JP7270194B2 - METHOD FOR MANUFACTURING DRY CELLULOSE NANOFIBER - Google Patents

Description

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

Cellulose nanofibers (CNF) are plant-derived fibers that are miniaturized to a fiber diameter of about several nanometers to several hundreds of nanometers. CNF has various characteristics such as low environmental impact, light weight, high strength, high gas barrier properties, small dimensional deformation due to heat, high specific surface area, high transparency, and high viscosity in water. For this reason, CNF is expected to be used in a wide range of fields such as not only automobile parts and food packaging materials, but also foods, medicines and cosmetics.

CNF is usually manufactured as a low-concentration aqueous dispersion (wet state). However, in the case of aqueous dispersions, there are problems such as high transportation and storage costs, contamination by bacteria, and the like. For this reason, methods for drying CNF have been proposed (for example, Patent Document 1, etc.).

WO2015/107995

The dried CNF is usually used after being redispersed in a dispersion medium such as water. In performing this redispersion, there may be a problem that the CNF is not sufficiently redispersed. In particular, the CNF obtained by drying the transparent CNF solution, especially the anion-modified CNF dried, especially the 2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) oxidized CNF has low redispersibility and transparency. I have a problem with not recovering. Therefore, there is a need for a new method that can dry CNF while maintaining sufficient redispersibility.

In one aspect, the present disclosure provides a method for producing dry CNF with improved redispersibility, in particular, a method for producing dry CNF with improved transparent dispersibility upon redispersion. The present disclosure, in one aspect, provides a method capable of improving the redispersibility of CNF. The present disclosure also provides, in one aspect, a method that can improve the clear dispersion upon redispersion of dry TEMPO-oxidized CNF. The “transparent dispersibility at the time of redispersion” in the present disclosure means that, in one or more embodiments, CNF is dispersed in a dispersion medium at a level close to microfibril units or microfibril units, and is dispersed in a highly transparent state. Say things.

In one aspect, the present disclosure includes mixing anionically modified cellulose nanofibers and a redispersibility improver to obtain an aqueous suspension of anionically modified cellulose nanofibers, and drying the aqueous suspension to produce dried cellulose. Dry cellulose nanofibers, including obtaining nanofibers, wherein the redispersibility improver is selected from the group consisting of sugars having a molecular weight of 50,000 or less, low-molecular-weight polypeptides, amino acids, and low-molecular-weight polyvinyl alcohols. related to the manufacturing method of

In one aspect, the present disclosure includes mixing anion-modified cellulose nanofibers and a redispersibility improver to obtain an aqueous suspension of anion-modified cellulose nanofibers, and drying the aqueous suspension. , The redispersibility improving agent is selected from the group consisting of saccharides having a molecular weight of 50,000 or less, low molecular weight polypeptides, amino acids, and low molecular weight polyvinyl alcohol.

In one aspect, the present disclosure is an agent for improving or improving the redispersibility of dry cellulose nanofibers in a dispersion medium, particularly the redispersibility, comprising a sugar having a molecular weight of 50,000 or less, a low molecular weight poly It relates to a redispersibility improver containing at least one selected from the group consisting of peptides, amino acids, and low-molecular-weight polyvinyl alcohols.

In one aspect, the present disclosure is a dry composition containing anion-modified cellulose nanofibers and a redispersibility improver, wherein the redispersibility improver comprises a saccharide having a molecular weight of 50,000 or less, a low molecular weight polypeptide, A dry composition comprising at least one selected from the group consisting of amino acids and low molecular weight polyvinyl alcohol.

According to the present disclosure, it is possible to provide a method for producing dry CNF with improved redispersibility, particularly a method for producing dry CNF with improved transparent dispersibility during redispersion. In addition, according to the present disclosure, it is possible to provide a method capable of improving or improving the redispersibility of CNF, particularly a method capable of improving or improving the transparent dispersibility at the time of redispersion. According to the present disclosure, preferably, it is possible to provide a method for producing dry TEMPO-oxidized CNF with improved transparency during redispersion, and a method capable of improving the transparency during redispersion of dry TEMPO-oxidized CNF. In addition, according to the present disclosure, it is possible to provide a method for producing dry carboxymethyl (CM) CNF with improved dispersibility during redispersion, and a method capable of improving dispersibility during redispersion of dry CM CNF. In addition, according to the present disclosure, it is possible to provide a method for producing dry phosphate esterified CNF with improved dispersibility during redispersion, and a method capable of improving transparent dispersibility during redispersion of dry phosphate ester CNF. .

The present disclosure improves the redispersibility of the resulting dried CNF by drying an aqueous suspension obtained by mixing anion-modified CNF with low-molecular-weight sugars such as cyclodextrin and low-molecular-weight polycarboxymethylcellulose (CMC). based on the finding that it can be In addition, when the anion-modified CNF is TEMPO-oxidized CNF, when it is mixed with the above-mentioned low-molecular-weight saccharides and dried, the transparency dispersibility at the time of redispersion of the dry CNF is improved, and the resulting dry CNF is dispersed in water or the like. It is based on the finding that highly transparent dry CNF redispersions can be obtained by contact with a medium.

The present disclosure is based on the finding that drying an aqueous suspension of a mixture of anionically modified CNF and low molecular weight polypeptides or amino acids can improve the redispersibility of the resulting dried CNF. In addition, when the anion-modified CNF is TEMPO-oxidized CNF, if it is mixed with a low-molecular-weight polypeptide or amino acid and dried, the transparency dispersibility at the time of redispersion of the dry CNF is improved, and the resulting dry CNF is dispersed in water or the like. It is based on the knowledge that a redispersion of dry CNF with high transparency can be obtained by contacting it with a dispersion medium.

The present disclosure is based on the finding that drying an aqueous suspension of a mixture of anionically modified CNF and low molecular weight polyvinyl alcohol (PVA) can improve the redispersibility of the resulting dried CNF. In addition, when the anion-modified CNF is TEMPO-oxidized CNF, if it is mixed with low-molecular-weight PVA and dried, the transparent dispersibility at the time of redispersion of the dry CNF is improved, and the resulting dry CNF is mixed with a dispersion medium such as water. It is based on the knowledge that a redispersion of dry CNF with high transparency can be obtained by contacting.

The present disclosure is the finding that low molecular weight sugars such as cyclodextrin and low molecular weight CMC, low molecular weight polypeptides, amino acids, and low molecular weight PVA can be used as dispersibility improvers when redispersing dried CNF. based on. In the present disclosure, "molecular weight of the redispersibility improver" refers to the average molecular weight, preferably the weight average molecular weight, when the redispersibility improver is a polymer. In the present disclosure, one type of redispersibility improver may be used, or multiple types may be used in combination.

As the "improvement or improvement of redispersibility" in the present disclosure, in one or more embodiments, dry CNF obtained by the method for producing dry CNF of the present disclosure is obtained by mixing with a dispersion medium such as water. CNF dispersion obtained by mixing the dried product obtained by drying the anion-modified CNF in the state (wet state) in which the CNF dispersion is dispersed in water (without adding a chemical agent) and the dispersion medium. Compared to the liquid (or CNF suspension), it means that the turbidity is low, or the amount of undispersed CNF pieces or gelation is small. "Improvement or improvement of transparent dispersibility at the time of redispersion" in the present disclosure means that, in one or more embodiments, CNF is dispersed in a dispersion medium at a level close to microfibril units or microfibril units, and in an undispersed state It means that the transparency is higher than that almost no CNF pieces or gels are observed. In one or more embodiments, the dry CNF obtained by the method for producing dry CNF of the present disclosure is mixed with a dispersion medium such as water and stirred, and the CNF is a microfibril unit or a level close to a microfibril unit. , the dry CNF can be dispersed in the dispersion medium in a state of high transparency. According to the dry CNF obtained by the production method of the present disclosure, in one or more embodiments, a highly transparent dry CNF redispersion liquid can be obtained. “Highly transparent” in the present disclosure includes high light transmittance in one or more embodiments.

Japanese Patent Application Laid-Open No. 9-165402 discloses that a third component (components other than BC and water) is added to an aqueous suspension of bacterial cellulose (BC), followed by drying to obtain dried and rehydrated BC. It is disclosed that the properties such as dispersibility and sedimentation of the resin are restored to their pre-drying state. Bacterial cellulose, however, is a naturally occurring cellulose fiber produced by bacteria and has no charge. On the other hand, the anion-modified CNF of the present disclosure is cellulose nanofibers obtained by chemical treatment as described later, and has an electric charge on the surface of the cellulose fibers due to the chemical treatment. Therefore, the anion-modified CNF and bacterial cellulose of the present disclosure are completely different. Furthermore, the same document describes that the original state of the disaggregated material is restored, specifically, the surface of the fine fibers or the voids of the mesh-like structure composed of the fine fibers are made to contain a large amount of liquid components. It is intended for For this reason, the reconstituted dried product obtained by the method of the literature (the product obtained by adding water to the dried bacterial cellulose and reconstituted to a wet state) is a whitish, cloudy, swollen substance. On the other hand, in the dry CNF redispersion liquid obtained by the present disclosure, the fibers (CNF) are separated and dispersed separately, so a highly transparent CNF redispersion liquid can be obtained. Therefore, the method disclosed in Japanese Patent Application Laid-Open No. 9-165402 is a method that is completely different from the method disclosed in the present disclosure not only in terms of processing objects but also in technical concept.

[Anion-modified CNF]
In the present disclosure, "anion-modified CNF" refers to cellulose nanofibers obtained by chemically treating cellulose, more specifically, nanofibers are made by defibrating cellulose fibers whose fiber surfaces have been chemically treated. Refers to fine fibers (nanofibers). In one or more embodiments, the anion-modified CNF in the present disclosure has an electric charge on the surface of the cellulose fiber due to chemical treatment. Anionically modified CNFs in the present disclosure, in one or more embodiments, do not include naturally occurring cellulose nanofibers such as bacterial cellulose produced from bacteria.

In one or more embodiments, the chemical treatment includes carboxymethylation (CM) treatment, carboxylation (oxidation) treatment, phosphorylation treatment, and the like.

[Carboxymethyl (CM) conversion]
As a method of carboxymethylating a cellulose raw material or defibrated cellulose fiber, for example, a method of mercerizing cellulose as a starting raw material and then etherifying it can be mentioned. A solvent is usually used in the carboxymethylation reaction. Examples of solvents include water, alcohols (eg, lower alcohols), and mixed solvents thereof. Specific examples of lower alcohols include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, isobutanol and tertiary butanol. The mixing ratio of the lower alcohol in the mixed solvent is usually 60% by weight or more as a lower limit and usually 95% by weight or less as an upper limit, preferably 60% to 95% by weight. The amount of solvent is usually 3 times or more by weight of the cellulose raw material or defibrated cellulose fiber. The upper limit of the amount of the solvent is not particularly limited, but it is usually 20 times or less by weight of the cellulose raw material or defibrated cellulose fiber. Therefore, the amount of the solvent is preferably 3 to 20 times the weight of the cellulose raw material or defibrated cellulose fiber.

Mercerization is usually carried out by mixing a cellulose raw material or defibrated cellulose fibers with a mercerizing agent. Mercerizing agents include, for example, alkali metal hydroxides (eg, sodium hydroxide, potassium hydroxide).

The lower limit of the amount of the mercerizing agent to be used is usually 0.5 mol or more per the anhydroglucose residue in the cellulose raw material or defibrated cellulose fiber. Moreover, the upper limit is usually 20-fold mol or less. Therefore, the amount of the mercerizing agent to be used is preferably 0.5-fold to 20-fold mol per anhydroglucose residue of the cellulosic raw material or defibrated cellulose fiber.

The lower limit of the reaction temperature for mercerization 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 reaction time for mercerization 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 carried out by adding a carboxymethylating agent to the reaction system after mercerization. Carboxymethylating agents include, for example, sodium monochloroacetate.

The lower limit of the amount of the carboxymethylating agent to be added is usually 0.05 moles or more per glucose residue in the cellulose raw material or defibrated cellulose fiber. The upper limit is usually 10.0 times mol or less. Therefore, the amount of the carboxymethylating agent to be added is usually 0.05 to 10.0 mol per mol of glucose residue in 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. The upper limit is usually 90°C or lower, preferably 80°C or lower. Accordingly, the etherification reaction temperature is generally 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 etherification reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours.

As a method for measuring the degree of carboxymethyl substitution per glucose unit of carboxymethylated cellulose fibers or carboxymethylated cellulose nanofibers, for example, the following method can be used. That is, 1) About 2.0 g of carboxymethylated cellulose fiber or carboxymethylated cellulose nanofiber (absolute dry) is accurately weighed and placed in a 300 mL conical flask with a common stopper. 2) Add 100 mL of nitric acid methanol solution obtained by adding 100 mL of special grade concentrated nitric acid to 1000 mL of methanol and shake for 3 hours to convert carboxymethyl cellulose salt (CM cellulose salt: eg Na-CMC) to H-CM cellulose. (H-CMC). 3) Accurately weigh 1.5 to 2.0 g of H-CM-modified cellulose (absolutely dry) and put it in a 300 mL Erlenmeyer flask equipped with a common stopper. 4) Wet 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) Backtitrate excess NaOH with 0.1N _H2SO4 using phenolphthalein as indicator _. 6) Calculate the degree of carboxymethyl substitution (DS) by the formula:
A=[(100×F′−(0.1N H ₂ SO ₄ ) (mL)×F)×0.1]/(absolute dry weight of H-CM cellulose (g))
DS = 0.162 x A/(1 - 0.058 x A)
A: Amount of 1N NaOH (mL) required to neutralize 1 g of H-CM cellulose
F': factor of 0.1N NaOH F: factor of _{0.1N H2SO4}

In the present disclosure, "carboxymethylated cellulose", which is a kind of modified cellulose used for preparing modified CNF, means that at least 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, no fibrous substance is observed in an aqueous dispersion of carboxymethyl cellulose, which is a type of water-soluble polymer. In addition, when "carboxymethylated cellulose" is measured by X-ray diffraction, a peak of cellulose type I crystals can be observed, but cellulose type I crystals are not observed in carboxymethyl cellulose, which is a water-soluble polymer.

[Carboxylation]
In the present disclosure, when carboxylated (oxidized) cellulose is used as 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, during 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. is preferable, and it is more preferable to adjust the concentration to be 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 bromides, iodides or mixtures thereof. A method can be mentioned. This oxidation reaction selectively oxidizes the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface, resulting in a cellulose fiber having an aldehyde group and a carboxyl group (--COOH) or carboxylate group ( ^--COO.sup.- ) on the surface. can be obtained. Although the concentration of cellulose during the reaction is not particularly limited, it is preferably 5% by mass or less.

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

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

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

Known oxidizing agents can be used, for example, halogens, hypohalous acids, halogenous acids, perhalogenates or salts thereof, halogen oxides, peroxides and the like can be used. Among them, sodium hypochlorite is preferable because it is inexpensive and has less environmental load. The amount of the oxidizing agent to be used is preferably 0.5 mmol to 500 mmol, more preferably 0.5 mmol to 50 mmol, even more preferably 1 mmol to 25 mmol, and most preferably 3 mmol to 10 mmol, relative to 1 g of absolute dry cellulose, for example. Further, for example, 1 mmol to 40 mol is preferable per 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. Since carboxyl groups are generated in the cellulose as the reaction progresses, the pH of the reaction solution decreases. In order to allow the oxidation reaction to proceed efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution at about 8-12, preferably about 10-11. Water is preferable as the reaction medium because it is easy to handle and less likely to cause side reactions.

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

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

Another example of the carboxylation (oxidation) method is a method of oxidizing by contacting a cellulose raw material with an ozone-containing gas. This oxidation reaction oxidizes at least the hydroxyl groups at the 2- and 6-positions of the glucopyranose ring and causes degradation of the cellulose chain. The ozone concentration in the ozone-containing gas is preferably 50 g/m ³ to 250 g/m ³ , 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 to 30 parts by mass, more preferably 5 to 30 parts by mass, when the solid content of the cellulose raw material is 100 parts by mass. . The ozone treatment temperature is preferably 0°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 ozone treatment conditions are within these ranges, cellulose can be prevented from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved. After the ozone treatment, additional oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used in the additional oxidation treatment is not particularly limited, but examples include chlorine-based compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. For example, the additional oxidation treatment can be performed by dissolving these oxidizing agents in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and immersing the cellulose raw material in the solution.

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

[Phosphating]
Phosphate-esterified cellulose can be used as the modified cellulose. The cellulose can be obtained by a method of mixing a cellulose raw material with powder or an aqueous solution of the phosphate compound A, or a method of adding an aqueous solution of the phosphate compound A to a slurry of the cellulose raw material.

Phosphoric acid compound A includes phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. These may be in the form of salts. Among these, compounds having a phosphate group are preferred because they are low in cost, easy to handle, and can improve defibration efficiency by introducing a phosphate group into the cellulose of pulp fibers. Compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, phosphorus Tripotassium acid, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate and the like. These can be used singly or in combination of two or more. Among these, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, phosphoric acid, from the viewpoint of high efficiency of introduction of phosphate group, easy fibrillation in the fibrillation process described below, and easy industrial application is more preferred. Sodium dihydrogen phosphate and disodium hydrogen phosphate are particularly preferred. Further, it is preferable to use the phosphoric acid-based compound A in the form of an aqueous solution, since the uniformity of the reaction is enhanced and the efficiency of introduction of the phosphoric acid group is enhanced. The pH of the aqueous solution of the phosphoric acid-based compound A is preferably 7 or less because the efficiency of introducing phosphate groups is high, but from the viewpoint of suppressing hydrolysis of pulp fibers, the pH is preferably 3 to 7.

The following method can be given as an example of the method for producing the phosphorylated cellulose. Phosphoric acid group is introduced into cellulose by adding phosphoric acid-based compound A to a dispersion liquid of cellulose raw material having a solid content concentration of 0.1% by mass to 10% by mass while stirring. When the cellulose raw material is 100 parts by mass, the amount of phosphoric acid compound A added is preferably 0.2 parts by mass to 500 parts by mass, and 1 part by mass to 400 parts by mass, as the elemental amount of phosphorus. is more preferred. If the proportion of the phosphoric acid-based compound A is at least the lower limit, the yield of fine fibrous cellulose can be further improved. However, if the above upper limit is exceeded, the effect of improving the yield reaches a ceiling, which is not preferable from the viewpoint of cost.

At this time, in addition to the cellulose raw material and the phosphoric acid-based compound A, a powder or an aqueous solution of a compound B other than these may be mixed. Compound B is not particularly limited, but a nitrogen-containing compound exhibiting basicity is preferred. "Basic" herein is defined as the pink-red color of the aqueous solution in the presence of the phenolphthalein indicator or the pH of the aqueous solution being greater than 7. The basic nitrogen-containing compound used in the present disclosure is not particularly limited as long as the effects of the present disclosure are achieved, but compounds having an amino group are preferred. Examples include, but are not limited to, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, urea is preferable because it is low in cost and easy to handle. The amount of compound B added is preferably 2 parts by mass to 1000 parts by mass, more preferably 100 parts by mass to 700 parts by mass, based on 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. Although the reaction time is not particularly limited, it is about 1 minute to 600 minutes, more preferably 30 minutes to 480 minutes. When the conditions for the phosphating reaction are within these ranges, cellulose can be prevented from being excessively phosphatized and easily dissolved, and the yield of phosphated cellulose can be improved. After dehydrating the obtained phosphate-esterified cellulose suspension, it is preferable to heat-treat at 100° C. to 170° C. from the viewpoint of suppressing hydrolysis of cellulose. Further, it is preferable to heat at 130° C. or less, preferably 110° C. or less while water is contained in the heat treatment, and heat at 100° C. to 170° C. after removing the water.

The degree of phosphate group substitution per glucose unit of the phosphated cellulose is preferably 0.001 to 0.40. By introducing a phosphate group substituent into cellulose, the celluloses electrically repel each other. Therefore, cellulose into which a phosphate group has been introduced can be easily nano-fibrillated. If the degree of phosphate group substitution per glucose unit is less than 0.001, sufficient nano-fibrillation cannot be achieved. On the other hand, if the degree of phosphate group substitution per glucose unit is greater than 0.40, the nanofibers may not be obtained due to swelling or dissolution. In order to efficiently defibrate, it is preferable that the phosphate-esterified cellulose raw material obtained above is washed by washing with cold water after boiling.

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

In the modified cellulose dispersion treatment, the modified cellulose is usually dispersed in a solvent. The solvent is not particularly limited as long as it can disperse the modified cellulose, and examples thereof include water, organic solvents (eg, hydrophilic organic solvents such as methanol), and mixed solvents thereof. Because of its use in food, the solvent is preferably 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, and more preferably 0.3% by weight or more. As a result, the amount of liquid becomes appropriate with respect to the amount of cellulose fiber raw material, which is efficient. The upper limit is usually 10% by weight or less, preferably 6% by weight or less. Thereby, fluidity can be maintained.

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

Cellulosic feedstocks, in one or more embodiments, include plant material, animal material, algae, and the like. Plant materials include, in one or more embodiments, wood, bamboo, hemp, jute, kenaf, cloth, pulp, recycled pulp, waste paper, or the like. Pulp, in one or more embodiments, includes kraft pulp (KP), sulfate pulp (SP), dissolved sulfite pulp (DSP), dissolved kraft pulp (DKP), powdered cellulose, microcrystalline cellulose powder, and the like. Animal materials, in one or more embodiments, include sea squirts and the like.

[Method for producing dry CNF]
In one aspect, the present disclosure includes mixing anion-modified CNF and a redispersibility improver to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension to obtain dry CNF. (Method for producing dried CNF of the present disclosure). According to the method for producing dry CNF of the present disclosure, in one or more embodiments, film-like dry CNF and / or powdery dry CNF having sufficient transparent dispersibility at the time of redispersion can be obtained. In one or more 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 dried CNF of the present disclosure, in one or more embodiments, it is possible to improve or improve the redispersibility of the dried TEMPO-oxidized CNF (dried CNF). Dispersibility can be enhanced or improved.
In addition, the method for producing dry CNF of the present disclosure can be used for CM-CNF in one or more embodiments. According to the dry CNF production method of the present disclosure, in one or more embodiments, it is possible to improve or improve the dispersibility of the dried CM-CNF (dry CNF) during redispersion.
In addition, in one or more embodiments, the method for producing dry CNF of the present disclosure can be preferably used for phosphate-esterified CNF among anion-modified CNFs. According to the method for producing dried CNF of the present disclosure, in one or more embodiments, it is possible to improve or improve the redispersibility of the dried phosphate esterified CNF (dry CNF), especially during redispersion can enhance or improve the transparency dispersibility of

According to the method for producing dry CNF of the present disclosure, in one or more embodiments, it is possible to obtain dry CNF with improved redispersibility, and in particular, dry CNF with improved transparent dispersibility during redispersion. Obtainable. The resulting dried CNF may have, in one or more non-limiting embodiments, a sufficiently transparent dispersibility upon redispersion. As "having sufficient transparent dispersibility at the time of redispersion", in one or more embodiments, transparency at a level comparable to or comparable to that of the anion-modified CNF suspension before drying and re-dispersion to the dispersion medium Having dispersibility is mentioned. In one or more embodiments, the dry CNF obtained is used in various chemical products, foods, cosmetics, pharmaceuticals, beverages, reinforcing materials (including paper-related products), absorbent products such as diapers, heat insulating materials, automobile parts, paints , pesticides, construction, batteries, household goods, water treatment, or cleaning agents.

Redispersibility improvers in the present disclosure, in one or more embodiments, include low molecular weight saccharides, low molecular weight polypeptides, amino acids, and low molecular weight PVA.

<Low-molecular-weight saccharides>
In one or more embodiments of the method for producing dry CNF of the present disclosure, an anion-modified CNF and a low-molecular-weight saccharide are mixed to obtain an aqueous suspension of anion-modified CNF, and the resulting aqueous suspension Including drying the liquid.

In the present disclosure, "low molecular weight saccharides" refers to saccharides having a molecular weight of 50,000 or less. Sugars, in one or more embodiments, include monosaccharides, disaccharides, oligosaccharides and polysaccharides. In one or more embodiments, the molecular weight of the low-molecular-weight saccharide is 50,000 or less, 20,000 or less, 15,000 or less, 10,000 or less, 5000 or less, 3000 or less, 2000 or less, or 200 or less, Or 150 or more.

Monosaccharides, in one or more embodiments, include glucose and the like. The molecular weight of the monosaccharide is 150 or more or 200 or less in one or more embodiments.

Disaccharides, in one or more embodiments, include maltose, lactose, and the like. The molecular weight of the disaccharide is, in one or more embodiments, 200 or greater, or 400 or less, 380 or less, 360 or less, or 350 or less.

Oligosaccharides include cyclodextrins in one or more embodiments. In one or more embodiments, the molecular weight (weight average molecular weight) of the oligosaccharides is 400 or more, 600 or more, 800 or more, or 900 or more, or 5000 or less, 4000 or less, 3000 or less, or 2000 or less. Cyclodextrins include α-cyclodextrin (natural molecular weight: 973), β-cyclodextrin (natural molecular weight: 1135), and γ-cyclodextrin (natural molecular weight: 1297). Cyclodextrins, in one or more embodiments, may be natural cyclodextrins or chemically modified cyclodextrins (cyclodextrin derivatives). Chemically modified cyclodextrins (cyclodextrin derivatives) include, in one or more embodiments, hydroxypropylated cyclodextrin, acetylated cyclodextrin, triacetylated cyclodextrin, methylated cyclodextrin, monochlorotriazinylated cyclodextrin, amino cyclodextrin, ethylenediaminated cyclodextrin, and the like.

Among the above low-molecular-weight saccharides, α-cyclodextrin and β-cyclodextrin derivatives having a molecular weight of 3,000 or less or 2,000 or less, in view of good redispersibility, particularly good transparent redispersibility at the time of redispersion. or γ-cyclodextrin, or glucose is preferred. Furthermore, α-cyclodextrin, β-cyclodextrin derivatives, or γ-cyclodextrin is more preferable from the viewpoint of not inhibiting the properties (thixotropy, viscosity, etc.) of anion-modified CNF.

Polysaccharides, in one or more embodiments, include dextrin, low molecular weight CMC, and the like.

In one or more embodiments, the dextrin has a molecular weight of 50,000 or less, 20,000 or less, 17,000 or less, 15,000 or less, 13,000 or less, 12,0000 or less, 11,000 or less, or 10,000 or less, 000 or less, or 200 or more, 500 or more, 1,000 or more, 2,000 or more, 3,000 or more, 4,000 or more, 5,000 or more, or 6,000 or more.

Low-molecular-weight CMC includes CMC having a molecular weight of 20,000 or less. The molecular weight of low molecular weight CMC is, in one or more embodiments, 20,000 or less, 15,000 or less, or 200 or more.

The degree of etherification (degree of carboxymethyl group substitution) of CMC is, in one or more embodiments not particularly limited, 0.55 to 1.6 or 0.65 to 1.1.

In one or more embodiments, the method for producing dry CNF of the present disclosure includes mixing anion-modified CNF in a wet state (dispersed in water) with a low-molecular-weight saccharide. Thereby, an aqueous suspension containing anion-modified CNF and low-molecular-weight saccharides can be obtained.

In one or more embodiments, the blending ratio of low-molecular-weight saccharides to anion-modified CNF (absolute dry solid content, 100 parts by mass) is 5 parts by mass or more, 5 parts by mass to 500 parts by mass, 5 parts by mass to 400 parts by mass. 5 to 300 parts by mass or 10 to 200 parts by mass, preferably 30 to 350 parts by mass or 30 to 150 parts by mass.

When the anion-modified CNF is carboxylated CNF such as TEPO-oxidized CNF, the blending ratio of the low-molecular-weight saccharide to the anion-modified CNF (bone dry solids, 100 parts by mass) is 5 parts by mass in one or more embodiments. Above, 5 parts by mass to 500 parts by mass, 5 parts by mass to 400 parts by mass, 5 parts by mass to 300 parts by mass or 10 parts by mass to 200 parts by mass, preferably 30 parts by mass to 250 parts by mass or 45 parts by mass 150 parts by mass.

When the anion-modified CNF is a CM-modified CNF, the blending ratio of the low-molecular-weight saccharide to the anion-modified CNF (bone dry solids, 100 parts by mass) is, in one or more embodiments, 5 parts by mass or more to 10 parts by mass. 500 parts by mass or 30 parts by mass to 400 parts by mass, preferably 50 parts by mass to 350 parts by mass or 75 parts by mass to 350 parts by mass.

When the anion-modified CNF is phosphate-esterified CNF, the blending ratio of the low-molecular-weight saccharide to the anion-modified CNF (bone dry solids, 100 parts by mass) is, in one or more embodiments, 5 parts by mass or more, 5 Parts by mass to 500 parts by mass, 5 parts by mass to 400 parts by mass, 5 parts by mass to 300 parts by mass or 10 parts by mass to 200 parts by mass, preferably 30 parts by mass to 250 parts by mass or 45 parts by mass to 150 parts by mass is.

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

<Low molecular weight polypeptide or amino acid>
In one or more embodiments of the method for producing dry CNF of the present disclosure, an anion-modified CNF and a low-molecular-weight polypeptide or amino acid are mixed to obtain an anion-modified CNF aqueous suspension, and Including drying the aqueous suspension.

In the present disclosure, "low-molecular-weight polypeptide" refers to a polypeptide having a molecular weight of 10,000 or less. The molecular weight of the low molecular weight polypeptide is, in one or more embodiments, 1000 or less, or 500 or less, or 150 or more. Amino acids, in one or more embodiments, include neutral amino acids such as glycine and glutamine.

In one or more embodiments, the method for producing dry CNF of the present disclosure includes mixing anion-modified CNF in a wet state (dispersed in water) with a low-molecular-weight polypeptide or amino acid. Thereby, an aqueous suspension containing anion-modified CNF and low-molecular-weight polypeptides or amino acids can be obtained.

The blending ratio of the low-molecular-weight polypeptide or amino acid to anion-modified CNF (absolute dry solid content, 100 parts by mass) is, in one or more embodiments, 5 parts by mass or more, 5 parts by mass to 500 parts by mass, 5 parts by mass 400 parts by mass to 300 parts by mass, or 10 parts by mass to 200 parts by mass, preferably 30 parts by mass to 350 parts by mass, or 30 parts by mass to 150 parts by mass.

The method for producing dried CNF of the present disclosure, in one or more embodiments, includes drying an aqueous suspension containing anion-modified CNF and low-molecular-weight polypeptides or amino acids. Aqueous suspensions, in one or more embodiments, may be dried by forming a thin film, or may be spray dried. Thereby, a dry film and/or dry powder containing anion-modified CNF and a low-molecular-weight polypeptide or amino acid can be obtained.

<Low molecular weight PVA>
In one or more embodiments, the method for producing dry CNF of the present disclosure includes mixing anion-modified CNF and low-molecular-weight PVA to obtain an anion-modified CNF aqueous suspension, and the resulting aqueous suspension Including drying the liquid.

In the present disclosure, "low molecular weight PVA" refers to PVA with a molecular weight of 3000 or less. The molecular weight of the low molecular weight PVA is, in one or more embodiments, 2500 or less, 2000 or less, or 1500 or less, or 100 or more.

In one or more embodiments, the method for producing dry CNF of the present disclosure includes mixing wet state (dispersed in water) anion-modified CNF and low-molecular-weight PVA. Thereby, an aqueous suspension containing anion-modified CNF and low-molecular-weight PVA can be obtained.

The blending ratio of low molecular weight PVA to anion-modified CNF (absolute dry solid content, 100 parts by mass) is, in one or more embodiments, 5 parts by mass or more, 5 parts by mass to 500 parts by mass, 5 parts by mass to 400 parts by mass. 5 to 300 parts by mass or 10 to 200 parts by mass, preferably 30 to 350 parts by mass or 30 to 150 parts by mass.

The method for producing dried CNF of the present disclosure, in one or more embodiments, includes drying an aqueous suspension containing anion-modified CNF and low-molecular-weight PVA. Aqueous suspensions, in one or more embodiments, may be dried by forming a thin film, or may be spray dried. Thereby, a dry film and/or dry powder containing anion-modified CNF and low-molecular-weight PVA can be obtained.

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

In one or more embodiments, dry CNF obtained by the method for producing dry CNF of the present disclosure is obtained by adding 0.1 g of dry CNF that has been pulverized to about 1 mm to 2 mm to 5 g of distilled water and using a point mixer for about 1 minute. After stirring, the mixture is allowed to stand at room temperature for about 24 hours, and then stirred again for about 1 minute with a point mixer.

In one or more embodiments, dry CNF obtained by the method for producing dry CNF of the present disclosure is obtained by crushing film-like dry CNF to about 3 × 3 mm and putting it in a 200 mL beaker. After adding distilled water to .7%, when stirring for 1 to 3 hours using a stirrer with a three-one motor at 600 rpm and a blade diameter of 3.5 cm, at least the same level as the CNF dispersion before drying Or it has transparent dispersibility at a comparable level.

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

[Dried CNF]
The present disclosure relates, in one aspect, to dry CNF (dry CNF of the present disclosure) comprising a redispersibility improver and anionically modified CNF. The dry CNF of the present disclosure can be obtained by the method for producing dry CNF of the present disclosure in one or more embodiments. In one or more embodiments, the dry CNF of the present disclosure is mainly composed of anion-modified CNF that is not particularly limited. The dry CNF of the present disclosure may be film-like or powder-like in one or more embodiments.

[Method for producing transparent redispersion of CNF]
The present disclosure, in one aspect, relates to a method of making a transparent redispersion of CNF (method of making a transparent redispersion of the present disclosure). In one or more embodiments, the method for producing a transparent redispersion product of the present disclosure includes obtaining an aqueous suspension containing an anion-modified CNF and a redispersibility improver, drying the aqueous suspension, and re-dispersing the resulting dried product in a dispersion medium. In one or more embodiments, the method for producing a transparent redispersion of CNF of the present disclosure includes redispersing dry CNF obtained by the method for producing dry CNF of the present disclosure in a dispersion medium. According to the method for producing a transparent redispersion of CNF of the present disclosure, in one or more embodiments, CNF at a level comparable or comparable to CNF aqueous suspension or aqueous dispersion that has not undergone drying of transparent redispersions can be obtained. According to the method for producing a transparent redispersion of CNF of the present disclosure, in one or more embodiments, a transparent redispersion of dry CNF having high transparency in which dry TEMPO-oxidized CNF is redispersed can be obtained. The redispersion may be liquid or gel in one or more embodiments.

In one or more embodiments, the dispersion medium includes an aqueous dispersion medium such as water. The dispersion medium may contain various polymers other than CNF in one or more embodiments.

The method of making a transparent redispersion of the present disclosure may further comprise removing the redispersibility improver from the resulting transparent redispersion. When the redispersibility improver is cyclodextrin, removal of the redispersibility improver, in one or more embodiments, involves mixing a linear aliphatic alcohol such as 1-decanol with a transparent redispersion, This can then be done by separating the cyclodextrin from the clear redispersion by applying physical stress. The amount of the linear aliphatic alcohol to be added is not particularly limited, and in one or more embodiments, it may be molar equivalent to the cyclodextrin contained in the transparent redispersion. Physical stress, in one or more embodiments, includes centrifugation and the like.

In one or more embodiments, the dispersion medium includes an aqueous dispersion medium such as water. The dispersion medium may contain various polymers other than CNF in one or more embodiments.

[Method for producing redispersion of CNF]
The present disclosure, in one aspect, relates to a method for producing a redispersion of CNF (method for producing a redispersion of the present disclosure). In one or more embodiments, the method for producing a redispersion of the present disclosure includes obtaining an aqueous suspension containing CM-CNF and a redispersibility improver, drying the aqueous suspension, and It includes re-dispersing the resulting dried product in a dispersion medium. In one or more embodiments, the method for producing a redispersion of CNF of the present disclosure includes redispersing dry CNF obtained by the method for producing dry CNF of the present disclosure in a dispersion medium. According to the method for producing a CNF redispersion of the present disclosure, in one or more embodiments, the dispersibility is comparable to or comparable to the CM-modified CNF aqueous suspension or aqueous dispersion that has not undergone drying. A redispersion of dry CM-CNF can be obtained. The redispersion may be liquid or gel in one or more embodiments. The method for removing the dispersion medium and the redispersibility improver is the same as the method for producing the transparent redispersion of the present disclosure.

[Method for improving redispersibility of CNF]
As described above, by drying the anion-modified CNF together with the redispersibility improver, it is possible to improve or improve the redispersibility of the resulting dried CNF, particularly the transparent dispersibility during redispersion. Therefore, in another aspect, the present disclosure provides an aqueous suspension of anion-modified cellulose nanofibers by mixing anion-modified CNF and a redispersibility improver, and drying the aqueous suspension. The present invention relates to a method for improving the redispersibility of CNF, particularly the transparency during redispersion. According to the method for improving redispersibility of the present disclosure, in one or more embodiments, it is possible to further improve or improve the transparent dispersibility at the time of redispersion of dried TEMPO-oxidized CNF among anion-modified CNFs. Further, according to the method for improving redispersibility of the present disclosure, in one or more embodiments, it is possible to further improve or improve the dispersibility at the time of redispersion of dried CM-modified CNF among anion-modified CNF.
According to the method for improving redispersibility of the present disclosure, in one or more embodiments, it is possible to further improve or improve the transparent dispersibility at the time of redispersion of dried phosphate-esterified CNF among anion-modified CNF. . The redispersibility improver and the blending ratio are the same as in the dry CNF production method of the present disclosure.

In one or more embodiments, the aqueous suspension may contain a third component other than the anion-modified CNF and the redispersibility improver during redispersion. A third component, in one or more embodiments, includes a water-soluble polymer or the like.

Drying of the aqueous suspension can be performed in one or more embodiments in the same manner as the method for producing dried CNF of the present disclosure.

[Redispersibility improver]
In another aspect, the present disclosure provides a redispersibility improver for improving or improving the redispersibility of dry cellulose nanofibers in an aqueous dispersion medium, particularly transparent dispersibility during redispersion (redispersion of the present disclosure property improver). The redispersibility improver of the present disclosure includes one or more selected from the group consisting of low molecular weight saccharides, low molecular weight polypeptides, amino acids, and low molecular weight PVC. In one or more embodiments, the redispersibility improver of the present disclosure is used in the production of dry cellulose nanofibers with improved or improved redispersibility in a dispersion medium, particularly transparent dispersibility during redispersion. can do. Low molecular weight saccharides, low molecular weight polypeptides, amino acids, and low molecular weight PVC are as described above.

[Dry composition]
In one aspect, the present disclosure is a dry composition containing anion-modified cellulose nanofibers and a redispersibility improver, wherein the redispersibility improver comprises a saccharide having a molecular weight of 50,000 or less, a low molecular weight polypeptide, A dry composition (dry composition of the present disclosure) comprising at least one selected from the group consisting of amino acids and low molecular weight PVC.

In one or more embodiments, the proportion of the redispersibility improver in the dry composition of the present disclosure is 5% by mass or more, 5% to 500% by mass, based on anion-modified CNF (bone dry solids), 5% to 400% by weight, 5% to 300% by weight, 10% to 200% by weight or 20% to 300% by weight, preferably 30% to 350% by weight or 30% to 150% by weight.

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

When the anion-modified CNF is CM-modified CNF, the proportion of the redispersibility improver in the dry composition of the present disclosure is, in one or more embodiments, 5 mass based on TEMPO oxidized CNF (bone dry solids) % or more, 10% to 500% by mass or 30% to 400% by mass, preferably 50% to 350% by mass or 75% to 350% by mass.

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

The dry composition of the present disclosure, in one or more embodiments, may contain a third component other than the anion-modified CNF and the redispersibility improver. A third component, in one or more embodiments, includes a water-soluble polymer or the like.

A dry composition of the present disclosure, in one or more embodiments, may be in the form of a film, a solid, or a powder. The film thickness of the dry composition of the present disclosure, in one or more embodiments, is 50 μm or more, or 100 μm or more, or 1000 μm or less, or 300 μm or less.

The dry composition of the present disclosure, in one or more embodiments, may be produced by mixing anion-modified CNF and a redispersibility improver, and optionally the third component, and drying it. Alternatively, it may be prepared by mixing the dry CNF of the present disclosure with said third component and drying it.

The disclosure further relates to one or more of the following embodiments.
[1] mixing anion-modified CNF and a redispersibility improver to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension to obtain dry CNF,
The method for producing dry CNF, wherein the redispersibility improver is selected from the group consisting of saccharides having a molecular weight of 50,000 or less, low molecular weight polypeptides, amino acids, and low molecular weight polyvinyl alcohol.
[2] The method for producing dry CNF according to [1], wherein the redispersibility improver is carboxymethyl cellulose having a molecular weight of 20,000 or less.
[3] Manufacture of dry CNF, comprising mixing anion-modified CNF and a low-molecular-weight saccharide to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension to obtain dry CNF. Method.
[4] The method for producing dry CNF according to [3], wherein the saccharide has a molecular weight of 50,000 or less.
[5] Manufacture of dry CNF, comprising mixing anion-modified CNF and low-molecular-weight CMC to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension to obtain dry CNF. Method.
[6] The method for producing dry CNF according to [5], wherein the CMC has a molecular weight of 20,000 or less.
[7] mixing anion-modified CNF with at least one of a low-molecular-weight polypeptide and an amino acid to obtain an anion-modified CNF aqueous suspension, and drying the aqueous suspension to obtain dry CNF. A method for producing dry CNF, comprising:
[8] Manufacture of dry CNF, comprising mixing anion-modified CNF and low-molecular-weight PVA to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension to obtain dry CNF. Method.
[9] The method for producing dry CNF according to any one of [1] to [8], wherein the anion-modified CNF is carboxylated CNF, CM-CNF or phosphorylated CNF.
[10] mixing an anion-modified CNF and a redispersibility improver to obtain an anion-modified CNF aqueous suspension, and drying the aqueous suspension,
The method for improving redispersibility of CNF, wherein the redispersibility improver is selected from the group consisting of sugars having a molecular weight of 50,000 or less, low molecular weight polypeptides, amino acids, and low molecular weight polyvinyl alcohol.
[11] A method for improving redispersibility of CNF, comprising mixing anion-modified CNF and a low-molecular-weight saccharide to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension.
[12] A method for improving redispersibility of CNF, comprising mixing anion-modified CNF and low-molecular-weight CMC to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension.
[13] Re-dispersing CNF, comprising mixing anion-modified CNF with at least one of a low-molecular-weight polypeptide and an amino acid to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension. sexual improvement method.
[14] A method for improving redispersibility of CNF, comprising mixing anion-modified CNF and low-molecular-weight PVA to obtain an aqueous suspension of anion-modified CNF, and drying the aqueous suspension.
[15] The method for improving redispersibility of CNF according to any one of [10] to [14], wherein the anion-modified CNF is carboxylated CNF, CM-CNF or phosphorylated CNF.
[16] An agent for improving or improving the redispersibility of dry CNF in an aqueous dispersion medium, selected from the group consisting of low-molecular-weight saccharides, low-molecular-weight polypeptides, amino acids, and low-molecular-weight polyvinyl alcohols A redispersibility improver containing one or more of
[17] A redispersibility improver, which is an agent for enhancing or improving the redispersibility of dry CNF in an aqueous dispersion medium, and which contains a low-molecular-weight CMC.
[18] A redispersibility improver for use in producing dry CNF, comprising one or more selected from the group consisting of low-molecular-weight saccharides, low-molecular-weight polypeptides, amino acids, and low-molecular-weight polyvinyl alcohol A redispersibility improver containing.
[19] A redispersibility improver for use in the production of dry CNF, the redispersibility improver comprising a low molecular weight CMC.
[20] A redispersibility improver for use in the method for producing dry CNF according to any one of [1] to [9] or the method for improving redispersibility according to any one of [10] to [15] A redispersibility improver containing at least one selected from the group consisting of low-molecular-weight saccharides, low-molecular-weight polypeptides, amino acids, and low-molecular-weight polyvinyl alcohols.
[21] A redispersibility improver for use in the method for producing dry CNF according to any one of [1] to [9] or the method for improving redispersibility according to any one of [10] to [15] and a redispersibility improver comprising a low molecular weight CMC.
[22] A dry composition comprising an anion-modified CNF and a redispersibility improver,
The composition, wherein the redispersibility improver comprises at least one selected from the group consisting of saccharides having a molecular weight of 50,000 or less, low-molecular-weight polypeptides, amino acids, and low-molecular-weight polyvinyl alcohols.
[23] The composition of [22], wherein the anion-modified CNF is carboxylated CNF, CM-CNF or phosphorylated CNF.

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

[Production of carboxylated cellulose nanofiber (anion-modified CNF1)]
5.00 g (absolute dry) of bleached unbeaten kraft pulp (85% whiteness) derived from softwood was mixed with 39 mg (0.05 mmol relative to 1 g of absolute dry cellulose) of TEMPO (Sigma Aldrich) and 514 mg (absolute dry) of sodium bromide. 1.0 mmol per 1 g of dry cellulose) was added to 500 ml of an aqueous solution 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 an oxidation reaction was initiated at room temperature. The pH in the system decreased during the reaction, but was adjusted to pH 10 by successively adding 3M sodium hydroxide aqueous solution. The reaction was terminated when the sodium hypochlorite was consumed and the pH in the system stopped changing.
The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was sufficiently washed with water to obtain an oxidized pulp (carboxylated cellulose). At this time, the pulp yield was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol/g. This is adjusted to a pulp solid content of 1.1% (w / v) with water, and treated with an ultrahigh pressure homogenizer (20 ° C., 150 Mpa) three times to produce carboxylated cellulose nanofibers (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)]
200 g of softwood bleached kraft pulp (manufactured by Nippon Paper Industries Co., Ltd.) in dry mass and 111 g in dry mass of sodium hydroxide (2.25 times mol per anhydroglucose residue of the bottom raw material) were placed in a stirrer capable of mixing pulp. ) and water was added to bring the pulp solids to 20% (w/v). Then, after stirring at 30° C. for 30 minutes, 216 g of sodium monochloroacetate (converted to 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 the mixture was stirred for 1 hour. After that, the reactant was taken out, neutralized and washed to obtain a carboxymethylated pulp having a degree of carboxymethyl substitution of 0.25 per glucose unit. This is made into a pulp solid content of 1.2% (w / v) with water, and is defibrated by a high-pressure homogenizer at 20 ° C. and a pressure of 150 MPa five times to obtain carboxymethylated cellulose nanofibers (hereinafter referred to as CM-CNF). ). The average fiber diameter was 12 nm and the aspect ratio was 130.

[Production of phosphorylated cellulose nanofiber (anion-modified CNF3)]
6.75 g of sodium dihydrogen phosphate dihydrate and 4.83 g of disodium hydrogen phosphate were dissolved in 19.62 g of water to obtain an aqueous solution of a phosphoric acid compound (hereinafter referred to as "phosphorylation reagent"). rice field. Water is added to softwood unbleached kraft pulp (NUKP, moisture content 80%, Canadian standard freeness (CSF) measured according to JIS P8121 580 ml) so that the pulp solid content becomes 4% (w / v). rice field. Then, using a double disc refiner, the irregular CSF (plain weave 80 mesh, according to JIS P8121 except that the amount of pulp collected was 0.3 g) was beaten to 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. rice field. This pulp sheet is immersed in 31.2 g of the phosphorylation reagent (80 parts by mass as the elemental amount of phosphorus with respect to 100 parts by mass of dry pulp), and after heating for 1 hour with a blower dryer (DKM400, Yamato Scientific Co., Ltd.) at 105 ° C. , and further heat-treated at 150°C for 1 hour to introduce phosphate groups into the cellulose fibers. Next, 500 ml of ion-exchanged water was added to the pulp sheet in which the phosphate group was introduced into the cellulose fiber, and after stirring and washing, dehydration was performed. The sheet after dehydration was diluted with 300 ml of deionized water, and 5 ml of 1N sodium hydroxide aqueous solution was added little by little while stirring to obtain a cellulose suspension having a pH of 12-13. Thereafter, this cellulose suspension was dehydrated and washed by adding 500 ml of deionized water. This dehydration wash was repeated two more times. After ion-exchanged water was added to the sheet obtained after washing and dehydration, the sheet was stirred to obtain a 0.5% by mass cellulose suspension. This cellulose suspension is defibrated for 30 minutes at 21500 rpm using a fibrillation treatment apparatus (M Technic Co., Clearmix-2.2S), and fibrillated 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 with a width of 4 nm was contained. Moreover, it was confirmed by X-ray diffraction that the cellulose maintained cellulose type I crystals. In addition, the measurement of the infrared absorption spectrum by FT-IR showed absorption based on the phosphate group at 1230 cm ^-1 to 1290 cm ^-1 , confirming the addition of the phosphate group. The amount of phosphate group introduced at this time was 2.1 mmol/g per 1 g (mass) of fine fibrous cellulose.

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

[Production of dry CNF]
To a 1% (w/v) aqueous suspension of pulp solid content of anion-modified CNF1, the agents shown in Table 1 were added as powders. The drug was added in an amount (parts by mass) shown in Table 1 with respect to 100 parts by mass of CNF. All of the agents used in the examples in Table 1 were water soluble, as they dissolved in either a clear or cloudy state when mixed with water at 25° C. at concentrations of 1% or 5%.
Drugs were added in an amount equal to the CNF solids in suspension. Then, the mixture was stirred and mixed with a stirrer, point mixer, homomixer, or the like until it became transparent. The obtained liquid was applied on a Teflon (trademark) plate or a Teflon (trademark) dish and dried with hot air at 60° C. to 105° C. to obtain film-like dry CNF.
Blanks were performed in the same manner as above except that no drug was added.

[Redispersion of dry CNF]
Film-like dry CNF was pulverized by hand to about 1 mm to 2 mm, and 0.1 g was weighed into a test tube. After adding 5 g of distilled water and stirring with a point mixer for about 1 minute, the mixture was 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 the anion-modified CNF was redispersed (solid content concentration 2% (w/v)).

[Evaluation of redispersibility]
The redispersibility was evaluated by visual inspection of the aqueous redispersion or suspension in the test tube. Evaluation was performed based on the following evaluation criteria. The results are shown in Table 1 below.
<Evaluation Criteria>
A: No undispersed CNF pieces were observed completely, showing high transparency equivalent to that of anion-modified CNF before drying.
B: A small amount of fine undispersed CNF pieces is observed, but exhibits high transparency.
C: A small amount of undispersed CNF pieces are observed. D: CNF is not dispersed at all and is cloudy.

As shown in Table 1, it was not possible to disperse the resulting dry CNF in any of the comparative examples in which the material was dried together with a strongly anionic substance, a cationic polymer, or a water-insoluble substance. On the other hand, in the examples in which the dried CNF was dried with a low-molecular-weight saccharide or PVA or an amino acid, it was confirmed that the obtained dry CNF could be dispersed, and the redispersibility, in particular, the transparent dispersibility at the time of redispersion was improved. did it.
Also, in blanks and comparative examples, white sediments and floating matter were observed, and they were cloudy. On the other hand, the test tubes of Examples were transparent with almost no precipitates or undispersed gel-like substances. Among them, in the test tube with the redispersibility evaluation of A, no sediment or undispersed gel-like matter was observed, and the transparency was particularly high.

[Evaluation of Refilming and Gelation]
The aqueous dispersions evaluated as A or B in the evaluation of redispersibility in Table 1 were evaluated for refilm formation and gelation.
Refilming was performed by weighing about 2 g of the aqueous dispersion (redispersion) on a Teflon (trademark) plate and drying it sufficiently with hot air at 70 ° C. to 80 ° C. Gelation was performed by by adding a few drops of a 20% calcium chloride solution into a test tube containing
As a result, both films and gels were formed. In other words, it was suggested that the physical properties of the dry CNF obtained by the production method of the present disclosure did not change significantly from the untreated (before drying) anion-modified CNF.

(Experimental example 2)
CMC (manufactured by Nippon Paper Industries Co., Ltd.) shown in Table 2 below was used to evaluate redispersibility of anion-modified CNF. Anion-modified CNF used anion-modified CNF1 (T-CNF, average fiber diameter: 3 nm, aspect ratio: 250). "Sunrose" is a registered trademark of Nippon Paper Industries Co., Ltd.

[Production and redispersion of dry CNF]
A film-like dry CNF was obtained in the same procedure as in Experimental Example 1 except that the CMC shown in Table 2 below was used instead of the chemicals in Table 1. Film-like dry CNF is pulverized to about 3 × 3 mm, adjusted with distilled water so that the solid content is 0.7% (w / v) in a 200 mL beaker, 600 rpm with a three-one motor, a stirrer with a blade diameter of 3.5 cm was stirred for 1 to 3 hours to obtain an aqueous redispersion or aqueous suspension.
Blanks were performed in the same manner as above except that no drug was added.

[Evaluation of redispersibility]
During the stirring for 1 to 3 hours, the dispersed state of CNF in the aqueous redispersion or aqueous suspension was observed every hour, and the redispersibility was evaluated based on the following evaluation criteria. The results are shown in Table 2 below.
<Evaluation Criteria>
A: Undispersed CNF pieces are not completely observed B: A very small amount of fine undispersed CNF pieces is observed C: A small amount of undispersed CNF pieces is observed D: CNF dispersion is not observed at all

As shown in Table 2, by using CMC with a molecular weight of 20,000 or less, it was possible to improve the redispersibility of dry CNF. In particular, in the test tube of the example in which CMC having a molecular weight of 20,000 or less was added and the stirring time was 2 hours or more, no precipitates or undispersed gels were observed, and anion-modified CNF dispersion before drying. A highly transparent CNF redispersion liquid equivalent to the liquid could be obtained.
In addition, it was confirmed that by using CMC with a molecular weight of 20,000 or less, the time required for redispersion of dry CNF can be shortened.

(Experimental example 3)
Using the agents shown in Table 3, anion-modified CNF2 (CM-CNF, average fiber width: 12 nm, aspect ratio: 130 or more) was used as anion-modified CNF, and the temperature of hot air during dry film production was 60 ° C. Production of dry CNF and redispersion of dry CNF were carried out in the same manner as in Experimental Example 1 except that the dry CNF was redispersed to obtain an aqueous dispersion or aqueous suspension.

[Evaluation of redispersibility]
The redispersibility was evaluated by visual inspection of the aqueous redispersion or suspension in the test tube. Evaluation was performed based on the following evaluation criteria. The results are shown in Table 3 below.
<Evaluation Criteria>
A: Undispersed CNF pieces are not completely observed B: A small amount of fine undispersed CNF pieces is observed C: A small amount of undispersed CNF pieces is observed D: CNF dispersion is not observed at all

As shown in Table 3, by drying with low molecular weight saccharides such as dextrin and α-cyclodextrin, it was possible to disperse the obtained dried CNF in distilled water even for CM-CNF.
In addition, it was confirmed that the redispersibility was improved compared to conventional agents used to improve the redispersibility of dry CNF.

Claims (7)

mixing anion-modified cellulose nanofibers and a redispersibility improver to obtain an aqueous suspension of anion-modified cellulose nanofibers, and drying the aqueous suspension to obtain dry cellulose nanofibers,
The cellulose nanofibers are anion-modified cellulose nanofibers selected from the group consisting of carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers and phosphate esterified cellulose nanofibers,
The method for producing dry cellulose nanofibers , wherein the redispersibility improver contains carboxymethyl cellulose having an average molecular weight of 20,000 or less, which is a water-soluble polymer . mixing an anion-modified cellulose nanofiber and a redispersibility improving agent to obtain an aqueous suspension of anion-modified cellulose nanofiber, and drying the aqueous suspension,
The cellulose nanofibers are anion-modified cellulose nanofibers selected from the group consisting of carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers and phosphate esterified cellulose nanofibers,
The method for improving redispersibility of cellulose nanofibers, wherein the redispersibility improver contains carboxymethyl cellulose having an average molecular weight of 20000 or less , which is a water-soluble polymer. 3. The method of claim 1 or 2, wherein the carboxymethylcellulose does not contain carboxymethylated cellulose nanofibers. The method according to any one of claims 1 to 3, wherein the water-soluble polymer , carboxymethyl cellulose , does not have an X-ray diffraction peak of cellulose type I crystals. 5. The method according to any one of claims 1 to 4, wherein the carboxylmethylated cellulose nanofibers have X-ray diffraction peaks of cellulose type I crystals. An agent for enhancing or improving the redispersibility of dry cellulose nanofibers in a dispersion medium, the agent comprising carboxymethyl cellulose having an average molecular weight of 20,000 or less, which is a water-soluble polymer,
The redispersibility improver, wherein the cellulose nanofibers are anion-modified cellulose nanofibers selected from the group consisting of carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers, and phosphorylated cellulose nanofibers. A dry composition comprising an anion-modified cellulose nanofiber and a redispersibility improver,
The cellulose nanofibers are anion-modified cellulose nanofibers selected from the group consisting of carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers and phosphate esterified cellulose nanofibers,
The composition , wherein the redispersibility improver comprises carboxymethyl cellulose having an average molecular weight of 20,000 or less, which is a water-soluble polymer .