JP2021143243A - Hydrophobicized anion modified cellulose or dry solid matter of its defibrated matter, dispersoid of hydrophobicized anion modified cellulose nanofiber, and their manufacturing method - Google Patents

Abstract

To provide a dispersoid of anion-modified cellulose nanofiber having an organic solvent having high transparency and decreased viscosity as a dispersion medium and its manufacturing method as well as hydrophobicized anion-modified cellulose usable in its manufacture or a dry solid material of its defibrated matter and its manufacturing method.SOLUTION: A hydrophobicizing agent and a surfactant are added to the dispersoid of anion modified cellulose to remove the dispersion medium to obtain a dry solid material having the solid content concentration higher than 90 mass%, followed by mixing with an organic solvent to defibrate the hydrophobicized anion-modified cellulose in the organic solvent to manufacture a hydrophobicized anion-modified cellulose nanofiber having the organic solvent as the dispersion medium. Before obtaining the dry solid material, optionally, the hydrophobicized anion-modified cellulose may be defibrated.SELECTED DRAWING: None

Description

The present invention provides a dry solid of hydrophobicized anion-modified cellulose or a dry solid of hydrophobicized and defibrated anion-modified cellulose, a dispersion of hydrophobicized anion-modified cellulose nanofibers, and a method for producing them. Regarding.

It is known that when anionic groups such as a carboxyl group and a carboxymethyl group are introduced into a cellulose molecular chain and mechanically treated (defibrated), they can be converted into cellulose nanofibers having a nanoscale fiber diameter. There is. Since cellulose nanofibers are light, have high strength, and are biodegradable, their application to various fields is being studied.

Normally, anionic modified cellulose nanofibers are highly hydrophilic because the introduced anionic group forms a salt such as a sodium salt, and thus is hydrophobic such as polyethylene terephthalate (PET) and polylactic acid (PLA). It has low compatibility with sexual polymers. Moreover, the dispersibility in a low-polarity organic solvent is low. One way to solve this problem is to acidify the anionic group of the metal salt type (for example, -COONa) to convert it to the acid type (for example, -COOH) and make the hydrophilicity of the anion-modified cellulose nanofiber. A method of lowering is conceivable.

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 dispersion of cellulose nanofibers to form a carboxylate-type group of cellulose nanofibers. Step of substituting a part of A method including a step of removing the aqueous solvent from the dispersion is described.

Further, in Patent Document 2, as a "first production method", a step of treating an aqueous dispersion of cellulose nanofibers substituted with a carboxylic acid type with an amine, and recovering the amine-treated cellulose nanofibers in a dispersion medium. A method including a step of preparing a cellulose nanofiber dispersion liquid by redispersing with is described.

International Publication No. 2010/134357 Japanese Unexamined Patent 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, dimethyl sulfoxide, N, N-dimethylformamide, and N, N-dimethylacetamide. Is a water-soluble organic solvent that is miscible with water. The method described in Patent Document 1 does not describe the use of an organic solvent having low polarity and hardly being soluble in water, such as toluene, as the dispersion medium of the cellulose nanofiber dispersion liquid. Further, Patent Document 2 does not describe the use of a low-polarity, water-insoluble organic solvent as a dispersion medium.

After producing a cellulose nanofiber dispersion liquid using a water-soluble organic solvent as a dispersion medium by using the methods described in Patent Documents 1 and 2, the water-soluble organic solvent is replaced with a low-polarity poorly water-soluble organic solvent. It is conceivable to produce a cellulose nanofiber dispersion liquid using an organic solvent that is sparingly soluble in water as a dispersion medium, but when replacing the solvent, it is necessary to repeatedly add the solvent and remove it by suction filtration or the like. There is a problem that it is costly and time-consuming, and cellulose nanofibers are lost during repeated solvent replacement operations, resulting in a decrease in yield.

In response to the above problems, Applicants added a specific amount or more of a hydrophobizing agent to a dispersion of anion-modified cellulose to produce a dispersion of hydrophobic anion-modified cellulose, and then a dispersion of hydrophobic anion-modified cellulose. The dispersion medium is removed from the mixture to produce a dry solid of hydrophobic anion-modified cellulose, and then the dry solid of hydrophobic anion-modified cellulose is defibrated in an organic solvent to obtain a hydrophobic anion using an organic solvent as a dispersion medium. A method for producing a dispersion of modified cellulose nanofibers has been proposed (Japanese Patent Application No. 2019-003113). By this method, a dispersion of hydrophobic anion-modified cellulose nanofibers using various organic solvents including a low-polarity organic solvent which is sparingly soluble in water as a dispersion medium can be produced in a high yield.

An object of the present invention is to provide a method for producing a dispersion of anion-modified cellulose nanofibers using an organic solvent as a dispersion medium, which has higher transparency and lower viscosity by applying the above-mentioned method. ..

As a result of diligent studies, the present inventors prepared a dispersion of hydrophobic anion-modified cellulose by adding a surfactant in addition to a hydrophobic agent to the dispersion of anion-modified cellulose, and arbitrarily obtained hydrophobicity. Disperse of defibrated anion-modified cellulose is defibrated to produce a dispersion of defibrated product of hydrophobic anion-modified cellulose, and the dispersion of defibrated product of hydrophobic anion-modified cellulose or defibrated product of hydrophobic anion-modified cellulose is used. The dispersion medium is removed to obtain a dry solid of a defibrated product of hydrophobic anion-modified cellulose or hydrophobic anion-modified cellulose, and this dry solid is defibrated in an organic solvent to obtain a dispersion of hydrophobic anion-modified cellulose nanofibers. It was found that the transparency of the dispersion of the hydrophobic anion-modified cellulose nanofibers using an organic solvent as a dispersion medium was improved and the viscosity was lowered. The present invention includes, but is not limited to, the following.
[1] Step 1 of adding a hydrophobizing agent and a surfactant to the dispersion of anion-modified cellulose to produce a dispersion of hydrophobic anion-modified cellulose, and a dispersion medium from the dispersion of the hydrophobic anion-modified cellulose. Step 2 to remove and produce a dry solid of hydrophobized anion-modified cellulose,
Including
The dry solid of the hydrophobized anion-modified cellulose has a solid content concentration of more than 90% by mass.
A method for producing a dry solid of hydrophobized anion-modified cellulose.
[2] Step 1 of adding a hydrophobizing agent and a surfactant to a dispersion of anion-modified cellulose to produce a dispersion of hydrophobic anion-modified cellulose.
Step 3 of defibrating the hydrophobized anion-modified cellulose to produce a dispersion of a defibrated product of the hydrophobic anion-modified cellulose.
Step 4, in which the dispersion medium is removed from the dispersion of the defibrated product of the hydrophobic anion-modified cellulose to produce a dry solid of the defibrated product of the hydrophobic anion-modified cellulose.
Including
The dry solid of the hydrophobized anion-modified cellulose defibrated product has a solid content concentration of more than 90% by mass.
A method for producing a dry solid of a defibrated product of hydrophobized anion-modified cellulose.
[3] Step 5 for producing a dry solid of hydrophobic anion-modified cellulose by steps 1 and 2 according to [1], and mixing the dry solid of hydrophobic anion-modified cellulose with an organic solvent to obtain the organic Step 6, in which the hydrophobic anion-modified cellulose is defibrated in a solvent to produce a dispersion of the hydrophobic anion-modified cellulose nanofibers using the organic solvent as a dispersion medium.
Including
The dry solid of the hydrophobized anion-modified cellulose has a solid content concentration of more than 90% by mass.
A method for producing a dispersion of hydrophobized anion-modified cellulose nanofibers.
[4] The step 7 for producing a dry solid of the defibrated product of the hydrophobic anion-modified cellulose by the steps 1, 3 and 4 according to [2], and the dry solid of the defibrated product of the hydrophobic anion-modified cellulose. Step 8 of mixing the product with an organic solvent, defibrating the hydrophobic anion-modified cellulose in the organic solvent, and producing a dispersion of hydrophobic anion-modified cellulose nanofibers using the organic solvent as a dispersion medium.
Including
The dry solid of the hydrophobized anion-modified cellulose defibrated product has a solid content concentration of more than 90% by mass.
A method for producing a dispersion of hydrophobized anion-modified cellulose nanofibers.
[5] The method according to any one of [1] to [4], wherein the anion-modified cellulose is cellulose having a carboxyl group or cellulose having a carboxylalkyl group.
[6] The method according to any one of [1] to [5], wherein the surfactant is a fluorine-based surfactant.
[7] Hydrophobicized anion-modified product containing a defibrated product of anion-modified cellulose to which a hydrophobizing agent is bound or anion-modified cellulose to which a hydrophobizing agent is bound, and a surfactant, and having a solid content concentration of more than 90% by mass. Dry solids of cellulose.
[8] A dispersion of hydrophobic anion-modified cellulose nanofibers, which comprises an anion-modified cellulose nanofiber to which a hydrophobic agent is bound and a surfactant, and uses an organic solvent as a dispersion medium.

INDUSTRIAL APPLICABILITY According to the present invention, in a method for efficiently producing a dispersion of hydrophobic anion-modified cellulose nanofibers using an organic solvent as a dispersion medium, a dispersion of hydrophobic anion-modified cellulose nanofibers having high transparency and reduced viscosity can be obtained. Can be done. It is considered that the obtained dispersion of anion-modified cellulose nanofibers can be used for various purposes utilizing high transparency. Further, it has an advantage that it is easy to handle because the viscosity of the dispersion is low. Further, the present invention is a dry solid of hydrophobic anion-modified cellulose or a defibrated product thereof, which can be suitably used for producing a dispersion of hydrophobic anion-modified cellulose nanofibers having high transparency and reduced viscosity. A manufacturing method is also provided. The dried solid of the hydrophobic anion-modified cellulose of the present invention or the defibrated product thereof is easily adapted to various organic solvents including a low-polarity organic solvent, and the hydrophobic anion-modified cellulose nanofibers using the organic solvent as a dispersion medium. It can be suitably used as a material for producing a dispersion. In addition, the dry solid has the advantage of being easy to store and transport.

According to the present invention, a dispersion of hydrophobized anion-modified cellulose nanofibers using an organic solvent as a dispersion medium can be obtained. Hereinafter, cellulose nanofibers may be referred to as "CNF". Specifically, the method for producing a hydrophobic anion-modified CNF of the present invention comprises adding a hydrophobic agent and a surfactant to a dispersion of anion-modified cellulose to produce a dispersion of hydrophobic anion-modified cellulose (). Step 1), the dispersion medium is removed from the dispersion of the hydrophobic anion-modified cellulose to produce a dry solid of the hydrophobic anion-modified cellulose (step 2), and the dry solid of the hydrophobic anion-modified cellulose is mixed with an organic solvent. Then, the hydrophobic anion-modified cellulose is defibrated in an organic solvent to produce a dispersion of the hydrophobic anion-modified CNF using the organic solvent as a dispersion medium (step 6). Alternatively, a hydrophobic agent and a surfactant are added to the dispersion of the anion-modified cellulose to produce a dispersion of the hydrophobic anion-modified cellulose (step 1), and the hydrophobic anion-modified cellulose is defibrated to deflate the hydrophobic anion. A dispersion of the denatured denatured cellulose is produced (step 3), and the dispersion medium is removed from the dispersion of the denaturated anion-modified cellulose to obtain a dry solid of the denaturated anion-modified cellulose defibrated product. Manufactured (step 4), a dry solid of hydrophobic anion-modified cellulose is mixed with an organic solvent, the hydrophobic anion-modified cellulose is defibrated in the organic solvent, and the hydrophobic anion modification using the organic solvent as a dispersion medium. It involves producing a dispersion of CNF (step 8). At this time, in step 1, a surfactant is added in addition to the hydrophobic agent. Further, in step 2 or 4, drying (removal of the dispersion medium) is performed until the solid content concentration of the dried solid matter becomes higher than 90% by mass. The dried solid of the hydrophobic anion-modified cellulose or its defibrated product produced in step 2 or 4 is suitably used as a material for producing a dispersion of the hydrophobic anion-modified CNF using an organic solvent as a dispersion medium. Can be done.

(1) Step 1
In step 1, a hydrophobizing agent and a surfactant are added to the dispersion of anion-modified cellulose. Anionic-modified cellulose is one in which an anionic group is introduced into the molecular chain of cellulose, as will be described in more detail below.

(1-1) Cellulose Raw Material 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 amorphous regions, etc., based on the origin, manufacturing method, and the like. In the present invention, any of these celluloses can be used as a raw material.

Examples of natural cellulose include bleached pulp or unbleached pulp (bleached wood pulp or unbleached wood pulp); linters, purified linters; cellulose produced by microorganisms such as acetic acid bacteria. The raw material of bleached pulp or unbleached pulp is not particularly limited, and examples thereof include wood, cotton, straw, bamboo, hemp, jute, and kenaf. Further, the method for producing bleached pulp or unbleached pulp is not particularly limited, and a mechanical method, a chemical method, or a method in which the two are combined may be used. The bleached pulp or unbleached pulp classified according to the production method includes, for example, mechanical pulp (thermomechanical pulp (TMP), crushed wood pulp), chemical pulp (conifer unbleached sulphite pulp (NUSP), conifer bleached sulphite pulp ( NBSPulp (NBSP) and the like; unbleached coniferous kraft pulp (NUKP), bleached coniferous kraft pulp (NBKP), unbleached broadleaf kraft pulp (LUKP), kraft pulp such as broadleaf bleached kraft pulp (LBKP)) and the like. Further, dissolved pulp may be used in addition to the pulp for papermaking. Dissolving pulp is chemically refined pulp, which is mainly dissolved in chemicals and used as a main raw material for artificial fibers, cellophane, and the like.

Examples of the regenerated cellulose include those obtained by dissolving cellulose in a solvent such as a cuprammonium rayon solution, a cellulose zantate solution, or a morpholine derivative and spinning it again. The fine cellulose is obtained by subjecting a cellulosic material such as the above-mentioned natural cellulose and regenerated cellulose to a depolymerization treatment (for example, acid hydrolysis, alkali hydrolysis, enzymatic decomposition, blasting treatment, vibration ball mill treatment, etc.). Examples thereof include those obtained by mechanically processing the cellulosic material.

(1-2) Anion denaturation Anion denaturation in "anion-modified cellulose" means introducing an anionic group into cellulose, specifically, introducing an anionic group into the pyranose ring of cellulose by an oxidation or substitution reaction. Say that. In the present invention, the oxidation reaction refers to a reaction in which the hydroxyl group of the pyranose ring is directly oxidized to a carboxyl group. Further, in the present invention, the substitution reaction means a reaction for introducing an anionic group into the pyranose ring by a substitution reaction other than the oxidation.

(1-2-1) Carboxylation (oxidation)
As an example of anion denaturation, carboxylation (introduction of a carboxyl group into cellulose, also referred to as "oxidation") can be mentioned. Anion-modified cellulose obtained by carboxylation of a cellulose raw material is called carboxylated cellulose (or oxidized cellulose). In the present specification, the carboxyl group means -COOH (acid type) and -COOM (metal salt type) (in the formula, M is a metal ion). Carboxylation (oxidation) of the cellulose raw material can be obtained, for example, by the method described later, but is not limited thereto. Further, commercially available carboxylated cellulose may be used in step 1. The amount of carboxyl groups in the carboxylated cellulose is preferably 0.6 to 3.0 mmol / g, more preferably 1.0 to 2.0 mmol / g, based on the absolute dry mass of the carboxylated cellulose, but is not limited thereto. ..

The amount of carboxyl groups in carboxylated cellulose can be measured by the following methods:
60 ml of a 0.5 mass% slurry (aqueous dispersion) of carboxylated cellulose was prepared, and a 0.1 M hydrochloric acid aqueous solution was added to adjust the pH to 2.5, and then a 0.05 N sodium hydroxide aqueous solution was added dropwise to adjust the pH to 11. The electrical conductivity is measured until
Amount of carboxyl group [mmol / g carboxylated cellulose] = a [ml] × 0.05 / mass of carboxylated cellulose [g].

As an example of the carboxylation (oxidation) method, a cellulose raw material is oxidized in water using an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromide, iodide, and a mixture thereof. There are ways to do this. This oxidation reaction, C6-position primary hydroxyl groups of the glucopyranose ring of the cellulose surface is selectively oxidized, and an aldehyde group on the surface, a carboxyl group (-COOH) or carboxylate groups (-COO ^-) and cellulosic fibers having a (Carboxylated cellulose) can be obtained. The concentration of cellulose during the reaction is not particularly limited, but is preferably 5% by mass or less.

The N-oxyl compound is a compound capable of generating a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it is a compound that promotes the desired oxidation reaction. For example, 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and its derivative (for example, 4-hydroxy TEMPO) can be mentioned. The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulose as a raw material. For example, 0.01 to 10 mmol is preferable, 0.01 to 1 mmol is more preferable, and 0.05 to 0.5 mmol is further preferable with respect to 1 g of cellulose that has been completely dried. Further, it is preferably about 0.1 to 4 mmol / L with respect to the reaction system.

The bromide is a compound containing bromine, and examples thereof include alkali metals bromide that can be dissociated and ionized in water. Further, the iodide is a compound containing iodine, and an example thereof includes an alkali metal iodide. The amount of bromide or iodide used can be selected within the range in which the oxidation reaction can be promoted. The total amount of bromide and iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, still more preferably 0.5 to 5 mmol, relative to 1 g of dry cellulose. The modification is a modification due to an oxidation reaction.

As the oxidizing agent, known ones can be used, and for example, halogen, hypohalogenic acid, subhalogenic acid, perhalogenic acid or salts thereof, halogen oxide, peroxide and the like can be used. Of these, sodium hypochlorite, which is inexpensive and has a low environmental load, is preferable. The appropriate amount of the oxidizing agent to be used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, still more preferably 1 to 25 mmol, and most preferably 3 to 10 mmol with respect to 1 g of cellulose that has been completely dried. .. Further, for example, 1 to 40 mol is preferable with respect to 1 mol of the N-oxyl compound.

In the cellulose oxidation step, the reaction can proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40 ° C, and may be room temperature of about 15 to 30 ° C. As the reaction progresses, carboxyl groups are generated in the cellulose, so that the pH of the reaction solution is lowered. 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 8 to 12, preferably about 10 to 11. Water is preferable as the reaction medium because it is easy to handle and side reactions are unlikely to occur. The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of oxidation, and is usually about 0.5 to 6 hours, for example, about 0.5 to 4 hours.

Further, 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 first-stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt produced as a by-product in the first-stage reaction. Can be oxidized well.

As another example of the carboxylation (oxidation) method, there is a method of oxidizing by contacting a gas containing ozone with a cellulose raw material. By this oxidation reaction, the hydroxyl groups at at least the 2nd and 6th positions of the glucopyranose ring are oxidized, and the cellulose chain is decomposed. Ozone concentration in the ozone containing gas is preferably 50 to 250 g / ^{m 3,} more preferably 50~220g / ^{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 to 50 ° C, more preferably 20 to 50 ° C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, preferably about 30 to 360 minutes. When the ozone treatment conditions are within these ranges, it is possible to prevent the cellulose from being excessively oxidized and decomposed, and the yield of the oxidized cellulose becomes good. After the ozone treatment, the additional oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used for the additional oxidation treatment is not particularly limited, and examples thereof include chlorine compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfate, 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 the carboxyl group of the carboxylated cellulose can be adjusted by controlling the reaction conditions such as the amount of the oxidizing agent added and the reaction time described above. The amount of carboxyl groups in 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 As an example of anion modification, introduction of a carboxyalkyl group such as a carboxymethyl group into cellulose can be mentioned. Anion-modified cellulose obtained by carboxyalkylation of a cellulose raw material is called carboxyalkylated cellulose. As used herein, the carboxyalkyl group refers to -RCOH (acid type) and -RCOOM (metal salt type). Here, R is an alkylene group such as a methylene group and an ethylene group, and M is a metal ion.

The carboxyalkylated cellulose used in step 1 may be obtained by a known method, or a commercially available product may be used. The degree of carboxyalkyl substitution of cellulose per anhydrous glucose unit is preferably less than 0.40. Further, when the carboxyalkyl group is a carboxymethyl group, the degree of carboxymethyl substitution is preferably less than 0.40. If the degree of substitution is less than 0.40, the dispersibility when CNF is used can be maintained to a certain extent. The lower limit of the carboxyalkyl substitution is preferably 0.01 or more. Considering operability, the degree of substitution is particularly preferably 0.02 to 0.35, and even more preferably 0.10 to 0.30. The anhydrous glucose unit means individual anhydrous glucose (glucose residue) constituting cellulose, and the carboxyalkyl substitution degree is carboxyalkyl among the hydroxyl groups (-OH) in the glucose residue constituting cellulose. The percentage of those substituted with ether groups (-ORCOOH or -ORCOOM) (number of carboxyalkyl ether groups per glucose residue) is shown.

As an example of the method for producing carboxyalkylated cellulose, a method including the following steps can be mentioned. The modification is a modification by a substitution reaction. Carboxymethylated cellulose will be described as an example.

i) A step of mixing a cellulose raw material, a solvent and a mercerizing agent, and performing a mercerization treatment at a reaction temperature of 0 to 70 ° C., preferably 10 to 60 ° C., and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. ,
ii) Next, a carboxymethylating agent is added in an amount of 0.05 to 10.0 times per glucose residue, and 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 carrying out an etherification reaction for 1 to 4 hours.

As the raw material, the above-mentioned cellulose raw material can be used. As the solvent, 3 to 20 times by mass of water or lower alcohol, specifically water, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, isobutanol, tertiary butanol, etc. alone or 2 A mixed medium of more than one species can be used. When the lower alcohol is mixed, the mixing ratio is preferably 60 to 95% by mass. As the mercerizing agent, it is preferable to use 0.5 to 20 times mol of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide, per anhydrous glucose residue of the bottoming material.

As described above, the degree of carboxymethyl substitution of cellulose per glucose unit is less than 0.40, preferably 0.01 or more and less than 0.40. By introducing a carboxymethyl substituent into cellulose, the celluloses electrically repel each other. Therefore, the cellulose into which the carboxymethyl substituent has been introduced can be nano-defibrated. If the carboxymethyl substituent per glucose unit is less than 0.01, nanodefibration may not be sufficient. The degree of carboxyalkyl substitution in carboxyalkylated cellulose and the degree of carboxyalkyl substitution when the same carboxyalkylated cellulose is used as a nanofiber are usually the same.

The degree of carboxymethyl substitution per glucose unit can be measured by the following method:
Weigh approximately 2.0 g of carboxymethylated cellulose (absolutely dry) and place in a 300 mL Erlenmeyer flask with a stopper. 100 mL of a solution prepared by adding 100 mL of special grade concentrated nitric acid to 900 mL of methanol is added, and the mixture is shaken for 3 hours to convert the carboxymethylated cellulose salt (CM-modified cellulose) into hydrogen-type CM-modified cellulose. Weigh 1.5 g to 2.0 g of hydrogen-type CM-formed cellulose (absolutely dry) and place it in an Erlenmeyer flask with a 300 mL stopper. Wet hydrogen-type CM-formed cellulose with 15 mL of 80 mass% methanol, add 100 mL of 0.1 N NaOH, and shake 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 carboxymethyl degree of substitution (DS) is calculated by the following equation:
A = [(100 x F'-(0.1 N H ₂ SO ₄ ) (mL) x F) x 0.1] / (absolute dry mass (g) of hydrogen-type CM-formed cellulose)
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required to neutralize 1 g of hydrogen-type CM-formed cellulose
F: 0.1N H ₂ SO ₄ factor F': 0.1N NaOH factor.

In addition, the amount of carboxymethyl group (anionic group) (mmol / g) can be calculated from the degree of carboxymethyl substitution (DS) using the following equation:
Amount of carboxymethyl group (mmol / g) = (DS / (DS × 58 + 162)) × 1000.

The degree of substitution of the carboxyalkyl group other than the carboxymethyl group can be obtained by the same method as described above, and the amount of the carboxyalkyl group can be calculated from the following formula using the degree of carboxyalkyl substitution (DS). can:
Amount of carboxyalkyl group (mmol / g) = [DS / {DS × (molecular weight of carboxyalkyl group-1) +162}] × 1000.

(1-2-3) Esterification As an example of anion modification, esterification can be mentioned. Anion-modified cellulose obtained by esterification of a cellulose raw material is called esterified cellulose, and esterified cellulose obtained by using a phosphoric acid-based compound described later is particularly called phosphoric acid esterified cellulose. In step 1, for example, esterified cellulose produced by the method described later may be used, but the present invention is not limited to this. Further, commercially available esterified cellulose may be used in step 1.

Examples of the method for esterifying the cellulose raw material include a method of mixing a powder or an aqueous solution of a phosphoric acid compound with the cellulose raw material, a method of adding an aqueous solution of the phosphoric acid compound to the slurry of the cellulose raw material, and the like. Examples of phosphoric acid-based compounds include phosphoric acid, polyphosphoric acid, phosphite, hypophosphoric acid, phosphonic acid, polyphosphonic acid, and esters thereof. These may be in the form of salts. Among the above, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium phosphite, etc., are low cost, easy to handle, and can improve defibration efficiency. 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 are preferable. These can be used alone or in combination of two or more. Of these, from the viewpoints of high efficiency of introducing phosphoric acid groups, easy defibration in the following defibration steps, and easy industrial application, phosphoric acid, sodium phosphate of phosphoric acid, potassium salt of phosphoric acid, and phosphoric acid Ammonium salt is more preferred. In particular, sodium dihydrogen phosphate and disodium hydrogen phosphate are preferable. In addition, it is desirable to use the phosphoric acid-based compound as an aqueous solution because the reaction can proceed uniformly and the efficiency of introducing a phosphoric acid group is high. The pH of the aqueous solution of the phosphoric acid-based compound is preferably 7 or less because the efficiency of introducing the phosphoric acid group is high, but is preferably 3 to 7 from the viewpoint of suppressing the hydrolysis of pulp fibers.

The following methods can be mentioned as examples of the method for producing phosphoric acid esterified cellulose. A phosphoric acid-based compound is added to a suspension of a cellulosic raw material having a solid content concentration of 0.1 to 10% by mass with 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 as the amount of phosphorus element. When the ratio of the phosphoric acid-based compound is at least the above lower limit value, the yield of fine fibrous cellulose can be further improved. The effect of improving the yield reaches a plateau near the upper limit.

In addition to the phosphoric acid-based compound, powders or aqueous solutions of other compounds may be mixed. The other compound that can be mixed in addition to the phosphoric acid-based compound is not particularly limited, but a nitrogen-containing compound exhibiting basicity is preferable. "Basic" here is defined as the aqueous solution exhibiting a pink to red color in the presence of a phenolphthalein indicator, or the pH of the aqueous solution being greater than 7. The basic nitrogen-containing compound used in the present invention is not particularly limited as long as the effects of the present invention are exhibited, but a compound having an amino group is preferable. For example, urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine and the like can be mentioned. Of these, urea, which is low in cost and easy to handle, is preferable. 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. The reaction time is not particularly limited, but is about 1 to 600 minutes, more preferably 30 to 480 minutes. When the conditions of the esterification reaction are within these ranges, it is possible to prevent the cellulose from being excessively esterified and easily dissolved, and the yield of the phosphate esterified cellulose becomes good. After dehydrating the obtained phosphoric acid esterified cellulose suspension, it is preferable to heat-treat it at 100 to 170 ° C. from the viewpoint of suppressing hydrolysis of cellulose. Further, it is preferable to heat at 130 ° C. or lower, preferably 110 ° C. or lower while water is contained in the heat treatment, remove water, and then heat-treat at 100 to 170 ° C.

The degree of phosphate group substitution per glucose unit of phosphoric acid esterified cellulose is preferably 0.001 or more and less than 0.40. By introducing a phosphate group substituent into cellulose, the celluloses are electrically repelled from each other. Therefore, the cellulose into which a phosphate group has been introduced can be easily nano-defibrated. If the degree of phosphate substitution per glucose unit is less than 0.001, nano-defibration cannot be sufficiently performed. On the other hand, if the degree of phosphate substitution per glucose unit is greater than 0.40, it swells or dissolves and may not be obtained as nanofibers. In order to efficiently perform defibration, it is preferable to obtain phosphoric acid esterified cellulose by the above method, boil it, and wash it with cold water. These esterification modifications are substitution reaction modifications. The degree of substitution in the esterified cellulose and the degree of substitution when the esterified cellulose is used as nanofibers are usually the same. The amount (mmol / g) of the phosphate group (anionic group) can be calculated from the degree of substitution of the phosphate group (DS) by using the following formula:
Amount of phosphate group (mmol / g) = (DS / (DS × 64 + 162)) × 1000.

(1-2-4) Zantateization As an example of anion denaturation, zantateization can be mentioned. The xanthate reduction, the alkali cellulose is treated cellulose material with an alkali metal hydroxide aqueous solution, followed by reacting carbon disulfide (CS ₂₎ in the alkali cellulose, alkali cellulose of the metal alkoxide (-O - ^{M +)} ( M is an alkali metal) ^{converted to xanthogenate (-OCSS-} M ⁺ ) to form cellulose zantate. In the present specification, anion-modified cellulose obtained by zantating a cellulose raw material is referred to as zantated cellulose.

The zantated cellulose used in step 1 may be obtained by a known method, or a commercially available product may be used. The degree of substitution of zantate per anhydrous glucose unit of the zantated cellulose is preferably 0.33 or more and 1.20 or less. If it is 0.33 or more, it leads to promotion of defibration in the subsequent step 3, and if it is 1.20 or less, a decrease in the yield of zantated cellulose can be suppressed. The degree of substitution of zantate can be adjusted by adjusting the supply amount of carbon disulfide and the contact time between carbon disulfide and alkali cellulose.

The following methods can be mentioned as an example of the method for producing zantated cellulose. The modification is a modification by a substitution reaction.
First, the cellulose raw material is treated with an aqueous alkali metal hydroxide solution such as sodium hydroxide or potassium hydroxide to obtain alkali cellulose. At this time, the concentration of the aqueous alkali metal hydroxide solution is preferably 4 to 9% by mass. When it is 4% by mass or more, mercerization of cellulose can be promoted, and when it is 9% by mass or less, the crystal structure of cellulose type I in the obtained alkaline cellulose can be maintained to a certain extent. The above treatment time is preferably 30 minutes or more and 6 hours or less, and more preferably 1 hour or more and 5 hours or less. The treatment temperature is preferably around room temperature. If the treatment temperature is low as in refrigeration conditions, the alkali metal hydroxide aqueous solution easily permeates the crystal region of cellulose. Therefore, when the treatment temperature is equal to or higher than the freezing temperature and less than 10 ° C., the alkali metal hydroxide aqueous solution is used. The concentration is preferably 4% by mass or more and 7% by mass or less, and when the temperature is 10 ° C. or higher, the concentration of the alkali metal hydroxide aqueous solution is preferably 4% by mass or more and 9% by mass or less.

It is preferable to solid-liquid separate the alkaline cellulose obtained by the above treatment to remove as much water as possible. Thereby, the reaction in the next zantate treatment can be promoted. As a solid-liquid separation method, for example, a general dehydration method such as centrifugation or filtration can be used. The concentration of the alkali metal hydroxide contained in the alkali cellulose after solid-liquid separation is preferably about 3 to 8% by mass.

Next, carbon disulfide is reacted with the above-mentioned alkali cellulose to perform a zantate treatment for converting the alkali metal alkoxide in the alkali cellulose into an alkali metal salt of xanthate. The carbon disulfide is preferably supplied in an amount of 10% by mass or more with respect to the mass of cellulose. The contact time between carbon disulfide and alkaline cellulose is preferably 30 minutes or longer, more preferably 1 hour or longer. The upper limit of the contact time is not particularly limited, but it is considered that the reaction is sufficiently completed in about 6 hours, so 6 hours or less is preferable.

In this zantate treatment, it is preferable to bring gaseous carbon disulfide into contact with the dehydrated alkaline cellulose at a temperature of 46 ° C. or lower. When the temperature is 46 ° C. or lower, a decrease in the degree of polymerization due to decomposition of alkaline cellulose can be suppressed.

It is preferable to wash the obtained zantated cellulose to remove impurities, alkalis, carbon disulfide, etc., because the load during defibration in the subsequent step 3 can be reduced. It is preferable to use water for washing because the pH due to alkali can be reduced, but there is almost no risk of damaging the fibers. The pH of the zantated cellulose slurry after washing is preferably 10.5 or less, more preferably 9.5 or less.

(1-3) Anion-modified cellulose By performing anion modification as illustrated above on cellulose as a raw material, anion-modified cellulose used in step 1 can be obtained. Further, commercially available anion-modified cellulose may be used in step 1. As the type of anion-modified cellulose, cellulose having a carboxyl group or cellulose having a carboxylalkyl 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 easy to uniformly defibrate.

As the anion-modified cellulose, those in which at least a part of the fibrous shape is maintained even when dispersed in water or a water-soluble organic solvent are used. If a fiber-like shape is not maintained (that is, a substance that dissolves) is used, nanofibers cannot be obtained. The fact that at least a part of the fibrous shape is maintained when dispersed means that a fibrous substance can be observed by observing the dispersion of anion-modified cellulose with an electron microscope. Further, anion-modified cellulose capable of observing the peak of cellulose type I crystal when measured by X-ray diffraction is preferable.

The crystallinity of cellulose in the anion-modified cellulose is preferably 50% or more, and more preferably 60% or more for crystal 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 have been refined by defibration. The crystallinity of cellulose can be controlled by the degree of crystallinity of the raw material cellulose and the degree of anion denaturation. The method for measuring the crystallinity of anion-modified cellulose is as follows:
The sample is placed on a glass cell and measured using an X-ray diffraction measuring device (LabX XRD-6000, manufactured by Shimadzu Corporation). The crystallinity is calculated using a method such as Segal, and the diffraction intensity of the 002 surface of 2θ = 22.6 ° and 2θ = are based on the diffraction intensity of 2θ = 10 ° to 30 ° in the X-ray diffraction diagram. It is calculated by the following formula from the diffraction intensity of the amorphous portion of 18.5 °.
Xc = (I002c-Ia) / I002c × 100
Xc: Cellulose type I crystallinity (%)
I002c: 2θ = 22.6 °, diffraction intensity of 002 surface Ia: 2θ = 18.5 °, diffraction intensity of amorphous part.

The ratio of cellulose type I crystals of anion-modified cellulose and the ratio of cellulose type I crystals when the same 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 a metal salt type (for example, −COO ⁻ M ⁺ or −RCOO ⁻ M ⁺ (M is a metal such as sodium or potassium). Yes, R is an alkylene group such as a methylene group or an ethylene group))). It is preferable to convert the metal salt type anionic group in the anion-modified cellulose to the acid type (for example, -COOH, -RCOOH, etc.) in order to promote the reaction with the subsequent hydrophobizing agent.

The method of converting to the acid type is not particularly limited, and examples thereof include a method of adding an acid to the anion-modified cellulose and a method of contacting the anion-modified cellulose with a cation exchange resin. When an acid is added, the type of acid used is not particularly limited, and for example, inorganic acids such as sulfuric acid, hydrochloric acid, nitrate, sulfite, nitrite, and phosphoric acid, acetic acid, lactic acid, oxalic acid, citric acid, formic acid, and adipic acid. , Sebacic acid, stearic acid, maleic acid, succinic acid, tartrate acid, fumaric acid, gluconic acid and other organic acids. General-purpose and readily available hydrochloric acid or sulfuric acid is preferred. The pH at the time of adding the acid is preferably in the range of 1 to 6, and more preferably 2 to 5. The amount of the acid added may be any amount as long as it can convert the metal salt type anionic modified cellulose into the acid type, and is not particularly limited. For example, in the case of a strong acid, 1 equivalent or more with respect to the anionic group is preferable, and a weak acid. If so, 10 equivalents or more is preferable. When contacting with an acidic ion exchange resin, examples of the acidic ion exchange resin include a strongly acidic cation exchange resin and a weakly acidic cation exchange resin.

(1-4) Dispersion of Anion-Modified Cellulose The dispersion of anion-modified cellulose used in Step 1 is obtained by dispersing or suspending the above-mentioned anion-modified cellulose in a dispersion medium. As the dispersion medium in the dispersion, water, an organic solvent, or a mixture thereof can be appropriately selected. The type of organic solvent is not limited, but for example, a polar solvent having a high affinity for hydroxyl groups in cellulose and a water-soluble organic solvent that can be mixed with water at a constant ratio are preferable, and methanol, ethanol, isopropanol, isobutanol, etc. sec-butanol, tert-butanol, methyl cellosolve, ethyl cellosolve, ethylene glycol, glycerin, ethylene glycol dimethyl ether, 1,4-dioxane, tetrahydrofuran, acetone, methyl ethyl ketone, methyl propyl ketone, N, N-dimethylformamide, N, N- Examples thereof include dimethylacetamide and dimethylsulfoxide. The dispersion medium may be used alone or in combination of two or more. For example, a form in which two or more kinds of organic solvents are mixed, a form containing water and an organic solvent, a form containing only water, and the like can be appropriately selected. It is preferable to use only water as the dispersion medium (that is, 100% water) from the viewpoint of ease of handling. The mixing ratio when water and the organic solvent are mixed is not particularly limited, and the mixing ratio may be appropriately adjusted according to the type of the organic solvent used.

The concentration of the anion-modified cellulose in the dispersion is preferably 0.01 to 50% by mass, preferably 1 to 45% by mass, and 2 to 40% by mass in consideration of the efficiency when mixed with the subsequent hydrophobizing agent. Is even more preferable.

(1-5) Hydrophobicizing Agent In Step 1, a hydrophobizing agent and a surfactant are added to the dispersion of the anion-modified cellulose to make the anion-modified cellulose hydrophobic to produce a dispersion of the hydrophobized anion-modified cellulose. Hydrophobization refers to a process of binding an anion-modified cellulose to a hydrophobizing agent to improve the hydrophobicity of the anion-modified cellulose.

As the hydrophobizing agent, a compound having an amine or phosphine capable of forming an onium salt by binding to an anionic group of anion-modified cellulose is preferable, and a primary amine, a secondary amine, a tertiary amine, or a quaternary ammonium is preferable. , Aromatic amines, diamines, polyether amines, phosphines, phosphoniums.

Examples of the hydrophobizing agent include, but are not limited to, JEFFAMINE (registered trademark) M-600, JEFFAMINE (registered trademark) M-1000, JEFFAMINE (registered trademark) M-2005, and JEFFAMIN (registered trademark) manufactured by HUNTSMAN. Polyetheramines such as M-2070, methylamines, ethylamines, oleylamines, propylamines, dodecylamines, stearylamines, tetradecylamines, 1-hexenylamines, 1-dodecenylamines, 9,12-octadecadienylamines (linolamines). ), 9,12,15-Octadecatrienylamine, primary amines such as linoleylamine, secondary amines such as dimethylamine and diethylamine, tertiary amines such as trimethylamine and triethylamine, benzalconium chloride, benzethonium chloride, Tertiary ammonium such as methylbenzethonium chloride, cetylpyridinium chloride, cetrimonium, dofanium chloride, tetraethylammonium bromide, didecyldimethylammonium chloride, aromatic amines such as aniline, pyridine and benzylamine, diamines such as ethylenediamine and hexamethylenediamine. , Triphenylphosphine, phosphine such as trimethylphosphine and the like.

The hydrophobizing agent is preferably added to the anion-modified cellulose so that the amount of the hydrophobizing agent bound to 1 g is 0.40 g or more. More preferably, the amount of the hydrophobizing agent bound is 0.50 g or more, and even more preferably 1.00 g or more. The method of calculating the binding amount of the hydrophobizing agent will be described later. The hydrophobizing agent binds to the anionic group of the anionic modified cellulose. When a sufficient amount of hydrophobizing agent is added according to the amount of anionic groups of the anion-modified cellulose, aggregation due to hydrogen bonds between the cellulose fibers during drying in the subsequent step 2 of producing a dry solid is inhibited. , The defibration and nanofiber formation in the subsequent step 3 are promoted. The upper limit of the amount of the hydrophobizing agent bound to 1 g of the anion-modified cellulose is not particularly limited. The amount of the hydrophobic agent bonded to 1 g of the modified cellulose is preferably 10.00 g or less, more preferably 5.00 g or less.

The hydrophobizing agent binds to the anionic group of the anionic modified cellulose. Due to the mode of reaction, the added hydrophobizing agent reacts with all anionic groups. The present inventors have found that 1 upon the addition of molar equivalent or more hydrophobic agents, anionic modified cellulose and an acid form (-COOH) are all -COO ^- that it has changed with infrared spectroscopy I'm checking. This indicates that the amine of the hydrophobizing agent was ionically bonded to all the anionic groups of the anionic modified cellulose. Therefore, the amount of the hydrophobizing agent bound to 1 g of the anion-modified cellulose can be calculated by the following formula according to the amount of the hydrophobizing agent added:
i) When the hydrophobic agent is added in an amount (number of moles) or more equal to the amount (number of moles) of the anionic group. Amount of group [mmol / g] x molecular weight of hydrophobicizing agent x 0.001 x valence of anionic group ii) The amount of substance added (number of moles) of the hydrophobicizing agent is less than the amount of anionic group (number of moles). Case: Amount of binding of hydrophobizing agent to 1 g of anion-modified cellulose [g] = amount of anionic group of anion-modified cellulose [mmol / g] x molecular weight of hydrophobizing agent x 0.001 x number of moles of hydrophobizing agent added [ mmol] / number of moles of anionic group [mmol]
In i), the valence of the anionic groups, when the anionic group is a carboxyl group or carboxyalkyl group is 1, anionic groups phosphate groups (e.g., H 2 _PO 4 - if it _is) is It is 2. In ii), the number of moles (mmol) of the anionic group can be determined from the amount of the anionic group (mmol / g) and the absolute dry mass (g) of the anionic modified cellulose.

The hydrophobizing agent may be added in an amount of 50 to 150% with respect to the amount (number of moles) of the anionic group of the anionic modified cellulose, preferably 70 to 130%, more preferably 80 to 120%. More preferably, it may be added in an amount of 100 to 120%.

The hydrophobizing agent may be added to the dispersion of anion-modified cellulose as it is or by mixing with water or a water-soluble organic solvent. The concentration of anion-modified cellulose in the anion-modified cellulose dispersion when the hydrophobizing agent is added is preferably 0.01 to 50% by mass, preferably 1 to 45% by mass, and even more preferably 2 to 40% by mass. .. By mixing the hydrophobizing agent and the anion-modified cellulose for a certain period of time with stirring, a dispersion of the hydrophobized anion-modified cellulose can be produced.

(1-6) Surfactant The type of surfactant is not particularly limited, and any of fluorine-based surfactant, silicone-based surfactant, hydrocarbon-based surfactant and the like can be used. Further, any of nonionic type, anion type, cationic type, amphoteric type, amine oxide type and the like can be used. Above all, the fluorine-based surfactant is preferable in that it can impart a low surface tension at a low concentration. The fluorine-based surfactant is a surfactant having a perfluoroalkyl group, and commercially available ones can be used. Commercially available fluorine-based surfactants include, but are not limited to, Surflon (registered trademark) S-242 and Surflon (registered trademark) S-, which are nonionic type fluorine-based surfactants manufactured by AGC Seimi Chemical Co., Ltd. 243, Surflon (registered trademark) S-211, which is an anionic type fluorine-based surfactant, Surflon (registered trademark) S-221, which is a cationic type fluorine-based surfactant, and amphoteric type fluorine-based surfactant. Examples thereof include Surflon (registered trademark) S-231 and Surflon (registered trademark) S-241 which is an amine oxide type fluorine-based surfactant. The silicone-based surfactant is a surfactant having a structure in which a substituent is introduced into a part of silicone having a siloxane bond as a main skeleton, and a commercially available one can be used. Examples of commercially available silicone-based surfactants include, but are not limited to, KF-640, KF-642, and KF-643, which are nonionic (polyether type) silicone-based surfactants manufactured by Shinetsu Silicone Co., Ltd. Can be mentioned. The hydrocarbon-based surfactant is a surfactant having a hydrocarbon group as a hydrophobic group, and commercially available ones can be used. Commercially available hydrocarbon-based surfactants include, for example, but not limited to these, an amine oxide-type hydrocarbon-based surfactant manufactured by Lion Specialty Chemicals Co., Ltd., Cadenax (registered trademark) DM10D-W, Cadenax (registered trademark). Examples include DM12D-W (C), Cadenax (registered trademark) DM14D-N, Cadenax (registered trademark) DMC-W, and Cadenax (registered trademark) APA-12W.

As the surfactant, for both the dispersion medium of the dispersion of the anion-modified cellulose used in step 1 and the dispersion medium (organic solvent) of the dispersion of the hydrophobic anion-modified CNF obtained in step 6 or 8 described later. It is preferable to use one having high solubility. Specifically, those that dissolve in 1% by mass or more are preferable, those that dissolve in 5% by mass or more are more preferable, and those that dissolve in 10% by mass or more are further preferable with respect to each dispersion medium (25 ° C.).

Considering the effect of improving the transparency, the surfactant is preferably added in an amount of 0.1 to 30% by mass, and in an amount of 0.5 to 20% by mass, based on the mass of the anion-modified cellulose. Is even more preferable.

The order of addition of the surfactant and the hydrophobic agent is not particularly limited, and the surfactant may be added after the hydrophobic agent is added, or the surfactant is added and then the hydrophobic agent is added. You may.
(1-7) Dispersion of Hydrophobicized Anion-Modified Cellulose By adding a hydrophobic agent and a surfactant to the above-mentioned dispersion of anion-modified cellulose, a dispersion of hydrophobic anion-modified cellulose can be produced. The dispersion medium in the dispersion of the hydrophobic anion-modified cellulose obtained in step 1 may be the same as the dispersion medium of the dispersion of the anion-modified cellulose described above. The concentration of the anion-modified cellulose (excluding the mass of the hydrophobizing agent) in the dispersion of the hydrophobic anion-modified cellulose obtained in step 1 is preferably 0.01 to 50% by mass, preferably 1 to 45% by mass. It is preferable, and more preferably 2 to 40% by mass.

(2) Step 3
After step 1, optionally, step 3 may be performed in which the hydrophobic anion-modified cellulose obtained in step 1 is defibrated to obtain a dispersion of a defibrated product of the hydrophobic anion-modified cellulose.

The device used for defibration is not particularly limited, and devices such as a high-speed rotary type, a colloid mill type, a high pressure type, a roll mill type, and an ultrasonic type can be used.
The degree of defibration is not particularly limited, and defibration may proceed until a hydrophobic anion-modified CNF, which will be described later, is obtained, or defibration may be stopped before that. For example, when defibration is carried out until CNF is obtained, defibration may be carried out until the average fiber diameter is about 2 to 500 nm, preferably about 2 to 150 nm, and more preferably about 2 to 20 nm. When the defibration is stopped before that, for example, the defibration may be performed until the average fiber diameter of the defibrated product is preferably about 500 nm to 20 μm, more preferably about 550 nm to 15 μm.

When the degree of defibration is increased in step 3, the transparency of the hydrophobic anion-modified CNF using the organic solvent obtained in step 8 as a dispersion medium tends to be further improved, and the viscosity tends to be further lowered. However, since performing step 3 and increasing the degree of defibration in step 3 requires a large amount of energy for defibration, whether or not to perform step 3 and whether to perform step 3 are performed. The degree of defibration in the case may be determined in consideration of the characteristics and cost of the desired CNF dispersion. Here, "increasing the degree of defibration" means further reducing the average fiber diameter of the defibrated product of the hydrophobized anion-modified cellulose obtained by defibration.

The dispersion medium of the dispersion in performing the step 3 is not particularly limited, and the dispersion medium of the dispersion of the hydrophobic anion-modified cellulose in the step 1 may be used as it is.
The concentration of the hydrophobic anion-modified cellulose in the dispersion when the step 3 is carried out is preferably 0.01 to 50% by mass, and is preferably 1 to 45% by mass in consideration of the efficiency at the time of subsequent drying. 2 to 40% by mass is more preferable.

(3) Step 2, step 4
In step 2 or step 4, the dispersion medium is removed from the dispersion of the hydrophobic anion-modified cellulose obtained in step 1 or the dispersion of the defibrated product of the hydrophobic anion-modified cellulose obtained in step 3 to remove the hydrophobic anion. Produce a dry solid of modified cellulose or its defibrated product. At this time, it is necessary to sufficiently remove the dispersion medium so that the solid content concentration in the dry solid matter is higher than 90% by mass. The solid content concentration in the dry solid is preferably higher than 95% by mass, more preferably 97% by mass or more, and further preferably 98% by mass or more. Cellulose easily swells by absorbing water or a water-soluble organic solvent, but in step 2 or 4, the water or water-soluble organic solvent absorbed by the cellulose is sufficiently sufficient to satisfy the above-mentioned solid content concentration. It needs to be removed. By sufficiently removing the dispersion medium which is water or a water-soluble organic solvent in step 2 or 4, the solvent replacement step can be omitted and the solvent can be dispersed in a low-polarity organic solvent in the subsequent step 6 or 8. become able to. On the other hand, when the dried solid contains 10% by mass or more of a dispersion medium (water and / or a water-soluble organic solvent), it is defibrated and dispersed in a low-polarity organic solvent such as toluene in step 6 or 8. If it is attempted to be allowed to do so, it cannot be sufficiently mixed with a low-polarity solvent, which may cause problems such as precipitation.

The solid content concentration in the dry solid 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 mass before and after drying.
Solid content concentration (mass%) of dried solids = mass after drying / mass before drying × 100.

The means for removing the dispersion medium is not particularly limited, and the dispersion medium may be removed by, for example, placing the dispersion medium at a temperature of 60 to 130 ° C. for 1 to 24 hours.
The obtained dried solid of hydrophobic anion-modified cellulose or its defibrated product can be easily converted into hydrophobic anion-modified CNF by defibrating in an organic solvent as in step 6 or 8 described later. Can be done. The dried solid of the hydrophobized anion-modified cellulose or the defibrated product thereof can be suitably used as a raw material for producing the hydrophobicized anion-modified CNF. Hereinafter, the "dry solid of hydrophobic anion-modified cellulose" obtained in step 2 and the "dry solid of defibrated product of hydrophobic anion-modified cellulose" obtained in step 4 are collectively referred to as "dry solid". Sometimes.

(4) Step 6 and step 8
In step 6 or step 8, the above-mentioned dry solid is mixed with an organic solvent, the hydrophobic anion-modified cellulose is defibrated in the organic solvent, and a dispersion of the hydrophobic anion-modified CNF using the organic solvent as a dispersion medium is prepared. To manufacture.

The type of the organic solvent used is not particularly limited and may be a water-soluble organic solvent as described above, but in the present invention, it has a lower polarity than the water-soluble organic solvent (such as separating when mixed with water). ) An organic solvent can also be used as a dispersion medium for the CNF dispersion. 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. Examples thereof include methane, trichlorotrifluoromethane, hexafluorobenzene, ethylbenzene, xylene, cyclopentyl methyl ether and methyl tertiary butyl ether. One or more of these can be appropriately selected and used depending on the final use of the anion-modified CNF.

The ratio of the organic solvent mixed with the dry solid is not particularly limited, but considering the efficiency of defibration, the solid content concentration of the anion-modified cellulose (not including the hydrophobizing agent portion) is 0.01 to 5% by mass. It is preferable to add an organic solvent so as to be, more preferably 0.5 to 3.0% by mass.

After mixing the dry solid with an organic solvent, cellulose is defibrated in the organic solvent to form a dispersion of hydrophobized anion-modified CNF using the organic solvent as a dispersion medium.
The apparatus used for defibration is not limited, but it is preferable to use an apparatus capable of applying a strong shearing force to a dispersion such as a high-speed rotary type, a colloid mill type, a high pressure type, a roll mill type, and an ultrasonic type. In order to efficiently defibrate, it is preferable to use a wet high-pressure or ultra-high pressure homogenizer capable of applying a pressure of 50 MPa or more to the dispersion and applying a strong shearing force. The pressure is more preferably 100 MPa or more, still more preferably 140 MPa or more. A high-pressure or ultra-high pressure homogenizer is an emulsification by the total energy such as collision between particles and shearing force due to pressure difference by pressurizing the fluid with a pump to make it high pressure and ejecting it from a very delicate gap provided in the flow path. , Dispersion, pulverization, crushing, and ultrafine. Prior to the defibration and dispersion treatment with a high-pressure homogenizer, pretreatment can be performed, if necessary, using a known mixing, stirring, emulsifying, and dispersing device such as a high-speed shear mixer.

By the above defibration, nanofibers of hydrophobic anion-modified cellulose can be obtained. CNF (cellulose nanofiber) is a fiber having an average fiber diameter of about 2 to 500 nm, preferably about 2 to 150 nm, and more preferably about 2 to 20 nm. The aspect ratio is 30 or more, preferably 50 or more, and more preferably 100 or more. The upper limit of the aspect ratio is not limited, but is about 500 or less.

The average fiber diameter and average fiber length of the hydrophobic anion-modified CNF are determined by using an atomic force microscope (AFM) when the diameter is less than 20 nm and a 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. The aspect ratio can be calculated by the following formula:
Aspect ratio = average fiber length / average fiber diameter.

(5) Dispersion of Hydrophobized Anion-Modified Cellulose Nanofibers According to the present invention, it is possible to obtain a dispersion having good dispersibility using a low-polarity organic solvent such as toluene as a dispersion medium. The dispersion of the hydrophobic anion-modified CNF using the organic solvent of the present invention as a dispersion medium includes the above-mentioned hydrophobic anion-modified CNF, a surfactant, and a dispersion medium which is an organic solvent. The concentration of the anion-modified CNF (excluding the mass of the hydrophobizing agent) in the dispersion of the hydrophobized anion-modified CNF may be appropriately set according to the intended use and is not particularly limited, but is preferably about 0.01 to 5% by mass. , 0.5 to 3.0% by mass is more preferable. The amount of the hydrophobizing agent in the dispersion is preferably such that the amount of the hydrophobizing agent bound to 1 g of the above-mentioned anion-modified cellulose is 0.40 g or more. The amount of the surfactant is preferably 0.1 to 30% by mass with respect to the mass of the anion-modified cellulose (excluding the mass of the hydrophobizing agent).

The dispersibility of the hydrophobized anion-modified CNF can be evaluated by measuring the transparency of the dispersion. Transparency is measured, for example, by the following methods:
A CNF dispersion having a predetermined concentration was prepared, and the transmittance of 660 nm light was measured using a UV-VIS spectrophotometer UV-1800 (manufactured by Shimadzu Corporation) and a square cell having an optical path length of 10 mm. Transparency.

In the present invention, for example, a hydrophobized anion-modified CNF dispersion having toluene as the dispersion medium and a solid content concentration (CNF conversion (without hydrophobizing agent)) of 1.0% by mass was measured by the above method. A dispersion having a transparency of 90% or more, more preferably 92% or more, still more preferably 94% or more can be produced.

It is not clear why the present invention provides a highly transparent dispersion of hydrophobic anion-modified CNF, but by adding a surfactant to the dispersion of hydrophobic anion-modified cellulose before producing a dry solid, It is presumed that the surface tension of the dispersion subjected to drying was reduced, excessive aggregation of the hydrophobic anion-modified cellulose during drying was suppressed, and the dispersibility of the dried solid was improved.

Further, according to the present invention, a CNF dispersion using an organic solvent having a relatively low viscosity as a dispersion medium can be produced. The viscosity of the CNF dispersion is measured, for example, by the following method:
A CNF dispersion having a predetermined concentration is prepared, and according to the method of JIS-Z-8803, using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.), the rotation speed is 60 rpm or 6 rpm for 3 minutes at 25 ° C. Measure the later value.

In the present invention, for example, a hydrophobized anion-modified CNF dispersion having toluene as the dispersion medium and a solid content concentration (CNF conversion (not including a hydrophobic agent)) of 1.0% by mass was measured by the above method. It is possible to form a dispersion having a B-type viscosity at 60 rpm of 1000 mPa · s or less, preferably 900 mPa · s or less, and more preferably 800 mPa · s or less.

(6) Dry solids of hydrophobized anion-modified cellulose or its defibrated product The hydrophilicity of the anion-modified cellulose has been reduced by the hydrophobization treatment of the dry solids obtained in Steps 2 and 4, and also in water or water. Since it contains almost no aqueous dispersion medium such as an aqueous organic solvent, it can be used by being satisfactorily mixed with various organic solvents and hydrophobic polymers. The above-mentioned dry solid contains an anion-modified cellulose to which a hydrophobizing agent is bound and a surfactant. The hydrophobizing agent is as described above, and the amount of the hydrophobizing agent bound to 1 g of the above-mentioned anion-modified cellulose is preferably 0.40 g or more. The surfactant is also as described above, and is preferably contained in an amount of 0.1 to 30% by mass with respect to the mass of the above-mentioned anion-modified cellulose. In the dry solid, the dispersion medium is sufficiently removed so that the solid content concentration is higher than 90% by mass, and the solid content concentration is more preferably higher than 95% by mass, more preferably 97% by mass or more. , More preferably 98% by mass or more.

In the present invention, aggregation of cellulose fibers during drying of the hydrophobic anion-modified cellulose dispersion or the dispersion of the defibrated product of the hydrophobic anion-modified cellulose is suppressed, and a highly bulky dry solid can be obtained. Therefore, the dry solid of the present invention is a cellulose fiber material that is easily dispersed in an organic solvent and has good handling performance.

The dry solid of the present invention is mainly composed of a hydrophobic anion-modified cellulose and a surfactant, and is an additive arbitrarily known depending on the application, such as before removing the dispersion medium from the dispersion of the hydrophobic anion-modified cellulose. (Antibacterial agent, colorant, resin base material, resin antistatic agent, antifogging agent, light stabilizer, ultraviolet absorber, pigment, inorganic filler, fungicide, preservative, foaming agent, flame retardant, etc.) Then, it may contain the above-mentioned additives by drying. When the dry solid contains additives other than the hydrophobic anion-modified cellulose and the surfactant, the proportion of the hydrophobic anion-modified cellulose in the dry solid is preferably 70% by mass or more, more preferably 80% by mass or more. 90% by mass or more is more preferable. The dry solid may contain no additives other than the surfactant and may consist only of the hydrophobized anion-modified cellulose and the surfactant (including a small amount of residual dispersion medium).

The form of the dry solid of the present invention is not particularly limited, and it may be in the form of a bulk (lump) after removing the dispersion medium, or it may be appropriately pulverized into a powder, and it may be selected according to the intended use. Just do it.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples.
<Example 1>
Add 500 g (absolutely dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from softwood 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, and the oxidation reaction was started. Although the pH in the system decreased during the reaction, a 3M aqueous sodium hydroxide solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system did not change. The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was thoroughly washed with water to obtain pulp having a carboxyl group introduced (carboxylated cellulose). The amount of carboxyl groups 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 into an acid type (-COOH). ). Then, suction filtration was performed using a glass filter to dehydrate the product. Again, the solid content concentration of the carboxylated cellulose was adjusted to 5% by mass with water, and then dehydrated. This step was repeated 3 times to obtain an acid-type carboxylated cellulose having a solid content concentration of 25% by mass.

The obtained acid-type carboxylated cellulose dispersion was diluted with water so as to have a solid content concentration of 4% by mass, and JEFFAMINE (registered trademark) M-1000 (manufactured by Huntsman Corporation, molecular weight 1000) was used as a hydrophobizing agent. 1 equivalent was added with respect to the amount of carboxyl groups. When the binding amount of the hydrophobizing agent is calculated according to the above formula, it is 1.42 g. The mixture was mixed with a homomixer (3000 rpm, 5 minutes) to produce a dispersion of carboxylated cellulose (hydrophobicized carboxylated cellulose) to which a hydrophobizing agent was bound. Next, a fluorine-based surfactant (Surflon (registered trademark) S-242, manufactured by AGC Seimi Chemical Co., Ltd.) was added so as to be 10% by mass with respect to the mass of carboxylated cellulose (excluding the mass of the hydrophobizing agent). Then, the mixture was mixed with a homomixer (3000 rpm, 5 minutes). The obtained dispersion of hydrophobically carboxylated cellulose was allowed to stand at a temperature of 70 ° C. for 15 hours to produce a dry solid of hydrophobically 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 the hydrophobizing agent), and the mixture was stirred at 3000 rpm for 10 minutes. Subsequently, the treatment (defibration) was performed once at 80 MPa at 20 ° C. and twice at 150 MPa using an ultra-high pressure homogenizer to obtain a dispersion of hydrophobized carboxylated CNF using toluene as a dispersion medium. The yield (ie, the ratio of the mass of the carboxylated CNF to the finally obtained hydrophobic carboxylated CNF to the mass of the carboxylated cellulose used) was 100%.

The transparency and viscosity of the obtained dispersion of the hydrophobically carboxylated CNF (dispersion medium: toluene, solid content concentration (converted to carboxylated CNF): 1.0% by mass) were measured by the above method. The results are shown in Table 1.

<Example 2>
Dispersion of hydrophobized carboxylated CNF (dispersion medium: toluene, solid content) in the same manner as in Example 1 except that the fluorine-based surfactant was changed to Surflon (registered trademark) S-243 (manufactured by AGC Seimi Chemical Co., Ltd.). (Carboxylated CNF conversion): 1.0% by mass) was obtained, and its transparency and viscosity were measured by the above-mentioned method. The results are shown in Table 1.

<Comparative example 1>
A dispersion of hydrophobized carboxylated CNF (dispersion medium: toluene, solid content (converted to carboxylated CNF): 1.0% by mass) was obtained in the same manner as in Example 1 except that a fluorine-based surfactant was not added. Its transparency and viscosity were measured by the method described above. The results are shown in Table 1.

<Example 3>
The acid-type carboxylated cellulose dispersion obtained in Example 1 was diluted with water so as to have a solid content concentration of 4% by mass, and used as a hydrophobic agent as JEFFAMINE (registered trademark) M-1000 (manufactured by HUNTSMAN). A molecular weight of 1000) was added in an amount equivalent to 1 equivalent with respect to the amount of carboxyl groups. When the binding amount of the hydrophobizing agent is calculated according to the above formula, it is 1.42 g. The mixture was mixed with a homomixer (3000 rpm, 5 minutes) to produce a dispersion of carboxylated cellulose (hydrophobicized carboxylated cellulose) to which a hydrophobizing agent was bound. Next, a fluorine-based surfactant (Surflon (registered trademark) S-243, manufactured by AGC Seimi Chemical Co., Ltd.) was added so as to be 10% by mass with respect to the mass of carboxylated cellulose (excluding the mass of the hydrophobizing agent). Then, the mixture was mixed with a homomixer (3000 rpm, 5 minutes). Subsequently, the dispersion was treated once with an ultrahigh pressure homogenizer at 20 ° C. and 150 MPa to obtain a defibrated product of hydrophobized carboxylated cellulose. The defibrated product of the hydrophobized carboxylated cellulose was allowed to stand at a temperature of 70 ° C. for 15 hours to produce a dry solid (solid content concentration: 98% by mass) of the defibrated product of the hydrophobized carboxylated cellulose.

Toluene was added to the obtained dry solid so that the solid content was 1% by mass in terms of carboxylated cellulose (without the hydrophobizing agent), and the mixture was stirred at 3000 rpm for 10 minutes. Subsequently, the treatment (defibration) was performed once at 80 MPa at 20 ° C. and twice at 150 MPa using an ultra-high pressure homogenizer to obtain a dispersion of hydrophobized carboxylated CNF using toluene as a dispersion medium. The yield (ie, the ratio of the mass of the carboxylated CNF to the finally obtained hydrophobic carboxylated CNF to the mass of the carboxylated cellulose used) was 100%.

The transparency and viscosity of the obtained dispersion of the hydrophobically carboxylated CNF (dispersion medium: toluene, solid content concentration (converted to carboxylated CNF): 1.0% by mass) were measured by the above method. The results are shown in Table 1.

<Comparative example 2>
A dispersion of hydrophobized carboxylated CNF (dispersion medium: toluene, solid content (converted to carboxylated CNF): 1.0% by mass) was obtained in the same manner as in Example 3 except that a fluorine-based surfactant was not added. Its transparency and viscosity were measured by the method described above. The results are shown in Table 1.

From the results in Table 1, by adding a surfactant to the dry solid of the hydrophobic anion-modified cellulose or the hydrophobic anion-modified cellulose defibrated product, the transparency is higher than that without the surfactant. It can be seen that a dispersion of hydrophobized anion-modified CNF having a low viscosity and using an organic solvent as a dispersion medium can be obtained.

Claims (8)

Step 1 of producing a dispersion of hydrophobic anion-modified cellulose by adding a hydrophobizing agent and a surfactant to the dispersion of anion-modified cellulose, and removing the dispersion medium from the dispersion of the hydrophobic anion-modified cellulose are performed. Step 2 of producing a dry solid of hydrophobized anion-modified cellulose,
Including
The dry solid of the hydrophobized anion-modified cellulose has a solid content concentration of more than 90% by mass.
A method for producing a dry solid of hydrophobized anion-modified cellulose. Step 1 to produce a dispersion of hydrophobized anion-modified cellulose by adding a hydrophobizing agent and a surfactant to the dispersion of anion-modified cellulose.
Step 3 of defibrating the hydrophobized anion-modified cellulose to produce a dispersion of a defibrated product of the hydrophobic anion-modified cellulose.
Step 4, in which the dispersion medium is removed from the dispersion of the defibrated product of the hydrophobic anion-modified cellulose to produce a dry solid of the defibrated product of the hydrophobic anion-modified cellulose.
Including
The dry solid of the hydrophobized anion-modified cellulose defibrated product has a solid content concentration of more than 90% by mass.
A method for producing a dry solid of a defibrated product of hydrophobized anion-modified cellulose. Step 5 for producing a dry solid of hydrophobic anion-modified cellulose by steps 1 and 2 according to claim 1, and mixing the dry solid of hydrophobic anion-modified cellulose with an organic solvent in the organic solvent. Step 6, in which the hydrophobized anion-modified cellulose is defibrated to produce a dispersion of the hydrophobized anion-modified cellulose nanofibers using the organic solvent as a dispersion medium.
Including
The dry solid of the hydrophobized anion-modified cellulose has a solid content concentration of more than 90% by mass.
A method for producing a dispersion of hydrophobized anion-modified cellulose nanofibers. The step 7 for producing a dried solid of the defibrated product of the hydrophobic anion-modified cellulose by the steps 1, 3 and 4 according to claim 2, and the dry solid of the defibrated product of the hydrophobic anion-modified cellulose are organic. Step 8 of mixing with a solvent to defibrate the hydrophobic anion-modified cellulose in the organic solvent to produce a dispersion of hydrophobic anion-modified cellulose nanofibers using the organic solvent as a dispersion medium.
Including
The dry solid of the hydrophobized anion-modified cellulose defibrated product has a solid content concentration of more than 90% by mass.
A method for producing a dispersion of hydrophobized anion-modified cellulose nanofibers. The method according to any one of claims 1 to 4, wherein the anion-modified cellulose is cellulose having a carboxyl group or cellulose having a carboxylalkyl group. The method according to any one of claims 1 to 5, wherein the surfactant is a fluorine-based surfactant. Drying of hydrophobized anion-modified cellulose containing a denatured product of anion-modified cellulose to which a hydrophobizing agent is bound or an anion-modified cellulose to which a hydrophobizing agent is bound, and a surfactant, and having a solid content concentration of more than 90% by mass. Solid matter. A dispersion of hydrophobic anion-modified cellulose nanofibers containing an anion-modified cellulose nanofiber to which a hydrophobic agent is bound and a surfactant, and using an organic solvent as a dispersion medium.