Method for producing microfibrillar cellulose / microfine inorganic layered compound inclusion and microfibrillar cellulose / microfine inorganic layered compound inclusion

Abstract

To provide a microfibrous cellulose / micro inorganic laminar compound-containing material having excellent particle dispersion properties.SOLUTION: The present invention relates to a method for producing a microfibrous cellulose / micro inorganic laminar compound-containing material, the method comprising a step for mixing an ionic substituent-containing cellulose fiber and an inorganic laminar compound, and then performing a refining treatment, wherein bubbling is suppressed in the step for performing the refining treatment. In addition, the present invention also relates to a microfibrous cellulose / micro inorganic laminar compound-containing material produced by the production method.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing a microfibrous cellulose - fine inorganic layered compound inclusion and a microfibrous cellulose - fine inorganic layered compound inclusion.

Background Art

[0002] Conventionally, cellulose fibers have been widely used in clothing, absorbent articles, paper products, etc. As cellulose fibers, in addition to fibrous cellulose with a fiber diameter of 10 μm or more and 50 μm or less, microfibrous cellulose with a fiber diameter of 1 μm or less is also known. Microfibrous cellulose has attracted attention as a new material and has a wide range of applications. For example, the use of microfibrous cellulose as a thickener or an additive to various compositions has been studied.

[0003] For example, Patent Document 1 discloses a coating liquid for forming a gas barrier layer containing a cellulose nanofiber dispersion, a water - soluble polymer, and an inorganic layered compound. In the examples of Patent Document 1, an inorganic layered compound is added to a dispersion having TEMPO - oxidized cellulose nanofibers and mixed under normal conditions to obtain a coating liquid.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, a mixture of cellulose nanofibers and an inorganic layered compound is known. However, in the prior art, after nanosizing cellulose fibers, a non - micronized inorganic layered compound is mixed, and at present, no specific studies have been made on a mixture containing cellulose nanofibers and a micronized inorganic layered compound, including its production method.

[0006] And, during the study on a mixture containing cellulose nanofibers and a micronized inorganic layered compound, the inventors found that when fine particles are dispersed in a mixture of cellulose nanofibers and an inorganic layered compound obtained by the prior art, the dispersibility of the fine particles may be insufficient.

[0007] Therefore, in order to solve such problems of the prior art, the inventors proceeded with the study aiming to provide a fine fibrous cellulose-fine inorganic layered compound inclusion having excellent particle dispersibility.

Means for Solving the Problems

[0008] As a result of intensive studies to solve the above problems, the inventors found that in a method for producing a fine fibrous cellulose-fine inorganic layered compound inclusion, after mixing a cellulose fiber having an ionic substituent and an inorganic layered compound, a micronization treatment is performed, and further, in the step of performing the micronization treatment, by suppressing bubbling, a fine fibrous cellulose-fine inorganic layered compound inclusion having excellent particle dispersibility can be obtained. Specifically, the present invention has the following configurations.

[0009] [1] A method for producing a fine fibrous cellulose-fine inorganic layered compound inclusion, comprising a step of mixing a cellulose fiber having an ionic substituent and an inorganic layered compound, and then performing a micronization treatment, In the step of performing the micronization treatment, bubbling is suppressed. [2] The method for producing a fine fibrous cellulose-fine inorganic layered compound inclusion according to [1], wherein in the step of performing the micronization treatment, the micronization treatment is performed using a high-pressure homogenizer. [3] The method for producing a fine fibrous cellulose-fine inorganic layered compound inclusion according to [1] or [2], wherein in the step of performing the micronization treatment, bubbling is suppressed by cooling. [4] The method for producing a fine fibrous cellulose-fine inorganic layered compound inclusion according to any one of [1] to [3], wherein the ionic substituent is an anionic group. [5] The method for producing the microfibrillar cellulose / fine inorganic layered compound inclusion according to any one of [1] to [4], wherein the ionic substituent is a phosphooxo acid group or a substituent derived from a phosphooxo acid group. [6] A microfibrillar cellulose / fine inorganic layered compound inclusion containing fibrillar cellulose having a fiber width of 1000 nm or less and having an ionic substituent and a fine inorganic layered compound, wherein the thixotropic index value (TI value) calculated under the following condition a is 2 or more; (Condition a) The microfibrillar cellulose / fine inorganic layered compound inclusion is dispersed in water to obtain a dispersion having a viscosity of 1000 cps measured with a B-type viscometer at 23 °C and a rotation speed of 3 rpm; the viscosity (η) of the dispersion measured with a B-type viscometer at 23 °C and a rotation speed of 60 rpm is measured, and the value of 1000 / η is defined as the thixotropic index value (TI value) of the microfibrillar cellulose / fine inorganic layered compound inclusion. [7] The microfibrillar cellulose / fine inorganic layered compound inclusion according to [6], wherein the ionic substituent is an anionic group. [8] The microfibrillar cellulose / fine inorganic layered compound inclusion according to [6] or [7], wherein the ionic substituent is a phosphooxo acid group or a substituent derived from a phosphooxo acid group. [9] The microfibrillar cellulose / fine inorganic layered compound inclusion according to any one of [6] to [8], which is for a paint.

[10] The microfibrillar cellulose / fine inorganic layered compound inclusion according to any one of [6] to [8], which is for a resin composition.

[11] The microfibrillar cellulose / fine inorganic layered compound inclusion according to any one of [6] to [8], which is for a concrete material.

[12] The microfibrillar cellulose / fine inorganic layered compound inclusion according to any one of [6] to [8], which is for a filamentous or plate-like structure.

[13] The microfibrillar cellulose / fine inorganic layered compound inclusion according to any one of [6] to [8], which is for a cosmetic.

[14] A paint containing the microfibrillar cellulose - fine inorganic layered compound inclusion described in any one of [6] to [8].

[15] A resin composition containing the microfibrillar cellulose - fine inorganic layered compound inclusion described in any one of [6] to [8].

[16] A concrete material containing the microfibrillar cellulose - fine inorganic layered compound inclusion described in any one of [6] to [8].

[17] A filamentous or plate - like structure containing the microfibrillar cellulose - fine inorganic layered compound inclusion described in any one of [6] to [8].

[18] A cosmetic containing the microfibrillar cellulose - fine inorganic layered compound inclusion described in any one of [6] to [8]. [Effect of the Invention]

[0010] According to the production method of the present invention, a microfibrillar cellulose - fine inorganic layered compound inclusion excellent in particle dispersibility can be obtained. [Brief Description of the Drawings]

[0011]

Figure 1

Figure 2

Figure 3

[0012] Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments.

[0013] (Production Method of Microfibrillar Cellulose - Fine Inorganic Layered Compound Inclusion) This embodiment is a method for producing a microfibrous cellulose - microfine inorganic layered compound inclusion containing microfibrous cellulose and a microfine inorganic layered compound. The method for producing the microfibrous cellulose - microfine inorganic layered compound inclusion of this embodiment includes a step of mixing a cellulose fiber having an ionic substituent and an inorganic layered compound, and then performing a fibrillation treatment. And in the step of performing the fibrillation treatment, bubbling is suppressed. In this specification, microfibrous cellulose refers to fibrous cellulose having a fiber width of 1000 nm or less. Also, in this specification, the inorganic layered compound is the inorganic layered compound before being refined (nanosized).

[0014] In the method for producing a microfibrous cellulose - microfine inorganic layered compound inclusion of this embodiment, after mixing a cellulose fiber having an ionic substituent and an inorganic layered compound, it includes a step of performing a fibrillation treatment. In this step of performing the fibrillation treatment, bubbling is suppressed. By going through such a manufacturing process, the microfibrous cellulose - microfine inorganic layered compound inclusion produced by the manufacturing method of this embodiment exhibits excellent particle dispersibility. The particle dispersibility in the microfibrous cellulose - microfine inorganic layered compound inclusion can be evaluated, for example, by preparing a dispersion of the microfibrous cellulose - microfine inorganic layered compound inclusion with a total dry solid concentration of 0.2% by mass, adding glass beads or the like thereto, and observing the presence or absence of sedimentation of the glass beads. When the sedimentation of the glass beads is slight or no sedimentation of the glass beads is observed, it can be determined that the dispersibility of the microfibrous cellulose and the microfine inorganic layered compound is good.

[0015] Moreover, since the microfibrous cellulose - microfine inorganic layered compound inclusion of this embodiment is produced by the above - mentioned manufacturing method, the characteristics of each material are exhibited without being impaired. The characteristics of each material in the microfibrous cellulose - microfine inorganic layered compound inclusion can be evaluated, for example, by calculating the TI value of the microfibrous cellulose - microfine inorganic layered compound inclusion and the like.

[0016] In the manufacturing method of the present embodiment, the step of performing the refinement treatment (hereinafter also referred to as the refinement treatment step) is carried out after mixing cellulose fibers having an ionic substituent and an inorganic layered compound. That is, the refinement treatment is carried out on a dispersion liquid containing cellulose fibers having an ionic substituent and an inorganic layered compound. Note that the refinement treatment in this specification is synonymous with the nanosizing treatment.

[0017] Conventionally, in the manufacturing method of a microfibrillar cellulose / fine inorganic layered compound inclusion, first, the cellulose fibers were refined (nanosized), and then the inorganic layered compound was mixed. Since the particle sizes and shapes of the refined cellulose fibers and the inorganic layered compound are quite different, it has been difficult to uniformly disperse these materials. Further, when the inorganic layered compound was refined (nanosized) alone, clogging of the refining apparatus and the like occurred, and it was difficult to obtain the fine inorganic layered compound itself. Therefore, in the present embodiment, the refinement treatment step is carried out after mixing cellulose fibers having an ionic substituent and an inorganic layered compound. As a result, in the present embodiment, since the refinement treatment step is carried out after mixing cellulose fibers having an ionic substituent and an inorganic layered compound, the dispersibility of each nanosized material has been successfully improved.

[0018] Before the refinement treatment step, a step of mixing cellulose fibers having an ionic substituent and an inorganic layered compound is provided. Here, the inorganic layered compound or a dispersion liquid of the inorganic layered compound is added to and mixed with the dispersion liquid of the cellulose fibers having an ionic substituent. The mixing ratio (mass ratio) of the cellulose fibers having an ionic substituent and the inorganic layered compound in the mixing step is preferably from 1:99 to 99:1, more preferably from 5:95 to 95:5, and even more preferably from 10:90 to 90:10.

[0019] In the micronization process, for example, a micronization apparatus can be used. The micronization apparatus is not particularly limited, and examples thereof include a high-speed defibrator, a grinder (stone mill type crusher), a high-pressure homogenizer or an ultra-high pressure homogenizer, a high-pressure impact type crusher, a ball mill, a bead mill, a disk type refiner, a conical refiner, a twin-screw kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, or a beater. Among the above-mentioned micronization apparatuses, it is preferable to use at least one selected from the group consisting of a high-speed defibrator, a high-pressure homogenizer, and an ultra-high pressure homogenizer, which are less affected by grinding media and have less risk of contamination. More preferably, a high-pressure homogenizer is used. Among them, it is preferable to use the high-pressure homogenizer (Beryu-Mini) manufactured by Mikari Co., Ltd.

[0020] In the micronization process, it is preferable to dilute the cellulose fiber having an ionic substituent and the inorganic layered compound with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and organic solvents such as polar organic solvents can be used. The polar organic solvent is not particularly limited, and examples thereof include alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents, etc. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, isobutyl alcohol, etc. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, glycerin, etc. Examples of ketones include acetone, methyl ethyl ketone (MEK), etc. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether, etc. Examples of esters include ethyl acetate, butyl acetate, etc. Examples of aprotic polar solvents include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP), etc.

[0021] The solid content concentration (total concentration of cellulose fibers and inorganic layered compounds) during the refinement treatment can be set as appropriate. Further, the dispersion liquid during the refinement treatment may contain various solid components used when obtaining ionically substituted cellulose fibers having hydrogen bonding, such as urea, and various solid components contained in the inorganic layered compound.

[0022] In the refinement treatment step in this embodiment, bubbling is suppressed, and by suppressing this bubbling, the refinement (nanosizing) of cellulose fibers and the refinement (nanosizing) of inorganic layered compounds are simultaneously and energy-efficiently performed. Further, by suppressing bubbling in the refinement treatment step, it becomes possible to more effectively suppress damage to each nanosized material, and as a result, a microfibrous cellulose·fine inorganic layered compound inclusion having excellent particle dispersibility and capable of sufficiently exhibiting the characteristics of each material is obtained.

[0023] In this specification, bubbling refers to a phenomenon in which, for example, in a micronization process, due to the presence of local pressure differences or velocity differences in a place where shear force acts, air dissolved in the solvent or air remaining in the solvent forms bubbles and is generated. Due to the occurrence of bubbling, in the micronization process, more energy may be required, or the micronization of the cellulose fiber and the inorganic layered compound may be insufficient or uneven. This is presumably because in the location where bubbling occurs, the solvent does not touch the cellulose fiber or the inorganic layered compound, and "wetting", which is essential for causing micronization (especially fibrillation and delamination), does not occur. Furthermore, since the bubbling location exhibits compression resistance against the pushing in of a high-pressure pump or the like, there is also a risk of leading to mechanical damage. In addition, there is also a risk that each material may be oxidized unintentionally by the bubbles generated by bubbling. In the present embodiment, by actively suppressing bubbling in the micronization process, the energy required in the micronization process can be suppressed, and furthermore, the micronization of the cellulose fiber and the inorganic layered compound can be performed more efficiently and with higher precision. Also, by suppressing bubbling, oxidation of the microfibrous cellulose and the fine inorganic layered compound can be suppressed.

[0024] In the process of performing the micronization process, it is preferable to suppress bubbling by cooling. That is, it is preferable that the bubbling suppression mechanism is a cooling mechanism, and it is preferable that the micronization apparatus includes a cooling device or a cooling mechanism. That is, the manufacturing method of the present embodiment includes a process of performing micronization after mixing a cellulose fiber having an ionic substituent and an inorganic layered compound, and in the process of performing micronization, it is preferable that cooling is performed. Also, the cooling may be performed after pressure release in the micronization process occurs, but it is preferably performed in a state where back pressure is applied, that is, during the micronization of the cellulose fiber having an ionic substituent and the inorganic layered compound.

[0025] As a cooling mechanism, for example, there is a jacket (shell) or an outer pipe through which a heat transfer medium flows on the outer periphery of the miniaturization processing device. In this case, when a dispersion of cellulose fibers and an inorganic layered compound is circulated through the inner peripheral side (inner pipe) of the miniaturization processing device and the miniaturization processing is performed, the dispersion can be cooled by circulating a heat transfer medium through the jacket (shell) or the outer pipe. Note that the inner pipe through which the dispersion of cellulose fibers and the inorganic layered compound is circulated is preferably a heat transfer pipe. Thereby, the dispersion can be efficiently cooled.

[0026] The bubbling suppression mechanism is preferably provided on the downstream side of the jet flow generation unit provided in the miniaturization processing device. The jet flow generation unit preferably includes a jet flow generation mechanism. As the jet flow generation mechanism, for example, a mechanism that makes the flow path abruptly or gradually narrower in the flow direction may be provided by providing a diamond nozzle, a slit, or the like in the jet flow generation unit. As shown in FIG. 1, the miniaturization processing device 100 includes a jet flow generation unit 10 and a bubbling suppression unit 20 provided on the downstream side of the jet flow generation unit 10. The bubbling suppression unit 20 preferably includes a coolable pipe (jacket), and such a pipe (jacket) is arranged to cover the inner pipe through which the dispersion flows. Then, by introducing, for example, cooling water or the like into the pipe (jacket), the dispersion flowing through the inner pipe can be cooled.

[0027] The length L (L in FIG. 1) of the coolable pipe provided in the bubbling suppression unit 20 is preferably 1 mm or more and 1000 mm or less, more preferably 10 mm or more and 750 mm or less, and even more preferably 100 mm or more and 500 mm or less. By setting the length (L) of the coolable pipe within the above range, it becomes easy to sufficiently cool the dispersion flowing through the inner pipe, and the generation of bubbling can be more effectively suppressed.

[0028] Also, in the miniaturization processing apparatus 100, it is preferable that a predetermined distance is provided between the upstream end of the bubbling suppression unit 20 and the downstream end of the jet flow generation unit 10. As shown in FIG. 1, the jet flow generation unit 10 and the bubbling suppression unit 20 are not connected, and a predetermined distance (D) is preferably provided between the downstream end of the jet flow generation unit 10 and the upstream end of the bubbling suppression unit 20. This predetermined distance (D) is preferably 1 mm or more and 500 mm or less, more preferably 10 mm or more and 300 mm or less, and even more preferably 20 mm or more and 200 mm or less. By providing the predetermined distance (D), the generation of bubbling can be suppressed more effectively.

[0029] When introducing cooling water into the pipe (outer jacket) of the bubbling suppression unit 20, the temperature of the cooling water is preferably 40°C or lower, more preferably 30°C or lower, and even more preferably 20°C or lower. The flow rate of the cooling water is preferably 1 L / min or more, more preferably 5 L / min or more, and even more preferably 10 L / min or more. In addition, the temperature of the cooled dispersion liquid after passing through the bubbling suppression unit 20 is preferably 60°C or lower, more preferably 40°C or lower, and even more preferably 20°C or lower.

[0030] In the bubbling suppression mechanism, it is preferable that a pressure (back pressure) of at least 5% or more (0.05P or more) is applied to the pressure (P) applied to the dispersion liquid by the jet flow generation unit, more preferably 10% or more (0.1P or more), and even more preferably 20% or more (0.2P or more). Also, since bubbling is more likely to occur when processed at ultra-high pressure, controlling the pressure of the jet flow generation unit from low pressure to high pressure is also effective for bubbling suppression. The processing pressure of the jet flow generation unit is preferably 1 MPa or more and 200 MPa or less, more preferably 10 MPa or more and 170 MPa or less, and even more preferably 20 MPa or more and 150 MPa or less.

[0031] Note that as the bubbling suppression mechanism, it is preferable to refer to the mechanism described in Japanese Patent No. 5791142 and appropriately adopt it. Also, for the miniaturization processing device, an emulsifying and dispersing device, a multi-stage pressure control device, etc. described in Japanese Patent No. 5791142 can be adopted.

[0032] As described above, by simultaneously miniaturizing the cellulose fiber and the inorganic layered compound in the miniaturization process with suppressed bubbling, a fine fiber-like cellulose · fine inorganic layered compound dispersion liquid containing fine fiber-like cellulose and fine inorganic layered compound is obtained. In this specification, the fine fiber-like cellulose · fine inorganic layered compound dispersion liquid obtained through the miniaturization process is also included in the fine fiber-like cellulose · fine inorganic layered compound-containing material. Further, the fine fiber-like cellulose · fine inorganic layered compound-containing material also includes a concentrate or a solid obtained by concentrating the fine fiber-like cellulose · fine inorganic layered compound dispersion liquid.

[0033] (Cellulose fiber) The cellulose fiber subjected to the above-described miniaturization process is a fiber raw material before miniaturization. The cellulose fiber is a coarse fiber, and the fiber width is larger than 1000 nm. Also, the average fiber width of the cellulose fiber is larger than 1000 nm.

[0034] Cellulose fibers having an ionic substituent are obtained from a fiber raw material containing cellulose. The fiber raw material containing cellulose is not particularly limited, but it is preferable to use pulp from the viewpoints of easy availability and low cost. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. Wood pulp is not particularly limited, and examples thereof include chemical pulps such as hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP), and oxygen-bleached kraft pulp (OKP), semi-chemical pulps such as semi-chemical pulp (SCP) and chemigroundwood pulp (CGP), and mechanical pulps such as groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP). Non-wood pulp is not particularly limited, and examples thereof include cotton-based pulps such as cotton linter and cotton lint, and non-wood-based pulps such as hemp, wheat straw, and bagasse. Deinked pulp is not particularly limited, and examples thereof include deinked pulp made from waste paper. The pulp of this embodiment may be used alone or in combination of two or more of the above. Among the above pulps, from the viewpoint of easy availability, for example, wood pulp and deinked pulp are preferable. Among wood pulps, from the viewpoints of a large cellulose ratio and a high yield of microfibrillar cellulose during fibrillation treatment, and a small decomposition of cellulose in the pulp and obtaining microfibrillar cellulose of long fibers with a large aspect ratio, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are even more preferable.

[0035] As the fiber raw material containing cellulose, for example, cellulose contained in jellyfish or bacterial cellulose produced by acetic acid bacteria can also be used. Further, instead of the fiber raw material containing cellulose, fibers formed from linear nitrogen-containing polysaccharide polymers such as chitin and chitosan can also be used.

[0036] The cellulose fiber has ionic substituents. As the ionic substituents, for example, either one or both of an anionic group and a cationic group can be included. In the present embodiment, it is particularly preferable to have an anionic group as the ionic substituent.

[0037] Examples of the anionic group include a phosphooxo acid group or a substituent derived from a phosphooxo acid group (sometimes simply referred to as a phosphooxo acid group), a carboxy group or a substituent derived from a carboxy group (sometimes simply referred to as a carboxy group), a sulfone group or a substituent derived from a sulfone group (sometimes simply referred to as a sulfone group), a xanthate group, a phosphonate group, a phosphine group, a carboxyalkyl group (including a carboxymethyl group), etc. When a sulfone group or a substituent derived from a sulfone group is introduced via an ester bond, the substituent may also be referred to as a sulfur oxo acid group or a substituent derived from a sulfur oxo acid group (sometimes simply referred to as a sulfur oxo acid group). Among them, the anionic group is preferably at least one selected from the group consisting of a phosphooxo acid group, a substituent derived from a phosphooxo acid group, a carboxy group, a carboxymethyl group, a sulfur oxo acid group and a substituent derived from a sulfur oxo acid group, more preferably at least one selected from the group consisting of a phosphooxo acid group, a substituent derived from a phosphooxo acid group, a carboxy group, a sulfur oxo acid group and a substituent derived from a sulfur oxo acid group, and particularly preferably a phosphooxo acid group. Examples of the cationic group as the ionic substituent include an ammonium group, a phosphonium group, a sulfonium group, etc. Among them, the cationic group is preferably an ammonium group.

[0038] The phosphooxo acid group or the substituent derived from a phosphooxo acid group is, for example, a substituent represented by the following formula (1). A plurality of substituents represented by the following formula (1) may be introduced into each cellulose fiber. In this case, the substituents represented by the following formula (1) introduced in plurality may be the same or different from each other.

[0039]

Chemical formula

[0040] In formula (1), a, b, and n are natural numbers, m is an arbitrary number (provided that a = b × m). At least one of the n α and α' is O - and the rest are R or OR. Note that all of each α and α' may be O - and it doesn't matter. The n α may all be the same or each may be different. β b+ is a monovalent or higher cation composed of an organic or inorganic substance.

[0041] R is each a hydrogen atom, a saturated - straight - chain hydrocarbon group, a saturated - branched - chain hydrocarbon group, a saturated - cyclic hydrocarbon group, an unsaturated - straight - chain hydrocarbon group, an unsaturated - branched - chain hydrocarbon group, an unsaturated - cyclic hydrocarbon group, an aromatic group, or a derivative group thereof. Also, in formula (1), n is preferably 1.

[0042] Examples of the saturated - straight - chain hydrocarbon group include a methyl group, an ethyl group, an n - propyl group, or an n - butyl group, etc., but it is not particularly limited. Examples of the saturated - branched - chain hydrocarbon group include an i - propyl group, or a t - butyl group, etc., but it is not particularly limited. Examples of the saturated - cyclic hydrocarbon group include a cyclopentyl group, or a cyclohexyl group, etc., but it is not particularly limited. Examples of the unsaturated - straight - chain hydrocarbon group include a vinyl group, or an allyl group, etc., but it is not particularly limited. Examples of the unsaturated - branched - chain hydrocarbon group include an i - propenyl group, or a 3 - butenyl group, etc., but it is not particularly limited. Examples of the unsaturated - cyclic hydrocarbon group include a cyclopentenyl group, a cyclohexenyl group, etc., but it is not particularly limited. Examples of the aromatic group include a phenyl group, or a naphthyl group, etc., but it is not particularly limited.

[0043] Also, as the derivative group in R, with respect to the main chain or side chain of the above various hydrocarbon groups, a carboxy group, a carboxylate group (-COO -) Examples include, but are not particularly limited to, functional groups to which at least one type selected from functional groups such as hydroxy groups, amino groups, and ammonium groups is added or substituted. The number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R within the above range, the molecular weight of the phosphonooxy group can be set within an appropriate range, facilitating penetration into the fiber raw material and increasing the yield of cellulose fibers. When there are multiple Rs in formula (1) or when multiple types of substituents represented by the above formula (1) are introduced into the cellulose fiber, the multiple Rs may be the same or different from each other.

[0044] β b+ is a monovalent or higher cation composed of an organic or inorganic substance. Examples of the monovalent or higher cation composed of an organic substance include organic onium ions. Examples of organic onium ions include organic ammonium ions and organic phosphonium ions. Examples of organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of organic phosphonium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of the monovalent or higher cation composed of an inorganic substance include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, hydrogen ions, ammonium ions, and the like. When there are multiple βs in formula (1) or when multiple types of substituents represented by the above formula (1) are introduced into the cellulose fiber, the multiple βs may be the same or different from each other. As the monovalent or higher cation composed of an organic or inorganic substance, sodium or potassium ions, which are less likely to cause yellowing when the fiber raw material containing β is heated and are easy to use industrially, are preferred, but are not particularly limited. b+ When there are multiple βs in formula (1) or when multiple types of substituents represented by the above formula (1) are introduced into the cellulose fiber, the multiple βs b+ may be the same or different from each other. As the monovalent or higher cation composed of an organic or inorganic substance, β b+ is preferably sodium or potassium ions, which are less likely to cause yellowing when the fiber raw material containing β is heated and are easy to use industrially, but are not particularly limited.

[0045] Examples of the phospho-oxo acid group or a substituent derived from the phospho-oxo acid group include, more specifically, a phosphoric acid group (-PO3H2), a salt of the phosphoric acid group, a phosphorous acid group (phosphonic acid group) (-PO2H2), and a salt of the phosphorous acid group (phosphonic acid group). Further, the phospho-oxo acid group or a substituent derived from the phospho-oxo acid group may be a group in which phosphoric acid groups are condensed (e.g., a pyrophosphoric acid group), a group in which phosphonic acids are condensed (e.g., a polyphosphonic acid group), a phosphoric acid ester group (e.g., a monomethylphosphoric acid group, a polyoxyethylene alkylphosphoric acid group), an alkylphosphonic acid group (e.g., a methylphosphonic acid group), or the like.

[0046] In addition, the sulfone group (sulfone group or a substituent derived from the sulfone group) is, for example, a substituent represented by the following formula (2). A plurality of types of the substituent represented by the following formula (2) may be introduced into each cellulose fiber. In this case, the substituents represented by the following formula (2) introduced in plurality may be the same or different from each other.

[0047] [Chemical formula]

[0048] In the above structural formula, b and n are natural numbers, p is 0 or 1, and m is an arbitrary number (provided that 1 = b × m). When n is 2 or more, the plurality of p's may be the same number or different numbers. In the above structural formula, β b+is a monovalent or higher cation composed of an organic or inorganic substance. Examples of the monovalent or higher cation composed of an organic substance include organic onium ions. Examples of the organic onium ions include organic ammonium ions and organic phosphonium ions. Examples of the organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of the organic phosphonium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of the monovalent or higher cation composed of an inorganic substance include ions of alkali metals such as sodium, potassium, or lithium, ions of divalent metals such as calcium or magnesium, hydrogen ions, ammonium ions, etc. When a plurality of types of substituents represented by the above formula (2) are introduced into the cellulose fiber, a plurality of β b+ may be the same or different from each other. As the monovalent or higher cation composed of an organic or inorganic substance, β b+ is preferably an ion of sodium or potassium, which is less likely to turn yellow when the fiber raw material containing it is heated and is easy to use industrially, but is not particularly limited.

[0049] The introduction amount of the ionic substituent with respect to the cellulose fiber is preferably, for example, 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, still more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, and particularly preferably 0.60 mmol / g or more per 1 g (mass) of the cellulose fiber. Also, the introduction amount of the ionic substituent with respect to the cellulose fiber is preferably, for example, 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, and still more preferably 3.00 mmol / g or less per 1 g (mass) of the cellulose fiber. Here, the denominator in mmol / g indicates the mass of the cellulose fiber when the counter ion of the ionic substituent is a hydrogen ion (H + ). By setting the introduction amount of the ionic substituent within the above range, the refinement of the fiber raw material can be facilitated, and the stability of the cellulose fiber can be enhanced.

[0050] The amount of ionic substituents introduced into the cellulose fiber can be measured, for example, by a neutralization titration method after subjecting the cellulose fiber to a fibrillation treatment. In the measurement by the neutralization titration method, the amount of introduction is measured by determining the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing the cellulose fiber.

[0051] Figure 2 is a graph showing the relationship between the amount of NaOH dropped and the pH with respect to the fine fibrous cellulose dispersion having a phosphonooxy group. The amount of phosphonooxy group introduced into the cellulose fiber is measured, for example, as follows. First, ion-exchanged water is added to the target cellulose fiber to prepare a slurry having a solid content concentration of 0.2% by mass. This slurry is treated 4 times at a pressure of 200 MPa with a wet atomization device (manufactured by Sugino Machine, Starburst) to obtain a fine fibrous cellulose dispersion (slurry) containing fine fibrous cellulose. Then, the fine fibrous cellulose dispersion is treated with a strongly acidic ion exchange resin. Next, while adding an aqueous sodium hydroxide solution, observe the change in pH to obtain a titration curve as shown in the upper part of FIG. 2. In the titration curve shown in the upper part of FIG. 2, the measured pH is plotted against the amount of alkali added, and in the titration curve shown in the lower part of FIG. 2, the increment (differential value) (1 / mmol) of pH with respect to the amount of alkali added is plotted. In this neutralization titration, in the curve obtained by plotting the measured pH against the amount of alkali added, two points where the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum are confirmed. Among these, the first maximum point of the increment obtained first after starting to add alkali is called the first end point, and the next maximum point of the increment is called the second end point. The amount of alkali required from the start of titration to the first end point is equal to the amount of the first dissociable acid of the fine fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the first end point to the second end point is equal to the amount of the second dissociable acid of the fine fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the start of titration to the second end point is equal to the total dissociable acid amount of the fine fibrous cellulose contained in the slurry used for titration. And the value obtained by dividing the amount of alkali required from the start of titration to the first end point by the solid content (g) in the titration target slurry becomes the amount of phosphonooxy group introduced (mmol / g). When simply referring to the amount of phosphonooxy group introduced (or the amount of phosphonooxy group), it represents the amount of the first dissociable acid. In addition, in FIG. 2, the region from the start of titration to the first end point is called the first region, and the region from the first end point to the second end point is called the second region. For example, when the phosphonooxy group is a phosphate group and this phosphate group undergoes condensation, apparently, the amount of the weakly acidic group in the phosphonooxy group (also referred to as the amount of the second dissociable acid in this specification) decreases, and the amount of alkali required in the second region becomes less than the amount of alkali required in the first region. On the other hand, the amount of the strongly acidic group in the phosphonooxy group (also referred to as the amount of the first dissociable acid in this specification) coincides with the amount of phosphorus atoms regardless of the presence or absence of condensation. Also, when the phosphonooxy group is a phosphite group, since there is no weakly acidic group in the phosphonooxy group, the amount of alkali required in the second region may decrease or the amount of alkali required in the second region may be zero. In this case, in the titration curve, there is only one point where the increment of pH becomes maximum.

[0052] Note that since the denominator of the above-introduced amount of phosphono-oxo acid group (mmol / g) indicates the mass of the acid-form microfibrillar cellulose, it represents the amount of phosphono-oxo acid group possessed by the acid-form microfibrillar cellulose (hereinafter referred to as the amount of phosphono-oxo acid group (acid form)). On the other hand, when the counter ion of the phosphono-oxo acid group is substituted with an arbitrary cation C so as to have an equivalent charge, by converting the denominator to the mass of the microfibrillar cellulose when the cation C is the counter ion, the amount of phosphono-oxo acid group possessed by the microfibrillar cellulose in which the cation C is the counter ion (hereinafter referred to as the amount of phosphono-oxo acid group (C form)) can be determined. That is, it is calculated by the following formula. Amount of phosphono-oxo acid group (C form) = Amount of phosphono-oxo acid group (acid form) / {1 + (W - 1) × A / 1000} A [mmol / g]: Total amount of anions derived from the phosphono-oxo acid group possessed by the microfibrillar cellulose (total amount of dissociated acids of the phosphono-oxo acid group) W: Formula weight per monovalent of the cation C (for example, Na is 23, Al is 9)

[0053] Figure 3 is a graph showing the relationship between the amount of NaOH dropped and the pH for a microfibrillar cellulose dispersion having a carboxy group as an ionic substituent. The amount of carboxy group introduced into the cellulose fiber is measured, for example, as follows. First, ion-exchanged water is added to the target cellulose fiber to prepare a slurry with a solid content concentration of 0.2 mass%. This slurry is processed 4 times at a pressure of 200 MPa using a wet atomization device (manufactured by Sugino Machine, Starburst) to obtain a microfibrillar cellulose dispersion (slurry) containing microfibrillar cellulose. Then, the microfibrillar cellulose dispersion is treated with a strongly acidic ion exchange resin. Next, while adding an aqueous sodium hydroxide solution, observe the change in pH to obtain a titration curve as shown in the upper part of FIG. 3. In the titration curve shown in the upper part of FIG. 3, the measured pH is plotted against the amount of alkali added, and in the titration curve shown in the lower part of FIG. 3, the increment (differential value) (1 / mmol) of pH with respect to the amount of alkali added is plotted. In this neutralization titration, in the curve where the measured pH is plotted against the amount of alkali added, one point where the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum is confirmed, and this maximum point is called the first end point. Here, the region from the start of titration to the first end point in FIG. 3 is called the first region. The amount of alkali required in the first region is equal to the amount of carboxy groups in the dispersion used for titration. Then, by dividing the amount of alkali (mmol) required in the first region of the titration curve by the solid content (g) in the dispersion containing the fine fibrous cellulose to be titrated, the amount of carboxy groups introduced (mmol / g) is calculated.

[0054] Note that since the denominator of the above-mentioned amount of carboxy groups introduced (mmol / g) is the mass of the acid-type fine fibrous cellulose, it indicates the amount of carboxy groups (hereinafter referred to as the amount of carboxy groups (acid type)) possessed by the acid-type fine fibrous cellulose. On the other hand, when the counter ion of the carboxy group is replaced with an arbitrary cation C so that the charge equivalent is achieved, by converting the denominator to the mass of the fine fibrous cellulose when the cation C is the counter ion, the amount of carboxy groups (hereinafter referred to as the amount of carboxy groups (C type)) possessed by the fine fibrous cellulose with the cation C as the counter ion can be obtained. That is, it is calculated by the following formula. Amount of carboxy groups (C type) = Amount of carboxy groups (acid type) / {1 + (W - 1) × (Amount of carboxy groups (acid type)) / 1000} W: Formula weight per monovalent of cation C (for example, Na is 23, Al is 9)

[0055] In the measurement of the amount of ionic substituents by titration, accurate values may not be obtained, such as when the dropping amount of a single drop of an aqueous sodium hydroxide solution is too large or the titration interval is too short, resulting in a lower amount of ionic substituents than the actual value. Appropriate dropping amounts and titration intervals are, for example, desirably titrating 10 to 50 μL of 0.1N aqueous sodium hydroxide solution every 5 to 30 seconds. Further, in order to eliminate the influence of carbon dioxide dissolved in the fine fibrous cellulose dispersion, it is desirable to perform the measurement while blowing an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration until the end of titration, for example.

[0056] Also, the amount of sulfonic groups introduced into the cellulose fibers can be calculated by measuring the sulfur amount of a sample obtained by freeze-drying a slurry containing the cellulose fibers and further pulverizing it. Specifically, a slurry containing cellulose fibers is freeze-dried, and the further pulverized sample is decomposed by pressurized heating using nitric acid in a sealed container, and then appropriately diluted and the sulfur amount is measured by ICP-OES. The value calculated by dividing by the absolute dry mass of the tested cellulose fibers is taken as the amount of sulfonic groups in the cellulose fibers (unit: mmol / g).

[0057] In order to obtain cellulose fibers into which the ionic substituents as described above are introduced, it is preferable to have an ionic substituent introduction step, a washing step, an alkali treatment step (neutralization step), and a fibrillation treatment step in this order for the fiber raw material containing the cellulose as described above. Instead of or in addition to the washing step, an acid treatment step may be provided. Examples of the ionic substituent introduction step include a phosphooxo acid group introduction step, a carboxy group introduction step, a sulfur oxo acid group introduction step, a xanthate group introduction step, a phosphonate or phosphine group introduction step, a sulfonic group introduction step, and a cation group introduction step. Each will be described below.

[0058] <Phosphooxo Acid Group Introduction Step> When obtaining cellulose fibers having an ionic substituent, it is preferable to provide an ionic substituent introduction step before the fibrillation treatment step. Examples of the ionic substituent introduction step include a phosphonooxy group introduction step. The phosphonooxy group introduction step is a step of allowing at least one compound (hereinafter also referred to as "compound A") selected from compounds capable of introducing a phosphonooxy group to act on a fiber raw material containing cellulose by reacting with a hydroxyl group of the fiber raw material containing cellulose. By this step, cellulose fibers having a phosphonooxy group can be obtained.

[0059] In the phosphonooxy group introduction step according to the present embodiment, the reaction between the fiber raw material containing cellulose and compound A may be carried out in the presence of at least one selected from urea and its derivatives (hereinafter also referred to as "compound B"). On the other hand, the reaction between the fiber raw material containing cellulose and compound A may be carried out in the absence of compound B.

[0060] As an example of a method of allowing Compound A to act on a fiber raw material in the co - presence of Compound B, there is a method of mixing Compound A and Compound B with the fiber raw material in a dry state, a wet state, or a slurry state. Among these, since the uniformity of the reaction is high, it is preferable to use a fiber raw material in a dry state or a wet state, and particularly preferably a fiber raw material in a dry state. The form of the fiber raw material is not particularly limited, but for example, it is preferably in a cotton - like or thin - sheet - like form. For Compound A and Compound B, there are methods of adding them to the fiber raw material in a powdery form, or in a solution state dissolved in a solvent, or in a state melted by heating to above the melting point. Among these, since the uniformity of the reaction is high, it is preferable to add them in a solution state dissolved in a solvent, particularly in an aqueous solution state. Also, Compound A and Compound B may be added to the fiber raw material simultaneously, separately, or as a mixture. The method of adding Compound A and Compound B is not particularly limited, but when Compound A and Compound B are in a solution state, after immersing the fiber raw material in the solution to absorb the liquid and then taking it out, or dropping the solution onto the fiber raw material may be possible. Also, the required amounts of Compound A and Compound B may be added to the fiber raw material, or after adding excessive amounts of Compound A and Compound B to the fiber raw material respectively, the excess Compound A and Compound B may be removed by pressing or filtration.

[0061] As the compound A used in this embodiment, any compound having a phosphorus atom and capable of forming an ester bond with cellulose may be used, and examples include phosphoric acid or its salts, phosphorous acid or its salts, dehydrated condensed phosphoric acid or its salts, and phosphoric anhydride (phosphorus pentoxide), but it is not particularly limited. As phosphoric acid, those with various purities can be used, for example, 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid can be used. As phosphorous acid, 99% phosphorous acid (phosphonic acid) can be mentioned. Dehydrated condensed phosphoric acid is a product obtained by condensing two or more molecules of phosphoric acid by a dehydration reaction, and examples include pyrophosphoric acid and polyphosphoric acid. As phosphates, phosphites, and dehydrated condensed phosphates, lithium salts, sodium salts, potassium salts, ammonium salts of phosphoric acid, phosphorous acid, or dehydrated condensed phosphoric acid can be mentioned, and these can have various degrees of neutralization. Among these, from the viewpoints of high introduction efficiency of the phosphate group, easier improvement of fibrillation efficiency in the fibrillation step described later, low cost, and easy industrial application, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, ammonium salt of phosphoric acid, or phosphorous acid, sodium salt of phosphorous acid, potassium salt of phosphorous acid, ammonium salt of phosphorous acid are preferred, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, or phosphorous acid, sodium phosphite are more preferred.

[0062] The addition amount of compound A to the fiber raw material is not particularly limited. For example, when the addition amount of compound A is converted to the amount of phosphorus atoms, the addition amount of phosphorus atoms to the fiber raw material (dry mass) is preferably 0.5% by mass or more and 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and even more preferably 2% by mass or more and 30% by mass or less. By setting the addition amount of phosphorus atoms to the fiber raw material within the above range, the yield of microfibrillar cellulose can be further improved. On the other hand, by setting the addition amount of phosphorus atoms to the fiber raw material below the above upper limit value, a balance between the effect of improving the yield and the cost can be achieved.

[0063] Compound B used in this embodiment is at least one selected from urea and its derivatives as described above. Examples of compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea. From the viewpoint of improving the uniformity of the reaction, compound B is preferably used as an aqueous solution. Further, from the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

[0064] The addition amount of compound B relative to the fiber raw material (dry mass) is not particularly limited, but for example, it is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, and even more preferably 100% by mass or more and 350% by mass or less.

[0065] In the reaction of the fiber raw material containing cellulose and compound A, in addition to compound B, for example, amides or amines may be included in the reaction system. Examples of amides include formamide, dimethylformamide, acetamide, dimethylacetamide, etc. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, etc. Among these, triethylamine is particularly known to act as a good reaction catalyst.

[0066] In the step of introducing a phosphooxo acid group, it is preferable to add or mix a compound A or the like to the fiber raw material and then subject the fiber raw material to a heat treatment. As the heat treatment temperature, it is preferable to select a temperature at which the phosphooxo acid group can be efficiently introduced while suppressing the thermal decomposition and hydrolysis reactions of the fiber. The heat treatment temperature is preferably, for example, 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower. Further, for the heat treatment, equipment having various heat media can be used. For example, a stirring dryer, a rotary dryer, a disk dryer, a roll-type heating device, a plate-type heating device, a fluidized bed dryer, a band-type dryer, a filtration dryer, a vibrating fluidized bed dryer, a pneumatic dryer, a vacuum dryer, an infrared heating device, a far-infrared heating device, a microwave heating device, and a high-frequency dryer can be used.

[0067] In the heat treatment according to this embodiment, for example, after adding compound A to a thin sheet-like fiber raw material by a method such as impregnation, a method of heating or a method of heating while kneading or stirring the fiber raw material and compound A with a kneader or the like can be adopted. Thereby, it becomes possible to suppress the concentration unevenness of compound A in the fiber raw material and to introduce the phosphooxo acid group more uniformly onto the surface of the cellulose fiber contained in the fiber raw material. This is presumably due to the fact that when water molecules move to the surface of the fiber raw material during drying, the dissolved compound A is attracted to the water molecules by surface tension and also moves to the surface of the fiber raw material (that is, concentration unevenness of compound A occurs), which can be suppressed.

[0068] In addition, the heating device used for the heat treatment is preferably a device that can always discharge the moisture held by the slurry and the moisture generated by the dehydration condensation (phosphoric esterification) reaction between the hydroxyl groups contained in the compound A and cellulose in the fiber raw material, etc., to the outside of the device system. Examples of such a heating device include a forced-air oven. By always discharging the moisture in the device system, in addition to suppressing the hydrolysis reaction of the phosphoric ester bond, which is the reverse reaction of phosphoric esterification, it is also possible to suppress the acid hydrolysis of the sugar chain in the fiber. Therefore, it becomes possible to obtain microfibrillar cellulose with a high axial ratio.

[0069] The heat treatment time is preferably, for example, 1 second or more and 300 minutes or less, more preferably 1 second or more and 1000 seconds or less, and even more preferably 10 seconds or more and 800 seconds or less, after substantially removing the moisture from the fiber raw material. In this embodiment, by setting the heating temperature and the heating time within an appropriate range, the introduction amount of the phosphonooxy group can be made within a preferable range.

[0070] The phosphonooxy group introduction step may be performed at least once, but can also be repeated two or more times. By performing the phosphonooxy group introduction step two or more times, a large amount of phosphonooxy groups can be introduced into the fiber raw material.

[0071] The introduction amount of the phosphooxo acid group to the fiber raw material is preferably, for example, 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, further preferably 0.20 mmol / g or more, still more preferably 0.40 mmol / g or more, even more preferably 0.50 mmol / g or more, even further preferably 0.60 mmol / g or more, and particularly preferably 1.00 mmol / g or more per 1 g (mass) of the cellulose fiber. Also, the introduction amount of the phosphooxo acid group to the fiber raw material is preferably, for example, 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, and further preferably 3.00 mmol / g or less per 1 g (mass) of the cellulose fiber. By setting the introduction amount of the phosphooxo acid group within the above range, the fibrillation of the cellulose fiber in the fibrillation treatment step can be facilitated, and the stability of the microfibrillar cellulose can be enhanced.

[0072] <Carboxy Group Introduction Step> As the ionic substituent introduction step, a carboxy group introduction step may be included. The carboxy group introduction step is carried out by subjecting the fiber raw material containing cellulose to an oxidation treatment such as ozonation, oxidation by the Fenton method, TEMPO oxidation treatment, or a compound having a group derived from a carboxylic acid or its derivative, or an acid anhydride of a compound having a group derived from a carboxylic acid or its derivative.

[0073] The compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include dicarboxylic acid compounds such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, and itaconic acid, and tricarboxylic acid compounds such as citric acid and aconitic acid. Also, the derivative of the compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include imidized products of acid anhydrides of compounds having a carboxy group and derivatives of acid anhydrides of compounds having a carboxy group. The imidized product of the acid anhydride of the compound having a carboxy group is not particularly limited, and examples thereof include imidized products of dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide.

[0074] Although not particularly limited, examples of the acid anhydride of the compound having a group derived from a carboxylic acid include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Further, although not particularly limited, examples of the derivative of the acid anhydride of the compound having a group derived from a carboxylic acid include those in which at least a part of the hydrogen atoms of the acid anhydride of the compound having a carboxy group, such as dimethyl maleic anhydride, diethyl maleic anhydride, and diphenyl maleic anhydride, are substituted with substituents such as an alkyl group and a phenyl group.

[0075] In the carboxy group introduction step, when performing TEMPO oxidation treatment, for example, it is preferable to perform the treatment under conditions where the pH is 6 or more and 8 or less. Such treatment is also referred to as neutral TEMPO oxidation treatment. The neutral TEMPO oxidation treatment can be performed, for example, by adding pulp as a fiber raw material, a nitroxyl radical such as TEMPO (2,2,6,6 - tetramethylpiperidine - 1 - oxyl) as a catalyst, and sodium hypochlorite as a sacrificial reagent to a sodium phosphate buffer solution (pH = 6.8). Further, by co - existing sodium hypochlorite, the aldehyde generated in the oxidation process can be efficiently oxidized to a carboxy group. Also, the TEMPO oxidation treatment may be performed under conditions where the pH is 10 or more and 11 or less. Such treatment is also referred to as alkaline TEMPO oxidation treatment. The alkaline TEMPO oxidation treatment can be performed, for example, by adding a nitroxyl radical such as TEMPO as a catalyst, sodium bromide as a co - catalyst, and sodium hypochlorite as an oxidizing agent to pulp as a fiber raw material.

[0076] The amount of carboxyl groups introduced into the cellulose fiber varies depending on the type of substituent. For example, when carboxyl groups are introduced by TEMPO oxidation, it is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, still more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, and particularly preferably 0.60 mmol / g or more per 1 g (mass) of the cellulose fiber. Also, the amount of carboxyl groups introduced into the cellulose fiber is preferably 3.65 mmol / g or less, and more preferably 3.00 mmol / g or less. Additionally, when the substituent is a carboxymethyl group, the amount of carboxyl groups introduced may be 5.8 mmol / g or less per 1 g (mass) of the cellulose fiber. By setting the amount of carboxyl groups introduced within the above range, the fibrillation of cellulose fibers in the fibrillation treatment step can be facilitated, and the stability of microfibrillated cellulose can be enhanced.

[0077] <Sulfonic Acid Group Introduction Step> As the ionic substituent introduction step, a sulfonic acid group introduction step may be included. In the sulfonic acid group introduction step, a cellulose fiber having a sulfonic acid group (sulfonic acid group-introduced fiber) can be obtained by reacting the hydroxyl group of the fiber raw material containing cellulose with a sulfur oxoacid.

[0078] In the sulfonic acid group introduction step, instead of compound A in the above-mentioned <phosphooxo acid group introduction step>, at least one compound (hereinafter also referred to as "compound C") selected from compounds capable of introducing a sulfonic acid group by reacting with the hydroxyl groups of the fiber raw material containing cellulose is used. As compound C, any compound having a sulfur atom and capable of forming an ester bond with cellulose may be used, and examples include sulfuric acid or its salts, sulfurous acid or its salts, sulfamic acid amides, etc., but are not particularly limited. As sulfuric acid, those with various purities can be used, for example, 96% sulfuric acid (concentrated sulfuric acid) can be used. As sulfurous acid, 5% sulfurous acid aqueous solution can be mentioned. As sulfates or sulfites, lithium salts, sodium salts, potassium salts, ammonium salts, etc. of sulfates or sulfites can be mentioned, and these can have various degrees of neutralization. As sulfamic acid amides, sulfamic acid, etc. can be used. In the sulfonic acid group introduction step, it is preferable to use compound B in the above-mentioned <phosphooxo acid group introduction step> in the same manner.

[0079] In the sulfonic acid group introduction step, it is preferable to mix an aqueous solution containing sulfur oxoacid, urea and / or urea derivatives with the cellulose raw material and then subject the cellulose raw material to heat treatment. As the heat treatment temperature, it is preferable to select a temperature at which the sulfonic acid group can be efficiently introduced while suppressing the thermal decomposition and hydrolysis reactions of the fiber. The heat treatment temperature is preferably 100 °C or higher, more preferably 120 °C or higher, and even more preferably 150 °C or higher. Also, the heat treatment temperature is preferably 300 °C or lower, more preferably 250 °C or lower, and even more preferably 200 °C or lower.

[0080] In the heat treatment step, it is preferable to heat until substantially no moisture remains. Therefore, the heat treatment time varies depending on the amount of moisture contained in the cellulose raw material, sulfur oxoacid, and the added amount of the aqueous solution containing urea and / or urea derivative. For example, it is preferably 10 seconds or more and 10,000 seconds or less. For the heat treatment, equipment having various heat media can be used. For example, a hot air dryer, a stirring dryer, a rotary dryer, a disk dryer, a roll-type heating device, a plate-type heating device, a fluidized bed dryer, a band-type dryer, a filtration dryer, a vibrating fluidized dryer, a pneumatic dryer, a vacuum dryer, an infrared heating device, a far-infrared heating device, a microwave heating device, and a high-frequency dryer can be used.

[0081] The introduction amount of the sulfone group with respect to the cellulose raw material is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, still more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.50 mmol / g or more, and particularly preferably 0.60 mmol / g or more. Also, the introduction amount of the sulfone group with respect to the cellulose raw material is preferably 5.00 mmol / g or less, and more preferably 3.00 mmol / g or less. By setting the introduction amount of the sulfone group within the above range, the fibrillation of the cellulose fiber in the fibrillation treatment step can be facilitated, and the stability of the microfibrillated cellulose can be enhanced.

[0082] <Oxidation step with a chlorine-based oxidizing agent (second carboxy group introduction step)> As the ionic substituent introduction step, it may include an oxidation step with a chlorine-based oxidizing agent. In the oxidation step with a chlorine-based oxidizing agent, a carboxy group is introduced into the fiber raw material by adding a chlorine-based oxidizing agent to the fiber raw material having a hydroxyl group in a wet or dry state and carrying out a reaction.

[0083] Examples of chlorine-based oxidizing agents include hypochlorous acid, hypochlorite, chlorous acid, chlorite, chloric acid, chlorate, perchloric acid, perchlorate, chlorine dioxide, etc. From the viewpoints of the introduction efficiency of substituents, and thus the fibrillation efficiency, cost, and ease of handling, the chlorine-based oxidizing agents are preferably sodium hypochlorite, sodium chlorite, and chlorine dioxide. When adding a chlorine-based oxidizing agent, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be dissolved in a suitable solvent and then added.

[0084] In the oxidation step using a chlorine-based oxidizing agent, the concentration of the chlorine-based oxidizing agent in the solution is preferably 1% by mass or more and 1,000% by mass or less, more preferably 5% by mass or more and 500% by mass or less, and even more preferably 10% by mass or more and 100% by mass or less, when converted to the available chlorine concentration, for example. The addition amount of the chlorine-based oxidizing agent with respect to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 10 parts by mass or more and 10,000 parts by mass or less, and even more preferably 100 parts by mass or more and 5,000 parts by mass or less.

[0085] The reaction time with the chlorine-based oxidizing agent in the oxidation step using the chlorine-based oxidizing agent can vary depending on the reaction temperature, but is preferably 1 minute or more and 1,000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 20 minutes or more and 400 minutes or less, for example. The pH during the reaction is preferably 5 or more and 15 or less, more preferably 7 or more and 14 or less, and even more preferably 9 or more and 13 or less. Also, it is preferable to maintain a constant value (for example, pH 11) by appropriately adding hydrochloric acid or sodium hydroxide at the start and during the reaction. Further, after the reaction, excess reaction reagents, by-products, etc. may be washed and removed by filtration or the like.

[0086] <Xanthate group introduction step (xanthic acid esterification step)> As the ionic substituent introduction step, for example, it may include a xanthate group introduction step (hereinafter, also referred to as the xanthation step). In the xanthation step, carbon disulfide and an alkali compound are added to a fiber raw material having a hydroxyl group in a wet or dry state and reacted, so that a xanthate group is introduced into the fiber raw material. Specifically, carbon disulfide is added to the fiber raw material alkalized cellulose by the method described later and reacted.

[0087] <<Alkalization of cellulose>> When introducing an ionic substituent into the fiber raw material, it is preferable to allow an alkali solution to act on the cellulose contained in the fiber raw material to alkalize the cellulose. By this treatment, a part of the hydroxyl groups of cellulose is ion-dissociated, and the nucleophilicity (reactivity) can be enhanced. The alkali compound contained in the alkali solution is not particularly limited, and may be an inorganic alkali compound or an organic alkali compound. Since it has high versatility, for example, it is preferable to use sodium hydroxide, potassium hydroxide, tetraethylammonium hydroxide, or tetrabutylammonium hydroxide. The alkalization of cellulose may be carried out simultaneously with the introduction of the ionic substituent, may be carried out as the previous step thereof, or may be carried out at both timings.

[0088] The solution temperature at the start of the alkalization of cellulose is preferably 0°C or higher and 50°C or lower, more preferably 5°C or higher and 40°C or lower, and even more preferably 10°C or higher and 30°C or lower.

[0089] The alkali concentration in the alkali solution is preferably 0.01 mol / L or higher and 4 mol / L or lower in terms of molar concentration, more preferably 0.1 mol / L or higher and 3 mol / L or lower, and even more preferably 1 mol / L or higher and 2.5 mol / L or lower. In particular, when the treatment temperature in the alkalization of cellulose is less than 10°C, the alkali concentration is preferably 1 mol / L or higher and 2 mol / L or lower.

[0090] The treatment time for alkalization of cellulose is preferably 1 minute or longer, more preferably 10 minutes or longer, and even more preferably 30 minutes or longer. Further, the treatment time for alkali treatment is preferably 6 hours or shorter, more preferably 5 hours or shorter, and even more preferably 4 hours or shorter.

[0091] By adjusting the type of alkali solution, treatment temperature, concentration, and immersion time as described above, penetration of the alkali solution into the crystalline region of cellulose can be suppressed, the crystalline structure of cellulose I is more likely to be maintained, and the yield of microfibrillar cellulose can be increased.

[0092] When ionic substituent introduction and alkalization of cellulose are not performed simultaneously, alkalization of cellulose is preferably carried out before ionic substituent introduction. In this case, the alkali cellulose obtained by the alkalization treatment is preferably subjected to solid-liquid separation and removal of moisture by a general liquid separation method such as centrifugation or filtration. Thereby, the reaction efficiency in the subsequent ionic substituent introduction step is improved. The cellulose fiber concentration after solid-liquid separation is preferably 5% or more and 50% or less, more preferably 10% or more and 40% or less, and even more preferably 15% or more and 35% or less.

[0093] <Step for introducing phosphonic group or phosphine group (phosphoalkylation step)> The ionic substituent introduction step may include a step for introducing a phosphonic group or a phosphine group (phosphoalkylation step). In the phosphoalkylation step, as essential components, a compound having a reactive group and a phosphonic group or a phosphine group (Compound E A ), and as optional components, an alkali compound and Compound B selected from the aforementioned urea and its derivatives are added to a fiber raw material having a hydroxyl group in a wet or dry state and reacted, whereby a phosphonic group or a phosphine group is introduced into the fiber raw material.

[0094] Examples of the reactive group include an alkyl halide group, a vinyl group, and an epoxy group (glycidyl group). Compound E A Examples thereof include vinyl phosphoric acid, phenylvinylphosphonic acid, phenylvinylphosphinic acid, etc. From the viewpoints of the introduction efficiency of substituents, and thus the fibrillation efficiency, cost, and ease of handling, Compound E A is preferably vinyl phosphoric acid. Furthermore, as an optional component, it is also preferable to similarly use Compound B in the <phosphorus oxo acid group introduction step> described above, and the addition amount is also preferably as described above.

[0095] Compound E A When adding, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be dissolved in an appropriate solvent and added. The fiber raw material is preferably alkali-celluloseized in advance or alkali-celluloseized simultaneously with the reaction. The method of alkali-celluloseization is as described above.

[0096] The temperature during the reaction is preferably, for example, 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0097] Compound E A The addition amount of Compound E with respect to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0098] The reaction time can vary depending on the reaction temperature, but is preferably, for example, 1 minute or more and 1,000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 20 minutes or more and 400 minutes or less. Also, after the reaction, excess reaction reagents, by-products, etc. may be washed with water and removed by filtration or the like.

[0099] <Sulfone group introduction step (sulfonylation step) (second sulfone group introduction step)> As the ionic substituent introduction step, a sulfone group introduction step (sulfalkylating step) may be included. In sulfalkylation, as essential components, a compound having a reactive group and a sulfone group (compound E B ), and as optional components, an alkali compound and a compound B selected from the above-mentioned urea and its derivatives are added to a fiber raw material having a hydroxyl group in a wet or dry state and reacted to introduce a sulfone group into the fiber raw material.

[0100] Examples of the reactive group include an alkyl halide group, a vinyl group, an epoxy group (glycidyl group), etc. Compound E B Examples of compound E B include sodium 2-chloroethanesulfonate, sodium vinylsulfonate, sodium p-styrenesulfonate, 2-acrylamido-2-methylpropanesulfonic acid, etc. Among them, from the viewpoints of the introduction efficiency of the substituent, and thus the defibration efficiency, cost, and ease of handling, vinyl compound E is preferably sodium sulfonate.

[0101] Compound E B When adding compound E

[0102] It may be added to the fiber raw material as it is as a reagent (solid or liquid), or it may be dissolved in an appropriate solvent and added. The fiber raw material is preferably pre-alkali celluloseized or alkali celluloseized simultaneously with the reaction. The method of alkali celluloseization is as described above.

[0103] Compound E BThe addition amount with respect to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0104] The reaction time can vary depending on the reaction temperature. For example, it is preferably 1 minute or more and 1,000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 20 minutes or more and 400 minutes or less. Further, after the reaction, excess reaction reagents, by-products, etc. may be washed with water and removed by filtration or the like.

[0105] <Carboxyalkylation step (third carboxy group introduction step)> As the ionic substituent introduction step, a carboxyalkylation step may be included. As an essential component, a compound having a reactive group and a carboxy group (compound E C ), an alkali compound as an optional component, and compound B selected from the aforementioned urea and its derivatives are added to a fiber raw material having a hydroxyl group in a wet or dry state and reacted to introduce a carboxy group into the fiber raw material.

[0106] Examples of the reactive group include an alkyl halide group, a vinyl group, an epoxy group (glycidyl group), etc. Compound E C Preferably includes monochloroacetic acid, sodium monochloroacetate, 2-chloropropionic acid, and sodium 2-chloropropionate from the viewpoints of substituent introduction efficiency, and thus defibrillation efficiency, cost, and ease of handling. Furthermore, as an optional component, it is also preferable to use compound B in the above-mentioned <phosphooxo acid group introduction step> in the same manner, and the addition amount is preferably the same as described above.

[0107] Compound E CWhen adding it, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be dissolved in an appropriate solvent and then added. It is preferable that the fiber raw material is alkalized to alkali cellulose in advance or is alkalized to alkali cellulose simultaneously with the reaction. The method of alkalizing to alkali cellulose is as described above.

[0108] The temperature during the reaction is preferably, for example, 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0109] Compound E C The addition amount with respect to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0110] The reaction time can vary depending on the reaction temperature, but is preferably, for example, 1 minute or more and 1,000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 20 minutes or more and 400 minutes or less. Further, after the reaction, excess reaction reagents, by-products, etc. may be washed and removed by filtration or the like with water.

[0111] <Cationic group introduction step (cationization step)> As an essential component, a compound having a reactive group and a cationic group (Compound E D ), as an optional component, an alkali compound, and Compound B selected from the aforementioned urea and its derivatives are added to a fiber raw material having a hydroxyl group in a wet or dry state to carry out a reaction, whereby a cation group is introduced into the fiber raw material.

[0112] Examples of the reactive group include an alkyl halide group, a vinyl group, an epoxy group (glycidyl group), etc. Examples of the cationic group include an ammonium group, a phosphonium group, a sulfonium group, etc. Among them, the cationic group is preferably an ammonium group. Compound E D Examples of such compounds include glycidyltrimethylammonium chloride, 3-chloro-2-hydroxypropyltrimethylammonium chloride, etc., which are preferred in terms of the introduction efficiency of substituents, and thus the fibrillation efficiency, cost, and ease of handling. Furthermore, as an optional component, it is also preferable to similarly use Compound B in the above-described <phosphooxo acid group introduction step>. The addition amount is preferably the same as described above.

[0113] Compound E D When adding Compound E, it may be added directly to the fiber raw material as a reagent (solid or liquid), or it may be dissolved in a suitable solvent and then added. The fiber raw material is preferably alkali-celluloseized in advance or alkali-celluloseized simultaneously with the reaction. The method of alkali-celluloseization is as described above.

[0114] The temperature during the reaction is preferably, for example, 50°C or higher and 300°C or lower, more preferably 100°C or higher and 250°C or lower, and even more preferably 130°C or higher and 200°C or lower.

[0115] Compound E D The addition amount of Compound E relative to 100 parts by mass of the fiber raw material is preferably 1 part by mass or more and 100,000 parts by mass or less, more preferably 2 parts by mass or more and 10,000 parts by mass or less, and even more preferably 5 parts by mass or more and 1,000 parts by mass or less.

[0116] The reaction time can vary depending on the reaction temperature, but is preferably, for example, 1 minute or more and 1,000 minutes or less, more preferably 10 minutes or more and 500 minutes or less, and even more preferably 20 minutes or more and 400 minutes or less. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed by filtration or the like.

[0117] <Washing step> In the step of obtaining the cellulose fiber having an ionic substituent, a washing step can be performed on the ionic substituent-introduced fiber as needed. The washing step is performed, for example, by washing the ionic substituent-introduced fiber with water or an organic solvent. Further, the washing step may be performed after each of the steps described later, and the number of washing times performed in each washing step is not particularly limited.

[0118] <Alkali treatment step> In the step of obtaining the cellulose fiber having an ionic substituent, an alkali treatment step may be provided between the ionic substituent introduction step and the fibrillation treatment step. The method of alkali treatment is not particularly limited, and examples thereof include a method of immersing the ionic substituent-introduced fiber in an alkali solution.

[0119] The alkali compound contained in the alkali solution is not particularly limited and may be an inorganic alkali compound or an organic alkali compound. In the present embodiment, since it has high versatility, for example, it is preferable to use sodium hydroxide or potassium hydroxide as the alkali compound. Further, the solvent contained in the alkali solution may be either water or an organic solvent. Among them, the solvent contained in the alkali solution is preferably a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. Since the alkali solution has high versatility, for example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is preferable.

[0120] The temperature of the alkaline solution in the alkali treatment step is not particularly limited, but is preferably, for example, 5°C or higher and 80°C or lower, and more preferably 10°C or higher and 60°C or lower. The immersion time of the ionically substituted group-introduced fiber in the alkaline solution in the alkali treatment step is not particularly limited, but is preferably, for example, 5 minutes or longer and 30 minutes or shorter, and more preferably 10 minutes or longer and 20 minutes or shorter. The amount of the alkaline solution used in the alkali treatment is not particularly limited, but is preferably, for example, 100% by mass or more and 100,000% by mass or less, and more preferably 1,000% by mass or more and 10,000% by mass or less, based on the absolute dry mass of the ionically substituted group-introduced fiber.

[0121] In order to reduce the amount of the alkaline solution used in the alkali treatment step, the ionically substituted group-introduced fiber may be washed with water or an organic solvent after the ionically substituted group introduction step and before the alkali treatment step. After the alkali treatment step and before the fibrillation treatment step, from the viewpoint of improving handleability, it is preferable to wash the ionically substituted group-introduced fiber subjected to the alkali treatment with water or an organic solvent.

[0122] <Acid treatment step> In the step of obtaining the cellulose fiber having an ionic substituent, an acid treatment step may be provided between the ionic substituent introduction step and the fibrillation treatment step. For example, the ionic substituent introduction step, the acid treatment, the alkali treatment, and the fibrillation treatment may be performed in this order.

[0123] The method of acid treatment is not particularly limited, and examples thereof include a method of immersing a fiber raw material in an acidic solution containing an acid. The concentration of the acidic solution to be used is not particularly limited, but for example, it is preferably 10% by mass or less, and more preferably 5% by mass or less. Further, the pH of the acidic solution to be used is not particularly limited, but for example, it is preferably 0 or more and 4 or less, and more preferably 1 or more and 3 or less. As the acid contained in the acidic solution, for example, an inorganic acid, a sulfonic acid, a carboxylic acid, etc. can be used. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, boric acid, etc. Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid, etc. Examples of the carboxylic acid include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, tartaric acid, etc. Among these, it is particularly preferable to use hydrochloric acid or sulfuric acid.

[0124] The temperature of the acid solution in the acid treatment is not particularly limited, but for example, 5°C or more and 100°C or less is preferable, and 20°C or more and 90°C or less is more preferable. The immersion time in the acid solution in the acid treatment is not particularly limited, but for example, 5 minutes or more and 120 minutes or less is preferable, and 10 minutes or more and 60 minutes or less is more preferable. The amount of the acid solution used in the acid treatment is not particularly limited, but for example, it is preferably 100% by mass or more and 100,000% by mass or less based on the absolute dry mass of the fiber raw material, and more preferably 1000% by mass or more and 10,000% by mass or less.

[0125] (Inorganic layered compound) The inorganic layered compound is an inorganic compound having a layered structure in which unit crystal layers are stacked on top of each other. In this specification, the inorganic layered compound is one in which all of the length, width, and thickness exceed 200 nm. Such an inorganic layered compound may be in the form of pellets compacted by a method such as pressing.

[0126] Specific examples of the inorganic layered compound include mica such as mica group and brittle mica group, bentonite, kaolinite (kaolin mineral), pyrophyllite, talc, smectite, vermiculite, chlorite, septchlorite, serpentine, stilpnomelane, montmorillonite, and the like. Among them, the inorganic layered compound is preferably at least one selected from the group consisting of bentonite and smectite. Note that bentonite is an aggregate of aluminosilicate unit crystal layers.

[0127] The end face of the inorganic layered compound has cationicity. Therefore, when the cellulose fiber has an anionic group as an ionic substituent, the inorganic layered compound and the cellulose fiber are bonded by the charges of each material. And while maintaining such a bonding state, a mixed solution containing a cellulose fiber having an ionic substituent, an inorganic layered compound, and a solvent is subjected to a fibrillation treatment step, so that at least a part of the fine fibrous cellulose and the fine inorganic layered compound are easily obtained as a fine fibrous cellulose - fine inorganic layered compound inclusion.

[0128] Commercially available products can also be used for the inorganic layered compound. Examples of commercially available products include bentonite manufactured by Kanto Chemical, smectite manufactured by Kunimine Industries, and the like.

[0129] (Optional component) The mixed solution containing a cellulose fiber having an ionic substituent and an inorganic layered compound, which is subjected to the fibrillation treatment step, may contain optional components in addition to the cellulose fiber and the inorganic layered compound. Examples of the optional components include vegetable oils, animal oils, mineral oils, resins, resin emulsions, inorganic particles, carbon materials such as graphite and carbon nanotubes. Among them, vegetable oils, animal oils, and mineral oils are preferably used because they have the property of being included in the card house structure formed by the inorganic layered compound. can be mentioned.

[0130] In addition, the content of the surfactant in the mixed liquid containing the cellulose fiber having an ionic substituent and the inorganic layered compound is preferably 1% by mass or less, and more preferably 0.1% by mass or less. That is, the mixed liquid containing the cellulose fiber having an ionic substituent and the inorganic layered compound preferably contains substantially no surfactant. By setting the content of the surfactant in the mixed liquid containing the cellulose fiber having an ionic substituent, the inorganic layered compound, and the solvent within the above range, the generation of bubbling can be suppressed more effectively.

[0131] (Microfibrillar cellulose·fine inorganic layered compound inclusion) This embodiment is also a microfibrillar cellulose·fine inorganic layered compound inclusion containing microfibrillar cellulose having an ionic substituent with a fiber width of 1000 nm or less and a fine inorganic layered compound. The thixotropic index value (TI value) calculated under the following condition a of the microfibrillar cellulose·fine inorganic layered compound inclusion of this embodiment is 2 or more. (Condition a) The microfibrillar cellulose·fine inorganic layered compound inclusion is dispersed in water to obtain a dispersion having a viscosity of 1000 cps measured with a B-type viscometer at a rotation speed of 23°C and 3 rpm; the viscosity (η) of the dispersion measured with a B-type viscometer at a rotation speed of 23°C and 60 rpm is measured, and the value of 1000 / η is defined as the thixotropic index value (TI value) of the microfibrillar cellulose·fine inorganic layered compound inclusion.

[0132] In this specification, the initial viscosity (1000 cps) used for calculating the thixotropic index value (TI value) is the value measured by a B-type viscometer (Analog viscometer T-LVT manufactured by BLOOKFIELD). The measurement conditions are a rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of measurement is measured. At this time, the fine fibrous cellulose·fine inorganic layered compound dispersion is appropriately diluted with ion-exchanged water so that the viscosity value becomes 1000 cps, but an error of about ±10% may occur in the diluted viscosity (initial viscosity). For example, by adjusting the content of the fine fibrous cellulose·fine inorganic layered compound in the dispersion to 0.3 to 3.0% by mass with respect to the total mass of the dispersion, the initial viscosity can be adjusted to about 1000 cps. After diluting the fine fibrous cellulose·fine inorganic layered compound dispersion with ion-exchanged water, it is stirred with a disperser at 1500 rpm for 5 minutes, and after standing in an environment of 23 °C and 50% relative humidity for 24 hours before measurement, the viscosity measurement is performed. The liquid temperature of the dispersion used for viscosity measurement is 23 °C. After measuring the initial viscosity, the viscosity (η) of the dispersion measured at 23 °C and a rotation speed of 60 rpm with a B-type viscometer is further measured. Then, the value of 1000 / η is taken as the thixotropic index value (TI value) of the fine fibrous cellulose·fine inorganic layered compound-containing material.

[0133] The thixotropic index value (TI value) of the fine fibrous cellulose·fine inorganic layered compound-containing material is preferably 2 or more, more preferably 5 or more, and even more preferably 10 or more. Also, the thixotropic index value (TI value) of the fine fibrous cellulose·fine inorganic layered compound-containing material is preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less. If the thixotropic index value (TI value) is equal to or higher than the above lower limit value, a fine fibrous cellulose·fine inorganic layered compound-containing material with high thixotropy can be obtained.

[0134] In the microfibrillar cellulose / fine inorganic layered compound inclusion, at least a part of the microfibrillar cellulose and the fine inorganic layered compound are complexed. Here, complexation means a state in which at least a part of the microfibrillar cellulose and the fine inorganic layered compound are in contact with each other.

[0135] (Microfibrillar cellulose) The microfibrillar cellulose contained in the microfibrillar cellulose / fine inorganic layered compound inclusion is microfibrillar cellulose having a fiber width of 1000 nm or less. The fiber width of the microfibrillar cellulose is more preferably 100 nm or less, and even more preferably 8 nm or less. In the present specification, fibrous cellulose having a fiber width of 1000 nm or less is referred to as microfibrillar cellulose.

[0136] The fiber width of the microfibrillar cellulose can be measured, for example, by electron microscope observation. The average fiber width of the microfibrillar cellulose is, for example, 1000 nm or less. The average fiber width of the microfibrillar cellulose is preferably, for example, 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, even more preferably 2 nm or more and 50 nm or less, and particularly preferably 2 nm or more and 10 nm or less. By setting the average fiber width of the microfibrillar cellulose to 2 nm or more, dissolution in water as cellulose molecules can be suppressed, and the effects of improving the strength, rigidity, and dimensional stability by the microfibrillar cellulose can be more easily expressed. Note that the microfibrillar cellulose is, for example, single-fiber cellulose.

[0137] The average fiber width of microfibrillar cellulose is measured as follows, for example, using an electron microscope. First, an aqueous suspension of microfibrillar cellulose with a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast onto a carbon film-coated grid that has been hydrophilized to obtain a sample for TEM observation. When fibers with a wide width are included, the SEM image of the surface cast on glass may be observed. Next, observation is performed on the electron microscope image at any one of magnifications of 1000 times, 5000 times, 10000 times, or 50000 times according to the width of the fiber to be observed. However, the sample, observation conditions, and magnification are adjusted so as to satisfy the following conditions.

[0138] (1) Draw a straight line X at an arbitrary position within the observation image, and more than 20 fibers intersect this straight line X. (2) Draw a straight line Y that intersects perpendicularly to this straight line within the same image, and more than 20 fibers intersect this straight line Y.

[0139] For the observation image that satisfies the above conditions, visually read the widths of the fibers that intersect the straight line X and the straight line Y. In this way, obtain 3 or more sets of observation images of surface portions that do not overlap with each other at least. Next, for each image, read the widths of the fibers that intersect the straight line X and the straight line Y. As a result, at least 20 × 2 × 3 = 120 fiber widths are read. Then, the average value of the read fiber widths is taken as the average fiber width of the microfibrillar cellulose.

[0140] The fiber length of the microfibrillar cellulose is not particularly limited, but for example, it is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and even more preferably 0.1 μm or more and 600 μm or less. By setting the fiber length within the above range, destruction of the crystal regions of the microfibrillar cellulose can be suppressed. Also, it becomes possible to set the slurry viscosity of the microfibrillar cellulose within an appropriate range. Incidentally, the fiber length of the microfibrillar cellulose can be determined, for example, by image analysis using TEM, SEM, or AFM.

[0141] The microfibrillar cellulose preferably has a type I crystal structure. Here, the fact that the microfibrillar cellulose has a type I crystal structure can be identified from the diffraction profile obtained from a wide-angle X-ray diffraction photograph using monochromatized CuKα (λ = 1.5418 Å) with graphite. Specifically, it can be identified from the presence of typical peaks at two positions near 2θ = 14° or more and 17° or less and near 2θ = 22° or more and 23° or less. The proportion of the type I crystal structure in the microfibrillar cellulose is preferably, for example, 30% or more, more preferably 40% or more, and even more preferably 50% or more. Thereby, further excellent performance can be expected in terms of heat resistance and manifestation of a low linear thermal expansion rate. Regarding the crystallinity, an X-ray diffraction profile is measured, and it is determined by a conventional method from the pattern (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

[0142] The axial ratio (fiber length / fiber width) of the microfibrillar cellulose is not particularly limited, but is preferably, for example, 20 or more and 10000 or less, and more preferably 50 or more and 1000 or less. By setting the axial ratio to the above lower limit value or more, it is easy to form a sheet containing the microfibrillar cellulose. In addition, sufficient thickening property is easily obtained when preparing a solvent dispersion. By setting the axial ratio to the above upper limit value or less, it is preferable in terms of easy handling such as dilution when, for example, the microfibrillar cellulose is handled as an aqueous dispersion.

[0143] The microfibrillar cellulose in the present embodiment has, for example, both a crystalline region and an amorphous region. The microfibrillar cellulose having both a crystalline region and an amorphous region and an axial ratio within the above range is realized by the method for producing microfibrillar cellulose described later.

[0144] The microfibrillar cellulose of the present embodiment has an ionic substituent. As the ionic substituent, for example, it can contain either one or both of an anionic group and a cationic group. In the present embodiment, it is particularly preferable to have an anionic group as the ionic substituent.

[0145] Examples of the anionic group include, for example, a phosphooxo acid group or a substituent derived from a phosphooxo acid group (sometimes simply referred to as a phosphooxo acid group), a carboxy group or a substituent derived from a carboxy group (sometimes simply referred to as a carboxy group), a sulfone group or a substituent derived from a sulfone group (sometimes simply referred to as a sulfone group), a xanthate group, a phosphonate group, a phosphine group, a carboxyalkyl group (including a carboxymethyl group), and the like. When a sulfone group or a substituent derived from a sulfone group is introduced via an ester bond, the substituent may also be referred to as a sulfur oxo acid group or a substituent derived from a sulfur oxo acid group (sometimes simply referred to as a sulfur oxo acid group). Among them, the anionic group is preferably at least one selected from the group consisting of a phosphooxo acid group, a substituent derived from a phosphooxo acid group, a carboxy group, a carboxymethyl group, a sulfur oxo acid group, and a substituent derived from a sulfur oxo acid group, more preferably at least one selected from the group consisting of a phosphooxo acid group, a substituent derived from a phosphooxo acid group, a carboxy group, a sulfur oxo acid group, and a substituent derived from a sulfur oxo acid group, and particularly preferably a phosphooxo acid group. Examples of the phosphooxo acid group or the substituent derived from a phosphooxo acid group can be the same as the substituents represented by the above formula (1). Examples of the cationic group as the ionic substituent include, for example, an ammonium group, a phosphonium group, a sulfonium group, and the like. Among them, the cationic group is preferably an ammonium group.

[0146] The amount of ionic substituents introduced into the microfibrillar cellulose is preferably, for example, 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, still more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, and particularly preferably 0.60 mmol / g or more per 1 g (mass) of the microfibrillar cellulose. Also, the amount of ionic substituents introduced into the microfibrillar cellulose is preferably, for example, 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, and still more preferably 3.00 mmol / g or less per 1 g (mass) of the microfibrillar cellulose. Here, the denominator in mmol / g indicates the mass of the microfibrillar cellulose when the counter ion of the ionic substituent is a hydrogen ion (H + +). By setting the amount of introduced ionic substituents within the above range, the fibrillation of the fiber raw material can be facilitated, and the stability of the microfibrillar cellulose can be enhanced.

[0147] (Fine inorganic layered compound) The fine inorganic layered compound contained in the microfibrillar cellulose - fine inorganic layered compound inclusion is a cleavage product of the inorganic layered compound. That is, in this specification, the fine inorganic layered compound is a compound in which at least one of the length, width, and thickness is 200 nm or less, and preferably, it is a unit crystal layer having a thickness of 200 nm or less. Note that it is preferable that the fine inorganic layered compound has a thickness of 200 nm or less and either the longitudinal or lateral length is 1000 nm or less. The length of one side of the fine inorganic layered compound particles is a value measured by observing a sample obtained by casting and drying the microfibrillar cellulose - fine inorganic layered compound inclusion (dispersion) with an electron microscope.

[0148] Examples of the fine inorganic layered compound include an aluminum phyllosilicate unit crystal layer and the like.

[0149] (Use) Examples of uses of the microfibrous cellulose - fine inorganic layered compound inclusion of the present embodiment include paints, resin compositions, concrete materials, filamentous or plate - like structures, cosmetics, and the like. Note that filamentous or plate - like structures include sheets, films, membranes, and non - woven fabrics. That is, another embodiment of the present invention is the use of the above - mentioned microfibrous cellulose - fine inorganic layered compound inclusion in the manufacture of paints, resin compositions, concrete materials, filamentous or plate - like structures, electromagnetic wave shields, or electrochemical devices.

[0150] When the microfibrous cellulose - fine inorganic layered compound inclusion of the present embodiment is used for a resin composition, the microfibrous cellulose - fine inorganic layered compound inclusion may be included as an additive in the resin composition, or the resin component may be included as an additive in the microfibrous cellulose - fine inorganic layered compound inclusion. Examples of the resin component contained in the resin composition include rubber - based resins, polyolefin resins, acrylic resins, urethane resins, polycarbonate resins, and the like.

[0151] The present embodiment may be a paint containing the above - described microfibrous cellulose - fine inorganic layered compound inclusion, a concrete material containing the microfibrous cellulose - fine inorganic layered compound inclusion, a filamentous or plate - like structure containing the microfibrous cellulose - fine inorganic layered compound inclusion, or a cosmetic containing the microfibrous cellulose - fine inorganic layered compound inclusion. Known materials can be cited as the constituent components of paints, concrete materials, electromagnetic wave shields, and electrochemical devices.

Examples

[0152] Examples and comparative examples are given below to more specifically explain the features of the present invention. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

[0153] <Production Example A1> As the raw material pulp, coniferous kraft pulp manufactured by Oji Paper Co., Ltd. (solid content: 93% by mass, basis weight: 245 g / m 2 in the form of a sheet, disintegrated, and having a Canadian Standard Freeness (CSF) measured in accordance with JIS P 8121-2:2012 of 700 ml was used.)

[0154] The raw material pulp was subjected to a phosphoxylation treatment as follows. First, an aqueous mixed solution of ammonium dihydrogen phosphate and urea was added to 100 parts by mass (dry mass) of the above raw material pulp, and adjusted to 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water to obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165°C for 250 seconds to introduce phosphate groups into the cellulose in the pulp, and a phosphorylated pulp was obtained.)

[0155] Next, the obtained phosphorylated pulp was subjected to a washing treatment. The washing treatment was performed by repeating the operation of pouring 10 L of ion-exchanged water into 100 g (dry mass) of the phosphorylated pulp to obtain a pulp dispersion, stirring the pulp dispersion so that the pulp was uniformly dispersed, and then filtering and dehydrating. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was reached.)

[0156] Next, the washed phosphorylated pulp was subjected to a neutralization treatment as follows. First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and then a 1N aqueous sodium hydroxide solution was added little by little while stirring to obtain a phosphorylated pulp slurry having a pH of 12 or more and 13 or less. Next, the phosphorylated pulp slurry was dehydrated and washed to obtain a phosphorylated pulp subjected to a neutralization treatment. Then, ion-exchanged water was added to the obtained phosphorylated pulp to obtain a dispersion having a concentration of 0.5% by mass, and the neutralization treatment of the cellulose fibers was completed.)

[0157] The obtained phosphorylated pulp was measured for its infrared absorption spectrum using FT-IR. As a result, 1230 cm -1Absorption based on P=O of phosphate groups was observed nearby, and it was confirmed that phosphate groups were added to the pulp. Further, when the obtained phosphorylated pulp was tested and analyzed with an X-ray diffractometer, typical peaks were confirmed at two positions near 2θ = 14° or more and 17° or less and near 2θ = 22° or more and 23° or less, and it was confirmed that it had cellulose I-type crystals. The amount of phosphate groups (the amount of the first dissociation acid, the amount of strongly acidic groups) measured by the measurement method described in [Measurement of the amount of phosphooxo acid groups] to be described later was 1.45 mmol / g. The total amount of dissociation acids was 2.45 mol / g.

[0158] <Production Example A2> With respect to a 0.5 mass% dispersion of the phosphorylated pulp obtained in Production Example A1, it was treated once at a pressure of 100 MPa with a high-pressure homogenizer (Beryu-Mini, manufactured by Misari Co., Ltd.). In addition, this apparatus was equipped with a mechanism for suppressing bubbling. The high-pressure homogenizer includes a jet flow generation unit equipped with a diamond nozzle and a bubbling suppression mechanism located downstream of this jet flow generation unit. In this apparatus, as the bubbling suppression mechanism, a coolable pipe (outer jacket) was adopted, and such a pipe (outer jacket) was arranged so as to cover the inner pipe through which the dispersion flows. The length of the coolable pipe was 350 mm, and the coolable pipe was arranged 100 mm downstream of the diamond nozzle of the jet flow generation unit. In this bubbling suppression mechanism, while applying back pressure to the jet flow generated by the diamond nozzle, cooling water at 15 °C was flowed through the outer jacket at a flow rate of 27 L / min. In this way, a cellulose fiber dispersion with a concentration of 0.5 mass% subjected to pretreatment was obtained. When the obtained cellulose fiber dispersion was observed with an optical microscope, a large number of cellulose fibers with a width of 20 μm or more were observed.

[0159] <Production Example A3> In the neutralization treatment, the same operation as in Production Example A1 was performed except that 40 mass% tetrabutylammonium hydroxide was used instead of sodium hydroxide, and a cellulose fiber dispersion with a concentration of 0.5 mass% was obtained. The cellulose fiber had tetrabutylammonium ions (TBA + ) as counter ions.

[0160] <Production Example B1> The operation was carried out in the same manner as in Production Example A1 except that 33 parts by mass of phosphorous acid (phosphonic acid) was used instead of ammonium dihydrogen phosphate, and a phosphonated pulp was obtained. Otherwise, the operation was carried out in the same manner as in Production Example A1 to obtain a cellulose fiber dispersion with a concentration of 0.5% by mass.

[0161] The infrared absorption spectrum of the obtained phosphonated pulp was measured using FT-IR. As a result, an absorption based on P=O of the phosphonic acid group, which is a tautomer of the phosphorous acid group, was observed near 1210 cm -1 It was confirmed that the phosphorous acid group (phosphonic acid group) was added to the pulp. Further, the obtained phosphonated pulp was tested and analyzed with an X-ray diffractometer. As a result, typical peaks were confirmed at two positions near 2θ = 14° or more and 17° or less and near 2θ = 22° or more and 23° or less, and it was confirmed that it had cellulose I-type crystals. The amount of phosphorous acid groups (first dissociation acid amount) measured by the measurement method described in [Measurement of the amount of phosphonooxy acid groups] to be described later was 1.51 mmol / g. The total dissociation acid amount was 1.54 mmol / g.

[0162] <Production Example C1> The operation was carried out in the same manner as in Production Example A1 except that 38 parts by mass of amidosulfuric acid (sulfamic acid) was used instead of ammonium dihydrogen phosphate and the heating time was extended to 19 minutes, and a sulfated pulp was obtained. Otherwise, the operation was carried out in the same manner as in Production Example A1 to obtain a cellulose fiber dispersion with a concentration of 0.5% by mass.

[0163] The infrared absorption spectrum of the obtained sulfated pulp was measured using FT-IR. As a result, 1220 - 1260 cm -1Absorption based on S=O of the sulfate ester group was observed in the vicinity, confirming that the sulfate ester group was added to the pulp. Also, when the obtained sulfated pulp was tested and analyzed with an X-ray diffractometer, typical peaks were confirmed at two positions around 2θ = 14° or more and 17° or less and around 2θ = 22° or more and 23° or less, confirming that it had cellulose I-type crystals. The amount of the sulfate ester group measured by the measurement method described in [Measurement of the Amount of Sulfate Ester Group] to be described later was 1.12 mmol / g.

[0164] <Production Example D1> As the raw material pulp, coniferous kraft pulp (undried) manufactured by Oji Paper Co., Ltd. was used. Alkaline TEMPO oxidation treatment was performed on this raw material pulp as follows.

[0165] First, 100 parts by mass of the above raw material pulp equivalent to the dry mass, 1.6 parts by mass of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), and 10 parts by mass of sodium bromide were dispersed in 10000 parts by mass of water. Next, a 13 mass% aqueous sodium hypochlorite solution was added so as to be 10 mmol per 1.0 g of pulp to start the reaction. During the reaction, a 0.5 M aqueous sodium hydroxide solution was dropped to maintain the pH at 10 or more and 10.5 or less, and the reaction was considered to be completed when no change in pH was observed.

[0166] Next, the obtained TEMPO-oxidized pulp was subjected to a washing treatment. The washing treatment was performed by repeating the operation of dehydrating the pulp slurry after TEMPO oxidation to obtain a dehydrated sheet, pouring 5000 parts by mass of ion-exchanged water, stirring to uniformly disperse, and then filtering and dehydrating. The washing end point was determined when the electrical conductivity of the filtrate became 100 μS / cm or less.

[0167] The post-oxidation treatment of the remaining aldehyde groups on this dehydrated sheet was carried out as follows. The above dehydrated sheet equivalent to 100 parts by mass of dry mass was dispersed in 10,000 parts by mass of 0.1 mol / L acetic acid buffer (pH 4.8). Then 113 parts by mass of 80% sodium chlorite was added, and immediately sealed. After that, it was reacted at room temperature for 48 hours while stirring at 500 rpm using a magnetic stirrer to obtain a pulp slurry.

[0168] Next, the post-oxidized TEMPO-oxidized pulp obtained was subjected to a washing treatment. The washing treatment was carried out by repeating the operation of dehydrating the pulp slurry after post-oxidation to obtain a dehydrated sheet, pouring 5,000 parts by mass of ion-exchanged water, stirring to disperse uniformly, and then filtering and dehydrating. When the electrical conductivity of the filtrate became 100 μS / cm or less, it was taken as the end point of washing. Then, ion-exchanged water was added to the obtained TEMPO-oxidized pulp to make a dispersion with a concentration of 0.5% by mass, and the neutralization treatment of the cellulose fibers was completed.

[0169] Regarding the obtained TEMPO-oxidized pulp, the amount of carboxyl groups measured by the measurement method described later was 1.80 mmol / g. Also, when the obtained TEMPO-oxidized pulp was tested and analyzed with an X-ray diffractometer, typical peaks were confirmed at two positions around 2θ = 14° or more and 17° or less and around 2θ = 22° or more and 23° or less, and it was confirmed that it had cellulose I-type crystals.

[0170] <Production Example E1> [Hypochlorous Acid Oxidation] A sheet made of softwood kraft pulp (NBKP) (solid content concentration: 90% by mass) was treated with a hand mixer (manufactured by Osaka Chemical Co., Ltd., Labomill Sur PLUS) at a rotational speed of 20,000 rpm for 15 seconds to obtain a cotton-like fluffy pulp (solid content concentration: 90% by mass). Next, sodium chlorite pentahydrate was added to ion-exchanged water to prepare an aqueous solution with a solid content concentration of sodium chlorite of 22% by mass. To 100 parts by mass of the cotton-like fluffy pulp, 9,000 parts by mass of the 22% by mass aqueous sodium chlorite solution was added, and the mixture was reacted for 2 hours while adjusting the temperature in a warm bath to 30°C to obtain a pulp with carboxyl groups introduced. During the reaction, 1N aqueous sodium hydroxide solution was added as appropriate to maintain the pH at 11.

[0171] Next, the obtained pulp with carboxyl groups introduced was subjected to a washing treatment. The washing treatment was performed by repeating the operation of pouring ion-exchanged water into the obtained pulp with carboxyl groups introduced to obtain a pulp dispersion, stirring it so that the pulp was uniformly dispersed, and then filtering and dehydrating it. The washing was terminated when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0172] Regarding the obtained pulp with carboxyl groups introduced, the amount of carboxyl groups measured by the measurement method described below was 0.70 mmol / g. In addition, when the obtained pulp with carboxyl groups introduced was tested and analyzed with an X-ray diffractometer, typical peaks were confirmed at two positions near 2θ = 14° or more and 17° or less and near 2θ = 22° or more and 23° or less, and it was confirmed that it had cellulose I-type crystals.

[0173] <Production Example F1> [Maleic Esterification] A sheet made of softwood kraft pulp (NBKP) (solid content concentration: 90% by mass) was treated with a hand mixer (manufactured by Osaka Chemical Co., Ltd., Labomill Sur PLUS) at a rotational speed of 20,000 rpm for 15 seconds to obtain a cotton-like fluffy pulp (solid content concentration: 90% by mass). An autoclave was filled with 100 parts by mass of the cotton-like fluffy pulp and 50 parts by mass of maleic anhydride, and the mixture was treated at 150°C for 2 hours to obtain a pulp with carboxyl groups introduced.

[0174] Next, the obtained pulp with carboxyl groups introduced was subjected to a washing treatment. The washing treatment was performed by repeating the operation of pouring ion-exchanged water into the obtained pulp with carboxyl groups introduced, stirring the resulting pulp dispersion so that the pulp was uniformly dispersed, and then performing filtration and dehydration. Washing was terminated when the electric conductivity of the filtrate reached 100 μS / cm or less.

[0175] The infrared absorption spectrum of the obtained pulp with carboxyl groups introduced was measured using FT-IR. As a result, absorption based on carboxyl groups was observed near 1580 and 1720 cm -1 −1, confirming that maleic acid esterification had occurred. For the obtained pulp with carboxyl groups introduced, the amount of carboxyl groups measured by the measurement method described below was 1.22 mmol / g. Further, when the pulp with carboxyl groups introduced was tested and analyzed using an X-ray diffractometer, typical peaks were confirmed at two positions near 2θ = 14° or more and 17° or less and near 2θ = 22° or more and 23° or less, confirming that it had cellulose I-type crystals.

[0176] <Production Example G1> [Carboxyethylation] As the raw material pulp, a softwood kraft pulp (solid content 93% by mass, basis weight 245 g / m 2 sheet-like, disintegrated, and having a Canadian Standard Freeness (CSF) of 700 ml measured according to JIS P 8121-2:2012) manufactured by Oji Paper Co., Ltd. was used.

[0177] To 100 parts by mass (dry mass) of this raw material pulp, 250 parts by mass of a 12N NaOH aqueous solution and a chemical solution (total 553 parts by mass) consisting of 163 parts by mass of 2-chloropropionic acid and 140 parts by mass of ion-exchanged water were added to obtain a chemical solution-impregnated pulp. Next, the obtained chemical solution-impregnated pulp was heated in a hot air dryer at 165°C for 10 minutes to introduce carboxyethyl groups (carboxyl groups) into the cellulose in the pulp, obtaining a pulp with carboxyl groups introduced.

[0178] Next, the obtained pulp with carboxyl groups introduced was subjected to a washing treatment. The washing treatment was performed by repeating the operation of pouring ion-exchanged water into the obtained pulp with carboxyl groups introduced to obtain a pulp dispersion, stirring it so that the pulp was uniformly dispersed, and then performing filtration and dehydration. The washing was terminated when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0179] Next, the neutralization treatment of the washed pulp with carboxyl groups introduced was carried out as follows. First, the washed pulp with carboxyl groups introduced was diluted with 10 L of ion-exchanged water, and then a 1N aqueous sodium hydroxide solution was added little by little while stirring to obtain a pulp slurry with carboxyl groups introduced having a pH of 12 or more and 13 or less. Next, the pulp slurry with carboxyl groups introduced was dehydrated and washed to obtain a pulp with carboxyl groups introduced that had been subjected to the neutralization treatment. Then, ion-exchanged water was added to the obtained pulp with carboxyl groups introduced to obtain a dispersion with a concentration of 0.5% by mass, and the neutralization treatment of the cellulose fibers was completed.

[0180] Regarding the obtained pulp with carboxyl groups introduced, the amount of carboxyl groups measured by the measurement method described later was 1.41 mmol / g. Further, when the pulp with carboxyl groups introduced was tested and analyzed with an X-ray diffractometer, typical peaks were confirmed at two positions near 2θ = 14° or more and 17° or less and near 2θ = 22° or more and 23° or less, and it was confirmed that it had cellulose I-type crystals.

[0181] <Production Example H1> [Sulfoethylation] As the raw material pulp, a softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 245 g / m 2 in sheet form, disintegrated, and the Canadian Standard Freeness (CSF) measured according to JIS P 8121-2:2012 was 700 ml) was used.

[0182] To 100 parts by mass (dry mass) of this raw material pulp, a chemical solution (total 960 parts by mass) consisting of 180 parts by mass of 2N NaOH aqueous solution and 780 parts by mass of an aqueous solution of sodium vinyl sulfonate with a concentration of 25% by mass was added to obtain a chemically impregnated pulp. Next, the obtained chemically impregnated pulp was heated in a hot air dryer at 165 °C for 16 minutes to introduce a sulfoethyl group (sulfone group) into the cellulose in the pulp, and a pulp with a sulfoethyl group introduced (pulp with a sulfone group introduced) was obtained.

[0183] Next, a washing treatment was performed on the obtained pulp with a sulfoethyl group introduced. The washing treatment was carried out by repeating the operation of pouring ion-exchanged water into the obtained pulp with a sulfoethyl group introduced to obtain a pulp dispersion, stirring it so that the pulp was uniformly dispersed, and then filtering and dehydrating. The washing was terminated when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0184] Regarding the obtained pulp with a sulfoethyl group introduced, the amount of sulfoethyl group (amount of sulfone group) measured by the measurement method described later was 1.48 mmol / g. Also, when the pulp with a sulfoethyl group introduced was tested and analyzed with an X-ray diffractometer, typical peaks were confirmed at two positions near 2θ = 14° or more and 17° or less and near 2θ = 22° or more and 23° or less, and it was confirmed that it had cellulose I-type crystals.

[0185] <Production Example J1> [Cationization treatment] As the raw material pulp, a softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 245 g / m 2 in sheet form, disintegrated, and having a Canadian Standard Freeness (CSF) measured according to JIS P 8121-2:2012 of 700 ml) was used.

[0186] To 100 parts by mass (dry mass) of this raw material pulp, 180 parts by mass of a 1N NaOH aqueous solution and 325 parts by mass of a chemical solution (total 505 parts by mass) composed of a cationizing agent (Cation Master G, manufactured by Yokkaichi Gosei Co., Ltd., glycidyltrimethylammonium chloride, pure content 73.1% by mass, water content 20.2% by mass) were added to obtain a chemical solution-impregnated pulp. Next, the obtained chemical solution-impregnated pulp was heated in a hot air dryer at 165 °C for 12 minutes to introduce cationic groups into the cellulose in the pulp, and a cationic group-introduced pulp was obtained.

[0187] Next, a washing treatment was performed on the obtained cationic group-introduced pulp. The washing treatment was carried out by repeating the operation of pouring ion-exchanged water into the obtained cationic group-introduced pulp to obtain a pulp dispersion, stirring it so that the pulp was uniformly dispersed, and then filtering and dehydrating. The washing was terminated when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0188] Next, a neutralization treatment was performed on the washed cationic group-introduced pulp as follows. First, the washed cationic group-introduced pulp was diluted with 10 L of ion-exchanged water, and then 1N hydrochloric acid was added little by little while stirring to obtain a cationic group-introduced pulp slurry with a pH of 1 or more and 2 or less. Next, the cationic group-introduced pulp slurry was dehydrated and washed to obtain a neutralization-treated cationic group-introduced pulp. Then, ion-exchanged water was added to the obtained cationic group-introduced pulp to obtain a 0.5% by mass dispersion, and the neutralization treatment of the cellulose fibers was completed.

[0189] Regarding the obtained cationic group-introduced pulp, a trace nitrogen analysis was performed, and when the amount of cationic groups was calculated by the following formula, it was 1.45 mmol / g. In addition, when the cationic group-introduced pulp was tested and analyzed with an X-ray diffractometer, typical peaks were confirmed at two positions near 2θ = 14° or more and 17° or less and near 2θ = 22° or more and 23° or less, and it was confirmed that it had cellulose I-type crystals. (Amount of cationic groups) [mmol / g] = (Amount of nitrogen) / 14 × 1000 / (Amount of cationic group-introduced pulp tested)

[0190] <Production Example A4> Ion-exchanged water was added to the phosphorylated pulp obtained in Production Example A1 to prepare a 1 mass% dispersion, which was then treated 6 times at a pressure of 240 MPa using a high-pressure homogenizer (Beryu-Mini, manufactured by Mikari Co., Ltd.). Note that, similar to the apparatus described in Production Example A2, this apparatus was not equipped with the bubbling suppression mechanism described above. In this way, a 1 mass% fine fibrillated cellulose dispersion subjected to pretreatment was obtained. After casting the obtained fine fibrillated cellulose dispersion and observing it with a transmission electron microscope, fine fibrillated cellulose with a width of 3-4 nm was observed. No cellulose fibers with a width of 1 μm or more were observed.

[0191] <Example 1-1> Bentonite (manufactured by Kanto Chemical Co., Inc.) was used as the inorganic layered compound. The inorganic layered compound was directly added to the 0.5 mass% cellulose fiber dispersion obtained in Production Example A1 to prepare a mixture such that the concentration of cellulose fibers was 0.5 mass% and the concentration of the inorganic layered compound was 1 mass%. The obtained mixed dispersion was treated 3 times at a pressure of 100 MPa using a high-pressure homogenizer (Beryu-Mini, manufactured by Mikari Co., Ltd.). Note that, this apparatus was equipped with the bubbling suppression mechanism described above in Production Example A2. After the high-pressure homogenizer treatment, a dispersion containing fine fibrillated cellulose and fine inorganic layered compound was obtained. The obtained dispersion was a glossy gel. The dispersibility and TI value of this dispersion were evaluated by the methods described below.

[0192] <Example 1-2> A fine fibrillated cellulose - fine inorganic layered compound dispersion was obtained in the same manner as in Example 1-1, except that the cellulose fiber dispersion obtained in Production Example A2 was used. The obtained dispersion was a glossy gel.

[0193] <Example 1-3> A fine fibrillated cellulose - fine inorganic layered compound dispersion was obtained in the same manner as in Example 1-1, except that the cellulose fiber dispersion obtained in Production Example A3 was used. The obtained dispersion was a glossy gel.

[0194] <Example 1-4> A microfibrous cellulose·fine inorganic layered compound dispersion was obtained in the same manner as in Example 1-1, except that the cellulose fiber dispersion obtained in Production Example B1 was used. The obtained dispersion was a shiny gel.

[0195] <Example 1-5> A microfibrous cellulose·fine inorganic layered compound dispersion was obtained in the same manner as in Example 1-1, except that the cellulose fiber dispersion obtained in Production Example C1 was used. The obtained dispersion was a shiny gel.

[0196] <Example 1-6> A microfibrous cellulose·fine inorganic layered compound dispersion was obtained in the same manner as in Example 1-1, except that the cellulose fiber dispersion obtained in Production Example D1 was used. The obtained dispersion was a shiny gel.

[0197] <Example 1-7> A microfibrous cellulose·fine inorganic layered compound dispersion was obtained in the same manner as in Example 1-1, except that the cellulose fiber dispersion obtained in Production Example E1 was used. The obtained dispersion was a shiny gel.

[0198] <Example 1-8> A microfibrous cellulose·fine inorganic layered compound dispersion was obtained in the same manner as in Example 1-1, except that the cellulose fiber dispersion obtained in Production Example F1 was used. The obtained dispersion was a shiny gel.

[0199] <Example 1-9> A microfibrous cellulose·fine inorganic layered compound dispersion was obtained in the same manner as in Example 1-1, except that the cellulose fiber dispersion obtained in Production Example G1 was used. The obtained dispersion was a shiny gel.

[0200] <Example 1-10> As a cellulose fiber dispersion, a microfibrillated cellulose - fine inorganic layered compound dispersion was obtained in the same manner as in Example 1 - 1, except that the one obtained in Production Example H1 was used. The obtained dispersion was a glossy gel.

[0201] <Example 1 - 11> As a cellulose fiber dispersion, a microfibrillated cellulose - fine inorganic layered compound dispersion was obtained in the same manner as in Example 1 - 1, except that the one obtained in Production Example J1 was used. The obtained dispersion was a glossy gel.

[0202] <Comparative Examples 1 - 11> A microfibrillated cellulose - fine inorganic layered compound dispersion was obtained in the same manner as in Examples 1 - 1 to 1 - 11, respectively, except that the dispersion treatment of the mixed dispersion with a high - pressure homogenizer was changed as follows. As a result of visually observing the obtained dispersions, the dispersion states were all sparse.

[0203] (Dispersion treatment methods in Comparative Examples 1 - 11) Treatment was carried out twice at a pressure of 240 MPa using a high - pressure homogenizer (Beryu - Mini, manufactured by Mikuni Corporation). Note that this apparatus was processed without a mechanism for suppressing bubbling.

[0204] <Comparative Example 12> Bentonite (manufactured by Kanto Chemical) was used as the inorganic layered compound. After directly adding the inorganic layered compound to the 1 mass% - concentration cellulose fiber dispersion obtained in Production Example A4, further ion - exchanged water was added to adjust the concentration of cellulose fibers to 0.5 mass% and the concentration of the inorganic layered compound to 1 mass%. The obtained mixed dispersion was treated three times at a pressure of 100 MPa using a high - pressure homogenizer (Beryu - Mini, manufactured by Mikuni Corporation). Note that this apparatus was equipped with the bubbling - suppressing mechanism described above in Production Example A2. After the high - pressure homogenizer treatment, a microfibrillated cellulose - fine inorganic layered compound dispersion was obtained. As a result of visually observing the obtained dispersion, the dispersion state was slightly sparse.

[0205] <Comparative Example 13> As the cellulose fiber, except that the softwood kraft pulp (undried) manufactured by Oji Paper Co., Ltd. was diluted to a concentration of 0.5 mass% with ion-exchanged water, the same procedure as in Example 1-1 was followed. Due to the blockage of the high-pressure homogenizer, it was not possible to obtain the microfibrillated cellulose·fine inorganic layered compound dispersion.

[0206] <Measurement and Evaluation> For the cellulose fibers or microfibrillated cellulose fibers obtained in Production Examples A1 to A4, B1, C1, D1, E1, F1, G1, H1, and J1, the supernatant yield and the amount of substituents were measured by the method described below. Also, for the microfibrillated cellulose·fine inorganic layered compound dispersions obtained in Examples 1-1 to 1-11 and Comparative Examples 1 to 12, the particle dispersibility and thixotropy were evaluated by the method described below. Note that for Comparative Example 13, the microfibrillated cellulose·fine inorganic layered compound dispersion was not obtained.

[0207] For Examples 1-1 to 1-11 and Comparative Examples 1 to 12, by observing the samples obtained by casting and drying the obtained dispersions with an electron microscope, the presence of microfibrillated cellulose with a fiber width of 20 nm or less and fine inorganic layered compounds in which at least one of the length, width, and thickness is 200 nm or less was confirmed.

[0208] 〔Measurement of the amount of phosphooxo acid groups〕 In the measurement of the amount of phosphooxo acid groups (phosphate group amount or phosphite group amount) in cellulose fibers, first, ion-exchanged water was added to the target cellulose fibers to prepare a slurry with a solid content concentration of 0.2 mass%. This slurry was treated 4 times at a pressure of 200 MPa with a wet atomization device (manufactured by Sugino Machine, Ltd., Starburst) to obtain a microfibrillated cellulose dispersion containing microfibrillated cellulose. After treating the obtained microfibrillated cellulose dispersion with an ion-exchange resin, it was measured by titration using an alkali. The treatment with the ion-exchange resin was carried out by adding a strongly acidic ion-exchange resin (Amberjet 1024; Organo Corporation, conditioned) with a volume of 1 / 10 of the above microfibrillar cellulose dispersion, performing a shaking treatment for 1 hour, and then pouring it onto a mesh with an opening size of 90 μm to separate the resin and the slurry. Also, the titration using an alkali was carried out by measuring the change in the pH value shown by the slurry while adding a 0.1 N aqueous sodium hydroxide solution to the microfibrillar cellulose dispersion after the treatment with the ion-exchange resin at a rate of 10 μL every 5 seconds. Nitrogen gas was blown into the slurry from 15 minutes before the start of the titration until the titration was completed. In this neutralization titration, two points where the increment (the differential value with respect to the amount of alkali dropped in terms of pH) becomes maximum are observed in the curve plotted with the measured pH against the amount of alkali added. Among these, the first maximum point of the increment obtained first after starting to add the alkali is called the first end point, and the next maximum point of the increment is called the second end point (Figure 2). The amount of alkali required from the start of the titration to the first end point is equal to the amount of the first dissociating acid in the slurry used for the titration. Also, the amount of alkali required from the start of the titration to the second end point is equal to the total amount of dissociating acid in the slurry used for the titration. The value obtained by dividing the amount of alkali required from the start of the titration to the first end point (mmol) by the solid content (g) in the titration target slurry was defined as the amount of phospho-oxo acid groups (mmol / g).

[0209] [Measurement of the amount of carboxyl groups] In the measurement of the amount of carboxyl groups of the cellulose fibers, first, ion-exchanged water was added to the target cellulose fibers to prepare a slurry with a solid content concentration of 0.2 mass%. This slurry was treated 4 times at a pressure of 200 MPa using a wet atomization device (manufactured by Sugino Machine, Starburst) to obtain a microfibrillar cellulose dispersion containing microfibrillar cellulose. The obtained microfibrillar cellulose dispersion was measured by performing a treatment with an ion-exchange resin and then carrying out a titration using an alkali. The treatment with an ion exchange resin was carried out by adding a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) with a volume of 1 / 10 of the above microfibrillar cellulose dispersion, performing a shaking treatment for 1 hour, and then pouring it onto a mesh with an opening of 90 μm to separate the resin and the slurry. Also, the titration using an alkali was carried out by measuring the change in the pH value shown by the microfibrillar cellulose dispersion after the treatment with the ion exchange resin while adding 50 μL of a 0.1 N aqueous sodium hydroxide solution once every 30 seconds. The amount of carboxyl groups (mmol / g) was calculated by dividing the amount of alkali (mmol) required in the region corresponding to the first region shown in Figure 3 in the measurement results by the solid content (g) in the slurry to be titrated.

[0210] [Measurement of amount of sulfate ester groups and amount of sulfone groups] The amount of sulfate ester groups and amount of sulfone groups of the cellulose fibers were measured as follows. The cellulose fibers obtained in Production Examples C1 and H1 were frozen in a freezer and then dried in a freeze dryer (FreeZone manufactured by Labconco) for 3 days. The obtained freeze-dried product was pulverized into a powder using a hand mixer (Labomill PLUS manufactured by Osaka Chemical Co., Ltd.) at a rotation speed of 20,000 rpm for 60 seconds. The sample after freeze-drying and pulverization treatment was decomposed by pressurized heating using nitric acid in a sealed container. Then, it was appropriately diluted and the sulfur amount was measured by ICP-OES. The value calculated by dividing by the absolute dry mass of the tested microfibrillar cellulose was taken as the amount of sulfate ester groups and amount of sulfone groups (unit: mmol / g) of the microfibrillar cellulose.

[0211] [Measurement of supernatant yield after centrifugation of cellulose fibers and microfibrillar cellulose dispersion] The supernatant yield after centrifuging the cellulose fiber or microfibrillated cellulose dispersion was measured by the method described below. The supernatant yield after centrifugation serves as an indicator of the yield of microfibrillated cellulose. If the supernatant yield exceeds 90%, substantially all of the cellulose fibers have become microfibrillated cellulose with a width of 1000 nm or less. On the other hand, if the supernatant yield is less than 70%, a significant amount of non-fibrillated cellulose fibers are still present. When measuring the supernatant yield, the cellulose fiber or microfibrillated cellulose dispersion was adjusted to a solid content concentration of 0.2 mass%, and centrifuged at 12000 G for 10 minutes using a cooling high-speed centrifuge (Kokusan Co., Ltd., H-2000B). The obtained supernatant was collected, and the solid content concentration of the supernatant was measured. The supernatant yield was determined based on the following formula. Supernatant yield (%) = Solid content concentration of supernatant (mass%) / 0.2 × 100

[0212] <Particle dispersibility of microfibrillated cellulose·fine inorganic layered compound dispersion> The particle dispersibility of the microfibrillated cellulose·fine inorganic layered compound dispersions obtained in the examples and comparative examples was evaluated according to the following criteria. The higher this particle dispersibility, the more highly the cellulose fibers and inorganic layered compounds are nano-sized and uniformly dispersed. Specifically, 1 volume% of glass beads (BZ-1 manufactured by AS ONE) was added to the microfibrillated cellulose·fine inorganic layered compound dispersion with a total dry solid content concentration of 0.2 mass%, and visually observed and evaluated as follows. A: No sedimentation of glass beads was observed B: A small amount of glass beads sedimented C: All of the glass beads sedimented

[0213] <Thixotropy (TI value) of microfibrillated cellulose·fine inorganic layered compound dispersion> The thixotropy (TI value) of the microfibrillar cellulose·fine inorganic layered compound dispersion obtained in the examples and comparative examples was evaluated. The larger the TI value and the higher the thixotropy, the more highly the cellulose fibers and inorganic layered compounds are nanosized and uniformly dispersed, and furthermore, the less damage to the obtained microfibrillar cellulose and fine inorganic layered compounds. When calculating the TI value of the microfibrillar cellulose·fine inorganic layered compound dispersion, the concentration of the microfibrillar cellulose·fine inorganic layered compound dispersion was appropriately diluted with ion-exchanged water so that the viscosity measured under the conditions described below became 1000 cps. Using the dispersion of the same concentration, the viscosity η was measured at 23 °C and a rotational speed of 60 rpm under the conditions described below. Thereafter, the value of 1000 / η (TI value) was calculated and classified according to the following criteria. A: TI value is 5 or more B: TI value is 2 or more and less than 5 C: TI value is less than 2

[0214] <Viscosity measurement of microfibrillar cellulose·fine inorganic layered compound dispersion> The viscosity of the microfibrillar cellulose·fine inorganic layered compound dispersion was measured as follows. First, the microfibrillar cellulose·fine inorganic layered compound dispersion was diluted so that the B-type viscosity of the microfibrillar cellulose·fine inorganic layered compound dispersion became 1000 cps. After dilution, it was stirred at 1500 rpm for 5 minutes with a disperser. Next, the viscosity of the obtained slurry was measured using a B-type viscometer (manufactured by BLOOKFIELD, analog viscometer T-LVT). The measurement conditions were a rotational speed of 3 rpm, and the viscosity value 3 minutes after the start of measurement was taken as the viscosity of the slurry (initial viscosity). Also, the slurry to be measured was allowed to stand for 24 hours in an environment of 23 °C and a relative humidity of 50% before measurement. The liquid temperature of the slurry at the time of measurement was 23 °C.

[0215]

Table 1

[0216]

Table 2

[0217] In the examples, a fine fibrous cellulose / fine inorganic layered compound inclusion having excellent particle dispersibility and high thixotropy was obtained. This is an effect due to the fact that the cellulose fibers and the inorganic layered compounds are more highly nano-sized and uniformly dispersed. Also, the high thixotropy means that the obtained fine fibrous cellulose and the fine inorganic layered compound are less damaged. Further, when the fine fibrous cellulose / fine inorganic layered compound inclusion (dispersion) obtained in the examples was applied to a substrate and dried, the dispersion dried in a short time and became a sheet with little segregation.

[0218] <Preparation of Ink Containing Fine Fibrous Cellulose / Fine Inorganic Layered Compound> <Example 2-1> The fine fibrous cellulose (cellulose nanofiber) / fine inorganic layered compound dispersion obtained in Example 1-1 was filled into a 10 mL syringe and extruded linearly onto a polypropylene substrate at an injection speed of 1 mL per second and a moving speed of 20 mm per second from the syringe. After extrusion, the substrate was tilted at 45° while keeping the line formed by the dispersion horizontal with the floor surface. The dispersion adhered closely to the substrate without dripping. Also, when the dispersion was dried, it adhered directly to the substrate. Therefore, the dispersion can be used as an ink.

[0219] <Preparation of Rubber Containing Fine Fibrous Cellulose / Fine Inorganic Layered Compound> <Example 3-1> To the fine fibrous cellulose (cellulose nanofiber) - fine inorganic layered compound dispersion obtained in Example 1-1, natural rubber latex (trade name: "Experimental Reagent Latex Solution Natural Rubber", manufactured by Kenis Co., Ltd.) was added and mixed with a high-speed rotary disperser. In addition, the mixture was prepared such that the total mass of the fine fibrous cellulose and the fine inorganic layered compound was 5 parts by mass with respect to 100 parts by mass of the rubber component. The obtained mixture was cast onto a Teflon tray, dried for 1 week under the conditions of 23 °C and 50% relative humidity, and then heat-treated at 105 °C for 15 minutes, whereby a rubber sheet containing the fine fibrous cellulose - fine inorganic layered compound was obtained. The obtained rubber sheet was free of unevenness, and the fine fibrous cellulose and the fine inorganic layered compound, either individually or in combination with each other, were uniformly dispersed in the rubber as a sheet.

[0220] <Preparation of Resin Containing Fine Fibrous Cellulose - Fine Inorganic Layered Compound> <Example 4-1> <Dissolution of Polyvinyl Alcohol> Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., Poval 105, degree of polymerization: 500, saponification degree: 98 - 99 mol%) was added to ion-exchanged water to a concentration of 20% by mass, and stirred at 95 °C for 1 hour to dissolve it.

[0221] <Sheet Formation> To the fine fibrous cellulose (cellulose nanofiber) - fine inorganic layered compound dispersion obtained in Example 1-1, a polyvinyl alcohol solution was added, and it was prepared such that the polyvinyl alcohol was 100 parts by mass with respect to a total mass of 100 parts by mass of the fine fibrous cellulose and the fine inorganic layered compound. Subsequently, the concentration was adjusted so that the total solid content concentration became 0.6% by mass. The suspension was weighed so that the basis weight of the finished sheet became 45 g / m 2 and spread on a commercially available acrylic plate, and dried in a dryer at 70 °C for 24 hours. A plate for weir was placed on the acrylic plate so as to obtain a predetermined basis weight. By the above procedure, a sheet was obtained, and its thickness was 30 μm. The obtained sheet was free of unevenness, and the fine fibrous cellulose and the fine inorganic layered compound, either individually or in combination with each other, were uniformly dispersed in the resin as a sheet.

[0222] <Preparation of Sheet Containing Microfibrillar Cellulose and Fine Inorganic Layered Compound> <Example 5-1> To the microfibrillar cellulose (cellulose nanofiber) - fine inorganic layered compound dispersion obtained in Example 1-1, ion-exchanged water was added and the concentration was adjusted so that the total solid content concentration became 0.5% by mass. The suspension was weighed so that the basis weight of the finished sheet would be 45 g / m 2 and spread on a commercially available acrylic plate, and dried in a dryer at 70°C for 24 hours. A dam plate was placed on the acrylic plate so as to obtain a predetermined basis weight. By the above procedure, a sheet was obtained, and its thickness was 30 μm. The obtained sheet had no unevenness, and no fibers or particles detached even when squeezed by hand, and it was a stable sheet.

[0223] <Preparation of Plate-Like Body Containing Microfibrillar Cellulose and Fine Inorganic Layered Compound> <Example 6-1> To the microfibrillar cellulose (cellulose nanofiber) - fine inorganic layered compound dispersion obtained in Example 1-1, pulp for papermaking (coniferous kraft pulp manufactured by Oji Paper Co., Ltd.) was added, and it was prepared so that the pulp for papermaking would be 400 parts by mass with respect to a total of 100 parts by mass of the microfibrillar cellulose and the fine inorganic layered compound. To the obtained mixed dispersion, 100 parts by mass of a 1% by mass aluminum sulfate aqueous solution was added, and filtration was performed with a papermaking wire to obtain a pulp cake. After mechanically squeezing the obtained cake, it was dried with a cylinder dryer set at 120°C, and a plate-like body with a thickness of 1 mm was obtained. The obtained plate-like body was strong against water and was suitable as a structure.

[0224] <Preparation of Thread Containing Microfibrillar Cellulose and Fine Inorganic Layered Compound> <Example 7-1> When the fine fibrous cellulose (cellulose nanofiber) - fine inorganic layered compound dispersion obtained in Example 1-1 was injected into ethanol containing 10% by mass of aluminum chloride using a syringe, a linear gel-like body was obtained. This linear gel-like body was pulled out from the solvent, dried in a dryer at 70°C for 24 hours, washed with ion-exchanged water, further immersed in acetone, pulled out, and air-dried. As a result, a thread with a fiber diameter of 1 to 3 mm that could not be torn even when pulled by hand was obtained.

[0225] <Preparation of Cosmetics Containing Fine Fibrous Cellulose - Fine Inorganic Layered Compound> <Example 8-1> To 100 parts by mass of the fine fibrous cellulose (cellulose nanofiber) - fine inorganic layered compound dispersion obtained in Example 1-1, 1.5 parts by mass of olive oil, 5 parts by mass of glycerin, 5 parts by mass of ethanol, and 0.05 parts by mass of fragrance were added and mixed well. The resulting mixture had a glossy appearance without liquid separation, was gel-like, and had a fresh and refreshing texture when applied to the skin. Therefore, it was suitable as a cosmetic.

[0226] <Preparation of Concrete Containing Fine Fibrous Cellulose - Fine Inorganic Layered Compound> <Example 9-1> The fine fibrous cellulose (cellulose nanofiber) - fine inorganic layered compound dispersion obtained in Example 1-1 was used by replacing it with water for hardening instant cement (manufactured by Toyo Materia Co., Ltd.). Specifically, 100 parts by mass of instant cement was mixed so that the amount of water contained in the dispersion of fine fibrous cellulose and fine inorganic layered compound was 15 parts by mass. After mixing, mortar was obtained by kneading, and this mortar was put into a mold so that the thickness was 2 cm and the length and width were 10 cm, and left to stand for 1 day to harden. As a result, concrete containing fine fibrous cellulose - fine inorganic layered compound was obtained. The obtained concrete was sufficiently hardened and had excellent strength.

Description of Reference Signs

[0227] 10 Jet flow generation section 20 Bubbling suppression section 100 Minimization processing device

Claims

1. A method for producing a microfibrous cellulose / fine inorganic layered compound inclusion, comprising a step of mixing a cellulose fiber having an ionic substituent and an inorganic layered compound, and then performing a fibrillation treatment, wherein in the step of performing the fibrillation treatment, bubbling is suppressed by cooling.

2. The method for producing a microfibrous cellulose / fine inorganic layered compound inclusion according to claim 1, wherein in the step of performing the fibrillation treatment, the fibrillation treatment is performed using a high-pressure homogenizer.

3. The method for producing a microfibrous cellulose / fine inorganic layered compound inclusion according to claim 1 or 2, wherein the ionic substituent is an anionic group.

4. The method for producing a microfibrous cellulose / fine inorganic layered compound inclusion according to any one of claims 1 to 3, wherein the ionic substituent is a phosphooxo acid group or a substituent derived from a phosphooxo acid group.

5. Containing fibrous cellulose having a fiber width of 1000 nm or less and having an ionic substituent, and a fine inorganic layered compound, wherein the ionic substituent is a phosphooxo acid group or a substituent derived from a phosphooxo acid group, and a microfibrous cellulose / fine inorganic layered compound inclusion having a thixotropic index value (TI value) of 2 or more calculated under the following condition a; (Condition a) The microfibrous cellulose / fine inorganic layered compound inclusion is dispersed in water to obtain a dispersion having a viscosity of 1000 cps measured at 23 ° C. and a rotation speed of 3 rpm with a B-type viscometer; the viscosity (η) of the dispersion measured at 23 ° C. and a rotation speed of 60 rpm with a B-type viscometer is measured, and the value of 1000 / η is defined as the thixotropic index value (TI value) of the microfibrous cellulose / fine inorganic layered compound inclusion.

6. The microfibrous cellulose / fine inorganic layered compound inclusion according to claim 5, which is for a paint.

7. The microfibrous cellulose / fine inorganic layered compound inclusion according to claim 5, which is for a resin composition.

8. The microfibrous cellulose / fine inorganic layered compound inclusion according to claim 5, which is for a concrete material.

9. The microfibrous cellulose / fine inorganic layered compound inclusion according to claim 5, which is for a filamentous or plate-like structure.

10. The microfibrous cellulose / fine inorganic layered compound inclusion according to claim 5, which is for a cosmetic.

11. A paint containing the microfibrous cellulose / fine inorganic layered compound inclusion according to claim 5.

12. A resin composition comprising the fine fibrous cellulose / fine inorganic layered compound inclusion according to claim 5.

13. A concrete material comprising the fine fibrous cellulose / fine inorganic layered compound inclusion according to claim 5.

14. A filamentous or plate-like structure comprising the fine fibrous cellulose / fine inorganic layered compound inclusion according to claim 5.

15. A cosmetic comprising the fine fibrous cellulose / fine inorganic layered compound inclusion according to claim 5.

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