Method for producing an alkali-soluble cellulose material from plant biomass

Abstract

To provide a method for producing a novel cellulose material soluble in alkaline solution.SOLUTION: The present invention provides a cellulose material soluble in alkaline solution, which is produced by treating vegetable biomass in a nitric acid solution at high temperature and high pressure and then treating the vegetable biomass with superheated steam.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for producing an alkali-soluble cellulose material from plant biomass.

Background Art

[0002] Cellulose is the most abundant renewable substance and has been continuously used from ancient times to modern technological societies. Cellulose, which is a plant-derived fiber, has a low environmental impact, is a sustainable resource, and has excellent properties such as a high elastic modulus, high strength, and a low linear expansion coefficient. Therefore, it is used in a wide range of applications, for example, as materials such as paper, films, and sheets, and as composite materials of resins (for example, reinforcing agents for resins).

[0003] In particular, refined nanocellulose (such as nanofibers) is required to be utilized in many fields and is being promoted as a national project. As a method for producing such nanocellulose, for example, a method of converting the cellulose surface from a hydroxyl group to a carboxylate using an oxidizing agent such as TEMPO and utilizing electrostatic repulsion (Patent Document 1) and a method of physically defibrating with a strong pressure have been proposed.

[0004] Thus, various studies have been conducted on cellulose materials, and the functionality of cellulose materials has been pursued.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present invention is to provide a method for producing a novel cellulose material soluble in an aqueous alkali solution.

Means for Solving the Problems

[0007] The inventors of the present invention have found that a cellulose material soluble in an alkaline aqueous solution can be obtained by treating plant biomass in a nitric acid aqueous solution at high temperature and high pressure and then subjecting it to superheated steam treatment, and have thus completed the present invention.

[0008] That is, the present invention is as follows. [1] A hydrothermal treatment step of treating plant biomass in a nitric acid aqueous solution at high temperature and high pressure, A superheated steam treatment step of subjecting the plant biomass that has undergone the hydrothermal treatment step to superheated steam treatment, A method for producing an alkali-soluble cellulose material, characterized by comprising the above steps. [2] The method for producing an alkali-soluble cellulose material according to the above [1], wherein the produced alkali-soluble cellulose material is a cellulose fiber having transparency. [3] A method for producing a cellulose aqueous solution, characterized by comprising an alkali dissolution step of dissolving the alkali-soluble cellulose material obtained by the production method according to the above [1] or [2] in an alkaline aqueous solution. [4] The method for producing a cellulose aqueous solution according to the above [3], wherein the alkali concentration of the alkaline aqueous solution is 1 to 30 w / v%.

[0009] [5] A method for producing a cellulose material, characterized by comprising a cellulose precipitation step of precipitating cellulose from the cellulose aqueous solution obtained by the production method according to the above [3] or [4]. [6] The method for producing a cellulose material according to the above [5], wherein the treatment in the cellulose precipitation step is a treatment of neutralizing the cellulose aqueous solution with an acid to precipitate cellulose. [7] The method for producing a cellulose material according to the above [5], wherein the treatment in the cellulose precipitation step is a treatment of mixing the cellulose aqueous solution with a poor solvent to precipitate cellulose. The method for producing a cellulose material according to any one of [5] to [7] above, characterized in that the precipitated cellulose is type II crystalline cellulose.

Advantages of the Invention

[0010] According to the present invention, a novel cellulose material soluble in an alkaline aqueous solution can be produced.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

[0012] <Method for Producing Alkali-Soluble Cellulose Material> The method for producing an alkali-soluble cellulose material of the present invention is characterized by having a hydrothermal treatment step of treating plant biomass in an aqueous nitric acid solution at high temperature and high pressure, and a superheated steam treatment step of treating the plant biomass that has undergone the hydrothermal treatment step with superheated steam.

[0013] According to the production method of the present invention, a cellulose material soluble in an aqueous alkali solution can be obtained from plant biomass. Plant biomass and cellulose materials obtained from plant biomass by ordinary methods are insoluble in an aqueous alkali solution. However, according to the production method of the present invention, for some unclear reason, a cellulose material soluble in an aqueous alkali solution can be obtained. In addition, when the order of the hydrothermal treatment and the superheated steam treatment of the present invention is reversed, a cellulose material soluble in an aqueous alkali solution cannot be obtained. Moreover, the production method of the present invention mainly utilizes high-pressure and high-temperature steam, and also uses fewer chemicals, so it has a small environmental impact and is suitable for large-scale synthesis.

[0014] Examples of the plant biomass used in the production method of the present invention include plant-derived biomass such as lignocellulosic biomass and herbaceous biomass, and lignocellulosic biomass is preferred. Lignocellulosic biomass is a renewable organic resource derived from wood. Examples of the originating wood include broad-leaved trees, coniferous trees, bamboo, oil palms, etc. These woods may be used alone or in combination of multiple species. In addition, examples of the parts of the wood include the trunk (stem), branches, roots, and leaves, and these parts can be used in combination. Moreover, as the shape of the plant biomass, various shapes such as firewood-like, chip-like, pellet-like, and particulate can be used.

[0015] The alkali-soluble cellulose material obtained by the production method of the present invention is cellulose fiber from which lignin and hemicellulose have been substantially removed from plant biomass and is soluble in an aqueous alkali solution such as an aqueous sodium hydroxide solution. This alkali-soluble cellulose material is preferably cellulose microfibril or cellulose nanofiber, and preferably has transparency.

[0016] Hereinafter, each step will be described. [Hydrothermal treatment step] The hydrothermal treatment step is a step of treating plant biomass in an aqueous nitric acid solution at high temperature and high pressure. In this step, for example, a container in which plant biomass is immersed in an aqueous nitric acid solution is placed in a high-pressure reactor such as an autoclave, heated, and reacted in the presence of high-temperature and high-pressure steam. By the hydrothermal treatment of this step, sufficient delignification of plant biomass can be achieved, and such sufficient delignification in this step is considered to be one of the factors enabling the obtainment of a cellulose material soluble in an alkaline aqueous solution.

[0017] The treatment temperature is, for example, above 100 to 200 °C, and from the viewpoint of performing the treatment efficiently, 110 to 180 °C is preferable, and 120 to 150 °C is more preferable. The pressure is the saturated steam pressure. Also, the treatment time depends on the temperature and pressure, but is, for example, about 1 to 360 minutes, and about 1 to 60 minutes is preferable.

[0018] Also, the nitric acid concentration of the aqueous nitric acid solution is, for example, 0.05 to 5.0 M, and from the viewpoint of more effectively achieving delignification, 0.1 to 3.0 M is preferable, and 0.2 to 2.0 M is more preferable.

[0019] [Superheated Steam Treatment Step] The superheated steam treatment step is a step of treating plant biomass that has undergone the hydrothermal treatment step with superheated steam. Such treatment can be performed, for example, using a heating steam generator such as a superheated steam oven. By the superheated steam treatment, the plant biomass can be pyrolyzed, and the structure of low-temperature decomposition substances such as hemicellulose contained in the plant biomass can be destroyed. By this step, an alkali-soluble cellulose material is obtained. This cellulose material is, for example, of a type I crystal structure (type I crystalline cellulose).

[0020] The treatment temperature (SHS temperature) is usually 120 to 500 °C, and from the viewpoint of performing the treatment efficiently, 150 to 400 °C is preferable, and 200 to 300 °C is more preferable. Also, the treatment time depends on the treatment temperature, but is, for example, about 1 to 360 minutes, and about 1 to 30 minutes is preferable.

[0021] [Bleaching Treatment Step] The method for producing an alkali-soluble cellulose material of the present invention may have a bleaching treatment step of bleaching the cellulose material obtained by superheated steam treatment. Such bleaching treatment can be performed using a chlorine-based bleaching agent such as sodium chlorite, for example. By the treatment in this step, it becomes possible to dissolve the cellulose material in an aqueous alkali solution. In addition, the cellulose material can be bleached, and the cellulose aqueous solution in which such cellulose material is dissolved becomes closer to colorless and transparent. Also, the cellulose material precipitated from the cellulose aqueous solution becomes highly transparent.

[0022] [Method for Producing Cellulose Aqueous Solution (Dissolution of Cellulose Material)] The method for producing a cellulose aqueous solution of the present invention is characterized by having an alkali dissolution step of dissolving the alkali-soluble cellulose material obtained by the above-described production method in an aqueous alkali solution.

[0023] According to the production method of the present invention, since a cellulose aqueous solution in which the cellulose material is dissolved can be obtained, the application range of the cellulose material can be expanded. That is, by solubilizing the cellulose material to make it a homogeneous system, reactions in an aqueous solution and mixing with other materials become possible. For example, efficient decomposition in a catalytic reaction and modification reactions of the side chains of cellulose also become possible. Also, a cellulose coating film can be formed by applying the cellulose aqueous solution and volatilizing the solvent.

[0024] The aqueous alkali solution is not particularly limited, and examples thereof include aqueous solutions of various alkalis such as sodium hydroxide, sodium carbonate, calcium hydroxide, potassium hydroxide, and aqueous ammonia.

[0025] The alkali concentration of the aqueous alkali solution is not particularly limited as long as the cellulose material can be dissolved, and is, for example, 1 to 30 w / v%, preferably 3 to 20 w / v%, and more preferably 5 to 15 w / v%.

[0026] <Method for producing cellulose material (precipitation of cellulose material)> The method for producing a cellulose material according to the present invention is characterized by having a cellulose precipitation step of precipitating cellulose from the aqueous cellulose solution obtained by the method for producing an aqueous cellulose solution described above.

[0027] The cellulose precipitated in the cellulose precipitation step of the method for producing a cellulose material according to the present invention has, for example, a type II crystal structure (type II crystalline cellulose).

[0028] Examples of the treatment in this step include a method of neutralizing the aqueous cellulose solution with an acid to precipitate cellulose (acidic neutralization) and a method of mixing the aqueous cellulose solution with a poor solvent to precipitate cellulose (solvent precipitation).

[0029] In the case of the method of neutralizing the aqueous cellulose solution with an acid to precipitate cellulose, as the acid, for example, inorganic acids such as hydrochloric acid, nitric acid, and sulfuric acid, and organic acids such as acetic acid and citric acid can be used.

[0030] In the case of the method of mixing the aqueous cellulose solution with a solvent to precipitate cellulose, examples of the solvent to be mixed include organic solvents such as methanol, ethanol, acetone, tetrahydrofuran, ethyl acetate, toluene, chloroform, dimethylformamide, and dimethyl sulfoxide.

Example

[0031] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0032] <Production of alkali-soluble cellulose material> An alkali-soluble cellulose material was produced using plant biomass. An overview is shown in FIG. 1. Also, FIG. 2 shows photographs of the products obtained in each step.

[0033] [Preparation of pulverized plant biomass] Chips of Moso bamboo, Matake bamboo, and oil palm fronds (OPF) were prepared as plant biomass. All plant biomass was dried in an oven for 48 hours to reduce the initial moisture content, and then ground to a particle size of 0.25 - 1 mm using a grinder (DC-HOUSE 15KG / H 110V electric grinder) to obtain ground biomass (Raw Biomass). The obtained ground biomass was stored at room temperature in a sealed plastic bag. Figure 3 shows the powder sizes of Moso bamboo ground biomass and Matake bamboo ground biomass.

[0034] [Hydrothermal treatment with nitric acid] 12.5 g of weighed ground biomass (Moso, Matake, OPF) was added to a 500 mL Erlenmeyer flask and mixed with 250 mL of 0.5 M nitric acid solution so that the ratio of the mass of the ground biomass to the volume of nitric acid was 1:20. Subsequently, the mouth of the Erlenmeyer flask was closed with aluminum foil, and the biomass mixture was treated under high-pressure steam at 132 °C for 30 minutes using an autoclave (AS ONE Science Autoclave NCC-1701). Then, the treated ground biomass was filtered, rinsed with distilled water to remove excess nitric acid until the solution became colorless. After washing, it was dried in an oven at 80 °C overnight to obtain nitric acid autoclave-treated biomass (Moso-NAAC, Matake-NAAC, OPF-NAAC).

[0035] [Superheated steam treatment] 5 g of the nitric acid autoclave-treated biomass (Moso-NAAC, Matake-NAAC, OPF-NAAC) obtained by hydrothermal treatment was thinly spread on an aluminum pan and placed in a superheated steam oven (Naomoto Kogyo Co., Ltd., small tabletop DC oven QF-5200C), and treated at an oven temperature of 230 °C, a treatment temperature (SHS temperature) of 265 °C, and a treatment time of 5 minutes. After the treatment was completed, the aluminum pan was taken out of the superheated steam oven and allowed to cool to obtain cellulose materials (Moso-NS, Matake-NS, OPF-NS). The thickness of the layer of nitric acid-treated biomass in the aluminum pan was set to approximately 1 mm.

[0036] [Bleaching treatment 1] To remove the color from the cellulose materials (Moso-NS, Matake-NS, OPF-NS) obtained by superheated steam treatment, bleaching treatment was carried out using sodium chlorite. Specifically, for the bleaching treatment, 5 g of the cellulose material was placed in a beaker and mixed with 4 g of sodium chlorite, 0.4 mL of glacial acetic acid, and 300 mL of hot water, and stirred at 70 °C for 1 hour. Subsequently, 4 g of sodium chlorite and 0.8 mL of glacial acetic acid were mixed and stirred at 70 °C for 1 hour. Further, 2 g of sodium chlorite and 0.4 mL of glacial acetic acid were mixed and stirred at 70 °C for 1 hour. Subsequently, the solution was filtered, rinsed with distilled water to remove excess sodium chlorite and acetic acid, rinsed with distilled water, then rinsed with a small amount of acetone to remove moisture. After natural drying, it was dried in an oven at 80 °C overnight to obtain bleached cellulose materials (Moso-NSblc1, Matake-NSblc1, OPF-NSblc1) (see Figure 2).

[0037] [Bleaching Treatment 2] Regarding the cellulose materials (Moso-NS, Matake-NS) produced from the above-mentioned Moso bamboo and true bamboo crushed biomass, bleaching treatment was carried out by changing the bleaching conditions.

[0038] Specifically, 4 g of the cellulose material was mixed with 3.2 g of sodium chlorite, 0.32 mL of glacial acetic acid, and 240 mL of hot water, and stirred at 70 °C for 1 hour. Subsequently, it was filtered, rinsed with distilled water to remove excess sodium chlorite and acetic acid, rinsed with distilled water, then rinsed with a small amount of acetone to remove moisture, and after natural drying, it was dried in an oven at 80 °C overnight to obtain bleached cellulose materials (Moso-NSblc2, Matake-NSblc2) (see Figure 4).

[0039] (Analysis of Alkali-Soluble Cellulose Material) The cellulose materials (Moso / Matake-NS, Moso / Matake-NSblc1 (bleaching treatment 1), Moso / Matake-NSblc2 (bleaching treatment 2)) produced from the above-mentioned moso bamboo and true bamboo crushed biomass were analyzed by thermogravimetry / differential thermogravimetry (TG / DTG), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The results are shown in Figs. 5 to 10.

[0040] Figs. 5 and 6 are diagrams showing the results of thermogravimetry / differential thermogravimetry analysis of the cellulose materials. The graph in Fig. 5 shows the cellulose materials (Moso-NS, Moso-NSblc1, Moso-NSblc2) obtained from moso bamboo crushed biomass, and the graph in Fig. 6 shows the cellulose materials (Matake-NS, Matake-NSblc1, Matake-NSblc2) obtained from true bamboo crushed biomass. For comparison, the nitric acid autoclave-treated biomass (Moso-NAAC, Matake-NAAC) before superheated steam treatment is also shown. As shown in Figs. 5 and 6, it was confirmed that the decomposition peak derived from hemicellulose disappeared.

[0041] Figs. 7 and 8 are diagrams showing the results of the IR spectra of the cellulose materials. The graph in Fig. 7 shows the cellulose materials (Moso-NS, Moso-NSblc1, Moso-NSblc2) obtained from moso bamboo crushed biomass, and the graph in Fig. 8 shows the cellulose materials (Matake-NS, Matake-NSblc1, Matake-NSblc2) obtained from true bamboo crushed biomass. For comparison, microcrystalline cellulose (Cellulose) manufactured by Sigma-Aldrich and the nitric acid autoclave-treated biomass (Moso-NAAC, Matake-NAAC) are also shown. The measurement was performed by the potassium bromide tablet method (KBr method), and the ratio of the sample to KBr was 1%.

[0042] As shown in Figs. 7 and 8, there is no significant difference in the surface functional groups of the cellulose materials obtained in this example. Also, similar to microcrystalline cellulose, about 1000 cm -1It was confirmed that the cellulose peak was shown.

[0043] Figures 9 and 10 are diagrams showing the results of X-ray diffraction of cellulose materials. The graph in Figure 9 shows the cellulose materials (Matake-NS, Matake-NSblc1) obtained from the pulverized bamboo biomass, and the graph in Figure 10 shows the cellulose materials (OPF-NS, OPF-NSblc1) obtained from the pulverized oil palm frond biomass. For comparison, the autoclaved biomass treated with nitric acid (Matake-NAAC, OPF-NAAC) before superheated steam treatment and microcrystalline cellulose (MCC-Sigma) manufactured by Sigma-Aldrich are also shown. As shown in Figures 9 and 10, it was confirmed that the cellulose materials obtained in this example have a crystalline structure of cellulose type I.

[0044] <Dissolution test of cellulose material (Production of aqueous cellulose solution)> 4 g of the bleached cellulose materials (Moso-NSblc1, Matake-NSblc1, OPF-NSblc1) obtained by bleaching treatment 1 were added at a ratio of 0.1 g to 2.5 mL of an 8.3 w / v% aqueous sodium hydroxide solution and mixed at room temperature (20 °C) for 40 minutes. As shown in Figure 2, 4 w / v% aqueous cellulose solutions (Dissolved Moso-NSblc1, Dissolved Matake-NSblc1, Dissolved OPF-NSblc1) in which the cellulose materials were dissolved in the alkaline aqueous solution were obtained.

[0045] Also, the bleached cellulose materials (Moso-NSblc2, Matake-NSblc2) obtained by bleaching treatment 2 were mixed with a 10 w / v% aqueous sodium hydroxide solution to obtain aqueous cellulose solutions (Dissolved Moso-NSblc2, Dissolved Matake-NSblc2). As shown in Figure 11, the bleached cellulose materials with the bleaching conditions of the bleaching treatment changed also dissolved in the alkaline aqueous solution without problems.

[0046] Furthermore, the solubility of unbleached cellulose materials (Moso-NS, Matake-NS) in an alkaline aqueous solution (sodium hydroxide aqueous solution) was confirmed. Specifically, the solubility was confirmed using a 1 w / v% mixed solution prepared by mixing the sample with an 8.3 w / v% sodium hydroxide aqueous solution. As a comparison, the solubility of the autoclaved biomass treated with nitric acid (Moso-NAAC) before the superheated steam treatment was also confirmed.

[0047] Figure 12 shows the results (photographs) of the cellulose material (Moso-NS) derived from Phyllostachys edulis, Figure 13 shows the results (photographs) of the cellulose material (Matake-NS) derived from Sasa palmata, and Figure 14 shows the results (photographs) of the autoclaved biomass treated with nitric acid (Moso-NAAC). As a comparison, the bleached cellulose materials (Moso-NSblc1, Matake-NSblc1) are arranged on the right side.

[0048] As shown in Figures 12 and 13, the unbleached cellulose materials also dissolved in the alkaline aqueous solution.

[0049] On the other hand, as shown in Figure 14, it was confirmed that the autoclaved biomass treated with nitric acid (Moso-NAAC) had a cloudy liquid and the cellulose material did not dissolve.

[0050] In addition, the biomass derived from coconut leaf stalks obtained in each step was dissolved at 1 w / v% in a 10 w / v% sodium hydroxide aqueous solution, and its solubility was confirmed. As shown in Figure 15, for the untreated ground biomass (Raw OPF) and the autoclaved biomass treated with nitric acid (OPF-NAAC), precipitates were observed and they did not dissolve in the sodium hydroxide aqueous solution, while for the unbleached cellulose material (OPF-NS) and the bleached cellulose material (OPF-NSblc1) according to the examples, no precipitates were observed and it was confirmed that the cellulose material was dissolved in the sodium hydroxide aqueous solution.

[0051] In addition, each of the obtained solutions was confirmed with a microscope. The results are shown in Figure 16. As shown in Fig. 16, aggregation of cellulose fibers was observed in the untreated ground biomass (Raw OPF) and the biomass treated with nitric acid autoclave (OPF-NAAC), while the unbleached cellulose material (OPF-NS) and the bleached cellulose material (OPF-NSblc1) according to the examples had the cellulose fibers separated and dissolved. In particular, it was confirmed that the bleached cellulose material was more dissolved.

[0052] <Precipitation of cellulose> (Acidic neutralization using acetic acid) 2 mL of the aqueous cellulose solution (Dissolved Moso-NSblc1, Dissolved Matake-NSblc1, Dissolved OPF-NSblc1) obtained in the production of the above aqueous cellulose solution was added to 10 mL of a 10 w / v% acetic acid solution for acidic neutralization, shaken, and centrifuged. Subsequently, it was rinsed with 20 mL of distilled water and 20 mL of acetone, the precipitate was collected and dried to obtain a cellulose material (Moso-NSblc1-AA, Matake-NSblc1-AA, OPF-NSblc1-AA).

[0053] (Solvent precipitation using ethanol) Also, as a precipitation method different from the above precipitation method of cellulose by neutralization, solvent precipitation using ethanol (poor solvent) was performed. Specifically, 2 mL of the aqueous cellulose solution (Dissolved Moso-NSblc1, Dissolved Matake-NSblc1, Dissolved OPF-NSblc1) obtained in the production of the above aqueous cellulose solution was added to 10 mL of 95% ethanol, shaken, and centrifuged. After repeating this twice, the precipitate was collected and dried to obtain a cellulose material (Moso-NSblc1-EtOH, Matake-NSblc1-EtOH, OPF-NSblc1-EtOH).

[0054] (Analysis of the precipitated cellulose material) The precipitated cellulose material (Regenerated Cellulose) was analyzed by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The results are shown in Figs. 17 to 19.

[0055] The graph in Fig. 17 shows the cellulose materials (Moso-NSblc1-AA, Matake-NSblc1-AA) precipitated by acidic neutralization using acetic acid, and the graph in Fig. 18 shows the cellulose materials (Moso-NSblc1-EtOH, Matake-NSblc1-EtOH) precipitated by solvent precipitation using ethanol. For comparison, the analysis results of microcrystalline cellulose (MCC-Cellulose) manufactured by Sigma-Aldrich are also shown.

[0056] As shown in Figs. 17 and 18, the cellulose materials of the present invention were confirmed to show cellulose peaks of about 1000 cm -1 similar to those of microcrystalline cellulose (MCC-Cellulose).

[0057] Fig. 19 shows a diagram showing the results of X-ray diffraction of the cellulose materials (OPF-NSblc1-AA, Matake-NSblc1-AA) precipitated by acidic neutralization using acetic acid. For comparison, the analysis results of microcrystalline cellulose (MCC-Sigma) manufactured by Sigma-Aldrich are also shown. As shown in Fig. 19, it was confirmed by X-ray diffraction that the cellulose materials of the present invention have a crystal structure of cellulose type II.

Industrial Applicability

[0058] Since the present invention can produce a novel cellulose material, it is industrially useful.

Claims

1. A hydrothermal treatment step of treating plant biomass in a nitric acid aqueous solution at high temperature and high pressure, and A superheated steam treatment step of subjecting the plant biomass that has undergone the hydrothermal treatment step to superheated steam treatment (excluding treatment using a base); A method for producing an alkali-soluble cellulose material, characterized by comprising these steps.

2. The method for producing an alkali-soluble cellulose material according to Claim 1, characterized in that the produced alkali-soluble cellulose material is a cellulose fiber having transparency.

3. A hydrothermal treatment step of treating plant biomass in a nitric acid aqueous solution at high temperature and high pressure, and A superheated steam treatment step of subjecting the plant biomass that has undergone the hydrothermal treatment step to superheated steam treatment; A method for producing a cellulose aqueous solution, characterized by comprising an alkali dissolution step of dissolving the alkali-soluble cellulose material that has undergone the superheated steam treatment step in an aqueous alkali solution.

4. The method for producing a cellulose aqueous solution according to Claim 3, characterized in that the alkali concentration of the aqueous alkali solution is 1 to 30 w / v%.

5. A method for producing a cellulose material, characterized by comprising a cellulose precipitation step of precipitating cellulose from the cellulose aqueous solution obtained by the production method according to Claim 3 or 4.

6. The method for producing a cellulose material according to Claim 5, characterized in that the treatment in the cellulose precipitation step is a treatment of neutralizing the cellulose aqueous solution with an acid to precipitate cellulose.

7. The method for producing a cellulose material according to Claim 5, characterized in that the treatment in the cellulose precipitation step is a treatment of mixing the cellulose aqueous solution with a poor solvent to precipitate cellulose.

8. The method for producing a cellulose material according to any one of Claims 5 to 7, characterized in that the precipitated cellulose is type II crystalline cellulose.

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