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WO2025158263A1 - Procédé de production d'un précurseur de fibre de carbone à partir de lignine et de xanthate de cellulose et précurseur de fibre de carbone - Google Patents

Procédé de production d'un précurseur de fibre de carbone à partir de lignine et de xanthate de cellulose et précurseur de fibre de carbone

Info

Publication number
WO2025158263A1
WO2025158263A1 PCT/IB2025/050570 IB2025050570W WO2025158263A1 WO 2025158263 A1 WO2025158263 A1 WO 2025158263A1 IB 2025050570 W IB2025050570 W IB 2025050570W WO 2025158263 A1 WO2025158263 A1 WO 2025158263A1
Authority
WO
WIPO (PCT)
Prior art keywords
lignin
cellulose
interval
precursor fiber
weight
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/IB2025/050570
Other languages
English (en)
Inventor
Robert Protz
Jens Erdmann
Johannes Ganster
André Lehmann
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Stora Enso Oyj
Original Assignee
Stora Enso Oyj
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Stora Enso Oyj filed Critical Stora Enso Oyj
Publication of WO2025158263A1 publication Critical patent/WO2025158263A1/fr
Pending legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L97/00—Compositions of lignin-containing materials
    • C08L97/02—Lignocellulosic material, e.g. wood, straw or bagasse
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B1/00—Preparatory treatment of cellulose for making derivatives thereof, e.g. pre-treatment, pre-soaking, activation
    • C08B1/003—Preparation of cellulose solutions, i.e. dopes, with different possible solvents, e.g. ionic liquids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B9/00—Cellulose xanthate; Viscose
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D1/00—Treatment of filament-forming or like material
    • D01D1/02—Preparation of spinning solutions
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/06—Wet spinning methods
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
    • D01F2/06—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof from viscose
    • D01F2/08—Composition of the spinning solution or the bath
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
    • D01F8/02—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from cellulose, cellulose derivatives, or proteins
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
    • D01F9/16—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from products of vegetable origin or derivatives thereof, e.g. from cellulose acetate
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
    • D01F9/16—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from products of vegetable origin or derivatives thereof, e.g. from cellulose acetate
    • D01F9/17—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from products of vegetable origin or derivatives thereof, e.g. from cellulose acetate from lignin

Definitions

  • the present invention generally relates to carbon fiber precursors and in particular to a method of producing lignin and cellulose containing precursor fibers suitable for the production of carbon fibers and to such lignin and cellulose containing precursor fibers.
  • Lignin is a polyaromatic polyol and is, after cellulose, the second most common material component in wood and other lignocellulosic plants.
  • chemical pulping cellulosic fibers are separated from softwoods, hardwoods, and annual plant biomass, for further processing to paper, board and tissue products.
  • Kraft pulping is the dominant chemical pulping process, whereas other pulping processes include soda pulping, sulfite pulping and the organosolv process.
  • alkaline pulping i.e., Kraft and soda pulping
  • large quantities of lignin become dissolved in the alkaline pulping liquor, known as black liquor.
  • This black liquor is a highly alkaline complex mixture containing used cooking chemicals, solubilized wood lignin, carbohydrates, and organic acids.
  • the lignin can be further processed from the black liquor to energy by combustion of the partly evaporated black liquor or, alternatively, be isolated in solid form by addition of acid.
  • the amount of carbon in lignin is approximately 60-65%.
  • Cellulose fibers produced by the viscose process and such cellulose fibers containing lignin have been suggested as raw material for production of carbon fibers, see for instance EP 2 889 401 .
  • lignin is more cost-competitive.
  • lignin is not a fiber forming material in its unmodified form.
  • cross-linked forms of lignin such as formaldehyde cross-linked sodium lignosulfonate or sodium lignate have been suggested in the art, such as in US 4,215,212.
  • cross-linking of lignin increases the complexity and cost of the production process and additionally leads to the inclusion of undesired cross-linking chemicals in the fibers.
  • An aspect of the invention relates to a method for producing a precursor fiber for the production of a carbon fiber.
  • the method comprises extruding a spinning dope comprising lignin having an average molecular weight selected within an interval of from 1 ,500 up to 25,000 g/mol and cellulose xanthate through a spinning nozzle into a spinning bath comprising from 20 g/L up to 400 g/L of sulfuric acid and from 10 g/L up to 120 g/L of divalent cation sulfate salt to produce a precursor fiber having a lignin and cellulose containing core and a cellulose-rich surface layer.
  • the precursor fiber comprises a lignin and cellulose containing core and a cellulose-rich surface layer and is obtainable by a method according to above.
  • the invention discloses the manufacture of precursor fibers that are suitable for production of carbon fibers.
  • the precursor fibers are manufactured from cellulose and lignin in a process wherein lignin leakage and losses are reduced without using lignin in a cross-linked form. This is possible by the formation of a cellulose-rich surface layer on the lignin and cellulose containing core of the precursor fiber and where this cellulose-rich surface layer effectively restricts lignin leakage from the core.
  • the invention therefore achieves a more cost effective and less complex production of precursor fibers that can be used in the production of carbon fibers.
  • Fig. 1 is an electron micrograph of a cross-sectional view of a precursor fiber produced according to Example 3;
  • Fig. 2 is an electron micrograph of a cross-sectional view of a precursor fiber produced according to Example 4;
  • Fig. 3 is an electron micrograph of a cross-sectional view of a precursor fiber produced according to Example 6;
  • Fig. 4 is an electron micrograph of a cross-sectional view of a precursor fiber produced according to Example 7;
  • Fig. 5 is a flow chart illustrating a method for producing a precursor fiber for the production of a carbon fiber according to various embodiments
  • Fig. 6 is a schematic illustration of a precursor fiber for the production of a carbon fiber.
  • Fig. 7 is a transmission electron microscopy (TEM) image of a cross-section view of a portion of a precursor fiber according to the invention.
  • TEM transmission electron microscopy
  • the present invention generally relates to carbon fiber precursors and in particular to a method of producing lignin and cellulose containing precursor fibers suitable for the production of carbon fibers and such lignin and cellulose containing precursor fibers.
  • the method of the invention enables a cost-efficient production of precursor fibers that are suitable for production of carbon fibers.
  • the method produces precursor fibers with very low lignin losses during formation of the precursor fibers but without the need for using cross-linked forms of lignin.
  • This is possible by forming a cellulose-rich surface layer on the precursor fibers that prevent or at least significantly inhibit lignin losses from the cellulose and lignin containing core of the precursor fibers.
  • embodiments of the invention can reduce the lignin losses during production of the precursor fibers to less than 1 % by weight due to the presence of the cellulose-rich surface layer.
  • This cellulose-rich surface layer is formed by extruding a spinning dope comprising cellulose and lignin into a spinning bath comprising sulfuric acid and divalent cation sulfate salt.
  • the presence of the divalent cation sulfate salt in the spinning bath induces formation of the "protecting” cellulose-rich surface layer, which forms a barrier around the cellulose and lignin containing fiber core and thereby reduces lignin leakage and losses.
  • replacing the divalent cation sulfate salt with a monovalent cation sulfate salt significantly increased the lignin losses since no corresponding cellulose-rich surface layer was formed on the fiber surface.
  • An aspect of the invention therefore relates to a method for producing a precursor fiber for the production of a carbon fiber, see Figs. 5 and 6.
  • the method comprises extruding, in step S5 of Fig. 5, a spinning dope comprising lignin having an average molecular weight selected within an interval of from 1 ,500 up to 25,000 g/mol and cellulose xanthate through a spinning nozzle into a spinning bath.
  • the spinning bath comprises from 20 g/L up to 400 g/L sulfuric acid (H2SO4) and from 10 g/L up to 120 g/L of a divalent cation sulfate salt.
  • H2SO4 sulfuric acid
  • the extrusion of the spinning dope into the spinning bath produces a precursor fiber 1 , see Fig.
  • Fig. 7 is a transmission electron microscopy (TEM) image of a cross-section view of a portion of a precursor fiber showing the lignin and cellulose containing core 2 and a cellulose-rich surface layer 5.
  • TEM transmission electron microscopy
  • the extrusion of the spinning dope into the spinning bath of the invention thereby creates a comparatively, when compared to the average diameter of the precursor fiber 1 and the average diameter of the lignin and cellulose containing core 2, thin cellulose-rich surface layer or sheath 5 on the lignin and cellulose containing core 2.
  • the cellulose-rich surface layer 5 typically has an average thickness of at least 2.5 nm, preferably at least 5 nm and more preferably at least 10 nm. This should be compared to the average diameter of the precursor fiber 1 , which is typically in the pm range as shown in Figs. 1 and 2. In fact, the cellulose-rich surface layer or sheath 5 is so thin that it cannot be distinguished in Figs. 1 and 2.
  • the TEM image of Fig. 7 indicates the thin cellulose-rich surface layer 5 on the lignin and cellulose containing core 2 containing a cellulose matrix with lignin particles.
  • the formed cellulose-rich surface layer 5 has higher weight percentage of cellulose as compared to the lignin and cellulose containing core 2.
  • the cellulose-rich surface layer 5 has a cellulose content of at least 75 % by weight (w/w), preferably at least 80 % by weight, and more preferably at least 90 % by weight.
  • the cellulose-rich surface layer 5 has a higher weight ratio of cellulose to lignin as compared to the lignin and cellulose containing core 2.
  • the lignin and cellulose containing core 2 comprises a weight ratio of cellulose to lignin selected within an interval of from 1 :0.8 up to 1 :2, preferably within an interval of from 1 :0.85 up to 1 :2, and more preferably within an interval of from 1 :0.9 up to 1 :2, such as within an interval of from 1 :1 up to 1 :2.
  • the lignin and cellulose containing core 2 preferably contains substantially the same amount (weight percentage) of lignin as the amount (weight percentage) of cellulose, or a higher amount (weight percentage) of lignin.
  • a spinning dope comprising substantially the same amount (weight percentage) of lignin and cellulose or a cellulose to lignin weight ratio of 1 :1.5 could be extruded into the spinning bath in step S5 to form a precursor fiber 1 with substantially the same weight percentage of lignin and cellulose or with a cellulose to lignin weight ratio of 1 : 1.5 in the lignin and cellulose containing core 2 but significantly higher weight percentage of cellulose than lignin in the cellulose-rich surface layer 5.
  • the method of the invention is, due to the formation of the cellulose-rich surface layer 5 on the precursor fiber 1 , characterized by a very low lignin leakage and loss during the formation of the precursor fiber 1 .
  • the method is characterized by a lignin loss equal to or less than 5 % by weight, preferably equal to or less than 3 % by weight, and more preferably equal to or less than 2 % by weight, such as equal to or less than 1 % by weight.
  • the method of the invention can achieve a lignin loss even equal to or less than 1 % by weight.
  • the spinning dope as extruded in step S5 is formed by mixing a lignin solution comprising lignin in an alkaline aqueous solution with a viscose solution comprising cellulose xanthate in an alkaline aqueous solution to form the spinning dope in step S3 of Fig. 5.
  • the lignin solution and the viscose solution are mixed in step S3 prior to extruding the spinning dope S5. It is believed that such a pre-mixing of the lignin and viscose solutions prior to extrusion promotes the formation of the cellulose-rich surface layer 5 on the lignin and cellulose containing core 2 during extrusion in step S5.
  • the mixing of the lignin solution and the viscose solution in step S3 is preferably performed at least 30 s prior to extrusion of the spinning dope in step S5, preferably at least 1 min, more preferably at least 5 min, such as at least 10 min, at least 15 min, at least 30 min, at least 45 min or even longer, such as at least 1 hour prior to extrusion in step S5.
  • the mixture of the lignin solution and the viscose solution is optionally processed in step S4 prior to extrusion in step S5.
  • Illustrative, but non-limiting, examples of such a processing include filtration of the mixture of the lignin solution and the viscose solution and/or degassing the mixture of the lignin solution and the viscose solution. The filtration may then remove larger cellulose and/or lignin particles or aggregates that may otherwise impede or even obstruct the extrusion of the spinning dope through a spinning nozzle in step S5.
  • degassing of the mixture of the lignin solution and the viscose solution is preferred to remove any gas bubbles in the mixture, which may otherwise block the spinning nozzle during extrusion.
  • the method also comprises preparing the lignin solution in step S1 of Fig. 5.
  • This step S1 preferably comprises dissolving or dispersing, preferably dissolving, lignin having an average molecular weight selected within an interval of from 1 ,500 up to 25,000 g/mol in the alkaline aqueous solution at an amount of lignin selected within an interval of from 15 up to 45 % by weight.
  • the alkaline aqueous solution prepared in step S1 comprises from 25 up to 45 % by weight of lignin, preferably from 25 up to 35 % by weight of lignin, such as about 30 % by weight of lignin.
  • the alkaline aqueous solution is a lye, i.e., an alkali metal hydroxide, and preferably an aqueous sodium hydroxide (NaOH) solution.
  • the alkali metal hydroxide, such as NaOH, content in the alkaline aqueous solution is preferably selected within an interval of from 3 up to 15 % by weight, more preferably within an interval of from 3 up to 10 % by weight.
  • a basicity of the lignin solution prepared in step S1 is substantially the same as a basicity of the viscose solution.
  • the pH of the lignin solution prepared in step S1 is preferably substantially the same as the pH of the viscose solution.
  • substantially the same pH as referred to herein encompass a difference in pH of no more than 10%, preferably of no more than 5 %, and more preferably of no more than 2.5%, such as of no more than 1 %.
  • the method also comprises preparing the viscose solution in step S2 of Fig. 5.
  • This preparation in step S2 can be performed according to any known process to produce cellulose xanthate and a viscose solution from cellulose.
  • the preparation in step S2 comprises an activation of cellulose by alkalization, followed by treatment with carbon disulfide (CS2) to produce cellulose xanthate.
  • CS2 carbon disulfide
  • cellulose in the form of pulp is treated with aqueous sodium hydroxide to form "alkali cellulose", which has the approximate formula [C6HgO4-ONa] n .
  • the alkali cellulose is then typically allowed to depolymerize, also referred to as ripe or mature in the art, to an extent.
  • the alkali cellulose is then treated with carbon disulfide to form sodium cellulose xanthate [C6HgO4-ONa] n + nCSg — > [C6H5(OH)4-OCS2Na] n .
  • the cellulose xanthate is then dissolved or dispersed, preferably dissolved, in an alkaline aqueous solution, i.e., a lye, and preferably an aqueous NaOH solution to form the viscose solution in step S2.
  • cellulose in the form of pulp such as Kraft pulp, and preferably prehydrolyse Kraft (PHK) pulp
  • alkali cellulose which following depolymerization preferably has a degree of polymerization (DPcuox) within an interval of from 200 up to 500, preferably within an interval of from 300 up to 400.
  • Carbon disulfide is then added to the alkali cellulose, preferably at an amount selected within an interval of from 18 up to 42 % based on the weight of cellulose, preferably within an interval of from 26 up 35 % based on the weight of cellulose, to produce the cellulose xanthate.
  • the cellulose xanthate is then dissolved or dispersed in aqueous sodium hydroxide at a temperature lower than room temperature (20-25°C), preferably at a temperature lower than 10°C to prepare the viscose solution in step S2.
  • the viscose solution preferably comprises cellulose xanthate at an amount of from 6 up to 14 % by weight, preferably from 8 up to 10 % by weight.
  • the alkali metal hydroxide, such as NaOH, content in the viscose solution is preferably selected within an interval of from 3 up to 15 % by weight, more preferably within an interval of from 5 up to 10 % by weight.
  • the lignin solution preferably as prepared in step S1
  • the mixing in step S3 is performed when the viscose solution has a stage of depolymerization selected within an interval of from 3 up to 20 degree Hottenroth (°H), also referred
  • the so-produced spinning dope preferably has a total polymer content, i.e., total amount of lignin and cellulose, of at least 8 % by weight, preferably at least 10 % by weight.
  • the lignin used in the method of Fig. 5 is preferably in the form of lignin from a chemical pulping process, preferably from an alkaline pulping process, and more preferably from a Kraft pulping process, i.e., Kraft lignin (KL).
  • KL Kraft lignin
  • Such a Kraft lignin generally has an average molecular weight within the preferred interval of from 1,500 up to 25,000 g/mol. This range of average molecular weight encompasses lignin molecules that achieve a desired lignin solubility in the lignin solution and the spinning dope and further promote the formation of the lignin and cellulose containing core 2 with a cellulose-rich surface layer 5 during extrusion in step S5 into the spinning bath.
  • the lignin has an average molecular weight selected within an interval of from 2,000 up to 20,000 g/mol, more preferably selected within an interval of from 5,000 up to 10,000 g/mol and most preferably selected within an interval of from 5,000 up to 8,000 g/mol.
  • the lignin has an ash content of no more than 0.8 % by weight.
  • the lignin has a sulfur (S) content of at least 1 % by weight.
  • the spinning dope comprises non-cross linked lignin and cellulose xanthate.
  • the lignin in the lignin solution and in the spinning dope and thereby in the produced precursor fiber 1 is preferably in a non-cross linked form.
  • This is in contrast to the prior art as represented by US 4,215,212, which requires the lignin to be cross-linked with formaldehyde in the form of sodium lignosulfonate or sodium lignate cross-linked with formaldehyde.
  • the spinning bath into which the spinning dope is extruded in step S5 of Fig. 5, comprises from 10 g/L up to 120 g/L divalent cation sulfate salt.
  • the divalent cation sulfate salt is selected from the group consisting of zinc sulfate (ZnSO ), magnesium sulfate (MgSO ), calcium sulfate (CaSO ), copper sulfate (CuSO ), and any mixture or combination thereof.
  • the divalent cation sulfate salt is zinc sulfate or a mixture or combination of zinc sulfate and at least one divalent cation sulfate salt selected from the group consisting of magnesium sulfate, calcium sulfate and copper sulfate.
  • the divalent cation sulfate salt is zinc sulfate.
  • the spinning bath also comprises at least one monovalent cation sulfate salt.
  • the spinning bath comprises at least one divalent cation sulfate salt, preferably zinc sulfate, and at least one monovalent cation sulfate salt.
  • the monovalent cation sulfate salt is selected from the group consisting of sodium sulfate (Na2SC>4), potassium sulfate (K2SO4), and a mixture or a combination thereof.
  • the monovalent cation sulfate salt is sodium sulfate.
  • the spinning bath preferably comprises zinc sulfate and sodium sulfate.
  • the spinning bath comprises an amount of monovalent cation sulfate salt selected within an interval of from 80 up to 240 g/L, preferably selected within an interval of from 100 up to 240 g/L.
  • the spinning bath has a total concentration of inorganic salts of no more than 400 g/L. In a particular embodiment, the spinning bath has a total concentration of inorganic salts selected within an interval of from 10 g/L up to 400 g/L, preferably selected within an interval of from 10 g/L up to 300 g/L, and more preferably selected within an interval of from 20 g/L up to 300 g/L.
  • the total concentration of inorganic salts in the spinning bath seem to affect the cross-sectional shape of the produced precursor fiber 1.
  • reducing the total concentration of inorganic salts from 270 g/L down to 135 g/L resulted in a precursor fiber 1 with a more circular cross section as is evident by comparing Figs. 1 and 2.
  • the inorganic salts present in the spinning bath are the divalent cation sulfate salt(s) and the optional monovalent cation sulfate salt(s).
  • the spinning dope comprises a lignin content selected within an interval of from 3 up to 9 % by weight.
  • the spinning dope comprises a weight ratio of cellulose to lignin selected within an interval of from 1 :0.8 up to 1 :2, preferably within an interval of from 1 :0.85 up to 1 :2, and more preferably within an interval of from 1 : 1 up to 1 :2.
  • the spinning dope preferably comprises substantially the same amount of cellulose as lignin or up to twice the amount of lignin as compared to cellulose.
  • step S5 of Fig. 5 comprises extruding the spinning dope through the spinning nozzle into the spinning bath having an average temperature selected within an interval of from 1 up to 60°C, preferably within an interval of from 1 up to 50°C, such as within an interval of from 5 up to 50°C, and more preferably within an interval of from 1 up to 45°C, such as within an interval of from 5 up to 45°C.
  • Experimental data as presented herein indicates that the temperature of the spinning bath may have an effect on the cross-sectional shape of the precursor fiber 1 .
  • reducing the temperature of the spinning bath from 42°C down to 7°C resulted in a more circular cross section of the precursor fiber 1 as is evident by comparing Figs. 1 and 2.
  • This reduction in the temperature of the spinning bath is preferably accompanied by a reduction in the total concentration of inorganic salts as mentioned in the foregoing.
  • the spinning nozzle used in step S5 of Fig. 5 comprises at least one hole but may optionally comprise multiple, i.e., at least two, holes, through which the spinning dope is extruded as a liquid filament jet or ray.
  • the at least one hole of the spinning nozzle is preferably mounted submerged into the spinning bath so that the liquid filament jet or ray is formed by extruding the spinning dope through the spinning nozzle in step S5 into the spinning bath.
  • the extruded spinning dope immediately solidifies by coagulation and is typically at the same time stretched, so called jet stretching.
  • This jet stretch represents the ratio between the extrusion velocity and the take-up velocity of the formed precursor fiber 1.
  • the jet stretch is selected within an interval of from 0.4 up to 2.9.
  • the method comprises an additional step S6, which comprises introducing the precursor fiber 1 into a decomposition bath comprising sulfuric acid.
  • the decomposition bath preferably comprises an amount of sulfuric acid selected within an interval of from 5 up to 200 g/L. Further, the decomposition bath preferably has an average temperature selected within an interval of from 70 up to 100°C.
  • the precursor fiber 1 is preferably drawn in the decomposition bath in step S7 with a drawing factor selected within an interval of from 1.1 up to 2.5.
  • a drawing factor of 1 .1-2.5 means that the length of the precursor fiber 1 drawn in step S7 is 1.1-2.5 of the length of the precursor fiber 1 introduced into the decomposition bath in step S6.
  • hot water steam can be applied to the decomposition bath during the drawing in step S7.
  • the method comprises step S8 of Fig. 5, which comprises washing the precursor fiber 1 with water or an aqueous solution at a temperature selected within an interval of from 40 up to 80°C, preferably selected within an interval of from 50 up to 70°C, such as about 60°C.
  • the washing in step S8 is preferably conducted for at least 1 min, preferably at least 2 min, and more preferably at least 5 min, such as from 5 up to 30 min, more preferably from 5 up to 10 min.
  • a preferred washing solution is water or a mixture of water and an organic solvent.
  • the washing solution used in step S8 preferably has a pH selected within an interval of from 1 up to 10, preferably selected within an interval of from 5 up to 8.
  • the precursor fiber 1 is preferably dried in step S9 at a temperature equal to or above 40°C, preferably equal to or above 50°C, and more preferably equal to or above 60°C.
  • the drying in step S9 is preferably conducted for at least 30 s, preferably at least 1 min, and more preferably at least 2 min, such as from 2 up to 15 min, more preferably from 2 up to 10 min.
  • the stretched and washed precursor fiber 1 is optionally treated, before drying in step S9, after drying in step S9 or both before and after drying in step S9, with a spinning oil with an antistatic effect.
  • the precursor fiber 1 comprises a lignin and cellulose containing core 2 and a cellulose-rich surface layer 5.
  • the precursor fiber 1 is obtainable by a method according to the invention, such as described in the foregoing in connection with Fig. 5.
  • the lignin and cellulose containing core 2 comprises a weight ratio of cellulose to lignin selected within an interval of from 1 :0.8 up to 1 :2, preferably within an interval of from 1 :0.85 up to 1 :2, and more preferably within an interval of from 1 :1 up to 1 :2.
  • the cellulose-rich surface layer 5 has an average thickness of at least 2.5 nm, preferably at least 5 nm, and more preferably at least 10 nm. In an embodiment, the cellulose-rich surface layer 5 has a higher weight ratio of cellulose to lignin as compared to the lignin and cellulose containing core 2.
  • the cellulose-rich surface layer 5 has a cellulose content of at least 75 % by weight.
  • the precursor fiber 1 has a water retention value (WRV) of less than 100 %.
  • WRV was determined by mixing 0.5 g of the precursor fiber with 50 mL deionized water and allowed to stand for 15 min in room temperature. The sample was then centrifuged in a filter dish for 15 min at 3000 g. The mass of this sample was measured (Mi). The sample was then dried overnight at 105°C in a convection oven and the mass of the dried sample was measured (M2). The WRV is then calculated in [%] as 100x(Mi - M 2 ) / M 2 .
  • the precursor fiber 1 has a sulfur content of no more than 2 % by weight.
  • the precursor fiber 1 has an ash content of no more than 0.02 % by weight.
  • the precursor fibers 1 of the invention are suitable as precursors or starting material for the production of carbon fibers and activated carbon fibers.
  • Carbon fibers are high-performance reinforcing fibers, which are used in composite materials in various fields, such as aircraft construction, high-performance vehicle construction, for sports equipment, wind energy plants, etc.
  • Carbon fibers are produced by heat treatment above 1 ,000°C of organic precursor fibers.
  • PAN polyacrylonitrile
  • copolymers of polyacrylonitrile are the dominating polymers for the production of precursors for carbon fibers.
  • PAN are products of the petrochemical industry and thereby not an environmental or sustainable precursor for carbon fibers.
  • the precursor fibers 1 of the invention are thereby suitable as more environmentally friendly and sustainable precursors for carbon fibers.
  • a viscose solution was produced by activating a prehydrolyse Kraft (PHK) pulp with a degree of polymerization (DPcuox) of 610 by sodium hydroxide (NaOH).
  • the activated cellulose had a DPcuox of 370, a cellulose content of 32.7 % (w/w) and a sodium hydroxide content of 15.1 % (w/w).
  • the activated cellulose was derivatized with 32 % (w/w) of carbon disulfide (CS2) in relation to cellulose to form cellulose xanthate.
  • the viscose solution was prepared by adding cellulose xanthate to an aqueous solution of sodium hydroxide to obtain a final alkali content of 7.1 % (w/w) in the viscose solution.
  • the viscose solution had a cellulose content of 9.1 % (w/w).
  • the viscose solution from Example 1 containing 9.1 % (w/w) of cellulose and 7.1 % (w/w) of sodium hydroxide was mixed with a lignin solution comprising 30 % (w/w) of Kraft lignin and 4.9 % sodium hydroxide (w/w).
  • a lignin solution comprising 30 % (w/w) of Kraft lignin and 4.9 % sodium hydroxide (w/w).
  • Spinning dopes with lignin contents between 3 % (w/w) and 9 % (w/w) turned out to be most promising for the desired precursor fiber quality.
  • the lignin containing spinning dope from Example 2 having 7.3 % (w/w) of cellulose, 7.3 % (w/w) of Kraft lignin and 6.5 % (w/w) sodium hydroxide was spun into an acidic spinning bath.
  • the filaments were spun through spinneret holes having a round shaped cross-section with a capillary diameter of 60 pm and a total hole number of 300.
  • the filaments were spun into a spinning bath comprising 210 g/L sodium sulfate, 60 g/L zinc sulfate and 60 g/L sulfuric acid and having a temperature of 42°C.
  • the tow was stretched by 30 % in a 2 % aqueous sulfuric acid solution at 95°C, washed with distilled 60°C hot water for 8 minutes and dried for 4 minutes at 60°C.
  • the obtained 3000 filaments had a single filament titer of 4.7 dtex, a filament tenacity of 12.1 cN/tex and an elongation at break of 16.4 %.
  • Fig. 1 is a cross-sectional view of a precursor fiber produced in accordance with Example 3 having a lobulated cross section.
  • Table 1 Textile physical properties of precursor fibers as a function of the jet-stretch using a sodium sulfate and zinc sulfate containing spinning bath according to Example 3
  • Titer in Table 1 was determined by the vibroscope method according to ISO 1973:2021 , Textile fibres, Determination of linear density, Gravimetric method and vibroscope method.
  • Tenacity, modulus and elongation at break in Table 1 was determined via the single filament tensile test according to ASTM D3822/D3822M-14 (2020), Standard test method for tensile properties of single textile fibers.
  • the lignin containing spinning dope from Example 2 having 7.3 % (w/w) of cellulose, 7.3 % (w/w) of Kraft lignin and 6.5 % (w/w) sodium hydroxide was spun into an acidic spinning bath.
  • the filaments were spun through spinneret holes having a round shaped cross-section with a capillary diameter of 60 pm and a total hole number of 300.
  • the filaments were spun into a spinning bath comprising 140 g/L sodium sulfate, 35 g/L zinc sulfate and 60 g/L sulfuric acid and having a temperature of 7°C.
  • the tow was stretched by 30 % in a 2 % aqueous sulfuric acid solution at 95°C, washed with distilled 60°C hot water for 8 minutes and dried for 4 minutes at 60°C.
  • Fig. 2 is a cross-sectional view of a precursor fiber produced in accordance with Example 4 having a circular cross section.
  • Precursor fiber production was performed in accordance with Example 3 but with the cellulose to lignin content ratio changed from 1 : 1 into 1 : 1.5.
  • the lignin containing spinning dope from Example 2 having 7.3 % (w/w) of cellulose, 7.3 % (w/w) of Kraft lignin and 6.5 % (w/w) sodium hydroxide was spun into an acidic spinning bath.
  • the filaments were spun through spinneret holes having a round shaped cross-section with a capillary diameter of 60 pm and a total hole number of 300.
  • the filaments were spun into a spinning bath comprising 264 g/L ammonium sulfate and 80 g/L sulfuric acid and having a temperature of 42°C.
  • the tow was stretched by 30 % in a 2 % aqueous sulfuric acid solution at 95°C, washed with distilled 60°C hot water for 8 minutes and dried for 4 minutes at 60°C.
  • the obtained 300 filaments had a single filament titer of 4.6 dtex, a filament tenacity of 13.3 cN/tex and an elongation at break of 7.8 % measured as described in Example 3.
  • Fig. 3 is a cross-sectional view of a precursor fiber produced in accordance with Example 6 having a circular cross section.
  • the lignin containing spinning dope from Example 2 having 7.3 % (w/w) of cellulose, 7.3 % (w/w) of Kraft lignin and 6.5 % (w/w) sodium hydroxide was spun into an acidic spinning bath.
  • the filaments were spun through spinneret holes having a round shaped cross-section with a capillary diameter of 60 pm and a total hole number of 300.
  • the filaments were spun into a spinning bath comprising 140 g/L sodium sulfate and 80 g/L sulfuric acid and having a temperature of 35°C.
  • the tow was stretched by 30 % in a 2 % aqueous sulfuric acid solution at 95°C, washed with distilled 60°C hot water for 8 minutes and dried for 4 minutes at 60°C.
  • the obtained 300 filaments had a single filament titer of 4.9 dtex, a filament tenacity of 11 .6 cN/tex and an elongation at break of 15.3 % measured as described in Example 3.
  • Fig. 4 is a cross-sectional view of a precursor fiber produced in accordance with Example 7 having a lobular cross section.
  • Elemental analysis was performed by determining the CHNS (carbon, hydrogen, nitrogen, sulfur) content using a FlashEA 1112 CHNS/O Automatic Elemental Analyser with 2 Autosampler MAS200R (Thermo Scientific). Samples weighed into thin-walled tin capsules were transferred into a quartz combustion tube with a constant helium flow. The samples were burnt over tungsten oxide with the addition of high-purity oxygen at temperature of approximately 1020°C. The resulting nitrogen oxides and sulfur trioxide were reduced to nitrogen and sulfur dioxide on copper filings. The four components N2, CO2, H2O and SO2 obtained were separated by gas chromatography in a packed Porapack PQS column and detection was carried out by means of a thermal conductivity detector.
  • the lignin content of the precursor fibers from Examples 3 to 7 were determined by elemental analysis as described above and summarized in Table 2.

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Abstract

Un procédé de production d'une fibre précurseur (1) pour la production d'une fibre de carbone et une telle fibre précurseur (1) sont divulgués. Le procédé comprend l'extrusion d'une solution de filage comprenant de la lignine ayant une masse moléculaire moyenne choisie comprise entre 1 500 et 25 000 g/mol et du xanthate de cellulose à travers une buse de filage dans un bain de filage comprenant de 20 g/l à 400 g/l d'acide sulfurique et de 10 g/l à 120 g/l de sel de sulfate de cation divalent pour produire une fibre précurseur (1) comportant une âme contenant de la lignine et de la cellulose (2) et une couche de surface riche en cellulose (5).
PCT/IB2025/050570 2024-01-22 2025-01-20 Procédé de production d'un précurseur de fibre de carbone à partir de lignine et de xanthate de cellulose et précurseur de fibre de carbone Pending WO2025158263A1 (fr)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4177236A (en) * 1976-07-20 1979-12-04 Akzona Inc. Process for producing regenerated cellulose containing cross linked sodium lignate or sodium lignosulfonate
EP2889401A1 (fr) * 2013-12-30 2015-07-01 Kelheim Fibres GmbH Fibre de cellulose régénérée
WO2017129231A1 (fr) * 2016-01-26 2017-08-03 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Procédé de filage au mouillé pour la production d'une fibre contenant de la lignine utilisée comme précurseur pour une fibre de carbone
AU2016333831A1 (en) * 2015-10-08 2018-04-12 Stora Enso Oyj A process for the manufacture of a shaped body
US10876226B2 (en) * 2013-06-17 2020-12-29 Dupont Industrial Biosciences Usa, Llc Polysaccharide fibers and method for producing same
US20230272559A1 (en) * 2020-07-01 2023-08-31 Rise Research Institutes of Sweden AB Method of wet spinning precursor fibers comprising lignin and dissolving pulp, and precursor fibers therefrom

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4177236A (en) * 1976-07-20 1979-12-04 Akzona Inc. Process for producing regenerated cellulose containing cross linked sodium lignate or sodium lignosulfonate
US10876226B2 (en) * 2013-06-17 2020-12-29 Dupont Industrial Biosciences Usa, Llc Polysaccharide fibers and method for producing same
EP2889401A1 (fr) * 2013-12-30 2015-07-01 Kelheim Fibres GmbH Fibre de cellulose régénérée
AU2016333831A1 (en) * 2015-10-08 2018-04-12 Stora Enso Oyj A process for the manufacture of a shaped body
WO2017129231A1 (fr) * 2016-01-26 2017-08-03 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Procédé de filage au mouillé pour la production d'une fibre contenant de la lignine utilisée comme précurseur pour une fibre de carbone
US20230272559A1 (en) * 2020-07-01 2023-08-31 Rise Research Institutes of Sweden AB Method of wet spinning precursor fibers comprising lignin and dissolving pulp, and precursor fibers therefrom

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