Dispersion

Abstract

To provide a sheet which is excellent in transparency and suppresses curling.SOLUTION: A dispersion liquid contains a fibrous cellulose that has a fiber width of 1,000 nm or less and has an ionic substituent, in which a content of the fibrous cellulose is 3.0 mass% or more with respect to the total mass of the dispersion liquid, and a TI value of the dispersion liquid calculated by the following condition (a) of 1 or more and 80,000 or less. Condition (a): viscosity (η1) on the condition of a shear rate of the dispersion liquid of 1 sec-1 and viscosity (η2) on the condition of shear rate of the dispersion liquid of 1,000 sec-1 are measured using a rheometer, and the TI value is calculated from the following expression: TI value=η1 / η2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a dispersion. Specifically, this invention relates to a dispersion containing fine fibrous cellulose. [Background technology]

[0002] Traditionally, cellulose fibers have been widely used in clothing, absorbent materials, paper products, and other applications. 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 is attracting attention as a new material, and its applications are diverse.

[0003] In the production of fine fibrous cellulose, the slurry containing the cellulose raw material is subjected to defibration treatment (mechanical treatment). For example, Patent Document 1 discloses a method for producing fine fibers that includes a step of treating the cellulose raw material with an enzyme and a step of defibrating the cellulose raw material after enzyme treatment. Here, the goal is to sufficiently refine the cellulose raw material by enzyme treatment and increase the yield of fine fibers. Furthermore, Patent Document 1 aims to produce fine fibers with long fiber length and a large aspect ratio.

[0004] Furthermore, Patent Document 2 discloses a fine fibrous cellulose having an average fiber width of 200 nm or less, a degree of polymerization of 50 to 500, and having a predetermined polar group. In this document, the goal is to obtain a fine fibrous cellulose that does not easily form aggregates when mixed with an emulsion resin. In the examples of Patent Document 2, a dispersion was obtained with a degree of polymerization of 248 to 454 and a viscosity of 108 to 740 at a 0.5% concentration. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2013 / 176033

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The uses of a dispersion containing microfibrillar cellulose are diverse, and various studies have been conducted on its processing methods. For example, forming a microfibrillar cellulose-containing sheet by coating or papermaking a microfibrillar cellulose dispersion has been studied. However, when trying to form a sheet from a conventional microfibrillar cellulose dispersion, it has been revealed by the studies of the present inventors that the transparency of the obtained sheet is poor or curling occurs in the sheet.

[0007] Therefore, the present inventors have proceeded with studies aiming to provide a sheet having excellent transparency and suppressed curling in order to solve such problems of the prior art.

Means for Solving the Problems

[0008] As a result of intensive studies to solve the above problems, the present inventors have found that in a dispersion containing fibrillar cellulose having a fiber width of 1000 nm or less and an ionic substituent, by setting the content of the fibrillar cellulose to 3.0% by mass or more based on the total mass of the dispersion and setting the TI value of the dispersion to 1 or more and 80000 or less, a sheet having excellent transparency and suppressed curling can be obtained. Specifically, the present invention has the following configuration.

[0009] [1] A dispersion containing fibrillar cellulose having a fiber width of 1000 nm or less and an ionic substituent, where the content of the fibrillar cellulose is 3.0% by mass or more based on the total mass of the dispersion, and the TI value of the dispersion calculated by the following condition (a) is 1 or more and 80000 or less; Condition (a): Using a rheometer, the shear rate of the dispersion is 1 sec , , ,

[0009] , -1 , , Viscosity (η1) under these conditions and shear rate of dispersion at 1000 sec -1 The viscosity (η²) is measured under the specified conditions, and the TI value is calculated using the following formula. TI value = η1 / η2 [2] The dispersion according to [1], wherein the fibrous cellulose content is 4.0% by mass or more of the total mass of the dispersion. [3] The dispersion according to [1], wherein the fibrous cellulose content is 5.0% by mass or more of the total mass of the dispersion. [4] The dispersion according to [1], wherein the fibrous cellulose content is 6.0% by mass or more relative to the total mass of the dispersion. [5] The dispersion according to any one of [1] to [4], wherein the ionic substituent is at least one selected from the group consisting of a phosphorus oxoacid group, a substituent derived from a phosphorus oxoacid group, a sulfur oxoacid group, and a substituent derived from a sulfur oxoacid group. [6] The dispersion according to any one of [1] to [5], wherein the haze is 95% or less when the dispersion is concentrated to 0.2% by mass. A sheet formed from any of the dispersions described in [7] [1] to [6]. [Effects of the Invention]

[0010] According to the present invention, a sheet with excellent transparency and suppressed curling can be obtained. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 illustrates a method for evaluating the curl resistance of a sheet. [Figure 2] Figure 2 is a graph showing the relationship between the amount of NaOH added to a slurry containing fibrous cellulose with phosphorus oxoacid groups and the pH. [Figure 3] Figure 3 is a graph showing the relationship between the amount of NaOH added to a slurry containing fibrous cellulose with carboxyl groups and the pH. [Modes for carrying out the invention]

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

[0013] (dispersion) The dispersion containing fibrous cellulose in this embodiment is a dispersion containing fibrous cellulose having a fiber width of 1000 nm or less and having ionic substituents, wherein the fibrous cellulose content is 3.0% by mass or more relative to the total mass of the dispersion, and the TI value of the dispersion calculated according to the following condition (a) is 1 or more and 80000 or less. Condition (a): Using a rheometer, the shear rate of the dispersion was 1 sec. -1 Viscosity (η1) under these conditions and shear rate of dispersion at 1000 sec -1 The viscosity (η²) is measured under the specified conditions, and the TI value is calculated using the following formula. TI value = η1 / η2

[0014] In this specification, fibrous cellulose with a fiber width of 1000 nm or less is also referred to as fine fibrous cellulose. Furthermore, a dispersion containing fine fibrous cellulose is also referred to as a fine fibrous cellulose dispersion, a fine fibrous cellulose-containing dispersion, or a fine fibrous cellulose-containing slurry.

[0015] Since the dispersion of this embodiment has the above-described configuration, it is possible to form a sheet with excellent transparency and suppressed curling. Conventionally, in dispersions containing 3.0% by mass or more of fine fibrous cellulose, the viscosity is high, making it impossible to form a sheet from such a dispersion, or even if a sheet is formed, the sheet has a large curl width. In addition, the formed sheet sometimes had poor transparency. However, in this embodiment, by increasing the concentration of the fine fibrous cellulose dispersion and controlling the TI value of such a high-concentration dispersion within a predetermined range, we succeeded in improving the transparency and curl resistance of the sheet formed from the dispersion. Thus, when a sheet is formed from the dispersion of this embodiment, a sheet with high transparency and suppressed curling can be obtained.

[0016] In the sheet formed from the dispersion of this embodiment, curling is suppressed. That is, the sheet formed from the dispersion of this embodiment has excellent curl resistance. When evaluating curl resistance, first, a sheet for evaluation is formed. Specifically, a coating solution is prepared by mixing solutions in which each component is dispersed such that the solid content mass of fine fibrous cellulose is 100 parts by mass and the solid content mass of polyethylene oxide is 20 parts by mass. Next, the coating solution is measured and a sheet is formed so that the finished thickness of the resulting sheet (the layer composed of the solid content of the coating solution) is 40 μm. Next, the obtained fine fibrous cellulose-containing sheet is cut into a test piece measuring 15 mm in width and 130 mm in length. As shown in Figure 1, one end of the test piece 50, including one of its short sides, is supported by a curl test jig 55 measuring 30 mm in width, 30 mm in length, and 25 mm in height (100 mm of the test piece is exposed from the jig). The test piece is then placed on a horizontal table at a temperature of 23°C and a relative humidity of 50%, with the width direction of the test piece perpendicular to the table (the longitudinal direction of the test piece parallel to the table). The curl width at the end of the test piece 50 is measured and defined as the curl width C0 (the distance of C0 in Figure 1). After standing for 24 hours, the curl width is measured again and defined as C1 (the distance of C1 in Figure 1), and C1-C0 is defined as the amount of curl. When the value of the amount of curl C1-C0 is calculated from the curl width measured in this way, C1-C0 is preferably 25 mm or less, and more preferably 5 mm or less. Note that C1-C0 may also be 0 mm. Furthermore, if the curl is 25 mm or less, the sheet can be judged to have excellent curl resistance.

[0017] Furthermore, the dispersion of this embodiment is not limited to sheet applications. As a high-concentration dispersion, the dispersion of this embodiment is expected to have a wider range of applications.

[0018] Furthermore, since the dispersion of this embodiment contains a high concentration of fine fibrous cellulose, it is possible to significantly reduce storage and transportation costs. Conventionally, in dispersions containing fine fibrous cellulose, the concentration of fine fibrous cellulose was about 2% by mass. On the other hand, in the dispersion of this embodiment, it is possible to have a high concentration of fine fibrous cellulose of 3.0% by mass or more, which enables a significant reduction in storage and transportation costs, and also improves the production efficiency of the dispersion.

[0019] The content of fine fibrous cellulose should be 3.0% by mass or more relative to the total mass of the dispersion, preferably 4.0% by mass or more, more preferably 5.0% by mass or more, and even more preferably 6.0% by mass or more. There is no particular upper limit to the content of fine fibrous cellulose in the dispersion, but it can be, for example, 20% by mass. Thus, the dispersion in this embodiment is a high-concentration fine fibrous cellulose dispersion. By setting the content of fine fibrous cellulose in the dispersion within the above range, the curl resistance of the sheet formed from the dispersion can be more effectively improved. This is because forming a sheet from a high-concentration fine fibrous cellulose dispersion reduces the amount of water introduced into the sheet manufacturing process, thereby suppressing thermal shrinkage during heating.

[0020] The TI value of the dispersion should be 1 or higher, preferably 10 or higher, more preferably 30 or higher, even more preferably 50 or higher, even more preferably 70 or higher, and particularly preferably 100 or higher. Furthermore, the TI value of the dispersion should be 80,000 or less, preferably 70,000 or less, more preferably 50,000 or less, even more preferably 30,000, and particularly preferably 20,000 or less. By setting the TI value of the dispersion within the above range, the curl resistance of the sheet formed from the dispersion can be more effectively enhanced. Additionally, by setting the TI value of the dispersion within the above range, it is possible to appropriately control the spread of the dispersion while imparting appropriate flowability when producing a sheet from the dispersion, thus enabling the production of a uniform sheet even with a highly concentrated dispersion.

[0021] Here, the TI value of the dispersion is calculated according to the following condition (a). Condition (a): Using a rheometer, the shear rate of the dispersion was 1 sec. -1 Viscosity (η1) under these conditions and shear rate of dispersion at 1000 sec -1 The viscosity (η²) is measured under the specified conditions, and the TI value is calculated using the following formula. TI value = η1 / η2 Specifically, viscosity (η1) and viscosity (η2) are measured under the following conditions. For the rheometer used for measurement, for example, a HAAKE RheoStress 6000 can be used. Measurement temperature: 23℃ Measuring jig: Cone plate (40mm diameter, 1° angle) Shear rate: 0.001~1000 sec -1 Number of data points: 100 Data distribution: Log interval Measurement time: 5 minutes

[0022] Shear rate of dispersion at 1 sec -1The viscosity (η1) under the conditions is preferably 1 Pa·s or more, more preferably 10 Pa·s or more, and even more preferably 50 Pa·s or more. Shear rate 1 sec -1 The viscosity (η1) under the conditions is preferably 5,000 Pa·s or less, more preferably 4,000 Pa·s or less, and even more preferably 3,000 Pa·s or less. Also, for the dispersion liquid, shear rate 1000 sec -1 The viscosity (η2) under the conditions is preferably 0.007 Pa·s or more, more preferably 0.01 Pa·s or more, and even more preferably 0.05 Pa·s or more. Shear rate 1000 sec -1 The viscosity (η2) under the conditions is preferably 100 Pa·s or less, more preferably 50 Pa·s or less, and even more preferably 10 Pa·s or less.

[0023] When the dispersion liquid has a concentration of 0.2% by mass, the haze is preferably 95% or less, more preferably 90% or less, even more preferably 80% or less, still more preferably 70% or less, even still more preferably 50% or less, yet even still more preferably 30% or less, particularly preferably 10% or less, and most preferably 5% or less. Incidentally, the haze when the dispersion liquid has a concentration of 0.2% by mass may be 0%. When measuring the haze of the dispersion liquid, the concentration of the microfibrillar cellulose is adjusted to 0.2% by mass and then the haze is measured. The haze of the dispersion liquid is the value measured using a haze meter (manufactured by Murakami Color Technology Laboratory, HM-150) in accordance with JIS K 7136:2000, with the dispersion liquid having a concentration adjusted to 0.2% by mass placed in a glass cell for liquids (manufactured by Fujiwara Seisakusho, MG-40, reverse optical path) with an optical path length of 1 cm. Incidentally, the dispersion liquid to be measured is left standing for 24 hours in an environment of 23°C and a relative humidity of 50% before measurement. Also, the zero-point measurement during haze measurement is performed using ion-exchanged water placed in the same glass cell. By setting the haze of the dispersion liquid with a concentration of 0.2% by mass within the above range, it becomes easier to form a sheet with excellent transparency.

[0024] When measuring the viscosity of a dispersion, the viscosity of a fine fibrous cellulose dispersion is measured without dilution. The viscosity of the dispersion is measured using a B-type viscometer at 23°C with a rotation speed of 0.3 rpm, and the viscosity value is recorded 3 minutes after the start of measurement. As a B-type viscometer, for example, a BLOOKFIELD DV2T digital viscometer can be used.

[0025] The viscosity of the dispersion at a concentration of 3.0% by mass is preferably 10 million mPa·s or less, more preferably 9 million mPa·s or less, and even more preferably 8 million mPa·s or less. Furthermore, the viscosity of the dispersion at a concentration of 3.0% by mass is preferably 100,000 mPa·s or more, more preferably 200,000 mPa·s or more, and even more preferably 300,000 mPa·s or more. The viscosity of the dispersion at a concentration of 6.0% by mass is preferably 50 million mPa·s or less, more preferably 30 million mPa·s or less, and even more preferably 20 million mPa·s or less. Furthermore, the viscosity of the dispersion at a concentration of 6.0% by mass is preferably 500,000 mPa·s or more, more preferably 700,000 mPa·s or more, and even more preferably 1 million mPa·s or more. The viscosity of the dispersion at a concentration of 13.0% by mass is preferably 100 million mPa·s or less, more preferably 50 million mPa·s or less, and even more preferably 30 million mPa·s or less. Furthermore, the viscosity of the dispersion at a concentration of 13.0% by mass is preferably 1 million mPa·s or more, more preferably 5 million mPa·s or more, and even more preferably 10 million mPa·s or more.

[0026] The dispersion in this embodiment is preferably a dispersion containing fine fibrous cellulose and a dispersion medium. The dispersion medium is not particularly limited, but it preferably contains water, and more preferably a solvent mainly composed of water. That is, the dispersion in this embodiment is preferably an aqueous dispersion containing fine fibrous cellulose. The dispersion medium may also be an organic solvent. Examples of organic solvents include dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), aniline, pyridine, quinoline, lutidine, acetonitrile, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), dioxane, ethanol, isopropanol, etc. Alternatively, a mixed solvent obtained by mixing these organic solvents with water can be used as the dispersion medium.

[0027] The dispersion of this embodiment is a high-concentration dispersion containing 3.0% by mass or more of fine fibrous cellulose, but it is obtained without a concentration process. Furthermore, the dispersion of this embodiment is distinct from, for example, a dispersion obtained by redispersing a solid body of fine fibrous cellulose. In other words, the dispersion of this embodiment is neither a concentrated dispersion nor a concentrated-reduced dispersion. The dispersion of this embodiment is the dispersion obtained after undergoing a defibration process as described later. For this reason, the dispersion of this embodiment does not contain any components involved in concentration and concentration-reducing, such as flocculants.

[0028] In conventional techniques, attempts have been made to increase the concentration of fine fibrous cellulose by adding a flocculant to the dispersion or by heating and concentrating it. However, our studies have shown that when flocculants are used or heating and concentrating is performed in this way, the fine fibrous cellulose aggregates unevenly, and in some cases aggregates are formed, resulting in the TI value of the dispersion exceeding 80,000. Furthermore, even in dispersions obtained by redispersing aggregates, the fine fibrous cellulose is unevenly dispersed, making it impossible to achieve the desired TI value of the dispersion.

[0029] Furthermore, with conventional technology, it was difficult to obtain high-concentration aqueous dispersions of 3.0% by mass or more, and it was impossible to obtain high-concentration aqueous dispersions of 6.0% by mass or 13.0% by mass at all. Moreover, even when a fine fibrous cellulose dispersion obtained with conventional technology was concentrated to an aqueous dispersion of 6.0% by mass or 13.0% by mass, the aqueous dispersion would become gel-like or granular material (agglomerations of fibers) would be generated, making it impossible to obtain a uniform aqueous dispersion. Naturally, it was impossible to measure the viscosity of such high-concentration aqueous dispersions. For example, when an aqueous dispersion of 0.5-2.0% by mass was subjected to defibration treatment and then concentrated by heat treatment or evaporator, film-like material would be generated on the walls during the concentration process, making it impossible to obtain a dispersion of 6.0% by mass or more in which fine fibrous cellulose is uniformly dispersed. Therefore, it is impossible to obtain high-concentration aqueous dispersions such as 6.0% by mass or 13.0% by mass, and it is not possible to obtain dispersions with a viscosity within the above range in high-concentration aqueous dispersions of 6.0% by mass or 13.0% by mass.

[0030] On the other hand, in this embodiment, since a dispersion obtained without a concentration process is used, a highly uniform dispersion can be obtained. Furthermore, the TI value of the dispersion can be set within the range of 1 to 80,000. For this reason, when a sheet is formed from the dispersion of this embodiment, for example, a sheet with high transparency and excellent curl resistance can be obtained. In addition, in this embodiment, the dispersion of phosphorylated pulp subjected to defibration treatment is made highly concentrated, and defibration treatment is applied to such a high-concentration pulp dispersion, and if necessary, a low-molecular-weight treatment as described later is also applied, making it possible to measure the viscosity of an aqueous dispersion containing 3.0% by mass or more of fine fibrous cellulose (for example, an aqueous dispersion of 6.0% by mass or 13.0% by mass), and succeeding in obtaining an aqueous dispersion with relatively low viscosity as a high-concentration dispersion.

[0031] (fibrous cellulose) The dispersion of this embodiment contains fibrous cellulose with a fiber width of 1000 nm or less. More preferably, the fiber width of the fibrous cellulose is 100 nm or less, and even more preferably 8 nm or less.

[0032] The fiber width of fibrous cellulose can be measured, for example, by electron microscopy. The average fiber width of fibrous cellulose is, for example, 1000 nm or less. Preferably, the average fiber width of fibrous cellulose is, for example, 2 nm to 1000 nm, more preferably 2 nm to 100 nm, even more preferably 2 nm to 50 nm, and particularly preferably 2 nm to 10 nm. By setting the average fiber width of fibrous cellulose to 2 nm or more, the dissolution of cellulose molecules in water is suppressed, and the effects of improved strength, rigidity, and dimensional stability due to fibrous cellulose can be more easily expressed. Fibrous cellulose is, for example, monocrystalline cellulose.

[0033] 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% to 0.1% by mass is prepared, and this suspension is cast onto a hydrophilic carbon film-coated grid to prepare a sample for TEM observation. If wide fibers are present, an SEM image of the surface cast on glass may be observed. Next, electron microscope images are observed at a magnification of 1000x, 5000x, 10000x, or 50000x depending on the width of the fibers to be observed. However, the sample, observation conditions, and magnification should be adjusted to meet the following conditions.

[0034] (1) A straight line X is drawn at any point in the observed image, and 20 or more fibers intersect with this straight line X. (2) A line Y is drawn perpendicular to the line in the same image, and 20 or more fibers intersect with line Y.

[0035] For observation images that satisfy the above conditions, the width of the fibers intersecting with lines X and Y is visually read. In this way, at least three sets of observation images of surface areas that do not overlap are obtained. Next, for each image, the width of the fibers intersecting with lines X and Y is read. This allows for the reading of at least 20 × 2 × 3 = 120 fiber widths. The average of the read fiber widths is then taken as the average fiber width of the fibrous cellulose.

[0036] The fiber length of fibrous cellulose is not particularly limited, but is preferably between 0.1 μm and 1000 μm, more preferably between 0.1 μm and 800 μm, and even more preferably between 0.1 μm and 600 μm. By keeping the fiber length within the above range, the fracture of the crystalline region of the fibrous cellulose can be suppressed. It is also possible to set the slurry viscosity of the fibrous cellulose within an appropriate range. The fiber length of fibrous cellulose can be determined, for example, by image analysis using TEM, SEM, or AFM.

[0037] It is preferable that the fibrous cellulose has a type I crystalline structure. The presence of a type I crystalline structure in fibrous cellulose can be identified by the diffraction profile obtained from a wide-angle X-ray diffraction photograph using graphite-monochromatized CuKα (λ=1.5418Å). Specifically, it can be identified by the presence of typical peaks at two locations: around 2θ=14° to 17° and around 2θ=22° to 23°. The proportion of type I crystalline structure in the fine fibrous cellulose is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. This allows for 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 analyzing its pattern using conventional methods (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

[0038] The axial ratio (fiber length / fiber width) of fibrous cellulose is not particularly limited, but is preferably 30 to 10,000, and more preferably 50 to 1,000. In this specification, fibrous cellulose with a fiber width of 1,000 nm or less (fine fibrous cellulose) is defined as cellulose nanofiber (CNF), and fibrous cellulose (fine fibrous cellulose) does not include cellulose nanocrystal (CNC). The axial ratio (fiber length / fiber width) of cellulose nanocrystal (CNC) is usually around 10 to 30. Furthermore, setting the axial ratio of fibrous cellulose to or above the above lower limit is preferable in that it facilitates handling, such as dilution, when handling fibrous cellulose as an aqueous dispersion.

[0039] The fibrous cellulose in this embodiment, for example, has both crystalline and amorphous regions. Fine fibrous cellulose having both crystalline and amorphous regions and having an axial ratio within the above range can be realized by the fine fibrous cellulose manufacturing method described later.

[0040] The fibrous cellulose in this embodiment has an ionic substituent. The ionic substituent may include, for example, either an anionic group or a cationic group, or both. In this embodiment, it is particularly preferable that the ionic substituent has an anionic group. Furthermore, it is preferable that the ionic substituent is a group that breaks the ester bond and links to the fibrous cellulose. In this case, the ester bond is formed by the dehydration condensation of the fibrous cellulose and the compound that becomes the ionic substituent.

[0041] The anionic substituent is preferably at least one selected from, for example, a phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group (sometimes simply referred to as a phosphorus oxoacid group), a carboxyl group or a substituent derived from a carboxyl group (sometimes simply referred to as a carboxyl group), and a sulfur oxoacid group or a substituent derived from a sulfur oxoacid group (sometimes simply referred to as a sulfur oxoacid group). It is more preferably at least one selected from a phosphorus oxoacid group and a carboxyl group, and particularly preferably a phosphorus oxoacid group. By introducing a phosphorus oxoacid group as an ionic substituent into fibrous cellulose, it becomes easier to obtain a highly transparent dispersion, and as a result, it becomes easier to obtain a sheet with superior transparency. Furthermore, introducing a phosphorus oxoacid group into fibrous cellulose can also improve the salt resistance of the fibrous cellulose.

[0042] A phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group is, for example, a substituent represented by the following formula (1). Multiple substituents represented by the following formula (1) may be introduced into each fibrous cellulose. In this case, the multiple substituents represented by the following formula (1) may be the same or different.

[0043] [ka]

[0044] In equation (1), a, b, and n are natural numbers, and m is any number (where a = b × m). Of the n α and α', at least one is O - The rest are R or OR. Note that all of each α and α' are O - It is acceptable for this to be the case. The n αs may all be the same, or they may all be different. β b+ It is a cation with one or more valencies, composed of organic or inorganic substances.

[0045] 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. In formula (1), n ​​is preferably 1.

[0046] Examples of saturated linear hydrocarbon groups include, but are not limited to, methyl, ethyl, n-propyl, or n-butyl groups. Examples of saturated branched hydrocarbon groups include, but are not limited to, i-propyl or t-butyl groups. Examples of saturated cyclic hydrocarbon groups include, but are not limited to, cyclopentyl or cyclohexyl groups. Examples of unsaturated linear hydrocarbon groups include, but are not limited to, vinyl or allyl groups. Examples of unsaturated branched hydrocarbon groups include, but are not limited to, i-propenyl or 3-butenyl groups. Examples of unsaturated cyclic hydrocarbon groups include, but are not limited to, cyclopentenyl or cyclohexenyl groups. Examples of aromatic groups include, but are not limited to, phenyl or naphthyl groups.

[0047] Furthermore, as derivative groups in R, carboxyl groups and carboxylate groups (-COO) are added to the main chain or side chain of the various hydrocarbon groups mentioned above. - Examples of functional groups include, but are not particularly limited to, a functional group in which at least one selected from functional groups such as hydroxyl groups, amino groups, and ammonium groups is added or substituted. Furthermore, the number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R within the above range, the molecular weight of the phosphorus oxoacid group can be set within an appropriate range, which facilitates penetration into the fiber raw material and can also increase the yield of fine cellulose fibers. In addition, when there are multiple Rs in formula (1) or when multiple substituents represented by the above formula (1) are introduced into fibrous cellulose, the multiple Rs may be the same or different.

[0048] β b+β is a cation with one or more valencies composed of organic or inorganic substances. Examples of cations with one or more valencies composed of organic substances include organic onium ions. Examples of organic onium ions include organic ammonium ions and organic phosphonium ions. Examples of organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of organic phosphonium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of cations with one or more valencies composed of inorganic substances include alkali metal ions such as sodium, potassium, or lithium, divalent metal ions such as calcium or magnesium, hydrogen ions, and ammonium ions. Note that β is included in formula (1). b+ If multiple β atoms exist, or if multiple substituents represented by formula (1) above are introduced into fibrous cellulose, then multiple β atoms exist. b+ These may be the same or different. As a monovalent or greater cation consisting of organic or inorganic material, β b+ Sodium or potassium ions are preferred because they do not easily yellow when the fiber raw material containing them is heated, and are also easily usable industrially, but the material is not particularly limited.

[0049] More specifically, substituents derived from a phosphorus oxoacid group include a phosphate group (-PO3H2), a salt of a phosphate group, a phosphonotic group (phosphonic acid group) (-PO2H2), and a salt of a phosphonotic group (phosphonic acid group). Furthermore, substituents derived from a phosphorus oxoacid group may also be groups formed by condensation of a phosphate group (e.g., a pyrophosphate group), groups formed by condensation of a phosphonic acid (e.g., a polyphosphonic acid group), phosphate ester groups (e.g., monomethyl phosphate group, polyoxyethylene alkyl phosphate group), alkylphosphonic acid groups (e.g., a methylphosphonic acid group), and the like.

[0050] Furthermore, the sulfur oxoacid group (sulfur oxoacid group or substituent derived from a sulfur oxoacid group) is, for example, a substituent represented by the following formula (2). Multiple substituents represented by the following formula (2) may be introduced into each fibrous cellulose. In this case, the substituents represented by the following formula (2) that are introduced may be the same or different.

[0051] [ka]

[0052] In the above structural formula, b and n are natural numbers, p is 0 or 1, and m is any number (where 1 = b × m). Note that if n is 2 or greater, the multiple p values ​​may be the same number or different numbers. In the above structural formula, β b+ β is a cation with one or more valencies composed of organic or inorganic substances. Examples of cations with one or more valencies composed of organic substances include organic onium ions. Examples of organic onium ions include organic ammonium ions and organic phosphonium ions. Examples of organic ammonium ions include aliphatic ammonium ions and aromatic ammonium ions, and examples of organic phosphonium ions include aliphatic phosphonium ions and aromatic phosphonium ions. Examples of cations with one or more valencies composed of inorganic substances include alkali metal ions such as sodium, potassium, or lithium, divalent metal ions such as calcium or magnesium, hydrogen ions, and ammonium ions. When multiple substituents represented by the above formula (2) are introduced into fibrous cellulose, multiple β atoms are present. b+ These may be the same or different. As a monovalent or greater cation consisting of organic or inorganic material, β b+ Sodium or potassium ions are preferred because they do not easily yellow when the fiber raw material containing them is heated, and are also easily usable industrially, but the material is not particularly limited.

[0053] The amount of ionic substituent introduced to fibrous cellulose is preferably 0.10 mmol / g or more per 1 g (mass) of fibrous cellulose, more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.60 mmol / g or more, even more preferably 0.90 mmol / g or more, and particularly preferably 1.00 mmol / g or more. In particular, when the amount of ionic substituent introduced to fibrous cellulose is 1.00 mmol / g or more, the load during defibration can be reduced, and the transparency of the resulting fine fibrous cellulose dispersion or sheet can be further increased. Furthermore, when the amount of ionic substituent introduced to fibrous cellulose is 1.00 mmol / g or more, the salt tolerance of the fibrous cellulose can also be improved. Furthermore, the amount of ionic substituent introduced to fibrous cellulose is preferably 5.20 mmol / g or less per 1 g (mass) of fibrous cellulose, more preferably 3.65 mmol / g or less, even more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, even more preferably 2.00 mmol / g or less, and particularly preferably 1.50 mmol / g or less. Here, the denominator in the unit mmol / g is the amount in which the counterion of the ionic substituent is a hydrogen ion (H + This indicates the mass of fibrous cellulose when ). By keeping the amount of ionic substituents within the above range, it is possible to easily refine the fiber raw material and improve the stability of fibrous cellulose. Furthermore, by keeping the amount of ionic substituents within the above range, it becomes easier to obtain a dispersion that contains a high concentration of fine fibrous cellulose while maintaining a haze value within a predetermined range.

[0054] The amount of ionic substituent introduced into fibrous cellulose can be measured, for example, by neutralization titration. In neutralization titration, the amount introduced is determined by measuring the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the resulting slurry containing fibrous cellulose.

[0055] Figure 2 is a graph showing the relationship between the amount of NaOH added to a slurry containing fibrous cellulose with phosphorus oxoacid groups and the pH. The amount of phosphorus oxoacid groups introduced into the fibrous cellulose can be measured, for example, as follows. First, the slurry containing fibrous cellulose is treated with a strong acid ion exchange resin. If necessary, a defibration treatment similar to the defibration treatment step described later may be performed on the sample to be measured before treatment with the strong acid ion exchange resin. Next, the pH change is observed while adding sodium hydroxide solution, and a titration curve like the one shown in the upper part of Figure 2 is obtained. In the titration curve shown in the upper part of Figure 2, the measured pH is plotted against the amount of alkali added, and in the titration curve shown in the lower part of Figure 2, the increment (derivative value) (1 / mmol) of pH with respect to the amount of alkali added is plotted. In this neutralization titration, two points are observed in the curve plotting the measured pH against the amount of alkali added where the increment (derivative value of pH with respect to the amount of alkali added) is maximum. 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 the titration to the first endpoint is equal to the amount of the first dissociated acid from 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 the second dissociated acid from the fibrous cellulose contained 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 from the fibrous cellulose contained in the slurry used for titration. The value obtained by dividing the amount of alkali required from the start of the titration to the first endpoint by the solid content (g) of the slurry being titrated is the amount of phosphorus oxoacid groups introduced (mmol / g). Note that when simply referred to as the amount of phosphorus oxoacid groups introduced (or amount of phosphorus oxoacid groups), it refers to the amount of the first dissociated acid. In Figure 2, the region from the start of titration to the first endpoint is called the first region, and the region from the first endpoint to the second endpoint is called the second region. For example, if the phosphorus oxoacid group is a phosphate group and this phosphate group undergoes condensation, the amount of weakly acidic group in the phosphorus oxoacid group (also referred to as the amount of the second dissociated acid in this specification) appears to decrease, and the amount of alkali required in the second region becomes less than the amount of alkali required in the first region. On the other hand, the amount of strongly acidic group in the phosphorus oxoacid group (also referred to as the amount of the first dissociated acid in this specification) is equal to the amount of phosphorus atoms, regardless of whether condensation occurs or not. Also, if the phosphorus oxoacid group is a phosphorous acid group, there is no weakly acidic group in the phosphorus oxoacid group, so the amount of alkali required in the second region becomes less, or in some cases, the amount of alkali required in the second region becomes zero. In this case, there is only one point on the titration curve where the pH increment is maximum.

[0056] The amount of phosphorus oxoacid groups introduced (mmol / g) mentioned above represents the amount of phosphorus oxoacid groups present in acid-type fibrous cellulose (hereinafter referred to as phosphorus oxoacid group amount (acid type)), since the denominator represents the mass of acid-type fibrous cellulose. On the other hand, if the counterion of the phosphorus oxoacid group is substituted with an arbitrary cation C such that it is equivalent in charge, the amount of phosphorus oxoacid groups present in fibrous cellulose with cation C as the counterion can be determined by converting the denominator to the mass of fibrous cellulose when cation C is the counterion (hereinafter referred to as phosphorus oxoacid group amount (C type)). In other words, it is calculated using the following formula. Phosphorus oxoacid group amount (C type) = Phosphorus oxoacid group amount (acid type) / {1 + (W - 1) × A / 1000} A [mmol / g]: Total amount of anions derived from the phosphorus oxoacid group in fibrous cellulose (total amount of dissociated acids from the phosphorus oxoacid group) W: Formula weight per unit charge of the cation C (for example, Na is 23, Al is 9)

[0057] Figure 3 is a graph showing the relationship between the amount of NaOH added to a dispersion containing fibrous cellulose having a carboxyl group as an ionic substituent and the pH. The amount of carboxyl group introduced into the fibrous cellulose can be measured, for example, as follows. First, a dispersion containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, a defibration treatment similar to the defibration treatment process described later may be performed on the sample before treatment with the strongly acidic ion exchange resin. Next, the pH change is observed while adding an aqueous sodium hydroxide solution to obtain a titration curve as shown in the upper part of Figure 3. In the titration curve shown in the upper part of Figure 3, the measured pH is plotted against the amount of alkali added, and in the titration curve shown in the lower part of Figure 3, the increment (derivative value) (1 / mmol) of pH with respect to the amount of alkali added is plotted. In this neutralization titration, one point is identified in the curve plotting the measured pH against the amount of alkali added where the increment (derivative value of pH with respect to the amount of alkali added) is maximum, and this maximum point is called the first endpoint. Here, the region from the start of titration to the first endpoint in Figure 3 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. Then, the amount of alkali required in the first region of the titration curve (mmol) is divided by the solid content (g) in the dispersion containing the fibrous cellulose to be titrated to calculate the amount of carboxyl groups introduced (mmol / g).

[0058] The above-mentioned amount of carboxyl groups introduced (mmol / g) represents the amount of carboxyl groups present in acidic fibrous cellulose (hereinafter referred to as carboxyl group amount (acidic type)), since the denominator is the mass of acidic fibrous cellulose. On the other hand, if the counterion of the carboxyl group is substituted with an arbitrary cation C such that it is equivalent in charge, the amount of carboxyl groups present in fibrous cellulose with cation C as the counterion (hereinafter referred to as carboxyl group amount (C type)) can be determined by converting the denominator to the mass of fibrous cellulose when the cation C is the counterion. That is, it is calculated using the following formula. Carboxylate group weight (C type) = Carboxylate group weight (acid type) / {1 + (W - 1) × (Carboxylate group weight (acid type)) / 1000} W: Formula weight per unit charge of the cation C (for example, Na is 23, Al is 9)

[0059] In measuring the amount of ionic substituents by titration, if the amount of sodium hydroxide aqueous solution added is too large or the titration interval is too short, accurate values ​​may not be obtained, resulting in a lower-than-actual amount of ionic substituents. Appropriate titration volumes and intervals include, for example, titrating with 10-50 μL of 0.1N sodium hydroxide aqueous solution every 5-30 seconds. Furthermore, to eliminate the influence of carbon dioxide dissolved in the fibrous cellulose-containing slurry, it is desirable to blow an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration until the end of the titration while performing the measurement.

[0060] Furthermore, the amount of sulfur oxoacid groups introduced into fibrous cellulose can be calculated by wet ashing a slurry containing fibrous cellulose, diluting the sample at an appropriate ratio, and measuring the sulfur content. Specifically, fibrous cellulose is wet ashing using perchloric acid and concentrated nitric acid, then diluted at an appropriate ratio, and the sulfur content is measured by ICP emission spectrometry. The value obtained by dividing the sulfur content by the oven-dry mass of the fibrous cellulose tested is defined as the amount of sulfur oxoacid groups (unit: mmol / g).

[0061] The degree of polymerization of the fine fibrous cellulose is preferably 800 or less, more preferably 700 or less, even more preferably 450 or less, and particularly preferably 300 or less. Furthermore, the degree of polymerization of the fibrous cellulose is preferably 100 or more, and even more preferably 150 or more. By setting the degree of polymerization of the fine fibrous cellulose within the above range, it becomes easier to obtain a dispersion with a TI value within a predetermined range while containing a high concentration of fine fibrous cellulose.

[0062] The degree of polymerization of fine fibrous cellulose is calculated from the pulp viscosity measured according to Tappi T230. Specifically, the viscosity (ηX) measured when the fine fibrous cellulose to be measured is dispersed in an aqueous copper ethylenediamine solution, and the blank viscosity (η0) measured using only the dispersion medium are measured. Then, the specific viscosity (ηsp) and intrinsic viscosity ([η]) are measured according to the following formula. ηsp = (ηX / η0) - 1 [η] = ηsp / (c(1 + 0.28 × ηsp)) Here, c in the formula represents the concentration of 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 the average degree of polymerization measured by the viscosity method, and is sometimes referred to as the "viscosity-average degree of polymerization."

[0063] The fibrous cellulose and the dispersion containing said fibrous cellulose according to this embodiment have been described above. In addition, as another embodiment, this specification describes a dispersion containing fine fibrous cellulose having a fiber width of 1000 nm or less and having ionic substituents, wherein the content of fine fibrous cellulose is 5.0% by mass or more and 14.0% by mass or less based on the total mass of the dispersion, the degree of polymerization of the fine fibrous cellulose is 165 or more and 290 or less, and the shear rate of the dispersion measured using a rheometer is 1 sec. -1 Under these conditions, the viscosity (η1) is between 60 Pa·s and 830 Pa·s, and the shear rate of the dispersion, measured using a rheometer, is 1000 sec. -1 A dispersion containing fine fibrous cellulose is also disclosed, having a viscosity (η2) of 0.02 Pa·s or more and 0.56 Pa·s or less under the specified conditions. The ionic substituent is preferably a phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group (among these, a phosphate group). Furthermore, the amount of ionic substituent introduced into the fine fibrous cellulose is preferably 0.90 mmol / g or more and 2.00 mmol / g or less. Further explanations are the same as those for the dispersion containing fibrous cellulose according to this embodiment described above, and are therefore omitted here.

[0064] (Method for producing microfiber cellulose) <Fiber raw materials> Fine fibrous cellulose is produced from cellulose-containing fiber raw materials (cellulose fibers). While there are no particular limitations on the cellulose-containing fiber raw materials, pulp is preferred because it is readily available and inexpensive. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), hardwood dissolved pulp (LDKP, LDSP), softwood dissolved pulp (NDKP, NDSP), soda pulp (AP), unbleached kraft pulp (UKP), and oxygen-bleached kraft pulp (OKP), as well as semi-chemical pulp such as semi-chemical pulp (SCP) and chemigroundwood pulp (CGP), and mechanical pulp such as crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP). Non-wood pulps are not particularly limited, but examples include cotton pulps such as cotton linters and cotton lint, and non-wood pulps such as hemp, straw, and bagasse. Deinking pulps are not particularly limited, but examples include deinking pulps made from recycled paper. The pulps in this embodiment may be one of the above types used alone, or two or more types may be used in mixture. Among the above pulps, wood pulp and deinking pulp are preferred from the viewpoint of ease of availability. Among wood pulps, chemical pulp is more preferred from the viewpoint of a high cellulose ratio and a high yield of fine fibrous cellulose during defibration, and from the viewpoint of obtaining long-fiber fine fibrous cellulose with a large axial ratio due to minimal cellulose decomposition in the pulp. Kraft pulp and sulfite pulp are even more preferred.

[0065] As fiber raw materials containing cellulose, for example, cellulose contained in sea squirts or bacterial cellulose produced by acetic acid bacteria can be used. Alternatively, instead of fiber raw materials containing cellulose, fibers formed from linear nitrogen-containing polysaccharide polymers such as chitin and chitosan can be used.

[0066] <Phosphorus oxoacid group introduction process> The manufacturing process for fine fibrous cellulose includes an ionic substituent introduction step. An example of an ionic substituent introduction step is the phosphorus oxoacid group introduction step. The phosphorus oxoacid group introduction step involves reacting the cellulose-containing fiber raw material with at least one compound (hereinafter also referred to as "compound A") selected from compounds that can introduce phosphorus oxoacid groups by reacting with the hydroxyl groups present in the cellulose-containing fiber raw material. This step yields phosphorus oxoacid group-introduced fibers.

[0067] 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 reaction of the cellulose-containing fiber raw material with compound A may be carried out in the absence of compound B.

[0068] One example of a method for reacting compound A with compound B to a fiber raw material is to mix compound A and compound B with the fiber raw material in a dry, wet, or slurry state. Of these, it is preferable to use a fiber raw material in a dry or wet state, and particularly preferable to use a fiber raw material in a dry state, due to the high uniformity of the reaction. The form of the fiber raw material is not particularly limited, but for example, it is preferably in the form of cotton or a thin sheet. Compounds A and B can be added to the fiber raw material in the form of powder, a solution dissolved in a solvent, or after being heated above the melting point and melted. Of these, it is preferable to add them in the form of a solution dissolved in a solvent, particularly an aqueous solution, due to the high uniformity of the reaction. Compounds A and B may be added to the fiber raw material simultaneously, separately, or as a mixture. The method of adding compounds A and B is not particularly limited, but if compounds A and B are in solution form, the fiber raw material may be immersed in the solution 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 pressing or filtration.

[0069] Compound A used in this embodiment may be any compound having a phosphorus atom and capable of forming an ester bond with cellulose, and is not particularly limited to, but includes phosphoric acid or its salts, phosphorous acid or its salts, dehydrated condensed phosphoric acid or its salts, and phosphoric anhydride (phosphorus pentoxide). As phosphoric acid, various purities can be used, for example, 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid can be used. As phosphorous acid, 99% phosphorous acid (phosphonic acid) can be used. Dehydrated condensed phosphoric acid is obtained by condensing two or more molecules of phosphoric acid through a dehydration reaction, and examples 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, and these can be neutralized to various degrees. Of these, phosphoric acid, sodium phosphoric acid, potassium phosphoric acid, ammonium phosphoric acid, or phosphorous acid, sodium phosphorous acid, potassium phosphorous acid, or ammonium phosphorous acid are preferred from the viewpoint of having high efficiency in introducing phosphate groups, easily improving the defibration efficiency in the defibration process described later, being low cost, and being easily applicable industrially. More preferably, phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, or phosphorous acid or sodium phosphorous acid are preferred.

[0070] 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 to the amount of phosphorus atoms, it is preferable that the amount of phosphorus atoms added to the fiber raw material (oven-dry mass) be 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 keeping 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 keeping the amount of phosphorus atoms added to the fiber raw material below the above upper limit, it is possible to balance the effect of improving yield with cost.

[0071] Compound B used in this embodiment is at least one selected from urea and its derivatives, as described above. Examples of compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea. From the viewpoint of improving the uniformity of the reaction, it is preferable to use compound B as an aqueous solution. 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.

[0072] The amount of compound B added to the fiber raw material (absolute dry weight) is not particularly limited, but is preferably 1% by mass or more and 500% by mass or less, more preferably 10% by mass or more and 400% by mass or less, and even more preferably 100% by mass or more and 350% by mass or less.

[0073] In the reaction of cellulose-containing fiber raw materials with compound A, in addition to compound B, other substances such as amides or amines may be included in the reaction system. 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 act as a particularly good reaction catalyst.

[0074] In the phosphorus oxoacid 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 to efficiently introduce phosphorus oxoacid groups while suppressing thermal decomposition and hydrolysis reactions of the fibers. 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 heat transfer devices can be used for the heat treatment, such as agitation dryers, rotary dryers, disc dryers, roll-type heaters, plate-type heaters, fluidized bed dryers, band-type dryers, filtration dryers, vibrating fluidized bed dryers, airflow dryers, vacuum dryers, infrared heaters, far-infrared heaters, microwave heaters, and high-frequency dryers.

[0075] In the heat treatment according to this embodiment, for example, a method can be employed in which compound A is added to a thin sheet-like fiber raw material by impregnation or other methods, and then heated, or a method can be employed in which the fiber raw material and compound A are kneaded or stirred while heating. This makes it possible to suppress uneven concentration of compound A in the fiber raw material and to introduce phosphorus oxoacid groups more uniformly to the surface of the cellulose fibers contained in the fiber raw material. This is thought to be because, as water molecules move to the surface of the fiber raw material during drying, dissolved compound A is attracted to the water molecules by surface tension and similarly moves to the surface of the fiber raw material (i.e., uneven concentration of compound A is produced), and this can be suppressed.

[0076] Furthermore, the heating device used for the heat treatment is preferably one that can constantly discharge, for example, the moisture held in the slurry and the moisture generated by the dehydration condensation (phosphate esterification) reaction between compound A and hydroxyl groups contained in cellulose, etc., in the fiber raw material, to the outside of the device system. Examples of such heating devices include a forced-air oven. By constantly discharging moisture from the device system, it is possible to 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 fibers. As a result, it becomes possible to obtain fine fibrous cellulose with a high axial ratio.

[0077] The heating time is preferably between 1 second and 300 minutes, more preferably between 1 second and 1000 seconds, and even more preferably between 10 seconds and 800 seconds, after substantially all moisture has been removed from the fiber raw material. In this embodiment, the amount of phosphorus oxoacid groups introduced can be kept within a preferred range by setting the heating temperature and heating time within an appropriate range.

[0078] The phosphorus oxoacid group introduction process only needs to be performed at least once, but it can also be repeated two or more times. By performing the phosphorus oxoacid group introduction process two or more times, a large number of phosphorus oxoacid groups can be introduced into the fiber raw material.

[0079] The amount of phosphorus oxoacid groups introduced into the fiber raw material is preferably 0.10 mmol / g or more per 1 g (mass) of fine fibrous cellulose, more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.60 mmol / g or more, even more preferably 0.90 mmol / g or more, and particularly preferably 1.00 mmol / g or more. Furthermore, the amount of phosphorus oxoacid groups introduced into the fiber raw material is preferably 5.20 mmol / g or less per 1 g (mass) of fine fibrous cellulose, more preferably 3.65 mmol / g or less, even more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, even more preferably 2.00 mmol / g or less, and particularly preferably 1.50 mmol / g or less. By keeping the amount of phosphorus oxoacid groups introduced within the above range, the micronization of the fiber raw material can be facilitated and the stability of the fine fibrous cellulose can be improved. Furthermore, by keeping the amount of phosphorus oxoacid groups introduced within the above range, it becomes easier to obtain a dispersion with a haze value within a predetermined range while still containing a high concentration of fine fibrous cellulose. In addition, by setting the amount of phosphorus oxoacid groups introduced to 1.00 mmol / g or more, the salt tolerance of the fibrous cellulose can also be improved.

[0080] <Carboxyloid introduction process> The manufacturing process for 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 treating the cellulose-containing fiber raw material with an oxidation treatment such as ozono-oxidation, Fenton oxidation, or TEMPO oxidation treatment, or with a compound having a carboxylic acid-derived group or a derivative thereof, or with an acid anhydride or a derivative thereof of a compound having a carboxylic acid-derived group.

[0081] Compounds having a carboxylic acid-derived group are not particularly limited, but examples 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, derivatives of compounds having a carboxylic acid-derived group are not particularly limited, but examples include imidides of acid anhydrides of compounds having a carboxyl group, and derivatives of acid anhydrides of compounds having a carboxyl group. Imidides of acid anhydrides of compounds having a carboxyl group are not particularly limited, but examples include imidides of dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide.

[0082] Acid anhydrides of compounds having a carboxylic acid-derived group are not particularly limited, but examples include acid anhydrides of dicarboxylic acid compounds such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Furthermore, derivatives of acid anhydrides of compounds having a carboxylic acid-derived group are not particularly limited, but examples include acid anhydrides of compounds having a carboxyl group, such as dimethyl maleic anhydride, diethyl maleic anhydride, and diphenyl maleic anhydride, in which at least some of the hydrogen atoms are substituted with substituents such as alkyl groups and phenyl groups.

[0083] In the carboxyl group introduction step, when performing TEMPO oxidation treatment, it is preferable to carry out the treatment under conditions where the pH is between 6 and 8. Such treatment is also called neutral TEMPO oxidation treatment. Neutral TEMPO oxidation treatment can be carried out, for example, by adding pulp as the fiber raw material, a nitroxyl radical such as TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst, and sodium hypochlorite as a sacrificial reagent to a sodium phosphate buffer (pH=6.8). Furthermore, by including sodium chlorite, the aldehyde generated during the oxidation process can be efficiently oxidized to the carboxyl group. Alternatively, the TEMPO oxidation treatment may be carried out under conditions where the pH is between 10 and 11. Such treatment is also called alkaline TEMPO oxidation treatment. Alkaline TEMPO oxidation treatment can be carried out, for example, by adding a nitroxyl radical such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidizing agent to pulp as the fiber raw material.

[0084] The amount of carboxyl groups introduced into fibrous cellulose varies depending on the type of substituent, but for example, when introducing carboxyl groups by TEMPO oxidation, it is preferably 0.10 mmol / g or more per 1 g (mass) of fine fibrous cellulose, more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.60 mmol / g or more, even more preferably 0.90 mmol / g or more, and particularly preferably 1.00 mmol / g or more. Furthermore, the amount of carboxyl groups introduced into fibrous cellulose is preferably 3.65 mmol / g or less, more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, even more preferably 2.00 mmol / g or less, and even more preferably 1.50 mmol / g or less. In addition, when the substituent is a carboxymethyl group, it may be 5.8 mmol / g or less per 1 g (mass) of fine fibrous cellulose. By keeping the amount of carboxyl groups introduced within the above range, it becomes easier to refine the fiber raw material and improve the stability of fibrous cellulose. Furthermore, by keeping the amount of carboxyl groups introduced within the above range, it becomes easier to obtain a dispersion that contains a high concentration of fine fibrous cellulose while maintaining a haze value within a predetermined range.

[0085] <Sulfur oxoacid group introduction process> The manufacturing process for fine fibrous cellulose may include, for example, a sulfur oxoacid group introduction step as an ionic substituent introduction step. In the sulfur oxoacid group introduction step, a cellulose fiber having a sulfur oxoacid group can be obtained by the reaction of a sulfur oxoacid with a hydroxyl group present in the cellulose-containing fiber raw material.

[0086] In the sulfur oxoacid group introduction step, instead of compound A in the <phosphorus oxoacid group introduction step> described above, at least one compound (hereinafter also referred to as "compound C") selected from compounds that can introduce sulfur oxoacid groups by reacting with hydroxyl groups present in the cellulose-containing fiber raw material is used. Compound C can be any compound that has a sulfur atom and can form an ester bond with cellulose, and examples include sulfuric acid or its salts, sulfurous acid or its salts, and sulfuric acid amides, but is not particularly limited. Sulfuric acid of various purities can be used, for example, 96% sulfuric acid (concentrated sulfuric acid) can be used. As sulfurous acid, 5% sulfurous acid water can be used. As sulfates or sulfurous acid salts, examples include lithium salts, sodium salts, potassium salts, and ammonium salts of sulfates or sulfurous acid salts, and these can be neutralized to various degrees. As sulfuric acid amides, sulfamic acid can be used. In the sulfur oxoacid group introduction step, it is preferable to use compound B in the <phosphorus oxoacid group introduction step> described above in the same manner.

[0087] In the sulfur oxoacid group introduction step, it is preferable to mix the cellulose raw material with an aqueous solution containing sulfur oxoacid and urea and / or a urea derivative, and then heat-treat the cellulose raw material. The heat treatment temperature is preferably selected to efficiently introduce sulfur oxoacid groups while suppressing thermal decomposition and hydrolysis reactions of the fibers. The heat treatment temperature is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 150°C or higher. Furthermore, the heat treatment temperature is preferably 300°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower.

[0088] In the heat treatment process, it is preferable to heat until substantially all moisture is removed. Therefore, the heat treatment time varies depending on the amount of moisture contained in the cellulose raw material, the amount of sulfur oxoacid and aqueous solution containing urea and / or urea derivatives added, but it is preferable to heat for 10 seconds or more and 10,000 seconds or less. Various heat transfer devices can be used for the heat treatment, such as hot air dryers, agitation dryers, rotary dryers, disc dryers, roll-type heaters, plate-type heaters, fluidized bed dryers, band-type dryers, filtration dryers, vibrating fluidized bed dryers, airflow dryers, vacuum dryers, infrared heaters, far-infrared heaters, microwave heaters, and high-frequency dryers.

[0089] The amount of sulfur oxoacid groups introduced into the cellulose raw material is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, even more preferably 0.20 mmol / g or more, even more preferably 0.40 mmol / g or more, even more preferably 0.60 mmol / g or more, even more preferably 0.90 mmol / g or more, and particularly preferably 1.00 mmol / g or more. Furthermore, the amount of sulfur oxoacid groups introduced into the cellulose raw material is preferably 5.00 mmol / g or less, more preferably 3.00 mmol / g or less, even more preferably 2.50 mmol / g or less, even more preferably 2.00 mmol / g or less, and particularly preferably 1.50 mmol / g or less. By keeping the amount of sulfur oxoacid groups introduced within the above range, it is possible to facilitate the refinement of the fiber raw material and improve the stability of the fibrous cellulose. Furthermore, by keeping the amount of sulfur oxoacid groups introduced within the above range, it becomes easier to obtain a dispersion that contains a high concentration of fine fibrous cellulose while maintaining a haze value within a predetermined range.

[0090] <Washing Process> In the method for producing fine fibrous cellulose according to this embodiment, a washing step can be performed on the ionic substituent-introduced fibers as needed. The washing step is performed, for example, by washing the ionic substituent-introduced fibers with water or an organic solvent. Furthermore, the washing step may be performed after each of the steps described later, and the number of washing steps performed in each washing step is not particularly limited.

[0091] <Alkali treatment process> When producing fine fibrous cellulose, an alkaline treatment may be performed on the fiber raw material between the ionic substituent introduction step and the defibration treatment step described later. The method of alkaline treatment is not particularly limited, but one example is immersing the ionic substituent-introduced fibers in an alkaline solution.

[0092] The alkali compound contained in the alkaline solution is not particularly limited and may be an inorganic alkali compound or an organic alkali compound. In this embodiment, it is preferable to use sodium hydroxide or potassium hydroxide as the alkali compound due to its high versatility. The solvent contained in the alkaline solution may be either water or an organic solvent. In particular, the solvent contained in the alkaline solution is preferably water or a polar solvent including a polar organic solvent such as alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferred due to its high versatility.

[0093] The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably, for example, 5°C to 80°C, and more preferably 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 preferably, for example, 5 minutes to 30 minutes, and more preferably 10 minutes to 20 minutes. The amount of alkaline solution used in the alkaline treatment is not particularly limited, but is preferably, for example, 100% by mass to 100,000% by mass, and more preferably 1,000% by mass to 10,000% by mass, relative to the absolute dry mass of the ionic substituent-introduced fiber.

[0094] To reduce the amount of alkaline solution used in the alkaline treatment process, the ionic substituent-introduced fibers may be washed with water or an organic solvent after the ionic substituent introduction process and before the alkaline treatment process. After the alkaline treatment process and before the defibration process, it is preferable to wash the alkaline-treated ionic substituent-introduced fibers with water or an organic solvent to improve handling.

[0095] <Acid treatment process> When producing fine fibrous cellulose, the fiber raw material may be treated with acid between the step of introducing ionic substituents and the defibration treatment step described later. For example, the ionic substituent introduction step, acid treatment, alkali treatment, and defibration treatment may be performed in this order.

[0096] The method of acid treatment is not particularly limited, but one example is immersing the fiber material in an acidic solution containing an acid. The concentration of the acidic 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 acidic solution used is not particularly limited, but is preferably 0 to 4, and more preferably 1 to 3. Examples of acids that can be included in the acidic solution include inorganic acids, sulfonic acids, carboxylic acids, etc. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric 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, the use of hydrochloric acid or sulfuric acid is particularly preferred.

[0097] The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 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 preferably 5 minutes to 120 minutes, and more preferably 10 minutes to 60 minutes. The amount of acid solution used in the acid treatment is not particularly limited, but is preferably 100% to 100,000% by mass, and more preferably 1,000% to 10,000% by mass, relative to the absolute dry mass of the fiber raw material.

[0098] <Fibrillation treatment> Fine fibrous cellulose can be obtained by defibrating (mechanically processing) ionic substituent-introduced fibers in a defibration process. In the defibration process, for example, a defibration processing device can be used. The defibration processing device is not particularly limited, but for example, a high-speed defibrator, grinder (stone mill type grinder), high-pressure homogenizer or ultra-high-pressure homogenizer, high-pressure impact grinder, ball mill, bead mill, disc type refiner, conical refiner, twin-screw kneader, vibrating mill, homomixer under high-speed rotation, ultrasonic disperser, or beater can be used. Among the above defibration processing devices, it is more preferable to use a high-speed defibrator, high-pressure homogenizer, or ultra-high-pressure homogenizer, which have less influence from the grinding media and less risk of contamination.

[0099] In the defibration process, for example, it is preferable to dilute the ionic substituent-introduced fibers with a dispersion medium to form a slurry. As the dispersion medium, one or more selected from water and organic solvents such as polar organic solvents can be used. The polar organic solvent is not particularly limited, but for example, alcohols, polyhydric alcohols, ketones, ethers, esters, and aprotic polar solvents are preferred. 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).

[0100] The concentration of cellulose fibers during the defibration process can be set as appropriate, but in this embodiment, the concentration of cellulose fibers during the defibration process is preferably 3.0% by mass or more, more preferably 4.0% by mass or more, even more preferably 5.0% by mass or more, and particularly preferably 6.0% by mass or more. Furthermore, there is no particular upper limit to the concentration of cellulose fibers during the defibration process, but for example, it may be 20.0% by mass. In this embodiment, by setting the concentration of cellulose fibers during the defibration process within the above range, it becomes easier to obtain a sheet with excellent transparency and suppressed curling. In addition, by setting the concentration of cellulose fibers during the defibration process within the above range, it becomes possible to obtain a high-concentration dispersion, which also makes it possible to reduce costs during transportation and storage.

[0101] Furthermore, the slurry obtained by dispersing the ionic substituent-introduced fibers in a dispersion medium may contain solid components other than the ionic substituent-introduced fibers, such as hydrogen-bonding urea.

[0102] <Viscosity reduction treatment> The method for producing fine fibrous cellulose according to this embodiment preferably includes a step of further reducing viscosity in addition to the steps described above. Specifically, it is preferable to include a step of defibrating cellulose fibers that have been appropriately treated as described above to obtain fibrous cellulose with a fiber width of 1000 nm or less, and a step of reducing viscosity to the fibrous cellulose. That is, the method for producing fine fibrous cellulose according to this embodiment preferably includes a step of reducing viscosity after defibrating cellulose fibers. The method may also include a step of reducing viscosity before the defibration step, for example, a step of reducing viscosity before the defibration step and then a step of reducing viscosity after the defibration step. Alternatively, the method may include a step of performing a defibration after the reduction in viscosity, then another step of reducing viscosity, and then another step of defibration. In particular, it is preferable to perform the reduction in viscosity after the defibration step in order to reduce viscosity more effectively.

[0103] The concentration of fine fibrous cellulose or cellulose fibers during the viscosity reduction treatment can be set as appropriate, but it is preferable that it be the same concentration as the concentration of cellulose fibers during the defibration treatment. For example, the concentration of fine fibrous cellulose or cellulose fibers during the viscosity reduction treatment is preferably 3.0% by mass or more, more preferably 4.0% by mass or more, even more preferably 5.0% by mass or more, and particularly preferably 6.0% by mass or more. Furthermore, there is no particular upper limit to the concentration of fine fibrous cellulose or cellulose fibers during the viscosity reduction treatment, but for example, it may be 20.0% by mass. In this embodiment, by setting the concentration of cellulose fibers during the viscosity reduction treatment within the above range, it becomes easier to obtain a sheet with excellent transparency and suppressed curling.

[0104] Examples of processes for reducing viscosity include ozone treatment, enzyme treatment, acid treatment, and subcritical water treatment. Preferably, the process for reducing viscosity is at least one selected from ozone treatment, enzyme treatment, and acid treatment, and particularly preferably at least one selected from ozone treatment and enzyme treatment.

[0105] In the ozone treatment process, 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 × 10⁻⁶. -4 It is preferable to use 1.0 × 10 g or more. -3 It is more preferable to have a value of 1.0 × 10 -2 It is even more preferable to use 1 g or more. The ozone addition rate per 1 g of fine fibrous cellulose is 1.0 × 10 1 It is preferable that the amount be less than or equal to g. After adding ozone to the fine fibrous cellulose dispersion (slurry), it is preferable to stir it for 10 seconds to 10 minutes under conditions of 10°C to 50°C, and then let it stand for 1 minute to 100 minutes.

[0106] In the enzyme treatment process, an enzyme is added to a fine fibrous cellulose dispersion (slurry). The enzyme used is preferably a cellulase enzyme. Cellulase enzymes are classified into a family of carbohydrate hydrolases based on the higher-order structure of the catalytic domain that has the function of hydrolyzing cellulose. Cellulase enzymes are broadly classified into endo-glucanases and cellobiohydrolases based on their cellulose degradation characteristics. Endo-glucanases have high hydrolytic activity towards the amorphous portion of cellulose, soluble cellooligosaccharides, or cellulose derivatives such as carboxymethylcellulose, randomly cleaving their molecular chains from the inside and reducing the degree of polymerization. In contrast, cellobiohydrolases decompose the crystalline portion of cellulose, yielding cellobiose. Cellobiohydrolases also hydrolyze from the ends of cellulose molecules and are also called exo-type or processive enzymes. While the enzyme used in the enzyme treatment process is not particularly limited, the use of endo-glucanases is preferred.

[0107] In the enzyme treatment step, it is preferable to add enzyme so that the enzyme activity is 0.1 nkat or more per 1 g of fine fibrous cellulose, more preferably 1.0 nkat or more, and even more preferably 10 nkat or more. Furthermore, it is preferable to add enzyme so that the enzyme activity is 100,000 nkat or less per 1 g of fine fibrous cellulose, more preferably 50,000 nkat or less, and even more preferably 10,000 nkat or less. After adding enzyme to the fine fibrous cellulose dispersion (slurry), it is preferable to treat it under conditions of 0°C to less than 80°C for 1 minute to 100 hours, and then deactivate the enzyme by placing it under conditions of 80°C or higher.

[0108] The acid treatment step involves mixing with, for example, sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, boric acid, sulfonic acid (e.g., methanesulfonic acid), etc. Among these, the acid treatment step is preferably a step in which the material is mixed with hypochlorous acid (hypochlorous acid treatment step). In the hypochlorous acid treatment step, sodium hypochlorite can also be used in the fine fibrous cellulose dispersion (slurry). The addition rate of sodium hypochlorite is 1.0 × 10⁻⁶ per 1 g of fine fibrous cellulose. -4 It is preferable that it be 1.0 × 10 g or more. -3 It is more preferably 1.0 × 10 g or more. -2 It is even more preferable that it be 1.0 × 10 g or more. -1 It is particularly preferable that the amount be 1 g or more. Also, the sodium hypochlorite addition rate is 1.0 × 10⁻⁶ per 1 g of fine fibrous cellulose. 2 It is preferable that the amount is less than or equal to g. After adding sodium hypochlorite to the fine fibrous cellulose dispersion (slurry), it is preferable to stir the mixture for 1 minute to 10 hours under conditions of 10°C to 50°C.

[0109] It is preferable to further provide a defibration treatment step after the viscosity reduction treatment step. In particular, it is preferable to provide a defibration treatment step before and after the viscosity reduction treatment step. In this case, the defibration treatment step can be exemplified by the same steps as described above, but in particular, it is preferable to use a high-pressure homogenizer or an ultra-high-pressure homogenizer in the defibration treatment step after the viscosity reduction treatment step.

[0110] This embodiment may also relate to a method for producing fine fibrous cellulose, comprising at least one step each of defibration treatment of cellulose fibers having ionic substituents and viscosity reduction treatment. By including at least one step each of defibration treatment of cellulose fibers having ionic substituents and low molecular weight treatment in the method for producing fine fibrous cellulose, the concentration of cellulose fibers during defibration can be increased. This makes it possible to efficiently obtain a high-concentration fine fibrous cellulose dispersion. In this case, the method for producing fine fibrous cellulose may include the defibration treatment step, viscosity reduction treatment step and defibration treatment step in this order, or it may include the viscosity reduction treatment step, defibration treatment step, viscosity reduction treatment step and defibration treatment step in this order. It is preferable that the above-mentioned ionic substituent introduction step, washing step, alkali treatment step, etc., be provided before the first defibration treatment step or viscosity reduction treatment step. In a method for producing such fine fibrous cellulose, the viscosity reduction treatment step is preferably at least one selected from an ozone treatment step, an enzyme treatment step, a hypochlorous acid treatment step, and a subcritical water treatment step, and is particularly preferably at least one selected from an ozone treatment step and an enzyme treatment step.

[0111] (Additives) The dispersion of this embodiment may contain other additives in addition to the fine fibrous cellulose and dispersion medium described above. Examples of other additives include defoamers, lubricants, UV absorbers, dyes, pigments, stabilizers, surfactants, and preservatives (e.g., phenoxyethanol). The fibrous cellulose dispersion may also contain hydrophilic polymers, hydrophilic low molecular weight molecules, organic ions, etc., as optional components.

[0112] The hydrophilic polymer is preferably a hydrophilic oxygen-containing organic compound (excluding the cellulose fibers mentioned above). Examples of oxygen-containing organic compounds 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, alkyl acrylate copolymers, urethane copolymers, and cellulose derivatives (hydroxyethylcellulose, carboxyethylcellulose, carboxymethylcellulose, etc.).

[0113] The hydrophilic low molecular weight is preferably a hydrophilic oxygen-containing organic compound, and more preferably a polyhydric alcohol. Examples of polyhydric alcohols include glycerin, sorbitol, and ethylene glycol.

[0114] 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. In addition, examples of tetrapropylonium ions and tetrabutylonium ions include tetra-n-propylonium ions and tetra-n-butylonium ions, respectively.

[0115] (Method for producing dispersion) This embodiment may also relate to a method for producing the fine fibrous cellulose dispersion described above. The method for producing the fine fibrous cellulose dispersion includes a step of defibrating cellulose fibers having ionic substituents (defibration step) and a step of reducing viscosity (viscosity reduction step). Here, the concentration of cellulose fibers in the defibration step is preferably 3.0% by mass or more, more preferably 4.0% by mass or more, even more preferably 5.0% by mass or more, and particularly preferably 6.0% by mass or more. Similarly, the concentration of fine fibrous cellulose or cellulose fibers in the viscosity reduction step is preferably 3.0% by mass or more, more preferably 4.0% by mass or more, even more preferably 5.0% by mass or more, and particularly preferably 6.0% by mass or more.

[0116] The viscosity reduction process may be performed before the defibration process or after it. Alternatively, the viscosity reduction process may be performed before or after the defibration process. For example, the viscosity reduction process may be performed before the defibration process, and then again after the defibration process. Alternatively, the viscosity reduction process may be performed, followed by the defibration process, followed by another viscosity reduction process, and then the defibration process again. Of these, it is preferable that the viscosity reduction process be performed after the defibration process. Examples of viscosity reduction processes include those described above.

[0117] In the method for producing the dispersion of this embodiment, both a defibration treatment step and a viscosity reduction treatment step are included, and by increasing the concentration of cellulose fibers in the defibration treatment step, it was successful to obtain a high-concentration dispersion with a fibrous cellulose content of 3.0% by mass or more relative to the total mass of the dispersion. Furthermore, in the method for producing the dispersion of this embodiment, by adding a viscosity reduction treatment step in addition to the defibration treatment step, it is possible to set the TI value of the dispersion to between 1 and 80000.

[0118] In the method for producing the dispersion of this embodiment, by setting the concentration of cellulose fibers in the defibration process to 3.0% by mass or more, the concentration of the fine fibrous cellulose dispersion obtained after the defibration process can be set to 3.0% by mass or more. Therefore, there is no need to include a concentration step in the method for producing the dispersion of this embodiment. It is preferable that the method for producing the dispersion of this embodiment does not include a concentration step. Examples of a concentration step include a step of concentration using a flocculant or a step of heat concentration.

[0119] (Application) The dispersion of this embodiment is a dispersion containing a high concentration of fine fibrous cellulose. Therefore, it is particularly suitable for applications where a high concentration of fine fibrous cellulose is desired. For example, the fine fibrous cellulose of this embodiment can be used as an additive in foods, cosmetics, cement, paints (for vehicle coatings such as automobiles, ships, and aircraft, building materials, and daily necessities), inks, pharmaceuticals, etc. Furthermore, the fine fibrous cellulose of this embodiment can be added to resin-based materials and rubber-based materials.

[0120] Furthermore, when a sheet or coating is formed from the dispersion of this embodiment containing a high concentration of fine fibrous cellulose, the mechanical strength of the resulting sheet or coating can be increased. For example, the tensile strength and tensile modulus of the sheet or coating can be more effectively increased. In addition, since the dispersion of this embodiment is highly transparent, the transparency of the resulting sheet or coating can also be increased. Thus, the fine fibrous cellulose dispersion of this embodiment is preferably a dispersion for sheet formation, and this embodiment may also relate to a sheet containing the fine fibrous cellulose described above.

[0121] Furthermore, when a sheet or coating film is formed from the dispersion of this embodiment containing a high concentration of fine fibrous cellulose, a sheet or coating film with a high basis weight can be obtained.

[0122] When manufacturing a sheet from the dispersion of this embodiment, it is preferable to include a coating step in which the dispersion is applied to a substrate, or a papermaking step in which the dispersion is used to make paper.

[0123] In the coating process, for example, a slurry (coating liquid) containing fibrous cellulose is coated onto a substrate, and a sheet is obtained by drying the slurry and peeling the resulting sheet off the substrate. By using a coating apparatus and a long substrate, sheets can be produced continuously. The papermaking process is carried out by making paper from the slurry using a papermaking machine. The papermaking machine used in the papermaking process is not particularly limited, but examples include continuous papermaking machines such as long-wire type, cylinder type, and inclined type, or multi-layer papermaking machines that combine these. In the papermaking process, known papermaking methods such as manual papermaking may be employed.

[0124] The sheet formed from the dispersion of this embodiment may further have a resin layer or an inorganic layer laminated onto it.

[0125] Furthermore, this embodiment may have the following configuration. <101> A dispersion containing fine fibrous cellulose having a fiber width of 1000 nm or less and having ionic substituents, The content of fine fibrous cellulose is 5.0% by mass or more and 14.0% by mass or less of the total mass of the dispersion. The degree of polymerization of the fine fibrous cellulose is between 165 and 290. The shear rate of the dispersion was measured using a rheometer at 1 sec. -1 The viscosity (η1) under these conditions is 60 Pa·s or more and 830 Pa·s or less. The shear rate of the dispersion was measured using a rheometer at 1000 sec. -1 The viscosity (η2) under these conditions is 0.02 Pa·s or more and 0.56 Pa·s or less. A dispersion containing fine fibrous cellulose. <102> The ionic substituent is a phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group. <101> A dispersion containing fine fibrous cellulose as described above. <103> The amount of ionic substituent introduced into the fine fibrous cellulose is between 0.90 mmol / g and 2.00 mmol / g. <101> or <102> A dispersion containing fine fibrous cellulose as described above.

[0126] <111> A process of obtaining fibrous cellulose with a fiber width of 1000 nm or less by subjecting cellulose fibers having ionic substituents to a defibration treatment, A method for producing a fibrous cellulose-containing dispersion, comprising the step of subjecting fibrous cellulose to a viscosity reduction treatment, The fibrous cellulose content is 3.0% by mass or more relative to the total mass of the dispersion. A method for producing a fibrous cellulose-containing dispersion in which the TI value of the dispersion calculated according to the following condition (a) is between 1 and 80,000; Condition (a): Using a rheometer, the shear rate of the dispersion was 1 sec. -1 Viscosity (η1) under these conditions and shear rate of dispersion at 1000 sec -1 The viscosity (η²) is measured under the specified conditions, and the TI value is calculated using the following formula. TI value = η1 / η2 <112> In the process of obtaining fibrous cellulose with a fiber width of 1000 nm or less by defibration treatment, the concentration of cellulose fibers is 3.0% by mass or more. <111> A method for producing a fibrous cellulose-containing dispersion as described above. <113> The viscosity reduction process is at least one selected from ozone treatment, enzyme treatment, acid treatment, and subcritical water treatment. <111> or <112> A method for producing a fibrous cellulose-containing dispersion as described above. <114> The process includes a step of performing a defibration treatment after a step of performing a viscosity reduction treatment. <111> ~ <113> A method for producing a fibrous cellulose-containing dispersion as described in any of the following. <115> <111> ~ <114> A dispersion produced by the method for producing a fibrous cellulose-containing dispersion described in any of the following. [Examples]

[0127] The features of the present invention will be further described below with reference to examples and comparative examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following specific examples.

[0128] <Manufacturing Example 1> [Production of phosphorylated microfibrous cellulose dispersion] The raw material pulp is softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solids content 93% by mass, basis weight 208 g / m²). 2 A sheet of pulp with a Canadian standard filtration efficiency (CSF) of 700 ml (measured according to JIS P 8121-2:2012) was used. This raw material pulp was subjected to phosphorus oxooxidation treatment as follows: First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea was added to 100 parts by mass (oven-dry mass) of the raw material pulp to adjust the mixture to 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water to obtain chemically impregnated pulp. Next, the obtained chemically impregnated pulp was heated in a hot air dryer at 165°C for 200 seconds to introduce phosphate groups into the cellulose in the pulp, thereby obtaining phosphorylated pulp.

[0129] Next, the obtained phosphorylated pulp was subjected to a washing treatment. The washing treatment was carried out by repeatedly adding 10 L of deionized water to 100 g (oven-dry mass) of phosphorylated pulp to obtain a pulp dispersion, stirring the mixture to ensure uniform dispersion of the pulp, and then filtering and dewatering it. The washing was terminated when the electrical conductivity of the filtrate fell to 100 μS / cm or less.

[0130] Next, the washed phosphorylated pulp was subjected to a neutralization treatment as follows. First, the washed phosphorylated pulp was diluted with 10 L of deionized water, and then a 1N sodium hydroxide aqueous solution was gradually added while stirring to obtain a phosphorylated pulp slurry with a pH of 12 to 13. Next, the phosphorylated pulp slurry was dehydrated to obtain phosphorylated pulp that had undergone neutralization treatment. Then, the phosphorylated pulp that had undergone neutralization treatment was subjected to the washing treatment described above.

[0131] The resulting phosphorylated pulp was subjected to infrared absorption spectroscopy using FT-IR. The result showed that 1230 cm⁻¹ -1 Absorption based on phosphate groups was observed in the vicinity, confirming that phosphate groups were attached to the pulp.

[0132] Furthermore, when the obtained phosphorylated pulp was tested and analyzed using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of type I cellulose crystals.

[0133] Deionized water was added to the obtained phosphorylated pulp to prepare a slurry with a solid content of 3% by mass. This slurry was treated once with a single disc refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Groups] below was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0134] <Manufacturing Example 2> Deionized water was added to the phosphorylated pulp obtained in Production Example 1 to prepare a slurry with a solid content of 6% by mass. This slurry was treated once with a single disc refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Groups] below was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0135] <Manufacturing Example 3> Deionized water was added to the phosphorylated pulp obtained in Production Example 1 to prepare a slurry with a solid content of 13% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Group Amount] below was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0136] <Manufacturing Example 4> Deionized water was added to the phosphorylated pulp obtained in Production Example 1 to prepare a slurry with a solid content of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Group Amount] below was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0137] <Manufacturing Example 5> [Production of TEMPO-oxidized fine fibrous cellulose dispersion] As the raw material pulp, softwood kraft pulp (undried) manufactured by Oji Paper Co., Ltd. was used. This raw material pulp was subjected to alkaline TEMPO oxidation treatment as follows: First, 100 parts by mass of the above raw material pulp (equivalent to 100 parts by mass by dry weight), 1.6 parts by mass of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), and 10 parts by mass of sodium bromide were dispersed in 10,000 parts by mass of water. Next, a 13% by mass sodium hypochlorite solution was added to 1.0 g of pulp so that the sodium hypochlorite content was 3.8 mmol, and the reaction was started. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to maintain the pH between 10 and 10.5, and the reaction was considered complete when no change in pH was observed.

[0138] Next, the obtained TEMPO-oxidized pulp was subjected to a washing treatment. The washing treatment was carried out by dewatering the pulp slurry after TEMPO oxidation to obtain a dewatered sheet, adding 5000 parts by mass of deionized water, stirring to uniformly disperse the sheet, and then repeating the filtration and dewatering process. The washing was terminated when the electrical conductivity of the filtrate became 100 μS / cm or less.

[0139] The remaining aldehyde groups in this dehydrated sheet were subjected to further oxidation treatment as follows: 100 parts by mass of the above dehydrated sheet (equivalent to 100 parts by mass by dry weight) was dispersed in 10,000 parts by mass of 0.1 mol / L acetate buffer (pH 4.8). Then, 113 parts by mass of 80% by mass sodium chlorite was added, and the mixture was immediately sealed. The mixture was then stirred at 500 rpm using a magnetic stirrer at room temperature for 48 hours to obtain a pulp slurry.

[0140] Next, the obtained oxidized TEMPO oxidized pulp was subjected to a washing treatment. The washing treatment was carried out by dewatering the pulp slurry after oxidization to obtain a dewatered sheet, adding 5000 parts by mass of deionized water, stirring to uniformly disperse the sheet, and then repeating the filtration and dewatering process. The washing was terminated when the electrical conductivity of the filtrate became 100 μS / cm or less.

[0141] Furthermore, when the obtained TEMPO-oxidized pulp was analyzed using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of type I cellulose crystals.

[0142] Deionized water was added to the obtained TEMPO-oxidized pulp to prepare a slurry with a solid content of 3% by mass. This slurry was processed once using a single-disc refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. The amount of carboxyl groups, as measured by the method described later, was 1.30 mmol / g.

[0143] <Manufacturing Example 6> Deionized water was added to the TEMPO-oxidized pulp obtained in Production Example 5 to prepare a slurry with a solid content of 6% by mass. This slurry was processed once in a single-disc refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. The amount of carboxyl groups, as measured by the measurement method described later, was 1.30 mmol / g.

[0144] <Manufacturing Example 7> Deionized water was added to the TEMPO-oxidized pulp obtained in Production Example 5 to prepare a slurry with a solid content of 13% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of carboxyl groups, as measured by the measurement method described later, was 1.30 mmol / g.

[0145] <Manufacturing Example 8> Deionized water was added to the TEMPO-oxidized pulp obtained in Production Example 5 to prepare a slurry with a solid content of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of carboxyl groups, as measured by the measurement method described later, was 1.30 mmol / g.

[0146] <Manufacturing Example 9> [Production of Phosphorous Acid Microfiber Cellulose Dispersion] The raw material pulp used is softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solids content 93% by mass, basis weight 245 g / m²). 2A sheet-like pulp with a Canadian standard filtration efficiency (CSF) of 700 ml (measured according to JIS P 8121-2:2012) was used. This raw material pulp was subjected to phosphorus oxooxidation treatment as follows: First, a mixed aqueous solution of phosphorous acid (phosphonic acid) and urea was added to 100 parts by mass (oven-dry mass) of the above raw material pulp to prepare a solution of 33 parts by mass of phosphorous acid (phosphonic acid), 120 parts by mass of urea, and 150 parts by mass of water to obtain chemically impregnated pulp. Next, the obtained chemically impregnated pulp was heated in a hot air dryer at 165°C for 250 seconds to introduce phosphorous acid groups into the cellulose in the pulp, thereby obtaining phosphorous oxyphosphate pulp.

[0147] Next, the obtained phosphite pulp was subjected to a washing treatment. The washing treatment was carried out by repeatedly adding 10 L of deionized water to 100 g (oven-dry mass) of phosphite pulp to obtain a pulp dispersion, stirring the dispersion to ensure uniform pulp distribution, and then filtering and dewatering it. The washing was terminated when the electrical conductivity of the filtrate fell to 100 μS / cm or less.

[0148] Next, the washed phosphorylated pulp was subjected to a neutralization treatment as follows. First, the washed phosphorylated pulp was diluted with 10 L of deionized water, and then a 1N sodium hydroxide aqueous solution was gradually added while stirring to obtain a phosphorylated pulp slurry with a pH of 12 to 13. Next, the phosphorylated pulp slurry was dehydrated to obtain neutralized phosphorylated pulp. Then, the neutralized phosphorylated pulp was subjected to the washing treatment described above.

[0149] The resulting phosphorylated pulp was subjected to infrared absorption spectroscopy using FT-IR. The result showed that at 1210 cm⁻¹, the absorption spectrum was measured. -1Absorption based on P=O of the phosphonic acid group, a tautomer of the phosphite group, was observed in the vicinity, confirming that (phosphite) groups (phosphonic acid groups) were added to the pulp. Furthermore, when the obtained phosphite-oxidized pulp was analyzed using an X-ray diffractometer, typical peaks were observed at two locations: around 2θ = 14° to 17° and around 2θ = 22° to 23°, confirming the presence of cellulose type I crystals.

[0150] Deionized water was added to the obtained phosphite pulp to prepare a slurry with a solid content of 3% by mass. This slurry was treated once with a single disc refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. The amount of phosphite groups (amount of first dissociated acid), measured by the method described in [Measurement of Phosphorus Oxoacid Groups] below, was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

[0151] <Manufacturing Example 10> Deionized water was added to the phosphorylated pulp obtained in Production Example 9 to prepare a slurry with a solid content of 6% by mass. This slurry was treated once with a single disc refiner (manufactured by Kumagai Riki Kogyo Co., Ltd.) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. The amount of phosphorous acid groups (amount of first dissociated acid), measured by the measurement method described later in [Measurement of Phosphorus Oxoacid Groups], was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

[0152] <Manufacturing Example 11> Deionized water was added to the phosphorylated pulp obtained in Production Example 9 to prepare a slurry with a solid content of 13% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. The amount of phosphorous acid groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Groups] below was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

[0153] <Manufacturing Example 12> Deionized water was added to the phosphorylated pulp obtained in Production Example 9 to prepare a slurry with a solid content of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion containing fine fibrous cellulose. The amount of phosphorous acid groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Groups] below was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

[0154] <Manufacturing Example 13> Phosphorylated pulp was obtained by performing the same treatment as in Production Example 1, except that the pulp used was hardwood pulp (dry sheet) manufactured by Oji Paper Co., Ltd. Deionized water was added to the obtained phosphorylated pulp to prepare a slurry with a solid content of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. Furthermore, the amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Group Amount] below was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0155] <Manufacturing Example 14> A fibrous cellulose dispersion containing fine fibrous cellulose was obtained by the same method as in Production Example 13, except that the slurry was prepared so that the solid content concentration of the phosphorylated pulp obtained in Production Example 13 was 13% by mass.

[0156] <Manufacturing Example 15> Except for using hardwood pulp (undried) manufactured by Oji Paper Co., Ltd. as in Production Example 5, the same treatment was carried out to obtain TEMPO-oxidized pulp. Ion-exchanged water was added to the obtained TEMPO-oxidized pulp to prepare a slurry with a solid content of 13% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of carboxyl groups measured by the measurement method described later was 1.30 mmol / g.

[0157] <Manufacturing Example 16> Except for using hardwood pulp (dry sheet) manufactured by Oji Paper Co., Ltd. as the pulp in Production Example 9, the same treatment was carried out to obtain phosphorous pulp. Ion-exchanged water was added to the obtained phosphorous pulp to prepare a slurry with a solid content of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet pulverizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. Furthermore, the amount of phosphorous oxyacid groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Group Amount] below was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

[0158] <Manufacturing Example 17> A fibrous cellulose dispersion containing fine fibrous cellulose was obtained by the same method as in Production Example 16, except that the slurry was prepared so that the solid content concentration of the phosphorylated pulp obtained in Production Example 16 was 13% by mass.

[0159] <Manufacturing Example 18> [Pre-hydrolysis] 300g of coniferous wood chips were collected by their oven-dry mass and soaked overnight in 10 liters of tap water. The chips were then removed and filtered through a 400-mesh sieve. The dehydrated chips were placed in a 2.5-liter autoclave, and tap water was added to achieve a liquid-to-mass ratio (where the oven-dry mass of the chips is considered 1) of 3. The autoclave was then heated at 165°C for 30 minutes to perform pre-hydrolysis. The P-factor at this stage was 380. [Cooking] After pre-hydrolysis, the waste gas was removed from the degassing cock of the autoclave, and after confirming that the pressure inside the autoclave had reached 0, the treated chips were sieved through a 400-mesh sieve and filtered. The filtered chips were placed back into a 2.5-liter autoclave, and thawing solution was added to achieve a liquid-to-liquid ratio of 5. Kraft thawing was performed under conditions of thawing temperature of 165°C and thawing time of 120 minutes. The thawing solution contained 21% by mass of active alkali relative to the oven-dry mass of the chips, and the degree of sulfidation was 28%. After thawing, the black liquor and pulp were separated, and the pulp was refined using a flat screen equipped with an 8-cut screen plate to obtain post-thawed pulp. [bleaching] 70 g of oven-dry pulp was collected after pulping, and 2.0% by mass of caustic soda was added to the total mass of the oven-dry pulp. The mixture was then diluted with deionized water to adjust the pulp concentration to 10% by mass. This slurry was placed in an indirect heating autoclave, and 99.9% compressed oxygen gas was injected to set the gauge pressure to 0.5 MPa. The mixture was then oxygenated at 100°C for 60 minutes. After oxygenation, the pressure was reduced to 0.05 MPa or less, the pulp was removed from the autoclave, washed with 7 liters of deionized water, and then dewatered. In this way, oxygen-treated pulp was obtained. 60g of oxygen-bleached pulp was taken by its oven-dry mass, placed in a plastic bag, and deionized water was added to adjust the pulp concentration to 10% by mass. Then, 1.8% by mass of chlorine dioxide was added to the total mass of the oven-dry pulp, and the mixture was immersed in a constant-temperature water bath at 70°C for 70 minutes (D0 stage treatment). After the D0 stage treatment, the pulp obtained was diluted to 3% by mass with deionized water, then dehydrated and washed using a Buchner funnel. The pulp after the D0 stage treatment was placed in a plastic bag, deionized water was added to adjust the pulp concentration to 10% by mass, and then 1.0% by mass of caustic soda and 0.3% by mass of hydrogen peroxide were added to the total mass of the oven-dry pulp and mixed well. Then, the mixture was immersed in a constant-temperature water bath at 70°C for 100 minutes to perform the E / P stage treatment. The obtained pulp was diluted to 3% by mass with deionized water, then dehydrated and washed using a Buchner funnel. The pulp after the E / P stage treatment was placed in a plastic bag, and the pulp concentration was adjusted to 10% by mass using deionized water. Then, 0.3% by mass of chlorine dioxide was added to the total mass of the oven-dried pulp, and the pulp was immersed in a constant temperature water bath at 70°C for 80 minutes to perform the D1 stage bleaching treatment. The obtained pulp was diluted to 3% by mass with deionized water, then dehydrated and washed using a Buchner funnel to obtain bleached pulp. [Phosphorylation] Using this bleached pulp, the same process as in Production Example 1 was performed to obtain phosphorylated pulp. [Fiber removal] Deionized water was added to the obtained phosphorylated pulp to prepare a slurry with a solid content of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Group Amount] below was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0160] <Manufacturing Example 19> A fibrous cellulose dispersion containing fine fibrous cellulose was obtained by the same method as in Production Example 18, except that the slurry was prepared so that the solid content concentration of the phosphorylated pulp obtained in Production Example 18 was 13% by mass.

[0161] <Manufacturing Example 20> Except for using the bleached pulp from Production Example 18, the same process as in Production Example 5 was carried out to obtain TEMPO-oxidized pulp. Ion-exchanged water was added to the obtained TEMPO-oxidized pulp to prepare a slurry with a solid content of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of carboxyl groups, as measured by the measurement method described later, was 1.30 mmol / g.

[0162] <Manufacturing Example 21> A fibrous cellulose dispersion containing fine fibrous cellulose was obtained by the same method as in Production Example 20, except that the slurry was prepared so that the solid content concentration of the TEMPO-oxidized pulp obtained in Production Example 20 was 13% by mass.

[0163] <Manufacturing Example 22> Except for using the bleached pulp from Production Example 18, the same treatment as in Production Example 9 was carried out to obtain phosphite pulp. Ion-exchanged water was added to the obtained phosphite pulp to prepare a slurry with a solid content of 13% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. Furthermore, the amount of phosphite groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Group Amount] below was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

[0164] <Manufacturing Example 23> Except for using hardwood kraft pulp (dry sheet) manufactured by Senibra as the pulp in Production Example 1, the same processing as in Production Example 1 was carried out to obtain phosphorylated pulp. Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry with a solid content of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet pulverizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. Furthermore, the amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Group Amount] below was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0165] <Manufacturing Example 24> A fibrous cellulose dispersion containing fine fibrous cellulose was obtained by the same method as in Production Example 23, except that the slurry was prepared so that the solid content concentration of the phosphorylated pulp obtained in Production Example 23 was 13% by mass.

[0166] <Manufacturing Example 25> For Production Example 5, the raw material pulp was hardwood kraft pulp (dry sheet) manufactured by Senibra, and deionized water was added to it to obtain a slurry with a pulp concentration of 2% by mass. After thoroughly stirring with a disperser at 4000 rpm to obtain a pulp slurry, the slurry was thoroughly dewatered in a mesh bag to obtain wet pulp. The obtained wet pulp was subjected to the same treatment as in Production Example 5 to obtain TEMPO-oxidized pulp. Deionized water was added to the obtained TEMPO-oxidized pulp to prepare a slurry with a solid content concentration of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of carboxyl groups measured by the measurement method described later was 1.30 mmol / g.

[0167] <Manufacturing Example 26> A fibrous cellulose dispersion containing fine fibrous cellulose was obtained by the same method as in Production Example 25, except that the slurry was prepared so that the solid content concentration of the TEMPO-oxidized pulp obtained in Production Example 25 was 13% by mass.

[0168] <Manufacturing Example 27> Except for using hardwood kraft pulp (dry sheet) manufactured by Senibra as the raw material pulp for Production Example 9, the same processing as in Production Example 9 was carried out to obtain phosphorous pulp. Ion-exchanged water was added to the obtained phosphorous pulp to prepare a slurry with a solid content of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet pulping apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. Furthermore, the amount of phosphorous oxyacid groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Group Amount] below was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

[0169] <Manufacturing Example 28> A fibrous cellulose dispersion containing fine fibrous cellulose was obtained by the same method as in Production Example 27, except that the slurry was prepared so that the solid content concentration of the phosphorylated pulp obtained in Production Example 27 was 13% by mass.

[0170] <Manufacturing Example 29> The raw material pulp is softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solids content 93% by mass, basis weight 208 g / m²). 2 A sheet-like pulp with a Canadian standard filtration efficiency (CSF) of 700 ml (measured according to JIS P 8121) after disintegration was used. This raw pulp was subjected to sulfation treatment as follows: First, a mixed aqueous solution of amidosulfuric acid and urea was added to 100 parts by mass (oven-dry mass) of the raw pulp to adjust the mixture to 38 parts by mass of amidosulfuric acid, 120 parts by mass of urea, and 150 parts by mass of water to obtain chemically impregnated pulp. Next, the obtained chemically impregnated pulp was heated in a hot air dryer at 165°C for 20 minutes to introduce sulfate groups into the cellulose in the pulp, thereby obtaining sulfated pulp.

[0171] Next, the obtained sulfated pulp was subjected to a washing treatment. The washing treatment was carried out by repeatedly adding 10 L of deionized water to 100 g (oven-dry mass) of sulfated pulp to obtain a pulp dispersion, stirring the mixture to ensure uniform dispersion of the pulp, and then filtering and dewatering it. The washing was terminated when the electrical conductivity of the filtrate was 100 μS / cm or less. Next, the washed sulfated pulp was subjected to a neutralization treatment as follows. First, the washed sulfated pulp was diluted with 10 L of deionized water, and then a 1N sodium hydroxide aqueous solution was gradually added while stirring to obtain a sulfated pulp slurry with a pH of 12 to 13. Next, the sulfated pulp slurry was dewatered to obtain sulfated pulp that had undergone neutralization treatment. Next, the sulfated pulp after neutralization treatment was subjected to the washing treatment described above.

[0172] The obtained sulfated pulp was subjected to infrared absorption spectroscopy using FT-IR. The results showed that 1220-1260 cm⁻¹ -1 Absorption based on sulfate (sulfone) groups was observed in the vicinity, confirming that sulfate (sulfone) groups were added to the pulp. Furthermore, X-ray diffraction confirmed that the obtained sulfated pulp maintained a cellulose type I crystal structure.

[0173] Deionized water was added to the obtained sulfated pulp to prepare a slurry with a solid content of 6% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of sulfate groups, as measured by the method described in [Measurement of Sulfur Oxoacid Groups] below, was 1.47 mmol / g.

[0174] <Example 1> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 1 (solid content concentration 3% by mass, solid content 30 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion.

[0175] The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing apparatus (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this dispersion was 3% by mass.

[0176] <Example 2> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 1 (solid content concentration 3% by mass, solid content 30 g), an enzyme-containing solution with an activity of 16500 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 3% by mass.

[0177] <Example 3> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 1 (solid content concentration 3.5% by mass, solid content 35 g), 145 g of sodium hypochlorite solution (effective chlorine concentration 12% by mass) was added and thoroughly mixed at room temperature. The sodium hypochlorite addition rate at this time was 0.5 parts by mass per 1 part by mass of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 3% by mass.

[0178] <Example 4> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 5 (solid content concentration 3% by mass, solid content 30 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 3% by mass.

[0179] <Example 5> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 5 (solid content concentration 3% by mass, solid content 30 g), an enzyme-containing solution with an activity of 16500 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst), and then thermally deactivated at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 3% by mass.

[0180] <Example 6> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 5 (solid content concentration 3.5% by mass, solid content 35 g), 145 g of sodium hypochlorite solution (effective chlorine concentration 12% by mass) was added and thoroughly mixed at room temperature. The sodium hypochlorite addition rate at this time was 0.5 parts by mass per 1 part by mass of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 3% by mass.

[0181] <Example 7> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 9 (solid content concentration 3% by mass, solid content 30 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 3% by mass.

[0182] <Example 8> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 9 (solid content concentration 3% by mass, solid content 30 g), an enzyme-containing solution with an activity of 16,500 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 3% by mass.

[0183] <Example 9> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 9 (solid content concentration 3.5% by mass, solid content 35 g), 145 g of sodium hypochlorite solution (effective chlorine concentration 12% by mass) was added and thoroughly mixed at room temperature. The sodium hypochlorite addition rate at this time was 0.5 parts by mass per 1 part by mass of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 3% by mass.

[0184] <Example 10> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 2 (solid content concentration 6% by mass, solid content 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0185] <Example 11> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 2 (solid content concentration 6% by mass, solid content 60 g), an enzyme-containing solution with an activity of 33,000 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing apparatus (Sugino Machine Co., Ltd., Starburst), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0186] <Example 12> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 6 (solid content concentration 6% by mass, solid content 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0187] <Example 13> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 6 (solid content concentration 6% by mass, solid content 60 g), an enzyme-containing solution with an activity of 33,000 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0188] <Example 14> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 10 (solid content concentration 6% by mass, solid content 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0189] <Example 15> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 10 (solid content concentration 6% by mass, solid content 60 g), an enzyme-containing solution with an activity of 33,000 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0190] <Example 16> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 3 (solid content concentration 13% by mass, solid content 130 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion, thereby obtaining a fine fibrous cellulose dispersion. The obtained fine fibrous cellulose dispersion was further processed four times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 13% by mass.

[0191] <Example 17> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 3 (solid content concentration 13% by mass, solid content 130 g), an enzyme-containing solution with an activity of 71500 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was further treated four times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst), and then thermally deactivated at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 13% by mass.

[0192] <Example 18> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 7 (solid content concentration 13% by mass, solid content 130 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion, thereby obtaining a fine fibrous cellulose dispersion. The obtained fine fibrous cellulose dispersion was further processed four times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 13% by mass.

[0193] <Example 19> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 7 (solid content concentration 13% by mass, solid content 130 g), an enzyme-containing solution with an activity of 71500 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was further treated four times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 13% by mass.

[0194] <Example 20> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 11 (solid content concentration 13% by mass, solid content 130 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion, thereby obtaining a fine fibrous cellulose dispersion. The obtained fine fibrous cellulose dispersion was further processed four times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 13% by mass.

[0195] <Example 21> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 11 (solid content concentration 13% by mass, solid content 130 g), an enzyme-containing solution with an activity of 71500 nkat was added and the mixture was enzymatically treated at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was further treated four times at a pressure of 200 MPa using a wet atomizing apparatus (Sugino Machine Co., Ltd., Starburst), and then thermally deactivated at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 13% by mass.

[0196] <Example 22> Deionized water was added to the phosphorylated pulp obtained in Production Example 1 to prepare a slurry with a solid content concentration of 6% by mass. Ozone was added to 1000 g of this slurry (solid content concentration of 6% by mass, solid content of 60 g) at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose, and the mixture was stirred in a sealed container at 25°C, then allowed to stand for 30 minutes. Next, the container was opened and stirred for 5 hours to volatilize the remaining ozone in the dispersion, obtaining a fibrous cellulose dispersion. The obtained fibrous cellulose dispersion was processed four times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0197] <Example 23> Deionized water was added to the phosphorylated pulp obtained in Production Example 1 to prepare a slurry with a solid content concentration of 6% by mass. To 1000 g of this slurry (solid content concentration of 6% by mass, solid content of 60 g), an enzyme-containing solution with an activity of 33000 nkat was added and the slurry was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. The obtained slurry was treated once at a pressure of 200 MPa in a wet atomizing device (Sugino Machine Co., Ltd., Starburst), and then the enzyme treatment was continued. Subsequently, it was treated three more times at a pressure of 200 MPa and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0198] <Example 24> Deionized water was added to the TEMPO-oxidized pulp obtained in Production Example 5 to prepare a slurry with a solid content concentration of 6% by mass. Ozone was added to 1000 g of this slurry (solid content concentration of 6% by mass, solid content of 60 g) at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose, and the mixture was stirred in a sealed container at 25°C, then allowed to stand for 30 minutes. Next, the container was opened and stirred for 5 hours to volatilize the remaining ozone in the dispersion, obtaining a fibrous cellulose dispersion. The obtained fibrous cellulose dispersion was processed four times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0199] <Example 25> Deionized water was added to the TEMPO oxidized pulp obtained in Production Example 5 to prepare a slurry with a solid content concentration of 6% by mass. To 1000 g of this slurry (solid content concentration of 6% by mass, solid content of 60 g), an enzyme-containing solution with an activity of 33000 nkat was added and the slurry was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. The obtained slurry was treated once at a pressure of 200 MPa in a wet atomizer (Sugino Machine Co., Ltd., Starburst), and then the enzyme treatment was continued. Subsequently, it was treated three more times at a pressure of 200 MPa and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0200] <Example 26> Deionized water was added to the phosphorylated pulp obtained in Production Example 9 to prepare a slurry with a solid content concentration of 6% by mass. Ozone was added to 1000 g of this slurry (solid content concentration of 6% by mass, solid content of 60 g) at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose, and the mixture was stirred in a sealed container at 25°C, then allowed to stand for 30 minutes. Next, the container was opened and stirred for 5 hours to volatilize the remaining ozone in the dispersion, obtaining a fibrous cellulose dispersion. The obtained fibrous cellulose dispersion was processed four times at a pressure of 200 MPa using a wet atomizing device (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0201] <Example 27> Deionized water was added to the phosphorylated pulp obtained in Production Example 9 to prepare a slurry with a solid content concentration of 6% by mass. To 1000 g of this slurry (solid content concentration of 6% by mass, solid content of 60 g), an enzyme-containing solution with an activity of 33000 nkat was added and the slurry was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. The obtained slurry was treated once at a pressure of 200 MPa in a wet atomizing device (Starburst, manufactured by Sugino Machine Co., Ltd.), and then the enzyme treatment was carried out. Subsequently, it was treated three more times at a pressure of 200 MPa and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0202] <Example 28> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 4 (solid content concentration 6% by mass, solid content 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0203] <Example 29> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 4 (solid content concentration 6% by mass, solid content 60 g), an enzyme-containing solution with an activity of 33,000 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing apparatus (Sugino Machine Co., Ltd., Starburst), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0204] <Example 30> Deionized water was added to the phosphorylated pulp obtained in Production Example 4 to prepare a slurry with a solid content concentration of 7.5% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. Then, 250 g of sodium hypochlorite solution (effective chlorine concentration 12% by mass) was added to 1000 g of this dispersion (solid content concentration 7.5% by mass, solid content 75 g) and mixed well at room temperature. The sodium hypochlorite addition rate at this time was 0.4 parts by mass per 1 part by mass of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa in a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0205] <Example 31> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 8 (solid content concentration 6% by mass, solid content 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0206] <Example 32> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 8 (solid content concentration 6% by mass, solid content 60 g), an enzyme-containing solution with an activity of 33,000 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0207] <Example 33> Deionized water was added to the TEMPO oxidized pulp obtained in Production Example 8 to prepare a slurry with a solid content concentration of 7.5% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. Then, 250 g of sodium hypochlorite solution (effective chlorine concentration 12% by mass) was added to 1000 g of this dispersion (solid content concentration 7.5% by mass, solid content 75 g) and stirred at room temperature. The sodium hypochlorite addition rate at this time was 0.4 parts by mass per 1 part by mass of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa in a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0208] <Example 34> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 12 (solid content concentration 6% by mass, solid content 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0209] <Example 35> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 12 (solid content concentration 6% by mass, solid content 60 g), an enzyme-containing solution with an activity of 33,000 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0210] <Example 36> Deionized water was added to the phosphorylated pulp obtained in Production Example 12 to prepare a slurry with a solid content of 7.5% by mass. This slurry was processed once at a pressure of 200 MPa in a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. Then, 250 g of sodium hypochlorite solution (effective chlorine concentration 12% by mass) was added to 1000 g of the fine fibrous cellulose dispersion (solid content of 7.5% by mass, solid content 75 g) and stirred at room temperature. The sodium hypochlorite addition rate at this time was 0.4 parts by mass per 1 part by mass of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa in a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0211] <Example 37> In 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 13 (solid content concentration 6% by mass, solid content 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was processed three times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0212] <Example 38> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 18 (solid content concentration 6% by mass, solid content 60 g), an enzyme-containing solution with an activity of 33,000 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing apparatus (Sugino Machine Co., Ltd., Starburst), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0213] <Example 39> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 14 (solid content concentration 13% by mass, solid content 130 g), an enzyme-containing solution with an activity of 71500 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added was 550 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated four times at a pressure of 200 MPa using a wet atomizing apparatus (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 13% by mass.

[0214] <Example 40> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 19 (solid content concentration 13% by mass, solid content 130 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was treated four times at a pressure of 200 MPa using a wet atomizing device (Starburst, manufactured by Sugino Machine Co., Ltd.), and then thermally deactivated at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 13% by mass.

[0215] <Example 41> In 1000 g of the microfibrillar cellulose dispersion obtained in Production Example 20 (solid content concentration: 6% by mass, solid content: 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of the microfibrillar cellulose, and the mixture was stirred at 25°C in a sealed container and then allowed to stand for 30 minutes. Subsequently, the container was opened and the mixture was stirred for 5 hours to volatilize the ozone remaining in the dispersion. The obtained microfibrillar cellulose dispersion was treated 3 times with a wet atomization device (Starburst, manufactured by Sugino Machine Ltd.) at a pressure of 200 MPa to obtain a microfibrillar cellulose dispersion. The concentration of the microfibrillar cellulose in this microfibrillar cellulose dispersion was 6% by mass.

[0216] <Example 42> To 1000 g of the microfibrillar cellulose dispersion obtained in Production Example 15 (solid content concentration: 13% by mass, solid content: 130 g), an enzyme-containing solution having an activity of 71500 nkat was added and enzyme treatment was carried out at a temperature of 50°C. The amount of enzyme added at this time was adjusted to 550 nkat per 1 g of the microfibrillar cellulose. The obtained microfibrillar cellulose dispersion was treated 4 times with a wet atomization device (Starburst, manufactured by Sugino Machine Ltd.) at a pressure of 200 MPa and then heat-inactivated at 100°C to obtain a microfibrillar cellulose dispersion. The concentration of the microfibrillar cellulose in this microfibrillar cellulose dispersion was 13% by mass.

[0217] <Example 43> In 1000 g of the microfibrillar cellulose dispersion obtained in Production Example 16 (solid content concentration: 6% by mass, solid content: 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of the microfibrillar cellulose, and the mixture was stirred at 25°C in a sealed container and then allowed to stand for 30 minutes. Subsequently, the container was opened and the mixture was stirred for 5 hours to volatilize the ozone remaining in the dispersion. The obtained microfibrillar cellulose dispersion was treated 3 times with a wet atomization device (Starburst, manufactured by Sugino Machine Ltd.) at a pressure of 200 MPa to obtain a microfibrillar cellulose dispersion. The concentration of the microfibrillar cellulose in this microfibrillar cellulose dispersion was 6% by mass.

[0218] <Example 44> To 1000 g of the microfibrillar cellulose dispersion obtained in Production Example 22 (solid content concentration: 13% by mass, solid content: 130 g), an enzyme-containing solution having an activity of 71500 nkat was added, and enzyme treatment was performed at a temperature of 50°C. The enzyme addition amount at this time was adjusted to 550 nkat per 1 g of microfibrillar cellulose. The obtained microfibrillar cellulose dispersion was treated 4 times with a wet atomization device (manufactured by Sugino Machine Limited, Starburst) at a pressure of 200 MPa, and then heated to 100°C for heat inactivation to obtain a microfibrillar cellulose dispersion. The concentration of microfibrillar cellulose in this microfibrillar cellulose dispersion was 13% by mass.

[0219] <Example 45> In 1000 g of the microfibrillar cellulose dispersion obtained in Production Example 23 (solid content concentration: 6% by mass, solid content: 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of microfibrillar cellulose, and the mixture was stirred at 25°C in a sealed container and then allowed to stand for 30 minutes. Next, the container was opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. The obtained microfibrillar cellulose dispersion was treated 3 times with a wet atomization device (manufactured by Sugino Machine Limited, Starburst) at a pressure of 200 MPa to obtain a microfibrillar cellulose dispersion. The concentration of microfibrillar cellulose in this microfibrillar cellulose dispersion was 6% by mass.

[0220] <Example 46> To 1000 g of the microfibrillar cellulose dispersion obtained in Production Example 24 (solid content concentration: 13% by mass, solid content: 130 g), an enzyme-containing solution having an activity of 104000 nkat was added, and enzyme treatment was performed at a temperature of 50°C. The enzyme addition amount at this time was adjusted to 800 nkat per 1 g of microfibrillar cellulose. The obtained microfibrillar cellulose dispersion was treated 4 times with a wet atomization device (manufactured by Sugino Machine Limited, Starburst) at a pressure of 200 MPa, and then heated to 100°C for heat inactivation to obtain a microfibrillar cellulose dispersion. The concentration of microfibrillar cellulose in this microfibrillar cellulose dispersion was 13% by mass.

[0221] <Example 47> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 25 (solid content concentration 6% by mass, solid content 60 g), an enzyme-containing solution with an activity of 48,000 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added was 800 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing apparatus (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0222] <Example 48> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 26 (solid content concentration 13% by mass, solid content 130 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was treated four times at a pressure of 200 MPa using a wet atomizing device (Sugino Machine Co., Ltd., Starburst), and then thermally deactivated at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 13% by mass.

[0223] <Example 49> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 27 (solid content concentration 6% by mass, solid content 60 g), ozone was added at a ratio of 0.2 parts by mass per 1 part by mass of fine fibrous cellulose. The mixture was stirred in a sealed container at 25°C and then allowed to stand for 30 minutes. Next, the container was opened and the mixture was stirred for 5 hours to volatilize any remaining ozone in the dispersion. The obtained fine fibrous cellulose dispersion was treated three times at a pressure of 200 MPa using a wet atomizing device (Starburst, manufactured by Sugino Machine Co., Ltd.), and then thermally deactivated at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 6% by mass.

[0224] <Example 50> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 28 (solid content concentration 13% by mass, solid content 130 g), an enzyme-containing solution with an activity of 104,000 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 800 nkat per 1 g of fine fibrous cellulose. The obtained fine fibrous cellulose dispersion was treated four times at a pressure of 200 MPa using a wet atomizing apparatus (Sugino Machine Co., Ltd., Starburst), and then deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this fine fibrous cellulose dispersion was 13% by mass.

[0225] <Example 51> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 4 (solid content concentration 6% by mass, solid content 60 g), an enzyme-containing solution with an activity of 33000 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. Subsequently, the mixture was deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this dispersion was 6% by mass.

[0226] <Example 52> To 1000 g of the fine fibrous cellulose dispersion obtained in Production Example 3 (solid content concentration 13% by mass, solid content 130 g), an enzyme-containing solution with an activity of 71500 nkat was added and the mixture was treated with enzymes at a temperature of 50°C. The amount of enzyme added at this time was 550 nkat per 1 g of fine fibrous cellulose. Subsequently, the mixture was deactivated by heat at 100°C to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this dispersion was 13% by mass.

[0227] <Example 53> A fine fibrous cellulose dispersion was obtained in the same manner as in Example 52, except that the fine fibrous cellulose dispersion obtained in Production Example 7 was used.

[0228] <Example 54> A fine fibrous cellulose dispersion was obtained in the same manner as in Example 52, except that the fine fibrous cellulose dispersion obtained in Production Example 11 was used.

[0229] <Example 55> A fine fibrous cellulose dispersion was obtained in the same manner as in Example 52, except that the fine fibrous cellulose dispersion obtained in Production Example 14 was used.

[0230] <Example 56> A fine fibrous cellulose dispersion was obtained in the same manner as in Example 52, except that the fine fibrous cellulose dispersion obtained in Production Example 15 was used.

[0231] <Example 57> A fine fibrous cellulose dispersion was obtained in the same manner as in Example 52, except that the fine fibrous cellulose dispersion obtained in Production Example 17 was used.

[0232] <Example 58> A fine fibrous cellulose dispersion was obtained in the same manner as in Example 52, except that the fine fibrous cellulose dispersion obtained in Production Example 19 was used.

[0233] <Example 59> A microfibrillar cellulose dispersion was obtained in the same manner as in Example 52, except that the microfibrillar cellulose dispersion obtained in Production Example 21 was used.

[0234] <Example 60> A microfibrillar cellulose dispersion was obtained in the same manner as in Example 52, except that the microfibrillar cellulose dispersion obtained in Production Example 22 was used.

[0235] <Example 61> To 1000 g of the microfibrillar cellulose dispersion obtained in Production Example 24 (solid content concentration: 13% by mass, solid content: 130 g), an enzyme-containing solution having an activity of 104000 nkat was added and enzyme treatment was carried out at a temperature of 50°C. The enzyme addition amount at this time was adjusted to 800 nkat per 1 g of microfibrillar cellulose. The obtained microfibrillar cellulose dispersion was heated to 100°C for heat inactivation to obtain a microfibrillar cellulose dispersion. The concentration of microfibrillar cellulose in this microfibrillar cellulose dispersion was 13% by mass.

[0236] <Example 62> A microfibrillar cellulose dispersion was obtained in the same manner as in Example 61, except that the microfibrillar cellulose dispersion obtained in Production Example 26 was used.

[0237] <Example 63> A microfibrillar cellulose dispersion was obtained in the same manner as in Example 61, except that the microfibrillar cellulose dispersion obtained in Production Example 28 was used.

[0238] <Example 64> A microfibrillar cellulose dispersion was obtained in the same manner as in Example 29, except that the microfibrillar cellulose dispersion obtained in Production Example 29 was used.

[0239] It was confirmed by X-ray diffraction that the microfibrillar cellulose of Examples 1 to 64 maintained cellulose I-type crystals. Further, when the fiber width of these microfibrillar celluloses was measured using a transmission electron microscope, all of them contained microfibrillar cellulose with a fiber width of 3 to 5 nm.

[0240] <Comparative Example 1> Deionized water was added to bleached coniferous kraft pulp (NBKP) to prepare a slurry with a solid content of 6% by mass. This slurry was processed six times at a pressure of 200 MPa in a wet atomizing device (Sugino Machine Co., Ltd., Starburst) to obtain a fine fibrous cellulose dispersion. The concentration of fine fibrous cellulose in this dispersion was 6% by mass.

[0241] X-ray diffraction confirmed that this fine fibrous cellulose maintained its type I cellulose crystal structure. Furthermore, the number-average fiber width of the fine fibrous cellulose contained in this dispersion was less than 1000 nm.

[0242] <Comparative Example 2> Deionized water was added to the phosphorylated pulp obtained in Production Example 1 to prepare a slurry with a solid content of 2% by mass. This slurry was processed five times at a pressure of 200 MPa in a wet atomizing apparatus (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. The amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Group Amount] below was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0243] <Comparative Example 3> The fine fibrous cellulose dispersion obtained by the same method as in Comparative Example 2 was concentrated by heating at 50°C until the concentration of fine fibrous cellulose reached 6% by mass to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. Furthermore, the amount of phosphate groups (amount of first dissociated acid) measured by the measurement method described in [Measurement of Phosphorus Oxoacid Group Amount] below was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

[0244] <Comparative Example 4> The dispersion of fine fibrous cellulose obtained by the same method as in Comparative Example 2 was diluted to 0.4% by mass. 1 g of calcium chloride was added to 100 mL of the diluted solution as a concentrating agent to induce gelation, and after filtration, it was compressed using filter paper. After immersion in 100 mL of 0.1 N hydrochloric acid aqueous solution for 30 minutes, it was filtered to obtain a concentrate with a solid content of 20% by mass. The obtained concentrate was diluted with deionized water to a concentration of 6% and then stirred, but a uniform dispersion could not be obtained.

[0245] <Measurement> [Measurement of phosphorus oxoacid group content] The amount of phosphorus oxoacid groups in microfibrous cellulose was measured by diluting a microfibrous cellulose dispersion containing the target microfibrous cellulose with ion-exchanged water to a content of 0.2% by mass, preparing a fibrous cellulose-containing slurry, treating it with an ion-exchange resin, and then performing titration with an alkali. The ion exchange resin treatment was performed by adding 1 / 10 the volume of strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) to the fibrous cellulose-containing slurry, shaking for 1 hour, and then pouring the mixture onto a 90 μm mesh to separate the resin from the slurry. Furthermore, the alkali titration was performed by adding 10 μL of 0.1 N sodium hydroxide aqueous solution to a fibrous cellulose-containing slurry after treatment with ion exchange resin, while measuring the change in the slurry's pH value. Nitrogen gas was blown into the slurry starting 15 minutes before the titration began. In this neutralization titration, two points were observed where the increment (the derivative of pH with respect to the amount of alkali added) was maximum on the curve plotting the measured pH against the amount of alkali added. Of these, the first maximum increment obtained after starting alkali addition is called the first endpoint, and the next maximum increment obtained is called the second endpoint (Figure 2). The amount of alkali required from the start of the titration to the first endpoint is equal to the amount of the first dissociated acid in the slurry used for titration. Also, 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. Furthermore, the amount of alkali (mmol) required from the start of the titration to the first endpoint was divided by the solid content (g) in the slurry being titrated to obtain the amount of phosphorus oxoacid groups (mmol / g).

[0246] [Measurement of carboxyl group content] The amount of carboxyl groups in microfibrous cellulose was measured by diluting a microfibrous cellulose dispersion containing the target microfibrous cellulose with deionized water to a content of 0.2% by mass, preparing a fibrous cellulose-containing slurry, treating it with an ion exchange resin, and then performing titration with an alkali. The ion exchange resin treatment was performed by adding 1 / 10 the volume of strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) to the fibrous cellulose-containing slurry, shaking for 1 hour, and then pouring the mixture onto a 90 μm mesh to separate the resin from the slurry. Also, the titration using an alkali was performed by measuring the change in the value of the electrical conductivity exhibited by the fibrous cellulose-containing slurry after treatment with an ion-exchange resin while adding 50 μL of a 0.1 N aqueous sodium hydroxide solution once every 30 seconds. The amount of carboxyl groups (mmol / g) was calculated by dividing the amount of alkali (mmol) required in the region corresponding to the first region shown in FIG. 3 in the measurement results by the solid content (g) in the slurry to be titrated.

[0247] 〔Measurement of the amount of sulfur oxoacid groups〕 After wet-ashing the obtained fibrous cellulose using perchloric acid and concentrated nitric acid, it was diluted at an appropriate magnification and the amount of sulfur was measured by ICP emission analysis. The value obtained by dividing this amount of sulfur by the absolute dry mass of the tested fibrous cellulose was defined as the amount of sulfur oxoacid groups (unit: mmol / g).

[0248] 〔Measurement of the viscosity of the microfibrillated cellulose dispersion by a rheometer〕 The viscosities of the microfibrillated cellulose dispersions obtained in Examples 1 to 64 and Comparative Examples 1 to 3 were measured using a rheometer (RheoStress6000, manufactured by HAAKE). The shear rate was changed under the following conditions. Measurement temperature: 23°C Measurement jig: Cone plate (diameter 40 mm, angle 1°) Shear rate: 0.001 to 1000 sec -1 Number of data points: 100 points Data distribution: Log interval Measurement time: 5 minutes

[0249] <Calculation of the TI value> The viscosity of the microfibrillated cellulose dispersion was measured by the method described above, and the value of the viscosity (η1) measured under the condition of a shear rate of 1 sec -1 was divided by the value of the viscosity (η2) measured under the condition of a shear rate of 1000 sec -1 to obtain a value defined as the thixotropic index value (TI value) of the thickener. That is, the TI value was calculated by the following formula. TI value = η1 / η2 η1: Shear rate 1 sec -1 Viscosity measured under these conditions η2: Shear rate 1000 sec -1 Viscosity measured under these conditions

[0250] [Measurement of specific viscosity and degree of polymerization of fine fibrous cellulose] The specific viscosity and degree of polymerization of fine fibrous cellulose were measured according to Tappi T230. Specifically, the viscosity (ηX) measured with the fine fibrous cellulose dispersed in a dispersion medium, and the blank viscosity (η0) measured with only the dispersion medium were measured, and then the specific viscosity (ηsp) and intrinsic viscosity ([η]) were measured according to the following formulas. ηsp = (ηX / η0) - 1 [η] = ηsp / (c(1 + 0.28 × ηsp)) Here, c in the formula represents the concentration of cellulose fibers 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 the average degree of polymerization measured by the viscosity method, and is sometimes referred to as the "viscosity-average degree of polymerization."

[0251] [Measurement of haze in a dispersion of fine fibrous cellulose] The haze of the fine fibrous cellulose dispersions obtained in Examples 1-64 and Comparative Examples 1-3 was measured after diluting the fine fibrous cellulose dispersion with deionized water to 0.2% by mass. The haze was then measured using a haze meter (HM-150, Murakami Color Technology Research Institute Co., Ltd.) with a liquid glass cell (MG-40, Fujiwara Seisakusho Co., Ltd., reverse path) with a path length of 1 cm, in accordance with JIS K 7136:2000. Zero point measurement was performed using deionized water in the same glass cell. The dispersions to be measured were left to stand for 24 hours at 23°C and 50% relative humidity before measurement. The temperature of the dispersion at the time of measurement was 23°C.

[0252] <Rating> [Visual evaluation of fine fibrous cellulose dispersion] The fine fibrous cellulose dispersions obtained in Examples 1-64 and Comparative Examples 1-3 were each diluted with deionized water to a solid content concentration of 3% by mass. Then, degassing was performed using a rotation-and-revolution type super mixer (Sinky Co., Ltd., ARE-250). After that, the transparency of the dispersion was evaluated visually. As an evaluation criterion, the dispersion was placed in a glass cell, a piece of paper with 11-point lettering on one side was placed on top, and the transparency was evaluated according to the following criteria. A: When viewed from the opposite side, the characters are clearly legible. B: Slightly blurry, but the text is legible. C: The image is blurry and the letters are illegible, but it is clear that there are letters. D: Completely undecipherable

[0253] <Creating an evaluation sheet> Polyethylene oxide (manufactured by Sumitomo Seika Co., Ltd., PEO-3P) was added to deionized water to a concentration of 5% by mass, stirred, and dissolved to obtain an aqueous polyethylene oxide solution. Next, the fine fibrous cellulose dispersions obtained in Examples 1-64 and Comparative Examples 1-3 were mixed with the above aqueous polyethylene oxide solution in a ratio of fine fibrous cellulose (solids):polyethylene oxide (solids) = 100 parts by mass:20 parts by mass. Furthermore, the solutions were diluted with deionized water as appropriate to obtain a coating solution, with a solids concentration of 2.5% by mass in Examples 1-9, 5% by mass in Examples 10-15, 22-38, 41, 43, 45, 47, 49, 51, and Comparative Examples 1, 3, and 4, 10% by mass in Examples 16-21, 39, 40, 42, 44, 46, 48, 50, and 52-64, and 1.5% by mass in Comparative Example 2. Next, the coating liquid was measured so that the finished thickness of the resulting sheet (a layer composed of the solid components of the coating liquid) would be 40 μm, and it was applied to a commercially available polycarbonate sheet and dried in a 100°C dryer for 30 minutes. A metal frame for damming (with inner dimensions of 180 mm x 180 mm and a height of 5 cm) was placed on the polycarbonate sheet to achieve the desired basis weight. Then, the dried sheet was peeled off the polycarbonate sheet to obtain a sheet containing fine fibrous cellulose.

[0254] [Evaluation of sheet transparency] The haze of the obtained fine fibrous cellulose-containing sheets was measured in accordance with JIS K 7136:2000, using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute). The sheet haze was judged according to the following criteria. A sheet with less than 95% haze was considered to have good transparency. A: 0% or more and less than 5% B: 5% or more, less than 30% C: 30% to less than 95% D: 95% or more

[0255] [Evaluation of seat curlability] The fine fibrous cellulose-containing sheet obtained by the method described above was cut into a test specimen measuring 15 mm in width and 130 mm in length. As shown in Figure 1, one end of the test specimen 50, including one of its short sides, was supported by a curl test jig 55 measuring 30 mm in width, 30 mm in length, and 25 mm in height (100 mm of the test specimen was exposed from the jig). The specimen was then placed on a horizontal table at a temperature of 23°C and a relative humidity of 50%, with the width of the specimen perpendicular to the table (the longitudinal direction of the specimen parallel to the table). The curl width at the end of the test specimen 50 was measured and defined as the curl width C0 (the distance of C0 in Figure 1). After standing for 24 hours, the curl width was measured again and defined as C1 (the distance of C1 in Figure 1), and the difference between C1 and C0 was defined as the amount of curl. The amount of curl was determined according to the following criteria. A curl length of 25 mm or less was considered to indicate good curl resistance. A: 5mm or less B: More than 5mm and less than 25mm C: More than 25mm

[0256] [Table 1]

[0257] [Table 2]

[0258] [Table 3]

[0259] [Table 4]

[0260] [Table 5]

[0261] [Table 6]

[0262] [Table 7]

[0263] [Table 8]

[0264] In the example, a highly concentrated fine fibrous cellulose dispersion was obtained, and a sheet with suppressed curling was formed from this dispersion. This is thought to be because forming a sheet from a highly concentrated fine fibrous cellulose dispersion reduces the amount of water introduced, thereby suppressing thermal shrinkage during drying. In Comparative Example 4, a uniform sample could not be prepared, and therefore viscosity and other parameters could not be measured. [Explanation of symbols]

[0265] 50 test specimens 55 Test fixtures

Claims

1. A step of obtaining fibrous cellulose with a fiber width of 1000 nm or less by subjecting cellulose fibers having ionic substituents to a defibration treatment, A method for producing a fibrous cellulose-containing dispersion, comprising the step of subjecting fibrous cellulose to a viscosity reduction treatment, In the process of obtaining fibrous cellulose with a fiber width of 1000 nm or less by defibration treatment, the concentration of cellulose fibers is 3.0% by mass or more. The fibrous cellulose content is 3.0% by mass or more relative to the total mass of the dispersion. A method for producing a fibrous cellulose-containing dispersion, wherein the TI value of the dispersion calculated according to the following condition (a) is 1 or more and 80,000 or less, the viscosity (η1) of the dispersion measured according to the following condition (a) is 1 Pa·s or more and 5,000 Pa·s or less, and the viscosity (η2) is 0.007 Pa·s or more and 100 Pa·s or less; Condition (a): Using a rheometer equipped with a cone plate (40 mm diameter, 1° angle), the shear rate of the dispersion was measured at a temperature of 23°C and a measurement time of 5 minutes. －１ Viscosity (η1) under these conditions and shear rate of dispersion at 1000 sec －１ The viscosity (η²) is measured under the specified conditions, and the TI value is calculated using the following formula. TI value = η1 / η2

2. A method for producing a fibrous cellulose-containing dispersion according to claim 1, wherein the concentration of cellulose fibers in the step of obtaining fibrous cellulose with a fiber width of 1000 nm or less by defibration treatment is 4.0% by mass or more.

3. A method for producing a fibrous cellulose-containing dispersion according to claim 1 or 2, wherein the concentration of cellulose fibers in the step of obtaining fibrous cellulose with a fiber width of 1000 nm or less by defibration treatment is 5.0% by mass or more.

4. A method for producing a fibrous cellulose-containing dispersion according to any one of claims 1 to 3, wherein the concentration of cellulose fibers in the step of obtaining fibrous cellulose with a fiber width of 1000 nm or less by defibration treatment is 6.0% by mass or more.

5. A method for producing a fibrous cellulose-containing dispersion according to any one of claims 1 to 4, wherein the step of applying a viscosity reduction treatment is at least one selected from an ozone treatment step, an enzyme treatment step, an acid treatment step, and a subcritical water treatment step.

6. A method for producing a fibrous cellulose-containing dispersion according to any one of claims 1 to 5, comprising a step of performing a defibration treatment after a step of performing a viscosity reduction treatment.

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