JP2020105429A - Modified cellulose fiber, dispersion liquid thereof, and method for producing the same - Google Patents

Abstract

To provide cellulose fibers which are modified so as to be dispersed in a hydrophobic solvent, polymer, or the like, and have an average fiber diameter of 1-500 nm; and a method for producing the same.SOLUTION: The modified cellulose fibers having the average fiber diameter of 1-500 nm have carboxyl groups at C6 positions of at least a part of structural units of cellulose, wherein ions derived from a metal salt are ionically bonded to at least a part of the carboxyl groups. The metal salt is represented by the formula: M(OH)m-n(OOCR)n, where M represents a multivalent metal having a valence of 2 or more; m represents an integer corresponding to the valence of the metal M, and n represents an integer of 1 to m; and R represents a hydrocarbon group.SELECTED DRAWING: Figure 5

Description

The present invention relates to a modified fine cellulose fiber (hereinafter, also referred to as “CNF”), and more specifically, a modified average fiber diameter of 1 to 500 nm that can be used for dispersing in a hydrophobic solvent or polymer. The present invention relates to the obtained cellulose fiber, a dispersion liquid in which the fiber is dispersed in a non-aqueous solvent, and a method for producing the fiber.

Since the technology for facilitating the defibration by developing the hydrophilicity by oxidizing the cellulose fibers (Non-patent Document 1, Patent Document 1), fine cellulose fibers having a fiber diameter of several nm to several hundreds nm have been developed. The applications used have expanded.
However, since such micronized cellulose fibers are hydrophilic, it was difficult to disperse them in a hydrophobic solvent or a hydrophobic polymer, and thus micronized for use in such applications. Technology for making hydrophilic cellulose fibers hydrophobic has been developed (Patent Documents 2 to 4, etc.).

JP2008-1728 JP2011-140738 JP2012-21081 International publication WO2013/077354

Biomacromolecule vol.7 No.6, 2006 1687-1691

An object of the present invention is to provide a cellulose fiber having an average fiber diameter of 1 to 500 nm modified for dispersion in a hydrophobic solvent or polymer, a dispersion thereof, and a method for producing the same.

It is known to introduce a hydrophobic group such as a hydrocarbon group onto the surface of cellulose in order to make the cellulose fiber hydrophobic (Patent Documents 2 to 4, etc.), but in the present invention, the cellulose fiber is a hydrophobic solvent. We have developed a new denaturing method to disperse it into polymers and polymers.
That is, the present invention is a cellulose fiber having an average fiber diameter of 1 to 500 nm having a carboxyl group at the C6 position of at least a part of the cellulose constitutional unit, and an ion derived from a metal salt is present in at least a part of the carboxyl group. An ionic bond is formed, and the metal salt is represented by the following formula: M(OH) _mn (OOCR) _n
(In the formula, M represents a polyvalent metal having a valence of 2 or more, m represents an integer corresponding to the valence of the metal M, n represents an integer of 1 to m, and R represents a hydrocarbon group. ) Is a modified cellulose fiber represented by.
Further, the present invention comprises a step of treating a cellulose fiber having an average fiber diameter of 1 to 500 nm having a carboxyl group at the C6 position of at least a part of the cellulose constitutional unit with a metal salt in the dispersion liquid. A method for producing a modified cellulose fiber in which ions derived from the metal salt are ion-bonded to at least a part of groups, wherein the metal salt is represented by the following formula: M(OH) _mn (OOCR) _n
(In the formula, M represents a polyvalent metal having a valence of 2 or more, m represents an integer corresponding to the valence of the metal M, n represents an integer of 1 to m, and R represents a hydrocarbon group. ) Is a manufacturing method.

The FTIR chart of CNF obtained in manufacture example 1 is shown. 1 shows an FTIR chart of modified CNF obtained in Example 1. 4 shows an FTIR chart of modified CNF obtained in Example 2. 4 shows an FTIR chart of modified CNF obtained in Example 3. It is a figure which shows a modified CNF dispersion liquid. A is the example 1, B is the example 2, C is the example 3, D is the example 4, E is the example 5, F is the example 6, and G is that of the comparative example 1.

このようなセルロース繊維は、例えば、下記のようにして用意することができる。 The average fiber diameter of the cellulose fiber of the present invention is 1 to 500 nm, preferably 1 to 100 nm, more preferably 1 to 10 nm, and a carboxyl group at the C6 position of at least a part of the cellulose structural unit (Chemical formula 1(a)). Have. Chemical formula 1(b) represents carboxylated cellulose, and chemical formula 1(c) represents carboxymethylated cellulose.

Such cellulose fibers can be prepared, for example, as follows.

(Cellulose raw material)
Examples of the cellulose raw material for producing anion-modified cellulose include plant materials (for example, wood, bamboo, hemp, jute, kenaf, agricultural land waste, cloth, pulp (softwood unbleached kraft pulp (NUKP), softwood bleaching). Kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP) thermomechanical pulp (TMP), recycled pulp , Waste paper, etc.), animal materials (for example, ascidians), algae, microorganisms (for example, acetic acid bacteria (acetobacter)), products derived from microorganisms, and the like, and any of them can be used. Is a plant- or microorganism-derived cellulose fiber, more preferably a plant-derived cellulose fiber.

(Carboxylated)
In the present invention, carboxylated cellulose (also referred to as oxidized cellulose) can be obtained by carboxylating (oxidizing) the above cellulose raw material by a known method. Although not particularly limited, at the time of carboxylation, the amount of the carboxyl group is preferably 0.05 to 6 mmol/g, more preferably 0.6 with respect to the absolute dry weight of the carboxylated cellulose nanofibers. ˜2.0 mmol/g, more preferably 1.0 mmol/g to 2.0 mmol/g.

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

The 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 is a compound that promotes the desired oxidation reaction. Examples thereof include 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and its derivatives (for example, 4-hydroxy TEMPO).

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 still more preferable, relative to 1 g of absolutely dried cellulose. Moreover, about 0.1 to 4 mmol/L is preferable for the reaction system.

Bromides are compounds containing bromine, examples of which include alkali metal bromides that can dissociate and ionize in water. Further, iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used can be selected within a range that can accelerate the oxidation reaction. 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, per 1 g of absolutely dried cellulose.

As the oxidizing agent, known ones can be used, for example, halogen, hypohalous acid, halogenous 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 oxidant 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 per 1 g of absolutely dried cellulose. .. 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. Since a carboxyl group is generated in the cellulose as the reaction progresses, 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 0.5 to 6 hours, for example, 0.5 to 4 hours.

The oxidation reaction may be carried out in two stages. For example, by oxidizing the oxidized cellulose obtained by filtering after the completion of the reaction in the first step again under the same or different reaction conditions, the reaction efficiency due to the reaction by the salt produced as a by-product in the reaction in the first step is not increased. Can be well oxidized.

As another example of the carboxylation (oxidation) method, there may be mentioned a method in which a gas containing ozone and a cellulose raw material are brought into contact with each other to be oxidized. By this oxidation reaction, at least the 2- and 6-position hydroxyl groups 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 weight, and more preferably 5 to 30 parts by weight, when the solid content of the cellulose raw material is 100 parts by weight. The ozone treatment temperature is preferably 0 to 50°C, more preferably 20 to 50°C. Although the ozone treatment time is not particularly limited, it is about 1 to 360 minutes, preferably about 30 to 360 minutes. When the conditions of the ozone treatment 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 performing the ozone treatment, an additional oxidizing treatment may be performed using an oxidizing agent. The oxidizing agent used in the additional oxidation treatment is not particularly limited, but examples thereof include chlorine-based compounds such as chlorine dioxide and sodium chlorite, and oxygen, hydrogen peroxide, persulfuric acid, peracetic acid and the like. For example, an additional oxidization 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.

(Carboxymethylation)
An example of a carboxymethylation method is to obtain anion-modified cellulose by using cellulose as a bottoming raw material, mixing with a mercerizing agent to perform mercerizing treatment, and then performing etherification using an etherifying agent. You can As the solvent, water alone or 3 to 20 times by weight lower alcohol, specifically methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary butanol, etc., or two kinds thereof A mixed medium of the above mixture and water is used. The mixing ratio of the lower alcohol is 60 to 95% by weight. As the mercerizing agent, 0.5 to 20 times mol of alkali metal hydroxide, specifically sodium hydroxide or potassium hydroxide, is used per glucose residue of the bottoming raw material. The mercerizing agent is an aqueous solution of 5 to 70% by weight, more preferably 30 to 60% by weight. Examples of the etherifying agent include monochloroacetic acid, sodium monochloroacetate, methyl monochloroacetate, ethyl monochloroacetate, isopropyl monochloroacetate and the like. Of these, monochloroacetic acid and sodium monochloroacetate are preferable from the viewpoint of easy availability of raw materials. An aqueous solution of an etherifying agent in an amount of 5 to 70% by weight, preferably 30 to 60% by weight, is used in an amount of 0.05 to 10.0 times the molar amount of the etherifying agent per glucose residue in the bottoming raw material. At this time, the total weight of the cellulosic solids and water relative to the cellulosic solids when the water of all the chemicals to be finally added is added from the water taken in from the bottoming raw material cellulose (liquid Ratio) to be 1.0 to 4.0.

In the mercerization treatment, the reaction temperature of the reactor is adjusted to 0 to 50° C., preferably 10 to 40° C., the aqueous solution of the mercerizing agent is added while mixing the cellulose, and the reaction time is 15 minutes to 8 hours, preferably 30. It is performed by stirring for 3 minutes to 3 hours. Thereby, alkali cellulose is obtained. Then, the aqueous solution of the etherifying agent was added to the alkali cellulose in the reactor and stirred for 15 minutes to 4 hours while keeping the temperature constant, and then the reaction temperature was 30 to 90°C, preferably 40 to 80°C, and The etherification reaction is carried out for a reaction time of 30 minutes to 10 hours, preferably 1 hour to 4 hours to obtain carboxymethylated cellulose.
The carboxyl group content of this carboxymethylated cellulose fiber is preferably 0.05 to 6 mmol/g, more preferably 0.1 to 2.0 mmol/g.

(Defibration)
The device used for defibrating these cellulose fibers is not particularly limited, but a high speed rotation type, colloid mill type, high pressure type, roll mill type, ultrasonic type device or the like can be used. At the time of defibration, it is preferable to apply a strong shearing force to the anion-modified cellulose aqueous dispersion. In particular, for efficient defibration, it is preferable to use a wet high-pressure or ultra-high-pressure homogenizer that can apply a pressure of 50 MPa or more and a strong shearing force to the water dispersion. The pressure is more preferably 100 MPa or more, further preferably 140 MPa or more. In addition, prior to the defibration and dispersion treatment with a high-pressure homogenizer, if necessary, a known treatment such as a high-speed shear mixer, stirring, emulsification, even if subjected to a preliminary treatment to the aqueous dispersion, using a dispersing device Good.

As a solid-liquid separation method, a known method can be used. For example, a centrifugal type, a vacuum type, or a pressure type device can be used, and a plurality of these can also be used in combination.

As the drying method, known methods can be used, and examples thereof include spray drying, pressing, air drying, hot air drying, and vacuum drying. The drying device is not particularly limited, but it is a continuous tunnel drying device, band drying device, vertical drying device, vertical turbo drying device, multi-stage disc drying device, aeration drying device, rotary drying device, airflow drying device, sprayer. Dryer dryer, spray dryer, cylinder dryer, drum dryer, belt dryer, screw conveyor dryer, rotary dryer with heating tube, vibration transport dryer, batch-type box dryer, aeration dryer, vacuum The box type drying device, the stirring drying device and the like can be used alone or in combination of two or more.

The modified cellulose fiber (modified CNF) of the present invention has a carboxyl group at the C6 position of at least a part of the cellulose constitutional unit (Chemical Formula 1(a)), and at least a part of this carboxyl group is derived from a metal salt. The ions are modified by ionic bonding, and the metal salt has a hydrophobic group.
The metal salt used in the present invention is represented by the following formula.
M(OH) _m-n (OOCR) _n
In the formula, M is a polyvalent metal having a valence of 2 or more, preferably 2 or 3, and specifically, divalent metals such as zinc, magnesium, calcium, strontium, barium and radium, aluminum, iron, Examples thereof include trivalent metals such as manganese, chromium and bismuth, and tetravalent metals such as tin and titanium.
m represents an integer corresponding to the valence of the metal M and is an integer of 2 or more.
n represents an integer of 1 to m.

R is a hydrophobic group and represents a hydrocarbon group. Examples of this hydrocarbon group include an aliphatic hydrocarbon group, an aromatic hydrocarbon group, an alicyclic hydrocarbon group, and the like, preferably an aliphatic hydrocarbon group and an aromatic hydrocarbon group, and more preferably an aliphatic hydrocarbon group. It is a hydrogen group. The carbon number of the hydrophobic group is preferably 1 to 30, more preferably 7 to 18, and further preferably 13 to 18.
The aliphatic hydrocarbon group is a linear or branched, preferably linear, saturated or unsaturated, preferably saturated hydrocarbon group, preferably an alkyl group.
Examples of this aromatic hydrocarbon group include an aryl group and an aralkyl group, and examples thereof include benzene, biphenyl, terphenyl, naphthalene, and anthracene.
These groups may have a substituent such as a hydroxyl group, a halogen atom or an alkoxy group, but the substituent is preferably a hydrophobic substituent such as a short chain alkyl group or a short chain aryl group.

Examples of the acid anion (RCOO ⁻ ) contained in this metal salt include, for example, lauric acid, myristic acid, pentadecyl acid, palmitic acid, margaric acid, stearic acid, 2-ethylhexanoic acid, neodecanoic acid, arachidic acid, henicosyl acid, Behenic acid, lignoceric acid, cerotic acid, montanic acid, melissic acid, myristoleic acid, palmitoleic acid, sapienoic acid, oleic acid, elaidic acid, vaccenic acid, vaccenic acid, gadoleic acid, eicosenoic acid, erucic acid, nervonic acid, linole Acid, eicosadienoic acid, docosadienoic acid, linolenic acid, pinolenic acid, eleostearic acid, mead acid, dihomo-γ-linolenic acid, eicosatrienoic acid, stearidonic acid, arachidonic acid, eicosatetraenoic acid, adrenic acid, boceopentaene Carboxyl anions such as acid, eicosapentaenoic acid, ozbondic acid, sardine acid, tetracosapentaenoic acid, docosahexaenoic acid, benzoic acid, toluic acid and cinnamic acid can be used.

The ion derived from such a metal salt is ionically bonded to the carboxyl group of the cellulose fiber, and in the carboxylated cellulose (Chemical formula 1(b)), the carboxyl group is a cellulose structural unit (Chemical formula 1(a)). In the carboxymethylated cellulose (Chemical Formula 1(c)), the C6 position and the C2 position and/or the C3 position of the cellulose constitutional unit (Chemical Formula 1(a)) are present.

In such a carboxyl group of the cellulose fiber, the ions derived from the metal salt are considered to have an ionic bond represented by the following formula.
Cellulose ^{-COO -: M m +: (} RCOO -) m-1
Wherein "cellulose -COO ^-" represents a carboxy ions C6 position or the like of the cellulose structural unit, "M ^{m +"} represents a metal ion derived from the metal salt, "RCOO ^-" represents a carboxy ions from metal salts , R are as defined above. ":" Denotes an ionic bond, i.e., "cellulose -COO ^-" and ionically bonded to the ^{"M m +",} and ^{"M m +"} "RCOO ^-" and are ionically bonded.
The method for performing such ionic bonding is not particularly limited, but for example, mixing and stirring CNF and a compound containing a metal salt, treating them with ultrasonic waves, or treating them with a disperser such as a homogenizer. Examples of the treatment include, but are not limited to, steps of treating, kneading these using a kneader, and the like. Further, a method of reacting a salt of CNF, a metal halide, a fatty acid or the like in a solvent, a reaction of CNF, a fatty acid, etc., an ammonia and a metal salt in a solvent, or the like may be adopted. Further, when these treatments are carried out, heating may be carried out in order to make the reaction efficient.

The modification ratio of the carboxyl group of the CNF with the hydrophobic group is preferably 10% or more, more preferably 40% or more, with respect to the carboxyl group detected before the modification.
The modified cellulose fiber of the present invention is a known molding method of a person skilled in the art or a means such as mixing or complexing with a known material or liquid material, or an impregnation agent, a thickener, a resin composite, an additive to a coating material, It can be used in applications such as rubber compounding, films, cosmetics, adhesives, oil rheocon agents, separators, porous membranes, cleaning agents, filters, mold release agents, and organic EL.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not intended to be limited thereto.
(i) The infrared (FTIR) spectrum of the cellulose fiber was measured using a Fourier transform infrared spectrophotometer (FT/IR-350 manufactured by JASCO).
(ii) The fiber morphology of the cellulose fiber was analyzed using an atomic force microscope (AFM) for 200 randomly selected fibers.
(iii) The carboxyl group content of the cellulose fiber was measured by the following method. 60 ml of 0.5% by weight slurry of cellulose fiber (aqueous dispersion) was prepared and adjusted to pH 2.5 by adding 0.1 M hydrochloric acid aqueous solution, and then pH was adjusted to 11 by adding 0.05 N sodium hydroxide aqueous solution. The electric conductivity was measured until the temperature reached a certain value, and the amount was calculated from the amount of sodium hydroxide (a) consumed in the neutralization step of the weak acid with a gradual change in electric conductivity using the following formula: Amount of carboxyl group [mmol/g Cellulose fiber]=a [ml]×0.05/cellulose fiber mass [g].
(iv) Regarding the viscosity of the cellulose fiber dispersion, the dispersion was adjusted to a solid content of 1% excluding the weight of the metal soap, and the viscosity was measured at 25° C. using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.). ． The B-type viscosity (mPa·s) after 3 minutes was measured with a 4-rotor at a rotation speed of 60 rpm and a rotation speed of 6 rpm. If the viscosity of the modified CNF dispersion is 10 mPa·s or more at a rotation speed of 60 rpm, it can be said that the cellulose fibers are well dispersed.

Production example 1
<Production of carboxyl group-containing CNF>
Bleached unbeaten kraft pulp from softwood (whiteness 85%) 500 g (absolute dryness) was added to 780 mg of TEMPO (Sigma Aldrich) and 500 ml of an aqueous solution in which sodium bromide 75.5 g was dissolved, until the pulp was uniformly dispersed. It was stirred. An aqueous sodium hypochlorite solution was added to the reaction system at 6.0 mmol/g to start the oxidation reaction. Although the pH in the system was lowered during the reaction, the pH was adjusted to 10 by sequentially adding a 3M sodium hydroxide aqueous solution. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system stopped changing. The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was sufficiently washed with water to obtain an oxidized pulp (hereinafter referred to as "TEMPO oxidized pulp"). The pulp yield at this time was 90%, and the time required for the oxidation reaction was 90 minutes.
5 parts by weight of the TEMPO oxidized pulp obtained in the above step was added to an aqueous solution of sodium hydroxide in which 5 parts by weight of sodium hydroxide was dissolved in 100 parts by weight of water, and the mixture was stirred at 30° C. for 30 minutes for alkali treatment. .. It was washed with 100 times amount of water with respect to the absolute dry weight of TEMPO oxidized pulp after alkali treatment for 30 minutes at 30° C., and solid-liquid separation was performed using a centrifuge (Tanabe Wiltech Co., Ltd.). At this time, the solid content of the alkali-treated TEMPO oxidized pulp was 40%.
The alkali-treated TEMPO oxidized pulp obtained in the above step was adjusted to 1.0% (w/v) with water, and fibrillated 5 times with an ultrahigh pressure homogenizer (20°C, 150 MPa) to obtain TEMPO oxidized fine particles. A cellulose fiber dispersion was obtained (hereinafter referred to as "TEMPO oxidized CNF"). The obtained TEMPO-oxidized CNF had an average fiber diameter of 4 nm and an aspect ratio of 150.
Hydrochloric acid was added to the obtained TEMPO-oxidized CNF to adjust the pH to 2.5, and then it was sufficiently washed with water to obtain an acid-type TEMPO-oxidized CNF. The amount of carboxyl groups in the obtained TEMPO-oxidized CNF was 1.60 mmol/g.

<Solvent replacement with a hydrophobic solvent>
Toluene was used as the hydrophobic solvent, and the CNF dispersion medium obtained above was solvent replaced with toluene.
After suspending 107.1 g of the 1.4 wt% acid-type TEMPO-oxidized CNF mixed solution obtained above in acetone, filtration and draining were repeated 5 times to obtain an acetone-substituted product of the acid-type TEMPO-oxidized CNF. .. This was further suspended in toluene and then filtered and drained to obtain a toluene-substituted product, which was repeated 5 times. When this toluene-substituted product was allowed to stand at room temperature overnight, precipitation of CNF was observed.
An FTIR chart of CNF obtained in Production Example 1 is shown in FIG. In the chart of FIG. 1, since absorption around 1714 cm ⁻¹ is observed, it can be confirmed that the carboxyl group of CNF is in the acid form.

Example 1
0.83 g of aluminum monostearate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added to the toluene-substituted product (corresponding to 1.5 g of CNF solid content) obtained in Production Example 1 so as to have the same equivalent weight to the carboxy group of CNF. The mixture was added and stirred with a homodisper at 8000 rpm for 10 minutes. The agitated product was further treated with an ultrahigh pressure homogenizer at 20° C. and 80 MPa once, and further at 20° C. and 150 MPa twice. The obtained CNF is called modified CNF, and the dispersion is called modified CNF dispersion.
The FTIR chart of the modified CNF obtained in Example 1 is shown in FIG. In this chart, the absorption at the vicinity of 1718 cm ^{-1 in} which the carboxyl group of CNF is derived from the acid form is lower than that in Production Example 1 (Fig. 1), while the absorption of the carboxyl group in the salt form is 1588 cm ^-1. Since absorption in the vicinity is observed, it can be confirmed that the acid group of the carboxyl group of CNF is converted to the salt type. Furthermore, regarding the absorption at around 2873 cm ^{−1, which} was derived from the shrinkage of CH derived from cellulose, which was slightly confirmed in Production Example 1 (FIG. 1), the introduction of stearic acid caused the absorption at around 2917 cm ⁻¹ and 2849 cm ^−1. It is confirmed that the stearic acid group has been introduced since the absorption of is clearly confirmed.

Example 2
A modified CNF dispersion was prepared in the same manner as in Example 1 except that 1.47 g of aluminum distearate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added in place of 0.83 g of aluminum monostearate used in Example 1. Obtained. The FTIR chart of the modified CNF obtained in Example 2 is shown in FIG.

Example 3
Modified CNF dispersion obtained in the same manner as in Example 1 except that 2.1 g of aluminum tristearate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added in place of 0.83 g of aluminum monostearate used in Example 1. Got The FTIR chart of the modified CNF obtained in Example 3 is shown in FIG.

Example 4
A modified CNF dispersion was prepared in the same manner as in Example 1 except that 1.52 g of zinc stearate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added instead of 0.83 g of aluminum monostearate used in Example 1. Obtained.

Example 5
A modified CNF dispersion was prepared in the same manner as in Example 1, except that 0.84 g of zinc 2-ethylhexanoate (manufactured by Nacalai Tesque) was added instead of 0.83 g of the aluminum monostearate used in Example 1. Obtained.

Example 6
A modified CNF dispersion was prepared in the same manner as in Example 1 except that 1.74 g of bismuth neodecanoate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added in place of 0.83 g of aluminum monostearate used in Example 1. Obtained.

Comparative Example 1
A modified CNF dispersion was prepared in the same manner as in Example 1 except that 0.74 g of sodium stearate (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.) was added instead of 0.83 g of aluminum monostearate used in Example 1. The production was tried, but even if it was stirred at 8000 rpm for 10 minutes using a homodisper, it was not dispersed at all, precipitation was generated, and defibration treatment could not be performed. Furthermore, it was the same when the treatment was performed once at 20° C. and 80 MPa using an ultrahigh pressure homogenizer, and further twice at 20° C. and 150 MPa.

The modified CNF dispersions obtained above were evaluated for toluene dispersibility according to the following criteria:
◯: The CNF dispersion was well dispersed and nothing was collected at the bottom.
(Triangle|delta): CNF swelled and disperse|distributed and the CNF dispersion liquid did not produce precipitation.
X: The CNF dispersion did not disperse at all, and precipitation occurred.
If the evaluation is ◯ or Δ, it can be said that the dispersibility is good.

The dispersibility of the metal salt used for modification and the modified CND dispersion is shown in the table below, and each dispersion is shown in FIG.

The modified CNFs of Examples 1 to 6 were excellent in dispersibility in toluene, and particularly in Examples 1 to 3, the dispersibility was particularly good because the viscosity was also increased. On the other hand, the modified CNF of Comparative Example 1 could not be defibrated by stirring even after the solvent was replaced with toluene.
It can be said that the modified CNFs of Examples 1 to 6 are sufficiently hydrophobized as compared with the modified CNF of Comparative Example 1.

Claims (5)

An average fiber diameter having a carboxyl group at the C6 position of at least a part of the cellulose constitutional unit is a cellulose fiber having an average fiber diameter of 1 to 500 nm, and an ion derived from a metal salt is ionically bonded to at least a part of the carboxyl group to form the metal. The salt has the following formula: M(OH) _mn (OOCR) _n
(In the formula, M represents a polyvalent metal having a valence of 2 or more, m represents an integer corresponding to the valence of the metal M, n represents an integer of 1 to m, and R represents a hydrocarbon group. ) A modified cellulose fiber represented by. The modified cellulose fiber according to claim 1, wherein the modified cellulose fiber containing a carboxyl group is an oxidized cellulose fiber or a carboxymethylated cellulose fiber. The modified cellulose fiber according to claim 1 or 2, wherein the modified cellulose fiber is defibrated. A dispersion liquid in which the modified cellulose fiber according to any one of claims 1 to 3 is dispersed in a non-aqueous solvent. At least a part of the carboxyl groups, which comprises a step of treating a cellulose fiber having a carboxyl group at the C6 position of at least a part of the cellulose structural unit and having an average fiber diameter of 1 to 500 nm with a metal salt in the dispersion liquid. A method for producing a modified cellulose fiber in which ions derived from the metal salt are ionically bonded, wherein the metal salt is represented by the following formula: M(OH) _mn (OOCR) _n
(In the formula, M represents a polyvalent metal having a valence of 2 or more, m represents an integer corresponding to the valence of the metal M, n represents an integer of 1 to m, and R represents a hydrocarbon group. ) The manufacturing method represented by.

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