Cellulose fine fiber composition, aqueous dispersion of cellulose fine fibers, polymer composition, molded article, and method for producing cellulose fine fiber composition

Abstract

The purpose of the present disclosure is to provide a cellulose fine fiber composition having excellent film formability when producing a molded article (e.g., a film) including cellulose fine fibers, an aqueous dispersion of cellulose fine fibers, a polymer composition prepared using the same, a molded article, and a method for producing the cellulose fine fiber composition. One aspect of an embodiment of the present invention is a cellulose fine fiber composition comprising cellulose fine fibers having an average fiber width of 1 nm or more and 1000 nm or less, and one or more salts selected from the group consisting of metal salts and ammonium salts, the cellulose fine fibers having a sulfate group represented by general formula (1), the cellulose fine fibers have an amount of sulfur derived from a sulfate group of 0.3 mmol / g or more and 3.0 mmol / g or less introduced into the cellulose fine fibers, and the cellulose fine fiber composition contains 0.002 parts by mass or more and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fine fibers. ... (1)

Description

Technical Field

[0001] The present disclosure relates to cellulosic fine fiber compositions, aqueous dispersions of cellulose fine fibers, polymer compositions, molded articles, and methods of producing the cellulosic fine fiber compositions. Background Art

[0002] Growing environmental awareness has led to the development of research on the practical application of biomass-derived materials around the world. For example, most of the cellulose extracted from wood (wood chips) is used for papermaking, which contributes significantly to people's lives and CO2 sequestration.

[0003] The use of biomass-derived materials in the paints, coatings, and cosmetics industries continues to gain momentum. Furthermore, the use of biomass-derived materials in the production of raw materials used in these industries continues to grow. In these and many other areas, the replacement of harmful organic solvents with aqueous solvents is desirable from a safety and quality of life perspective.

[0004] Among cellulose, cellulose nanofibers are used or expected to be used in many fields. Cellulose nanofibers are biomass-derived compounds made from cellulose fibers that have been defibrated (fiber separation) into nanometer sizes. They are well dispersed in water, and by drying the dispersion, transparent nanocellulose films can be easily obtained. In addition, cellulose nanofibers improve various properties such as strength, flexibility, elongation, etc. by mixing with resins or rubbers, and have received attention as environmentally friendly new materials, and various proposals have been proposed in the past.

[0005] For example, Patent Document 1 discloses a metal salt-containing cellulose nanofiber comprising cellulose nanofibers, a metal salt, and a hydrophobizing agent containing silicon atoms. Patent Document 1 discloses oxidized cellulose nanofibers, which are prepared by oxidizing the hydroxyl groups of cellulose molecules using 2,2,6,6-tetramethylpiperidinyl-N-oxyl (hereinafter "TEMPO") as a catalyst. Patent Document 1 discloses that metal salt-containing cellulose nanofibers can be easily and uniformly dispersed in resin and rubber compositions, and that their addition to the compositions can improve the physical properties of the resin and rubber.

[0006] Citation List

[0007] Patent Literature

[0008] PTL 1 JP 2019-094460 A Summary of the Invention

[0009] Technical issues

[0010] Typically, cellulose nanofibers have a fiber length ranging from several hundred nanometers to a maximum of several tens of micrometers and a fiber width ranging from 1 nm to several hundred nanometers. When an aqueous dispersion of cellulose nanofibers is used to produce a cellulose nanofiber film, the coating film may partially separate from the base material during drying after applying the aqueous dispersion, and therefore, improvement in film formability is sought.

[0011] Therefore, the purpose of the present disclosure is to provide a cellulose fiber composition having excellent film formability when producing molded articles (such as films) comprising cellulose fibers, an aqueous dispersion of cellulose fibers, a polymer composition prepared using them, a molded article, and a method for producing a cellulose fiber composition.

[0012] Solution to the problem

[0013] The present inventors conducted intensive research to solve the above-mentioned problems and found that highly smooth molded products can be prepared by using a cellulose fine fiber composition containing a specific salt and an aqueous dispersion of cellulose fine fibers containing a specific salt, thereby obtaining the present disclosure.

[0014] Aspects of embodiments of the present invention are as follows.

[0015] (1) A cellulose fine fiber composition comprising cellulose fine fibers and one or more salts selected from metal salts and ammonium salts, wherein:

[0016] The cellulose fine fibers have an average fiber width of 1 nm or more and 1000 nm or less,

[0017] The cellulose fine fibers have sulfate groups represented by the following general formula (1):

[0018] The cellulose fine fibers have an amount of sulfur derived from sulfate groups introduced into the cellulose fine fibers of 0.3 mmol / g or more and 3.0 mmol / g or less, and

[0019] The cellulose fine fiber composition contains 0.002 parts by mass or more and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fine fibers:

[0020] Formula 1

[0021] ... (1)

[0022] (In the general formula (1), n ​​is an integer of 1 or more and 3 or less, M n+ is an n-valent cation, and the wavy lines indicate bonding sites with other atoms).

[0023] (2) The cellulose fine fiber composition according to (1), wherein the salt is one or more salts selected from sulfates, carboxylates, borates, phosphates and ammonium salts.

[0024] (3) The cellulose fine fiber composition according to (1) or (2), which has a water content of 10% by mass or less.

[0025] (4) The cellulose fine fiber composition according to any one of (1) to (3), which is in a powder form.

[0026] (5) An aqueous dispersion of cellulose fine fibers, comprising cellulose fine fibers, one or more salts selected from metal salts and ammonium salts, and water, wherein:

[0027] The cellulose fine fibers have an average fiber width of 1 nm or more and 1000 nm or less,

[0028] The cellulose fine fibers have sulfate groups represented by the following general formula (1):

[0029] the cellulose fine fibers have an amount of sulfur derived from sulfate ester groups introduced into the cellulose fine fibers of 0.3 mmol / g or more and 3.0 mmol / g or less,

[0030] The aqueous dispersion of the cellulose fine fibers contains 0.002 parts by mass or more and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fine fibers, and

[0031] The aqueous dispersion of the cellulose fine fibers contains 10 parts by mass or more of water based on 1 part by mass of the total amount of the cellulose fine fibers and the salt:

[0032] Formula 2

[0033] ... (1)

[0034] (In the general formula (1), n ​​is an integer of 1 or more and 3 or less, M n+ is an n-valent cation, and the wavy lines indicate bonding sites with other atoms).

[0035] (6) The aqueous dispersion of cellulose fine fibers as described in (5), wherein the salt is one or more salts selected from sulfates, carboxylates, borates, phosphates and ammonium salts.

[0036] (7) The aqueous dispersion of cellulose fine fibers according to (5) or (6), comprising at least one or more compounds selected from monomers, prepolymers and polymers.

[0037] (8) The aqueous dispersion of cellulose fine fibers as described in (7), comprising 400 parts by mass or more and 20,000 parts by mass or less of the at least one or more compounds selected from monomers, prepolymers and polymers based on 100 parts by mass of the cellulose fine fibers.

[0038] (9) A polymer composition comprising cellulose fine fibers, one or more salts selected from metal salts and ammonium salts, and a polymer, wherein:

[0039] The cellulose fine fibers have an average fiber width of 1 nm or more and 1000 nm or less,

[0040] The cellulose fine fibers have sulfate groups represented by the following general formula (1):

[0041] The cellulose fine fibers have an amount of sulfur derived from sulfate ester groups introduced into the cellulose fine fibers of 0.3 mmol / g or more and 3.0 mmol / g or less, and

[0042] The polymer composition comprises 0.002 parts by mass or more and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fine fibers:

[0043] Formula 3

[0044] ... (1)

[0045] (In the general formula (1), n ​​is an integer of 1 or more and 3 or less, M n+ is an n-valent cation, and the wavy lines indicate bonding sites with other atoms).

[0046] (10) The polymer composition as described in (9), wherein the salt is one or more salts selected from sulfates, carboxylates, borates, phosphates and ammonium salts.

[0047] (11) The polymer composition as described in (9) or (10), comprising 400 parts by mass or more and 20,000 parts by mass or less of the polymer based on 100 parts by mass of the cellulose fine fibers.

[0048] (12) A molded article comprising a layer formed from the polymer composition according to any one of (9) to (11).

[0049] (13) A method for producing a cellulose fine fiber composition, the method comprising the steps of:

[0050] preparing an aqueous dispersion of cellulose fine fibers by mixing an aqueous solution of one or more salts selected from metal salts and ammonium salts with the cellulose fine fibers; and

[0051] The aqueous dispersion of the cellulose fine fibers is dried to obtain a cellulose fine fiber composition comprising the cellulose fine fibers and one or more salts selected from metal salts and ammonium salts, wherein

[0052] The cellulose fine fibers have an average fiber width of 1 nm or more and 1000 nm or less,

[0053] The cellulose fine fibers have sulfate groups represented by the following general formula (1):

[0054] The cellulose fine fibers have an amount of sulfur derived from sulfate groups introduced into the cellulose fine fibers of 0.3 mmol / g or more and 3.0 mmol / g or less, and

[0055] In the step of preparing the aqueous dispersion of cellulose fine fibers, 0.002 parts by mass or more and 10 parts by mass or less of the salt is used based on 100 parts by mass of the cellulose fine fibers:

[0056] Formula 4

[0057] ... (1)

[0058] (In the general formula (1), n ​​is an integer of 1 or more and 3 or less, M n+ is an n-valent cation, and the wavy lines indicate bonding sites with other atoms).

[0059] This description encompasses the contents disclosed in Japanese Patent Application No. 2023-023948 to which this application claims priority.

[0060] Advantageous Effects of the Invention

[0061] The present disclosure can provide cellulose fine fiber compositions having excellent film formability when producing molded articles (e.g., films) comprising cellulose fine fibers, aqueous dispersions of cellulose fine fibers, polymer compositions prepared using them, molded articles, and methods for producing cellulose fine fiber compositions. DETAILED DESCRIPTION

[0062] The cellulose fine fiber composition, the aqueous dispersion of cellulose fine fibers, the polymer composition, the molded article, and the method for producing the cellulose fine fiber composition according to the embodiments of the present invention are described in detail.

[0063] One aspect of an embodiment of the present invention is a cellulose fiber composition comprising cellulose fibers, and one or more salts selected from metal salts and ammonium salts, wherein the average fiber width of the cellulose fibers is 1 nm or greater and 1000 nm or less, the cellulose fibers have sulfate groups represented by the following general formula (1), the cellulose fibers have an amount of sulfur derived from the sulfate groups introduced into the cellulose fibers of 0.3 mmol / g or greater and 3.0 mmol / g or less, and the cellulose fiber composition contains 0.002 parts by mass or greater and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fibers.

[0064] One aspect of an embodiment of the present invention is an aqueous dispersion of cellulose fibrils, which comprises cellulose fibrils, one or more salts selected from metal salts and ammonium salts, and water, wherein the average fiber width of the cellulose fibrils is 1 nm or greater and 1000 nm or less, the cellulose fibrils have sulfate groups represented by the following general formula (1), the cellulose fibrils have an amount of sulfur derived from the sulfate groups introduced into the cellulose fibrils of 0.3 mmol / g or greater and 3.0 mmol / g or less, the aqueous dispersion of the cellulose fibrils contains 0.002 parts by mass or greater and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fibrils, and the aqueous dispersion of the cellulose fibrils contains 10 parts by mass or greater of water based on 1 part by mass of the total amount of the cellulose fibrils and the salt.

[0065] One aspect of an embodiment of the present invention is a polymer composition comprising cellulose fine fibers, a salt of one or more selected from metal salts and ammonium salts, and a polymer, wherein the average fiber width of the cellulose fine fibers is 1 nm or greater and 1000 nm or less, the cellulose fine fibers have sulfate groups represented by the following general formula (1), the cellulose fine fibers have an amount of sulfur derived from the sulfate groups introduced into the cellulose fine fibers of 0.3 mmol / g or greater and 3.0 mmol / g or less, and the polymer composition contains 0.002 parts by mass or greater and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fine fibers.

[0066] One aspect of an embodiment of the present invention is a molded article comprising a layer formed from the polymer composition.

[0067] One aspect of an embodiment of the present invention is a method for producing a cellulose fiber composition, the method comprising the steps of preparing an aqueous dispersion of cellulose fibers by mixing an aqueous solution of one or more salts selected from metal salts and ammonium salts with cellulose fibers, and drying the aqueous dispersion of cellulose fibers to obtain a cellulose fiber composition comprising the cellulose fibers and one or more salts selected from metal salts and ammonium salts, the cellulose fibers having an average fiber width of 1 nm or greater and 1000 nm or less, the cellulose fibers having a sulfate group represented by the following general formula (1), the cellulose fibers having an amount of sulfur derived from the sulfate group of 0.3 mmol / g or greater and 3.0 mmol / g or less introduced into the cellulose fibers, and in the step of preparing the aqueous dispersion of cellulose fibers, using 0.002 parts by mass or greater and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fibers.

[0068] The cellulose fine fiber composition and aqueous dispersion of cellulose fine fibers according to embodiments of the present invention are excellent in film formability when producing molded articles (e.g., films) comprising cellulose fine fibers. Since local separation is suppressed in the polymer composition and the molded articles produced using them, they can be easily formed into a desired shape.

[0069] Hereinafter, embodiments of the present invention will be described in detail.

[0070] cellulose fine fibers

[0071] The cellulose fine fiber composition, aqueous dispersion of cellulose fine fibers, polymer composition, and molded article according to an embodiment of the present invention comprise: cellulose fine fibers; and the cellulose fine fibers are used in the method for producing the cellulose fine fiber composition according to an embodiment of the present invention. Typical cellulose (unmodified cellulose) is a polysaccharide having glucose linked by β-1,4-glycosidic bonds and is composed of (C6H 10 O5) n The cellulose fine fibers in the embodiment of the present invention are made of modified cellulose, which is obvious from the fact that the cellulose fine fibers have sulfate groups.

[0072] The cellulose fine fibers have an average fiber width of 1 nm to 1000 nm, preferably 1 nm to 100 nm, and more preferably 2 nm to 10 nm. The average fiber length of the cellulose fine fibers is not particularly limited, and is generally 0.1 μm to 6 μm, and preferably 0.1 μm to 2 μm.

[0073] The average fiber width and average fiber length can be calculated by measuring the fiber width (fiber diameter (equivalent circular diameter)) and fiber length of 50 randomly selected fibers using an atomic force microscope (SPM-9700HT manufactured by Shimadzu Corporation), and taking the arithmetic average of the values. The average fiber width and average fiber length can be adjusted to a desired range by adjusting the sulfation time or the blending ratio of the reagents.

[0074] Cellulose fine fibers have sulfate groups represented by the following general formula (1). Cellulose fine fibers can also be referred to as cellulose nanofibers esterified with sulfate. Sulfate groups are generally introduced into cellulose fine fibers by replacing a portion of the OH groups in the cellulose constituting the fibers with sulfate groups represented by the following general formula (1). Cellulose fine fibers can be produced, for example, by sulfate esterifying and defibrillating raw material pulp (pulp), as shown in the Examples.

[0075] Formula 5

[0076] ... (1)

[0077] (In general formula (1), n ​​is an integer of 1 to 3, M n+ is an n-valent cation, and the wavy lines indicate bonding sites with other atoms).

[0078] M n+ Examples include hydrogen ions (H+), metal ions, and ammonium ions. n+ When it is a multivalent cation, M n+ In two or three-OSO3 - An ionic bond is formed between the ions. A preferred aspect is that for M n+ , n is 1 and M n+ M + (monovalent cation).

[0079] Examples of the metal ion include alkali metal ions, alkaline earth metal ions, transition metal ions, and other metal ions.

[0080] Examples of alkali metal ions include lithium ions (Li + ), sodium ion (Na + ), potassium ion (K + ), rubidium ions (Rb + ) and cesium ions (Cs + Examples of alkaline earth metal ions may include calcium ions (Ca 2+ ) and strontium ions (Sr 2+). Examples of transition metal ions include iron ions, nickel ions, palladium ions, copper ions, and silver ions. Examples of other metal ions include beryllium ions, magnesium ions, zinc ions, and aluminum ions.

[0081] Examples of ammonium ions include not only NH4 + , also including NH4 + Ammonium ions derived from various amines in which one or more hydrogen atoms are replaced by organic groups. Examples of ammonium ions include NH4 + , quaternary ammonium cations, alkanolamine ions and pyridinium ions.

[0082] M n+ From the viewpoint of processability of cellulose fine fiber solids in various applications, hydrogen ions, sodium ions, potassium ions, calcium ions or quaternary ammonium cations are preferred, and hydrogen ions, sodium ions, potassium ions or calcium ions are more preferred, and sodium ions (Na + ). The sulfate group represented by the above general formula (1) may have an M n+ , or have two or more.

[0083] When sulfate groups are introduced into cellulose fibrils by substituting a portion of the OH groups in the cellulose-constituting fibers with sulfate groups represented by general formula (1), the wavy lines indicate the bonding sites to the carbon atoms to which the OH groups are bonded.

[0084] The cellulose fine fibers may have a substituent different from the sulfate group represented by the above-mentioned general formula (1). When the cellulose fine fibers have a group different from the sulfate group represented by the above-mentioned general formula (1) (i.e., another substituent), generally, at least one OH group in the cellulose constituting the cellulose fine fibers is substituted with another substituent. Examples of other substituents include, but are not particularly limited to, anionic substituents and salts thereof, ester groups, ether groups, acyl groups, aldehyde groups, alkyl groups, alkylene (alkenyl) groups, aryl groups, and combinations of two or more thereof. When the other substituent is a combination of two or more substituents, the content ratio of each substituent is not limited. Among them, from the perspective of nanodispersibility, anionic substituents and salts thereof and acyl groups are preferred as other substituents. In particular, carboxyl groups, phosphate groups, phosphite groups, and xanthate groups are preferred as anionic substituents and salts thereof. When the anionic substituent is in the form of a salt, sodium salts, potassium salts, and calcium salts are particularly preferred from the perspective of nanodispersibility. In addition, as an acyl group, acetyl groups are particularly preferred from the perspective of nanodispersibility.

[0085] The amount of sulfur derived from sulfate groups introduced into the cellulose fine fibers is 0.3 mmol / g or greater and 3.0 mmol / g or less. The amount of sulfate groups introduced can be set to an optional suitable value within the above range according to the application, etc. The amount of sulfur derived from sulfate groups introduced into the cellulose fine fibers can be expressed as a ratio (mmol) of the sulfur content per 1 g of cellulose fine fibers. Preferably, the amount of sulfur introduced is 0.5 mmol / g or greater and 3.0 mmol / g or less. More preferably, the amount of sulfur introduced is 0.7 mmol / g or greater and 3.0 mmol / g or less. The amount of sulfur introduced is preferred within the above range because the cellulose fine fiber composition may be highly water-dispersible.

[0086] The amount of sulfur introduced can be determined, for example, by combustion absorption-ion chromatography (IC) (combustion IC) as described in the examples. The amount of sulfur introduced can be adjusted, for example, by controlling the concentration of the reagent (e.g., sulfuric acid) in the solution used for pulp defibration (fibrillation solution), the amount of pulp relative to the fibrillation solution, the reaction time, and the reaction temperature.

[0087] Salt

[0088] The cellulose fine fiber composition, aqueous dispersion of cellulose fine fibers, polymer composition, and molded article according to embodiments of the present invention contain one or more salts selected from metal salts and ammonium salts. In the method for producing the cellulose fine fiber composition according to embodiments of the present invention, one or more salts selected from metal salts and ammonium salts are used. One or more of these salts may be used, or two or more of these salts may be used. In a preferred aspect, the salts are one or more salts selected from sulfates, carboxylates, borates, phosphates, and ammonium salts.

[0089] Examples of the sulfate include one or more salts selected from sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, barium sulfate, strontium sulfate, silver (I) sulfate, and ammonium sulfate.

[0090] Carboxylate is a salt of a compound (carboxylic acid) with one or more carboxyl groups per molecule and an alkali. Carboxylate is not particularly limited, and if a complex with a polymer (such as rubber or resin) is to be formed, a carboxylate soluble in water and an organic solvent is preferably used. Examples of carboxylic acids include aliphatic carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, 3-chloropropionic acid and 2-chloropropionic acid, hydroxycarboxylic acids such as lactic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid and mandelic acid, and aliphatic heterocyclic carboxylic acids. Preferred aspects of carboxylic acids include acetic acid. Aliphatic heterocyclic carboxylic acids are compounds in which a carboxyl group is bonded to an aliphatic heterocycle, and may include substituents other than carboxylic acids. Examples of alkalis that form salts with carboxylic acids include alkali metal ions such as sodium ions, potassium ions and lithium ions, alkaline earth metal ions such as calcium ions, and amines such as methylamine, ethylamine and triethylamine. Preferred aspects of carboxylates include sodium carboxylate and calcium carboxylate.

[0091] Borates are salts of boric acid (B(OH)3), or metaboric acid or polyboric acid formed by dehydration condensation of boric acid, with an alkali metal, alkaline earth metal, or ammonium. Examples of borates include sodium tetraborate, lithium tetraborate, potassium tetraborate, calcium tetraborate, sodium metaborate, potassium metaborate, lithium metaborate, calcium metaborate, and ammonium tetraborate.

[0092] Phosphate is phosphoric acid (PO4 3- ) or polyphosphoric acid (which is a polymer of phosphoric acid) with an alkali metal, an alkaline earth metal or ammonium. Examples of phosphates include sodium phosphate, potassium phosphate, calcium phosphate, lithium phosphate, ammonium phosphate, sodium polyphosphate, potassium polyphosphate, calcium polyphosphate, lithium polyphosphate and ammonium polyphosphate.

[0093] Ammonium salts are represented by NH4X (X is a monovalent base) or NR4X (R is each independently a hydrogen atom or an alkyl group, and X is a monovalent base). X, for example, is preferably a halide ion, sulfate ion, acetate ion, nitrate ion, or hydroxide ion from the perspective of dispersibility. R is preferably each independently an alkyl group having 1 to 4 carbon atoms from the perspective of high dispersibility when mixed with a polymer (such as rubber or resin). Examples of ammonium salts include ammonium sulfate, ammonium acetate, ammonium formate, tetramethylammonium chloride, tetraethylammonium chloride, and tetraethylammonium hydroxide.

[0094] Cellulose fine fiber composition

[0095] The cellulose fine fiber composition according to an embodiment of the present invention comprises cellulose fine fibers and one or more salts selected from metal salts and ammonium salts, and contains 0.002 parts by mass or more and 10 parts by mass or less of the salts based on 100 parts by mass of the cellulose fine fibers. The cellulose fine fiber composition may include components other than the cellulose fine fibers and the salts, or may include only the cellulose fine fibers and the salts. In addition, the cellulose fine fiber composition may not be completely free of water and generally includes a small amount of water.

[0096] The water content of the cellulose fine fiber composition of the embodiment of the present invention varies depending on the type and amount of components included in the cellulose fine fiber composition, in particular, components other than the cellulose fine fibers and salts. The cellulose fine fiber composition of the embodiment of the present invention may, for example, have a water content of 10% by mass or less, 7% by mass or less, or 5% by mass or less. The lower limit of the water content of the cellulose fine fiber composition is not particularly limited, and may, for example, be 1% by mass or greater, or 3% by mass or greater. In particular, in the case where the cellulose fine fiber composition of the embodiment of the present invention is composed of cellulose fine fibers, the salt and water as main components, more specifically, in the case where the cellulose fine fiber composition includes 95% by mass or greater, preferably 97% by mass or greater, of the cellulose fine fibers, the salt and water based on 100% by mass of the cellulose fine fiber composition, in a preferred aspect, the water content is within the above range. Typically, the cellulose fine fiber composition of the embodiment of the present invention has a solid appearance. In the present disclosure, water is exemplified by tap water, ion-exchanged water, distilled water, purified water, and natural water, and is preferably tap water, ion-exchanged water, distilled water, and purified water, and more preferably ion-exchanged water, distilled water, and purified water.

[0097] The water content of the cellulose fine fiber composition can be determined, for example, in accordance with JIS P8203.

[0098] The amount of cellulose fine fibers in the cellulose fine fiber composition is usually 70% by mass or more, preferably 90% by mass or more and more preferably 95% by mass or more. The amount of cellulose fine fibers is preferably 99% by mass or less and more preferably 97% by mass or less.

[0099] The amount of the salt contained in the cellulose fine fiber composition is 0.002 parts by mass or more and 10 parts by mass or less, preferably 0.01 parts by mass or more and 5 parts by mass or less, and more preferably 0.02 parts by mass or more and 1 part by mass or less, based on 100 parts by mass of the cellulose fine fibers. The above range is preferred because separation is suppressed during film formation and dispersibility is achieved when preparing an aqueous dispersion.

[0100] The form of the cellulose fine fiber composition is not particularly limited and may be in the form of powder, chips, flakes, or films, and is preferably in the form of a powder. Powder refers to, for example, a powder having a median diameter of 0.1 to 1000 μm. The median diameter of the cellulose fine fiber composition can be measured, for example, using a dry particle size analyzer in accordance with ISO 13320 and JIS Z 8825, which are standards for laser diffraction scattering methods. The powder form refers to cellulose fine fibers and salts aggregated in a powdered form, and does not refer to cellulose particles.

[0101] The cellulose fine fiber composition includes the cellulose fine fibers and the salt described above, and may include water. The cellulose fine fiber composition may include components other than the cellulose fine fibers and the salt. In the case where the cellulose fine fiber composition includes components other than the cellulose fine fibers and the salt, the cellulose fine fiber composition may include additives. The additives may be inorganic additives or organic additives.

[0102] Examples of inorganic additives include inorganic fine particles. Examples of inorganic fine particles include fine particles of silica, mica, talc, clay, carbon, carbonates (e.g., calcium carbonate, magnesium carbonate), oxides (e.g., aluminum oxide, titanium oxide, zinc oxide, iron oxide), ceramics (e.g., ferrite), and mixtures thereof. The cellulose fine fiber composition may include, for example, 0.09 to 5% by mass of inorganic fine particles.

[0103] The cellulose fine fiber composition may include a functional compound as an organic additive. Examples of the functional compound include pigments, UV absorbers, antioxidants, antistatic agents, and surfactants. The cellulose fine fiber composition may include, for example, 0.09 to 5% by mass of the organic additive.

[0104] The cellulose fine fiber composition of the embodiment of the present invention can be used in various applications in the form of an aqueous dispersion of cellulose fine fibers described later. The cellulose fine fiber composition of the embodiment of the present invention can be used as a material for preparing molded products (such as films and sheets) by the method described in the examples, for example. In other words, in the embodiment, the cellulose fine fiber composition is a cellulose fine fiber composition for molded products (for example, a cellulose fine fiber composition for forming films and sheets). The present disclosure also includes the use of the cellulose fine fiber composition for the manufacture of molded products and the use of the cellulose fine fiber composition for the manufacture of films and sheets.

[0105] Method for producing cellulose fine fiber composition

[0106] A method for producing a cellulose fiber composition according to an embodiment of the present invention includes the steps of mixing an aqueous solution of one or more salts selected from metal salts and ammonium salts with cellulose fibers to prepare an aqueous dispersion of cellulose fibers, and drying the aqueous dispersion of cellulose fibers to obtain a cellulose fiber composition comprising cellulose fibers and one or more salts selected from metal salts and ammonium salts. In the step of preparing the aqueous dispersion of cellulose fibers, 0.002 parts by mass or more and 10 parts by mass or less of the salt is used per 100 parts by mass of the cellulose fibers. The above cellulose fiber composition can be produced by the production method according to an embodiment of the present invention.

[0107] In the step of preparing the water dispersion, for example, an aqueous solution of one or more salts selected from the group consisting of metal salts and ammonium salts, which is prepared in advance, is mixed with the cellulose fine fibers. When the cellulose fine fibers used in the above step can be solid cellulose fine fibers (for example, powder), a water dispersion of the cellulose fine fibers to which the above salts are not added can be prepared separately from the aqueous solution of the above salts, and the aqueous solution of the above salts can be mixed with the water dispersion of the cellulose fine fibers to which the above salts are not added to perform the above step of preparing the water dispersion.

[0108] Further, in the step of preparing the water dispersion of the cellulose fine fibers, 0.002 parts by mass or more and 10 parts by mass or less of the salt is used based on 100 parts by mass of the cellulose fine fibers. It is preferable to use 0.01 parts by mass or more and 5 parts by mass or less of the salt, and it is more preferable to use 0.02 parts by mass or more and 1 part by mass or less of the salt. The above range is preferable because the obtained water dispersion has excellent dispersibility.

[0109] The concentration of the cellulose fine fibers in the water dispersion prepared in the step of preparing the water dispersion of the cellulose fine fibers is not particularly limited. The concentration is usually 0.05 to 10 mass%, and it is preferably 0.3 to 2 mass%. The water dispersion of the cellulose fine fibers prepared in the step of preparing the water dispersion contains water preferably 10 parts by mass or more, more preferably 90 parts by mass or more, and particularly preferably 98 parts by mass or more, based on 1 part by mass of the total amount of the cellulose fine fibers and the salt. The upper limit of the amount of water is not particularly limited. The water dispersion of the cellulose fine fibers prepared in the step of preparing the water dispersion contains water preferably 99.9 parts by mass or less, and more preferably 99.5 parts by mass or less, based on 1 part by mass of the total amount of the cellulose fine fibers and the salt, from the viewpoint of handleability.

[0110] The water dispersion of the cellulose fine fibers prepared without mixing the salt can be prepared, for example, by purifying and dispersing the sulfate group in water by the method described in the examples at the time of fibrillating the cellulose fibers to nanosize.

[0111] In the step of preparing the cellulose fine fiber composition, the cellulose fine fiber composition comprising one or more salts selected from metal salts and ammonium salts can be obtained by removing (drying) dispersion medium from the aqueous dispersion of cellulose fine fibers. The drying method can use known methods, and the method is not particularly limited. Its examples include freeze drying, spray drying, extrusion, air drying, hot air drying, crystallization and vacuum drying. The dryer is not particularly limited, and its examples include freeze drying devices, conical dryers, continuous tunnel dryers, belt dryers, vertical dryers, vertical turbine dryers, multi-stage disc dryers, through-flow dryers, rotary dryers, flash dryers, spray dryers, drum dryers, drum dryers, belt dryers, spiral conveying dryers, rotary dryers with tube furnaces, vibrating conveying dryers, intermittent box dryers, vacuum box dryers and stirring dryers. The dryer can be used alone or in combination of two or more. The drying method is preferably freeze drying because it only takes a short time and suppresses the risk of degradation due to heat.

[0112] The cellulose fine fiber composition can be pulverized as needed using a dry pulverizer, etc. The cellulose fine fiber composition can be formed into powder having a desired size and used, stored, and distributed.

[0113] The cellulose fine fiber composition prepared by the method for producing a cellulose fine fiber composition may contain components other than cellulose fine fibers, salt, and water. More specifically, the cellulose fine fiber composition may contain the additives described in the above section (Cellulose Fine Fiber Composition).

[0114] Aqueous dispersion of cellulose fine fibers

[0115] The aqueous dispersion of cellulose fibers according to an embodiment of the present invention comprises cellulose fibers, one or more salts selected from metal salts and ammonium salts, and water. The aqueous dispersion comprises 0.002 parts by mass or more and 10 parts by mass or less of the salt per 100 parts by mass of the cellulose fibers, and 10 parts by mass or more of water per 1 part by mass of the total amount of the cellulose fibers and the salt. The aqueous dispersion of cellulose fibers may include components other than the cellulose fibers, the salt, and water, or may include only the cellulose fibers, the salt, and water.

[0116] The amount of the salt contained in the aqueous dispersion of cellulose fine fibers is 0.002 parts by mass or more and 10 parts by mass or less, preferably 0.01 parts by mass or more and 5 parts by mass or less, and more preferably 0.02 parts by mass or more and 1 part by mass or less, based on 100 parts by mass of the cellulose fine fibers. The above range is preferred because the resulting aqueous dispersion has excellent dispersibility.

[0117] The aqueous dispersion of cellulose fine fibers contains 10 parts by mass or more, preferably 90 parts by mass or more, and more preferably 98 parts by mass or more of water, based on 1 part by mass of the total amount of cellulose fine fibers and the salt. The upper limit of the amount of water is not particularly limited. From the perspective of handleability, the aqueous dispersion of cellulose fine fibers contains preferably 99.9 parts by mass or less, and more preferably 99.5 parts by mass or less of water, based on 1 part by mass of the total amount of cellulose fine fibers and the salt.

[0118] The aqueous dispersion of cellulose fibers according to an embodiment of the present invention may include components other than the cellulose fibers, the salt, and water. As components other than the cellulose fibers, the salt, and water, various components blended in aqueous compositions in the fields of materials, paints, coatings, and cosmetics may be used, depending on the application of the aqueous dispersion of cellulose fibers. More specifically, the aqueous dispersion of cellulose fibers may include the additives described in the above section (Cellulose Fiber Composition).

[0119] The aqueous dispersion of cellulose fine fibers according to embodiments of the present invention may contain at least one or more compounds selected from monomers, prepolymers, and polymers. In this aspect, when the aqueous dispersion of cellulose fine fibers is applied to form a layer with the monomer or prepolymer, the process can be performed under conditions where polymerization proceeds to obtain a layer composed of a polymer composition, more specifically, a composition comprising cellulose fine fibers, a salt, and a polymer. Alternatively, when the aqueous dispersion of cellulose fine fibers is applied to form a layer, the process can be performed under conditions where crosslinking occurs such that the resulting polymer composition includes a crosslinked rubber.

[0120] Examples of polymers include at least one polymer selected from resins and rubbers, such as phenolic resins, melamine resins, urea resins, alkyd resins, epoxy resins, unsaturated polyester resins, polyurethane resins, polyethylene resins (e.g., high-density polyethylene, medium-density polyethylene, low-density polyethylene), polypropylene resins, polystyrene resins, acrylic resins, polyvinyl alcohol, acrylamide resins, silicone resins, natural rubber, and synthetic rubber. Examples of monomers and prepolymers include monomers and prepolymers that form the above-mentioned polymers by polymerization.

[0121] In the case where the aqueous dispersion of cellulose fine fibers according to an embodiment of the present invention contains at least one or more compounds selected from monomers, prepolymers and polymers, based on 100 parts by mass of the cellulose fine fibers, preferably 400 parts by mass or more and 20,000 parts by mass or less, more preferably 10,000 parts by mass or more and 15,000 parts by mass or less, and further preferably 5,000 parts by mass or more and 10,000 parts by mass or less of the at least one or more compounds selected from monomers, prepolymers and polymers.

[0122] The method for preparing an aqueous dispersion of cellulose fine fibers according to an embodiment of the present invention is not particularly limited. The aqueous dispersion may be an aqueous dispersion prepared in the step of preparing an aqueous dispersion described in the above section (Method for Producing a Cellulose Fine Fiber Composition), or an aqueous dispersion prepared by redispersing the cellulose fine fiber composition described in the above section (Cellulose Fine Fiber Composition) in water. Components other than the cellulose fine fibers, the salt, and water, such as at least one or more compounds selected from monomers, prepolymers, and polymers, may be added at any time during the preparation of the aqueous dispersion, and the method is not particularly limited.

[0123] The aqueous dispersion of cellulose fine fibers according to the embodiments of the present invention can be used as a material for preparing molded articles (e.g., films and sheets) by, for example, the methods described in the examples. In other words, in the embodiments, the aqueous dispersion of cellulose fine fibers is an aqueous dispersion of cellulose fine fibers for molded articles (e.g., an aqueous dispersion of cellulose fine fibers for forming films and sheets). The present disclosure also includes the use of the aqueous dispersion of cellulose fine fibers for producing molded articles, as well as the use of the aqueous dispersion of cellulose fine fibers for producing films or sheets.

[0124] polymer composition

[0125] The polymer composition of the present embodiment includes cellulose fine fibers, one or more salts selected from metal salts and ammonium salts, and a polymer, and contains 0.002 parts by mass or more and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fine fibers.

[0126] The amount of the salt contained in the polymer composition is 0.002 parts by mass or more and 10 parts by mass or less, preferably 0.01 parts by mass or more and 5 parts by mass or less, and more preferably 0.02 parts by mass or more and 1 part by mass or less, based on 100 parts by mass of the cellulose fine fibers. The above range is preferred because the salt is well dispersed in the polymer composition.

[0127] Examples of the polymer contained in the polymer composition include the polymers listed in the above section (Aqueous dispersion of cellulose fine fibers). The polymer composition contains the polymer in an amount of preferably 400 parts by mass or more and 20,000 parts by mass or less, more preferably 1,000 parts by mass or more and 15,000 parts by mass or less, and further preferably 5,000 parts by mass or more and 10,000 parts by mass or less, based on 100 parts by mass of the cellulose fine fibers.

[0128] The method for preparing the polymer composition according to the embodiment of the present invention is not particularly limited. The polymer composition can be prepared by drying the aqueous dispersion of cellulose fine fibers containing a polymer described in the above section (Aqueous dispersion of cellulose fine fibers), or by drying an aqueous dispersion of cellulose fine fibers containing a monomer or prepolymer and, if necessary, heating under conditions where polymerization of the monomer or prepolymer is performed.

[0129] Molded products

[0130] The molded article of the embodiment of the present invention has a layer formed from the above-mentioned polymer composition. It is necessary that the molded article has a layer formed from the polymer composition, and the molded article may have only a layer formed from the polymer composition (a molded article having a single-layer structure) or may have a layer formed from the polymer composition and another layer (a laminate).

[0131] For the molded article of the embodiment of the present invention, for example, a molded article (laminated body) consisting of a base material and a layer formed of the polymer composition can be produced by forming the above-mentioned polymer composition into a specific shape (e.g., a film or sheet) on a base material. In addition, a molded article having a single-layer structure can be produced by removing the base material from the molded article (laminated body). The form of the molded article of the embodiment of the present invention is not particularly limited, and examples thereof include films and sheets.

[0132] Examples of the base material include, but are not particularly limited to, polymers, glass, metal, paper, and fabrics (woven fabrics, nonwoven fabrics).

[0133] Example

[0134] Hereinafter, embodiments of the present invention will be described with reference to Examples, but the present disclosure is not limited to these Examples.

[0135] Average fiber width

[0136] The average fiber width of the cellulose fine fibers in Examples and Comparative Examples was calculated by measuring the fiber widths of 50 randomly selected fibers using an atomic force microscope (SPM-9700HT manufactured by SHIMADZU CORPORATION) and arithmetically averaging the values. Evaluation samples prepared by the following method were used.

[0137] Weigh powdered cellulose fine fiber composition (sample) so that the amount of cellulose fine fiber is 3g.Sample is added to distilled water, the amount of weighing distilled water is so that the total amount with sample is 1000 g, and by using mixer (G5200 manufactured by Biolomix) the mixture is stirred for 3 minutes, to obtain the uniform cellulose fine fiber aqueous dispersion (cellulose fine fiber aqueous dispersion) of 0.3 mass %.Subsequently, using high pressure disperser, i.e. high pressure homogenizer (M-110EH-30, manufactured by Microfluidics), high dispersion treatment is carried out by 3 processings at 200MPa, and the high pressure homogenizer is attached with 200 microns of auxiliary processing modules and 87 microns of interaction chambers.Then, the distilled water of 149.0 g is added to the uniform cellulose fine fiber aqueous dispersion of 0.3 mass % of 1.0 g after high dispersion treatment, and by using mixer (G5200 manufactured by Biolomix company) stir 3 minutes, obtain the uniform cellulose fine fiber aqueous dispersion of 0.002 mass %. Then, 30 microliters of a 0.002 mass % uniform aqueous dispersion of cellulose fine fibers was dropped onto a natural mica (natural muscovite) base material plate (15 mm×15 mm×0.15 mm thickness) using a micropipette, and the dispersion was naturally dried for 0.5 hours to obtain an evaluation sample.

[0138] The amount of sulfur introduced

[0139] The amount (mmol / g) of sulfur incorporated into the cellulose fine fibers in Examples and Comparative Examples was determined by the following method.

[0140] The amount of sulfur introduced into the cellulose fine fibers was quantified by the combustion absorption-IC method using ICS-1500 manufactured by NIPPON DIONEX KK. Dried cellulose fine fibers (0.01 g) were placed on a magnetic plate and burned in an annular furnace (1350°C) in an oxygen atmosphere (flow rate: 1.5 L / min), and the resulting gas components were absorbed into a 3% hydrogen peroxide solution (20 mL) to obtain an absorption solution. Pure water was added to 100 mL of the resulting absorption solution, and the diluted solution was subjected to ion chromatography. Based on the results of the measurement, the concentration (mass %) of sulfate ions in the cellulose fine fibers was measured, and the amount (mmol / g) of sulfuric acid introduced into each 1 g of cellulose fine fibers was calculated. Dried cellulose fine fibers were prepared by drying an aqueous dispersion of cellulose fine fibers at 105°C until a constant weight was reached.

[0141] Methods for evaluating water content

[0142] The moisture content (water content) (mass %) of the cellulose fine fiber compositions (dried cellulose fine fibers) containing cellulose fine fibers, a metal salt, and an ammonium salt prepared in Examples and Comparative Examples can be expressed as the amount of water relative to the mass of the cellulose fine fiber composition in accordance with JIS P8203. In short, the moisture content (mass %) can be calculated using the following formula.

[0143] Moisture content (mass %) = ((mass of cellulose fine fiber composition - mass of solid content of cellulose fine fiber composition) / mass of cellulose fine fiber composition) × 100

[0144] (The mass of the cellulose fine fiber composition means the mass (g) of the cellulose fine fiber composition used for measurement; the mass of the solid content of the cellulose fine fiber composition means the mass (g) of the solid content remaining after the same amount of the cellulose fine fiber composition as that used for measurement is dried in an atmosphere of 105° C. for 2 hours until a constant weight is reached.)

[0145] Evaluation of the suppression of membrane separation during film formation

[0146] Cellulose fine fiber composition (dried cellulose fine fibers)

[0147] Into a 10 cm×10 cm×3 cm polystyrene resin container, 30 g of an aqueous dispersion containing cellulose fine fibers and salt at a solid concentration of 0.5% was poured, and the dispersion was naturally dried for 5 days to stack a dried film having a thickness of 10 μm on the polystyrene.

[0148] The powdered cellulose fine fiber compositions (dried cellulose fine fibers) prepared in Examples 1 to 17 and Comparative Examples 1 to 5 were dispersed in water to prepare aqueous dispersions containing cellulose fine fibers and salt at a solid concentration of 0.5%.

[0149] Natural rubber sheet

[0150] The natural rubber sheets (dried films) having a thickness of 10 μm formed on Teflon(R) prepared in Examples and Comparative Examples were observed.

[0151] Urethane resin sheet

[0152] The urethane resin sheets (dried films) having a thickness of 10 μm formed on Teflon(R) prepared in Examples and Comparative Examples were observed.

[0153] Evaluation of inhibition of membrane separation

[0154] In the room of illumination 750lx (lux), use magnifying glass (MAGDEPO Eye Loupe, Magnifier Factory manufacture) of 10 times of magnifying power to observe whether the dried film is separated, and the periphery of the part with film separation is marked with a permanent marker (Mackey pen, extra-fine, Zebra Co., Ltd. manufacture). Then, the dried film as a whole is peeled off from the polystyrene resin container as the base material, and weighed with an electronic balance (AUW220D, manufactured by SHIMADZUCORPORATION) to measure the gross mass of the dried film. Subsequently, along the line marked with a permanent pen on the dried film, the whole part with film separation is cut out with a box cutter, and the total amount of cutting is weighed as the part with film separation by an electronic balance (AUW220D, manufactured by SHIMADZUCORPORATION) to measure the mass of the part with film separation. The area ratio of the portion with membrane separation was then calculated by the following formula: Area ratio of the portion with membrane separation = mass of the portion with membrane separation / mass of the entire dried membrane × 100 {%} Whether membrane separation was suppressed during film formation was evaluated based on the following criteria.

[0155] AA: The area ratio of the portion with membrane separation is less than 0.5%

[0156] BB: The area ratio of the portion with membrane separation is 0.5% or more and less than 2%

[0157] CC: The area ratio of the portion with membrane separation is 2% or more and less than 5%

[0158] DD: The area ratio of the portion with membrane separation is 5% or more

[0159] Evaluation of tensile strength

[0160] The natural rubber sheets or urethane resin sheets prepared in Examples 18 to 26 and Comparative Examples 6 to 9 were cut into 10 mm wide and 100 mm long pieces by a sample cutter (SDL200 manufactured by DUMBBELL CO., LTD.) to give dumbbell-shaped samples. Dumbbell-shaped samples of natural rubber sheets (comparative products) and urethane resin sheets (comparative products) not including cellulose fine fibers were prepared by the same method as comparative products. The natural rubber sheets (comparative products) and urethane resin sheets (comparative products) were produced by the following methods.

[0161] The dumbbell-shaped sample was stretched using Tensilon RTF-2410 (manufactured by A&D Company Limited.) at a grip distance of 50 mm and a speed of 200 mm / min according to JIS-C-2151 and ASTM-D-882, and the strength at break was measured three times, and the average value was calculated.

[0162] Next, the average value of the obtained breaking strength was used to determine the improvement rate of the breaking strength of the natural rubber sheet (breaking strength of Examples 18, 20, 22, 24 or Comparative Example 6 / breaking strength of the natural rubber sheet (comparative product)), and the breaking strength was evaluated based on the following criteria.

[0163] Similarly, the improvement rate of the breaking strength of the urethane composite film (breaking strength of Examples 19, 21, 23, 25, 26 or Comparative Examples 7 to 9 / breaking strength of the urethane resin sheet (comparative product)) was determined, and the breaking strength was evaluated based on the following criteria.

[0164] AA: The improvement rate of breaking strength is 2.0 times or more

[0165] BB: The improvement rate of breaking strength is 1.2 times or more and less than 2.0 times

[0166] CC: The improvement rate of breaking strength is less than 1.2 times

[0167] Method for producing natural rubber sheet (comparative product)

[0168] To 20 g of natural rubber latex (manufactured by KENIS, Ltd.) having a solids concentration of 50% by mass was added 2000 g of distilled water and 0.3 g of a radical initiator ("Perhexa 25B-40", manufactured by NOF CORPORATION). 20 g of this mixture was placed in a 10 cm × 10 cm × 3 cm Teflon® tray and dried at 80°C for 3 days to obtain a natural rubber sheet having a film thickness of 10 μm (comparative product).

[0169] Method for producing urethane resin sheet (comparative product)

[0170] 1977 g of distilled water and 0.05 g of a blocked isocyanate curing agent ("Duranate 17B-60P", manufactured by Asahi Kasei Corporation) were added to 28.5 g of a urethane emulsion (UCOATUWS-145, manufactured by Sanyo Chemical Industries, Ltd.) having a solid concentration of 35% by mass. 20 g of this mixture was placed in a 10 cm × 10 cm × 3 cm Teflon (R) tray and dried at room temperature for 7 days to obtain a polyurethane resin sheet (comparative product) having a film thickness of 10 μm.

[0171] The following raw materials were used in Examples and Comparative Examples.

[0172] raw materials

[0173] DMSO (dimethyl sulfoxide) (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0174] Acetic anhydride (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0175] 98% sulfuric acid (manufactured by SANWA KAGAKU CORP.)

[0176] Sodium hydroxide (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0177] NaCl (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0178] Sodium acetate (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0179] Sodium sulfate (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0180] Ammonium sulfate (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0181] Calcium acetate monohydrate (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0182] Sodium phosphate (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0183] Lithium tetraborate (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0184] Lithium silicate (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0185] 2,2,6,6-Tetramethylpiperidinyl-N-oxyl (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0186] Sodium bromide (manufactured by FUJIFILM Wako Pure Chemical Corporation)

[0187] Example 1

[0188] 150 g of DMSO, 25 g of acetic anhydride, and 3.35 g of 98% sulfuric acid were placed in a 300 mL sample bottle and stirred at room temperature (23° C.) for 30 seconds using a magnetic stirrer to prepare a defibration solution.

[0189] Next, 5.0 g of conifer kraft pulp NBKP (manufactured by NIPPON PAPERINDUSTRIES CO., LTD.) was added to the defibration solution, and the mixture was stirred at room temperature of 23°C for 120 minutes to perform sulfuric acid esterification. After stirring, 250 mL of distilled water was added to the defibration solution containing cellulose to stop the reaction, and then a 5% by mass aqueous sodium hydroxide solution was added until the pH reached 7 to neutralize the reaction solution. The supernatant was then removed by centrifugation.

[0190] 1350 ml of distilled water and 1350 ml of ethanol were added and the mixture was stirred until uniformly dispersed, and then the supernatant was removed by centrifugation. The same procedure was repeated to wash the solution a total of six times. The centrifugation rate was 12,000 rpm, and the centrifugation time was 50 minutes in each procedure. After the centrifugal washing, distilled water was added to dilute the solution until the total weight reached 1000 g.

[0191] Next, the solution was stirred for 3 minutes using a mixer (G5200, manufactured by Biolomix) to obtain an aqueous dispersion of cellulose fine fibers having sulfate groups (0.5% by mass). The amount of sulfur introduced into the cellulose fine fibers having sulfate groups (the amount of introduced sulfur derived from the sulfate groups) was 2.5 mmol / g. Cellulose fine fibers having sulfate groups are also described as cellulose fine fibers esterified with sulfuric acid.

[0192] To 400 g (0.5 mass %) of the aqueous dispersion of cellulose fine fibers having sulfate groups, 0.1 g of a 20 mass % NaCl aqueous solution was added, and stirred with a stirrer for 5 minutes to obtain an aqueous dispersion (1) containing 1 mass part of NaCl based on 100 mass parts of the cellulose fine fibers esterified with sulfate.

[0193] Next, the obtained aqueous dispersion (1) was dried for 72 hours using a freeze drying apparatus (FDU-2110, manufactured by TOKYO RIKAKIKAI CO., LTD.). Subsequently, the resultant was treated in a dry pulverizer (Wonder Blender WB1, manufactured by OSAKACHEMICAL Co., Ltd.) for 1 minute to give a powdered cellulose fine fiber composition (dried cellulose fine fibers) (1) containing 1 part by mass of NaCl based on 100 parts by mass of the cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur was 2.5 mmol / g).

[0194] Example 2

[0195] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (2) containing 0.002 parts by mass of NaCl based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur: 2.5 mmol / g) was prepared in the same manner as in Example 1, except that the concentration of the 20% by mass NaCl aqueous solution in Example 1 was changed to 0.04% by mass.

[0196] Example 3

[0197] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (3) containing 1 part by mass of sodium sulfate based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur being 2.5 mmol / g) was prepared in the same manner as in Example 1, except that the 20% by mass NaCl aqueous solution in Example 1 was changed to a 20% by mass sodium sulfate aqueous solution.

[0198] Example 4

[0199] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (4) containing 0.002 parts by mass of sodium sulfate based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur: 2.5 mmol / g) was prepared in the same manner as in Example 3, except that the concentration of the 20% by mass sodium sulfate aqueous solution in Example 3 was changed to 0.04% by mass.

[0200] Example 5

[0201] A powdered cellulose fiber composition (dried cellulose fibers) (5) containing 1 part by mass of sodium acetate based on 100 parts by mass of cellulose fibers esterified with sulfuric acid (the amount of introduced sulfur being 2.5 mmol / g) was prepared in the same manner as in Example 1, except that the 20% by mass NaCl aqueous solution in Example 1 was changed to a 20% by mass sodium acetate aqueous solution.

[0202] Example 6

[0203] A powdered cellulose fiber composition (dried cellulose fibers) (6) containing 0.002 parts by mass of sodium acetate based on 100 parts by mass of cellulose fibers esterified with sulfuric acid (the amount of introduced sulfur: 2.5 mmol / g) was prepared in the same manner as in Example 5, except that the concentration of the 20% by mass sodium acetate aqueous solution in Example 5 was changed to 0.04% by mass.

[0204] Example 7

[0205] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (7) containing 1 part by mass of ammonium sulfate based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur: 2.5 mmol / g) was prepared in the same manner as in Example 1, except that the 20% by mass NaCl aqueous solution in Example 1 was changed to a 20% by mass ammonium sulfate aqueous solution.

[0206] Example 8

[0207] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (8) containing 0.002 parts by mass of ammonium sulfate based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur: 2.5 mmol / g) was prepared in the same manner as in Example 7, except that the concentration of the 20% by mass ammonium sulfate aqueous solution in Example 7 was changed to 0.04% by mass.

[0208] Example 9

[0209] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (9) containing 0.1 parts by mass of sodium phosphate based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur being 2.5 mmol / g) was prepared in the same manner as in Example 1, except that the 20% by mass NaCl aqueous solution in Example 1 was changed to a 2% by mass sodium phosphate aqueous solution.

[0210] Example 10

[0211] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (10) containing 0.1 parts by mass of lithium tetraborate based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur being 2.5 mmol / g) was prepared in the same manner as in Example 1, except that the 20% by mass NaCl aqueous solution in Example 1 was changed to a 2% by mass lithium tetraborate aqueous solution.

[0212] Example 11

[0213] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (11) containing 0.1 parts by mass of lithium silicate based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur being 2.5 mmol / g) was prepared in the same manner as in Example 1, except that the 20% by mass NaCl aqueous solution in Example 1 was changed to a 2% by mass lithium silicate aqueous solution.

[0214] Example 12

[0215] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (12) containing 0.05 parts by mass of sodium sulfate and 0.05 parts by mass of sodium acetate based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur is 2.5 mmol / g) was prepared in the same manner as in Example 1, except that 0.1 g of the 20 mass% NaCl aqueous solution in Example 1 was replaced with 0.05 g of a 2 mass% sodium sulfate aqueous solution and 0.05 g of a 2 mass% sodium acetate aqueous solution.

[0216] Example 13

[0217] A powdered cellulose fiber composition (dried cellulose fibers) (13) containing 0.005 parts by mass of sodium sulfate and 0.005 parts by mass of sodium acetate based on 100 parts by mass of cellulose fibers esterified with sulfate (the amount of introduced sulfur being 2.5 mmol / g) was prepared in the same manner as in Example 12, except that the concentrations of the sodium sulfate aqueous solution and the sodium acetate aqueous solution in Example 12 were respectively changed to 0.2% by mass.

[0218] Example 14

[0219] After adding coniferous kraft pulp NBKP (manufactured by NIPPON PAPERINDUSTRIES CO., LTD.) to the defibration solution in Example 5, the stirring time at room temperature of 23°C was changed from 120 minutes to 30 minutes, and the concentration of the sodium acetate aqueous solution was changed from 20 mass % to 2 mass %, and a powdered cellulose fine fiber composition (dried cellulose fine fibers) (14) was prepared in the same manner as in Example 5, which contained 0.1 mass parts of sodium acetate based on 100 mass parts of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur was 0.4 mmol / g).

[0220] Example 15

[0221] A powdered cellulose fiber composition (dried cellulose fibers) (15) containing 0.1 parts by mass of sodium acetate based on 100 parts by mass of cellulose fibers esterified with sulfuric acid (the amount of introduced sulfur: 2.5 mmol / g) was prepared in the same manner as in Example 5, except that the concentration of the 20% by mass sodium acetate aqueous solution in Example 5 was changed to 2% by mass.

[0222] Example 16

[0223] A powdered cellulose fiber composition (dried cellulose fibers) (16) containing 0.1 parts by mass of sodium acetate based on 100 parts by mass of cellulose fibers esterified with sulfuric acid (the amount of introduced sulfur: 2.8 mmol / g) was prepared in the same manner as in Example 15, except that the amount of 98% sulfuric acid added used in the preparation of the defibrillation solution in Example 15 was changed from 3.35 g to 3.75 g.

[0224] Comparative Example 1

[0225] A powdered cellulose fiber composition (dried cellulose fibers) (c1) containing no salt and containing cellulose fibers esterified with sulfuric acid (the amount of introduced sulfur being 2.5 mmol / g) was prepared in the same manner as in Example 1, except that 20% by mass NaCl aqueous solution was not added relative to 400 g (0.5% by mass) of the aqueous dispersion of cellulose fibers having sulfate groups in Example 1.

[0226] Comparative Example 2

[0227] A powdered cellulose fiber composition (dried cellulose fibers) (c2) containing 0.1 parts by mass of sodium acetate based on 100 parts by mass of cellulose fibers esterified with sulfuric acid (the amount of introduced sulfur being 0.2 mmol / g) was prepared in the same manner as in Example 14, except that the amount of 98% sulfuric acid added used in the preparation of the defibrillation solution in Example 14 was changed from 3.35 g to 1.70 g.

[0228] Comparative Example 3

[0229] A powdered cellulose fiber composition (dried cellulose fibers) (c3) containing 0.1 parts by mass of sodium acetate based on 100 parts by mass of cellulose fibers esterified with sulfuric acid (the amount of introduced sulfur being 3.5 mmol / g) was prepared in the same manner as in Example 15, except that the amount of 98% sulfuric acid added used in the preparation of the defibrillation solution in Example 15 was changed from 3.35 g to 4.69 g.

[0230] Comparative Example 4

[0231] 0.13 mmol of 2,2,6,6-tetramethylpiperidin-N-oxyl (TEMPO) and 10 mmol of sodium bromide were dissolved in water to obtain 250 mL of an aqueous solution.

[0232] 5 g of coniferous kraft pulp NBKP (manufactured by NIPPON PAPER INDUSTRIES CO., LTD.) was added to the aqueous solution and the mixture was stirred until the pulp was uniformly dispersed. The temperature of the mixture was adjusted to 20°C, and then 32 mmol of an aqueous sodium hypochlorite solution (manufactured by FUJIFILM Wako Pure Chemical Corporation) was added thereto to initiate an oxidation reaction. During the reaction, the temperature of the reaction system was maintained at 20°C, and the pH was maintained at 10 by sequentially adding a 3N aqueous sodium hydroxide solution. After reacting for 3 hours, the resultant was filtered with a glass filter, and the filtrate was thoroughly washed with water. The above operation provided an oxidized pulp.

[0233] Ion-exchanged water was added to the oxidized slurry to adjust the solid concentration of the slurry to 0.5 mass %, and the slurry was treated three times with an ultrahigh pressure homogenizer at 140 MPa to obtain an aqueous dispersion of TEMPO oxidized cellulose fine fibers (0.5 mass %).

[0234] To 400 g (0.5 mass %) of an aqueous dispersion of TEMPO-oxidized cellulose fine fibers, 0.1 g of a 2 mass % aqueous sodium acetate solution was added, and the mixture was stirred with a stirrer for 5 minutes to obtain an aqueous dispersion (c4) containing 0.1 mass parts of sodium acetate based on 100 mass parts of TEMPO-oxidized cellulose fine fibers.

[0235] Subsequently, the obtained water dispersion (c4) was dried for 72 hours using a freeze-drying apparatus (FDU-2110, manufactured by TOKYO RIKAKIKAI CO., LTD.) to obtain a powder cellulose fine fiber composition (dried cellulose fine fiber) (c4) containing 0.1 parts by mass of sodium acetate based on 100 parts by mass of the TEMPO-oxidized cellulose fine fiber.

[0236] Comparative Example 5

[0237] Coniferous kraft pulp NBKP (manufactured by NIPPON PAPER INDUSTRIES CO., LTD.) was previously beaten for 2 hours and 30 minutes by using a Niagara beater. Next, two defibrillation treatments were performed using a stone mill defibrillator (“Supermasscolloider”, manufactured by MASUKO SANGYO CO., LTD.) to obtain a water dispersion (0.5 mass%) of cellulose fine fibers prepared by mechanical defibrillation.

[0238] To 400 g of the water dispersion (0.5 mass%) of cellulose fine fibers prepared by mechanical defibrillation, 0.1 g of a 2 mass% sodium acetate aqueous solution was added, and the mixture was stirred with a stirrer for 5 minutes to obtain a water dispersion (c5) containing 0.1 parts by mass of sodium acetate based on 100 parts by mass of the cellulose fine fibers prepared by mechanical defibrillation.

[0239] Subsequently, the obtained water dispersion (c5) was dried for 72 hours using a freeze-drying apparatus (FDU-2110, manufactured by TOKYO RIKAKIKAI CO., LTD.) to obtain a powder cellulose fine fiber composition (dried cellulose fine fiber) (c5) containing 0.1 parts by mass of sodium acetate based on 100 parts by mass of the cellulose fine fibers.

[0240] Example 17

[0241] A 20 mass% NaCl aqueous solution in Example 1 was changed to a 2 mass% calcium acetate aqueous solution, and otherwise, a powder cellulose fine fiber composition (dried cellulose fine fiber) (17) containing 0.1 parts by mass of calcium acetate based on 100 parts by mass of the cellulose fine fibers sulfated with sulfur (amount of introduced sulfur 2.5 mmol / g) was prepared in the same manner as in Example 1.

[0242] The types of cellulose nanofibers (CNFs) contained in the powdered cellulose fine fiber compositions prepared in Examples 1 to 17 and Comparative Examples 1 to 5, their average fiber widths, the amount of sulfur introduced therein, the type of salt, and the amount of salt based on 100 parts by mass of the fine cellulose are shown in Table 1. The results of evaluation of the water content in the cellulose fine fiber compositions and the inhibition of membrane separation during film formation are shown in Table 2.

[0243] [Table 1]

[0244] Table 1

[0245]

[0246] [Table 2]

[0247] Table 2

[0248]

[0249] The film formability of the examples was higher than that of the comparative examples.

[0250] Example 18

[0251] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (18) containing 0.1 parts by mass of sodium sulfate based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur: 2.5 mmol / g) was prepared in the same manner as in Example 3, except that the concentration of the 20% by mass sodium sulfate aqueous solution in Example 3 was changed to 2% by mass.

[0252] Next, 2150 g of distilled water was added to 0.5 g of the obtained dried cellulose fine fibers (18), and the mixture was stirred with a stirrer for 30 minutes to obtain an aqueous dispersion. The aqueous dispersion was mixed with 20 g of natural rubber latex (manufactured by KENIS Ltd.) having a solid concentration of 50% by mass and stirred with a stirrer at room temperature for 1 hour. 0.3 g of a free radical initiator ("Perhexa 25B-40", manufactured by NOF Corporation) was added thereto, and 20 g of the mixture was placed in a 10 cm × 10 cm × 3 cm Teflon (R) tray and dried at 80°C for 3 days to obtain a 10 μm thick natural rubber sheet on Teflon containing cellulose fine fibers esterified with sulfuric acid and 0.1 parts by mass of sodium sulfate based on 100 parts by mass of the cellulose fine fibers esterified with sulfuric acid.

[0253] Example 19

[0254] A powdered cellulose fine fiber composition (dried cellulose fine fibers) (19) containing 0.1 parts by mass of sodium sulfate based on 100 parts by mass of cellulose fine fibers esterified with sulfuric acid (the amount of introduced sulfur: 2.5 mmol / g) was prepared in the same manner as in Example 3, except that the concentration of the 20% by mass sodium sulfate aqueous solution in Example 3 was changed to 2% by mass.

[0255] Next, 2127 g of distilled water was added to 0.5 g of the dried cellulose fine fibers (19), and the mixture was stirred with a stirrer for 30 minutes to obtain an aqueous dispersion. The aqueous dispersion was mixed with 28.5 g of a urethane emulsion (UCOAT UWS-145, manufactured by Sanyo Chemical Industries, Ltd.) having a solid concentration of 35% by mass and stirred with a stirrer for 1 hour at room temperature. 0.05 g of a blocked isocyanate curing agent ("Duranate 17B-60P", manufactured by Asahi Kasei Corporation) was added thereto, and 20 g of the mixture was placed in a 10 cm × 10 cm × 3 cm Teflon (R) tray and dried at room temperature for 7 days to obtain a 10 micron thick urethane resin sheet on Teflon, which contained cellulose fine fibers esterified with sulfuric acid and 0.1 parts by mass of sodium sulfate based on 100 parts by mass of the cellulose fine fibers esterified with sulfuric acid.

[0256] Example 20

[0257] A 10 μm thick natural rubber sheet containing cellulose fine fibers esterified with sulfate and 0.1 part by mass of sodium acetate per 100 parts by mass of the cellulose fine fibers esterified with sulfate was prepared on Teflon in the same manner as in Example 18, except that the 2 mass % aqueous sodium sulfate solution in Example 18 was replaced with a 2 mass % aqueous sodium acetate solution.

[0258] Example 21

[0259] A 10 μm thick urethane resin sheet containing cellulose fine fibers esterified with sulfuric acid and 0.1 part by mass of sodium acetate per 100 parts by mass of the cellulose fine fibers esterified with sulfuric acid was prepared on Teflon in the same manner as in Example 19, except that the 2 mass % sodium sulfate aqueous solution in Example 19 was replaced with a 2 mass % sodium acetate aqueous solution.

[0260] Example 22

[0261] A 10 μm thick natural rubber sheet containing cellulose fine fibers esterified with sulfate, 0.05 parts by mass of sodium sulfate, and 0.05 parts by mass of sodium acetate based on 100 parts by mass of the cellulose fine fibers esterified with sulfate was prepared on Teflon in the same manner as in Example 18, except that 0.1 g of the 2 mass % sodium sulfate aqueous solution in Example 18 was replaced with 0.05 g of a 2 mass % sodium sulfate aqueous solution and 0.05 g of a 2 mass % sodium acetate aqueous solution.

[0262] Example 23

[0263] A 10 μm thick urethane resin sheet containing cellulose fine fibers esterified with sulfate, 0.05 parts by mass of sodium sulfate, and 0.05 parts by mass of sodium acetate based on 100 parts by mass of the cellulose fine fibers esterified with sulfate was prepared on Teflon in the same manner as in Example 19, except that 0.1 g of the 2 mass% sodium sulfate aqueous solution in Example 19 was replaced with 0.05 g of a 2 mass% sodium sulfate aqueous solution and 0.05 g of a 2 mass% sodium acetate aqueous solution.

[0264] Example 24

[0265] A 10 μm thick natural rubber sheet containing cellulose fine fibers esterified with sulfate and 0.1 part by mass of ammonium sulfate per 100 parts by mass of the cellulose fine fibers esterified with sulfate was prepared on Teflon in the same manner as in Example 18, except that the 2% by mass aqueous sodium sulfate solution in Example 18 was replaced with a 2% by mass aqueous ammonium sulfate solution.

[0266] Example 25

[0267] A 10 μm thick urethane resin sheet containing cellulose fine fibers esterified with sulfuric acid and 0.1 part by mass of ammonium sulfate per 100 parts by mass of the cellulose fine fibers esterified with sulfuric acid was prepared on Teflon in the same manner as in Example 19, except that the 2% by mass aqueous sodium sulfate solution in Example 19 was replaced with a 2% by mass aqueous ammonium sulfate solution.

[0268] Comparative Example 6

[0269] A 10 μm-thick natural rubber sheet containing cellulose fine fibers esterified with sulfuric acid was prepared on Teflon in the same manner as in Example 18, except that the 2 mass % sodium sulfate aqueous solution in Example 18 was not added.

[0270] Comparative Example 7

[0271] A 10 μm-thick urethane resin sheet containing cellulose fine fibers esterified with sulfuric acid was prepared on Teflon in the same manner as in Example 19, except that the 2 mass % sodium sulfate aqueous solution in Example 19 was not added.

[0272] Comparative Example 8

[0273] 0.13 mmol of 2,2,6,6-tetramethylpiperidin-N-oxyl (TEMPO) and 10 mmol of sodium bromide were dissolved in water to obtain 250 mL of an aqueous solution.

[0274] 5 g of coniferous kraft pulp NBKP (manufactured by NIPPON PAPER INDUSTRIES CO., LTD.) was added to the aqueous solution and the mixture was stirred until the pulp was uniformly dispersed. The temperature of the mixture was adjusted to 20°C, and then 32 mmol of an aqueous sodium hypochlorite solution (manufactured by FUJIFILM Wako Pure Chemical Corporation) was added thereto to initiate an oxidation reaction. During the reaction, the temperature of the reaction system was maintained at 20°C, and the pH was maintained at 10 by sequentially adding a 3N aqueous sodium hydroxide solution. After reacting for 3 hours, the resultant was filtered with a glass filter, and the filtrate was thoroughly washed with water. The above operation provided an oxidized pulp.

[0275] Ion-exchanged water was added to the oxidized slurry to adjust the solid concentration of the slurry to 0.5 mass %, and the slurry was treated three times with an ultrahigh pressure homogenizer at 140 MPa to obtain an aqueous dispersion of TEMPO oxidized cellulose fine fibers (0.5 mass %).

[0276] To 400 g (0.5 mass %) of an aqueous dispersion of TEMPO-oxidized cellulose fine fibers was added 0.1 g of a 2 mass % aqueous sodium acetate solution, and the mixture was stirred with a stirrer for 5 minutes to obtain an aqueous dispersion (c8) containing 0.1 mass parts of sodium acetate based on 100 mass parts of TEMPO-oxidized cellulose fine fibers.

[0277] Subsequently, the obtained aqueous dispersion (c8) was dried for 72 hours using a freeze drying apparatus (FDU-2110, manufactured by TOKYO RIKAKIKAI CO., LTD.) to obtain a powdered cellulose fine fiber composition (dried cellulose fine fibers) (c8) containing 0.1 parts by mass of sodium acetate based on 100 parts by mass of TEMPO-oxidized cellulose fine fibers.

[0278] Next, 2127 g of distilled water was added to 0.5 g of the dried cellulose fine fibers (c8), and the mixture was stirred with a stirrer for 30 minutes to obtain an aqueous dispersion. The aqueous dispersion was mixed with 28.5 g of a urethane emulsion (UCOAT UWS-145, manufactured by Sanyo Chemical Industries, Ltd.) having a solids concentration of 35% by mass and stirred with a stirrer for 1 hour at room temperature. 0.05 g of a blocked isocyanate curing agent ("Duranate 17B-60P", manufactured by Asahi Kasei Corporation) was added thereto, and 20 g of the mixture was placed in a 10 cm × 10 cm × 3 cm Teflon (R) tray and dried at room temperature for 7 days to obtain a 10 micron thick urethane resin sheet on Teflon containing TEMPO-oxidized cellulose fine fibers and 0.1 parts by mass of sodium acetate based on 100 parts by mass of the TEMPO-oxidized cellulose fine fibers.

[0279] Comparative Example 9

[0280] Coniferous tree kraft pulp NBKP (manufactured by NIPPON PAPER INDUSTRIES CO., LTD.) was pre-beaten for 2 hours and 30 minutes using a Niagara beater. Subsequently, it was subjected to two defibration treatments using a stone mill mechanical defibrator ("Supermasscolloider", manufactured by MASUKO SANGYO CO., LTD.) to obtain an aqueous dispersion (0.5% by mass) of cellulose fine fibers prepared by mechanical defibration.

[0281] To 400 g of an aqueous dispersion (0.5% by mass) of cellulose fine fibers prepared by mechanical defibration was added 0.1 g of a 2% by mass aqueous sodium acetate solution, and the mixture was stirred with a stirrer for 5 minutes to obtain an aqueous dispersion (c9) containing 0.1 parts by mass of sodium acetate based on 100 parts by mass of the cellulose fine fibers prepared by mechanical defibration.

[0282] Subsequently, the obtained aqueous dispersion (c9) was dried for 72 hours using a freeze drying apparatus (FDU-2110, manufactured by TOKYO RIKAKIKAI CO., LTD.) to obtain a powdered cellulose fine fiber composition (dried cellulose fine fibers) (c9) containing 0.1 parts by mass of sodium acetate based on 100 parts by mass of the cellulose fine fibers.

[0283] Then, 2127 g of distilled water is added to 0.5 g of the dried cellulose fine fibers (c9) obtained, and the mixture is stirred with a stirrer for 30 minutes to obtain an aqueous dispersion. The aqueous dispersion is mixed with 28.5 g of a urethane emulsion (UCOAT UWS-145, manufactured by Sanyo Chemical Industries, Ltd.) having a solid concentration of 35% by mass, and stirred with a stirrer for 1 hour at room temperature. 0.05 g of a blocked isocyanate curing agent ("Duranate 17B-60P", manufactured by Asahi Kasei Corporation) is added thereto, and the mixture is placed in a Teflon (R) tray of 10 cm × 10 cm × 3 cm, and dried at room temperature for 7 days to obtain a 10 micron thick urethane resin sheet on Teflon, which contains cellulose fine fibers prepared by mechanical fiberization and 0.1 parts by mass of sodium acetate based on 100 parts by mass of the cellulose fine fibers prepared by mechanical fiberization.

[0284] Example 26

[0285] A 10 μm-thick urethane resin sheet containing cellulose fine fibers esterified with sulfuric acid and 0.1 part by mass of calcium acetate per 100 parts by mass of the cellulose fine fibers esterified with sulfuric acid was prepared on Teflon in the same manner as in Example 19, except that the 2% by mass sodium sulfate aqueous solution in Example 19 was replaced with a 2% by mass calcium acetate aqueous solution.

[0286] The type of cellulose fine fibers (CNFs) contained in the powdered cellulose fine fiber compositions prepared in Examples 18 to 26 and Comparative Examples 6 to 9, their average fiber widths, the amount of sulfur introduced therein, the type of salt, and the amount of salt per 100 parts by mass of the fine cellulose are shown in Table 3. Table 4 shows the material used for sheet formation (natural rubber or urethane rubber), the evaluation results of the suppression of film separation during film formation, and the evaluation results of tensile strength.

[0287] [Table 3]

[0288] Table 3

[0289]

[0290] [Table 4]

[0291] Table 4

[0292]

[0293] It was confirmed that the system including rubber or resin of the examples also had higher film formability than that of the comparative examples, and further, the strength was significantly improved in the examples compared to the comparative examples.

[0294] The upper limit and / or lower limit of the numerical range described in this specification can be optionally combined to specify a preferred range respectively. For example, the upper limit and lower limit of the numerical range can be optionally combined to specify a preferred range, the upper limit of the numerical range can be optionally combined to specify a preferred range, and the lower limit of the numerical range can be optionally combined to specify a preferred range. In addition, in this application, the numerical range recorded using "~" includes each value recorded before and after "~" as the lower limit and upper limit.

[0295] Unless otherwise specified, singular expressions should be interpreted as including their plural expressions throughout this specification. Unless otherwise specified, singular articles (for example, "a," "an," and "the" in English) should be interpreted as including plural meanings.

[0296] The embodiment of the present invention is described in detail above, but the specific structure is not limited to this embodiment. The present disclosure covers design changes (if any) that do not depart from the subject matter of the present disclosure.

[0297] All publications, patents, and patent applications cited in this specification are hereby incorporated by reference in their entirety.

Claims

1. A cellulose fine fiber composition comprising cellulose fine fibers and one or more salts selected from metal salts and ammonium salts, wherein: The cellulose fine fibers have an average fiber width of 1 nm or more and 1000 nm or less, The cellulose fine fibers have sulfate groups represented by the following general formula (1): The cellulose fine fibers have an amount of sulfur derived from sulfate groups introduced into the cellulose fine fibers of 0.3 mmol / g or more and 3.0 mmol / g or less, and The cellulose fine fiber composition contains 0.002 parts by mass or more and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fine fibers: [Formula 1] ... (1)， (In the general formula (1), n ​​is an integer of 1 or more and 3 or less, M n+ is an n-valent cation, and the wavy lines indicate bonding sites with other atoms).

2. The cellulose fine fiber composition according to claim 1, wherein the salt is one or more salts selected from sulfates, carboxylates, borates, phosphates and ammonium salts. 3 . The cellulose fine fiber composition according to claim 1 , having a water content of 10% by mass or less. The cellulose fine fiber composition according to claim 1 , which is in a powder form.

5. An aqueous dispersion of cellulose fine fibers, comprising cellulose fine fibers, one or more salts selected from metal salts and ammonium salts, and water, wherein: The cellulose fine fibers have an average fiber width of 1 nm or more and 1000 nm or less, The cellulose fine fibers have sulfate groups represented by the following general formula (1): the cellulose fine fibers have an amount of sulfur derived from sulfate ester groups introduced into the cellulose fine fibers of 0.3 mmol / g or more and 3.0 mmol / g or less, The aqueous dispersion of the cellulose fine fibers contains 0.002 parts by mass or more and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fine fibers, and The aqueous dispersion of the cellulose fine fibers contains 10 parts by mass or more of water based on 1 part by mass of the total amount of the cellulose fine fibers and the salt: [Formula 2] ... (1)， (In the general formula (1), n ​​is an integer of 1 or more and 3 or less, M n+ is an n-valent cation, and the wavy lines indicate bonding sites with other atoms). 6 . The aqueous dispersion of cellulose fine fibers according to claim 5 , wherein the salt is one or more salts selected from sulfates, carboxylates, borates, phosphates, and ammonium salts.

7. The aqueous dispersion of cellulose fine fibers according to claim 5, comprising at least one or more compounds selected from the group consisting of monomers, prepolymers and polymers.

8. The aqueous dispersion of cellulose fine fibers according to claim 7, comprising 400 parts by mass or more and 20,000 parts by mass or less of the at least one or more compounds selected from monomers, prepolymers and polymers based on 100 parts by mass of the cellulose fine fibers.

9. A polymer composition comprising cellulose fine fibers, one or more salts selected from metal salts and ammonium salts, and a polymer, wherein: The cellulose fine fibers have an average fiber width of 1 nm or more and 1000 nm or less, The cellulose fine fibers have sulfate groups represented by the following general formula (1): The cellulose fine fibers have an amount of sulfur derived from sulfate groups introduced into the cellulose fine fibers of 0.3 mmol / g or more and 3.0 mmol / g or less, and The polymer composition comprises 0.002 parts by mass or more and 10 parts by mass or less of the salt based on 100 parts by mass of the cellulose fine fibers: [Formula 3] ... (1)， (In the general formula (1), n ​​is an integer of 1 or more and 3 or less, M n+ is an n-valent cation, and the wavy lines indicate bonding sites with other atoms).

10. The polymer composition according to claim 9, wherein the salt is one or more salts selected from sulfates, carboxylates, borates, phosphates and ammonium salts. 11 . The polymer composition according to claim 9 , comprising 400 parts by mass or more and 20,000 parts by mass or less of the polymer based on 100 parts by mass of the cellulose fine fibers.

12. A molded article comprising a layer formed from the polymer composition according to claim 9.

13. A method for producing a cellulose fine fiber composition, the method comprising the steps of: preparing an aqueous dispersion of cellulose fine fibers by mixing an aqueous solution of one or more salts selected from metal salts and ammonium salts with the cellulose fine fibers; and The aqueous dispersion of the cellulose fine fibers is dried to obtain a cellulose fine fiber composition comprising the cellulose fine fibers and one or more salts selected from metal salts and ammonium salts, wherein The cellulose fine fibers have an average fiber width of 1 nm or more and 1000 nm or less, The cellulose fine fibers have sulfate groups represented by the following general formula (1): The cellulose fine fibers have an amount of sulfur derived from sulfate groups introduced into the cellulose fine fibers of 0.3 mmol / g or more and 3.0 mmol / g or less, and In the step of preparing the aqueous dispersion of cellulose fine fibers, 0.002 parts by mass or more and 10 parts by mass or less of the salt is used based on 100 parts by mass of the cellulose fine fibers: [Formula 4] ... (1)， (In the general formula (1), n ​​is an integer of 1 or more and 3 or less, M n+ is an n-valent cation, and the wavy lines indicate bonding sites with other atoms).

Images