Fibrous cellulose-containing materials and their applications

Abstract

To provide a fine fibrous cellulose-containing substance that exhibits excellent dispersion stability in every use mode.SOLUTION: A fibrous cellulose-containing substance contains fibrous cellulose having a fiber width of 1,000 nm or less and at least one kind selected from organic acid salts and / or inorganic acid salts. The content of the at least one kind selected from organic acid salts and inorganic acid salts is 1-1,000 pts.mass to 100 pts.mass of the fibrous cellulose.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fibrous cellulose-containing material and its applications. [Background technology]

[0002] In recent years, materials made from renewable natural fibers have been attracting attention due to the need to replace petroleum resources and growing environmental awareness. Among natural fibers, fibrous cellulose with a fiber diameter of 10 μm to 50 μm, especially wood-derived fibrous cellulose (pulp), has been widely used mainly in paper products.

[0003] As fibrous cellulose, fine fibrous cellulose with a fiber diameter of 1 μm or less is also known. Because such fine fibrous cellulose can exhibit a thickening effect, its use as a thickener in various applications has been investigated.

[0004] For example, Patent Document 1 discloses a thickener containing fine fibrous cellulose having a fiber width of 1000 nm or less and in which some of the hydroxyl groups of the cellulose constituting the fibers have been substituted with phosphorus oxoacid groups, while Patent Document 2 discloses a thickener for brine containing fine cellulose fibers and a water-soluble polymer, and the use of the thickener for brine in drilling fluids is being considered. Furthermore, Patent Document 3 discloses a viscous aqueous composition containing water and cellulose fibers having a number-average fiber diameter of 2 to 150 nm and containing any of aldehyde groups, ketone groups, and carboxyl groups. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-189698 [Patent Document 2] International Publication No. 2016 / 060120 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-87256 Summary of the Invention [Problem to be solved by the invention]

[0006] When using fine fibrous cellulose as a thickener, it is necessary for the fine fibrous cellulose to be uniformly dispersed in the dispersion and for the dispersion to be stably maintained. Depending on the mode of use, the dispersion may contain salt or other components, and even in such cases, the fine fibrous cellulose is required to exhibit excellent dispersion stability.

[0007] Therefore, in order to solve the problems of the conventional technology, the present inventors have conducted research with the aim of providing a fine fibrous cellulose-containing material that exhibits excellent dispersion stability in all modes of use. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, the inventors have discovered that by adding a predetermined amount of at least one selected from organic acid salts and inorganic acid salts to a fibrous cellulose-containing material containing fibrous cellulose having a fiber width of 1000 nm or less, a fine fibrous cellulose-containing material that exhibits excellent dispersion stability in any usage mode can be obtained. Specifically, the present invention has the following configuration.

[0009] [1] A fiber fibrous cellulose having a fiber width of 1000 nm or less and at least one selected from an organic acid salt and an inorganic acid salt, A material containing fibrous cellulose, wherein the content of at least one selected from organic acid salts and inorganic acid salts is 1 to 1000 parts by mass per 100 parts by mass of fibrous cellulose. [2] The fibrous cellulose-containing material according to [1], wherein the at least one selected from organic acid salts and inorganic acid salts is at least one selected from the group consisting of carbonates, phosphates and acetates. [3] A fibrous cellulose-containing material according to [1] or [2], wherein the fibrous cellulose has an anionic group. [4] The fibrous cellulose-containing material according to [3], wherein the anionic group is a phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group. [5] The fibrous cellulose-containing material according to any one of [1] to [4], wherein the fibrous cellulose-containing material is a slurry having a pH of 6.0 or higher. [6] The fibrous cellulose-containing material according to any one of [1] to [5], which is a slurry having a haze of 2.0% or less. [7] The fibrous cellulose-containing material according to any one of [1] to [6], which is used for a topical skin preparation, a cement dispersant, or a granulation promoter. [8] A thickener comprising the fibrous cellulose-containing material according to any one of [1] to [7]. [9] A dispersant comprising the fibrous cellulose-containing material according to any one of [1] to [7].

[10] A reinforcing agent comprising the fibrous cellulose-containing material according to any one of [1] to [7].

[11] A skin external preparation comprising the fibrous cellulose-containing material according to any one of [1] to [7].

[12] A cement composition comprising the fibrous cellulose-containing material according to any one of [1] to [7].

[13] A granulated material comprising the fibrous cellulose-containing material according to any one of [1] to [7]. [Effects of the Invention]

[0010] According to the present invention, it is possible to obtain a fine fibrous cellulose-containing material that exhibits excellent dispersion stability in all modes of use. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a graph showing the relationship between the amount of NaOH dropped onto a slurry containing fibrous cellulose having phosphorus oxo acid groups and pH. [Figure 2]FIG. 2 is a graph showing the relationship between the amount of NaOH dropped onto a slurry containing fibrous cellulose having a carboxy group and the pH. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below. The following description of the components may be based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.

[0013] (fibrous cellulose-containing material) The present invention relates to a fibrous cellulose-containing material comprising fibrous cellulose having a fiber width of 1000 nm or less and at least one selected from organic acid salts and inorganic acid salts. Here, in the fibrous cellulose-containing material, the content of the at least one selected from organic acid salts and inorganic acid salts is 1 to 1000 parts by mass per 100 parts by mass of the fibrous cellulose. In this specification, fibrous cellulose having a fiber width of 1000 nm or less is also referred to as fine fibrous cellulose. Therefore, the fibrous cellulose-containing material of the present invention can also be referred to as a fine fibrous cellulose-containing material.

[0014] The fibrous cellulose-containing material of the present invention has the above-mentioned configuration, and therefore has excellent dispersion stability of the fine fibrous cellulose. Such dispersion stability is exhibited, for example, in salt water and in dispersions containing other components. The dispersion stability of the fine fibrous cellulose can be evaluated, for example, by evaluating the viscosity and appearance of the dispersion containing the fine fibrous cellulose.

[0015] The content of at least one selected from organic acid salts and inorganic acid salts may be 1 part by mass or more, preferably 2 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more, per 100 parts by mass of fine fibrous cellulose. The content of at least one selected from organic acid salts and inorganic acid salts may be 1,000 parts by mass or less, preferably 900 parts by mass or less, more preferably 800 parts by mass or less, even more preferably 700 parts by mass or less, even more preferably 600 parts by mass or less, even more preferably 300 parts by mass or less, and particularly preferably 50 parts by mass or less, per 100 parts by mass of fine fibrous cellulose. By setting the content of at least one selected from organic acid salts and inorganic acid salts within the above range, the dispersion stability of the fine fibrous cellulose in the fibrous cellulose-containing material can be improved. Furthermore, by setting the content of at least one selected from organic acid salts and inorganic acid salts within the above range, the dispersion stability of fine fibrous cellulose can be improved even in a dispersion containing salt. In this way, a fibrous cellulose-containing material that shows excellent dispersion stability even in a dispersion containing salt can also be said to have excellent salt tolerance. The content of at least one selected from organic acid salts and inorganic acid salts in a fibrous cellulose-containing material can be quantified by spectroscopic measurements such as NMR and IR, MS fragment analysis, or UV analysis.

[0016] The form of the fibrous cellulose-containing material is not particularly limited, and it can exist in various forms such as powder, slurry, solid, etc. Among these, the fibrous cellulose-containing material is preferably in the form of a slurry.

[0017] When the fibrous cellulose-containing material is a slurry, the slurry viscosity is preferably 10 mPa·s or more, more preferably 100 mPa·s or more, and even more preferably 1000 mPa·s or more. The slurry viscosity is preferably 100,000 mPa·s or less, more preferably 50,000 mPa·s or less, and even more preferably 30,000 mPa·s or less. Here, the slurry viscosity is measured using a Brookfield viscometer. The measurement conditions are a rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of measurement is taken as the viscosity of the slurry. The dispersion to be measured is allowed to stand for 24 hours in an environment of 23°C and 50% relative humidity before measurement, and the temperature of the dispersion during measurement is 23°C. For example, a Brookfield T-LVT analog viscometer can be used as the Brookfield viscometer.

[0018] The viscosity of a slurry containing 0.5% by mass of sodium chloride is preferably 100 mPa·s or more, more preferably 2000 mPa·s or more, and even more preferably 3000 mPa·s or more. The viscosity of a slurry containing 0.5% by mass of sodium chloride is preferably 30000 mPa·s or less, more preferably 20000 mPa·s or less, and even more preferably 10000 mPa·s or less. The viscosity of a slurry containing 0.5% by mass of sodium chloride is a value measured using the same method as described above.

[0019] When the fibrous cellulose-containing material is a slurry, the haze of the slurry is preferably 2.0% or less, more preferably 1.5% or less, and even more preferably 1.0% or less. The haze of the slurry may be 0.0%. Here, the haze of the slurry is the haze value measured using a glass cell with a 1 cm optical path length in accordance with JIS K 7136:2000, assuming a solids concentration of fibrous cellulose of 0.2% by mass. Specifically, the measurement is performed using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory Co., Ltd.). For example, a glass cell for liquids with a 1 cm optical path length (MG-40, reverse optical path, manufactured by Fujiwara Seisakusho Co., Ltd.) can be used as the glass cell with a 1 cm optical path length. Furthermore, the dispersion to be measured is allowed to stand for 24 hours in an environment of 23°C and 50% relative humidity before measurement, and the liquid temperature of the dispersion during measurement is set to 23°C. The zero-point measurement is performed using ion-exchanged water placed in the same glass cell.

[0020] When the fibrous cellulose-containing material is a slurry, the pH of the slurry is preferably 6.0 or higher, more preferably 6.5 or higher, and even more preferably 7.0 or higher. The pH of the slurry is preferably 10 or lower. By adjusting the pH of the slurry within the above range, the dispersion stability of the fine fibrous cellulose can be more effectively improved.

[0021] (organic acid salts / inorganic acid salts) The fibrous cellulose-containing material of the present invention contains at least one selected from organic acid salts and inorganic acid salts. The organic acid salts and inorganic acid salts herein are preferably water-soluble.

[0022] Examples of organic acids constituting the organic acid salt include formic acid, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, stearic acid, oleic acid, naphthenic acid, octylic acid, octanoic acid, benzoic acid, decanoic acid, toluic acid, butyric acid, palmitic acid, myristic acid, lauric acid, linoleic acid, linolenic acid, ricinoleic acid, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, phthalic acid, glutaric acid, adipic acid, tartaric acid, citric acid, pyruvic acid, and malic acid. Among these, acetic acid is preferred. Examples of salts include sodium salts, potassium salts, lithium salts, magnesium salts, aluminum salts, and calcium salts. Among these, sodium salts and potassium salts are preferred. More specifically, sodium acetate is preferred as the organic acid salt.

[0023] Examples of inorganic acids constituting inorganic acid salts include sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, carbonic acid, silicic acid, and boric acid. Of these, the inorganic acid is preferably phosphoric acid, carbonic acid, silicic acid, and the like. Examples of salts include sodium salts, potassium salts, lithium salts, magnesium salts, aluminum salts, and calcium salts. Of these, the salt is preferably sodium salts or potassium salts. More specifically, the inorganic acid salt is preferably disodium hydrogen phosphate, sodium hydrogen carbonate, or a carbonate ion-containing hydrotalcite or bentonite.

[0024] Among these, the at least one selected from organic acid salts and inorganic acid salts is preferably at least one selected from the group consisting of carbonates, phosphates, and acetates, and more preferably at least one selected from the group consisting of disodium hydrogen phosphate, sodium hydrogen carbonate, and sodium acetate. Note that the at least one selected from organic acid salts and inorganic acid salts may be one or a combination of two or more of the above-mentioned salts.

[0025] In this embodiment, at least one selected from organic acid salts and inorganic acid salts is added separately to a dispersion containing fine fibrous cellulose obtained by the method described below. In this case, the at least one selected from organic acid salts and inorganic acid salts is added in an amount of 1 to 1,000 parts by mass per 100 parts by mass of the fibrous cellulose. The amount of the at least one selected from organic acid salts and inorganic acid salts added is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more, per 100 parts by mass of the fine fibrous cellulose. Furthermore, the amount of the at least one selected from organic acid salts and inorganic acid salts added is preferably 900 parts by mass or less, more preferably 800 parts by mass or less, even more preferably 700 parts by mass or less, even more preferably 600 parts by mass or less, even more preferably 300 parts by mass or less, and particularly preferably 50 parts by mass or less, per 100 parts by mass of the fine fibrous cellulose.

[0026] (fine fibrous cellulose) The fibrous cellulose-containing material of the present invention contains fine fibrous cellulose having a fiber width of 1000 nm or less. The fiber width of the fibrous cellulose is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 20 nm or less, even more preferably 10 nm or less, and particularly preferably 8 nm or less.

[0027] The fiber width of fibrous cellulose can be measured, for example, by observation under an electron microscope. The average fiber width of fibrous cellulose is, for example, 1000 nm or less. The average fiber width of fibrous cellulose is, for example, preferably 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 making the average fiber width of fibrous cellulose 2 nm or more, dissolution of cellulose molecules in water can be suppressed, and the effects of fibrous cellulose, such as improved strength, rigidity, and dimensional stability, can be more easily achieved. The fibrous cellulose is, for example, monofilament cellulose.

[0028] The fiber width of fibrous cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of fibrous 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 hydrophilically treated carbon film-coated grid to prepare a sample for TEM observation. When wide fibers are included, an SEM image of the surface cast onto glass may be observed. Next, electron microscope images are observed at magnifications of 1000x, 5000x, 10000x, or 50000x, depending on the width of the fibers to be observed. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.

[0029] (1) Draw a line X at any point in the observed image, and 20 or more fibers intersect with the line X. (2) Draw a line Y that intersects the line perpendicularly within the same image, and 20 or more fibers intersect the line Y.

[0030] For observation images that satisfy the above conditions, the widths of the fibers intersecting with lines X and Y are visually read. In this way, three or more sets of observation images of at least the surface portions that do not overlap each other are obtained. Next, for each image, the widths of the fibers intersecting with lines X and Y are read. In this way, the widths of at least 20 fibers x 2 x 3 = 120 fibers are read. The average value of the read fiber widths is then taken as the average fiber width of the fibrous cellulose.

[0031] The fiber length of the fibrous cellulose is not particularly limited, but 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 crystalline regions of the fibrous cellulose can be suppressed. It also becomes possible to set the slurry viscosity of the fibrous cellulose within an appropriate range. The fiber length of the fibrous cellulose can be determined, for example, by image analysis using TEM, SEM, or AFM.

[0032] The fibrous cellulose preferably has a type I crystal structure. The presence of type I crystal structure in fibrous cellulose can be identified by a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ=1.5418 Å) monochromated with graphite. Specifically, it can be identified by the presence of two typical peaks at two positions: 2θ=14° to 17° and 2θ=22° to 23°. The proportion of type I crystal structure in the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. This can be expected to provide even better performance in terms of heat resistance and low linear thermal expansion coefficient. The degree of crystallinity can be determined by measuring the X-ray diffraction profile and using the pattern in a conventional manner (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

[0033] The axial ratio (fiber length / fiber width) of the fibrous cellulose is not particularly limited, but is preferably, for example, 20 to 10,000, and more preferably 50 to 1,000. By setting the axial ratio to the above lower limit or more, it is easy to form a sheet containing fine fibrous cellulose. In addition, sufficient viscosity is easily obtained when a solvent dispersion is prepared. By setting the axial ratio to the above upper limit or less, it is preferable in that, for example, when the fibrous cellulose is used as an aqueous dispersion, handling such as dilution is easier.

[0034] Fibrous cellulose has, for example, both crystalline and amorphous regions. Fine fibrous cellulose having both crystalline and amorphous regions and having an axial ratio within the above range can be realized by the method for producing fine fibrous cellulose described below.

[0035] The fibrous cellulose preferably has an ionic substituent. The ionic substituent may include, for example, either or both of an anionic group and a cationic group. In this embodiment, it is particularly preferable that the ionic substituent is an anionic group. Furthermore, the ionic substituent is preferably a group that is introduced into the fibrous cellulose via an ester bond or an ether bond, and more preferably a group that is introduced into the fibrous cellulose via an ester bond. In this case, the ester bond is formed by dehydration condensation of a hydroxyl group of the fibrous cellulose and a compound that becomes the ionic substituent.

[0036] Examples of anionic groups as ionic substituents include phosphorus oxo acid groups or substituents derived from phosphorus oxo acid groups (sometimes simply referred to as phosphorus oxo acid groups), carboxy groups or substituents derived from carboxy groups (sometimes simply referred to as carboxy groups), sulfur oxo acid groups or substituents derived from sulfur oxo acid groups (sometimes simply referred to as sulfur oxo acid groups), xanthate groups or substituents derived from xanthate groups (sometimes simply referred to as xanthate groups), phosphonic groups or substituents derived from phosphonic groups (sometimes simply referred to as phosphonic groups), phosphine groups or substituents derived from phosphine groups (sometimes simply referred to as phosphine groups), sulfone groups or substituents derived from sulfone groups (sometimes simply referred to as sulfone groups), and carboxyalkyl groups (including carboxymethyl groups and carboxyethyl groups). Among these, the anionic group is preferably at least one selected from the group consisting of a phosphorus oxoacid group, a substituent derived from a phosphorus oxoacid group, a carboxy group, a substituent derived from a carboxy group, a sulfur oxoacid group, and a substituent derived from a sulfur oxoacid group, more preferably at least one selected from the group consisting of a phosphorus oxoacid group, a substituent derived from a phosphorus oxoacid group, a sulfur oxoacid group, and a substituent derived from a sulfur oxoacid group, and particularly preferably a phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group. By using an ionic substituent as the above substituent, the dispersion stability of the fine fibrous cellulose can be more effectively improved.

[0037] Examples of the cationic group include an ammonium group, a phosphonium group, a sulfonium group, etc. Among these, the cationic group is preferably an ammonium group.

[0038] The phosphorus oxo acid group or the substituent derived from the phosphorus oxo 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 fibrous cellulose. In this case, the plurality of introduced substituents represented by the following formula (1) may be the same or different.

[0039] [ka]

[0040] In formula (1), a, b, and n are natural numbers, and m is an arbitrary number (where 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 α and α' are O - The n α's may all be the same or may be different. b+ is a cation of one or more valences consisting of organic or inorganic substances.

[0041] R is a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, an unsaturated branched hydrocarbon group, an unsaturated cyclic hydrocarbon group, an aromatic group, or a group derived therefrom. In formula (1), n ​​is preferably 1.

[0042] Examples of saturated linear hydrocarbon groups include, but are not limited to, methyl, ethyl, n-propyl, and n-butyl groups. Examples of saturated branched hydrocarbon groups include, but are not limited to, i-propyl and t-butyl groups. Examples of saturated cyclic hydrocarbon groups include, but are not limited to, cyclopentyl and cyclohexyl groups. Examples of unsaturated linear hydrocarbon groups include, but are not limited to, vinyl and allyl groups. Examples of unsaturated branched hydrocarbon groups include, but are not limited to, i-propenyl and 3-butenyl groups. Examples of unsaturated cyclic hydrocarbon groups include, but are not limited to, cyclopentenyl and cyclohexenyl groups. Examples of aromatic groups include, but are not limited to, phenyl and naphthyl groups.

[0043] In addition, the derivative group in R is a carboxy group, a carboxylate group (-COO -), a hydroxy group, an amino group, an ammonium group, or another functional group to which at least one functional group has been added or substituted, but is not particularly limited. Furthermore, 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 phosphorus oxoacid group can be set within an appropriate range, facilitating penetration into the fiber raw material and increasing the yield of fine cellulose fibers. When multiple Rs are present in formula (1) or when multiple types of substituents represented by the above formula (1) are introduced into the fibrous cellulose, the multiple Rs may be the same or different.

[0044] β b+ is a monovalent or higher cation made of an organic or inorganic substance. Examples of the monovalent or higher cation made 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 made 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. It should be noted that in formula (1), β b+ When a plurality of β b+ may be the same or different. The monovalent or higher cations consisting of organic or inorganic substances include β b+ Sodium or potassium ions are preferred because they are less likely to yellow when the fiber raw material containing the cation is heated and are easy to use industrially, but there is no particular limitation.

[0045] More specifically, examples of the phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group include a phosphate group (-POH), a salt of a phosphate group, a phosphorous acid (phosphonic acid) group (-POH), and a salt of a phosphite (phosphonic acid) group. The phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group may also be a group in which a phosphate group is condensed (e.g., a pyrophosphate group), a group in which a phosphonic acid is condensed (e.g., a polyphosphonic acid group), a phosphate ester group (e.g., a monomethyl phosphate group, a polyoxyethylene alkyl phosphate group), or an alkyl phosphonic acid group (e.g., a methylphosphonic acid group).

[0046] The sulfur oxoacid group (a sulfur oxoacid group or a substituent derived from a sulfur oxoacid group) is, for example, a substituent represented by the following formula (2). A plurality of substituents represented by the following formula (2) may be introduced into each fibrous cellulose. In this case, the plurality of introduced substituents represented by the following formula (2) may be the same or different. [ka]

[0047] In the above structural formula, b and n are natural numbers, p is 0 or 1, and m is an arbitrary number (where 1 = b × m). When n is 2 or more, multiple 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. Note that when multiple types of substituents represented by the above formula (2) are introduced into the fibrous cellulose, the multiple β b+ may be the same or different. The monovalent or higher cations consisting of organic or inorganic substances include β b+ Sodium or potassium ions are preferred because they are less likely to yellow when the fiber raw material containing the cation is heated and are easy to use industrially, but there is no particular limitation.

[0048] The amount of ionic substituent introduced into fibrous cellulose is, for example, preferably 0.10 mmol / g or more per 1 g (mass) of fibrous cellulose, 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. The amount of ionic substituent introduced into fibrous cellulose is, for example, preferably 5.20 mmol / g or less per 1 g (mass) of fibrous cellulose, more preferably 3.65 mmol / g or less, even more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, and particularly preferably 2.00 mmol / g or less. Here, the denominator in the unit mmol / g is calculated based on the fact that the counter ion of the ionic substituent is a hydrogen ion (H +By setting the amount of ionic substituents introduced within the above range, it is possible to easily pulverize the fiber raw material and more effectively improve the dispersion stability of the fibrous cellulose.

[0049] In the past, in order to improve the dispersibility of fine fibrous cellulose, increasing the amount of ionic substituents introduced has been considered in order to strengthen the electrostatic repulsion between the individual fine fibrous celluloses. In particular, because aggregation of fine fibrous cellulose is likely to occur in salt water or in a dispersion containing other components, increasing the amount of ionic substituents introduced has been considered. However, in this embodiment, salt tolerance can be improved by mixing a predetermined amount of fine fibrous cellulose with at least one selected from organic acid salts and inorganic acid salts, so there is no need to increase the amount of ionic substituents introduced in order to improve salt tolerance. As a result, the cost of obtaining fine fibrous cellulose can be reduced. Furthermore, the time required to introduce ionic substituents can be shortened, thereby improving the production efficiency of fine fibrous cellulose.

[0050] The amount of ionic substituents introduced into the fibrous cellulose can be measured, for example, by neutralization titration, which involves measuring the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to a slurry containing the obtained fibrous cellulose.

[0051] 1 is a graph showing the relationship between the amount of NaOH added dropwise to a slurry containing fibrous cellulose having phosphorus oxo acid groups and pH. The amount of phosphorus oxo acid groups introduced into the fibrous cellulose is measured, for example, as follows. First, a slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the measurement object may be subjected to a defibration treatment similar to the defibration treatment step described below before the treatment with the strongly acidic ion exchange resin. Next, the change in pH is observed while adding aqueous sodium hydroxide solution, and a titration curve like the one shown in the upper part of Figure 1 is obtained. The titration curve shown in the upper part of Figure 1 plots the measured pH against the amount of alkali added, while the titration curve shown in the lower part of Figure 1 plots the pH increment (derivative value) (1 / mmol) against the amount of alkali added. In this neutralization titration, two points of maximum increment (derivative value of pH with respect to the amount of alkali added) are confirmed on the curve plotting the measured pH against the amount of alkali added. Of these, the first maximum increment obtained after starting to add alkali is called the first endpoint, and the next maximum increment obtained is called the second endpoint. The amount of alkali required from the start of titration to the first endpoint is equal to the amount of first dissociated acid of the fibrous cellulose contained in the slurry used for titration; the amount of alkali required from the first endpoint to the second endpoint is equal to the amount of second dissociated acid of the fibrous cellulose contained in the slurry used for titration; and the amount of alkali required from the start of titration to the second endpoint is equal to the total amount of dissociated acid of the fibrous cellulose contained in the slurry used for titration. The value obtained by dividing the amount of alkali required from the start of titration to the first endpoint by the solids content (g) of the slurry to be titrated is the amount of phosphorus oxo acid groups introduced (mmol / g). Note that the term "amount of phosphorus oxo acid groups introduced" simply refers to the amount of first dissociated acid. In Figure 1, the region from the start of titration to the first endpoint is referred to as Region 1, and the region from the first endpoint to the second endpoint is referred to as Region 2. For example, if the phosphorus oxoacid group is a phosphate group and this phosphate group undergoes condensation, the apparent amount of weakly acidic groups in the phosphorus oxoacid group (also referred to herein as the second dissociated acid amount) decreases, and the amount of alkali required in Region 2 is less than the amount required in Region 1. On the other hand, the amount of strongly acidic groups in the phosphorus oxoacid group (also referred to herein as the first dissociated acid amount) corresponds to the amount of phosphorus atoms regardless of whether condensation occurs. Furthermore, if the phosphorus oxoacid group is a phosphite group, the phosphorus oxoacid group no longer contains weakly acidic groups, and the amount of alkali required in Region 2 is reduced or may even be zero. In this case, there is only one point on the titration curve where the pH increment is maximized.

[0052] The above-mentioned amount of introduced phosphorus oxoacid groups (mmol / g) indicates the amount of phosphorus oxoacid groups in the acid-form fibrous cellulose (hereinafter referred to as the amount of phosphorus oxoacid groups (acid form)) because the denominator indicates the mass of the acid-form fibrous cellulose. On the other hand, when the counter ions of the phosphorus oxoacid groups are substituted with an arbitrary cation C so as to be charge equivalent, the amount of phosphorus oxoacid groups in the fibrous cellulose with the cation C as the counter ion (hereinafter referred to as the amount of phosphorus oxoacid groups (C form)) can be determined by converting the denominator to the mass of the fibrous cellulose when the cation C is the counter ion. That is, it is calculated using the following formula. Amount of phosphorus oxoacid group (C type) = Amount of phosphorus oxoacid group (acid type) / {1 + (W - 1) × A / 1000} A [mmol / g]: total amount of anions derived from phosphorus oxoacid groups in fibrous cellulose (total amount of dissociated acid from phosphorus oxoacid groups) W: Formula weight per valence of cation C (for example, Na is 23, Al is 9)

[0053] 2 is a graph showing the relationship between the amount of NaOH added dropwise to a dispersion containing fibrous cellulose having carboxy groups as ionic substituents and pH. The amount of carboxy groups introduced into the fibrous cellulose is measured, for example, as follows. First, a dispersion containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the measurement object may be subjected to a defibration treatment similar to the defibration treatment step described below before the treatment with the strongly acidic ion exchange resin. Next, the change in pH was observed while adding aqueous sodium hydroxide solution, and a titration curve like the one shown in the upper part of Figure 2 was obtained. The titration curve shown in the upper part of Figure 2 plots the measured pH against the amount of added alkali, while the titration curve shown in the lower part of Figure 2 plots the pH increment (derivative value) (1 / mmol) against the amount of added alkali. In this neutralization titration, a single point was identified in the curve plotting the measured pH against the amount of added alkali, where the increment (derivative value of pH with respect to the amount of added alkali) reached a maximum. This maximum point is called the first endpoint. Here, the region from the start of the titration to the first endpoint in Figure 2 is called the first region. The amount of alkali required in the first region is equal to the amount of carboxyl groups in the dispersion used for titration. The amount of alkali required in the first region of the titration curve (mmol) is then divided by the solids content (g) in the dispersion containing the fibrous cellulose to be titrated to calculate the amount of carboxyl groups introduced (mmol / g).

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

[0055] When measuring the amount of ionic substituents by titration, adding too many drops of sodium hydroxide or titrating too quickly can result in lower ionic substituents than expected, leading to inaccurate values. An appropriate amount and interval is, for example, titrating 10–50 μL of 0.1 N sodium hydroxide every 5–30 seconds. To eliminate the influence of carbon dioxide dissolved in the fibrous cellulose-containing slurry, it is also recommended to measure the amount of ionic substituents 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.

[0056] The amount of sulfur oxoacid groups introduced into fibrous cellulose can be calculated by freeze-drying a slurry containing fibrous cellulose and then pulverizing the sample to measure the amount of sulfur. Specifically, the slurry containing fibrous cellulose is freeze-dried and then pulverized. The resulting sample is subjected to pressure-heat decomposition using nitric acid in a sealed container, appropriately diluted, and the amount of sulfur is measured by ICP-OES. The amount of sulfur oxoacid groups (unit: mmol / g) of the fibrous cellulose is calculated by dividing the value by the bone-dry mass of the fibrous cellulose used.

[0057] The amount of xanthate groups introduced into fibrous cellulose can be measured using the Bredee method as follows. First, 40 mL of saturated ammonium chloride solution is added to 1.5 parts by mass (bone dry mass) of fibrous cellulose. The sample is crushed with a glass rod and mixed thoroughly. After leaving for approximately 15 minutes, the sample is filtered through GFP filter paper (GS-25, manufactured by Advantec) and thoroughly washed with saturated ammonium chloride solution. Next, the sample, including the GFP filter paper, is placed in a 500 mL tall beaker, and 50 mL of 0.5 M sodium hydroxide solution (5 °C) is added, stirred, and left for 15 minutes. Phenolphthalein solution is added until the solution turns pink, and then 1.5 M acetic acid is added. The point at which the solution changes from pink to colorless is considered the neutralization point. After neutralization, 250 mL of distilled water is added and stirred thoroughly. 10 mL of 1.5 M acetic acid and 10 mL of 0.05 mol / L iodine solution are added using a volumetric pipette. Then, this solution is titrated with 0.05 mol / L sodium thiosulfate solution, and the amount of xanthate groups is calculated using the following formula from the titration amount of sodium thiosulfate and the bone dry mass of the fibrous cellulose. Amount of xanthate group (mmol / g) = (0.05 × 10 × 2 - 0.05 × sodium thiosulfate titration (mL)) / 1000 / bone-dry mass of fibrous cellulose (g)

[0058] (Method of producing fine fibrous cellulose) <Fiber raw materials> Fine fibrous cellulose is produced from a cellulose-containing fiber raw material. While the cellulose-containing fiber raw material is not particularly limited, pulp is preferably used due to its availability and low cost. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include, but are not limited to, 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 chemi-ground wood pulp (CGP); and mechanical pulps such as groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP). Examples of non-wood pulp include, but are not limited to, cotton-based pulps such as cotton linters and cotton lint, and non-wood pulps such as hemp, wheat straw, and bagasse. The deinked pulp is not particularly limited, but examples thereof include deinked pulp made from waste paper. The pulp of this embodiment may be one of the above types used alone, or two or more types may be used in combination. Among the above pulps, wood pulp and deinked pulp are preferred from the viewpoint of ease of availability. Furthermore, among wood pulps, chemical pulp is more preferred, and kraft pulp and sulfite pulp are even more preferred, from the viewpoints of having a high cellulose ratio and a high yield of fine fibrous cellulose during defibration treatment, and of obtaining long-fiber fine fibrous cellulose with little decomposition of cellulose in the pulp and a large axial ratio. Note that the viscosity tends to increase when long-fiber fine fibrous cellulose with a large axial ratio is used.

[0059] Examples of cellulose-containing fiber raw materials include cellulose contained in sea squirts and bacterial cellulose produced by acetic acid bacteria.Furthermore, instead of cellulose-containing fiber raw materials, fibers formed from linear nitrogen-containing polysaccharide polymers such as chitin and chitosan can also be used.

[0060] <Phosphorus oxoacid group introduction step> The process for producing fine fibrous cellulose preferably includes a step of introducing an ionic substituent, and an example of the step of introducing an ionic substituent is a step of introducing a phosphorus oxo acid group. The step of introducing a phosphorus oxo acid group is a step of reacting a cellulose-containing fiber raw material with at least one compound (hereinafter also referred to as "compound A") selected from compounds capable of introducing a phosphorus oxo acid group by reacting with a hydroxyl group possessed by the cellulose-containing fiber raw material. This step results in the production of a fiber into which a phosphorus oxo acid group has been introduced.

[0061] In the phosphorus oxoacid group introduction step according to this embodiment, the reaction of the cellulose-containing fiber raw material with 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"). Alternatively, the cellulose-containing fiber raw material with compound A may be reacted in the absence of compound B.

[0062] An example of a method for reacting compound A with a fiber raw material in the presence of compound B is a method in which compound A and compound B are mixed with a fiber raw material in a dry, wet, or slurry state. Among these methods, it is preferable to use a fiber raw material in a dry or wet state, and it is particularly preferable to use a fiber raw material in a dry state, because this method results in a high degree of reaction uniformity. The form of the fiber raw material is not particularly limited, but is preferably in the form of a cotton or thin sheet. Compound A and compound B may be added to the fiber raw material in the form of a powder, a solution dissolved in a solvent, or a melted state obtained by heating to a melting point or higher. Among these methods, it is preferable to add compound A and compound B in the form of a solution dissolved in a solvent, particularly an aqueous solution, because this method results in a high degree of reaction uniformity. Compound A and compound B may be added to the fiber raw material simultaneously, separately, or as a mixture. The method for adding compound A and compound B is not particularly limited. When compound A and compound B are in the form of a solution, the fiber raw material may be immersed in the solution to absorb the liquid and then removed, or the solution may be added dropwise to the fiber raw material. Alternatively, the required amounts of compound A and compound B may be added to the fiber raw material, or excess amounts of compound A and compound B may be added to the fiber raw material, and then the excess compound A and compound B may be removed by squeezing or filtration.

[0063] The compound A used in this embodiment may be any compound that has a phosphorus atom and is capable of forming an ester bond with cellulose, and examples thereof include, but are not limited to, phosphoric acid or a salt thereof, phosphorous acid or a salt thereof, dehydrated condensed phosphoric acid or a salt thereof, and phosphoric anhydride (diphosphorus pentoxide). Phosphoric acid can be used with various purities, such as 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid. Phosphorous acid can be 99% phosphorous acid (phosphonic acid). Dehydrated condensed phosphoric acid is formed by condensing two or more molecules of phosphoric acid through a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Phosphates, phosphites, and dehydrated condensed phosphates include lithium salts, sodium salts, potassium salts, and ammonium salts of phosphoric acid, phosphorous acid, or dehydrated condensed phosphoric acid, which can be neutralized to various degrees. Among these, from the viewpoints of high efficiency of introduction of phosphate groups, ease of further improving defibration efficiency in the defibration step described below, low cost, and ease of 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.

[0064] The amount of compound A added to the fiber raw material is not particularly limited, but for example, when the amount of compound A added is converted into the amount of phosphorus atoms, the amount of phosphorus atoms added to the fiber raw material (bone 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 amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by setting the amount of phosphorus atoms added to the fiber raw material to the above upper limit or less, a balance can be achieved between the yield improvement effect and costs.

[0065] As described above, the compound B used in this embodiment is at least one selected from urea and its derivatives. Examples of the compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea. From the viewpoint of improving the uniformity of the reaction, it is preferable to use an aqueous solution of compound B. Furthermore, 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.

[0066] The amount of compound B added relative to the fiber raw material (bone dry mass) is not particularly limited, but is preferably, for example, 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.

[0067] In the reaction of a fiber raw material containing cellulose with compound A, the reaction system may contain, in addition to compound B, amides or amines, for example. Examples of amides include formamide, dimethylformamide, acetamide, and dimethylacetamide. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, triethylamine in particular is known to act as a good reaction catalyst.

[0068] In the phosphorus oxo acid group introduction step, it is preferable to add or mix compound A or the like to or with the fiber raw material, and then heat-treat the fiber raw material. The heat treatment temperature is preferably selected so that the phosphorus oxo acid group can be efficiently introduced while suppressing thermal decomposition and hydrolysis of the fiber. The heat treatment temperature is preferably, for example, from 50°C to 300°C, more preferably from 100°C to 250°C, and even more preferably from 130°C to 200°C. Various types of equipment having heat transfer media can be used for the heat treatment, including, for example, a hot air dryer, agitator dryer, rotary dryer, disk dryer, roll-type heater, plate-type heater, fluidized-bed dryer, band-type dryer, filtration dryer, vibration fluidized dryer, flash dryer, reduced-pressure dryer, infrared heater, far-infrared heater, microwave heater, and high-frequency dryer.

[0069] In the heat treatment according to this embodiment, for example, compound A may be added to a thin sheet-like fiber raw material by impregnation or other methods, followed by heating, or heating while kneading or stirring the fiber raw material and compound A in a kneader or the like. This makes it possible to suppress unevenness in the concentration of compound A in the fiber raw material and more uniformly introduce phosphorus oxoacid groups onto the surface of the cellulose fibers contained in the fiber raw material. This is thought to be because, when water molecules move to the surface of the fiber raw material as it dries, dissolved compound A is attracted to the water molecules by surface tension, preventing it from migrating to the surface of the fiber raw material (i.e., causing unevenness in the concentration of compound A).

[0070] Furthermore, the heating device used for the heat treatment is preferably one that can constantly discharge, to the outside of the device system, for example, the water retained in the slurry and the water generated in the dehydration condensation (phosphorylation) reaction between compound A and hydroxyl groups contained in cellulose or the like in the fiber raw material. Examples of such heating devices include an oven with a blower system. Constantly discharging the water from the device system can suppress the hydrolysis reaction of phosphate ester bonds, which is the reverse reaction of phosphate esterification, as well as the acid hydrolysis of sugar chains in the fiber. This makes it possible to obtain fine fibrous cellulose with a high axial ratio.

[0071] The heat treatment time is preferably from 1 second to 300 minutes after the water content has been substantially removed from the fiber raw material, more preferably from 1 second to 1,000 seconds, and even more preferably from 10 seconds to 800 seconds. In this embodiment, the amount of phosphorus oxo acid groups introduced can be kept within a preferred range by setting the heating temperature and heating time within appropriate ranges.

[0072] The phosphorus oxo acid group introduction step may be carried out at least once, but may also be carried out twice or more. By carrying out the phosphorus oxo acid group introduction step twice or more, a large number of phosphorus oxo acid groups can be introduced into the fiber raw material.

[0073] The amount of phosphorus oxoacid groups introduced into the fiber raw material is, for example, preferably 0.10 mmol / g or more per 1 g (mass) of fiber raw material, more preferably 0.20 mmol / g or more, even more preferably 0.50 mmol / g or more, and particularly preferably 1.00 mmol / g or more. The amount of phosphorus oxoacid groups introduced into the fiber raw material is, for example, preferably 5.20 mmol / g or less per 1 g (mass) of fiber raw material, more preferably 3.65 mmol / g or less, and even more preferably 3.00 mmol / g or less. By keeping the amount of phosphorus oxoacid groups introduced within the above range, it is possible to facilitate the micronization of the fiber raw material and more effectively improve the dispersion stability of the fine fibrous cellulose.

[0074] <Carboxy group introduction step> The process for producing fine fibrous cellulose may include, for example, a carboxyl group introduction step as an ionic substituent introduction step. The carboxyl group introduction step is carried out by subjecting a cellulose-containing fiber raw material to an oxidation treatment such as ozone oxidation, oxidation by the Fenton method, or TEMPO oxidation treatment, or by treating the cellulose-containing fiber raw material with a compound having a carboxylic acid-derived group or a derivative thereof, or an acid anhydride of a compound having a carboxylic acid-derived group or a derivative thereof.

[0075] The compound having a group derived from carboxylic acid is not particularly limited, but 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. Furthermore, the derivative of the compound having a group derived from carboxylic acid is not particularly limited, but examples thereof include imidized products of acid anhydrides of compounds having carboxy groups, and derivatives of acid anhydrides of compounds having carboxy groups. The imidized products of acid anhydrides of compounds having carboxy groups are not particularly limited, but examples thereof include imidized products of dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide.

[0076] The acid anhydride of a compound having a group derived from carboxylic acid is not particularly limited, but examples thereof include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride, etc. Furthermore, the derivative of an acid anhydride of a compound having a group derived from carboxylic acid is not particularly limited, but examples thereof include acid anhydrides of compounds having carboxy groups such as dimethylmaleic anhydride, diethylmaleic anhydride, diphenylmaleic anhydride, etc. in which at least some of the hydrogen atoms have been substituted with substituents such as alkyl groups or phenyl groups.

[0077] When TEMPO oxidation is performed in the carboxyl group introduction step, it is preferable to perform the treatment under conditions of pH 6 or higher and pH 8 or lower. This type of treatment is also called neutral TEMPO oxidation. Neutral TEMPO oxidation can be performed, for example, by adding pulp as the fiber raw material, a nitroxy 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). The presence of sodium chlorite further allows aldehydes generated during the oxidation process to be efficiently oxidized to carboxyl groups. The TEMPO oxidation may also be performed under conditions of pH 10 or higher and pH 11 or lower. This type of treatment is also called alkaline TEMPO oxidation. The alkaline TEMPO oxidation can be performed, for example, by adding a nitroxy radical such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidizing agent to pulp as the fiber raw material.

[0078] The amount of carboxyl groups introduced into the fiber raw material varies depending on the type of substituent. For example, when carboxyl groups are introduced by TEMPO oxidation, the amount is preferably 0.10 mmol / g or more, 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 gram (mass) of fiber raw material. The amount of carboxyl groups introduced into the fibrous cellulose is preferably 3.65 mmol / g or less, more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, even more preferably 2.00 mmol / g or less, even more preferably 1.50 mmol / g or less, and particularly preferably 1.00 mmol / g or less. Furthermore, when the substituent is a carboxymethyl group, the amount of carboxyl groups introduced may be 5.8 mmol / g or less per gram (mass) of fine fibrous cellulose. By setting the amount of carboxyl groups introduced within the above range, the fiber raw material can be easily refined and the dispersion stability of the fibrous cellulose can be more effectively improved.

[0079] <Sulfur oxoacid group introduction step> The process for producing fine fibrous cellulose may include, for example, a sulfur oxoacid group introduction step as an ionic substituent introduction step, in which hydroxyl groups in a cellulose-containing fiber raw material react with sulfur oxoacid to obtain cellulose fibers having sulfur oxoacid groups (sulfur oxoacid group-introduced fibers).

[0080] In the sulfur oxo acid group introduction step, instead of compound A in the above-described <Phosphorus oxo acid group introduction step>, at least one compound (hereinafter also referred to as "compound C") selected from compounds capable of introducing sulfur oxo acid groups by reacting with hydroxyl groups in cellulose-containing fiber raw materials is used. Compound C may be any compound containing a sulfur atom and capable of forming an ester bond with cellulose, including, but not limited to, sulfuric acid or its salts, sulfurous acid or its salts, and sulfuric acid amides. Sulfuric acid of various purities can be used, for example, 96% sulfuric acid (concentrated sulfuric acid). Sulfurous acid can be 5% aqueous sulfurous acid. Sulfates or sulfites can be lithium, sodium, potassium, or ammonium salts of sulfates or sulfites, which can be neutralized to various degrees. Sulfamic acid or the like can be used as the sulfuric acid amide. In the sulfur oxo acid group introduction step, it is preferable to use compound B in the above-described <Phosphorus oxo acid group introduction step> as well.

[0081] In the sulfur oxoacid group introduction step, the cellulose raw material is preferably mixed with an aqueous solution containing a sulfur oxoacid and urea and / or a urea derivative, and then the cellulose raw material is subjected to a heat treatment. The heat treatment temperature is preferably selected so that the sulfur oxoacid groups can be efficiently introduced while suppressing thermal decomposition and hydrolysis 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. The heat treatment temperature is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower.

[0082] In the heat treatment step, heating is preferably performed until substantially all moisture is removed. Therefore, the heat treatment time varies depending on the amount of moisture contained in the cellulose raw material and the amount of aqueous solution containing sulfur oxoacid and urea and / or a urea derivative added, but is preferably, for example, 10 to 10,000 seconds. For the heat treatment, various devices having a heat medium can be used, such as a hot air dryer, a stirring dryer, a rotary dryer, a disk dryer, a roll-type heater, a plate-type heater, a fluidized bed dryer, a band-type dryer, a filtration dryer, a vibration fluidized dryer, an airflow dryer, a reduced-pressure dryer, an infrared heater, a far-infrared heater, a microwave heater, or a high-frequency dryer.

[0083] The amount of sulfur oxoacid groups introduced into the cellulose raw material is preferably 0.50 mmol / g or more, more preferably 0.70 mmol / g or more, and even more preferably 1.00 mmol / g or more. The amount of sulfur oxoacid groups introduced into the cellulose raw material is preferably 5.00 mmol / g or less, and more preferably 3.00 mmol / g or less. By keeping the amount of sulfur oxoacid groups introduced within the above range, it is possible to easily pulverize the fiber raw material and more effectively improve the dispersion stability of the fibrous cellulose.

[0084] <Xanthate group introduction step> The process for producing fine fibrous cellulose may include a xanthate group introduction step as an ionic substituent introduction step. In the xanthate group introduction step, hydroxyl groups in a fiber raw material containing cellulose are substituted with xanthate groups represented by the following formula (3), thereby obtaining cellulose fibers having xanthate groups (xanthate group-introduced fibers). -OCSS - M + ...(3) where M + is at least one selected from the group consisting of hydrogen ions, monovalent metal ions, ammonium ions, and aliphatic or aromatic ammonium ions.

[0085] In the xanthate group introduction process, the cellulose-containing fiber raw material is first treated with an alkaline solution to obtain alkali cellulose. Examples of alkaline solutions include an aqueous alkali metal hydroxide solution and an aqueous alkaline earth metal hydroxide solution. Among these, the alkaline solution is preferably an aqueous alkali metal hydroxide solution such as sodium hydroxide or potassium hydroxide, and particularly preferably an aqueous sodium hydroxide solution. When the alkaline solution is an aqueous alkali metal hydroxide solution, the alkali metal hydroxide concentration in the aqueous alkali metal hydroxide solution is preferably 4% by mass or more, more preferably 5% by mass or more. Furthermore, the alkali metal hydroxide concentration in the aqueous alkali metal hydroxide solution is preferably 9% by mass or less. By setting the alkali metal hydroxide concentration at or above the lower limit, the mercerization of cellulose can be sufficiently promoted, the amount of by-products generated during the subsequent xanthation can be reduced, and as a result, the yield of xanthate group-introduced fiber can be increased. This allows the defibration process described below to be performed more effectively. Furthermore, by setting the alkali metal hydroxide concentration to the above upper limit or less, it is possible to prevent the aqueous alkali metal hydroxide solution from penetrating into the crystalline regions of cellulose while allowing mercerization to proceed, which makes it easier to maintain the cellulose type I crystal structure and further increases the yield of fine fibrous cellulose.

[0086] The alkali treatment time is preferably 30 minutes or more, more preferably 1 hour or more. The alkali treatment time is preferably 6 hours or less, more preferably 5 hours or less. By setting the alkali treatment time within the above range, the final yield can be increased, and productivity can be improved.

[0087] The alkali cellulose obtained by the alkali treatment is preferably subjected to solid-liquid separation to remove as much aqueous solution as possible. This reduces the water content during the subsequent xanthate treatment, thereby accelerating the reaction. As a method for solid-liquid separation, a general dehydration method such as centrifugation or filtration can be used. The concentration of alkali metal hydroxide contained in the alkali cellulose after solid-liquid separation is preferably 3% by mass or more and 8% by mass or less based on the total mass of the alkali cellulose after solid-liquid separation.

[0088] In the xanthate group introduction step, a xanthate treatment step is carried out after alkali treatment. In the xanthate treatment step, alkali cellulose is reacted with carbon disulfide (CS2) to form (-O - Na + ) group (-OCSS - Na + ) group to obtain xanthate group-introduced fibers. In the above, the metal ions introduced into the alkali cellulose are typically Na + However, similar reactions occur with other alkali metal ions.

[0089] In the xanthation treatment, it is preferable to supply 10% by mass or more of carbon disulfide relative to the bone dry mass of cellulose in the alkali cellulose. Furthermore, in the xanthation treatment, the contact time between carbon disulfide and alkali cellulose is preferably 30 minutes or more, more preferably 1 hour or more. Although the contact of carbon disulfide with alkali cellulose allows xanthation to proceed quickly, it takes time for carbon disulfide to penetrate into the interior of the alkali cellulose, so it is preferable to set the reaction time within the above range. On the other hand, the contact time between carbon disulfide and alkali cellulose can be 6 hours or less, which allows sufficient penetration into the alkali cellulose mass after dehydration, allowing reactive xanthation to be almost completed.

[0090] The reaction temperature in the xanthate treatment is preferably 46 ° C or less. By setting the reaction temperature within the above range, it is easy to suppress the decomposition of alkali cellulose. In addition, by setting the reaction temperature within the above range, it is easy to react uniformly, so it is possible to suppress the generation of by-products, and further, it is also possible to suppress the removal of the generated xanthate group.

[0091] The amount of xanthate group introduced in the xanthate group introduction step is preferably 0.05 mmol / g or more per 1 g (mass) of fiber raw material, more preferably 0.10 mmol / g or more, even more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, and particularly preferably 0.50 mmol / g or more. In addition, the amount of xanthate group introduced is, for example, preferably 5.00 mmol / g or less per 1 g (mass) of fiber raw material, more preferably 3.00 mmol / g or less. By making the amount of xanthate group introduced within the above range, it is possible to facilitate the pulverization of fiber raw material, and more effectively improve the dispersion stability of fibrous cellulose.

[0092] <Oxidation step using a chlorine-based oxidizing agent (second carboxyl group introduction step)> The process for producing fine fibrous cellulose may include an oxidation step using a chlorine-based oxidizing agent as an ionic substituent introduction step. In the oxidation step using a chlorine-based oxidizing agent, the chlorine-based oxidizing agent is added to a wet or dry fiber raw material having a hydroxyl group to cause a reaction, thereby introducing a carboxyl group into the fiber raw material.

[0093] Examples of chlorine-based oxidizing agents include hypochlorous acid, hypochlorites, chlorous acid, chlorites, chloric acid, chlorates, perchloric acid, perchlorates, and chlorine dioxide. From the viewpoints of the efficiency of introducing substituents, and therefore the defibration efficiency, cost, and ease of handling, the chlorine-based oxidizing agent is preferably sodium hypochlorite, sodium chlorite, or 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 may be dissolved in an appropriate solvent and then added.

[0094] The concentration of the chlorine-based oxidizing agent in the solution in the oxidation step using the chlorine-based oxidizing agent, converted into an effective chlorine concentration, is preferably 1 to 1,000% by mass, more preferably 5 to 500% by mass, and even more preferably 10 to 100% by mass. The amount of the chlorine-based oxidizing agent added per 100 parts by mass of the fiber raw material is preferably 1 to 100,000 parts by mass, more preferably 10 to 10,000 parts by mass, and even more preferably 100 to 5,000 parts by mass.

[0095] The reaction time with the chlorine-based oxidizing agent in the oxidation step using the chlorine-based oxidizing agent varies depending on the reaction temperature, but is preferably, for example, from 1 minute to 1,000 minutes, more preferably from 10 minutes to 500 minutes, and even more preferably from 20 minutes to 400 minutes. The pH during the reaction is preferably from 5 to 15, more preferably from 7 to 14, and even more preferably from 9 to 13. At the start of the reaction, the pH is preferably maintained constant (for example, pH 11) during the reaction by appropriately adding hydrochloric acid or sodium hydroxide. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed with water by filtration or the like.

[0096] <Phosphonic or Phosphine Group Introduction Step (Phosphoalkylation Step)> The process for producing fine fibrous cellulose may include a step of introducing a phosphonic or phosphine group (phosphoalkylation step) as an ionic substituent introduction step. In the phosphoalkylation step, a compound having a reactive group and a phosphonic or phosphine group (compound E) is used as an essential component. A ), an optional alkali compound, and a compound B selected from the above-mentioned urea and its derivatives are added to a wet or dry fiber raw material having hydroxyl groups and reacted to introduce phosphonic or phosphine groups into the fiber raw material.

[0097] Examples of the reactive group include a halogenated alkyl group, a vinyl group, and an epoxy group (glycidyl group). Compound E A Examples of suitable compounds include vinyl phosphonic acid, phenyl vinyl phosphonic acid, and phenyl vinyl phosphinic acid. From the viewpoints of the efficiency of introducing substituents, the defibration efficiency, cost, and ease of handling, Compound E A is preferably vinylphosphonic acid. Furthermore, as an optional component, it is also preferable to use the compound B in the above-mentioned <Phosphorus oxo acid group introduction step> in the same manner, and the amount added is also preferably as described above.

[0098] Compound E A When adding, it may be added to the fiber raw material as a reagent (solid or liquid) as is, or it may be dissolved in an appropriate solvent and added. The fiber raw material is preferably converted into alkali cellulose in advance or simultaneously with the reaction. The method for converting into alkali cellulose is as described above.

[0099] The temperature during the reaction is, for example, preferably 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.

[0100] Compound E A The amount added per 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.

[0101] The reaction time may vary depending on the reaction temperature, but is preferably from 1 minute to 1,000 minutes, more preferably from 10 minutes to 500 minutes, and even more preferably from 20 minutes to 400 minutes. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed with water by filtration or the like.

[0102] <Sulfonic acid group introduction step (sulfoalkylation step)> The ionic substituent introduction step may include a sulfone group introduction step (sulfoalkylation step). In the sulfoalkylation, a compound having a reactive group and a sulfone group (compound E) is used as an essential component. B ) and, as an optional component, an alkali compound and a compound B selected from the aforementioned urea and its derivatives are added to a wet or dry fiber raw material having a hydroxyl group and reacted to introduce a sulfonic acid group into the fiber raw material.

[0103] Examples of the reactive group include a halogenated alkyl group, a vinyl group, and an epoxy group (glycidyl group). Compound E B Examples of suitable olefin sulfonates include sodium 2-chloroethanesulfonate, sodium vinylsulfonate, sodium p-styrenesulfonate, and 2-acrylamido-2-methylpropanesulfonic acid. Among these, compound E is particularly preferred in terms of the efficiency of introducing substituents, and therefore the defibration efficiency, cost, and ease of handling. B is preferably sodium vinyl sulfonate. Furthermore, as an optional component, it is also preferable to use the compound B in the above-mentioned <Phosphorus oxo acid group introduction step> in the same manner, and the amount added is also preferably as described above.

[0104] Compound E B When adding, it may be added to the fiber raw material as a reagent (solid or liquid) as is, or it may be dissolved in an appropriate solvent and added. The fiber raw material is preferably converted into alkali cellulose in advance or simultaneously with the reaction. The method for converting into alkali cellulose is as described above.

[0105] The temperature during the reaction is, for example, preferably 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.

[0106] Compound E BThe amount added per 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.

[0107] The reaction time may vary depending on the reaction temperature, but is preferably, for example, from 1 minute to 1,000 minutes, more preferably from 10 minutes to 500 minutes, and even more preferably from 15 minutes to 400 minutes. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed with water by filtration or the like.

[0108] <Carboxyalkylation step (third carboxy group introduction step)> The process for producing fine fibrous cellulose may include a carboxyalkylation step as an ionic substituent introduction step. As an essential component, a compound having a reactive group and a carboxy group (compound E C ), an optional alkaline compound, and compound B selected from the aforementioned urea and its derivatives are added to a wet or dry fiber raw material having a hydroxyl group and reacted to introduce a carboxyl group into the fiber raw material.

[0109] Examples of the reactive group include a halogenated alkyl group, a vinyl group, and an epoxy group (glycidyl group). Compound E C As the chloroisothiazolinone, monochloroacetic acid, sodium monochloroacetate, 2-chloropropionic acid, 3-chloropropionic acid, sodium 2-chloropropionate, and sodium 3-chloropropionate are preferred from the standpoints of efficiency in introducing substituents, and therefore defibration efficiency, cost, and ease of handling. Furthermore, as an optional component, it is also preferable to use the compound B in the above-mentioned <Phosphorus oxo acid group introduction step> in the same manner, and the amount added is also preferably as described above.

[0110] Compound E CWhen adding, it may be added to the fiber raw material as a reagent (solid or liquid) as is, or it may be dissolved in an appropriate solvent and added. The fiber raw material is preferably converted into alkali cellulose in advance or simultaneously with the reaction. The method for converting into alkali cellulose is as described above.

[0111] The temperature during the reaction is, for example, preferably 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.

[0112] Compound E C The amount added per 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.

[0113] The reaction time may vary depending on the reaction temperature, but is preferably from 1 minute to 1,000 minutes, more preferably from 3 minutes to 500 minutes, and even more preferably from 5 minutes to 400 minutes. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed with water by filtration or the like.

[0114] <Cationic group introduction step (cationization step)> As an essential component, a compound having a reactive group and a cationic group (compound E D ), an optional alkaline compound, and a compound B selected from the aforementioned urea and its derivatives are added to a wet or dry fiber raw material having hydroxyl groups and reacted to introduce cationic groups into the fiber raw material.

[0115] Examples of the reactive group include a halogenated alkyl group, a vinyl group, and an epoxy group (glycidyl group). Examples of the cationic group include an ammonium group, a phosphonium group, a sulfonium group, etc. Among these, the cationic group is preferably an ammonium group. Compound E D As the alkyl group, glycidyl trimethyl ammonium chloride, 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, etc. are preferred from the viewpoints of the efficiency of introducing substituents, and therefore the defibration efficiency, cost, and ease of handling. Furthermore, it is also preferable to use the compound B in the above-mentioned <Phosphorus oxo acid group introduction step> as an optional component in the same manner. The amount added is also preferably as described above.

[0116] Compound E D When adding, it may be added to the fiber raw material as a reagent (solid or liquid) as is, or it may be dissolved in an appropriate solvent and added. The fiber raw material is preferably converted into alkali cellulose in advance or simultaneously with the reaction. The method for converting into alkali cellulose is as described above.

[0117] The temperature during the reaction is, for example, preferably 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.

[0118] Compound E D The amount added per 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.

[0119] The reaction time may vary depending on the reaction temperature, but is preferably from 1 minute to 1,000 minutes, more preferably from 10 minutes to 500 minutes, and even more preferably from 20 minutes to 400 minutes. After the reaction, excess reaction reagents, by-products, etc. may be washed and removed with water by filtration or the like.

[0120] <Cleaning process> In the method for producing fine fibrous cellulose according to the present embodiment, a washing step can be carried out on the ionic substituent-introduced fibers as needed. The washing step is carried out by washing the ionic substituent-introduced fibers with water or an organic solvent, for example. The washing step may be carried out after each step described below, and the number of washing steps carried out in each washing step is not particularly limited.

[0121] <Alkali treatment process> When producing fine fibrous cellulose, the fiber raw material may be subjected to an alkali treatment between the step of introducing an ionic substituent and the defibration treatment step described below. The alkali treatment method is not particularly limited, but examples thereof include a method of immersing the ionic substituent-introduced fiber in an alkali solution.

[0122] The alkaline compound contained in the alkaline solution is not particularly limited and may be an inorganic alkaline compound or an organic alkaline compound. In this embodiment, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkaline compound because of their high versatility. The solvent contained in the alkaline solution may be either water or an organic solvent. Among these, the solvent contained in the alkaline solution is preferably a polar solvent including water or a polar organic solvent such as an alcohol, and more preferably an aqueous solvent including at least water. As the alkaline solution, for example, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is preferable because of their high versatility.

[0123] The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably, for example, from 5°C to 80°C, and more preferably from 10°C to 60°C. The immersion time of the ionic substituent-introduced fiber in the alkaline solution in the alkaline treatment step is not particularly limited, but is, for example, preferably from 5 minutes to 30 minutes, and more preferably from 10 minutes to 20 minutes. The amount of alkaline solution used in the alkaline treatment is not particularly limited, but is, for example, preferably from 100% by mass to 100,000% by mass, and more preferably from 1,000% by mass to 10,000% by mass, based on the absolute dry mass of the ionic substituent-introduced fiber.

[0124] In order to reduce the amount of alkaline solution used in the alkali treatment step, the ionic substituent-introduced fiber may be washed with water or an organic solvent after the ionic substituent-introducing step and before the alkali treatment step. From the viewpoint of improving handleability, it is preferable to wash the alkali-treated ionic substituent-introduced fiber with water or an organic solvent after the alkali treatment step and before the defibrating step.

[0125] <Acid treatment process> When producing fine fibrous cellulose, the fiber raw material may be subjected to an acid treatment between the step of introducing an ionic substituent and the defibration treatment step described below. For example, the step of introducing an ionic substituent, the acid treatment, the alkali treatment, and the defibration treatment may be performed in this order.

[0126] The acid treatment method is not particularly limited, but examples include a method of immersing the fiber raw material in an acid-containing acid solution. The concentration of the acid solution used is not particularly limited, but is preferably 10% by mass or less, and more preferably 5% by mass or less. The pH of the acid solution used is also not particularly limited, but is preferably 0 to 4, and more preferably 1 to 3. Examples of the acid contained in the acid solution include inorganic acids, sulfonic acids, and carboxylic acids. Examples of inorganic acids include sulfuric acid, nitric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, and boric acid. Examples of sulfonic acids include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid. Examples of carboxylic acids include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, and tartaric acid. Among these, hydrochloric acid or sulfuric acid is particularly preferred.

[0127] The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably, for example, 5°C to 100°C, and more preferably, 20°C to 90°C. The immersion time in the acid solution in the acid treatment is not particularly limited, but is, for example, preferably, 5 minutes to 120 minutes, and more preferably, 10 minutes to 60 minutes. The amount of the acid solution used in the acid treatment is not particularly limited, but is, for example, preferably, 100 mass% to 100,000 mass%, and more preferably, 1,000 mass% to 10,000 mass%, based on the absolute dry mass of the fiber raw material.

[0128] <Defibrillation processing> The ionic substituent-introduced fibers are defibrated in a defibration treatment step to obtain fine fibrous cellulose. In the defibration treatment step, for example, a defibration treatment device can be used. The defibration treatment device is not particularly limited, but examples that can be used include a high-speed defibrator, a grinder (stone mill), a high-pressure homogenizer, an ultra-high-pressure homogenizer, a high-pressure collision grinder, a ball mill, a bead mill, a disk 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 defibration treatment devices, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, or an ultra-high-pressure homogenizer, which are less affected by the grinding media and have less risk of contamination.

[0129] In the defibration process, for example, the ionic substituent-introduced fibers are preferably diluted with a dispersion medium to form a slurry. The dispersion medium can be one or more selected from water and organic solvents such as polar organic solvents. The polar organic solvent is not particularly limited, but examples thereof include alcohols, polyhydric alcohols, ketones, ethers, esters, and aprotic polar solvents. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutyl alcohol. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, and glycerin. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, and propylene glycol monomethyl ether. Examples of esters include ethyl acetate and butyl acetate. Examples of aprotic polar solvents include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), and N-methyl-2-pyrrolidinone (NMP).

[0130] The solid content concentration of the fine fibrous cellulose during the defibration treatment can be appropriately set. The slurry obtained by dispersing the ionic substituent-introduced fibers in a dispersion medium may contain solids other than the ionic substituent-introduced fibers, such as urea having hydrogen bonding properties.

[0131] (optional ingredient) The fibrous cellulose-containing material of this embodiment may contain optional components other than those described above. Examples of optional components include hydrophilic polymers, thermoplastic resins, thermosetting resins, photocurable resins, cement, inorganic particles, inorganic powders, organic powders, antifoaming agents, lubricants, UV absorbers, dyes, pigments, stabilizers, surfactants, pH adjusters, etc. Organic ions may also be added as optional components.

[0132] The inorganic powder can be appropriately selected from inorganic powders used in fertilizers, soil conditioners, and snow-melting agents. The inorganic powder is a component other than the inorganic acid salts described above, and examples of the inorganic powder include calcium carbonate nitrogen, superphosphate, heavy calcium phosphate, fused phosphate fertilizer, calcined phosphate fertilizer, quicklime, slaked lime, calcium carbonate nitrogen, perlite, vermiculite, zeolite, bentonite, calcium chloride, sodium chloride, magnesium chloride, carbon black, and kaolin. Examples of the inorganic powder include water-insoluble inorganic acid salts such as calcium carbonate, dibasic calcium phosphate (calcium hydrogen phosphate and its dihydrate), tribasic calcium phosphate (calcium phosphate), and calcium sulfate.

[0133] The organic powder can be appropriately selected from organic powders used in foods, cosmetics, pharmaceuticals, and fertilizers. The organic powder is a component other than the organic acid salts described above, and examples of the organic powder include microcrystalline cellulose, powdered cellulose, dextrates, dextrin, glucose additives, fructose, lactitol, anhydrous lactose, lactose, maltitol, maltodextrin, maltose, mannitol, sorbitol, starch, corn starch, potato starch, pregelatinized starch, modified pregelatinized starch, tapioca starch, wheat starch, refined white sugar, and compressible sugar.

[0134] Examples of hydrophilic polymers include polyethylene glycol, cellulose derivatives (hydroxyethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, etc.), casein, dextrin, starch, modified starch, polyvinyl alcohol, modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol, etc.), polyethylene oxide, polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylates, polyacrylamide, acrylic acid alkyl ester copolymers, and urethane copolymers.

[0135] In the past, the use of a hydrophilic polymer in combination has been considered to improve salt tolerance. However, in highly viscous fibrous cellulose-containing materials, mixing with a hydrophilic polymer is difficult, and handling may be impaired. However, in this embodiment, salt tolerance can be improved by mixing a predetermined amount of fine fibrous cellulose with at least one selected from organic acid salts and inorganic acid salts, thereby eliminating the need to add a hydrophilic polymer for the purpose of improving salt tolerance. As a result, handling can be improved when obtaining a fibrous cellulose-containing material. That is, in one embodiment, the fibrous cellulose-containing material is substantially free of a hydrophilic polymer.

[0136] Examples of thermoplastic resins include styrene-based resins, acrylic-based resins, aromatic polycarbonate-based resins, aliphatic polycarbonate-based resins, aromatic polyester-based resins, aliphatic polyester-based resins, aliphatic polyolefin-based resins, cyclic olefin-based resins, polyamide-based resins, polyphenylene ether-based resins, thermoplastic polyimide-based resins, polyacetal-based resins, polysulfone-based resins, amorphous fluorine-based resins, etc. The thermoplastic resin may be a thermoplastic resin emulsion.

[0137] (Method of producing fibrous cellulose-containing material) A method for producing a fibrous cellulose-containing material includes a step of mixing a dispersion containing fibrous cellulose having a fiber width of 1000 nm or less with at least one selected from organic acid salts and inorganic acid salts. In the mixing step, the amount of the at least one selected from organic acid salts and inorganic acid salts is 1 to 1000 parts by mass per 100 parts by mass of the fibrous cellulose. The amount of the at least one selected from organic acid salts and inorganic acid salts added is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more per 100 parts by mass of the fibrous cellulose. Furthermore, the amount of the at least one selected from organic acid salts and inorganic acid salts added is preferably 900 parts by mass or less, more preferably 800 parts by mass or less, even more preferably 700 parts by mass or less, even more preferably 600 parts by mass or less, even more preferably 300 parts by mass or less, and particularly preferably 50 parts by mass or less per 100 parts by mass of the fine fibrous cellulose.

[0138] In this embodiment, at least one selected from organic acid salts and inorganic acid salts is mixed with the fine fibrous cellulose dispersion after defibration treatment. In this embodiment, by mixing the fine fibrous cellulose dispersion after defibration treatment with at least one selected from organic acid salts and inorganic acid salts in this manner, the dispersion stability of the fine fibrous cellulose can be more effectively improved.

[0139] When producing a fibrous cellulose-containing material, it is preferable to prepare a fine fibrous cellulose dispersion to a concentration of 0.4 to 0.7% by mass, and then add, in small amounts with stirring, an organic acid salt solution or an inorganic acid salt solution prepared to a concentration of 0.7 to 3% by mass.

[0140] (Application) The fibrous cellulose-containing material of the present invention is not limited in its use, but can be used for various purposes as a thickener, dispersant, or reinforcing agent. That is, the present invention may be a thickener containing the above-mentioned fibrous cellulose-containing material, a dispersant containing the above-mentioned fibrous cellulose-containing material, or a reinforcing agent containing the above-mentioned fibrous cellulose-containing material. A dispersant containing a fibrous cellulose-containing material can uniformly disperse components such as fine particles and cement in a dispersion. Furthermore, a reinforcing agent containing a fibrous cellulose-containing material can reinforce granules, cement particles, resin molded bodies, etc.

[0141] The fibrous cellulose-containing material can also be used as a reinforcing agent for a coating film made of a resin derived from at least one selected from an aqueous resin emulsion and an aqueous resin dispersion. In this case, examples of the resin constituting the coating film include urethane resin, acrylic resin, polyolefin resin, polyester resin, epoxy resin, and polystyrene resin.

[0142] Furthermore, the fibrous cellulose-containing material of the present invention can be used for various purposes such as for external use on the skin, for cement dispersants, or for granulation promoters. That is, the present invention may be an external use on the skin containing the above-mentioned fibrous cellulose-containing material, a cement composition containing the above-mentioned fibrous cellulose-containing material, or a granule containing the above-mentioned fibrous cellulose-containing material.

[0143] The topical skin preparation contains, in addition to the fibrous cellulose-containing material, various ingredients generally contained in topical skin preparations. The topical skin preparation containing the above-mentioned fibrous cellulose-containing material may be a cosmetic. The cosmetic preferably contains, in addition to the fibrous cellulose-containing material, a water-soluble polymer, an inorganic powder (excluding the above-mentioned inorganic acid salts), an organic powder (excluding the above-mentioned organic acid salts), an anionic surfactant, etc. By including fine fibrous cellulose in the topical skin preparation, the dispersibility of other ingredients can be improved, and a topical skin preparation with excellent usability can be obtained.

[0144] The cement composition contains cement particles in addition to the fibrous cellulose content. In the cement composition, the fine fibrous cellulose can enhance the dispersibility of the cement particles. This allows the formation of cement with excellent strength. The cement composition may be in a liquid or solid form.

[0145] The granulated material contains, in addition to the fibrous cellulose-containing material, at least one powder selected from the group consisting of inorganic powders and organic powders (excluding the inorganic acid salts and organic acid salts described above). The at least one powder selected from the group consisting of inorganic powders and organic powders is a water-insoluble powder. In this specification, a granulated material refers to a powder molding obtained by processing a powder raw material consisting of a single or multiple components into larger particles than the raw material using a binder or the like. In the granulated material, the fine fibrous cellulose acts as a binder and can improve the dispersibility of the powder raw material. This allows for the production of a granulated material with excellent particle hardness. Furthermore, the inclusion of fine fibrous cellulose in the granulated material can also improve its disintegrability in water. Thus, the granulated material obtained in this embodiment has high particle hardness and disintegrability in water, making it suitable for various applications such as food, cosmetics, pharmaceuticals, fertilizers, soil conditioners, and snow-melting agents. [Example]

[0146] The features of the present invention will be explained in more detail below with reference to examples and comparative examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate 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.

[0147] <Production Example 1> (Phosphated pulp production) The raw pulp used was softwood kraft pulp (solid content 93% by mass, basis weight 208 g / m) manufactured by Oji Paper. 2A sheet-like pulp (with a Canadian Standard Freeness (CSF) of 700 mL when disintegrated and measured in accordance with JIS P 8121:2012) was used. This raw pulp was subjected to a phosphorus oxo-oxidation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea was added to 100 parts by mass (bone dry mass) of the raw pulp to prepare a mixture of 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water, thereby obtaining a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165°C for 200 seconds to introduce phosphate groups into the cellulose in the pulp, thereby obtaining a phosphorylated pulp.

[0148] The resulting phosphorylated pulp was then washed. 100 g (bone dry mass) of phosphorylated pulp was mixed with 10 L of ion-exchanged water to obtain a pulp dispersion. The pulp was stirred to uniformly disperse the pulp, and then repeatedly filtered and dehydrated. The washing was completed when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0149] Next, the washed phosphorylated pulp was subjected to an alkali treatment (neutralization treatment) as follows: First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and then a 1 N aqueous solution of sodium hydroxide was added little by little while stirring to obtain a phosphorylated pulp slurry with a pH of 12 to 13. Next, the phosphorylated pulp slurry was dehydrated to obtain phosphorylated pulp that had been subjected to an alkali treatment (neutralization treatment).

[0150] Next, the neutralized phosphorylated pulp was subjected to the above-mentioned washing treatment. The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. -1 The absorption due to the P=O of the phosphate group was observed around the 2θ=14° to 17° and the 2θ=22° to 23° angle, confirming that the pulp had phosphate groups. The phosphorylated pulp was analyzed using an X-ray diffractometer, and typical peaks were observed at two positions, around 2θ=14° to 17° and 2θ=22° to 23°, confirming the presence of cellulose type I crystals.

[0151] (Defibrillation processing) Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry with a solid content of 2% by mass. This slurry was treated four times at a pressure of 200 MPa in a wet pulverization device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion (A) containing fine fibrous cellulose.

[0152] X-ray diffraction confirmed that this fine fibrous cellulose maintained cellulose type I crystal structure. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm. The amount of phosphate groups (amount of first dissociated acid) measured by the method for measuring the amount of phosphorus oxoacid groups described below was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0153] <Production Example 2> (Phosphitic pulp production) A phosphite pulp was obtained by the same procedure as in Production Example 1, except that 33 parts by mass of phosphorous acid (phosphonic acid) was used instead of ammonium dihydrogen phosphate.

[0154] The infrared absorption spectrum of the obtained phosphorous pulp was measured using FT-IR. -1 The absorption due to P=O of the phosphonic acid group, which is a tautomer of the phosphorous acid group, was observed near the α-axis, confirming that the phosphorous acid group (phosphonic acid group) had been added to the pulp. Furthermore, when the obtained phosphorous-oxidized pulp was analyzed using an X-ray diffractometer, typical peaks were observed at two positions, around 2θ=14° to 17° and around 2θ=22° to 23°, confirming the presence of cellulose type I crystals.

[0155] (Defibrillation processing) Ion-exchanged water was added to the obtained phosphite pulp to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated four times at a pressure of 200 MPa using a wet pulverizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion (B) containing fine fibrous cellulose. X-ray diffraction confirmed that the fine fibrous cellulose maintained cellulose type I crystal structure. The fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm. The amount of phosphite groups (amount of first dissociated acid) measured by the method for measuring the amount of phosphorus oxo acid groups described below was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

[0156] <Production Example 3> (TEMPO oxidized pulp manufacturing) Softwood kraft pulp (undried) manufactured by Oji Paper Co., Ltd. was used as the raw material pulp. This raw material pulp was subjected to an alkaline TEMPO oxidation treatment as follows: First, 100 parts by weight of the raw material pulp (dry mass equivalent), 1.6 parts by weight of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), and 10 parts by weight of sodium bromide were dispersed in 10,000 parts by weight of water. Next, a 13% by weight aqueous solution of sodium hypochlorite was added to 1.0 g of pulp to achieve a concentration of 3.8 mmol to initiate the reaction. During the reaction, a 0.5 M aqueous solution of sodium hydroxide was added dropwise to maintain the pH at 10 to 10.5. The reaction was considered complete when no further change in pH was observed.

[0157] The resulting TEMPO-oxidized pulp was then washed. The pulp slurry after TEMPO oxidation was dehydrated to obtain a dehydrated sheet, to which 5,000 parts by mass of ion-exchanged water was added, and the sheet was stirred to uniformly disperse the pulp. This process was repeated until the electrical conductivity of the filtrate reached 100 μS / cm or less, marking the end of the washing process.

[0158] The obtained TEMPO-oxidized pulp was analyzed using an X-ray diffractometer. Typical peaks were observed at two positions, around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0159] (Defibrillation processing) Ion-exchanged water was added to the obtained TEMPO-oxidized pulp to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated four times at a pressure of 200 MPa using a wet pulverizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion (C) containing fine fibrous cellulose. X-ray diffraction confirmed that the fine fibrous cellulose maintained cellulose type I crystals. The fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm. The carboxyl group content measured by the carboxyl group content measurement method described below was 1.30 mmol / g.

[0160] <Production Example 4> (Production of sulfur oxy-oxidized pulp) The raw pulp used was softwood kraft pulp (solid content 93% by mass, basis weight 245 g / m) manufactured by Oji Paper. 2 A sheet-like pulp (with a Canadian Standard Freeness (CSF) of 700 ml when disintegrated and measured in accordance with JIS P 8121) was used. This raw pulp was subjected to sulfur oxo-oxidation treatment as follows. First, a mixed aqueous solution of amidosulfuric acid and urea was added to 100 parts by mass (bone dry mass) of the raw pulp to prepare a mixture of 38 parts by mass of amidosulfuric acid, 120 parts by mass of urea, and 150 parts by mass of water, thereby obtaining a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165°C for 19 minutes to introduce sulfate groups into the cellulose in the pulp, thereby obtaining a sulfur oxo-oxidized pulp.

[0161] The resulting sulfur oxidized pulp was then washed. 100 g (bone dry mass) of sulfur oxidized pulp was mixed with 10 L of ion-exchanged water to obtain a pulp dispersion. The pulp was stirred to uniformly disperse the pulp, and then repeatedly filtered and dehydrated. The washing was completed when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0162] The washed sulfur oxo-oxidized pulp was then neutralized as follows: First, the washed sulfur oxo-oxidized pulp was diluted with 10 L of ion-exchanged water, and then a 1 N aqueous sodium hydroxide solution was added little by little while stirring to obtain a sulfur oxo-oxidized pulp slurry with a pH of 12 to 13. The sulfur oxo-oxidized pulp slurry was then dewatered to obtain a neutralized sulfur oxo-oxidized pulp. The neutralized sulfur oxo-oxidized pulp was then washed as described above to obtain a sulfur oxo-oxidized pulp (neutralized once).

[0163] The obtained sulfur oxo-oxidized pulp was subjected to the above neutralization treatment and washing treatment four more times to obtain sulfur oxo-oxidized pulp (neutralized five times).

[0164] (Defibrillation processing) The resulting sulfur-oxidized pulp (neutralized five times) was mixed with ion-exchanged water and stirred to form a slurry with a solids concentration of 0.5% by mass. This slurry was defibrated for 30 minutes at 21,500 rpm using a high-speed rotary defibrator (Clearmix 2.2S, manufactured by M-Technique Co., Ltd.), yielding a fine fibrous cellulose dispersion (D) with a fiber width of 3-5 nm. The sulfur oxoacid group content, as measured by the sulfonic acid group content measurement method described below, was 1.12 mmol / g.

[0165] <Production Example 5> (Hypochlorite pulp production) A sheet (solids concentration 90% by mass) made from softwood bleached kraft pulp (NBKP) was mixed in a hand mixer (Lab Millser PLUS, manufactured by Osaka Chemical Co., Ltd.) at 20,000 rpm for 15 seconds to produce a fluffy fluffed pulp (solids concentration 90% by mass). Sodium hypochlorite pentahydrate was then added to ion-exchanged water to prepare an aqueous solution with a sodium hypochlorite solids concentration of 22% by mass. 9,000 parts by mass of a 22% sodium hypochlorite aqueous solution was added to 100 parts by mass of the fluffy fluffed pulp, and the mixture was reacted for 2 hours in a warm bath at 30°C to obtain carboxylated pulp. During the reaction, the pH was maintained at 11 by adding 1N aqueous sodium hydroxide solution as needed.

[0166] The resulting carboxylated pulp was then washed. The washing process involved pouring ion-exchanged water over the resulting carboxylated pulp to obtain a pulp dispersion, which was then stirred to uniformly disperse the pulp, followed by filtration and dehydration. The washing was completed when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0167] In addition, the obtained carboxyl-introduced pulp was analyzed using an X-ray diffraction device, and typical peaks were confirmed at two positions, around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0168] (Defibrillation processing) Ion-exchanged water was added to the obtained carboxyl-introduced pulp to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated four times at a pressure of 200 MPa in a wet pulverization device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion (E) containing fine fibrous cellulose.

[0169] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained cellulose type I crystals. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm. The amount of carboxyl groups measured using the carboxyl group measurement method described below was 0.70 mmol / g.

[0170] <Production Example 6> (Production of maleated pulp) A sheet (solids concentration 90% by mass) made from bleached softwood kraft pulp (NBKP) was mixed for 15 seconds at 20,000 rpm using a hand mixer (Lab Millser PLUS, manufactured by Osaka Chemical Co., Ltd.) to produce a fluffy fluffing pulp (solids concentration 90% by mass). 100 parts by mass of the fluffy fluffing pulp and 50 parts by mass of maleic anhydride were placed in an autoclave and mixed at 150°C for 2 hours to obtain a carboxyl-introduced pulp.

[0171] The resulting carboxylated pulp was then washed. The washing process involved pouring ion-exchanged water over the resulting carboxylated pulp to obtain a pulp dispersion, which was then stirred to uniformly disperse the pulp, followed by filtration and dehydration. The washing was completed when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0172] The infrared absorption spectrum of the obtained carboxyl-introduced pulp was measured using FT-IR. -1 The absorption due to carboxyl groups was observed around 2θ = 14° to 17° and 2θ = 22° to 23°, confirming that the pulp had been maleated. Furthermore, when the carboxyl-group-introduced pulp was analyzed using an X-ray diffractometer, typical peaks were observed at two positions, around 2θ = 14° to 17° and 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0173] (Defibrillation processing) Ion-exchanged water was added to the obtained carboxyl-introduced pulp to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated four times at a pressure of 200 MPa in a wet pulverization device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion (F) containing fine fibrous cellulose.

[0174] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained cellulose type I crystals. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm. The amount of carboxyl groups measured using the carboxyl group measurement method described below was 1.22 mmol / g.

[0175] <Production Example 7> (Production of carboxymethylated pulp) The raw pulp used was softwood kraft pulp (solid content 93% by mass, basis weight 245 g / m) manufactured by Oji Paper Co., Ltd. 2 A sheet-like product with a Canadian Standard Freeness (CSF) of 700 ml when disintegrated and measured in accordance with JIS P 8121-2:2012 was used.

[0176] To 100 parts by mass (bone dry mass) of this raw pulp, a chemical solution consisting of 83 parts by mass of 12N NaOH aqueous solution, 175 parts by mass of sodium monochloroacetate, and 313 parts by mass of ion-exchanged water (total 571 parts by mass) was added to obtain a chemical-impregnated pulp. The obtained chemical-impregnated pulp was then heated in a water bath at 95°C for 60 minutes to introduce carboxymethyl groups (carboxy groups) into the cellulose in the pulp, thereby obtaining a carboxy-introduced pulp.

[0177] The resulting carboxylated pulp was then washed. The washing process involved pouring ion-exchanged water over the resulting carboxylated pulp to obtain a pulp dispersion, which was then stirred to uniformly disperse the pulp, followed by filtration and dehydration. The washing was completed when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0178] In addition, when the carboxyl-group-introduced pulp was analyzed using an X-ray diffractometer, typical peaks were confirmed at two positions, around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0179] (Defibrillation processing) Ion-exchanged water was added to the obtained carboxyl-introduced pulp to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated four times at a pressure of 200 MPa in a wet pulverization device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion (G) containing fine fibrous cellulose.

[0180] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained cellulose type I crystals. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm. The amount of carboxyl groups in the obtained fine fibrous cellulose, as measured by the method described below, was 1.21 mmol / g.

[0181] <Production Example 8> (Production of carboxyethylated pulp) The raw pulp used was softwood kraft pulp (solid content 93% by mass, basis weight 245 g / m) manufactured by Oji Paper Co., Ltd. 2 A sheet-like product with a Canadian Standard Freeness (CSF) of 700 ml when disintegrated and measured in accordance with JIS P 8121-2:2012 was used.

[0182] To 100 parts by mass (bone dry mass) of this raw pulp, a chemical solution consisting of 250 parts by mass of 12N NaOH aqueous solution, 163 parts by mass of 2-chloropropionic acid, and 140 parts by mass of ion-exchanged water (total 553 parts by mass) was added to obtain a chemical-impregnated pulp. The obtained chemical-impregnated pulp was then heated in a hot air dryer at 165°C for 10 minutes to introduce carboxyethyl groups (carboxy groups) into the cellulose in the pulp, thereby obtaining a carboxy-introduced pulp.

[0183] The resulting carboxylated pulp was then washed. The washing process involved pouring ion-exchanged water over the resulting carboxylated pulp to obtain a pulp dispersion, which was then stirred to uniformly disperse the pulp, followed by filtration and dehydration. The washing was completed when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0184] Next, the washed carboxylated pulp was neutralized as follows: First, the washed carboxylated pulp was diluted with 10 L of ion-exchanged water, and then a 1 N aqueous sodium hydroxide solution was added little by little while stirring to obtain a carboxylated pulp slurry with a pH of 12 to 13. Next, the carboxylated pulp slurry was dehydrated and washed to obtain a neutralized carboxylated pulp.

[0185] In addition, when the carboxyl-group-introduced pulp was analyzed using an X-ray diffractometer, typical peaks were confirmed at two positions, around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0186] (Defibrillation processing) Ion-exchanged water was added to the obtained carboxyl-introduced pulp to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated four times at a pressure of 200 MPa in a wet pulverization device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion (H) containing fine fibrous cellulose.

[0187] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained cellulose type I crystals. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3 to 5 nm. The amount of carboxyl groups measured using the carboxyl group measurement method described below was 1.41 mmol / g.

[0188] <Production Example 9> (Production of sulfoethylated pulp) The raw pulp used was softwood kraft pulp (solid content 93% by mass, basis weight 245 g / m) manufactured by Oji Paper Co., Ltd. 2 A sheet-like product with a Canadian Standard Freeness (CSF) of 700 ml when disintegrated and measured in accordance with JIS P 8121-2:2012 was used.

[0189] To 100 parts by mass (bone dry mass) of this raw pulp, a chemical solution consisting of 180 parts by mass of a 2N NaOH aqueous solution and 780 parts by mass of a 25% by mass sodium vinyl sulfonate aqueous solution (total 960 parts by mass) was added to obtain a chemical solution-impregnated pulp. The obtained chemical solution-impregnated pulp was then heated in a hot air dryer at 165°C for 16 minutes to introduce sulfoethyl groups (sulfonic groups) into the cellulose in the pulp, yielding a sulfoethyl group-introduced pulp (sulfonic group-introduced pulp).

[0190] The resulting sulfoethyl group-introduced pulp was then washed. The washing process involved pouring ion-exchanged water over the resulting sulfoethyl group-introduced pulp to obtain a pulp dispersion, which was then stirred to uniformly disperse the pulp, followed by filtration and dehydration. The washing was completed when the electrical conductivity of the filtrate reached 100 μS / cm or less.

[0191] In addition, when sulfoethyl group-introduced pulp was tested and analyzed using an X-ray diffractometer, typical peaks were confirmed at two positions, around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0192] (Defibrillation processing) Ion-exchanged water was added to the obtained sulfoethyl group-introduced pulp to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated four times at a pressure of 200 MPa in a wet pulverization device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion (I) containing fine fibrous cellulose.

[0193] X-ray diffraction confirmed that the obtained fine fibrous cellulose maintained cellulose type I crystallinity. Furthermore, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope and found to be 3-5 nm. The sulfoethyl group content (sulfonic acid content), as measured by the method for measuring sulfur oxoacid and sulfonic acid content described below, was 1.48 mmol / g.

[0194] <Measurement> (Measurement of phosphorus oxoacid group content) The amount of phosphorus oxo acid groups in the fine fibrous cellulose (equivalent to the amount of phosphorus oxo acid groups in the phosphorus oxo-oxidized pulp) was measured by adding ion-exchanged water to a fine fibrous cellulose dispersion containing the target fine fibrous cellulose to adjust the content to 0.2 mass%, treating the dispersion with ion-exchange resin, and then titrating it with alkali. Treatment with ion exchange resin was carried out by adding 1 / 10 by volume of a strongly acidic ion exchange resin (Amberjet 1024; manufactured by Organo Corporation, conditioned) to the above-mentioned fine fibrous cellulose-containing slurry, shaking for 1 hour, and then pouring it onto a mesh with 90 μm openings to separate the resin from the slurry. In addition, alkali titration was performed by measuring the change in the pH of a slurry containing fine fibrous cellulose after ion exchange resin treatment while adding 10 μL of 0.1 N sodium hydroxide solution every 5 seconds. Nitrogen gas was bubbled through the slurry for 15 minutes before the start of the titration. In this neutralization titration, two maximum points of increment (the derivative of pH with respect to the amount of alkali added) were observed on the plot of pH versus the amount of alkali added. The first maximum point of increment after starting the alkali addition is called the first endpoint, and the second maximum point is called the second endpoint (Figure 1). The amount of alkali required from the start of the titration to the first endpoint is equal to the amount of first dissociated acid in the slurry used for titration. The amount of alkali required from the start of the titration to the second endpoint is equal to the total amount of dissociated acid in the slurry used for titration. The amount of alkali (mmol) required from the start of titration to the first endpoint divided by the solid content (g) in the titrated slurry was defined as the amount of phosphorus oxo acid group (first dissociated acid amount) (mmol / g). The amount of alkali (mmol) required from the start of titration to the second endpoint divided by the solid content (g) in the titrated slurry was defined as the total dissociated acid amount (mmol / g).

[0195] (Measurement of Carboxy Group Amount) The amount of carboxyl groups in the fine fibrous cellulose (equivalent to the amount of carboxyl groups in the TEMPO-oxidized pulp) was measured by adding ion-exchanged water to a fine fibrous cellulose dispersion containing the target fine fibrous cellulose to adjust the content to 0.2 mass%, treating the dispersion with ion-exchange resin, and then titrating it with alkali. Treatment with ion exchange resin was carried out by adding 1 / 10 by volume of a strongly acidic ion exchange resin (Amberjet 1024; manufactured by Organo Corporation, conditioned) to a 0.2% by mass slurry containing fine fibrous cellulose, shaking for 1 hour, and then pouring the mixture onto a mesh with 90 μm openings to separate the resin from the slurry. In addition, alkali titration was performed by measuring the change in the pH of the fibrous cellulose-containing slurry after treatment with an ion exchange resin while adding 0.1 N aqueous sodium hydroxide. Observing the change in pH while adding aqueous sodium hydroxide yielded a titration curve like the one shown in Figure 3. As shown in Figure 3, in this neutralization titration, a single point was observed where the increment (the differential value of pH with respect to the amount of alkali added) reached a maximum on the curve plotting the measured pH against the amount of alkali added. This maximum increment was called the first endpoint. The region from the start of the titration to the first endpoint in Figure 3 is called the first region. The amount of alkali required in the first region was equal to the amount of carboxyl groups in the slurry used for titration. The amount of alkali required in the first region of the titration curve (mmol) was then divided by the solids content (g) of the fine fibrous cellulose-containing slurry to be titrated to calculate the amount of carboxyl groups introduced (mmol / g). The amount of carboxyl groups introduced (mmol / g) is calculated based on the amount of carboxyl groups introduced (mmol / g) when the counter ions of the carboxyl groups are hydrogen ions (H + ) (hereinafter referred to as the amount of carboxy groups (acid type)) per 1 g of fibrous cellulose.

[0196] (Measurement of sulfur oxoacid and sulfonic acid groups) The amount of sulfur oxoacid or sulfonic acid groups in the fine fibrous cellulose was measured by subjecting freeze-dried and pulverized samples to pressure-heat decomposition with nitric acid in a sealed container, diluting appropriately, and measuring the amount of sulfur by ICP-OES. The value calculated by dividing by the bone-dry mass of the fine fibrous cellulose used was used as the amount of sulfur oxoacid or sulfonic acid groups (mmol / g) in the fine fibrous cellulose.

[0197] Example 1 (Preparation of disodium hydrogen phosphate aqueous solution) Disodium hydrogen phosphate (manufactured by Kanto Chemical Co., Inc.) was added to ion-exchanged water to a concentration of 7% by mass, and the mixture was stirred and dissolved. By the above procedure, an aqueous solution of disodium hydrogen phosphate was obtained. The pH of the obtained aqueous solution was 9.0.

[0198] (Preparation of material containing fine fibrous cellulose) The fine fibrous cellulose dispersion (A) and an aqueous solution of disodium hydrogen phosphate were mixed so that the disodium hydrogen phosphate content was 10 parts by mass per 100 parts by mass of the fine fibrous cellulose. Ion-exchanged water was added to adjust the concentration of the fine fibrous cellulose to 0.7% by mass.

[0199] <Example 2> In Example 1 (preparation of a material containing fine fibrous cellulose), a material containing fine fibrous cellulose was obtained in the same manner as in Example 1, except that the amount of disodium hydrogen phosphate aqueous solution added was changed so that the amount of disodium hydrogen phosphate blended was 25 parts by mass.

[0200] Example 3 In Example 1 (preparation of a material containing fine fibrous cellulose), a material containing fine fibrous cellulose was obtained in the same manner as in Example 1, except that the amount of disodium hydrogen phosphate aqueous solution added was changed so that the amount of disodium hydrogen phosphate blended was 100 parts by mass.

[0201] Example 4 In Example 1 (preparation of a material containing fine fibrous cellulose), a material containing fine fibrous cellulose was obtained in the same manner as in Example 1, except that the amount of disodium hydrogen phosphate aqueous solution added was changed so that the amount of disodium hydrogen phosphate blended was 200 parts by mass.

[0202] <Example 5> In Example 1 (preparation of a material containing fine fibrous cellulose), a material containing fine fibrous cellulose was obtained in the same manner as in Example 1, except that the amount of disodium hydrogen phosphate aqueous solution added was changed so that the amount of disodium hydrogen phosphate blended was 500 parts by mass.

[0203] Example 6 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 2, except that in Example 2, (Preparation of disodium hydrogen phosphate aqueous solution) was replaced with (Preparation of sodium bicarbonate) below, and in (Preparation of fine fibrous cellulose-containing material), sodium bicarbonate aqueous solution was used instead of disodium hydrogen phosphate aqueous solution.

[0204] (Preparation of aqueous sodium bicarbonate solution) Sodium hydrogen carbonate (manufactured by Kanto Chemical Co., Inc.) was added to ion-exchanged water to a concentration of 7% by mass, and the mixture was stirred and dissolved. An aqueous sodium hydrogen carbonate solution was obtained by the following procedure.

[0205] Example 7 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 2, except that in Example 2, (Preparation of disodium hydrogen phosphate aqueous solution) was replaced by (Preparation of sodium acetate) below, and in (Preparation of fine fibrous cellulose-containing material), sodium acetate aqueous solution was used instead of disodium hydrogen phosphate aqueous solution.

[0206] (Preparation of aqueous sodium acetate solution) Sodium acetate (manufactured by Kanto Chemical Co., Inc.) was added to ion-exchanged water to a concentration of 7% by mass, and the mixture was stirred and dissolved. An aqueous sodium acetate solution was obtained by the following procedure.

[0207] Example 8 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 2 (Preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (B) was used.

[0208] Example 9 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 6 (Preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (B) was used.

[0209] Example 10 A material containing fine fibrous cellulose was obtained in the same manner as in Example 2 (Preparation of a material containing fine fibrous cellulose), except that the fine fibrous cellulose dispersion (C) was used.

[0210] Example 11 A material containing fine fibrous cellulose was obtained in the same manner as in Example 6 (Preparation of a material containing fine fibrous cellulose), except that the fine fibrous cellulose dispersion (C) was used.

[0211] Example 12 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 2 (Preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (D) was used.

[0212] Example 13 A material containing fine fibrous cellulose was obtained in the same manner as in Example 6 (Preparation of a material containing fine fibrous cellulose), except that the fine fibrous cellulose dispersion (D) was used.

[0213] Example 14 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 2 (Preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (E) was used.

[0214] Example 15 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 6 (Preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (E) was used.

[0215] Example 16 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 2 (Preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (F) was used.

[0216] Example 17 A material containing fine fibrous cellulose was obtained in the same manner as in Example 6 (Preparation of a material containing fine fibrous cellulose), except that the fine fibrous cellulose dispersion (F) was used.

[0217] Example 18 A material containing fine fibrous cellulose was obtained in the same manner as in Example 2 (Preparation of a material containing fine fibrous cellulose), except that the fine fibrous cellulose dispersion (G) was used.

[0218] Example 19 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 6 (Preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (G) was used.

[0219] Example 20 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 2 (Preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (H) was used.

[0220] <Example 21> A fine fibrous cellulose-containing material was obtained in the same manner as in Example 6 (preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (H) was used.

[0221] <Example 22> A material containing fine fibrous cellulose was obtained in the same manner as in Example 2 (Preparation of a material containing fine fibrous cellulose), except that the fine fibrous cellulose dispersion (I) was used.

[0222] Example 23 A fine fibrous cellulose-containing material was obtained in the same manner as in Example 6 (Preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (I) was used.

[0223] <Comparative Example 1> A fine fibrous cellulose-containing material was obtained in the same manner as in Example 1 (preparation of a fine fibrous cellulose-containing material), except that the aqueous disodium hydrogen phosphate solution was not added.

[0224] <Comparative Example 2> A fine fibrous cellulose-containing material was obtained in the same manner as in Example 1 (preparation of a fine fibrous cellulose-containing material), except that the amount of disodium hydrogen phosphate added was changed to 1,500 parts by mass.

[0225] <Comparative Example 3> Instead of (Preparation of disodium hydrogen phosphate aqueous solution) in Example 2, the following (Preparation of calcium chloride aqueous solution) was carried out, and in (Preparation of fine fibrous cellulose-containing material), calcium chloride aqueous solution was used instead of disodium hydrogen phosphate aqueous solution, and the amount of calcium chloride aqueous solution added was changed so that the calcium chloride content was 25 mass parts.A fine fibrous cellulose-containing material was obtained in the same manner as in Example 2, except that

[0226] (Preparation of calcium chloride aqueous solution) Calcium chloride (manufactured by Kanto Chemical Co., Inc.) was added to ion-exchanged water to a concentration of 2% by mass, and the mixture was stirred and dissolved. By the above procedure, an aqueous calcium chloride solution was obtained.

[0227] <Comparative Example 4> A fine fibrous cellulose-containing material was obtained in the same manner as in Comparative Example 3 (preparation of a fine fibrous cellulose-containing material), except that the fine fibrous cellulose dispersion (B) was used.

[0228] <Evaluation method> (Viscosity measurement) The viscosity of the dispersion obtained by adding a 5% by mass aqueous sodium chloride solution to the total mass of the fine fibrous cellulose-containing material so that the sodium chloride concentration was 0% by mass and 0.5% by mass was measured. A Brookfield analog viscometer (T-LVT, manufactured by Brookfield) was used for the measurement. The measurement was performed at a rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of the measurement was taken as the viscosity of the dispersion. The dispersion to be measured was left to stand for 24 hours in an environment of 23°C and 50% relative humidity before measurement. The temperature of the dispersion during measurement was 23°C.

[0229] (Haze measurement) A 5% aqueous sodium chloride solution was added to the fine fibrous cellulose-containing material to give a sodium chloride concentration of 0.5% by mass. The resulting dispersion was then diluted with ion-exchanged water to give a fibrous cellulose solids concentration of 0.2% by mass, and the haze was measured. The sodium chloride concentration was 0.14% by mass. The measurement was performed using a haze meter (Murakami Color Research Laboratory, HM-150) and a glass liquid cell with a 1 cm optical path length (Fujiwara Manufacturing Co., Ltd., MG-40, reverse optical path) in accordance with JIS K 7136:2000. Zero-point measurement was performed using ion-exchanged water placed in the same glass cell. The dispersion to be measured was allowed to stand for 24 hours in an environment of 23°C and 50% relative humidity before measurement. The liquid temperature of the dispersion during measurement was 23°C.

[0230] (Evaluation of dispersion stability) A 5% by mass aqueous solution of sodium chloride was added to the fine fibrous cellulose-containing material so that the concentration of sodium chloride was 0.5% by mass, and the dispersion stability of the obtained dispersion was evaluated based on the following criteria. A: A decrease in the viscosity of the dispersion was observed depending on the salt concentration, but the fine fibrous cellulose remained uniformly dispersed. B: A decrease in the viscosity of the dispersion depending on the salt concentration was observed, and slight aggregates were observed in the dispersion. C: Aggregates of fine fibrous cellulose and gel lumps were generated in the dispersion, making it impossible to measure the viscosity of the dispersion after adding salt.

[0231] [Table 1]

[0232] [Table 2]

[0233] [Table 3]

[0234] [Table 4]

[0235] [Table 5]

[0236] <Result> The fine fibrous cellulose-containing material obtained in the examples had excellent dispersion stability.

[0237] Example 24 (Preparation of disodium hydrogen phosphate aqueous solution) Disodium hydrogen phosphate (manufactured by Kanto Chemical Co., Inc.) was added to ion-exchanged water to a concentration of 7% by mass, and the mixture was stirred to dissolve.

[0238] (Preparation of cement dispersant) The fine fibrous cellulose dispersion (A) and an aqueous solution of disodium hydrogen phosphate were mixed so that the content of disodium hydrogen phosphate was 25 parts by mass per 100 parts by mass of the fine fibrous cellulose, and ion-exchanged water was added to adjust the concentration of the fine fibrous cellulose to 1% by mass.

[0239] (Preparation of cement composition) Portland cement (manufactured by Taiheiyo Cement Corporation) was added to the cement dispersant so that the solid content concentration was 5 mass % to obtain a cement composition.

[0240] Example 25 A cement dispersant and a cement composition were obtained in the same manner as in Example 24, except that (Preparation of disodium hydrogen phosphate aqueous solution) and (Preparation of cement dispersant) in Example 24 were changed as follows.

[0241] (Preparation of Hydrotalcite Dispersion) Hydrotalcite (manufactured by Fujifilm Wako Chemical Co., Ltd.) was added to ion-exchanged water to a concentration of 10 mass %, and the mixture was stirred to disperse. By the above procedure, a hydrotalcite dispersion was obtained.

[0242] (Preparation of cement dispersant) The fine fibrous cellulose dispersion (A) and the hydrotalcite dispersion were mixed so that the hydrotalcite was 100 parts by mass per 100 parts by mass of the fine fibrous cellulose, to obtain a cement dispersant. Ion-exchanged water was added to adjust the fine fibrous cellulose concentration to 0.4% by mass.

[0243] Example 26 In Example 25, (Preparation of hydrotalcite dispersion) was replaced with (Preparation of bentonite dispersion) below, and in (Preparation of cement dispersant), a bentonite dispersion was used instead of the hydrotalcite dispersion. Except for this, a cement dispersant and a cement composition were obtained in the same manner as in Example 25.

[0244] (Preparation of Bentonite Dispersion) Bentonite (manufactured by Fujifilm Wako Chemical Co., Ltd.) was added to ion-exchanged water so as to have a concentration of 10 mass %, and the mixture was stirred and dispersed. A bentonite dispersant was obtained by the following procedure.

[0245] Example 27 A cement dispersant and a cement composition were obtained in the same manner as in Example 24 (Preparation of cement dispersant), except that the fine fibrous cellulose dispersion (B) was used.

[0246] <Comparative Example 5> A cement dispersant and a cement composition were obtained in the same manner as in Example 24 (preparation of cement dispersant), except that disodium hydrogen phosphate was not used.

[0247] <Evaluation method> (Viscosity measurement) The viscosity of the cement compositions obtained in the examples and comparative examples was measured. A B-type viscometer (analog viscometer T-LVT, manufactured by BLOOKFIELD) was used to measure the viscosity. The measurement conditions were a rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of measurement was taken as the viscosity of the cement composition. The measurement was also carried out immediately after mixing the cement.

[0248] (dispersion stability) The cement compositions obtained in the examples and comparative examples were dispensed into 50 mL screw tubes (manufactured by AS ONE Corporation) and allowed to stand for 24 hours. After standing, the inside of the screw tubes was visually observed, and the dispersion stability of the fine fibrous cellulose was evaluated based on the following criteria. A: Microfibrous cellulose does not aggregate in the cement composition, and cement particles are uniformly dispersed. B: Fine fibrous cellulose aggregates in the cement composition and forms aggregates with cement particles.

[0249] [Table 6]

[0250] <Result> In the examples, cement compositions in which fine fibrous cellulose was uniformly dispersed were obtained.

[0251] Example 28 (Preparation of disodium hydrogen phosphate aqueous solution) Disodium hydrogen phosphate (manufactured by Kanto Chemical Co., Inc.) was added to ion-exchanged water to a concentration of 7% by mass, and the mixture was stirred and dissolved. By the above procedure, an aqueous solution of disodium hydrogen phosphate was obtained.

[0252] (Preparation of Granulation Accelerator) The fine fibrous cellulose dispersion (A) and an aqueous solution of disodium hydrogen phosphate were mixed so that the disodium hydrogen phosphate content was 25 parts by mass per 100 parts by mass of the fine fibrous cellulose, and ion-exchanged water was added to adjust the concentration of the fine fibrous cellulose to 0.7% by mass to obtain a granulation promoter.

[0253] (Preparation of granulated material) 0.2 parts by mass of granulation accelerator was added to 100 parts by mass of lime powder (manufactured by Oji Wood Greening Co., Ltd.), and the mixture was granulated by rotating in a cement mixer for 2 minutes. The granules were dried in a hot air dryer at 100°C for 30 minutes. The resulting granules were sieved to obtain granules with particle sizes of 1 to 4 mm.

[0254] Example 29 In Example 28 (Preparation of Granulation Promoter), a granulated material was obtained in the same manner as in Example 28, except that the amount of disodium hydrogen phosphate aqueous solution added was changed so that the amount of disodium hydrogen phosphate blended was 50 parts by mass.

[0255] Example 30 In Example 28 (Preparation of Granulation Promoter), a granulated material was obtained in the same manner as in Example 28, except that the amount of disodium hydrogen phosphate aqueous solution added was changed so that the amount of disodium hydrogen phosphate blended was 100 parts by mass.

[0256] Example 31 Granules were obtained in the same manner as in Example 28 (Preparation of Granulation Accelerator), except that the fine fibrous cellulose dispersion (B) was used.

[0257] <Comparative Example 6> Granules were obtained in the same manner as in Example 28 (preparation of granulation promoter), except that the aqueous disodium hydrogen phosphate solution was not added.

[0258] <Evaluation method> (dispersion stability) Lime was added to the granulation accelerator so that the amount was 5% by mass, and the resulting dispersion was dispensed into 50 mL screw tubes (manufactured by AS ONE Corporation) and allowed to stand for 24 hours. After standing, the inside of the screw tubes was visually observed, and the dispersion stability of the fine fibrous cellulose was evaluated based on the following criteria. A: The fine fibrous cellulose is uniformly dispersed in the dispersion without agglomeration. B: Fine fibrous cellulose forms aggregates with lime in the dispersion.

[0259] (grain hardness) The hardness of 10 granules having a particle size of 1 to 4 mm obtained in the examples and comparative examples was measured using a Kiya hardness tester, and the average value was calculated. The particle hardness was then evaluated based on the following criteria. A: Grain hardness is 60g or more B: Grain hardness is 50g or more and less than 60g C: Grain hardness less than 50g

[0260] (Underwater disintegration) Twenty granules with a particle size of 3 mm or more obtained in the Examples and Comparative Examples were arranged on a 2000 μm sieve, placed in a container of an appropriate size, and water was poured over them until the granules were fully submerged. After leaving the container to stand overnight, the number of undisintegrated granules with a particle size of 1 mm or more remaining on the sieve was counted, and a disintegration rate of 80% or more was judged to be disintegratable.

[0261] [Table 7]

[0262] <Result> In the granulation accelerator obtained in the examples, fibrous cellulose showed excellent dispersion stability even in lime. Furthermore, the granules obtained by adding this granulation accelerator showed high particle hardness, and the granulation accelerator exerted an excellent reinforcing effect.

[0263] Example 32 (Preparation of Thickener) The fine fibrous cellulose dispersion (A) and an aqueous solution of disodium hydrogen phosphate were mixed so that the disodium hydrogen phosphate content was 25 parts by mass per 100 parts by mass of the fine fibrous cellulose, and ion-exchanged water was added to give a thickener for topical skin preparations.

[0264] (Preparation of topical skin preparations) The components of the aqueous phase listed in Table 5 were mixed uniformly. Separately, the oil phase was mixed uniformly while being heated to 80°C. The oil phase was added to the aqueous phase while stirring, and emulsified using a homomixer (5000 rpm, 5 minutes). A topical skin preparation was obtained by the above procedure.

[0265] Example 33 An external skin preparation was obtained in the same manner as in Example 32, except that in Example 25 (preparation of thickener), the fine fibrous cellulose dispersion (B) was used.

[0266] <Comparative Example 7> An external skin preparation was obtained in the same manner as in Example 32, except that disodium hydrogen phosphate was not added.

[0267] <Evaluation> (dispersion stability) The prepared skin topical preparations were left to stand at 45°C for one month, and the dispersion stability of the fine fibrous cellulose was evaluated based on the following criteria. A: No separation of oil or water or aggregation of fine fibrous cellulose is observed, and the formulation is glossy. B: No separation of oil or water is observed, but fine fibrous cellulose is aggregated.

[0268] (Rough feeling when applied) When the external skin preparations prepared in the Examples and Comparative Examples were applied to the back of the hand and spread, if a rough feeling was observed, it was judged as having a rough feeling.

[0269] [Table 8]

[0270] <Result> In the topical skin preparations obtained in the Examples, the fibrous cellulose was uniformly dispersed without aggregation, and the roughness of the topical skin preparations obtained in the Examples was suppressed.

Claims

1. The present invention comprises fibrous cellulose having a fiber width of 1000 nm or less and at least one selected from an organic acid salt and an inorganic acid salt, The fibrous cellulose has anionic groups, the at least one selected from the organic acid salts and the inorganic acid salts is at least one selected from the group consisting of sodium hydrogen carbonate, disodium hydrogen phosphate, and sodium acetate; The fibrous cellulose-containing material has a content of 5 to 1,000 parts by mass of at least one selected from the group consisting of organic acid salts and inorganic acid salts relative to 100 parts by mass of the fibrous cellulose.

2. The fibrous cellulose-containing material according to claim 1, wherein the anionic group is a phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group.

3. The fibrous cellulose-containing material according to claim 1 or 2, wherein the fibrous cellulose-containing material is a slurry having a pH of 6.0 or higher.

4. The fibrous cellulose-containing material according to any one of claims 1 to 3, wherein the fibrous cellulose-containing material is a slurry having a haze of 2.0% or less.

5. The fibrous cellulose-containing material according to any one of claims 1 to 4, which is used for an external preparation for skin, a cement dispersant, or a granulation promoter.

6. A thickener comprising the fibrous cellulose-containing material according to any one of claims 1 to 5.

7. A dispersant comprising the fibrous cellulose-containing material according to any one of claims 1 to 5.

8. A reinforcing agent comprising the fibrous cellulose-containing material according to any one of claims 1 to 5.

9. A skin external preparation comprising the fibrous cellulose-containing material according to any one of claims 1 to 5.

10. A cement composition comprising the fibrous cellulose-containing material according to any one of claims 1 to 5.

11. A granulated product comprising the fibrous cellulose-containing material according to any one of claims 1 to 5.

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