WO2021107146A1

WO2021107146A1 - Fibrous cellulose, fibrous cellulose dispersion, and sheet

Info

Publication number: WO2021107146A1
Application number: PCT/JP2020/044374
Authority: WO
Inventors: ▲祥▼行堤; 悠介松原; 真代野口; 剛之白尾; 貴之大渕; 山根　教郎
Original assignee: 王子ホールディングス株式会社
Priority date: 2019-11-29
Filing date: 2020-11-27
Publication date: 2021-06-03
Also published as: JPWO2021107146A1

Abstract

The present invention addresses the problem of providing a microfibrous cellulose dispersion which has a high concentration and is highly transparent. The present invention pertains to a fibrous cellulose having a fiber width of at most 1,000 nm and having an ionic substituent, wherein the degree of polymerization of the fibrous cellulose is at most 230, and when the fibrous cellulose is made into an aqueous dispersion having a concentration of 0.5 mass%, the viscosity of the aqueous dispersion at 23ºC is less than 108 mPa∙s.

Description

Fibrous cellulose, fibrous cellulose dispersion and sheet

The present invention relates to fibrous cellulose, fibrous cellulose dispersion and sheet.

Conventionally, cellulose fibers have been widely used in clothing, absorbent articles, paper products, and the like. As the cellulose fibers, in addition to fibrous cellulose having a fiber diameter of 10 μm or more and 50 μm or less, fine fibrous cellulose having a fiber diameter of 1 μm or less is also known. Fine fibrous cellulose is attracting attention as a new material, and its uses are wide-ranging.

When producing fine fibrous cellulose, a slurry containing a cellulose raw material is defibrated (mechanically treated). For example, Patent Document 1 discloses a method for producing fine fibers, which comprises a step of treating a cellulose raw material with an enzyme and a step of defibrating the cellulose raw material after the enzyme treatment. Here, it is studied to sufficiently refine the cellulose raw material and increase the yield of fine fibers by performing enzyme treatment. Further, Patent Document 1 aims to produce fine fibers having a long fiber length and a large aspect ratio.

Further, Patent Document 2 discloses fine fibrous cellulose having an average fiber width of 200 nm or less, a degree of polymerization of 50 or more and 500 or less, and a predetermined polar group. Here, it is studied to obtain fine fibrous cellulose that does not easily form aggregates when mixed with an emulsion resin. In the examples of Patent Document 2, a dispersion having a degree of polymerization of 248 to 454 and a viscosity of 108 to 740 at a concentration of 0.5% is obtained.

International Publication No. 2013/176033 Japanese Unexamined Patent Publication No. 2014-34673

Fine fibrous cellulose exerts an excellent thickening effect in a dispersion liquid, and may be used for paints and cosmetics. However, since the fine fibrous cellulose exerts an excellent thickening effect, it is difficult to obtain a fine fibrous cellulose dispersion having a high concentration (for example, 3% by mass or more). Further, when an attempt is made to obtain a high-concentration dispersion of fine fibrous cellulose, the fine fibrous cellulose is not uniformly dispersed in the dispersion, and in some cases, agglomerates (lumps) of fine fibrous cellulose are generated. It became clear by the examination of the present inventors.

As described above, in the prior art, it is difficult to obtain a high-concentration fine fibrous cellulose dispersion, and further, it is difficult to obtain a fine fibrous cellulose dispersion having excellent uniformity at a high concentration. It was. Therefore, in order to solve the problems of the prior art, the present inventors provide a high-concentration fine fibrous cellulose dispersion liquid in which fine fibrous cellulose is uniformly dispersed. We proceeded with the study for the purpose of doing so.

As a result of diligent studies to solve the above problems, the present inventors set the degree of polymerization of fine fibrous cellulose having an ionic substituent within a predetermined range, and further, water having a concentration of 0.5% by mass. By obtaining fine fibrous cellulose having a viscosity within a predetermined range in the dispersion, a high-concentration fine fibrous cellulose dispersion in which fine fibrous cellulose is uniformly dispersed can be obtained. I found that.
Specifically, the present invention has the following configuration.

[1] A fibrous cellulose having a fiber width of 1000 nm or less and having an ionic substituent.
The degree of polymerization of fibrous cellulose is 230 or less,
When the fibrous cellulose is an aqueous dispersion having a concentration of 0.5% by mass, the fibrous cellulose has a viscosity of less than 108 mPa · s at 23 ° C.
[2] When the fibrous cellulose is used as an aqueous dispersion having a concentration of 6.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is 500,000 mPa · s or more and 10,000,000 mPa · s or less. [1] The fibrous cellulose described in.
[3] When fibrous cellulose is used as an aqueous dispersion having a concentration of 13.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is 1,000,000 mPa · s or more and 5,000,000 mPa · s or less. The fibrous cellulose according to 1] or [2].
[4] The ionic substituent is at least one selected from the group consisting of a phosphorus oxo acid group, a substituent derived from a phosphorus oxo acid group, a sulfur oxo acid group and a substituent derived from a sulfur oxo acid group, [4]. 1] The fibrous cellulose according to any one of [3].
[5] A fibrous cellulose dispersion containing the fibrous cellulose according to any one of [1] to [4].
[6] The fibrous cellulose dispersion according to [5], wherein the concentration of fibrous cellulose is 3.0% by mass or more.
[7] A sheet containing the fibrous cellulose according to any one of [1] to [4].

According to the present invention, it is possible to obtain a fine fibrous cellulose dispersion liquid in which fine fibrous cellulose is uniformly dispersed, which is a high-concentration fine fibrous cellulose dispersion liquid.

FIG. 1 is a graph showing the relationship between the amount of NaOH added dropwise and the pH of a fibrous cellulose-containing slurry having a phosphorus oxo acid group. FIG. 2 is a graph showing the relationship between the amount of NaOH added dropwise to the fibrous cellulose-containing slurry having a carboxy group and the pH.

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

(Fibrous cellulose)
The fibrous cellulose of the present embodiment has a fiber width of 1000 nm or less, is a fibrous cellulose having an ionic substituent, has a degree of polymerization of the fibrous cellulose of 230 or less, and contains 0.5 mass of the fibrous cellulose. When the aqueous dispersion has a% concentration, it is a fibrous cellulose having a viscosity of the aqueous dispersion at 23 ° C. of less than 108 mPa · s. When the fibrous cellulose is used as an aqueous dispersion having a concentration of 0.5% by mass, the viscosity of the aqueous dispersion at 23 ° C. is preferably 107 mPa · s or less, more preferably 100 mPa · s or less, and 95 mPa. -It is more preferably s or less. In the present specification, fibrous cellulose having a fiber width of 1000 nm or less is also referred to as fine fibrous cellulose.

The viscosity of the fine fibrous cellulose dispersion (aqueous dispersion) is the viscosity value 3 minutes after the start of measurement, at 23 ° C. and a rotation speed of 3 rpm using a B-type viscometer. As the B-type viscometer, for example, an analog viscometer T-LVT manufactured by BLOOKFIELD can be used. When the fine fibrous cellulose was diluted with an aqueous dispersion having a concentration of 0.5% by mass, it was stirred with a disperser at 4000 rpm for 3 minutes, and then a rotating and revolving supermixer (Sinky, ARE-250). Defoaming treatment of the fine fibrous cellulose dispersion liquid is performed at.

When the fine fibrous cellulose is used as an aqueous dispersion having a concentration of 6.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is preferably 500,000 mPa · s or more, preferably 700,000 mPa · s or more. It is more preferably 1,000,000 mPa · s or more, further preferably 1,500,000 mPa · s or more, and particularly preferably 1,800,000 mPa · s or more. .. Further, when the fine fibrous cellulose is used as an aqueous dispersion having a concentration of 6.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is preferably 1,000,000 mPa · s or less, preferably 7,500,000 mPa. It is more preferably s or less, further preferably 4,000,000 mPa · s or less, further preferably 3.5 million mPa · s or less, and 3.100,000 mPa · s or less. It is even more preferable, and it is particularly preferable that it is 3,000,000 mPa · s or less. When the fine fibrous cellulose is used as an aqueous dispersion having a concentration of 13.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is preferably 1,000,000 mPa · s or more, preferably 3,000,000 mPa. -S or more is more preferable, and 5,000,000 mPa · s or more is particularly preferable. When the fine fibrous cellulose is used as an aqueous dispersion having a concentration of 13.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is preferably 50,000,000 mPa · s or less, preferably 30,000,000 mPa. It is more preferably s or less, and particularly preferably less than 18,000,000 mPa · s. The viscosity of the water dispersion with a concentration of 6.0% by mass or the water dispersion with a concentration of 13.0% by mass was set to a rotation speed of 0.3 rpm at 23 ° C. using a B-type viscometer, and 3 minutes after the start of measurement. Is the viscosity value of. As the B-type viscometer, for example, an analog viscometer T-LVT or a digital viscometer DV2T manufactured by BLOOKFIELD can be used. When fine fibrous cellulose was prepared in an aqueous dispersion having a concentration of 6.0% by mass or 13.0% by mass, it was stirred with a disperser at 4000 rpm for 3 minutes, and then a rotating and revolving supermixer (Sinky). The fine fibrous cellulose dispersion is defoamed with ARE-250) manufactured by the company. When preparing an aqueous dispersion having a concentration of 6.0% by mass or a concentration of 13.0% by mass, an aqueous dispersion having a concentration higher than the concentration of 6.0% by mass or 13.0% by mass is obtained. An aqueous dispersion having a concentration of 6.0% by mass or a concentration of 13.0% by mass may be obtained by diluting the aqueous dispersion with water.

In the prior art, it is difficult to obtain a high-concentration aqueous dispersion of 3.0% by mass or more, and it is not possible to obtain a high-concentration aqueous dispersion of 6.0% by mass or 13.0% by mass. It was possible. Further, even when the fine fibrous cellulose dispersion obtained in the prior art is concentrated to obtain an aqueous dispersion having a concentration of 6.0% by mass or 13.0% by mass, the aqueous dispersion is in the form of a gel. It was not possible to obtain a uniform aqueous dispersion because of the above-mentioned problems and the formation of granules (aggregates of fibers) in the aqueous dispersion. As a matter of course, it was impossible to measure the viscosity of such a high-concentration aqueous dispersion. For example, when an aqueous dispersion having a concentration of 0.5 to 2.0% by mass is subjected to a defibration treatment and then concentrated by heat treatment or an evaporator, a film-like substance is generated on the wall surface during the concentration process. Therefore, it is not possible to obtain a dispersion liquid of 6.0% by mass or more in which fine fibrous cellulose is uniformly dispersed. Therefore, even if the viscosity of the aqueous dispersion having a concentration of 0.5 to 2.0% by mass is equivalent to the viscosity of the aqueous dispersion having the same concentration in the present embodiment, 6.0% by mass or 13. It is impossible to obtain a high-concentration aqueous dispersion such as 0% by mass, and a dispersion having a viscosity within the above range can be obtained in a high-concentration aqueous dispersion such as 6.0% by mass or 13.0% by mass. It is not possible.

On the other hand, in the present embodiment, the degree of polymerization of the fine fibrous cellulose is within the above range, and the viscosity of the aqueous dispersion at 23 ° C. is within the above range when the aqueous dispersion has a concentration of 0.5% by mass. By obtaining the fine fibrous cellulose, we succeeded in obtaining a dispersion liquid of the fine fibrous cellulose having a high concentration and in which the fine fibrous cellulose was uniformly dispersed. Further, in the present embodiment, the dispersion liquid of the phosphorylated pulp to be subjected to the defibration treatment is made to have a high concentration, and the defibration treatment is performed on such a high concentration pulp dispersion liquid, and if necessary, it will be described later. By also applying the low molecular weight treatment, the viscosity of the aqueous dispersion containing 3.0% by mass or more of fine fibrous cellulose (for example, 6.0% by mass or 13.0% by mass) can be increased. It became possible to measure and succeeded in obtaining an aqueous dispersion having a relatively low viscosity as a high-concentration dispersion.

As described above, in the present embodiment, a dispersion liquid containing fine fibrous cellulose at a high concentration can be obtained. Therefore, it is possible to significantly reduce the storage cost and the transportation cost of the dispersion liquid. Further, in the present embodiment, the production efficiency of the fine fibrous cellulose dispersion can be increased.

In the present embodiment, the degree of polymerization of the fibrous cellulose may be 230 or less, preferably 225 or less, more preferably 220 or less, further preferably 215 or less, and 210 or less. Is particularly preferable. The degree of polymerization of the fibrous cellulose is preferably 100 or more, more preferably 150 or more, further preferably 160 or more, and particularly preferably 170 or more.

The degree of polymerization of the fine fibrous cellulose is a value calculated from the pulp viscosity measured according to Tappi T230. Specifically, the viscosity (referred to as η1) measured by dispersing the fine fibrous cellulose to be measured in an aqueous solution of copper ethylenediamine and the blank viscosity (referred to as η0) measured only with the dispersion medium are measured and then the ratio. Viscosity (ηsp) and intrinsic viscosity ([η]) are measured according to the following formulas.
ηsp = (η1 / η0) -1
[Η] = ηsp / (c (1 + 0.28 × ηsp))
Here, c in the formula indicates the concentration of fine fibrous cellulose at the time of viscosity measurement.
Further, the degree of polymerization (DP) is calculated from the following formula.
DP = 1.75 × [η]
Since this degree of polymerization is the average degree of polymerization measured by the viscosity method, it is sometimes called "viscosity average degree of polymerization".

In the present embodiment, when the degree of polymerization of the fine fibrous cellulose is within the above range and the aqueous dispersion has a concentration of 0.5% by mass, the viscosity of the aqueous dispersion at 23 ° C. is within the above range. By obtaining the fibrous cellulose, it is possible to obtain a fine fibrous cellulose dispersion having a high concentration and in which the fine fibrous cellulose is uniformly dispersed. Such a high-concentration fine fibrous cellulose dispersion is preferably used for various purposes. For example, it is preferably used for sheet forming, reinforcing material, and paint, and is particularly preferably used for applications where transparency is required.

In this embodiment, a high-concentration fine fibrous cellulose dispersion can be obtained. For example, the concentration of the fine fibrous cellulose dispersion is preferably 3.0% by mass or more, more preferably 4.0% by mass or more, and further preferably 5.0% by mass or more. It is more preferably 6.0% by mass or more, and particularly preferably 10.0% by mass or more. In the present specification, the concentration of the fine fibrous cellulose dispersion means the content of the fine fibrous cellulose with respect to the total mass of the fine fibrous cellulose dispersion. Further, in the present specification, a dispersion liquid containing 3.0% by mass or more of fine fibrous cellulose with respect to the total mass of the dispersion liquid (that is, a dispersion liquid having a fine fibrous cellulose dispersion liquid concentration of 3.0% by mass or more). ) Is called a high-concentration fine fibrous cellulose dispersion.

The fine fibrous cellulose is uniformly dispersed in the high-concentration fine fibrous cellulose dispersion obtained by dispersing the fine fibrous cellulose of the present embodiment in a solvent such as water. Therefore, the high-concentration fine fibrous cellulose dispersion is highly transparent. For example, when fine fibrous cellulose is dispersed in a solvent such as water to obtain a high-concentration dispersion liquid of 6.0% by mass, the fine fibrous cellulose is dispersed in the dispersion liquid, so that the fine fibrous cellulose can be visually confirmed. Can not do it. In such a case, it can be evaluated that the fine fibrous cellulose is uniformly dispersed in the high-concentration fine fibrous cellulose dispersion liquid. Further, in such a case, the high-concentration fine fibrous cellulose dispersion liquid does not become cloudy and is translucent or transparent.

The fibrous cellulose of the present embodiment is a fine fibrous cellulose having a fiber width of 1000 nm or less. The fiber width of the fibrous cellulose is more preferably 100 nm or less, and further preferably 8 nm or less.

The fiber width of fibrous cellulose can be measured, for example, by observation with an electron microscope. The average fiber width of the fibrous cellulose is, for example, 1000 nm or less. The average fiber width of the fibrous cellulose is, for example, 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Especially preferable. By setting the average fiber width of the fibrous cellulose to 2 nm or more, it is possible to suppress the dissolution of the fibrous cellulose as a cellulose molecule in water, and to make it easier to exhibit the effects of the fibrous cellulose on improving strength, rigidity, and dimensional stability. it can. The fibrous cellulose is, for example, monofibrous cellulose.

The average fiber width of fibrous cellulose is measured as follows, for example, using an electron microscope. First, an aqueous suspension of fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast on a hydrophilized carbon film-coated grid to prepare a sample for TEM observation. And. If it contains wide fibers, an SEM image of the surface cast on the glass may be observed. Next, observation is performed using an electron microscope image at a magnification of 1000 times, 5000 times, 10000 times, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification should be adjusted so as to satisfy the following conditions.

(1) A straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y that intersects the straight line perpendicularly is drawn in the same image, and 20 or more fibers intersect the straight line Y.

For an observation image that satisfies the above conditions, visually read the width of the fiber that intersects the straight line X and the straight line Y. In this way, at least three sets of observation images of surface portions that do not overlap each other are obtained. Next, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. As a result, at least 20 fibers × 2 × 3 = 120 fibers are read. Then, the average value of the read fiber widths is taken as the average fiber width of the fibrous cellulose.

The fiber length of the fibrous cellulose is not particularly limited, but is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and further preferably 0.1 μm or more and 600 μm or less. preferable. By setting the fiber length within the above range, destruction of the crystal region of the fibrous cellulose can be suppressed. It is also possible to set the slurry viscosity of the fibrous cellulose in an appropriate range. The fiber length of the fibrous cellulose can be obtained by, for example, image analysis by TEM, SEM, or AFM.

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

The axial ratio (fiber length / fiber width) of the fibrous cellulose is not particularly limited, but is preferably 20 or more and 10000 or less, and more preferably 50 or more and 1000 or less. In the present specification, the fibrous cellulose (fine fibrous cellulose) having a fiber width of 1000 nm or less is cellulose nanofiber (CNF), and the fibrous cellulose (fine fibrous cellulose) is cellulose nanocrystal (CNC). Is not included. The axial ratio (fiber length / fiber width) of cellulose nanocrystal (CNC) is usually about 10 or more and 30 or less. Further, by setting the axial ratio of the fibrous cellulose to the above lower limit value or more, it is preferable in that handling such as dilution becomes easy when, for example, the fibrous cellulose is treated as an aqueous dispersion.

The fibrous cellulose in this embodiment has, for example, both a crystalline region and a non-crystalline region. The fine fibrous cellulose having both a crystalline region and a non-crystalline region and having an axial ratio within the above range is realized by a method for producing fine fibrous cellulose described later.

The fibrous cellulose of this embodiment has an ionic substituent. The ionic substituent can include, for example, either one or both of an anionic group and a cationic group. In this embodiment, it is particularly preferable to have an anionic group as the ionic substituent. Further, the ionic substituent is preferably a group that breaks the ester bond and connects to the fibrous cellulose. In this case, the ester bond is formed by dehydration condensation of the fibrous cellulose and the compound serving as an ionic substituent.

Examples of the anionic group as an ionic substituent include a phosphate group or a substituent derived from a phosphorusoxo acid group (sometimes referred to simply as a phosphorusoxo acid group), a carboxy group or a substituent derived from a carboxy group (simply a carboxy group). It is preferably at least one selected from a sulfur oxo acid group or a substituent derived from a sulfur oxo acid group (sometimes simply referred to as a sulfur oxo acid group), a phosphorus oxo acid group and a carboxy. It is more preferably at least one selected from the groups, and particularly preferably a phosphoroxoic acid group. By introducing a phosphorus oxo acid group into the fibrous cellulose, the transparency of the dispersion can be more effectively enhanced when the dispersion is made into a high-concentration dispersion. Further, by introducing a phosphorus oxo acid group into the fibrous cellulose, the salt resistance of the fibrous cellulose can be improved.

The phosphoric acid group or the substituent derived from the phosphoric acid group is, for example, a substituent represented by the following formula (1). A plurality of types of substituents represented by the following formula (1) may be introduced into each fibrous cellulose. In this case, the substituents represented by the following formula (1) to be introduced may be the same or different.

In the formula (1), a, b and n are natural numbers, and m is an arbitrary number (where a = b × m). At least one of the n α and α'is O ⁻ and the rest are R or OR. It is also possible that all of each α and α'are O ^−. The n αs may all be the same or different. β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance.

R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, and an unsaturated-branched chain hydrocarbon, respectively. A hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. Further, in the formula (1), n is preferably 1.

Examples of the saturated-linear hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group and the like, but are not particularly limited. Examples of the saturated-branched chain hydrocarbon group include an i-propyl group and a t-butyl group, but are not particularly limited. Examples of the saturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentyl group, a cyclohexyl group and the like. Examples of the unsaturated-linear hydrocarbon group include a vinyl group, an allyl group and the like, but are not particularly limited. Examples of the unsaturated-branched chain hydrocarbon group include an i-propenyl group and a 3-butenyl group, but the group is not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentenyl group, a cyclohexenyl group and the like. Examples of the aromatic group include a phenyl group and a naphthyl group, but are not particularly limited.

As the derivative groups in R, to the main chain or side chain of the various hydrocarbon group, a carboxy group, a carboxylate group (-COO ^-), hydroxy group, selected from the functional groups such as an amino group and an ammonium group Examples thereof include functional groups in which at least one type is added or substituted, but the functional group is not particularly limited. 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 to the above range, the molecular weight of the phosphorus oxo acid group can be set to an appropriate range, the penetration into the fiber raw material is facilitated, and the yield of the fine cellulose fiber is increased. You can also do it. When a plurality of Rs are present in the formula (1) or when a plurality of types of substituents represented by the above formula (1) are introduced into the fibrous cellulose, the plurality of Rs present are the same. It may or may not be different.

β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or higher cations composed of organic substances include organic onium ions. Examples of the organic onium ion include an organic ammonium ion and an organic phosphonium ion. Examples of the organic ammonium ion include an aliphatic ammonium ion and an aromatic ammonium ion, and examples of the organic phosphonium ion include an aliphatic phosphonium ion and an aromatic phosphonium ion. Examples of monovalent or higher cations composed of inorganic substances include alkali metal ions such as sodium, potassium, and lithium, divalent metal ions such as calcium and magnesium, hydrogen ions, and ammonium ions. When a ^{plurality of β b +} are present in the formula (1) or when a plurality of types of substituents represented by the above formula (1) are introduced into the fibrous cellulose, the plurality of β ^{b + present} are each. It may be the same or different. The monovalent or higher cation composed of an organic substance or an inorganic substance is preferably sodium or potassium ion which is hard to yellow when the fiber raw material containing ^{β b + is heated and is easily industrially used, but is not particularly limited.} ..

More specifically, the phosphate group or the substituent derived from the phosphorous acid group includes a phosphoric acid group (-PO ₃ H ₂ ), a salt of a phosphoric acid group, and a phosphite group (phosphonic acid group) (-PO). ₂ H _2), and salts of phosphorous acid (phosphonic acid group). Further, the phosphoric acid group or the substituent derived from the phosphoric acid group includes a group in which a phosphoric acid group is condensed (for example, a pyrophosphate group), a group in which a phosphonic acid is condensed (for example, a polyphosphonic acid group), and a phosphoric acid ester group (for example). For example, it may be a monomethylphosphoric acid group, a polyoxyethylene alkylphosphoric acid group), an alkylphosphonic acid group (for example, a methylphosphonic acid group), or the like.

The sulfur oxoacid group (sulfur oxoacid group or a substituent derived from the sulfur oxoacid group) is, for example, a substituent represented by the following formula (2). A plurality of types of 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) to be introduced may be the same or different.

In the above structural formula, b and n are natural numbers, p is 0 or 1, and m is an arbitrary number (where 1 = b × m). When n is 2 or more, a plurality of ps may be the same number or different numbers. In the above structural formula, β ^{b +} is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or higher cations composed of organic substances include organic onium ions. Examples of the organic onium ion include an organic ammonium ion and an organic phosphonium ion. Examples of the organic ammonium ion include an aliphatic ammonium ion and an aromatic ammonium ion, and examples of the organic phosphonium ion include an aliphatic phosphonium ion and an aromatic phosphonium ion. Examples of monovalent or higher cations composed of inorganic substances include alkali metal ions such as sodium, potassium, and lithium, divalent metal ions such as calcium and magnesium, hydrogen ions, and ammonium ions. When a plurality of types of substituents represented by the above formula (2) are introduced into the fibrous cellulose, the plurality of β ^{b +} existing may be the same or different. The monovalent or higher cation composed of an organic substance or an inorganic substance is preferably sodium or potassium ion which is hard to yellow when the fiber raw material containing ^{β b + is heated and is easily industrially used, but is not particularly limited.} ..

The amount of the ionic substituent introduced into the fibrous cellulose is, for example, 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.40 mmol / g per 1 g (mass) of the fibrous cellulose. It is more preferably / g or more, more preferably 0.60 mmol / g or more, further preferably 0.90 mmol / g or more, and particularly preferably 1.00 mmol / g or more. In particular, when the amount of the ionic substituent introduced into the fibrous cellulose is 1.00 mmol / g or more, the load at the time of defibration can be reduced, and the transparency of the obtained fine fibrous cellulose dispersion liquid or sheet is further enhanced. Further, when the amount of the ionic substituent introduced into the fibrous cellulose is 1.00 mmol / g or more, the salt resistance of the fibrous cellulose can be improved. The amount of the ionic substituent introduced into the fibrous cellulose is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less per 1 g (mass) of the fibrous cellulose, for example, 3 It is more preferably 0.00 mmol / g or less, further preferably 2.50 mmol / g or less, further preferably 2.00 mmol / g or less, and particularly preferably 1.50 mmol / g or less. preferable. Here, the denominator in the unit mmol / g indicates the mass of fibrous cellulose when the counter ion of the ionic substituent is a hydrogen ion (H ^+). By setting the amount of the ionic substituent introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fibrous cellulose. Further, by setting the amount of the ionic substituent introduced within the above range, it becomes easy to obtain a fine fibrous cellulose dispersion having a high concentration and high transparency.

The amount of the ionic substituent introduced into the fibrous cellulose can be measured by, for example, the neutralization titration method. In the measurement by the neutralization titration method, the introduction amount is measured by determining the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing fibrous cellulose.

FIG. 1 is a graph showing the relationship between the amount of NaOH added dropwise and the pH of a fibrous cellulose-containing slurry having a phosphorus oxo acid group. The amount of the phosphorus oxo acid group introduced into the fibrous cellulose is measured, for example, as follows.
First, the slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the defibration treatment similar to the defibration treatment step described later may be performed on the measurement target before the treatment with the strongly acidic ion exchange resin.
Next, the change in pH is observed while adding an aqueous sodium hydroxide solution, and a titration curve as shown in the upper part of FIG. 1 is obtained. The titration curve shown in the upper part of FIG. 1 plots the measured pH with respect to the amount of alkali added, and the titration curve shown in the lower part of FIG. 1 plots the pH with respect to the amount of alkali added. The increment (differential value) (1 / mmol) is plotted. In this neutralization titration, two points are confirmed in which the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is added is called the first end point, and the maximum point of the increment obtained next is called the second end point. The amount of alkali required from the start of titration to the first end point is equal to the amount of first dissociating acid of the fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the first end point to the second end point. The amount is equal to the amount of the second dissociating acid of the fibrous cellulose contained in the slurry used for the titration, and the amount of alkali required from the start to the second end point of the titration is the fibrous cellulose contained in the slurry used for the titration. Is equal to the total amount of dissociated acid. Then, the value obtained by dividing the amount of alkali required from the start of titration to the first end point by the solid content (g) in the slurry to be titrated is the amount of phosphorus oxo acid group introduced (mmol / g). The amount of phosphorus oxo acid group introduced (or the amount of phosphorus oxo acid group) simply means the amount of the first dissociated acid.
In FIG. 1, the region from the start of titration to the first end point is referred to as a first region, and the region from the first end point to the second end point is referred to as a second region. For example, when the phosphoric acid group is a phosphoric acid group and this phosphoric acid group causes condensation, the amount of weakly acidic groups in the phosphoric acid group (also referred to as the second dissociated acid amount in the present specification) is apparently It decreases, and the amount of alkali required for the second region is smaller than the amount of alkali required for the first region. On the other hand, the amount of strongly acidic groups in the phosphorus oxo acid group (also referred to as the first dissociated acid amount in the present specification) matches the amount of phosphorus atoms regardless of the presence or absence of condensation. When the phosphorous acid group is a phosphorous acid group, the weakly acidic group does not exist in the phosphorous acid group, so that the amount of alkali required for the second region is reduced or the amount of alkali required for the second region is reduced. May be zero. In this case, there is only one point on the titration curve where the pH increment is maximized.

Since the denominator of the above-mentioned phosphorus oxo acid group introduction amount (mmol / g) indicates the mass of the acid-type fibrous cellulose, the phosphorus oxo acid group amount of the acid-type fibrous cellulose (hereinafter referred to as the phosphorus oxo acid group amount). (Called (acid type))). On the other hand, when the counterion of the phosphorus oxo acid group is replaced with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of fibrous cellulose when the cation C is a counterion. This makes it possible to determine the amount of phosphorus oxo acid groups (hereinafter, the amount of phosphorus oxo acid groups (C type)) possessed by the fibrous cellulose in which the cation C is a counterion.
That is, it is calculated by the following formula.
Phosphoric acid group amount (C type) = Phosphoric acid group amount (acid type) / {1+ (W-1) x A / 1000}
A [mmol / g]: Total amount of anion derived from phosphoric acid group of fibrous cellulose (total amount of dissociated acid of phosphoric acid group)
W: Formula amount per valence of cation C (for example, Na is 23, Al is 9)

FIG. 2 is a graph showing the relationship between the amount of NaOH added dropwise and the pH of a dispersion containing fibrous cellulose having a carboxy group as an ionic substituent. The amount of the carboxy group introduced into the fibrous cellulose is measured, for example, as follows.
First, the dispersion liquid containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, the defibration treatment similar to the defibration treatment step described later may be performed on the measurement target before the treatment with the strongly acidic ion exchange resin.
Next, the change in pH is observed while adding an aqueous sodium hydroxide solution, and a titration curve as shown in the upper part of FIG. 2 is obtained. The titration curve shown in the upper part of FIG. 2 plots the measured pH with respect to the amount of alkali added, and the titration curve shown in the lower part of FIG. 2 plots the pH with respect to the amount of alkali added. The increment (differential value) (1 / mmol) is plotted. In this neutralization titration, in the curve plotting the measured pH with respect to the amount of alkali added, one point was confirmed where the increment (differential value of pH with respect to the amount of alkali dropped) became maximum, and this maximum point was the first. Called one end point. Here, the region from the start of titration to the first end point in FIG. 2 is referred to as a first region. The amount of alkali required in the first region is equal to the amount of carboxy groups in the dispersion used for titration. Then, the amount of alkali (mmol) required in the first region of the titration curve is divided by the solid content (g) in the dispersion containing the fibrous cellulose to be titrated, so that the amount of carboxy group introduced (mmol). / G) is calculated.

Since the denominator of the above-mentioned carboxy group introduction amount (mmol / g) is the mass of the acid type fibrous cellulose, the carboxy group amount of the acid type fibrous cellulose (hereinafter, the carboxy group amount (acid type)). ) Is shown. On the other hand, when the counterion of the carboxy group is replaced with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of fibrous cellulose when the cation C is a counterion. Then, the amount of carboxy groups (hereinafter, the amount of carboxy groups (C type)) possessed by the fibrous cellulose in which the cation C is a counter ion can be determined. That is, it is calculated by the following formula.
Carboxylic acid group amount (C type) = Carboxylic acid group amount (acid type) / {1+ (W-1) x (carboxyl group amount (acid type)) / 1000}
W: Formula amount per valence of cation C (for example, Na is 23, Al is 9)

In the measurement of the amount of ionic substituents by the titration method, if the amount of one drop of sodium hydroxide aqueous solution is too large, or if the titration interval is too short, the amount of ionic substituents will be lower than it should be. It may not be obtained. As an appropriate dropping amount and titration interval, for example, it is desirable to titrate 10 to 50 μL of a 0.1 N sodium hydroxide aqueous solution every 5 to 30 seconds. Further, in order to eliminate the influence of carbon dioxide dissolved in the fibrous cellulose-containing slurry, for example, it is desirable to measure while blowing an inert gas such as nitrogen gas into the slurry from 15 minutes before the start of titration to the end of titration.

The amount of sulfur oxoacid group introduced into fibrous cellulose can be calculated by measuring the amount of sulfur in a sample obtained by wet-ashing a slurry containing fibrous cellulose and then diluting it at an appropriate magnification. Specifically, fibrous cellulose is wet-ashed with perchloric acid and concentrated nitric acid, diluted at an appropriate magnification, and the amount of sulfur is measured by ICP emission analysis. The value obtained by dividing the fibrous cellulose tested by the absolute dry mass is defined as the amount of sulfur oxoacid groups (unit: mmol / g).

The fibrous cellulose according to the present embodiment and the dispersion liquid containing the fibrous cellulose have been described above. Further, in the present specification, as another embodiment, it is a fine fibrous cellulose-containing dispersion having a fiber width of 1000 nm or less and having an ionic substituent, and the content of the fine fibrous cellulose is the dispersion liquid. Also disclosed is a fine fibrous cellulose-containing dispersion having a total mass of 5.0% by mass or more and 14.0% by mass or less and a degree of polymerization of fine fibrous cellulose of 160 or more and 205 or less. The viscosity of the fine fibrous cellulose-containing dispersion measured using a B-type viscometer ^{is particularly preferably 1800 × 10 3} mPa · s or more and 13000 × 10 ³ mPa · s or less. As the ionic substituent of the fine fibrous cellulose, a phosphoric acid group or a substituent derived from the phosphoric acid group (among them, a phosphoric acid group) is particularly preferable. The amount of the ionic substituent introduced into the fine fibrous cellulose is particularly preferably 0.90 mmol / g or more and 2.00 mmol / g or less. The other description is the same as the description of the fibrous cellulose according to the present embodiment and the dispersion liquid containing the fibrous cellulose, and thus is omitted here.

(Manufacturing method of fine fibrous cellulose)
<Fiber raw material>
Fine fibrous cellulose is produced from a fiber raw material containing cellulose. The fiber raw material containing cellulose is not particularly limited, but pulp is preferably used because it is easily available and inexpensive. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited, but for example, broad-leaved kraft pulp (LBKP), coniferous kraft pulp (NBKP), sulfite pulp (SP), broad-leaved dissolved pulp (LDKP, LDSP), coniferous dissolved pulp (NDKP, NDSP), Chemical pulp such as soda pulp (AP), unbleached kraft pulp (UKP) and oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemiground wood pulp (CGP), crushed wood pulp (GP) ) And mechanical pulp such as thermomechanical pulp (TMP, BCTMP). The non-wood pulp is not particularly limited, and examples thereof include cotton pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw and bagasse. The deinking pulp is not particularly limited, and examples thereof include deinking pulp made from recycled paper. As the pulp of the present embodiment, one of the above types may be used alone, or two or more types may be mixed and used. Among the above pulps, for example, wood pulp and deinked pulp are preferable from the viewpoint of availability. Further, among wood pulp, long fiber fine fibrous cellulose having a large cellulose ratio and a high yield of fine fibrous cellulose during defibration treatment and a large axial ratio with less decomposition of cellulose in the pulp can be obtained. From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are further preferable. Among them, softwood-derived pulp is preferably used because it has good defibration properties during defibration treatment, which will be described later, and transparency when made into a dispersion liquid is further improved.

As the fiber raw material containing cellulose, for example, cellulose contained in ascidians and bacterial cellulose produced by acetic acid bacteria can be used. Further, instead of the fiber raw material containing cellulose, a fiber formed by a linear nitrogen-containing polysaccharide polymer such as chitin or chitosan can also be used.

<Linoxo acid group introduction process>
The step of producing the fine fibrous cellulose includes a step of introducing an ionic substituent. Examples of the ionic substituent introduction step include a phosphorus oxo acid group introduction step. In the phosphorus oxo acid group introduction step, at least one compound (hereinafter, also referred to as “compound A”) selected from compounds capable of introducing a phosphorus oxo acid group by reacting with a hydroxyl group of a fiber raw material containing cellulose is introduced into cellulose. It is a step of acting on a fiber raw material containing. By this step, a phosphorus oxo acid group-introduced fiber can be obtained.

In the phosphorus oxo acid group introduction step according to the present embodiment, the reaction between the fiber raw material containing cellulose and Compound A is carried out in the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “Compound B”). You may. On the other hand, the reaction of the fiber raw material containing cellulose with the compound A may be carried out in the absence of the compound B.

As an example of the method of allowing the compound A to act on the fiber raw material in the coexistence with the compound B, there is a method of mixing the compound A and the compound B with the fiber raw material in a dry state, a wet state or a slurry state. Of these, since the reaction uniformity is high, it is preferable to use a fiber raw material in a dry state or a wet state, and it is particularly preferable to use a fiber raw material in a dry state. The form of the fiber raw material is not particularly limited, but is preferably cotton-like or thin sheet-like, for example. Examples of the compound A and the compound B include a method of adding the compound A and the compound B to the fiber raw material in the form of a powder or a solution dissolved in a solvent, or in a state of being heated to a melting point or higher and melted. Of these, since the reaction is highly homogeneous, it is preferable to add the mixture in the form of a solution dissolved in a solvent, particularly in the form of an aqueous solution. Further, the compound A and the compound B may be added to the fiber raw material at the same time, may be added separately, or may be added as a mixture. The method for adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in the form of a solution, the fiber raw material may be immersed in the solution to absorb the liquid and then taken out, or the fiber raw material may be taken out. The solution may be dropped into the water. Further, the required amounts of compound A and compound B may be added to the fiber raw material, or after the excess amounts of compound A and compound B are added to the fiber raw material, respectively, the surplus compound A and compound B are added by pressing or filtering. It may be removed.

The compound A used in this embodiment may be a compound having a phosphorus atom and capable of forming an ester bond with cellulose, and may be phosphoric acid or a salt thereof, phosphoric acid or a salt thereof, dehydration-condensed phosphoric acid or a salt thereof. Examples thereof include salts and anhydrous phosphoric acid (diphosphorus pentoxide), but the present invention is not particularly limited. As the phosphoric acid, those having various puritys can be used, and for example, 100% phosphoric acid (normal phosphoric acid) or 85% phosphoric acid can be used. Examples of phosphorous acid include 99% phosphorous acid (phosphonic acid). The dehydration-condensed phosphoric acid is one in which two or more molecules of phosphoric acid are condensed by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Phosphates, phosphorous acids, dehydration-condensed phosphates include phosphoric acid, phosphorous acid or dehydration-condensed phosphoric acid lithium salts, sodium salts, potassium salts, ammonium salts, etc. It can be a sum. Of these, from the viewpoints that the introduction efficiency of phosphoric acid groups is high, the defibration efficiency is more likely to be improved in the defibration step described later, the cost is low, and it is easy to apply industrially, sodium phosphate and sodium phosphate are easy to apply. Salt, potassium salt of phosphoric acid, ammonium or phosphite of phosphoric acid, sodium salt of phosphite, potassium salt of phosphite, ammonium salt of phosphite are preferred, phosphoric acid, sodium dihydrogen phosphate, Disodium hydrogen phosphate, ammonium dihydrogen phosphate, or phosphoric acid and sodium phosphite are more preferred.

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 phosphorus atomic weight, the amount of phosphorus atom added to the fiber raw material (absolute dry mass) is 0.5% by mass or more. It is preferably 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and further preferably 2% by mass or more and 30% by mass or less. By setting the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by setting the addition amount of phosphorus atoms to the fiber raw material to be equal to or less than the above upper limit value, the effect of improving the yield and the cost can be balanced.

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, 1-ethylurea and the like. From the viewpoint of improving the uniformity of the reaction, compound B is preferably used as an aqueous solution. Further, from the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

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

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

In the phosphorus oxo acid group introduction step, it is preferable to add or mix compound A or the like to the fiber raw material and then heat-treat the fiber raw material. As the heat treatment temperature, it is preferable to select a temperature at which a phosphorus oxo acid group can be efficiently introduced while suppressing the thermal decomposition and hydrolysis reaction of the fiber. The heat treatment temperature is, for example, preferably 50 ° C. or higher and 300 ° C. or lower, more preferably 100 ° C. or higher and 250 ° C. or lower, and further preferably 130 ° C. or higher and 200 ° C. or lower. In addition, equipment having various heat media can be used for the heat treatment, for example, a stirring drying device, a rotary drying device, a disk drying device, a roll type heating device, a plate type heating device, a fluidized layer drying device, and a band. A mold drying device, a filtration drying device, a vibration flow drying device, an air flow drying device, a vacuum drying device, an infrared heating device, a far infrared heating device, a microwave heating device, and a high frequency drying device can be used.

In the heat treatment according to the present embodiment, for example, compound A is added to a thin sheet-shaped fiber raw material by a method such as impregnation and then heated, or the fiber raw material and compound A are heated while kneading or stirring with a kneader or the like. Can be adopted. This makes it possible to suppress uneven concentration of the compound A in the fiber raw material and more uniformly introduce the phosphorus oxo acid group onto the surface of the cellulose fiber contained in the fiber raw material. This is because when the water molecules move to the surface of the fiber raw material due to drying, the dissolved compound A is attracted to the water molecules by the surface tension and also moves to the surface of the fiber raw material (that is, the concentration unevenness of the compound A is caused. It is considered that this is due to the fact that it can be suppressed.

Further, the heating device used for the heat treatment always keeps the water content retained by the slurry and the water content generated by the dehydration condensation (phosphoric acid esterification) reaction between the compound A and the hydroxyl group contained in the cellulose or the like in the fiber raw material. It is preferable that the device can be discharged to the outside of the device system. Examples of such a heating device include a ventilation type oven and the like. By constantly discharging the water in the apparatus system, it is possible to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the phosphate esterification, and also to suppress the acid hydrolysis of the sugar chain in the fiber. it can. Therefore, it is possible to obtain fine fibrous cellulose having a high axial ratio.

The heat treatment time is preferably 1 second or more and 300 minutes or less, more preferably 1 second or more and 1000 seconds or less, and 10 seconds or more and 800 seconds or less after the water is substantially removed from the fiber raw material. Is more preferable. In the present embodiment, the amount of the phosphorus oxo acid group introduced can be within a preferable range by setting the heating temperature and the heating time within an appropriate range.

The phosphorus oxo acid group introduction step may be performed at least once, but may be repeated twice or more. By performing the phosphorus oxo acid group introduction step two or more times, many phosphorus oxo acid groups can be introduced into the fiber raw material.

The amount of the phosphorus oxo acid group introduced into the fiber raw material is preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.50 mmol / g per 1 g (mass) of the fibrous cellulose, for example. It is more preferably 0.60 mmol / g or more, further preferably 0.90 mmol / g or more, and particularly preferably 1.00 mmol / g or more. The amount of the phosphorus oxo acid group introduced into the fiber raw material is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, and 3.00 mmol per 1 g (mass) of the fibrous cellulose, for example. It is more preferably / g or less, further preferably 2.50 mmol / g or less, further preferably 2.00 mmol / g or less, and particularly preferably 1.50 mmol / g or less. By setting the amount of the phosphorus oxo acid group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous cellulose. Further, by setting the amount of the phosphorus oxo acid group introduced within the above range, it becomes easy to obtain a fine fibrous cellulose dispersion having a high concentration and high transparency. Further, the salt resistance of the fibrous cellulose can be improved by setting the introduction amount of the phosphorus oxo acid group to 1.00 mmol / g or more.

<Carboxylic acid group introduction process>
The process for producing fine fibrous cellulose may include, for example, a carboxy group introduction step as an ionic substituent introduction step. The carboxy group introduction step has an oxidation treatment such as ozone oxidation, oxidation by the Fenton method, TEMPO oxidation treatment, a compound having a group derived from carboxylic acid or a derivative thereof, or a group derived from carboxylic acid with respect to the fiber raw material containing cellulose. This is done by treating with an acid anhydride of the compound or a derivative thereof.

The compound having a group derived from a carboxylic acid is not particularly limited, but for example, a dicarboxylic acid compound such as maleic acid, succinic acid, phthalic acid, fumaric acid, glutaric acid, adipic acid, itaconic acid, citric acid, aconitic acid and the like. Examples include tricarboxylic acid compounds. The derivative of the compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include an imide of an acid anhydride of a compound having a carboxy group and a derivative of an acid anhydride of a compound having a carboxy group. The imide of the acid anhydride of the compound having a carboxy group is not particularly limited, and examples thereof include an imide of a dicarboxylic acid compound such as maleimide, succinateimide, and phthalateimide.

The acid anhydride of the compound having a group derived from carboxylic acid is not particularly limited, but for example, a dicarboxylic acid compound such as maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, and itaconic anhydride. Acid anhydrides can be mentioned. The derivative of the acid anhydride of the compound having a group derived from carboxylic acid is not particularly limited, but for example, a compound having a carboxy group such as dimethylmaleic acid anhydride, diethylmaleic acid anhydride, diphenylmaleic acid anhydride and the like. Examples thereof include those in which at least a part of the hydrogen atom of the acid anhydride is substituted with a substituent such as an alkyl group or a phenyl group.

When the TEMPO oxidation treatment is performed in the carboxy group introduction step, it is preferable to perform the treatment under conditions of pH 6 or more and 8 or less, for example. Such a treatment is also referred to as a neutral TEMPO oxidation treatment. Neutral TEMPO oxidation treatment includes, for example, sodium phosphate buffer (pH = 6.8), pulp as a fiber raw material, TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) as a catalyst, and the like. This can be done by adding a nitroxy radical and sodium hypochlorite as a sacrificial reagent. Further, by coexisting with sodium chlorite, the aldehyde generated in the oxidation process can be efficiently oxidized to the carboxy group. Further, the TEMPO oxidation treatment may be carried out under the condition that the pH is 10 or more and 11 or less. Such a treatment is also referred to as an alkaline TEMPO oxidation treatment. The alkaline TEMPO oxidation treatment can be carried out, for example, by adding a nitroxy radical such as TEMPO as a catalyst, sodium bromide as a co-catalyst, and sodium hypochlorite as an oxidizing agent to pulp as a fiber raw material. ..

The amount of carboxy group introduced into fibrous cellulose varies depending on the type of substituent, but when a carboxy group is introduced by TEMPO oxidation, for example, it is preferably 0.10 mmol / g or more per 1 g (mass) of fibrous cellulose. , 0.20 mmol / g or more, more preferably 0.40 mmol / g or more, further preferably 0.60 mmol / g or more, and 0.90 mmol / g or more. Even more preferably, it is particularly preferably 1.00 mmol / g or more. The amount of the carboxy group introduced into the fibrous cellulose is preferably 3.65 mmol / g or less, more preferably 3.00 mmol / g or less, and further preferably 2.50 mmol / g or less. , 2.00 mmol / g or less, 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 setting the amount of the carboxy group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fibrous cellulose. Further, by setting the amount of the carboxy group introduced within the above range, it becomes easy to obtain a fine fibrous cellulose dispersion having a high concentration and high transparency.

<Sulfur oxoacid group introduction process>
The process for producing 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, cellulose fibers having a sulfur oxoacid group (sulfur oxoacid group-introduced fiber) can be obtained by reacting the hydroxyl group of the fiber raw material containing cellulose with sulfur oxoacid.

In the sulfur oxoacid group introduction step, instead of compound A in the above-mentioned <phosphooxoacid group introduction step>, a compound capable of introducing a sulfur oxoacid group by reacting with a hydroxyl group of a fiber raw material containing cellulose is selected. At least one compound (hereinafter, also referred to as "Compound C") is used. The compound C may be any compound having a sulfur atom and capable of forming an ester bond with cellulose, and examples thereof include sulfuric acid or a salt thereof, sulfite or a salt thereof, sulfuric acid amide, and the like, but the compound C is not particularly limited. As the sulfuric acid, those having various puritys can be used, and for example, 96% sulfuric acid (concentrated sulfuric acid) can be used. Examples of sulfurous acid include 5% sulfurous acid water. Examples of the sulfate or sulfite include lithium salts, sodium salts, potassium salts and ammonium salts of sulfates or sulfites, and these can have various neutralization degrees. As the sulfuric acid amide, sulfamic acid or the like can be used. In the sulfur oxoacid group introduction step, it is preferable to use the compound B in the above-mentioned <phosphooxoacid group introduction step> in the same manner.

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. As the heat treatment temperature, it is preferable to select a temperature at which the sulfur oxoacid group can be efficiently introduced while suppressing the 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. The heat treatment temperature is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, and even more preferably 200 ° C. or lower.

In the heat treatment step, it is preferable to heat until the water content is substantially eliminated. Therefore, the heat treatment time varies depending on the amount of water contained in the cellulose raw material and the amount of the aqueous solution containing sulfur oxoacid and urea and / or a urea derivative, but is, for example, 10 seconds or more and 10000 seconds or less. It is preferable to do so. Equipment having various heat media can be used for the heat treatment, for example, a hot air drying device, a stirring drying device, a rotary drying device, a disk drying device, a roll type heating device, a plate type heating device, and a fluidized layer drying device. , Band type drying device, filtration drying device, vibration flow drying device, air flow drying device, vacuum drying device, infrared heating device, far infrared heating device, microwave heating device, high frequency drying device can be used.

The amount of the sulfur oxoacid group introduced into the cellulose raw material is preferably 0.05 mmol / g or more, more preferably 0.10 mmol / g or more, still more preferably 0.20 mmol / g or more. It is more preferably 0.40 mmol / g or more, further preferably 0.60 mmol / g or more, further preferably 0.90 mmol / g or more, and 1.00 mmol / g or more. Is particularly preferable. The amount of sulfur oxoacid group introduced into the cellulose raw material is preferably 5.00 mmol / g or less, more preferably 3.00 mmol / g or less, and further preferably 2.50 mmol / g or less. It is more preferably 2.00 mmol / g or less, and particularly preferably 1.50 mmol / g or less. By setting the amount of the sulfur oxoacid group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fibrous cellulose. Further, by setting the amount of the sulfur oxoacid group introduced within the above range, it becomes easy to obtain a fine fibrous cellulose dispersion having a high concentration and high transparency.

<Washing process>
In the method for producing fine fibrous cellulose in the present embodiment, a washing step can be performed on the ionic substituent-introduced fiber, if necessary. The washing step is performed by washing the ionic substituent-introduced fiber with, for example, water or an organic solvent. Further, the cleaning step may be performed after each step described later, and the number of cleanings performed in each cleaning step is not particularly limited.

<Alkaline treatment process>
When producing fine fibrous cellulose, an alkali treatment may be performed on the fiber raw material between the step of introducing an ionic substituent and the step of defibration treatment described later. The alkaline treatment method is not particularly limited, and examples thereof include a method of immersing the ionic substituent-introduced fiber in an alkaline solution.

The alkaline compound contained in the alkaline solution is not particularly limited, and may be an inorganic alkaline compound or an organic alkaline compound. In the present embodiment, for example, sodium hydroxide or potassium hydroxide is preferably used as the alkaline compound because of its high versatility. Further, the solvent contained in the alkaline solution may be either water or an organic solvent. Among them, the solvent contained in the alkaline solution is preferably a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of its high versatility.

The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is preferably 5 ° C. or higher and 80 ° C. or lower, and more preferably 10 ° C. or higher and 60 ° C. or lower. The immersion time of the ionic substituent-introduced fiber in the alkaline solution in the alkali treatment step is not particularly limited, but is preferably 5 minutes or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less. The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but is preferably 100% by mass or more and 100,000% by mass or less, and 1000% by mass or more and 10000% by mass or less, based on the absolute dry mass of the ionic substituent-introduced fiber. The following is more preferable.

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

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

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

The temperature of the acid solution in the acid treatment is not particularly limited, but is preferably 5 ° C. or higher and 100 ° C. or lower, and more preferably 20 ° C. or higher and 90 ° C. or lower. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably 5 minutes or more and 120 minutes or less, and more preferably 10 minutes or more and 60 minutes or less. The amount of the acid solution used in the acid treatment is not particularly limited, but is preferably 100% by mass or more and 100,000% by mass or less, and 1000% by mass or more and 10,000% by mass or less, for example, with respect to the absolute dry mass of the fiber raw material. Is more preferable.

<Fiber processing>
Fine fibrous cellulose can be obtained by defibrating (mechanically treating) the ionic substituent-introduced fiber in the defibration treatment step. In the defibration treatment step, for example, a defibration treatment apparatus can be used. The defibrating apparatus is not particularly limited, but for example, a high-speed defibrator, a grinder (stone mill type crusher), a high-pressure homogenizer or an ultra-high pressure homogenizer, a high-pressure collision type crusher, a ball mill, a bead mill, a disc type refiner, a conical refiner, and a twin shaft. A kneader, a vibration mill, a homomixer under high speed rotation, an ultrasonic disperser, or a beater can be used. Among the above-mentioned defibration processing devices, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, and an ultra-high-pressure homogenizer, which are less affected by crushed media and have less risk of contamination.

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

The concentration of the cellulose fiber at the time of the defibration treatment can be appropriately set, but in the present embodiment, the concentration of the cellulose fiber at the time of the defibration treatment is preferably 3.0% by mass or more, and 4.0% by mass or more. It is more preferably 5.0% by mass or more, and 6.0% by mass or more is particularly preferable. The upper limit of the concentration of the cellulose fibers during the defibration treatment is not particularly limited, but may be, for example, 20.0% by mass. In the present embodiment, by setting the concentration of the cellulose fibers at the time of the defibration treatment within the above range, it is possible to uniformly disperse the fine fibrous cellulose and obtain a highly transparent high-concentration dispersion liquid. Further, by setting the concentration of the cellulose fiber during the defibration treatment within the above range, it is possible to increase the production efficiency of the fine fibrous cellulose, and as a result, a processed product such as a dispersion liquid or a sheet containing the fine fibrous cellulose can be produced. It is also possible to produce efficiently. In addition, by setting the concentration of cellulose fibers during the defibration treatment within the above range, it is possible to obtain a highly concentrated dispersion, and it is possible to reduce costs during transportation and storage.

Further, the slurry obtained by dispersing the ionic substituent-introduced fiber in a dispersion medium may contain a solid content other than the ionic substituent-introduced fiber such as urea having a hydrogen bond property.

<Low molecular weight treatment>
The method for producing fine fibrous cellulose of the present embodiment preferably includes a step of further reducing the molecular weight in addition to the steps as described above. Specifically, as described above, a step of subjecting appropriately treated cellulose fibers to a defibration treatment to obtain a fibrous cellulose having a fiber width of 1000 nm or less, and a step of subjecting the fibrous cellulose to a low molecular weight treatment. Is preferably included. That is, it is preferable that the method for producing fine fibrous cellulose of the present embodiment includes, for example, a step of subjecting the cellulose fibers to a defibration treatment and then a molecular weight reduction treatment. The molecular weight reduction treatment may be performed before the defibration treatment step. For example, the molecular weight reduction treatment may be performed before the defibration treatment and then the molecular weight reduction treatment after the defibration treatment. Good. Further, the defibration treatment may be performed again after the molecular weight reduction treatment is performed, and then the defibration treatment may be performed again after the molecular weight reduction treatment is performed. Above all, in order to reduce the molecular weight more effectively, it is preferable to perform the molecular weight reduction treatment after the defibration treatment.

In the present specification, in the step of applying the molecular weight reduction treatment, when the fine fibrous cellulose is made into an aqueous dispersion having a concentration of 0.5% by mass, the viscosity of the aqueous dispersion at 23 ° C. is 100 mPa · s or less. For example, it is a step of reducing the degree of polymerization of fine fibrous cellulose. Specifically, the step of applying the molecular weight reduction treatment is preferably a step of reducing the degree of polymerization of fibrous cellulose having a fiber width of 1000 nm or less to 230 or less.

Examples of the step of performing the low molecular weight treatment include an ozone treatment step, an enzyme treatment step, an acid treatment step, a sub-critical water treatment step, and the like. The step of applying the low molecular weight treatment is preferably at least one selected from the ozone treatment step, the enzyme treatment step, the acid treatment step and the subcritical water treatment step, and is selected from the ozone treatment step and the enzyme treatment step. It is particularly preferable that there is at least one type.

In the ozone treatment step, ozone is added to the fine fibrous cellulose dispersion (slurry). When adding ozone, for example, it is preferable to add it as an ozone / oxygen mixed gas. At this time, the ozone addition rate with respect to 1 g of the fine fibrous cellulose contained in the fine fibrous cellulose dispersion (slurry) ^{is preferably 1.0 × 10 -4} g or more, preferably 1.0 × 10 ^-3 g. The above is more preferable, and 1.0 × ^10-2 g or more is further preferable. The ozone addition rate with respect to 1 g of fine fibrous cellulose ^{is preferably 1.0 × 10 1} g or less. After adding ozone to the fine fibrous cellulose dispersion (slurry), the mixture may be stirred for 10 seconds or more and 10 minutes or less under the conditions of 10 ° C. or more and 50 ° C. or less, and then allowed to stand for 1 minute or more and 100 minutes or less. preferable.

In the enzyme treatment step, the enzyme is added to the fine fibrous cellulose dispersion (slurry). The enzyme used at this time is preferably a cellulase-based enzyme. Cellulase-based enzymes are classified into the sugar hydrolase family based on the higher-order structure of the catalytic domain having the function of hydrolyzing cellulose. Cellulase-based enzymes are roughly classified into endo-glucanase and cellobiohydrolase according to their cellulolytic properties. Endo-type glucanase is highly hydrolyzable to amorphous portions of cellulose, soluble cellooligosaccharides, and cellulose derivatives such as carboxymethyl cellulose, and randomly cleaves their molecular chains from the inside to reduce the degree of polymerization. In contrast, cellobiohydrolase decomposes the crystalline portion of cellulose to give cellobiose. In addition, cellobiohydrolase hydrolyzes from the end of the cellulose molecule and is also called an exo-type or processive enzyme. The enzyme used in the enzyme treatment step is not particularly limited, but it is preferable to use endo-type glucanase.

In the enzyme treatment step, it is preferable to add the enzyme so that the enzyme activity is 0.1 nkat or more, more preferably 1.0 nkat or more, and 10 nkat or more with respect to 1 g of the fine fibrous cellulose. It is more preferable to add the enzyme so that it becomes. Further, it is preferable to add the enzyme so as to be 100,000 nkat or less with respect to 1 g of the fine fibrous cellulose, more preferably to add the enzyme so as to be 50,000 nkat or less, and further preferably to add the enzyme so as to be 10,000 nkat or less. After adding the enzyme to the fine fibrous cellulose dispersion (slurry), it is treated under the condition of 0 ° C. or higher and lower than 80 ° C. for 1 minute or more and 100 hours or less, and then placed under the condition of 80 ° C. or higher. It is preferable to inactivate the enzyme.

The acid treatment step includes, for example, sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochloric acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, boric acid, sulfonic acid (eg methane). This is a step of mixing with sulfonic acid) or the like. Above all, the acid treatment step is preferably a step of mixing 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 preferably 1.0 × 10 -4} g or more, more preferably 1.0 × 10 ^-3 g or more, with respect to 1 g of fine fibrous cellulose. It is more preferably 0 × 10 ⁻² g or more, and ^{particularly preferably 1.0 × 10 -1} g or more. ^{The addition rate of sodium hypochlorite is preferably 1.0 × 10 2} g or less with respect to 1 g of fine fibrous cellulose. After adding sodium hypochlorite to the fine fibrous cellulose dispersion (slurry), it is preferable to stir for 1 minute or more and 10 hours or less under the conditions of 10 ° C. or higher and 50 ° C. or lower.

In the sub-critical water treatment step, the fine fibrous cellulose dispersion (slurry) is subjected to high-temperature and high-pressure treatment to bring it into a sub-critical state. Fine fibrous cellulose is hydrolyzed in a subcritical state. Specifically, after the fine fibrous cellulose dispersion (slurry) is placed in the reaction vessel, the temperature is raised to 150 ° C. or higher and 500 ° C. or lower, preferably 150 ° C. or higher and 350 ° C. or lower, and the pressure in the reaction vessel is increased. Pressurize to 10 MPa or more and 80 MPa or less, preferably 10 MPa or more and 20 MPa or less. The heating and pressurizing time at this time is preferably 0.1 seconds or more and 100 seconds or less, and more preferably 3 seconds or more and 50 seconds or less.

It is preferable to further provide a defibration treatment step after the low molecular weight treatment step. Above all, it is preferable to provide a defibration treatment step before and after the low molecular weight treatment step. In this case, as the defibration treatment step, the same steps as those described above can be exemplified, but among them, in the defibration treatment step after the low molecular weight treatment step, a high pressure homogenizer or an ultrahigh pressure homogenizer can be used. preferable.

The present embodiment may relate to a method for producing fine fibrous cellulose, which comprises at least one step of defibrating a cellulose fiber having an ionic substituent and one step of reducing the molecular weight. The method for producing fine fibrous cellulose further increases the concentration of cellulose fibers during the defibration treatment by including at least one step of defibrating the cellulose fibers having an ionic substituent and one step of reducing the molecular weight. be able to. As a result, a high-concentration fine fibrous cellulose dispersion can be efficiently obtained. In this case, the method for producing fine fibrous cellulose may include a defibration treatment step, a low molecular weight treatment step, and a defibration treatment step in this order, and the low molecular weight treatment step and the defibration treatment. The step, the low molecular weight treatment step, and the defibration treatment step may be included in this order. In addition, it is preferable that the above-mentioned ionic substituent introduction step, washing step, alkali treatment step and the like are provided before the first defibration treatment step or low molecular weight treatment step. In such a method for producing fine fibrous cellulose, the molecular weight reduction treatment step is preferably at least one selected from an ozone treatment step, an enzyme treatment step, an acid treatment step and a subcritical water treatment step, and ozone. It is particularly preferable that it is at least one selected from the treatment step and the enzyme treatment step.

(Fibrous cellulose dispersion)
The present embodiment may be an invention relating to the fibrous cellulose dispersion liquid containing the above-mentioned fine fibrous cellulose. The fibrous cellulose dispersion liquid is a fibrous cellulose dispersion liquid (also referred to as a fine fibrous cellulose-containing dispersion liquid, a fine fibrous cellulose-containing slurry or a slurry) obtained by dispersing fine fibrous cellulose in a solvent containing water. Is preferable, and a fibrous cellulose aqueous dispersion liquid obtained by dispersing in a solvent containing water as a main component is more preferable.

The content of fine fibrous cellulose (concentration of fine fibrous cellulose) in the fibrous cellulose dispersion is preferably 3.0% by mass or more with respect to the total mass of the fibrous cellulose dispersion. It is more preferably 0% by mass or more, further preferably 5.0% by mass or more, and particularly preferably 6.0% by mass or more. The content of the fine fibrous cellulose (concentration of the fine fibrous cellulose) is preferably 30.0% by mass or less, preferably 20.0% by mass or less, based on the total mass of the fibrous cellulose dispersion. More preferably.

When the fibrous cellulose dispersion is a fibrous cellulose dispersion having a fine fibrous cellulose concentration of 0.5% by mass, the viscosity of the dispersion at 23 ° C. may be less than 108 mPa · s, and is 100 mPa · s. It is preferably 5 mPa · s or less, and more preferably 95 mPa · s or less. The viscosity of the fine fibrous cellulose dispersion is a viscosity value 3 minutes after the start of measurement, at 23 ° C. and a rotation speed of 3 rpm using a B-type viscometer. As the B-type viscometer, for example, an analog viscometer T-LVT manufactured by BLOOKFIELD can be used. When preparing a fibrous cellulose dispersion having a concentration of 0.5% by mass of fine fibrous cellulose, after stirring with a disperser at 4000 rpm for 3 minutes, a rotating and revolving supermixer (manufactured by Shinky Co., Ltd., ARE-). In 250), the fine fibrous cellulose dispersion is defoamed.

When the fine fibrous cellulose is used as an aqueous dispersion having a concentration of 6.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is preferably 500,000 mPa · s or more, preferably 700,000 mPa · s or more. Is more preferable, and 1,000,000 mPa · s or more is particularly preferable. Further, when the fine fibrous cellulose is used as an aqueous dispersion having a concentration of 6.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is preferably 1,000,000 mPa · s or less, preferably 7,500,000 mPa. -S or less is more preferable, and 4,000,000 mPa · s or less is particularly preferable. When the fine fibrous cellulose is used as an aqueous dispersion having a concentration of 13.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is preferably 1,000,000 mPa · s or more, preferably 3,000,000 mPa. -S or more is more preferable, and 5,000,000 mPa · s or more is particularly preferable. When the fine fibrous cellulose is used as an aqueous dispersion having a concentration of 13.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is preferably 50,000,000 mPa · s or less, preferably 30,000,000 mPa. It is more preferably s or less, and particularly preferably less than 18,000,000 mPa · s. The viscosity of the water dispersion with a concentration of 6.0% by mass or the water dispersion with a concentration of 13.0% by mass was set to a rotation speed of 0.3 rpm at 23 ° C. using a B-type viscometer, and 3 minutes after the start of measurement. Is the viscosity value of. As the B-type viscometer, for example, an analog viscometer T-LVT or a digital viscometer DV2T manufactured by BLOOKFIELD can be used. When fine fibrous cellulose was prepared in an aqueous dispersion having a concentration of 6.0% by mass or 13.0% by mass, it was stirred with a disperser at 4000 rpm for 3 minutes, and then a rotating and revolving supermixer (Sinky). The fine fibrous cellulose dispersion is defoamed with ARE-250) manufactured by the company. When preparing an aqueous dispersion having a concentration of 6.0% by mass or a concentration of 13.0% by mass, an aqueous dispersion having a concentration higher than the concentration of 6.0% by mass or 13.0% by mass is obtained. An aqueous dispersion having a concentration of 6.0% by mass or a concentration of 13.0% by mass may be obtained by diluting the aqueous dispersion with water.

When the fibrous cellulose dispersion is a fibrous cellulose dispersion having a fine fibrous cellulose concentration of 0.2% by mass, the haze of the dispersion is preferably 80% or less, preferably 60% or less. Is more preferably 40% or less, further preferably 30% or less, further preferably 15% or less, and particularly preferably 5% or less. When the haze of the dispersion liquid is in the above range, it means that the fibrous cellulose dispersion liquid has high transparency and the fine fibrous cellulose has good dispersibility. Here, the haze of the fine fibrous cellulose dispersion (fine fibrous cellulose concentration 0.2% by mass) is a fibrous cellulose dispersed in a liquid glass cell (manufactured by Fujiwara Seisakusho, MG-40, backlit path) having an optical path length of 1 cm. It is a value measured by adding a liquid and conforming to JIS K 7136: 2000 and using a haze meter (HM-150 manufactured by Murakami Color Technology Research Institute). Before the measurement, the dispersion liquid to be measured is allowed to stand in an environment of 23 ° C. and a relative humidity of 50% for 24 hours. In addition, the zero point measurement at the time of haze measurement is performed with ion-exchanged water contained in the same glass cell.

The fibrous cellulose dispersion may contain a solvent containing water and other additives in addition to the fine fibrous cellulose. Examples of other additives include antifoaming agents, lubricants, ultraviolet absorbers, dyes, pigments, stabilizers, surfactants, preservatives (for example, phenoxyethanol) and the like. Further, the fibrous cellulose dispersion liquid may contain a hydrophilic polymer, a hydrophilic low molecule, an organic ion or the like as optional components.

The hydrophilic polymer is preferably a hydrophilic oxygen-containing organic compound (excluding the above-mentioned cellulose fibers), and examples of the oxygen-containing organic compound include polyethylene glycol, polyethylene oxide, casein, dextrin, starch, and modification. Distillate, polyvinyl alcohol, modified polyvinyl alcohol (acetoacetylated polyvinyl alcohol, etc.), polyethylene oxide, polyvinylpyrrolidone, polyvinylmethyl ether, polyacrylates, acrylic acid alkyl ester copolymer, urethane copolymer, cellulose derivative (hydroxy) Ethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, etc.) and the like.

The hydrophilic low molecule is preferably a hydrophilic oxygen-containing organic compound, and more preferably a polyhydric alcohol. Examples of the polyhydric alcohol include glycerin, sorbitol, ethylene glycol and the like.

Examples of the organic ion include tetraalkylammonium ion and tetraalkylphosphonium ion. Examples of the tetraalkylammonium ion include tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, tetrahexylammonium ion, tetraheptylammonium ion, tributylmethylammonium ion, and lauryltrimethyl. Examples thereof include ammonium ion, cetyltrimethylammonium ion, stearyltrimethylammonium ion, octyldimethylethylammonium ion, lauryldimethylethylammonium ion, didecyldimethylammonium ion, lauryldimethylbenzylammonium ion and tributylbenzylammonium ion. Examples of the tetraalkylphosphonium ion include tetramethylphosphonium ion, tetraethylphosphonium ion, tetrapropylphosphonium ion, tetrabutylphosphonium ion, and lauryltrimethylphosphonium ion. Further, examples of the tetrapropyl onium ion and the tetrabutyl onium ion include tetra n-propyl onium ion and tetra n-butyl onium ion, respectively.

(Use)
The fine fibrous cellulose of the present embodiment can be a highly concentrated dispersion. Therefore, it is particularly preferably used in applications where it is desired to add fine fibrous cellulose at a high concentration. For example, the fine fibrous cellulose of the present embodiment is used as an additive to foods, cosmetics, cement, paints (for painting vehicles such as automobiles, ships, aircraft, etc., for building materials, for daily necessities, etc.), inks, pharmaceuticals, and the like. Can be done. Further, the fine fibrous cellulose of the present embodiment can be applied to daily necessities by adding it to a resin-based material or a rubber-based material.

Further, when the sheet or the coating film is formed from the dispersion liquid containing the fine fibrous cellulose of the present embodiment at a high concentration, the content of the fine fibrous cellulose in the sheet or the coating film can be increased. Thereby, the mechanical strength of the obtained sheet or coating film can be increased. For example, the tensile strength and tensile elastic modulus of the sheet or coating film can be increased more effectively. As described above, the fine fibrous cellulose dispersion liquid of the present embodiment is preferably a dispersion liquid for forming a sheet, and the present embodiment may relate to the above-mentioned sheet containing the fine fibrous cellulose.

When forming a sheet or a coating film from the dispersion liquid containing the fine fibrous cellulose of the present embodiment at a high concentration, a coating step of applying the fine fibrous cellulose dispersion liquid on the base material, or for forming the sheet. It is preferable to include a papermaking step of making the composition. A resin layer or an inorganic layer may be further laminated on the sheet thus obtained.

In addition, the present embodiment may have the following configurations.
<101> A fine fibrous cellulose-containing dispersion having a fiber width of 1000 nm or less and having an ionic substituent.
The content of the fine fibrous cellulose is 5.0% by mass or more and 14.0% by mass or less with respect to the total mass of the dispersion liquid.
The degree of polymerization of the fine fibrous cellulose is 160 or more and 205 or less.
Fine fibrous cellulose-containing dispersion.
<102> The fine fibrous cellulose-containing dispersion according to <101>, wherein the viscosity measured using a B-type viscometer is 1800 × 10 ³ mPa · s or more and 13000 × 10 ^{3 mPa · s or less.}
<103> The fine fibrous cellulose-containing dispersion according to <101> or <102>, wherein the ionic substituent is a phospholic acid group or a substituent derived from a phosphoxoic acid group.
<104> The fine fibrous cellulose-containing according to any one of <101> to <103>, wherein the amount of the ionic substituent introduced into the fine fibrous cellulose is 0.90 mmol / g or more and 2.00 mmol / g or less. Dispersion solution.

<111> A step of subjecting a cellulose fiber having an ionic substituent to a defibration treatment to obtain a fibrous cellulose having a fiber width of 1000 nm or less.
A method for producing fibrous cellulose, which comprises a step of subjecting fibrous cellulose to a low molecular weight treatment.
A method for producing fibrous cellulose, wherein the viscosity of the aqueous dispersion at 23 ° C. is less than 108 mPa · s when the fibrous cellulose is used as an aqueous dispersion having a concentration of 0.5% by mass.
<112> The method for producing fibrous cellulose according to <111>, wherein the concentration of cellulose fibers in the step of obtaining fibrous cellulose having a fiber width of 1000 nm or less by performing a defibration treatment is 3.0% by mass or more.
<113> The method for producing fibrous cellulose according to <111> or <112>, wherein the step of applying the molecular weight reduction treatment is a step of reducing the degree of polymerization of the fibrous cellulose to 230 or less.
<114> The step of applying the low molecular weight treatment is any one of <111> to <113>, which is at least one selected from an ozone treatment step, an enzyme treatment step, an acid treatment step, and a subcritical water treatment step. The method for producing fibrous cellulose according to the above.
<115> The method for producing fibrous cellulose according to any one of <111> to <114>, which comprises a step of further performing a defibration treatment after the step of performing a low molecular weight treatment.
<116> A fibrous cellulose produced by the method for producing a fibrous cellulose according to any one of <111> to <115>.

The features of the present invention will be described in more detail below with reference to Examples and Comparative Examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention should not be construed in a limited manner by the specific examples shown below.

<Manufacturing example 1>
[Manufacturing of phosphorylated pulp]
As raw material pulp, softwood kraft pulp made by Oji Paper (solid content 93% by mass, basis weight 245 g / m ² sheets, disintegrated and measured according to JIS P 811-2: 2012 Canadian standard drainage degree (CSF) ) Used 700 ml). The raw material pulp was subjected to phosphorus oxo oxidation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to obtain 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. To obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165 ° C. for 250 seconds to introduce a phosphoric acid group into the cellulose in the pulp to obtain a phosphorylated pulp.

Next, the obtained phosphorylated pulp was washed. The washing treatment is carried out by repeating the operation of pouring 10 L of ion-exchanged water into 100 g (absolute dry mass) of phosphorylated pulp, stirring the pulp dispersion liquid so that the pulp is uniformly dispersed, and then filtering and dehydrating the pulp. went. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

Next, the phosphorylated pulp after washing was neutralized as follows. First, the washed phosphorylated pulp was diluted with 10 L of ion-exchanged water, and then a 1N aqueous sodium hydroxide solution was added little by little with stirring to obtain a phosphorylated pulp slurry having a pH of 12 or more and 13 or less. .. Next, the phosphorylated pulp slurry was dehydrated to obtain a phosphorylated pulp that had been neutralized. Next, the phosphorylated pulp after the neutralization treatment was subjected to the above-mentioned washing treatment to obtain phosphorylated pulp A.

The infrared absorption spectrum of the phosphorylated pulp A thus obtained was measured using FT-IR. As a result, ^{absorption based on the phosphate group was observed around 1230 cm -1} , and it was confirmed that the phosphate group was added to the pulp.

Further, when the obtained phosphorylated pulp A was tested and analyzed by an X-ray diffractometer, two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less, were located. A typical peak was confirmed in, and it was confirmed that it had cellulose type I crystals.

<Manufacturing example 2>
The same treatment as in Production Example 1 was carried out except that the heating time in the hot air dryer was changed to 150 seconds to obtain phosphorylated pulp B.

<Manufacturing example 3>
Phosphorylated pulp C was obtained by further performing the phosphorylation treatment and the washing treatment of Production Example 1 once on the washed phosphorylated pulp obtained in Production Example 1.

<Manufacturing example 4>
The same treatment as in Production Example 1 was carried out except that the raw material pulp used in Production Example 1 was hardwood pulp (dry sheet) manufactured by Oji Paper Co., Ltd. to obtain phosphorylated pulp D.

<Manufacturing example 5>
Phosphorylated pulp E was obtained by performing the same treatment as in Production Example 1 except that the raw material pulp used in Production Example 1 was hardwood kraft pulp (dry sheet) manufactured by Celulose Nipo.

<Manufacturing example 6>
[Pre-hydrolysis]
300 g of softwood chips were collected by absolute dry mass and immersed in 10 liters of tap water overnight. Then, the chips were taken out, emptied into a 400 mesh sieve, and filtered. The dehydrated chips are placed in a 2.5 liter capacity autoclave, tap water is added so that the liquid mass ratio (assuming the mass of the chips after absolute drying is 1) is 3, and then 30 at 165 ° C. It was heated for minutes and pre-hydrolyzed. The P factor at this time was 380.
[Cooking]
After pre-hydrolysis, waste gas was extracted from the degassing cock of the autoclave, and after confirming that the pressure in the autoclave became 0, the treated chips were passed through a 400 mesh sieve and filtered. The chips after filtration were placed in an autoclave having a capacity of 2.5 liters again, a cooking solution was added so that the liquid ratio was 5, and craft cooking was performed under the conditions of a cooking temperature of 165 ° C. and a cooking time of 120 minutes. The cooking liquid contained 21% by mass of active alkali with respect to the absolute dry mass of the chips, and the sulfurization degree was 28%. After cooking, the black liquor and pulp were separated, and the pulp was carefully selected on a flat screen equipped with an 8-cut screen plate to obtain pulp after cooking.
[bleaching]
After cooking, 70 g of pulp was collected by absolute dry mass, and 2.0 mass% of caustic soda was added to the total mass of the absolute dry pulp, and then diluted with ion-exchanged water to adjust the pulp concentration to 10 mass%. This slurry was placed in an indirect heating type autoclave, 99.9% compressed oxygen gas was injected to adjust the gauge pressure to 0.5 MPa, and oxygen exposure was performed at 100 ° C. for 60 minutes. After the oxygen exposure was completed, the pressure was reduced until the gauge pressure became 0.05 MPa or less, the pulp was taken out from the autoclave, washed with 7 liters of ion-exchanged water, and then dehydrated. In this way, pulp was obtained after oxygen exposure.
After oxygen exposure, 60 g of pulp was collected by absolute dry mass, placed in a plastic bag, and ion-exchanged 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 absolute dry pulp, and the pulp was immersed in a constant temperature water bath at a temperature of 70 ° C. for 70 minutes (D0 stage treatment). The pulp obtained after the D0 step treatment was diluted to 3% by mass with ion-exchanged water, and then dehydrated and washed with Buchner funnel. Put the pulp after the D0 stage treatment in a plastic bag, add ion-exchanged water to adjust the pulp concentration to 10% by mass, and then add 1.0% by mass of caustic soda and hydrogen peroxide to the total mass of the absolute dry pulp. It was added so as to be 0.3% by mass and mixed well. Then, the E / P stage treatment was performed by immersing in a constant temperature water tank having a temperature of 70 ° C. for 100 minutes. The obtained pulp was diluted to 3% by mass with ion-exchanged water, and then dehydrated and washed with Buchner funnel. The pulp after the E / P stage treatment is placed in a plastic bag, the pulp concentration is adjusted to 10% by mass using ion-exchanged water, and then 0.3% by mass of chlorine dioxide is added to the total mass of the absolute dry pulp. It was immersed in a constant temperature water tank having a temperature of 70 ° C. for 80 minutes to perform a D1 stage bleaching treatment. The obtained pulp was diluted to 3% by mass with ion-exchanged water, and then dehydrated and washed with Büchner funnel to obtain bleached pulp.
[Phosphorylation]
The bleached pulp was adjusted to have 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water to obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165 ° C. for 250 seconds to introduce a phosphoric acid group into the cellulose in the pulp to obtain phosphorylated pulp F.

<Manufacturing example 7>
[Manufacturing of TEMPO oxidized pulp]
As the raw material pulp, softwood kraft pulp (undried) made by Oji Paper was used. Alkaline TEMPO oxidation treatment was carried out on this raw material pulp as follows. First, the raw material pulp equivalent to 100 parts by mass of dry mass, 1.6 parts by mass of TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl), and 10 parts by mass of sodium bromide are added to 10000 parts by mass of water. It was dispersed in the parts. Then, 13% by mass sodium hypochlorite solution was added to 1.0 g of pulp so as to be 3.8 mmol, and the reaction was started. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to keep the pH at 10 or more and 10.5 or less, and the reaction was considered to be completed when no change was observed in the pH.

Next, the obtained TEMPO oxide pulp was washed. The washing treatment is carried out by dehydrating the pulp slurry after TEMPO oxidation to obtain a dehydrated sheet, pouring 5000 parts by mass of ion-exchanged water, stirring and uniformly dispersing, and then repeating the operation of filtration and dehydration. It was. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

The dehydrated sheet was subjected to additional oxidation treatment of the remaining aldehyde groups as follows. The dehydrated sheet corresponding to 100 parts by mass of dry mass was dispersed in 10000 parts by mass of 0.1 mol / L acetate buffer (pH 4.8). Next, 113 parts by mass of 80% by mass of sodium chlorite was added, and the mixture was immediately sealed and then reacted at room temperature for 48 hours with stirring at 500 rpm using a magnetic stirrer to obtain a pulp slurry.

Next, the obtained top-oxidized TEMPO oxide pulp was washed. The washing treatment is carried out by dehydrating the post-oxidized pulp slurry to obtain a dehydrated sheet, pouring 5000 parts by mass of ion-exchanged water, stirring and uniformly dispersing the slurry, and then repeating the operation of filtering and dehydrating. It was. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set and TEMPO oxide pulp A was obtained.

Further, when the obtained TEMPO oxide pulp A was tested and analyzed by an X-ray diffractometer, two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less, were located. A typical peak was confirmed in, and it was confirmed that it had cellulose type I crystals.

<Manufacturing example 8>
The same treatment as in Production Example 7 was carried out except that the raw material pulp used in Production Example 7 was a broad-leaved pulp pulp (undried) manufactured by Oji Paper Co., Ltd. to obtain TEMPO oxidized pulp B.

<Manufacturing example 9>
The same treatment as in Production Example 7 was carried out except that the raw material pulp used in Production Example 7 was broadleaf kraft pulp (undried) manufactured by Oji Paper Co., Ltd. to obtain TEMPO oxidized pulp C.

<Manufacturing example 10>
[Manufacturing of subphosphorylated pulp]
As raw material pulp, softwood kraft pulp made by Oji Paper (solid content 93% by mass, basis weight 245 g / m ² sheets, disintegrated and measured according to JIS P 811-2: 2012 Canadian standard drainage degree (CSF) ) Used 700 ml). The raw material pulp was subjected to phosphorus oxo oxidation treatment as follows. First, a mixed aqueous solution of phosphorous acid (phosphonic acid) and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to add 33 parts by mass of phosphorous acid (phosphonic acid), 120 parts by mass of urea, and 150 parts of water. The amount was adjusted to be parts by mass, and a chemical-impregnated pulp was obtained. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165 ° C. for 250 seconds to introduce a phosphorous acid group into the cellulose in the pulp to obtain a phosphorylated pulp.

Next, the obtained subphosphorylated pulp was washed. In the washing treatment, the pulp dispersion obtained by pouring 10 L of ion-exchanged water into 100 g (absolute dry mass) of subphosphorized pulp is stirred so that the pulp is uniformly dispersed, and then the operation of filtering and dehydrating is repeated. Was done by. When the electrical conductivity of the filtrate became 100 μS / cm or less, the washing end point was set.

Next, the washed subphosphorylated pulp was neutralized as follows. First, the washed subphosphorylated pulp is diluted with 10 L of ion-exchanged water, and then a 1N aqueous sodium hydroxide solution is added little by little with stirring to obtain a subphosphorylated pulp slurry having a pH of 12 or more and 13 or less. Obtained. Then, the subphosphorylated pulp slurry was dehydrated to obtain a neutralized subphosphorylated pulp. Next, the neutralized subphosphorylated pulp was subjected to the above washing treatment to obtain subphosphorylated pulp A.

The infrared absorption spectrum of the subphosphorylated pulp A thus obtained was measured using FT-IR. As a result, P = O-based absorption of the phosphonic acid group, which is a tautomer of the phosphite group, was observed near ^{1210 cm -1, and a (sub) phosphorous acid group (phosphonic acid group) was added to the pulp.} It was confirmed that there was. Further, when the obtained subphosphorylated pulp was tested and analyzed by an X-ray diffractometer, two positions were found: 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. A typical peak was confirmed in, and it was confirmed that it had cellulose type I crystals.

<Manufacturing example 11>
Subphosphorized pulp B was obtained by performing the same treatment as in Production Example 10 except that the raw material pulp used in Production Example 10 was hardwood pulp (dry sheet) manufactured by Oji Paper Co., Ltd.

<Manufacturing example 12>
Subphosphorylated pulp C was obtained by performing the same treatment as in Production Example 10 except that the raw material pulp used in Production Example 10 was hardwood kraft pulp (dry sheet) manufactured by Celulose Nipo.

<Manufacturing example 13>
[Manufacturing of sulfur oxooxidized pulp]
In the production of phosphorylated pulp, 38 parts by mass of amidosulfate (sulfamic acid) was used instead of ammonium dihydrogen phosphate, and the same operation as in Production Example 1 was carried out except that the heating time was extended to 20 minutes to perform sulfation. Obtained pulp.

The infrared absorption spectrum of the sulfated pulp thus obtained was measured using FT-IR. As a result, it was confirmed that a sulfate group (absorption based on a sulfone group was observed and a sulfate group (sulfone group) was added to the pulp in the vicinity of ^{1220-1260 cm -1. Also, it was obtained by X-ray diffraction.} It was confirmed that the sulfated pulp maintained the cellulose type I crystal.

<Example 1>
Ion-exchanged water was added to the phosphorylated pulp A obtained in Production Example 1 to prepare a slurry having a solid content concentration of 6.0% by mass. This slurry was treated once with a high-pressure homogenizer at a pressure of 200 MPa to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. An enzyme-containing solution having an activity of 33000 nkat was added to 1000 g of this dispersion (solid content concentration 6.0% by mass, solid content 60 g) and subjected to enzyme treatment at a temperature of 50 ° C. The amount of enzyme added at this time was set to 550 nkat per 1 g of fine fibrous cellulose. Then, it was treated three times with a high-pressure homogenizer at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion. The temperature of the obtained dispersion was set to 100 ° C., and the enzyme was heat-inactivated. The amount of phosphate group (first dissociated acid amount) measured by the measuring method described in [Measurement of phosphorus oxo acid group amount] described later was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

<Example 2>
Ion-exchanged water was added to the phosphorylated pulp A obtained in Production Example 1 to prepare a slurry having a solid content concentration of 7.5% by mass. This slurry is treated once with a high-pressure homogenizer at a pressure of 200 MPa, and a solution of sodium hypochlorite (effective chlorine concentration 12% by mass) is applied to 1000 g (solid content concentration 7.5% by mass, solid content 75 g). 250 g was added and mixed well at room temperature. Then, it was treated three times with a high-pressure homogenizer at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion.

<Example 3>
In 1000 g of the fibrous cellulose dispersion liquid of Example 1 (solid content concentration 6.0% by mass, solid content 60 g), ozone was added so as to be a ratio of 0.2 parts by mass with respect to 1 part by mass of fine fibrous cellulose. Then, after stirring at 25 ° C. in a closed container, the mixture was allowed to stand for 30 minutes. Then, the container was opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. Then, it was treated three times with a high-pressure homogenizer at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion.

<Example 4>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 1 except that the TEMPO oxidized pulp A obtained in Production Example 7 was used. The amount of carboxy group measured by the measuring method described later was 1.30 mmolg.

<Example 5>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 2 except that the TEMPO oxidized pulp A obtained in Production Example 7 was used.

<Example 6>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 3 except that the TEMPO oxidized pulp A obtained in Production Example 7 was used.

<Example 7>
Production Example 10 A fine fibrous cellulose dispersion was obtained in the same manner as in Example 1 except that the obtained subphosphorylated pulp was used. The amount of phosphite group (first dissociated acid amount) measured by the measuring method described in [Measurement of phosphorus oxo acid group amount] described later was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

<Example 8>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 2 except that the subphosphorylated pulp obtained in Production Example 10 was used.

<Example 9>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 3 except that the subphosphorylated pulp obtained in Production Example 10 was used.

<Example 10>
The phosphorylated pulp A obtained in Production Example 1 was treated once with a single disc refiner to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. For other treatments, a fine fibrous cellulose dispersion was obtained in the same manner as in Example 1.

<Example 11>
The TEMPO oxidized pulp A obtained in Production Example 7 was treated once with a single disc refiner to obtain a fibrous cellulose dispersion E containing fine fibrous cellulose. For other treatments, a fine fibrous cellulose dispersion was obtained in the same manner as in Example 3.

<Example 12>
The subphosphorylated pulp obtained in Production Example 10 was treated once with a single disc refiner to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. For other treatments, a fine fibrous cellulose dispersion was obtained in the same manner as in Example 3.

<Example 13>
Ion-exchanged water was added to the phosphorylated pulp A obtained in Production Example 1 to prepare a pulp slurry having a solid content concentration of 6.0% by mass. To 1000 g of this slurry (solid content 60 g), an enzyme-containing liquid having an activity of 33000 nkat was added and enzyme-treated at a temperature of 50 ° C. The amount of enzyme added at this time was set to 550 nkat per 1 g of fine fibrous cellulose. The obtained slurry was treated once with a wet atomizing device (manufactured by Sugino Machine Limited, Starburst) at a pressure of 200 MPa, and then the enzyme treatment was proceeded. Then, the treatment was carried out three times at a pressure of 200 MPa, and the obtained dispersion was heat-inactivated at 100 ° C. to obtain a fine fibrous cellulose dispersion.

<Example 14>
Ion-exchanged water was added to the phosphorylated pulp A obtained in Production Example 1 to prepare a pulp slurry having a solid content concentration of 6.0% by mass. Ozone was added so as to have a ratio of 0.2 parts by mass with respect to 1 part by mass of pulp, and the mixture was stirred at 25 ° C. in a closed container and then allowed to stand for 30 minutes. Then, the container was opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. Then, it was treated with a high-pressure homogenizer at a pressure of 200 MPa four times to obtain a fine fibrous cellulose dispersion.

<Example 15>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 14 except that the TEMPO oxidized pulp A obtained in Production Example 7 was used.

<Example 16>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 13 except that the subphosphorylated pulp A obtained in Production Example 10 was used.

<Example 17>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 1 except that the phosphorylated pulp D obtained in Production Example 4 was used.

<Example 18>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 3 except that the phosphorylated pulp E obtained in Production Example 5 was used.

<Example 19>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 1 except that the phosphorylated pulp F obtained in Production Example 6 was used.

<Example 20>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 3 except that the TEMPO oxidized pulp B obtained in Production Example 8 was used.

<Example 21>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 3 except that the subphosphorylated pulp B obtained in Production Example 11 was used.

<Example 22>
Ion-exchanged water was added to the subphosphorylated pulp C obtained in Production Example 12 to prepare a slurry having a solid content concentration of 6.0% by mass. This slurry was treated once with a high-pressure homogenizer at a pressure of 200 MPa to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. An enzyme-containing solution having an activity of 48,000 nkat was added to 1000 g of this dispersion (solid content concentration 6.0% by mass, solid content 60 g) and subjected to enzyme treatment at a temperature of 50 ° C. The amount of enzyme added at this time was set to 800 nkat per 1 g of fine fibrous cellulose. Then, it was treated three times with a high-pressure homogenizer at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion. The temperature of the obtained dispersion was set to 100 ° C., and the enzyme was heat-inactivated.

<Example 23>
Ion-exchanged water was added to the phosphorylated pulp A obtained in Production Example 1 to prepare a slurry having a solid content concentration of 13.0% by mass. This slurry was treated once with a high-pressure homogenizer at a pressure of 200 MPa to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. An enzyme-containing solution having an activity of 71500 nkat was added to 1000 g of this dispersion (solid content concentration 13.0% by mass, solid content 130 g) and subjected to enzyme treatment at a temperature of 50 ° C. The amount of enzyme added at this time was set to 550 nkat per 1 g of fine fibrous cellulose. Then, it was treated with a high-pressure homogenizer at a pressure of 200 MPa four times to obtain a fine fibrous cellulose dispersion. The temperature of the obtained dispersion was set to 100 ° C., and the enzyme was heat-inactivated. The amount of phosphate group (first dissociated acid amount) measured by the measuring method described in [Measurement of phosphorus oxo acid group amount] described later was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

<Example 24>
Ozone was added to the fibrous cellulose dispersion obtained in Example 23 so as to have a ratio of 0.2 parts by mass with respect to 1 part by mass of pulp, and the mixture was stirred at 25 ° C. in a closed container for 30 minutes. It was left still. Then, the container was opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. Then, it was treated with a high-pressure homogenizer at a pressure of 200 MPa four times to obtain a fine fibrous cellulose dispersion.

<Example 25>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 23 except that the TEMPO oxidized pulp A obtained in Production Example 7 was used.

<Example 26>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 24 except that the TEMPO oxidized pulp A obtained in Production Example 7 was used.

<Example 27>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 23 except that the subphosphorylated pulp A obtained in Production Example 10 was used.

<Example 28>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 24 except that the subphosphorylated pulp A obtained in Production Example 10 was used.

<Example 29>
Ion-exchanged water was added to the phosphorylated pulp A obtained in Production Example 1 to prepare a pulp slurry having a solid content concentration of 13.0% by mass. To 1000 g of this pulp slurry (solid content concentration 13.0% by mass, solid content 130 g), an enzyme-containing liquid having an enzyme activity of 71500 nkat was added and subjected to enzyme treatment at a temperature of 50 ° C. The amount of enzyme added at this time was set to 550 nkat per 1 g of fine fibrous cellulose. The obtained slurry was treated once with a wet atomizing device (manufactured by Sugino Machine Limited, Starburst) at a pressure of 200 MPa, and then the enzyme treatment was proceeded. Then, the treatment was carried out four times at a pressure of 200 MPa, and the obtained dispersion was heat-inactivated at 100 ° C. to obtain a fine fibrous cellulose dispersion. The amount of phosphate group (first dissociated acid amount) measured by the measuring method described in [Measurement of phosphorus oxo acid group amount] described later was 1.45 mmol / g. The total amount of dissociated acid was 2.45 mmol / g.

<Example 30>
Ion-exchanged water was added to the TEMPO oxidized pulp A obtained in Production Example 7 to prepare a pulp slurry having a solid content concentration of 13.0% by mass. Ozone was added so as to have a ratio of 0.2 parts by mass with respect to 1 part by mass of pulp, and the mixture was stirred at 25 ° C. in a closed container and then allowed to stand for 30 minutes. Then, the container was opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. Then, it was treated with a high-pressure homogenizer at a pressure of 200 MPa five times to obtain a fine fibrous cellulose dispersion.

<Example 31>
Ion-exchanged water was added to the subphosphorylated pulp A obtained in Production Example 10 to prepare a pulp slurry having a solid content concentration of 13.0% by mass. Ozone was added so as to have a ratio of 0.2 parts by mass with respect to 1 part by mass of pulp, and the mixture was stirred at 25 ° C. in a closed container and then allowed to stand for 30 minutes. Then, the container was opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. Then, it was treated with a high-pressure homogenizer at a pressure of 200 MPa five times to obtain a fine fibrous cellulose dispersion.

<Example 32>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 23 except that the phosphorylated pulp D obtained in Production Example 4 was used.

<Example 33>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 24 except that the phosphorylated pulp E obtained in Production Example 5 was used.

<Example 34>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 23 except that the phosphorylated pulp F obtained in Production Example 6 was used.

<Example 35>
Ion-exchanged water was added to the TEMPO oxidized pulp C obtained in Production Example 9 to prepare a slurry having a solid content concentration of 13.0% by mass. This slurry was treated once with a high-pressure homogenizer at a pressure of 200 MPa to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. An enzyme-containing solution having an activity of 104,000 nkat was added to 1000 g of this dispersion (solid content concentration 13.0% by mass, solid content 130 g) and subjected to enzyme treatment at a temperature of 50 ° C. The amount of enzyme added at this time was set to 800 nkat per 1 g of fine fibrous cellulose. Then, it was treated with a high-pressure homogenizer at a pressure of 200 MPa four times to obtain a fine fibrous cellulose dispersion. The temperature of the obtained dispersion was set to 100 ° C., and the enzyme was heat-inactivated.

<Example 36>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 24 except that the TEMPO oxidized pulp B obtained in Production Example 8 was used.

<Example 37>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 35 except that the subphosphorylated pulp C obtained in Production Example 12 was used.

<Example 38>
A fine fibrous cellulose dispersion was obtained in the same manner as in Example 24 except that the subphosphorylated pulp B obtained in Production Example 11 was used.

<Example 39>
Ion-exchanged water was added to the phosphorylated pulp B obtained in Production Example 2 to prepare a pulp slurry having a solid content concentration of 6.0% by mass. Ozone was added so as to have a ratio of 0.2 parts by mass with respect to 1 part by mass of pulp, and the mixture was stirred at 25 ° C. in a closed container and then allowed to stand for 30 minutes. Then, the container was opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. Then, it was treated with a high-pressure homogenizer at a pressure of 200 MPa four times to obtain a fine fibrous cellulose dispersion. The amount of phosphate group (first dissociated acid amount) measured by the measuring method described in [Measurement of phosphorus oxo acid group amount] described later was 0.90 mmol / g. The total amount of dissociated acid was 1.60 mmol / g.

<Example 40>
Ion-exchanged water was added to the phosphorylated pulp C obtained in Production Example 3 to prepare a pulp slurry having a solid content concentration of 6.0% by mass. Ozone was added so as to have a ratio of 0.2 parts by mass with respect to 1 part by mass of pulp, and the mixture was stirred at 25 ° C. in a closed container and then allowed to stand for 30 minutes. Then, the container was opened and stirred for 5 hours to volatilize the ozone remaining in the dispersion. Then, it was treated with a high-pressure homogenizer at a pressure of 200 MPa four times to obtain a fine fibrous cellulose dispersion. The amount of phosphate group (first dissociated acid amount) measured by the measuring method described in [Measurement of phosphorus oxo acid group amount] described later was 2.00 mmol / g. The total amount of dissociated acid was 3.35 mmol / g.

<Example 41>
Ion-exchanged water was added to the sulfated pulp obtained in Production Example 13 to prepare a slurry having a solid content concentration of 6% by mass. This slurry was treated once with a wet atomizing device (manufactured by Sugino Machine Limited, Starburst) at a pressure of 200 MPa to obtain a fibrous cellulose dispersion containing fine fibrous cellulose. To 1000 g of the obtained fine fibrous cellulose dispersion (solid content concentration 6% by mass, solid content 60 g), an enzyme-containing liquid having an activity of 33000 nkat was added and enzyme-treated at a temperature of 50 ° C. The amount of enzyme added at this time was set to 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 with a wet atomizing device (manufactured by Sugino Machine Co., Ltd., Starburst), and then heat-inactivated at 100 ° C. to obtain fine fibrous cellulose. A dispersion was obtained. The concentration of the fine fibrous cellulose in the fine fibrous cellulose dispersion was 6% by mass. The amount of sulfate group measured by the measuring method described in [Measurement of sulfur oxoacid group amount] described later was 1.47 mmol / g.

Regarding the fine fibrous celluloses of Examples 1 to 41, it was confirmed by X-ray diffraction that these fine fibrous celluloses maintained cellulose type I crystals. Moreover, when the fiber width of these fine fibrous celluloses was measured using a transmission electron microscope, they were all 3 to 5 nm.

Using the fine fibrous cellulose dispersions of Examples 1-41, a sheet was prepared by the following procedure. Polyethylene oxide (PEO-3P, manufactured by Sumitomo Seika Chemical Co., Ltd.) was added to ion-exchanged water in an amount of 5% by mass, and the mixture was stirred and dissolved to obtain an aqueous polyethylene oxide solution. Next, the obtained fine fibrous cellulose dispersion and the above polyethylene oxide aqueous solution are mixed and coated so that the ratio of fine fibrous cellulose (solid content): polyethylene oxide (solid content) = 100 parts by mass: 20 parts by mass. It was made into a liquid. At that time, in Examples 1 to 22, 39, 40 and 41, the solid content concentration was 5% by mass, and in Examples 23 to 38, the solid content concentration was appropriately diluted with ion-exchanged water so as to be 10% by mass, and the coating liquid was used. did. Next, the coating liquid is weighed so that the finished thickness of the obtained sheet (layer composed of the solid content of the coating liquid) is 40 μm, coated on a commercially available polycarbonate plate, and placed in a dryer at 100 ° C. It was dried for 30 minutes. A metal frame for damming (a gold frame having an inner dimension of 180 mm × 180 mm and a height of 5 cm) was arranged on the polycarbonate plate so as to have a predetermined basis weight. Next, the dried sheet was peeled off from the polycarbonate plate to obtain a fine fibrous cellulose-containing sheet.

<Comparative example 1>
Ion-exchanged water was added to the phosphorylated pulp A obtained in Production Example 1 to prepare a pulp slurry having a solid content concentration of 2% by mass. The prepared pulp slurry was treated with a high-pressure homogenizer 6 times to obtain a fine fibrous cellulose dispersion. The obtained fine fibrous cellulose dispersion was concentrated in a blow dryer at 100 ° C. until the solid content concentration reached 6.0% by mass to obtain a fine fibrous cellulose dispersion.

<Comparative example 2>
A fine fibrous cellulose dispersion was obtained by concentrating in the same manner as in Comparative Example 1 except that the TEMPO oxidized pulp A obtained in Production Example 7 was used.

<Comparative example 3>
A fine fibrous cellulose dispersion was obtained by concentrating in the same manner as in Comparative Example 1 except that the subphosphorylated pulp A obtained in Production Example 10 was used.

<Comparative example 4>
Ion-exchanged water was added to softwood pulp (undried) manufactured by Oji Paper Co., Ltd. to prepare a slurry having a solid content concentration of 6.0% by mass. This slurry was treated with a high-pressure homogenizer at a pressure of 200 MPa 6 times to obtain a fibrous cellulose dispersion.

<Comparative example 5>
Ion-exchanged water was added to the phosphorylated pulp A obtained in Production Example 1 to prepare a pulp slurry having a solid content concentration of 2% by mass. The prepared pulp slurry was treated with a high-pressure homogenizer 6 times to obtain a fine fibrous cellulose dispersion. Then, the dispersion liquid of this fine fibrous cellulose was diluted to 0.4% by mass. 1 g of calcium chloride was added as a concentrating agent to 100 mL of the diluted solution to gelate the mixture, and the mixture was filtered and pressed with a filter paper. After immersing in 100 mL of a 0.1 N hydrochloric acid aqueous solution for 30 minutes, the mixture was filtered to obtain a concentrate having a solid content concentration of 20% by mass. After diluting with ion-exchanged water so that the concentration of the obtained concentrate was 6.0% by mass, the mixture was stirred, but a uniform dispersion was not obtained.

<Measurement>
[Measurement of phosphorus oxo acid group amount]
The amount of phosphorus oxo acid groups in the fine fibrous cellulose is a fibrous form prepared by diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion exchange water so that the content is 0.2% by mass. The measurement was performed by treating the cellulose-containing slurry with an ion exchange resin and then performing titration with an alkali.
In the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, which has been conditioned) with a volume of 1/10 is added to the fibrous cellulose-containing slurry, and the mixture is shaken for 1 hour. , The resin and the slurry were separated by pouring on a mesh having a mesh size of 90 μm.
For titration using alkali, the change in pH value indicated by the slurry is measured while adding 10 μL of a 0.1 N sodium hydroxide aqueous solution to the fibrous cellulose-containing slurry treated with an ion exchange resin every 5 seconds. I went by doing. The titration was performed while blowing nitrogen gas into the slurry from 15 minutes before the start of the titration. In this neutralization titration, two points are observed where the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is added is called the first end point, and the maximum point of the increment obtained next is called the second end point (FIG. 1). The amount of alkali required from the start of titration to the first end point is equal to the amount of first dissociated acid in the slurry used for titration. Further, the amount of alkali required from the start of titration to the second end point becomes equal to the total amount of dissociated acid in the slurry used for titration. The amount of alkali (mmol) required from the start of titration to the first end point divided by the solid content (g) in the slurry to be titrated was defined as the amount of phosphorus oxo acid groups (mmol / g).

[Measurement of carboxy group amount]
The amount of carboxy group of the fine fibrous cellulose is a fibrous cellulose prepared by diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion exchange water so that the content is 0.2% by mass. The contained slurry was treated with an ion exchange resin and then titrated with an alkali to measure the content.
In the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, which has been conditioned) with a volume of 1/10 is added to the fibrous cellulose-containing slurry, and the mixture is shaken for 1 hour. , The resin and the slurry were separated by pouring on a mesh having a mesh size of 90 μm.
In the titration using alkali, 50 μL of a 0.1 N sodium hydroxide aqueous solution is added to the fibrous cellulose-containing slurry treated with an ion exchange resin once every 30 seconds to obtain the electrical conductivity of the slurry. This was done by measuring the change in value. The amount of carboxy group (mmol / g) is obtained by dividing the amount of alkali (mmol) required in the region corresponding to the first region shown in FIG. 2 of the measurement results by the solid content (g) in the slurry to be titrated. Calculated.

[Measurement of sulfur oxoacid group amount]
The obtained fibrous cellulose was wet-ashed with perchloric acid and concentrated nitric acid, diluted at an appropriate magnification, and the amount of sulfur was measured by ICP emission spectrometry. The value obtained by dividing this amount of sulfur by the absolute dry mass of the fibrous cellulose used was defined as the amount of sulfur oxoacid groups (unit: mmol / g).

[Measurement of viscosity of 0.5% by mass fine fibrous cellulose dispersion]
The viscosities of the fine fibrous cellulose dispersions obtained in Examples 1 to 41 and Comparative Examples 1 to 5 were measured as follows. First, the fine fibrous cellulose dispersion was diluted with ion-exchanged water so that the solid content concentration was 0.5% by mass, and then stirred with a disperser at 4000 rpm for 3 minutes. The obtained dispersion liquid was defoamed with a rotation / revolution type super mixer (ARE-250 manufactured by Shinky Co., Ltd.). Next, the viscosity of the dispersion liquid thus obtained was measured using a B-type viscometer (analog viscometer T-LVT manufactured by BLOOKFIELD). The measurement conditions were a rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of the measurement was taken as the viscosity of the dispersion liquid.

[Measurement of viscosity of 6.0% by mass fine fibrous cellulose dispersion]
The viscosities of the fine fibrous cellulose dispersions obtained in Examples 1 to 22, 39, 40 and 41 and Comparative Examples 1 to 4 were measured as follows. First, the defoaming treatment of the fine fibrous cellulose dispersion was performed with a rotation / revolution type super mixer (ARE-250 manufactured by Shinky Co., Ltd.). Next, the viscosity of the obtained dispersion was measured using a B-type viscometer (analog viscometer T-LVT manufactured by BLOOKFIELD). The measurement conditions were a rotation speed of 0.3 rpm, and the viscosity value 3 minutes after the start of measurement was taken as the viscosity of the dispersion liquid.

[Measurement of viscosity of 13.0 mass% fine fibrous cellulose dispersion]
The viscosities of the fine fibrous cellulose dispersions obtained in Examples 23 to 38 were measured as follows. First, the defoaming treatment of the fine fibrous cellulose dispersion was performed with a rotation / revolution type super mixer (ARE-250 manufactured by Shinky Co., Ltd.). Next, the viscosity of the obtained dispersion was measured using a B-type viscometer (digital viscometer DV2T manufactured by BLOOKFIELD). The measurement conditions were a rotation speed of 0.3 rpm, and the viscosity value 3 minutes after the start of measurement was taken as the viscosity of the dispersion liquid.

[Measurement of specific viscosity and degree of polymerization of fine fibrous cellulose]
The specific viscosity and degree of polymerization of the fine fibrous cellulose were measured according to Tappi T230. That is, after measuring the viscosity (referred to as η1) measured by dispersing the fine fibrous cellulose to be measured in a dispersion medium and the blank viscosity (referred to as η0) measured only with the dispersion medium, the specific viscosity (ηsp), The intrinsic viscosity ([η]) was measured according to the following formula.
ηsp = (η1 / η0) -1
[Η] = ηsp / (c (1 + 0.28 × ηsp))
Here, c in the formula indicates the concentration of cellulose fibers at the time of viscosity measurement.
Further, the degree of polymerization (DP) of the fine fibrous cellulose was calculated from the following formula.
DP = 1.75 × [η]
Since this degree of polymerization is the average degree of polymerization measured by the viscosity method, it is sometimes called "viscosity average degree of polymerization". Further, in Comparative Examples 1 to 3 and 5, fine fibrous cellulose before concentration was measured.

[Measurement of haze of fine fibrous cellulose dispersion]
The haze of the fine fibrous cellulose dispersions obtained in Examples 1 to 41 and Comparative Examples 1 to 5 was measured by diluting the fine fibrous cellulose dispersions with ion-exchanged water to 0.2% by mass and then rotating. The defoaming treatment was performed with a revolution type super mixer (ARE-250 manufactured by Shinky Co., Ltd.). Based on JIS K 7136: 2000 using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute) and a glass cell for liquid (manufactured by Fujiwara Seisakusho, MG-40, backlight path) with an optical path length of 1 cm. It was measured. The zero point measurement was performed with ion-exchanged water contained in the same glass cell.

[Appearance evaluation of fine fibrous cellulose dispersion]
The fine fibrous cellulose dispersions obtained in Examples 1 to 41 and Comparative Examples 1 to 5 were defoamed with a rotation / revolution type super mixer (ARE-250 manufactured by Shinky Co., Ltd.). Then, the appearance was visually evaluated according to the following criteria.
A: The fibers can hardly be confirmed visually, and the dispersion liquid is transparent.
B: The fibers can be visually confirmed, and the dispersion liquid is translucent.
C: The fibers are not uniformly dispersed and the dispersion liquid is cloudy, or granules (aggregates of fibers) can be confirmed.

In the examples, a high-concentration and uniform fine fibrous cellulose dispersion was obtained, and the high-concentration fine fibrous cellulose dispersion was highly transparent. In Comparative Examples 1 to 3 and 5, there were granules (aggregates of fibers) in the dispersion liquid, and the viscosity could not be measured at a concentration of 6.0% by mass.

Claims

A fibrous cellulose having a fiber width of 1000 nm or less and having an ionic substituent.
The degree of polymerization of the fibrous cellulose is 230 or less, and the degree of polymerization is 230 or less.
When the fibrous cellulose is used as an aqueous dispersion having a concentration of 0.5% by mass, the fibrous cellulose has a viscosity of less than 108 mPa · s at 23 ° C.
When the fibrous cellulose is used as an aqueous dispersion having a concentration of 6.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is 500,000 mPa · s or more and 10,000,000 mPa · s or less. The fibrous cellulose described in.
The claim that when the fibrous cellulose is used as an aqueous dispersion having a concentration of 13.0% by mass, the viscosity of the aqueous dispersion at 23 ° C. is 1,000,000 mPa · s or more and 5,000,000 mPa · s or less. The fibrous cellulose according to 1 or 2.
The ionic substituent is at least one selected from the group consisting of a phosphorus oxo acid group, a substituent derived from a phosphorus oxo acid group, a sulfur oxo acid group and a substituent derived from a sulfur oxo acid group, claims 1 to 3. The fibrous cellulose according to any one of the above items.
A fibrous cellulose dispersion liquid containing the fibrous cellulose according to any one of claims 1 to 4.
The fibrous cellulose dispersion according to claim 5, wherein the concentration of the fibrous cellulose is 3.0% by mass or more.
A sheet containing fibrous cellulose according to any one of claims 1 to 4.