Electronic member having bound water and power storage body including same

Abstract

The purpose of the present invention is to provide an electronic member containing a cellulose fiber layer and a power storage body, which have higher power storage efficiency, and a method for efficiently manufacturing the electronic member and the power storage body. The present invention provides an electronic member containing a cellulose fiber layer containing bound water, and a method for manufacturing an electronic member such as a power storage body, the method including step A: a step for applying a dispersion liquid containing cellulose fibers, such as those oxidized or carboxymethylated, to at least one surface of an electrode material to form a coating film, and step B: a step for drying the coating film at a maximum temperature of 70-195°C to form a cellulose fiber layer that is a dry coating film. The cellulose fiber layer containing bound water preferably contains anion-modified cellulose fibers, and more preferably contains salt-type anion-modified cellulose fibers. The bound water is preferably bound to the salt of the salt-type anion-modified cellulose fibers.

Description

Electronic component having bound water and power storage device including the same

[0001] The present invention relates to an electronic component having bound water, a power storage unit including the same, and a method for manufacturing the electronic component.

[0002] Capacitors are electronic components that store and discharge electric charge (electrical energy) through capacitance. They are essential components for mobile electronic devices such as personal computers and mobile phones, providing power supply stability, backup circuits, coupling elements, and noise filters. In recent years, the rapid evolution of high-performance IT products such as mobile phones and ultra-compact storage devices, as well as batteries for electric vehicles, has led to increased demand for smaller capacitors with high capacity and advanced functions such as memory. In particular, there is a demand for products that are compatible with a smart grid (next-generation power transmission network) society, which is in line with green innovation (low-carbonization) aimed at preventing global warming. For example, the capacitor market, which includes automobiles, IT devices, and energy-saving inverters, has been expanding steadily at an average annual rate of approximately 3.7%, reaching a market size of 1 trillion yen.

[0003] Such capacitors are desirable because they do not use flammable elements such as lithium or environmental pollutants, i.e., materials that are solid rather than liquid, are harmless to health, and are inexpensive.

[0004] Capacitors are broadly divided into those for high-voltage power circuits (heavy electrical equipment) and those for electronic and electrical equipment circuits (low-voltage equipment). Of these, ceramic capacitors are mainly used for low-voltage electronic and electrical equipment circuits, and secondary batteries are also widely used for storing electricity in mobile phones and other devices. In contrast, capacitors for heavy electrical equipment have not yet been put to practical use due to their insufficient voltage resistance and storage capacity.

[0005] Capacitors using conventional lumped-element circuits are widely used as key components of electronic and electrical devices, ranging in capacitance from 1 pF to several tens of mF. The capacitance C (F) is given by the following formula: C = Q / V = ε × (A / d) (where the symbols represent the following: Q: charge, V: voltage, ε: dielectric constant, A: electrode area, d: inter-electrode distance). Therefore, the larger the electrode area and the smaller the inter-electrode distance, the higher the charge capacity. However, from the perspective of miniaturizing electronic and electrical devices and the required capacitance, it is difficult to achieve an extremely large capacitance by increasing the electrode area A and reducing the inter-electrode distance d, or to achieve an extremely small capacitance by reducing the electrode area A and increasing the inter-electrode distance d. Furthermore, the capacitance of current dielectric-specification capacitors using lumped-element circuits has already saturated.

[0006] A method using an electric distributed constant circuit is a storage method that surpasses conventional capacitance. For example, an electric double layer capacitor, in which an electrolytic solution is wetted in activated carbon, has recently been put to practical use. However, a solid-state electric double layer capacitor has not yet been used.

[0007] Regarding solid-state electricity storage materials, the present inventors have discovered that electric charges can be stored in Si-(Al, Ti, V) alloys from which Al, Ti, and V have been removed by surface extraction, as well as TiO-coated Ti-Ni-Si and AlO-coated Al-Y amorphous alloys, regardless of whether they are DC or AC (see, for example, Non-Patent Documents 1 to 7 and Patent Documents 1 and 2).

[0008] Furthermore, the present inventors have discovered that when compound particles are 40 nm or less, preferably 10 nm or less, a "quantum size effect" occurs due to electron shielding that occurs on the surface of a nanosized solid. Energy storage materials utilizing this phenomenon have been developed, including amorphous titania, amorphous alumina, and amorphous fluoropolymers with nanosized irregularities formed on their surfaces (see, for example, Non-Patent Documents 4, 7-9, and Patent Document 2). In these energy storage materials, due to the quantum nanosize effect, the smaller the nanosized diameter of the protrusions, the greater the van der Waals electrostatic force acting as the negative sixth power of the diameter of the protrusions, thereby increasing the electron adsorption capacity of the protrusions (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, for example, Non-Patent Document 7) and 10.3 eV to 13.35 eV for amorphous fluoropolymers (see, for example, Non-Patent Document 4 and Patent Document 2).

[0009] Furthermore, the present inventors have developed an amorphous material whose surface is composed primarily of AlO6 and has multiple irregularities with diameters of 0.1 to 50 nm and height differences of 0.1 to 50 nm, as a material with a work function larger than these electricity storage materials and capable of storing large amounts of electricity (see, for example, Non-Patent Documents 9 and 10).It has been reported that anionic cellulose fibers such as oxidized cellulose nanofibers function as a solid electrolyte due to the oxidized surface, forming a strong electric double layer of adsorbed electrons and protons (Non-Patent Document 10), and can be used as a material for electricity storage devices with the qualities of a supercapacitor.

[0010] All of the above capacitors are artificial compounds made from inorganic or organic compounds. Currently, the production of artificial compounds that increase carbon dioxide gas and the production of microplastics that cause marine pollution are being avoided around the world from the perspective of protecting plants and animals and preserving the global environment. From this perspective, developing a biomass capacitor that uses wood and plant fiber (cellulose) obtained from plants, which has a low environmental impact in terms of production and disposal, is lightweight, and has high elasticity, is a timely direction for preserving the global environment.

[0011] Currently, two sheets of capacitor paper 8 to 15 micrometers thick are coated with a thin layer of lacquer, then vacuum-deposited with metals such as nickel, aluminum, or zinc, then rolled up and impregnated with an impregnating agent. These paper capacitors, however, use vegetable oil or silicone oil as the impregnating agent and are based on a wet lumped constant circuit (see, for example, Non-Patent Document 12).

[0012] The electricity storage material described in Non-Patent Document 7 is amorphous titania, the electricity storage materials described in Non-Patent Documents 9 and 10 are amorphous alumina, and the electricity storage material described in Non-Patent Document 8 is an amorphous polymer, and all of these materials are characterized by having uneven electrical insulating material on the surface, but all of them have the problem of being artificial.

[0013] In response to the above-mentioned issues, Patent Document 3 focuses on the use of environmentally friendly, recyclable plant fibers and describes an electricity storage material and ultra-electricity storage device that are capable of storing electricity in both DC and AC modes and are made using a fiber material of cellulose molecules obtained from wood and plant fibers (pulp). This electricity storage material is a lightweight, solid material that uses TEMPO-oxidized cellulose nanofibers (CNF), which are cellulose that has been surface-oxidized using an enzyme and electrostatically defibrated. It is characterized by its ability to instantly charge at high voltages of up to 500 V and its ability to operate over a wide temperature range from -200 to +150°C.

[0014] M. Fukuhara, T. Araki, K. Nagayama and H. Sakuraba, “Electric storage in de-alloyed Si-Al alloy ribbons”, EuroPhys. Lett., 2012, 99 ,47001M. Fukuhara, “Electric Charging / Discharging Characteristics of Capacitor, Using De-alloyed Si-20Al Alloy Ribbons”, Elect. Electr. Eng., 2013, 3(2), p.72-76M. Fukuhara and H. Yoshida, “AC charging / discharging of de-alloyed Si-Al-V alloy ribbons”, J. Alloys and Comp., 2014, 586, S130-S133M. Fukuhara, H. Yoshida, M. Sato, K. Sugawara, T. Takeuchi, I. Seki, and T. Sueyoshi, “Superior electric storage in de-alloyed and anodic oxidized Ti-Ni-Si glassy alloy ribbons”, Phys. Stat. Sol. RRL, 2013, 7(7), p.477-480M. Fukuhara and K. Sugawara, “Electric charging / discharging characteristics of super capacitor, using de-alloying and anodic oxidized Ti-Ni-Si amorphous alloy ribbons”, Nanoscale. Res. Lett., 2014, 9, p.253M. Fukuhara and K.Sugawara, “Anodic oxidization of Ti-Ni-Si amorphous alloy ribbons and their capacitive and resistive properties”, Thin Solid Films, 2015, 595, p.1-4M. Fukuhara, T. Kuroda and F. Hasegawa, “Amorphous titanium-oxide supercapacitors”, Sci. Rep., 2016, 6, 35870M. Fukuhara, T. Kuroda, F. Hasegawa and T. Sueyoshi, “Superior electric storage on an amorphous perfluorinated polymer surface,” Sci. Rep., 2016, 6, 22012M. Fukuhara, T. Kuroda, F. Hasegawa, T. Hashida, E. Kwon and K. Konno, “Amorphous aluminum-oxide supercapacitors,” EuroPhys. Lett., 2018, 123, 58004M. Fukuhara, T. Yokotsuka, T. Hashida, K.Yamaguch and N. Fujima, “Amorphous alumina supercapacitors with voltage-charging performance,” EuroPhys. Lett., 2023, 141, 36003M. Fukuhara, T. Kuroda, F. Hasegawa, Y. Shirai, T. Suwa, T. Hashida, and M. Nishijima, “Amorphous titanium-oxide supercapacitors with high capacitance,” EuroPhys. Lett., 2019, 128, 58001Encyclopedia of Japan (Nipponica) “Paper Capacitor”, Shogakukan, 1994, Volume 26.

[0015] JP 2016-134934 A JP 2017-41578 A International Publication No. 2021 / 166813

[0016] The constituent materials of conventional commercially available and practical energy storage materials are all artificial substances such as metals, inorganic compounds, and organic compounds, and are generally thought to contain no adsorbed or bound water. Adsorbed and bound water can cause electrical leakage and short circuits, making them a plague on electronic products. For this reason, electronic products that use these materials are equipped with countermeasures against seasonal humidity fluctuations and water leakage, such as humidity-sensing and water-leakage-preventing polymer film coatings.

[0017] An object of the present invention is to provide an electronic component and an electricity storage unit containing a cellulose fiber layer that can exhibit physical properties such as higher electricity storage efficiency, and to provide a method for efficiently producing such an electronic component and an electricity storage unit.

[0018] The inventors noticed that while ordinary storage batteries are easily affected by humidity in the humid summer months, storage batteries with laminated cellulose fiber layers are not affected by humidity in the summer and can perform the same functions as in the dry winter months.By recognizing the presence of bound water contained in cellulose fibers, they discovered unique properties not found in conventional artificial storage batteries, leading to the present invention.

[0019] The present invention provides the following items [1] to

[21] . [1] An electronic component comprising a cellulose fiber layer containing bound water and anion-modified cellulose fibers. [2] The electronic component according to [1], wherein the cellulose fibers are anion-modified cellulose fibers. [3] The electronic component according to [2], wherein the anion-modified cellulose fibers are salt-type anion-modified cellulose fibers. [4] The electronic component according to [2] or [3], wherein the anion-modified cellulose fibers are oxidized cellulose fibers. [5] The electronic component according to [3], wherein the bound water is bound to a salt of the salt-type anion-modified cellulose fibers. [6] The electronic component according to [5], wherein the bound water crosslinks adjacent salt-type anion-modified cellulose fibers via hydration with the salt of each of the salts of the salt-type anion-modified cellulose fibers. [7] The electronic component according to [5] or [6], wherein the cellulose fiber layer comprises a surface layer containing crosslinked salt-type anion-modified cellulose fibers and an inner layer containing cellulose fibers. [8] The electronic component according to any one of [3] to [7], wherein the salt is a sodium salt. [9] The electronic component according to any one of [2] to [7], wherein the cellulose fibers are crystalline and amorphous.

[10] The electronic component according to any one of [1] to [9], wherein the anion-modified cellulose fibers are amorphous cellulose fibers having atomic vacancies.

[11] The electronic component according to any one of [1] to

[10] , wherein the cellulose fiber layer has irregularities with a diameter of 1 nm to 500 nm on the surface.

[12] The electronic component according to any one of [1] to

[10] , wherein the capacitance is 10 mJ / m ２

[13] The electronic component according to any one of [1] to

[11] , wherein the specific surface area of ​​the surface of the cellulose fiber layer is 10 to 900 m 2 / g.

[14] The electronic component according to any one of [1] to

[13] , wherein the cellulose fiber layer is a coating film of a dispersion containing cellulose fibers dried at a maximum temperature of 70 to 195°C.

[15] A power storage unit including the electronic component according to any one of [1] to

[14] .

[16] A method for producing an electronic component, comprising: Step A: applying a dispersion containing cellulose fibers to at least one surface of an electrode material to form a coating film; and Step B: drying the coating film at a maximum temperature of 70 to 195°C to form a cellulose fiber layer as a dried coating film.

[17] The method according to

[16] , wherein the drying time in Step B is 800 minutes or less.

[18] The method according to

[16] or

[17] , wherein the coating in Step A is coating by electrodeposition coating.

[19] The method according to any one of

[16] to

[18] , wherein the film thickness of the cellulose fiber layer in Step B is 50 μm or less.

[20] The method according to any one of

[16] to

[19] , wherein the cellulose fiber comprises an anionically modified cellulose fiber.

[21] The method according to

[20] , wherein the anionically modified cellulose fiber comprises an oxidized cellulose fiber and / or a carboxymethylated cellulose fiber.

[0020] According to the present invention, it is possible to provide an electronic component and a power storage unit that exhibit excellent electricity storage properties and are capable of storing electricity in both DC and AC modes, as well as a method for manufacturing the same. The present invention is expected to provide electronic materials that utilize natural resources such as wood and pulp as an alternative to conventional electronic components, and to further promote global environmental conservation.

[0021] Fig. 1 is a diagram showing the electricity storage properties of electricity storage units using unmodified (mechanically defibrated) cellulose nanofibers and TEMPO-oxidized cellulose nanofibers. Fig. 2 is a circuit diagram showing an example of an electric distributed constant circuit of an electricity storage unit of the present invention. Fig. 3 is a graph showing the change in the amount of stored electricity of an electricity storage unit with increasing temperature in an example. Fig. 4 is a graph showing the change in the amount of evaporation depending on the heating temperature of an electricity storage unit with increasing temperature in an example. Fig. 5 is a graph showing the change in the amount of evaporation depending on the heating temperature of an electricity storage unit of an example at 20°C before heating and at 180°C after heating. 13 FIG. 1 is a comparative diagram of C NMR spectra.

[0022] [1. Cellulose Fiber] The cellulose fiber layer included in the electronic component is mainly composed of cellulose fibers such as anion-modified cellulose fibers. The anion-modified cellulose fibers are cellulose fibers to which anion modification has been introduced.

[0023] [Examples of Cellulose Fibers] Cellulose fibers are usually cellulose fibers derived from living organisms, and examples thereof include cellulose fibers derived from plants (e.g., wood, bamboo, hemp, jute, kenaf, rice), animals (e.g., ascidians), algae, microorganisms (e.g., acetic acid bacteria (Acetobacter)), microbial products, etc. The cellulose fibers are preferably cellulose fibers derived from plants or microorganisms, more preferably cellulose fibers derived from plants, especially wood. Examples of cellulose fibers derived from plants or microorganisms include 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 chemical pulps such as kraft pulp (e.g., softwood kraft pulp such as unbleached softwood kraft pulp (NUKP) and bleached softwood kraft pulp (NBKP); hardwood kraft pulp such as unbleached hardwood kraft pulp (LUKP) and bleached hardwood kraft pulp (LBKP)), sulfite pulp (e.g., softwood sulfite pulp such as unbleached softwood sulfite pulp (NUSP) and bleached softwood sulfite pulp (NBSP)), mechanical pulp such as thermomechanical pulp (TMP), and recycled pulp, with chemical pulp being preferred. The cellulose fiber may be cellulose fiber that has been subjected to a micronization treatment, such as cellulose nanofiber or cellulose microfibril. Alternatively, cellulose fiber obtained by enzymatically treating various pulps to promote fibrillation may be used. Furthermore, the cellulose fibers may be chemically modified cellulose fibers (e.g., pulp, cellulose nanofibers, cellulose microfibrils). In this specification, chemically modified cellulose fibers refer to cellulose fibers that have been subjected to a chemical modification treatment. Chemically modified cellulose fibers and chemical modification treatments will be described later.

[0024] [Size of Cellulose Fibers] The size of the cellulose fibers (for example, average fiber diameter, average fiber length, aspect ratio) is not particularly limited, but examples are as follows.

[0025] (Pulp Size) The number average fiber diameters of common softwood kraft pulp and hardwood kraft pulp 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 common refining) is usually about 50 μm. In the case of pulp obtained by refining pieces of chips or the like that are several centimeters in size, it is preferable to adjust the number average fiber diameter to about 50 μm as necessary by a refining treatment described below.

[0026] (Size of Cellulose Microfibrils) In this specification, cellulose microfibrils refer to cellulose fibers that have been subjected to a micronization treatment and have a fiber diameter on the order of microns. The average fiber diameter of cellulose microfibrils is usually 500 nm or more, preferably 1 μm or more, and more preferably 10 μm or more. This allows for higher water retention than undefibrated cellulose fibers (e.g., pulp), and even a small amount can provide higher strength-imparting effects and yield-improving effects than finely defibrated cellulose nanofibers. 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 there is no particular limit.

[0027] 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.

[0028] The aspect ratio of the 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. There is no particular upper limit to the aspect ratio, but it is preferably 1,000 or less, more preferably 100 or less, and even more preferably 80 or less.

[0029] (Size of Cellulose Nanofibers) In this specification, cellulose nanofibers (CNFs) refer to cellulose fibers that have undergone a micronization process and have a fiber diameter on the nanometer order. The use of CNFs can more efficiently realize the quantum size effect of electricity storage devices. The average fiber diameter (length-weighted average fiber diameter) of CNFs is 500 nm or less, preferably 300 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. While the lower limit is not particularly limited, it is typically 1 nm or more, preferably 2 nm or more. Therefore, the average fiber diameter (length-weighted average fiber diameter) of CNFs is typically 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 typically 50 to 2,000 nm, preferably 100 to 1,000 nm. The aspect ratio of CNFs is typically 10 or more, preferably 50 or more. There is no particular upper limit, but it is usually 1000 or less.

[0030] In this specification, the average fiber diameter and average fiber length are determined by observing each fiber using an atomic force microscope (AFM) or a transmission electron microscope (TEM). The average aspect ratio can be calculated using the formula: average aspect ratio = average fiber length / average fiber diameter.

[0031] The size of the cellulose fibers can be adjusted by the conditions of a micronization treatment or a chemical modification treatment such as an anion modification.

[0032] [Examples of Chemical Modification and Modification Methods] Chemically modified cellulose fibers can be obtained by chemically modifying unmodified cellulose fibers (e.g., unmodified pulp, unmodified powdered cellulose). Examples of chemical modification treatments include anionization (e.g., carboxylation (oxidation), dicarboxylation, ozone oxidation, etherification (e.g., carboxymethylation), esterification (phosphoric acid, phosphorous acid, sulfuric acid)), and cationization. A cellulose fiber layer containing anion-modified cellulose fibers as its main component can exhibit a high electricity storage effect. Among these, carboxylated and etherified cellulose fibers are more preferred, and carboxylated cellulose fibers are even more preferred. By introducing anionic groups (preferably carboxyl groups) into cellulose fibers, a cellulose fiber layer containing anion-modified cellulose fibers becomes a solid electrolyte and can form an electric double layer. Therefore, an electricity storage material containing such a layer can exhibit a higher electricity storage capacity than a material containing only unmodified cellulose fibers (e.g., Figure 1), and is expected to be useful as a supercapacitor. The chemical modification treatment is usually performed before or after the micronization treatment, preferably before.

[0033] (Carboxylation (Oxidation)) Carboxylated cellulose fibers (oxidized cellulose fibers) usually have a structure in which at least one of the carbon atoms having a primary hydroxyl group contained in the glucopyranose unit that constitutes the cellulose molecular chain (for example, the carbon atom having a primary hydroxyl group at the C6 position) is oxidized. The amount of carboxyl groups in carboxylated cellulose fibers is preferably 0.6 to 3.0 mmol / g, and more preferably 1.0 to 2.0 mmol / g. The amount of carboxyl groups can be adjusted by controlling the conditions for carboxylating the cellulose fibers (for example, the amount of oxidizing agent added, the reaction time).

[0034] The amount of carboxy groups can be calculated using the following procedure. 60 ml of a 0.5% by mass slurry (aqueous dispersion) of oxidized cellulose is prepared. 0.1 M aqueous hydrochloric acid is added to the prepared slurry to adjust the pH to 2.5. 0.05 N aqueous sodium hydroxide is then added dropwise, and the electrical conductivity is measured until the pH reaches 11. The amount of carboxy groups is calculated using the following formula from the amount of sodium hydroxide (a) consumed in the neutralization stage of a weak acid, where the change in electrical conductivity is gradual: Amount of carboxy groups [mmol / g oxidized cellulose] = a [ml] × 0.05 / mass of oxidized cellulose [g]

[0035] Carboxylated cellulose fibers can be produced by carboxylating (oxidizing) unmodified cellulose fibers (cellulose raw material: for example, pulp). One example of the carboxylation (oxidation) method is a method in which the 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. This oxidation reaction selectively oxidizes the carbon atom bearing a primary hydroxyl group at the C6 position of the glucopyranose ring on the surface of the cellulose, leaving aldehyde groups and carboxyl groups (-COOH) or carboxylate groups (-COO － The concentration of the cellulose raw material during the reaction is not particularly limited, but is preferably 5% by mass or less.

[0036] An N-oxyl compound refers to a compound capable of generating a nitroxy radical. Any compound can be used as the N-oxyl compound as long as it promotes the target oxidation reaction. Examples include 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and its derivatives (e.g., 4-hydroxyTEMPO).

[0037] 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, the amount is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and even more preferably 0.05 to 0.5 mmol, per 1 g of bone-dry cellulose raw material. The amount is preferably about 0.1 to 4 mmol / L of the reaction system.

[0038] Bromides are compounds containing bromine, such as alkali metal bromides that can dissociate and ionize in water. Iodides are compounds containing iodine, such as alkali metal iodides. The amount of bromide or iodide used can be selected within a range that can promote 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, and even more preferably 0.5 to 5 mmol, per 1 g of bone-dry cellulose raw material.

[0039] Known oxidizing agents can be used, such as halogens, hypohalous acids, halous acids, perhalogen acids or their salts, halogen oxides, and peroxides. Among these, sodium hypochlorite is preferred because it is inexpensive and has a low environmental impact. The appropriate amount of oxidizing agent used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, even more preferably 1 to 25 mmol, and even more preferably 3 to 10 mmol, per 1 g of bone-dry cellulose raw material. Furthermore, for example, 1 to 40 mol is preferred per 1 mol of the N-oxyl compound.

[0040] The oxidation process of cellulose raw materials proceeds efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40°C, or may be room temperature, about 15 to 30°C. As the reaction proceeds, carboxyl groups are generated in the cellulose, causing a decrease in the pH of the reaction solution. To efficiently proceed with the oxidation reaction, 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 to 12, preferably about 10 to 11. Water is preferred as the reaction medium because it is easy to handle and is less likely to cause side reactions.

[0041] The reaction time in the oxidation reaction can be appropriately set depending on the degree of progress of the oxidation, and is usually from 0.5 to 6 hours, for example, from about 0.5 to 4 hours.

[0042] The oxidation reaction may be carried out in two stages. For example, the oxidized cellulose obtained by filtration after the completion of the first-stage reaction can be oxidized again under the same or different reaction conditions, thereby enabling efficient oxidation without reaction inhibition by sodium chloride produced as a by-product in the first-stage reaction.

[0043] Another example of a carboxylation (oxidation) method is a method in which cellulose raw materials are oxidized by contacting them with an ozone-containing gas. This oxidation reaction oxidizes at least the hydroxyl groups at positions 2 and 6 of the glucopyranose ring, and decomposes the cellulose chain. The ozone concentration in the ozone-containing gas is 50 to 250 g / m. ３ is preferred, and 50 to 220 g / m ３ is more preferred. The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by mass, and more preferably 5 to 30 parts by mass, based on 100 parts by mass of the solids content of the cellulose raw material. The ozone treatment temperature is preferably 0 to 50°C, and more preferably 20 to 50°C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, and preferably about 30 to 360 minutes. When the ozone treatment conditions are within these ranges, excessive oxidation and decomposition of the cellulose raw material can be prevented, and a good yield of oxidized cellulose can be achieved.

[0044] After the ozone treatment, a further oxidation treatment may be carried out using an oxidizing agent. The oxidizing agent used in the further oxidation treatment is not particularly limited, but examples include chlorine compounds such as chlorine dioxide and sodium chlorite, as well as oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. For example, the further oxidation treatment can be carried out by dissolving these oxidizing agents in water or a polar organic solvent such as alcohol to prepare an oxidizing agent solution, and then immersing the oxidized cellulose in the solution.

[0045] (Salt-type oxidized cellulose) Salt-type oxidized cellulose usually has a salt-type carboxyl group (—COO -Counter cations of the salt-type carboxyl groups include, for example, alkali metals such as Li, Na, and K; alkaline earth metals such as Mg and Ca; Fe; and metals such as Al, with Li, Na, and Ca being preferred, and Na being more preferred. The counter cation in oxidized cellulose obtained by a conventional oxidation method is Na, and when it is desired to replace Na with a desired metal, a compound containing that metal (LiCl ２ , CaCl ２ The substrate may be immersed in an aqueous solution of

[0046] (Acid-type oxidized cellulose and desalted cellulose) Oxidized cellulose contains carboxyl groups as a result of oxidation, but the acid-type carboxyl groups (—COOH) are converted to salt-type carboxyl groups (—COOH). -) or may contain more salt-type carboxyl groups than acid-type carboxyl groups, with the latter being preferred. The amounts of salt-type carboxyl groups and acid-type carboxyl groups can be adjusted by desalting treatment. Desalting treatment can convert salt-type carboxyl groups to acid-type carboxyl groups. In this specification, oxidized cellulose (which has undergone desalting) is referred to as acid-type oxidized cellulose, and oxidized cellulose (which has not undergone the desalting treatment described below) is referred to as salt-type oxidized cellulose. Salt-type oxidized cellulose usually contains primarily salt-type carboxyl groups (—COO−). On the other hand, acid-type oxidized cellulose contains many acid-type carboxyl groups, and the proportion of acid-type carboxyl groups in the 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 before desalting treatment is prepared, with a solids concentration of 0.1% by mass. 0.1 M aqueous hydrochloric acid is added to the prepared aqueous dispersion to adjust the pH to 2.5, and then 0.1 N aqueous sodium hydroxide is added and the electrical conductivity is measured until the pH reaches 11. The amount of acid-type carboxyl groups and the amount of salt-type carboxyl groups, i.e., the total amount of carboxyl groups, is calculated using the amount of sodium hydroxide (a) consumed in the neutralization stage of a weak acid, where the change in electrical conductivity is gradual, using the following formula: Total amount of carboxyl groups (mmol / g oxidized cellulose (salt form)) = a (ml) × 0.1 / mass (g) of oxidized cellulose (salt form) 2) 250 mL of an aqueous dispersion of desalted acid-type oxidized cellulose with a solids concentration of 0.1% by mass is prepared. 0.1 N aqueous sodium hydroxide is added to the prepared aqueous dispersion, and the electrical conductivity is measured until the pH reaches 11. The amount of acid-type carboxyl groups is calculated using the following formula from the amount of sodium hydroxide (b) consumed in the neutralization stage of a weak acid where the change in electrical conductivity is gradual: Amount of acid-type carboxyl groups (mmol / g acid-type oxidized cellulose) = b (ml) × 0.1 / mass of acid-type oxidized cellulose (g) 3) The proportion of acid-type carboxyl groups is calculated using the following formula from the calculated total amount of carboxyl groups and the amount of acid-type carboxyl groups: Proportion of acid-type carboxyl groups (%) = (amount of acid-type carboxyl groups / total amount of carboxyl groups) × 100

[0047] The timing of desalting may be after oxidation, and may be either before or after defibration (before or after step (2)), but is usually after oxidation, and preferably before step (2). Desalting is usually carried out by substituting salts (e.g., sodium salts) contained in the salt-form oxidized cellulose with protons. Examples of desalting methods include a method of adjusting the system to an acidic state and a method of contacting oxidized cellulose with a cation exchange resin. In the method of adjusting the system to an acidic state, the pH of the system is preferably adjusted to 2 to 6, more preferably 2 to 5, and even more preferably 2.3 to 5. To adjust the system to an acidic state, an acid (e.g., 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) is usually used. After the addition of the acid, a washing treatment may be carried out as appropriate. The cation exchange resin is a cation exchange resin having a counter ion of H + As long as the cation exchange resin satisfies the above condition, either a strongly acidic ion exchange resin or a weakly acidic ion exchange resin can be used. The ratio of the oxidized cellulose and the cation exchange resin when contacting them is not particularly limited, and can be appropriately determined by a person skilled in the art from the viewpoint of efficient proton substitution. The cation exchange resin after contact can be recovered by a conventional method such as suction filtration.

[0048] (Etherification) Examples of the etherification include etherification by a reaction selected from carboxyalkylation, methylation, ethylation, cyanoethylation, hydroxyethylation, hydroxypropylation, ethylhydroxyethylation, and hydroxypropylmethylation, with carboxyalkylation being preferred and carboxymethylation being more preferred.

[0049] Carboxyalkylated cellulose fibers typically have a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom bearing a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is carboxymethylated.

[0050] 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, even more preferably 0.15 or more, even more preferably 0.20 or more, and particularly preferably 0.25 or more. This ensures a degree of substitution sufficient to obtain the effects of chemical modification. 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, allowing the fiber form to be maintained in water. Therefore, the degree of carboxyalkyl substitution is preferably 0.01 to 0.50, more preferably 0.01 to 0.45, even more preferably 0.02 to 0.40, 0.10 to 0.35, or 0.20 to 0.30.

[0051] The degree of substitution, for example, the degree of carboxymethyl substitution, can be measured by the following method. Approximately 2.0 g of carboxymethylated cellulose (bone dry) is weighed out and placed in a 300 mL Erlenmeyer flask with a ground stopper. 100 mL of a solution of 1,000 mL of methanol and 100 mL of concentrated nitric acid is added, and the mixture is shaken for 3 hours to convert the salt-form carboxymethylated cellulose (hereinafter also referred to as "salt-form carboxymethylated cellulose") to the acid-form carboxymethylated cellulose (hereinafter also referred to as "acid-form carboxymethylated cellulose"). 1.5 to 2.0 g of acid-form carboxymethylated cellulose (bone dry) is weighed out and placed in a 300 mL Erlenmeyer flask with a ground stopper. The acid-form carboxymethylated cellulose is wetted with 15 mL of 80% methanol, 100 mL of 0.1 N NaOH is added, and the mixture is shaken at room temperature for 3 hours. Using phenolphthalein as an indicator, excess NaOH is back-titrated with 0.1N H2SO4, and the degree of carboxymethyl substitution (DS) can be calculated by the following formula: A = [(100 x F - (0.1N H2SO4 (mL)) x F') x 0.1] / (bone-dry mass (g) of acid-type carboxymethylated cellulose) DS = 0.162 x A / (1 - 0.058 x A) A: amount (mL) of 1N NaOH required to neutralize 1 g of acid-type carboxymethylated cellulose F': factor of 0.1N H2SO4 F: factor of 0.1N NaOH

[0052] The degree of carboxyalkyl substitution can be adjusted by controlling the reaction conditions such as the amount of carboxyalkylating agent to be reacted, the amount of mercerizing agent, and the composition ratio of water to organic solvent.

[0053] As a method of carboxyalkylation, for example, a method in which a cellulosic raw material as a starting material (bottom raw material) is mercerized and then etherified can be mentioned. Carboxymethylation will be explained below as an example.

[0054] Carboxymethylated cellulose can be produced by using unmodified cellulose fibers (cellulose raw material: for example, pulp) as the starting material and subjecting them to a mercerization treatment in the presence of 3 to 20 times the mass of a solvent, followed by an etherification reaction. Examples of the solvent that can be used include water and lower alcohols (e.g., methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, and tertiary butanol), either alone or in combination. When a lower alcohol is added, the mixing ratio of the lower alcohol is preferably 60 to 95% by mass.

[0055] As the mercerizing agent, an alkali metal hydroxide (for example, sodium hydroxide or potassium hydroxide) is used in an amount of 0.5 to 20 times the molar amount of the anhydrous glucose residues in the starting material.

[0056] The starting material, solvent, and mercerizing agent are mixed and subjected to mercerization treatment 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 in an amount of 0.05 to 10.0 times the amount, in terms of moles, per glucose residue, and carboxymethylated cellulose can be produced by carrying out an etherification reaction at a reaction temperature of 30 to 90°C, preferably 40 to 80°C, for a reaction time of 30 minutes to 10 hours, preferably 1 hour to 4 hours.

[0057] (Differences from Carboxymethyl Cellulose) It is preferable that carboxyalkylated cellulose fibers maintain at least a portion of their fibrous shape even when dispersed in water. Carboxyalkylated cellulose fibers are distinguished from cellulose powders such as carboxymethyl cellulose, 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 under an electron microscope, fibrous substances can be observed. On the other hand, when an aqueous dispersion of carboxymethyl cellulose, a type of water-soluble polymer, is observed, no fibrous substances are observed. Furthermore, when carboxymethylated cellulose fibers are measured by X-ray diffraction, peaks of cellulose type I crystals can be observed, but when carboxymethyl cellulose powder, a water-soluble polymer, is similarly measured, cellulose type I crystals are usually not observed.

[0058] (Acid-Type Carboxyalkylated Cellulose) 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, with the latter being preferred. The amounts of salt-type carboxyl groups and acid-type carboxyl groups can be adjusted by desalting treatment. Desalting treatment can convert salt-type carboxyl groups to acid-type carboxyl groups. In this specification, carboxyalkylated cellulose (which has undergone desalting) is referred to as acid-type carboxyalkylated cellulose, and carboxyalkylated cellulose (which has not undergone the desalting treatment described below) is referred to as salt-type carboxyalkylated cellulose. Salt-type carboxyalkylated cellulose usually contains primarily salt-type carboxyl groups (—COO−). On the other hand, acid-type carboxyalkylated cellulose contains many acid-type carboxyl groups, and the ratio of the amount of acid-type carboxyl groups to the amount of carboxyl groups in the acid-type carboxyalkylated cellulose is preferably 40% or more, more preferably 60% or more, and even more preferably 85% or more. The method for calculating the proportion of acid-type carboxyl groups is as described above.

[0059] The desalting is usually carried out after carboxyalkylation, preferably after etherification and before fibrillation. For example, the desalting method may be a method of contacting the carboxyalkylated cellulose with a cation exchange resin. The cation exchange resin has a counter ion of H + As long as the cation exchange resin is strong acidic or weak acidic, either a strong acidic or a weak acidic ion exchange resin can be used. The ratio of the carboxyalkylated cellulose and the cation exchange resin when contacting them is not particularly limited, and can be appropriately determined by a person 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 to the carboxyalkylated cellulose aqueous dispersion is preferably 2 to 6, more preferably 2 to 5. The cation exchange resin after contact can be recovered by a conventional method such as suction filtration.

[0060] (Esterification (Phosphorylation)) A first example of an esterified cellulose fiber is phosphorylated cellulose. Phosphorylated cellulose usually has a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom bearing a primary hydroxyl group at C6 constituting the glucopyranose unit) is phosphorylated.

[0061] The amount of ionic substituent introduced into the phosphated cellulose fiber (ionic substituent amount, phosphorus oxo acid substituent amount) may be 0.10 mmol / g or more per 1 g (mass) of phosphated CNF, preferably 0.20 mmol / g or more, more preferably 0.30 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.50 mmol / g or more, even more preferably 0.60 mmol / g or more, and particularly preferably 0.70 mmol / g or more. The amount of ionic substituent introduced into the phosphated CNF may be 1.50 mmol / g or less per 1 g (mass) of cellulose fiber, preferably 1.35 mmol / g or less, more preferably 1.20 mmol / g or less, and even more preferably 1.10 mmol / g or less. The amount of ionic substituent introduced into the phosphated cellulose fiber is also preferably 1.00 mmol / g or less per 1 g (mass) of phosphated cellulose fiber, more preferably 0.95 mmol / g or less. Here, the denominator in the unit mmol / g is the value when the counter ion of the ionic substituent is a hydrogen ion (H ＋ The amount of phosphorus oxo acid substituents can be measured by the following method.

[0062] [Measurement of phosphorus oxoacid group content] The phosphorus oxoacid group content of fine cellulose fibers can be measured by treating a cellulose fiber-containing slurry prepared by diluting a fine cellulose fiber dispersion containing the target fine cellulose fibers with ion-exchanged water to a content of 0.2 mass %, followed by titration with an alkali.

[0063] The treatment with ion exchange resin was carried out by adding 1 / 10 by volume of a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) to the above cellulose fiber-containing slurry, shaking for 1 hour, and then pouring it onto a mesh with 90 μm openings to separate the resin from the slurry.

[0064] In addition, the alkali titration was performed by adding 10 μL of 0.1 N sodium hydroxide aqueous solution every 5 seconds to the cellulose fiber-containing slurry after treatment with the ion exchange resin, while measuring the change in the pH value of the slurry. Nitrogen gas was blown into the slurry 15 minutes before the start of the titration. In this neutralization titration, two maximum points of increment (differential value of pH with respect to the amount of alkali added) were observed on the curve plotting the measured pH against the amount of alkali added. Of these, the maximum point of increment obtained first after starting the addition of alkali is called the first endpoint, and the maximum point of increment obtained next is called the second endpoint. The amount of alkali required from the start of the titration to the first endpoint is equal to the amount of first dissociated acid in the slurry used in the titration. Furthermore, the amount of alkali required from the start of the titration to the second endpoint is equal to the total amount of dissociated acid in the slurry used in the titration. The amount of alkali (mmol) required from the start of titration to the first endpoint was divided by the solid content (g) in the slurry to be titrated to determine the amount of phosphorus oxoacid groups (mmol / g). The presence or absence of phosphate groups was confirmed by measuring the infrared absorption spectrum, and the absorption due to phosphate groups (1230 cm －１ This may be done by checking the area around the

[0065] The amount of phosphate groups 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 added as needed.

[0066] Examples of phosphorylation methods include reacting unmodified cellulose fibers with a compound having a phosphate group (phosphorylation). Examples of phosphorylation methods include mixing a powder or an aqueous solution of a compound having a phosphate group with a cellulosic raw material, and adding an aqueous solution of a compound having a phosphate group to an aqueous dispersion of the cellulosic raw material, with the latter being preferred. This can increase the uniformity of the reaction and the esterification efficiency.

[0067] Examples of 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, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, and ammonium metaphosphate. One or more compounds having a phosphate group can be used in combination. 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, and even more preferably 2 to 200 parts by mass, calculated as elemental phosphorus, per 100 parts by mass of the solids content of the cellulose raw material. The reaction temperature is preferably 0 to 95°C, more preferably 30 to 90°C. The reaction time is not particularly limited, but is usually about 1 to 600 minutes, preferably 30 to 480 minutes. When the esterification reaction conditions are within any of these ranges, excessive esterification of cellulose and its tendency to become easily soluble can be suppressed, thereby improving the yield of phosphorylated cellulose. When reacting a compound having a phosphate group, a basic compound (e.g., a compound having an amino group that exhibits basicity, such as urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, or hexamethylenediamine) may be further added to the reaction system.

[0068] (Esterification (Phosphite Esterification)) A second example of a method for producing esterified cellulose fibers is a method for producing phosphite-esterified cellulose fibers. Phosphite-esterified 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 bearing a primary hydroxyl group at the C6 position constituting a glucopyranose unit) is phosphoritized. The degree of substitution of the phosphite group per glucose unit in the phosphite-esterified cellulose fiber (hereinafter simply referred to as the "phosphite group substitution degree") is preferably 0.001 or more and less than 0.40. The degree of substitution of the phosphite group can be measured by the same method as that for measuring the degree of phosphate group substitution. The degree of substitution of the phosphite group can be adjusted by controlling reaction conditions such as the amount of phosphorous acid or a salt thereof added, and the amount of an alkali metal ion-containing substance, urea, or a derivative thereof, added as needed.

[0069] As a method for phosphite esterification, for example, a method in which phosphorous acid or a metal salt thereof (preferably sodium hydrogen phosphite) is reacted with unmodified cellulose fibers to introduce an ester group of phosphorous acid can be mentioned.

[0070] Examples of phosphorous acid and its metal salts include phosphorous acid compounds such as phosphorous acid, sodium hydrogen phosphite, ammonium hydrogen phosphite, potassium hydrogen phosphite, sodium dihydrogen phosphite, sodium phosphite, lithium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite, triethyl phosphite, triphenyl phosphite, and pyrophosphorous acid, as well as combinations of two or more selected from these, with sodium hydrogen phosphite being preferred. This allows alkali metal ions to be introduced into the cellulose fibers. The amount of phosphorous acid or its metal salts added is preferably 1 to 10,000 g, more preferably 100 to 5,000 g, and even more preferably 300 to 1,500 g per kg of unmodified cellulose fibers. In addition to phosphorous acid and its metal salts, an alkali metal ion-containing substance (e.g., hydroxide, metal sulfate, metal nitrate, metal chloride, metal phosphate, or metal carbonate) may also be added to the reaction system.

[0071] Urea or a derivative thereof may also be added to the reaction system. This allows carbamate groups to be introduced into the cellulose fibers. Examples of urea and urea derivatives include 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 derivative added is preferably 0.01 to 100 mol, more preferably 0.2 to 20 mol, and even more preferably 0.5 to 10 mol per mol of phosphorous acid or its metal salt.

[0072] The reaction temperature is preferably 100 to 200°C, more preferably 100 to 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 phosphite groups per glucose unit is preferably 0.01 or more and less than 0.23.

[0073] (Esterification (Sulfuric Acid Esterification)) A third example of a method for producing an esterified cellulose fiber is a sulfated cellulose fiber. Cellulose sulfate usually has a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom bearing a primary hydroxyl group at C6 constituting the glucopyranose unit) is phosphorylated.

[0074] The amount of sulfate groups per glucose unit in sulfated cellulose fibers (hereinafter simply referred to as "sulfate group amount") is preferably 0.1 to 3.0 mmol / g. Introducing cationic substituents into the cellulose raw material causes electrical repulsion between cellulose molecules. Therefore, cationized cellulose with cationic substituents introduced can be easily nano-fibrillated. When the degree of cationic substitution per glucose unit is 0.02 or more, sufficient nano-fibrillation can be achieved due to the electrical repulsion between cellulose molecules. On the other hand, when the degree of cationic substitution per glucose unit is 0.50 or less, swelling or dissolution can be suppressed, preventing the failure to obtain nanofibers. For efficient fibrillation, it is preferable to wash the cationized cellulose obtained above.

[0075] The amount of sulfate groups per glucose unit can be measured by the following method. An aqueous dispersion of sulfated CNF is solvent-substituted with ethanol and then 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. 10 ml of 0.5 N aqueous sodium hydroxide solution is then added, and the mixture is stirred at 70°C for 30 minutes, and then at 30°C for a further 24 hours. Phenolphthalein is then added as an indicator, and the mixture is titrated with hydrochloric acid, and the amount of sulfate groups per glucose unit is calculated using the following formula: Amount of sulfate groups [mmol / g sample] = (5 - (0.1 × titration amount of hydrochloric acid [ml] × 2)) / 0.2.

[0076] The amount of sulfate groups can be adjusted by controlling the reaction conditions such as the amount of sulfate compound added to the reaction mixture.

[0077] An example of a method for sulfate esterification is a method in which unmodified cellulose fibers are reacted with a sulfate compound to introduce sulfate groups derived from the sulfate compound into cellulose to produce sulfated cellulose. Examples of sulfate compounds include sulfuric acid, sulfamic acid, chlorosulfonic acid, sulfur trioxide, and esters or salts thereof. Among these, sulfamic acid is preferred because it has low cellulose solubility and low acidity.

[0078] For example, when sulfamic acid is used as the sulfate compound, the amount of sulfamic acid used can be appropriately adjusted taking into consideration the amount of anionic groups introduced into the cellulose chain, and is preferably 0.01 to 50 mol, more preferably 0.1 to 3.0 mol, per mol of glucose unit in the cellulose molecule.

[0079] (Salt type / acid type) 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, with the latter being preferred. Among esterified celluloses, those that have not undergone desalting treatment and those that have undergone desalting treatment are called salt type esterified cellulose and acid type esterified cellulose, respectively. Salt type esterified cellulose mainly contains salt type carboxyl groups. The counter cations of the salt type carboxyl groups and the preparation method thereof are as explained in the explanation of oxidized cellulose.

[0080] (Cationization) Cationized cellulose usually has a structure in which at least one of the carbon atoms constituting the cellulose molecular chain (for example, the carbon atom bearing a primary hydroxyl group at the C6 position constituting the glucopyranose unit) is cationized. The degree of cationic substitution per glucose unit in cationized cellulose is preferably 0.02 to 0.50. The degree of cationic substitution per glucose unit can be measured by the following method. After drying the cationized cellulose fiber, the nitrogen content is measured using a total nitrogen analyzer (TN-10 manufactured by Mitsubishi Chemical Corporation), and the degree of cationic substitution (the average number of moles of substituents per mole of anhydroglucose unit) is calculated using the following formula: Degree of cationic substitution=(162×N) / (1−151.6×N), where N is the nitrogen content.

[0081] The degree of cation substitution can be adjusted by adjusting the 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.

[0082] Examples of the cationization method include a method in which unmodified cellulose fibers are reacted with a cationizing agent (e.g., glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrialkylammonium hydrite, or a halohydrin type thereof) and an alkali metal hydroxide (e.g., sodium hydroxide, potassium hydroxide) as a catalyst in the presence of water and / or an alcohol having 1 to 4 carbon atoms.

[0083] (Base-type cationized cellulose fibers) After cationization, the cationized cellulose fibers are preferably converted into base-type cationized cellulose or base-type cationized cellulose nanofibers by desalting. By desalting, the salt in the cationized cellulose can be converted into a base. In this specification, cationized cellulose (nanofibers) that has undergone desalting is referred to as base-type cationized cellulose (nanofibers) or cationized cellulose (nanofibers) (base type). Furthermore, 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 type). Desalting may be carried out either before defibration (cationized cellulose) or after defibration (cationized cellulose nanofibers), as described below. Desalting removes salts (e.g., Cl) contained in the cationized cellulose (salt type) and cationized cellulose nanofibers (salt type). - ) is replaced with a base to form a base. For example, a method for desalting after cationization includes contacting the cationized cellulose or cationized cellulose nanofiber with an anion exchange resin. Anion exchange resins are used for cations in which the counter ions are OH. － As long as the anion exchange resin is strong-basic or weak-basic, both can be used. The ratio of the two when contacting the modified cellulose with the anion exchange resin is not particularly limited, and a person skilled in the art can appropriately set it from the viewpoint of efficiently carrying out cation substitution. As an example, the ratio can be adjusted so that the pH of the aqueous dispersion after addition of the anion exchange resin to the cationized cellulose nanofiber aqueous dispersion is preferably 8 to 13, more preferably 9 to 13. The anion exchange resin after contact can be recovered by a conventional method such as suction filtration.

[0084] [Fine-Filming Treatment] Fine-fibrillation is usually carried out by mechanical treatment. The mechanical treatment (preferably beating or defibration treatment) is usually carried out wet (i.e., in the form of an aqueous dispersion of cellulose fibers). Examples of equipment used for the mechanical treatment include refiners (e.g., disc type, conical type, cylinder type), high-speed defibrators, shear-type agitators, colloid mills, high-pressure jet dispersers, beaters, PFI mills, kneaders, dispersers, high-speed defibrators (top finers), high-pressure or ultra-high-pressure homogenizers, grinders (stone-type grinders), ball mills, vibration mills, bead mills, single-screw, twin-screw, or multi-screw kneaders / extruders, homomixers under high-speed rotation, refiners, defibrators, friction grinders, high-shear defibrators, etc. Examples of such a device include a device capable of applying a mechanical defibration force, such as a high-speed disintegrator, a homogenizer (e.g., a microfluidizer), etc., and since they can apply a pressure of 50 MPa or more and a strong shear force, devices capable of applying a wet defibration force are preferred, and high-speed disintegrators and refiners are more preferred, but are not particularly limited. The pressure is more preferably 100 MPa or more, and even more preferably 140 MPa or more. The number of treatments (passes) in the defibration device may be one or two or more, and two or more is preferred.

[0085] When defibration is performed by a wet method, a dispersion of cellulose fibers is usually prepared. The dispersion medium is not particularly limited as long as it can disperse cellulose fibers, and examples thereof include water, organic solvents (e.g., hydrophilic organic solvents such as methanol), and mixed solvents thereof. Since anion-modified cellulose fibers are hydrophilic, water is preferred as the solvent. The solids concentration of the modified cellulose in the dispersion is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more. 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 mechanical treatment, pH adjustment (e.g., 7 or less, 6 or less, or 5 or less) may be performed as necessary.

[0086] Prior to preparing the dispersion, a pretreatment such as dry pulverization (e.g., pulverization after drying) may be performed. Examples of equipment used for dry pulverization include, but are not limited to, impact mills such as hammer mills and pin mills, media mills such as ball mills and tower mills, and jet mills. Furthermore, post-treatment may be performed after defibration. Examples of post-treatment include, but are not limited to, drying (e.g., freeze drying, spray drying, tray drying, drum drying, belt drying, thin spreading on a glass plate or the like and drying, fluidized bed drying, microwave drying, heated fan-type reduced pressure drying, and reduced pressure (degassing) drying), re-dispersion in water (the dispersion device is not limited), and pulverization (e.g., pulverization using equipment such as a cutter mill, hammer mill, pin mill, or jet mill).

[0087] [Physical Properties of Anion-Modified Cellulose Fiber] The anion-modified cellulose fiber constituting the cellulose fiber layer preferably has the following physical properties: (Specific Surface Area) The anion-modified cellulose fiber has a specific surface area of ​​10 m 2 / g or more is preferable, and 100m 2 / g or more is more preferable, and 300m 2 / g or more, 400m 2 / g or more, 500m 2 / g or more, 600m 2 / g or more, 700m or more 2 / g or above 800m 2 / g or more is more preferable. This allows for instantaneous or relatively short-term storage of electricity, and allows for large-capacity storage. Short-term storage of electricity is possible, and large-capacity storage is possible. The upper limit is not particularly limited, but is, for example, 900 m 2 / g or less.

[0088] The specific surface area can be measured by the following steps (1) to (9) with reference to the nitrogen gas adsorption method (JIS Z8830). (1) A 3% cellulose fiber slurry (dispersion medium: water) is separated into a centrifuge container with a solid content of approximately 0.1 g, and 100 ml of ethanol is added. (2) The mixture is stirred in the container at 3000 rpm for 30 minutes using a Homodisper 2.5 (manufactured by Primix Corporation). (3) After stirring, the cellulose fibers are allowed to settle in a centrifuge at 7000 G for 30 minutes at 30°C. (4) The supernatant is removed, taking care to minimize the removal of the settled cellulose fibers. (5) After removing the supernatant, 100 ml of ethanol is added, and the stirring under the conditions of (2), centrifugation under the conditions of (3), and 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 the stirring, centrifugation, and supernatant removal are repeated three times in the same manner as in (5) at room temperature above the melting point of t-butanol. (7) After the final removal of the supernatant, 30 ml of t-butanol is added and gently mixed, then the mixture is transferred to a conical tube and frozen using liquid nitrogen. (8) The conical tube is placed in a freeze-dryer and freeze-dried for three days. (9) Then, BET measurements are performed (pretreatment conditions: 2 hours at 105°C under a nitrogen stream, relative pressure 0.01-0.30, sample amount approximately 30 mg).

[0089] (Crystallization) Cellulose fibers such as anion-modified cellulose fibers preferably have crystalline portions, and more preferably have crystalline portions within the fiber layer. This allows uniform unevenness to be formed on the surface of the cellulose fiber layer, thereby increasing the amount of stored electricity. The crystalline portions may be monocrystalline or polycrystalline, and the proportion of polycrystalline portions in the cellulose fiber layer is preferably 10 vol% or less.

[0090] (Amorphous) Cellulose fibers such as anion-modified cellulose fibers preferably have amorphous portions, and more preferably have amorphous surfaces (e.g., surfaces in contact with electrodes). This allows for charge storage. For example, in the case of carboxylated or etherified cellulose fibers, the flexibility of the bond between the carbon atoms at C5 and C6 (C5-C6 bond) of the glucopyranose units constituting the cellulose fibers allows for rotation of the anionic group at C6 (e.g., a C6 carboxyl group), resulting in high charge storage. The presence or absence of amorphous portions can be confirmed by determining whether a broad peak is observed by X-ray analysis or whether a halo pattern is observed by electron beam analysis.

[0091] (Atomic vacancies) Cellulose fibers such as anion-modified cellulose fibers preferably have atomic vacancies. The presence of atomic vacancies enables proton conduction, forming an electric double layer and enabling the fiber to function as a storage battery. Atomic vacancies are an inherent characteristic of amorphous materials. The size and quantity of atomic vacancies can be confirmed by positron annihilation spectroscopy.

[0092] [2. Cellulose Fiber Layer] The cellulose fibers can be used as materials for constituting electronic components. Examples of electronic components include those composed of a laminate having at least one cellulose fiber layer containing cellulose fibers such as the anion-modified cellulose fibers described above. The cellulose fiber layer is a layer containing one or more types of cellulose fibers. The cellulose fiber layer preferably contains at least anion-modified cellulose fibers, and may contain a combination of anion-modified cellulose fibers and other cellulose fibers (e.g., unmodified cellulose fibers, other modified cellulose fibers). The cellulose fiber layer typically contains cellulose fibers as a substantial main component, with the cellulose fiber content being, for example, 90% by mass or more, 95% by mass or more, 97% by mass or more, or 99% by mass or more, preferably 100% by mass. Examples of components other than cellulose fibers that may be contained in the cellulose fiber layer include wood-derived components such as lignin and hemicellulose polysaccharides.

[0093] [Thickness of Cellulose Fiber Layer] The thickness of the cellulose fiber layer is usually 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less, preferably 10 μm or less or 5 μm or less, and more preferably 3 μm or less, 2 μm or less, or 1 μm or less. This allows the weight of the device to be reduced even in the case of an electronic component that is a multilayer laminate. Furthermore, since static electricity is attached and detached on the surface, making it thin film-like allows the power density and energy density to be increased.

[0094] [Bound Water] The cellulose fiber layer contains bound water. Examples of the location of bound water include between adjacent anion-modified cellulose fibers. Specifically, bound water is preferably bound to the salt of adjacent salt-type anion-modified cellulose fibers, and is preferably bound via hydration with the salt of each of the adjacent salt-type anion-modified cellulose fibers. Such cross-linked salt-type anion-modified cellulose fibers may serve as a surface layer covering the surface of the cellulose fiber layer, covering an internal layer containing cellulose fibers therein. On the other hand, the cellulose fiber layer preferably has a unit in which the surface layer encapsulates an internal layer containing cellulose fibers (for example, a unit consisting of a surface layer consisting of 12 salt-type anion-modified cellulose fibers and an internal layer consisting of 6 unmodified or modified cellulose fibers encapsulated in the surface layer). By including bound water in the cellulose fiber layer (preferably by including bound water up to the upper limit of salt hydration), the distance between the cellulose fibers constituting the surface layer can be increased, thereby increasing the energy gap and suppressing electrical conduction between the fibers. In other words, when the stored charge is used, the charge stored in the electric double layer by the adsorbed electrons and protons propagates through the cellulose fibers that make up the inner layer, suppressing circumferential conduction of the fiber that would release the stored charge, thereby enabling immediate use of the charge. When the cellulose is a salt-type anion-modified cellulose and the salt is a sodium salt, the upper limit of the number of water molecules that the sodium salt can hydrate is four.

[0095] The amount of bound water contained in the cellulose fiber layer can be adjusted by the preparation conditions of the cellulose fiber layer (for example, the drying temperature when forming the cellulose fiber layer on the electrode substrate).

[0096] [Amorphous] The cellulose fiber layer preferably contains an amorphous portion at least in a part thereof (preferably on the surface), thereby enabling the layer to exhibit an electricity storage effect, semiconductor properties, and the like.

[0097] [Electrical resistivity] The cellulose fiber layer has an electrical resistivity of 10- ２ ~10 7 Ωcm, preferably 10 to 10 6 Ωcm, more preferably 10 3 ~10 5 It is preferable that the solid electrolyte has a resistance of Ωcm, which allows an electric double layer of electrons and protons to be formed in the solid.

[0098] [Surface Unevenness] The cellulose fiber layer preferably has an uneven surface. Having unevenness (preferably, convex portions arranged approximately uniformly on a two-dimensional plane on the contact surface) increases the contact area between the electrode substrate and the convex surface, and by utilizing the electron adsorption phenomenon due to the quantum size effect that occurs at the convex portions, the amount of electricity stored can be increased. As a result, when an electricity storage unit is constructed, it can achieve an electricity storage effect equivalent to that of a distributed constant capacitor having multiple microcapacitors perpendicular to each external electrode, corresponding to the number of convex portions. In other words, the microconvex portions themselves have high electrical resistance, each becoming a capacitor consisting of a solid / gas electric double layer, which can be represented by a parallel equivalent circuit of C and R. Furthermore, as shown in Figure 2, a distributed constant circuit can be formed in which multiple capacitors are connected in parallel in a finite number. The size of the unevenness (e.g., the diameter of the convex portion) is preferably approximately 1 nm to 500 nm.

[0099] [3. Electrode Layer] The electronic component including the cellulose fiber layer may further include an electrode layer. The electrode layer is a layer including an electrode material. The electrode material may be any material capable of forming an electrode. Examples of the electrode material include conductive resins such as polythiophene, polyethylenedioxythiophene, polyacetylene, polyacene, polyaniline, polypyrrole, polyphenylenevinylene, polyamine, polyferrocene, polyphthalocyanine, polyphenylene, polyfluorene, polyphenylenevinylene, and polythienylenevinylene; metals such as aluminum, copper, and gold; and carbon materials such as carbon black and graphite.

[0100] The thickness of the electrode layer is usually 0.01 μm to 500 μm, preferably 1 μm to 100 μm.

[0101] [4. Electronic Components] The electronic components preferably include an electrode layer and a cellulose fiber layer. Examples of electronic components include electronic components composed of a laminate including one or more laminate units of an electrode layer and a cellulose fiber layer. The electronic components are preferably in the form of a thin film (sheet). The thickness of the electronic component is, for example, 100 μm or less, preferably 50 μm or less. Since static electricity is attached and detached on the surface of the material, forming the electronic component into a thin film can increase the power density and energy density.

[0102] The electrical resistance of the electronic member is preferably 0.1 MΩ or more, more preferably 1000 MΩ or more. The electrical capacitance of the electronic member is 10 mJ / m ２or higher. Furthermore, the electronic component is preferably capable of long-term discharge for one day or more by storing electricity for 1 ms to 1 minute (instantaneous or short-term storage, large-capacity storage). Furthermore, the electronic component is preferably capable of rapid response charging and discharging at 1 mHz to 100 kHz, preferably 0.1 to 100 Hz. The electronic component is preferably capable of storing current from a generator every 50 / 1000 to 60 / 1000 seconds by converting 50 Hz or 60 Hz AC to DC using an AC / DC converter. The operating temperature is preferably -100 to 100°C. The withstand voltage is preferably 1 GV / m or higher. By satisfying at least one (preferably multiple) of the above electrical characteristics, the solid power storage device can be transported even when power transmission lines are abolished, and can be freely transported domestically and internationally not only by automobile but also by ship, airplane, etc.

[0103] [Other Components] Electronic components may generally contain components other than the cellulose fiber layer and the electrode layer, such as an adhesive layer, an insulating layer, an electrode connector, an external electrode, and a substrate.

[0104] - Adhesive Layer - By directly laminating the cellulose fiber layer and the electrode layer without providing an adhesive layer, an increase in the thickness of the laminate can be suppressed, but providing an adhesive layer is not an issue. Examples of materials (adhesive members) that form the adhesive layer include materials containing electrically conductive components (e.g., carbon), such as electrically conductive double-sided tape. The thickness of the adhesive layer is usually 300 μm or less, and preferably 150 μm or less.

[0105] Insulating Layer An insulating layer is usually provided around the laminate and can be made of an insulating material (for example, an organic insulating material such as resin or rubber).

[0106] -External Electrodes- A pair of external electrodes is usually arranged on both outer sides of the electronic material (which may be a laminate of two or more electronic materials). The electrode material of the external electrodes can be appropriately selected from the same materials as the electrode materials described above.

[0107] [5. Manufacturing Method of Electronic Member] The electronic member can be manufactured by applying a dispersion containing cellulose fibers to an electrode substrate and drying the applied dispersion. Examples of the manufacturing method include a method including the following steps A and B.

[0108] [5.1 Step A: Formation of Dispersion Layer] In step A, a dispersion containing cellulose fibers is applied to the surface of the electrode substrate to form a dispersion layer.

[0109] [Dispersion containing cellulose fibers] The dispersion (slurry) to be applied to the surface of the electrode substrate can be prepared by dispersing cellulose fibers in a dispersion medium (e.g., water, alcohol, preferably water). The cellulose fibers contained in the dispersion may be of one type alone or a combination of two or more types. The dispersion used may be of one type alone or a combination of two or more types. That is, a dispersion containing one or more types of cellulose fibers may be used alone, or a first dispersion containing one or two types of cellulose fibers and a second dispersion containing one or a combination of two or more types of cellulose fibers different from the first dispersion may be used, and these may be applied sequentially. The dispersion may contain other components in addition to the cellulose fibers and the dispersion medium.

[0110] The solids concentration of the dispersion is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.4% by mass or more, and the upper limit of the concentration is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1.5% by mass or less or 1.0% by mass or less.

[0111] [Electrode substrate] The electrode substrate may be a substrate containing an electrode material. Examples of the electrode material are the same as those described above.

[0112] [Coating Method] Examples of methods for applying a dispersion containing cellulose fibers to an electrode substrate include electrophoresis, bar coating, and spin coating, with electrophoresis being preferred. This allows for the formation of a cellulose fiber layer with a uniformly uneven surface. That is, by uniformly arranging the convex portions on a two-dimensional plane over the contact surface area, the contact area between the electrode substrate and the convex surface is increased, thereby increasing the amount of electricity stored. By providing the convex portions, when a power storage unit is constructed, it can achieve an electricity storage effect equivalent to that of a distributed constant capacitor having multiple microcapacitors perpendicular to each metal electrode, corresponding to the number of microcapacitors. That is, the microscopic (nano-sized) convex portions themselves become a solid electrolyte consisting of an electric double layer, which can be represented by a parallel equivalent circuit of C and R. Furthermore, electrophoresis allows for the formation of a thinner cellulose fiber layer. The diameter of the convex portions (e.g., the diameter of the convex portions) is preferably 1 nm to 500 nm.

[0113] (Electrophoresis Method (Electrodeposition Coating Method)) The electrophoresis method is a method in which 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 a current is passed between the electrode material and the counter electrode, thereby depositing a coating film on the electrode material. When a current is passed, the electrode material may be either an anode (anionic electrodeposition) or a cathode (cationic electrodeposition). The counter electrode can be selected from commonly used electrodes that are suitable for the electrode material, and examples include a metal electrode such as Pt.

[0114] The conditions for applying current can be adjusted appropriately depending on the thickness of the cellulose fiber layer, etc., but an example is as follows: The voltage is usually 0.1 V or more, preferably 5 V or more or 10 V or more. This increases the density of the cellulose fibers in the cellulose fiber layer. The upper limit is usually 1000 V or less, preferably 500 V or less. The current density is usually 0.00001 to 10000 mA / cm. 2 , preferably 0.00001 to 100 mA / cm 2The current application time is usually 0.1 minutes or more, preferably 1 minute or more, and more preferably 2 minutes or more. The upper limit is usually 100 minutes or less, preferably 60 minutes or less. When it is desired to increase the density of the cellulose fibers, the voltage can be set higher (for example, 50 V or more, preferably 100 V or more) and the current application time can be shortened (for example, 10 minutes or less, preferably 5 minutes or less). The thickness of the cellulose fiber layer can be controlled by the current application conditions (for example, voltage, current, migration time).

[0115] After energization, the substrate may be washed (for example, washed with water) as needed. Furthermore, energization may be performed during the washing. Examples of energization conditions during washing are 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.

[0116] (Bar Coating Method) The bar coating method is a method in which a slurry is applied onto an electrode material by combing it with a flow bar. The bar is preferably combed in one direction.

[0117] (Spin Coating Method) The spin coating method involves pouring a slurry onto an electrode, rotating the electrode horizontally, and utilizing centrifugal force to form a thin film of the slurry. A device such as a spin coater can be used to rotate the electrode. The thickness of the cellulose fiber layer and the surface irregularities can be controlled by the rotation speed, rotation time, etc., and these can be adjusted by adjusting the settings of the spin coater. The rotation speed (circumferential speed) is typically 200 to 2,000 rpm, preferably 300 to 1,500 rpm, and more preferably 500 to 1,000 rpm. Spin coating can be performed once, or two or more times to form multiple layers. By performing the coating two or more times, the occurrence of defects can be suppressed and the current flow and charge storage efficiency can be improved.

[0118] [Coating Surface] The cellulose fiber-containing dispersion may be applied to at least a portion of at least one surface of an electrode substrate (usually in sheet form), or may be applied to both surfaces. Alternatively, two or more electrode substrates may be arranged side by side, and the dispersion may be applied to opposing surfaces of the substrates so as to sandwich the surfaces of the substrates, thereby forming a laminate having a plurality of units each consisting of an electrode substrate layer and a cellulose fiber dispersion layer in contact therewith.

[0119] [5.2 Step B: Formation of Dispersion Layer] In step B, the dispersion layer formed in step A is dried to form a cellulose fiber layer, which is a dried coating film.

[0120] [Maximum temperature during drying] Drying can be performed by heating. The maximum temperature during heating is usually 195°C or less, preferably 190°C or less, more preferably 185°C or less, and even more preferably 180°C or less or 175°C or less. By setting the temperature at this level, the bound water can be evaporated and the oxides formed by the reaction of the bound water with the salt (for example, when the salt is Na ＋ In the case of Na ２ O), which can suppress an increase in electrical resistance and the approach of the phase angle to zero, and can maintain energy storage properties. The lower limit of the maximum temperature is usually 70°C or higher, preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. This allows water molecules (e.g., free water) contained in the membrane before drying to evaporate appropriately, forming a cellulose fiber layer with uniformly uneven surfaces, and improving the amount of stored electricity. Therefore, the maximum drying temperature is usually 70 to 195°C, preferably 80 to 190°C, more preferably 90 to 185°C, and even more preferably 100 to 180°C.

[0121] [Drying Time] The drying time (heating time) is usually 800 minutes or less, preferably 780 minutes or less. This can prevent excessive drying from causing evaporation of water molecules and a resulting decrease in the amount of stored electricity. On the other hand, the lower limit is usually more than 600 minutes, preferably 610 minutes or more.

[0122] [Drying Temperature Rise Conditions] Drying is preferably carried out by first heating to a temperature (temperature A) below the maximum temperature and then raising the temperature to the maximum temperature. This can suppress the generation of bubbles inside the film, cracks due to uneven drying between the surface and the interior, and surface damage such as warping, which can lead to a decrease in quality. Temperature A may be lower than the maximum temperature, and the difference from the maximum temperature is preferably 5°C or more, more preferably 8°C or more, and even more preferably 10°C or more. Temperature A is usually 65°C or less, preferably 60°C or less, and more preferably 55°C or less. The lower limit is usually 30°C or more, preferably 35°C or more, and more preferably 40°C or more. Therefore, it is usually 30 to 65°C, preferably 35 to 60°C, and more preferably 40 to 55°C. The temperature rise rate from temperature A to the maximum temperature is usually 5 to 15°C / min, preferably 7 to 13°C / min, and more preferably 9 to 12°C / min. Heating at temperature A is performed for a certain period of time (for example, 300 minutes or more, preferably 420 minutes or more, more preferably 540 minutes or more, and the upper limit is usually 650 minutes or less, preferably 630 minutes or less, more preferably 620 minutes or less). After the temperature is increased and reaches the maximum temperature, it is preferable to stop heating.

[0123] Drying can be carried out using any heating device such as an oven.

[0124] [5.3 Other Processes] In manufacturing an electronic component, processes other than processes A and B may be performed. Examples include process C, in which two or more units, each consisting of an electrode layer and a cellulose fiber layer (one layer of each), are stacked; process D, in which an insulating layer is formed around the laminate; process E, in which a pair of external electrodes is formed on the exterior of the laminate; and process F, in which a substrate is installed. Other processes include a process of cutting the laminate to a predetermined size, a process of installing a substrate (e.g., an organic material such as plastic, or an inorganic material such as silicon or glass), and a process of forming into a desired shape (e.g., bending or curving by hot molding). These processes can be performed by conventional methods.

[0125] [Step C: Unit Stacking Step] In step C, two or more electrode layer-cellulose fiber layer units are stacked. The stacking is preferably performed so that the electrode layer of one unit is in contact with the cellulose fiber layer of another unit. An adhesive member may be interposed between each unit (preferably between the surface of the cellulose fiber layer and the electrode layer). Examples of the adhesive member include electrically conductive members (for example, double-sided tape, adhesive). N(M)EMS (Nano(Micro) Electro Mechanical Systems) can be used to stack the units.

[0126] The units may be stacked so that the end faces of each unit (the end faces as viewed from the front of the sheet) are aligned, or they may be stacked so that they are offset. Furthermore, units of different sizes (thickness, area on the sheet side) may be used. After stacking, a portion of the electrode layer (preferably near the end face) may be removed, and an exposed / protruding portion (a portion bonded to the electrode layer) may be provided in a portion (preferably the end) of the cellulose fiber layer. This facilitates connection of each unit. The exposed / protruding portion can be prepared by removing the electrode material by etching (dry or wet etching).

[0127] [Step D: Insulating Layer Forming Step] The insulating layer forming step is a step of forming an insulating layer around the laminate. The insulating layer can be formed by injecting an insulating material (e.g., an organic insulating material such as resin or rubber). It is preferable to inject the insulating material so that it fills the joints of the laminate.

[0128] [Step E: External Electrode Forming Step] The external electrode forming step is a step of arranging a pair of external electrodes on the outside of the insulating layer. Examples of methods for forming the external electrodes include vacuum deposition (e.g., chemical vapor deposition (CVD) such as sputtering, physical vapor deposition (PVD) such as evaporation), casting methods such as slip casting, and mechanical sandwiching. Materials for the external electrodes can be those exemplified for the electrode materials. The lamination process may be performed using NEMS.

[0129] [Step F: Substrate Installation Step] The substrate installation step is a step of installing a substrate at an end of the laminate unit (in the stacking direction and / or in a direction perpendicular thereto). The installation position of the substrate is preferably a position in contact with the outer surface of the electrode layer (in the case of using two or more electrode layers, the outermost electrode layer).

[0130] The electronic material may be a parallel assembly in which a plurality of laminates each including a cellulose fiber layer and an electrode layer (two or more of each type) are arranged between a pair of metal electrodes, which can provide a voltage resistance of 1 GV / m or more when used as a power storage device.

[0131] [6. Uses of Electronic Components (Electricity Storage Units, etc.)] The electronic components described above can be used as various electronic components such as semiconductors and electricity storage units, and are preferably used as electricity storage units. In general, electricity storage units that have a larger specific surface area than conventional capacitors and are formed by an electricity storage system consisting of an electric double layer are called supercapacitors, and electricity storage units with an electricity storage capacity three orders of magnitude larger are called ultracapacitors. The electricity storage unit of the present invention can be either a supercapacitor or an ultracapacitor.

[0132] Examples of the electric storage device include AC capacitors in microelectronic circuits and electric storage devices on the backside of solar cell panels. It can also be used in electronic and electrical boards such as various backup power supply modules, coupling elements, noise filters, high-sensitivity acceleration sensors, high-power transformer cutoff prevention devices, and emergency power supply devices for automobiles or ships. In the future, it is expected to be used as a direct DC storage material from sunlight in outer space. The electric storage device can store, for example, 3 mA / m 2 When exposed to a powerful electron beam, it can withstand up to 200 keV, which is more than twice the 80 keV of carbon nanotubes. Furthermore, since the electronic components are expected to have semiconducting properties, they can be used as semiconductor elements (transistors, etc.).

[0133] Generally, there are seven physical conditions for using a solid as a power storage device: (1) The surface must be uneven with a surface roughness of 20 nm or less to produce the quantum size effect. (2) The material must have a high work function (electron adsorption capacity). (3) The structure must have a localized positive charge. (4) The electrical circuit on the surface must be an electrical distributed constant circuit (parallel connection) (layering effect of the charge amount). (5) The electrical resistance must be high, at least 100 MΩ, to prevent leakage of the stored charge. (6) The upper layer must be a solid electrolyte with an electrical resistivity of 0.01 to 100,000 Ω cm. (7) The adsorbed electrons must instantaneously create a solid electric double layer through platonic solitons.

[0134] The above-described electronic component and electricity storage unit can satisfy all of these seven conditions, and thus can exhibit excellent performance as a solid quantum electricity storage material and quantum electricity storage unit.

[0135] Examples are shown below. Note that the following examples are provided merely to explain the present invention and to provide reference for specific embodiments thereof, and are not intended to limit or restrict the scope of the invention disclosed in this specification.

[0136] Example 1 Electricity storage materials were produced as shown in Table 1. Table 1 shows the sample type, processing method, drying conditions, and crystal form of the CNF sheet used in the electricity storage material, as well as the density, electrical resistance (MΩ), and electricity storage capacity (mJ / m 2 ) is shown.

[0137] (1) Preparation of Sample 1 (TEMPO-oxidized CNF) 500 g (bone dry) of bleached, unbeaten kraft pulp derived from softwood (brightness 85%) was added to 50 L of an aqueous solution containing 780 mg of TEMPO (Sigma-Aldrich) and 75.5 g of sodium bromide, followed by stirring until the pulp was uniformly dispersed. An aqueous solution of sodium hypochlorite was added to the reaction system to a concentration of 6.0 mmol / g to initiate the oxidation reaction. The pH of the system decreased during the reaction, but was adjusted to pH 10 by sequential addition of 3 M aqueous sodium hydroxide. The reaction was terminated when the sodium hypochlorite was consumed and the pH of the system no longer changed. The reaction mixture was adjusted to pH 3 with 10% hydrochloric acid, filtered through a glass filter, and thoroughly washed with water to obtain TEMPO-oxidized pulp. The pulp yield was 90%, and the oxidation reaction took 90 minutes.

[0138] The TEMPO-oxidized pulp obtained in the above process was adjusted to 3.0% (w / v) with water, adjusted to pH 7 with 12% aqueous sodium hydroxide, and subjected to five defibration treatments using an ultra-high-pressure homogenizer (20°C, 150 MPa) to obtain a TEMPO-oxidized fine cellulose fiber dispersion (Sample 1: hereinafter referred to as "TEMPO-oxidized CNF"). Ion-exchanged water was added to the resulting 3.0% (w / v) TEMPO-oxidized CNF dispersion, and the mixture was stirred at 3000 rpm for 10 minutes using a homogenizer. The resulting dispersion was diluted to a concentration of 0.5% (w / v), yielding a TEMPO-oxidized CNF (Sample 1) aqueous dispersion. The resulting TEMPO-oxidized CNF had an average fiber diameter of 4 nm and an aspect ratio of 150. The carboxyl group content of the resulting TEMPO-oxidized CNF was 1.42 mmol / g. The specific surface area of ​​the TEMPO-oxidized CNF was also measured by the method described above.

[0139] (2) Preparation of TEMPO-oxidized CNF Sheets Electrophoretic deposition was performed in a water tank containing the slurry of Sample 1 (0.5% solids), using an aluminum thin film as the positive electrode and a platinum electrode as the negative electrode. The electrodeposition conditions were a DC voltage of 10 V and 3 minutes. The thickness of the film formed after electrodeposition (before drying) was approximately 1 mm. The sheet was then dried at 50°C for 10 hours, and the temperature was raised to 100°C at a rate of 10°C / min, at which point the drying process was terminated to produce TEMPO-oxidized CNF sheets measuring 10 cm square and 5 μm thick. The X-ray diffraction pattern of the TEMPO-oxidized CNF sheet confirmed peaks suggesting an amorphous structure.

[0140] (3) Verification 1: Physical Properties of the Energy Storage Unit The energy storage unit was fabricated by laminating the TEMPO-oxidized CNF sheets obtained in (2). The energy storage capacity of this energy storage unit was determined from the discharge curve (see, for example, Figure 1) at a constant current of 1 nA after 4 minutes of charging at 1 mA and 250 V. The electrical resistance was also determined from a Nyquist diagram (Table 1). Furthermore, the energy storage unit obtained by charging at 2 mA and 300 V for 5 seconds was heated in air at temperatures ranging from room temperature to 210 °C for 10 minutes, and the results are shown in Figure 3. The energy storage capacity gradually decreased up to 175 °C, but then dropped sharply from 175 °C, becoming almost zero at 210 °C. This result indicates that the energy storage mechanism still exists even above 100 °C.

[0141] (4) Verification 2: Confirmation of free water present in the energy storage material The evaporation amount of the energy storage material obtained in (2) was measured using a heating moisture meter from room temperature to 200°C. The results are shown in Figure 4. It can be seen that the water volatilizes almost linearly. Therefore, it is clear that bound water is involved in the decrease in energy storage capacity due to heating in verification 1. If it were the effect of attached water (free water), it would completely disappear at 100°C, but the fact that energy storage capacity is maintained even at temperatures above 100°C makes it extremely likely that bound water is involved in energy storage capacity.

[0142] (5) Verification 3: Confirmation of bound water in TEMPO-oxidized CNF To further investigate the above effects, the TEMPO-oxidized CNF sheet obtained in (3) was 13C NMR spectrum analysis was performed. As is clear from Figure 5, TEMPO-oxidized CNF has a spectrum of C(COONa) group at 175 ppm and a spectrum of C(COONa-(HO)) group at approximately 185 ppm. n The spectrum of the 185 ppm peak clearly indicates that the CNF has bound water. In fact, this peak disappears at 180°C, at which point the charge storage capacity disappears.

[0143] (6) Verification 4: Confirmation of the arrangement of bound water in TEMPO-oxidized CNF In the TEMPO-oxidized CNF sheet obtained in (3), the arrangement of adjacent glucose units (C 12 H 17 O 11 Na and C 12 H 17 O 11 Na-(HO) n The optimized local atomic configurations of the ZnO (units) were determined using plane-wave based first-principles density functional calculations (VASP 5.3: Gutierrez, G. & Johansson, B., Phys.Rev. B65, 104202 (2002). doi.org / 10.1103 / PhysRevB.65.104202).

[0144] As a result, a surface layer with a cyclic structure was detected, where four water molecules per Na molecule bonded between adjacent TEMPO-oxidized CNFs, forming a cross-linked structure. The surface layer consisted of 12 CNFs, while the interior consisted of six, for a total of 18 CNFs. In this unit, the current during discharge flowed from the electric circuit through the glucose unit molecules in the CNFs to the negative electrode.

[0145] From this, it can be seen that as a result of the heat treatment when laminating onto the electrode material, the Na ions of the TEMPO-oxidized CNF easily bind to the bound water that remains even after drying, and the resulting hydrated complex is Na(HO). nIt was found that the interaction between Na and water stabilized the material. It was also speculated that if the heating temperature during drying was high, the water molecules would gradually evaporate to form Na2O, which would increase the electrical resistance and pull the phase angle to zero, resulting in a deterioration of the energy storage characteristics.

[0146]

[0147] Example 2 The same treatment as in Example 1 was carried out except that the temperature was raised to 130°C.

[0148] Example 3 The same treatment as in Example 1 was carried out except that the temperature was raised to 150°C.

[0149] Example 4 The same treatment as in Example 1 was carried out except that the temperature was raised to 180°C.

[0150] Example 5 (1) Preparation of Sample 2 (Carboxymethylated CNF) 130 parts of water and a solution of 20 parts of sodium hydroxide dissolved in a mixed solvent of 10 parts of water and 90 parts of isopropanol (IPA) were added to a twin-screw kneader adjusted to 150 rpm. 100 parts of hardwood pulp (LBKP, manufactured by Nippon Paper Industries Co., Ltd.) was added (dry mass) at 100°C for 60 minutes. The mixture was stirred and mixed at 35°C for 80 minutes, and a mercerization treatment was performed. While further stirring, a mixed solvent of 23 parts of water and 207 parts of IPA and 40 parts of sodium monochloroacetate were added. After stirring for 30 minutes, the mixture was heated to 70°C and etherification treatment was performed for 90 minutes. After completion of the reaction, the mixture was neutralized with acetic acid to pH 7, washed with aqueous methanol, deliquored, and then side water was added to obtain an aqueous solution of sodium salt of carboxymethylated pulp. The degree of carboxymethyl ether substitution in the resulting carboxymethylated pulp was 0.30.

[0151] The carboxymethylated pulp obtained in the above process was adjusted to 3.0% (w / v) with water and subjected to defibration treatment five times using an ultra-high pressure homogenizer (20°C, 150 MPa) to obtain a carboxymethylated microfine cellulose fiber dispersion (hereinafter referred to as "carboxymethylated CNF"). Ion-exchanged water was added to the obtained carboxymethylated CNF 3.0% (w / v) dispersion, and the mixture was stirred with a homogenizer at 3000 rpm for 10 minutes, followed by dilution to a concentration of 0.5% (w / v), to obtain a carboxymethylated CNF (sample 2) aqueous dispersion. The resulting carboxymethylated CNF had a degree of carboxymethyl substitution of 0.30, an average fiber diameter of 4 nm, and an aspect ratio of 52.

[0152] Electrophoretic deposition was performed in a water tank containing the slurry of Sample 2 (0.5% solids) using an aluminum thin film as the positive electrode and a platinum electrode as the negative electrode. The deposition conditions were a DC voltage of 10 V and 3 minutes. The sample was then dried at 50°C for 10 hours, and the temperature was raised to 100°C at a rate of 10°C / min. The drying process was terminated at this point, producing a 5 μm-thick, 10 cm square TEMPO-oxidized CNF sheet.

[0153] Example 6 The same treatment as in Example 5 was carried out except that the temperature was raised to 130°C.

[0154] Example 7 The same treatment as in Example 5 was carried out except that the temperature was raised to 150°C.

[0155] Example 8 The same treatment as in Example 5 was carried out except that the temperature was raised to 180°C.

[0156] Comparative Example 1 The same treatment as in Example 1 was carried out except that the temperature was raised to 200°C.

[0157] Comparative Example 2 The same treatment as in Example 5 was carried out except that the temperature was raised to 200°C.

[0158] The amount of charge stored in each sheet was determined by overlaying an aluminum thin film on the CNF sheet, charging it at a constant current and constant voltage (CC-CV charging) with a set current of 2 mA and an upper limit voltage of 10 V for 5 seconds, and then by calculating the area of ​​the voltage drop curve (horizontal axis: time, vertical axis: voltage) when the current was set to a constant 1 μA.

[0159]

[0160] The electronic components and power storage devices containing bound water of the present invention can be used, for example, as AC capacitors in microelectronic circuits or power storage devices on the backside of solar panels. They can also be used, for example, in various backup power supply modules for lightning arresters, welding, and over-discharge prevention, as well as in electronic and electrical circuit boards such as coupling elements, noise filters, high-sensitivity acceleration sensors, high-output transformer cutoff prevention devices, and emergency power supply devices for automobiles or ships. Because they can exhibit high-temperature storage properties and are resistant to seasonal humidity changes, they are expected to be highly beneficial in applications subject to thermal loads and outdoor use.

Claims

1. An electronic component comprising a cellulose fiber layer containing bound water and cellulose fibers.

2. The electronic component according to claim 1, wherein the cellulose fibers are anionically modified cellulose fibers.

3. The electronic component according to claim 2, wherein the anion-modified cellulose fiber is a salt-type anion-modified cellulose fiber.

4. The electronic component according to claim 2 or 3, wherein the anionically modified cellulose fiber is an oxidized cellulose fiber.

5. The electronic component according to claim 3, wherein the bound water is bound to the salt of the salt-type anion-modified cellulose fiber.

6. The electronic component according to claim 5, wherein the bound water crosslinks adjacent salt-type anion-modified cellulose fibers through hydration with the respective salts of the fibers.

7. The electronic component according to claim 5 or 6, wherein the cellulose fiber layer comprises a surface layer containing cross-linked salt-type anion-modified cellulose fibers and an inner layer containing cellulose fibers.

8. The electronic component according to claim 3, wherein the salt is a sodium salt.

9. The electronic component according to claim 1 or 2, wherein the cellulose fibers are crystalline and amorphous.

10. The electronic component according to claim 1 or 2, wherein the cellulose fibers have atomic vacancies and are amorphous cellulose fibers.

11. The electronic component according to claim 1 or 2, wherein the cellulose fiber layer has a surface having irregularities with a diameter of 1 nm to 500 nm.

12. Capacitance is 10mJ / m ２ The electronic device according to claim 1 or 2.

13. The specific surface area of ​​the cellulose fiber layer is 10 to 900 m 2 The electronic device according to claim 1 or 2, wherein the molecular weight is 1 / g.

14. The electronic device according to claim 1 or 2, comprising an electrode layer and a cellulose fiber layer provided in contact with at least one surface of the electrode layer, the cellulose fiber layer being a coating film formed by drying a dispersion liquid containing cellulose fibers at a maximum temperature of 70 to 195°C.

15. A power storage unit comprising the electronic component according to claim 1 or 2.

16. A method for manufacturing an electronic component, comprising: step A: applying a dispersion liquid containing cellulose fibers to at least one surface of an electrode material to form a coating film; and step B: drying the coating film at a maximum temperature of 70 to 195°C to form a cellulose fiber layer which is a dried coating film.

17. The method according to claim 16, wherein the drying time in step B is 800 minutes or less.

18. The method according to claim 16 or 17, wherein the coating in step A is by electrocoating.

19. The method according to claim 16 or 17, wherein the thickness of the cellulose fiber layer in step B is 50 μm or less.

20. The method of claim 16 or 17, wherein the cellulose fibers comprise anionically modified cellulose fibers.

21. The method of claim 20, wherein the anionically modified cellulose fibers comprise oxidized cellulose fibers and / or carboxymethylated cellulose fibers.

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