JP7199229B2 - Method for producing hydrophobized anion-modified cellulose nanofiber dispersion and dry solid of hydrophobized anion-modified cellulose - Google Patents

Description

The present invention relates to a method for producing a dispersion of hydrophobized anionically modified cellulose nanofibers and a dry solid of hydrophobized anionically modified cellulose.

It is known that by introducing anionic groups such as carboxyl groups and carboxymethyl groups into the cellulose molecular chain and mechanically processing (fibrillating) it can be converted into cellulose nanofibers with nanoscale fiber diameters. there is Cellulose nanofibers are light, have high strength, and are biodegradable, so their applications in various fields are being investigated.

Usually, anion-modified cellulose nanofibers are highly hydrophilic because the introduced anionic groups form salts such as sodium salts. It has low compatibility with high-molecular-weight polymers. In addition, the dispersibility in low-polarity organic solvents is low. As a method to solve this problem, by acidifying the metal salt type anionic group (eg, —COONa), it is converted to the acid type (eg, —COOH), and the hydrophilicity of the anion-modified cellulose nanofiber is increased. There are ways to lower it.

In Patent Document 1, when dispersing cellulose nanofibers in a medium containing an organic solvent, as a "second production method", an acid is added to an aqueous cellulose nanofiber dispersion to obtain a carboxylate-type group of cellulose nanofibers. a step of substituting a portion of with a carboxylic acid type group, a step of adding an organic solvent to a cellulose nanofiber gel in which a portion of the group has been substituted with a carboxylic acid type, and cellulose nanofiber water to which the organic solvent has been added A method is described that includes removing the aqueous solvent from the dispersion.

In addition, Patent Document 2 discloses, as a “first production method”, a step of subjecting an aqueous dispersion of cellulose nanofibers substituted with a carboxylic acid type to an amine treatment, and recovering the amine-treated cellulose nanofibers and dispersing them in a dispersion medium. and redispersing at to prepare a cellulose nanofiber dispersion.

WO2010/134357 Japanese Unexamined Patent Application Publication No. 2012-21081

In the method described in Patent Document 1, the organic solvent that can be used as the final dispersion medium is limited to three types of dimethylsulfoxide, N,N-dimethylformamide, and N,N-dimethylacetamide. is a water-soluble organic solvent that is arbitrarily miscible with water. The method described in Patent Document 1 does not describe the use of an organic solvent such as toluene, which has low polarity and is almost insoluble in water, as the dispersion medium for the cellulose nanofiber dispersion. Also, Patent Document 2 does not describe the use of a low-polarity, sparingly water-soluble organic solvent as a dispersion medium.

After producing a cellulose nanofiber dispersion using a water-soluble organic solvent as a dispersion medium using the methods described in Patent Documents 1 and 2, the water-soluble organic solvent is replaced with a low-polarity water-insoluble organic solvent. It is conceivable to produce a cellulose nanofiber dispersion using an organic solvent that is poorly soluble in water as a dispersion medium, but when replacing the solvent, it is necessary to repeat addition of the solvent and removal by suction filtration or the like many times. However, there is a problem that the cellulose nanofibers are lost during the repetition of the solvent replacement operation, resulting in a decrease in yield. In addition, in the methods described in Patent Documents 1 and 2, at least two defibration processes (a mixer or (Mechanical treatment using a homogenizer or the like) is required, and there is a problem that the cellulose fibers are damaged as the number of defibrations increases.

An object of the present invention is to provide a method capable of more efficiently producing a dispersion of anion-modified cellulose nanofibers using an organic solvent as a dispersion medium.

As a result of intensive studies by the present inventors, before defibrating the anion-modified cellulose into nanofibers, the anion-modified cellulose is hydrophobized so that the amount of the hydrophobizing agent bound to 1 g is 0.40 g or more. A hydrophobizing agent is added to make the anion-modified cellulose hydrophobic, and the dispersion medium is removed from the obtained dispersion of the hydrophobized anion-modified cellulose to obtain a dry solid of the hydrophobized anion-modified cellulose (the solid content concentration is higher than 90% by mass). It was found that by dispersing this dry solid in an organic solvent while fibrillating, it is possible to efficiently produce a dispersion of anion-modified cellulose nanofibers using an organic solvent as a dispersion medium. This method can reduce the number of fibrillation operations, and can omit the process of solvent replacement that has conventionally been necessary when using a low-polarity organic solvent as a dispersion medium. The invention includes, but is not limited to:
(1) Step 1 of preparing an anion-modified cellulose dispersion,
Step 2 of adding a hydrophobizing agent to a dispersion of anion-modified cellulose to produce a dispersion of hydrophobized anion-modified cellulose;
Step 3 of removing the dispersion medium from the dispersion of the hydrophobized anion-modified cellulose to produce a dry solid of the hydrophobized anion-modified cellulose, and mixing the dry solid of the hydrophobized anion-modified cellulose with an organic solvent, Step 4 of defibrating the hydrophobized anion-modified cellulose in the organic solvent to produce a dispersion of hydrophobized anion-modified cellulose nanofibers using the organic solvent as a dispersion medium;
including
The amount of the hydrophobizing agent bound to 1 g of the anion-modified cellulose is 0.40 g or more,
A method for producing a dispersion of hydrophobized anion-modified cellulose nanofibers, wherein the dry solids of the hydrophobized anion-modified cellulose have a solid content concentration higher than 90% by mass.
(2) The method according to (1), wherein the anion-modified cellulose is a cellulose having a carboxyl group or a cellulose having a carboxyalkyl group.
(3) Hydrophobized anion-modified cellulose containing anion-modified cellulose bound with a hydrophobizing agent, having a solid content concentration of higher than 90% by mass, and having a binding amount of the hydrophobizing agent per 1 g of anion-modified cellulose of 0.40 g or more. dry solids.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to efficiently produce a dispersion of anion-modified cellulose nanofibers using an organic solvent as a dispersion medium. In the method of the present invention, there is no need to perform a solvent replacement step that repeats centrifugation, suction filtration, etc. for replacing water or a highly polar water-soluble organic solvent with a less polar organic solvent. Since the anion-modified cellulose nanofibers can be dispersed in the medium, cost and time can be saved. In addition, conventionally, after fibrillation into cellulose nanofibers, a hydrophobizing agent is added, followed by fibrillation again in an organic solvent to produce a dispersion using an organic solvent as a dispersion medium. In , the number of times of defibration can be reduced by manufacturing hydrophobized cellulose and then fibrillating it in an organic solvent, which is advantageous in that the cellulose fibers are less damaged. In addition, cellulose nanofiber is a material that swells in an aqueous medium and exhibits high viscosity. However, in the present invention, the anion-modified cellulose, which is not very viscous before being fibrillated into cellulose nanofibers, is hydrophobized, so the concentration is higher. of cellulose (for example, 2 to 10% by mass) can be used for hydrophobization treatment, and the efficiency of hydrophobization is high.

TECHNICAL FIELD The present invention relates to a method for producing a dispersion of hydrophobized anion-modified cellulose nanofibers using an organic solvent as a dispersion medium. Hereinafter, cellulose nanofiber may be referred to as "CNF". Specifically, in the method of the present invention, an anion-modified cellulose dispersion is prepared (step 1), and a hydrophobizing agent is added to the anion-modified cellulose dispersion to produce a hydrophobized anion-modified cellulose dispersion. (Step 2), the dispersion medium is removed from the dispersion of the hydrophobized anion-modified cellulose to produce a dry solid of the hydrophobized anion-modified cellulose (Step 3), and the dry solid of the hydrophobized anion-modified cellulose is dissolved in an organic solvent. and defibrating the hydrophobized anion-modified cellulose in an organic solvent to produce a dispersion of hydrophobized anion-modified CNF using the organic solvent as a dispersion medium (step 4). At this time, in step 2, the hydrophobizing agent is added so that the binding amount of the hydrophobizing agent to 1 g of anion-modified cellulose is 0.40 g or more, and in step 3, the solid content concentration of the dry solid is 90 mass. Drying (removal of dispersion medium) is carried out until it is higher than %.

(1) Process 1
In step 1, a dispersion of anion-modified cellulose is prepared. Anion-modified cellulose is cellulose in which an anionic group is introduced into the molecular chain, as described in more detail below.

(1-1) Cellulose The type of cellulose used as a raw material for anion-modified cellulose is not particularly limited. Cellulose is generally classified into natural cellulose, regenerated cellulose, fine cellulose, microcrystalline cellulose excluding non-crystalline regions, etc., according to its origin, production method, and the like. Any of these celluloses can be used as a raw material in the present invention.

Examples of natural cellulose include bleached or unbleached pulp (bleached wood pulp or unbleached wood pulp); linters, purified linters; cellulose produced by microorganisms such as acetic acid bacteria. Raw materials for bleached or unbleached pulp are not particularly limited, and examples thereof include wood, cotton, straw, bamboo, hemp, jute, and kenaf. Also, the method for producing the bleached pulp or the unbleached pulp is not particularly limited, and may be a mechanical method, a chemical method, or a combination of the two. Examples of bleached pulp or unbleached pulp classified by manufacturing method include mechanical pulp (thermomechanical pulp (TMP), groundwood pulp), chemical pulp (softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP) ), softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP) and other kraft pulps). Further, dissolving pulp may be used in addition to paper pulp. Dissolving pulp is pulp that has been chemically refined, and is mainly used by dissolving it in chemicals, and serves as a main raw material for artificial fibers, cellophane, and the like.

Examples of regenerated cellulose include those obtained by dissolving cellulose in some solvent such as cuprammonium solution, cellulose xanthate solution, morpholine derivative, and spinning again.
The fine cellulose is obtained by subjecting cellulosic materials such as the natural cellulose and regenerated cellulose to depolymerization (for example, acid hydrolysis, alkaline hydrolysis, enzymatic decomposition, explosion treatment, vibration ball mill treatment, etc.). and those obtained by mechanically processing the above cellulosic materials.

(1-2) Anion Modification Anion modification refers to the introduction of an anionic group into cellulose, specifically the introduction of an anionic group into the pyranose ring of cellulose by oxidation or substitution reaction. In the present invention, the oxidation reaction means a reaction of directly oxidizing a hydroxyl group of a pyranose ring to a carboxyl group. Further, in the present invention, a substitution reaction means a reaction for introducing an anionic group into a pyranose ring by a substitution reaction other than the oxidation.

(1-2-1) carboxylation (oxidation)
An example of anionic modification is carboxylation (introduction of carboxyl groups to cellulose, also called "oxidation"). As used herein, a carboxyl group refers to -COOH (acid form) and -COOM (metal salt form) (wherein M is a metal ion). 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, the amount of carboxyl groups is preferably 0.6 mmol/g to 3.0 mmol/g, more preferably 1.0 mmol/g to 2.0 mmol/g, relative to the absolute dry weight of the carboxylated cellulose.

The carboxyl group content of carboxylated cellulose can be measured by the following method:
60 ml of a 0.5% by mass slurry (aqueous dispersion) of carboxylated cellulose was prepared, and 0.1 M aqueous hydrochloric acid solution was added to adjust the pH to 2.5. and calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of the weak acid, where the change in conductivity is gradual, using the following formula:
Carboxyl group amount [mmol/g carboxylated cellulose]=a [ml]×0.05/carboxylated cellulose mass [g].

As an example of a carboxylation (oxidation) method, a cellulose feedstock is oxidized in water with an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides, and mixtures thereof. You can mention how to do it. 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- ⁾ 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. The modification is modification by an oxidation reaction.

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. An appropriate amount of the oxidizing agent to be used is, for example, 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. . Further, for example, 1 mol to 40 mol is preferable with respect to 1 mol of the N-oxyl compound.

The oxidation process 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 stages. 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 gas containing ozone 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, these oxidizing agents can be dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and the cellulose raw material can be immersed in the solution for additional oxidation treatment.

The amount of carboxyl groups in the carboxylated cellulose can be adjusted by controlling the reaction conditions such as the amount of the oxidizing agent added and the reaction time. The amount of carboxyl groups in the carboxylated cellulose and the amount of carboxyl groups when the same carboxylated cellulose is used as nanofibers are usually the same.

(1-2-2) Carboxyalkylation An example of anion modification is the introduction of a carboxyalkyl group such as a carboxymethyl group into cellulose. As used herein, a carboxyalkyl group refers to -RCOOH (acid form) and -RCOOM (metal salt form). Here, R is an alkylene group such as a methylene group or ethylene group, and M is a metal ion.

Carboxyalkylated cellulose may be obtained by a known method, or a commercially available product may be used. Preferably, the degree of carboxyalkyl substitution per anhydroglucose unit of the cellulose is less than 0.40. Furthermore, when the anionic group is a carboxymethyl group, the degree of carboxymethyl substitution is preferably less than 0.40. If the degree of substitution is 0.40 or more, the dispersibility of CNF is lowered. Also, the lower limit of the degree of carboxyalkyl substitution is preferably 0.01 or more. Considering workability, the degree of substitution is particularly preferably 0.02 to 0.35, more preferably 0.10 to 0.30. The anhydroglucose unit means an individual anhydroglucose (glucose residue) constituting cellulose, and the degree of carboxyalkyl substitution refers to the hydroxyl group (—OH) in the glucose residue constituting cellulose. The percentage of those substituted with ether groups (-ORCOOH or -ORCOOM) (the number of carboxyalkyl ether groups per glucose residue) is shown.

An example of a method for producing carboxyalkylated cellulose includes the following steps. The modification is modification by a substitution reaction. Carboxymethylated cellulose will be described as an example.

i) Mix the raw material, solvent and mercerizing agent, and mercerize at a reaction temperature of 0 to 70° C., preferably 10 to 60° C., for a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. process,
ii) Then, a carboxymethylating agent is added in an amount of 0.05 to 10.0 times mol per glucose residue, the reaction temperature is 30 to 90° C., preferably 40 to 80° C., and the reaction time is 30 minutes to 10 hours, preferably A step of performing an etherification reaction for 1 to 4 hours.

The above-mentioned cellulose raw material can be used as the bottom raw material. As the solvent, 3 to 20 times by weight of water or a lower alcohol, specifically water, methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol, etc. alone, or two Mixed media of more than one species can be used. When a lower alcohol is mixed, the mixing ratio is preferably 60 to 95% by mass. As the mercerizing agent, it is preferable to use an alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide, in an amount of 0.5 to 20 times the moles of the anhydroglucose residue of the starting material.

As described above, the degree of carboxymethyl substitution per glucose unit of cellulose is less than 0.40, preferably 0.01 or more and less than 0.40. By introducing carboxymethyl substituents into cellulose, the celluloses electrically repel each other. Therefore, cellulose into which carboxymethyl substituents have been introduced can be nano-fibrillated. If the number of carboxymethyl substituents per glucose unit is less than 0.02, nano-fibrillation may not be sufficient. The degree of carboxyalkyl substitution in the carboxyalkylated cellulose is generally the same as the degree of carboxyalkyl substitution when the carboxyalkylated cellulose is made into nanofibers.

The degree of carboxymethyl substitution per glucose unit can be measured by the following method:
About 2.0 g of carboxymethylated cellulose (absolute dry) is precisely weighed and placed in a 300 mL conical flask with a common stopper. 100 mL of a solution obtained by adding 100 mL of special grade concentrated nitric acid to 900 mL of methanol is added and shaken for 3 hours to convert carboxymethylated cellulose salt (CM cellulose) into hydrogenated CM cellulose. 1.5 g to 2.0 g of hydrogenated CM cellulose (absolutely dried) is accurately weighed and placed in a 300 mL Erlenmeyer flask equipped with a common stopper. Hydrogenated CM-cellulose is wetted with 15 mL of 80% by mass methanol, 100 mL of 0.1 N NaOH is added, and shaken at room temperature for 3 hours. Excess NaOH is back-titrated with 0.1 N H ₂ SO ₄ using phenolphthalein as an indicator. The degree of carboxymethyl substitution (DS) is calculated by the formula:
A=[(100×F′−(0.1N H ₂ SO ₄ ) (mL)×F)×0.1]/(absolute dry weight of hydrogen-type 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 hydrogenated CM-cellulose
F: factor of _{0.1N H2SO4} F': factor of 0.1N NaOH.

Also, the amount of carboxymethyl groups (anionic groups) (mmol/g) can be calculated from the degree of carboxymethyl substitution (DS) using the following formula:
Amount of carboxymethyl groups (mmol/g) = (DS/(DS x 58 + 162)) x 1000
The degree of substitution of carboxyalkyl groups other than carboxymethyl groups can be obtained in the same manner as described above, and the amount of carboxyalkyl groups can be calculated from the following formula using the degree of carboxyalkyl substitution (DS). can:
Amount of carboxyalkyl group (mmol/g) = [DS/{DS x (molecular weight of carboxyalkyl group - 1) + 162}] x 1000
(1-2-3) Esterification One example of anion modification is esterification. Examples of the esterification method include a method of mixing a cellulose raw material with powder or an aqueous solution of a phosphoric acid compound, a method of adding an aqueous solution of a phosphoric acid compound to a slurry of a cellulose raw material, and the like. Phosphoric acid compounds include phosphoric acid, polyphosphoric acid, phosphorous acid, hypophosphorous acid, phosphonic acid, polyphosphonic acid, and esters thereof. These may be in the form of salts. Among the above, a compound having a phosphate group is preferable because it is low cost, easy to handle, and can introduce a phosphate group into the cellulose of the pulp fiber to improve defibration efficiency. Compounds having a phosphate group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium phosphite, potassium phosphite, sodium hypophosphite, potassium hypophosphite , sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate , ammonium pyrophosphate, ammonium metaphosphate and the like. Phosphate groups can be introduced into cellulose by using one or more of these in combination. 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 preferred. Sodium dihydrogen phosphate and disodium hydrogen phosphate are particularly preferred. Further, it is desirable to use the phosphoric acid-based compound in the form of an aqueous solution, since the reaction can proceed uniformly and the efficiency of introduction of the phosphoric acid group is increased. The pH of the aqueous solution of the phosphoric acid-based compound is preferably 7 or less because the efficiency of introducing phosphoric acid groups is increased, but from the viewpoint of suppressing hydrolysis of pulp fibers, pH 3 to 7 is preferable.

Examples of the method for producing the phosphorylated cellulose include the following method. A phosphoric acid compound is added to a suspension of a cellulosic raw material having a solid concentration of 0.1 to 10% by mass while stirring to introduce a phosphoric acid group into the cellulose. When the cellulosic raw material is 100 parts by mass, the amount of the phosphoric acid compound added is preferably 0.2 to 500 parts by mass, more preferably 1 to 400 parts by mass, in terms of elemental phosphorus. If the proportion of the phosphoric acid-based compound 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.

In addition to the phosphoric acid-based compound, powders or aqueous solutions of other compounds may be mixed. The compound other than the phosphoric acid-based compound is not particularly limited, but a basic nitrogen-containing compound is preferable. "Basic" here is defined as a pink to red color of the aqueous solution in the presence of the phenolphthalein indicator or pH of the aqueous solution greater than 7. The basic nitrogen-containing compound used in the present invention is not particularly limited as long as the effect of the present invention is exhibited, but a compound having an amino group is preferable. Examples include urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like. Among them, urea is preferable because it is inexpensive and easy to handle. The amount of the other compound added is preferably 2 to 1000 parts by mass, more preferably 100 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 to 95°C, more preferably 30 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 esterification reaction conditions are within these ranges, cellulose can be prevented from being excessively esterified and easily dissolved, and the yield of phosphate-esterified cellulose is improved. After dehydrating the obtained phosphate-esterified cellulose suspension, it is preferable to heat-treat at 100 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 or more and less than 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 nanofibrillation 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 defibrate efficiently, it is preferable to wash the cellulose-based raw material obtained above with cold water after boiling it. Modification by these esterifications is modification by a substitution reaction. The degree of substitution in the esterified cellulose and the degree of substitution when the same esterified cellulose is made into nanofibers are usually the same. The amount (mmol/g) of the phosphate group (anionic group) can be calculated from the degree of substitution (DS) of the phosphate group using the following formula:
The amount of phosphate groups (mmol/g) = (DS/(DS x 64 + 162)) x 1000.

(1-3) Anion-Modified Cellulose Anion-modified cellulose can be obtained by anion-modifying the raw material cellulose as exemplified above. Moreover, you may use a commercial thing. As the type of anion-modified cellulose, cellulose having a carboxyl group or cellulose having a carboxyalkyl group is preferable. In particular, carboxylated cellulose obtained by oxidizing cellulose with an N-oxyl compound and an oxidizing agent is preferable in that anionic groups are uniformly introduced and it is easily fibrillated uniformly.

As the anion-modified cellulose, one that maintains at least a part of its fibrous shape even when dispersed in water or a water-soluble organic solvent is used. Nanofibers cannot be obtained by using materials that do not maintain their fibrous shape (that is, materials that dissolve). The expression that at least a part of the fibrous shape is maintained when dispersed means that a fibrous substance can be observed when an anion-modified cellulose dispersion is observed with an electron microscope. In addition, anion-modified cellulose is preferable, since a peak of cellulose type I crystals can be observed when measured by X-ray diffraction.

The degree of crystallinity of cellulose in the anion-modified cellulose is preferably 50% or more, more preferably 60% or more for crystalline type I. By adjusting the crystallinity to the above range, it is possible to sufficiently obtain crystalline cellulose fibers that do not dissolve even after the fibers are refined by fibrillation. The crystallinity of cellulose can be controlled by the crystallinity of the raw material cellulose and the degree of anion modification. The method for measuring the crystallinity of anion-modified cellulose is as follows:
A sample is placed in a glass cell and measured using an X-ray diffraction measurement device (LabX XRD-6000, manufactured by Shimadzu Corporation). The degree of crystallinity is calculated using the method of Segal et al. Using the diffraction intensity at 2θ = 10° to 30° in the X-ray diffraction diagram as a baseline, the diffraction intensity at 2θ = 22.6° at the 002 plane and 2θ = It is calculated from the diffraction intensity of the amorphous portion at 18.5° by the following equation.
Xc=(I002c−Ia)/I002c×100
Xc: Crystallinity of type I of cellulose (%)
I002c: 2θ=22.6°, diffraction intensity of 002 plane Ia: 2θ=18.5°, diffraction intensity of amorphous portion.

The proportion of cellulose type I crystals in the anion-modified cellulose and the proportion of cellulose type I crystals when the anion-modified cellulose is used as nanofibers are usually the same.
In the anion-modified cellulose obtained by the above method, the introduced anionic group is usually in the form of a metal salt (for example, -COO ^- M ⁺ or -RCOO ^- M ⁺ (M is a metal such as sodium or potassium). and R is an alkylene group such as a methylene group or an ethylene group)). It is preferable to convert the metal salt-type anionic groups in the anion-modified cellulose to acid-type (eg, —COOH, —RCOOH, etc.) in order to facilitate the subsequent reaction with the hydrophobizing agent.

The method for converting to the acid form is not particularly limited, and examples thereof include a method of adding acid to anion-modified cellulose and a method of contacting anion-modified cellulose with a cation exchange resin. When an acid is added, the type of acid used is not particularly limited, and examples include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, sulfurous acid, nitrous acid, and phosphoric acid, acetic acid, lactic acid, oxalic acid, citric acid, formic acid, and adipic acid. , sebacic acid, stearic acid, maleic acid, succinic acid, tartaric acid, fumaric acid, gluconic acid and the like. Hydrochloric acid or sulfuric acid, which are common and readily available, are preferred. The pH at which the acid is added is preferably in the range of 1-6, more preferably 2-5. The amount of acid to be added is not particularly limited as long as it is an amount that can convert the metal salt-type anion-modified cellulose into an acid form. If so, it is preferably 10 equivalents or more. When contacting with an acidic ion exchange resin, examples of acidic ion exchange resins include strongly acidic cation exchange resins and weakly acidic cation exchange resins.

(1-4) Dispersion of Anion-Modified Cellulose As the dispersion medium for the dispersion of anion-modified cellulose prepared in step 1, water, an organic solvent, or a mixture thereof can be appropriately selected. Although the type of organic solvent does not matter, for example, a polar solvent that has a high affinity for hydroxyl groups in cellulose, and a water-soluble organic solvent that can be mixed with water in any proportion are preferred, such as methanol, ethanol, isopropanol, isobutanol, sec-butanol, tert-butanol, methyl cellosolve, ethyl cellosolve, ethylene glycol, glycerin, ethylene glycol dimethyl ether, 1,4-dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl Sulfoxide and the like can be mentioned. The dispersion medium may be used alone, or two or more of them may be mixed and used. For example, a form in which two or more kinds of organic solvents are mixed, a form in which water and an organic solvent are contained, a form in which only water is used, or the like can be appropriately selected. Using only water as the dispersion medium (ie, 100% water) is preferred for ease of handling. When water and an organic solvent are mixed, the mixing ratio is not particularly limited, and the mixing ratio may be appropriately adjusted according to the type of organic solvent used.

The concentration of anion-modified cellulose in the dispersion is preferably 0.01 to 15% by mass, preferably 1 to 10% by mass, and 2 to 6% by mass in consideration of the efficiency when mixed with the hydrophobizing agent later. is more preferred.

(2) Process 2
In step 2, a hydrophobizing agent is added to the anion-modified cellulose dispersion to hydrophobize the anion-modified cellulose to produce a hydrophobized anion-modified cellulose dispersion. Hydrophobization refers to a treatment for imparting hydrophobic groups to anion-modified cellulose to improve the hydrophobicity of the anion-modified cellulose.

The hydrophobizing agent is preferably a compound having an amine or phosphine capable of forming an onium salt by bonding with the anionic group of the anion-modified cellulose, such as primary amine, secondary amine, tertiary amine and quaternary ammonium. , aromatic amines, diamines, polyetheramines, and phosphines.

The hydrophobizing agent is added so that the binding amount of the hydrophobizing agent per 1 g of the anion-modified cellulose is 0.40 g or more. More preferably, the binding amount of the hydrophobizing agent is 0.50 g or more, and still more preferably 1.00 g or more. A method for calculating the binding amount of the hydrophobizing agent will be described later. Hydrophobizing agents bind to the anionic groups of the anionically modified cellulose. Step 3 of adding a sufficient amount of hydrophobizing agent according to the amount of anionic groups of the anion-modified cellulose to lower the solid content concentration of the anion-modified cellulose in the entire dispersion, thereby producing a subsequent dry solid. Aggregation due to hydrogen bonding between cellulose fibers during drying can be inhibited, and defibration can be advanced in the subsequent step 4 to obtain a nanofiber dispersion.
In step 2, if the amount of hydrophobizing agent bound to 1 g of anion-modified cellulose is less than 0.40 g, defibration does not proceed in step 4, and a nanofiber dispersion cannot be obtained. The upper limit of the amount of the hydrophobizing agent bound to 1 g of the anion-modified cellulose is not particularly limited, but if the amount of the hydrophobizing agent bound is too high, the hydrophobized anion-modified cellulose (that is, the anion-modified cellulose to which the hydrophobizing agent is bound ), the amount of hydrophobizing agent bound to 1 g of anion-modified cellulose is preferably 10.00 g or less, more preferably 5.00 g or less.

Hydrophobizing agents bind to the anionic groups of the anionically modified cellulose. Due to the mode of reaction, the added hydrophobizing agents all react with the anionic groups. The present inventors have found that when 1 molar equivalent or more of a hydrophobizing agent (amine type) is added, the anion-modified cellulose, which was in the acid form (-COOH), was all changed to -COO- ^by infrared spectroscopy. Confirmed by law. This indicates that the amine of the hydrophobizing agent was ionically bonded to all of the anionic groups of the anionically modified cellulose. Therefore, the binding amount of the hydrophobizing agent to 1 g of the anion-modified cellulose when 1 molar equivalent or more of the hydrophobizing agent is added to the anionic group can be calculated by the following formula:
i) When the amount (number of moles) of the hydrophobizing agent is added to the amount (number of moles) of the anionic group, the binding amount of the hydrophobizing agent to 1 g of the anion-modified cellulose [g] = the anionicity of the anion-modified cellulose Amount of group [mmol/g] x molecular weight of hydrophobizing agent x 0.001 x valence of anionic group ii) The amount (number of moles) of the hydrophobizing agent added is less than the amount (number of moles) of the anionic group Case Binding amount of hydrophobizing agent to 1 g of anion-modified cellulose [g] = amount of anionic groups in anion-modified cellulose [mmol/g] x molecular weight of hydrophobizing agent x 0.001 x valence of anionic group x added Number of moles of hydrophobizing agent [mmol] / Number of moles of anionic group [mmol]
In i) and ii), the valence of the anionic group is 1 when the anionic group is a carboxyl group or a carboxyalkyl group, and 2 when the anionic group is a phosphate group. In ii), the number of moles (mmol) of anionic groups can be determined from the amount of anionic groups (mmol/g) and the absolute dry mass (g) of anion-modified cellulose.

Examples of hydrophobizing agents include, but are not limited to, JEFFAMINE (registered trademark) M-600, JEFFAMINE (registered trademark) M-1000, JEFFAMINE (registered trademark) M-2005, and JEFFAMINE (registered trademark) manufactured by HUNTSMAN. Polyetheramines such as M-2070, methylamine, ethylamine, oleylamine, propylamine, dodecylamine, stearylamine, tetradecylamine, 1-hexenylamine, 1-dodecenylamine, 9,12-octadecadienylamine (linoleamine ), primary amines such as 9,12,15-octadecatrienylamine and linoleylamine, secondary amines such as dimethylamine and diethylamine, tertiary amines such as trimethylamine and triethylamine, benzalkonium chloride, benzethonium chloride, quaternary ammonium such as methylbenzethonium chloride, cetylpyridinium chloride, cetrimonium, dophanium chloride, tetraethylammonium bromide and didecyldimethylammonium chloride; aromatic amines such as aniline, pyridine and benzylamine; diamines such as ethylenediamine and hexamethylenediamine; , triphenylphosphine, trimethylphosphine and the like.

The amount of the hydrophobizing agent to be added is determined according to the molecular weight of the hydrophobizing agent to be used and the amount of anionic groups in the anion-modified cellulose, and is added within a range that satisfies the above binding amount of the hydrophobizing agent. For example, it may be added in an amount of 50 to 150%, preferably 70 to 130, relative to the amount (number of moles) of anionic groups in the anion-modified cellulose, within the range that satisfies the binding amount of the hydrophobizing agent. %, more preferably 80-120%, more preferably 100-120%.

The hydrophobizing agent may be added to the anion-modified cellulose dispersion as it is or after being mixed with water or a water-soluble organic solvent. The concentration of the anion-modified cellulose in the anion-modified cellulose dispersion when the hydrophobizing agent is added is preferably 0.01 to 15% by mass, preferably 1 to 10% by mass, and more preferably 2 to 6% by mass. . By mixing the hydrophobizing agent and the anion-modified cellulose for a certain period of time while stirring, a dispersion of the hydrophobized anion-modified cellulose can be produced.

(3) Process 3
In step 3, the dispersion medium is removed from the dispersion of hydrophobized anion-modified cellulose obtained in step 2 to produce a dry solid of hydrophobized anion-modified cellulose. At this time, it is necessary to sufficiently remove the dispersion medium so that the solid content concentration in the dry solid is higher than 90% by mass. The solid content concentration in the dry solids is preferably higher than 95% by mass, more preferably 97% by mass or more, and still more preferably 98% by mass or more. Cellulose tends to swell by absorbing water or a water-soluble organic solvent, but in Step 3, it is necessary to sufficiently remove the water or water-soluble organic solvent absorbed by the cellulose. By sufficiently removing the dispersion medium, which is water or a water-soluble organic solvent, in step 3, the solvent replacement step can be omitted, and dispersion in a low-polar organic solvent can be carried out in the subsequent step 4. . On the other hand, if the solid after drying contains 10% by mass or more of a dispersion medium (water and/or water-soluble organic solvent), defibrate and disperse in a low-polar organic solvent such as toluene in step 4. In this case, it becomes impossible to sufficiently mix with a low-polarity solvent, causing problems such as the occurrence of precipitation and a decrease in the transparency of the resulting dispersion.

Solids concentration in dry solids can be measured by the following procedure:
The dry solid is dried in an oven at 105° C. for 12 hours, and the solid content concentration of the dry solid is calculated from the masses before and after drying.
Solid content concentration (% by mass) of dry solids=mass after drying/mass before drying.

The means for removing the dispersion medium is not particularly limited, and for example, the dispersion medium may be dried by placing at a temperature of 60 to 130° C. for 3 to 24 hours.
(4) Step 4
In step 4, the dry solid of hydrophobized anion-modified cellulose is mixed with an organic solvent, the hydrophobized anion-modified cellulose is fibrillated in the organic solvent, and a dispersion of hydrophobized anion-modified CNF using the organic solvent as a dispersion medium is obtained. to manufacture.

The type of organic solvent to be used is not particularly limited, and it may be a water-soluble organic solvent as described above. ) Even if an organic solvent is used as a dispersion medium, a uniformly dispersed CNF dispersion can be produced. The type of organic solvent may be selected according to the use of the CNF dispersion.

Low polarity organic solvents include, but are not limited to, benzene, toluene, xylene, n-hexane, n-octane, cyclohexane, methylcyclohexane, dichloromethane, dichloroethane, chloroform, methylene chloride, carbon tetrachloride, fluorotrichloro. methane, trichlorotrifluoromethane, hexafluorobenzene, tetrahydrofuran, 1,2-dimethoxyethane, cyclopentyl methyl ether, methyl tertiary butyl ether and the like. One or more of these can be appropriately selected and used depending on the final application of the anion-modified CNF.

The mixing ratio of the organic solvent to the dry solid of the hydrophobized anion-modified cellulose is not particularly limited. The organic solvent is preferably added in an amount of 01 to 5% by mass, more preferably 0.5 to 3.0% by mass.

After mixing the dry solid of hydrophobized anion-modified cellulose with an organic solvent, the cellulose is defibrated by mechanical treatment in the organic solvent, and a dispersion of hydrophobized anion-modified CNF using the organic solvent as a dispersion medium is obtained. Form.

Although the device used for fibrillation is not limited, it is preferable to use a device capable of applying a strong shearing force to the dispersion, such as a high-speed rotation type, colloid mill type, high pressure type, roll mill type, and ultrasonic type. 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 dispersion and a strong shearing force. The pressure is more preferably 100 MPa or higher, still more preferably 140 MPa or higher. A high-pressure or ultra-high-pressure homogenizer pressurizes a fluid with a pump to make it high pressure, and by jetting it out from very fine gaps provided in the flow path, it emulsifies with total energy such as shear force due to collision between particles and pressure difference. , dispersing, disintegrating, pulverizing, and ultra-fine. Prior to fibrillation and dispersion treatment with a high-pressure homogenizer, pretreatment can be performed using a known mixing, stirring, emulsifying, and dispersing device such as a high-speed shear mixer, if necessary.

Nanofibers of hydrophobized anion-modified cellulose can be obtained by the above defibration. CNF (cellulose nanofiber) is a fiber having an average fiber diameter of about 3 to 500 nm, preferably about 3 to 150 nm, more preferably about 3 to 20 nm. The aspect ratio is 30 or more, preferably 50 or more, more preferably 100 or more. Although the upper limit of the aspect ratio is not limited, it is about 500 or less.

The average fiber diameter and average fiber length of the hydrophobized anion-modified CNF are atomic force microscope (AFM) when the diameter is less than 20 nm, and field emission scanning electron microscope (FE-SEM) when the diameter is 20 nm or more. It can be measured by analyzing 200 randomly selected fibers and calculating the average. Also, the aspect ratio can be calculated by the following formula:
Aspect ratio = average fiber length/average fiber diameter.

INDUSTRIAL APPLICABILITY According to the present invention, a dispersion of hydrophobized anion-modified CNF using an organic solvent as a dispersion medium can be efficiently produced. The dispersion obtained in the present invention is characterized by uniform dispersion and high transparency even when a low-polarity organic solvent such as toluene is used as the dispersion medium. Transparency is measured, for example, in the following way:
A CNF dispersion with a predetermined concentration is prepared, and a UV-VIS spectrophotometer UV-1800 (manufactured by Shimadzu Corporation) is used to measure the transmittance of 660 nm light using a prismatic cell with an optical path length of 10 mm, Make it transparent.

In the present invention, for example, for a hydrophobized anion-modified CNF dispersion in which the dispersion medium is toluene and the solid content (in terms of CNF (not including the hydrophobizing agent)) is 1.0% by mass, the transparency measured by the above method is 75% or more, more preferably 80% or more, more preferably 85% or more, even more preferably 90% or more.

In addition, since the method of the present invention can reduce damage to cellulose fibers when producing a CNF dispersion using an organic solvent as a dispersion medium, it is possible to produce a CNF dispersion having a high viscosity. Viscosity of CNF dispersions is measured, for example, by the following method:
Prepare a CNF dispersion of a predetermined concentration, according to the method of JIS-Z-8803, using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.), at 25 ° C., rotation speed 60 rpm or 6 rpm, 3 minutes. Measure the later value.

In the present invention, for example, toluene is used as a dispersion medium, and a hydrophobized anion-modified CNF dispersion having a solid content (in terms of CNF (not including a hydrophobizing agent)) of 1.0% by mass is measured by the above method at 60 rpm. A dispersion having a B-type viscosity of 200 mPa·s or more, preferably 600 mPa·s or more, more preferably 1000 mPa·s or more, and still more preferably 1500 mPa·s or more can be formed.

(5) Dry Solid of Hydrophobized Anion-Modified Cellulose The dry solid of the hydrophobized anion-modified cellulose obtained in step 3 has the hydrophilicity of the anion-modified cellulose reduced by the hydrophobization treatment, and is water or water-soluble. Since it contains almost no aqueous dispersion medium such as an organic solvent, it can be used by being well mixed with various organic solvents and hydrophobic polymers. The dry solids of hydrophobized anionically modified cellulose comprise anionically modified cellulose with attached hydrophobizing agents. The hydrophobizing agent is as described above, and at least the amount of the hydrophobizing agent bound to 1 g of the anion-modified cellulose is 0.40 g or more. The dispersion medium is sufficiently removed so that the solid content concentration in the dry solid is higher than 90% by mass, the solid content concentration is higher than 95% by mass, more preferably 97% by mass or more, and further Preferably, it is 98% by mass or more.

In the present invention, when the hydrophobized anion-modified cellulose is dried, aggregation of the cellulose fibers can be suppressed, resulting in an increase in bulk. Therefore, the dry solid of the obtained hydrophobized anion-modified cellulose becomes a cellulose fiber that is easily dispersed in an organic solvent and has good handling performance.

The dry solid of the hydrophobized anion-modified cellulose is mainly composed of the hydrophobized anion-modified cellulose, and optionally conventional additives ( antibacterial agents, coloring agents, resin base materials, resin antistatic agents, antifogging agents, light stabilizers, UV absorbers, pigments, inorganic fillers, antifungal agents, preservatives, foaming agents, flame retardants, etc.) It may contain small amounts of the above additives by drying. When the dry solid of the hydrophobized anion-modified cellulose contains additives other than the hydrophobized anion-modified cellulose, the proportion of the hydrophobized anion-modified cellulose in the dry solid is preferably 80% by mass or more, and more preferably 90% by mass or more. Preferably, 95% by mass or more is more preferable. The dry solids may be free of additives and consist solely of hydrophobized anionically modified cellulose (with a small amount of residual carrier medium).

The form of the dried solid of the hydrophobized anion-modified cellulose is not particularly limited. can be selected.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.
<Example 1>
500 g (absolutely dry) of bleached unbeaten kraft pulp (85% whiteness) derived from softwood is added to 500 ml of an aqueous solution of 780 mg of TEMPO (Sigma Aldrich) and 75.5 g of sodium bromide, until the pulp is uniformly dispersed. Stirred. An aqueous sodium hypochlorite solution was added to the reaction system so as to have a concentration of 6.0 mmol/g to initiate an oxidation reaction. 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 a pulp (carboxylated cellulose) into which carboxyl groups were introduced. The carboxyl group content of this carboxylated cellulose was 1.42 mmol/g.

The solid content concentration of the carboxylated cellulose was adjusted to 5% by mass with water, and hydrochloric acid having a concentration of 10% was added to convert the sodium salt type carboxyl group (-COONa) in the carboxylated cellulose to an acid type (-COOH ). After that, using a glass filter, suction filtration was performed to dehydrate. Again, the solid content concentration of the carboxylated cellulose was adjusted to 5 mass % with water, and then dehydrated. This process was repeated three times to obtain acid-type carboxylated cellulose with a solid concentration of 25% by mass.

The obtained dispersion of acid-type carboxylated cellulose was diluted with water so that the solid content concentration was 4% by mass, and JEFFAMINE (registered trademark) M-600 (manufactured by HUNTSMAN, molecular weight 600) was added as a hydrophobizing agent. One equivalent was added with respect to the amount of carboxyl groups. The binding amount of hydrophobizing agent calculated according to the above formula is 0.85 g. Mixed with a homogenizer (1500 rpm, 10 minutes) to produce a dispersion of carboxylated cellulose with a hydrophobizing agent (hydrophobicized carboxylated cellulose). The dispersion of hydrophobized carboxylated cellulose was allowed to stand at a temperature of 70° C. for 15 hours to produce a dry solid of hydrophobized carboxylated cellulose (solid content concentration 98% by mass). Toluene was added to the obtained dry solid so that the solid content was 1% by mass in terms of carboxylated cellulose (without hydrophobizing agent), and the mixture was stirred at 8000 rpm for 10 minutes. Subsequently, using an ultrahigh-pressure homogenizer, the mixture was treated (fibrillated) once at 20° C. at 80 MPa and further at 150 MPa five times to obtain a dispersion of hydrophobized carboxylated CNF using toluene as a dispersion medium. The yield (ie the ratio of the mass of carboxylated CNF in the finally obtained hydrophobized carboxylated CNF to the mass of carboxylated cellulose used) was 100%.

The obtained dispersion of hydrophobized carboxylated CNF (dispersion medium: toluene, solid content (converted to carboxylated CNF): 1% by mass) was measured for transparency and viscosity by the methods described above. Table 1 shows the results.

<Example 2>
JEFFAMINE (registered trademark) M-1000 (manufactured by HUNTSMAN, molecular weight 1000) was used as a hydrophobizing agent, and the treatment with an ultrahigh-pressure homogenizer was performed once at 80 MPa and three times at 150 MPa in the same manner as in Example 1. , prepared a dispersion of hydrophobized carboxylated CNF in toluene as a dispersion medium. The amount of hydrophobizing agent bound is 1.42 g. The transparency and viscosity of the obtained hydrophobized carboxylated CNF dispersion (dispersion medium: toluene, solid content (in terms of carboxylated CNF): 1% by mass) were measured in the same manner as in Example 1. Table 1 shows the results.

<Example 3>
JEFFAMINE (registered trademark) M-2005 (manufactured by HUNTSMAN, molecular weight 2000) was used as a hydrophobizing agent, and the treatment with an ultrahigh-pressure homogenizer was performed once at 80 MPa and three times at 150 MPa in the same manner as in Example 1. , prepared a dispersion of hydrophobized carboxylated CNF in toluene as a dispersion medium. The amount of hydrophobizing agent bound is 2.84 g. The transparency and viscosity of the obtained hydrophobized carboxylated CNF dispersion (dispersion medium: toluene, solid content (in terms of carboxylated CNF): 1% by mass) were measured in the same manner as in Example 1. Table 1 shows the results.

<Comparative Example 1>
An attempt was made to produce a dispersion of hydrophobized carboxylated CNF using toluene as a dispersion medium in the same manner as in Example 1, except that octylamine (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 129) was used as a hydrophobizing agent. , defibration did not proceed, and a CNF dispersion was not obtained. The binding amount of hydrophobizing agent is 0.18 g.

<Comparative Example 2>
An attempt was made to produce a dispersion of hydrophobized carboxylated CNF using toluene as a dispersion medium in the same manner as in Example 1, except that stearylamine (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 270) was used as a hydrophobizing agent. , defibration did not proceed, and a CNF dispersion was not obtained. The amount of hydrophobizing agent bound is 0.38 g.

<Comparative Example 3>
Carboxylated cellulose having a carboxyl group content of 1.42 mmol/g was produced in the same manner as in Example 1. The carboxylated cellulose was adjusted to a solid content concentration of 1% by mass with water, and treated (defibrated) at 20° C. at 80 MPa once and then at 150 MPa three times using an ultrahigh-pressure homogenizer (fibrillation). An aqueous dispersion of CNF was obtained.

A cation exchange resin was added to the aqueous dispersion of carboxylated CNF, and the sodium salt type carboxyl group (-COONa) in the carboxylated CNF was converted to an acid form (-COOH). After that, it was separated from the cation exchange resin by suction filtration using a metal mesh, and the filtrate was recovered. After adding acetone to the obtained acid-form carboxylated CNF, centrifugation (3000 rpm, 10 minutes, device: 7800 manufactured by Kubota Seisakusho Co., Ltd.) was performed. After acetone was added to the obtained precipitate and mixed, centrifugation was performed again under the same conditions. Next, after adding acetone to the precipitate, suction filtration (diaphragm type vacuum pump, DCT-40, manufactured by ULVAC KIKO CO., LTD.) was performed using a glass filter (15G3, manufactured by Shibata Scientific Co., Ltd.). This addition of acetone and suction filtration was repeated three times. Further, toluene was used in place of acetone, and the addition of toluene and suction filtration were repeated three times to replace the dispersion medium of the carboxylated CNF with toluene.

To the obtained mixture of carboxylated CNF and toluene (solid content concentration 1% by mass), JEFFAMINE (registered trademark) M-600 (manufactured by HUNTSMAN, molecular weight 600) as a hydrophobizing agent is added to 1 equivalent with respect to the amount of carboxyl groups. After mixing and stirring with a homogenizer at 8000 rpm for 10 minutes, the toluene is dispersed by treating (defibrating) with an ultrahigh pressure homogenizer at 20 ° C. once at 80 MPa and twice at 150 MPa. A dispersion of hydrophobized carboxylated CNF as a vehicle was obtained. The amount of hydrophobizing agent bound is 0.85 g. The yield (ie the ratio of the mass of carboxylated CNF in the finally obtained hydrophobized carboxylated CNF to the mass of carboxylated cellulose used) was 85%. The transparency and viscosity of the obtained hydrophobized carboxylated CNF dispersion (dispersion medium: toluene, solid content (in terms of carboxylated CNF): 1% by mass) were measured in the same manner as in Example 1. Table 1 shows the results.

<Comparative Example 4>
A dispersion of hydrophobized carboxylated CNF using toluene as a dispersion medium was produced in the same manner as in Comparative Example 3 except that JEFFAMINE (registered trademark) M-1000 (manufactured by HUNTSMAN, molecular weight 1000) was used as a hydrophobizing agent. . The amount of hydrophobizing agent bound is 1.42 g. The transparency and viscosity of the obtained hydrophobized carboxylated CNF dispersion (dispersion medium: toluene, solid content (in terms of carboxylated CNF): 1% by mass) were measured in the same manner as in Example 1. Table 1 shows the results.

<Comparative Example 5>
A dispersion of hydrophobized carboxylated CNF using toluene as a dispersion medium was produced in the same manner as in Comparative Example 3 except that JEFFAMINE (registered trademark) M-2005 (manufactured by HUNTSMAN, molecular weight 2000) was used as a hydrophobizing agent. . The amount of hydrophobizing agent bound is 2.84 g. The transparency and viscosity of the obtained hydrophobized carboxylated CNF dispersion (dispersion medium: toluene, solid content (in terms of carboxylated CNF): 1% by mass) were measured in the same manner as in Example 1. Table 1 shows the results.

<Comparative Example 6>
A dispersion of hydrophobized carboxylated CNF using toluene as a dispersion medium was produced in the same manner as in Comparative Example 3 except that octylamine (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 129) was used as a hydrophobizing agent. The binding amount of hydrophobizing agent is 0.18 g. The transparency and viscosity of the obtained hydrophobized carboxylated CNF dispersion (dispersion medium: toluene, solid content (in terms of carboxylated CNF): 1% by mass) were measured in the same manner as in Example 1. Table 1 shows the results.

<Comparative Example 7>
A dispersion of hydrophobized carboxylated CNF using toluene as a dispersion medium was produced in the same manner as in Comparative Example 3 except that stearylamine (manufactured by Tokyo Chemical Industry Co., Ltd., molecular weight 270) was used as a hydrophobizing agent. The amount of hydrophobizing agent bound is 0.38 g. The transparency and viscosity of the obtained hydrophobized carboxylated CNF dispersion (dispersion medium: toluene, solid content (in terms of carboxylated CNF): 1% by mass) were measured in the same manner as in Example 1. Table 1 shows the results.

From the results in Table 1, the anion-modified cellulose was hydrophobized so that the amount of hydrophobizing agent bound to 1 g of the anion-modified cellulose was 0.40 g or more, and in Examples 1 to 3 produced according to the procedure of the present invention, the conventional It can be seen that dispersions with transparency equal to or higher than those of Comparative Examples 3-7 using the solvent substitution of 1 were able to be produced in high yields. The methods of Examples 1 to 3 do not require conventional solvent replacement, which repeats solvent addition and centrifugation or suction filtration, so compared to methods using conventional solvent replacement, cost and time savings. Become. In addition, when adding the hydrophobizing agent, the viscosity of the CNF dispersion is high in Comparative Examples 3 to 7, so the solid content of the CNF dispersion is 1% by mass to achieve sufficient mixing with the hydrophobizing agent. Although it was necessary to adjust, in Examples 1 to 3, it was sufficient to add the hydrophobizing agent to the carboxylated cellulose before making it into CNF, and the hydrophobizing agent was added to the carboxylated cellulose having a solid content of 4% by mass. It is efficient because it can Furthermore, in the present invention, since the number of mechanical treatments such as an ultra-high pressure homogenizer is small, cellulose fibers can be prevented from being damaged and a highly viscous dispersion can be obtained. On the other hand, in Comparative Examples 1 and 2 in which the amount of hydrophobizing agent bound to 1 g of anion-modified cellulose was less than 0.40 g, the cellulose fibers in the dry solid of the hydrophobized carboxylated cellulose were strongly aggregated and could not be disaggregated in toluene. However, defibration did not proceed. In order to defibrate dry solids in an organic solvent such as toluene, it is necessary to increase the bonding amount of the hydrophobizing agent to inhibit the aggregation of cellulose fibers during drying (when removing the dispersion medium). Conceivable.

As described above, from Table 1, in the method of the present invention (Examples 1 to 3), compared to Comparative Examples 1 to 7, hydrophobized anion-modified CNF using a low-polarity organic solvent such as toluene as a dispersion medium It can be seen that the dispersion can be produced efficiently.

<Example 4>
Toluene was added to the dry solids of the hydrophobized carboxylated cellulose produced in Examples 1 to 3 and Comparative Example 2 so that the solid content was 1% by mass in terms of carboxylated cellulose (without hydrophobizing agent). The mixture was stirred at 8000 rpm for 10 minutes, placed in a vial and allowed to stand still for 24 hours, and then the state of dispersion was visually evaluated. In addition, as Comparative Example 8, a dry solid of carboxylated cellulose produced in the same manner as in Example 1 except that no hydrophobizing agent was added was also evaluated in the same manner. As a result, in Comparative Examples 2 and 8, a dense sediment was observed at the bottom of the bottle after standing for 24 hours. A sediment was also observed at the bottom of the bottle in Example 1, but the degree of sedimentation was weaker than in Comparative Example 2, and the sedimentation was loose. In Example 2, the degree of precipitation was further weakened, and in Example 3, almost no precipitation was observed. From these results, it can be seen that the dry solid of hydrophobized anion-modified cellulose having a binding amount of the hydrophobizing agent of 0.40 g or more is less likely to form a dense precipitate during storage. If precipitation occurs, when the liquid is sent to the next process such as defibration, the liquid tends to be fed in a non-uniform state (a state in which high-density portions and low-density portions are mixed), and defibration progresses smoothly. or the device may not operate properly. The dry solid of the hydrophobized anion-modified cellulose of the present invention, which does not tend to form dense precipitates, can be easily dispersed in an organic solvent or the like.

Claims (3)

Step 1 of preparing a dispersion of anion-modified cellulose,
Step 2 of adding a hydrophobizing agent to a dispersion of anion-modified cellulose to produce a dispersion of hydrophobized anion-modified cellulose;
Step 3 of removing the dispersion medium from the dispersion of the hydrophobized anion-modified cellulose to produce a dry solid of the hydrophobized anion-modified cellulose, and mixing the dry solid of the hydrophobized anion-modified cellulose with an organic solvent, Step 4 of defibrating the hydrophobized anion-modified cellulose in the organic solvent to produce a dispersion of hydrophobized anion-modified cellulose nanofibers using the organic solvent as a dispersion medium;
including
The amount of the hydrophobizing agent bound to 1 g of the anion-modified cellulose is 1.00 g or more,
the hydrophobizing agent comprises a polyetheramine;
A method for producing a dispersion of hydrophobized anion-modified cellulose nanofibers, wherein the dry solids of the hydrophobized anion-modified cellulose have a solid content concentration higher than 90% by mass. The method according to claim 1, wherein the anion-modified cellulose is a cellulose having a carboxyl group or a cellulose having a carboxyalkyl group. It contains an anion-modified cellulose to which a hydrophobizing agent is bound, the solid content concentration is higher than 90% by mass, the amount of the hydrophobizing agent bound to 1 g of the anion-modified cellulose is 1.00 g or more, and the hydrophobizing agent is a polyetheramine A dry solid of hydrophobized anionically modified cellulose comprising :