Fibrous cellulose, fibrous cellulose dispersion, and method for producing fibrous cellulose

Abstract

To provide a fine fibrous cellulose capable of exhibiting excellent dispersion stability and excellent application aptitude when added to the coating material.SOLUTION: According to the present invention, fine fibrous cellulose having a fiber width of 1000 nm or less and an ionic substituent is provided in which: ionic substituent amount in the fibrous cellulose is 0.10 mmol / g or more and 1.50 mmol / g or less; the degree of polymerization of the fibrous cellulose is 150 or more and 515 or less; fluid dispersion obtained by dispersing the fibrous cellulose in a dispersion solvent including water and isopropanol has a mass ratio of water and isopropanol of 7:3, and has a viscosity at 23°C of 2500 mPa s; and when the fluid dispersion is stirred under the predetermined stirring condition, the viscosity change rate calculated by the following formula is within ±50%. Viscosity change rate (%)=(viscosity after being stirred-viscosity before being stirred) / viscosity before being stirred×100.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to fibrous cellulose, a fibrous cellulose dispersion, and a method for producing fibrous cellulose. [Background technology]

[0002] Cellulose fibers have traditionally been widely used in clothing, absorbent articles, paper products, etc. In addition to fibrous cellulose with a fiber diameter of 10 μm to 50 μm, fine fibrous cellulose with a fiber diameter of 1 μm or less is also known. Fine fibrous cellulose has attracted attention as a new material and has a wide range of applications.

[0003] Fine fibrous cellulose is sometimes used, for example, as an additive for paints. In this case, the fine fibrous cellulose can function as a viscosity modifier in the paint. For example, Patent Document 1 discloses a bright pigment dispersion containing water, a viscosity modifier (A), and a scaly bright pigment (B). Patent Document 2 discloses a bright pigment dispersion containing water, a scaly aluminum pigment, and a cellulose-based viscosity modifier. Patent Documents 1 and 2 discuss the use of cellulose nanofibers as a viscosity modifier. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 012014 [Patent Document 2] International Publication No. 2017 / 175468 Summary of the Invention [Problem to be solved by the invention]

[0005] Cellulose nanofibers have traditionally been used in paints to improve the dispersibility of pigments and other particles. However, no attention has been paid to the problem of reduced coatability due to viscosity changes (thixotropy) caused by shearing the paint before coating, leaving room for improvement in coatability.

[0006] Therefore, in order to solve the problems of the conventional art, the present inventors have conducted studies with the aim of providing a fine fibrous cellulose that can exhibit excellent dispersibility stability and excellent coating suitability when added to a coating material. [Means for solving the problem]

[0007] As a result of intensive research to solve the above problems, the present inventors have found that by dispersing a specified fine fibrous cellulose in water to form a dispersion and stirring the dispersion under specified conditions, fine fibrous cellulose can be obtained that has a viscosity change rate (%) before and after stirring within a specified range, and by adding this fine fibrous cellulose to a paint, it is possible to improve the coatability of the paint while maintaining excellent dispersibility stability. Specifically, the present invention has the following configuration.

[0008] [1] Fibrous cellulose having a fiber width of 1000 nm or less and having an ionic substituent, The amount of ionic substituents in fibrous cellulose is 0.10 mmol / g or more. 0.95 mmol / g or less, The degree of polymerization of the fibrous cellulose is 150 or more and 515 or less, Fibrous cellulose is dissolved in water and isopropanol. Consists of Fibrous cellulose that is dispersed in a dispersion solvent to form a dispersion liquid having a mass ratio of water to isopropanol of 7:3 and a viscosity of 2500 mPa·s at 23°C, and that, when stirred under the following stirring conditions, exhibits a viscosity change rate calculated by the following formula within ±50%; Viscosity change rate (%) = (viscosity after stirring - viscosity before stirring) / viscosity before stirring × 100 (Mixing conditions) A dispersion liquid with a viscosity of 2500 mPa·s at 23°C is poured into a cylindrical container with a diameter of 10 cm to a height of 5 cm, and stirred at 23°C for 24 hours using an oval stirrer that is 5 cm long, 2 cm wide at the center, and 1 cm wide at the end, while maintaining a 2 cm depression in the center of the liquid surface. [2] The fibrous cellulose according to [1], wherein the ionic substituent is a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group. [3] Fibrous cellulose according to [1] or [2], in which when the fibrous cellulose is dispersed in water to a concentration of 0.4% by mass to form a dispersion, the viscosity of the dispersion at 23°C is 20 mPa·s or more and 4700 mPa·s or less. [4] The fibrous cellulose according to any one of [1] to [3], wherein when the fibrous cellulose is dispersed in water to a concentration of 0.2% by mass to form a dispersion, the haze of the dispersion is 20% or less. [5] The fibrous cellulose according to any one of [1] to [4], wherein the degree of polymerization of the fibrous cellulose is 460 or more and 515 or less. [ 6 ] It is used for paints[1]~[ 5 ] The fibrous cellulose according to any one of the above. [ 7 ] [1]~[ 6 1. A fibrous cellulose dispersion obtained by dispersing the fibrous cellulose according to any one of the above items in a solvent containing water. [ 8 ] Ionic substituents 0.10mmol / g or more 0.95 a step of subjecting cellulose fibers having a density of 100 mmol / g or less to a defibration treatment to obtain fibrous cellulose having a fiber width of 1000 nm or less; and a step of subjecting the fibrous cellulose to a low-thixotropy treatment, A method for producing fibrous cellulose, wherein the step of subjecting the fibrous cellulose to a low thixotropy treatment is a step of reducing the degree of polymerization of the fibrous cellulose to 150 or more and 515 or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to obtain fine fibrous cellulose that, when added to a paint, can exhibit excellent dispersion stability for particles such as pigments and excellent coating suitability. [Brief explanation of the drawings]

[0010] [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

[0011] 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.

[0012] (fine fibrous cellulose) This embodiment relates to fibrous cellulose having a fiber width of 1000 nm or less and having an ionic substituent. The amount of ionic substituent in the fibrous cellulose of this embodiment is 0.10 mmol / g or more and 1.50 mmol / g or less, and the degree of polymerization of the fibrous cellulose is 150 or more and 515 or less. In this specification, fibrous cellulose having a fiber width of 1000 nm or less is also referred to as fine fibrous cellulose. Here, when the fibrous cellulose of this embodiment is dispersed in a dispersion solvent containing water and isopropanol to obtain a dispersion having a water to isopropanol mass ratio of 7:3 and a viscosity of 2500 mPa s at 23°C, and when the dispersion is stirred under the following stirring conditions, the viscosity change rate calculated by the following formula is within ±50%. Viscosity change rate (%) = (viscosity after stirring - viscosity before stirring) / viscosity before stirring × 100 (Mixing conditions) A dispersion liquid with a viscosity of 2500 mPa·s at 23°C is poured into a cylindrical container with a diameter of 10 cm to a height of 5 cm, and stirred at 23°C for 24 hours using an oval stirrer that is 5 cm long, 2 cm wide at the center, and 1 cm wide at the end, while maintaining a 2 cm depression in the center of the liquid surface.

[0013] In this embodiment, fine fibrous cellulose is dispersed in a dispersion solvent containing water and isopropanol to obtain a dispersion having a water to isopropanol mass ratio of 7:3 and a viscosity of 2500 mPa·s at 23°C, and by controlling the viscosity change rate when stirred under the above conditions to within ±50%, fine fibrous cellulose that can exhibit excellent coating suitability when added to a coating material is obtained. In general, when fine fibrous cellulose with a fiber width of 1000 nm or less is added to paints, etc., it can improve the viscosity of the paint and the dispersibility of particles in the paint. However, because fine fibrous cellulose has high thixotropy, when a relatively high shear force is applied to paints containing the added fine fibrous cellulose, the viscosity decreases excessively, causing problems such as dripping and settling of additives such as pigments. The dispersion in which the fine fibrous cellulose of this embodiment is dispersed has thixotropy controlled within an appropriate range, and can exhibit excellent coating suitability. For example, even when a paint containing the fine fibrous cellulose of this embodiment is stored or transported, the change in viscosity of the paint is suppressed within an appropriate range, so that dripping during coating and sedimentation of additives such as pigments can be suppressed. Furthermore, even when a paint containing the fine fibrous cellulose of this embodiment is stirred for a long period of time and subjected to a relatively strong shear force, dripping caused by a decrease in the viscosity of the paint and sedimentation of additives such as pigments can be effectively suppressed. Furthermore, the fine fibrous cellulose of this embodiment has an appropriate viscosity adjusting ability, and adding the fine fibrous cellulose to a paint can improve the dispersion stability of particles such as pigments in the paint (hereinafter simply referred to as "dispersion stability"). That is, the fine fibrous cellulose of this embodiment can improve the dispersion stability of particles in the paint while keeping the thixotropy within an appropriate range, thereby imparting excellent coatability and dispersibility stability to the paint.

[0014] The fine fibrous cellulose of this embodiment is preferably used for paints, and as described above, can improve the coating suitability of the paint. Furthermore, when the fine fibrous cellulose of this embodiment is used as a paint additive, it can also improve the smoothness and design of the coating film after coating. Specifically, in this embodiment, a coating film with a smooth surface can be obtained. The smoothness of the coating film can be evaluated by the surface roughness (Ra) of the coating film, and a surface roughness (Ra) of 0.30 μm or less can be evaluated as smooth. The surface roughness (Ra) of the coating film is preferably 0.10 μm or more, more preferably 0.12 μm or more. The surface roughness (Ra) of the coating film is more preferably 0.28 μm or less, and even more preferably 0.20 μm or less. The surface roughness (Ra) of the coating film was measured using an optical interference non-contact surface profiler (Ryoka Systems Co., Ltd., non-contact surface / layer cross-sectional profile measuring system VertScan2.0, model: R5500GML) with a ×10 objective lens to measure the arithmetic mean roughness (Ra) of the cured coating film over a measurement range of 470.92 μm × 353.16 μm.

[0015] When the fine fibrous cellulose of this embodiment is used as an additive for a paint, it is possible to suppress the generation of aggregates in the paint film. As a result, the design properties of the resulting paint film can be improved. Furthermore, the suppression of the generation of aggregates in the paint film also enhances the smoothness and strength of the paint film.

[0016] The viscosity change rate of the dispersion calculated by the above formula may be within ±50%. Note that in this specification and the present embodiment, "within ±50%" means "-50% or more +50% or less." Generally, applying shear to a dispersion often reduces the viscosity change rate of the dispersion, and therefore the viscosity change rate calculated by the above formula is often a negative value. In other words, the viscosity change rate of the dispersion is preferably between -50% and 0%. The viscosity change rate of the dispersion calculated by the above formula is preferably −40% or more, more preferably −35% or more, even more preferably −30% or more, and is preferably −5% or less, more preferably −10% or less, even more preferably −15% or less, and even more preferably −18% or less, from the viewpoint of achieving both a low viscosity change rate and the viscosity adjustment ability due to the addition of fine fibrous cellulose, and obtaining fine fibrous cellulose that is excellent in transparency, defoaming properties, and particle dispersibility when incorporated into a coating material. The viscosity change rate of the dispersion calculated by the above formula can be achieved, for example, by controlling the type and conditions of treatment of the fine fibrous cellulose, the degree of polymerization of the fine fibrous cellulose, the amount of ionic substituents, and the like, within appropriate ranges.

[0017] In this specification, the viscosity before and after stirring used to calculate the viscosity change rate of a dispersion is the viscosity value measured one minute after the start of measurement using a Brookfield viscometer at 23°C and a rotation speed of 6 rpm. As a Brookfield viscometer, for example, an analog viscometer T-LVT manufactured by Brookfield Corporation can be used. The viscosity before stirring is the viscosity of a dispersion adjusted to a viscosity of approximately 2500 mPa·s. Therefore, the actual viscosity value of the dispersion is preferably 2500 mPa·s, although an error of approximately ±15% is acceptable. In other words, in the formula for calculating the viscosity change rate, the viscosity before stirring is the actual viscosity measured one minute after the start of measurement using a Brookfield viscometer at 23°C and a rotation speed of 6 rpm. However, when measuring the viscosity before stirring, the fine fibrous cellulose dispersion is poured into a cylindrical container with a diameter of 10 cm to a height of 5 cm, stirred for 5 minutes at 1500 rpm using a disperser, and the measurement is taken 1 minute after the end of stirring. To adjust the viscosity of the dispersion before stirring to approximately 2500 mPa·s, the amount of fine fibrous cellulose added is adjusted appropriately. For example, the viscosity of the dispersion before stirring can be adjusted to approximately 2500 mPa·s by adjusting the content of fine fibrous cellulose to 0.2-3.0% by mass relative to the total mass of the dispersion.

[0018] When measuring the viscosity after stirring in the viscosity change rate calculation formula, first, the dispersion used for viscosity measurement before stirring is further stirred using a stirrer. To do this, the microfibrous cellulose dispersion is placed in a cylindrical container with a diameter of 10 cm to a height of 5 cm. An oval stirrer measuring 5 cm in length, 2 cm in width at the center, and 1 cm in width at the end is used to stir the dispersion for 24 hours, maintaining a 2 cm depression in the center of the liquid surface. The liquid temperature during stirring is maintained at 23°C. Then, one minute after the end of stirring, the viscosity is measured using a Brookfield viscometer at 23°C and a rotation speed of 6 rpm. The viscosity value one minute after the start of measurement is the viscosity after stirring.

[0019] When preparing a dispersion for measuring the viscosity before and after stirring, fibrous cellulose is dispersed in a dispersion solvent containing water and isopropanol. In this case, the fibrous cellulose may be contained in the aqueous dispersion. In such cases, it is preferable to add water to the aqueous dispersion of fibrous cellulose as needed, and then add isopropanol. If a sufficient amount of water is present in the aqueous dispersion of fibrous cellulose, only isopropanol may be added. In this way, the dispersion is prepared so that the ratio of the total mass of water contained in the aqueous dispersion of fibrous cellulose and water added as needed to the mass of the isopropanol added is 7:3.

[0020] When the fine fibrous cellulose of this embodiment is dispersed in water to a concentration of 0.4% by mass to form a dispersion, the viscosity of the dispersion at 23°C is preferably 20 mPa·s or more, more preferably 200 mPa·s or more, even more preferably 300 mPa·s or more, even more preferably 350 mPa·s or more, even more preferably 400 mPa·s or more, even more preferably 600 mPa·s or more, even more preferably 1000 mPa·s or more, particularly preferably 1500 mPa·s or more, and most preferably 1900 mPa·s or more, from the viewpoint that the dispersion functions as a viscosity modifier when added to a paint and improves the dispersibility and stability of the particles. Also, from the same viewpoint, the viscosity of the dispersion at 23°C is preferably 4700 mPa·s or less, more preferably 4000 mPa·s or less, even more preferably 3500 mPa·s or less, even more preferably 3000 mPa·s or less, and even more preferably 2500 mPa·s or less. The viscosity of a dispersion with a fine fibrous cellulose concentration of 0.4% by mass can be measured using a Brookfield analog viscometer (T-LVT). The measurement conditions are 23°C, a rotation speed of 3 rpm, and the viscosity is measured 3 minutes after the start of the measurement.

[0021] The fibrous cellulose of this embodiment is fine fibrous cellulose having a fiber width of 1000 nm or less. The fiber width of the fibrous cellulose is more preferably 100 nm or less, and even more preferably 8 nm or less.

[0022] 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, even more preferably 2 nm or more and 10 nm or less, and particularly preferably 2 nm or more and 8 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.

[0023] The average 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. (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.

[0024] 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.

[0025] The fiber length of the fibrous cellulose is not particularly limited, but is preferably, for example, 0.1 μm to 1000 μm, more preferably 0.1 μm to 800 μm, and even more preferably 0.1 μm to 600 μm. The fiber length of the fibrous cellulose is also preferably, for example, 0.15 μm or more or 0.2 μm or more. The fiber length of the fibrous cellulose is also preferably, for example, 100 μm or less, 10 μm or less, or 1 μm or less. By keeping the fiber length within the above range, destruction of the crystalline regions of the fibrous cellulose can be suppressed. It also becomes possible to maintain 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.

[0026] 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).

[0027] The axial ratio (fiber length / fiber width) of the fibrous cellulose is not particularly limited, but is preferably, for example, 20 to 10,000, more preferably 50 to 1,000, even more preferably 50 to 500, and even more preferably 50 to 250. 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.

[0028] The fibrous cellulose in this embodiment has, for example, both crystalline regions and amorphous regions. In particular, fine fibrous cellulose having both crystalline regions and amorphous regions and a high axial ratio is realized by the method for producing fine fibrous cellulose described below.

[0029] The fibrous cellulose in this embodiment has, for example, at least one of an ionic substituent and a nonionic substituent. From the viewpoint of improving the dispersibility of fibers in a dispersion medium and increasing the defibration efficiency in the defibration treatment, it is more preferable that the fibrous cellulose has an ionic substituent. The ionic substituent may include, for example, either one or both of an anionic group and a cationic group. Furthermore, the nonionic substituent may include, for example, an alkyl group and an acyl group. In this embodiment, it is particularly preferable that the ionic substituent has an anionic group. Examples of anionic groups as ionic substituents include ester groups or substituents derived from ester groups (sometimes simply referred to as ester groups), carboxy groups or substituents derived from carboxy groups (sometimes simply referred to as carboxy groups), etc. Examples of ester groups include phosphorus oxo acid groups or substituents derived from phosphorus oxo acid groups (sometimes simply referred to as phosphorus oxo acid groups), sulfur oxo acid groups or substituents derived from sulfur oxo acid groups (sometimes simply referred to as sulfur oxo acid groups), etc.

[0030] The anionic group as the ionic substituent is preferably at least one selected from, for example, a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group, a carboxy group or a substituent derived from a carboxy group, and a sulfur oxo acid group or a substituent derived from a sulfur oxo acid group, more preferably at least one selected from a phosphorus oxo acid group and a carboxy group, and particularly preferably a phosphorus oxo acid group. When added to a coating material, fine fibrous cellulose having a phosphorus oxo acid group can exhibit superior coating suitability. Furthermore, from the viewpoint of the transparency of the dispersion, coating material, and coating film, the anionic group as the ionic substituent is preferably an ester group.

[0031] The phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group is, for example, a substituent represented by the following formula (1). The phosphorus oxoacid group is a divalent functional group obtained by removing a hydroxy group from phosphoric acid, for example. Specifically, it is a group represented by -PO3H2. The substituent derived from a phosphorus oxoacid group includes a salt of the phosphorus oxoacid group, a phosphorus oxoacid ester group, and the like. The substituent derived from a phosphorus oxoacid group may be contained in the fibrous cellulose as a group in which a phosphate group is condensed (for example, a pyrophosphate group). The phosphorus oxoacid group may also be, for example, a phosphorous acid group (phosphonic acid group), and the substituent derived from a phosphorous oxoacid group may be a salt of the phosphorous acid group, a phosphite ester group, or the like.

[0032] [ka]

[0033] In formula (1), a, b, and n are natural numbers (where a = b × m). 1 ,α 2 ,···,α n And a of α' are O - The rest are either R or OR. Note that each α n and all of α' are O - Each 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 derivative thereof. Furthermore, n is preferably 1.

[0034] 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.

[0035] Furthermore, examples of the derivative group in R include, but are not limited to, functional groups in which at least one of functional groups such as a carboxy group, a hydroxy group, or an amino group is added to or substituted on the main chain or side chain of the above-mentioned hydrocarbon groups. 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 oxo acid group can be set within an appropriate range, which facilitates penetration into the fiber raw material and increases the yield of fine fibrous cellulose.

[0036] 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 aliphatic ammonium or aromatic ammonium, and examples of the monovalent or higher cation made of an inorganic substance include, but are not limited to, ions of alkali metals such as sodium, potassium, or lithium, cations of divalent metals such as calcium or magnesium, or hydrogen ions. These can be applied alone or in combination of two or more. Examples of the monovalent or higher cation made of an organic or inorganic substance include β b+Sodium or potassium ions are preferred because they are less likely to yellow when the fiber raw material containing β is heated and are easy to use industrially, but are not particularly limited thereto. b+ may be an organic onium ion, and in this case, is particularly preferably an organic ammonium ion.

[0037] The amount of ionic substituent introduced into the fibrous cellulose may be 0.10 mmol / g or more per gram (mass) of fibrous cellulose, preferably 0.20 mmol / g or more, more preferably 0.30 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.50 mmol / g or more, even more preferably 0.60 mmol / g or more, and particularly preferably 0.70 mmol / g or more. The amount of ionic substituent introduced into the fibrous cellulose may be 1.50 mmol / g or less per gram (mass) of fibrous cellulose, preferably 1.35 mmol / g or less, more preferably 1.20 mmol / g or less, and even more preferably 1.10 mmol / g or less. The amount of ionic substituent introduced into the fibrous cellulose may be 1.00 mmol / g or less per gram (mass) of fibrous cellulose, more preferably 0.95 mmol / g or less. Here, the denominator in the unit mmol / g is the value of the counter ion of the ionic substituent, which is a hydrogen ion (H + ) indicates the mass of fibrous cellulose when the amount of ionic substituent introduced is within the above range, it is possible to improve the dispersion stability of the fibrous cellulose in the coating material. Furthermore, by setting the amount of ionic substituent introduced within the above range, it is possible to set the thixotropy of the coating material when the fine fibrous cellulose is added to the coating material within an appropriate range, thereby more effectively improving the coating suitability.

[0038] 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.

[0039] 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.

[0040] 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 (e.g., Na is 23, Al is 9)

[0041] 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 the 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).

[0042] 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 (e.g., Na is 23, Al is 9)

[0043] 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.

[0044] The amount of sulfur oxoacid groups introduced into the fine fibrous cellulose is measured using wet ashing and ICP atomic emission spectrometry. Specifically, the fibrous cellulose-containing slurry is dried and then weighed. Perchloric acid is added to carbonize the slurry, and concentrated nitric acid is added to oxidize the carbon to carbon dioxide, yielding a sample solution consisting solely of inorganic substances. This sample solution is then diluted appropriately, and the sulfate ion concentration is measured using ICP atomic emission spectrometry. The amount of sulfur atoms contained in the sample solution is then divided by the weighed dry mass of the fibrous cellulose to determine the amount of sulfur oxoacid groups (unit: mmol / g).

[0045] The degree of polymerization of the fine fibrous cellulose may be 150 or more, preferably 200 or more, more preferably 300 or more, even more preferably 320 or more, even more preferably 340 or more, even more preferably 360 or more, even more preferably 380 or more, even more preferably 400 or more, and particularly preferably 460 or more. The degree of polymerization of the fine fibrous cellulose may be 515 or less, preferably 500 or less, and more preferably 490 or less. By controlling the degree of polymerization of the fine fibrous cellulose within the above range, the thixotropy of the paint when the fine fibrous cellulose is added to the paint can be reduced (de-thixotropic) to an appropriate range, thereby more effectively improving the coatability. Furthermore, by controlling the degree of polymerization of the fine fibrous cellulose within the above range, the smoothness, designability, and strength of the paint film can be more effectively improved. Furthermore, controlling the degree of polymerization within the above range is preferable because it improves the transparency of the fine fibrous cellulose dispersion.

[0046] The degree of polymerization of the fine fibrous cellulose is a value calculated from the pulp viscosity measured in accordance with Tappi T 230. Specifically, the fine fibrous cellulose to be measured is dispersed in an aqueous copper ethylenediamine solution to measure the viscosity (referred to as η1), and the blank viscosity (referred to as η0) is measured using only the dispersion medium, and then the specific viscosity (ηsp) and intrinsic viscosity ([η]) are measured according to the following formulas. ηsp=(η1 / η0)-1 [η]=ηsp / (c(1+0.28×ηsp)) Here, c in the formula represents the concentration (g / mL) of the fine fibrous cellulose at the time of viscosity measurement. Furthermore, the degree of polymerization (DP) is calculated using the following formula. DP=1.75×[η] This degree of polymerization is an average degree of polymerization measured by a viscosity method, and is therefore sometimes called the "viscosity-average degree of polymerization."

[0047] In this embodiment, preferably, the degree of polymerization of the fine fibrous cellulose is 300 to 515 and the amount of ionic substituents in the fine fibrous cellulose is 0.40 mmol / g to 1.20 mmol / g, and more preferably, the degree of polymerization of the fine fibrous cellulose is 460 to 490 and the amount of ionic substituents in the fine fibrous cellulose is 0.70 mmol / g to 0.95 mmol / g, thereby reducing the thixotropy of the paint when the fine fibrous cellulose is added to the paint and improving particle dispersibility, thereby more effectively improving the coatability of the paint. It is believed that maintaining the degree of polymerization and the amount of ionic substituents of the fine fibrous cellulose within appropriate ranges contributes to improving particle dispersibility while the dispersion in which the fine fibrous cellulose is dispersed exhibits low thixotropy, thereby improving the coatability of the paint.

[0048] (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 a large axial ratio due to minimal decomposition of cellulose in the pulp. Note that the viscosity tends to increase when long-fiber fine fibrous cellulose with a large axial ratio is used.

[0049] Examples of cellulose-containing fiber raw materials include cellulose contained in sea squirts and bacterial cellulose produced by acetic acid bacteria.Furthermore, fibers formed from linear nitrogen-containing polysaccharide polymers such as chitin and chitosan can also be used instead of cellulose-containing fiber raw materials.

[0050] <Phosphorus oxoacid group introduction step> The process for producing fine fibrous cellulose includes a step of introducing an ionic substituent. 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.

[0051] 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.

[0052] 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, using a fiber raw material in a dry or wet state is preferred because of the high uniformity of the reaction, and using a fiber raw material in a dry state is particularly preferred. The form of the fiber raw material is not particularly limited, but is preferably, for example, in a cotton-like or thin sheet form. Examples of methods include adding compound A and compound B to the fiber raw material in the form of a powder, a solution dissolved in a solvent, or a melted state heated to or above the melting point. Among these, adding compound A and compound B in the form of a solution dissolved in a solvent, particularly an aqueous solution, is preferred because of the high uniformity of the reaction. 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.

[0053] 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 may be used in a variety of purities, such as 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid. Phosphorous acid may 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 may 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] In the reaction of a fiber raw material containing cellulose with compound A, the reaction system may contain, in addition to compound B, for example, amides or amines. 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 is known to function as a particularly good reaction catalyst.

[0058] In the phosphorus oxo acid group introduction step, it is preferable to add or mix compound A or the like to 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, 50°C to 300°C, more preferably 100°C to 250°C, and even more preferably 130°C to 200°C. Furthermore, various types of equipment having heat transfer media can be used for the heat treatment, including, for example, a stirring 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.

[0059] 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).

[0060] 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.

[0061] The heat treatment time is, for example, 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, by setting the heating temperature and heating time within appropriate ranges, the amount of phosphorus oxo acid groups introduced can be kept within a preferred range.

[0062] 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.

[0063] The amount of phosphorus oxoacid groups introduced into the fiber raw material may be, for example, 0.10 mmol / g or more per gram (mass) of fine fibrous cellulose, preferably 0.20 mmol / g or more, more preferably 0.30 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.50 mmol / g or more, even more preferably 0.60 mmol / g or more, and particularly preferably 0.70 mmol or more. The amount of phosphorus oxoacid groups introduced into the fiber raw material may be, for example, 1.50 mmol / g or less per gram (mass) of fine fibrous cellulose, preferably 1.35 mmol / g or less, more preferably 1.20 mmol / g or less, and even more preferably 1.10 mmol / g or less. The amount of phosphorus oxoacid groups introduced into the fibrous cellulose may be, for example, 1.00 mmol / g or less per gram (mass) of fibrous cellulose, more preferably 0.95 mmol / g or less. By adjusting the amount of phosphorus oxo acid groups introduced within the above range, it is possible to improve the dispersion stability of the fine fibrous cellulose in the coating material. Furthermore, by adjusting the amount of phosphorus oxo acid groups introduced within the above range, the thixotropy of the coating material when the fine fibrous cellulose is added to the coating material can be reduced to an appropriate range, the dispersion stability of the particles can be improved, and thereby the coating suitability can be more effectively improved.

[0064] <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.

[0065] 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.

[0066] The acid anhydride of a compound having a group derived from carboxylic acid is not particularly limited, and 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, and examples thereof include acid anhydrides of compounds having carboxy groups such as dimethyl maleic anhydride, diethyl maleic anhydride, diphenyl maleic anhydride, etc., in which at least some of the hydrogen atoms have been substituted with a substituent such as an alkyl group or a phenyl group.

[0067] When TEMPO oxidation treatment is performed in the carboxyl group introduction step, it is preferable to perform the treatment under conditions of, for example, pH 6 or higher and pH 8 or lower. This type of treatment is also called neutral TEMPO oxidation treatment. Neutral TEMPO oxidation treatment 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). Furthermore, by adding sodium chlorite, aldehydes generated during the oxidation process can be efficiently oxidized to carboxyl groups. The TEMPO oxidation treatment 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 treatment. The alkaline TEMPO oxidation treatment 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.

[0068] The amount of carboxyl groups introduced into the fibrous cellulose varies depending on the type of substituent. For example, when carboxyl groups are introduced by TEMPO oxidation, the amount per gram (mass) of fine fibrous cellulose should be 0.10 mmol / g or more, preferably 0.20 mmol / g or more, more preferably 0.30 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.50 mmol / g or more, and particularly preferably 0.60 mmol / g or more. The amount of carboxyl groups introduced into the fibrous cellulose should be 1.50 mmol / g or less, preferably 1.35 mmol / g or less, more preferably 1.20 mmol / g or less, and even more preferably 1.10 mmol / g or less. The amount of carboxyl groups introduced into the fibrous cellulose should be 1.00 mmol / g or less, more preferably 0.95 mmol / g or less, per gram (mass) of fibrous cellulose. By keeping the amount of carboxyl groups introduced within the above range, the dispersion stability of the fine fibrous cellulose in coating materials can be improved. Furthermore, by keeping the amount of carboxyl groups introduced within the above range, the thixotropy of the paint when the fine fibrous cellulose is added to the paint can be reduced to an appropriate range, thereby more effectively improving the coating suitability.

[0069] <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).

[0070] 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.

[0071] 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.

[0072] 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 an 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.

[0073] The amount of sulfur oxoacid groups introduced into the cellulose raw material should be 0.10 mmol / g or more, preferably 0.20 mmol / g or more, more preferably 0.30 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.50 mmol / g or more, even more preferably 0.60 mmol / g or more, and even more preferably 0.70 mmol / g or more. The amount of sulfur oxoacid groups introduced into the cellulose raw material should be 1.50 mmol / g or less, preferably 1.35 mmol / g or less, more preferably 1.20 mmol / g or less, and even more preferably 1.10 mmol / g or less. The amount of sulfur oxoacid groups introduced into the fibrous cellulose should be 1.00 mmol / g or less, more preferably 0.95 mmol / g or less, per gram (mass) of fibrous cellulose. By adjusting the amount of sulfur oxoacid groups introduced within the above range, it is possible to improve the dispersion stability of the fine fibrous cellulose in the coating material. Furthermore, by adjusting the amount of sulfur oxoacid groups introduced within the above range, the thixotropy of the coating material when the fine fibrous cellulose is added to the coating material can be reduced to an appropriate range, thereby more effectively improving the coating suitability.

[0074] <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, for example, water or an organic solvent. 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.

[0075] <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.

[0076] 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 its 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 its high versatility.

[0077] 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.

[0078] 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.

[0079] <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.

[0080] 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.

[0081] 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.

[0082] <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-type grinder), a high-pressure homogenizer, an ultra-high-pressure homogenizer, a high-pressure collision grinder, a ball mill, a bead mill, a disk-type refiner, a conical refiner, a twin-screw kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, or a beater. Among the above 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.

[0083] In the defibration treatment step, 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).

[0084] 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.

[0085] <Low thixotropy treatment> The method for producing fine fibrous cellulose of this embodiment preferably includes, in addition to the steps described above, a step of performing a thixotropy-reducing treatment. Specifically, as described above, it preferably includes a step of subjecting appropriately treated cellulose fibers to a defibration treatment to obtain fibrous cellulose having a fiber width of 1000 nm or less, and a step of subjecting the fibrous cellulose to a thixotropy-reducing treatment. That is, the method for producing fine fibrous cellulose of this embodiment preferably includes, for example, a step of subjecting cellulose fibers to a defibration treatment and then a thixotropy-reducing treatment. Note that, as described above, it is preferable to further include a step of introducing ionic substituents into the cellulose fibers before the defibration treatment step, and in the step of introducing the ionic substituents, the ionic substituents are introduced so that the amount of ionic substituents in the fibrous cellulose is 0.10 mmol / g or more and 1.50 mmol / g or less. Note that, in addition to the step of introducing the ionic substituents, it is also preferable to further include a washing step or an alkali treatment step before the defibration treatment step. Since the amount of ionic substituents in the fine fibrous cellulose hardly changes even after the thixotropy reduction treatment, the amount of ionic substituents in the fine fibrous cellulose before the thixotropy reduction treatment can be approximated as the amount of ionic substituents in the fine fibrous cellulose after the thixotropy reduction treatment.

[0086] In this specification, the step of carrying out thixotropy reduction is a step of carrying out a treatment to reduce the thixotropy of a dispersion containing fine fibrous cellulose to an appropriate range. Specifically, the step of carrying out thixotropy reduction is a step of reducing the degree of polymerization of fibrous cellulose having a fiber width of 1000 nm or less to 150 or more and 515 or less. Therefore, thixotropy reduction can also be called a polymerization degree reduction treatment. The degree of polymerization of the fine fibrous cellulose obtained by the thixotropy reduction treatment step may be 150 or more, preferably 200 or more, more preferably 300 or more, even more preferably 320 or more, even more preferably 340 or more, even more preferably 360 or more, even more preferably 380 or more, even more preferably 400 or more, and particularly preferably 460 or more. The degree of polymerization of the fine fibrous cellulose obtained in the step of subjecting it to thixotropy reduction treatment may be 515 or less, preferably 500 or less, and more preferably 490 or less.

[0087] Examples of the process for carrying out the thixotropy reduction treatment include an ozone treatment process, an enzyme treatment process, a hypochlorous acid treatment process, and a subcritical water treatment process. The process for carrying out the thixotropy reduction treatment is preferably at least one selected from an ozone treatment process, an enzyme treatment process, a hypochlorous acid treatment process, and a subcritical water treatment process, and is particularly preferably an ozone treatment process. What is common to the ozone treatment process, the enzyme treatment process, the hypochlorous acid treatment process, and the subcritical water treatment process is the reduction in the degree of polymerization, and the reduction in the degree of polymerization results in the reduction in thixotropy treatment, resulting in the production of the fine fibrous cellulose and the fine fibrous cellulose dispersion of the present embodiment.

[0088] In the ozone treatment step, ozone is added to the fine fibrous cellulose dispersion (slurry). When adding ozone, it is preferable to add it as an ozone / oxygen mixed gas, for example. In this case, the ozone addition rate per 1 g of fine fibrous cellulose contained in the fine fibrous cellulose dispersion (slurry) is 1.0 × 10 -4 g or more, and 1.0 × 10-3 The ozone addition rate per 1 g of fine fibrous cellulose is preferably 1.0 × 10 1 g or less, and 1.0 × 10 0 g or less, and more preferably 1.0 × 10 -1 g or less, and more preferably 3.0 × 10 -2 g or less, and more preferably 1.5 × 10 -2 g or less, and more preferably 1.0 × 10 -2 g or less, and more preferably 6.0 × 10 -3 After adding ozone to the fine fibrous cellulose dispersion (slurry), it is preferable to stir the mixture at a temperature of 10°C to 50°C for 10 seconds to 10 minutes, and then leave it to stand for 1 minute to 100 minutes.

[0089] In the enzyme treatment step, an enzyme is added to a fine fibrous cellulose dispersion (slurry). The enzyme used here is preferably a cellulase enzyme. Cellulase enzymes are classified into the carbohydrate hydrolase family based on the higher-order structure of the catalytic domain that functions to hydrolyze cellulose. Cellulase enzymes are broadly classified into endo-glucanases and cellobiohydrolases based on their cellulose degradation properties. Endo-glucanases have high hydrolytic activity against the amorphous portion of cellulose, soluble cellooligosaccharides, and cellulose derivatives such as carboxymethylcellulose, randomly cleaving the molecular chains from the inside and reducing the degree of polymerization. In contrast, cellobiohydrolases decompose the crystalline portion of cellulose to produce cellobiose. Cellobiohydrolases hydrolyze cellulose from the end of the molecule and are also called exo- or processive enzymes. While the enzyme used in the enzyme treatment step is not particularly limited, endo-glucanases are preferred.

[0090] In the enzyme treatment process, the enzyme addition rate was 1.0 × 10 per 1 g of fine fibrous cellulose. -7g or more, and 1.0 × 10 -6 g or more, and more preferably 5.0 × 10 -6 g or more, and more preferably 1.0 × 10 -5 The enzyme addition rate is preferably 1.0×10 to 1 g of fine fibrous cellulose. -2 After adding the enzyme to the fine fibrous cellulose dispersion (slurry), it is preferable to stir the mixture at a temperature of 30°C to 70°C for 1 minute to 10 hours, and then place the mixture at a temperature of 90°C or higher to inactivate the enzyme.

[0091] In the hypochlorite treatment process, sodium hypochlorite is added to the fine fibrous cellulose dispersion (slurry). The sodium hypochlorite addition rate is 1.0 × 10 per 1 g of fine fibrous cellulose. -4 g or more, and 1.0 × 10 -3 g or more, and more preferably 1.0 × 10 -2 The sodium hypochlorite addition rate is more preferably 1.0 × 10 per 1 g of fine fibrous cellulose. 2 g or less, and 1.0 × 10 1 g or less, and more preferably 3×10 0 After adding sodium hypochlorite to the fine fibrous cellulose dispersion (slurry), it is preferable to stir the mixture at a temperature of 10°C to 50°C for 1 minute to 10 hours.

[0092] In the subcritical water treatment step, a fine fibrous cellulose dispersion (slurry) is subjected to high-temperature and high-pressure treatment to bring it to a subcritical state. The fine fibrous cellulose is hydrolyzed in the subcritical state. Specifically, the fine fibrous cellulose dispersion (slurry) is placed in a reaction vessel, and the temperature is increased to 150°C to 500°C, preferably 150°C to 350°C, and the pressure inside the reaction vessel is increased to 10 MPa to 80 MPa, preferably 10 MPa to 20 MPa. The heating and pressurizing time is preferably 0.1 seconds to 100 seconds, more preferably 0.3 seconds to 50 seconds.

[0093] After the above-described thixotropy reduction treatment, a second defibration treatment step may be performed. The second defibration treatment step may be the same as the above-described defibration treatment step for obtaining fibrous cellulose having a fiber width of 1000 nm or less.

[0094] (fibrous cellulose dispersion) This embodiment also relates to a fibrous cellulose dispersion (also referred to as a fine fibrous cellulose-containing slurry or slurry) obtained by dispersing the above-mentioned fine fibrous cellulose in a solvent containing water. The fibrous cellulose dispersion may be, for example, a paint dispersion to be added to paint.

[0095] The content of fine fibrous cellulose in the fibrous cellulose dispersion is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, and even more preferably 1.5% by mass or more, relative to the total mass of the fibrous cellulose dispersion. The content of fine fibrous cellulose is preferably 8.0% by mass or less, more preferably 7.0% by mass or less, even more preferably 6.0% by mass or less, and even more preferably 5.0% by mass or less, relative to the total mass of the fibrous cellulose dispersion.

[0096] When fine fibrous cellulose is dispersed in water to a fine fibrous cellulose concentration of 0.2% by mass to prepare a fibrous cellulose dispersion, the haze of the dispersion is preferably 20% or less, more preferably 15% or less, even more preferably 10% or less, and even more preferably 9.5% or less. A dispersion haze within the above range means that the fibrous cellulose dispersion has high transparency and the fine fibrous cellulose is well refined. When such a fibrous cellulose dispersion is added to a coating material, the coating material can exhibit excellent coating suitability. Here, the haze of the fibrous cellulose dispersion (fine fibrous cellulose concentration 0.2% by mass) is measured in accordance with JIS K 7136:2000 using a haze meter (Murakami Color Research Laboratory, HM-150) after the fibrous cellulose dispersion is placed in a glass liquid cell (Fujiwara Seisakusho, MG-40, reverse light path) with a light path length of 1 cm. Zero-point measurement is performed using ion-exchanged water placed in the same glass cell. The haze tends to be lower as the amount of ionic groups introduced increases, and the type of ionic groups introduced affects the haze. The haze also tends to be lower when the concentration during defibration treatment and the dispersion concentration are low. Furthermore, the haze tends to be lower due to thixotropy reduction treatment, and the haze also tends to be lower due to defibration treatment after thixotropy reduction treatment.

[0097] The fibrous cellulose dispersion may contain other additives in addition to the water-containing solvent and the fine fibrous cellulose. Examples of the other additives include antifoaming agents, lubricants, UV absorbers, dyes, pigments, stabilizers, surfactants, and preservatives (e.g., phenoxyethanol). The fibrous cellulose dispersion may also contain optional components such as hydrophilic polymers and organic ions.

[0098] The hydrophilic polymer is preferably a hydrophilic oxygen-containing organic compound (excluding the above-mentioned cellulose fibers), and examples of the oxygen-containing organic compound include hydrophilic polymers such as polyethylene glycol, polyethylene oxide, casein, dextrin, starch, modified starch, polyvinyl alcohol, modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol, etc.), polyethylene oxide, polyvinylpyrrolidone, polyvinyl methyl ether, polyacrylates, acrylic acid alkyl ester copolymers, urethane copolymers, and cellulose derivatives (hydroxyethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, etc.); and hydrophilic low-molecular-weight compounds such as glycerin, sorbitol, and ethylene glycol.

[0099] Examples of organic ions include tetraalkylammonium ions and tetraalkylphosphonium ions. Examples of tetraalkylammonium ions include tetramethylammonium ions, tetraethylammonium ions, tetrapropylammonium ions, tetrabutylammonium ions, tetrapentylammonium ions, tetrahexylammonium ions, tetraheptylammonium ions, tributylmethylammonium ions, lauryltrimethylammonium ions, cetyltrimethylammonium ions, stearyltrimethylammonium ions, octyldimethylethylammonium ions, lauryldimethylethylammonium ions, didecyldimethylammonium ions, lauryldimethylbenzylammonium ions, and tributylbenzylammonium ions. Examples of tetraalkylphosphonium ions include tetramethylphosphonium ions, tetraethylphosphonium ions, tetrapropylphosphonium ions, tetrabutylphosphonium ions, and lauryltrimethylphosphonium ions. Examples of tetrapropylonium ions and tetrabutylonium ions include tetra-n-propylonium ions and tetra-n-butylonium ions, respectively.

[0100] (Application) The fine fibrous cellulose of this embodiment is preferably used as a thickener for various applications. For example, the fine fibrous cellulose of this embodiment can be used as an additive for foods, cosmetics, cement, paints (for painting vehicles such as automobiles, ships, and aircraft, for building materials, for daily necessities, etc.), inks, pharmaceuticals, etc. Furthermore, the fine fibrous cellulose of this embodiment can also be applied to daily necessities by adding it to resin-based materials or rubber-based materials. In particular, the fine fibrous cellulose of this embodiment is particularly preferably fine fibrous cellulose for paints. [Example]

[0101] 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.

[0102] <Production Example 1> [Production of phosphorylated fine fibrous cellulose dispersion] The raw pulp used was softwood kraft pulp (solid content 93% by mass, basis weight 208 g / m) manufactured by Oji Paper Co., Ltd. 2 Sheet-type pulp with a Canadian Standard Freeness (CSF) of 700 mL when disintegrated and measured in accordance with JIS P 8121-2:2012 was used.

[0103] This raw pulp was subjected to a phosphorylation 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 adjust the composition to 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water, to obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 140°C for 200 seconds to introduce phosphate groups into the cellulose in the pulp, thereby obtaining a phosphorylated pulp.

[0104] 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.

[0105] Next, the washed phosphorylated pulp was neutralized 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 a neutralized phosphorylated pulp. Next, the neutralized phosphorylated pulp was subjected to the above-mentioned washing treatment.

[0106] The infrared absorption spectrum of the phosphorylated pulp obtained was measured using FT-IR. -1 Absorption due to phosphate groups was observed near the pulp, confirming that phosphate groups had been added to the pulp.

[0107] In addition, the obtained phosphorylated 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 that it contained cellulose type I crystals.

[0108] 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 six times at a pressure of 200 MPa in a wet pulverizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose.

[0109] X-ray diffraction confirmed that this 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 phosphate groups (amount of first dissociated acid) measured by the method described below in [Measurement of amount of phosphorus oxo acid group] was 0.80 mmol / g.

[0110] <Production Example 2> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1, except that the drying temperature of the chemical-impregnated pulp during phosphorylation was 140°C and the drying time was 230 seconds. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described below in [Measurement of amount of phosphorus oxo acid group] was 1.00 mmol / g.

[0111] <Production Example 3> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1, except that the drying temperature of the chemical-impregnated pulp during phosphorylation was 165°C and the drying time was 170 seconds. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described below in [Measurement of amount of phosphorus oxo acid group] was 1.20 mmol / g.

[0112] <Production Example 4> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1, except that the drying temperature of the chemical-impregnated pulp during phosphorylation was 165° C. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described below in [Measurement of amount of phosphorus oxo acid groups] was 1.45 mmol / g.

[0113] <Production Example 5> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 4, except that the washed phosphorylated pulp before the neutralization treatment was further subjected to the above phosphorylation treatment and the above washing treatment, in that order, once each. The amount of phosphoric acid groups (amount of first dissociated acid) measured by the method described below in [Measurement of amount of phosphorus oxo acid groups] was 2.00 mmol / g.

[0114] <Production Example 6> [Production of Phosphorous-Substituted Microfibrous Cellulose Dispersion] The raw pulp used was softwood kraft pulp (solid content 93% by mass, basis weight 245 g / m) manufactured by Oji Paper. 2 Sheet-type pulp with a Canadian Standard Freeness (CSF) of 700 mL when disintegrated and measured in accordance with JIS P 8121-2:2012 was used.

[0115] This raw pulp was subjected to phosphorus oxo-oxidation treatment as follows. First, a mixed aqueous solution of phosphorous acid (phosphonic acid) and urea was added to 100 parts by mass (bone dry mass) of the raw pulp to prepare a mixture of 33 parts by mass of phosphorous acid (phosphonic acid), 120 parts by mass of urea, and 150 parts by mass of water, yielding a chemical-impregnated pulp. Next, the resulting chemical-impregnated pulp was heated in a hot air dryer at 165°C for 150 seconds to introduce phosphite groups into the cellulose in the pulp, yielding a phosphited pulp.

[0116] The resulting phosphited pulp was then washed. 100 g (bone dry mass) of phosphited 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.

[0117] The washed phosphited pulp was then neutralized as follows: First, the washed phosphited 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 phosphited pulp slurry with a pH of 12 to 13. The phosphited pulp slurry was then dewatered to obtain a neutralized phosphited pulp. The neutralized phosphited pulp was then subjected to the above-mentioned washing treatment.

[0118] The infrared absorption spectrum of the obtained phosphorous pulp was measured using FT-IR. -1The 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.

[0119] Ion-exchanged water was added to the obtained phosphited pulp to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated six 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 containing fine fibrous cellulose.

[0120] X-ray diffraction confirmed that this 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 phosphorous acid groups (amount of first dissociated acid) measured by the method described below in [Measurement of amount of phosphorus oxo acid groups] was 0.74 mmol / g.

[0121] <Production Example 7> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 6, except that the heating time of the chemical-impregnated pulp during the phosphite treatment was changed to 220 seconds. The amount of phosphite groups (amount of first dissociated acid) measured by the method described in [Measurement of amount of phosphorus oxo acid groups] below was 1.41 mmol / g.

[0122] <Production Example 8> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 6, except that the heating time of the chemical-impregnated pulp during the phosphite treatment was changed to 400 seconds. The amount of phosphite groups (amount of first dissociated acid) measured by the method described later in [Measurement of amount of phosphorus oxo acid groups] was 1.86 mmol / g.

[0123] <Production Example 9> A sulfated pulp was obtained in the same manner as in Production Example 6, except that 38 parts by mass of amidosulfonic acid (sulfamic acid) was used instead of phosphorous acid (phosphonic acid) and the heating time was extended to 13 minutes.

[0124] The infrared absorption spectrum of the sulfated pulp obtained was measured using FT-IR. -1 Absorption due to sulfate groups was observed in the vicinity, confirming that sulfate groups had been added to the pulp.

[0125] The obtained sulfated pulp was also 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. Ion-exchanged water was added to the obtained sulfated pulp, and the mixture was stirred to form a 2% by mass slurry. This slurry was treated six times in a wet pulverization apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose-containing slurry. X-ray diffraction confirmed that this 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 to 5 nm. The amount of sulfate groups (sulfonic acid groups) measured by the method described below in "Measurement of sulfur oxoacid group amount" was 0.88 mmol / g.

[0126] <Production Example 10> [Production of TEMPO-oxidized fine fibrous cellulose dispersion] 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 1.3 mmol per 1.0 g of pulp 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.

[0127] 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.

[0128] The remaining aldehyde groups in this dehydrated sheet were further oxidized as follows: 100 parts by weight of the dehydrated sheet (dry mass equivalent) was dispersed in 10,000 parts by weight of 0.1 mol / L acetate buffer (pH 4.8). 113 parts by weight of 80% sodium chlorite was then added, the container was immediately sealed, and the mixture was stirred at 500 rpm using a magnetic stirrer for 48 hours at room temperature to produce a pulp slurry.

[0129] The resulting TEMPO-oxidized pulp was then washed. The pulp slurry after the additional 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.

[0130] In addition, the obtained TEMPO-oxidized pulp was analyzed using an X-ray diffractometer, and 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.

[0131] 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 six 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 containing fine fibrous cellulose.

[0132] X-ray diffraction confirmed that this 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 by the method described below was 0.70 mmol / g.

[0133] <Production Example 11> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1, except that the heating time of the chemical-impregnated pulp during phosphorylation was 180 seconds. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described below in [Measurement of amount of phosphorus oxo acid group] was 0.60 mmol / g.

[0134] <Production Example 12> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1, except that the heating time of the chemical solution-impregnated pulp during phosphorylation was changed to 220 seconds. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described below in [Measurement of amount of phosphorus oxo acid group] was 0.95 mmol / g.

[0135] <Production Example 13> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 9, except that the heating time of the chemical-impregnated pulp during sulfation was changed to 15 minutes. The sulfate group (sulfonic acid group) content measured by the measurement method described later in [Measurement of sulfur oxo acid group content] was 0.94 mmol / g.

[0136] <Production Example 14> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1, except that the solid content concentration during the defibration treatment was 2.4 mass %.

[0137] <Production Example 15> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1, except that the solid content concentration during the defibration treatment was 2.9 mass %.

[0138] <Production Example 16> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1, except that the solid content concentration during defibration treatment was 4.0 mass % and the treatment was performed once in the wet atomization device.

[0139] <Production Example 17> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1, except that the solid content concentration during defibration treatment was 4.9 mass % and the treatment was performed once in the wet atomization device.

[0140] <Production Example 18> A fine fibrous cellulose dispersion was obtained in the same manner as in Production Example 1, except that the solid content concentration during defibration treatment was 12.0 mass % and the treatment was performed once in the wet atomization device.

[0141] Example 1 (Low thixotropy due to ozone treatment) An ozone concentration of 200 g / m was added to 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 1 (solid content concentration 2% by mass, solid content 20 g). 3 The mixture was stirred for 2 minutes at 25°C in a sealed container and then allowed to stand for 60 minutes. The ozone addition rate was 2.0 x 10 per 1 g of fine fibrous cellulose. -2g. The vessel was then opened and stirred for 5 hours to volatilize any ozone remaining in the dispersion. The mixture was then treated three times with a high-pressure homogenizer at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion. The fine fibrous cellulose was thus subjected to thixotropy reduction, and the viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low-thixotropy fine fibrous cellulose dispersion were measured using the methods described below. The thixotropy reduction treatment did not change the amount of ionic substituents in the fine fibrous cellulose. Similarly, in the following examples, the amount of ionic substituents in the fine fibrous cellulose did not change.

[0142] <Example 2> An ozone concentration of 200 g / m was added to 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 1 (solid content concentration 2% by mass, solid content 20 g). 3 The mixture was stirred for 2 minutes at 25°C in a sealed container and then allowed to stand for 60 minutes. The ozone addition rate was 2.0 x 10 per 1 g of fine fibrous cellulose. -2 g. The vessel was then opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. In this way, the thixotropy of the fine fibrous cellulose was reduced, and the viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low-thixotropy fine fibrous cellulose dispersion were measured by the methods described below.

[0143] Example 3 (Low thixotropy due to ozone treatment) An ozone concentration of 200 g / m was added to 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 1 (solid content concentration 2% by mass, solid content 20 g). 3 The mixture was stirred for 2 minutes at 25°C in a sealed container and then allowed to stand for 30 minutes. The ozone addition rate was 1.0 x 10 per 1 g of fine fibrous cellulose. -2g. The vessel was then opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. In this way, the thixotropy of the fine fibrous cellulose was reduced, and the viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low-thixotropy fine fibrous cellulose dispersion were measured by the methods described below.

[0144] Example 4 Ozone concentration: 40g / m 3 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 3, except that an ozone / oxygen mixed gas of 2.0×10 was used. The ozone addition rate at this time was 2.0×10 per 1 g of fine fibrous cellulose. -3 The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0145] <Example 5> (Low thixotropy due to enzyme treatment) To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 1 (solid content concentration 2% by mass, solid content 20 g), 20 g of an enzyme-containing solution (manufactured by AB Enzymes, ECOPULP R, enzyme content approximately 5% by mass) diluted 1000 times was added, and the mixture was stirred at a temperature of 50°C for 1 hour. The enzyme addition rate at this time was approximately 5.0 × 10 per 1 g of fine fibrous cellulose. -5 g. The mixture was then stirred at 100°C for 1 hour to inactivate the enzyme. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the resulting low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0146] Example 6 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 5, except that 4 g of an enzyme-containing solution (manufactured by AB Enzymes, ECOPULP R, enzyme content approximately 5% by mass) was diluted 1000 times and added to 1000 g of a fine fibrous cellulose dispersion (solid concentration 2% by mass, solid content 20 g). The enzyme addition rate at this time was approximately 1.0 × 10 per 1 g of fine fibrous cellulose. -5The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0147] Example 7 (Low thixotropy due to sodium hypochlorite treatment) To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 1 (solid content concentration 2% by mass, solid content 20 g), 170 g of sodium hypochlorite solution (available chlorine concentration 12% by mass) was added and stirred at room temperature for 1 hour. The sodium hypochlorite addition rate at this time was 1.02 g per 1 g of fine fibrous cellulose. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0148] Example 8 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 7, except that 1.70 g of sodium hypochlorite solution (effective chlorine concentration 12% by mass) was added to 1000 g of fine fibrous cellulose dispersion (solid content concentration 2% by mass, solid content 20 g). The sodium hypochlorite addition rate at this time was 1.02 × 10 -2 The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0149] Example 9 (Low thixotropy achieved by subcritical water treatment) The fine fibrous cellulose dispersion obtained in Production Example 1 was placed in a reactor, heated to 200°C, and heated for 10 seconds. The pressure inside the reactor at this time was 20 MPa. After heating, the reactor was cooled with water, and the low thixotropy fine fibrous cellulose dispersion inside the reactor was recovered. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropy fine fibrous cellulose dispersion were measured by the methods described below.

[0150] Example 10 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 9, except that the heating time was set to 1 second. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0151] Example 11 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 1, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0152] Example 12 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 2, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0153] Example 13 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 3, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0154] Example 14 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 4, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0155] Example 15 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 5, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0156] Example 16 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 6, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0157] Example 17 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 7, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0158] Example 18 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 8, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0159] Example 19 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 9, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0160] Example 20 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 10, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0161] Example 21 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 3, except for using the fine fibrous cellulose dispersion obtained in Production Example 2. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0162] Example 22 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 3, except for using the fine fibrous cellulose dispersion obtained in Production Example 3. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0163] Example 23 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 3, except for using the fine fibrous cellulose dispersion obtained in Production Example 4. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0164] Example 24 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 3, except for using the fine fibrous cellulose dispersion obtained in Production Example 7. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0165] Example 25 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 3, except for using the fine fibrous cellulose dispersion obtained in Production Example 9. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0166] <Example 26> A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 3, except for using the fine fibrous cellulose dispersion obtained in Production Example 10. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0167] Example 27 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 4, except for using the fine fibrous cellulose dispersion obtained in Production Example 11. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0168] Example 28 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 6, except for using the fine fibrous cellulose dispersion obtained in Production Example 11. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0169] Example 29 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 8, except for using the fine fibrous cellulose dispersion obtained in Production Example 11. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0170] Example 30 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 10, except for using the fine fibrous cellulose dispersion obtained in Production Example 11. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0171] Example 31 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 4, except for using the fine fibrous cellulose dispersion obtained in Production Example 12. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0172] Example 32 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 6, except for using the fine fibrous cellulose dispersion obtained in Production Example 12. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0173] Example 33 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 8, except for using the fine fibrous cellulose dispersion obtained in Production Example 12. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0174] Example 34 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 10, except for using the fine fibrous cellulose dispersion obtained in Production Example 12. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0175] Example 35 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 4, except for using the fine fibrous cellulose dispersion obtained in Production Example 14. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0176] Example 36 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 6, except for using the fine fibrous cellulose dispersion obtained in Production Example 14. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0177] Example 37 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 8, except for using the fine fibrous cellulose dispersion obtained in Production Example 14. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0178] Example 38 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 10, except for using the fine fibrous cellulose dispersion obtained in Production Example 14. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0179] Example 39 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 4, except for using the fine fibrous cellulose dispersion obtained in Production Example 15. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0180] <Example 40> A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 6, except for using the fine fibrous cellulose dispersion obtained in Production Example 15. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0181] <Example 41> A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 8, except for using the fine fibrous cellulose dispersion obtained in Production Example 15. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0182] <Example 42> A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 10, except for using the fine fibrous cellulose dispersion obtained in Production Example 15. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0183] <Example 43> The fine fibrous cellulose dispersion obtained in Production Example 16 was used, and an ozone concentration of 40 g / m 3 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 1, except that an ozone / oxygen mixed gas of 2.0×10 was used. The ozone addition rate at this time was 2.0×10 per 1 g of fine fibrous cellulose. -3 The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0184] <Example 44> The fine fibrous cellulose dispersion obtained in Production Example 17 was used, and the ozone concentration was 40 g / m 3 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 1, except that an ozone / oxygen mixed gas of 2.0×10 was used. The ozone addition rate at this time was 2.0×10 per 1 g of fine fibrous cellulose.-3 The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0185] Example 45 A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 4, except for using the fine fibrous cellulose dispersion obtained in Production Example 13. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0186] <Comparative Example 1> An ozone concentration of 200 g / m was added to 500 g of the fine fibrous cellulose dispersion obtained in Production Example 1 (solid content concentration 2% by mass, solid content 20 g). 3 The mixture was stirred for 2 minutes at 25°C in a sealed container and then allowed to stand for 120 minutes. The ozone addition rate was 4.0 x 10 per 1 g of fine fibrous cellulose. -2 g. The vessel was then opened and stirred for 5 hours to volatilize any ozone remaining in the dispersion. The mixture was then treated three times with a high-pressure homogenizer at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion. Thus, the fine fibrous cellulose was made less thixotropic, and the viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained less thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0187] <Comparative Example 2> For 100 g of the phosphorylated pulp obtained in Production Example 5 (solid content concentration 20 mass%, solid content 20 g), an ozone concentration of 200 g / m 3 The mixture was stirred for 2 minutes at 25°C in a sealed container and then allowed to stand for 30 minutes. The ozone addition rate was 1.0 x 10 per 1 g of fine fibrous cellulose. -2g. The phosphorylated pulp was then washed to remove any remaining ozone. The resulting pulp was then used to prepare a slurry with a solids concentration of 2% by mass. This slurry was treated six times with a wet atomization device (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. The resulting fine fibrous cellulose dispersion was used as is to measure the viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze using the methods described below.

[0188] <Comparative Example 3> A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Comparative Example 1, except for using the fine fibrous cellulose dispersion obtained in Production Example 6. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0189] <Comparative Example 4> A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Comparative Example 2, except for using the phosphorylated pulp obtained in Production Example 8. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0190] <Comparative Example 5> The fine fibrous cellulose dispersion obtained in Production Example 1 was used as it was to measure the viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze by the methods described below.

[0191] <Comparative Example 6> The fine fibrous cellulose dispersion obtained in Production Example 6 was used as it was to measure the viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze by the methods described below.

[0192] <Comparative Example 7> The fine fibrous cellulose dispersion obtained in Production Example 9 was used as it was to measure the viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze by the methods described below.

[0193] <Comparative Example 8> The fine fibrous cellulose dispersion obtained in Production Example 10 was used as it was to measure the viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze by the methods described below.

[0194] <Comparative Example 9> A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 4, except for using the fine fibrous cellulose dispersion obtained in Production Example 5. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0195] <Comparative Example 10> A low thixotropic fine fibrous cellulose dispersion was obtained in the same manner as in Example 6, except for using the fine fibrous cellulose dispersion obtained in Production Example 5. The viscosity, degree of polymerization, viscosity change rate, fiber width, fiber length, and haze of the obtained low thixotropic fine fibrous cellulose dispersion were measured by the methods described below.

[0196] <Comparative Example 11> A low-thixotropy fine fibrous cellulose dispersion was obtained in the same manner as in Example 3, except that the fine fibrous cellulose dispersion obtained in Production Example 18 was used. The obtained low-thixotropy fine fibrous cellulose dispersion clearly contained residual coarse fibers, and the haze (haze value at 0.2% concentration) and dispersibility were poor. Therefore, the viscosity, viscosity change rate, and coatability of the dispersion, as well as the surface roughness and agglomerates of the coating film, were not measured or evaluated.

[0197] <Measurement> [Measurement of phosphorus oxoacid group content] The amount of phosphorus oxoacid groups in the fine fibrous cellulose was measured by treating a fibrous cellulose-containing slurry with an ion exchange resin after diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion exchange water to a content of 0.2 mass% and then titrating the slurry with an alkali. Treatment with ion exchange resin was carried out by adding 1 / 10 by volume of a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) to the above 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 fibrous cellulose-containing slurry 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 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 was divided by the solid content (g) in the slurry to be titrated, and the value was taken as the amount of phosphorus oxo acid groups (mmol / g).

[0198] [Measurement of sulfur oxoacid group content] The amount of sulfate groups was measured using wet ashing of the sample and ICP emission spectrometry. Specifically, the fibrous cellulose-containing slurry obtained in Production Example 7 was dried and then weighed, and perchloric acid was added to carbonize it. Concentrated nitric acid was then added to oxidize the carbon to carbon dioxide, yielding a sample solution consisting only of inorganic substances. This sample solution was diluted to an appropriate ratio, and the sulfate ion concentration was measured by ICP emission spectrometry. The amount of sulfate groups was determined by dividing the amount of sulfur atoms contained in the sample solution by the mass of the weighed fibrous cellulose.

[0199] [Measurement of Carboxy Group Amount] The amount of carboxyl groups in the fine fibrous cellulose was measured by adding ion-exchanged water to a fine fibrous cellulose-containing slurry containing the target fine fibrous cellulose to adjust the content to 0.2 mass%, treating the slurry with an ion-exchange resin, and then titrating the slurry with an 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 pH of the fibrous cellulose-containing slurry after ion exchange resin treatment while adding 10 μL of 0.1 N aqueous sodium hydroxide every 5 seconds. Observing the change in pH while adding aqueous sodium hydroxide yielded the titration curve shown in Figure 2. As shown in Figure 2, 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 2 is called Region 1. The amount of alkali required in Region 1 was equal to the amount of carboxyl groups in the slurry used for titration. The amount of alkali required in Region 1 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.

[0200] [Fiber length measurement] The fiber length of the fine fibrous cellulose after the thixotropy reduction treatment was determined by AFM image analysis of samples prepared by diluting the fine fibrous cellulose dispersion to 0.001% by mass. The fiber lengths of Examples 1 to 45 were 250 nm at the shortest and 610 nm at the longest, while the fiber lengths of Comparative Examples 1 to 11 were 230 nm at the shortest and 760 nm at the longest. The fiber width of the fine fibrous cellulose after the thixotropy reduction treatment was determined using an electron microscope. The fiber widths of Examples 1 to 45 and Comparative Examples 1 to 10 were 3 to 5 nm.

[0201] [Measurement of viscosity of fine fibrous cellulose dispersion] The viscosity of the fine fibrous cellulose dispersions obtained in the Examples and Comparative Examples was measured as follows. First, the fine fibrous cellulose dispersion was diluted with ion-exchanged water to a solids concentration of 0.4% by mass, and then stirred in a disperser at 1500 rpm for 5 minutes. Next, the viscosity of the dispersion thus obtained was measured using a B-type viscometer (BLOOKFIELD, analog viscometer T-LVT). 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 dispersion. Furthermore, the dispersion to be measured was left to stand for 24 hours in an environment of 23°C and relative humidity 50% before measurement. The liquid temperature of the dispersion during measurement was 23°C.

[0202] [Measurement of specific viscosity and degree of polymerization of fine fibrous cellulose] The specific viscosity and degree of polymerization of the fine fibrous cellulose obtained in the examples and comparative examples were measured according to Tappi T 230. The cellulose fiber to be measured was dispersed in a dispersion medium to measure the viscosity (referred to as η1), and the blank viscosity (referred to as η0) was measured using only the dispersion medium, and then the specific viscosity (ηsp) and intrinsic viscosity ([η]) were measured according to the following formulas. ηsp=(η1 / η0)-1 [η]=ηsp / (c(1+0.28×ηsp)) Here, c in the formula represents the concentration (g / mL) of the fine fibrous cellulose at the time of viscosity measurement. Furthermore, the degree of polymerization (DP) of the fine fibrous cellulose was calculated using the following formula. DP=1.75×[η] This degree of polymerization is an average degree of polymerization measured by a viscosity method, and is therefore sometimes called the "viscosity-average degree of polymerization."

[0203] [Measurement of viscosity change rate of fine fibrous cellulose dispersion] The viscosity change rate of the fine fibrous cellulose dispersion was measured as follows. (Measurement of viscosity before stirring) First, water and isopropanol were added sequentially to the fine fibrous cellulose dispersions obtained in the Examples and Comparative Examples so that the viscosity, measured by the method described below, was approximately 2500 mPa·s and the mass ratio of water to isopropanol contained in the dispersion was 7:3. The dispersions thus obtained were placed in a cylindrical container with a diameter of 10 cm to a height of 5 cm and stirred at 1500 rpm for 5 minutes using a disperser. One minute after the end of stirring, the viscosity of the obtained fine fibrous cellulose dispersions was measured using a Brookfield analog viscometer (T-LVT). The measurement conditions were a rotation speed of 6 rpm, and the viscosity value one minute after the start of measurement was taken as the viscosity of the dispersion. The temperature of the dispersions during measurement was 23°C. (Stirring with a stir bar) The resulting fine fibrous cellulose dispersion, with a viscosity of approximately 2500 mPa s, was then poured into a cylindrical container with a diameter of 10 cm to a height of 5 cm and stirred for 24 hours using an oval stirrer with a length of 5 cm, a width of 2 cm at the center, and a width of 1 cm at the edge, while maintaining a 2 cm depression in the center of the liquid surface. The temperature of the dispersion during stirring was 23°C. (Measurement of viscosity after stirring) One minute after the stirring with the stirrer was completed, the viscosity of the fine fibrous cellulose dispersion was immediately measured using a Brookfield analog viscometer (T-LVT). The measurement was performed at a rotation speed of 6 rpm, and the viscosity value one minute after the start of the measurement was recorded as the viscosity of the dispersion. The temperature of the dispersion during the measurement was 23°C. (Calculation of viscosity change rate) The viscosity change rate before and after stirring with a stirring bar was calculated using the following formula. Viscosity change rate (%) = (viscosity after stirring - viscosity before stirring) / viscosity before stirring × 100

[0204] [Measurement of haze of fine fibrous cellulose dispersion] The haze of the fine fibrous cellulose dispersion was measured as follows. The fine fibrous cellulose dispersions obtained in the Examples and Comparative Examples were diluted with ion-exchanged water to a solids concentration of 0.2% by mass, and then degassed using a planetary centrifugal supermixer (ARE-250, manufactured by Thinky Corporation). The haze of the dispersion thus obtained was then measured using a haze meter (HM-150, manufactured by Murakami Color Research Laboratory Co., Ltd.) in accordance with JIS K 7136:2000, using a glass cell for liquids with an optical path length of 1 cm (MG-40, manufactured by Fujiwara Seisakusho Co., Ltd., reverse optical path). The zero-point measurement was performed using ion-exchanged water placed in the same glass cell.

[0205] [Evaluation of Appearance of Fine Fibrous Cellulose Dispersion] The fine fibrous cellulose dispersions obtained in the examples and comparative examples were subjected to a degassing treatment using an automatic revolution type super mixer (ARE-250, manufactured by Thinky Corporation), after which the appearance was visually evaluated according to the following criteria. A: Fibres are barely visible to the naked eye and the dispersion is transparent. B: Almost no fibers can be seen with the naked eye, and the dispersion liquid is translucent. C: The fibers are not uniformly dispersed and the dispersion is cloudy, or granular matter (fiber aggregates) can be seen.

[0206] [Evaluation of defoaming properties of fine fibrous cellulose] The fine fibrous cellulose dispersions obtained in the Examples and Comparative Examples were diluted with ion-exchanged water to a solids concentration of 1% by mass, then stirred at 4000 rpm for 3 minutes in a disperser, and defoamed using an automatic orbital super mixer (ARE-250, manufactured by Thinky Corporation). The defoaming ability was evaluated based on the time required to complete the defoaming treatment, using the following evaluation criteria. A: The degassing process was completed within 2 minutes. B: The defoaming process was completed within 2 to 4 minutes. C: The defoaming treatment was completed within 4 to 8 minutes. D: It took more than 8 minutes to complete the degassing process.

[0207] [Evaluation of particle dispersibility of fine fibrous cellulose dispersion] The fine fibrous cellulose dispersions obtained in the Examples and Comparative Examples were diluted with ion-exchanged water to a solids concentration of 1% by mass, and then stirred at 4000 rpm for 3 minutes in a disperser. The mixture was then degassed using an automatic orbital super mixer (ARE-250, manufactured by Thinky Corporation). Glass beads (diameter 3 mm, specific gravity 2.5 g / cm) were added to the cellulose dispersions. 3 The beads were added to the dispersion, and the settling of the beads was confirmed. The particle dispersibility was evaluated according to the following criteria. A: The beads are uniformly dispersed for more than 24 hours. B: The beads are uniformly dispersed for 5 hours or more but less than 24 hours. C: The beads are uniformly dispersed for 10 minutes or more but less than 5 hours. D: Beads settle in less than 10 minutes.

[0208] [Evaluation of paint application suitability] The coating suitability of the paints using the fine fibrous cellulose dispersions obtained in the Examples and Comparative Examples was evaluated as follows. (Preparation of paint containing fine fibrous cellulose) To 100 parts by mass of a fine fibrous cellulose dispersion with a viscosity of approximately 2500 mPa·s obtained by the same method as above, 1 part by mass of a glittering material (aluminum paste WXM7640, manufactured by Toyo Aluminum Co., Ltd., aluminum concentration 58-61% by mass) was added, and the mixture was stirred in a disperser at 1500 rpm for 5 minutes to obtain a paint containing fine fibrous cellulose. (Paint circulation and spray coating) The resulting fine fibrous cellulose-containing paint was then circulated through the piping for 24 hours using a pump-type circulation device. Immediately after the circulation was completed, the fine fibrous cellulose-containing paint was applied to the wall surface using a spray gun, and the presence or absence of dripping was confirmed. In addition, the presence or absence of settling of the lustrous material in the fine fibrous cellulose-containing paint during application was visually confirmed. Based on the results of paint dripping and lustrous material settling, the coating suitability of the fine fibrous cellulose-containing paint was evaluated on a four-point scale. A: No dripping or settling of the glitter material was observed during coating after the paint was circulated, and the coating suitability was very good. B: Either dripping or settling of the glitter material is observed during coating after paint circulation, but it is minor and the coating suitability is good. C: Dripping and settling of the glitter material were observed during coating after the paint was circulated, and the coating suitability was somewhat poor, but this was not a problem in practice. D: There was a lot of dripping and settling of the glitter material during coating after the paint was circulated, making the coating suitability poor and problematic for practical use.

[0209] [Evaluation of coating film appearance] The appearance of the coating film of the paint using the fine fibrous cellulose dispersion obtained in this embodiment was evaluated as follows. (Preparation of paint containing fine fibrous cellulose) 24.9 g of a fine fibrous cellulose dispersion with a solids concentration of 0.4% by mass was placed in a beaker, and 34.4 g of ion-exchanged water, 35.2 g of acrylic resin, and 5.49 g of curing agent were added in that order. The addition was carried out while stirring at 1500 rpm using a TK Homodisper (manufactured by Tokushu Kika Kogyo). After all the ingredients were added, the mixture was stirred for an additional 5 minutes and then degassed using a degassing device (Thinky Corporation, planetary centrifugal mixer AR-250). In this way, a fine fibrous cellulose-containing coating material was obtained with a solids ratio of 78% acrylic resin, 22% curing agent, and 0.5% fine fibrous cellulose (by mass).

[0210] (Preparation of coating film for evaluation) The resulting coating was applied to a PET (polyethylene terephthalate) film (manufactured by Toray Industries, Inc., product name: Lumirror T60, thickness 75 μm) substrate using an applicator so that the coating thickness after drying would be 30 μm. Immediately after coating, the film was heated in a dryer at 80°C for 30 minutes to obtain a cured coating film with the PET film as the substrate.

[0211] (Surface roughness of coating film) The surface roughness of the resulting cured coating was measured. Specifically, an optical interference non-contact surface profiler (Ryoka Systems Co., Ltd., non-contact surface / layer cross-sectional profile measurement system VertScan2.0, model R5500GML) was used to measure the arithmetic mean roughness (Ra (μm)) of the cured coating over a measurement range of 470.92 μm × 353.16 μm using a ×10 objective lens. Measurements were performed five times per level, and the arithmetic mean roughness was calculated from the average value. Details of the definition, measurement conditions, and calculation method of arithmetic mean roughness (Ra) were in accordance with JIS B 0601:2013.

[0212] (Number of aggregates) The coating material with a PET film substrate was observed using an optical microscope (Nikon Corporation), and the thickness was measured at 1 mm. 2 The number of aggregates N (pieces / mm 2 ) was checked at 100 points, and the arithmetic mean value (N / 100) was calculated. The results were evaluated as follows: A: The arithmetic mean value of aggregates with a size of 5 μm or more is 3 / mm 2 is less than B: The arithmetic mean value of aggregates with a size of 5 μm or more is 3 / mm 2 or more but less than 8 C: The arithmetic mean value of aggregates with a size of 5 μm or more is 8 / mm 2 More than 13 pieces / mm 2 is less than D: The arithmetic mean value of aggregates with a size of 5 μm or more is 13 / mm 2 That's all The size of the aggregates was measured as the equivalent circle diameter, and the details of the measurement conditions, calculation method, etc. were in accordance with JIS Z 8827-1:2008.

[0213] [Table 1]

[0214] [Table 2]

[0215] [Table 3]

[0216] [Table 4]

[0217] [Table 5]

[0218] [Table 6]

[0219] The fine fibrous cellulose obtained in the examples had excellent particle dispersibility, and the paints using it exhibited excellent coating suitability. Furthermore, when the paints using the fine fibrous cellulose obtained in the examples were used, coating films with smooth surfaces and little generation of aggregates were obtained. Furthermore, the fine fibrous cellulose obtained in the examples had excellent dispersion transparency and also good defoaming properties.

Claims

1. A fibrous cellulose having a fiber width of 1000 nm or less and having an ionic substituent, the amount of the ionic substituent in the fibrous cellulose is 0.10 mmol / g or more and 0.95 mmol / g or less, The degree of polymerization of the fibrous cellulose is 150 or more and 515 or less, When the fibrous cellulose is dispersed in water to a concentration of 0.2% by mass to prepare a dispersion, the haze of the dispersion is 20% or less, A fibrous cellulose in which, when the fibrous cellulose is dispersed in a dispersion solvent comprising water and isopropanol to obtain a dispersion having a water to isopropanol mass ratio of 7:3 and a viscosity of 2500 mPa s at 23°C, and when the dispersion is stirred under the following stirring conditions, a viscosity change rate calculated by the following formula is within ±50%; Viscosity change rate (%) = (viscosity after stirring - viscosity before stirring) / viscosity before stirring × 100 (Mixing conditions) A dispersion liquid having a viscosity of 2500 mPa s at 23°C is poured into a cylindrical container having a diameter of 10 cm to a height of 5 cm, and stirred at 23°C for 24 hours using an oval stirrer having a length of 5 cm, a width of 2 cm at the center, and a width of 1 cm at the end, while maintaining a depression of 2 cm in the center of the liquid surface.

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

3. 3. The fibrous cellulose according to claim 1, wherein when the fibrous cellulose is dispersed in water to a concentration of 0.4% by mass to form a dispersion, the viscosity of the dispersion at 23°C is 20 mPa·s or more and 4700 mPa·s or less.

4. The fibrous cellulose according to any one of claims 1 to 3, wherein the degree of polymerization of the fibrous cellulose is 460 or more and 515 or less.

5. The fibrous cellulose according to any one of claims 1 to 4, which is used for paints.

6. A fibrous cellulose dispersion obtained by dispersing the fibrous cellulose according to any one of claims 1 to 5 in a solvent containing water.

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