WO2020100752A1 - Aerogel material for deodorization and method for producing same - Google Patents

Aerogel material for deodorization and method for producing same Download PDF

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WO2020100752A1
WO2020100752A1 PCT/JP2019/043934 JP2019043934W WO2020100752A1 WO 2020100752 A1 WO2020100752 A1 WO 2020100752A1 JP 2019043934 W JP2019043934 W JP 2019043934W WO 2020100752 A1 WO2020100752 A1 WO 2020100752A1
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transition metal
airgel
metal ion
airgel material
complex
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PCT/JP2019/043934
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French (fr)
Japanese (ja)
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一郎 坂田
文志 古月
アダヴァン・キリヤンキル・ビピン
植木　貴之
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国立大学法人 東京大学
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Priority to JP2020555640A priority Critical patent/JP7462953B2/en
Publication of WO2020100752A1 publication Critical patent/WO2020100752A1/en

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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
    • A61L9/00—Disinfection, sterilisation or deodorisation of air
    • A61L9/01—Deodorant compositions
    • A61L9/014—Deodorant compositions containing sorbent material, e.g. activated carbon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/22—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising organic material
    • B01J20/24—Naturally occurring macromolecular compounds, e.g. humic acids or their derivatives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
    • C08B15/00—Preparation of other cellulose derivatives or modified cellulose, e.g. complexes
    • C08B15/02—Oxycellulose; Hydrocellulose; Cellulosehydrate, e.g. microcrystalline cellulose
    • C08B15/04—Carboxycellulose, e.g. prepared by oxidation with nitrogen dioxide
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J3/00—Processes of treating or compounding macromolecular substances
    • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
    • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
    • C08J3/075—Macromolecular gels
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
    • C08J9/26—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a solid phase from a macromolecular composition or article, e.g. leaching out
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof

Definitions

  • the present invention relates to a novel airgel material composed of a composite of cellulose nanofibers and a transition metal ion, which is suitable for deodorizing odorous substances, and a method for producing the same.
  • biomass materials which are renewable resources
  • it can be obtained from cellulose, which is a naturally occurring biomass in large amounts.
  • Cellulose nanofibers are attracting attention.
  • Cellulose nanofibers with a nano-sized fiber diameter have a small environmental load related to production and disposal because they are derived from vegetable fibers, and also have excellent specifications such as strength, elasticity, thermal stability, and water-based dispersibility. .. Therefore, it is expected to be used in various fields such as an industrial application such as a filler for compounding a filter member, a resin and a rubber, or an application of a compounding agent for cosmetics and foods.
  • Cellulose nanofibers can typically be obtained by refining wood fibers (pulp).
  • a natural cellulose fiber is chemically modified (oxidized) using a TEMPO catalyst (2,2,6,6-tetramethylpiperidine-1-oxyl), which makes it easy to defibrate the pulp and has a uniform width.
  • TEMPO catalyst 2,2,6,6-tetramethylpiperidine-1-oxyl
  • Non-Patent Document 2 a composite of metal particles supported on cellulose nanofibers obtained by such a manufacturing method has a property of adsorbing a compound such as a malodorous component.
  • Non-Patent Document 2 a compound such as a malodorous component
  • an object of the present invention is to provide a novel adsorption material derived from cellulose nanofibers, which is rich in adsorption sites for adsorbing odorous substances and has excellent adsorption efficiency, and a method for producing the same.
  • the present inventors have brought oxidized cellulose nanofibers into contact with an excessive amount of transition metal ions to form a cellulose nanofiber / transition metal complex via a chelate bond. It was found that the airgel material having a large non-surface area and an ultra-low density sponge-like three-dimensional structure can be efficiently synthesized by freeze-drying under the predetermined conditions. In addition, it was found that such an airgel material has abundant adsorption sites for adsorbing compounds such as odorous substances, and has an excellent adsorption rate and adsorption capacity. Furthermore, it was also found that the adsorption property is remarkably improved by using an airgel material containing a carbon nanomaterial in addition to the composite of cellulose nanofiber / transition metal. The present invention has been completed based on these findings.
  • ⁇ 1> A method for producing an airgel material in which a composite of cellulose nanofibers and a transition metal ion forms a three-dimensional network structure, wherein (a) a suspension of cellulose nanofibers contains a transition metal ion.
  • the production method which comprises a step of removing a transition metal ion in a free state from the solution, and a step of (d) freeze-drying the complex obtained in the step (c) to obtain an airgel structure;
  • the production method according to ⁇ 1> further including a step of oxidizing the plant fiber using an N-oxyl compound as a catalyst to obtain the cellulose nanofiber used in the step (a);
  • ⁇ 3> The production method according to ⁇ 1> or ⁇ 2>, wherein the cellulose nanofiber has a carboxyl group or a carboxylate group;
  • ⁇ 4> The production method according to ⁇ 3>, wherein the content of the carboxyl group and the carboxylate group in the cellulose nanofiber is 0.1 to 5.0 mmol / g.
  • ⁇ 5> The production method according to any one of ⁇ 1> to ⁇ 4>, wherein the complex has a structure in which a transition metal ion is bound to a cellulose nanofiber through a chelate bond to form a complex.
  • step (c) includes removing the transition metal ion in a free state by centrifugation and / or washing with deionized water.
  • Method; ⁇ 7> The step (c) further includes a step of removing the transition metal ion in a free state from the composite obtained in the step (b), and then adding a dispersion liquid of the carbon nanomaterial and mixing the composite with the composite.
  • the transition metal ion is one or more divalent compounds selected from the group consisting of copper, cobalt, nickel, vanadium, titanium, chromium (III), manganese, zinc, and iron.
  • the present invention also relates to an airgel material obtained by the above production method and a deodorizing method using the same, ⁇ 10> a composite of cellulose nanofibers and a transition metal ion forms a three-dimensional network structure.
  • the composite has a structure in which a transition metal ion is bound to cellulose nanofibers through a chelate bond to form a complex, and the density of the airgel material is 5 to
  • the airgel material is in the range of 15 mg / cm 3 , and the content of the transition metal in the airgel material is 0.1 to 200 mol% based on the cellulose nanofibers.
  • the airgel material according to ⁇ 10> further including a carbon nanomaterial; ⁇ 12> The airgel material according to ⁇ 10> or ⁇ 11>, in which the cellulose nanofiber has a carboxyl group or a carboxylate group; ⁇ 13> The airgel material according to ⁇ 12>, wherein the content of the carboxyl group and the carboxylate group in the cellulose nanofiber is 0.1 to 5.0 mmol / g; ⁇ 14> The airgel material according to any one of ⁇ 10> to ⁇ 13>, which has a linear shape with a diameter of 3 to 5 nm; ⁇ 15>
  • the transition metal ion is one or more divalent metal ions selected from the group consisting of copper, cobalt, nickel, vanadium, titanium, chromium (III), manganese, zinc, and iron.
  • the airgel material according to any one of ⁇ 10> to ⁇ 14>; ⁇ 16> The airgel material according to any one of ⁇ 10> to ⁇ 15>, which is a deodorant adsorbent for adsorbing an odorant; and ⁇ 17> the odorant is ammonia or trimethylamine.
  • the airgel material according to ⁇ 16> above which is one or more compounds selected from the group consisting of hydrogen sulfide, methyl mercaptan, formaldehyde, and xylene. Is provided.
  • a novel airgel material composed of a composite of cellulose nanofibers and transition metal ions and having a large non-surface area and ultra-low density sponge-like three-dimensional structure can be efficiently produced. it can.
  • the airgel material of the present invention has abundant adsorption sites and can adsorb and immobilize compounds such as odorants with an excellent adsorption rate and adsorption capacity, and at the same time decomposes adsorbed odorants and the like. Can self-recover the adsorption site. As a result, the effect of deodorizing the concentration of the odorous substance or the like to a level below the detection limit is exerted, and thus it is suitable as a deodorizing adsorbent. Furthermore, by including a carbon nanomaterial in addition to the cellulose nanofiber / transition metal composite in the airgel material, the effect of significantly improving the adsorption property can be obtained.
  • FIG. 1 is an image showing the outer shape of the airgel of the present invention.
  • FIG. 2 is a TEM image of the CNF / M 2+ complex in the airgel of the present invention.
  • FIG. 3 is an electron microscope image showing the internal structure of the airgel of the present invention.
  • FIG. 4 is an electron microscope image showing the internal structure of the airgel of the present invention.
  • FIG. 5 is an EDS elemental analysis chart performed on the airgel of the present invention.
  • FIG. 6 is a graph showing the results of an adsorption test for ammonia.
  • FIG. 7 is a graph showing the results of an adsorption test for trimethylamine.
  • FIG. 8 is a graph showing the results of an adsorption test for hydrogen sulfide.
  • FIG. 9 is a graph showing a comparison of the amount of airgel used with respect to the result of adsorption on ammonia.
  • FIG. 10 is a graph showing the results of adsorption tests for various odorous substances using the CNT-containing aerogel of the present invention, the CNT-free aerogel, and activated carbon (comparative example).
  • the production method of the present invention is a method for producing an airgel material in which a composite of cellulose nanofibers and a transition metal ion forms a three-dimensional network structure. More specifically, the manufacturing method of the present invention is characterized by including the following steps (a) to (d).
  • step (A) a step of adding a solution containing a transition metal ion to a suspension of cellulose nanofibers to obtain a mixed solution
  • step B a step of stirring the mixed solution to obtain a composite of cellulose nanofibers and a transition metal ion
  • step C) a step of removing free-state transition metal ions from the complex obtained in step (b)
  • step (d) the complex obtained in step (c) is lyophilized to obtain an airgel structure.
  • Steps (a) and (b) are steps of contacting cellulose nanofibers with transition metal ions to obtain a cellulose nanofiber / transition metal complex that forms the skeleton of the airgel material.
  • step (a) a solution in which cellulose nanofibers are suspended and a solution containing a transition metal ion are prepared, and these two solutions are mixed to obtain a mixed solution.
  • the solvent in the cellulose nanofiber suspension may preferably be water, for example deionized water.
  • the content of cellulose nanofibers in the cellulose nanofiber suspension is not particularly limited, but is typically 0.1 to 5.0% by weight, preferably 0.5 to 2.0% by weight. it can.
  • cellulose nanofibers means fine cellulose fibers obtained by defibrating plant fibers (pulp), and generally have a fiber diameter (width) of the nanometer order (1 to 1000 nm). is there.
  • the length is not particularly limited, but usually has a length of about several micrometers.
  • the cellulose nanofiber used as a raw material in the step (a) has a functional group capable of forming a complex by a chelate bond (coordination bond), and preferably has a carboxyl group or a carboxylate group as such a functional group.
  • a functional group capable of forming a complex by a chelate bond (coordination bond) preferably has a carboxyl group or a carboxylate group as such a functional group.
  • the content of carboxyl group and carboxylate group in the cellulose nanofiber is 0.1 to 5.0 mmol / g, preferably 0.5 to 2.0 mmol / g.
  • the content of the carboxyl group or the carboxylate group in the cellulose nanofiber can be determined by a known method such as neutralization titration (for example, JP 2008-001728 A).
  • Cellulose nanofibers having a carboxyl group or a carboxylate group can generally be obtained by chemically modifying plant fibers such as natural cellulose fibers and defibrating them by a micronization treatment.
  • plant fibers such as natural cellulose fibers and defibrating them by a micronization treatment.
  • a known method for oxidizing plant fiber by a chemical modification reaction using N-oxyl compound 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as a catalyst is used.
  • TEMPO N-oxyl compound 2,2,6,6-tetramethylpiperidine-1-oxyl
  • the production method of the present invention includes, as a step prior to step (a), a step of oxidizing the vegetable fiber using an N-oxyl compound as a catalyst to obtain the cellulose nanofiber used in step (a).
  • Non-Patent Document 1 For TEMPO-catalyzed oxidation, detailed steps are described in, for example, Isogai et al., Nanoscale, 3, 71-85, 2011 (Non-Patent Document 1).
  • a compound other than TEMPO can be used as long as it can generate a nitroxy radical and accelerate the oxidation reaction of plant fibers.
  • a known co-oxidant may be additionally used in the reaction solution for the oxidation reaction.
  • an oxidizing agent for example, halogen, hypohalous acid, halogenous acid, perhalogenic acid or salts thereof, halogen oxide, peroxide and the like can be used.
  • sodium hypochlorite which is inexpensive and has a low environmental load, is preferable.
  • reaction conditions such as the amount of plant fiber, the amount of catalyst, the amount of co-oxidant, the pH of the reaction solution, or the reaction time and the reaction temperature in the chemical modification reaction for obtaining the cellulose nanofibers.
  • the plant fiber that is the raw material of the cellulose nanofibers is not particularly limited, but natural cellulose is preferable.
  • natural cellulose for example, pulp obtained by pulping a wood raw material can be used.
  • the wood raw material red pine, black pine, todo pine, spruce pine, black pine, larch, fir, hemlock, cedar, cypress, larch, silabe, spruce, hiba, Douglas fir, hemlock, white fir, spruce, balsam fir, cedar, pine, pine, Softwood such as mercantia pine, radiata pine, and their mixed materials, beech, birch, alder, oak, oak, tub, shii, birch, cottonwood, poplar, tamo, droyagi, eucalyptus, mangrove, lauan, acacia, etc., and mixtures thereof
  • the material can be illustrated.
  • micronization after chemical modification is carried out by mechanical methods such as a grinder method of grinding pulp between rotating grindstones, an opposed collision method using a high-pressure homogenizer, a grinding method using a ball mill, a roll mill, a cutter mill, or the like. Processing. Usually, the defibration treatment is repeatedly performed until the obtained cellulose nanofibers have a desired size.
  • the fiber length and fiber diameter (width) of the cellulose nanofibers are not particularly limited, but for example, the fiber length may be 0.1 to 10 ⁇ m, the fiber diameter may be about 1 to 100 nm, and preferably about 2.5 to 20 nm.
  • the fiber length and fiber diameter can be obtained from a scanning or transmission electron microscope image (SEM or TEM) or an atomic force microscope image (AFM).
  • the solution containing the transition metal ion used in step (a) can be prepared by dissolving a salt of the transition metal in a solvent.
  • the solvent may preferably be water, for example deionized water.
  • the transition metal ion is not particularly limited as long as it can bind to the cellulose nanofibers, but is preferably an ion of a transition metal element belonging to Group 8 to 12 of the periodic table, more preferably these divalent metals. Ion.
  • the transition metal ion can be one or more divalent metal ions selected from the group consisting of copper, cobalt, nickel, vanadium, titanium, chromium (III), manganese, zinc, and iron.
  • the transition metal has a function of decomposing an odor substance adsorbed on the airgel material by a catalytic action.
  • the transition metal salt salts of these transition metal cations and arbitrary anions can be used.
  • halides, nitrates, sulfates, and acetates of these transition metals can be used.
  • the concentration of the transition metal ion solution is preferably a metal ion concentration that is in excess of the theoretical value of the metal ion capable of binding to the cellulose nanofibers by a chelate bond (coordination bond).
  • the molar amount is preferably 0.1 to 10 times, more preferably 0.5 to 2 times, the amount of the carboxyl group and the carboxylate group in the cellulose nanofiber.
  • the concentration of the transition metal ion solution can be in the range of 0.1 to 1000 mmol / l.
  • step (b) is a step of stirring the mixed solution prepared in step (a) to obtain a composite of cellulose nanofibers and a transition metal ion.
  • conditions such as stirring time and temperature can be appropriately set.
  • the obtained cellulose nanofiber / transition metal complex formed a complex by binding a transition metal ion to the cellulose nanofiber through a chelate bond at a carboxyl group or a carboxylate group in the cellulose nanofiber.
  • the step (c) is a free state from the cellulose nanofiber / transition metal complex obtained in the step (b), that is, an excess amount of the transition metal which remains in the solution without being used for complexing with the cellulose nanofiber.
  • This is a step of removing ions.
  • Such transition metal ions can be removed by centrifugation and / or washing with deionized water. Preferably, after centrifugation, washing with deionized water can be further performed a plurality of times.
  • the step (c) is a step of removing the transition metal ion in a free state from the complex obtained in the step (b), and then adding a dispersion liquid of the carbon nanomaterial and mixing with the complex. Can be further included. This makes it possible to obtain an airgel structure further containing a carbon nanomaterial in addition to the cellulose nanofiber / transition metal composite.
  • the carbon nanomaterial used here refers to a substance including a graphene sheet having a carbon six-membered ring, and may contain an element other than carbon such as boron or nitrogen.
  • Examples of carbon nanomaterials include carbon nanotubes (CNT), carbon nanofibers (CNF), graphene, carbon nanohorns (CNH), fullerenes, or combinations thereof, and substances obtained by chemically modifying these. May be
  • the method for producing the carbon nanomaterial is not particularly limited, and it can be produced by a conventionally known method, or a commercially available one can be used as it is.
  • the carbon nanomaterial is carbon nanotube.
  • Carbon nanotubes are generally materials that have a tubular structure with a diameter of several nanometers in which a single sheet of graphite (graphene sheet) having a carbon six-membered ring array structure is rolled into a cylinder.
  • carbon nanotubes include single-walled carbon nanotubes composed of one sheet of graphite, and multi-walled carbon nanotubes in which the tubular sheets are stacked in a direction perpendicular to the axis ( Furthermore, a multi-walled carbon nanotube containing one or more small-diameter carbon nanotubes), a carbon nanohorn in which the end of a single-walled carbon nanotube is conical and closed, and a carbon nanotube containing fullerene inside are included. These carbon nanotubes can be used alone or in combination of two or more.
  • the average diameter of the carbon nanotubes can be selected from the range of, for example, 0.5 nm to 1 ⁇ m, preferably 1 to 100 nm. For example, it is about 0.5 to 10 nm, preferably about 1 to 5 nm, and in the case of multi-walled carbon nanotubes, it is about 5 to 300 nm, preferably about 10 to 100 nm.
  • the average length of the carbon nanotubes is, for example, in the range of 1 to 1000 ⁇ m, preferably 5 to 500 ⁇ m.
  • the carbon nanomaterial dispersion used in the step (c) is a solution in which the carbon nanomaterial is dispersed in a solvent.
  • the solvent may be water, an organic solvent, or a mixed solvent thereof, but water is preferable.
  • the dispersion liquid may contain a dispersant, if necessary, and as the dispersant, a surfactant, various polymer materials (water-soluble polymer material, etc.) and the like can be used. In the present invention, either an ionic surfactant or a nonionic surfactant can be used, but an ionic surfactant is preferred from the viewpoint of high dispersibility.
  • the content of the carbon nanomaterial in the dispersion is not particularly limited, but is, for example, 1 to 300 g / L, preferably 10 to 200 g / L. Also, the carbon nanomaterial in the final airgel material can be, for example, 0.5 to 30% by weight, preferably 1 to 10% by weight.
  • Step (d) is a step of binding and drying the cellulose nanofiber / transition metal composite obtained in step (c) to obtain an airgel structure.
  • the "aerogel” means a non-crystalline nanoporous material structure in which most of the volume is voids by the cellulose nanofiber / transition metal complex forming a three-dimensional network structure. Due to its porous structure, the airgel has a large non-surface area and has an ultra-low density sponge-like structural characteristic.
  • Such freeze-drying is typically performed by dissolving the cellulose nanofiber / transition metal complex in a solvent such as deionized water to form a colloidal solution, and then diluting the colloidal solution as needed. Is adjusted, frozen with liquid nitrogen or the like, and dried using a dryer.
  • the colloidal solution preferably contains 3-10% by weight, preferably 3-7% by weight of the complex. When a diluent is used, it can be diluted to a concentration of 0.5 to 5% by weight.
  • the complex has already formed a three-dimensional network structure close to a gel state in the state of colloidal solution, and by freeze-drying in this state, the non-surface area It is possible to obtain an aerogel which is a nanoporous material having a large three-dimensional network structure with a very low density sponge.
  • the airgel obtained by the production method of the present invention has a large non-surface area sponge-like structure, it has abundant adsorption sites for adsorbing compounds such as odorants. It is suitable as a deodorant adsorbent. Details of the properties of the airgel will be described later.
  • Airgel Material further relates to an airgel material obtained by the above production method. That is, the airgel material according to the present invention, An airgel material in which a composite of cellulose nanofibers and a transition metal ion forms a three-dimensional network structure, The complex has a structure in which a transition metal ion is bound to a cellulose nanofiber through a chelate bond to form a complex, The airgel material has a density in the range of 5 to 15 mg / cm 3 ; The content of the transition metal in the airgel material is 0.1 to 200 mol% based on the cellulose nanofiber, It is characterized by
  • the cellulose nanofiber in the composite of cellulose nanofiber / transition metal is as described above.
  • the cellulose nanofiber has a carboxyl group or a carboxylate group, and the content thereof is preferably 0.1 to 5.0 mmol / g, more preferably 0.5 to 2.0 mmol / g. is there.
  • the types of transition metals are also as described above, and preferably, the transition metal ions forming the cellulose nanofiber / transition metal complex are copper, cobalt, nickel, vanadium, titanium, chromium (III), It is one or more kinds of divalent metal ions selected from the group consisting of manganese, zinc, and iron.
  • the airgel material of the present invention is a nanoporous body having a large non-surface area and an ultra-low density sponge-like three-dimensional network structure.
  • the density of the airgel material is in the range of 5 to 15 mg / cm 3 , and preferably about 10 mg / cm 3 .
  • the content of the transition metal in the airgel material may be 0.1 to 200 mol% with respect to the cellulose nanofibers (molar ratio of 1 mol of the cellulose nanofibers). Alternatively, in terms of weight percent, it can be 1 to 20 weight percent, preferably 5 to 15 weight percent, of the total airgel material.
  • the content of such a transition metal can be measured by, for example, elemental analysis by energy dispersive X-ray analysis (EDS).
  • the shape and the like of the airgel material are not particularly limited, but typically have a linear shape with a diameter (fiber diameter) of 3 to 5 nm.
  • the airgel material of the present invention can further include a carbon nanomaterial in addition to the cellulose nanofiber / transition metal composite.
  • a carbon nanomaterial in addition to the cellulose nanofiber / transition metal composite.
  • the presence of the carbon nanomaterial isolated and dispersed in the aerogel significantly improves the adsorption property for a compound such as an odorous substance, and a higher deodorizing performance can be obtained.
  • the details of the carbon nanomaterial are as described above.
  • the carbon nanomaterial in the airgel material can be, for example, 0.5 to 30% by weight, preferably 1 to 10% by weight.
  • the airgel material of the present invention has a large non-surface area sponge-like structure, an adsorption site where a transition metal forms a chelate bond with a carboxyl group or a carboxylate group present on the surface of cellulose nanofibers. Since it has abundant content, it has excellent adsorption ability for compounds such as odorous substances. Therefore, it is suitable for use as a deodorant adsorbent for adsorbing odorous substances.
  • Such an odorous substance can be, for example, one or more compounds selected from the group consisting of ammonia, trimethylamine, hydrogen sulfide, methyl mercaptan, formaldehyde, and xylene, but is not necessarily limited thereto.
  • the airgel material of the present invention can adsorb and decompose odorous substances by the following mechanism.
  • the cellulose nanofiber / transition metal complex in the airgel material binds with ammonia or trimethylamine through a chelate bond with the transition metal in an ionic state, and immobilizes (adsorbs) this in the airgel material.
  • hydrogen sulfide it is possible to immobilize (adsorb) this extremely toxic harmful gas by forming a sulfide of a transition metal.
  • the transition metal in the metal state functions as a catalyst, decomposes odorous substances such as ammonia, trimethylamine, and hydrogen sulfide, and the adsorption site self-recovers. With such a mechanism, an excellent adsorption rate and adsorption capacity can be achieved.
  • the present invention is useful in a deodorizing method including adsorbing an odorous substance using the airgel material.
  • the airgel material of the present invention can exert a deodorizing effect by being installed in an air purifier, an air conditioner, or the like, or a gas mask for emergency situations in which hydrogen sulfide, which is a poisonous gas, is dealt with, and livestock excrement. It can be preferably used in applications such as reducing or solving the problem of bad odor.
  • the cellulose nanofiber / transition metal complex has an absorption band in the visible light region, and the odorous substance binds to the transition metal in the complex through a chelate bond as described above.
  • the absorber shifts, and its color tone changes. That is, since the airgel material of the present invention can sense that the odorous substance is adsorbed by a change in its color tone, it can be suitably used in an application as an odor sensor using the airgel material.
  • cellulose nanofiber / transition metal complex (CNF / M 2+ ) was centrifuged at 10,000 rpm for 20 minutes to separate a precipitate. The resulting precipitate was washed 5 times with deionized water to remove excess metal ions.
  • the copper sulfate was replaced with cobalt sulfate and nickel sulfate, respectively, and the CNF / M 2+ complex was similarly synthesized.
  • FIG. 3 and 4 are electron microscope images showing the internal structure of the airgel. As shown in FIGS. 3 and 4, it was confirmed that the airgel of the present invention has a sponge-like three-dimensional porous body structure having a large void ratio.
  • FIG. 5 shows the results for CNF aerogel, CNF 2 / Co 2+ composite airgel, NF 2 / Ni 2+ composite airgel, and CNF 2 / Cu 2+ composite airgel, respectively, from the top.
  • the transition metal contents in the airgel were 0% by weight, 9.1% by weight, 13.3% by weight and 6.0% by weight, respectively.
  • the density of the obtained airgel it was found to be 5 to 15 mg / cm 3 .
  • the content of the carboxyl group and the carboxylate group in the obtained airgel was measured and found to be 0.2 mmol / g.
  • Adsorption experiment 3-1 Airgel Adsorption Experiment Using Various Transition Metals 500 mg of the three kinds of aerogels (Cu, Co, Ni) obtained above were placed in a polyvinyl fluoride bag and sealed. Then 9 L of air and test gas were added to obtain the desired gas concentration. The test gases used were ammonia, trimethylamine, and hydrogen sulfide, respectively. The gas concentration in the bag was measured with a gas detection tube at regular time intervals. As a comparative example, the same experiment was conducted using an airgel (CNF) consisting of cellulose nanofibers containing no transition metal. The results are shown in FIGS. 6 to 9.
  • CNF airgel
  • the CNT-containing airgel was the same as the above 1. except that the CNF dispersion was added before freeze-drying. And 2. It was prepared by the same procedure as the synthetic method shown in. That is, after removing excess metal ions, 100 mL of a 0.5 to 5% by weight solution of the CNF 3 / M 2+ complex was prepared, and 100 mL of a 200 g / L CNT dispersion liquid was added thereto. It was confirmed that the mixed solution was gelled. The gel solution was dispersed in deionized water and poured into a molding container. This solution was frozen in liquid nitrogen and dried using a freeze dryer to obtain a CNT-containing airgel.
  • the CNTs used had an average diameter of 12 nm and an average length of 5 ⁇ m (manufactured by Nanocyl, trade name “NC7000C”).
  • the dispersion used water as a solvent and a 1.0 wt% sodium dodecylbenzenesulfonate (Kanto Chemical Co., Inc.) surfactant as a dispersant.
  • FIG. 10 shows the results of an adsorption experiment for odorants such as ammonia, trimethylamine, methyl mercaptan, and hydrogen sulfide.
  • Specimen (1) in the figure is an airgel consisting only of CNF / Cu 2+ complex
  • specimen (2) is an airgel of CNF / Cu 2+ complex containing CNT.
  • the control product is activated carbon, and the blank test shows a change in gas concentration when not contacted with the adsorbent.
  • the sample (2) containing CNT exhibited excellent adsorption characteristics as compared with the sample (1) containing no CNT.
  • the sample (2) showed an improvement in the adsorption ability of 15% or more with respect to trimethylamine, methyl mercaptan, and hydrogen sulfide.
  • the activated carbon of the comparative example showed almost no adsorptivity to ammonia, whereas the samples (1) and (2) showed excellent adsorption characteristics to any odorous substance. It has been found that the inventive airgel has adsorptivity for a wide variety of odorants.
  • the airgel material of the present invention composed of a cellulose nanofiber / transition metal composite has excellent adsorption ability and deodorizing effect for odorous substances.

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Abstract

[Problem] The present invention addresses the problem of providing: a novel material for adsorption, which has a large number of adsorption sites that adsorb odorous substances and exhibits excellent adsorption efficiency, while being derived from cellulose nanofibers; and a method for producing this novel material for adsorption. [Solution] A method for producing an aerogel material wherein a composite body of cellulose nanofibers and transition metal ions forms a three-dimensional network structure, said method comprising: (a) a step wherein a solution containing transition meal ions is added into a suspension of cellulose nanofibers, thereby obtaining a mixed solution; (b) a step wherein a composite body of the cellulose nanofibers and the transition metal ions is obtained by stirring the mixed solution; (c) a step wherein transition metal ions in a free state are removed from the composite body obtained in the step (b); and (d) a step wherein an aerogel structure is obtained by freeze-drying the composite body obtained in the step (c).

Description

消臭用エアロゲル材料及びその製造方法Deodorant airgel material and method for producing the same
　本発明は、セルロースナノファイバーと遷移金属イオンとの複合体により構成され、臭気物質の消臭に好適な新規エアロゲル材料及びその製造方法に関する。 The present invention relates to a novel airgel material composed of a composite of cellulose nanofibers and a transition metal ion, which is suitable for deodorizing odorous substances, and a method for producing the same.
　従来の石油由来の高分子材料に代替として、近年、環境面から再生可能資源であるバイオマス材料の実用化が重要な課題となっており、例えば、天然に多量に存在するバイオマスであるセルロースから得られるセルロースナノファイバーが注目されている。 As an alternative to conventional petroleum-derived polymer materials, in recent years, the practical application of biomass materials, which are renewable resources, has become an important issue from the environmental aspect.For example, it can be obtained from cellulose, which is a naturally occurring biomass in large amounts. Cellulose nanofibers are attracting attention.
　ナノサイズの繊維径をもったセルロースナノファイバーは、植物繊維由来であることから生産・廃棄に関する環境負荷が小さいことに加え、強度、弾性、熱安定性、水系分散性等の優れた特定を有する。そのため、フィルター部材、樹脂及びゴムの配合用充填剤等の工業上の用途、或いは、化粧品や食品の配合剤の用途など様々な分野における利用が期待されている。 Cellulose nanofibers with a nano-sized fiber diameter have a small environmental load related to production and disposal because they are derived from vegetable fibers, and also have excellent specifications such as strength, elasticity, thermal stability, and water-based dispersibility. .. Therefore, it is expected to be used in various fields such as an industrial application such as a filler for compounding a filter member, a resin and a rubber, or an application of a compounding agent for cosmetics and foods.
　セルロースナノファイバーは、典型的には、木材繊維（パルプ）を微細化することによって得ることができる。例えば、ＴＥＭＰＯ触媒（２，２，６，６-テトラメチルピペリジン－1－オキシル）を用いて天然セルロース繊維を化学変性（酸化）し、これによりパルプが解繊しやすく均一な幅を有するセルロースナノファイバーを得る製造方法が知られている（非特許文献１等）。 Cellulose nanofibers can typically be obtained by refining wood fibers (pulp). For example, a natural cellulose fiber is chemically modified (oxidized) using a TEMPO catalyst (2,2,6,6-tetramethylpiperidine-1-oxyl), which makes it easy to defibrate the pulp and has a uniform width. A manufacturing method for obtaining fibers is known (Non-Patent Document 1, etc.).
　また、かかる製造方法によって得られたセルロースナノファイバーに金属粒子を担持させた複合体が、悪臭成分等の化合物を吸着する性質を有することが報告されている（非特許文献２）。しかしながら、従来のセルロースナノファイバー／金属の複合体では、化合物を吸着する官能基（吸着サイト）が少なく及び吸着体のトータル有効比表面積が小さいため、吸着速度が遅く、吸着容量も十分ではないなどの吸着体の構造に由来する本質的な問題点があった。 Also, it has been reported that a composite of metal particles supported on cellulose nanofibers obtained by such a manufacturing method has a property of adsorbing a compound such as a malodorous component (Non-Patent Document 2). However, in the conventional cellulose nanofiber / metal composite, since the number of functional groups (adsorption sites) that adsorb the compound is small and the total effective specific surface area of the adsorbent is small, the adsorption rate is slow and the adsorption capacity is not sufficient. There was an essential problem due to the structure of the adsorbent.
　そこで、本発明は、臭気性物質を吸着する吸着サイトを豊富に含み吸着効率に優れた、セルロースナノファイバー由来の新規吸着用材料、及びその製造方法を提供することを課題とするものである。 Therefore, an object of the present invention is to provide a novel adsorption material derived from cellulose nanofibers, which is rich in adsorption sites for adsorbing odorous substances and has excellent adsorption efficiency, and a method for producing the same.
　本発明者らは、上記課題を解決するべく鋭意検討を行った結果、酸化セルロースナノファイバーを過剰量の遷移金属イオンと接触させ、キレート結合を介したセルロースナノファイバー／遷移金属の複合体を形成させ、これ所定条件下で凍結乾燥させることにより、非表面積が大きく超低密度スポンジ状の三次元構造を有するエアロゲル材料を効率的に合成できることを見出した。併せて、かかるエアロゲル材料は、臭気性物質等の化合物を吸着するための吸着サイトを豊富に有しており、優れた吸着速度及び吸着容量を有することを見出した。さらに、セルロースナノファイバー／遷移金属の複合体に加えて、カーボンナノ材料を含むエアロゲル材料とすることで、吸着特性が著しく向上することも見出した。これらの知見に基づき、本発明を完成するに至ったものである。 As a result of intensive studies to solve the above problems, the present inventors have brought oxidized cellulose nanofibers into contact with an excessive amount of transition metal ions to form a cellulose nanofiber / transition metal complex via a chelate bond. It was found that the airgel material having a large non-surface area and an ultra-low density sponge-like three-dimensional structure can be efficiently synthesized by freeze-drying under the predetermined conditions. In addition, it was found that such an airgel material has abundant adsorption sites for adsorbing compounds such as odorous substances, and has an excellent adsorption rate and adsorption capacity. Furthermore, it was also found that the adsorption property is remarkably improved by using an airgel material containing a carbon nanomaterial in addition to the composite of cellulose nanofiber / transition metal. The present invention has been completed based on these findings.
　すなわち、本発明は、一態様において、
＜１＞セルロースナノファイバーと遷移金属イオンとの複合体が三次元ネットワーク構造を形成しているエアロゲル材料の製造方法であって、（ａ）セルロースナノファイバーの懸濁液に、遷移金属イオンを含有する溶液を添加し、混合溶液を得る工程、（ｂ）前記混合溶液を撹拌して、セルロースナノファイバーと遷移金属イオンの複合体を得る工程、（ｃ）工程（ｂ）で得られた複合体から遊離状態の遷移金属イオンを除去する工程、及び（ｄ）工程（ｃ）で得られた複合体を凍結乾燥して、エアロゲル構造体を得る工程を含む、当該製造方法；
＜２＞Ｎ－オキシル化合物を触媒として植物繊維を酸化することにより、工程（ａ）で用いられる前記セルロースナノファイバーを得る工程をさらに含む、上記＜１＞に記載の製造方法；
＜３＞前記セルロースナノファイバーが、カルボキシル基又はカルボキシレート基を有する、上記＜１＞又は＜２＞に記載の製造方法；
＜４＞前記セルロースナノファイバー中におけるカルボキシル基及びカルボキシレート基の含有量が０．１～５．０ｍｍｏｌ／ｇである、上記＜３＞に記載の製造方法；
＜５＞前記複合体が、キレート結合を介して遷移金属イオンがセルロースナノファイバーと結合することで錯体を形成した構造を有する、上記＜１＞～＜４＞のいずれか１に記載の製造方法；
＜６＞工程（ｃ）が、遠心分離及び／又は脱イオン水による洗浄により、遊離状態の遷移金属イオンを除去することを含む、上記＜１＞～＜５＞のいずれか１に記載の製造方法；
＜７＞工程（ｃ）が、工程（ｂ）で得られた複合体から遊離状態の遷移金属イオンを除去した後に、カーボンナノ材料の分散液を添加して複合体と混合する工程をさらに含む、上記＜１＞～＜６＞のいずれか１に記載の製造方法；
＜８＞工程（ｄ）が、３～１０重量％の複合体を含有する溶液を調整し、当該溶液の希釈液を凍結乾燥することを含む、上記＜１＞～＜７＞のいずれか１に記載の製造方法；及び
＜９＞前記遷移金属イオンが、銅、コバルト、ニッケル、バナジウム、チタン、クロム（ＩＩＩ）、マンガン、亜鉛、及び鉄よりなる群から選択される１種以上の２価の金属イオンである、上記＜１＞～＜８＞のいずれか１に記載の製造方法； 
を提供するものである。 That is, the present invention, in one aspect,
<1> A method for producing an airgel material in which a composite of cellulose nanofibers and a transition metal ion forms a three-dimensional network structure, wherein (a) a suspension of cellulose nanofibers contains a transition metal ion. Solution to obtain a mixed solution, (b) stirring the mixed solution to obtain a composite of cellulose nanofibers and a transition metal ion, (c) the composite obtained in step (b) The production method, which comprises a step of removing a transition metal ion in a free state from the solution, and a step of (d) freeze-drying the complex obtained in the step (c) to obtain an airgel structure;
<2> The production method according to <1>, further including a step of oxidizing the plant fiber using an N-oxyl compound as a catalyst to obtain the cellulose nanofiber used in the step (a);
<3> The production method according to <1> or <2>, wherein the cellulose nanofiber has a carboxyl group or a carboxylate group;
<4> The production method according to <3>, wherein the content of the carboxyl group and the carboxylate group in the cellulose nanofiber is 0.1 to 5.0 mmol / g.
<5> The production method according to any one of <1> to <4>, wherein the complex has a structure in which a transition metal ion is bound to a cellulose nanofiber through a chelate bond to form a complex. ;
<6> The production according to any one of the above <1> to <5>, wherein the step (c) includes removing the transition metal ion in a free state by centrifugation and / or washing with deionized water. Method;
<7> The step (c) further includes a step of removing the transition metal ion in a free state from the composite obtained in the step (b), and then adding a dispersion liquid of the carbon nanomaterial and mixing the composite with the composite. The manufacturing method according to any one of the above items <1> to <6>;
<8> Any one of the above <1> to <7>, wherein the step (d) includes preparing a solution containing 3 to 10% by weight of the complex and freeze-drying a diluted solution of the solution. <9> The transition metal ion is one or more divalent compounds selected from the group consisting of copper, cobalt, nickel, vanadium, titanium, chromium (III), manganese, zinc, and iron. The production method according to any one of the above items <1> to <8>, which is a metal ion of
Is provided.
　また、別の態様において、本発明は、上記製造方法によって得られるエアロゲル材料及びそれを用いる消臭方法にも関し
＜１０＞セルロースナノファイバーと遷移金属イオンとの複合体が三次元ネットワーク構造を形成しているエアロゲル材料であって、前記複合体が、キレート結合を介して遷移金属イオンがセルロースナノファイバーと結合することで錯体を形成した構造を有しており、前記エアロゲル材料の密度が５～１５ｍｇ／ｃｍ３の範囲であり、前記エアロゲル材料中の遷移金属の含有量が、セルロースナノファイバーに対して０．１～２００モル％である、ことを特徴とするエアロゲル材料；
＜１１＞カーボンナノ材料をさらに含む、上記＜１０＞に記載のエアロゲル材料；
＜１２＞前記セルロースナノファイバーが、カルボキシル基又はカルボキシレート基を有する、上記＜１０＞又は＜１１＞に記載のエアロゲル材料；
＜１３＞前記セルロースナノファイバー中におけるカルボキシル基及びカルボキシレート基の含有量が０．１～５．０ｍｍｏｌ／ｇである、上記＜１２＞に記載のエアロゲル材料；
＜１４＞直径３～５ｎｍの直線状の形状を有する、上記＜１０＞～＜１３＞のいずれか１に記載のエアロゲル材料；
＜１５＞前記遷移金属イオンが、銅、コバルト、ニッケル、バナジウム、チタン、クロム（ＩＩＩ）、マンガン、亜鉛、及び鉄よりなる群から選択される１種以上の２価の金属イオンである、上記＜１０＞～＜１４＞のいずれか１に記載のエアロゲル材料；
＜１６＞臭気性物質を吸着するための消臭用吸着体である、上記＜１０＞～＜１５＞のいずれか１に記載のエアロゲル材料；及び
＜１７＞前記臭気性物質が、アンモニア、トリメチルアミン、硫化水素、メチルメルカプタン、ホルムアルデヒド、及びキシレンより成る群から選択される１以上の化合物である、上記＜１６＞に記載のエアロゲル材料； 
を提供するものである。 In another aspect, the present invention also relates to an airgel material obtained by the above production method and a deodorizing method using the same, <10> a composite of cellulose nanofibers and a transition metal ion forms a three-dimensional network structure. The composite has a structure in which a transition metal ion is bound to cellulose nanofibers through a chelate bond to form a complex, and the density of the airgel material is 5 to The airgel material is in the range of 15 mg / cm 3 , and the content of the transition metal in the airgel material is 0.1 to 200 mol% based on the cellulose nanofibers.
<11> The airgel material according to <10>, further including a carbon nanomaterial;
<12> The airgel material according to <10> or <11>, in which the cellulose nanofiber has a carboxyl group or a carboxylate group;
<13> The airgel material according to <12>, wherein the content of the carboxyl group and the carboxylate group in the cellulose nanofiber is 0.1 to 5.0 mmol / g;
<14> The airgel material according to any one of <10> to <13>, which has a linear shape with a diameter of 3 to 5 nm;
<15> The transition metal ion is one or more divalent metal ions selected from the group consisting of copper, cobalt, nickel, vanadium, titanium, chromium (III), manganese, zinc, and iron. The airgel material according to any one of <10> to <14>;
<16> The airgel material according to any one of <10> to <15>, which is a deodorant adsorbent for adsorbing an odorant; and <17> the odorant is ammonia or trimethylamine. The airgel material according to <16> above, which is one or more compounds selected from the group consisting of hydrogen sulfide, methyl mercaptan, formaldehyde, and xylene.
Is provided.
　本発明の製造方法によれば、セルロースナノファイバーと遷移金属イオンとの複合体により構成され、非表面積が大きく超低密度スポンジ状の三次元構造を有する新規エアロゲル材料を効率的に製造することができる。 According to the production method of the present invention, a novel airgel material composed of a composite of cellulose nanofibers and transition metal ions and having a large non-surface area and ultra-low density sponge-like three-dimensional structure can be efficiently produced. it can.
　本発明のエアロゲル材料は、吸着サイトを豊富に有しており、優れた吸着速度及び吸着容量で臭気性物質等の化合物を吸着及び固定化でき、併せて、吸着した臭気性物質等を分解して吸着サイトを自己回復することができる。これにより、臭気性物質等の濃度が検出限界以下のレベルまで消臭する効果を奏するため、消臭用吸着体として好適である。さらに、さらに、当該エアロゲル材料中に、セルロースナノファイバー／遷移金属の複合体に加えて、カーボンナノ材料を含むことにより、吸着特性が著しく向上するという効果も得られる。 The airgel material of the present invention has abundant adsorption sites and can adsorb and immobilize compounds such as odorants with an excellent adsorption rate and adsorption capacity, and at the same time decomposes adsorbed odorants and the like. Can self-recover the adsorption site. As a result, the effect of deodorizing the concentration of the odorous substance or the like to a level below the detection limit is exerted, and thus it is suitable as a deodorizing adsorbent. Furthermore, by including a carbon nanomaterial in addition to the cellulose nanofiber / transition metal composite in the airgel material, the effect of significantly improving the adsorption property can be obtained.
図１は、本発明のエアロゲルの外形を示す画像である。FIG. 1 is an image showing the outer shape of the airgel of the present invention. 図２は、本発明のエアロゲルにおけるＣＮＦ／ Ｍ２＋複合体のＴＥＭ画像である。FIG. 2 is a TEM image of the CNF / M 2+ complex in the airgel of the present invention. 図３は、本発明のエアロゲルの内部構造を示す電子顕微鏡イメージ画像である。FIG. 3 is an electron microscope image showing the internal structure of the airgel of the present invention. 図４は、本発明のエアロゲルの内部構造を示す電子顕微鏡イメージ画像である。FIG. 4 is an electron microscope image showing the internal structure of the airgel of the present invention. 図５は、本発明のエアロゲルについて行ったＥＤＳ元素分析チャートである。FIG. 5 is an EDS elemental analysis chart performed on the airgel of the present invention. 図６は、アンモニアに対する吸着試験の結果を示すグラフである。FIG. 6 is a graph showing the results of an adsorption test for ammonia. 図７は、トリメチルアミンに対する吸着試験の結果を示すグラフである。FIG. 7 is a graph showing the results of an adsorption test for trimethylamine. 図８は、硫化水素に対する吸着試験の結果を示すグラフである。FIG. 8 is a graph showing the results of an adsorption test for hydrogen sulfide. 図９は、アンモニアに対する吸着の結果について、使用エアロゲル量の比較を示すグラフである。FIG. 9 is a graph showing a comparison of the amount of airgel used with respect to the result of adsorption on ammonia. 図１０は、本発明のＣＮＴを含むエアロゲル、ＣＮＴを含まないエアロゲル、及び活性炭（比較例）を用いた、各種臭気物質に対する吸着試験の結果を示すグラフである。FIG. 10 is a graph showing the results of adsorption tests for various odorous substances using the CNT-containing aerogel of the present invention, the CNT-free aerogel, and activated carbon (comparative example).
　以下、本発明の実施形態について説明する。本発明の範囲はこれらの説明に拘束されることはなく、以下の例示以外についても、本発明の趣旨を損なわない範囲で適宜変更し実施することができる。 An embodiment of the present invention will be described below. The scope of the present invention is not limited to these descriptions, and other than the following examples, the scope of the present invention can be appropriately modified and implemented without departing from the spirit of the present invention.
１．エアロゲル材料の製造
　本発明の製造方法は、セルロースナノファイバーと遷移金属イオンとの複合体が三次元ネットワーク構造を形成しているエアロゲル材料を製造するための方法である。より具体的には、本発明の製造方法は、以下の（ａ）～（ｄ）の工程を含むことを特徴とする。
（ａ）セルロースナノファイバーの懸濁液に、遷移金属イオンを含有する溶液を添加し、混合溶液を得る工程、
（ｂ）前記混合溶液を撹拌して、セルロースナノファイバーと遷移金属イオンの複合体を得る工程、
（ｃ）工程（ｂ）で得られた複合体から遊離状態の遷移金属イオンを除去する工程、及び
（ｄ）工程（ｃ）で得られた複合体を凍結乾燥して、エアロゲル構造体を得る工程。 1. Production of Airgel Material The production method of the present invention is a method for producing an airgel material in which a composite of cellulose nanofibers and a transition metal ion forms a three-dimensional network structure. More specifically, the manufacturing method of the present invention is characterized by including the following steps (a) to (d).
(A) a step of adding a solution containing a transition metal ion to a suspension of cellulose nanofibers to obtain a mixed solution,
(B) a step of stirring the mixed solution to obtain a composite of cellulose nanofibers and a transition metal ion,
(C) a step of removing free-state transition metal ions from the complex obtained in step (b), and (d) the complex obtained in step (c) is lyophilized to obtain an airgel structure. Process.
　工程（ａ）と（ｂ）は、セルロースナノファイバーと遷移金属イオンを接触させ、エアロゲル材料の骨格を形成するセルロースナノファイバー／遷移金属の複合体を得る工程である。 Steps (a) and (b) are steps of contacting cellulose nanofibers with transition metal ions to obtain a cellulose nanofiber / transition metal complex that forms the skeleton of the airgel material.
　まず、工程（ａ）では、セルロースナノファイバーを懸濁させた溶液と、遷移金属イオンを含有する溶液をそれぞれ調製し、これら２つの溶液を混ぜて混合溶液が得られる。セルロースナノファイバー懸濁液における溶媒は、好ましくは水、例えば、脱イオン水を用いることができる。セルロースナノファイバー懸濁液におけるセルロースナノファイバー含有量は、特に限定されないが、典型的には、０．１～５．０重量％、好ましくは、０．５～２．０重量％とすることができる。 First, in step (a), a solution in which cellulose nanofibers are suspended and a solution containing a transition metal ion are prepared, and these two solutions are mixed to obtain a mixed solution. The solvent in the cellulose nanofiber suspension may preferably be water, for example deionized water. The content of cellulose nanofibers in the cellulose nanofiber suspension is not particularly limited, but is typically 0.1 to 5.0% by weight, preferably 0.5 to 2.0% by weight. it can.
　ここで、「セルロースナノファイバー」とは、植物繊維（パルプ）を解繊して得られる微細なセルロース繊維を意味し、一般に繊維径（幅）がナノメートルオーダー（１～１０００ｎｍ）を有するものである。その長さは、特に限定されないが、通常数マイクロメートル程度の長さを有する。 Here, "cellulose nanofibers" means fine cellulose fibers obtained by defibrating plant fibers (pulp), and generally have a fiber diameter (width) of the nanometer order (1 to 1000 nm). is there. The length is not particularly limited, but usually has a length of about several micrometers.
　工程（ａ）で原料として用いられるセルロースナノファイバーは、キレート結合（配位結合）により錯形成し得る官能基を有するものであり、好ましくは、そのような官能基としてカルボキシル基又はカルボキシレート基を有する。より好ましくは、セルロースナノファイバー中におけるカルボキシル基及びカルボキシレート基の含有量が０．１～５．０ｍｍｏｌ／ｇ、好ましくは、０．５～２．０ｍｍｏｌ／ｇである。セルロースナノファイバー中のカルボキシル基又はカルボキシレート基の含有量は、中和滴定などの公知の手法によって求めることができる（例えば特開２００８－００１７２８号公報）。 The cellulose nanofiber used as a raw material in the step (a) has a functional group capable of forming a complex by a chelate bond (coordination bond), and preferably has a carboxyl group or a carboxylate group as such a functional group. Have. More preferably, the content of carboxyl group and carboxylate group in the cellulose nanofiber is 0.1 to 5.0 mmol / g, preferably 0.5 to 2.0 mmol / g. The content of the carboxyl group or the carboxylate group in the cellulose nanofiber can be determined by a known method such as neutralization titration (for example, JP 2008-001728 A).
　カルボキシル基又はカルボキシレート基を有するセルロースナノファイバーは、一般に、天然のセルロース繊維等の植物繊維を化学変性させ、微細化処理により解繊して得ることができる。典型的には、Ｎ－オキシル化合物である２，２，６，６-テトラメチルピペリジン－1－オキシル（ＴＥＭＰＯ）を触媒として用いた化学変性反応により、植物繊維を酸化させる公知の方法を用いることができる。かかる酸化反応により、セルロース繊維等の植物繊維表面のグルコピラノース環のＣ６位の一級水酸基が選択的に酸化され、表面にカルボキシル基またはカルボキシレート基を有するセルロース系ファイバーを得ることができる。したがって、本発明の製造方法は、工程（ａ）の前工程として、　Ｎ－オキシル化合物を触媒として植物繊維を酸化することにより、工程（ａ）で用いられる前記セルロースナノファイバーを得る工程を含むことができる。 Cellulose nanofibers having a carboxyl group or a carboxylate group can generally be obtained by chemically modifying plant fibers such as natural cellulose fibers and defibrating them by a micronization treatment. Typically, a known method for oxidizing plant fiber by a chemical modification reaction using N- oxyl compound 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as a catalyst is used. You can By such an oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the surface of the plant fiber such as cellulose fiber is selectively oxidized, and a cellulosic fiber having a carboxyl group or a carboxylate group on the surface can be obtained. Therefore, the production method of the present invention includes, as a step prior to step (a), a step of oxidizing the vegetable fiber using an N-oxyl compound as a catalyst to obtain the cellulose nanofiber used in step (a). You can
　ＴＥＭＰＯ触媒酸化は、例えば、Ｉｓｏｇａｉら、Ｎａｎｏｓｃａｌｅ, ３, ７１－８５、２０１１（非特許文献１）等に詳細な工程が説明されている。ここで、触媒として用いられ得るＮ－オキシル化合物は、ニトロキシラジカルを生じさせ、植物繊維の酸化反応を促進し得るものであれば、ＴＥＭＰＯ以外の化合物も用いることができる。また、酸化反応には、公知の共酸化剤を反応溶液中に追加的に用いてもよい。そのような酸化剤としては、例えば、ハロゲン、次亜ハロゲン酸、亜ハロゲン酸、過ハロゲン酸またはそれらの塩、ハロゲン酸化物、過酸化物などを使用できる。中でも、安価で環境負荷の少ない次亜塩素酸ナトリウムは好ましい。 For TEMPO-catalyzed oxidation, detailed steps are described in, for example, Isogai et al., Nanoscale, 3, 71-85, 2011 (Non-Patent Document 1). Here, as the N-oxyl compound that can be used as a catalyst, a compound other than TEMPO can be used as long as it can generate a nitroxy radical and accelerate the oxidation reaction of plant fibers. A known co-oxidant may be additionally used in the reaction solution for the oxidation reaction. As such an oxidizing agent, for example, halogen, hypohalous acid, halogenous acid, perhalogenic acid or salts thereof, halogen oxide, peroxide and the like can be used. Of these, sodium hypochlorite, which is inexpensive and has a low environmental load, is preferable.
　上記セルロースナノファイバーを得るための化学変性反応における植物繊維の量、触媒量、共酸化剤の量、反応溶液のｐＨ、或いは反応時間や反応温度等の反応条件は、当業者が適宜設定することができる。 Those skilled in the art can appropriately set the reaction conditions such as the amount of plant fiber, the amount of catalyst, the amount of co-oxidant, the pH of the reaction solution, or the reaction time and the reaction temperature in the chemical modification reaction for obtaining the cellulose nanofibers. You can
　セルロースナノファイバーの原料となる植物繊維は、特に限定されないが、天然セルロースであることが好ましい。天然セルロースとしては、例えば、木材原料をパルプ化したものを用いることができる。木材原料としては、アカマツ、クロマツ、トドマツ、エゾマツ、ベニマツ、カラマツ、モミ、ツガ、スギ、ヒノキ、カラマツ、シラベ、トウヒ、ヒバ、ダグラスファー、ヘムロック、ホワイトファー、スプルース、バルサムファー、シーダ、パイン、メルクシマツ、ラジアータパイン等の針葉樹、及びこれらの混合材、ブナ、カバ、ハンノキ、ナラ、タブ、シイ、シラカバ、ハコヤナギ、ポプラ、タモ、ドロヤナギ、ユーカリ、マングローブ、ラワン、アカシア等の広葉樹及びこれらの混合材を例示することができる。 The plant fiber that is the raw material of the cellulose nanofibers is not particularly limited, but natural cellulose is preferable. As the natural cellulose, for example, pulp obtained by pulping a wood raw material can be used. As the wood raw material, red pine, black pine, todo pine, spruce pine, black pine, larch, fir, hemlock, cedar, cypress, larch, silabe, spruce, hiba, Douglas fir, hemlock, white fir, spruce, balsam fir, cedar, pine, pine, Softwood such as mercantia pine, radiata pine, and their mixed materials, beech, birch, alder, oak, oak, tub, shii, birch, cottonwood, poplar, tamo, droyagi, eucalyptus, mangrove, lauan, acacia, etc., and mixtures thereof The material can be illustrated.
　化学変性（酸化）後の微細化処理は、例えばパルプを回転する砥石間で磨砕するグラインダー法、高圧ホモジナイザーを用いた対向衝突法、ボールミル、ロールミル、カッターミル等を用いる粉砕法などの機械的処理が挙げられる。通常、得られるセルロースナノファイバーが所望のサイズになるまで、解繊処理が繰り返し行われる。 The micronization after chemical modification (oxidation) is carried out by mechanical methods such as a grinder method of grinding pulp between rotating grindstones, an opposed collision method using a high-pressure homogenizer, a grinding method using a ball mill, a roll mill, a cutter mill, or the like. Processing. Usually, the defibration treatment is repeatedly performed until the obtained cellulose nanofibers have a desired size.
　セルロースナノファイバーの繊維長、繊維径（幅）は特に限定されないが、例えば、繊維長０．１～１０μｍ、繊維径１～１００ｎｍ程度、好ましくは２．５～２０ｎｍ程度であることができる。かかる繊維長や繊維径は走査型または透過型電子顕微鏡像（ＳＥＭまたはＴＥＭ）、あるいは原子間力顕微鏡像（ＡＦＭ）から求めることができる。 The fiber length and fiber diameter (width) of the cellulose nanofibers are not particularly limited, but for example, the fiber length may be 0.1 to 10 μm, the fiber diameter may be about 1 to 100 nm, and preferably about 2.5 to 20 nm. The fiber length and fiber diameter can be obtained from a scanning or transmission electron microscope image (SEM or TEM) or an atomic force microscope image (AFM).
　また、工程（ａ）で用いられる遷移金属イオンを含有する溶液は、遷移金属の塩を溶媒に溶解させることで調製することができる。溶媒は、好ましくは水、例えば、脱イオン水を用いることができる。遷移金属イオンは、セルロースナノファイバーと結合し得るものであれば特に制限されないが、好ましくは、周期表８～１２族に属する遷移金属元素のイオンであり、より好ましくは、これらの２価の金属イオンである。例えば、遷移金属イオンは、銅、コバルト、ニッケル、バナジウム、チタン、クロム（ＩＩＩ）、マンガン、亜鉛、及び鉄なる群から選択される１種以上の２価の金属イオンであることができる。後述のように、当該遷移金属は、エアロゲル材料に吸着した臭気物質を触媒作用によって分解する機能を奏するものである。遷移金属塩としては、これら遷移金属カチオンと任意のアニオンとの塩を用いることができるが、例えば、これら遷移金属のハロゲン化物、硝酸塩、硫酸塩、および酢酸塩を用いることができる。 The solution containing the transition metal ion used in step (a) can be prepared by dissolving a salt of the transition metal in a solvent. The solvent may preferably be water, for example deionized water. The transition metal ion is not particularly limited as long as it can bind to the cellulose nanofibers, but is preferably an ion of a transition metal element belonging to Group 8 to 12 of the periodic table, more preferably these divalent metals. Ion. For example, the transition metal ion can be one or more divalent metal ions selected from the group consisting of copper, cobalt, nickel, vanadium, titanium, chromium (III), manganese, zinc, and iron. As described later, the transition metal has a function of decomposing an odor substance adsorbed on the airgel material by a catalytic action. As the transition metal salt, salts of these transition metal cations and arbitrary anions can be used. For example, halides, nitrates, sulfates, and acetates of these transition metals can be used.
　遷移金属イオン溶液の濃度は、セルロースナノファイバーとキレート結合（配位結合）により結合し得る金属イオンの理論値よりも過剰量となるような金属イオン濃度であることが好ましい。例えば、セルロースナノファイバー中のカルボキシル基及びカルボキシレート基の量に対して、モル量で、０．１～１０倍が好ましく、０．５～２倍がさらに好ましい。例えば、遷移金属イオン溶液の濃度は、０．１～１０００ｍｍｏｌ／ｌの範囲とすることができる。 The concentration of the transition metal ion solution is preferably a metal ion concentration that is in excess of the theoretical value of the metal ion capable of binding to the cellulose nanofibers by a chelate bond (coordination bond). For example, the molar amount is preferably 0.1 to 10 times, more preferably 0.5 to 2 times, the amount of the carboxyl group and the carboxylate group in the cellulose nanofiber. For example, the concentration of the transition metal ion solution can be in the range of 0.1 to 1000 mmol / l.
　次に、工程（ｂ）は、工程（ａ）で調製した混合溶液を撹拌して、セルロースナノファイバーと遷移金属イオンの複合体を得る工程である。ここで、撹拌の時間や温度等の条件は、適宜設定することができる。ここで、得られるセルロースナノファイバー／遷移金属の複合体は、セルロースナノファイバー中のカルボキシル基又はカルボキシレート基において、キレート結合を介して遷移金属イオンがセルロースナノファイバーと結合することで錯体を形成した構造を有する。 Next, step (b) is a step of stirring the mixed solution prepared in step (a) to obtain a composite of cellulose nanofibers and a transition metal ion. Here, conditions such as stirring time and temperature can be appropriately set. Here, the obtained cellulose nanofiber / transition metal complex formed a complex by binding a transition metal ion to the cellulose nanofiber through a chelate bond at a carboxyl group or a carboxylate group in the cellulose nanofiber. Have a structure.
　工程（ｃ）は、工程（ｂ）で得られたセルロースナノファイバー／遷移金属の複合体から遊離状態、すなわちセルロースナノファイバーとの錯形成に用いられずに溶液中に残存する過剰量の遷移金属イオンを除去する工程である。かかる遷移金属イオンは、遠心分離及び／又は脱イオン水による洗浄によって除去することができる。好ましくは、遠心分離を行った後、さらに脱イオン水による洗浄を複数回行うことができる。 The step (c) is a free state from the cellulose nanofiber / transition metal complex obtained in the step (b), that is, an excess amount of the transition metal which remains in the solution without being used for complexing with the cellulose nanofiber. This is a step of removing ions. Such transition metal ions can be removed by centrifugation and / or washing with deionized water. Preferably, after centrifugation, washing with deionized water can be further performed a plurality of times.
　また、好ましい態様において、工程（ｃ）は、工程（ｂ）で得られた複合体から遊離状態の遷移金属イオンを除去した後に、カーボンナノ材料の分散液を添加して複合体と混合する工程をさらに含むことができる。これにより、上記セルロースナノファイバー／遷移金属の複合体に加えて、カーボンナノ材料をさらに含むエアロゲル構造体を得ることができる。 In a preferred embodiment, the step (c) is a step of removing the transition metal ion in a free state from the complex obtained in the step (b), and then adding a dispersion liquid of the carbon nanomaterial and mixing with the complex. Can be further included. This makes it possible to obtain an airgel structure further containing a carbon nanomaterial in addition to the cellulose nanofiber / transition metal composite.
　ここで用いられるカーボンナノ材料としては、炭素の六員環を有するグラフェンシートを含む物質をいい、ホウ素や窒素等の炭素以外の元素を含有していてもよい。カーボンナノ材料の例としては、カーボンナノチューブ（ＣＮＴ）、カーボンナノファイバー（ＣＮＦ）、グラフェン、カーボンナノホーン（ＣＮＨ）、フラーレン、又はそれらの組み合わせを挙げることができるし、これらを化学的に修飾した物質であってもよい。カーボンナノ材料の製造方法は特に制限されず、従来から公知の方法によって製造することができ、また、市販のものをそのまま用いることもできる。好ましくは、カーボンナノ材料は、カーボンナノチューブである。 The carbon nanomaterial used here refers to a substance including a graphene sheet having a carbon six-membered ring, and may contain an element other than carbon such as boron or nitrogen. Examples of carbon nanomaterials include carbon nanotubes (CNT), carbon nanofibers (CNF), graphene, carbon nanohorns (CNH), fullerenes, or combinations thereof, and substances obtained by chemically modifying these. May be The method for producing the carbon nanomaterial is not particularly limited, and it can be produced by a conventionally known method, or a commercially available one can be used as it is. Preferably, the carbon nanomaterial is carbon nanotube.
　カーボンナノチューブは、一般に、炭素の六員環配列構造を有する１枚のシート状グラファイト（グラフェンシート）が円筒状に巻かれた直径数ｎｍ程度のチューブ状構造を有する材料である。本明細書において「カーボンナノチューブ」には、１枚のシート状グラファイトで構成された単層カーボンナノチューブの他、前記筒状のシートが軸直角方向に複数積層した多層カーボンナノチューブ（カーボンナノチューブの内部にさらに径の小さいカーボンナノチューブを１個以上内包する多層カーボンナノチューブ）、単層カーボンナノチューブの端部が円錐状で閉じた形状のカーボンナノホーン、内部にフラーレンを内包するカーボンナノチューブなども包含される。これらのカーボンナノチューブは、単独で又は二種以上組み合わせて使用できる。 Carbon nanotubes are generally materials that have a tubular structure with a diameter of several nanometers in which a single sheet of graphite (graphene sheet) having a carbon six-membered ring array structure is rolled into a cylinder. In the present specification, "carbon nanotubes" include single-walled carbon nanotubes composed of one sheet of graphite, and multi-walled carbon nanotubes in which the tubular sheets are stacked in a direction perpendicular to the axis ( Furthermore, a multi-walled carbon nanotube containing one or more small-diameter carbon nanotubes), a carbon nanohorn in which the end of a single-walled carbon nanotube is conical and closed, and a carbon nanotube containing fullerene inside are included. These carbon nanotubes can be used alone or in combination of two or more.
　カーボンナノチューブの平均径（軸方向に対して直交する方向の直径又は横断面径）は、例えば、０．５ｎｍ～１μｍ、好ましくは１～１００ｎｍの範囲から選択でき、単層カーボンナノチューブの場合には、例えば、０．５～１０ｎｍ、好ましくは１～５ｎｍ程度であり、多層カーボンナノチューブの場合は、例えば、５～３００ｎｍ、好ましくは１０～１００ｎｍ程度である。カーボンナノチューブの平均長は、例えば、１～１０００μｍ、好ましくは５～５００μｍの範囲である。 The average diameter of the carbon nanotubes (diameter in the direction orthogonal to the axial direction or cross-sectional diameter) can be selected from the range of, for example, 0.5 nm to 1 μm, preferably 1 to 100 nm. For example, it is about 0.5 to 10 nm, preferably about 1 to 5 nm, and in the case of multi-walled carbon nanotubes, it is about 5 to 300 nm, preferably about 10 to 100 nm. The average length of the carbon nanotubes is, for example, in the range of 1 to 1000 μm, preferably 5 to 500 μm.
　工程（ｃ）で用いられるカーボンナノ材料の分散液は、カーボンナノ材料を溶媒中に分散させた溶液である。溶媒としては、水、有機溶媒、又はこれらの混合溶媒であってもよいが、好ましくは、水である。当該分散液は、必要に応じて、分散剤を含むことができ、かかる分散剤としては、界面活性剤、各種高分子材料（水溶性高分子材料等）などを用いることができる。本発明では、イオン性界面活性剤と非イオン性界面活性剤のいずれを用いることも可能であるが、分散能が高い点からイオン性界面活性剤が好ましい。 The carbon nanomaterial dispersion used in the step (c) is a solution in which the carbon nanomaterial is dispersed in a solvent. The solvent may be water, an organic solvent, or a mixed solvent thereof, but water is preferable. The dispersion liquid may contain a dispersant, if necessary, and as the dispersant, a surfactant, various polymer materials (water-soluble polymer material, etc.) and the like can be used. In the present invention, either an ionic surfactant or a nonionic surfactant can be used, but an ionic surfactant is preferred from the viewpoint of high dispersibility.
　分散液中のカーボンナノ材料の含有量は、特に制限されないが、例えば、１～３００ｇ／Ｌ、好ましくは、１０～２００ｇ／Ｌである。また、最終的なエアロゲル材料中のカーボンナノ材料は、例えば、０．５～３０重量％、好ましくは、１～１０重量％であることができる。 The content of the carbon nanomaterial in the dispersion is not particularly limited, but is, for example, 1 to 300 g / L, preferably 10 to 200 g / L. Also, the carbon nanomaterial in the final airgel material can be, for example, 0.5 to 30% by weight, preferably 1 to 10% by weight.
　工程（ｄ）は、工程（ｃ）で得られたセルロースナノファイバー／遷移金属の複合体を結乾燥して、エアロゲル構造体を得る工程である。ここで、「エアロゲル」とは、セルロースナノファイバー／遷移金属の複合体が、三次元ネットワーク構造を形成することにより、体積の大部分が空隙から成る非結晶質のナノ多孔体構造を意味する。当該エアロゲルは、その多孔体構造により、非表面積が大きく、超低密度スポンジ状の構造特性を有する。 Step (d) is a step of binding and drying the cellulose nanofiber / transition metal composite obtained in step (c) to obtain an airgel structure. Here, the "aerogel" means a non-crystalline nanoporous material structure in which most of the volume is voids by the cellulose nanofiber / transition metal complex forming a three-dimensional network structure. Due to its porous structure, the airgel has a large non-surface area and has an ultra-low density sponge-like structural characteristic.
　かかる凍結乾燥は、典型的には、セルロースナノファイバー／遷移金属の複合体を脱イオン水等の溶媒中に溶解させ、コロイド状の溶液とした後に、必要に応じて当該コロイド状溶液の希釈液を調整し、液体窒素等により凍結し、乾燥器を用いて乾燥することによって行われる。このコロイド状の溶液は、好ましくは、３～１０重量％、好ましくは、３～７重量％の複合体を含有する。希釈液を用いる場合には、０．５～５重量％の濃度まで希釈することができる。かかる比較的濃厚な複合体含有量とすることで、コロイド状溶液の状態で、既に複合体がゲル状態に近い三次元ネットワーク構造を形成しており、この状態で凍結乾燥させることにより、非表面積が大きく超低密度スポンジ状の三次元ネットワーク構造を有するナノ多孔体であるエアロゲルを得ることができる。 Such freeze-drying is typically performed by dissolving the cellulose nanofiber / transition metal complex in a solvent such as deionized water to form a colloidal solution, and then diluting the colloidal solution as needed. Is adjusted, frozen with liquid nitrogen or the like, and dried using a dryer. The colloidal solution preferably contains 3-10% by weight, preferably 3-7% by weight of the complex. When a diluent is used, it can be diluted to a concentration of 0.5 to 5% by weight. By setting such a relatively high concentration of the complex, the complex has already formed a three-dimensional network structure close to a gel state in the state of colloidal solution, and by freeze-drying in this state, the non-surface area It is possible to obtain an aerogel which is a nanoporous material having a large three-dimensional network structure with a very low density sponge.
　このように、本発明の製造方法によって得られるエアロゲルは、非表面積が大きいスポンジ状構造を有しているため、吸着サイトを豊富に有しており、臭気性物質等の化合物を吸着するための消臭用吸着体として好適である。かかるエアロゲルの特性等の詳細については後述する。 Thus, since the airgel obtained by the production method of the present invention has a large non-surface area sponge-like structure, it has abundant adsorption sites for adsorbing compounds such as odorants. It is suitable as a deodorant adsorbent. Details of the properties of the airgel will be described later.
２．エアロゲル材料
　本発明は、さらに、上記製造方法によって得られるエアロゲル材料にも関する。すなわち、本発明に係るエアロゲル材料は、
　セルロースナノファイバーと遷移金属イオンとの複合体が三次元ネットワーク構造を形成しているエアロゲル材料であって、
　前記複合体が、キレート結合を介して遷移金属イオンがセルロースナノファイバーと結合することで錯体を形成した構造を有しており、
　前記エアロゲル材料の密度が５～１５ｍｇ／ｃｍ３の範囲であり、
　前記エアロゲル材料中の遷移金属の含有量が、セルロースナノファイバーに対して０．１～２００モル％である、
ことを特徴とする。 2. Airgel Material The present invention further relates to an airgel material obtained by the above production method. That is, the airgel material according to the present invention,
An airgel material in which a composite of cellulose nanofibers and a transition metal ion forms a three-dimensional network structure,
The complex has a structure in which a transition metal ion is bound to a cellulose nanofiber through a chelate bond to form a complex,
The airgel material has a density in the range of 5 to 15 mg / cm 3 ;
The content of the transition metal in the airgel material is 0.1 to 200 mol% based on the cellulose nanofiber,
It is characterized by
　セルロースナノファイバー／遷移金属の複合体におけるセルロースナノファイバーについては、既に述べたとおりである。好ましくは、当該セルロースナノファイバーはカルボキシル基又はカルボキシレート基を有し、それらの含有量は、好ましくは０．１～５．０ｍｍｏｌ／ｇ、より好ましくは、０．５～２．０ｍｍｏｌ／ｇである。また、遷移金属の種類等についても上述したとおりであり、好ましくは、セルロースナノファイバー／遷移金属の複合体を形成する遷移金属イオンは、銅、コバルト、ニッケル、バナジウム、チタン、クロム（ＩＩＩ）、マンガン、亜鉛、及び鉄よりなる群から選択される１種以上の２価の金属イオンである。 The cellulose nanofiber in the composite of cellulose nanofiber / transition metal is as described above. Preferably, the cellulose nanofiber has a carboxyl group or a carboxylate group, and the content thereof is preferably 0.1 to 5.0 mmol / g, more preferably 0.5 to 2.0 mmol / g. is there. The types of transition metals are also as described above, and preferably, the transition metal ions forming the cellulose nanofiber / transition metal complex are copper, cobalt, nickel, vanadium, titanium, chromium (III), It is one or more kinds of divalent metal ions selected from the group consisting of manganese, zinc, and iron.
　上述のとおり、本発明のエアロゲル材料は、非表面積が大きく超低密度スポンジ状の三次元ネットワーク構造を有するナノ多孔体である。当該エアロゲル材料の密度は、５～１５ｍｇ／ｃｍ３の範囲であり、１０ｍｇ／ｃｍ３程度であることが好ましい。 As described above, the airgel material of the present invention is a nanoporous body having a large non-surface area and an ultra-low density sponge-like three-dimensional network structure. The density of the airgel material is in the range of 5 to 15 mg / cm 3 , and preferably about 10 mg / cm 3 .
　また、前記エアロゲル材料中の遷移金属の含有量が、セルロースナノファイバーに対して０．１～２００モル％（１ｍｏｌのセルロースナノファイバー対するモル率）であることができる。或いは、重量％での表示では、エアロゲル材料全体において１～２０重量％、好ましくは５～１５重量％であることができる。かかる遷移金属の含有量は、例えば、エネルギー分散型Ｘ線分析法（ＥＤＳ）による元素分析によって測定することができる。 The content of the transition metal in the airgel material may be 0.1 to 200 mol% with respect to the cellulose nanofibers (molar ratio of 1 mol of the cellulose nanofibers). Alternatively, in terms of weight percent, it can be 1 to 20 weight percent, preferably 5 to 15 weight percent, of the total airgel material. The content of such a transition metal can be measured by, for example, elemental analysis by energy dispersive X-ray analysis (EDS).
　前記エアロゲル材料の形状等は特に限定されないが、典型的には、直径（繊維径）が３～５ｎｍの直線状の形状を有する。 The shape and the like of the airgel material are not particularly limited, but typically have a linear shape with a diameter (fiber diameter) of 3 to 5 nm.
　好ましい態様において、本発明のエアロゲル材料は、セルロースナノファイバー／遷移金属の複合体に加えて、カーボンナノ材料をさらに含むことができる。エアロゲル中に孤立分散されたカーボンナノ材料が存在することにより、臭気性物質等の化合物に対する吸着特性が著しく向上し、より高い消臭性能が得られる。かかるカーボンナノ材料の詳細については、既に述べたとおりである。上述のとおり、エアロゲル材料中のカーボンナノ材料は、例えば、０．５～３０重量％、好ましくは、１～１０重量％であることができる。 In a preferred embodiment, the airgel material of the present invention can further include a carbon nanomaterial in addition to the cellulose nanofiber / transition metal composite. The presence of the carbon nanomaterial isolated and dispersed in the aerogel significantly improves the adsorption property for a compound such as an odorous substance, and a higher deodorizing performance can be obtained. The details of the carbon nanomaterial are as described above. As mentioned above, the carbon nanomaterial in the airgel material can be, for example, 0.5 to 30% by weight, preferably 1 to 10% by weight.
　本発明のエアロゲル材料は、上述のとおり、非表面積が大きいスポンジ状構造を有し、セルロースナノファイバーの表面上に存在するカルボキシル基又はカルボキシレート基と遷移金属がキレート結合を形成している吸着サイトを豊富に有しているため、臭気性物質等の化合物の吸着能に優れている。そのため、臭気性物質を吸着するための消臭用吸着体としての用途に好適である。そのような臭気性物質としては、例えば、アンモニア、トリメチルアミン、硫化水素、メチルメルカプタン、ホルムアルデヒド、及びキシレンより成る群から選択される１以上の化合物であることができるが、必ずしもこれらに限らない。 The airgel material of the present invention, as described above, has a large non-surface area sponge-like structure, an adsorption site where a transition metal forms a chelate bond with a carboxyl group or a carboxylate group present on the surface of cellulose nanofibers. Since it has abundant content, it has excellent adsorption ability for compounds such as odorous substances. Therefore, it is suitable for use as a deodorant adsorbent for adsorbing odorous substances. Such an odorous substance can be, for example, one or more compounds selected from the group consisting of ammonia, trimethylamine, hydrogen sulfide, methyl mercaptan, formaldehyde, and xylene, but is not necessarily limited thereto.
　必ずしも理論に拘束されるものではないが、本発明のエアロゲル材料は、以下の機構により臭気性物質の吸着・分解を行うことができると考えられる。エアロゲル材料中のセルロースナノファイバー／遷移金属の複合体は、イオン状態の遷移金属とのキレート結合を介してアンモニアやトリメチルアミンと結合し、これをエアロゲル材料中に固定化（吸着）する。一方、硫化水素に対しては、遷移金属の硫化物を形成することにより、この毒性の極めて高い有害ガスを固定化（吸着）することができる。さらに、金属状態（無電荷状態）となった遷移金属は、触媒として機能し、アンモニア、トリメチルアミン並びに硫化水素等の臭気性物質を分解し、吸着サイトが自己回復する。かかる機構により、優れた吸着速度及び吸着容量を達成することができる。 Although not necessarily bound by theory, it is considered that the airgel material of the present invention can adsorb and decompose odorous substances by the following mechanism. The cellulose nanofiber / transition metal complex in the airgel material binds with ammonia or trimethylamine through a chelate bond with the transition metal in an ionic state, and immobilizes (adsorbs) this in the airgel material. On the other hand, with respect to hydrogen sulfide, it is possible to immobilize (adsorb) this extremely toxic harmful gas by forming a sulfide of a transition metal. Furthermore, the transition metal in the metal state (uncharged state) functions as a catalyst, decomposes odorous substances such as ammonia, trimethylamine, and hydrogen sulfide, and the adsorption site self-recovers. With such a mechanism, an excellent adsorption rate and adsorption capacity can be achieved.
　このように、かかるエアロゲル材料を用いて、臭気性物質を効率的に吸着・分解することができる。したがって、本発明は、当該エアロゲル材料を用いて臭気性物質を吸着させることを含む消臭方法において有用である。 In this way, odorous substances can be efficiently adsorbed and decomposed using such airgel materials. Therefore, the present invention is useful in a deodorizing method including adsorbing an odorous substance using the airgel material.
　例えば、本発明のエアロゲル材料は、空気清浄機やエアコンなどに搭載することで消臭効果を発揮でき、或いは、劇毒ガスである硫化水素を対処する非常事態に備えるガスマスクや、家畜のし尿に起因する悪臭問題の軽減または解決等の用途において好適に用いることができる。 For example, the airgel material of the present invention can exert a deodorizing effect by being installed in an air purifier, an air conditioner, or the like, or a gas mask for emergency situations in which hydrogen sulfide, which is a poisonous gas, is dealt with, and livestock excrement. It can be preferably used in applications such as reducing or solving the problem of bad odor.
　また、セルロースナノファイバー／遷移金属の複合体（錯体）は、可視光領域に吸収帯を有しており、臭気性物質が上述のように複合体中の遷移金属とキレート結合を介して結合することによって吸収体がシフトするため、その色調が変化する。すなわち、本発明のエアロゲル材料は、臭気性物質吸が吸着されたことをその色調の変化によってセンシング可能であるため、当該エアロゲル材料を用いた臭気センサとしての用途において好適に用いることができる。 In addition, the cellulose nanofiber / transition metal complex (complex) has an absorption band in the visible light region, and the odorous substance binds to the transition metal in the complex through a chelate bond as described above. As a result, the absorber shifts, and its color tone changes. That is, since the airgel material of the present invention can sense that the odorous substance is adsorbed by a change in its color tone, it can be suitably used in an application as an odor sensor using the airgel material.
　以下、実施例により本発明をさらに詳細に説明するが、本発明はこれらによって限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.
１．セルロースナノファイバー／遷移金属の複合体の合成
　文献（Ｓａｉｔｏら、 Ｂｉｏｍａｃｒｏｍｏｌｅｃｕｌｅｓ、 ８、 ２４８５－２４９１ 、２００７）の記載に従い、セルロース繊維をＴＥＭＰＯ触媒により化学変性の後、微細化処理を行い、カルボキシル基を豊富に含む酸化セルロースナノファイバーを合成した。 1. Synthesis of Cellulose Nanofiber / Transition Metal Composite According to the description of Saito et al., Biomacromolecules, 8, 2485-2491, 2007, cellulose fibers were chemically modified with TEMPO catalyst and then subjected to a fine treatment to reduce carboxyl groups. We have synthesized abundant oxidized cellulose nanofibers.
　上記で得た酸化セルロースナノファイバー１００ｇを３００ｍＬの脱イオン水に分散させ（２ｗｔ％）、銅の１Ｍ硫酸塩１００ｍＬを添加し、混合溶液を機械的に撹拌した。混合物を一晩放置して反応を収量させた。得られたセルロースナノファイバー／遷移金属の複合体（ＣＮＦ ／ Ｍ２＋）を１０，０００ｒｐｍで２０分間遠心分離して、沈殿物を分離した。得られた沈殿物を脱イオン水で５回洗浄して、過剰の金属イオンを除去した。銅硫酸塩を、それぞれコバルト硫酸塩及びニッケル硫酸塩に換えて、同様にＣＮＦ ／ Ｍ２＋複合体を合成した。 100 g of the oxidized cellulose nanofibers obtained above was dispersed in 300 mL of deionized water (2 wt%), 100 mL of 1M copper sulfate was added, and the mixed solution was mechanically stirred. The mixture was left overnight to allow the reaction to yield. The obtained cellulose nanofiber / transition metal complex (CNF / M 2+ ) was centrifuged at 10,000 rpm for 20 minutes to separate a precipitate. The resulting precipitate was washed 5 times with deionized water to remove excess metal ions. The copper sulfate was replaced with cobalt sulfate and nickel sulfate, respectively, and the CNF / M 2+ complex was similarly synthesized.
２．セルロースナノファイバー／遷移金属エアロゲルの合成
　次いで、ＣＮＦＣＮＦ／ Ｍ２＋複合体／ Ｍ２＋複合体の０．５～５重量％溶液を調製し、ゲル化していることを確認した。当該ゲル溶液を脱イオン水に分散させ、成形容器に注入した。この溶液を液体窒素中で凍結させ、凍結乾燥機を用いて乾燥させてエアロゲルを得た（図１）。 2. Synthesis of Cellulose Nanofiber / Transition Metal Aerogel Next, a 0.5 to 5 wt% solution of CNFCNF / M 2+ complex / M 2+ complex was prepared and confirmed to be gelled. The gel solution was dispersed in deionized water and poured into a molding container. The solution was frozen in liquid nitrogen and dried using a freeze dryer to obtain an airgel (Fig. 1).
　当該エアロゲルのＴＥＭ（透過電子顕微鏡）による拡大イメージ画像を図２に示す。得られたエアロゲル中のＣＮＦ／ Ｍ２＋複合体は、図２に示すように繊維状の外形を有していた。また、図３及び図４は、エアロゲルの内部構造を示す電子顕微鏡画像である。図３及び図４に示すように、本発明のエアロゲルは、空孔比率が大きいスポンジ状の三次元多孔体構造を有していることを確認した。 An enlarged image image of the airgel by TEM (transmission electron microscope) is shown in FIG. The CNF / M 2+ composite in the obtained airgel had a fibrous outer shape as shown in FIG. 3 and 4 are electron microscope images showing the internal structure of the airgel. As shown in FIGS. 3 and 4, it was confirmed that the airgel of the present invention has a sponge-like three-dimensional porous body structure having a large void ratio.
　また、得られたエアロゲルについて、ＥＤＳ元素分析を行った結果を図５に示す。図５は、それぞれ、上から、ＣＮＦエアロゲル、ＣＮＦ ／ Ｃｏ２＋複合体のエアロゲル、ＮＦ ／ Ｎｉ２＋複合体のエアロゲル、及びＣＮＦ ／ Ｃｕ２＋複合体のエアロゲルについての結果である。この結果、エアロゲル中の遷移金属含有量は、それぞれ０重量％、９．１重量％、１３．３重量％、６．０重量％であることが分かった。 The results of EDS elemental analysis of the obtained airgel are shown in FIG. FIG. 5 shows the results for CNF aerogel, CNF 2 / Co 2+ composite airgel, NF 2 / Ni 2+ composite airgel, and CNF 2 / Cu 2+ composite airgel, respectively, from the top. As a result, it was found that the transition metal contents in the airgel were 0% by weight, 9.1% by weight, 13.3% by weight and 6.0% by weight, respectively.
　さらに、得られたエアロゲルの密度を測定した結果、５～１５ｍｇ／ｃｍ３であることが分かった。得られたエアロゲル中のカルボキシル基及びカルボキシレート基の含有量を測定した結果、０．２ｍｍｏｌ／ｇであった。 Further, as a result of measuring the density of the obtained airgel, it was found to be 5 to 15 mg / cm 3 . The content of the carboxyl group and the carboxylate group in the obtained airgel was measured and found to be 0.2 mmol / g.
３．吸着実験
３－１．種々の遷移金属を用いたエアロゲルの吸着実験
　上記で得られた３種のエアロゲル（Ｃｕ、Ｃｏ、Ｎｉ）５００ｍｇを、それぞれポリフッ化ビニル製の袋に入れ、密封した。次いで、９Ｌの空気及び試験ガスを添加して、所望のガス濃度が得られるようにした。用いた試験ガスは、アンモニア、トリメチルアミン、及び硫化水素をそれぞれ用いた。一定の各時間間隔でバッグ内のガス濃度をガス検出管で測定した。比較例として、遷移金属を含まないセルロースナノファイバーのみからなるエアロゲル（ＣＮＦ）を用いて同様の実験を行った。結果を図６～図９に示す。 3. Adsorption experiment 3-1. Airgel Adsorption Experiment Using Various Transition Metals 500 mg of the three kinds of aerogels (Cu, Co, Ni) obtained above were placed in a polyvinyl fluoride bag and sealed. Then 9 L of air and test gas were added to obtain the desired gas concentration. The test gases used were ammonia, trimethylamine, and hydrogen sulfide, respectively. The gas concentration in the bag was measured with a gas detection tube at regular time intervals. As a comparative example, the same experiment was conducted using an airgel (CNF) consisting of cellulose nanofibers containing no transition metal. The results are shown in FIGS. 6 to 9.
　図６～８の結果から、本発明のエアロゲルを用いた場合には、アンモニア、トリメチルアミン、及び硫化水素のいずれに対しても、３０分以内に、これら臭気物質の濃度が検出限界以下のレベルまで消臭されることが実証された。一方、遷移金属を含まない比較例（ＣＮＦ）では、１８０分経過後でも、ほとんど消臭効果は得られなかった。 From the results of FIGS. 6 to 8, when the airgel of the present invention was used, the concentration of these odorous substances was reduced to the level below the detection limit within 30 minutes for any of ammonia, trimethylamine, and hydrogen sulfide. It was proven to be deodorized. On the other hand, in Comparative Example (CNF) containing no transition metal, almost no deodorizing effect was obtained even after 180 minutes.
　また、図９に示すように、用いるエアロゲル（ＣＮＦ ／ Ｃｕ２＋）の量を５００ｍｇから７５０ｍｇに増加させたところ、アンモニアに対する消臭能が有意に増加することも確認された。 Further, as shown in FIG. 9, it was also confirmed that when the amount of airgel (CNF / Cu 2+ ) used was increased from 500 mg to 750 mg, the deodorizing ability against ammonia was significantly increased.
３－２．ＣＮＴを含有するエアロゲル、及び活性炭との比較実験
　次に、本発明のエアロゲル（ＣＮＦ ／ Ｃｕ２＋複合体）にカーボンナノチューブ（ＣＮＴ）を添加した場合の吸着特性の変化を測定した。また、比較例として、市販の活性炭を用いた場合の吸着特性も併せて測定した。吸着実験は、３－１．と同様の手順で行った。 3-2. Comparison Experiment with CNT-Containing Airgel and Activated Carbon Next, changes in adsorption characteristics were measured when carbon nanotubes (CNT) were added to the airgel (CNF 2 / Cu 2+ composite) of the present invention. Further, as a comparative example, the adsorption characteristics when using commercially available activated carbon were also measured. The adsorption experiment is 3-1. The same procedure was performed.
　ＣＮＴ含有エアロゲルは、凍結乾燥前にＣＮＦ分散液を添加した以外は、上記１．及び２．に示した合成方法と同様の手順で作製した。すなわち、過剰の金属イオンを除去した後に、ＣＮＦ ／ Ｍ２＋複合体の０．５～５重量％溶液を100ｍＬ調製し、これに２００ｇ／ＬのＣＮＴ分散液１００ｍＬを添加した。混合溶液がゲル化していることを確認した。当該ゲル溶液を脱イオン水に分散させ、成形容器に注入した。この溶液を液体窒素中で凍結させ、凍結乾燥機を用いて乾燥させてＣＮＴ含有エアロゲルを得た。なお、用いたＣＮＴは、平均径１２ｎｍ、平均長５μｍのものを用いた（Ｎａｎｏｃｙｌ社製、商品名「ＮＣ７０００Ｃ」）。また、分散液は、水を溶媒とし、分散剤として１．０ｗｔ％ドデシルベンゼンスルホン酸ナトリウム（関東化学株式会社製）の界面活性剤を用いた。 The CNT-containing airgel was the same as the above 1. except that the CNF dispersion was added before freeze-drying. And 2. It was prepared by the same procedure as the synthetic method shown in. That is, after removing excess metal ions, 100 mL of a 0.5 to 5% by weight solution of the CNF 3 / M 2+ complex was prepared, and 100 mL of a 200 g / L CNT dispersion liquid was added thereto. It was confirmed that the mixed solution was gelled. The gel solution was dispersed in deionized water and poured into a molding container. This solution was frozen in liquid nitrogen and dried using a freeze dryer to obtain a CNT-containing airgel. The CNTs used had an average diameter of 12 nm and an average length of 5 μm (manufactured by Nanocyl, trade name “NC7000C”). The dispersion used water as a solvent and a 1.0 wt% sodium dodecylbenzenesulfonate (Kanto Chemical Co., Inc.) surfactant as a dispersant.
　図１０に、臭気物質であるアンモニア、トリメチルアミン、メチルメルカプタン、硫化水素に対する吸着実験の結果を示す。図中の検体（１）は、ＣＮＦ ／ Ｃｕ２＋複合体のみからなるエアロゲルであり、検体（２）は、ＣＮＴを含有するＣＮＦ ／ Ｃｕ２＋複合体のエアロゲルである。また、対照品は、活性炭であり、空試験は吸着物質と接触させない場合のガス濃度変化を示すものである。 FIG. 10 shows the results of an adsorption experiment for odorants such as ammonia, trimethylamine, methyl mercaptan, and hydrogen sulfide. Specimen (1) in the figure is an airgel consisting only of CNF / Cu 2+ complex, and specimen (2) is an airgel of CNF / Cu 2+ complex containing CNT. The control product is activated carbon, and the blank test shows a change in gas concentration when not contacted with the adsorbent.
　図１０の結果から、ＣＮＴを含有する検体（２）は、ＣＮＴを含有しない検体（１）と比べて優れた吸着特性を示すことが分かった。特に、検体（２）は、トリメチルアミン、メチルメルカプタン、及び硫化水素に対して、１５％以上の吸着能の向上が見られた。 From the results shown in FIG. 10, it was found that the sample (2) containing CNT exhibited excellent adsorption characteristics as compared with the sample (1) containing no CNT. In particular, the sample (2) showed an improvement in the adsorption ability of 15% or more with respect to trimethylamine, methyl mercaptan, and hydrogen sulfide.
　また、比較例の活性炭は、アンモニアに対する吸着性はほとんど示さなかったのに対し、検体（１）及び（２）は、いずれの臭気物質に対しても優れた吸着特性を示したことから、本発明のエアロゲルは、幅広い種類の臭気物質に対する吸着性を有することが分かった。 In addition, the activated carbon of the comparative example showed almost no adsorptivity to ammonia, whereas the samples (1) and (2) showed excellent adsorption characteristics to any odorous substance. It has been found that the inventive airgel has adsorptivity for a wide variety of odorants.
　以上の結果は、セルロースナノファイバー／遷移金属複合体よりなる本発明のエアロゲル材料が、臭気物質に対して優れた吸着能及び消臭効果を有することを実証するものである。 The above results demonstrate that the airgel material of the present invention composed of a cellulose nanofiber / transition metal composite has excellent adsorption ability and deodorizing effect for odorous substances.

Claims (17)

  1. 　セルロースナノファイバーと遷移金属イオンとの複合体が三次元ネットワーク構造を形成しているエアロゲル材料の製造方法であって、
    （ａ）セルロースナノファイバーの懸濁液に、遷移金属イオンを含有する溶液を添加し、混合溶液を得る工程、
    （ｂ）前記混合溶液を撹拌して、セルロースナノファイバーと遷移金属イオンの複合体を得る工程、
    （ｃ）工程（ｂ）で得られた複合体から遊離状態の遷移金属イオンを除去する工程、及び
    （ｄ）工程（ｃ）で得られた複合体を凍結乾燥して、エアロゲル構造体を得る工程
    を含む、当該製造方法。     A method for producing an airgel material in which a composite of cellulose nanofibers and a transition metal ion forms a three-dimensional network structure,
    (A) a step of adding a solution containing a transition metal ion to a suspension of cellulose nanofibers to obtain a mixed solution,
    (B) a step of stirring the mixed solution to obtain a composite of cellulose nanofibers and a transition metal ion,
    (C) a step of removing free-state transition metal ions from the complex obtained in step (b), and (d) the complex obtained in step (c) is lyophilized to obtain an airgel structure. The manufacturing method including a step.
  2. 　Ｎ－オキシル化合物を触媒として植物繊維を酸化することにより、工程（ａ）で用いられる前記セルロースナノファイバーを得る工程をさらに含む、請求項１に記載の製造方法。 The production method according to claim 1, further comprising a step of obtaining the cellulose nanofiber used in the step (a) by oxidizing the plant fiber using an N-oxyl compound as a catalyst.
  3. 　前記セルロースナノファイバーが、カルボキシル基又はカルボキシレート基を有する、請求項１又は２に記載の製造方法。 The method according to claim 1 or 2, wherein the cellulose nanofiber has a carboxyl group or a carboxylate group.
  4. 　前記セルロースナノファイバー中におけるカルボキシル基及びカルボキシレート基の含有量が０．１～５．０ｍｍｏｌ／ｇである、請求項３に記載の製造方法。 The production method according to claim 3, wherein the content of the carboxyl group and the carboxylate group in the cellulose nanofiber is 0.1 to 5.0 mmol / g.
  5. 　前記複合体が、キレート結合を介して遷移金属イオンがセルロースナノファイバーと結合することで錯体を形成した構造を有する、請求項１～４のいずれか１に記載の製造方法。 The production method according to any one of claims 1 to 4, wherein the complex has a structure in which a transition metal ion is bound to a cellulose nanofiber through a chelate bond to form a complex.
  6. 　工程（ｃ）が、遠心分離及び／又は脱イオン水による洗浄により、遊離状態の遷移金属イオンを除去することを含む、請求項１～５のいずれか１に記載の製造方法。 The method according to any one of claims 1 to 5, wherein step (c) includes removing the transition metal ion in a free state by centrifugation and / or washing with deionized water.
  7. 　工程（ｃ）が、工程（ｂ）で得られた複合体から遊離状態の遷移金属イオンを除去した後に、カーボンナノ材料の分散液を添加して複合体と混合する工程をさらに含む、請求項１～６のいずれか１に記載の製造方法。 The step (c) further comprises a step of removing a transition metal ion in a free state from the composite obtained in the step (b), and then adding a dispersion liquid of the carbon nanomaterial and mixing the composite with the composite. 7. The manufacturing method according to any one of 1 to 6.
  8. 　工程（ｄ）が、３～１０重量％の複合体を含有する溶液を調整し、当該溶液の希釈液を凍結乾燥することを含む、請求項１～７のいずれか１に記載の製造方法。 The production method according to any one of claims 1 to 7, wherein step (d) includes preparing a solution containing 3 to 10% by weight of the complex, and freeze-drying a diluted solution of the solution.
  9. 　前記遷移金属イオンが、銅、コバルト、ニッケル、バナジウム、チタン、クロム（ＩＩＩ）、マンガン、亜鉛、及び鉄よりなる群から選択される１種以上の２価の金属イオンである、請求項１～８のいずれか１に記載の製造方法。 The transition metal ion is one or more divalent metal ions selected from the group consisting of copper, cobalt, nickel, vanadium, titanium, chromium (III), manganese, zinc, and iron. 8. The manufacturing method according to any one of 8.
  10. 　セルロースナノファイバーと遷移金属イオンとの複合体が三次元ネットワーク構造を形成しているエアロゲル材料であって、
    　前記複合体が、キレート結合を介して遷移金属イオンがセルロースナノファイバーと結合することで錯体を形成した構造を有しており、
    　前記エアロゲル材料の密度が５～１５ｍｇ／ｃｍ３の範囲であり、
    　前記エアロゲル材料中の遷移金属の含有量が、セルロースナノファイバーに対して０．１～２００モル％である、
    ことを特徴とするエアロゲル材料。     An airgel material in which a composite of cellulose nanofibers and a transition metal ion forms a three-dimensional network structure,
    The complex has a structure in which a transition metal ion is bound to a cellulose nanofiber through a chelate bond to form a complex,
    The airgel material has a density in the range of 5 to 15 mg / cm 3 ;
    The content of the transition metal in the airgel material is 0.1 to 200 mol% based on the cellulose nanofiber,
    An airgel material characterized in that
  11. 　カーボンナノ材料をさらに含む、請求項１０に記載のエアロゲル材料。 The airgel material according to claim 10, further comprising a carbon nanomaterial.
  12. 　前記セルロースナノファイバーが、カルボキシル基又はカルボキシレート基を有する、請求項１０又は１１に記載のエアロゲル材料。 The airgel material according to claim 10 or 11, wherein the cellulose nanofiber has a carboxyl group or a carboxylate group.
  13. 　前記セルロースナノファイバー中におけるカルボキシル基及びカルボキシレート基の含有量が０．１～５．０ｍｍｏｌ／ｇである、請求項１２に記載のエアロゲル材料。 The airgel material according to claim 12, wherein the content of carboxyl groups and carboxylate groups in the cellulose nanofibers is 0.1 to 5.0 mmol / g.
  14. 　直径３～５ｎｍの直線状の形状を有する、請求項１０～１３のいずれか１に記載のエアロゲル材料。 The airgel material according to any one of claims 10 to 13, which has a linear shape with a diameter of 3 to 5 nm.
  15. 　前記遷移金属イオンが、銅、コバルト、ニッケル、バナジウム、チタン、クロム（ＩＩＩ）、マンガン、亜鉛、及び鉄よりなる群から選択される１種以上の２価の金属イオンである、請求項１０～１４のいずれか１に記載のエアロゲル材料。 The transition metal ion is one or more divalent metal ions selected from the group consisting of copper, cobalt, nickel, vanadium, titanium, chromium (III), manganese, zinc, and iron. 14. The airgel material according to any one of 14.
  16. 　臭気性物質を吸着するための消臭用吸着体である、請求項１０～１５のいずれか１に記載のエアロゲル材料。 The airgel material according to any one of claims 10 to 15, which is a deodorant adsorbent for adsorbing odorous substances.
  17. 　前記臭気性物質が、アンモニア、トリメチルアミン、硫化水素、メチルメルカプタン、ホルムアルデヒド、及びキシレンより成る群から選択される１以上の化合物である、請求項１６に記載のエアロゲル材料。 The airgel material according to claim 16, wherein the odorant is one or more compounds selected from the group consisting of ammonia, trimethylamine, hydrogen sulfide, methyl mercaptan, formaldehyde, and xylene.
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