WO2024157967A1

WO2024157967A1 - Fibrous structure containing carbon nanomaterial and organic polymer, and method for manufacturing same

Info

Publication number: WO2024157967A1
Application number: PCT/JP2024/001820
Authority: WO
Inventors: 貴大馬場; 健向; 理仁渡辺
Original assignee: 旭化成株式会社
Priority date: 2023-01-24
Filing date: 2024-01-23
Publication date: 2024-08-02

Abstract

According to the present disclosure, provided are: a fibrous structure comprising a carbon nanomaterial and an organic polymer, the fibrous structure having a wide range of conductivity with little variation in conductivity along the longitudinal direction of fibers; and a method for manufacturing same. This fibrous structure comprises an organic polymer and a carbon nanomaterial dispersed in the organic polymer. The carbon nanomaterial is at least one selected from the group consisting of carbon nanotubes, graphene, and graphene oxide. The content of the carbon nanomaterial is 0.05-50 mass% on the basis of the total mass of the fibrous structure. In addition, when the cross section of the fibrous structure is observed using a scanning electron microscope (SEM) and the observed image is binarized by the Otsu method, the proportion of the area displayed as a bright part is at least 85% of the entire cross section of the fibrous structure.

Description

Fibrous structure containing carbon nanomaterial and organic polymer and method for producing same

This disclosure relates to a fibrous structure containing a carbon nanomaterial and an organic polymer, and a method for producing the same. This international application claims priority to Japanese Patent Application No. 2023-008492, filed on January 24, 2023, and the entire contents of said Japanese patent application are incorporated herein by reference.

Many smart textiles using conductive fibers have been proposed, such as wearable wiring, stretchable sensors, and heaters, and various conductive fibers have been reported for use in smart textiles.

For example, in the following Patent Document 1, multi-walled CNTs, which are carbon nanomaterials, are dispersed in a cellulose solution at high concentrations and then turned into fibers by a wet spinning method to produce conductive fibers that are wash-resistant.

In the following Patent Documents 2, 3, and 4, single-walled CNTs, which are carbon nanomaterials, are dispersed in a cellulose solution and then wet-spun to produce CNT/cellulose composite fibers, with the aim of improving the mechanical properties of cellulose fibers.

JP 2017-160562 A JP 2015-105441 A JP 2021-21151 A JP 2011-208327 A

However, since the electrical properties required for smart textiles vary depending on the application, it is necessary to select conductive fibers whose electrical properties can be controlled according to the application. There is therefore a demand for conductive fibers that have a wide range of electrical conductivity and little variation in electrical conductivity in the longitudinal direction of the fiber.

However, in Patent Document 1, because the cellulose is dissolved and the multi-walled CNTs are dispersed simultaneously, undissolved cellulose and poor dispersion of the multi-walled CNTs occur in the solution, reducing the dispersibility and uniformity of the CNTs and causing variations in the electrical conductivity of the fibers in the longitudinal direction.

In the kneading of a cellulose solution and a CNT dispersion using an organic solvent or ionic liquid as described in Patent Documents 2 to 4, the CNTs tend to aggregate during kneading, so the CNT component remains at a low concentration relative to the cellulose. Therefore, although Patent Documents 2 to 4 show an improvement in the strength of the CNT/cellulose composite fiber, they do not mention electrical conductivity.

In the above-mentioned conventional techniques, it is not possible to obtain an organic polymer solution in which a carbon nanomaterial is uniformly dispersed at any concentration, and therefore the network structure of the carbon nanomaterial in the organic polymer matrix of the fibrous structure becomes non-uniform, resulting in only fibrous structures with low electrical conductivity or large variations in electrical conductivity in the longitudinal direction.

Therefore, in view of the state of the prior art, one of the objectives of the present disclosure is to provide a fibrous structure containing a carbon nanomaterial and an organic polymer, which has a wide range of electrical conductivity and little variation in electrical conductivity in the longitudinal direction of the fiber, and a method for producing the same.

Examples of embodiments of the present disclosure are listed in the following items [1] to [11].
[1]
A fibrous structure comprising an organic polymer and a carbon nanomaterial dispersed in the organic polymer,
The carbon nanomaterial is at least one selected from the group consisting of carbon nanotubes, graphene, and graphene oxide;
The content of the carbon nanomaterial is 0.05% by mass or more and 50% by mass or less based on the total mass of the fibrous structure,
A fibrous structure, wherein the cross section of the fibrous structure is observed using a scanning electron microscope (SEM) under the following measurement conditions, and when the observed image is binarized using the Otsu method, the proportion of carbon nanomaterial dispersion regions displayed as bright areas is 85% or more of the entire cross section of the fibrous structure, and the measurement conditions are as follows: no conductive treatment of the cross section, acceleration voltage: 1 to 5 kV, and detector: upper detector.
[2]
2. The fibrous structure according to item 1, wherein the ratio of the area displayed as the bright portion is 95% or more.
[3]
A fibrous structure comprising an organic polymer and a carbon nanomaterial dispersed in the organic polymer,
The carbon nanomaterial is at least one selected from the group consisting of carbon nanotubes, graphene, and graphene oxide;
The content of the carbon nanomaterial is 0.05% by mass or more and 50% by mass or less based on the total mass of the fibrous structure,
A fibrous structure having a specific conductivity of 0.01 Scm ² /g or more and 2500 Scm ² /g or less, and a linear resistance variation coefficient per cm in the longitudinal direction of 10% or less.
[4]
3. A fibrous structure according to item 1 or 2, having a specific conductivity of 0.01 Scm ² /g or more and 2500 Scm ² /g or less, and a linear resistance variation coefficient per cm in the longitudinal direction of 10% or less.
[5]
5. The fibrous structure according to any one of items 1 to 4, wherein the carbon nanomaterial is a carbon nanotube.
[6]
The fibrous structure according to any one of items 1 to 5, wherein the organic polymer is a polysaccharide.
[7]
7. The fibrous structure according to any one of items 1 to 6, wherein the carbon nanomaterial is a carbon nanotube and the organic polymer is a polysaccharide.
[8]
A method for producing a fibrous structure, the method comprising the steps of:
A step of preparing a carbon nanomaterial dispersion in which a carbon nanomaterial is dispersed in water;
Providing an organic polymer solution;
mixing the carbon nanomaterial dispersion liquid and the organic polymer solution at an oxygen concentration of 1000 ppm or less, a reduced pressure of −0.1 MPa to −0.01 MPa, and a liquid temperature of 20° C. to 40° C. to prepare a mixed dispersion liquid containing a carbon nanomaterial and an organic polymer;
a step of wet-spinning the obtained mixed dispersion in a liquid, and removing the solvent component by washing with an acid and water to obtain an organic polymer fiber containing a carbon nanomaterial;
A step of drying the obtained organic polymer fiber to obtain a fibrous structure;
A method for producing a fibrous structure comprising the steps of:
[9]
Item 9. The method for producing a fibrous structure according to item 8, wherein in the step of preparing the mixed dispersion, the mass ratio of the carbon nanomaterial dispersion to the organic polymer solution (mass of the carbon nanomaterial dispersion:mass of the organic polymer solution) is 0.1:1 to 15:1.
[10]
The method for producing a fibrous structure according to item 8 or 9, wherein when a cross section of the fibrous structure is observed using a scanning electron microscope (SEM) under the following measurement conditions, and the observed image is binarized by the Otsu method, the ratio of the area displayed as a bright area is 85% or more of the entire cross section of the fibrous structure, and the measurement conditions are: no conductive treatment of the cross section, an acceleration voltage of 1 to 5 kV, and a detector using an upper detector.
[11]
11. The method for producing a fibrous structure according to any one of items 8 to 10, wherein the fibrous structure has a specific conductivity of 0.01 Scm ² /g or more and 2500 Scm ² /g or less, and a linear resistance variation coefficient per cm in the longitudinal direction of 10% or less.

The present disclosure provides a composite fiber containing a carbon nanomaterial and an organic polymer, which has a wide range of electrical conductivity and little variation in electrical conductivity along the length of the fiber, and a method for producing the same.

1A and 1B are electron microscope images showing an example of a uniform CNT network structure in a cross section of a fibrous structure (fiber) according to the present disclosure. Fig. 1A is an electron microscope image of the entire cross section of the fibrous structure. FIG. 1B is an image obtained by binarizing the electron micrograph of FIG. 1A. Fig. 2 is an electron microscope image showing an example of a non-uniform CNT network structure in a cross section of a fibrous structure (fiber) of a comparative example. Fig. 2A is an electron microscope image of the entire cross section of the fibrous structure. FIG. 2B is an image obtained by binarizing the electron micrograph image of FIG. 2A.

<<Fibrous Structure>>
The fibrous structure of the present disclosure includes an organic polymer and a carbon nanomaterial dispersed in the organic polymer. In the present disclosure, the term "fibrous structure" refers to a structure having a ratio of the long axis direction to the short axis direction (long axis length/short axis length) of 1000 or more. Specifically, it is a continuous long fiber or a short fiber. The carbon nanomaterial is at least one selected from the group consisting of carbon nanotubes, graphene, and graphene oxide. The fibrous structure contains 0.05% by mass or more and 50% by mass or less of the carbon nanomaterial based on the total mass of the fibrous structure. In one embodiment, the specific conductivity of the fibrous structure is 0.01 Scm ² /g or more and 2500 Scm ² /g or less, and the linear resistance variation coefficient per 1 cm in the longitudinal direction of the fibrous structure is 10% or less. By having the above-mentioned configuration, the fibrous structure of the present disclosure can provide a composite fiber containing a carbon nanomaterial and an organic polymer, which has a wide range of electrical conductivity and little variation in electrical conductivity in the longitudinal direction of the fiber.

In one aspect, from the viewpoint of obtaining a fibrous structure having a wide range of electrical conductivity and small variation in electrical conductivity in the longitudinal direction, the proportion of regions in the cross section of the fibrous structure where the amount of carbon nanomaterial is relatively greater than the amount in other regions (hereinafter, in this disclosure, referred to as "carbon nanomaterial dispersion regions") is 85% or more, preferably 90% or more, and more preferably 95% or more. The upper limit of the carbon nanomaterial dispersion region that can be arbitrarily combined with these lower limit values is not limited, but may be 100% or less, less than 100%, or 99.9% or less. In this disclosure, a "carbon nanomaterial dispersion region" refers to a region that is displayed as a bright area when the cross section of a fibrous structure is observed using a scanning electron microscope (SEM) under the following measurement conditions and the observed image is binarized using the Otsu method. The measurement conditions are: no conductive treatment of the cross section, acceleration voltage: 1-5 kV, and detector: upper detector. The proportion of the carbon nanomaterial dispersion region is an index showing the uniformity of the carbon nanomaterial network formed in the organic polymer matrix in the fiber structure, and the higher the proportion of the carbon nanomaterial dispersion region, the more uniformly the carbon nanomaterial is dispersed. The inventors of the present application have found a method for uniformly dispersing nanomaterials in an organic polymer solution at any concentration, uniformly constructing a carbon nanomaterial network in the organic polymer matrix in the fiber, and making the proportion of the "carbon nanomaterial dispersion region" 85% or more. As a result, they have succeeded for the first time in obtaining a fibrous structure that has a wide range of electrical conductivity at various carbon nanomaterial concentrations and has small longitudinal electrical conductivity variation, which was not possible with conventional technology.

Carbon nanomaterials
Graphene is a carbon-based material having a structure in which six-membered rings formed by sp2 bonds between carbon and carbon are laid out in a two-dimensional sheet shape. Graphene generally has unique conductive properties and optical properties, and is also a material that is lightweight, has high strength, and has a high elastic modulus. Graphene may be graphene oxide. Graphene oxide is obtained by oxidizing graphene, and generally has functional groups such as hydroxyl groups, carboxyl groups, and epoxy groups, and has high dispersibility in water and polar organic solvents.

Carbon nanotubes (CNTs) are carbon-based materials that have a cylindrical shape made of graphene sheets. Various types of CNTs are known, but they can be broadly classified into single-wall carbon nanotubes (SWCNTs), double-wall carbon nanotubes (DWCNTs), and multi-wall carbon nanotubes (MWCNTs) with three or more walls, based on the number of walls that they have. They can also be classified into chiral (spiral) type, zigzag type, and armchair type, based on the structure of the graphene sheets. The physical properties of individual CNTs themselves are said to be approximately 150 GPa in strength, 100,000 S/cm or more in electrical conductivity, 0.9 TPa in Young's modulus, and 3,000 W/mK in thermal conductivity.

Among the carbon nanomaterials, carbon nanotubes are preferred. Because carbon nanotubes have a fibrous shape, they tend to form a network structure (CNT network) between carbon nanotubes, which tends to provide high electrical conductivity and strength. In addition to carbon nanotubes, the carbon nanomaterial may further contain graphene and/or graphene oxide.

As the carbon nanotube, any type of CNT may be used as long as it is so-called CNT. For example, even if it contains multi-walled carbon nanotubes (MWCNT) with three or more walls, high electrical conductivity and specific conductivity can be achieved. More preferably, the carbon nanotube is at least one selected from the group consisting of single-walled carbon nanotubes (SWCNT) and double-walled carbon nanotubes (DWCNT). By using SWCNT and/or DWCNT as raw materials, a fibrous structure with higher electrical conductivity can be obtained. The diameter of SWCNT and DWCNT is preferably 5 nm or less. From the viewpoint of obtaining a fibrous structure with higher electrical conductivity, the ratio of CNTs with a diameter of 5 nm or less in the CNTs is preferably 50% or more, more preferably 70% or more, even more preferably 80% or more, even more preferably 90% or more, and may be 100%.

In a spectrum obtained by resonance Raman scattering measurement of a carbon nanomaterial, when the maximum peak intensity in the range of 1550 to 1650 cm ⁻¹ is G and the maximum peak intensity in the range of 1300 to 1400 cm ⁻¹ is D, the ratio of G/D is preferably 0.1 or more, more preferably 1 or more, even more preferably 2 or more, even more preferably 10 or more, even more preferably 20 or more, even more preferably 30 or more. The peak in the range of 1550 to 1650 cm ⁻¹ is called the G band, which is a peak derived from a graphite structure, and the peak in the range of 1300 to 1400 cm ⁻¹ is called the D band, which is a peak derived from lattice defects in graphene, graphene oxide, or CNT. The relative occurrence rate of defective sites in graphene, graphene oxide, and CNT can be quantified using the G/D ratio. A G/D ratio of 0.1 or more, particularly 1 or more, means that the material is composed of high-quality graphene, graphene oxide, or CNT with few lattice defects. In particular, when the G/D ratio is 2 or more, further 10 or more, 20 or more, particularly 30 or more, the graphene, graphene oxide, or CNT is of higher quality, and is more excellent in thermal conductivity, electrical conductivity, and heat resistance. In addition, the manufacturing method of graphene, graphene oxide, and CNT is not particularly limited.

<Organic polymers>
The organic polymer is preferably an organic substance having a weight average molecular weight of 10,000 or more. The type of organic polymer is not limited, but examples thereof include synthetic polymers such as polysaccharides, polyamines, polyamides, polyurethanes, polyethers, nylons, vinylons, polyesters, polyethylene terephthalates, silicone resins, synthetic rubbers, natural rubbers, polypeptides, proteins, DNA, RNA, lignin, and asphaltene, as well as copolymers thereof. The fibrous structure is preferably such that the total content of transition metals and post-transition metals in the organic polymer is 1,000 ppm or less relative to the total mass of the fibrous structure. However, the fibrous structure may contain an alkali metal, an alkaline earth metal, or a halogen in the organic polymer.

The presence or absence of metal elements and organic polymer elements can be determined by performing elemental analysis of the fibrous structures using energy dispersive X-ray analysis (EDX) or CHN analysis equipment. The chemical structure of organic polymers can also be identified by solubility tests, nuclear magnetic resonance (NMR), infrared absorption spectroscopy (IR), enzymatic decomposition, dyeing tests using dyes, crystallinity, strength and elongation, and thermal analysis, etc.

The organic polymer is preferably a polysaccharide. A polysaccharide is a polymer in which a large number of monosaccharides such as glucose are bonded together through glycosidic bonds, and examples of such polysaccharides include amylose, amylopectin, cellulose, curdlan, paramylon, chitin, dextran, agarose, carrageenan, alginic acid, hyaluronic acid, α-1,3-glucan, α-1,2-glucan, β-1,2-glucan, glucomannan, xylan, and levan. Preferred examples include cellulose, curdlan, paramylon, chitin, agarose, carrageenan, alginic acid, and hyaluronic acid. As polysaccharides, curdlan, alginic acid, and cellulose are preferred from the viewpoint of low water solubility and washing durability, and cellulose is even more preferred.

Cellulose is a type of polysaccharide, a polymer in which many glucose molecules are linked in a linear chain by β-1,4-glycosidic bonds. Cellulose has low water solubility and high water resistance, so it has long been used in recycled fibers and paper.

In this disclosure, the term "cellulose" includes both unmodified cellulose and partially modified cellulose (modified cellulose). Examples of modified cellulose include carboxymethyl cellulose (CMC), hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, cellulose acetate, cellulose propionate, cellulose butyrate, methyl cellulose, ethyl cellulose, and nitrocellulose. Preferred are carboxymethyl cellulose, hydroxypropyl cellulose, and cellulose acetate, and more preferred are carboxymethyl cellulose and cellulose acetate. In addition, from the viewpoint of being water-insoluble, the degree of substitution of the modified cellulose is preferably 0.5 or less. The organic polymer may contain a small amount of other polysaccharides in addition to cellulose.

Cellulose raw materials include so-called wood pulps such as coniferous pulp and hardwood pulp, and non-wood pulp. Non-wood pulp can include cotton-derived pulp such as cotton linter pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp. Cotton-derived pulp, hemp-derived pulp, bagasse-derived pulp, kenaf-derived pulp, bamboo-derived pulp, and straw-derived pulp respectively refer to purified pulp obtained from raw materials such as cotton lint or cotton linter, hemp-based abaca (for example, many of which are produced in Ecuador or the Philippines), zaisal, bagasse, kenaf, bamboo, and straw, through delignification by cooking treatment, and a refining process and bleaching process aimed at removing hemicellulose. In addition, refined products such as seaweed-derived cellulose and sea squirt cellulose can also be used as raw materials for cellulose fine fibers. Furthermore, cut yarns of regenerated cellulose fibers and cut yarns of cellulose derivative fibers can also be used as cellulose raw materials, and cut yarns of ultra-fine yarns of regenerated cellulose or cellulose derivatives obtained by electrospinning can also be used as cellulose. Among these, refined pulp derived from cotton lint or cotton linter, hemp-based abaca, zaisal, bagasse, kenaf, bamboo, straw, etc. is particularly preferred.

General methods can be used to determine whether a material is cellulose or a cellulose derivative. For example, spectral analysis using XRD or IR can be used. Also, if the material can be broken down with cellulase, it can be determined that the material is cellulose or a cellulose derivative.

The organic polymer content in the fibrous structure is 50% by mass or more and 99.95% by mass or less, based on the total mass of the fibrous structure. The lower limit of the organic polymer content may preferably be 60% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more. The upper limit of the organic polymer content that can be combined with these lower limits may preferably be 99.9% by mass or less, 99.5% by mass or less, 99.0% by mass or less, 97.0% by mass or less, or 95.0% by mass or less.

<Uses of fibrous structures>
The fibrous structure of the present disclosure is not limited to a specific application, but can be suitably used, for example, as electrodes for acquiring bioelectric potentials such as electrocardiogram, electromyogram, and electroencephalogram in smart textiles, electrodes for electrical stimulation, wiring for wearables, electromagnetic wave shielding members, stretch sensors, humidity sensors, heaters, etc. "Smart textile" refers to a textile material with new functions that cannot be obtained with ordinary fiber materials, or a textile material in which existing functions can be obtained by new technology.

When smart textiles come into direct contact with the skin, they are preferably flexible, stretchable, and breathable, such as wearable electrodes, sensors, and heaters. Organic polymer electrodes are also preferred so as not to cause metal allergies. Furthermore, it is preferable for them to have mechanical strength that can withstand the stress of washing, and chemical stability that can withstand detergents and bleaches. The conductivity required for conductive fibers used in smart textiles varies depending on the application, and it is preferable that the conductivity can be controlled to any value. For example, heaters are expected in low conductivity regions, electrodes and sensors in high conductivity regions, and electrical wires in even higher conductivity regions. Furthermore, there is a demand for materials that can improve sensitivity and precision in each application by reducing the variation in conductivity in the longitudinal direction.

<Carbon nanomaterial content>
The content of the carbon nanomaterial in the fibrous structure is 0.05% by mass or more and 50% by mass or less, based on the total mass of the fibrous structure. The lower limit of the carbon nanomaterial content may be preferably 0.1% by mass or more, 0.5% by mass or more, 1.0% by mass or more, 3.0% by mass or more, or 5.0% by mass or more. The upper limit of the carbon nanomaterial content that can be combined with these lower limits may be preferably 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less. By having the fibrous structure have these carbon nanomaterial contents, it can be suitably used in the various applications described above. For example, in a heater, the carbon nanomaterial content is preferably 0.05% by mass or more from the viewpoint of the amount of heat generated. In applications such as electrodes for acquiring bioelectric potentials such as electrocardiograms, electromyograms, and electroencephalograms, wearable stretch sensors, and humidity sensors, the carbon nanomaterial content is preferably 0.5% by mass or more and 25% by mass or less from the viewpoint of sensor accuracy. In terms of power loss, the carbon nanomaterial content is preferably 5.0% by mass or more and 50% by mass or less for wearable electric wire applications. By having the carbon nanomaterial content of 50% by mass or less, the strength is improved, defects such as single yarn breakage during the manufacturing process are unlikely to occur, and electrical conductivity is unlikely to decrease significantly or vary significantly in the longitudinal direction, resulting in improved electrical properties.

<Linear resistance variation coefficient>
The linear resistance variation coefficient of the fibrous structure is 10% or less. By setting the linear resistance variation coefficient to 10% or less, a fibrous structure with small variation in electrical conductivity in the longitudinal direction can be obtained. When the fibrous structure is used as, for example, a heater, uneven heat generation caused by local variation in resistance value can be suppressed. In addition, when the fibrous structure is used as, for example, an electrode for acquiring bioelectric potential such as electrocardiogram, electromyogram, and electroencephalogram, an expansion sensor, a humidity sensor, etc., detection sensitivity and accuracy can be improved by reducing data noise caused by variation in resistance value. Since the smaller the variation in electrical conductivity in the longitudinal direction of the fiber, the more uniform the heat generation of the heater and the accuracy of the sensor can be improved, the linear resistance variation coefficient is preferably 8% or less, more preferably 5% or less, and even more preferably 1% or less.

<Fineness>
The fibrous structure may be a monofilament or a multifilament. When the fibrous structure is a monofilament, the fineness (single yarn fineness) is preferably 0.5 dtex or more and 500 dtex or less, more preferably 1 dtex or more and 300 dtex or less, and even more preferably 1.5 dtex or more and 200 dtex or less. When the fibrous structure is a multifilament, the single yarn fineness is preferably 0.5 dtex or more and 500 dtex or less, more preferably 1 dtex or more and 300 dtex or less, and even more preferably 1.5 dtex or more and 200 dtex or less. In either case of a monofilament or a multifilament, if the single yarn fineness of the fibrous structure is 0.5 dtex or more and 500 dtex or less, the inside and outside of the single yarn are uniformly solidified during solidification, and it is easier to suppress the variation in electrical conductivity in the longitudinal direction.

When the fibrous structure is a multifilament, the total fineness of the fibrous structure is preferably 1.0 dtex or more and 1000 dtex or less, more preferably 5 dtex or more and 1,000 dtex or less, even more preferably 10 dtex or more and 900 dtex or less, and even more preferably 20 dtex or more and 750 dtex or less. When the total fineness is 1.0 dtex or more, the strength of the yarn is high and breakage and significant loss of conductivity are unlikely to occur. When the total fineness is 1000 dtex or less, the spinnability is improved and single yarn breakage due to friction during yarn running is unlikely to occur, making it easier to suppress variation in electrical conductivity in the longitudinal direction of the fiber. In the case of a monofilament, the single yarn fineness and the total fineness are the same.

<Specific Conductivity>
The specific conductivity of the fibrous structure is preferably 0.01 Scm ² /g or more and 2,500 Scm ² /g or less. The lower limit of the specific conductivity may be, for example, 0.05 Scm ² /g or more, 0.1 Scm ² /g or more, 0.5 Scm ² /g or more, 1.0 Scm ² /g or more, 5.0 Scm ² /g or more, 10 Scm ² /g or more, 50 Scm ² /g or more, 100 Scm ² /g or more, 200 Scm ² /g or more, 300 Scm ² /g or more, 400 Scm ² /g or more, 500 Scm ² /g or more, 1,000 Scm ² /g or more, 1,500 Scm ² /g or more, or 2,000 Scm ² /g or more. The upper limit of the specific conductivity that can be combined with these lower limit values may be, for example, 2,000 ^Scm2 /g or less, 1,500 ^Scm2 /g or less, 1,000 ^Scm2 /g or less, ⁵⁰⁰ ^Scm2 /g or less, ⁴⁰⁰ Scm2/g or less, 300 Scm2/g or less, ²⁰⁰ Scm2/g or less, ¹⁰⁰ Scm2/g or less, ⁵⁰ Scm2/g or less, ¹⁰ Scm2/g or less, 5.0 ^Scm2 /g or less, or 1.0 ^Scm2 /g or less. The specific conductivity of 0.01 ^Scm2 /g or more and 2,500 ^Scm2 /g or less makes it particularly suitable for use in smart textiles. The fibrous structure of the present disclosure preferably has a wide range of controllable specific conductivity by adjusting the concentration of the carbon nanomaterial within a specific range, and has small variation in the longitudinal direction of the fiber, resulting in an excellent balance of electrical properties, particularly the specific conductivity and the variation in the coefficient of variation.

<Breaking strength>
The breaking strength of the fibrous structure is preferably 0.1 cN/dtex or more and 10 cN/dtex or less. When the breaking strength is 0.1 cN/dtex or more, the weaving and knitting properties are good. The breaking strength is more preferably 0.3 cN/dtex or more and 7 cN/dtex or less, and even more preferably 0.4 cN/dtex or more and 5 cN/dtex or less.

<<Method for producing a fibrous structure>>
The fibrous structure includes the steps of dispersing a carbon nanomaterial in water to prepare a dispersion of the carbon nanomaterial (hereinafter referred to as the "carbon nanomaterial dispersion"), preparing a solution of an organic polymer (hereinafter referred to as the "organic polymer solution"), mixing the carbon nanomaterial dispersion and the organic polymer solution under predetermined conditions to prepare a mixed dispersion containing the carbon nanomaterial and the organic polymer, wet-spinning the mixed dispersion to obtain an organic polymer fiber containing the carbon nanomaterial, and drying the organic polymer fiber to obtain a fibrous structure. The conditions for mixing the carbon nanomaterial dispersion and the organic polymer solution are not limited, but it is preferable to control at least one condition selected from the group consisting of oxygen concentration, reduced pressure (pressure), and liquid temperature (temperature of the mixed liquid). For example, the oxygen concentration is preferably 1000 ppm or less. The reduced pressure is preferably -0.1 MPa or more and -0.01 MPa or less. And the liquid temperature is preferably 20°C to 40°C.

The fibrous structure obtained by the above process is constituted by a uniform carbon nanomaterial network, and in one embodiment, the ratio of the aforementioned "carbon nanomaterial dispersion region" is 85% or more, and in one embodiment, the specific conductivity is 0.01 Scm ² /g or more and 2500 Scm ² /g or less, and the linear resistance variation coefficient per 1 cm in the longitudinal direction is 10% or less. Although the present inventors do not wish to be bound by a specific theory, the present inventors presume that the above process can form a uniform carbon nanomaterial network structure in the fiber, and can obtain a conductive fiber that exhibits conductivity at any carbon nanomaterial concentration and has small variation in the longitudinal direction of the fiber as follows. That is, in order for a carbon nanomaterial of any concentration in the fiber to exhibit uniform conductivity, it is preferable that the carbon nanomaterial network is formed uniformly in the fiber. If foreign matter other than the uniform polymer matrix and carbon nanomaterial network is contained in the fiber, the uniformity of the carbon nanomaterial network is reduced, which can reduce the electrical conductivity and the uniformity of the electrical conductivity in the longitudinal direction. Therefore, in the process of mixing the carbon nanomaterial dispersion liquid and the organic polymer solution, it is important to reduce the inclusion of foreign matter such as air bubbles and aggregates of organic polymers. However, the mixed dispersion liquid containing the carbon nanomaterial and the organic polymer prepared in the process of mixing the carbon nanomaterial dispersion liquid and the organic polymer solution has high viscosity due to the carbon nanomaterial network and the organic polymer formed in the liquid, so air bubbles are likely to be mixed in. In addition, when the components contained in the dissolution system, such as ammonia, volatilize, organic polymer aggregates are generated, making it difficult to manufacture a uniform mixed dispersion liquid that does not contain foreign matter. In this regard, the inventors of the present application, as a result of various studies, have succeeded in obtaining a uniform mixed dispersion liquid in which foreign matter is reduced by adjusting the oxygen concentration, the degree of vacuum, and the temperature during kneading, and have found that uniform conductive fibers can be obtained by wet spinning the obtained mixed dispersion. By reducing the oxygen concentration during kneading, the decomposition of the organic polymer due to oxygen can be reduced, and the generation of foreign matter associated with the decomposition can be suppressed. By controlling the degree of vacuum, defoaming by vacuum can be promoted, and the volatilization of the components contained in the dissolution system due to excessive vacuum can be suppressed, and the generation of aggregates can be suppressed. By controlling the temperature during kneading, it is possible to suppress the volatilization of the components contained in the solution system and to promote degassing by adjusting the viscosity of the organic polymer solution.

The method for producing a fibrous structure preferably includes the following steps:
preparing a CNT dispersion in which CNTs are dispersed in water;
preparing a cellulose solution in which cellulose is dissolved in cuprammonium;
mixing the CNT dispersion and the cellulose solution at an oxygen concentration of 1000 ppm or less, a reduced pressure of −0.1 MPa to −0.01 MPa, and a liquid temperature of 20° C. to 40° C. to prepare a mixed dispersion;
A step of wet-spinning the obtained CNT/cellulose dispersion in a warm water coagulation bath and removing the copper component by washing with an acid and water;
and drying the resulting CNT-containing cellulose fibers at an elevated temperature.

Preparation of Carbon Nanomaterial Dispersion
The carbon nanomaterial can be dispersed in a solvent including water, an organic solvent, or an ionic liquid. A dispersant may be used for the dispersion. As the dispersant, any of a nonionic surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and an aromatic ring-containing compound may be used.

Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, sorbitan fatty acid esters, sucrose fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene polyoxypropylene block copolymers, and more specifically, poly(oxyethylene) octylphenyl ether (e.g., Triton (registered trademark) X-100), polyoxyethylene sorbitan monolaurate (e.g., Tween (registered trademark) 20), and the like.

Anionic surfactants include alkylbenzenesulfonates (e.g., sodium dodecylbenzenesulfonate, etc.), alkyl alcohol sulfates (e.g., sodium dodecyl sulfate, etc.), sodium alkyldiphenyletherdisulfonate, sodium polyoxyethylene alkylether sulfate, sodium dialkylsulfosuccinate, sodium alkylarylsulfosuccinate, sodium N-lauroylsarcosine, sodium polyoxyethylene alkylphenylether sulfate, sodium (meth)acryloylpolyoxyalkylene sulfate, alkyl alcohol phosphates, and bile salts (e.g., sodium cholate, sodium deoxycholate, etc.), with preferred examples being bile salts such as sodium cholate.

From the viewpoint of improving electrical conductivity while maintaining high mechanical properties by reducing defects in the carbon nanomaterial contained in the obtained fibrous structure and by dispersing the carbon nanomaterial uniformly in the fibrous structure, the surfactant is preferably a bile salt, more preferably sodium deoxycholate, and even more preferably sodium taurodeoxycholate. In particular, when using CNTs, sodium taurodeoxycholate is particularly preferred in order to suppress the occurrence of defects and obtain a CNT dispersion and composite fibrous structure in which the CNTs are uniformly dispersed while maintaining their length.

Cationic surfactants include tetraalkylammonium halides, alkylpyridinium halides, and alkylimidazoline halides. Amphoteric surfactants include alkylbetaines, alkylimidazolinium betaines, and lecithin.

Aromatic ring-containing compounds include naphthalene derivatives, anthracene derivatives, tetracene derivatives, phenanthrene derivatives, pyrene derivatives, acridine-containing compounds, and isoalloxazine-containing compounds.

Organic solvents include lower alcohols such as ethanol, methanol, propanol, and isopropanol; ketones such as acetone, methyl ethyl ketone, and 4-methyl-2-pentanone (MIBK); ethers such as tetrahydrofuran and dioxane; esters such as propylene carbonate; amides such as DMF, acetamide, formamide, dimethylacetamide, and N-methylpyrrolidone; glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and glycerin; alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether; dimethyl sulfoxide; and acetonitrile.

Ionic liquids are salts composed of anions and cations, and have a melting point of 100°C or less. Examples include imidazolium salts such as 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium diethylphosphate, and 1-ethyl-3-methylimidazolium acetate, piperidinium salts such as 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide, ammonium salts such as tetrabutylammonium acetate, phosphonium salts such as tributyl(ethyl)phosphonium diethylphosphate, pyrrolidinium salts such as 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, and sulfonium salts such as triethylsulfonium bis(trifluoromethanesulfonyl)imide.

The amount of carbon nanomaterial in the carbon nanomaterial dispersion is preferably 0.1% by mass to 20% by mass, more preferably 0.1% by mass to 15% by mass, and even more preferably 0.2% by mass to 10% by mass. The amount of dispersant in the carbon nanomaterial dispersion is preferably 0.2% by mass to 20% by mass, more preferably 0.3% by mass to 16% by mass, and even more preferably 0.5% by mass to 10% by mass.

Preparation of organic polymer solutions
The organic polymer can be dissolved in a solvent containing water, an organic solvent, or an ionic liquid. Examples of the organic solvent include lower alcohols such as ethanol, methanol, propanol, and isopropanol, ketones such as acetone, methyl ethyl ketone, and 4-methyl-2-pentanone (MIBK), ethers such as tetrahydrofuran and dioxane, amides such as dimethylformamide, acetamide, formamide, dimethylacetamide, and N-methylpyrrolidone, glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and glycerin, alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, dimethyl sulfoxide, and acetonitrile.

Ionic liquids include imidazolium salts such as 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium diethyl phosphate, and 1-ethyl-3-methylimidazolium acetate; piperidinium salts such as 1-butyl-1-methylpiperidinium bis(trifluoromethanesulfonyl)imide; ammonium salts such as tetrabutylammonium acetate; phosphonium salts such as tributyl(ethyl)phosphonium diethylphosphate; pyrrolidinium salts such as 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide; and sulfonium salts such as triethylsulfonium bis(trifluoromethanesulfonyl)imide. Any combination of cations and anions can be used.

The solvent for dissolving the organic polymer may contain any substance, such as inorganic or organic substances, either alone or in combination. Examples include hydroxides of alkali metals, alkaline earth metals, and transition metals, and preferably lithium hydroxide, sodium hydroxide, potassium hydroxide, copper hydroxide, etc.

Salts include alkali metal salts, alkaline earth metal salts, and transition metal salts, more preferably sodium salts, potassium salts, lithium salts, calcium salts, magnesium salts, barium salts, strontium salts, and copper salts, and even more preferably sodium salts, calcium salts, magnesium salts, and copper salts. Anions of salts include chloride ions, fluoride ions, bromide ions, iodide ions, sulfate ions, sulfite ions, phosphate ions, nitrate ions, nitrite ions, methanesulfonate ions, benzenesulfonate ions, toluenesulfonate ions, citrate ions, oxalate ions, malate ions, tartrate ions, maleate ions, fumarate ions, and acetate ions.

Preferred salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, sodium bromide, potassium bromide, calcium bromide, magnesium bromide, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate, calcium nitrate, magnesium nitrate, sodium phosphate, disodium monohydrogen phosphate, monosodium dihydrogen phosphate, sodium phosphate, disodium monohydrogen phosphate, monosodium dihydrogen phosphate, potassium phosphate, dipotassium monohydrogen phosphate, monopotassium dihydrogen phosphate, potassium phosphate, dipotassium monohydrogen phosphate, monopotassium dihydrogen phosphate, etc.

Additionally, ammonia, carbon disulfide, paraformaldehyde, 4-methylmorpholine N-oxide, dinitrogen tetroxide, chloral, pyridine, N-ethylpyridinium chloride, hydrazine, trifluoroacetic acid, urea, ammonium thiocyanate, calcium thiocyanate, zinc chloride, sulfur trioxide, polyphosphoric acid, and tetrabutylammonium acetate can also be used as additives.

In particular, a large number of solvent systems that dissolve cellulose are commonly known. For example, viscose method dissolution system, cuprammonium method dissolution system, 4-methylmorpholine N-oxide/water system, dimethyl sulfoxide/carbon disulfide/amine system, dimethylformamide/dinitrogen tetroxide system, dimethyl sulfoxide/paraformaldehyde system, dimethylformamide/chloral/pyridine system, N-ethylpyridinium chloride system, dimethylacetamide/lithium chloride system, hydrazine system, trifluoroacetic acid/dichloromethane system, formic acid/lithium chloride system, urea/sodium hydroxide/water system, liquid ammonia/ammonium thiocyanate system, calcium thiocyanate/water system, zinc chloride/water system, dimethylformamide/sulfur trioxide system, sulfuric acid aqueous solution system, sulfuric acid/polyphosphoric acid/water system, caustic soda/water system, dimethyl sulfoxide/tetrabutylammonium acetate system, 1-ethyl-3-methylimidazolium diethylphosphate system, 1-ethyl-3-methylimidazolium acetate system, etc.

In the manufacturing method of the fibrous structure, a viscose method dissolution system, a cuprammonium method dissolution system, a sulfuric acid/water system, a sulfuric acid/polyphosphoric acid/water system, or a caustic soda/water system is preferably used. More preferred are a viscose method dissolution system, a cuprammonium method dissolution system, and a caustic soda/water system. Most preferred is a cuprammonium method dissolution system.

The concentration of each component in the solvent that dissolves the organic polymer is determined by the combination of the solvent, additive, and organic polymer, and each can be set to any desired concentration. The amount of organic polymer in the organic polymer solution is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and even more preferably 5% by mass or more and 15% by mass or less.

<Preparation of Mixed Dispersion>
By mixing the carbon nanomaterial dispersion liquid obtained above with an organic polymer solution, a mixed dispersion liquid (spinning dope) in which the carbon nanomaterial and the organic polymer are uniformly kneaded can be obtained.

As described above, the mixing conditions preferably satisfy all conditions selected from the group consisting of oxygen concentration, degree of vacuum (pressure), and liquid temperature (temperature of the mixed liquid). For example, the oxygen concentration is preferably 1000 ppm or less. The degree of vacuum is preferably -0.1 MPa or more and -0.01 MPa or less. And the liquid temperature is preferably 20°C to 40°C. By satisfying at least one of these conditions, it is easier to uniformly disperse the carbon nanomaterial in the resulting fiber structure.

The mass ratio of the carbon nanomaterial dispersion liquid to the organic polymer solution when mixed (mass of carbon nanomaterial dispersion liquid: mass of organic polymer solution) is preferably 0.1:1 to 15:1, more preferably 0.1:1 to 10:1, and even more preferably 0.1:1 to 5:1. By having this mass ratio within the above range, it is easier to uniformly disperse the carbon nanomaterial in the obtained fiber structure. From the same perspective, it is even more preferable that the concentration of the carbon nanomaterial in the carbon nanomaterial dispersion liquid and the concentration of the organic polymer in the organic polymer solution are adjusted to one of the preferred ranges mentioned above, and that the mass ratio of the carbon nanomaterial dispersion liquid to the organic polymer solution is within the above range.

The concentration of the organic polymer contained in the mixed dispersion is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.5% by mass or more and 15% by mass or less, even more preferably 1% by mass or more and 12.5% by mass or less, and even more preferably 1.5% by mass or more and 10.5% by mass or less, based on the total mass of the mixed dispersion. The concentration of the carbon nanomaterial contained in the mixed dispersion is preferably 0.1% by mass or more and 50% by mass or less, based on the total mass of the mixed dispersion. The lower limit of the concentration of the carbon nanomaterial contained in the mixed dispersion may be, for example, 0.5% by mass or more, 1.0% by mass or more, 3.0% by mass or more, or 5.0% by mass or more. The upper limit of the concentration of the carbon nanomaterial that can be combined with these lower limits may be, for example, 40% by mass or less, 30% by mass or less, 20% by mass or less, or 10% by mass or less. The concentration of carbon nanomaterial contained in the mixed dispersion is correlated with the carbon nanomaterial residual index in the fibrous structure, and the mass percentage of carbon nanomaterial relative to the total mass of the fibrous structure can be calculated by multiplying the carbon nanomaterial residual index by 0.71.

<Spinning process>
By wet spinning the mixed dispersion, organic polymer fibers containing carbon nanomaterials can be obtained. Typically, the mixed dispersion is discharged from a syringe, spinneret, or the like into a coagulation bath in a spinning process, and a composite gel containing a carbon nanomaterial and an organic polymer in the form of a thread (hereinafter simply referred to as a "composite gel"). In the spinning process, it is preferable to continuously pull up the composite gel from the coagulation bath so that it does not slacken. The diameter of the syringe, spinneret, or the like when discharging is preferably 5 μm or more and 5000 μm or less, more preferably 10 μm or more and 3000 μm or less, and even more preferably 15 μm or more and 1000 μm or less. By adjusting this diameter, the coagulation rate and the diameter of the fibrous structure can be adjusted. The dispersion is discharged directly from the spinneret into the coagulation bath in the direction of gravity or in a direction perpendicular to gravity, and the direction is changed by a change roll or a change rod, and the composite gel is continuously pulled up from the coagulation bath by a rotating roll such as a Nelson roll. When discharged in the direction of gravity, it may also be discharged from the spinneret into the coagulation bath through the air. In some cases, the syringe or spinneret is immersed in the bottom of the coagulation bath and the gel is discharged in the direction of a rotating roll that pulls the gel out of the coagulation bath. In either case, it is preferable that the fibrous composite gel is continuously pulled out of the coagulation bath so that it does not slacken. In some cases, the gel is stretched in the coagulation bath.

The solvent for the coagulation bath is preferably water. Acids and salts may be added to the water used for the coagulation bath. If the organic polymer species, which is one of the elements constituting the fibrous structure, does not contain acids or salts, the fibrous composite gel cannot be in a coagulated state in which it can be continuously pulled up from the coagulation bath without loosening. Examples of acids include inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as carboxylic acids such as formic acid, acetic acid, benzoic acid, citric acid, and oxalic acid, and sulfonic acids such as toluenesulfonic acid. The salts may be either inorganic salts or organic salts, but inorganic salts are preferred. The salts are water-soluble. The salts are preferably alkali metal salts and alkaline earth metal salts, more preferably sodium salts, potassium salts, lithium salts, calcium salts, magnesium salts, barium salts, and strontium salts, and even more preferably sodium salts, calcium salts, and magnesium salts. Examples of anions of salts include chloride ions, fluoride ions, bromide ions, iodide ions, sulfate ions, sulfite ions, phosphate ions, nitrate ions, nitrite ions, methanesulfonate ions, benzenesulfonate ions, toluenesulfonate ions, citrate ions, oxalate ions, malate ions, tartrate ions, maleate ions, fumarate ions, and acetate ions.

Preferred salts include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, sodium bromide, potassium bromide, calcium bromide, magnesium bromide, sodium sulfate, potassium sulfate, sodium nitrate, potassium nitrate, calcium nitrate, magnesium nitrate, sodium acetate, calcium acetate, sodium phosphate, disodium monohydrogen phosphate, monosodium dihydrogen phosphate, sodium phosphate, disodium monohydrogen phosphate, monosodium dihydrogen phosphate, potassium phosphate, dipotassium monohydrogen phosphate, monopotassium dihydrogen phosphate, potassium phosphate, dipotassium monohydrogen phosphate, monopotassium dihydrogen phosphate, etc.

In another embodiment, the solvent of the coagulation bath may be an organic solvent. The organic solvent in the coagulation bath is preferably an organic solvent miscible with water, and examples of the organic solvent include lower alcohols such as ethanol, methanol, propanol, and isopropanol, ketones such as acetone, methyl ethyl ketone, and 4-methyl-2-pentanone (MIBK), ethers such as tetrahydrofuran and dioxane, esters such as propylene carbonate, amides such as dimethylformamide, acetamide, formamide, dimethylacetamide, N-methylpyrrolidone, and 1,3-dimethyl-2-imidazolidinone, glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and glycerin, alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, dimethyl sulfoxide, and acetonitrile. The solvent of the coagulation bath is preferably a water-containing organic solvent. Even when an organic solvent is used as the coagulation bath, salts can be added to the coagulation bath.

The concentration of the salts added to the coagulation bath is preferably 0% by mass or more and 40% by mass or less, preferably 0% by mass or more and 35% by mass or less, and more preferably about 0% by mass or less and 30% by mass or less. The salts are dissolved in the coagulation bath either alone or in combination of two or more types of salts.

There are no particular limitations on the temperature of the coagulation bath, but it is determined by the combination of salts and salt concentrations so that the fibrous composite gel is in a coagulated state in which it can be continuously pulled out of the coagulation bath without loosening. 5°C to 80°C is preferable in terms of ease of temperature control.

The immersion time of the extruded composite gel in the coagulation bath varies depending on the conditions of the coagulation bath, and there are no particular limitations as long as the fibrous composite gel is in a coagulated state in which it can be continuously pulled out of the coagulation bath without loosening. The coagulation bath may be a stationary bath or a flowing bath using a tube, etc.

The fibrous composite gel removed from the coagulation bath can be further immersed in water or the same organic solvent as used in the coagulation bath to wash away surfactants, transition metals, and salts. When transition metals are used, it is preferable to wash using an acid with a pH of 3 or less. There is no particular limit to the temperature of the water or organic solvent in this washing step, but it can be, for example, 5°C to 80°C, and preferably about room temperature. There is also no particular limit to the immersion time, but it can be, for example, 2 hours or more, and preferably 24 hours or more. This water immersion step results in fibers containing carbon nanomaterials from which appropriate amounts of surfactant, or surfactant, transition metal, and salts have been removed.

The fibrous composite gel may be subjected to the next stretching step in a wet state. The stretching is performed between rotating rolls such as Nelson rolls, and stretching is performed by varying the rotation speed. The stretching ratio is preferably about 5% to 500%, more preferably about 10% to 300%. The alignment of the carbon nanomaterial in the fibrous structure in the fiber axis direction and the orientation of the organic polymer are promoted, improving the electrical and mechanical properties.
The stretching ratio is defined by the following formula.
Stretching ratio (%)=[(length after stretching)−(length before stretching)}/(length before stretching)]×100

After stretching, the obtained fiber may be washed with water or the same organic solvent as used in the coagulation bath, if necessary. After washing, the obtained fiber can be dried to obtain a fiber containing a carbon nanomaterial. When drying, the obtained fiber may be heated, if necessary. The heating temperature may be determined according to the type of organic polymer, and is not limited, but when polysaccharides are used, it may be, for example, 100°C to 300°C, or 150°C to 250°C.

Below, the present disclosure will be explained in detail using examples and comparative examples. Note that the present disclosure is not limited to the following examples. The physical properties of the fibrous structures were measured and evaluated as follows.

Measurement and evaluation methods
[Content of CNTs with a diameter of 5 nm or less]
The content of CNTs with a diameter of 5 nm or less in the CNTs was observed at 200,000 to 1,000,000 times magnification, which allows the diameter of a single CNT to be measured by image analysis using a transmission electron microscope. 100 locations where the CNT bundles were loosened and single CNTs were present were selected from the field of view, and the diameters of the 100 CNTs were evaluated using image analysis software. The content (%) of CNTs with a diameter of 5 nm or less was measured by measuring the number of CNTs with a diameter of 5 nm or less. At this time, if a part of a CNT present in a single state in the field of view is visible, it is counted as one, and it is not necessary that both ends (the entire CNT) are visible. In addition, even if two CNTs are recognized in the field of view, they may be connected outside the field of view to form one CNT, in which case they are counted as two.

[Fineness]
The single yarn fineness and the total fineness were measured as follows. That is, the spun fibrous structure was left to stand in an environment of 23°C and 50.5% RH for 24 hours or more, and then a 10 m sample was measured. The weight of the sample was measured using a precision balance (XPE205) manufactured by METTLER TOLEDO. The single yarn fineness and the total fineness were measured by calculating the weight per 10,000 m from the weight.

[Specific Conductivity and Linear Resistance Variation Coefficient]
The specific conductivity was calculated from the resistance value obtained from the current-voltage slope and the weight of the fibrous structure using a four-terminal method. 100 test pieces were taken from the fibrous structure, and repeated measurements were performed using a measuring tool with a fixed terminal distance of 5.6 cm, a potentio/galvanostat (manufactured by Biologic, SP-50), to obtain a resistance value. The linear resistance (resistance per cm) was calculated using the obtained resistance value and the value of the distance between the terminals of the measuring tool, and the reciprocal of the linear resistance was calculated by taking the reciprocal. In addition, the weight of the fibrous structure per 10 m was measured using a precision balance (manufactured by METTLER TOLEDO, XPE205), and the weight per cm was calculated from the weight and length. Finally, the specific conductivity was calculated by dividing the weight per cm from the reciprocal of the linear resistance. On the other hand, in the case of a high fibrous structure with a resistance value of more than 10,000Ω per cm, the resistance value at 1 cm between the terminals was calculated using a resistance meter (HIOKI Corporation, RM3544). For a high fibrous structure with a resistance value of more than 3.5 MΩ per mm, the linear resistance was calculated as 35 MΩ or more, and the specific conductivity was quantified as a value obtained by dividing the reciprocal of the linear resistance of 35 MΩ by the mass per cm. In addition, the linear resistance variation coefficient in the longitudinal direction of the fiber was calculated using the following formula from the arithmetic mean value and unbiased variance of the linear resistance of 100 test pieces obtained as described above.
Coefficient of variation of linear resistance in the longitudinal direction of fiber (%) = (V/E) x 100
V: Square root of the unbiased variance of the linear resistance E: Average value of the linear resistance

[Observation of CNT network structure in fiber cross section]
The cross-sectional structure of the fibrous structure was examined using a scanning electron microscope (Regulus 8220, manufactured by Hitachi High-Tech Corporation, hereinafter also referred to as SEM) to confirm the uniformity of the CNT network structure. The cross-section was exposed by freezing the fibrous structure with liquid nitrogen or the like, and then cutting it with a hammer, blade, or the like.

[Calculation of the ratio of carbon nanomaterial dispersion region in the cross section of the fibrous structure]
The carbon nanomaterial dispersion region is calculated from the scanning electron microscope (SEM) image of the fiber cross section obtained in the previous section. In the region where the carbon nanomaterial is not sufficiently dispersed, charging occurs due to the organic polymer, which is an insulator, and the region appears dark in the electron microscope image. On the other hand, the fiber cross section of the region where the carbon nanomaterial is sufficiently dispersed (carbon nanomaterial dispersion region) appears bright. Therefore, the proportion of the carbon nanomaterial dispersion region can be calculated from the area ratio of the bright part to the fiber cross section area in the electron microscope image. The measurement conditions for the electron microscope image were: no conductive treatment of the cross section, acceleration voltage: 1 to 5 kV, emission current: 20 μA, working distance: 7 to 9 mm, detector: upper detector, measurement magnification: 250 times to 1000 times. The measurement magnification may be appropriately adjusted so that contrast is obtained according to the thickness of the fibrous structure.

The ratio of the carbon nanomaterial dispersion region is calculated from the scanning electron microscope image of the fiber cross section obtained above. OpenCV was used for image processing in calculating the ratio. In order to trim only the fiber cross section from the electron microscope image of the fiber cross section, the Canny method was applied, and then the contour with the largest area was extracted. At that time, the contour was corrected by a closing process to prevent it from being interrupted. (0, 100) was input for (threshold1, threshold2), which are options of the Canny method. After extracting the contour of the fiber cross section, the outer region of the contour was masked with the minimum brightness value in the image for the original electron microscope image, and the circumscribed rectangular region of the contour was trimmed. Then, the trimmed image was subjected to binarization processing by the Otsu method, and the light and dark regions in the fiber cross section generated due to the difference in the content rate of the carbon nanomaterial were distinguished in black and white. Figure 1b is an example of an image obtained by binarizing an electron microscope image of a fiber cross section of an embodiment of the present disclosure, and Figure 2b is an example of an image obtained by binarizing an electron microscope image of a fiber cross section of a comparative example. The number of pixels within the outline of the fiber cross section corresponds to the "area of the fiber cross section," and the number of pixels in the white area after binarization corresponds to the "area of the carbon nanomaterial dispersed area," so the proportion of the carbon nanomaterial dispersed area can be calculated using the following formula.
Percentage of carbon nanomaterial dispersion region (%) = 100 x (area of carbon nanomaterial dispersion region) / (area of fiber cross section)
The above calculation of the proportion of the carbon nanomaterial-dispersed region was carried out for 10 test pieces, and the average value was taken as the proportion of the carbon nanomaterial-dispersed region.

[Measurement of carbon nanomaterial residual index and calculation of carbon nanomaterial content]
The fibrous structure was dried in an oven (AVO-250SB, AS ONE Corporation) at 105°C in air for 5 hours, and then its weight was measured using a precision balance (XPE205, METTLER TOLEDO). After the weight was measured, the structure was immersed in 95% sulfuric acid in air at room temperature for 72 hours. After the sulfuric acid immersion, water replacement and water immersion were performed, and the structure was dried in an oven at 105°C in air for 5 hours, and the weight of the fibrous structure was measured. The weight of the fibrous mulberry after sulfuric acid immersion was divided by the weight of the fibrous structure before sulfuric acid immersion, and the result was multiplied by 100 to calculate the carbon nanomaterial residual index. The carbon nanomaterial content was calculated using the following formula:
Carbon nanomaterial content (mass%) = carbon nanomaterial residual index × 0.71
It is defined by:

[Breaking strength and elongation]
The breaking strength was measured in accordance with the test method for tensile strength and elongation of JIS L 1013. More specifically, stress-strain measurement was performed, and the strength (cN/dtex) was calculated from the stress at the cutting position and the fineness. The elongation is the elongation (%) at break.

Examples and Comparative Examples
[Example 1]
5 g of Tuball-CNT (manufactured by OCSiAl, Tuball, hereinafter also referred to as Tuball-CNT) and 10 g of sodium taurodeoxycholate (manufactured by Sigma-Aldrich, also referred to as TDOC) as a dispersant were added to 985 g of water, and dispersion was performed for 10 hours using an in-line mixer (manufactured by IKA, magic LAB). Then, degassing was performed for 10 minutes using a planetary centrifugal mixer (manufactured by Thinky Corporation, Awatori Rentaro ARE-310) to obtain a Tuball-CNT dispersion liquid with a weight concentration of Tuball-CNT of 0.5% by mass. Copper hydroxide was dissolved in a 6.1% by mass ammonia aqueous solution so that the copper component was 3.6% by mass, and cellulose was added thereto so that the content was 10.15% by mass, and kneaded to prepare a cuprammonium cellulose solution.

After purging the inside of a flask equipped with a stirring unit with nitrogen to bring the oxygen concentration to 992 ppm, the above-mentioned Tuball-CNT dispersion and cuprammonium cellulose solution were mixed in a mass ratio (mass of Tuball-CNT dispersion:mass of cuprammonium cellulose solution) of 1:4, with a Tuball-CNT concentration of 1.22 mass% relative to cellulose, and then poured into the flask. The flask was adjusted to -0.08 MPa and 30°C, and the mixture was kneaded with a helical ribbon impeller for 5 hours, then left to stand for 10 hours to degas, yielding a uniform Tuball-CNT/cuprammonium cellulose dispersion.

This Tuball-CNT/cuprammonium cellulose dispersion was used for wet spinning. The spinneret had a hole diameter of 0.2 mm and 10 holes, and the dispersion was discharged in the direction of gravity at a discharge rate of 0.72 ml/min while the spinneret was immersed in a coagulation bath filled with 40°C warm water. After coagulation, the yarn was turned using a rotating roll in the warm water, and then pulled out of the water bath using a rotating roll running at 9 m/min. A cleaning process was performed by running the yarn through a 2.0% by mass sulfuric acid bath at 40°C and then a water bath at 40°C. The obtained coagulated yarn was then dried using a dryer at 200°C and wound up at a speed of 10 m/min to obtain a Tuball-CNT/cellulose composite fiber.

[Example 2]
Dispersion was performed in the same manner as in Example 1, except that 10 g of Tuball-CNT and 20 g of TDOC were added to 970 g of water, to obtain a Tuball-CNT dispersion with a weight concentration of Tuball-CNT of 1.0 mass%. The Tuball-CNT dispersion and the cuprammonium cellulose solution were blended so that the Tuball-CNT concentration relative to cellulose was 2.40 mass%, and kneaded in the same manner as in Example 1 to obtain a Tuball-CNT dispersion/cuprammonium cellulose dispersion. Spinning was performed under the same conditions as in Example 1 to obtain a Tuball-CNT/cellulose composite fiber.

[Example 3]
A Tuball-CNT dispersion concentrated to 2.0% by mass was blended with a cuprammonium cellulose solution so that the Tuball-CNT concentration relative to the cellulose in Example 2 was 4.69% by mass, and the mixture was kneaded in the same manner as in Example 1. Except for this, a Tuball-CNT/cellulose composite fiber was obtained in the same manner as in Example 1.

[Example 4]
A Tuball-CNT dispersion concentrated to 3.0% by mass so that the Tuball-CNT concentration relative to the cellulose in Example 2 was 16.46% by mass was blended with a cuprammonium cellulose solution and kneaded in the same manner as in Example 1 to obtain a Tuball-CNT/cuprammonium cellulose dispersion. Spinning was performed under the same conditions as in Example 1 to obtain a Tuball-CNT/cellulose composite fiber.

[Example 5]
A Tuball-CNT dispersion concentrated to 3.0% by mass so that the Tuball-CNT concentration relative to the cellulose in Example 2 was 22.81% by mass was blended with a cuprammonium cellulose solution and kneaded in the same manner as in Example 1 to obtain a Tuball-CNT/cuprammonium cellulose dispersion. Spinning was performed under the same conditions as in Example 1 to obtain a Tuball-CNT/cellulose composite fiber.

[Example 6]
A Tuball-CNT dispersion concentrated to 3.0% by mass so that the Tuball-CNT concentration relative to the cellulose in Example 2 was 28.27% by mass was blended with a cuprammonium cellulose solution and kneaded in the same manner as in Example 1 to obtain a Tuball-CNT/cuprammonium cellulose dispersion. Spinning was performed under the same conditions as in Example 1 to obtain a Tuball-CNT/cellulose composite fiber.

[Example 7]
A Tuball-CNT dispersion concentrated to 3.0% by mass so that the Tuball-CNT concentration relative to the cellulose in Example 2 was 37.15% by mass was blended with a cuprammonium cellulose solution and kneaded in the same manner as in Example 1 to obtain a Tuball-CNT/cuprammonium cellulose dispersion. Spinning was performed under the same conditions as in Example 1 to obtain a Tuball-CNT/cellulose composite fiber.

[Example 8]
Zeonano-CNT/cellulose composite fibers were obtained in the same manner as in Example 1, except that the raw material used was changed to CNT produced by the super-growth method (Zeonano, manufactured by Zeon Corporation; hereinafter, also referred to as Zeonano-CNT) and the concentration of Zeonano-CNT relative to cellulose was changed to 0.54 mass%.

[Example 9]
A Zeonano-CNT/cuprammonium cellulose dispersion was obtained under the same conditions as in Example 1, except that the raw material used was changed to Zeonano-CNT. Spinning was performed under the same conditions as in Example 1 to obtain Zeonano-CNT/cellulose composite fibers.

[Example 10]
Except for changing the raw material used to CNTs produced by the improved direct injection pyrolysis synthesis method (eDIPS method) (manufactured by Meijo Nano Carbon Co., Ltd., EC-DX2P, hereinafter also referred to as eDIPS-CNT), an eDIPS-CNT/cuprammonium cellulose dispersion was obtained under the same conditions as in Example 1. Spinning was performed under the same conditions as in Example 1 to obtain eDIPS-CNT/cellulose composite fibers.

[Example 11]
Except for changing the raw material to eDIPS-CNT, an eDIPS-CNT/cuprammonium cellulose dispersion was obtained under the same conditions as in Example 2. Spinning was performed under the same conditions as in Example 1 to obtain an eDIPS-CNT/cellulose composite fiber.

[Example 12]
The raw material used was changed to eDIPS-CNT, and the eDIPS-CNT dispersion concentrated to 1.0% by mass was blended with a cuprammonium cellulose solution so that the eDIPS-CNT concentration relative to cellulose was 49.63% by mass, and kneaded under the same conditions as in Example 1 to obtain an eDIPS-CNT/cuprammonium cellulose dispersion. The obtained eDIPS-CNT/cuprammonium cellulose dispersion was packed into a syringe, and then coagulated into a filamentous form by discharging it laterally into pure water at 40 ° C. at a discharge rate of 1.10 ml/min using a high-pressure microfeeder (manufactured by Sanyo Technos Co., Ltd., JP-HR) equipped with an injection spinning nozzle with an inner diameter of 0.3 mm and one hole. The speed of the winding device was set at a rotation speed of 12 m/min so that the coagulated yarn did not loosen, and the coagulated yarn was pulled up from the pure water at 40 ° C. and wound up. Next, the coagulated yarn was immersed in 5.0% by mass dilute sulfuric acid using a feed roller to remove the copper components, and then immersed in a water tank, and pulled out of the water using a winding device and dried to obtain an eDIPS-CNT/cellulose composite fiber.

[Example 13]
Sodium carboxymethylcellulose (manufactured by Fujifilm Wako Pure Chemical Industries, product code: 039-01335, hereinafter also referred to as CMC) was dissolved in pure water to a concentration of 10.0% by mass to prepare a 10.0% by mass CMC solution. A 1.0% by mass eDIPS-CNT dispersion prepared in the same manner as in Example 1 was blended into the 10.0% by mass CMC aqueous solution so that the eDIPS-CNT concentration relative to the CMC was 23.08% by mass, and the mixture was kneaded under the same conditions as in Example 1 to obtain an eDIPS-CNT/CMC dispersion.

After filling a syringe with this eDIPS-CNT/CMC dispersion, a high-pressure microfeeder (JP-HR, manufactured by Sanyo Technos Co., Ltd.) equipped with a one-hole injection spinning nozzle with an inner diameter of 0.3 mm was used to eject the dispersion laterally into ethanol at an ejection rate of 1.10 ml/min, solidifying it into a filamentous form. The filamentous filament was then pulled out of the ethanol and dried at a winding speed of 12 m/min to prevent it from loosening, yielding an eDIPS-CNT/CMC composite fiber.

[Example 14]
A 10.0 mass% CMC aqueous solution and a 1.0 mass% eDIPS-CNT dispersion were blended and kneaded so that the eDIPS-CNT concentration relative to the CMC in Example 13 was 37.50 mass%, and then the mixture was coagulated into a thread-like form by extruding laterally into ethanol at a discharge rate of 0.90 ml/min. The coagulated thread was then pulled up from the ethanol at a winding speed of 12 m/min so as not to loosen, and dried to obtain an eDIPS-CNT/CMC composite fiber.

[Example 15]
A cuprammonium curdlan solution was prepared in the same manner as in Example 1, except that the organic polymer was curdlan (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.). The eDIPS-CNT dispersion concentrated to 3.0 mass% was kneaded in the same manner as in Example 1 to obtain an eDIPS-CNT/cellulose dispersion. The obtained eDIPS-CNT dispersion was spun under the same conditions as in Example 12, except that the discharge speed was 1.30 ml/min and the take-up speed was 10 m/min, to obtain an eDIPS-CNT/cellulose composite fiber.

[Example 16]
Sodium alginate (Nacalai Tesque, Inc., 300 cps) was dissolved in pure water to a concentration of 10.0% by mass to prepare a 10.0% by mass sodium alginate solution. A 1.0% by mass eDIPS-CNT dispersion prepared in the same manner as in Example 1 was kneaded with the 10.0% by mass sodium alginate solution for 5 minutes using a planetary centrifugal mixer (Thinky Corporation, Awatori Rentaro ARE-310) so that the eDIPS-CNT concentration relative to the sodium alginate was 9.09% by mass, thereby obtaining an eDIPS-CNT/sodium alginate solution.

After filling a syringe with this eDIPS-CNT/sodium alginate solution, a high-pressure microfeeder (JP-HR, manufactured by Sanyo Technos Co., Ltd.) equipped with a one-hole injection spinning nozzle with an inner diameter of 0.3 mm was used to eject the solution laterally into a 5% by mass aqueous calcium chloride solution at an ejection speed of 1.10 m/min, causing it to solidify into a filamentous form. The speed of the winding device was set at a rotation speed of 10 m/min so as not to loosen the solidified thread, and the solidified thread was pulled up from the 5% by mass aqueous calcium chloride solution and wound up. The solidified thread was then immersed in pure water using a feed roller to remove the calcium chloride component, and then pulled up from the water using a winding device and dried, yielding an eDIPS-CNT/alginate composite fiber.

[Example 17]
The same procedure as in Example 16 was carried out except that the eDIPS-CNT was kneaded so that the concentration of the eDIPS-CNT relative to the sodium alginate in Example 16 was 16.67 mass %, to obtain eDIPS-CNT/alginic acid composite fibers.

[Example 18]
The same procedure as in Example 16 was carried out except that the eDIPS-CNT concentration relative to the sodium alginate in Example 16 was 23.08 mass %, and eDIPS-CNT/alginic acid composite fibers were obtained.

[Example 19]
Except for changing the dispersant in Example 7 from TDOC to sodium deoxycholate (Sigma-Aldrich, also referred to as DOC) and blending so that the Tuball-CNT concentration relative to the cellulose was 22.81% by mass, kneading was performed in the same manner as in Example 1 to obtain a Tuball-CNT/cuprammonium cellulose dispersion. The obtained Tuball-CNT/cuprammonium cellulose dispersion was spun under the same conditions as in Example 12 to obtain a Tuball-CNT/cellulose composite fiber.

[Example 20]
Tuball-CNT/cellulose composite fibers were obtained under the same conditions as in Example 19, except that the coagulation bath in Example 19 was changed from 40° C. pure water to ethanol.

[Example 21]
Tuball-CNT/cellulose composite fibers were obtained under the same conditions as in Example 19, except that the coagulation bath in Example 19 was changed from 40° C. pure water to dimethyl sulfoxide.

[Example 22]
Tuball-CNT/cellulose composite fibers were obtained under the same conditions as in Example 19, except that the coagulation bath in Example 19 was changed from 40° C. pure water to 1,3-dimethyl-2-imidazolidinone.

[Example 23]
Except for changing the dispersant in Example 7 from TDOC to DOC and blending so that the Tuball-CNT concentration relative to the cellulose was 37.15% by mass, kneading was performed in the same manner as in Example 1 to obtain a Tuball-CNT/cuprammonium cellulose dispersion. The obtained Tuball-CNT/cuprammonium cellulose dispersion was spun under the same conditions as in Example 19 to obtain a Tuball-CNT/cellulose composite fiber.

[Example 24]
Except for changing the raw material of Example 7 to multi-walled CNT Jeno6A (manufactured by JEIO, hereinafter also referred to as Jeno6A-CNT) and blending so that the concentration of Jeno6A-CNT relative to cellulose was 22.81% by mass, kneading was performed in the same manner as in Example 1 to obtain a Jeno6A-CNT/cuprammonium cellulose dispersion. The obtained Jeno6A-CNT/cuprammonium cellulose dispersion was spun under the same conditions as in Example 19 to obtain a Jeno6A-CNT/cellulose composite fiber.

[Comparative Example 1]
A Tuball-CNT dispersion and a cuprammonium cellulose solution were obtained under the same conditions as in Example 2. After the oxygen concentration was adjusted to 992 ppm by purging the inside of a flask equipped with a stirring unit with nitrogen, the obtained Tuball-CNT dispersion and the cuprammonium cellulose solution were mixed so that the Tuball-CNT concentration relative to cellulose was 2.40 mass% and charged into the flask. The flask was adjusted to -1.5 MPa and 30°C, and the mixture was kneaded for 5 hours with a helical ribbon blade, and then left to stand for 10 hours for degassing to obtain a Tuball-CNT/cuprammonium cellulose dispersion. Spinning was performed under the same conditions as in Example 1 to obtain a Tuball-CNT/cellulose composite fiber.

[Comparative Example 2]
A Tuball-CNT dispersion and a cuprammonium cellulose solution were obtained under the same conditions as in Example 2. After the oxygen concentration was adjusted to 992 ppm by purging the inside of a flask equipped with a stirring unit with nitrogen, the obtained Tuball-CNT dispersion and the cuprammonium cellulose solution were mixed so that the Tuball-CNT concentration relative to cellulose was 2.40 mass% and charged into the flask. The flask was adjusted to -0.08 MPa and 5°C, and the mixture was kneaded for 5 hours with a helical ribbon blade, and then left to stand for 10 hours for degassing to obtain a Tuball-CNT/cuprammonium cellulose dispersion. Spinning was performed under the same conditions as in Example 1 to obtain a Tuball-CNT/cellulose composite fiber.

[Comparative Example 3]
A Tuball-CNT dispersion and a cuprammonium cellulose solution were obtained under the same conditions as in Example 2. After the oxygen concentration was adjusted to 992 ppm by purging the inside of a flask equipped with a stirring unit with nitrogen, the obtained Tuball-CNT dispersion and the cuprammonium cellulose solution were mixed so that the Tuball-CNT concentration relative to cellulose was 2.40 mass% and charged into the flask. The flask was adjusted to -0.08 MPa and 60°C, and the mixture was kneaded for 5 hours with a helical ribbon blade, and then left to stand for 10 hours for degassing to obtain a Tuball-CNT/cuprammonium cellulose dispersion. Spinning was performed under the same conditions as in Example 1 to obtain a Tuball-CNT/cellulose composite fiber.

[Comparative Example 4]
A dispersion was produced and spun under the same conditions as in Comparative Example 1, except that the step of mixing the Tuball-CNT dispersion and the cuprammonium cellulose solution was carried out in air, to obtain a Tuball-CNT/cellulose composite fiber.

[Comparative Example 5]
A dispersion was produced and spun under the same conditions as in Comparative Example 3, except that the raw material used was changed to eDIPS-CNT, to obtain eDIPS-CNT/cellulose composite fibers.

[Comparative Example 6]
Except for the fact that the kneading conditions were the same as those in Comparative Example 2, the production of a dispersion and spinning were carried out under the same conditions as those in Example 12 to obtain eDIPS-CNT/cellulose composite fibers.

[Comparative Example 7]
50% by mass 4-methylmorpholine N-oxide (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter also referred to as NMMO) was concentrated under reduced pressure to prepare an aqueous solution containing 70% by mass of NMMO. A 1% by mass eDIPS-CNT dispersion prepared in the same manner as in Example 10 and an aqueous solution containing 70% by mass of NMMO were kneaded therein at a weight ratio of 1:4 to prepare a mixed solution of 0.2% by mass eDIPS-CNT / 56% by mass NMMO / 43.8% by mass water. Cellulose was added therein and concentrated to finally obtain a mixed solution of 0.3% by mass eDIPS-CNT / 5% by mass cellulose / 85% by mass NMMO / 9.7% by mass water.

After filling a syringe with this mixed solution of 0.3% by mass eDIPS-CNT/5% by mass cellulose/85% by mass NMMO/9.7% by mass water, a high-pressure microfeeder (JP-HR, manufactured by Sanyo Technos Co., Ltd.) equipped with a 1-hole injection spinning nozzle with an inner diameter of 0.3 mm was used to eject the solution laterally into a 30% by mass NMMO aqueous solution at an ejection rate of 1.00 ml/min, allowing it to solidify into a filament. The speed of the winding device was set at a rotation speed of 8 m/min so that the solidified yarn would not loosen, and the solidified yarn was pulled up from the 30% by mass NMMO aqueous solution and wound up. The solidified yarn was then immersed in pure water using a feed roller to remove the NMMO component, and the yarn was then pulled up from the water using a winding device and dried to obtain an eDIPS-CNT/cellulose composite fiber.

[Comparative Example 8]
To 1-ethyl-3-methylimidazolium diethyl phosphate (manufactured by Tokyo Chemical Industry Co., Ltd., hereinafter also referred to as EMIMDEP), which is an ionic liquid, eDIPS-CNT was added so that the CNT concentration was 0.20 mass%, and cellulose was added so that the cellulose concentration was 5.0 mass%, and the mixture was kneaded for 30 minutes or more in an agate mortar to obtain a 0.2 mass% eDIPS-CNT/5.0 mass% cellulose/EMIMDEP solution.

After filling a syringe with this 0.2% by mass eDIPS-CNT/5.0% by mass cellulose/EMIMDEP solution, a high-pressure microfeeder (JP-HR, manufactured by Sanyo Technos Co., Ltd.) equipped with a 1-hole injection spinning nozzle with an inner diameter of 0.3 mm was used to eject the solution laterally into pure water at a discharge speed of 0.90 m/min, causing it to solidify into a thread-like shape. The speed of the winding device was set at a rotation speed of 15 m/min so as not to loosen the solidified thread, and the solidified thread was pulled out of the pure water and dried to obtain an eDIPS-CNT/cellulose composite fiber.

[Comparative Example 9]
To dimethyl sulfoxide (Kanto Chemical Co., Ltd., hereinafter also referred to as DMSO), eDIPS-CNT was added so that the CNT concentration was 0.2% by mass, and curdlan (FUJIFILM Wako Pure Chemical Industries, Ltd.) was added so that the concentration was 3 wt %, and the mixture was kneaded in an agate mortar for 30 minutes or more to obtain a 0.2% by mass eDIPS-CNT/3% by mass curdlan/DMSO solution.

The 0.2% by mass eDIPS-CNT/3% by mass curdlan/DMSO solution was loaded into a syringe, and a one-hole injection spinning nozzle with an inner diameter of 0.3 mm was attached. Then, using a high-pressure microfeeder (JP-HR, manufactured by Sanyo Technos Co., Ltd.), the solution was discharged laterally into pure water at a discharge speed of 1.3 m/min to solidify it into a thread-like shape. The speed of the winding device was set at a rotation speed of 7 m/min so that the solidified thread would not loosen, and the solidified thread was pulled out of the pure water and dried to obtain an eDIPS-CNT/curdlan composite fiber.

The physical properties of the composite fibers obtained in the examples and comparative examples are shown in Tables 1 to 4 below. In Tables 3 and 4, the symbols "-" for strength and elongation indicate that the values were not measured.

Electron microscope images showing an example of a uniform CNT network structure in the cross section of a fibrous structure (fiber) are shown in Figures 1 and 2, respectively. Figure 1A is an electron microscope image of the entire cross section of a fibrous structure of an embodiment of the present disclosure, and Figure 2A is an electron microscope image of the entire cross section of a fibrous structure of a comparative example. Figures 1B and 2B are images obtained by binarizing the electron microscope images of Figures 1A and 2A. As is clear from Figures 1 and 2, the fibrous structure of the present disclosure has a uniform CNT network structure, whereas the fibrous structure of the comparative example has a non-uniform distribution of carbon nanomaterial non-dispersed regions (10) where there is relatively little or no carbon nanomaterial, and carbon nanomaterial dispersed regions (20) where there is relatively more carbon nanomaterial than the carbon nanomaterial non-dispersed regions (10).

[Calculation of carbon nanomaterial residual index]
The composite fibers produced in Examples 1, 2, 3, 4, 5, 7, and 11 were dried in air at 105°C for 5 hours, their weights were measured, and then they were immersed in 95% sulfuric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., chemical code: 192-04696) for 72 hours. After immersion in 95% sulfuric acid, they were washed with water and then dried in air at 105°C for 5 hours, and their weights after drying were measured. The carbon nanomaterial residual index was calculated from the weights before and after immersion in sulfuric acid.

Table 5 shows the relationship between the CNT concentration calculated from the CNT loading amount and the carbon nanomaterial residual index. As a result, it was found that there is a correlation between the CNT concentration and the carbon nanomaterial residual index, and that the mass percentage of CNT relative to the total amount of fiber can be calculated by multiplying the carbon nanomaterial residual index by 0.71.

The fibrous structure disclosed herein has a wide range of electrical conductivity and is uniform in the longitudinal direction, making it suitable for use as electrodes for acquiring bioelectric potentials such as electrocardiograms, electromyograms, and electroencephalograms in smart textiles, electrodes for electrical stimulation, wiring for wearables, heaters, stretch sensors, temperature and humidity sensors, electromagnetic shielding, antistatic, filters, etc.

10 Carbon nano material non-dispersed region 20 Carbon nano material dispersed region

Claims

A fibrous structure comprising an organic polymer and a carbon nanomaterial dispersed in the organic polymer,
The carbon nanomaterial is at least one selected from the group consisting of carbon nanotubes, graphene, and graphene oxide;
The content of the carbon nanomaterial is 0.05% by mass or more and 50% by mass or less based on the total mass of the fibrous structure,
A fibrous structure, wherein the cross section of the fibrous structure is observed using a scanning electron microscope (SEM) under the following measurement conditions, and when the observed image is binarized using the Otsu method, the proportion of carbon nanomaterial dispersion regions displayed as bright areas is 85% or more of the entire cross section of the fibrous structure, and the measurement conditions are as follows: no conductive treatment of the cross section, acceleration voltage: 1 to 5 kV, and detector: upper detector.
The fibrous structure of claim 1, in which the ratio of the area displayed as the bright portion is 95% or more.
A fibrous structure comprising an organic polymer and a carbon nanomaterial dispersed in the organic polymer,
The carbon nanomaterial is at least one selected from the group consisting of carbon nanotubes, graphene, and graphene oxide;
The content of the carbon nanomaterial is 0.05% by mass or more and 50% by mass or less based on the total mass of the fibrous structure,
A fibrous structure having a specific conductivity of 0.01 Scm 2 /g or more and 2500 Scm 2 /g or less, and a linear resistance variation coefficient per cm in the longitudinal direction of 10% or less.
3. The fibrous structure according to claim 1 or 2, which has a specific conductivity of 0.01 Scm 2 /g or more and 2500 Scm 2 /g or less, and a linear resistance variation coefficient per cm in the longitudinal direction of 10% or less.
The fibrous structure according to any one of claims 1 to 3, wherein the carbon nanomaterial is a carbon nanotube.
The fibrous structure according to any one of claims 1 to 3, wherein the organic polymer is a polysaccharide.
The fibrous structure according to any one of claims 1 to 3, wherein the carbon nanomaterial is a carbon nanotube and the organic polymer is a polysaccharide.
A method for producing a fibrous structure, the method comprising the steps of:
A step of preparing a carbon nanomaterial dispersion in which a carbon nanomaterial is dispersed in water;
Providing an organic polymer solution;
mixing the carbon nanomaterial dispersion liquid and the organic polymer solution at an oxygen concentration of 1000 ppm or less, a reduced pressure of −0.1 MPa to −0.01 MPa, and a liquid temperature of 20° C. to 40° C. to prepare a mixed dispersion liquid containing a carbon nanomaterial and an organic polymer;
a step of wet-spinning the obtained mixed dispersion in a liquid, and removing the solvent component by washing with an acid and water to obtain an organic polymer fiber containing a carbon nanomaterial;
drying the obtained organic polymer fiber to obtain a fibrous structure;
A method for producing a fibrous structure comprising the steps of:
The method for producing a fibrous structure according to claim 8, wherein in the step of preparing the mixed dispersion, the mass ratio of the carbon nanomaterial dispersion to the organic polymer solution (mass of the carbon nanomaterial dispersion: mass of the organic polymer solution) is 0.1:1 to 15:1.
The method for producing a fibrous structure according to claim 8 or 9, wherein the cross section of the fibrous structure is observed using a scanning electron microscope (SEM) under the following measurement conditions, and when the observed image is binarized by the Otsu method, the ratio of the area displayed as a bright area is 85% or more of the entire cross section of the fibrous structure, and the measurement conditions are: cross section conductive treatment: none, acceleration voltage: 1 to 5 kV, and detector: upper detector.
10. The method for producing a fibrous structure according to claim 8, wherein the fibrous structure has a specific conductivity of 0.01 Scm2 /g to 2500 Scm2 /g and a linear resistance variation coefficient per cm in the longitudinal direction of 10% or less.