Wet-spun fibers and their manufacturing method, and submicron fibrils and their manufacturing method

Abstract

To provide wet-spinning fibers of β-1,3-glucan containing β-1,3-glucan as the sole constituent molecule and a method for their production, and submicron fibrils and a method for their production.SOLUTION: Wet-spinning fibers containing only β-1,3-glucan represented by a specific chemical formula (1) as a constituent molecule. A method for producing wet-spinning fibers, comprising preparing viscose from a raw material β-1,3-glucan represented by a specific chemical formula (1) (I), or preparing spun fibers from the raw material β-1,3-glucan by a method (II) of dissolving the raw material β-1,3-glucan in a good solvent.SELECTED DRAWING: Figure 5B

Description

[Technical Field]

[0001] The present invention relates to wet-spun fibers and methods for producing the same, and to submicron fibrils and methods for producing the same. [Background technology]

[0002] Rayon, known as a wet-spun natural polymer fiber, is generally a regenerated fiber made primarily from cellulose, a plant-derived polysaccharide composed of β-1,4-glucan. As spun fibers made primarily from natural polysaccharides other than cellulose, for example, Non-Patent Documents 1 and 2 propose spun fibers made primarily from chitin or chitosan derivatives.

[0003] Paramylon, a storage polysaccharide produced by Euglena, is a β-1,3-glucan with a structure in which glucose units are linked by β-1,3 bonds. Paramylon is a polysaccharide produced by Euglena (algae), which is both an autotrophic and heterotrophic organism, and has attracted attention as a highly sustainable material. Paramylon has a unique helical structure, and if spun fibers containing only paramylon as a constituent molecule can be obtained, it is expected that they will become natural fibers that can exhibit various properties derived from the helical structure (e.g., high moisture absorption rate, etc.).

[0004] Paramylon is extracted from Euglena cells as particles several micrometers in diameter. To process paramylon into various materials, the particles must first be dissolved and then processed into the desired shape. However, paramylon particles are not soluble in water or common organic solvents, making processing extremely difficult.

[0005] Patent Document 1 proposes a method for preparing paramylon-containing cellulose fibers by embedding paramylon particles in viscose, which is a cellulose derivative dissolved in an alkaline aqueous solution, and then wet-spinning the resulting material. However, the amount of paramylon contained in the wet-spun fibers in Patent Document 1 is approximately 0.5 to 10% by weight, and no wet-spun fibers containing 100% paramylon have been reported. Therefore, no evaluation has been made of the presence or absence of the above-mentioned properties that are expected to be exhibited when only paramylon is spun into fibers.

[0006] One known method for using paramylon as a fiber raw material is to chemically modify and dissolve it. The present inventors have previously investigated a method in which paramylon is acetylated to prepare acetylated paramylon, which is then melt-spun (Non-Patent Document 3). Wet-spun fibers of acetylated paramylon, a semi-synthetic fiber, are presumed to be biodegradable, but because the structure of the acetylated paramylon is different from that of natural paramylon (β-1,3-glucan), they cannot be considered natural fibers. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 6654264 [Patent Document 2] Japanese Patent Publication No. 2021-036039 [Patent Document 3] Japanese Patent Publication No. 2020-090744 [Non-Patent Document 1] J.Appl.Polym.Sci.,110,1208(2008). [Non-patent document 2] Carbohydr.Polym.,47,121(2002). [Non-patent document 3] Heliyon,5(11),e02843(2019). Summary of the Invention [Problem to be solved by the invention]

[0008] As a result of extensive research, the present inventors have found that wet-spun fibers containing β-1,3-glucan as the sole constituent molecule can be obtained by either chemically modifying β-1,3-glucan to prepare viscose, extruding the viscose from a nozzle into a coagulating solution, and wet-spinning while regenerating the β-1,3-glucan, or by wet-spinning a dope solution in which β-1,3-glucan is dissolved in a good solvent and extruding the dope from a nozzle into a coagulating solution. Surprisingly, they have also found that submicron fibrils containing only β-1,3-glucan as the sole constituent molecule can be prepared by mechanically defibrating the resulting wet-spun fibers in water under conditions easier than those for rayon.

[0009] Small fibers (fibrils) with a fiber diameter of less than 1 μm (submicron) are known to have a large specific surface area and excellent properties as reinforcing fillers. However, because cellulose materials are strong materials, cellulose fibrils cannot be obtained by directly mechanically defibrating rayon. In contrast, Patent Documents 2 and 3 describe a method for producing cellulose fine fibers by the following steps: (1) preparing alkali cellulose from pulp (containing cellulose), (2) reacting alkali cellulose with carbon disulfide to prepare cellulose xanthate, (3) dispersing the cellulose xanthate in water and homogenizing it to prepare cellulose xanthate fine fibers (cellulose xanthate nanofibers), and (4) treating the resulting cellulose xanthate nanofibers with sulfuric acid to obtain regenerated cellulose nanofibers. However, this method still requires three steps: chemical modification of rayon, defibration, and regeneration. The inventors of the present invention have found that submicron fibrils composed solely of β-1,3-glucan can be prepared by subjecting the above-mentioned wet-spun fibers to a defibration treatment in water.

[0010] That is, an object of the present invention is to provide wet-spun β-1,3-glucan fibers containing β-1,3-glucan as the only constituent molecule and a method for producing the same, as well as submicron fibrils and a method for producing the same. [Means for solving the problem]

[0011] The present invention has the following aspects. [1] A wet-spun fiber containing only β-1,3-glucan represented by the following chemical formula (1) as a constituent molecule. [ka] (In chemical formula (1), n ​​represents an integer of 60 to 3,000.) [2] The wet-spun fiber according to [1], wherein the β-1,3-glucan contains regenerated paramylon. [3] The wet-spun fiber according to [1], wherein the β-1,3-glucan contains purified paramylon. [4] The wet-spun fiber according to [1] or [2], wherein the moisture absorption rate of the wet-spun fiber at a temperature of 20°C and a humidity of 65% is greater than 11%. [5] A wet-spun fiber according to any one of [1] to [4], wherein the monofilament of the wet-spun fiber is an aggregate of submicron fibrils containing only the β-1,3-glucan as a constituent molecule. [6] A method for producing a wet-spun fiber according to any one of [1] to [5], comprising preparing a spun fiber from a raw material β-1,3-glucan by a method (I) of preparing viscose from the raw material β-1,3-glucan represented by the following chemical formula (1), or by a method (II) of dissolving the raw material β-1,3-glucan in a good solvent. [ka] (In chemical formula (1), n ​​represents an integer of 60 to 3,000.) [7] The method (I) comprises (i) introducing xanthate groups into the raw material β-1,3-glucan in an alkaline aqueous solution to prepare viscose, and (ii) extruding the viscose through a nozzle into a coagulation liquid to remove the xanthate groups and obtain spun β-1,3-glucan fibers. [6] The manufacturing method described in. [8] The manufacturing method described in [6], wherein the method (II) comprises extruding a dope solution obtained by dissolving the raw material β-1,3-glucan in a good solvent containing an aprotic solvent through a nozzle into a coagulation liquid to obtain spun fibers of β-1,3-glucan. [9] The method according to any one of [6] to [8], wherein the steps (I) and (II) comprise immersing the obtained spun fibers in alcohol to dehydrate them.

[10] A manufacturing method according to any one of [6] to [9], wherein the raw material β-1,3-glucan contains paramylon.

[11] A compound for producing wet-spun fibers according to any one of [1] to [5], wherein the compound is a xanthate group-containing β-1,3-glucan represented by the following chemical formula (2): [ka] (In chemical formula (2), R is hydrogen or C(=S)S - Na + and at least one R is C(=S)S - Na + where n represents an integer of 60 to 3,000.

[12] A method for producing a compound for producing wet-spun fibers according to

[11] , comprising introducing a xanthate group into a raw material β-1,3-glucan represented by the following chemical formula (1) in an alkaline aqueous solution. [ka] (In chemical formula (1), n ​​represents an integer of 60 to 3,000.)

[13] The manufacturing method described in

[12] , wherein the raw material β-1,3-glucan contains paramylon.

[14] Submicron fibrils containing only β-1,3-glucan represented by the following chemical formula (1) as constituent molecules. [ka] (In chemical formula (1), n ​​represents an integer of 60 to 3,000.)

[15] The submicron fibrils described in

[14] , wherein the β-1,3-glucan contains at least one paramylon selected from purified paramylon and regenerated paramylon.

[16] A method for producing submicron fibrils according to

[14] or

[15] , comprising subjecting the wet-spun fibers according to any one of [1] to [5] to a fiber defibration treatment in water. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide wet-spun β-1,3-glucan fibers containing β-1,3-glucan as the only constituent molecule and a method for producing the same, as well as submicron fibrils and a method for producing the same. [Brief explanation of the drawings]

[0013] [Figure 1A] 1 is a micrograph showing an overall view of wet-spun fiber 1 produced by method (I). [Figure 1B] 1 is a scanning electron microscope photograph of wet-spun fiber 1. [Figure 1C] This is an enlarged image of Figure 1B. [Figure 2A] 1 is a bright-field micrograph showing an overall view of wet-spun fiber 2 produced by method (II). [Figure 2B] 1 is a scanning electron microscope photograph of wet-spun fiber 2. [Figure 3A] 1 is a bright-field micrograph showing an overall view of wet-spun fiber 3 produced by method (II). [Figure 3B] 1 is a scanning electron microscope photograph of wet-spun fiber 3. [Figure 4A]1 is a bright-field micrograph showing an overall view of wet-spun fiber 4 produced by method (II). [Figure 4B] 1 is a scanning electron microscope photograph of wet-spun fiber 4. [Figure 5A] 1 is a scanning electron micrograph showing one embodiment of a wet-spun fiber having a peach skin on the surface. [Figure 5B] 1 is a scanning electron micrograph showing one embodiment of a porous fiber. [Figure 5C] FIG. 5B is an enlarged view of FIG. 5B. [Figure 6] 1 is a scanning electron microscope photograph showing the state of wet-spun fiber 1 after defibration treatment for 20 minutes. [Figure 7A] 1 is a scanning electron microscope photograph showing the state of wet-spun fiber 2 after defibration treatment for 3 minutes. [Figure 7B] 1 is a scanning electron microscope photograph showing the state of wet-spun fiber 2 after defibration treatment for 15 minutes. [Figure 7C] 1 is a scanning electron microscope photograph showing the state of wet-spun fiber 2 after defibration treatment for 60 minutes. [Figure 8A] 1 is a scanning electron microscope photograph showing the state of wet-spun fiber 3 after defibration treatment for 3 minutes. [Figure 8B] 1 is a scanning electron microscope photograph showing the state of wet-spun fiber 3 after defibration treatment for 15 minutes. [Figure 8C] 1 is a scanning electron microscope photograph showing the state of wet-spun fiber 3 after defibration treatment for 60 minutes. [Figure 9A] 1 is a scanning electron microscope photograph showing the state of wet-spun fiber 4 after defibration treatment for 5 minutes. [Figure 9B] 1 is a scanning electron microscope photograph showing the state of wet-spun fiber 4 after defibration treatment for 60 minutes. [Figure 10] FIG. 1 is a schematic diagram of a spinning apparatus used in the examples. [Figure 11] 1 is a thermogram of wet-spun fibers of Examples and Comparative Examples. [Figure 12A] 1 is a scanning electron microscope photograph showing the state of the cellulose fibers of Comparative Example 1 after defibration treatment for 20 minutes. [Figure 12B] FIG. 12B is an enlarged view of FIG. 12A. [Figure 13A] 1 is a scanning electron microscope photograph showing the state of the mixed fibers of Comparative Example 2 after being defibrated in water. [Figure 13B] FIG. 13B is an enlarged view of FIG. 13A. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will be described in detail below. The present invention is not limited to the following embodiment, and can be carried out by making appropriate modifications within the scope that does not impair the effects of the present invention. In this specification, the notation "to" means "greater than or equal to." As used herein, "wet-spun fibers" refers to fibers that are spun by a wet process. In this specification, the term "monofilament" refers to a single fiber obtained by being discharged from a nozzle. The "fiber diameter" of the fibers according to the first to fourth aspects of this specification means the thickness (diameter) of a single monofilament. In this specification, "room temperature" means "18 to 28°C."

[0015] [Wet-spun fiber] A first aspect of the present invention is a wet-spun fiber containing only β-1,3-glucan represented by the following chemical formula (1) as a constituent molecule. [ka]

[0016] In chemical formula (1), n ​​represents an integer of 60 to 3000. n is preferably 500 to 2800, more preferably 700 to 2500, still more preferably 800 to 2200, and particularly preferably 1000 to 2000. Wet-spun fibers containing only β-1,3-glucan represented by the above chemical formula (1) (hereinafter simply referred to as "β-1,3-glucan") as a constituent molecule are novel spun fibers that have not been known until now.

[0017] "β-1,3-glucan" refers to a polysaccharide having a structure in which glucose is linked by a β-1,3 bond. That is, a β-1,3-glucan has a structure in which the 1-position of a β-glucose and the 3-position of another β-glucose form a β-1,3-glucoside bond. The term "β-1,3-glucan" includes β-1,3-glucans and their derivatives. β-1,3-glucans are mainly produced by algae and fungi.

[0018] Examples of β-1,3-glucan derivatives include laminaran (a linear polysaccharide containing β-1,3 and β-1,6 bonds), schizophyllan (a branched polysaccharide containing β-1,3 and β-1,6 bonds), pachyman (a polysaccharide with a main chain consisting of β-1,3 bonds and 3 to 6 side chains per molecule), lentinan (a polysaccharide with a main chain consisting of β-1,3 bonds and 2 side chain glucoses for every 5 glucose units in the main chain), and curdlan (a polysaccharide that is almost linear but has one side chain for approximately 200 glucose units).

[0019] The β-1,3-glucan constituting the wet-spun fiber according to the first embodiment preferably contains at least one paramylon selected from purified paramylon and regenerated paramylon, and from the viewpoint of easier processing and preparation, it is preferable to contain purified paramylon. As mentioned above, paramylon is an energy storage substance synthesized and accumulated by Euglena, a type of microalgae, and exists as egg-shaped micro-sized particles (paramylon particles) within Euglena cells. Paramylon is a β-1,3-glucan represented by the above chemical formula (1), and among these, paramylon with n of 1,500 to 2,000 is preferred.

[0020] As used herein, "regenerated paramylon" refers to paramylon that has been chemically modified and then regenerated to its original molecular structure. Wet-spun fibers containing regenerated paramylon can be prepared, for example, by method (I) described below. Furthermore, "purified paramylon" refers to paramylon obtained by dissolving paramylon particles in a good solvent and then introducing them into a poor solvent to re-aggregate them. Wet-spun fibers containing purified paramylon can be prepared, for example, by wet-spinning a dope solution containing paramylon using method (II) described below. Here, "good solvent" refers to a solvent that dissolves β-1,3-glucan. Furthermore, "poor solvent" refers to a solvent that does not dissolve β-1,3-glucan.

[0021] In the first aspect, poor solvents for "regenerated paramylon" include, for example, aqueous solutions of inorganic acids such as aqueous sulfuric acid, hydrochloric acid, aqueous phosphoric acid, and aqueous nitric acid; and aqueous solutions of organic acids such as acetic acid. These may be used alone or in combination of two or more. The aqueous solutions of inorganic acids may also contain inorganic salts such as sodium sulfate and zinc sulfate. Examples of poor solvents for "purified paramylon" include aqueous dimethyl sulfoxide (DMSO) solutions; alcohols or their aqueous solutions; halogenated solvents such as chloroform, dichloromethane, carbon tetrachloride, and 1,2-dichloroethane; nonpolar solvents such as benzene and hexane; and aprotic solvents such as acetone, tetrahydrofuran, and ethyl acetate or their aqueous solutions. These may be used alone or in combination of two or more. When using a mixed solvent as the poor solvent, different types of solvents from the same group may be combined. For example, a mixed solvent of ethanol and methanol may be used. The aqueous solution may also contain inorganic salts such as sodium sulfate and zinc sulfate.

[0022] In one aspect, the β-1,3-glucan constituting the wet-spun fiber according to the first embodiment may be a mixture of at least one paramylon selected from purified paramylon and regenerated paramylon with a β-1,3-glucan other than the paramylon. The mixture may contain, for example, a β-1,3-glucan produced by algae or fungi other than Euglena, or a derivative of the aforementioned β-1,3-glucan.

[0023] The wet-spun fiber according to the first embodiment may be a high moisture absorption fiber. Generally, cellulose-based rayon (hereinafter sometimes referred to as "cellulose fiber") has a moisture absorption rate of approximately 11%. The moisture absorption rate of the wet-spun fiber according to the first embodiment may be greater than 11%. Such high moisture absorption rates are easily achieved with wet-spun fibers containing regenerated paramylon as a constituent molecule. In one preferred aspect, the moisture absorption rate of wet-spun fibers containing regenerated paramylon as a constituent molecule at a temperature of 20°C and a humidity of 65% is preferably greater than 11%, more preferably 13% or greater, and particularly preferably 16% or greater. Among known regenerated cellulose fibers, purified cellulose fibers, and natural fibers, wool exhibits the highest moisture absorption rate. However, the wet-spun fiber containing regenerated paramylon as a constituent molecule preferably has a moisture absorption rate comparable to that of wool. The moisture absorption rate refers to a value measured using a method equivalent to the official moisture regain standard of JIS 0105:2020.

[0024] Furthermore, the moisture absorption rate of wet-spun fibers containing recycled paramylon as a constituent molecule at a temperature of 20°C and a humidity of 97% is preferably greater than 27%, and more preferably greater than 30%. The moisture absorption rate of cellulose fibers measured under the same conditions is approximately 27%. As mentioned above, wet-spun fibers containing recycled paramylon as a constituent molecule are likely to achieve high moisture absorption rates. Wet-spun fibers with such high moisture absorption rates are also promising as moisture-absorbing heat-generating fibers (fibers that generate heat by converting the energy of absorbed water molecules into thermal energy). Furthermore, since the wet-spun fibers according to the first embodiment can be made into continuous fibers, the contact area with the skin is increased, unlike spun yarns made from short fibers such as wool. Therefore, they feel cool to the touch in summer, and their high moisture absorption rate prevents stuffiness during wear, making them useful as refreshing fibers.

[0025] The wet-spun fiber according to the first embodiment preferably contains only purified paramylon as a constituent molecule, because the manufacturing process is easier and the fiber is easier to prepare. The wet-spun fiber according to the first embodiment may also have high elongation. Wet-spun fibers with high elongation are more likely to be achieved with wet-spun fibers containing purified paramylon as a constituent molecule. In one preferred aspect, the elongation of wet-spun fibers containing purified paramylon as a constituent molecule may be 2% or more, or even 10% or more. Wet-spun fibers with such elongation are also promising as fibers for medical sheets, which require stretchability, biocompatibility, and mechanical strength.

[0026] The wet-spun fiber according to the first aspect is a fiber with a 100% natural content, making it an advantageous material for carbon offset. It is also considered to be biodegradable, which reduces the environmental impact.

[0027] Figures 1 to 4 are micrographs showing one embodiment of the wet-spun fiber according to the first aspect. Figures 1A to 1C show wet-spun fiber 1 obtained by method (I) described below, and Figures 2 to 4 show wet-spun fibers 2 to 4 obtained by method (II) described below. The wet-spun fiber according to the first embodiment has a plurality of lines formed on its surface along the length of the fiber, as shown in Figure 1C. These lines are the bonding surfaces between the submicron fibrils that make up the wet-spun fiber. In this way, the wet-spun fiber according to the first embodiment may have a monofilament formed by bundling a plurality of submicron fibrils. The wet-spun fiber in Figure 1C is composed of submicron fibrils with an average fiber diameter of 1 µm or less, which are gathered together to form a monofilament with a fiber diameter of approximately 20 µm. The fiber diameter of the wet-spun monofilament can be any diameter, and a monofilament with the desired fiber diameter can be obtained by changing the nozzle diameter. The wet-spun fiber in Figure 1C has a relatively smooth surface, except for the submicron fibrils that are gathered together to form the monofilament. Therefore, the wet-spun fiber according to the first embodiment is expected to be used for linings of fabric products such as clothing, as well as for moisture-absorbing and heat-generating fibers, as described above. Details of the submicron fibrils will be described later. While Figure 1C shows a wet-spun monofilament, the wet-spun fiber according to the first embodiment also includes a multifilament (a single thread) formed by converging multiple monofilaments spun simultaneously from multiple outlets in a spinning nozzle.

[0028] [Wet-spun fiber manufacturing method] A second aspect of the present invention is a method for producing wet-spun fibers according to the first aspect. The second aspect involves preparing spun fibers from the raw material β-1,3-glucan by method (I) of preparing viscose from the raw material β-1,3-glucan represented by the following chemical formula (1), or by method (II) of dissolving the raw material β-1,3-glucan in a good solvent. [ka]

[0029] In chemical formula (1), n ​​represents an integer of 60 to 3,000. n is preferably 500 to 2,800, more preferably 700 to 2,500, even more preferably 800 to 2,200, and particularly preferably 1,000 to 2,000. Details of method (I) or method (II) will be described below.

[0030] <Method (I)> Method (I) is a method for preparing viscose from a raw material β-1,3-glucan represented by the above chemical formula (1) (hereinafter referred to as "raw material β-1,3-glucan") and preparing spun fibers from the raw material β-1,3-glucan. Method (I) preferably includes (i) introducing xanthate groups into the raw material β-1,3-glucan in an alkaline aqueous solution to prepare viscose, and (ii) extruding the viscose through a nozzle into a coagulation liquid to remove the xanthate groups and obtain spun fibers of β-1,3-glucan. Furthermore, the raw material β-1,3-glucan preferably contains paramylon, and more preferably contains only paramylon.

[0031] As mentioned above, paramylon particles are insoluble in water or common organic solvents, making it extremely difficult to use paramylon particles as a raw material for wet spinning. However, the present inventors discovered that by chemically modifying raw material β-1,3-glucan, which may be paramylon, in an alkaline aqueous solution to prepare viscose, and then extruding the viscose into a coagulation solution, the chemically modified β-1,3-glucan can be restored to its original structure, resulting in wet-spun fibers containing only β-1,3-glucan as a constituent molecule.

[0032] (Step (i)) Step (i) is a step of preparing viscose by introducing xanthate groups into raw material β-1,3-glucan in an alkaline aqueous solution. Examples of alkaline aqueous solutions include aqueous sodium hydroxide and aqueous potassium hydroxide. Of these, aqueous sodium hydroxide is preferred from the viewpoint of ease of handling. From the viewpoint of ease of handling, the concentration of the aqueous sodium hydroxide solution is preferably 0.5 to 2.0 mol / L, and more preferably 0.8 to 1.2 mol / L.

[0033] In step (i), the raw material β-1,3-glucan is preferably reacted with carbon disulfide in an alkaline aqueous solution to introduce xanthate groups into the raw material β-1,3-glucan. The reaction temperature is preferably 35 to 45°C, more preferably 38 to 42°C. The reaction time is preferably 2 to 6 hours, more preferably 3 to 4 hours. The degree of substitution of the xanthate group is preferably 0.5 to 1.2 per glucose residue, from the viewpoint of ease of regeneration in a coagulation bath.

[0034] In addition, the xanthate group-containing β-1,3-glucan prepared in step (i) preferably has a structure represented by the following chemical formula (2), for example. [ka]

[0035] In chemical formula (2), R is hydrogen or C(=S)S - Na + and at least one R is C(=S)S - Na + where n represents an integer of 60 to 3,000. The degree of substitution of the xanthate group per glucose residue is preferably 0.5 to 1.2, more preferably 0.8 to 1.0. In addition, in the chemical formula (2), n is preferably 500 to 2,800, more preferably 700 to 2,500, further preferably 800 to 2,200, and particularly preferably 1,000 to 2,000.

[0036] The xanthate group-containing β-1,3-glucan can also be stored, for example, dissolved in an alkaline aqueous solution (viscose) and used as a compound (manufacturing raw material) for producing the wet-spun fiber according to the first embodiment.

[0037] (Step (ii)) Step (ii) is a step in which the viscose prepared in step (i) is extruded through a nozzle into a coagulation liquid to eliminate the xanthate groups, thereby obtaining spun fibers of β-1,3-glucan. The coagulation liquid has the function of removing xanthate groups from xanthate group-containing β-1,3-glucan and coagulating the regenerated β-1,3-glucan.Such coagulation liquid includes, for example, hydrochloric acid, sulfuric acid, etc.Among these, sulfuric acid is preferred from the viewpoint of ease of removal of xanthate. The concentration of sulfuric acid is preferably 1 to 3 mol / L, and more preferably 1.8 to 2.0 mol / L.

[0038] It is preferable to further include a refining step after step (ii). The spun fibers prepared through step (ii) tend to swell in water or an aqueous solution when wet. Therefore, it is preferable that the refining step includes dehydrating the spun fibers by immersing them in alcohol. Examples of alcohols include alcohols having 1 to 5 carbon atoms. Among these, methanol, ethanol, isopropyl alcohol, and normal propyl alcohol are preferred, with methanol being particularly preferred. It is also preferable that the dehydration step be carried out for 0.5 to 3 hours. The purified spun fiber can be dried to obtain the wet-spun fiber according to the first embodiment. The drying conditions are not particularly limited. For example, the fiber may be dried at 50 to 70°C for 1 to 10 hours.

[0039] In the second embodiment, when method (I) is adopted, the obtained wet-spun fiber contains only "regenerated β-1,3-glucan" as a constituent molecule. In other words, when paramylon is used as the raw material β-1,3-glucan, a wet-spun fiber composed of regenerated paramylon can be obtained. Note that whether the xanthate group is released from the xanthate group-containing β-1,3-glucan and the β-1,3-glucan is regenerated can be determined by examining the obtained wet-spun fiber. 13 This can be confirmed by measuring C-NMR and FT-IR. Specific methods will be described later.

[0040] Method (I) can produce, for example, a wet-spun fiber 1 as shown in Figures 1A to 1C. Figure 1A is a micrograph showing an overall image of the obtained wet-spun fiber 1, and Figures 1B to 1C are enlarged views of the wet-spun fiber 1 taken with a scanning electron microscope.

[0041] As described above, method (I) is a method for producing the wet-spun fiber according to the first embodiment by the viscose method, which is also known as a method for producing the cellulose fiber described above, for example. The viscose process for producing rayon involves the following steps: (1) immersing cellulose raw materials in a high-concentration (over 6 mol / L) aqueous sodium hydroxide solution for 18 hours or more to swell the cellulose and prepare alkali cellulose; (2) removing water to extract the alkali cellulose, which is then reacted with carbon disulfide to introduce xanthate groups; (3) dissolving the cellulose xanthate again in aqueous sodium hydroxide to prepare viscose; and (4) extruding the viscose into dilute sulfuric acid to remove the xanthate groups and obtain regenerated cellulose spun fibers. The present inventors have discovered that the viscose process, which uses a high-concentration aqueous sodium hydroxide solution, cannot produce xanthate-containing β-1,3-glucan. Method (I) involves dissolving β-1,3-glucan in a relatively low-concentration aqueous alkali solution and then directly adding carbon disulfide to the aqueous alkali solution to prepare xanthate-containing β-1,3-glucan. Method (I) allows for the preparation of wet-spun fibers in fewer steps than the conventional viscose method.

[0042] <Method (II)> Next, a method for producing the wet-spun fiber according to the first embodiment by method (II) will be described. Method (II) is a method for preparing the wet-spun fiber by dissolving the raw material β-1,3-glucan in a good solvent. The good solvent may be at least one selected from aprotic solvents, alkaline aqueous solutions, ionic liquids, and deep eutectic solvents. The aprotic solvents, alkaline aqueous solutions, ionic liquids, and deep eutectic solvents are not particularly limited as long as they can dissolve β-1,3-glucan, and examples are described below. Examples of aprotic solvents include a single solvent such as N,N-dimethylacetamide, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylmorpholine-N-oxide (NMMO), or lithium chloride; a mixed solvent containing two or more of the above solvents; a mixed solvent of one or more of the above solvents with a protic solvent (e.g., methanol); or a mixed solvent of one or more of the above solvents with water. An example of an alkaline aqueous solution is a cuprammonium solution. Examples of ionic liquids include 1-ethyl-3-methylimidazolium acetate, N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium, 2-methoxyacetate, etc. These ionic liquids may be used alone or in combination of two or more. An example of a deep eutectic solvent is a mixture of choline chloride and zinc chloride. The good solvent used in method (II) preferably contains an aprotic solvent from the viewpoint of ease of solvent recovery. That is, method (II) preferably includes extruding a dope solution, in which raw material β-1,3-glucan is dissolved in a good solvent containing an aprotic solvent, through a nozzle into a coagulation liquid to obtain spun β-1,3-glucan fibers. Furthermore, the aprotic solvent preferably contains at least one selected from DMSO and NMMO, and more preferably contains DMSO.

[0043] The proportion of β-1,3-glucan in the dope is not particularly limited. From the viewpoint of the viscosity of the dope suitable for spinning, the proportion of β-1,3-glucan in the dope may be 5 to 12 mass % or 7 to 10 mass %. Furthermore, the coagulation liquid used to obtain purified paramylon in the coagulation step can be the aforementioned "poor solvent for purified paramylon." In one aspect, the coagulation liquid preferably contains an aprotic solvent or an aqueous solution thereof, a halogenated solvent, a nonpolar solvent, or an alcohol having 1 to 5 carbon atoms. From the viewpoint of reusing the coagulation liquid, it preferably contains an alcohol having 1 to 5 carbon atoms, and more preferably contains ethanol. A mixed solvent containing two or more solvents may also be used as the coagulation liquid. When an aqueous solution of an aprotic solvent is used as the coagulation liquid, the proportion of the aprotic solvent in the aqueous solution can be appropriately adjusted so that it is 10% or more.

[0044] Method (II) also preferably includes a refining step. As with method (I), the refining step preferably includes a step of immersing the spun fiber in alcohol to dehydrate it. The alcohol preferably has, for example, 1 to 3 carbon atoms. The same alcohol as used in the coagulation liquid may also be used. The dehydration step is preferably carried out at 18 to 28°C for 3 to 24 hours. The refined spun fiber can be dried to obtain the wet-spun fiber according to the first embodiment, i.e., the wet-spun fiber containing only β-1,3-glucan as a constituent molecule. The drying conditions are not particularly limited. For example, drying can be performed under reduced pressure at 80 to 100°C for 1 to 6 hours.

[0045] When method (II) is adopted as the second embodiment, the resulting wet-spun fibers contain only "purified β-1,3-glucan" as a constituent molecule. In other words, when paramylon is used as the raw material β-1,3-glucan, wet-spun fibers composed of purified paramylon can be obtained.

[0046] Method (II) can be used to prepare wet-spun fibers 2 to 4, as shown in Figures 2A to 4B. Figures 2A to 3B are micrographs of wet-spun fibers 2 and 3 prepared using DMSO as a good solvent. Figures 4A and 4B are micrographs of wet-spun fiber 4 prepared using aqueous sodium hydroxide as a good solvent.

[0047] When the wet-spun fiber according to the first embodiment is defibrated, for example, by the method described below, small fibers (fibrils) become exposed from the fiber surface (hereinafter, the fiber surface with exposed fibrils will be referred to as "peach skin"). Further defibration unravels not only the fiber surface but also the interior of the fiber, resulting in a porous fiber. If the defibration process is continued, all of the monofilaments are unravelled, leaving only submicron fibrils. In this way, the wet-spun fiber according to the first embodiment is easily transformed by defibration into a fiber having peach skin on the fiber surface, a porous fiber, and submicron fibrils. The above-mentioned fibers and fibrils obtained by defibrating wet-spun fibers will be described below in order.

[0048] [Wet-spun fiber with peach skin on the fiber surface] When the wet-spun fiber according to the first embodiment is subjected to a defibration treatment so that the fiber surface is raised, fibrils are raised from the surface of the monofilament, forming peach skin. In other words, the third embodiment of the present invention is a wet-spun fiber having peach skin on its surface. The wet-spun fiber having peach skin can be prepared, for example, by defibrating only the fiber surface of the wet-spun fiber. An example of a fiber according to the third embodiment is the fiber shown in Figure 5A. Figure 5A is a scanning electron microscope photograph showing one embodiment of a monofilament in a wet-spun fiber having peach skin. As shown in Figure 5A, peach skin is formed on the surface of the monofilament. In the fiber according to the third embodiment, the fibrils forming the peach skin may be submicron fibrils, may be microfibrils, or may be fibrils having a fiber diameter of 1 μm or more.

[0049] The fibers according to the third embodiment are preferably prepared by loosening wet-spun fibers so that fibrils are raised from the surface of the monofilament. Specifically, the fibers may be prepared by immersing the wet-spun fibers in water and then subjecting them to a mechanical shearing treatment such as homogenization for 1 to 60 minutes, preferably 1 to 20 minutes, and more preferably 5 to 20 minutes, thereby raising the fiber surface. The homogenization conditions are not particularly limited, as long as they are capable of applying a shear force sufficient to raise the fiber surface.

[0050] <Porous fiber> When the wet-spun fiber according to the first aspect or the wet-spun fiber according to the third aspect is further defibrated, for example, by the method described below, the interior of the monofilament is also defibrated, and multiple pores are formed on the surface and inside of the monofilament. A fourth aspect of the present invention is a porous fiber having multiple pores on the surface and inside of the monofilament. A "porous fiber" is a fiber having multiple pores on the surface and inside of the monofilament, and refers to, for example, the fiber present in the scanning electron microscope photographs of Figures 5B to 5C.

[0051] Figure 5B is a scanning electron microscope photograph of a portion of the fiber (porous fiber) in Figure 5A at a further magnification. As shown in Figure 5B, the porous fiber has multiple pores on the surface of its monofilament, but the fibrous structure (i.e., a structure extending long in the length direction of the fiber) is maintained. In Figure 5B, the fibrils present on the left side of the porous fiber include submicron-sized fibrils (submicron fibrils). Submicron fibrils will be described later.

[0052] Figure 5C is a scanning electron microscope photograph further enlarging the surface of the porous fiber in Figure 5B. The wavy structures extending from the lower left to the upper right in Figure 5C are submicron fibrils that make up the monofilament. It can be seen that circular holes are formed between the submicron fibrils. The holes are stretched in the longitudinal direction of the monofilament and have a roughly elliptical shape. The holes shown as dark shadows in Figure 5C indicate holes formed deep in the thickness direction of the monofilament (inside the fiber). In other words, it can be seen that the porous fiber according to the fourth embodiment has multiple holes formed not only on the surface of the monofilament but also inside it. In the porous fiber, the submicron fibrils that were tightly adhered to each other to form a single monofilament are partially peeled off in the longitudinal direction of the monofilament, resulting in gaps between the submicron fibrils. Such porous fibers are expected to be used, for example, as moisture-absorbing and heat-generating fibers. In Fig. 5C, fine fibrous matter is further attached to the surface of the monofilament, which is considered to be the aforementioned peach skin (raised nap). That is, the porous fiber according to the fourth embodiment may have peach skin on the fiber surface.

[0053] [Method of manufacturing porous fibers] The porous fiber according to the fourth aspect can be prepared by a method including defibrating the wet-spun fiber according to the first aspect or the fiber according to the third aspect. Specifically, the wet-spun fiber according to the first and / or third aspect is immersed in water and then defibrated by a mechanical shearing treatment such as homogenization for 5 minutes or more but less than 60 minutes, preferably 5 to 20 minutes, thereby loosening the wet-spun fiber and creating pores (micropores) on the surface and inside the fiber. In one preferred aspect, the method may include homogenizing a monofilament of at least one fiber selected from the fibers according to the first and third aspects in water for 5 minutes or more. The homogenization conditions are not particularly limited, as long as they are sufficient to apply a shear force to the wet-spun fiber that loosens the wet-spun fiber and creates multiple pores on the surface and inside the fiber, as shown in Figures 5B and 5C. The defibration time can also be adjusted appropriately depending on the homogenization conditions.

[0054] [Submicron fibrils] A fifth aspect of the present invention is a submicron fibril containing only β-1,3-glucan represented by the following chemical formula (1) as a constituent molecule. [ka]

[0055] In chemical formula (1), n ​​represents an integer of 60 to 3000. n is preferably 500 to 2800, more preferably 700 to 2500, still more preferably 800 to 2200, and particularly preferably 1000 to 2000.

[0056] When the fibers according to the first to fourth aspects, preferably the monofilaments, are further subjected to a fibrillation treatment, the monofilaments are completely defibrated to form fibrils having an average fiber diameter of less than 1 μm (submicron fibrils). As used herein, "submicron fibrils" refer to fibrils in which the average fiber diameter (average thickness) of a single fibril is greater than 100 nm and less than 1,000 nm. The submicron fibrils according to the fifth embodiment do not include those in which multiple submicron fibrils are bundled together and the fiber structure of a monofilament is maintained. Those that maintain the fiber structure of a monofilament are defined as "fibers" according to any of the first to fourth embodiments. In other words, the submicron fibrils according to the fifth embodiment refer to those in which the submicron fibrils are defibrated into individual fibers. The average fiber diameter of fibrils can be measured by measuring three points on any 20 fibrils observed under a scanning electron microscope and calculating the average value.

[0057] The monofilament of the wet-spun fiber according to the first embodiment is preferably an aggregate of submicron fibrils according to the fifth embodiment. Similarly, the monofilament of the wet-spun fiber according to the third embodiment and the porous fiber according to the fourth embodiment is preferably an aggregate of submicron fibrils. Note that "the monofilament is an aggregate of submicron fibrils" refers to a structure in which submicron fibrils are aligned in the length direction and / or thickness (fiber diameter) direction of the monofilament to form the monofilament, and which can be defibrated into individual submicron fibrils by the defibration treatment described below. Note that the fibrils produced when the aggregate is defibrated may include, in addition to submicron fibrils, micron-sized fibrils and fibrils with a fiber diameter of 1 μm or more.

[0058] The β-1,3-glucan represented by chemical formula (1) preferably contains at least one paramylon selected from purified paramylon and regenerated paramylon. In another aspect, the β-1,3-glucan may be a mixture of at least one paramylon selected from purified paramylon and regenerated paramylon with a β-1,3-glucan other than the paramylon. The mixture may contain, for example, a β-1,3-glucan produced by algae or fungi other than Euglena, or a derivative of the aforementioned β-1,3-glucan. From the viewpoints of ease of availability, production, and purification, the submicron fibrils according to the third aspect preferably contain only at least one paramylon selected from purified paramylon and regenerated paramylon as constituent molecules. From the viewpoints of easier processing and ease of preparation, it is preferable to contain only purified paramylon as constituent molecules. From the viewpoint of more easily obtaining submicron fibrils with a high moisture absorption rate, it is preferable to contain only regenerated paramylon as constituent molecules.

[0059] The average fiber diameter of the submicron fibrils is more than 100 nm and less than 1,000 nm, preferably 200 to 800 nm, and more preferably 400 to 600 nm. Such an average fiber diameter makes them suitable for use as fillers, separation membrane materials, etc.

[0060] The physical properties of submicron fibrils vary depending on their length and the raw material (purified paramylon or regenerated paramylon) from which they are made. In one aspect, submicron fibrils containing regenerated paramylon as a constituent molecule may have a higher moisture absorption rate than cellulose fibers. Furthermore, submicron fibrils containing purified paramylon as a constituent molecule may have a higher mechanical strength than cellulose fibers.

[0061] [Method of manufacturing submicron fibrils] A sixth aspect of the present invention is a method for producing submicron fibrils according to the fifth aspect. The sixth aspect includes subjecting the wet-spun fiber according to the first aspect to a fiber defibration treatment in water. The submicron fibrils according to the fifth aspect may be prepared from the fiber according to the third aspect or the fourth aspect, or may be prepared from a mixture of these fibers. That is, the production method according to the sixth aspect includes subjecting at least one fiber selected from the fibers according to the first, third, and fourth aspects to a fiber defibration treatment in water. In addition, in one preferred aspect, the method may include subjecting a monofilament of at least one fiber selected from the fibers according to the first, third, and fourth aspects to a mechanical fiber defibration treatment in water. The fibres according to the first, third and fourth aspects may be used as precursors to the submicron fibrils according to the fifth aspect.

[0062] In the sixth aspect, the defibration step is preferably a homogenization treatment. Specifically, the submicron fibrils according to the fifth aspect can be produced by immersing at least one fiber selected from the fibers of the first, third, and fourth aspects in water and then subjecting the fiber to mechanical shearing using a homogenizer, preferably for 5 minutes or more, more preferably for 5 to 20 minutes. The homogenization conditions are not particularly limited as long as they are within a range that can impart a shear force sufficient to completely defibrate the fibers (preferably monofilaments). For example, the fibers may be defibrated using a homogenizer at a rotation speed of 10,000 to 15,000 rpm. The manufacturing method according to the sixth aspect may include a step of preparing a raw material solution by immersing the above-mentioned fiber (preferably monofilament) in water. The solid content of the raw material solution is preferably 1 to 10% by mass, more preferably 1 to 3% by mass. The temperature of the water for immersion is preferably 15 to 30°C, more preferably 15 to 25°C.

[0063] The above-mentioned production method can prepare a dispersion of submicron fibrils in which the submicron fibrils of the fifth embodiment are dispersed in water. Therefore, the production method according to the sixth embodiment may include a dehydration step. The dehydration step may be, for example, a step of (1) centrifuging the dispersion to separate the submicron fibrils, and (2) heating and drying the separated submicron fibrils at a temperature of 60 to 80°C under reduced pressure for 3 to 8 hours to obtain dehydrated submicron fibrils.

[0064] Figures 6, 7C, 8C, and 9A-9B are scanning electron micrographs of submicron fibrils prepared by the production method of the sixth embodiment. Figure 6 is a scanning electron micrograph of submicron fibrils obtained by homogenizing wet-spun fiber 1 prepared by method (I). Figures 7C-9B are scanning electron micrographs of submicron fibrils obtained by homogenizing wet-spun fibers 2-4 prepared by method (II). As shown in the above figures, it is clear that submicron fibrils can be prepared by mechanically defibrating wet-spun fibers prepared by either method (I) or (II).

[0065] As described above, the method of preparing submicron fibrils by mechanically defibrating the fibers according to the first to fourth embodiments has been described, but the fibers according to the first, third, and fourth embodiments are not easily defibrated in normal use. In other words, even if these fibers are used as textile raw materials for clothing, bedding, etc., and are washed or dry-cleaned during use, they will not be defibrated within the range of normal use. Furthermore, unlike cellulose fibers, the fibers according to the first to fourth aspects can be mechanically defibrated to prepare submicron fibrils. Therefore, the fibers according to this embodiment can be recovered in the form of submicron fibrils from clothing, bedding, etc. containing these fibers. Furthermore, the recovered submicron fibrils can be spun, for example, by the above-mentioned method (II) and reused as wet-spun fibers. [Example]

[0066] The present invention will be explained in more detail below by showing examples, but the interpretation of the present invention is not limited to these examples.

[0067] [Example 1: Preparation of wet-spun fiber 1 by method (I)] 1. Viscose Preparation Using paramylon as the β-1,3-glucan, an aqueous solution (viscose) containing xanthate group-containing β-1,3-glucan (paramylon xanthate) was prepared by the following method. 499 mg of paramylon was dispersed in 10 mL of 1 mol / L aqueous sodium hydroxide solution and stirred at room temperature for 1 hour to prepare the sodium salt of paramylon. Next, 1.08 g of carbon disulfide was added to the aqueous solution, and the mixture was heated in a water bath (40 °C) and vigorously stirred for 3.5 hours to prepare an aqueous solution of paramylon xanthate (viscose) (Reaction Scheme (3)). [ka]

[0068] 2. Spinning A schematic diagram of the spinning apparatus (wet spinning apparatus, manufactured by Nakamura Service Co., Ltd.) is shown in Figure 10. The viscose prepared in step 1 above was extruded from a nozzle (spinneret, 30-hole nozzle) with 30 0.4 mm diameter holes into a coagulation bath (500 mL of 2 mol / L aqueous sulfuric acid solution, length 500 mm × width 50 mm × depth 40 mm) using a 10 mL syringe. When the extruded gel-like fiber came into contact with the coagulation solution (dilute sulfuric acid), the xanthate groups were released, and paramylon was regenerated (reaction formula (4)). The resulting fiber was wound on a winding roller (diameter 80 mm) to obtain spun fiber. [ka]

[0069] 3. Refining The resulting spun fibers were purified to remove water-containing residues in the following manner. In the case of cellulose fibers, the target rayon is finally obtained through a multi-step process including water washing, desulfurization, and bleaching. The wet-spun fibers of the present invention, especially in the wet state immediately after spinning, can easily swell when exposed to water or an aqueous solution, resulting in a loss of mechanical strength. Therefore, the water washing step was omitted, and the fibers were dehydrated with methanol and then air-dried to prepare wet-spun fiber 1. Specifically, the spun fiber wound on a roller was immersed in a 500-mL beaker containing 400 mL of methanol for 30 minutes, and then air-dried for 18 hours to obtain wet-spun fiber 1. The resulting wet-spun fiber 1 was observed using a microscope and a scanning electron microscope. The results are shown in Figures 1A to 1C.

[0070] 4.Analysis The wet-spun fiber 1 prepared in Example 1 was spun under the following conditions: 13 C-NMR and FT-IR measurements were performed to confirm whether paramylon (β-1,3-glucan) had been regenerated. < 13 C-NMR and FT-IR Analysis 30 mg of wet-spun fiber 1 was dispersed in 646 mg of a 1.8 mol / L solution of deuterated sodium hydroxide (NaOD) / heavy water (DO) and stirred at room temperature for 2 days. 550 mg of heavy water was added to the resulting homogeneous solution to prepare a sample. 13 C-NMR and FT-IR measurements confirmed that paramylon was regenerated from paramylon xanthate. 13 C-NMR: (0.9mol / L NaOD / D2O), δ(ppm) 106.5(C1), 89.8(C3), 79.6(C5), 76.7(C2), 71.7(C4), 64.2(C6) FT-IR (cm -1 ):3305, 2917, 1633, 1367, 1363, 1253, 1175, 1111, 1043, 1032, 888.

[0071] For the wet spun fiber 1 of Example 1, the moisture absorption rate, thermal properties, and physical properties of the fiber were measured under the following conditions.

[0072] <Wet-spun fiber moisture absorption measurement (20℃ / 65%)> The moisture absorption rate of the fiber was measured using a measurement method equivalent to JIS0105:2020. First, 500 mg of wet-spun fiber 1 was dried under reduced pressure at 90°C for 15 hours, and the fiber weight after drying (A1) was measured. The wet-spun fiber 1 was then left in a constant temperature and humidity chamber (20°C, 65% relative humidity) for 10 days, after which the fiber weight (A2) was measured. The fiber weight (A1) was subtracted from the fiber weight (A2) to calculate the weight of absorbed water (A3), and the moisture absorption rate was calculated using the following formula (a). The results are shown in Table 1. Moisture absorption rate (%) = 100 × (weight of absorbed water (A3) / weight of fiber after drying (A1)) (a)

[0073] <Wet-spun fiber moisture absorption measurement (20℃ / 97%)> 500 mg of wet-spun fiber 1 was dried under reduced pressure at 90°C for 15 hours, and the fiber weight (A1) after drying was measured. The wet-spun fiber 1 was then placed in a thermo-hygrostat (20°C, 97% relative humidity) for 3 days, after which the fiber weight (A2) was measured. The fiber weight (A1) was subtracted from the fiber weight (A2) to calculate the weight of absorbed water (A3), and the moisture absorption rate was calculated using the above formula (a). The results are shown in Table 1.

[0074] <Evaluation of thermal properties of wet-spun fibers> Thermogravimetric analysis of the wet-spun fibers was carried out using a thermogravimetric analyzer (Rigaku Corporation, product name: Thermo plus EVO2 TG8120). 10 mg of wet-spun fiber 1 was heated from 25°C to 500°C at a rate of 10°C / min under a nitrogen atmosphere, and the weight change was measured. The decomposition temperature was determined from the intersection of the tangent to the graph in the temperature range from 100°C to 200°C, where almost no weight change was observed, and the tangent to the minimum temperature of the differential curve of the measured graph. The thermogram is shown in Figure 12, and the decomposition temperatures are shown in Table 1. In Figure 12, "paramylon fiber" refers to wet-spun fiber 1, "cellulose fiber" refers to the cellulose fiber of Comparative Example 1, and "blend fiber" refers to the mixed fiber of Comparative Example 2.

[0075] <Evaluation of mechanical and physical properties of wet-spun fibers> A tensile test was carried out using 20 wet-spun fibers 1 using a universal testing machine (manufactured by A&I Co., Ltd., product name: Tensilon RTG-1225). The results are shown in Table 1. The measurement conditions were as follows: Chuck distance: 20mm Pulling speed: 2 mm / min

[0076] <Preparation of submicron fibrils> The wet-spun fiber 1 of Example 1 was defibrated to study the preparation of submicron fibrils. 26 mg of wet-spun fiber 1 was placed in 10 mL of Milli-Q water and defibrated using a homogenizer (AS ONE Corporation, product name "AHG-160A") equipped with a shaft generator (AS ONE Corporation, product name "HT1008"). Defibration was performed at 13,500 rpm for 5, 20, and 60 minutes, respectively. After 5 minutes of defibration, wet-spun fiber with peach skin on the fiber surface was obtained (Figure 5A). Further defibration resulted in a mixture of porous fibers (Figures 5B and 5C) and submicron fibrils with a fiber diameter of approximately 500 nm. After 20 minutes or more of defibration, wet-spun fiber 1 was completely defibrated, yielding submicron fibrils with an average fiber diameter of approximately 500 nm (Figure 6). Figure 6 shows a scanning electron micrograph of wet-spun fiber 1 after 20 minutes of defibration.

[0077] [Example 2: Preparation of wet-spun fiber 2 by method (II)] 1. Preparation of Dope Solution Wet-spun fiber 2 was prepared by method (II) using paramylon as the β-1,3-glucan. First, 797 mg of paramylon was dissolved in 10 mL of DMSO and stirred at room temperature for 6 hours to prepare a homogeneous dope solution. The paramylon content in the dope solution was 8% by mass.

[0078] 2. Spinning and refining Using a 10 mL syringe, the dope solution was extruded through a 30-hole nozzle into an ethanol coagulation bath (500 mL of ethanol, 500 mm long x 50 mm wide x 40 mm deep). The extruded gel-like fiber was wound at 6 rpm and then immersed in a 500 mL beaker containing 400 mL of ethanol to obtain a spun fiber. The spun fiber before air-drying was observed under a bright-field microscope. The results are shown in Figure 2A. The obtained spun fiber was air-dried and then dried under reduced pressure at 100 °C for 3 hours to prepare wet-spun fiber 2. The obtained wet-spun fiber 2 was observed under a scanning electron microscope. The results are shown in Figure 2B. The moisture absorption rate, thermal properties, and physical properties of wet spun fiber 2 were measured under the same conditions as those for wet spun fiber 1. The results are shown in Table 1. We also performed defibration under the same conditions as for wet-spun fiber 1 to investigate whether submicron fibrils could be prepared. First, wet-spun fiber 2 was treated for 1 to 3 minutes to obtain wet-spun fiber with a peach skin on the fiber surface. Continuing the defibration process further yielded a mixture of porous fiber and submicron fibrils with a fiber diameter of approximately 500 nm. Continuing the defibration process further resulted in all of the fibers being defibrated, leaving only submicron fibrils. Figure 7A is a scanning electron micrograph of wet-spun fiber 2 after 3 minutes of defibration treatment, and Figure 7B is a scanning electron micrograph after 15 minutes of defibration treatment. Figure 7C is a scanning electron micrograph of wet-spun fiber 2 after 60 minutes of defibration treatment. Under the same conditions as wet-spun fiber 1, wet-spun fiber 2 was not completely defibrated after 20 minutes of defibration treatment, leaving porous fibers. After 60 minutes of defibration treatment, all fibers were defibrated into submicron fibrils, as shown in Figure 7C. As shown in Figures 7A-7C, defibration treatment of wet-spun fiber 2 produced fibers with peach skin, porous fibers, and submicron fibrils.

[0079] [Example 3: Preparation of wet-spun fiber 3 by method (II)] 1. Preparation of Dope Solution Paramylon was used as the β-1,3-glucan to prepare wet-spun fiber 3 by method (II). For wet-spun fiber 3, the content of paramylon in the dope solution was 9% by mass. 908 mg of paramylon was dissolved in 10 mL of DMSO and stirred at room temperature for 6 hours to prepare a homogeneous dope solution. 2. Spinning and refining Wet-spun fiber 3 was prepared by spinning in the same manner as in Example 2, except that the vacuum drying time was changed to 100°C and 2 hours. Figure 3A shows a bright-field micrograph before air drying, and Figure 3B shows a scanning electron micrograph after vacuum drying. For wet spun fiber 3, the moisture absorption rate, thermal properties, and physical properties of the fiber were measured under the same conditions as for wet spun fiber 1. The results are shown in Table 1. We also performed defibration treatment under the same conditions as for wet-spun fiber 1 to investigate whether submicron fibrils could be prepared. First, wet-spun fiber 3 was treated for 1 to 3 minutes, resulting in wet-spun fibers with a peach skin on the fiber surface. Continuing the defibration treatment further produced porous fibers. Continuing the defibration treatment further resulted in the fibers being completely defibrated, leaving only submicron fibrils. Figure 8A is a scanning electron micrograph of wet-spun fiber 3 after defibration treatment for 3 minutes, and Figure 8B is a scanning electron micrograph after defibration treatment for 15 minutes. Figure 8C is a scanning electron micrograph of wet-spun fiber 3 after defibration treatment for 60 minutes. As shown in Figures 8A to 8C, defibration treatment of wet-spun fiber 3 produced fibers with peach skin, porous fibers, and submicron fibrils.

[0080] [Example 4: Preparation of wet-spun fiber 4 by method (II)] 1. Preparation of Dope Solution Paramylon was used as the β-1,3-glucan to prepare wet-spun fiber 4 by method (II). For wet-spun fiber 4, an aqueous solution of sodium hydroxide was used as a good solvent. 507 mg of paramylon was dissolved in 10 mL of aqueous sodium hydroxide solution, and the solution was stirred at room temperature (23°C) for 1 hour to prepare a homogeneous dope solution.

[0081] 2. Spinning and refining Wet-spun fiber 4 was prepared by spinning in the same manner as in Example 2, except that the scouring step was changed to immersion in 200 mL of methanol for 30 minutes. Figure 4A shows a bright-field micrograph before air drying, and Figure 4B shows a scanning electron micrograph after vacuum drying. Wet-spun fiber 4 maintained its fiber structure immediately after spinning, but its strength was weak, and the fiber structure collapsed due to thermal and physical properties. Therefore, it was not possible to measure its thermal and physical properties. Wet-spun fiber 4 was defibrated under the same conditions as wet-spun fiber 1 to investigate whether submicron fibrils could be produced. Wet-spun fiber 4 had low strength, and under the same conditions as wet-spun fiber 1, most of the fibers were defibrated to submicron fibrils after 1 to 5 minutes of defibration treatment. Figure 9A is a scanning electron micrograph after 5 minutes of defibration treatment, and Figure 9B is a scanning electron micrograph after 60 minutes of defibration treatment. Figure 9A shows that most of the fibers were defibrated to submicron fibrils. Even after 60 minutes of defibration treatment, submicron fibrils with an average fiber diameter similar to that of Figure 9A were obtained. It is believed that peach skin and porous fibers can be produced from wet-spun fiber 4 by defibrating it under milder conditions.

[0082] Comparative Example 1: Preparation of cellulose fiber using cellulose xanthate / sulfuric acid coagulation bath 1. Preparation of Cellulose Xanthate 499 mg of dissolving pulp (manufactured by Nippon Paper Industries Co., Ltd., product name: NSPP-HR) was immersed in 5.0 mL of 6 mol / L aqueous sodium hydroxide solution at room temperature for 18 hours. Subsequently, excess sodium hydroxide solution was removed with filter paper, yielding 1.515 g of wet pulp (alkali cellulose). This alkali cellulose was placed in a 20 mL glass container, 503 mg of carbon disulfide was added, the lid was closed, and the mixture was left at room temperature for 18 hours. 10 mL of 1 mol / L aqueous sodium hydroxide solution was added to the glass container, and the mixture was stirred at room temperature for 5 hours to obtain viscose containing cellulose xanthate (Reaction Scheme (5)).

[0083] [ka]

[0084] 2. Spinning Spinning was carried out under the same conditions as in Example 1. 3. Refining The fibers wound on a roll were refined to obtain cellulose fibers as follows: (1) Wash with running water for 1 minute, (2) Immerse in warm water (90°C) for 1 minute, (3) Immerse in 200 mL of 0.04 mol / L sodium hydroxide solution at room temperature for 1 minute, (4) Immerse in warm water (90°C) for 1 minute, (5) Immerse in 200 mL of 0.8% by weight sodium hypochlorite solution at room temperature for 1 minute, (6) Immerse in warm water (90°C) for 1 minute, (7) Immerse in 80 mL of 0.8% by weight sodium hypochlorite solution at room temperature for 1 minute, (8) Immerse in warm water (90°C) for 1 minute, and (9) Air-dry for 18 hours. FT-IR analysis of the resulting cellulose fibers confirmed that they were composed of regenerated cellulose. FT-IR (cm -1 ):3338, 2875, 1635, 1380, 1371, 1312, 1265, 1125, 1020, 891.

[0085] The moisture absorption rate, thermal properties, and physical properties of the cellulose fiber were measured under the same conditions as those for wet-spun fiber 1. The results are shown in Table 1. We also performed defibration under the same conditions as for wet-spun fiber 1 to examine whether submicron fibrils could be produced, but no submicron fibrils were obtained. Figure 12A is a scanning electron microscope photograph showing the state of cellulose fibers after defibration treatment in water for 20 minutes. Figure 12B is an enlarged view of Figure 12A. As shown in Figures 12A and 12B, defibration treatment of cellulose fibers in water alone did not produce many submicron fibrils. Figure 12B also shows that fibrils were peeled from the cellulose fiber surface, but no peach skin was formed. Furthermore, porous fibers with multiple holes formed on the surface and inside of the monofilament were not produced. This is thought to be because the bonds between the fibrils constituting the cellulose fiber monofilament were strong, preventing the fibrils from being released under the same defibration treatment conditions as for wet-spun fiber 1.

[0086] Comparative Example 2: Preparation of mixed fibers composed of cellulose and β-1,3-glucan using a blended xanthate / sulfuric acid coagulation bath 1. Preparation of Blended Xanthates Paramylon was used as the β-1,3-glucan, and paramylon xanthate was prepared in the same manner as in Example 1. Cellulose xanthate was also prepared in the same manner as in Comparative Example 1. Paramylon xanthate and cellulose xanthate were mixed in equal amounts and stirred at room temperature for 2 hours to prepare a blended xanthate. 2. Spinning Spinning was carried out in the same manner as in Example 1 to obtain fibers containing cellulose and paramylon (β-1,3-glucan). 3. Refining A blended fiber of cellulose and paramylon was prepared by the same method as in Comparative Example 1. FT-IR analysis of the resulting blended fiber confirmed that the fiber was composed of regenerated cellulose and regenerated paramylon. In other words, Comparative Example 2 is a wet-spun fiber containing cellulose and paramylon in a 50:50 ratio. FT-IR (cm -1 ):3310, 2881, 1635, 1423, 1369, 1309, 1256, 1119, 1019, 889.

[0087] The moisture absorption rate, thermal properties, and physical properties of the blended fiber were measured under the same conditions as those for wet-spun fiber 1. The results are shown in Table 1. We also performed defibration treatment under the same conditions as for wet-spun fiber 1 to examine whether submicron fibrils could be produced, but no submicron fibrils were obtained. Figure 13A is a scanning electron microscope photograph showing the state of the mixed fiber after defibration treatment in water for 20 minutes. Figure 13B is an enlarged view of Figure 13A. As shown in Figures 13A and 13B, defibration treatment of the mixed fiber in water alone did not produce many submicron fibrils. Figure 13B shows that lines (streaks) were formed on the surface of the monofilament of the mixed fiber, but no fiber with peach skin or porous fiber was produced. This is thought to be because the bonds between the fibrils constituting the monofilament were strong in the mixed fiber, and fibrils could not be released under the same defibration treatment conditions as for wet-spun fiber 1, which consists only of β-1,3-glucan. These results confirmed that the property of easily preparing submicron fibrils by defibration treatment in water is unique to wet-spun fibers containing only β-1,3-glucan as a constituent molecule.

[0088] [Table 1]

[0089] As shown in Table 1, by adopting the wet-spun fiber manufacturing method of the present invention, it was possible to obtain wet-spun fibers containing only β-1,3-glucan as a constituent molecule. Wet-spun fibers 1-4 described in Examples 1-4 are fibers made of 100% paramylon. Furthermore, wet-spun fiber 1, which is made of 100% regenerated paramylon, exhibited a higher moisture absorption rate than the cellulose fiber of Comparative Example 1. It was also found that wet-spun fiber 1 had a higher decomposition temperature than the cellulose fiber. Furthermore, the results of tensile tests showed that wet-spun fibers 1-4 had higher elongation than the fibers of Comparative Examples 1-2. In particular, wet-spun fibers 2-3, which are made of 100% purified paramylon, had elongation two to three times that of the cellulose fiber of Comparative Example 1. The wet-spun fibers of the present invention, which have such properties, are expected to be used in moisture-absorbing and heat-generating fibers, clothing linings, and the like. Furthermore, it was found that wet-spun fibers 1-4 could be defibrated in water to produce submicron fibrils. It was found that wet-spun fibers 1-3 were defibrated in stages, from peach skin fibers to porous fibers to submicron fibrils, depending on the defibration time. It is also presumed that wet-spun fiber 4 could be defibrated under milder conditions to produce peach skin fibers and porous fibers. Defibration of wet-spun fibers 1-4 in water for approximately 5-60 minutes, depending on the defibration conditions, completely defibrated the monofilaments, leaving only submicron fibrils. On the other hand, when cellulose fibers and mixed fibers were defibrated under the same conditions, only a small amount of submicron fibrils peeled off from the monofilament surface, and the monofilaments were not completely defibrated. These results also demonstrate that the wet-spun fibers of the present invention can be defibrated to produce submicron fibrils containing only β-1,3-glucan as a constituent molecule. The prepared submicron fibrils can be used not only as fillers for reinforcing resins, but also as fibers by re-spinning. The wet-spun fibers and submicron fibrils of the present invention are novel wet-spun fibers and fibrils that have not been known before.

Claims

1. A wet-spun fiber containing only β-1,3-glucan represented by the following chemical formula (1) as a constituent molecule: The β-1,3-glucan contains regenerated paramylon, The wet-spun fiber, wherein the monofilament of the wet-spun fiber is an aggregate of submicron fibrils containing only the β-1,3-glucan as a constituent molecule. 【Chemistry 1】 (In chemical formula (1), n ​​represents an integer of 60 to 3,000.)

2. 10. The wet-spun fiber of claim 1, wherein the wet-spun fiber has a moisture absorption rate of greater than 11% at 20°C and 65% humidity.

3. A method for producing wet-spun fibers, comprising: The production method includes preparing spun fibers from the raw material β-1,3-glucan by a method (I) of preparing viscose from a raw material β-1,3-glucan represented by the following chemical formula (1), or a method (II) of dissolving the raw material β-1,3-glucan in at least one good solvent selected from an aprotic solvent, an alkaline aqueous solution, an ionic liquid, and a deep eutectic solvent: The raw material β-1,3-glucan contains paramylon, The wet-spun fiber obtained by the production method is a wet-spun fiber containing only β-1,3-glucan represented by the following chemical formula (1) as a constituent molecule, The β-1,3-glucan contains paramylon, A method for producing a wet-spun fiber, wherein the monofilament of the wet-spun fiber is an aggregate of submicron fibrils containing only the β-1,3-glucan as a constituent molecule. 【Chemistry 2】 (In chemical formula (1), n ​​represents an integer of 60 to 3,000.)

4. The method (I) comprises (i) introducing xanthate groups into the raw material β-1,3-glucan in an alkaline aqueous solution to prepare viscose, and (ii) extruding the viscose through a nozzle into a coagulation liquid to remove the xanthate groups and obtain a spun β-1,3-glucan fiber. A method for producing a wet-spun fiber according to claim 3.

5. The method for producing a wet-spun fiber according to claim 3, wherein the method (II) comprises extruding a dope solution obtained by dissolving the raw material β-1,3-glucan in a good solvent containing an aprotic solvent through a nozzle into a coagulation liquid to obtain a spun fiber of β-1,3-glucan.

6. 6. The method for producing wet-spun fibers according to any one of claims 3 to 5, wherein steps (I) and (II) comprise dehydrating the resulting spun fibers by immersion in alcohol.

7. 3. A compound for producing wet-spun fibers according to claim 1 or 2, The compound for producing wet-spun fibers is a xanthate group-containing β-1,3-glucan represented by the following chemical formula (2): 【Transformation 3】 (In chemical formula (2), R is hydrogen or C(=S)S － Na ＋ and at least one R is C(=S)S － Na ＋ and n represents an integer of 60 to 3,000.

8. 8. A method for producing the compound for producing wet-spun fibers according to claim 7, comprising the steps of: A method for producing a compound for producing wet-spun fibers, comprising introducing a xanthate group into a raw material β-1,3-glucan represented by the following chemical formula (1) in an alkaline aqueous solution. 【Chemistry 4】 (In chemical formula (1), n ​​represents an integer of 60 to 3,000.)

9. The method for producing a compound for producing wet-spun fibers according to claim 8, wherein the raw material β-1,3-glucan contains paramylon.

10. It contains only β-1,3-glucan represented by the following chemical formula (1) as a constituent molecule, The β-1,3-glucan is a submicron fibril containing regenerated paramylon. 【Transformation 5】 (In chemical formula (1), n ​​represents an integer of 60 to 3,000.)

11. 11. A method for producing submicron fibrils according to claim 10, comprising: A method for producing submicron fibrils, comprising subjecting the wet-spun fiber according to claim 1 or 2 to a defibration treatment in water.

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