WO2018143150A1

WO2018143150A1 - Method for producing dry cellulose nanofibers

Info

Publication number: WO2018143150A1
Application number: PCT/JP2018/002847
Authority: WO
Inventors: 藤槻薫麗; 半埜賢治
Original assignee: 株式会社片山化学工業研究所; 日本製紙株式会社
Priority date: 2017-02-03
Filing date: 2018-01-30
Publication date: 2018-08-09
Also published as: JP6861972B2; JPWO2018143150A1

Abstract

Provided are a method for producing dry cellulose nanofibers (CNF) having adequate redispersibility, and a method with which it is possible to improve the redispersibility of CNF. The present invention pertains to: a method for producing dry CNF, the method including mixing anion-modified CNF and a redispersibility-improving agent to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension to obtain dry CNF, the redispersibility-improving agent being a water-soluble nonionic surfactant; and a method for improving the redispersibility of CNF, the method including mixing anion-modified CNF and a redispersibility-improving agent to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension, the redispersibility-improving agent being a water-soluble nonionic surfactant.

Description

Method for producing dry cellulose nanofiber

The present disclosure relates to a method for producing dry cellulose nanofibers and a method for improving the redispersibility of dry cellulose nanofibers.

Cellulose nanofiber (CNF) is a plant-derived fiber refined to a fiber diameter of about several nm to several hundred nm. CNF has a small environmental load and has various characteristics such as light weight, high strength, high gas barrier property, small dimensional deformation due to heat, high specific surface area, high permeability, and high viscosity in water. For this reason, CNF is expected to be used not only in automobile parts and food packaging materials but also in a wide range of fields such as foods, pharmaceuticals and cosmetics.

CNF is usually produced as a low concentration aqueous dispersion (wet state). However, in the case of an aqueous dispersion, there are problems such as high transportation and storage costs and contamination with bacteria. For this reason, a method of drying CNF has been proposed (for example, Patent Document 1).

WO2015 / 107995

The dried CNF is usually used after being redispersed in a dispersion medium such as water. When performing this redispersion, there may be a problem that CNF is not sufficiently redispersed. In particular, among the dried CNFs, there is a problem that the redispersibility of dried anion-modified CNF, particularly 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) oxidized CNF is low. For this reason, a new method capable of drying CNF while maintaining sufficient redispersibility is demanded.

In one aspect, the present disclosure provides a method for producing dry CNF with improved redispersibility and a method capable of improving the redispersibility of CNF.

In one aspect, the present disclosure provides an aqueous suspension of anion-modified cellulose nanofibers by mixing an anion-modified cellulose nanofiber and a redispersibility improver, and drying the aqueous suspension to dry cellulose. The method for producing dry cellulose nanofibers, comprising obtaining nanofibers, wherein the redispersibility improving agent is a water-soluble nonionic surfactant.

In one aspect, the present disclosure includes mixing an anion-modified cellulose nanofiber and a redispersibility improver to obtain an aqueous suspension of the anion-modified cellulose nanofiber, and drying the aqueous suspension. The redispersibility improving agent relates to a method for improving the redispersibility of cellulose nanofiber, which is a water-soluble nonionic surfactant.

The present disclosure, in one aspect, relates to a redispersibility improving agent containing a water-soluble nonionic surfactant, which is an agent for improving or improving the redispersibility of dry cellulose nanofibers in an aqueous dispersion medium.

In one aspect, the present disclosure relates to a dry composition including an anion-modified cellulose nanofiber and a redispersibility improver, wherein the redispersibility improver includes a water-soluble nonionic surfactant.

According to the present disclosure, it is possible to provide a method for producing dry CNF with improved redispersibility and a method capable of improving the redispersibility of CNF. According to the present disclosure, it is preferable to provide a method for producing dry TEMPO-oxidized CNF having improved redispersibility and a method capable of improving the redispersibility of dry TEMPO-oxidized CNF. In addition, according to the present disclosure, it is possible to provide a method for producing dry carboxymethyl (CM) -modified CNF having improved dispersibility during re-dispersion and a method capable of improving the dispersibility during re-dispersion of dry C-merized CNF. Further, according to the present disclosure, it is possible to provide a method for producing dry phosphate esterified CNF having improved dispersibility during redispersion and a method capable of improving the dispersibility during redispersion of dry phosphate ester CNF.

In the present disclosure, by drying an aqueous suspension obtained by mixing an anion-modified CNF and a water-soluble nonionic surfactant, the redispersibility of the obtained dry CNF is improved, and the obtained dry CNF is dispersed in water or the like. This is based on the knowledge that a dry CNF re-dispersion with improved dispersibility can be obtained by contacting with a medium.

This disclosure is based on the finding that a water-soluble nonionic surfactant can be used as a redispersibility improving agent when redispersing dry CNF.

In one or a plurality of embodiments, as “improvement or improvement of redispersibility” in the present disclosure, a dispersion obtained by mixing dry CNF obtained by the dry CNF production method of the present disclosure with a dispersion medium ( Or a suspension) is obtained by mixing an anion-modified CNF in a state dispersed in water (wet state) as it is (without adding a chemical agent) and a dispersion medium. Compared with the dispersion (or suspension), it means that the turbidity is low or the amount of undispersed CNF pieces or gelled products is small. According to the dry CNF obtained by the dry CNF production method of the present disclosure, in one or a plurality of embodiments, when redispersed in a dispersion medium such as water, the CNF is at a level close to a microfibril unit or a microfibril unit. It can be separated and redispersed.

[Anion-modified CNF]
In the present disclosure, “anion-modified CNF” refers to cellulose nanofibers obtained by chemically treating cellulose, and more specifically, nanofibers are obtained by fibrillating cellulose fibers whose fiber surfaces are chemically treated. It refers to fine fibers (nanofibers). In one or a plurality of embodiments, the anion-modified CNF in the present disclosure has a charge on the surface of the cellulose fiber by chemical treatment. In one or a plurality of embodiments, the anion-modified CNF in the present disclosure does not include naturally-derived cellulose nanofibers such as bacterial cellulose produced from bacteria.

Examples of the chemical treatment include carboxymethyl (CM) treatment, carboxylation (oxidation) treatment, phosphate esterification treatment and the like in one or a plurality of embodiments.

[Carboxymethyl (CM)]
Examples of the method for carboxymethylation of the cellulose raw material or the defibrated cellulose fiber include a method in which cellulose as a bottoming raw material is mercerized and then etherified. In the carboxymethylation reaction, a solvent is usually used. Examples of the solvent include water, alcohol (eg, lower alcohol), and mixed solvents thereof. Specific examples of the lower alcohol include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, isobutanol, and tertiary butanol. As for the mixing ratio of the lower alcohol in the mixed solvent, the lower limit is usually 60% by weight or more, and the upper limit is usually 95% by weight or less, preferably 60% by weight to 95% by weight. The amount of the solvent is usually 3 times or more by weight based on the cellulose raw material or defibrated cellulose fiber. Moreover, although the upper limit of the quantity of a solvent is not specifically limited, Usually, it is 20 weight times or less with respect to a cellulose raw material or a defibrated cellulose fiber. Therefore, the amount of the solvent is preferably 3 to 20 times by weight with respect to the cellulose raw material or defibrated cellulose fiber.

Mercerization is usually performed by mixing a cellulose raw material or defibrated cellulose fiber and a mercerizing agent. Examples of mercerizing agents include alkali metal hydroxides (eg, sodium hydroxide, potassium hydroxide).

The lower limit of the amount of the mercerizing agent used is usually 0.5 times mol or more per anhydroglucose residue of cellulose raw material or defibrated cellulose fiber. Moreover, an upper limit is 20 times mole or less normally. Therefore, the amount of the mercerizing agent used is preferably 0.5 to 20 times mol per anhydroglucose residue of the cellulose raw material or defibrated cellulose fiber.

The lower limit of the mercerization reaction temperature is usually 0 ° C or higher, preferably 10 ° C or higher. The upper limit is usually 70 ° C. or lower, preferably 60 ° C. or lower. Therefore, the reaction temperature for mercerization is usually 0 ° C. to 70 ° C., preferably 10 ° C. to 60 ° C.

The lower limit of the mercerization reaction time is usually 15 minutes or longer, preferably 30 minutes or longer. The lower limit is usually 8 hours or less, preferably 7 hours or less. Therefore, the reaction time for mercerization is usually 15 minutes to 8 hours, preferably 30 minutes to 7 hours.

The etherification reaction is usually performed by adding a carboxymethylating agent to the reaction system after mercerization. Examples of the carboxymethylating agent include sodium monochloroacetate.

The lower limit of the addition amount of the carboxymethylating agent is usually 0.05 times mole or more per glucose residue of the cellulose raw material or defibrated cellulose fiber. The upper limit is usually 10.0 times mol or less. Accordingly, the addition amount of the carboxymethylating agent is usually 0.05 times to 10.0 times moles per glucose residue of the cellulose raw material or defibrated cellulose fiber. The lower limit of the etherification reaction temperature is usually 30 ° C or higher, preferably 40 ° C or higher. An upper limit is 90 degrees C or less normally, Preferably it is 80 degrees C or less. Accordingly, the reaction temperature for etherification is usually 30 ° C. to 90 ° C., preferably 40 ° C. to 80 ° C.

The lower limit of the etherification reaction time is usually 30 minutes or longer, preferably 1 hour or longer. The upper limit is usually 10 hours or less, preferably 4 hours or less. Therefore, the reaction time for etherification is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours.

As a measuring method of the carboxymethyl substitution degree per glucose unit of carboxymethylated cellulose fiber or carboxymethylated cellulose nanofiber, for example, it can be obtained by the following method. That is, 1) About 2.0 g of carboxymethylated cellulose fiber or carboxymethylated cellulose nanofiber (absolutely dried) is precisely weighed and placed in a 300 mL conical stoppered Erlenmeyer flask. 2) Add 100 mL of special concentrated nitric acid solution to 1000 mL of methanol, add 100 mL of methanol solution of nitric acid, and shake for 3 hours to convert carboxymethyl cellulose salt (CM-modified cellulose salt: eg Na-CMC) into H-CM-converted cellulose. (H-CMC). 3) Weigh accurately 1.5 to 2.0 g of H-CM-modified cellulose (absolutely dry) and place in a 300 mL Erlenmeyer flask with a stopper. 4) Wet the H-CM cellulose with 15 mL of 80% methanol, add 100 mL of 0.1N NaOH, and shake at room temperature for 3 hours. 5) Back titrate excess NaOH with 0.1N H ₂ SO ₄ using phenolphthalein as indicator. 6) The degree of carboxymethyl substitution (DS) is calculated by the following formula:
A = [(100 × F ′ − (0.1 N H ₂ SO ₄ ) (mL) × F) × 0.1] / (absolute dry mass of H-CCM cellulose (g))
DS = 0.162 × A / (1-0.058 × A)
A: Amount of 1N NaOH required for neutralizing 1 g of H-CM cellulose (mL)
F ′: Factor of 0.1N NaOH F: Factor of 0.1N H ₂ SO ₄

In the present disclosure, “carboxymethylated cellulose”, which is a kind of modified cellulose used for the preparation of modified CNF, means that at least a part of the fibrous shape is maintained even when dispersed in water. Therefore, it is distinguished from carboxymethyl cellulose (CMC) which is a kind of water-soluble polymer described later. When an aqueous dispersion of “carboxymethylated cellulose” is observed with an electron microscope, a fibrous substance can be observed. On the other hand, even when an aqueous dispersion of carboxymethyl cellulose, which is a kind of water-soluble polymer, is observed, a fibrous substance is not observed. In addition, “carboxymethylated cellulose” can observe the peak of cellulose I-type crystals when measured by X-ray diffraction, but cellulose I-type crystals are not observed in the water-soluble polymer carboxymethylcellulose.

[Carboxylation]
In the present disclosure, when carboxylated (oxidized) cellulose is used as the modified cellulose, carboxylated cellulose (also referred to as oxidized cellulose) can be obtained by carboxylating (oxidizing) the above cellulose raw material by a known method. . Although not particularly limited, at the time of carboxylation, the amount of carboxyl groups should be adjusted to 0.6 mmol / g to 2.0 mmol / g with respect to the absolute dry mass of anion-modified CNF. It is preferable to adjust the concentration to 1.0 mmol / g to 2.0 mmol / g.

As an example of a carboxylation (oxidation) method, a cellulose raw material is oxidized in water using an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromide, iodide, or a mixture thereof. A method can be mentioned. By this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, and the cellulose fiber having an aldehyde group and a carboxyl group (—COOH) or carboxylate group (—COO—) on the surface. Can be obtained. The concentration of cellulose during the reaction is not particularly limited, but is preferably 5% by mass or less.

N-oxyl compound refers to a compound capable of generating a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it promotes the target oxidation reaction. Examples include 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and its derivatives (eg, 4-hydroxy TEMPO).

The amount of N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulose as a raw material. For example, with respect to 1 g of absolutely dry cellulose, 0.01 mmol to 10 mmol is preferable, 0.01 mmol to 1 mmol is more preferable, and 0.05 mmol to 0.5 mmol is more preferable. Further, about 0.1 to 4 mmol / L is preferable for the reaction system.

Bromide is a compound containing bromine, and examples thereof include alkali metal bromide that can be dissociated and ionized in water. Further, an iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used can be selected as long as the oxidation reaction can be promoted. The total amount of bromide and iodide is, for example, preferably from 0.1 mmol to 100 mmol, more preferably from 0.1 mmol to 10 mmol, and even more preferably from 0.5 mmol to 5 mmol with respect to 1 g of absolutely dry cellulose.

As the oxidizing agent, known ones can be used, and for example, halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, peroxide and the like can be used. Of these, sodium hypochlorite is preferable because it is inexpensive and has a low environmental impact. The amount of the oxidizing agent used is, for example, preferably 0.5 mmol to 500 mmol, more preferably 0.5 mmol to 50 mmol, further preferably 1 mmol to 25 mmol, and most preferably 3 mmol to 10 mmol with respect to 1 g of absolutely dry cellulose. Further, for example, 1 to 40 mol is preferable with respect to 1 mol of the N-oxyl compound.

The carboxylation (oxidation) of cellulose allows the reaction to proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 ° C. to 40 ° C., and may be room temperature of about 15 ° C. to 30 ° C. As the reaction proceeds, a carboxyl group is generated in the cellulose, so that the pH of the reaction solution is reduced. In order to make the oxidation reaction proceed efficiently, an alkaline solution such as an aqueous sodium hydroxide solution is added to maintain the pH of the reaction solution at about 8 to 12, preferably about 10 to 11. The reaction medium is preferably water because it is easy to handle and hardly causes side reactions.

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

Moreover, the oxidation reaction may be carried out in two stages. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first-stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt generated as a by-product in the first-stage reaction. Can be oxidized well.

Another example of the carboxylation (oxidation) method is a method of oxidizing by contacting a gas containing ozone and a cellulose raw material. By this oxidation reaction, at least the 2-position and 6-position hydroxyl groups of the glucopyranose ring are oxidized and the cellulose chain is decomposed. The ozone concentration in the gas containing ozone is preferably 50 g / m ³ to 250 g / m ³ , and more preferably 50 g / m ³ to 220 g / m ³ . The amount of ozone added to the cellulose raw material is preferably 0.1 parts by mass to 30 parts by mass, and more preferably 5 parts by mass to 30 parts by mass when the solid content of the cellulose raw material is 100 parts by mass. . The ozone treatment temperature is preferably 0 ° C. to 50 ° C., more preferably 20 ° C. to 50 ° C. The ozone treatment time is not particularly limited, but is about 1 minute to 360 minutes, preferably about 30 minutes to 360 minutes. When the conditions for the ozone treatment are within these ranges, the cellulose can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved. After the ozone treatment, an additional oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used for the additional oxidation treatment is not particularly limited, and examples thereof include chlorine compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. For example, these oxidizing agents can be dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and a cellulose raw material can be immersed in the solution for additional oxidation treatment.

The amount of carboxyl groups in the oxidized cellulose can be adjusted by controlling the reaction conditions such as the amount of the oxidant added and the reaction time.

[Phosphate esterification]
As the modified cellulose, phosphorylated cellulose can be used. The said cellulose is obtained by the method of mixing the powder and aqueous solution of phosphoric acid type compound A with a cellulose raw material, and the method of adding the aqueous solution of phosphoric acid type compound A to the slurry of a cellulose raw material.

Examples of the phosphoric acid compound A include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. These may be in the form of salts. Among these, a compound having a phosphate group is preferable because it is low in cost, easy to handle, and can improve the fibrillation efficiency by introducing a phosphate group into cellulose of the pulp fiber. Compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phosphorus Examples include tripotassium acid, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, and the like. These can be used alone or in combination of two or more. Among these, phosphoric acid, phosphoric acid sodium salt, phosphoric acid potassium salt, phosphoric acid, from the viewpoint that phosphoric acid group introduction efficiency is high, is easy to be defibrated in the following defibrating process, and is industrially applicable. The ammonium salt is more preferred. In particular, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferred. In addition, the phosphoric acid compound A is preferably used as an aqueous solution because the uniformity of the reaction is enhanced and the efficiency of introduction of phosphate groups is increased. The pH of the aqueous solution of the phosphoric acid compound A is preferably 7 or less because of the high efficiency of introducing phosphate groups, but is preferably pH 3 to 7 from the viewpoint of suppressing hydrolysis of pulp fibers.

The following method can be mentioned as an example of the manufacturing method of phosphoric ester cellulose. Phosphoric acid compound A is added to a cellulose raw material dispersion having a solid content concentration of 0.1% by mass to 10% by mass with stirring to introduce phosphate groups into the cellulose. When the cellulose raw material is 100 parts by mass, the addition amount of the phosphoric acid compound A is preferably 0.2 to 500 parts by mass, preferably 1 to 400 parts by mass as the amount of phosphorus element. Is more preferable. If the ratio of the phosphoric acid type compound A is more than the said lower limit, the yield of a fine fibrous cellulose can be improved more. However, if the upper limit is exceeded, the effect of improving the yield reaches its peak, which is not preferable from the viewpoint of cost.

At this time, in addition to the cellulose raw material and the phosphoric acid compound A, powders and aqueous solutions of other compounds B may be mixed. Compound B is not particularly limited, but a nitrogen-containing compound showing basicity is preferable. “Basic” as used herein is defined as an aqueous solution exhibiting a pink to red color in the presence of a phenolphthalein indicator, or an aqueous solution having a pH greater than 7. The basic nitrogen-containing compound used in the present disclosure is not particularly limited as long as the effect of the present disclosure is exhibited, but a compound having an amino group is preferable. For example, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like can be mentioned, but not particularly limited. Among these, urea which is easy to handle at low cost is preferable. The amount of compound B added is preferably 2 parts by mass to 1000 parts by mass, and more preferably 100 parts by mass to 700 parts by mass with respect to 100 parts by mass of the solid content of the cellulose raw material. The reaction temperature is preferably 0 ° C. to 95 ° C., more preferably 30 ° C. to 90 ° C. The reaction time is not particularly limited, but is about 1 to 600 minutes, more preferably 30 to 480 minutes. When the conditions of the phosphoric esterification reaction are within these ranges, it is possible to prevent the cellulose from being excessively phosphorylated and easily dissolved, and the yield of phosphorylated esterified cellulose is improved. From the viewpoint of suppressing hydrolysis of cellulose, it is preferable to heat-treat the obtained phosphoric esterified cellulose suspension at 100 ° C. to 170 ° C. Further, while water is contained in the heat treatment, it is preferably heated at 130 ° C. or lower, preferably 110 ° C. or lower, after removing water, it is preferably heat treated at 100 ° C. to 170 ° C.

The phosphate group substitution degree per glucose unit of the phosphorylated cellulose is preferably 0.001 to 0.40. By introducing a phosphate group substituent into cellulose, the celluloses are electrically repelled. For this reason, the cellulose which introduce | transduced the phosphate group can be nano-defibrated easily. In addition, when the phosphate group substitution degree per glucose unit is smaller than 0.001, nano-defibration cannot be sufficiently performed. On the other hand, if the degree of phosphate group substitution per glucose unit is greater than 0.40, it may swell or dissolve, and may not be obtained as a nanofiber. In order to perform defibration efficiently, it is preferable that the phosphoric esterified cellulose raw material obtained above is washed by boiling water and then washing with cold water.

[Defibration]
In the present disclosure, an apparatus for defibrating is not particularly limited, but a strong shearing force is applied to the aqueous dispersion of the modified cellulose by using an apparatus such as a high-speed rotation type, a colloid mill type, a high-pressure type, a roll mill type, or an ultrasonic type. It is preferable to apply. In particular, for efficient defibration, it is preferable to use a wet high-pressure or ultrahigh-pressure homogenizer that can apply a pressure of 50 MPa or more to the aqueous dispersion and can apply a strong shearing force. The pressure is more preferably 100 MPa or more, and further preferably 140 MPa or more. In addition, prior to defibration / dispersion treatment with a high-pressure homogenizer, if necessary, the modified cellulose may be pretreated using a known mixing, stirring, emulsifying, and dispersing device such as a high-speed shear mixer. Is possible. The number of treatments (passes) in the defibrating device may be one time, two times or more, and preferably two times or more.

In the modified cellulose dispersion treatment, the modified cellulose is usually dispersed in a solvent. Although a solvent will not be specifically limited if a modified cellulose can be disperse | distributed, For example, water, organic solvents (for example, hydrophilic organic solvents, such as methanol), and those mixed solvents are mentioned. Since it uses for foodstuffs, it is preferred that a solvent is water.

The solid content concentration of the modified cellulose in the dispersion is usually 0.1% by weight or more, preferably 0.2% by weight or more, more preferably 0.3% by weight or more. Thereby, the liquid quantity with respect to the quantity of a cellulose fiber raw material becomes an appropriate quantity, and is efficient. The upper limit is usually 10% by weight or less, preferably 6% by weight or less. Thereby, fluidity | liquidity can be hold | maintained.

In the present disclosure, the fiber width of the anion-modified CNF is, in one or more embodiments, about 1 nm to 500 nm or 2 nm to 100 nm, preferably 1 nm to less than 20 nm, 2 nm to 15 nm, or 3 nm to 5 nm. . The average aspect ratio of anion-modified CNF is usually 100 or more. The upper limit of the average aspect ratio is not particularly limited, but is usually 1000 or less. The average aspect ratio can be calculated by the following formula:
Average aspect ratio = average fiber length / average fiber diameter

Examples of the cellulose raw material include plant materials, animal materials, and algae in one or more embodiments. In one or a plurality of embodiments, examples of the plant material include wood, bamboo, hemp, jute, kenaf, cloth, pulp, recycled pulp, and waste paper. Examples of the pulp include kraft pulp (KP), sulfate pulp (SP), dissolved sulfite pulp (DSP), dissolved kraft pulp (DKP), powdered cellulose, and microcrystalline cellulose powder in one or more embodiments. Examples of the animal material include squirts in one or a plurality of embodiments. The anion-modified CNF in the present disclosure does not include bacterial cellulose produced from bacteria and cellulose derived therefrom in one or more embodiments.

[Method for producing dry CNF]
In one aspect, the present disclosure includes mixing an anion-modified CNF and a redispersibility improver to obtain an aqueous suspension of the anion-modified CNF, and drying the aqueous suspension to obtain a dry CNF. The present invention relates to a method for producing dry CNF (a method for producing dry CNF of the present disclosure). According to the method for producing dry CNF of the present disclosure, in one or a plurality of embodiments, film-like dry CNF and / or powder-like dry CNF having sufficient redispersibility can be obtained. In one or a plurality of embodiments, the method for producing dry CNF of the present disclosure can be preferably used for TEMPO-oxidized CNF among anion-modified CNFs. According to the method for producing dry CNF of the present disclosure, in one or a plurality of embodiments, the redispersibility of a dried product of TEMPO-oxidized CNF (dry CNF) can be improved or improved.

Moreover, the manufacturing method of the dry CNF of this indication can be utilized for CCM CNF in one or some embodiment. According to the method for producing dry CNF of the present disclosure, in one or a plurality of embodiments, the dispersibility at the time of redispersion of the dried product of CCM CNF (dry CNF) can be improved or improved.
Moreover, the manufacturing method of the dry CNF of this indication can be utilized for phosphate esterified CNF in one or some embodiment. According to the method for producing dry CNF of the present disclosure, in one or a plurality of embodiments, it is possible to improve or improve the dispersibility during redispersion of the dried product (dried CNF) of phosphate esterified CNF.

According to the dry CNF manufacturing method of the present disclosure, in one or a plurality of embodiments, dry CNF with improved redispersibility can be obtained. The obtained dry CNF may have sufficient redispersibility in one or more embodiments that are not particularly limited. “Having sufficient redispersibility” means that, in one or a plurality of embodiments, it has redispersibility in an aqueous dispersion medium at the same level as that of an anion-modified CNF suspension before drying or at an inferior level. Is mentioned. In one or a plurality of embodiments, the obtained dry CNF is a variety of chemical products, foods, cosmetics, pharmaceuticals, beverages, reinforcing materials (including paper), heat insulating materials, automobile members, paints, agricultural chemicals, architecture, batteries, homes. It can be used for sundries, water treatment, cleaning agents, etc.

In the present disclosure, the term “water-soluble nonionic surfactant” means a nonion that dissolves in a transparent or cloudy state in one or a plurality of embodiments when mixed with water at 25 ° C. at a concentration of 1% or 5%. Refers to a surfactant.

In one or a plurality of embodiments, the HLB of the water-soluble nonionic surfactant is 10 or more, 12 or more, 14 or more, 16 or more, or 19.5 or less. In the present disclosure, “HLB (hydrophilic lipophilic balance)” can be calculated using a Griffin equation in one or a plurality of embodiments. In addition, as the HLB, a value described in a catalog or the like of a surfactant manufacturer can be used.

In one or more embodiments, the molecular weight of the water-soluble nonionic surfactant is 200 or more, 500 or more, or 1000 or more, or 5000 or less, 4000 or less, or 3000 or less.

Examples of the water-soluble nonionic surfactant include, in one or more embodiments, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene alkyl ether, sucrose fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene Examples include ethylene polyoxypropylene alkylamine, polyoxyethylene polyoxypropylene alkyl ether, or an ethylene oxide adduct of sorbitan fatty acid ester.

In one or a plurality of embodiments, the method for producing dry CNF according to the present disclosure includes mixing an anion-modified CNF in a wet state (dispersed in water) and a water-soluble nonionic surfactant. Thereby, an aqueous suspension containing an anion-modified CNF and a water-soluble nonionic surfactant can be obtained.

The blending ratio of the water-soluble nonionic surfactant to the anion-modified CNF (absolutely dry solid content, 100 parts by mass) is 5 parts by mass or more, 5 parts by mass to 500 parts by mass, and 5 parts by mass in one or more embodiments. 400 parts by weight, 5 parts by weight to 300 parts by weight or 10 parts by weight to 200 parts by weight, more preferably 30 parts by weight to 350 parts by weight or 30 parts by weight to 150 parts by weight.

When the anion-modified CNF is a carboxylated CNF such as TEMPO-oxidized CNF, the blending ratio of the water-soluble nonionic surfactant to the anion-modified CNF (absolutely dry solid content, 100 parts by mass) is one or more embodiments. 5 parts by weight or more, 5 parts by weight to 500 parts by weight, 5 parts by weight to 400 parts by weight, 5 parts by weight to 300 parts by weight, or 10 parts by weight to 200 parts by weight, preferably 30 parts by weight to 250 parts by weight or 45 parts by weight. Parts by mass to 150 parts by mass.

When the anion-modified CNF is C-modified CNF, the blending ratio of the water-soluble nonionic surfactant to the anion-modified CNF (absolutely dry solid content, 100 parts by mass) is 5 parts by mass or more in one or more embodiments, It is 10 to 500 parts by mass or 30 to 400 parts by mass, preferably 50 to 350 parts by mass or 75 to 350 parts by mass.

When the anion-modified CNF is phosphate esterified CNF, the mixing ratio of the water-soluble nonionic surfactant to the anion-modified CNF (absolutely dry solid content, 100 parts by mass) is 5 parts by mass in one or a plurality of embodiments. 5 parts by weight to 500 parts by weight, 5 parts by weight to 400 parts by weight, 5 parts by weight to 300 parts by weight or 10 parts by weight to 200 parts by weight, preferably 30 parts by weight to 250 parts by weight or 45 parts by weight. 150 parts by mass.

In one or a plurality of embodiments, the method for producing dry CNF of the present disclosure includes drying an aqueous suspension containing an anion-modified CNF and a nonionic surfactant. In one or more embodiments, the aqueous suspension may be dried by forming a thin film, or may be spray-dried. Thereby, a dry film and / or a dry powder containing an anion-modified CNF and a nonionic surfactant can be obtained.

In the present disclosure, the drying method of the aqueous suspension is not particularly limited, and in one or a plurality of embodiments, spray drying, air drying, hot air drying, vacuum drying, pressing, and the like can be given.

In one or a plurality of embodiments, the dry CNF obtained by the dry CNF production method of the present disclosure is added to 0.1 g of dry CNF refined to about 1 to 2 mm to 5 g of distilled water, and about 1 minute with a point mixer. After stirring, when left for about 24 hours at room temperature and then again stirred for about 1 minute with a point mixer, it has redispersibility at least at the same level as CNF before drying or at a comparable level.

The dry CNF obtained by the method for producing dry CNF according to the present disclosure may be a dry product, and in one or more embodiments, in the form of a film, from the viewpoint of further improving dispersibility in the dispersion medium to be redispersed. It may be in a powder form.

[Dry CNF]
In one aspect, the present disclosure relates to a dry CNF comprising a water-soluble nonionic surfactant and an anion-modified CNF (the dry CNF of the present disclosure). The dry CNF of this indication can be obtained by the manufacturing method of dry CNF of this indication in one or some embodiment. The dry CNF of the present disclosure is mainly composed of anion-modified CNF in one or more embodiments that are not particularly limited. In one or a plurality of embodiments, the dry CNF of the present disclosure may be in the form of a film or powder.

[Method for producing CNF redispersion]
In one aspect, the present disclosure relates to a method for producing a CNF redispersion (a method for producing a CNF redispersion of the present disclosure). In one or a plurality of embodiments, the method for producing a CNF redispersion of the present disclosure includes obtaining an aqueous suspension containing an anion-modified CNF and a redispersibility improving agent, drying the aqueous suspension, And redispersing the obtained dried product in a dispersion medium. In one or a plurality of embodiments, the method for producing a CNF redispersion liquid according to the present disclosure includes redispersing the dry CNF obtained by the method for producing a dry CNF according to the present disclosure in a dispersion medium. According to the method for producing a CNF redispersion of the present disclosure, in one or a plurality of embodiments, CNF redispersion having a level of dispersibility comparable to or comparable to an aqueous CNF suspension or an aqueous dispersion that does not pass through a dry state You can get things. In one or a plurality of embodiments, the redispersion may be a liquid or a gel.

Examples of the dispersion medium include an aqueous dispersion medium such as water in one or a plurality of embodiments. In one or a plurality of embodiments, the dispersion medium may contain various polymers other than CNF.

[Method for improving CNF redispersibility]
As described above, by drying the anion-modified CNF together with the redispersibility improving agent, the redispersibility of the obtained dry CNF can be improved or improved. Therefore, in another aspect, the present disclosure includes mixing an anion-modified CNF and a redispersibility improver to obtain an aqueous suspension of anion-modified cellulose nanofibers, and drying the aqueous suspension. The present invention relates to a method for improving redispersibility of CNF. According to the CNF redispersibility improving method of the present disclosure, in one or a plurality of embodiments, among the anion-modified CNFs, the redispersibility of the dried product of TEMPO-oxidized CNF, C-merized CNF, and phosphate-esterified CNF is further improved. Can be improved. The redispersibility improving agent and the blending ratio are the same as in the method for producing dry CNF of the present disclosure.

In one or a plurality of embodiments, the aqueous suspension may contain a third component other than the anion-modified CNF and the redispersibility improving agent during redispersion. Examples of the third component include a water-soluble polymer in one or a plurality of embodiments.

In one or a plurality of embodiments, the aqueous suspension can be dried in the same manner as the dry CNF production method of the present disclosure.

[Redispersibility improver]
In another aspect, the present disclosure relates to a redispersibility improver (redispersibility improver of the present disclosure) for improving or improving the redispersibility of dry cellulose nanofibers in an aqueous dispersion medium. The redispersibility improving agent of the present disclosure includes a water-soluble nonionic surfactant. In one or a plurality of embodiments, the redispersibility improving agent of the present disclosure can be used in the production of dry cellulose nanofibers having improved or improved redispersibility in an aqueous dispersion medium. The water-soluble nonionic surfactant is as described above.

[Dry composition]
In one aspect, the present disclosure provides a dry composition comprising an anion-modified cellulose nanofiber and a redispersibility improver, wherein the redispersibility improver comprises a water-soluble nonionic surfactant (present book). Also referred to as the disclosed dry composition).

In one or a plurality of embodiments, the proportion of the redispersibility improving agent in the dry composition of the present disclosure is 5% by mass or more, 5 to 500% by mass, 5 to 5% with respect to anion-modified CNF (absolutely dry solid content). It is 400% by mass, 5 to 300% by mass, or 20 to 300% by mass, 10 to 200% by mass, or 20 to 300% by mass, preferably 30 to 350% by mass or 30 to 150% by mass.

When the anion-modified CNF is TEMPO oxidized CNF, the proportion of the redispersibility improver in the dry composition of the present disclosure is 5 masses based on TEMPO oxidized CNF (absolutely dry solid content) in one or more embodiments. % Or more, 5 mass% to 500 mass%, 5 mass% to 400 mass%, 5 mass% to 300 mass%, or 10 mass% to 200 mass%, preferably 30 mass% to 250 mass% or 45 mass%. ~ 150% by weight.

When the anion-modified CNF is CCM CNF, the proportion of the redispersibility improver in the dry composition of the present disclosure is, in one or more embodiments, 5 masses per CCM CNF (absolutely dry solids). % Or more, 10 mass% to 500 mass%, or 30 mass% to 400 mass%, preferably 50 mass% to 350 mass%, or 75 mass% to 350 mass%.

When the anion-modified CNF is phosphate esterified CNF, the proportion of the redispersibility improver in the dry composition of the present disclosure is, in one or more embodiments, based on phosphate esterified CNF (absolutely dry solids). 5 mass% or more, 5 mass% to 500 mass%, 5 mass% to 400 mass%, 5 mass% to 300 mass%, or 10 mass% to 200 mass%, preferably 30 mass% to 250 mass%. Or 45 mass% to 150 mass%.

In one or a plurality of embodiments, the dry composition of the present disclosure may include a third component other than the anion-modified CNF and the redispersibility improving agent. Examples of the third component include a water-soluble polymer in one or a plurality of embodiments.

In one or more embodiments, the dry composition of the present disclosure may be a film, a solid, or a powder. The film thickness of the dry composition of this indication is 50 micrometers or more or 100 micrometers or more, or 1000 micrometers or less or 300 micrometers or less in one or some embodiment.

In one or a plurality of embodiments, the dry composition of the present disclosure may be produced by mixing an anion-modified CNF and a redispersibility improver, and, if necessary, the third component and drying it. Alternatively, the dry CNF of the present disclosure and the third component may be mixed and dried.

The present disclosure further relates to one or more of the following embodiments.
[1] An anion-modified CNF and a redispersibility improver are mixed to obtain an aqueous suspension of the anion-modified CNF, and the aqueous suspension is dried to obtain a dry CNF.
The redispersibility improving agent is a water-soluble nonionic surfactant, and a method for producing dry CNF [2] The anion-modified CNF is carboxylated CNF, C-converted CNF, or phosphate esterified cellulose nanofiber, [1] The method for producing dry CNF according to [1].
[3] including mixing an anion-modified CNF and a redispersibility improver to obtain an aqueous suspension of the anion-modified CNF, and drying the aqueous suspension.
The method for improving redispersibility of CNF, wherein the redispersibility improver is a water-soluble nonionic surfactant.
[4] The method for improving redispersibility according to [3], wherein the anion-modified CNF is carboxylated CNF, CCM CNF, or phosphate ester CNF.
[5] An agent for improving or improving the redispersibility of dry CNF in an aqueous dispersion medium, which comprises a water-soluble nonionic surfactant.
[6] A dry composition comprising an anion-modified CNF and a redispersibility improver,
The dry composition in which the redispersibility improving agent contains a water-soluble nonionic surfactant.
[7] The composition according to [6], wherein the anion-modified CNF is carboxylated CNF, CCM CNF, or phosphate ester CNF.

Hereinafter, the present disclosure will be further described using examples and comparative examples. However, the present disclosure is not construed as being limited to the following examples.

[Production of carboxylated cellulose nanofiber (anion-modified CNF1)]
Bleached unbeaten kraft pulp derived from conifers (whiteness 85%), 5.00 g (absolutely dry), 39 mg of TEMPO (Sigma Aldrich) and 0.05 mmol of sodium bromide (absolutely dry) The solution was added to 500 ml of an aqueous solution in which 1.0 mmol) was dissolved in 1 g of cellulose, and stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system so that sodium hypochlorite was 5.5 mmol / g, and the oxidation reaction was started at room temperature. During the reaction, the pH in the system was lowered, but a 3M sodium hydroxide aqueous solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system no longer changed.
The reaction mixture was filtered through a glass filter to separate the pulp, and the pulp was sufficiently washed with water to obtain oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol / g. This was adjusted to a pulp solid content of 1.1% (w / v) with water, treated three times with an ultra-high pressure homogenizer (20 ° C., 150 Mpa), and carboxylated cellulose nanofiber (hereinafter referred to as T-CNF). An aqueous dispersion was obtained. The average fiber diameter was 3 nm and the aspect ratio was 250.

[Production of Carboxymethylated Cellulose Nanofiber (Anion-Modified CNF2)]
In a stirrer capable of mixing pulp, 200 g dry needle bleached kraft pulp (manufactured by Nippon Paper Industries Co., Ltd.) and 111 g sodium hydroxide dry mass (2.25 times mol per anhydroglucose residue of the bottoming material) In addition, water was added so that the pulp solid content was 20% (w / v). Thereafter, after stirring at 30 ° C. for 30 minutes, 216 g of sodium monochloroacetate (in terms of active ingredient, 1.5 times mol per glucose residue of pulp) was added. After stirring for 30 minutes, the temperature was raised to 70 ° C. and stirred for 1 hour. Thereafter, the reaction product was taken out, neutralized and washed to obtain a carboxymethylated pulp having a carboxymethyl substitution degree of 0.25 per glucose unit. The pulp solid content is 1.2% (w / v) with water, and the fiber is fibrillated by treating with a high-pressure homogenizer five times at 20 ° C. and a pressure of 150 MPa. The carboxymethylated cellulose nanofiber (hereinafter referred to as CM-CNF) ) The average fiber diameter was 12 nm and the aspect ratio was 130.

[Production of Phosphate Ester Cellulose Nanofiber (Anion-Modified CNF3)]
6.75 g of sodium dihydrogen phosphate dihydrate and 4.83 g of disodium hydrogen phosphate are dissolved in 19.62 g of water to obtain an aqueous solution of a phosphoric acid compound (hereinafter referred to as “phosphorylation reagent”). It was. Water is added to unbleached kraft pulp (NUKP, moisture 80%, Canadian standard freeness (CSF) 580 ml measured according to JIS P8121) so that the pulp solid content is 4% (w / v). It was. After that, using a double disc refiner, it was beaten until an irregular CSF (plain mesh 80 mesh, according to JIS P8121 except that the amount of pulp collected was 0.3 g) was 200 ml, and the length average fiber length was 0.66 mm. The cellulose suspension thus obtained was diluted to a pulp solid content of 0.3% (w / v), and a pulp sheet (thickness 200 μm) having a moisture content of 90% and a solid content (absolute dry mass) of 3 g was obtained by a papermaking method. It was. This pulp sheet was immersed in 31.2 g of the phosphorylating reagent (80 parts by mass as the amount of phosphorus element with respect to 100 parts by mass of the dried pulp), and heated for 1 hour with an air dryer at 105 ° C. (Yamato Scientific Co., Ltd. DKM400) Further, heat treatment was performed at 150 ° C. for 1 hour to introduce phosphate groups into the cellulose fibers. Subsequently, 500 ml of ion-exchanged water was added to the pulp sheet in which the phosphate group was introduced into the cellulose fiber, and the mixture was dehydrated after washing with stirring. The dehydrated sheet was diluted with 300 ml of ion-exchanged water, and 5 ml of 1N aqueous sodium hydroxide solution was added little by little with stirring to obtain a cellulose suspension having a pH of 12 to 13. Thereafter, the cellulose suspension was dehydrated and washed by adding 500 ml of ion exchange water. This dehydration washing was repeated two more times. Ion exchange water was added to the sheet obtained after washing and dehydration, and the mixture was stirred to obtain a 0.5 mass% cellulose suspension. This cellulose suspension was defibrated for 30 minutes using a defibrating apparatus (Cleamix-2.2S, manufactured by M Technique Co., Ltd.) at 21500 rpm, and defibrated cellulose (phosphate ester) Cellulose nanofiber) suspension was obtained. When the cellulose contained in the defibrated cellulose suspension was observed with a transmission electron microscope, it was confirmed that fine fibrous cellulose having a width of 4 nm was contained. Moreover, it was confirmed by X-ray diffraction that the cellulose maintained the cellulose I type crystal. Further, the infrared absorption spectrum was measured by FT-IR. Absorption based on phosphate groups was observed at 1230 cm ⁻¹ to 1290 cm ⁻¹ , confirming the addition of phosphate groups. The amount of phosphate group introduced at this time was 2.1 mmol / g per 1 g (mass) of fine fibrous cellulose.

Example 1
Using the chemicals shown in Table 1, production of dry anion-modified CNF (dry CNF) and redispersibility of dry CNF were evaluated. As the anion-modified CNF, anion-modified CNF1 (T-CNF, average fiber width: 3 nm, aspect ratio: 250) was used.

[Production of dry CNF]
The drugs shown in Table 1 were added as powders to an aqueous suspension of anion-modified CNF1 in a 1% (w / v) solid content of the pack. The chemical | medical agent was added so that it might become the quantity (mass part) of Table 1 with respect to 100 mass parts of CNFs. The chemicals used in the examples in Table 1 were both water-soluble because they were dissolved in a clear or cloudy state when mixed with 25 ° C. water at a concentration of 1% or 5%.
The drug was added in an amount equivalent to the CNF solid content in the suspension. Subsequently, the mixture was stirred and mixed until it became transparent with a stirrer or a point mixer. The obtained liquid was applied on a Teflon (trademark) plate or a Teflon (trademark) dish, and dried with hot air of 60 ° C. to 105 ° C. to obtain a film-like dry CNF.
The blank was the same as above except that no drug was added.

[Redispersion of dry CNF]
The film-like dry CNF was refined by hand to about 1 mm to 2 mm, and 0.1 g was weighed into a test tube. Distilled water (5 g) was added, the mixture was stirred for about 1 minute with a point mixer, and then allowed to stand at room temperature for about 24 hours. This was again stirred with a point mixer for about 1 minute to obtain an aqueous dispersion or aqueous suspension in which anion-modified CNF was redispersed (solid content concentration 2% (w / v)).

[Evaluation of redispersibility]
The redispersibility of the aqueous dispersion or suspension in the test tube was evaluated visually. Evaluation was performed based on the following evaluation criteria. The results are shown in Table 1 below.
<Evaluation criteria>
A: Undispersed CNF pieces are not completely recognized B: Fine undispersed CNF pieces are observed in a very small amount C: No CNF dispersion is observed

As shown in Table 1, in the comparative examples dried together with anionic, cationic and amphoteric drugs, the obtained dry CNF could not be dispersed. On the other hand, in the example dried with the water-soluble nonionic surfactant, it was confirmed that the obtained dry CNF could be dispersed and the redispersibility was improved.
Moreover, undispersed CNF was confirmed in the blank and the comparative example. On the other hand, in the test tubes of the Examples, almost no undispersed CNF precipitates or undispersed gel-like substances were observed. In particular, in the test tube having an evaluation of redispersibility of A, no undispersed CNF precipitate or undispersed gel was confirmed. Moreover, all the nonionic chemical | medical agents used in the Example showed high solubility with respect to water.

[Evaluation of refilming and gelation]
The aqueous dispersion evaluated as A or B in the evaluation of redispersibility in Table 1 was evaluated for refilming and gelation.
Refilming was performed by weighing about 2 g of an aqueous dispersion (redispersion) on a Teflon (trademark) plate and sufficiently drying with hot air of 70 ° C. to 80 ° C. Gelation was performed by adding a few drops of a 20% calcium chloride solution into a test tube containing an aqueous dispersion (redispersion).
As a result, both formed a film and a gel. That is, it was suggested that the physical properties of dry CNF obtained by the production method of the present disclosure are not significantly different from those of untreated (before drying treatment) anion-modified CNF.

(Example 2)
Using the chemicals shown in Table 2, anion-modified CNF2 (CM-CNF, average fiber width: 12 nm, aspect ratio: 130 or more) was used as anion-modified CNF. The redispersibility was evaluated. The results are shown in Table 2.

As shown in Table 2, it was confirmed that by drying CCM CNF together with a water-soluble nonionic surfactant, it was possible to disperse the obtained dry CNF and further improve redispersibility.

Claims

Mixing an anion-modified cellulose nanofiber and a redispersibility improver to obtain an aqueous suspension of the anion-modified cellulose nanofiber, and drying the aqueous suspension to obtain a dry cellulose nanofiber,
The method for producing dry cellulose nanofibers, wherein the redispersibility improving agent is a water-soluble nonionic surfactant.
The method for producing dry cellulose nanofibers according to claim 1, wherein the anion-modified cellulose nanofibers are carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers or phosphate esterified cellulose nanofibers.
Mixing an anion-modified cellulose nanofiber and a redispersibility improver to obtain an aqueous suspension of the anion-modified cellulose nanofiber, and drying the aqueous suspension,
The method for improving redispersibility of cellulose nanofibers, wherein the redispersibility improver is a water-soluble nonionic surfactant.
The method for improving redispersibility according to claim 3, wherein the anion-modified cellulose nanofiber is a carboxylated cellulose nanofiber, a carboxymethylated cellulose nanofiber or a phosphate esterified cellulose nanofiber.
A redispersibility improving agent containing a water-soluble nonionic surfactant for improving or improving the redispersibility of dry cellulose nanofibers in an aqueous dispersion medium.
A dry composition comprising an anion-modified cellulose nanofiber and a redispersibility improver,
The composition wherein the redispersibility improving agent comprises a water-soluble nonionic surfactant.
The composition according to claim 6, wherein the anion-modified cellulose nanofiber is a carboxylated cellulose nanofiber, a carboxymethylated cellulose nanofiber, or a phosphate esterified cellulose nanofiber.