WO2023090362A1

WO2023090362A1 - Method for producing cellulose fiber layer-containing multilayer body

Info

Publication number: WO2023090362A1
Application number: PCT/JP2022/042561
Authority: WO
Inventors: 幹夫福原; 俊之橋田; 昌浩森田; 丈史中谷; 啓吾渡部; 達規伊藤
Original assignee: 国立大学法人東北大学; 日本製紙株式会社
Priority date: 2021-11-17
Filing date: 2022-11-16
Publication date: 2023-05-25

Abstract

The present invention addresses the problem of providing a production method which is capable of efficiently producing a multilayer body that comprises a cellulose fiber layer and is capable of achieving a high amount of power storage. The present invention provides a method for producing a cellulose fiber layer-containing multilayer body, the method comprising a process for obtaining a multilayer unit, which comprises a cellulose fiber layer and an electrode layer, by applying a slurry of cellulose fibers such as pulp and cellulose nanofibers to at least a part of the electrode layer so as to form a film thereon by means of a bar coating method, a spin coating method, an electrophoresis method or the like.

Description

Method for producing laminate containing cellulose fiber layer

The present invention relates to a method for manufacturing a laminate containing cellulose fiber layers.

A capacitor is essentially an electronic component that stores and discharges electric charge (electrical energy) through electrostatic capacitance. BACKGROUND ART Capacitors play roles such as power source stability, backup circuits, coupling elements, and noise filters in mobile electronic devices such as personal computers and mobile phones, and are indispensable components for electronic devices. In recent years, high-performance IT products such as mobile phones and micro-storage devices and batteries for electric vehicles have rapidly evolved, and the demand for capacitors that are more compact and have high performance such as large-capacity memory is increasing. In particular, there is a demand for products suitable for a smart grid (next-generation power grid) society that is compatible with green innovation (low carbonization) to prevent global warming. For example, the market for capacitors in automobiles, IT equipment, energy-saving inverters, etc. is steadily expanding at an average annual rate of about 3.7%, reaching a market of 1 trillion yen.

It is preferable that such capacitors do not use flammable elements such as lithium or environmental pollutants. That is, there is a demand for materials that are solid rather than liquid, harmless to health, and inexpensive.

Capacitors are broadly classified into high-voltage power circuits (heavy electric) and electronic/electrical equipment circuits (light electric) according to their application. Among them, ceramic capacitors are mainly used as capacitors for electronic/electrical equipment circuits in the field of light current, and secondary batteries are also heavily used for storing electricity in mobile phones and the like.

Capacitors using conventional electric lumped constant circuits have a wide range of storage capacities from 1 pF to several tens of mF, and are used as main components of electronic and electrical equipment. The storage capacity C(F) is given by the following formula:
C=Q/V=ε×(A/d)
(Here, Q: electric charge, V: voltage, ε: permittivity, A: electrode area, d: distance between electrodes)
Therefore, the larger the electrode area and the smaller the distance between the electrodes, the higher the charge capacity obtained. However, from the viewpoint of lightness, thinness, shortness and miniaturization of electronic and electrical equipment and the required storage capacity, it is necessary to increase the electrode area A and reduce the distance d between the electrodes to achieve a maximum capacity, reduce the electrode area A, It is difficult to increase the inter-electrode distance d to make the capacitance extremely small. In addition, current capacitors with dielectric specifications based on electric lumped constant circuits are already saturated in capacitance.

As a storage method that surpasses conventional electric capacity, there is a method using an electric distributed constant circuit. For example, recently, an electric double layer capacitor made by moistening an electrolytic solution in activated carbon has been put to practical use. However, a solid-state electric double layer capacitor has not yet been put to practical use.

With respect to solid storage materials, the present inventors have proposed Si--(Al, Ti, V) alloys from which Al, Ti, and V have been extracted and removed from the surface, Ti--Ni--Si systems coated _with _TiO.sub.2 , and Ti--Ni--Si systems coated with _{Al.sub.2O.sub.3} It has been discovered that an electric charge can be accumulated in an Al--Y system amorphous alloy regardless of direct current or alternating current (for example, see Non-Patent Documents 1 to 7 and Patent Documents 1 to 4).

In addition, the inventors of the present invention have found that when the compound particles are 40 nm or less, preferably 10 nm or less, a "quantum size effect" occurs due to electron shielding occurring on the nano-sized solid surface, and amorphous titania, The present inventors have developed nano-sized unevenness on the surface of amorphous alumina, amorphous fluoropolymer, and amorphous cellulose nanofiber (for example, Non-Patent Documents 4, 7 to 9, 11 , see Patent Documents 4 and 5). In these storage materials, due to the quantum nano-size effect, the smaller the diameter of the projections is, the more the Van der Waals electrostatic force acts on the diameter of the projections to the power of minus 6, and the more electrons can be attracted to the projections. increase (see, for example, Non-Patent Document 7). The work function, which is a measure of the magnitude of the electron adsorption capacity, is -5.5 eV for amorphous titania (see Non-Patent Document 7), and -10.3 eV to -13.35 eV for amorphous fluoropolymer (Non-Patent Document 4, Patent Document 4), −20.5 eV for amorphous alumina (see Non-Patent Document 9 and Patent Document 3), and −22.5 eV for amorphous cellulose nanofiber (see Non-Patent Document 11 and Patent Document 5).

Focusing on the use of recyclable vegetable fibers that are friendly to the global environment, Patent Document 5 discloses a power storage material having fibers mainly composed of fibers such as wood and vegetable fibers and having unevenness on the surface. Ultra capacitors are described.

Japanese Patent No. 6498945 Japanese Patent No. 6628241 JP 2016-134934 A JP 2017-41578 A WO2021/166813

All the capacitors described in Non-Patent Documents 1 to 11 and Patent Documents 1 to 4 are artificial compounds of inorganic compounds or organic compounds. The production of microplastics, which are found in plastics, is being avoided all over the world from the viewpoint of animal and plant protection and global environmental conservation.

On the other hand, the electricity storage material described in Patent Document 5 is a material with low environmental impact that uses recycled natural fibers that are environmentally friendly, and is an electricity storage body that can store electricity in direct current and alternating current. Patent Document 5 realizes a biomass capacitor that uses wood and plant fibers (cellulose) obtained from plants that are lightweight, have high elastic performance, and have a small environmental load related to production and disposal. There is a demand for a method that can efficiently produce materials that are environmentally friendly and that can exhibit a high storage capacity.

An object of the present invention is to provide a method for efficiently manufacturing a power storage body capable of expressing a higher storage capacity from cellulose fiber, which is a natural material.

The present invention provides the following [1] to [15].
[1] A method for producing a laminate containing a cellulose fiber layer, which comprises applying a cellulose fiber slurry to at least a part of an electrode layer to form a film to obtain a laminate unit comprising a cellulose fiber layer and an electrode layer.
[2] The manufacturing method according to [1], wherein the electrode layer is an electrode sheet, and the cellulose fiber slurry is applied to one or both sides of the electrode sheet to form the film.
[3] The production method according to [1] or [2], wherein the cellulose fiber slurry is applied by bar coating, spin coating, or electrophoresis.
[4] The production method according to any one of [1] to [3], wherein the cellulose fiber has a specific surface area of 10 m ² /g or more.
[5] The production method according to any one of [1] to [4], wherein the cellulose fibers are cellulose nanofibers.
[6] The production method according to any one of [1] to [5], wherein the cellulose fibers are chemically modified cellulose fibers.
[7] The production method of [6], wherein the chemically modified cellulose fibers are carboxylated, carboxymethylated, or esterified cellulose fibers.
[8] The production method according to any one of [1] to [7], wherein the cellulose fiber further comprises a metal.
[9] The production method of [7], wherein the chemically modified cellulose fiber is a cellulose fiber containing a metal as a counterion.
[10] The production method according to [8] or [9], wherein the metal is one or more selected from Na, Mg, Li, Ca, Al, K, Zn and Fe.
[11] The production method according to any one of [1] to [10], wherein the laminate is an electricity storage material.
[12] The manufacturing method according to any one of [1] to [10], further comprising laminating a plurality of lamination units.
[13] comprising at least one laminated unit having an electrode layer and a cellulose fiber layer;
the cellulose fiber layer comprises cellulose fibers containing an anionic modifying group;
A laminate containing a cellulose fiber layer.
[14] The laminate according to [13], wherein the cellulose fibers containing an anionic modifying group and metal are carboxylated, carboxymethylated, or esterified cellulose fibers.
[15] The laminate according to [13] or [14], which is a power storage body.

The present invention also provides the following [1-1] to [1-7].
[1-1] A method for producing a cellulose fiber layer-containing power storage body, comprising coating a cellulose fiber slurry on at least one surface of an electrode layer to form a film.
[1-2] The production method according to [1-1], wherein the cellulose fiber slurry is applied to both surfaces of the electrode layer to form the film.
[1-3] The production method according to [1-1] or [1-2], wherein the cellulose fiber slurry is applied by bar coating, spin coating, or electrophoresis (electrodeposition coating method).
[1-4] The production method according to any one of [1-1] to [1-3], wherein the cellulose fiber has a specific surface area of 10 m ² /g or more.
[1-5] The production method according to any one of [1-1] to [1-4], wherein the cellulose fibers are cellulose nanofibers.
[1-6] The production method according to any one of [1-1] to [1-5], wherein the cellulose fibers are chemically modified cellulose fibers.
[1-7] The manufacturing method according to any one of [1-1] to [1-6], wherein a plurality of the power storage bodies are laminated.

The present invention further provides the following [2-1] to [2-11].
[2-1] Including applying a cellulose fiber slurry to the electrode to form a film,
The cellulose fiber slurry comprises cellulose fibers containing anionic modifying groups and metals,
A method for manufacturing a sheet material with electrodes.
[2-2] The production method of [2-1], wherein the electrode-attached sheet material is provided with a cellulose fiber layer in contact with one or both sides of the electrodes.
[2-3] The cellulose fiber containing an anionic modifying group and a metal is a carboxylated, carboxymethylated, or esterified cellulose fiber containing a metal as a counterion, [2-1 ] or [2-2].
[2-4] Any one of [2-1] to [2-3], wherein the metal is one or more selected from Na, Mg, Li, Ca, Al, K, Zn and Fe. manufacturing method.
[2-5] The production method according to any one of [2-1] to [2-4], wherein the cellulose fiber has a specific surface area of 10 m ² /g or more.
[2-6] having an electrode layer and a cellulose fiber layer,
The cellulose fiber layer comprises cellulose fibers containing anionic modifying groups and metals,
Sheet material with electrodes.
[2-7] A cellulose fiber layer is provided in contact with one side of the electrode layer, or
A cellulose fiber layer is provided on both sides of the electrode layer,
The sheet material according to [2-6].
[2-8] The cellulose fiber containing an anionic modifying group and a metal is a carboxylated, carboxymethylated, or esterified cellulose fiber containing a metal as a counterion, [2-6 ] or [2-7].
[2-9] Any one of [2-6] to [2-8], wherein the metal is one or more selected from Na, Mg, Li, Ca, Al, K, Zn and Fe. sheet material.
[2-10] The sheet material of any one of [2-6] to [2-9], wherein the cellulose fibers have a specific surface area of 10 m ² /g or more.
[2-11] The sheet material according to any one of [2-6] to [2-10], which is an electricity storage material.

According to the present invention, it is possible to efficiently manufacture a laminate that includes a cellulose fiber layer and is capable of exhibiting a high storage capacity.

FIG. 1 is a schematic diagram showing the procedure of coating by the bar coating method in the example. FIG. 2 is a schematic diagram showing the application procedure by the spin coating method in the example. FIG. 3 is a schematic diagram showing the procedure of coating by the electrodeposition coating method in the example.

[1. Laminate]
The laminate (sheet material with electrodes) in the present invention contains a cellulose fiber layer.
[1.1 Cellulose fiber layer]
A cellulose fiber layer is a layer containing cellulose fibers.

[Cellulose fiber]
Cellulose fibers are usually bio-derived cellulose fibers, for example, plants (for example, wood, bamboo, hemp, jute, kenaf, rice), animals (for example, sea squirts), algae, microorganisms (for example, acetic acid bacteria (Acetobacter )), cellulose fibers derived from microbial products and the like. Cellulose fibers are preferably plant- or microorganism-derived cellulose fibers, more preferably plant-derived cellulose fibers. Cellulose fibers derived from plants or microorganisms include, for example, pulp, powdered cellulose, crystalline cellulose, cellulose nanofibers, cellulose microfibrils, and regenerated cellulose, and the processing method and degree are not particularly limited. Examples of pulp include kraft pulp (e.g., softwood kraft pulp such as unbleached softwood kraft pulp (NUKP) and bleached softwood kraft pulp (NBKP); unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), etc.). hardwood kraft pulp), sulfite pulp (e.g. softwood sulfite pulp such as softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP)), chemical pulp such as thermomechanical pulp (TMP) Mechanical pulp and recycled pulp are mentioned, and chemical pulp is preferred. Cellulose fibers may be cellulose fibers that have undergone a refining process, such as cellulose nanofibers and cellulose microfibrils. Cellulose fibers obtained by a method of promoting fibrillation by enzymatically treating various pulps may also be used. Additionally, the cellulose fibers may be chemically modified cellulose fibers (eg, pulp, cellulose nanofibers, cellulose microfibrils). As used herein, chemically modified cellulose fibers mean cellulose fibers that have undergone chemical modification treatment. The chemically modified cellulose fiber and the chemical modification treatment will be described later.

[Cellulose fiber size]
The size of the cellulose fibers (eg, average fiber diameter, average fiber length, aspect ratio) is not particularly limited, but examples are as follows.

(pulp)
The number average fiber diameters of softwood kraft pulp and hardwood kraft pulp, which are general pulps, are usually about 30 to 60 μm and about 10 to 30 μm, respectively. The number average fiber diameter of other pulps (those that have undergone general refining) is usually about 50 μm. In the case of pulp obtained by refining chips and the like having a size of several centimeters, it is preferable to adjust the number average fiber diameter to about 50 μm by a pulverization treatment described later, if necessary.

(size of cellulose microfibrils)
As used herein, cellulose microfibrils refer to cellulose fibers that have undergone a micronization treatment and have a micro-order fiber diameter. The average fiber diameter of cellulose microfibrils is usually 500 nm or more, preferably 1 μm or more, more preferably 10 μm or more. As a result, it is possible to exhibit higher water retention than undissolved cellulose fibers (e.g. pulp), and it is possible to obtain a high strength imparting effect and a yield improvement effect even in a small amount compared to finely disintegrated cellulose nanofibers. be done. The upper limit of the average fiber diameter is preferably 40 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less, 18 μm or less, or 17 μm or less, but is not particularly limited.

The average fiber length is preferably 10 μm or more or 20 μm or more, more preferably 30 μm or more, 40 μm or more, or 50 μm or more. The upper limit of the average fiber length is not particularly limited, but is preferably 1000 µm or less, preferably 500 µm or less, more preferably 300 µm or less, and even more preferably 200 µm or less.

The aspect ratio of cellulose microfibrils is preferably 30 or more or 35 or more, more preferably 40 or more, even more preferably 50 or more, and even more preferably 60 or more. Although the upper limit of the aspect ratio is not particularly limited, it is preferably 1000 or less, more preferably 100 or less, and even more preferably 80 or less.

(Cellulose nanofiber size)
As used herein, cellulose nanofibers (CNF) mean cellulose fibers that have undergone a refining treatment and have a nano-order fiber diameter. By using CNF, the quantum size effect of the laminate can be realized more efficiently. The average fiber diameter (length-weighted average fiber diameter) of CNF is 500 nm or less, preferably 300 nm or less, more preferably 100 nm or less, still more preferably 50 nm or less. Although the lower limit is not particularly limited, it is usually 1 nm or more, preferably 2 nm or more. Therefore, the average fiber diameter (length-weighted average fiber diameter) of CNF is usually 1 to 500 nm or 2 to 500 nm, preferably 2 to 300 nm or 2 to 100 nm, more preferably 2 to 50 nm or 3 to 30 nm. The average fiber length (length-weighted average fiber length) is usually 50 to 2000 nm, preferably 100 to 1000 nm. The aspect ratio of CNF is usually 10 or more, preferably 50 or more. Although the upper limit is not particularly limited, it is usually 1000 or less.

In this specification, the average fiber diameter and average fiber length are determined by observing each fiber using an atomic force microscope (AFM) or transmission electron microscope (TEM). The average aspect ratio can be calculated according to the formula: average aspect ratio=average fiber length/average fiber diameter.

　The size of the cellulose fibers can be adjusted by adjusting the conditions of the miniaturization process and chemical modification process.

[Chemically modified cellulose fiber]
Chemically modified cellulose fibers are obtained by chemically modifying unmodified cellulose fibers (eg, unmodified pulp, unmodified powdered cellulose). Examples of the chemical modification treatment include cationization and anionization (carboxylation (oxidation), etherification (eg, carboxymethylation), esterification), with anionization being preferred, and carboxylation and etherification being more preferred. . By chemical modification treatment (for example, oxidation), the cellulose fiber becomes a solid electrolyte and an electric double layer is formed, so it can be expected to be used as a supercapacitor. The chemical modification treatment is usually performed before or after the refinement treatment, preferably before the refinement treatment.

[Cellulose fiber containing anion-modified group]
The cellulose fiber layer preferably contains cellulose fibers containing anion-modifying groups. As used herein, cellulose fibers containing an anion modifying group include anionization (carboxylation (oxidation, dicarboxylation, ozone oxidation), etherification (e.g., carboxymethylation), esterification (phosphoric acid, phosphorous acid , sulfuric acid)). Examples of anion-modifying groups include carboxyl groups, carboxyalkyl groups (e.g., carboxymethyl groups), ester groups (e.g., phosphate groups, phosphite groups, sulfate ester groups). Methyl groups are preferred.

(carboxylation (oxidation))
Carboxylated cellulose fibers (oxidized cellulose fibers) usually have at least one carbon atom having a primary hydroxyl group contained in the glucopyranose unit constituting the cellulose molecular chain (for example, a carbon atom having a primary hydroxyl group at the C6 position). has a structure in which is oxidized. The carboxyl group content of the carboxylated cellulose fiber is preferably 0.6 to 3.0 mmol/g, more preferably 1.0 to 2.0 mmol/g. The amount of carboxyl groups can be adjusted by controlling the conditions (for example, amount of oxidizing agent to be added, reaction time) in carboxylating the cellulose fibers.

The carboxy group content can be calculated by the following procedure. 60 ml of a 0.5% by weight slurry (aqueous dispersion) of oxidized cellulose is prepared. A 0.1 M hydrochloric acid aqueous solution is added to the prepared slurry to adjust the pH to 2.5. Then, 0.05N sodium hydroxide aqueous solution is added dropwise and the electrical conductivity is measured until the pH reaches 11. From the amount of sodium hydroxide (a) consumed in the neutralization step of the weak acid, whose electrical conductivity changes slowly, the amount of carboxyl groups is calculated using the following formula:
Carboxy group amount [mmol/g oxidized cellulose] = a [ml] x 0.05/oxidized cellulose mass [g]

Carboxylated cellulose fibers can be produced by carboxylating (oxidizing) unmodified cellulose fibers (cellulose raw material, eg pulp). As an example of a carboxylation (oxidation) method, a cellulose raw material is oxidized in water using an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides or mixtures thereof. You can mention how to do it. This oxidation reaction selectively oxidizes the carbon atom having a primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface, resulting in an aldehyde group, a carboxyl group (-COOH) or a carboxylate group ( ^-COO- ) on the surface. , can be obtained. The concentration of the cellulose raw material during the reaction is not particularly limited, but is preferably 5% by mass or less.

An N-oxyl compound is a compound that can generate a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it promotes the desired oxidation reaction. Examples include 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and derivatives thereof (eg, 4-hydroxy TEMPO).　

The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount that can oxidize the cellulose raw material. For example, it is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, even more preferably 0.05 to 0.5 mmol, relative to 1 g of absolute dry cellulose raw material. Further, it is preferable that the concentration is about 0.1 to 4 mmol/L with respect to the reaction system.　

A bromide is a compound containing bromine, for example, an alkali metal bromide that can be dissociated and ionized in water. Also, iodides are compounds containing iodine, and examples thereof include iodides of alkali metals. The amount of bromide or iodide to be used can be selected within a range capable of promoting the oxidation reaction. The total amount of bromide and iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, even more preferably 0.5 to 5 mmol, relative to 1 g of absolute dry cellulose raw material.　

As the oxidizing agent, a known one can be used, for example, halogen, hypohalous acid, halogenous acid, perhalogen acid or salts thereof, halogen oxides, peroxides, and the like can be used. Among them, sodium hypochlorite is preferable because it is inexpensive and has less environmental load. An appropriate amount of the oxidizing agent to be used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, even more preferably 1 to 25 mmol, further preferably 3 to 10 mmol, relative to 1 g of absolute dry cellulose raw material. more preferred. Further, for example, 1 to 40 mol is preferable per 1 mol of the N-oxyl compound.　

In the oxidation process of cellulose raw materials, the reaction proceeds efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40°C, and may be room temperature of about 15 to 30°C. Since carboxyl groups are generated in the cellulose as the reaction progresses, the pH of the reaction solution decreases. In order to allow the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution at about 8-12, preferably about 10-11. Water is preferable as the reaction medium because it is easy to handle and less likely to cause side reactions.　

The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of oxidation, and is usually 0.5 to 6 hours, for example, about 0.5 to 4 hours.　

The oxidation reaction may be carried out in two steps. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the reaction in the first step, again under the same or different reaction conditions, the reaction can be efficiently It can be oxidized well.　

Another example of the carboxylation (oxidation) method is a method of oxidizing by contacting a cellulose raw material with an ozone-containing gas. This oxidation reaction oxidizes at least the 2-position and 6-position hydroxyl groups of the glucopyranose ring and causes degradation of the cellulose chain. The ozone concentration in the ozone-containing gas is preferably 50-250 g/m ³ , more preferably 50-220 g/m ³ . The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by mass, more preferably 5 to 30 parts by mass, when the solid content of the cellulose raw material is 100 parts by mass. The ozone treatment temperature is preferably 0 to 50°C, more preferably 20 to 50°C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, preferably about 30 to 360 minutes. When the ozone treatment conditions are within these ranges, the cellulose raw material can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved.

After the ozone treatment, additional oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used in the additional oxidation treatment is not particularly limited, but examples include chlorine-based compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. For example, the additional oxidation treatment can be performed by dissolving these oxidizing agents in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and immersing the oxidized cellulose in the solution.　

(Salt-type oxidized cellulose)
Salt-type oxidized cellulose usually mainly has salt-type carboxyl groups (--COO--). Examples of the counter cation of the salt-type carboxyl group include alkali metals such as Li, Na and K; alkaline earth metals such as Mg and Ca; metals such as Fe; Al; zinc group elements such as Zn; , Li, Na, Ca, K and Zn are preferred, and Na is more preferred. The counter cation is Na in oxidized cellulose obtained by a conventional oxidation method, and when it is desired to replace Na with a desired metal, an aqueous solution of a compound (LiCl ₂ , CaCl _{2 ,} KCl, ZnCl _{2 ,} etc.) having that metal is used. should be immersed in

(Acid-type oxidized cellulose and desalting)
Oxidized cellulose contains carboxyl groups as a result of oxidation, but may contain more acid-type carboxyl groups (-COOH) than salt-type carboxyl groups (-COO-), or salt-type carboxyl groups may be converted to acid-type carboxyl groups. You may contain more than a carboxyl group. The amounts of salt-type carboxyl groups and acid-type carboxyl groups can be adjusted by desalting. The desalting treatment can convert salt-type carboxyl groups to acid-type carboxyl groups. In the present specification, oxidized cellulose (which has undergone desalting) is referred to as acid-type oxidized cellulose, and oxidized cellulose (which has not undergone desalting treatment, which will be described later) is referred to as salt-type oxidized cellulose. Salt-type oxidized cellulose usually mainly has salt-type carboxyl groups (--COO--). On the other hand, acid-type oxidized cellulose has many acid-type carboxyl groups, and the ratio of acid-type carboxyl groups to carboxyl groups is preferably 40% or more, more preferably 60% or more, and even more preferably 85% or more. The proportion of acid-type carboxyl groups can be calculated by the following procedure.
1) First, 250 mL of an aqueous dispersion of acid-type oxidized cellulose with a solid content concentration of 0.1% by mass before desalting treatment is prepared. A 0.1 M hydrochloric acid aqueous solution is added to the prepared aqueous dispersion to adjust the pH to 2.5, and then a 0.1 N sodium hydroxide aqueous solution is added to measure the electrical conductivity until the pH reaches 11. From the amount of sodium hydroxide (a) consumed in the neutralization step of a weak acid whose electrical conductivity changes slowly, using the following formula, the amount of acid-type carboxyl groups and the amount of salt-type carboxyl groups, that is, the total amount of carboxyl groups Compute :
Total amount of carboxyl groups (mmol/g oxidized cellulose (salt form)) = a (ml) x 0.1/mass (g) of oxidized cellulose (salt form)
2) 250 mL of an aqueous dispersion of desalted acid-type oxidized cellulose having a solid content concentration of 0.1% by mass is prepared. A 0.1 N sodium hydroxide aqueous solution is added to the prepared water dispersion, and the electrical conductivity is measured until the pH reaches 11. From the amount (b) of sodium hydroxide consumed in the neutralization step of the weak acid whose electrical conductivity changes slowly, the amount of acid-type carboxyl groups is calculated using the following formula:
Acid-form carboxyl group amount (mmol/g acid-form oxidized cellulose) = b (ml) x 0.1/mass (g) of acid-form oxidized cellulose
3) From the calculated total amount of carboxyl groups and the amount of acid-type carboxyl groups, the ratio of acid-type carboxyl groups is calculated using the following formula.
Proportion of acid-type carboxyl groups (%) = (amount of acid-type carboxyl groups/total amount of carboxyl groups) x 100

Desalting may be performed after oxidation, or before or after defibration (before or after step (2)), but usually after oxidation, preferably before step (2). Desalting is usually carried out by substituting protons for salts (eg, sodium salts) contained in the salt-type oxidized cellulose. Methods of desalting include, for example, a method of adjusting the inside of the system to be acidic, and a method of contacting oxidized cellulose with a cation exchange resin. In the case of the method of adjusting the inside of the system to be acidic, the pH inside the system is preferably adjusted to 2-6, more preferably 2-5, and still more preferably 2.3-5. Acids (eg inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, sulfurous acid, nitrous acid and phosphoric acid; organic acids such as acetic acid, lactic acid, oxalic acid, citric acid and formic acid) are usually used to adjust to acidity. After addition of the acid, a washing treatment may be performed as appropriate. As the cation exchange resin, both strongly acidic ion exchange resins and weakly acidic ion exchange resins can be used as long as the counter ion is H ⁺ . The ratio between the oxidized cellulose and the cation exchange resin when the oxidized cellulose is brought into contact with the cation exchange resin is not particularly limited, and can be appropriately set by those skilled in the art from the viewpoint of efficient proton substitution. Recovery of the cation exchange resin after contact may be performed by a conventional method such as suction filtration.

(Etherification)
Etherification includes, for example, etherification by a reaction selected from carboxyalkylation, methylation, ethylation, cyanoethylation, hydroxyethylation, hydroxypropylation, ethylhydroxyethylation, and hydroxypropylmethylation, and carboxy Alkylation is preferred and carboxymethylation is more preferred.

Carboxyalkylated cellulose fibers usually have a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom having a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is carboxymethylated. have.

The degree of carboxyalkyl substitution (DS, preferably the degree of carboxymethyl substitution) per anhydroglucose unit of the carboxyalkylated cellulose is preferably 0.01 or more, 0.02 or more, or 0.05 or more, more preferably 0.10 or more. , is more preferably 0.15 or more, even more preferably 0.20 or more, and particularly preferably 0.25 or more. Thereby, the degree of substitution for obtaining the effect of chemical modification can be ensured. The upper limit of the degree of substitution is preferably 0.50 or less, more preferably 0.45 or less, 0.40 or less, or 0.35 or less. This makes it difficult for the cellulose fibers to dissolve in water, so that the fiber form can be maintained in water. Therefore, the degree of carboxyalkyl substitution is preferably 0.01-0.50, more preferably 0.01-0.45, 0.02-0.40, 0.10-0.35 or 0.20-0. .30 is more preferred.

The degree of substitution, such as the degree of carboxymethyl substitution, can be measured by the method described below. About 2.0 g of carboxymethylated cellulose (absolute dry) is precisely weighed and put into a 300 mL conical flask with a common stopper. Add 100 mL of a liquid obtained by adding 100 mL of special grade concentrated nitric acid to 1,000 mL of methanol and shake for 3 hours to convert salt-type carboxymethylated cellulose (hereinafter also referred to as "salt-type CM-modified cellulose") to acid-type carboxymethyl It is converted into cellulose (hereinafter also referred to as "acid-type CM-modified cellulose"). Accurately weigh 1.5 to 2.0 g of acid-type CM-modified cellulose (absolute dry) and put it in a 300-mL conical flask with a common stopper. Wet the acid-type CM-modified cellulose with 15 mL of 80% methanol, add 100 mL of 0.1N NaOH, and shake at room temperature for 3 hours. Using phenolphthalein as _an indicator, the excess NaOH can be back-titrated with 0.1 N _H2SO4 and the degree of carboxymethyl substitution (DS) can be calculated by the formula:
A=[(100×F−(0.1N H ₂ SO ₄ (mL))×F′)×0.1]/(absolute dry weight of acid-type CM-cellulose (g))
DS = 0.162 x A/(1 - 0.058 x A)
A: Amount of 1N NaOH (mL) required to neutralize 1 g of acid-type CM-cellulose
F': Factor of 0.1N _H2SO4 F: Factor of 0.1N _NaOH

The degree of carboxyalkyl substitution can be adjusted by controlling the reaction conditions such as the amount of carboxyalkylating agent to be added, the amount of mercerizing agent, and the composition ratio of water and organic solvent.

Carboxyalkylation methods include, for example, a method of mercerizing a cellulosic raw material as a starting raw material (raw raw material) and then etherifying it. Carboxymethylation will be described below as an example.

Using unmodified cellulose fiber (cellulose raw material: pulp, for example) as a starting material, mercerizing in the presence of 3 to 20 times by mass of solvent, followed by etherification to produce carboxymethylated cellulose. can. Examples of solvents include water, lower alcohols (e.g., methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, tertiary butanol) alone or a mixture of two or more. Solvents may be used. When a lower alcohol is mixed, the mixing ratio of the lower alcohol is preferably 60 to 95% by mass.

As the mercerizing agent, an alkali metal hydroxide (eg, sodium hydroxide, potassium hydroxide) is used in an amount of 0.5 to 20 times the mole of the anhydroglucose residue of the starting material.

The starting material, solvent, and mercerizing agent are mixed and mercerized at a reaction temperature of 0 to 70°C, preferably 10 to 60°C, for a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Thereafter, a carboxymethylating agent (e.g., sodium monochloroacetate) is added per glucose residue in terms of 0.05 to 10.0 times in terms of moles, the reaction temperature is 30 to 90 ° C., preferably 40 to 80 ° C., and the reaction Carboxymethylated cellulose can be produced by carrying out the etherification reaction for 30 minutes to 10 hours, preferably 1 hour to 4 hours.

(Difference from carboxymethyl cellulose)
The carboxyalkylated cellulose fibers preferably retain at least a portion of their fibrous shape even when dispersed in water. Carboxyalkylated cellulose fibers are distinguished from cellulose powders such as carboxymethylcellulose, which is a type of water-soluble polymer that dissolves in water and imparts viscosity. When an aqueous dispersion of carboxyalkylated cellulose fibers is observed with an electron microscope, fibrous substances can be observed. On the other hand, no fibrous substance is observed in an aqueous dispersion of carboxymethyl cellulose, which is a type of water-soluble polymer. In addition, when the anion-modified cellulose fiber is measured by X-ray diffraction, a peak of cellulose type I crystals can be observed. Cellulose type I crystals are not observed.

(acid-type carboxyalkylated cellulose)
The carboxyalkylated cellulose may contain more acid-type carboxyl groups than salt-type carboxyl groups, or may contain more salt-type carboxyl groups than acid-type carboxyl groups. The amounts of salt-type carboxyl groups and acid-type carboxyl groups can be adjusted by desalting. The desalting treatment can convert salt-type carboxyl groups to acid-type carboxyl groups. In the present specification, carboxyalkylated cellulose (desalted) is referred to as acid-form carboxyalkylated cellulose, and carboxyalkylated cellulose (not desalted as described below) is referred to as salt-form carboxyalkylated cellulose. Salt-type carboxyalkylated cellulose usually mainly has salt-type carboxyl groups (--COO--). On the other hand, acid-type carboxyalkylated cellulose has many acid-type carboxyl groups, and the ratio of the amount of acid-type carboxyl groups to the amount of carboxyl groups possessed by acid-type carboxyalkylated cellulose is preferably 40% or more, and 60%. 85% or more is more preferable. The method for calculating the proportion of acid-type carboxyl groups is as described above.

Desalting is usually performed after carboxyalkylation, preferably after etherification and before fibrillation. Examples of the desalting method include a method of contacting carboxyalkylated cellulose with a cation exchange resin. As the cation exchange resin, both strongly acidic ion exchange resins and weakly acidic ion exchange resins can be used as long as the counter ion is H ⁺ . The ratio between the carboxyalkylated cellulose and the cation exchange resin when the carboxyalkylated cellulose is brought into contact with the cation exchange resin is not particularly limited, and can be appropriately set by those skilled in the art from the viewpoint of efficient proton substitution. For example, the ratio can be adjusted so that the pH of the aqueous dispersion after addition of the cation exchange resin is preferably 2-6, more preferably 2-5, relative to the carboxyalkylated cellulose aqueous dispersion. Recovery of the cation exchange resin after contact may be performed by a conventional method such as suction filtration.

(Esterification (Phosphate esterification))
A first example of an esterified cellulose fiber includes phosphorylated cellulose. Phosphorylated cellulose usually has a structure in which at least one carbon atom constituting a cellulose molecular chain (for example, a carbon atom having a primary hydroxyl group at the C6 position constituting a glucopyranose unit) is phosphorylated.

The amount of ionic substituents introduced into the phosphorylated cellulose fiber (the amount of ionic substituents, the amount of phosphorous acid substituents) may be 0.10 mmol / g or more per 1 g (mass) of phosphorylated CNF. It is preferably 0.20 mmol/g or more, more preferably 0.30 mmol/g or more, still more preferably 0.40 mmol/g or more, and even more preferably 0.50 mmol/g or more. , more preferably 0.60 mmol/g or more, and particularly preferably 0.70 mmol/g or more. In addition, the amount of ionic substituents introduced into the phosphorylated CNF may be 1.50 mmol/g or less per 1 g (mass) of cellulose fiber, preferably 1.35 mmol/g or less, and 1.20 mmol. /g or less, more preferably 1.10 mmol/g or less. In addition, the amount of the ionic substituent introduced into the phosphorylated cellulose fiber is preferably 1.00 mmol/g or less per 1 g (mass) of the phosphorylated cellulose fiber, and preferably 0.95 mmol/g or less. is more preferred. Here, the denominator in units of mmol/g indicates the mass of the cellulose fiber when the counter ion of the ionic substituent is hydrogen ion (H+). The amount of phosphorus oxo acid substituents can be measured by the following method.　

[Measurement of Phosphorus Acid Group Amount]
The phosphorous acid group content of the fine cellulose fibers is obtained by diluting a fine cellulose fiber dispersion containing the target fine cellulose fibers with ion-exchanged water so that the content is 0.2% by mass. On the other hand, it can be measured by titration with an alkali after treatment with an ion exchange resin.

In the treatment with an ion exchange resin, 1/10 by volume of a strongly acidic ion exchange resin (Ambarjet 1024; Organo Co., Ltd., conditioned) was added to the slurry containing cellulose fibers, and after shaking for 1 hour, The slurry was separated from the resin by pouring it over a mesh with an opening of 90 μm.　

In addition, titration with alkali is performed by adding 10 μL of 0.1N sodium hydroxide aqueous solution every 5 seconds to the cellulose fiber-containing slurry after treatment with the ion exchange resin, and measuring the change in the pH value of the slurry. I went by. The titration was performed while nitrogen gas was blown into the slurry from 15 minutes before the start of the titration. In this neutralization titration, two points where the increment (the differential value of the pH with respect to the amount of alkali added) are maximized are observed in the curve obtained by plotting the measured pH against the amount of alkali added. Among these, the maximum point of the increment obtained first when the alkali is first added is called the first end point, and the maximum point of the increment obtained next is called the second end point. The amount of alkali required from the start of titration to the first end point is equal to the amount of first dissociated acid in the slurry used for titration. Also, the amount of alkali required from the start of titration to the second end point is equal to the total amount of dissociated acid in the slurry used for titration. The amount of alkali (mmol) required from the start of titration to the first end point was divided by the solid content (g) in the slurry to be titrated to obtain the amount of phosphate group (mmol/g). The presence or absence of introduction of a phosphate group may also be confirmed by measuring the absorption (around 1230 cm ⁻¹ ) based on the phosphate group by measuring the infrared absorption spectrum.

The amount of phosphate group can be adjusted by controlling the reaction conditions such as the amount of the compound having a phosphate group added and the amount of the basic compound used as necessary.

Examples of phosphorylation methods include a method of reacting unmodified cellulose fibers with a compound having a phosphoric acid group (phosphorylation). Examples of the phosphoric acid esterification method include a method of mixing a cellulose-based raw material with a powder or an aqueous solution of a compound having a phosphate group, and a method of adding an aqueous solution of a compound having a phosphate group to an aqueous dispersion of the cellulose-based raw material. with the latter being preferred. Thereby, the uniformity of the reaction can be improved and the esterification efficiency can be improved.

Compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phosphorus tripotassium acid, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium metaphosphate. The compounds having a phosphate group can be used singly or in combination of two or more. The amount of the compound having a phosphate group added to the cellulose raw material is preferably 0.1 to 500 parts by mass, more preferably 1 to 400 parts by mass, in terms of phosphorus element, with respect to 100 parts by mass of the solid content of the cellulose raw material. 2 to 200 parts by mass is more preferable. The reaction temperature is preferably 0 to 95°C, more preferably 30 to 90°C. Although the reaction time is not particularly limited, it is usually about 1 to 600 minutes, preferably 30 to 480 minutes. If the conditions for the esterification reaction are within any of these ranges, excessive esterification of cellulose and its susceptibility to dissolution can be suppressed, and the yield of phosphate esterified cellulose can be improved. When reacting a compound having a phosphate group, a basic compound (e.g., urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, etc.) (compound having an amino group showing) may be added to the reaction system.

(Esterification (phosphite esterification))
A second example of a method for producing esterified cellulose fibers includes phosphite esterified cellulose fibers. Phosphite cellulose fibers usually have a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom having a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is phosphorylated. .
The degree of phosphite group substitution per glucose unit in the phosphite-esterified cellulose fiber (hereinafter simply referred to as "phosphite group substitution degree") is preferably 0.001 or more and less than 0.40. The degree of phosphite group substitution can be measured by the same method as the method for measuring the degree of phosphate group substitution. The degree of phosphite group substitution can be adjusted by controlling reaction conditions such as the amount of phosphorous acid or a salt thereof added, the amount of an alkali metal ion-containing substance used as necessary, and the amount of urea or a derivative thereof added.

As a method of phosphite esterification, for example, an unmodified cellulose fiber is reacted with phosphorous acid or a metal salt thereof (preferably sodium hydrogen phosphite) to introduce an ester group of phosphorous acid. method.

Examples of phosphorous acid and metal salts thereof include phosphorous acid, sodium hydrogen phosphite, ammonium hydrogen phosphite, potassium hydrogen phosphite, sodium dihydrogen phosphite, sodium phosphite, and lithium phosphite. , potassium phosphite, magnesium phosphite, calcium phosphite, triethyl phosphite, triphenyl phosphite, phosphorous acid compounds such as pyrophosphite, and combinations of two or more selected from these. Sodium hydride is preferred. Thereby, alkali metal ions can also be introduced into the cellulose fibers. The amount of phosphorous acid or its metal salt to be added is preferably 1 to 10,000 g, more preferably 100 to 5,000 g, still more preferably 300 to 1,500 g, per 1 kg of unmodified cellulose fibers. Apart from phosphorous acid and its metal salts, alkali metal ion-containing substances (e.g., hydroxides, metal sulfates, metal nitrates, metal chlorides, metal phosphates, metal carbonates) are further added to the reaction system. You may

Also, urea or a derivative thereof may be further added to the reaction system. This can also introduce carbamate groups into the cellulose fibers. Urea and urea derivatives include, for example, urea, thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, and combinations of two or more selected from these, with urea being preferred. The amount of urea and urea derivatives to be added is preferably 0.01 to 100 mol, more preferably 0.2 to 20 mol, still more preferably 0.5 to 10 mol, per 1 mol of phosphorous acid or its metal salt.

The reaction temperature is preferably 100-200°C, more preferably 100-180°C. The reaction time is usually about 10 to 180 minutes, more preferably 30 to 120 minutes. The phosphite-esterified cellulose fibers are preferably washed prior to defibration. The degree of substitution of the phosphite group per glucose unit is preferably 0.01 or more and less than 0.23.

(Esterification (sulfate esterification))
A third example of a method for producing an esterified cellulose fiber includes a sulfate esterified cellulose fiber. Sulfated cellulose usually has a structure in which at least one carbon atom constituting a cellulose molecular chain (for example, a carbon atom having a primary hydroxyl group at the C6 position constituting a glucopyranose unit) is phosphorylated.

The amount of sulfate-based groups per glucose unit in the sulfate-esterified cellulose fiber (hereinafter simply referred to as "amount of sulfate groups") is preferably 0.1 to 3.0 mmol/g. By introducing a cationic substituent into the cellulose raw material, the celluloses electrically repel each other. Therefore, cationized cellulose into which cationic substituents have been introduced can be easily nanofiberized. In addition, when the degree of cation substitution per glucose unit is 0.02 or more, the electrical repulsion between the celluloses enables sufficient nano-fibrillation. On the other hand, when the degree of cation substitution per glucose unit is 0.50 or less, swelling or dissolution can be suppressed, and a situation in which nanofibers cannot be obtained can be prevented. In order to defibrate efficiently, it is preferable to wash the cationized cellulose obtained above.

The amount of sulfate groups per glucose unit can be measured by the following method. The aqueous dispersion of sulfated CNF is subjected to solvent substitution in the order of ethanol and t-butanol, and then freeze-dried. 15 ml of ethanol and 5 ml of water are added to 200 mg of the obtained sample, and the mixture is stirred for 30 minutes. After that, 10 ml of 0.5N sodium hydroxide aqueous solution is added, and the mixture is stirred at 70° C. for 30 minutes and further stirred at 30° C. for 24 hours. Then, add phenolphthalein as an indicator, titrate with hydrochloric acid, and calculate using the following formula:
Sulfate group amount [mmol/g sample]=(5−(0.1×hydrochloric acid titration amount [ml]×2))/0.2.

The amount of sulfate groups can be adjusted by controlling the reaction conditions such as the amount of sulfuric acid compound to be reacted.

Examples of the method of sulfate esterification include a method of reacting unmodified cellulose fibers with a sulfuric acid compound to introduce a sulfuric acid group derived from the sulfuric acid compound into cellulose to obtain sulfated cellulose. . Examples of sulfuric acid compounds include sulfuric acid, sulfamic acid, chlorosulfonic acid, sulfur trioxide, and esters or salts thereof. Among these, sulfamic acid is preferably used because cellulose has low solubility and low acidity.

For example, when sulfamic acid is used as the sulfuric acid compound, the amount of sulfamic acid used can be appropriately adjusted in consideration of the amount of anionic groups to be introduced into the cellulose chain. For example, it is preferably 0.01 to 50 mol, more preferably 0.1 to 3.0 mol, per 1 mol of glucose units in the cellulose molecule.

(salt form/acid form)
The esterified cellulose may contain more acid-type carboxyl groups than salt-type carboxyl groups, or may contain more salt-type carboxyl groups than acid-type carboxyl groups. Among the esterified cellulose, those that have not undergone desalting treatment and those that have undergone desalting treatment are referred to as salt-esterified cellulose and acid-esterified cellulose, respectively. Salt-type esterified cellulose mainly has salt-type carboxyl groups. The counter cation of the salt-type carboxyl group and the preparation method thereof are as described in the description of the oxidized cellulose.

(cationization)
Cationized cellulose usually has a structure in which at least one carbon atom constituting a cellulose molecular chain (for example, a carbon atom having a primary hydroxyl group at the C6 position constituting a glucopyranose unit) is cationized. The degree of cation substitution per glucose unit in the cationized cellulose is preferably 0.02 to 0.50. The degree of cation substitution per glucose unit can be measured by the following method. After drying the cationized cellulose fibers, the nitrogen content was measured using a total nitrogen analyzer (TN-10 manufactured by Mitsubishi Chemical Corporation), and the degree of cation substitution (the number of substituents per mole of anhydroglucose unit) was calculated by the following formula. Calculate the mean number of moles):
Cation substitution degree = (162 × N) / (1-151.6 × N)
N: nitrogen content.

The degree of cation substitution can be adjusted by adjusting reaction conditions such as the amount of cationizing agent to be reacted and the composition ratio of water or alcohol having 1 to 4 carbon atoms.

As a method of cationization, for example, unmodified cellulose fibers are treated with a cationizing agent (eg, glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydrate or its halohydrin type) and an alkali catalyst. A method of reacting a metal hydroxide (eg, sodium hydroxide, potassium hydroxide) in the presence of water and/or an alcohol having 1 to 4 carbon atoms can be mentioned.

(Base type cationized cellulose fiber)
The cationized cellulose fibers after cationization are preferably converted into base-type cationized cellulose or base-type cationized cellulose nanofibers by desalting. Desalting can convert the salts in the cationized cellulose to bases. In this specification, the cationized cellulose (nanofibers) that has undergone desalting is referred to as base-type cationized cellulose (nanofibers) or cationized cellulose (nanofibers) (base type). In addition, cationized cellulose and cationized cellulose nanofibers that have not undergone desalting are referred to as salt-type cationized cellulose (nanofibers) or cationized cellulose (nanofibers) (salt form). Desalting may be performed at any time before defibration (cationized cellulose) or after defibration (cationized cellulose nanofibers), which will be described later. Desalting means substituting a salt (for example, Cl ⁻ ) contained in cationized cellulose (salt form) and cationized cellulose nanofibers (salt form) with a base to obtain a base form. Examples of the desalting method after cationization include a method of contacting cationized cellulose or cationized cellulose nanofibers with an anion exchange resin. Both strongly basic ion exchange resins and weakly basic ion exchange resins can be used as the anion exchange resin, as long as the counterion is OH ^- . The ratio between the modified cellulose and the anion exchange resin is not particularly limited, and a person skilled in the art can appropriately set the ratio from the viewpoint of efficient cation substitution. For example, the pH of the water dispersion after addition of the anion exchange resin is preferably 8 to 13, more preferably 9 to 13, with respect to the cationized cellulose nanofiber water dispersion. be able to. Recovery of the anion exchange resin after contact may be performed by a conventional method such as suction filtration.

[Metal contained in cellulose fiber layer]
Preferably, the cellulose fiber layer further contains a metal. The metal is preferably included as a counterion (eg, —COO ⁻ M, —CH ₂ COO ⁻ M; M represents a metal) of a chemical modifying group (eg, anion modifying group). Examples of metals include alkali metals such as lithium (Li), sodium (Na) and potassium (K); alkaline earth metals such as magnesium (Mg), calcium (Ca) and barium (Ba); iron (Fe); , manganese (Mn), cobalt (Co), nickel (Ni) and other transition metals; aluminum (Al); zinc group elements such as zinc (Zn), etc., forming monovalent ions and divalent or higher ions Na, Mg, Li, Ca, Al, K, Zn and Fe are preferred, Li, Na, Ca, K and Zn are more preferred, and Na is even more preferred. The metal contained in the cellulose fiber layer may be of one type or a combination of two or more types.

(Acid modified cellulose fiber)
The cellulose fibers may have either acid-type/salt-type cellulose fibers or both. Usually have both. Acid-type cellulose fibers are cellulose fibers having acid-type modifying groups (eg, —COOH, —CH ₃ COOH). The chemically modified cellulose fibers obtained by each modification method described above contain salt-type (usually sodium salt) cellulose fibers, but usually also contain acid-type cellulose fibers. The acid-type/salt-type ratio can be adjusted by the presence or absence of desalting treatment.

(refinement (defibration, fibrillation))
Refinement is usually performed by mechanical processing. Mechanical treatment (preferably beating or defibration treatment) is usually carried out wet (ie in the form of an aqueous dispersion of cellulose fibers). Devices used for mechanical treatment include, for example, refiners (refiners; e.g., disk type, conical type, cylinder type), high-speed fibrillation machines, shearing stirrers, colloid mills, high-pressure jet dispersers, beaters, PFI mills, Kneader, disperser, high-speed disaggregator (topfiner), high-pressure or ultra-high-pressure homogenizer, grinder (stone mill type crusher), ball mill, vibration mill, bead mill, single-screw, twin-screw or multi-screw kneader/extruder high speed Homogenizers under rotation, refiners, defibrators, friction grinders, high-share defibrators, dispergers, homogenizers (e.g. microfluidizers ( A device capable of imparting a mechanical defibration force such as a microfluidizer) is preferred, and a device capable of imparting a fibrillation force in a wet manner is preferred, and a high-speed defibrator and a refining device are more preferred, but are not particularly limited.

When defibrating in a wet process, an aqueous dispersion of cellulose fibers is usually prepared. The solid content concentration of the modified cellulose in the aqueous dispersion is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more. preferable. The upper limit of the concentration is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less. During the mechanical treatment, pH adjustment (eg, 7 or less, 6 or less, 5 or less) may be performed as necessary.

Prior to the preparation of the aqueous dispersion, pretreatment such as dry pulverization (eg, pulverization after drying) may be performed. Examples of devices used for dry pulverization include, but are not limited to, impact mills such as hammer mills and pin mills, medium mills such as ball mills and tower mills, and jet mills. In addition, post-treatment may be performed after fibrillation. As the post-treatment, for example, drying (e.g., freeze drying, spray drying, tray drying, drum drying, belt drying, drying by spreading thinly on a glass plate, etc., fluidized bed drying, micro wave drying method, heat-generating fan type vacuum drying method, vacuum (degassing) drying), redispersion in water (dispersion device is not limited), pulverization (e.g. equipment such as cutter mill, hammer mill, pin mill, jet mill, etc.) pulverization using, but not particularly limited to.

[Physical properties of cellulose fiber]
(Specific surface area)
The cellulose fiber preferably has a specific surface area of 10 m ² /g or more, more preferably 100 m ² /g or more, and even more preferably 300 m ² /g or more. As a result, it is possible to store electricity in a shorter time, and to store electricity in a large amount.

The specific surface area can be measured by the following procedures (1) to (9) with reference to the nitrogen gas adsorption method (JIS Z8830).
(1) An approximately 3% slurry of cellulose fibers (dispersion medium: water) is divided so that the solid content becomes approximately 0.1 g, placed in a centrifugal container, and 100 ml of ethanol is added.
(2) Stir in the container at 3000 rpm for 30 minutes using Homo Disper Model 2.5 (manufactured by Primix).
(3) After stirring, the cellulose fibers are sedimented under the conditions of 7000 G, 30 minutes, and 30° C. using a centrifuge.
(4) Remove the supernatant while removing as little of the settled cellulose fibers as possible.
(5) After removing the supernatant, 100 ml of ethanol is added, and the stirring under the conditions of (2), the centrifugation under the conditions of (3), and the removal of the supernatant under the conditions of (4) are repeated three times.
(6) The solvent in (5) is changed from ethanol to t-butanol, and at room temperature above the melting point of t-butanol, stirring, centrifugation and supernatant removal are repeated three times in the same manner as in (5).
(7) After removing the final supernatant, add 30 ml of t-butanol, mix gently, transfer to a conical tube, and freeze using liquid nitrogen.
(8) Attach the conical tube to the lyophilizer and lyophilize for 3 days.
(9) After that, BET measurement is performed (pretreatment conditions: 105° C. for 2 hours under nitrogen stream, relative pressure 0.01 to 0.30, sample amount about 30 mg).

(crystallization)
Cellulose fibers preferably have a crystalline portion, and more preferably have a crystalline portion inside the fiber layer. As a result, uniform irregularities can be formed on the surface of the cellulose fiber layer, and the amount of electricity stored can be increased. The crystal portion may be either single crystal or polycrystal, and the ratio of the polycrystal portion is preferably 10 vol % or less of the cellulose fiber layer.

(amorphous)
Cellulose fibers preferably have an amorphous portion, and more preferably have an amorphous surface (for example, the surface in contact with the electrode). Thereby, electric storage property can be produced. For example, in the case of anion-modified cellulose fibers, due to the flexibility of the bond (C5-C6 bond) between the carbon atom at the C5 position and the carbon atom at the C6 position of the glucopyranose unit constituting the cellulose fiber, an anion group at the C6 position (for example, C6 Carbosyl group) can be rotated, resulting in high chargeability. The presence or absence of an amorphous portion can be confirmed by whether or not a broad peak is generated by X-ray analysis or whether or not a halo pattern is generated by electron beam analysis.

(atomic vacancy)
Cellulose fibers preferably have atomic vacancies. Due to the presence of atomic vacancies, proton electric conduction is possible, an electric double layer can be formed, and the laminate can be used as a power storage body. Atomic vacancies are an inherent feature of amorphousness. The size and amount of atomic vacancies can be confirmed by the positron annihilation method.

The cellulose fibers contained in the cellulose fiber layer may be of one type alone, or may be a combination of two or more types. The cellulose fiber layer may contain components other than cellulose fibers.

The cellulose fiber layer is usually sheet-like, and its thickness is preferably 100 µm or less, more preferably 50 µm or less, and even more preferably 30 µm or less. This makes it possible to reduce the weight of the device. In addition, the power density and energy density can be increased by forming a thin film where static electricity attaches and detaches from the surface.
The laminate (sheet material with electrodes) may have one cellulose fiber layer, or may have two or more layers.

[1.2 Electrode material]
A laminate (sheet material with electrodes) usually contains an electrode layer containing an electrode material. Electrode materials include, for example, carbon (C), aluminum (Al), copper (Cu), gold (Au), silver (Ag), molybdenum (Mo), chromium (Cr), iron (Fe), and zinc (Zn). , titanium (Ti), nickel (Ni), lead (Pb), platinum (Pt), tungsten (W), bismuth (Bi), silicon wafer (SiO ₂ ), Ag alloy, Al alloy, Mo alloy, Fe alloy ( For example, it is composed of a metal such as stainless steel, a metal oxide such as ZnO, or a conductive resin such as polyacetylene or polythiophene. When having two or more electrode layers, the electrode materials of each electrode layer may be different.
The electrode layer is usually in the form of a sheet and has a thickness of usually 0.01 μm to 500 μm, preferably 1 μm to 100 μm or 0.5 μm to 50 μm, more preferably 1 μm to 5 μm.

[1.3 Other layers (substrate)]
The laminate may normally contain layers other than the cellulose fiber layer and the electrode layer. Other layers include, for example, a substrate.

The substrate is usually provided in contact with the electrode layer (the outermost electrode layer when two or more electrode layers are used). Materials for the substrate include, for example, organic materials such as plastics, and inorganic materials such as silicon and glass.

[1.4 Applications and electrical properties of laminate]
The laminated body can be used as a power storage body as it is or in combination (for example, laminated or arranged in parallel). The electric resistance of the storage battery is preferably 0.01 MΩ to 500 MΩ. Moreover, the electric capacity is preferably 100 mJ/m ² or more. It is preferable that the power storage unit can be discharged for a long time of one day or more by instantaneous or short-time power storage for 1 ms to 1 minute and large-capacity power storage. Also, it is preferable that rapid response charge/discharge of 1 mHz to 100 kHz, preferably 0.1 to 100 Hz is possible. It is thought that a power storage unit with the above electrical characteristics can store current from a generator every 50/1000 to 60/1000 seconds by converting 50 Hz and 60 Hz alternating current into direct current using an AC/DC converter. be done. The operating temperature is preferably -100 to 100°C. Voltage resistance is preferably 1 GV/m or more. By satisfying at least one (preferably more than one) of the above electrical characteristics, it becomes possible to transport the solid power storage by abolition of power transmission lines, and it can be freely transported domestically and internationally not only by automobile, but also by ship, airplane, etc. is expected.

The laminate can be used as a power storage unit. Specific uses of the capacitor include, for example, AC capacitors in microelectronic circuits and capacitors on the backside of solar panels. In addition, for example, various backup power supply modules for lightning arresters, welding, overdischarge prevention, etc., coupling elements, noise filters, high-sensitivity acceleration sensors, high-output transformer cutoff prevention devices, and emergency power supply devices for automobiles and ships. Applications such as electronic and electric boards such as

[2. Laminate manufacturing method]
The laminate can be produced by applying a cellulose fiber slurry to at least part of the electrode to form a film.

[2.1 Cellulose fiber slurry]
Cellulose fiber slurry is prepared by dispersing cellulose fibers in a solvent. Examples of cellulose fibers are described above. The solvent is usually water, and the dispersion obtained during preparation of the cellulose fibers may be used as it is. The solid content concentration of cellulose fibers in the cellulose fiber slurry is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more. preferable. Thereby, a power storage body can be manufactured efficiently. The upper limit of the concentration is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 8% by mass or less or 5% by mass or less. As a result, the slurry can be adjusted to have an appropriate viscosity, and a decrease in film-forming properties can be suppressed.

[Coating/film formation]
Examples of electrode materials are as described above. As a method for applying the cellulose fiber slurry to the electrode material and forming a film, for example, a bar coating method, a spin coating method, and an electrophoresis method (electrodeposition coating method) are preferable. In the case of the bar coating method, the surface can be leveled with a bar, in the case of the spin coating method, the slurry can be uniformly formed into a film by centrifugal force, and in the case of the electrodeposition coating method, the entire electrode can be electrophoretically applied. can be done. Therefore, according to these methods, compared to methods such as slip casting, the surface and thickness of the coating film can be made more uniform. A surface having uniform unevenness can be presented, and defects are less likely to occur, and the amount of electricity stored can be improved. That is, since the amount of stored electricity is calculated by the following formula (1), the contact surface between the metal electrode and the convex surface is increased by arranging the convex portions substantially uniformly on the two-dimensional plane in the area of the contact surface. can increase the amount of electricity stored. By having unevenness, it becomes equivalent to a distributed constant type capacitor having a plurality of minute capacitors perpendicular to each metal electrode corresponding to the number. That is, the fine (nano-sized) unevenness itself becomes a solid electrolyte composed of an electric double layer, and can be represented by a parallel equivalent circuit of C and R. Among these methods, the electrophoresis method can form a thinner cellulose fiber layer. The diameter of the unevenness is preferably 1 nm to 500 nm. The thickness of the film is preferably thin from the viewpoint of improving the storage performance, but on the other hand, the thickness of the film can suppress the effects of defects such as pinholes and cracks, and the possibility of short circuits. can be appropriately determined within a range that can reduce the For example, the thickness of the film is preferably 0.1 µm or more, more preferably 0.5 µm or more, and more preferably 1.0 µm or more. Although the upper limit is not particularly limited, it is preferably 100 μm or less, more preferably 50 μm or less, and still more preferably 30 μm or less. Therefore, it is preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm, even more preferably 1 to 30 μm.

(Bar coat method)
The bar coating method is a method in which a slurry is poured onto an electrode and combed with a bar to apply the slurry. The direction of combing the bar is preferably unidirectional (eg FIG. 1). The gap distance between the bar and the electrode thin film can be appropriately adjusted according to the desired film thickness (eg, 800 μm or less, preferably 700 μm or less, more preferably 600 μm or less). Drying after coating can be performed by a drying treatment such as heating (for example, 80° C. or higher or 90° C. or higher), and may be performed using a drying device such as a hot plate.

(Spin coating method)
The spin coating method is a method in which a slurry is poured onto an electrode, the electrode is rotated horizontally, and the slurry is made into a thin film using centrifugal force. A device such as a spin coater (eg, FIG. 2) can be used for rotating the electrode. The thickness of the cellulose fiber layer and the unevenness of the surface can be controlled by the rotation speed, rotation time, etc., and these can be adjusted by setting the spin coater. The rotational speed (peripheral speed) is usually 200 to 2,000 rpm, preferably 300 to 1,500 rpm, more preferably 500 to 1,000 rpm. Coating by spin coating may be performed once, or may be repeated two or more times. By performing the heat treatment two times or more, preferably three times or more, or four times or more, it is possible to suppress the occurrence of defective portions and improve the efficiency of energization and power storage. When coating is carried out multiple times, it is preferable that the next coating treatment is carried out after drying with a drying device such as a hot plate (for example, at 40° C. to 60° C.).

(Electrophoresis method)
In the electrophoresis method (electrodeposition coating method), an electrode material to be coated and a counter electrode are immersed in a slurry, the electrode material is used as a cathode or an anode, and an electric current is passed between the electrode material and the counter electrode. This is a method of depositing a coating film on a material. When electrifying, the electrode material may be either an anode (anion electrodeposition) or a cathode (cation electrodeposition). The counter electrode can be selected from commonly used electrodes suitable for the electrode material, and examples thereof include metal electrodes such as Pt.

The condition of energization can be appropriately adjusted according to the thickness of the cellulose fiber layer, etc., and an example is as follows. The voltage is usually 0.1 V or higher, preferably 5 V or higher or 10 V or higher, more preferably 50 V or higher, still more preferably 100 V or higher. Thereby, the density of the cellulose fibers in the cellulose fiber layer can be increased. The upper limit is usually 1000 V or less, preferably 10 to 500 V or less. Current density is usually 0.00001 to 10000 mA/cm ² , preferably 0.00001 to 100 mA/cm ² , more preferably 0.1 to 10000 mA/cm ² , still more preferably 1 to 10000 mA/cm ² . be. The energization time is usually 0.1 minute or longer, preferably 1 minute or longer, and more preferably 2 minutes or longer. The upper limit is usually 100 minutes or less, preferably 60 minutes or less. When increasing the density of cellulose fibers, it is preferable to set the voltage higher (eg, 50 V or higher, preferably 100 V or higher) and shorten the energization time (eg, 10 minutes or less, preferably 5 minutes or less). . The thickness of the cellulose fiber layer can be controlled by energizing conditions (for example, voltage, current, migration time). During energization, the temperature of the CNF slurry may be adjusted to room temperature or lower (for example, 20° C. or lower, 15° C. or lower, 10° C. or lower, or 8° C. or lower).

Electricity can be energized using a container (electrolytic bath) that can accommodate the electrode material, the counter electrode, and the cellulose fiber slurry. Electrodes and electrode materials in the electrolytic bath are connected to a power supply for energization (see, for example, FIG. 3).

After energization, it may be washed (for example, washed with water) as necessary. Moreover, you may electrify in the case of washing|cleaning. An example of energization conditions during cleaning is as follows. The voltage is 0.1 to 1000 V, more preferably 10 to 500 V, and the energization time is preferably 1 to 100 minutes, more preferably 5 to 60 minutes. After energization and washing, drying treatment (eg, heating at 40° C. to 60° C.) may be performed (eg, 16 hours or longer, 10 hours or longer, or 12 hours or longer).

[2.2 Coated surface]
When the cellulose fiber slurry is applied to the electrode, the surface to be coated may be at least a part of the electrode (usually in the form of a sheet), but both surfaces are preferable.

[2.3 Lamination]
A laminate comprising two layers, an electrode layer and a cellulose fiber layer, by applying a cellulose fiber slurry to at least a portion of the electrode (for example, at least one surface of the electrode layer in the form of a sheet) to form a film, or A laminate comprising three layers of two cellulose fiber layers sandwiching an electrode layer is formed. Using these as laminated units (basic units), other laminated units can be laminated, and lamination can be repeated as necessary. Lamination may be performed using NEMS (Nano Electro Mechanical Systems).

The present invention will be described below based on the drawings and examples. It should be noted that the following examples are provided merely to illustrate the present invention and for reference to specific embodiments thereof, and are not intended to limit or limit the scope of the invention disclosed herein. not a thing

The cellulose fibers (samples 1 to 3) used in the examples were produced as follows.

Production Example 1 <Preparation of Sample 1 (TEMPO-oxidized CNF)>
500 g (absolute dry) of bleached unbeaten kraft pulp (85% whiteness) derived from softwood is added to 500 ml of an aqueous solution in which 780 mg of TEMPO (Sigma Aldrich) and 75.5 g of sodium bromide are dissolved, and the pulp is uniformly dispersed. Stir until done. An aqueous sodium hypochlorite solution was added to the reaction system so as to have a concentration of 6.0 mmol/g to initiate an oxidation reaction. The pH in the system decreased during the reaction, but was adjusted to pH 10 by successively adding 3M sodium hydroxide aqueous solution. The reaction was terminated when the sodium hypochlorite was consumed and the pH in the system stopped changing. After the reaction, 10% hydrochloric acid was added to the mixture to adjust the pH to 3, the mixture was filtered through a glass filter to separate the pulp, and the pulp was thoroughly washed with water to obtain TEMPO oxidized pulp. The pulp yield at this time was 90%, and the time required for the oxidation reaction was 90 minutes.

The TEMPO oxidized pulp obtained in the above steps was adjusted to 3.0% (w/v) with water, adjusted to pH 7 with a 12% aqueous sodium hydroxide solution, and homogenized 5 times with an ultrahigh pressure homogenizer (20°C, 150 MPa). A fibrillation treatment was performed to obtain a TEMPO-oxidized fine cellulose fiber dispersion (Sample 1: hereinafter referred to as "TEMPO-oxidized CNF"). The resulting TEMPO-oxidized CNF had an average fiber diameter of 4 nm and an aspect ratio of 150. The amount of carboxyl groups in the obtained TEMPO-oxidized CNF was 1.42 mmol/g. Moreover, the specific surface area of the obtained TEMPO-oxidized CNF was 386 m ² /g.

Production Example 2 <Preparation of Sample 2 (CM-CNF)>
130 parts of water and 20 parts of sodium hydroxide dissolved in a mixed solvent of 10 parts of water and 90 parts of isopropanol (IPA) are added to a twin-screw kneader whose rotation speed is adjusted to 150 rpm, and hardwood pulp (Nippon Paper Industries LBKP (manufactured by Co., Ltd.) was charged at 100° C. for 60 minutes with a dry mass of 100 parts. The mixture was stirred and mixed at 35° C. for 80 minutes and mercerized. With further stirring, a mixed solvent of 23 parts of water and 207 parts of IPA and 40 parts of sodium monochloroacetate were added, stirred for 30 minutes, then heated to 70° C. and etherified for 90 minutes. After completion of the reaction, the mixture was neutralized with acetic acid until the pH reached 7, washed with water-containing methanol, deliquored, and side water was added to obtain a sodium salt aqueous solution of CM pulp. The degree of carboxymethyl ether substitution in the obtained CM pulp was 0.30.

The CM pulp obtained in the above step was adjusted to 3.0% (w/v) with water, and defibrated five times with an ultra-high pressure homogenizer (20°C, 150 MPa) to obtain a CM fine cellulose fiber. A dispersion was obtained (hereinafter referred to as "CM-CNF"). Ion-exchanged water was added to the obtained CM-CNF 3.0% (w / v) dispersion, stirred at 3000 rpm for 10 minutes with a homogenizer, diluted to a concentration of 0.5% (w / v), and CM-CNF ( Sample 2) A water dispersion was obtained. The resulting CM-oxidized CNF had a degree of carboxymethyl substitution of 0.30, an average fiber diameter of 4 nm, and an aspect ratio of 52.

Production Example 3 <Preparation of Sample 3 (Li salt type of TEMPO-oxidized CNF)>
A TOCN-COOLi aqueous dispersion (Sample 3) was obtained in the same manner as in Sample 1, except that the TEMPO oxidized pulp was adjusted to pH 7 with a 5% lithium hydroxide aqueous solution.

Production Example 4 <Preparation of Sample 4 (K salt form of TEMPO-oxidized CNF)>
A TOCN-COOK aqueous dispersion (Sample 4) was obtained in the same manner as in Sample 1, except that the TEMPO oxidized pulp was adjusted to pH 7 with a 10% potassium aqueous solution.

Examples of the method for manufacturing a sheet material using the cellulose slurry according to the embodiment of the present invention are shown below.

Example 1 <Sample 1, bar coating method>
As shown in FIG. 1, an Al thin film (thickness 25 μm) as an electrode material is laid under it, the slurry of sample 1 (solid content 1.0%) is poured over it, and a bar is used with a gap of 500 μm from the top surface of the Al thin film. It was applied horizontally in one direction. After that, it was dried on a hot plate at 100° C. to prepare a sheet having a thickness of 5 μm.

Example 2 <Sample 1, spin coating method>
Using the spin coater shown in FIG. 2, droplets of the slurry of Sample 1 (solid content: 1.5%) were dropped onto the Al thin film to uniformly coat the Al thin film at a peripheral speed of 200 rpm for 5 seconds. This was dried on a hot plate at 50°C. Next, the dry sheet-coated Al thin film was again placed on the rotating disk of the spin coater, and droplets of the slurry of Sample 2 were dropped to uniformly coat it at a peripheral speed of 500 to 1,000 rpm for 10 to 20 seconds. The operation of further coating the cellulose fiber layer was repeated five times to produce a cellulose fiber sheet with a thickness of 27 μm. The diameter of the unevenness on the surface of the cellulose fiber layer was 5.7 μm.

Example 3 <Sample 1, electrophoresis method>
In a water tank (water temperature 5 ° C) containing 500 ml of CNF slurry (sample 1: solid content 0.5%) as shown in FIG. gone. Electrodeposition conditions were DC 8 V for 2 minutes. After electrodeposition, it was washed with distilled water and dried at 50° C. for a whole day and night to prepare a cellulose fiber sheet with a thickness of 5 μm.

Example 4 <Sample 2, electrophoresis method (electrodeposition coating method)>
A cellulose fiber sheet having a thickness of 5 μm was produced in the same manner as in Example 3, except that Sample 2 was used instead of Sample 1.

Example 5 <Sample 1, bar coating method>
The procedure of Example 1 was repeated except that the thickness of the cellulose fiber sheet was adjusted to 1 μm.

Example 6 <Sample 1, spin coating method>
The procedure of Example 2 was repeated except that the thickness of the cellulose fiber sheet was adjusted to 1 μm.

Example 7 <Sample 1, electrophoresis method (electrodeposition coating method)>
The procedure of Example 3 was repeated except that the thickness of the cellulose fiber sheet was adjusted to 1 μm.

Example 8 <Sample 1, slip casting method>
The slurry (solid content: 1.0%) of sample 1 was poured into a mold having a silicone rubber frame placed on an Al thin film, and allowed to stand at 50°C for 2 days. After confirming that the water contained in the slurry was evaporated and dried, the slurry was removed from the mold to prepare a cellulose fiber sheet with a thickness of 1 μm.

Example 9 <Sample 2, slip casting method>
A cellulose fiber sheet having a thickness of 1 μm was produced in the same manner as in Comparative Example 1 except that the sample was used instead of the sample 1.

Table 1 shows the electrical resistance (MΩ) and storage capacity (mJ/m ² ) of the sheets obtained in Examples 1 to 9. The electrical resistance was obtained by sandwiching the obtained sheet of 5 cm square between two stainless steel plates and measuring the electrical resistance in the thickness direction using a DC resistance meter. The amount of stored electricity is a voltage drop curve (horizontal axis: time, vertical axis: voltage).

As shown in Table 1, each of the power storage bodies of Samples 1 to 2 of Examples 1 to 9 has an electrical resistance of 63 MΩ to 465 MΩ and a storage amount of 146 mJ/m ² to 1,705 mJ/m ² . confirmed. The CNF fiber diameter of the sheet of each example is too small, 3 nm on average, so even a high-precision atomic force microscope cannot observe pores of 1 nm or less in size, but the sheet structure of each sample is dense. is presumed. The samples of Examples 5-9 were confirmed to operate at 100V.

The specific surface areas of the cellulose fibers of Samples 1 and 2 were 386 m ² /g and 325 m ² /g, respectively, as a result of measuring according to the measurement method described in the previous paragraph by the BET adsorption method.

These results show that, according to the present invention, it is possible to efficiently manufacture a power storage body that includes a cellulose fiber layer and is capable of exhibiting a high storage capacity.

Example 10 <Sample 3, Electrophoresis>
A sheet was produced in the same manner as in Example 3, except that Sample 3 (0.5% solid content) was used instead of Sample 1. The thickness of the cellulose fiber layer was 4 μm.

Example 11 <Sample 4, Electrophoresis>
A sheet was produced in the same manner as in Example 3, except that Sample 4 (0.5% solid content) was used instead of Sample 1. The thickness of the cellulose fiber layer was 4 μm.

Example 12 <Preparation of Ca salt type sheet of TEMPO-oxidized CNF>
The sheet produced in Example 1 was immersed in a 1 mol/L calcium chloride aqueous solution for 2 hours to produce a sheet. The thickness of the cellulose fiber layer was 5 μm.

Example 13 <Preparation of Mg salt type sheet of TEMPO-oxidized CNF>
The sheet produced in Example 3 was immersed in a 1 mol/L aqueous solution of magnesium chloride for 2 hours to produce a sheet. The thickness of the cellulose fiber layer was 5 μm.

Example 14 <Preparation of Cu salt type sheet of TEMPO oxidized CNF>
The sheet produced in Example 3 was immersed in a 1 mol/L copper chloride aqueous solution for 2 hours to produce a sheet. The thickness of the cellulose fiber layer was 5 μm.

Example 15 <Preparation of Al salt type sheet of TEMPO-oxidized CNF>
The sheet produced in Example 3 was immersed in a 1 mol/L aluminum chloride aqueous solution for 2 hours to produce a sheet. The thickness of the cellulose fiber layer was 5 μm.

Table 2 shows the electric resistance (MΩ) and storage capacity (mJ/cm ² ) of the sheets obtained in Examples 10 to 15. The electrical resistance was obtained by sandwiching the obtained sheet of 5 cm square between two stainless steel plates and measuring the electrical resistance in the thickness direction using a DC resistance meter. The amount of stored electricity is a voltage drop curve (horizontal axis: time, vertical axis: voltage).

As shown in Table 2, it was confirmed that each electricity storage material of each example had an electrical resistance of 59 MΩ to 497 MΩ and an electricity storage amount of 102 mJ/m ² to 535 mJ/m ² . The sheet of each example has an average CNF fiber diameter of 3 nm, which is too small, so even a high-precision atomic force microscope cannot observe pore sizes of 1 nm or less, but the sheet structure is dense. Presumed.

The specific surface areas of the cellulose fibers of Samples 1 to 4 used for each sheet were 386 m ² /g, 325 m ² /g, 379 m ² /g and 331 m ² /g, respectively, as a result of measurement by the BET adsorption method.

These results show that the electrode-attached sheet material containing the cellulose fiber layer can exhibit a high amount of electricity storage.

Claims

A method for producing a laminate containing a cellulose fiber layer, comprising applying a cellulose fiber slurry to at least a part of an electrode layer to form a film to obtain a laminate unit comprising a cellulose fiber layer and an electrode layer.
The manufacturing method according to claim 1, wherein the electrode layer is an electrode sheet, and the cellulose fiber slurry is applied to one or both sides of the electrode sheet to form the film.
The manufacturing method according to claim 1 or 2, wherein the cellulose fiber slurry is applied by bar coating, spin coating, or electrophoresis.
The production method according to any one of claims 1 to 3, wherein the cellulose fiber has a specific surface area of 10 m 2 /g or more.
The production method according to any one of claims 1 to 4, wherein the cellulose fibers are cellulose nanofibers.
The manufacturing method according to any one of claims 1 to 5, wherein the cellulose fibers are chemically modified cellulose fibers.
The manufacturing method according to claim 6, wherein the chemically modified cellulose fibers are carboxylated, carboxymethylated, or esterified cellulose fibers.
The manufacturing method according to any one of claims 1 to 7, wherein the cellulose fiber further contains a metal.
The manufacturing method according to claim 7, wherein the chemically modified cellulose fibers are cellulose fibers containing metals as counterions.
The manufacturing method according to claim 8 or 9, wherein the metal is one or more selected from Na, Mg, Li, Ca, Al, K, Zn and Fe.
The manufacturing method according to any one of claims 1 to 10, wherein the laminate is an electricity storage material.
The manufacturing method according to any one of claims 1 to 10, further comprising laminating a plurality of laminated units.
comprising at least one laminate unit having an electrode layer and a cellulose fiber layer;
the cellulose fiber layer comprises cellulose fibers containing an anionic modifying group;
A laminate containing a cellulose fiber layer.
The laminate according to claim 13, wherein the cellulose fibers containing anionic modifying groups and metals are carboxylated, carboxymethylated, or esterified cellulose fibers.
The laminate according to claim 13 or 14, which is a power storage body.