JP7415675B2 - Fibrous cellulose dispersion and molded body - Google Patents

Description

The present invention relates to a fibrous cellulose dispersion and a molded article.

Conventionally, cellulose fibers have been widely used in clothing, absorbent articles, paper products, and the like. As 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. For example, sheets, resin composites, and thickeners containing fine fibrous cellulose are being developed.

Generally, fine fibrous cellulose is stably dispersed in an aqueous solvent, so it is often provided in the form of an aqueous dispersion and used for various purposes. On the other hand, when mixing fine fibrous cellulose with a resin to produce a composite or the like, there is also a desire to use fine fibrous cellulose mixed with an organic solvent. As a technique to meet such demands, a technique for producing a fine fibrous cellulose-containing dispersion in which fine fibrous cellulose is dispersed in a dispersion medium containing an organic solvent is being considered.

For example, Patent Document 1 discloses a fine fibrous cellulose composite in which a surfactant is adsorbed on fine fibrous cellulose having a carboxy group. Here, there are two methods: one is to micronize cellulose fibers in an aqueous solvent, then aggregate the microfibrous cellulose and disperse it in an organic solvent, and the other is to micronize the cellulose fibers in an organic solvent to obtain microfiber cellulose. Disclosed. Furthermore, Patent Document 2 discloses that a reaction product fiber obtained by reacting natural cellulose with an N-oxyl compound and a co-oxidizing agent is subjected to a wet dispersion treatment in the presence of an organic ammonium compound or an organic phosphonium compound. A method for producing characterized finely modified cellulose fibers is disclosed.

Patent Document 3 describes a fine fibrous cellulose having a phosphoric acid group or a substituent derived from a phosphoric acid group, the fibrous cellulose having an organic ammonium ion as a counter ion of the phosphoric acid group or a substituent derived from the phosphoric acid group. is disclosed. Note that Patent Document 3 does not specifically consider the use of organic phosphonium ions as organic onium ions.

Japanese Patent Application Publication No. 2011-140738 Japanese Patent Application Publication No. 2011-127067 International Publication No. 2018/159743

When mixing fibrous cellulose with a resin to form a composite, the fibrous cellulose may be dispersed in an organic solvent, but in this case, the fibrous cellulose may not be sufficiently dispersed in the organic solvent. Ta. When the dispersibility of fibrous cellulose in organic solvents is low, the transparency of the resulting composites and molded bodies decreases, so improvements are required.

Therefore, in order to solve the problems of the prior art, the present inventors have developed a fibrous cellulose dispersion containing fibrous cellulose and an organic solvent, in which fibrous cellulose is uniformly dispersed in an organic solvent. The study progressed with the aim of providing a cellulose dispersion.

As a result of intensive studies to solve the above problems, the present inventors discovered that in order to obtain a fibrous cellulose dispersion containing fibrous cellulose and an organic solvent, inorganic oxoacid groups or inorganic oxoacid groups derived from inorganic oxoacid groups By dispersing fibrous cellulose having a substituent and containing an organic phosphonium ion as a counter ion of an inorganic oxoacid group or a substituent derived from an inorganic oxoacid group in an organic solvent having a predetermined Hansen solubility parameter. It has been discovered that a fibrous cellulose dispersion in which fibrous cellulose is uniformly dispersed in an organic solvent can be obtained.
Specifically, the present invention has the following configuration.

[1] A fibrous cellulose having an inorganic oxo acid group or a substituent derived from an inorganic oxo acid group and having a fiber width of 1000 nm or less,
A fibrous cellulose dispersion comprising an organic solvent,
The fibrous cellulose has an organic phosphonium ion as a counter ion of an inorganic oxoacid group or a substituent derived from an inorganic oxoacid group,
A fibrous cellulose dispersion in which the coordinates of Hansen solubility parameters of an organic solvent are within the range of a sphere with a radius of 8 MPa ^1/2 centered at δd = 16.5, δp = 12.5, δh = 14.5.
[2] The fibrous cellulose dispersion according to [1], wherein δh in the Hansen solubility parameter of the organic solvent is 8 MPa ^1/2 or more.
[3] The fibrous cellulose dispersion according to [1] or [2], wherein δh in the Hansen solubility parameter of the organic solvent is 11.5 MPa ^1/2 or more.
[4] The fibrous cellulose dispersion according to any one of [1] to [3], wherein the organic phosphonium ion satisfies at least one condition selected from the following (a) and (b);
(a) Contains a hydrocarbon group having 5 or more carbon atoms;
(b) The total number of carbon atoms is 17 or more.
[5] The fibrous cellulose according to any one of [1] to [4], wherein the inorganic oxo acid group or the substituent derived from the inorganic oxo acid group is a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group. dispersion liquid.
[6] The fibrous cellulose dispersion according to any one of [1] to [5], wherein the water content is 100 parts by mass or less per 100 parts by mass of solids in the fibrous cellulose dispersion.
[7] The fibrous cellulose dispersion according to any one of [1] to [6], further comprising a resin.
[8] A molded article formed from the fibrous cellulose dispersion according to any one of [1] to [7].

According to the present invention, it is possible to provide a fibrous cellulose dispersion containing fibrous cellulose and an organic solvent, in which the fibrous cellulose is uniformly dispersed in the organic solvent.

FIG. 1 is a graph showing the relationship between the amount of NaOH dropped and pH for a fibrous cellulose-containing slurry having phosphorus oxoacid groups. FIG. 2 is a graph showing the relationship between the amount of NaOH dropped and pH for a slurry containing fibrous cellulose having carboxy groups.

In the following, the present invention will be explained in detail. Although the constituent elements described below may be explained based on typical embodiments and specific examples, the present invention is not limited to such embodiments.

(Fibrous cellulose dispersion)
The present invention relates to a fibrous cellulose dispersion containing fibrous cellulose having an inorganic oxoacid group or a substituent derived from an inorganic oxoacid group and having a fiber width of 1000 nm or less, and an organic solvent. Here, the fibrous cellulose has an organic phosphonium ion as a counter ion to an inorganic oxoacid group or a substituent derived from an inorganic oxoacid group. Further, the coordinates of the Hansen solubility parameters of the organic solvent are within the range of a sphere with a radius of 8 MPa ^1/2 centered at δd = 16.5, δp = 12.5, and δh = 14.5.

Since the fibrous cellulose dispersion of the present invention has the above structure, the fibrous cellulose is uniformly dispersed in the organic solvent. That is, the fibrous cellulose in the present invention has excellent dispersibility in organic solvents. In the present invention, since the fibrous cellulose is uniformly dispersed in the organic solvent, no sediments or aggregates are generated in the dispersion liquid. Further, the fibrous cellulose dispersion of the present invention is highly transparent, and a molded article such as a sheet formed from the fibrous cellulose dispersion of the present invention is also highly transparent.

The uniform dispersibility of the fibrous cellulose in the fibrous cellulose dispersion can be evaluated, for example, by measuring the light transmittance of the fibrous cellulose dispersion at a wavelength of 600 nm. When measuring the light transmittance of the fibrous cellulose dispersion at a wavelength of 600 nm, a quartz cell with an optical path length of 1 cm is used to measure the light transmittance of the fine fibrous cellulose dispersion at a wavelength of 600 nm. At this time, the concentration of the fine fibrous cellulose dispersion is 2.0% by mass. Further, an ultraviolet-visible near-infrared spectrophotometer is used to measure the light transmittance at a wavelength of 600 nm.

The light transmittance of the fibrous cellulose dispersion in this embodiment at a wavelength of 600 nm is preferably 60% or more, more preferably 65% or more, and even more preferably 70% or more. If the light transmittance of the fibrous cellulose dispersion at a wavelength of 600 nm is within the above range, it can be determined that the fibrous cellulose is uniformly dispersed in the fibrous cellulose dispersion. That is, it can be determined that the fibrous cellulose used in the present invention has excellent dispersibility in organic solvents.

The viscosity of the fibrous cellulose dispersion in this embodiment is preferably 400 mPa·s or more, more preferably 600 mPa·s or more, and even more preferably 800 mPa·s or more. Here, the viscosity of the fibrous cellulose dispersion is the value measured using a B-type viscometer after allowing the fibrous cellulose dispersion with a fibrous cellulose concentration of 2.0% by mass to stand at 23°C for 24 hours. It is. At this time, the measurement is performed at 23° C., and the viscosity is measured after rotating at 3 rpm for 3 minutes. As the B-type viscometer, for example, an analog viscometer T-LVT manufactured by BLOOKFIELD can be used.

In this embodiment, the water content per 100 parts by mass of solids in the fibrous cellulose dispersion is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, and 50 parts by mass or less. is more preferable, and particularly preferably 35% by mass or less. Note that the water content may be 0 parts by mass with respect to 100 parts by mass of solids in the fibrous cellulose dispersion. This means that the water content of the fibrous cellulose-containing material (containing at least fibrous cellulose and water) that is dispersed in an organic solvent when producing a fibrous cellulose dispersion is low. The moisture content of the fibrous cellulose-containing material (containing at least fibrous cellulose and water) to be dispersed in an organic solvent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and 12 parts by mass. It is more preferable that it is the following.

The solid content concentration in the fibrous cellulose dispersion is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, based on the total mass of the fibrous cellulose dispersion. , more preferably 1.0% by mass or more. Further, the solid content concentration in the fibrous cellulose dispersion is preferably 30% by mass or less, more preferably 20% by mass or less, and 15% by mass or less based on the total mass of the fibrous cellulose dispersion. It is more preferable that

(organic solvent)
The fibrous cellulose dispersion of the present invention contains an organic solvent. Here, the coordinates of the Hansen solubility parameters of the organic solvent are within the range of a sphere with a radius of 8 MPa ^1/2 centered at δd = 16.5, δp = 12.5, δh = 14.5. When the fibrous cellulose dispersion contains two or more organic solvents, the coordinates of the Hansen solubility parameters of the two or more mixed solvents are centered around δd = 16.5, δp = 12.5, δh = 14.5. It may be within the range of a sphere with a radius of 8 MPa ^1/2 . Note that the HSP value of the mixed solvent can be calculated from the HSP value of each organic solvent constituting the mixed solvent and the mixing ratio.

Here, the Hansen solubility parameter (hereinafter also referred to as "HSP") is defined by Charles M. Hansen announced this value and is used to predict the solubility of substances. The Hansen solubility parameter is a parameter based on the idea that "two substances that have similar interactions between molecules are likely to dissolve in each other." HSP is composed of the following three parameters (unit: MPa ^1/2 ), and these three parameters can be considered as coordinates in a three-dimensional space (Hansen space), and the HSP of two substances can be expressed in Hansen space. This shows that the closer the distance between two points, the easier they are to dissolve into each other.
δd: Energy due to intermolecular dispersion force δp: Energy due to intermolecular dipole interaction δh: Energy due to intermolecular hydrogen bonding

The coordinates of the Hansen solubility parameters of the organic solvent used in the present invention are within the range of a sphere with a radius of 8 MPa ^1/2 centered at δd = 16.5, δp = 12.5, δh = 14.5. . For example, if the coordinates of the Hansen solubility parameters of an organic solvent are δ(x)d, δ(x)p, δ(x)h, then the center (δd=16.5, δp=12.5, δh=14. 5) can be calculated using the following formula.
Distance (MPa ^1/2 ) = [(δ(x)d-16.5) ² + (δ(x)p-12.5) ² + (δ(x)h-14.5) ² ] ^{1/ 2}
In the present invention, it is sufficient that the distance (MPa ^1/2 ) calculated by the above formula is 8 MPa ^1/2 or less, that is, the coordinates of the Hansen solubility parameter of the organic solvent are centered at δd=16.5, δp = 12.5 and δh = 14.5, it is sufficient if it is within the range of a sphere with a radius of 8 MPa ^1/2 . The distance (MPa ^1/2 ) calculated by the above formula is preferably 7.9 MPa ^1/2 or less, more preferably 6.0 MPa ^1/2 or less.

Conventionally, when dispersing fibrous cellulose in an organic solvent, it has been considered to add organic onium ions or the like to the fibrous cellulose to make the fibrous cellulose hydrophobic. However, even with the fibrous cellulose that has been made hydrophobic in this way, the fibrous cellulose may not be sufficiently dispersed in certain organic solvents. Therefore, the present inventors have repeatedly investigated organic solvents in which conventional fibrous cellulose is not sufficiently dispersed. As a result, the present inventors found that in the Hansen solubility parameter coordinates, the ^organic It was discovered that conventional fibrous cellulose tends not to be sufficiently dispersed in solvents. As described above, the present inventors first classified organic solvents in which conventional fibrous cellulose is not sufficiently dispersed using the Hansen solubility parameter. Through further intensive study, the present inventors determined that, in the coordinates of the Hansen solubility parameter, a radius of 8 MPa ^1/2 centered at δd = 16.5, δp = 12.5, δh = 14.5. We succeeded in discovering fibrous cellulose that exhibits excellent dispersibility even in organic solvents within the spherical range. Such fibrous cellulose is a fibrous cellulose that has an inorganic oxo acid group or a substituent derived from an inorganic oxo acid group and has a fiber width of 1000 nm or less, and has an inorganic oxo acid group or an inorganic oxo acid group. It has an organic phosphonium ion as a counter ion to the substituent derived from the group. As described above, the present invention combines a specific organic solvent and a specific fibrous cellulose, so that the fibrous cellulose can be dispersed evenly in organic solvents where it was not possible to uniformly disperse the fibrous cellulose in conventional techniques. We succeeded in obtaining a fibrous cellulose dispersion in which cellulose was uniformly dispersed.

The δd in the Hansen solubility parameter of the organic solvent is preferably 8.5 MPa ^1/2 or more, more preferably 13.0 MPa ^1/2 or more, and even more preferably 14.5 MPa ^{1/2 or} more. . Furthermore, δd is preferably 24.5 MPa ^1/2 or less, more preferably 20.0 MPa ^1/2 or less, and even more preferably 18.5 MPa ^1/2 or less.

The δp in the Hansen solubility parameter of the organic solvent is preferably 4.5 MPa ^1/2 or more, more preferably 5.0 MPa ^1/2 or more, and even more preferably 5.5 MPa ^1/2 or more. . Further, δp is preferably 20.5 MPa ^1/2 or less, more preferably 16.5 MPa ^1/2 or less, and even more preferably 15.0 MPa ^1/2 or less.

δh in the Hansen solubility parameter of the organic solvent is preferably 8 MPa ^1/2 or more, more preferably 8.5 MPa ^1/2 or more, even more preferably 9.0 MPa ^1/2 or more, and 11 It is particularly preferable that the pressure is .5 MPa ^1/2 or more. Furthermore, δh is preferably 22.5 MPa ^1/2 or less, more preferably 22.3 MPa ^1/2 or less, and even more preferably 20.0 MPa ^1/2 or less.

In the Hansen solubility parameter coordinates, examples of organic solvents within a sphere with a radius of 8 MPa ^1/2 centered at δd = 16.5, δp = 12.5, δh = 14.5 include methanol, ethanol, , dimethylacetamide (DMAc), dimethylformamide (DMF), isopropyl alcohol (IPA), 1-propanol, 1-butanol, 2-butanol, isobutyl alcohol, t-butyl alcohol, 1-pentanol, 2-pentanol, 2 -Methyl-1-butanol, 2-methyl-2-butanol, isoamyl alcohol, 3-methyl-2-butanol, 1-hexanol, allyl alcohol, benzyl alcohol, furfuryl alcohol, diacetone alcohol, phenol, m-cresol, Formic acid, acetic acid, trichloroacetic acid, trifluoroacetic acid, formaldehyde, acetaldehyde, acetone, ethyl formate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, propylene glycol, propylene glycol monomethyl ether, Propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monoisopropyl ether, propylene glycol mono t-butyl ether, propylene glycol monophenyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether , 1,3-butanediol, 2-methoxymethanol, 3-methoxybutanol, ethanolamine, diethylformamide, acetamide, diethylacetamide and the like. Among these, methanol, ethanol, dimethylacetamide (DMAc), and dimethylformamide (DMF) are preferably used.

In addition, in the coordinates of the Hansen solubility parameter, two or more types of organic solvents are within the range of a sphere with a radius of 8 MPa ^1/2 centered on δd = 16.5, δp = 12.5, and δh = 14.5. A mixed solvent obtained by mixing organic solvents can also be used. Such mixed solvents include, for example, a mixed solvent of methanol and isopropyl alcohol mixed at a volume ratio of 1:1, a mixed solvent of methanol and ethanol mixed at a volume ratio of 1:1, and a mixed solvent of dimethylacetamide and dimethylformamide mixed at a volume ratio of 1:1. Examples include mixed solvents prepared by mixing 1:1. Note that the Hansen solubility parameter of a mixed solvent consisting of two types of organic solvents A and B (volume ratio a:b) can be determined as follows. Let the coordinates of the Hansen solubility parameters of organic solvent A be (δd _A , δp _A , δh _A ), and the coordinates of the Hansen solubility parameters of organic solvent B be (δd _B , δp _B , δh _B ). At this time, the coordinates (δd _M , δp _M , δh _M ) of the Hansen solubility parameters of the mixed solvent M consisting of organic solvents A and B (volume ratio a:b) can be determined from the following formula.
δd _M = (a×δd _A +b×δd _B )/(a+b)
δp _M = (a×δp _A +b×δp _B )/(a+b)
δh _M = (a×δh _A +b×δh _B )/(a+b)
Note that even in the case of a mixed solvent consisting of three or more types of organic solvents, the coordinates of the Hansen solubility parameter can be determined using the above equation. For example, the coordinates of the Hansen solubility parameter for a mixed solvent consisting of organic solvents A, B, and C (volume ratio a:b:c) are as follows: Organic solvent C is mixed with mixed solvent M at a volume ratio of (a+b):c. You can find it as

The content of the organic solvent is preferably 10% by mass or more, more preferably 50% by mass or more, based on the total mass of solids contained in the fibrous cellulose dispersion. Further, the content of the organic solvent is preferably 99.9% by mass or less, more preferably 99.0% by mass or less, based on the total mass of solids contained in the fibrous cellulose dispersion. It is preferably 95.0% by mass or less, and more preferably 95.0% by mass or less.

(fibrous cellulose)
The fibrous cellulose dispersion of the present invention contains fibrous cellulose having an inorganic oxo acid group or a substituent derived from an inorganic oxo acid group and having a fiber width of 1000 nm or less. The fiber width of the fibrous cellulose is more preferably 100 nm or less, and even more preferably 8 nm or less. In this specification, fibrous cellulose having a fiber width of 1000 nm or less is also referred to as fine fibrous cellulose or CNF.

The fiber width of fibrous cellulose can be measured, for example, by electron microscopic observation. The average fiber width of fibrous cellulose is, for example, 1000 nm or less. The average fiber width of the fibrous cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, even more preferably 2 nm or more and 50 nm or less, and 2 nm or more and 10 nm or less. Particularly preferred. By setting the average fiber width of fibrous cellulose to 2 nm or more, dissolution of cellulose molecules in water can be suppressed, and the effects of improving strength, rigidity, and dimensional stability due to fibrous cellulose can be more easily expressed. can. Note that the fibrous cellulose is, for example, monofilament cellulose.

The fiber width of fibrous cellulose can be measured, for example, by electron microscopic observation. The fiber width of fibrous cellulose is measured using, for example, an electron microscope as follows. First, an aqueous suspension of fibrous cellulose with a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast onto a hydrophilic carbon film-coated grid to provide a sample for TEM observation. shall be. If wide fibers are included, a SEM image of the surface cast on glass may be observed. Next, observation using an electron microscope is performed at a magnification of 1000 times, 5000 times, 10000 times, or 50000 times, depending on the width of the fiber to be observed. However, the sample, observation conditions, and magnification should be adjusted to satisfy the following conditions.
(1) Draw a straight line X at any location in the observed image, and 20 or more fibers intersect with the straight line X.
(2) Draw a straight line Y that intersects the straight line perpendicularly within the same image, and 20 or more fibers intersect with the straight line Y.
For an observed image that satisfies the above conditions, visually read the width of the fibers that intersect the straight lines X and Y. In this way, at least three sets of observation images of surface portions that do not overlap with each other are obtained. Then, for each image, the width of the fibers intersecting the straight lines X and Y is read. In this way, the width of at least 20 x 2 x 3 = 120 fibers is read. The average value of the read fiber widths becomes the average fiber width of the fibrous cellulose.

The fiber length of the fibrous cellulose is not particularly limited, but for example, it is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and even more preferably 0.1 μm or more and 600 μm or less. preferable. By setting the fiber length within the above range, destruction of the crystalline region of fibrous cellulose can be suppressed. Furthermore, it is also possible to adjust the viscosity of the slurry of fibrous cellulose within an appropriate range. Note that the fiber length of fibrous cellulose can be determined, for example, by image analysis using TEM, SEM, or AFM.

It is preferable that the fibrous cellulose has a type I crystal structure. Here, the fact that fibrous cellulose has a type I crystal structure can be identified in the diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ=1.5418 Å) monochromated with graphite. Specifically, it can be identified because it has typical peaks at two positions: around 2θ=14° or more and 17° or less and around 2θ=22° or more and 23° or less. The proportion of type I crystal structure in the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and still more 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 degree of crystallinity is determined by measuring an X-ray diffraction profile and using the pattern in a conventional manner (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, for example, 20 or more and 10,000 or less, more preferably 50 or more and 1,000 or less. By setting the axial ratio to the above lower limit value or more, it is easy to form a sheet containing fine fibrous cellulose. By setting the axial ratio to the above upper limit value or less, it is preferable that handling such as dilution becomes easier when handling fibrous cellulose as a dispersion liquid, for example.

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

Fibrous cellulose has an inorganic oxoacid group or a substituent derived from an inorganic oxoacid group. Here, the inorganic oxoacid group is a group composed of an oxoacid inorganic compound in which the central element of the oxoacid is not a carbon atom. Examples of inorganic oxo acid groups or substituents derived from inorganic oxo acid groups include phosphorus oxo acid groups or substituents derived from phosphorus oxo acid groups (sometimes simply referred to as phosphorus oxo acid groups), sulfur oxo acid groups, or sulfur oxo acid groups. A substituent derived from a boron oxo acid group (sometimes simply called a sulfur oxo acid group), a boron oxo acid group or a substituent derived from a boron oxo acid group (sometimes simply called a boron oxo acid group), a silicon oxo acid group, or a silicon oxo acid group A substituent derived from a group (sometimes simply referred to as a silicon oxoacid group) can be mentioned. Among these, the inorganic oxo acid group or the substituent derived from the inorganic oxo acid group is selected from a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group, and a sulfur oxo acid group or a substituent derived from a sulfur oxo acid group. The substituent is preferably at least one type of phosphorus oxo acid group, and more preferably a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group.

The phosphorus oxo acid group or the substituent derived from the phosphorus oxo acid group is, for example, a substituent represented by the following formula (1). A phosphorus oxoacid group is a divalent functional group, for example, equivalent to phosphoric acid with a hydroxyl group removed. Specifically, it is a group represented by -PO ₃ H ₂ . The substituents derived from the phosphorus oxo acid group include substituents such as salts of the phosphorus oxo acid group and phosphorus oxo acid ester groups. Note that the substituent derived from the phosphorus oxoacid group may be included in the fibrous cellulose as a group (for example, a pyrophosphate group) in which a phosphoric acid group is condensed. Further, the phosphorus oxo acid group may be, for example, a phosphorous acid group (phosphonic acid group), and the substituent derived from the phosphorus oxo acid group may be a salt of a phosphorous acid group, a phosphite ester group, etc. Good too.

In formula (1), a, b and n are natural numbers (a=b×m). Of α ¹ , α ² , . . . , α ⁿ and α′, a number are O ⁻ , and the rest are either R or OR. Note that all of α ⁿ and α′ may be O ^{2 −} . R is a hydrogen atom, a saturated linear hydrocarbon group, a saturated branched hydrocarbon group, a saturated cyclic hydrocarbon group, an unsaturated linear hydrocarbon group, or an unsaturated branched hydrocarbon group, respectively. A hydrogen group, an unsaturated cyclic hydrocarbon group, an aromatic group, or a group derived from these. Moreover, it is preferable that n is 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 hydrocarbon group include i-propyl group and t-butyl group, but are not particularly limited. Examples of the saturated cyclic hydrocarbon group include a cyclopentyl group and a cyclohexyl group, but are not particularly limited. Examples of the unsaturated linear hydrocarbon group include a vinyl group and an allyl group, but are not particularly limited. Examples of the unsaturated branched hydrocarbon group include an i-propenyl group and a 3-butenyl group, but are not particularly limited. Examples of the unsaturated cyclic hydrocarbon group include a cyclopentenyl group and a cyclohexenyl group, but are not particularly limited. Examples of the aromatic group include a phenyl group and a naphthyl group, but are not particularly limited.

In addition, the derivative group in R is a functional group in which at least one functional group such as a carboxy group, a hydroxy group, or an amino group is added or substituted to the main chain or side chain of the various hydrocarbon groups mentioned above. Examples include, but are not particularly limited to, groups. Further, the number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R within the above range, the molecular weight of the phosphorus oxo acid group can be set in an appropriate range, facilitating penetration into the fiber raw material and increasing the yield of fine cellulose fibers. You can also do that.

β ^b+ is a counter ion of a phosphorus oxoacid group or a substituent derived from a phosphorus oxoacid group. This counter ion is an organic phosphonium ion as described below. In addition, as a counter ion of a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group, all β ^b+ may be organic phosphonium ions, but some of them may be ions of alkali metals such as sodium, potassium, or lithium. It may also be a cation of a divalent metal such as calcium or magnesium, or a hydrogen ion.

The amount of phosphorus oxo acid groups introduced into the fibrous cellulose (the amount of phosphorus oxo acid groups) is preferably 0.10 mmol/g or more, more preferably 0.20 mmol/g or more per 1 g (mass) of fibrous cellulose. It is preferably at least 0.50 mmol/g, more preferably at least 1.00 mmol/g, and particularly preferably at least 1.00 mmol/g. Further, the amount of phosphorus oxoacid groups 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 fibrous cellulose, and 3. More preferably, it is 00 mmol/g or less. Here, the unit mmol/g indicates the amount of substituents per 1 g of mass of fibrous cellulose when the counter ion of the phosphorus oxoacid group is a hydrogen ion (H ⁺ ). By introducing the amount of phosphorus oxo acid groups within the above range, the content of organic phosphonium ions that can be contained in fibrous cellulose can be adjusted to an appropriate range, thereby improving the dispersibility of fibrous cellulose in organic solvents. can be enhanced more effectively.

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

FIG. 1 is a graph showing the relationship between the amount of NaOH dropped and pH for a fibrous cellulose-containing slurry having phosphorus oxoacid groups. The amount of phosphorus oxoacid groups introduced into fibrous cellulose is measured, for example, as follows.
First, a slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. Note that, if necessary, a defibration process similar to the defibration process described below may be performed on the measurement target before the treatment with the strongly acidic ion exchange resin.
Next, a 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 Figure 1 plots the measured pH against the amount of alkali added, and the titration curve shown in the lower part of Figure 1 plots the pH measured against the amount of alkali added. Increment (differential value) (1/mmol) is plotted. In this neutralization titration, two points at which the increment (differential value of pH with respect to the amount of alkali dropped) becomes maximum are confirmed on a curve in which the measured pH is plotted against the amount of alkali added. Among these, the maximum point of increment obtained first after starting to add the alkali is called the first end point, and the maximum point of 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 dissociated acid of fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the first end point to the second end point is equal to the amount of alkali required from the first end point to the second end point. The amount is equal to the amount of second dissociated acid in the fibrous cellulose contained in the slurry used for titration, and the amount of alkali required from the start of titration to the second end point is the amount of fibrous cellulose contained in the slurry used for titration. is equal to the total amount of dissociated acids. 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 becomes the amount of phosphorus oxo acid group introduced (mmol/g). In addition, when it is simply referred to as the amount of phosphorus oxo acid groups introduced (or the amount of phosphorus oxo acid groups), it refers to the amount of the first dissociated acid.
In FIG. 1, the region from the start of titration to the first end point is called the first region, and the region from the first end point to the second end point is called the second region. For example, when the phosphorus oxo acid group is a phosphoric acid group and this phosphoric acid group causes condensation, the amount of weak acid groups (also referred to herein as the second dissociated acid amount) in the phosphorus oxo acid group appears to be The amount of alkali required in the second region is smaller than the amount of alkali required in the first region. On the other hand, the amount of strong acid groups in the phosphorus oxo acid group (also referred to as the first dissociated acid amount in this specification) matches the amount of phosphorus atoms regardless of the presence or absence of condensation. In addition, when the phosphorus oxo acid group is a phosphorous acid group, there is no weakly acidic group in the phosphorus oxo acid group, so 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, in the titration curve, there is one point where the pH increment becomes maximum.

Note that the above-mentioned amount of phosphorus oxo acid groups introduced (mmol/g) has a denominator indicating the mass of acid type fibrous cellulose. (called the acid form). On the other hand, if the counter ion of the phosphorus oxo acid group is substituted with any cation C so as to have a charge equivalent, convert the denominator to the mass of the fibrous cellulose when the cation C is the counter ion. By doing so, the amount of phosphorus oxo acid groups (hereinafter referred to as the amount of phosphorus oxo acid groups (C type)) that the fibrous cellulose having the cation C as a counter ion can be determined.
That is, it is calculated using the following calculation formula.
Amount of phosphorus oxo acid groups (C type) = Amount of phosphorus oxo acid groups (acid type)/{1+(W-1)×A/1000}
A [mmol/g]: Total amount of anions derived from phosphorus oxo acid groups possessed by fibrous cellulose (total amount of dissociated acids of phosphorus oxo acid groups)
W: formula weight per valence of cation C (for example, 23 for Na, 9 for Al)

When measuring the amount of phosphorus oxo acid groups using the titration method, if the amount of one drop of sodium hydroxide aqueous solution dropped is too large, or if the titration interval is too short, the amount of phosphorus oxo acid groups may be lower than originally expected, and an accurate value may not be obtained. Sometimes there isn't. As for an appropriate dropping amount and titration interval, for example, it is desirable to titrate a 0.1N aqueous sodium hydroxide solution at a rate of 10 to 50 μL every 5 to 30 seconds. In addition, in order to eliminate the influence of carbon dioxide dissolved in the fibrous cellulose-containing slurry, it is desirable to measure while blowing an inert gas such as nitrogen gas into the slurry, for example, from 15 minutes before the start of titration until the end of titration.

When the inorganic oxo acid group or the substituent derived from the inorganic oxo acid group is a sulfur oxo acid group or a substituent derived from a sulfur oxo acid group, the sulfur oxo acid group or the substituent derived from the sulfur oxo acid group is A group represented by the following structural formula is preferable.

In the above structural formula, n is a natural number, and m is 0 or 1. Note that when n is 2 or more, a plurality of m may be the same number or different numbers. M is the counterion of the sulfur oxoacid group. This counter ion is an organic phosphonium ion as described below. As counter ions for the sulfur oxoacid group, all M may be organic phosphonium ions, but some of them may be ions of alkali metals such as sodium, potassium, or lithium, or ions of 2 such as calcium or magnesium. It may be a valence metal cation, a hydrogen ion, or the like.

The amount of sulfur oxoacid groups introduced into the fibrous cellulose is preferably 0.50 mmol/g or more, more preferably 0.70 mmol/g or more, and even more preferably 1.00 mmol/g or more. . Further, the amount of sulfur oxo acid groups introduced into the fibrous cellulose is preferably 5.00 mmol/g or less, more preferably 3.00 mmol/g or less. Here, the amount of sulfur oxoacid groups introduced into fibrous cellulose can be calculated by freeze-drying a slurry containing fibrous cellulose and then measuring the amount of sulfur in a pulverized sample. Specifically, a slurry containing fibrous cellulose is freeze-dried, a pulverized sample is decomposed under pressure and heat using nitric acid in a closed container, and then diluted appropriately and the amount of sulfur is measured using ICP-OES. . The value calculated by dividing by the absolute dry mass of the fibrous cellulose tested is defined as the amount of sulfur oxoacid groups in the fibrous cellulose (unit: mmol/g).

<Production process of fine fibrous cellulose>
<Fiber raw materials>
Fine fibrous cellulose is produced from a fibrous raw material containing cellulose. The fiber raw material containing cellulose is not particularly limited, but it is preferable to use pulp because it is easily available and inexpensive. Pulps include, for example, wood pulp, non-wood pulp, and deinked pulp. Examples of wood pulp include, but are not limited to, hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolving pulp (DP), soda pulp (AP), and unbleached kraft pulp (UKP). ) and chemical pulp such as oxygen bleached kraft pulp (OKP), semi-chemical pulp such as semi-chemical pulp (SCP) and chemical ground wood pulp (CGP), ground wood pulp (GP) and thermomechanical pulp (TMP, BCTMP), etc. Examples include mechanical pulp. Examples of the non-wood pulp include, but are not particularly limited to, cotton-based pulps such as cotton linters and cotton lint, and non-wood-based pulps such as hemp, wheat straw, and bagasse. Deinked pulp is not particularly limited, but includes, for example, deinked pulp made from waste paper. The pulp of this embodiment may be used alone or in combination of two or more of the above. Among the above-mentioned pulps, wood pulp and deinked pulp are preferable from the viewpoint of easy availability. In addition, among wood pulps, the cellulose ratio is high and the yield of fine fibrous cellulose during fibrillation treatment is high, and the decomposition of cellulose in the pulp is small and long fiber fine fibrous cellulose with a large axial ratio can be obtained. From this point of view, for example, chemical pulp is more preferred, and kraft pulp and sulfite pulp are even more preferred. Note that when long fiber fine fibrous cellulose with a large axial ratio is used, the viscosity tends to increase.

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

<Phosphorus oxoacid group introduction step>
The manufacturing process of fibrous cellulose includes a step of introducing an inorganic oxoacid group. Examples of the step of introducing an inorganic oxoacid group include a step of introducing a phosphorus oxoacid group. In the step of introducing phosphorus oxoacid groups, at least one compound selected from compounds capable of introducing phosphorus oxoacid groups (hereinafter also referred to as "compound A") is added to cellulose by reacting with hydroxyl groups possessed by fiber raw materials containing cellulose. This is a process of acting on fiber raw materials containing. Through this step, fibers introduced with phosphorus oxo acid groups are obtained.

In the phosphorus oxoacid group introduction step according to the present embodiment, a reaction between a cellulose-containing fiber raw material and compound A is performed in the presence of at least one selected from urea and its derivatives (hereinafter also referred to as "compound B"). You can. On the other hand, the cellulose-containing fiber raw material and compound A may be reacted in the absence of compound B.

An example of a method for causing compound A to act on a fiber raw material in the coexistence of compound B includes a method of mixing compound A and compound B with respect to a fiber raw material in a dry state, a wet state, or a slurry state. Among these, it is preferable to use dry or wet fiber raw materials, and it is particularly preferable to use dry fiber raw materials, since the reaction uniformity is high. The form of the fiber raw material is not particularly limited, but it is preferably cotton-like or thin sheet-like, for example. Compound A and compound B may be added to the fiber raw material in the form of a powder, a solution dissolved in a solvent, or a melted state by heating to a temperature higher than the melting point. Among these, it is preferable to add them in the form of a solution dissolved in a solvent, particularly an aqueous solution, since the reaction is highly uniform. Moreover, compound A and compound B may be added to the fiber raw material simultaneously, may be added separately, or may be added as a mixture. The method of adding Compound A and Compound B is not particularly limited, but if Compound A and Compound B are in the form of a solution, the fiber raw material may be immersed in the solution and taken out after absorption; The solution may be added dropwise. Alternatively, the necessary amounts of Compound A and Compound B may be added to the fiber raw material, or after adding excessive amounts of Compound A and Compound B to the fiber raw material, excess Compound A and Compound B may be removed by compression or filtration. May be removed.

The compound A used in this embodiment may be any compound having a phosphorus atom and capable of forming an ester bond with cellulose, such as phosphoric acid or its salt, phosphorous acid or its salt, dehydrated condensed phosphoric acid or its salt. Examples include salts, phosphoric anhydride (diphosphorus pentoxide), etc., but are not particularly limited. Phosphoric acid of various purity can be used, for example, 100% phosphoric acid (orthophosphoric acid) or 85% phosphoric acid. Examples of phosphorous acid include 99% phosphorous acid (phosphonic acid). Dehydrated condensed phosphoric acid is one in which two or more molecules of phosphoric acid are condensed through a dehydration reaction, and examples include pyrophosphoric acid and polyphosphoric acid. Examples of phosphates, phosphites, and dehydrated condensed phosphates include lithium salts, sodium salts, potassium salts, and ammonium salts of phosphoric acid, phosphorous acid, or dehydrated condensed phosphoric acid, which are It can be made into peace. Among these, phosphoric acid, sodium phosphate Salts, potassium salts of phosphoric acid, ammonium salts of phosphoric acid or phosphorous acid, sodium salts of phosphorous acid, potassium salts of phosphorous acid, ammonium salts of phosphorous acid are preferred; phosphoric acid, sodium dihydrogen phosphate, More preferred are disodium hydrogen phosphate, ammonium dihydrogen phosphate, phosphorous acid, and sodium phosphite.

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 phosphorus atomic weight, the amount of phosphorus atoms added to the fiber raw material (absolute dry mass) is 0.5% by mass or more. The content is preferably 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and even more preferably 2% by mass or more and 30% by mass or less. By controlling the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fibrous cellulose can be further improved. On the other hand, by controlling the amount of phosphorus atoms added to the fiber raw material to be equal to or less than the above upper limit, it is possible to balance the yield improvement effect and cost.

Compound B used in this embodiment is at least one selected from urea and its derivatives as described above. Examples of compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea.
From the viewpoint of improving the uniformity of the reaction, compound B is preferably used as an aqueous solution. Moreover, 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, 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 of the cellulose-containing fiber raw material and compound A, in addition to compound B, for example, amides or amines may be included in the reaction system. Examples of amides include formamide, dimethylformamide, acetamide, dimethylacetamide, and the like. Examples of amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, triethylamine is known to act as a particularly good reaction catalyst.

In the phosphorus oxoacid group introduction step, it is preferable to heat-treat the fiber raw material after adding or mixing compound A and the like to the fiber raw material. As the heat treatment temperature, it is preferable to select a temperature at which phosphorus oxo acid groups can be efficiently introduced while suppressing thermal decomposition and hydrolysis reactions of the fibers. The heat treatment temperature is, for example, preferably 50°C or more and 300°C or less, more preferably 100°C or more and 250°C or less, and even more preferably 130°C or more and 200°C or less. In addition, for heat treatment, equipment having various heat media can be used, such as a stirring dryer, a rotary dryer, a disc dryer, a roll type heating device, a plate type heating device, a fluidized bed dryer, and a band dryer. A mold dryer, a filtration dryer, a vibration fluid dryer, a flash dryer, a vacuum dryer, 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 this embodiment, for example, the compound A is added to a thin sheet-like 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. A method can be adopted. This makes it possible to suppress uneven concentration of compound A in the fiber raw material and more uniformly introduce phosphorus oxoacid groups onto the surface of the cellulose fibers contained in the fiber raw material. This is because when water molecules move to the surface of the fiber raw material during drying, the dissolved compound A is attracted to the water molecules by surface tension and similarly moves to the surface of the fiber raw material (in other words, the concentration unevenness of compound A is reduced). This is thought to be due to the fact that this can be suppressed.

In addition, the heating device used for the heat treatment constantly removes, for example, the water retained in the slurry and the water generated due to the dehydration condensation (phosphate esterification) reaction between Compound A and hydroxyl groups contained in cellulose, etc. in the fiber raw material. Preferably, the device is capable of being discharged outside the device system. Examples of such a heating device include a blower type oven and the like. By constantly draining water from the equipment system, it is possible to suppress the hydrolysis reaction of phosphate ester bonds, which is the reverse reaction of phosphoric acid esterification, and also to suppress acid hydrolysis of sugar chains in fibers. can. Therefore, it becomes possible to obtain fibrous cellulose with 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 water is substantially removed from the fiber raw material, for example. It is more preferable that In this embodiment, by setting the heating temperature and heating time within appropriate ranges, the amount of phosphorus oxo acid groups introduced can be within a preferable range.

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

The amount of phosphorus oxo acid groups 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 fibrous cellulose. It is more preferably at least 1.00 mmol/g, particularly preferably at least 1.00 mmol/g. Further, the amount of phosphorus oxo acid groups 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/g per 1 g (mass) of fibrous cellulose. It is more preferable that it is below /g. By setting the amount of phosphorus oxo acid groups introduced within the above range, it becomes easy to control the amount of counter ions introduced into the fibrous cellulose within an appropriate range, and as a result, the dispersion of the fibrous cellulose in the organic solvent is improved. You can improve your sex more effectively.

<Sulfur oxoacid group introduction step>
The manufacturing process of fibrous cellulose includes a step of introducing an inorganic oxoacid group. Examples of the inorganic oxoacid group introduction step include a sulfur oxoacid group introduction step. In the sulfur oxoacid group introduction step, cellulose fibers having sulfur oxoacid groups (sulfur oxoacid group-introduced fibers) can be obtained by reacting the hydroxyl groups of the fiber raw material containing cellulose with the sulfur oxoacid.

In the sulfur oxoacid group introduction step, instead of compound A in the <phosphorus oxoacid group introduction step> described above, a compound is selected from compounds that can introduce sulfur oxoacid groups by reacting with the hydroxyl groups possessed by the fiber raw material containing cellulose. At least one type of compound (hereinafter also referred to as "compound C") is used. Compound C may be any compound that has a sulfur atom and is capable of forming an ester bond with cellulose, and includes, but is not particularly limited to, sulfuric acid (phosphonic acid) or its salt, sulfurous acid or its salt, sulfuric acid amide, and the like. Sulfuric acid (phosphonic acid) of various purity can be used, for example, 96% sulfuric acid (concentrated sulfuric acid) can be used. Examples of sulfite include 5% sulfite water. Examples of the sulfate or sulfite include lithium, sodium, potassium, and ammonium salts of sulfate or sulfite, which can have various degrees of neutralization. As the sulfuric acid amide, sulfamic acid or the like can be used. In the sulfur oxo acid group introduction step, it is preferable to use the compound B in the above-mentioned <phosphorus oxo acid group introduction step> in the same manner.

In the step of introducing sulfur oxoacid groups, it is preferable that the cellulose raw material is mixed with a sulfur oxoacid and an aqueous solution containing urea and/or a urea derivative, and then subjected to a heat treatment on the cellulose raw material. As the heat treatment temperature, it is preferable to select a temperature at which sulfur oxoacid groups can be efficiently introduced while suppressing thermal decomposition and hydrolysis reactions of the fibers. The heat treatment temperature is preferably 100°C or higher, more preferably 120°C or higher, and even more preferably 150°C or higher. Further, 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 water is substantially eliminated. Therefore, the heat treatment time varies depending on the amount of water contained in the cellulose raw material, the amount of sulfur oxoacid, and the aqueous solution containing urea and/or urea derivatives, but for example, it is 10 seconds or more and 10,000 seconds or less. It is preferable to do so. For heat treatment, equipment having various heat media can be used, such as stirring drying equipment, rotary drying equipment, disc drying equipment, roll type heating equipment, plate type heating equipment, fluidized bed drying equipment, and band type drying equipment. A filtration drying device, a vibrating fluidized drying device, a flash 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.

The amount of sulfur oxoacid group introduced into the cellulose raw material is preferably 0.50 mmol/g or more, more preferably 0.70 mmol/g or more, and even more preferably 1.00 mmol/g or more. Further, the amount of sulfur oxoacid groups introduced into the cellulose raw material is preferably 5.00 mmol/g or less, more preferably 3.00 mmol/g or less. By setting the amount of sulfur oxoacid groups introduced within the above range, it becomes easy to control the amount of counter ions introduced into the fibrous cellulose within an appropriate range, and as a result, the resistance of the fibrous cellulose to organic solvents increases. Dispersibility can be improved more effectively.

<Cleaning process>
In the method for producing fibrous cellulose in this embodiment, the inorganic oxoacid group-introduced fibers can be subjected to a washing step, if necessary. The washing step is carried out by washing the inorganic oxoacid group-introduced fiber with water or an organic solvent, for example. Further, the cleaning step may be performed after each step described below, and the number of times of cleaning performed in each cleaning step is not particularly limited.

<Alkali treatment process>
When producing fibrous cellulose, the fiber raw material may be subjected to alkali treatment after the inorganic oxoacid group introduction step. The method of alkali treatment is not particularly limited, but includes, for example, a method of immersing the inorganic oxoacid group-introduced fiber in an alkaline solution.

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

The temperature of the alkaline solution in the alkali treatment step is not particularly limited, but is preferably, for example, 5°C or more and 80°C or less, and more preferably 10°C or more and 60°C or less. The immersion time of the inorganic oxoacid group-introduced fibers in the alkaline solution in the alkali treatment step is not particularly limited, but is preferably, for example, 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 10,000% by mass based on the absolute dry mass of the inorganic oxoacid group-introduced fiber. It is more preferable that it is below.

In order to reduce the amount of alkaline solution used in the alkali treatment step, the inorganic oxo acid group-introduced fibers may be washed with water or an organic solvent after the inorganic oxo acid group introduction step and before the alkali treatment step. When a defibration process is provided after the alkali treatment process, the alkali-treated inorganic oxoacid group-introduced fibers are washed with water or an organic solvent before the defibration process to improve handling. It is preferable to do so.

<Acid treatment process>
When producing fibrous cellulose, the fiber raw material may be subjected to acid treatment after the step of introducing inorganic oxoacid groups.

The acid treatment method is not particularly limited, but includes, for example, a method of immersing the inorganic oxoacid group-introduced fiber in an acidic solution containing an acid. The concentration of the acidic liquid used is not particularly limited, but is preferably, for example, 10% by mass or less, more preferably 5% by mass or less. Further, the pH of the acidic liquid used is not particularly limited, but is preferably, for example, 0 or more and 4 or less, more preferably 1 or more and 3 or less. As the acid contained in the acidic liquid, for example, an inorganic acid, a sulfonic acid, a carboxylic acid, etc. can be used. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, phosphoric acid, and boric acid. Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid. Examples of carboxylic acids include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, and tartaric acid. Among these, 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, for example, 5°C or higher and 100°C or lower, 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, for example, 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 for example, it 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 based on the absolute dry mass of the inorganic oxoacid group-introduced fiber. It is more preferable that it is below.

<Defibration treatment>
Fine fibrous cellulose is obtained by defibrating the inorganic oxoacid group-introduced fibers in the defibrating process. In the defibration processing step, for example, a defibration processing device can be used. The defibration processing equipment is not particularly limited, but includes, for example, a high-speed defibrator, a grinder (stone mill-type crusher), a high-pressure homogenizer, 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 biaxial refiner. A kneader, a vibratory 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 the crushing media and have less risk of contamination.

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

The solid content concentration of the fibrous cellulose during the defibration treatment can be set as appropriate. Further, the slurry obtained by dispersing the inorganic oxoacid group-introduced fibers in a dispersion medium may contain solid content other than the inorganic oxoacid group-introduced fibers, such as urea having hydrogen bonding properties.

(Organic phosphonium ion)
Fibrous cellulose has an organic phosphonium ion as a counter ion to an inorganic oxoacid group or a substituent derived from an inorganic oxoacid group. Note that in this embodiment, at least some organic phosphonium ions exist as counter ions of fibrous cellulose, but free organic phosphonium ions do not exist in the fibrous cellulose-containing material as described below. You can leave it there. Note that the organic phosphonium ion does not form a covalent bond with fibrous cellulose.

The organic phosphonium ion preferably satisfies at least one of the conditions selected from (a) and (b) below.
(a) Contains a hydrocarbon group having 5 or more carbon atoms.
(b) The total number of carbon atoms is 17 or more.
That is, the fibrous cellulose contains at least one selected from an organic phosphonium ion containing a hydrocarbon group having a carbon number of 5 or more and an organic phosphonium ion having a total carbon number of 17 or more as a counter ion to an inorganic oxoacid group. It is preferable. By using an organic phosphonium ion that satisfies at least one of the conditions selected from (a) and (b) above, the dispersibility of fibrous cellulose in an organic solvent can be more effectively improved.

The hydrocarbon group having 5 or more carbon atoms is preferably an alkyl group having 5 or more carbon atoms or an alkylene group having 5 or more carbon atoms, and an alkyl group having 6 or more carbon atoms or an alkylene group having 6 or more carbon atoms. A group is more preferable, an alkyl group having 7 or more carbon atoms or an alkylene group having 7 or more carbon atoms is even more preferable, an alkyl group having 10 or more carbon atoms or an alkylene group having 10 or more carbon atoms. It is particularly preferable that there be. Among these, the organic phosphonium ion is preferably one having an alkyl group having 5 or more carbon atoms, and more preferably an organic phosphonium ion containing an alkyl group having 5 or more carbon atoms and having a total carbon number of 17 or more. preferable.

The organic phosphonium ion is preferably an organic phosphonium ion represented by the following general formula (A).

In the above general formula (A), M is a phosphorus atom, and R ₁ to R ₄ each independently represent a hydrogen atom or an organic group. However, it is preferable that at least one of R ₁ to R ₄ is an organic group having 5 or more carbon atoms, or the total number of carbon atoms of R _{1 to} R ₄ is ₁₇ or more; Preferably, at least one is an alkyl group having 5 or more carbon atoms, and the total number of carbon atoms of R ₁ to R ₄ is 17 or more.

Examples of such organic phosphonium ions include trihexyltetradecylphosphonium ion, tributyldodecylphosphonium ion, tributylhexadecylphosphonium ion, tributyl-n-octylphosphonium ion, tributylhexylphosphonium ion, tetra-n-octylphosphonium ion, Tri-n-octylphosphonium ion, lauryltrimethylphosphonium ion, cetyltrimethylphosphonium ion, stearyltrimethylphosphonium ion, octyldimethylethylphosphonium ion, lauryldimethylethylphosphonium ion, didecyldimethylphosphonium ion, lauryldimethylbenzylphosphonium ion, tributylbenzylphosphonium ion ion, methyltri-n-octylphosphonium ion, hexylphosphonium ion, n-octylphosphonium ion, dodecylphosphonium ion, tetradecylphosphonium ion, hexadecylphosphonium ion, stearylphosphonium ion, dimethyldodecylphosphonium ion, dimethyltetradecylphosphonium ion, dimethyl hexadecylphosphonium ion, dimethyl-n-octadecylphosphonium ion, dihexylphosphonium ion, di(2-ethylhexyl)phosphonium ion, di-n-octylphosphonium ion, didecylphosphonium ion, didodecylphosphonium ion, didecylmethylphosphonium ion, Dodecylmethylphosphonium ion, polyoxyethylenedodecylphosphonium ion, alkyldimethylbenzylphosphonium ion, di-n-alkyldimethylphosphonium ion, behenyltrimethylphosphonium ion, tetraphenylphosphonium ion, tetraoctylphosphonium ion, acetonyltriphenylphosphonium ion, allyl Triphenylphosphonium ion, amyltriphenylphosphonium ion, benzyltriphenylphosphonium ion, butyltriphenylphosphonium ion, ethyltriphenylphosphonium ion, methyltriphenylphosphonium ion, isopropyltriphenylphosphonium ion, hexyltriphenylphosphonium ion, triphenylpropyl Examples include phosphonium ion, triphenyltetradecylphosphonium ion, diphenylpropylphosphonium ion, triphenylphosphonium ion, tricyclohexylphosphonium ion, tri-n-octylphosphonium ion, and the like. Among these, the organic phosphonium ion is preferably trihexyltetradecylphosphonium ion (THTP ⁺ ) or tributyldodecylphosphonium ion (TBDP ⁺ ).

Note that, as shown in the general formula (A), the central element of the organic phosphonium ion is bonded to a total of four groups or hydrogen. In the above-mentioned names of organic phosphonium ions, if less than four groups are bonded, the remaining hydrogen atoms are bonded to form an organic phosphonium ion.

When the organic phosphonium ion contains an O atom, the mass ratio of C atoms to O atoms (C/O ratio) is preferably as large as possible; for example, it is preferable that C/O>5. By increasing the C/O ratio to more than 5, a fibrous cellulose concentrate can be easily obtained when organic phosphonium ions or a compound that forms organic phosphonium ions upon neutralization are added to the fibrous cellulose-containing slurry. Become.

The molecular weight of the organic phosphonium ion is preferably 2,000 or less, more preferably 1,800 or less. By controlling the molecular weight of the organic phosphonium ion within the above range, the handling properties of the fibrous cellulose can be improved.

The content of organic phosphonium ions is preferably 1.0% by mass or more, more preferably 1.5% by mass or more, and 2.0% by mass or more based on the total mass of the fibrous cellulose. It is even more preferable. Further, the content of organic phosphonium ions is preferably 90% by mass or less, more preferably 80% by mass or less based on the total mass of the fibrous cellulose.

Further, the content of organic phosphonium ions in the fibrous cellulose is preferably from an equimolar amount to twice the molar amount of the amount of inorganic oxoacid groups contained in the fibrous cellulose, but is not particularly limited. Note that the content of organic phosphonium ions can be calculated by measuring the amount of phosphorus atoms contained in the organic phosphonium ions. In addition, if the fibrous cellulose contains phosphorus atoms in addition to organic phosphonium ions, it is sufficient to perform a method to extract only the organic phosphonium ions, such as extraction with an acid, and then measure the amount of the target atoms. .

(optional ingredient)
The fibrous cellulose dispersion may further contain a resin. Although the type of resin is not particularly limited, examples thereof include thermoplastic resins and thermosetting resins.

Examples of resins include acrylic resin, polycarbonate resin, polyester resin, polyamide resin, silicone resin, fluorine resin, chlorine resin, epoxy resin, melamine resin, phenol resin, polyurethane resin, diallyl phthalate. Examples include resins based on alcohols, cellulose derivatives, and precursors of these resins. Note that examples of cellulose derivatives include carboxymethyl cellulose, methyl cellulose, and hydroxyethyl cellulose.

The fibrous cellulose dispersion may contain a resin precursor as the resin. The type of resin precursor is not particularly limited, but examples include precursors of thermoplastic resins and thermosetting resins. The term "thermoplastic resin precursor" refers to monomers or oligomers having a relatively low molecular weight that are used to produce thermoplastic resins. Further, the term "thermosetting resin precursor" refers to monomers or oligomers with a relatively low molecular weight that can undergo a polymerization reaction or a crosslinking reaction to form a thermosetting resin under the action of light, heat, or a curing agent.

The fibrous cellulose dispersion may further contain a water-soluble polymer as a resin in addition to the above-mentioned resin species. Examples of water-soluble polymers include synthetic water-soluble polymers (e.g., carboxyvinyl polymer, polyvinyl alcohol, alkyl methacrylate/acrylic acid copolymer, polyvinylpyrrolidone, sodium polyacrylate, polyethylene glycol, diethylene glycol, triethylene glycol, propylene). Glycol, dipropylene glycol, polypropylene glycol, isoprene glycol, hexylene glycol, 1,3-butylene glycol, polyacrylamide, etc.), polysaccharide thickeners (e.g. xanthan gum, guar gum, tamarind gum, carrageenan, locust bean gum, quince seed) , alginic acid, pullulan, carrageenan, pectin, etc.), cationized starch, raw starch, oxidized starch, etherified starch, esterified starch, starches such as amylose, glycerin such as glycerin, diglycerin, polyglycerin, etc., hyaluronic acid , metal salts of hyaluronic acid, and the like.

The content of the resin contained in the fibrous cellulose dispersion is preferably 90% by mass or less, and 80% by mass or less, based on the total mass of solids contained in the fibrous cellulose dispersion. is preferable, and more preferably 50% by mass or less.

The fibrous cellulose dispersion may further contain other optional components. As an optional component, for example, a moisture absorbent can be mentioned. Examples of moisture absorbing agents include silica gel, zeolite, alumina, carboxymethyl cellulose, polyvinyl alcohol-soluble cellulose acetate, polyethylene glycol, sepiolite, calcium oxide, diatomaceous earth, activated carbon, activated clay, white carbon, calcium chloride, magnesium chloride, potassium acetate. , dibasic sodium phosphate, sodium citrate, and water-absorbing polymers.

Furthermore, optional components include surfactants, organic ions, coupling agents, inorganic layered compounds, inorganic compounds, leveling agents, preservatives, antifoaming agents, organic particles, lubricants, antistatic agents, ultraviolet protection agents, Examples include dyes, pigments, stabilizers, magnetic powders, alignment promoters, plasticizers, dispersants, crosslinking agents, and the like.

(Method for producing fibrous cellulose dispersion)
A method for producing a fibrous cellulose dispersion is to add organic phosphonium ions or a compound that forms organic phosphonium ions by neutralization to the fine fibrous cellulose-containing slurry obtained through the above-mentioned defibration step. The method includes the steps of obtaining a content (concentrate) and dispersing the fibrous cellulose content (concentrate) in an organic solvent.

In the step of obtaining a fibrous cellulose-containing material (concentrate), the above-mentioned organic phosphonium ions or organic phosphonium ions are formed by neutralization in the fine fibrous cellulose-containing slurry obtained in the above-mentioned defibration treatment step. Add compound. At this time, the organic phosphonium ions are preferably added as a solution containing organic phosphonium ions, and more preferably added as an aqueous solution containing organic phosphonium ions.

An aqueous solution containing organic phosphonium ions usually contains the organic phosphonium ions and a counter ion (anion). When preparing an aqueous solution of organic phosphonium ions, if the organic phosphonium ions and the corresponding counter ions have already formed a salt, it may be dissolved as is in water. When preparing an aqueous solution of organic phosphonium ions, if the organic phosphonium ions and the corresponding counter ions have already formed a salt, it is preferable to dissolve them in water or hot water.

Furthermore, organic phosphonium ions may be produced only after being neutralized with an acid, such as tri-n-octylphosphine. In this case, organic phosphonium ions are obtained by reaction of a compound which forms organic phosphonium ions upon neutralization with an acid. In this case, examples of acids used for neutralization include inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, and organic acids such as lactic acid, acetic acid, formic acid, and oxalic acid. In the aggregation step, a compound that forms organic onium by neutralization may be directly added to the fibrous cellulose-containing slurry, and organic phosphonium may be ionized using the inorganic oxoacid group contained in the fibrous cellulose as a counter ion.

The amount of organic phosphonium ions added is preferably 2% by mass or more, more preferably 10% by mass or more, even more preferably 50% by mass or more, and even more preferably 100% by mass or more, based on the total mass of the fibrous cellulose. It is particularly preferable that the amount is at least % by mass. Note that the amount of organic phosphonium ions added is preferably 1000% by mass or less based on the total mass of the fibrous cellulose.
Further, the number of moles of organic phosphonium ions to be added is preferably 0.2 times or more, and 0.5 times the value obtained by multiplying the amount (number of moles) of inorganic oxoacid groups contained in the fibrous cellulose by the valence. It is more preferably at least 1.0 times, even more preferably at least 1.0 times. Note that the number of moles of the organic phosphonium ion to be added is preferably 10 times or less the value obtained by multiplying the amount (number of moles) of inorganic oxoacid groups contained in the fibrous cellulose by the valence.

When organic phosphonium ions are added and stirred, aggregates (concentrates) are generated in the fibrous cellulose-containing slurry. In this specification, such aggregates (concentrates) are also referred to as fibrous cellulose-containing materials. This aggregate is an aggregate of fibrous cellulose having an organic phosphonium ion as a counterion. The fibrous cellulose-containing material can be recovered by filtering the fibrous cellulose-containing slurry in which aggregates have formed under reduced pressure.

The obtained fibrous cellulose-containing material may be washed with ion-exchanged water.By repeatedly washing the fibrous cellulose-containing material with ion-exchanged water, excess organic phosphonium ions, etc. contained in the fibrous cellulose-containing material are removed. can do.

The content of fibrous cellulose in the fibrous cellulose-containing material is preferably 80% by mass or more, more preferably 85% by mass or more, based on the total mass of the fibrous cellulose-containing material. Note that the content of fibrous cellulose may be 99.5% by mass or less based on the total mass of the fibrous cellulose-containing material.

The moisture content of the fibrous cellulose-containing material may be 0% by mass, 0.5% by mass or more, or 1% by mass or more, based on the total mass of the fibrous cellulose-containing material. It may be 3% by mass or more, or it may be 5% by mass or more. Further, the moisture content of the fibrous cellulose-containing material is preferably 20% by mass or less, more preferably 15% by mass or less, based on the total mass of the fibrous cellulose-containing material. The moisture content in the fibrous cellulose-containing material can be measured by placing 200 mg of the fibrous cellulose-containing material on a moisture meter (MS-70, manufactured by A&D Co., Ltd.) and heating it at 140°C. can. The moisture content in the fibrous cellulose-containing material can be calculated from the measured moisture content.

The obtained fibrous cellulose-containing material is further subjected to a drying process, an aging process, a spray drying process, a granulation process, a sheeting process, a heating process, a wetting process, a crushing process, a spraying process, a dipping process, a filtration process, a freezing process, It may also undergo a sublimation process, a water squeezing process, a pressure dehydration process, a centrifugal dehydration process, a surface treatment process, etc.

In the step of dispersing the fibrous cellulose-containing material (concentrate) in an organic solvent, the fibrous cellulose-containing material (concentrate) obtained in the step of obtaining the fibrous cellulose-containing material (concentrate) described above is dispersed in an organic solvent. disperse. Here, the organic solvent in which the fibrous cellulose-containing material (concentrate) is dispersed is the above-mentioned organic solvent, and in the coordinates of the Hansen solubility parameter, δd = 16.5, δp = 12.5, δh = 14.5. It is an organic solvent within the range of a sphere with a radius of 8 MPa ^1/2 centered on . Note that such a dispersion step is also called a redispersion step because it is a step of dispersing the fibrous cellulose-containing material (concentrate) in a solvent again.

As a dispersion device used when dispersing the fibrous cellulose-containing material (concentrate) in an organic solvent, the same one as the defibration treatment device described in the above-mentioned defibration treatment can be used, for example. Furthermore, the fibrous cellulose-containing material (concentrate) may be dispersed in an organic solvent by ultrasonication.

The manufacturing process of the fibrous cellulose dispersion may include a step of further dispersing a resin and optional components in the obtained fibrous cellulose dispersion. Examples of the resin and optional components used in this case include the resins and optional components described above.

(Application)
The fibrous cellulose dispersion of the present invention is preferably used for forming molded bodies. The shape of the molded product is not particularly limited, and may be, for example, a sheet-like, granular, or thread-like molded product. Among these, the fibrous cellulose dispersion of the present invention is preferably used for sheet-like molded products. For example, the fibrous cellulose dispersion of the present invention can be formed into a film and used as various films.

Molded objects obtained by coating a fibrous cellulose dispersion on a substrate can be used as reinforcing materials, interior materials, exterior materials, packaging materials, electronic materials, optical materials, acoustic materials, process materials, and transportation equipment components. It is also suitable for applications such as components of electronic devices and components of electrochemical devices.

(molded object)
The present invention may also relate to a molded article formed from the above-described fibrous cellulose dispersion. In this case, the fibrous cellulose dispersion preferably contains a resin. In the present invention, since fibrous cellulose having excellent compatibility with organic solvents and resins is used, the molded article has excellent flexural modulus and is also excellent in strength and dimensional stability. In addition, the molded article of the present invention also has excellent transparency.

Although the form of the molded article of the present invention is not particularly limited, it is preferable that the molded article is, for example, sheet-like. The present invention may also relate to a sheet formed from the above-described fibrous cellulose dispersion.

When the molded article is a sheet, the haze of the sheet is preferably 20% or less, more preferably 15% or less, and even more preferably 12% or less. Here, the haze of the sheet is a value measured using a haze meter (manufactured by Murakami Color Research Institute, HM-150) in accordance with JIS K 7136.

There are no particular restrictions on the method of molding the molded body, and injection molding, heating and pressure molding, or the like can be employed. Moreover, when molding a molded object from a sheet, it may be molded by a press molding method or a vacuum molding method.

When the molded body is in the form of a sheet, the method for molding the molded body preferably includes a step of coating the above-mentioned liquid composition onto a base material. The material of the base material used in the coating process is not particularly limited, but materials with high wettability to the composition are better because they can suppress shrinkage of the sheet during drying. It is preferable to select one that can be easily peeled off. Among these, resin films and plates and metal films and plates are preferred, but they are not particularly limited. For example, films and plates made of resin such as acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polypropylene, polycarbonate, and polyvinylidene chloride; films and plates made of metal such as aluminum, zinc, copper, and iron; and those whose surfaces have been oxidized. , stainless steel film or plate, brass film or plate, etc. can be used.

In the coating process, if the viscosity of the composition is low and it spreads on the substrate, a dam frame may be fixed on the substrate in order to obtain a sheet with a predetermined thickness and basis weight. You may. The damming frame is not particularly limited, but it is preferable to select one that allows the edges of the sheet to be easily peeled off after drying, for example. From this point of view, it is more preferable to use a molded resin plate or metal plate. In this embodiment, for example, resin plates such as acrylic plates, polyethylene terephthalate plates, vinyl chloride plates, polystyrene plates, polypropylene plates, polycarbonate plates, and polyvinylidene chloride plates, and metal plates such as aluminum plates, zinc plates, copper plates, iron plates, etc. , and those whose surfaces have been oxidized, stainless steel plates, brass plates, etc. can be used.

The coating machine for coating the composition on the substrate is not particularly limited, and for example, a roll coater, gravure coater, die coater, curtain coater, air doctor coater, etc. can be used. A die coater, a curtain coater, and a spray coater are particularly preferred because they can make the thickness of the film (sheet) more uniform.

The temperature of the liquid composition and the ambient temperature when applying the composition to the substrate are not particularly limited, but are preferably, for example, 5°C or more and 80°C or less, more preferably 10°C or more and 60°C or less. The temperature is preferably 15°C or higher and 50°C or lower, more preferably 20°C or higher and 40°C or lower.

In the coating process, the composition is applied so that the finished basis weight of the sheet is preferably 10 g/m ² or more and 100 g/m ² or less, more preferably 20 g/m ² or more and 60 g/m ² or less. It is preferable to coat the base material. By coating so that the basis weight is within the above range, a sheet with even greater strength can be obtained.

The coating step includes a step of drying the composition coated on the substrate. The step of drying the composition is not particularly limited, and may be performed, for example, by a non-contact drying method, a method of drying while restraining the sheet, or a combination thereof. The non-contact drying method is not particularly limited, but for example, a method of drying by heating with hot air, infrared rays, far infrared rays, or near infrared rays (heat drying method), or a method of drying under vacuum (vacuum drying method) is applied. can do. Although the heat drying method and the vacuum drying method may be combined, the heat drying method is usually applied. Drying using infrared rays, far infrared rays, or near infrared rays is not particularly limited, and can be performed using, for example, an infrared device, a far infrared device, or a near infrared device. The heating temperature in the heating drying method is not particularly limited, but is preferably, for example, 20°C or higher and 150°C or lower, more preferably 25°C or higher and 105°C or lower. If the heating temperature is equal to or higher than the above lower limit, the dispersion medium can be quickly volatilized. Moreover, if the heating temperature is below the above-mentioned upper limit, it is possible to suppress the cost required for heating and suppress discoloration of the fibrous cellulose due to heat.

The present invention will be explained in more detail with reference to the following examples, but the scope of the present invention is not limited by the following examples.

<Manufacture example 1>
[Manufacture of fine fibrous cellulose dispersion A]
As raw material pulp, softwood kraft pulp manufactured by Oji Paper (solid content 93% by mass, basis weight 245g/m ² sheet form, Canadian standard freeness (CSF) measured according to JIS P 8121 after disintegration is 700ml) It was used. This 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 (absolutely dry mass) of the above 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. A pulp impregnated with a chemical solution was obtained. Next, the resulting chemical solution-impregnated pulp was heated for 250 seconds in a hot air dryer at 165°C to introduce phosphoric acid groups into the cellulose in the pulp, thereby obtaining phosphorylated pulp.

Next, the obtained phosphorylated pulp was subjected to a washing treatment. The washing process was carried out by repeating the following steps: pouring 10 L of ion-exchanged water into 100 g (absolutely dry mass) of phosphorylated pulp, stirring the pulp dispersion liquid so that the pulp was evenly dispersed, and then filtering and dehydrating it. went. The washing end point was determined when the electrical conductivity of the filtrate became 100 μS/cm or less.

The phosphorylated pulp after washing was further subjected to the above phosphorus oxo oxidation treatment and the above washing treatment once in this order.

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

The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. As a result, absorption based on phosphoric acid groups was observed near 1230 cm ⁻¹ , confirming that phosphoric acid groups were added to the pulp. In addition, when the obtained phosphorylated pulp was sampled and analyzed using an X-ray diffraction device, it was found that there were two positions near 2θ = 14° or more and 17° or less and 2θ = 22° or more and 23° or less. A typical peak was confirmed, and it was confirmed that cellulose type I crystals were present.

Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated six times at a pressure of 200 MPa using a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion A containing fine fibrous cellulose.

It was confirmed by X-ray diffraction that this fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. The amount of phosphoric acid groups (first amount of dissociated acid) measured by the measuring method described in [Measurement of amount of phosphorus oxo acid groups] described below was 2.00 mmol/g.

<Manufacture example 2>
[Production of fine fibrous cellulose dispersion B]
The same procedure as in Production Example 1 was carried out, except that 33 parts by mass of phosphorous acid (phosphonic acid) was used instead of ammonium dihydrogen phosphate, and the second phosphorous oxoacid treatment and washing treatment were not performed. Oxidized pulp was obtained. Other operations were performed in the same manner as in Production Example 1 to obtain a fine fibrous cellulose dispersion B with a concentration of 2% by mass.

The infrared absorption spectrum of the obtained phosphorous pulp was measured using FT-IR. As a result, an absorption based on P=O of a phosphonic acid group, which is a tautomer of a phosphorous acid group, was observed near 1210 cm ^-1 , indicating that a phosphorous acid group (phosphonic acid group) was added to the pulp. was confirmed. In addition, when the obtained phosphorous pulp was analyzed using an X-ray diffraction device, two positions were found: around 2θ = 14° or more and 17° or less and around 2θ = 22° or more and 23° or less. A typical peak was observed, and it was confirmed that cellulose type I crystals were present. The amount of phosphorous acid groups (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. Note that the total amount of dissociated acids was 1.54 mmol/g.

<Manufacture example 3>
[Production of fine fibrous cellulose dispersion C]
Sulfur oxo oxidation treatment was performed using 38 parts by mass of amidosulfuric acid (sulfamic acid) instead of ammonium dihydrogen phosphate, the heating time was extended to 19 minutes, and the second sulfur oxo oxidation treatment and cleaning treatment were not performed. Except for this, the same operation as in Production Example 1 was performed to obtain sulfated pulp. Other operations were performed in the same manner as in Production Example 1 to obtain a fine fibrous cellulose dispersion C having a concentration of 2% by mass.

The infrared absorption spectrum of the obtained sulfated pulp was measured using FT-IR. As a result, absorption based on S=O of sulfuric acid groups (sulfonic acid groups) was observed around 1220-1260 cm ^-1 , and it was confirmed that sulfuric acid groups (sulfonic acid groups) were added to the pulp. In addition, when the obtained sulfated pulp was sampled and analyzed using an X-ray diffraction device, it was found that there were two positions near 2θ = 14° or more and 17° or less and 2θ = 22° or more and 23° or less. A typical peak was confirmed, and it was confirmed that cellulose type I crystals were present. The amount of sulfuric acid groups (sulfonic acid groups) measured by the measuring method described in [Measurement of sulfur oxoacid group amount] described later was 1.12 mmol/g.

<Manufacture example 4>
[Manufacture of fine fibrous cellulose dispersion D]
As raw material pulp, softwood kraft pulp manufactured by Oji Paper (solid content 93% by mass, basis weight 208 g/m ² sheet form, Canadian standard freeness (CSF) measured according to JIS P 8121 after disintegration is 700 ml) It was used.

This raw material pulp was subjected to TEMPO oxidation treatment as follows. First, the above raw material pulp equivalent to 100 parts by mass of dry mass, 1.6 parts by mass of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl), and 10 parts by mass of sodium bromide were added to 10,000 parts by mass of water. It was distributed to different departments. Next, a 13% by mass aqueous sodium hypochlorite solution was added in an amount of 10 mmol per 1.0 g of pulp to start the reaction. During the reaction, a 0.5M aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10 or more and 10.5 or less, and the reaction was considered complete when no change in pH was observed.

Next, the obtained TEMPO oxidized pulp was subjected to a washing treatment. The cleaning treatment was carried out by dehydrating the pulp slurry after TEMPO oxidation to obtain a dehydrating sheet, pouring 5000 parts by mass of ion-exchanged water, stirring to uniformly disperse it, and repeating the following steps: filtration and dehydration. Ta. The washing end point was determined when the electrical conductivity of the filtrate became 100 μS/cm or less.

When the obtained TEMPO oxidized pulp was sampled and analyzed using an X-ray diffraction device, it was found that there were two positions near 2θ = 14° or more and 17° or less and 2θ = 22° or more and 23° or less. A typical peak was confirmed, and it was confirmed that cellulose type I crystals were present.

Ion-exchanged water was added to the obtained TEMPO oxidized pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated six times at a pressure of 200 MPa using a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) to obtain a fine fibrous cellulose dispersion D containing fine fibrous cellulose.

It was confirmed by X-ray diffraction that this fine fibrous cellulose maintained cellulose type I crystals. Further, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. In addition, the amount of carboxy groups measured by the measuring method described below was 1.80 mmol/g.

<Example 1>
[Production of fine fibrous cellulose-containing material (concentrate)]
100 g of a 3.43% by mass aqueous solution of trihexyltetradecylphosphonium chloride was added to 100 g of the fine fibrous cellulose dispersion A obtained in Production Example 1, and stirred for 5 minutes with a disperser, resulting in fine fibrous cellulose. Aggregates were formed in the dispersion. Fine fibrous cellulose aggregates were obtained by vacuum filtration of the fine fibrous cellulose dispersion in which aggregates were formed. By repeatedly washing the obtained fine fibrous cellulose aggregate with ion-exchanged water, excess trihexyltetradecylphosphonium chloride and eluted ions contained in the fine fibrous cellulose aggregate were removed. The obtained fine fibrous cellulose aggregate was dried under conditions of 30° C. and 40% relative humidity to obtain a fine fibrous cellulose-containing material (concentrate).
The counter ion of the phosphate group contained in the fine fibrous cellulose-containing material was trihexyltetradecylphosphonium ion (THTP ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 90% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Methanol (MeOH) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion (fibrous cellulose dispersion). The resulting fine fibrous cellulose redispersion was further diluted with methanol to a concentration of 0.05% by mass or more and 0.1% by mass or less, and the thin film obtained by casting onto a carbon membrane-coated grid was subjected to transmission electron microscopy. When observed under a microscope, fine fibrous cellulose with a fiber width of less than 10 nm was observed. Further, the light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

[Sheeting]
The fine fibrous cellulose redispersion obtained above was weighed and poured onto a glass Petri dish so that the finished basis weight of the sheet was 100 g/ ^m2 , and the solvent was substantially volatilized in a hot air dryer at 70°C. The mixture was dried to obtain a fine fibrous cellulose-containing sheet. The haze of the obtained fine fibrous cellulose-containing sheet was measured by the method described below.

<Example 2>
A fine fibrous cellulose redispersion liquid was obtained in the same manner as in Example 1, except that ethanol (EtOH) was used instead of methanol as the redispersion organic solvent added to the fine fibrous cellulose-containing material. When the resulting fine fibrous cellulose redispersion was further diluted with ethanol and dried, the resulting thin film was observed with a transmission electron microscope, fine fibrous cellulose with a fiber width of less than 10 nm was observed. Further, the light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Example 3>
A fine fibrous cellulose redispersion liquid was obtained in the same manner as in Example 1, except that dimethylacetamide (DMAc) was used instead of methanol as the redispersion organic solvent added to the fine fibrous cellulose-containing material. The resulting fine fibrous cellulose redispersion was further diluted with dimethylacetamide and the resulting thin film was observed with a transmission electron microscope, and fine fibrous cellulose with a fiber width of less than 10 nm was observed. Further, the light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Example 4>
A fine fibrous cellulose redispersion liquid was obtained in the same manner as in Example 1 except that dimethylformamide (DMF) was used instead of methanol as the redispersion organic solvent added to the fine fibrous cellulose-containing material. The obtained fine fibrous cellulose redispersion was further diluted with dimethylformamide and the resulting thin film was observed with a transmission electron microscope, and fine fibrous cellulose with a fiber width of less than 10 nm was observed. Further, the light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Example 5>
Same as Example 1 except that a mixed solvent (MeOH + IPA) in which methanol and 2-propanol (IPA) were mixed at a volume ratio of 1:1 was used instead of methanol as the redispersion organic solvent added to the fine fibrous cellulose-containing material. In the same manner, a fine fibrous cellulose redispersion liquid was obtained. The resulting fine fibrous cellulose redispersion was further diluted with the above mixed solvent and the resulting thin film was observed with a transmission electron microscope, and fine fibrous cellulose with a fiber width of less than 10 nm was observed. Further, the light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Example 6>
[Manufacture of fine fibrous cellulose-containing material]
A fine fibrous cellulose-containing material was obtained in the same manner as in Example 1, except that 2.98% by mass of tributyldodecylphosphonium bromide aqueous solution was used instead of 3.43% by mass of trihexyltetradecylphosphonium chloride aqueous solution. . The counter ion of the phosphate group contained in the fine fibrous cellulose-containing material was tributyldodecylphosphonium ion (TBDP ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 88% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Methanol (MeOH) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion. When the resulting fine fibrous cellulose redispersion was further diluted with methanol and dried and the obtained thin film was observed with a transmission electron microscope, fine fibrous cellulose with a fiber width of less than 10 nm was observed. Further, the light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Example 7>
[Manufacture of fine fibrous cellulose-containing material]
Using the fine fibrous cellulose dispersion B obtained in Production Example 2 instead of the fine fibrous cellulose dispersion A, the concentration of the trihexyltetradecylphosphonium chloride aqueous solution was increased from 3.43% by mass to 1.60% by mass. A fine fibrous cellulose-containing material was obtained in the same manner as in Example 1 except for the following changes.
The counter ion of the phosphorous acid group contained in the fine fibrous cellulose-containing material was trihexyltetradecylphosphonium ion (THTP ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 91% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Methanol (MeOH) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion. When the resulting fine fibrous cellulose redispersion was further diluted with methanol and dried and the obtained thin film was observed with a transmission electron microscope, fine fibrous cellulose with a fiber width of less than 10 nm was observed. Further, the light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Example 8>
[Manufacture of fine fibrous cellulose-containing material]
The fine fibrous cellulose dispersion C obtained in Production Example 3 was used instead of the fine fibrous cellulose dispersion A, and the concentration of the trihexyltetradecylphosphonium chloride aqueous solution was increased from 3.43% by mass to 1.16% by mass. A fine fibrous cellulose-containing material was obtained in the same manner as in Example 1 except for the following changes.
The counter ion of the sulfuric acid group (sulfonic acid group) contained in the fine fibrous cellulose-containing material was trihexyltetradecylphosphonium ion (THTP ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 92% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Methanol (MeOH) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion. When the resulting fine fibrous cellulose redispersion was further diluted with methanol and dried and the obtained thin film was observed with a transmission electron microscope, fine fibrous cellulose with a fiber width of less than 10 nm was observed. Further, the light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Comparative example 1>
A fine fibrous cellulose redispersion liquid was obtained in the same manner as in Example 1, except that methyl ethyl ketone (MEK) was used instead of methanol as the redispersion organic solvent added to the fine fibrous cellulose-containing material. The light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Comparative example 2>
[Manufacture of fine fibrous cellulose-containing material]
Except that a 3.86% by mass aqueous solution of di-n-alkyldimethylammonium chloride (the number of carbon atoms in the alkyl chain is 16 or 18) was used instead of a 3.43% by mass aqueous solution of trihexyltetradecylphosphonium chloride. A fine fibrous cellulose-containing material was obtained in the same manner as in Example 1.
The counter ion of the phosphate group contained in the fine fibrous cellulose-containing material was di-n-alkyldimethylammonium ion (DADMA ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 93% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Methanol (MeOH) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion. The light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Comparative example 3>
[Manufacture of fine fibrous cellulose-containing material]
Example except that a 2.33% by mass aqueous solution of alkyldimethylbenzylammonium chloride (the number of carbon atoms in the alkyl chain is 8 to 18) was used instead of a 3.43% by mass aqueous solution of trihexyltetradecylphosphonium chloride. In the same manner as in 1, a fine fibrous cellulose-containing material was obtained.
The counter ion of the phosphate group contained in the fine fibrous cellulose-containing material was an alkyldimethylbenzylammonium ion (ADMBA ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 86% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Methanol (MeOH) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion. The light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Comparative example 4>
[Manufacture of fine fibrous cellulose-containing material]
A fine fibrous cellulose-containing material was obtained in the same manner as in Example 1, except that 2.30% by mass of trimethylstearylammonium chloride aqueous solution was used instead of 3.43% by mass of trihexyltetradecylphosphonium chloride aqueous solution. .
The counter ion of the phosphate group contained in the fine fibrous cellulose-containing material was trimethylstearylammonium ion (TMSA ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 90% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Methanol (MeOH) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion. The light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Comparative example 5>
[Manufacture of fine fibrous cellulose-containing material]
Except that a 2.43% by weight aqueous N,N-didodecylmethylamine solution, which had been neutralized in advance by adding 0.59 g of lactic acid, was used instead of a 3.43% by weight aqueous solution of trihexyltetradecylphosphonium chloride. A fine fibrous cellulose-containing material was obtained in the same manner as in Example 1.
The counter ion of the phosphate group contained in the fine fibrous cellulose-containing material was N,N-didodecylmethylammonium ion (DDMA ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 95% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Dimethylformamide (DMF) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion. The light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Comparative example 6>
[Manufacture of fine fibrous cellulose-containing material]
Except that a 1.80% by mass aqueous solution of di-n-alkyldimethylammonium chloride (the number of carbon atoms in the alkyl chain is 16 or 18) was used instead of a 1.60% by mass aqueous solution of trihexyltetradecylphosphonium chloride. A fine fibrous cellulose composition was obtained in the same manner as in Example 7.
The counter ion of the phosphorous acid group contained in the fine fibrous cellulose-containing material was di-n-alkyldimethylammonium ion (DADMA ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 92% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Methanol (MeOH) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion. The light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Comparative example 7>
[Manufacture of fine fibrous cellulose-containing material]
Except that a 1.31% by mass aqueous solution of di-n-alkyldimethylammonium chloride (the number of carbon atoms in the alkyl chain is 16 or 18) was used instead of a 1.16% by mass aqueous solution of trihexyltetradecylphosphonium chloride. A fine fibrous cellulose composition was obtained in the same manner as in Example 8.
The counter ion of the sulfuric acid group (sulfonic acid group) contained in the fine fibrous cellulose-containing material was di-n-alkyldimethylammonium ion (DADMA ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 93% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Methanol (MeOH) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion. The light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

<Comparative example 8>
[Manufacture of fine fibrous cellulose-containing material]
The fine fibrous cellulose dispersion D obtained in Production Example 4 was used instead of the fine fibrous cellulose dispersion A, and the concentration of the trihexyltetradecylphosphonium chloride aqueous solution was increased from 3.43% by mass to 1.87% by mass. A fine fibrous cellulose-containing material was obtained in the same manner as in Example 1 except for the following changes.
The counter ion of the carboxy group contained in the fine fibrous cellulose-containing material was trihexyltetradecylphosphonium ion (THTP ⁺ ). The solid content concentration of the obtained fine fibrous cellulose-containing material was 91% by mass. Further, when the fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose-containing material was measured using a transmission electron microscope, it was less than 10 nm.

[Redispersion of fine fibrous cellulose-containing material]
Methanol (MeOH) was added as a redispersion organic solvent to the obtained fine fibrous cellulose-containing material to adjust the fine fibrous cellulose content to 2.0% by mass. Thereafter, ultrasonic treatment was performed for 10 minutes using an ultrasonic treatment device (manufactured by Hielscher, UP400S) to obtain a fine fibrous cellulose redispersion. The light transmittance of the obtained fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured by the method described below.

[Sheeting]
The fine fibrous cellulose redispersion obtained above was weighed and poured onto a glass Petri dish so that the finished basis weight of the sheet was 100 g/ ^m2 , and the solvent was substantially volatilized in a hot air dryer at 70°C. The mixture was dried to obtain a fine fibrous cellulose-containing sheet. The haze of the obtained fine fibrous cellulose-containing sheet was measured by the method described below.

The total number of carbon atoms of the organic onium ions introduced as counter ions to the anionic groups of the fine fibrous cellulose obtained in Examples and Comparative Examples was as follows.
Trihexyltetradecylphosphonium ion (THTP ⁺ ): 32
Tributyldodecylphosphonium ion (TBDP ⁺ ): 24
Di-n-alkyldimethylammonium ion (DADMA ⁺ ): 34-38
Alkyldimethylbenzylammonium ion (ADMBA ⁺ ): 17-27
Trimethylstearylammonium ion (TMSA ⁺ ): 21
N,N-didodecylmethylammonium ion (DDMA ⁺ ): 25

For the organic solvents used as redispersion organic solvents in Examples and Comparative Examples, the coordinates of HSP values and the distance from the coordinates to point P (δd = 16.5, δp = 12.5, δh = 14.5) were as follows (all units are MPa ^1/2 ).
Methanol (MeOH)
δd=15.1, δp=12.3, δh=22.3, distance from point P=7.9
Ethanol (EtOH)
δd=15.8, δp=8.8, δh=19.4, distance from point P=6.2
Dimethylacetamide (DMAc)
δd=16.8, δp=11.5, δh=9.4, distance from point P=5.2
Dimethylformamide (DMF)
δd=17.4, δp=13.7, δh=11.3, distance from point P=3.5
Mixed solvent of methanol and 2-propanol (MeOH+IPA)
δd=15.5, δp=9.2, δh=19.4, distance from point P=6.0
Methyl ethyl ketone (MEK)
δd=16.0, δp=9.0, δh=5.1, distance from point P=10.0

<Measurement>
[Measurement of phosphorus oxoacid group amount]
The amount of phosphorus oxo acid groups in the fine fibrous cellulose is determined by diluting the fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion-exchanged water to a content of 0.2% by mass. The measurement was performed by treating a cellulose-containing slurry with an ion exchange resin and then titrating it with an alkali.
For the treatment with ion exchange resin, 1/10 of the volume of strongly acidic ion exchange resin (Amber Jet 1024; Organo Co., Ltd., conditioned) was added to the fibrous cellulose-containing slurry, and the mixture was shaken for 1 hour. The slurry was poured onto a mesh having an opening of 90 μm to separate the resin and the slurry.
In addition, titration using an alkali is performed by adding 10 μL of 0.1N sodium hydroxide aqueous solution every 5 seconds to the fibrous cellulose-containing slurry after treatment with an ion exchange resin, and measuring the change in the pH value of the slurry. It was done by doing. Note that the titration was performed while blowing nitrogen gas into the slurry 15 minutes before the start of the titration. In this neutralization titration, on a curve in which the measured pH is plotted against the amount of alkali added, two points are observed where the increment (differential value of pH with respect to the amount of alkali added) becomes maximum. Among these, the maximum point of increment obtained first after starting to add the alkali is called the first end point, and the maximum point of 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 is equal to the total amount of dissociated acid in the slurry used for titration. The amount of alkali (mmol) required from the start of titration to the first end point divided by the solid content (g) in the slurry to be titrated was defined as the amount of phosphorus oxoacid group (mmol/g).

[Measurement of carboxy group amount]
The carboxy group content of the fine fibrous cellulose is determined by diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion-exchanged water to a content of 0.2% by mass. The slurry contained was treated with an ion exchange resin, and then titrated with an alkali for measurement.
For treatment with ion exchange resin, 1/10 volume of strongly acidic ion exchange resin (Amber Jet 1024; manufactured by Organo Co., Ltd., conditioned) was added to a slurry containing 0.2% by mass of fine fibrous cellulose, and the mixture was left for 1 hour. After the shaking treatment, the slurry was poured onto a mesh having an opening of 90 μm to separate the resin and the slurry.
In addition, titration using an alkali is performed by adding 10 μL of 0.1N sodium hydroxide aqueous solution every 5 seconds to the fibrous cellulose-containing slurry after treatment with an ion exchange resin, and measuring the change in the pH value of the slurry. It was done by doing. In this neutralization titration, on a curve in which the measured pH is plotted against the amount of alkali added, one point is observed where the increment (differential value of pH with respect to the amount of alkali added) becomes maximum. The maximum point of this increment is called the first end point (FIG. 2). The amount of alkali required from the start of titration to the first end point is equal to the amount of carboxy groups in the slurry used for titration. Note that the amount of carboxy group introduced (mmol/ g) was calculated.

[Measurement of sulfur oxoacid group amount]
The amount of sulfur oxoacid groups in the fine fibrous cellulose was measured as follows. First, the sample after freeze-drying and pulverization was decomposed under pressure and heat using nitric acid in a closed container. Thereafter, it was diluted appropriately and the amount of sulfur was measured by ICP-OES. The value calculated by dividing by the absolute dry mass of the fine fibrous cellulose tested was defined as the amount of sulfur oxoacid groups in the fine fibrous cellulose (unit: mmol/g).

[Measurement of light transmittance of fine fibrous cellulose redispersion liquid (fibrous cellulose dispersion liquid) at a wavelength of 600 nm]
The light transmittance of the fine fibrous cellulose redispersion liquid at a wavelength of 600 nm was measured using an ultraviolet-visible near-infrared spectrophotometer (manufactured by JASCO Corporation, V-770) using a quartz cell with an optical path length of 1 cm. The concentration of the fine fibrous cellulose redispersion liquid at the time of measurement was 2.0% by mass. Note that the zero point measurement in the measurement of light transmittance was performed using the organic solvent in each redispersion liquid.

[Haze measurement of sheet containing fine fibrous cellulose]
The haze of the fine fibrous cellulose-containing sheet was measured in accordance with JIS K 7136 using a haze meter (HM-150, manufactured by Murakami Color Research Institute).

The fine fibrous cellulose redispersion obtained in Examples 2 to 8 was poured onto a glass Petri dish and dried at the boiling point of each solvent + 5°C until the solvent was substantially volatilized. It was confirmed that fine fibrous cellulose-containing sheets with excellent transparency could be obtained from any of the dispersions.

In the examples, fibrous cellulose dispersions (redispersions) with excellent dispersibility in organic solvents were obtained. On the other hand, in the fibrous cellulose dispersion (redispersion) obtained in the comparative example, the dispersibility of the fibrous cellulose was not sufficient.

Claims (8)

A fibrous cellulose having an inorganic oxo acid group or a substituent derived from an inorganic oxo acid group and having a fiber width of 1000 nm or less,
A fibrous cellulose dispersion comprising an organic solvent,
The fibrous cellulose has an organic phosphonium ion as a counter ion of the inorganic oxo acid group or a substituent derived from the inorganic oxo acid group,
A fibrous cellulose dispersion, wherein the coordinates of the Hansen solubility parameters of the organic solvent are within the range of a sphere with a radius of 8 MPa ^1/2 centered at δd = 16.5, δp = 12.5, δh = 14.5. . The fibrous cellulose dispersion according to claim 1, wherein the organic solvent has a Hansen solubility parameter δh of 8 MPa ^1/2 or more. The fibrous cellulose dispersion according to claim 1 or 2, wherein the organic solvent has a Hansen solubility parameter δh of 11.5 MPa ^1/2 or more. The fibrous cellulose dispersion according to any one of claims 1 to 3, wherein the organic phosphonium ion satisfies at least one condition selected from the following (a) and (b);
(a) Contains a hydrocarbon group having 5 or more carbon atoms;
(b) The total number of carbon atoms is 17 or more. The fibrous cellulose dispersion according to any one of claims 1 to 4, wherein the inorganic oxo acid group or a substituent derived from the inorganic oxo acid group is a phosphorus oxo acid group or a substituent derived from a phosphorus oxo acid group. liquid. The fibrous cellulose dispersion according to any one of claims 1 to 5, wherein the water content is 100 parts by mass or less per 100 parts by mass of solids in the fibrous cellulose dispersion. The fibrous cellulose dispersion according to any one of claims 1 to 6, further comprising a resin. A molded article formed from the fibrous cellulose dispersion according to any one of claims 1 to 7.