceding clauses, wherein the coagulating liquid contains water and an ionic liquid, and the ionic liquid is present at 1 to 60% by weight based on the total mass of the coagulating liquid. 57. The method according to any of the preceding clauses, wherein the coagulating liquid contains water and an ionic liquid, and the ionic liquid is present at 1 to 30% by weight based on the total mass of the coagulating liquid. 58. The method according to any of the preceding clauses, wherein the coagulating liquid contains water and an ionic liquid, and the ionic liquid is present at 1 to 15% by weight based on the total mass of the coagulating liquid. 59. The method according to any of the preceding clauses, wherein the coagulating liquid contains water and an ionic liquid, and the ionic liquid is present at 5 to 15% or 5 to 10% by weight based on the total mass of the coagulating liquid. 60. The method according to any of the preceding clauses, wherein the coagulating liquid contains water and sodium sulfate. 61. The method according to clause 60, wherein the coagulation bath contains an aqueous sodium sulfate solution at a concentration of 0.5 to 1.5 M. 62. The step of preparing the spinning dope is a) dissolving lignin in a doping solvent to obtain a lignin solution; b) combining the lignin solution with a carbon nanomaterial; c) optionally, dispersing the carbon nanomaterial in the doping solvent by shear to obtain a spinning dope The method according to any one of the preceding clauses. 63. The method according to clause 62, wherein the dissolution of lignin is carried out at a temperature of 10 °C to 100 °C. 64. The method according to clause 63, wherein the dissolution of lignin is carried out at a temperature of 20 °C to 60 °C. 65. The method according to clause 64, wherein the dissolution of lignin is carried out at a temperature of 20 °C to 30 °C. 66. The method according to any one of the preceding clauses, wherein the spinning dope is prepared by a process comprising a step of preparing a lignin solution and a step of combining the lignin solution with a carbon nanomaterial. 67. The lignin solution is a) contacting a lignocellulosic biomass containing lignin and cellulose with a composition containing an ionic liquid and water to dissolve the lignin and produce a cellulose pulp; b) separating the cellulose pulp to obtain a liquor containing the ionic liquid, water and lignin; c) optionally, adjusting the amount of the ionic liquid and / or water in the liquor to obtain a lignin solution The method according to clause 66, prepared by. 68. The method according to clause 62, 66 or 67, further comprising a step of aging the lignin solution for at least 2 minutes before combining it with the carbon nanomaterial. 69. The method according to clause 62, 66 or 67, further comprising a step of aging the lignin solution for at least 5 minutes before combining it with the carbon nanomaterial. 70. The method according to clause 62, 66 or 67, further comprising a step of aging the lignin solution for at least 30 minutes before combining it with the carbon nanomaterial. 71. The method according to clause 62, 66 or 67, further comprising the step of aging the lignin solution for at least 1 hour before combining it with the carbon nanomaterial. 72. The method according to clause 62, 66 or 67, further comprising the step of aging the lignin solution for at least 1 day before combining it with the carbon nanomaterial. 73. The method according to clause 62, 66 or 67, further comprising the step of aging the lignin solution for at least 5 days before combining it with the carbon nanomaterial. 74. The method according to clause 62, 66 or 67, further comprising the step of aging the lignin solution for at least 10 days before combining it with the carbon nanomaterial. 75. The method according to any one of clauses 68 to 74, wherein the lignin solution is heated at a temperature of at least 30 °C during aging. 76. The method according to any one of clauses 68 to 74, wherein the lignin solution is heated at a temperature of at least 60 °C during aging. 77. The method according to any one of clauses 68 to 76, wherein the lignin solution is heated at a temperature up to 150 °C during aging. 78. The method according to any one of clauses 67 to 77, wherein the composition comprising the ionic liquid and water has a water content of 2 to 40% by weight. 79. The method according to clause 78, wherein the composition comprising the ionic liquid and water has a water content of 5 to 40% by weight. 80. The method according to clause 79, wherein the composition comprising the ionic liquid and water has a water content of 5 to 10% by weight. 81. The method according to any one of clauses 67 to 80, wherein the lignocellulosic biomass contacted with the composition is heated to 100 to 180 °C. 82. The method according to any one of clauses 67 to 80, wherein the lignocellulosic biomass contacted with the composition is heated to 120 to 170 °C. 83. The method according to any one of clauses 67 to 80, wherein the lignocellulosic biomass contacted with the composition is heated to 120 to 150 °C. 84. The method according to any one of clauses 67 to 83, wherein the lignocellulosic biomass is contacted with the composition for 1 minute to 22 hours. 85. The method according to any one of clauses 67 to 83, wherein the lignocellulosic biomass is contacted with the composition for 10 minutes to 22 hours. 86. The method according to any one of clauses 67 to 83, wherein the lignocellulosic biomass is contacted with the composition for 10 minutes to 10 hours. 87. The method according to any one of clauses 67 to 83, wherein the lignocellulosic biomass is contacted with the composition for 15 minutes to 8 hours. 88. The method according to any one of clauses 67 to 83, wherein the lignocellulosic biomass is contacted with the composition for 30 minutes to 8 hours. 89. The method according to any of the preceding clauses, further comprising the step of drying one or more fibers under mechanical tension. 90. The method according to any of the preceding clauses, further comprising the step of heating one or more fibers in air. 91. The method according to clause 90, comprising the step of heating one or more fibers in air at 150 to 300 °C. 92. The method according to any of the preceding clauses, further comprising the step of carbonizing one or more fibers to obtain carbon fibers. 93. The method according to clause 92, wherein the carbonization comprises the step of heating one or more fibers in an inert atmosphere to 800 to 3000 °C. 94. The method according to clause 93, wherein the carbonization comprises the step of heating one or more fibers in an inert atmosphere to 1200 to 1800 °C. 95. The method according to any of the preceding clauses, wherein the spinning dope comprises a cellulose loading of 10 wt% or less based on the mass of the spinning dope excluding the masses of cellulose, lignin and carbon nanomaterials. 96. The method according to any of the preceding clauses, wherein the spinning dope comprises a cellulose loading of 5 wt% or less. 97. The method according to any of the preceding clauses, wherein the spinning dope comprises a cellulose loading of 4 wt% or less. 98. The method according to any one of the preceding clauses, wherein the dope for spinning contains a cellulose loading rate of 1% by weight or less. 99. Fibers obtainable by the method according to any one of the preceding clauses. 100. Fibers obtained by the method according to any one of the preceding clauses. 101. A spinning dope comprising a dope solvent, lignin and a carbon nanomaterial, wherein the dope solvent contains an ionic liquid and optionally water. 102. A dispersion comprising carbon nanotubes and [DMBA][HSO4]. 103. The dispersion according to clause 102, wherein the dispersion is a dispersion of carbon nanotubes in any of the dope solvents as described in any of the preceding clauses, and the ionic liquid is [DMBA][HSO4].

[0104] Here, the present invention will be described with reference to the following examples and the accompanying drawings, which are only for illustrative purposes and should not be construed as a limitation to the present invention.

Examples

[0105] Materials Optical micrographs were visually observed with a Leica DM2500 optical microscope connected to a Basler camera and related software for capturing and processing images.

[0106] Single-walled carbon nanotubes (SWCNTs) were obtained from OCSiAl. TUBALL 75 (diameter <2 nm, length >1 μm, metal impurities >15%). TUBALL 99 (diameter >2 nm, length >5 μm, metal impurities <1%).

[0107] Eucalyptus biomass (Eucalytpus grandis), hardwood lignin was obtained from W.L West & sons Ltd. Ethanol (anhydrous) was purchased from VWR.

[0108] Lignin extraction was carried out according to the ionoSolv pretreatment procedure (Gschwend, F. J. v. et al. Journal of Visualized Experiments 2016, 2016 (114), 4 - 9).

[0109] Method [Example 1] Synthesis of ionic liquid The ionic liquid [DMBA][HSO4] was synthesized from N,N - dimethylbutylamine and 66.3% sulfuric acid solution in a custom - made flow reactor. All reagents were used as received. The precursors were cooled and pumped into the stirred flow reactor at a flow rate of 5 ml / min for the acid and 7.8 ml / min for the base. The acid / base ratio of the produced IL was checked in triplicate using an automatic titrator (Mettler Toledo G205), and the HSO4 - anion was titrated with an aqueous NaOH solution. To correct the acid / base ratio, a calculated amount of DMBA or 66.3% sulfuric acid was gradually added to the IL cooled in an ice bath.

[0110] The water content of the IL was measured using a volumetric Karl Fischer titrator (Mettler Toledo). The IL was determined to have an initial water content of 4.22%. This was adjusted by adding additional water if necessary, but the desired water content was 4.74 - 5%. [DMBA][HSO4] 95% / water 5% will be denoted as DH5. The lignin (12 wt%) dissolved in DH5 will be denoted as lig - DH5.

[0111] [Example 2] SWCNT dispersion in DH5 1) SWCNT (2 mg, TUBALL purity 99%) was added to a mortar (marble). The ionic liquid - water mixture (DH5, 200 mg) was drawn into a syringe and added drop - wise, starting with a minimum of 2 drops (38 mg). Since transfer losses can occur from the syringe, the weight of the syringe was recorded on a scale after each addition, and the mass of the added DH5 was calculated by Equation 1.

[0112] 2) The minimum amount of DH5 (38 mg) was milled with SWCNT (5.2 wt%) using a milk stick over 7 - 10 minutes, applying high shear to break up large aggregates until a smooth paste formed. The mixture was milled for a total of 30 minutes.

[0113] 3) For analysis by optical microscopy (OM), a small amount of the dispersion was placed on a labeled glass slide and covered with a cover glass.

[0114]

Number

[0115] Dispersions of SWCNT in [DMBA][HSO4] were prepared at various concentrations. The dispersions of SWCNT in [DMBA][HSO4] resulted in different sample textures at thick and thin concentrations. The consistency of the 5.2 wt% dispersion (15 minutes of shear) resembled a dried smooth solid that retained its shape when cut in half. Conversely, the diluted samples containing 1.3 wt% and 0.5 wt% of SWCNT were similar to gels or soft solids. They formed a wet paste and a gray film when placed on a glass slide in the OM analysis.

[0116] High - purity high - quality SWCNT (TUBALL 99) was dispersed in DH5 to obtain a uniform and proper dispersion without large aggregates under optimized conditions.

[0117] Rheology The SWCNT dispersions in DH5 were found to have a decrease in viscosity when the shear rate was increased (shear thinning, results for SWCNT dispersions at 0.25, 0.5, and 1 wt% of SWCNT are shown in Figure 1). Shear thinning is due to dissolved and broken - down materials unraveling or aligning in the flow and can be advantageous for generating alignment in spun fibers, which can then lead to an improvement in the graphite structure in the resulting carbon fibers.

[0118] The viscosity of the SWCNT dispersion was measured using an AR 2000ex rheometer with a cone-and-plate geometry (cone angle 2°, plate diameter 20 mm and gap 53 μm). The measurements were carried out at 25 °C (RT) for dynamic steady state, strain, and sweep rate. The gel / dope stability was measured over 30 minutes at a constant strain of 1.5% and a frequency of 0.1 rad / s. Strain sweeps were later performed linearly to identify the linear viscoelastic region (LVR), where the strain % was set from 0.1% to 1000% at an angular frequency of 10 rad / s. The LVR was identified to be about 1 - 2% for all gels, so frequency sweeps were performed at a strain of 1.5% over a frequency range of 0.1 - 100 rad / s to identify the gel / dope dominant behavior.

[0119] The zero-shear rate viscosity was measured at room temperature at low shear rates from 3.00×10-6 to 30 s-1 using an AR 2000ex rheometer with a cone-and-plate geometry (cone angle 2°, plate diameter 20 mm and gap 53 μm). The zero-shear rate was between 117,100 and 101,300 Pa.s at -4 ~4.65×10 -4 s -1 shear rates and was recorded for 0.5 (w / w)% dispersions in DH5. Strain Strain sweeps identified the linear viscoelastic region (LVR) to be 1.5 - 2% and the critical strain to be 12 - 29% (Figure 2). The LVR enabled the identification of the dominant behavior of the gel, which was characterized by frequency sweeps. As the concentration of SWCNT increased, the G’ value (elastic behavior) was found to increase, suggesting the formation of an elastic network at higher concentrations (Figure 3, 1.0 wt%). All gels were found to be elastic-dominant (0.25, 0.5 and 1.0 wt%).

[0120] [Example 3] Preparation of Composite Material Dope and Wet Spinning of Lignin Nanocomposite Fibers 1) Lignin was added to a flask containing a stirring bar and an ionic liquid solution DH5 to achieve a polymer loading of 12 wt%. The flask was fixed on an oil / water bath, heated to 60 °C, and stirring was continued for 1.5 h (900 RPM). The homogeneity of the solution was checked by OM.

[0121] 2) Lig-DH5 was drawn into a 1 ml syringe and its weight was recorded. The minimum amount of lig-DH5 (50 - 70 mg) was added dropwise to a mortar containing SWCNT (0.5 wt%, TUBALL 99). The minimum amount of lig-DH5 and SWCNT were vigorously sheared for 15 min using a pestle. The remaining mixture was added gradually over 30 min, and high shear was applied each time to disperse the SWCNT and produce a lignin CNT composite dopant. When the volume of SWCNT was increased (>4 mg), the shear time was extended.

[0122] 3) When a good dispersion was obtained and observed by OM, the composite dopant was drawn into a syringe. The composite dopant was extruded wet with a syringe pump (the needle diameter can range from 24 - 27G and the extrusion rate was 0.009 ml / min) into a rotating coagulation bath containing deionized water. The fiber was coagulated for 15 min and carefully fixed to a drying stand using tape. A foil weight (10 - 20 mg) was attached to the lower end of the fiber.

[0123] Lig-DH5 alone without additives could not be spun in deionized (DI) water. Conversely, when SWCNT was incorporated into the dopant, lignin was spinable. Fibers containing lignin (96%) and SWCNT (4%) were continuously spun and could retain their shape after 30 min of coagulation in DI water. The SWCNT was properly dispersed in lig-DH5, and the fiber surface had smooth texture and regions of uniformity.

[0124] Thermogravimetric analysis (TGA) was carried out to mimic the carbonization process occurring in the precursor fibers. After drying overnight, the lignin CNT composite fibers were analyzed by TGA performed on a Mettler Toledo TGA / DSC 1LF / UMX. The sample was placed in a platinum pan and heated from 25 °C to 100 °C in a nitrogen flow of 10 °C min -1 and held at a constant temperature for 30 minutes at 100 °C to drive out the moisture, and then the temperature was ramped to 900 °C at 10 °C min -1 . The process was repeated in air. The results are shown in Figures 4 and 5. Figure 5 shows that pyrolysis in N2 resulted in a carbonization yield of 54.0%.

[0125] [Example 4] Integrated lignin extraction and lignin fiber spinning Biomass pretreatment (lignin extraction into [DMBA][HSO4]) Lignin extraction was carried out according to the ionoSolv pretreatment procedure (Gschwend, F. J. V et al., J. Vis. Exp. 2016, 2016(114), 4 - 9). 9 or 12 g of biomass (oven-dried weight, ODW) was added to a 100 mL pressure tube (Ace Glass, Vineland, NJ, USA, front sealing), followed by [DMBA][HSO4] 83% / water 17%Approximately 30 g was added to obtain a suspension with a biomass loading rate of 30% or 40% and a water content of 20%. The biomass and ionic liquid solution were thoroughly mixed using a vortex shaker (VWR) until all biomass particles were in contact with the IL. The pressure tube was placed in a preheated oven at 150 °C for 1 hour. The mixture in the pressure tube was cooled and transferred to a 500 mL glass bottle, followed by mixing with 180 g of anhydrous ethanol (EtOH), shaking well, and allowing to rest at room temperature for 1 hour. After 1 hour, the mixture was separated using vacuum filtration into a cellulose-rich solid and a liquid (liquor) containing ionic liquid, ethanol, and dissolved lignin. The cellulose was air-dried. The pulp was washed three more times with EtOH and subsequently Soxhlet extracted in ethanol for 24 hours. The liquor was collected, and most of the water and EtOH were evaporated from the combined liquor fractions using a rotary evaporator. Lignin extraction was performed in triplicate. The liquor obtained from lignin extraction at biomass loading rates of 30% and 40% was labeled as liquor 30 and liquor 40.

[0126] Composition analysis of biomass and pulp Following the published standard procedure, the National Renewable Energy Laboratory (NREL) (Sluiter, A. et al., Natl. Renew. Energy Lab. 2008, No. April 2008, 17) conducted a compositional analysis. Using EtOH in a Soxhlet extractor, extracts were removed from milled eucalyptus wood over 24 hours, and the extract content was quantified by measuring the weight difference. Approximately 300 mg of air-dried extract-free biomass (oven-dry weight basis, sieved to 180 - 850 μm) or recovered pulp was weighed into a 100 ml pressure tube (Ace Glass), and the exact weight was recorded. 3 mL of 72% sulfuric acid (Fluka) was added, the sample was stirred with a Teflon stirring rod, and the pressure tube was placed in a water bath preheated to 30 °C. The samples were stirred again every 10 minutes for 1 hour. Then they were diluted with 84 mL of distilled water and capped. The samples were autoclaved at 121 °C for 1 hour (Sanyo Labo Autoclave ML5 3020 U) and cooled until approaching ambient temperature. The samples were filtered through filtering ceramic crucibles of known weight. The filtrate was filled into two Falcon tubes (to determine the acid-soluble lignin content and sugar content), and the black solid was washed with distilled water. The crucibles containing acid-insoluble lignin and ash were dried in a convection oven (VWR Venti-Line 115) at 105 °C for 24 ± 2 hours. They were placed in a desiccator for 15 minutes, and then their weights were recorded. The crucibles were placed in a muffle oven (Nabertherm + controller P 330) and ashed to a constant weight at 575 °C. They were placed in the desiccator again for 15 minutes, and then their weights were recorded again. The content of acid-insoluble lignin (AIL) was determined by Equation 1:

[0127] [Equation]

[0128] [where Wcrucible plus AIR is the weight of the oven-dried crucible and acid-insoluble residue, W crucible plus ash is the weight of the crucible after ashing to a constant temperature of 575 °C.]

[0129] The acid-soluble lignin content (ASL) was determined by UV analysis (Perkin Elmer Lambda 650 UV / Vis spectrometer) of the autoclave filtrate at 286 nm. 200 μL of the sample and 800 μL of D.I. water were added to the cuvette (1:4 dilution), mixed well, and the absorbance A was recorded. ASL was calculated according to Equation 2:

[0130] [Number]

[0131] [where A is the absorbance at 286 nm, l is the path length of the cuvette in cm (1 cm in this case), ε is the extinction coefficient (25 L / g cm), c is the concentration in mg / mL, ODW is the oven-dried weight of the sample in mg, V filtrate is the volume of the filtrate in mL, equal to 86.73 mL.]

[0132] Calcium carbonate was added to the remaining filtrate until the solution pH reached 5. The liquid was filtered through a 0.2 μm PTFE syringe filter and subjected to HPLC analysis (Shimadzu, Aminex HPX-97P manufactured by Bio rad, 300×7.8 mm, purified water as the mobile phase at 0.6 ml / min, column temperature 85 °C) to determine the total sugar content. Calibration standards containing glucose, xylose, mannose, arabinose, and galactose at concentrations of 0.1, 1, 2, and 4 mg / mL were used. A sugar recovery standard was prepared as 10 mL of an aqueous solution close to the predicted sugar concentration of the sample and transferred to a pressure tube. 278 μL of 72% sulfuric acid was added, the pressure tube was closed, and it was subjected to an autoclave, and the sugar content was determined as described above. The sugar recovery coefficient (SRC) and the sugar content of the analyzed sample were determined according to Equations 3 and 4, respectively:

[0133] [Number]

[0134] [Wherein, CHPLC is the sugar concentration detected by HPLC, V is the initial volume in mL of the solution (10.00 mL for the sugar recovery standard and 86.73 mL for the sample), initial weight is the mass of the weighed sugar, corr anhydro is the correction value for the mass increase during hydrolysis of the polymeric sugar obtained by dividing the molecular weight of one polymeric sugar by its monomer weight (0.90 for glucose, galactose and mannose of C6 sugars, and 0.88 for xylose and arabinose of C5 sugars), and ODW is the oven-dried weight of the sample in mg].

[0135] Determination of the liquor composition The lignin content of the IL / lignin solution (liquor) used for spinning was calculated based on the difference between the lignin content of the raw biomass and the lignin content in the ionosolv pulp (as determined by compositional analysis), the pulp yield (oven-dried weight basis), and the weight of the resulting liquor. The equations are shown below (Equations 5, 6 and 7):

[0136] [Number]

[0137] [Wherein, W lignin(biomass) and W lignin(pulp) are the weights of lignin in the raw biomass and eucalyptus pulp, respectively; ODW biomass and ODW pulp are the oven-dried weights of the raw wood and pulp, respectively; %Lignin(lq) is the lignin concentration in weight percentage in the liquor, and W liquor is the weight of the liquor].

[0138] The water content was determined using a Coulometric Karl-Fischer titrator. The ionic liquid and residual ethanol contents were determined using the 1 1H-NMR spectrum of the liquor. The signals of the methyl group on ethanol (δH(400 MHz, DMSO-d6) / ppm: 1.05, t) and the methyl group on the butyl chain of [DMBA][HSO4] (δH(400 MHz, DMSO-d6) / ppm: 0.90, t) were used to calculate the molar ratio of IL to EtOH, which was then converted to a weight ratio by multiplying by the molecular weight of each molecule. The IL and EtOH contents in the liquor can be calculated according to Equations (8) and (9):

[0139] [Equation]]

[0140] [where %IL(lq), %EtOH(lq) and %Water(lq) are the weight percentages of IL, EtOH and water in the liquor, respectively. W %Il,EtOh is the weight ratio of IL and EtOH calculated from the molar ratio obtained from 1H-NMR spectral analysis]. 1

[0141] Preparation of the spinning dope The spinning dope can be prepared by adding carbon nanomaterials to the liquor produced in the previous step and optionally adjusting the water content if necessary. Shearing can be applied to disperse the carbon nanomaterials and prepare the spinning dope. The spinning dope can then be extruded into the coagulation bath as described herein to produce fibers.

[0142] [Example 5] Aging study ​In this example, the effect of the length of time during which a lignin solution (lignin dissolved in [DMBA][HSO4] having a water content of 5%) is stored is investigated. Two experiments were conducted. One experiment was carried out when the lignin solution was prepared (0-day experiment), and the other was carried out after one month (30 days).

[0143] Method 1. A THINKY mixer (ARM-310) was used at 2000 rpm for 1 hour to prepare a solution containing lignin (12% by weight) dissolved in [DMBA][HSO4] (containing 5.02% H2O). 2. This solution was used to disperse single-walled carbon nanotubes (SWNTs) in a mortar and pestle for 60 minutes. The spinning dope was transferred to a syringe and wet-spun into a rotary coagulation bath containing H2O (200 ml) at an extrusion rate of 0.009 ml / min using a 27G needle. 3. The fibers were coagulated for 15 minutes, picked up with tweezers, and suspended on a drying line using a foil weight (15 - 20 mg) to keep them straight under tension. 4. The lignin solution in the remaining [DMBA][HSO4] was aged for one month (30 days) and then used to disperse SWNTs in the same manner using a mortar and pestle. 5. The dope containing the aged lignin solution (30 days) was transferred to a syringe and wet-spun in the same manner as described above. 6. Since the 30-day fibers were continuously spun and had higher fiber bonding than the 0-day fibers, the 30-day fibers were thermally stabilized by heat treatment (from 25 to 100 °C at 1 °C / min, then from 100 to 250 °C at 0.2 °C / min, held at 250 °C for 1 hour), and then subsequently carbonized by heating to 1000 °C at 1 °C / min and holding at 1000 °C for 1 hour. 7. The fibers were collected and prepared for a tensile test.

[0144] Optical microscopy When examined by optical microscopy, visually, there was no difference between the doped samples. Both had a good quality of SWNT dispersion (well-dispersed CNTs), which was evaluated by the absence of large CNT aggregates (>20 μm). Since many dopes appeared to be homogeneous, they were considered suitable for wet spinning.

[0145] Rheology The composite material dopes showed a slight difference in their shear viscosities. The 0-day dope was found to have a higher viscosity than the 30-day dope (Figure 6). Both dopes showed shear-thinning behavior. The lower-viscosity dope (30 days) may be related to improved spinnability compared to the higher-viscosity 0-day dope.

[0146] Fiber characterization From the 0-day dope, it was possible to obtain short fibers (6 - 7 cm), which could be used for characterizations that required short-length fibers (scanning electron microscopy (SEM) and TGA). For the purpose of this study, for carbonization, the fibers needed to be at least 13 - 14 cm in length because a graphite bridge with a fixed length (10 cm) was used to place the fibers.

[0147] The fibers prepared from the 30-day dope were more uniform and were continuously spun. The fibers had higher binding properties when lifted, so longer fibers (>40 cm) could be obtained. The cross-sectional area of the fibers was also considered to be more circular than that of the fibers obtained from the 0-day dope. These fibers were transferred to the next stage of the process, heat-stabilized, and then carbonized.

[0148] Tensile test When testing the mechanical properties of the 30-day fibers, it was found to fall within the range of 200 to 400 MPa (Table 1).

[0149] [Table 1]

[0150] The foregoing description has been created by way of example and it will be appreciated that it is not a limitation on the claims, including any equivalents as fall within the scope of the claims. Various modifications are possible and will be readily apparent to those skilled in the art. Similarly, the features of the described embodiments can be combined in any suitable manner with any of the above-described suitable aspects, and the optional features of any one aspect can be combined with any other suitable aspect.

Claims

1. A method for producing fibers, The steps include: preparing a spinning dope comprising a doping solvent, lignin and carbon nanomaterials dissolved in the doping solvent, wherein the doping solvent may include an ionic liquid and may also include water; The steps include extruding the spinning dope into a coagulation solution to obtain one or more fibers, and A method that includes this.

2. The method according to claim 1, wherein the water content in the doped solvent is 0 to 30% by weight, 0 to 20% by weight, 0 to 15% by weight, 0 to 10% by weight, or 0 to 5% by weight.

3. The method according to claim 1, wherein the doping solvent comprises at least 1% by weight of water, at least 2% by weight of water, or at least 3% by weight of water.

4. The method according to claim 1, wherein the lignin is present at a loading rate of at least 10% with respect to the mass of the spinning dope excluding the mass of the lignin and carbon nanomaterials.

5. The method according to claim 4, wherein the lignin is present in a load of 10-50%, 10-40%, and 10-30% of the mass of the spinning dope excluding the mass of the lignin and carbon nanomaterials.

6. The method according to claim 1, wherein the carbon nanomaterial is present in a load of at least 0.001%, at least 0.01%, or at least 0.1% relative to the mass of the spinning dope excluding the mass of lignin and the carbon nanomaterial.

7. The method according to claim 1, wherein the carbon nanomaterial is present in a load of 0.001 to 10%, 0.001 to 8%, 0.01 to 8%, 0.1 to 5%, 0.1 to 1%, or 0.3 to 0.7% relative to the mass of the spinning dope excluding the mass of lignin and carbon nanomaterial.

8. The method according to claim 1, wherein the weight ratio of lignin to carbon nanomaterial in the spinning dope is 5:1 to 10000:1, 5:1 to 5000:1, 10:1 to 1000:1, or 20:1 to 200:

1.

9. The method according to claim 1, wherein the carbon nanomaterial is dispersed in the doping solvent.

10. The method according to claim 1, wherein the carbon nanomaterial includes carbon nanotubes, carbon nanoribbons, graphene nanoplates, or a combination thereof.

11. The method according to claim 10, wherein the carbon nanomaterial includes carbon nanotubes, and the carbon nanotubes may be single-walled carbon nanotubes (SWCNTs).

12. where the ionic liquid has a cation and C － , － , ３ , ４ , ２－ , － , － alkyl sulfate ([alkyl SO ４ ), C － alkyl sulfonate ([alkyl SO １～２０ ), hydrogen sulfate ([HSO ３ ), hydrogen sulfite ([HSO － ), dihydrogen phosphate ([H ２ PO － ), hydrogen phosphate ([HPO ４ ), chloride (Cl － ), bromide (Br － ), trifluoromethanesulfonate ([OTf] － ), formate ([HCOO] － ), and acetate ([MeCO ２ ), and the anion is selected from [HSO ４ and [HCOO] － , the method according to claim 1.​​​​​​​​​​​​​​​​

13. The ionic liquid comprises a cation and anion, wherein the cation contains a nitrogen-containing heterocyclic moiety, or the cation is a cation of formula I. 【Chemistry 1】 [In the formula, A １ ~A ４ These are H, aliphatic, and C, respectively, independently. ３～６ carbocycle, C ６～１０ [Selected from aryl, alkylaryl, and heteroaryl] The method according to claim 1.

14. The aforementioned ionic liquid is [alkylammonium] [HSO] ４ The method according to claim 1, wherein the liquid is either [alkylammonium] [HClOO] ionic liquid.

15. The ionic liquid is triethylammonium hydrogen sulfate [TEA] [HSO4] ４ ], N,N-dimethylbutylammonium hydrogen sulfide [DMBA] [HSO ４ ], diethylammonium hydrogen sulfate [DEA] [HSO ４ ], N,N-dimethylethylammonium hydrogen sulfate ([DMAA][HSO ４ ]), diethanolammonium chloride [DEtOHA]Cl, 1-methylimidazolium chloride [HMim]Cl, 1-ethyl-3-methylimidazolium chloride [EMim]Cl, and 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [EMim][OTf], 1-butylimidazolium hydrogen sulfate ([HBim][HSO ４ ]), methylbutylammonium hydrogen sulfate ([MBA][HSO ４ ]), 1-methylimidazolium formate ([HMim][HCOO]), N,N-dimethylbutylammonium formate ([DMBA][HCOO]), N,N-dimethylethylammonium hydrogen sulfide ([DMAA][HSO ４ ]), 1-butyl-3-methylimidazolium hydrogen sulfate [BMim] [HSO ４ ] or N,N-dimethylbutylammonium acetate ([DMBA][OAc]), or a mixture thereof, preferably the ionic liquid is [DMBA][HSO4] ４ The method according to claim 1.

16. The method according to claim 1, wherein the doping solvent further contains ethanol, and the ethanol may be present in an amount of 1 to 20% by weight, preferably 5 to 15% by weight, relative to the total weight of the doping solvent.

17. The method according to claim 1, wherein the coagulation solution contains water.

18. The aforementioned coagulation solution (a) comprising water and an ionic liquid, wherein the ionic liquid is present in an amount of 60% by weight or less, 30% by weight or less, or 15% by weight or less, preferably 1 to 60% by weight, 1 to 30% by weight or 1 to 15% by weight, more preferably 5 to 10% by weight, based on the total mass of the coagulation solution: or (b) The method according to claim 1, comprising water and sodium sulfate.

19. The spinning dope is prepared by a process comprising the steps of preparing a lignin solution and combining the lignin solution with the carbon nanomaterial; the lignin solution is a) Lignocellulosic biomass containing lignin and cellulose is brought into contact with a composition containing an ionic liquid and water (preferably 5 to 40% by weight of water) to dissolve the lignin and produce cellulose pulp; b) Separating the cellulose pulp to obtain a liquor containing the ionic liquid, water, and lignin; It is prepared by doing so, and at this time, c) The method according to claim 1, wherein the amount of ionic liquid and / or water in the liquor may be adjusted to obtain the lignin solution.

20. The method according to claim 19, wherein the lignocellulosic biomass is brought into contact with the composition at 100 to 180°C, preferably 120 to 170°C.

21. One or more fields of view: (a) under mechanical tension; and / or (b) The method according to claim 1, further comprising the step of drying one or more fibers in air at a temperature which may be 150 to 300°C.

22. The method according to claim 1, further comprising the step of carbonizing one or more of the aforementioned fibers to obtain carbon fibers, wherein the carbonization may include the step of heating the one or more of the aforementioned fibers to 800 to 3000°C, preferably 1200 to 1800°C, in an inert atmosphere.

23. A fiber that can be obtained by the method described in claim 1.

24. A spinning dope comprising a doping solvent, lignin, and carbon nanomaterials, wherein the doping solvent may include an ionic liquid and may also include water.

25. Carbon nanotubes and [DMBA][HSO] ４ A dispersion containing ].

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