JP6780730B2 - Fine fibrous cellulose-containing composition and method for producing the same - Google Patents

Description

The present invention relates to a fine fibrous cellulose-containing composition and a method for producing the same.

Fine fibrous cellulose having a fiber width of 1,000 nm or less is called cellulose nanofiber, and is used in various fields such as reinforcing materials for composite materials, high-performance filters, displays and solar cells, electronics, transportation equipment, building materials, and medical treatment. Expected to expand to.
Generally, fine fibrous cellulose is obtained as a dispersion liquid, but there is a problem that it is colored when the dispersion liquid is heated. If coloring occurs during heating, there is a problem that the product is colored when fine fibrous cellulose is used industrially, especially when it is molded by heat processing.
Patent Document 1 describes a method for producing anion-modified cellulose nanofibers, which comprises the following steps (A) to (C), for the purpose of providing a method for producing anion-modified cellulose nanofibers that are not colored when heated. ..
Step (A) Step of chemically modifying the cellulose raw material to obtain anion-modified cellulose Step (B) Water, an alkalizing agent, the anion-modified cellulose obtained in (A), water: alkalizing agent: anion-modified cellulose = 100 : 0.01 to 10: 0.01 to 10 (parts by mass) of mixing, and then stirring under the conditions of 0 to 40 ° C. for 10 minutes to 10 hours (alkali treatment step), and (C) Step of defibrating the alkali-treated anion-modified cellulose to obtain cellulose nanofibers

JP-A-2017-71700

The method described in Patent Document 1 requires a specific treatment before defibration.
An object of the present invention is to provide a fine fibrous cellulose-containing composition in which yellowing during heating is suppressed, and a method for producing the same.

The present inventors have found that the above-mentioned problems can be solved by a composition containing fine fibrous cellulose having a phosphite group and a protease or a protein derived from the protease.
That is, the present invention relates to the following <1> to <7>.
<1> A fine fibrous cellulose-containing composition containing fine fibrous cellulose having a phosphite group having a fiber width of 1,000 nm or less and a protease or a protein derived from the protease.
<2> The fine fibrous cellulose-containing composition according to <1>, wherein the change in yellow index during heating is 30 or less.
<3> The fine fibrous cellulose-containing composition according to <1> or <2>, which is in the form of a slurry.
<4> The fine fibrous cellulose-containing composition according to <1> or <2>, which is in the form of a powder.
<5> The fine fibrous cellulose-containing composition according to <1> or <2>, which is in the form of a sheet.
<6> A step of defibrating the fibrous cellulose in the solvent to obtain a dispersion liquid containing the fine fibrous cellulose and a step of adding a protease to the dispersion liquid containing the fine fibrous cellulose are provided in this order. , A method for producing a fine fibrous cellulose-containing composition.
<7> The method for producing a fine fibrous cellulose-containing composition according to <6>, wherein the amount of protease added to 1 mg of fine fibrous cellulose is 0.001 U or more and 10 U or less.

According to the present invention, it is possible to provide a fine fibrous cellulose-containing composition in which yellowing during heating is suppressed, and a method for producing the same.

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

[Fine fibrous cellulose-containing composition]
The fine fibrous cellulose-containing composition of the present invention comprises fine fibrous cellulose having a phosphite group with a fiber width of 1,000 nm or less (sometimes referred to simply as fine fibrous cellulose) and a protease or a protein derived from the protease. And contains.
Conventionally, there has been a problem that when a fine fibrous cellulose-containing composition is heated, it turns yellow.
Through diligent studies, the present inventors have found that yellowing during heating is suppressed by treating a dispersion containing fine fibrous cellulose with a protease, and have completed the present invention. It was.
The detailed reason for obtaining the above effect is unknown, but some are presumed as follows. The yellowing of the fine fibrous cellulose-containing composition involves a protein contained in a small amount of the cellulose raw material, and even if a protein is mixed in during storage for some reason, such a protein turns yellow. It is considered to be involved. In the present invention, it is considered that the protein causing yellowing is decomposed by treating the fine fibrous cellulose-containing dispersion with a protease, and the yellowing due to heating is suppressed.
The protease does not need to be inactivated, but may be inactivated after the treatment by heat-treating the fine fibrous cellulose-containing composition or the like to become a protein derived from the protease. In addition, the protease to be added and the protein derived from the protease inactivated by the protease are both proteins, but the amount added is extremely small, and the effect of heating the fine cellulose-containing composition on yellowing is minor. Conceivable.
Hereinafter, the present invention will be described in more detail.

<Fine fibrous cellulose>
The fine fibrous cellulose-containing composition of the present invention contains fine fibrous cellulose, and the fine fibrous cellulose is a fine fibrous cellulose having a phosphorous acid group having a fiber width of 1,000 nm or less. The fiber width of the fine fibrous cellulose can be measured by, for example, observation with an electron microscope.

The fiber width of the fine fibrous cellulose is 1000 nm or less, preferably 100 nm or less, more preferably 50 nm or less, still more preferably 30 nm or less, still more preferably 10 nm or less, still more preferably 8 nm or less. The fiber width is preferably 2 nm or more, and more preferably 3 nm or more.
The average fiber width of the fine fibrous cellulose is, for example, 1000 nm or less. The average fiber width of the fine fibrous cellulose is, for example, preferably 2 nm or more, more preferably 3 nm or more, and preferably 1000 nm or less, more preferably 100 nm or less, still more preferably 50 nm or less, still more preferably 10 nm or less. Even more preferably, it is 8 nm or less. By setting the average fiber width of the fine fibrous cellulose to 2 nm or more, it is possible to suppress the dissolution of the fine fibrous cellulose in water as a cellulose molecule, and to more easily exhibit the effects of the fine fibrous cellulose to improve strength, rigidity and dimensional stability. be able to. The fine fibrous cellulose is, for example, monofibrous cellulose.

The average fiber width of the fine fibrous cellulose is measured as follows, for example, using an electron microscope. First, an aqueous suspension of fine fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast on a hydrophilized carbon film-coated grid for TEM observation. Use as a sample. If it contains wide fibers, an SEM image of the surface cast on the glass may be observed. Next, observation is performed using an electron microscope image at a magnification of 1000 times, 5000 times, 10000 times, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification should be adjusted so as to satisfy the following conditions.
(1) A straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y that intersects the straight line perpendicularly is drawn in the same image, and 20 or more fibers intersect the straight line Y.
The width of the fiber intersecting the straight line X and the straight line Y is visually read with respect to the observation image satisfying the above conditions. In this way, at least three sets of observation images of surface portions that do not overlap each other are obtained. Next, for each image, the width of the fiber intersecting the straight line X and the straight line Y is read. As a result, at least 20 fibers × 2 × 3 = 120 fibers are read. Then, the average value of the read fiber widths is taken as the average fiber width of the fine fibrous cellulose.

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

The degree of polymerization of the fine fibrous cellulose is preferably 400 or more, more preferably 450 or more, still more preferably 505 or more, and the fine fibrous cellulose dispersion is low, from the viewpoint of functions as a reinforcing material, a thickener, and the like. From the viewpoint of thickening, it is preferably 700 or less, more preferably 650 or less, and further preferably 600 or less.
Further, when it is desired to reduce the viscosity of the dispersion liquid and particularly improve the handleability, the viscosity may be 250 or more and 400 or less.

The fine fibrous cellulose preferably has an I-type crystal structure. Here, the fact that the fine fibrous cellulose has an I-type crystal structure can be identified in the diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418 Å) monochromatic with graphite. Specifically, it can be identified by having typical peaks at two positions, 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less.
The ratio of the type I crystal structure to the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. As a result, even better performance can be expected in terms of heat resistance and low coefficient of linear thermal expansion. The crystallinity is determined by a conventional method from the X-ray diffraction profile measured and the pattern (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).
The crystallinity of the fine fibrous cellulose is preferably 30% or more, more preferably 40% or more, further preferably 50% or more, and preferably 100% or less, more preferably 95% or less, further. It is preferably 90% or less.

The axial ratio (fiber length / fiber width) of the fine fibrous cellulose is not particularly limited, but is, for example, preferably 20 or more, more preferably 50 or more, and preferably 10,000 or less, more preferably 1000 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, and it is easy to obtain an appropriate viscosity increase when a solvent dispersion is produced. By setting the axial ratio to the above upper limit value or less, for example, when treating fine fibrous cellulose as an aqueous dispersion, it is preferable in that handling such as dilution becomes easy.

The fine fibrous cellulose in the present embodiment has, for example, both a crystalline region and a non-crystalline region. In particular, fine fibrous cellulose having both a crystalline region and a non-crystalline region and having a high axial ratio is realized by a method for producing fine fibrous cellulose described later.

The fine fibrous cellulose in the present embodiment has a phosphorous acid group or a group derived from a phosphorous acid group (sometimes referred to simply as a phosphorous acid group).

The phosphorous acid group or the group derived from the phosphorous acid group is, for example, a substituent represented by the following formula (1).

In equation (1), b is a natural number and m ₁ is an arbitrary number (where b × m ₁ = 1). α ₁ is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, and an unsaturated-branched chain, respectively. A hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. Above all, it is particularly preferable that α ₁ is a hydrogen atom. Note that α ₁ in the formula (1) does not include a group derived from the cellulose molecular chain.

Examples of the saturated-linear hydrocarbon group represented by α ₁ of the formula (1) include a methyl group, an ethyl group, an n-propyl group, an n-butyl group and the like, but are not particularly limited. Examples of the saturated-branched chain hydrocarbon group include an i-propyl group and a t-butyl group, but are not particularly limited. Examples of the saturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentyl group, a cyclohexyl group and the like. Examples of the unsaturated-linear hydrocarbon group include, but are not limited to, a vinyl group, an allyl group and the like. Examples of the unsaturated-branched chain 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, but are not limited to, a cyclopentenyl group, a cyclohexenyl group and the like. Examples of the aromatic group include, but are not limited to, a phenyl group, a naphthyl group and the like.

Further, as the inducing group in α ₁ , at least one of functional groups such as a carboxy group, a hydroxy group, or an amino group is added or substituted with respect to the main chain or side chain of the above-mentioned various hydrocarbon groups. Functional groups can be mentioned, but are not particularly limited.
The number of carbon atoms constituting the main chain of α ₁ is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of α ₁ to the above range, the molecular weight of the phosphite group can be set to an appropriate range, the penetration into the fiber raw material is facilitated, and the yield of fine fibrous cellulose is obtained. You can also increase the rate.

Β ₁ ^{b +} in the formula (1) is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of monovalent or higher cations composed of organic substances include aliphatic ammonium or aromatic ammonium, and examples of monovalent or higher valent cations composed of inorganic substances include ions of alkali metals such as sodium, potassium, and lithium. Examples thereof include cations of divalent metals such as calcium and magnesium, hydrogen ions, and the like, but the present invention is not particularly limited. These may be applied alone or in combination of two or more. The monovalent or higher cation composed of an organic substance or an inorganic substance is preferably sodium or potassium ion which is hard to yellow when the fiber raw material containing β ₁ is heated and is easily industrially used, but is not particularly limited. ..

The fine fibrous cellulose may have a phosphorous acid group or a group derived from the phosphorous acid group in addition to the phosphorous acid group or the substituent derived from the phosphorous acid group. The phosphoric acid group or the group derived from the phosphoric acid group may be, for example, a substituent represented by the following formula (2) or (3). The phosphoric acid group or the group derived from the phosphoric acid group may be a condensed phosphorus oxo acid group as represented by the following formula (3).

In equation (2), a and b'are natural numbers, and m ₂ is an arbitrary number (where a = b'x m ₂ ). Of α ₂ and α ₂ ', a are O ⁻ and the rest are OR. Here, R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, or an unsaturated-branched chain. A hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. In addition, α ₂ in the formula (2) may be a group derived from a cellulose molecular chain.

In equation (3), a'and b'' are natural numbers, m ₃ is an arbitrary number, and n is a natural number of 2 or more (where a'= b'' × m ₃ ). Of α ₃ ¹ , α ₃ ² , ..., α ₃ ⁿ and α ₃ ', a'is O ⁻ , and the rest is either R or OR. Here, R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, or an unsaturated-branched chain. A hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or an inducing group thereof. In addition, α ₃ in the formula (3) may be a group derived from a cellulose molecular chain.

The specific examples of each group in the formulas (2) and (3) are the same as the specific examples of each group in the formula (1). Further, the specific examples of β ₂ ^b'+ in the formula (2) and β ₃ ^b''+ in the formula (3) are the same as the specific examples of β ₁ ^{b +} in the formula (1).

The fact that the fine fibrous cellulose has a phosphite group as a substituent means that the infrared absorption spectrum of the dispersion containing the fine fibrous cellulose was measured, and a tautomer of the phosphite group was measured around 1210 cm ^-1. This can be confirmed by observing the P = O-based absorption of a phosphonate group. Further, the fact that the fine fibrous cellulose has a phosphoric acid group as a substituent means that the infrared absorption spectrum of the dispersion liquid containing the fine fibrous cellulose is measured and is based on P = O of the phosphoric acid group in the vicinity of 1230 cm ^-1. It can be confirmed by observing absorption. Further, the fact that the fine fibrous cellulose has a phosphorous acid group or a phosphorous acid group as a substituent can be confirmed by a method of confirming a chemical shift by using NMR or a method of combining titration with elemental analysis.

The amount of phosphorous acid group introduced into the fine fibrous cellulose, that is, the content of the phosphorous acid group in the fine fibrous cellulose is preferably 0.10 mmol / g or more per 1 g (mass) of the fine fibrous cellulose, for example. , 0.20 mmol / g or more, more preferably 0.50 mmol / g or more, even more preferably 0.60 mmol / g or more, and 1.00 mmol / g or more. Is particularly preferable. The amount of phosphite group introduced into the fine fibrous cellulose is preferably 5.20 mmol / g or less per 1 g (mass) of the fine fibrous cellulose, and more preferably 3.65 mmol / g or less. , 3.50 mmol / g or less, and even more preferably 3.00 mmol / g or less. By setting the amount of the phosphorous acid group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous cellulose. Further, by setting the amount of the phosphorous acid group introduced within the above range, good properties can be exhibited in various applications such as a thickener for fine fibrous cellulose.
Here, the denominator in the unit mmol / g indicates the mass of fine fibrous cellulose when the counter ion of the phosphite group is a hydrogen ion (H ⁺ ).
The amount of phosphite group introduced into the fine fibrous cellulose can be measured by, for example, a neutralization titration method. In the measurement by the neutralization titration method, the amount of phosphorous acid group introduced is measured by determining the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing fine fibrous cellulose.

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

Since the denominator of the above-mentioned phosphorus oxo acid group introduction amount (mmol / g) indicates the mass of the acid-type fine fibrous cellulose, the phosphorus oxo acid group amount (hereinafter, phosphorus oxo acid) possessed by the acid-type fine fibrous cellulose It is called the base amount (acid type)). On the other hand, when the counterion of the phosphorus oxo acid group is replaced with an arbitrary cation C so as to have a charge equivalent, the denominator is converted to the mass of fine fibrous cellulose when the cation C is a counterion. By doing so, the amount of phosphorus oxo acid groups (hereinafter, the amount of phosphorus oxo acid groups (C type)) possessed by the fine fibrous cellulose in which the cation C is a counter ion can be obtained.
That is, it is calculated by the following formula.
Phosphoric acid group amount (C type) = Phosphoric acid group amount (acid type) / {1+ (W-1) x A / 1000}
A [mmol / g]: Total amount of anions derived from phosphoric acid groups of fine fibrous cellulose (value obtained by adding the amount of strongly acidic groups and the amount of weakly acidic groups of phosphoric acid groups)
W: Formula amount per valence of cation C (for example, Na is 23, Al is 9)

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

In addition, which of the phosphite, the phosphoric acid, and the condensed phosphoric acid is the phosphoric acid detected when the phosphoric acid group, the condensed phosphoric acid group, or both is contained in addition to the phosphite group? As a method for distinguishing between, for example, a method of performing a treatment for cutting a condensed structure such as acid hydrolysis and then performing a titration operation described above, or a treatment for converting a phosphite group into a phosphate group such as an oxidation treatment is performed. Examples thereof include a method of performing the above-mentioned titration operation after the operation.

<Manufacturing method of fine fibrous cellulose>
(Fiber raw material containing cellulose)
Fine fibrous cellulose has a phosphorous acid group and is produced from a fiber raw material containing cellulose (hereinafter, also simply referred to as "fiber raw material").
The fiber raw material containing cellulose is not particularly limited, but pulp is preferably used because it is easily available and inexpensive. Examples of pulp include wood pulp, non-wood pulp, and deinked pulp. The wood pulp is not particularly limited, but is, for example, broadleaf kraft pulp (LBKP), coniferous kraft pulp (NBKP), sulfite pulp (SP), dissolved 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 chemiground wood pulp (CGP), crushed wood pulp (GP) and thermomechanical pulp (TMP, BCTMP), etc. Examples include mechanical pulp. The non-wood pulp is not particularly limited, and examples thereof include cotton pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw and bagasse. The deinking pulp is not particularly limited, and examples thereof include deinking pulp made from used paper. As the pulp of the present embodiment, one of the above types may be used alone, or two or more types may be mixed and used.
Among the above pulps, for example, wood pulp and deinked pulp are preferable from the viewpoint of availability. Further, among wood pulps, from the viewpoint of high cellulose ratio and high yield of fine fibrous cellulose during defibration treatment, long fiber fine fibrous cellulose having a small decomposition of cellulose in pulp and a large axial ratio can be obtained. From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are further preferable. When long fiber fine fibrous cellulose having a large axial ratio is used, the viscosity tends to increase.

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

Here, in order to obtain fine fibrous cellulose into which a phosphite group has been introduced, a phosphite group introduction step, a washing step, and an alkali treatment step (inside) in which the phosphite group is introduced into the fiber raw material containing cellulose described above. The sum step) and the defibration treatment step are preferably carried out in this order, and an acid treatment step may be provided instead of the washing step or in addition to the washing step. Further, a pretreatment step may be provided before the phosphite group introduction step. Each will be described below.

(Phosphorous acid group introduction process)
The step of introducing a phosphorous acid group into a fiber raw material containing cellulose (phosphorous acid group introduction step) will be described below.
In the phosphite group introduction step, at least one compound (hereinafter, also referred to as “compound A”) selected from compounds capable of introducing a phosphorous acid group by reacting with a hydroxyl group of a fiber raw material containing cellulose is introduced. This is a step of acting on a fiber raw material containing cellulose. By this step, a phosphite group-introduced fiber can be obtained.

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

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

The compound A used in this embodiment is at least one selected from a compound having a phosphorous acid group and a salt thereof. Examples of the compound having a phosphorous acid group include phosphorous acid, and examples of phosphorous acid include 99% phosphorous acid (phosphonic acid). Examples of the salt of the compound having a phosphorous acid group include a lithium salt, a sodium salt, a potassium salt, and an ammonium salt of phosphorous acid, and these can have various neutralization degrees. Of these, phosphorous acid and phosphorous acid are highly efficient in introducing phosphorous acid groups, are more likely to improve defibration efficiency in the defibration treatment step described later, are low in cost, and are easy to apply industrially. A sodium salt of phosphoric acid, a potassium salt of phosphorous acid, or an ammonium salt of phosphorous acid is preferably used.

The amount of compound A added to the fiber raw material is not particularly limited, but for example, when the amount of compound A added is converted to the phosphorus atomic weight, phosphorus is added to the fiber raw material (absolute dry mass, hereinafter also referred to as “absolute dry mass”). The amount of the atom added is preferably 0.5% by mass or more, more preferably 1% by mass or more, further preferably 2% by mass or more, and preferably 100% by mass or less, more preferably 50% by mass or less, further. It is preferably 30% by mass or less. By setting the amount of phosphorus atoms added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by setting the addition amount of the phosphorus atom to the fiber raw material to be equal to or less than the above upper limit value, the effect of improving the yield and the cost can be balanced. Here, the "absolute dry mass (absolute dry mass)" is the mass in the absolute dry state which has reached a constant amount as measured by the method described in ISO 638: 2008.

Compound B used in this embodiment is at least one selected from urea and its derivatives as described above. Examples of the compound B include urea, thiourea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea, dimethylurea, diethylurea, tetramethylurea and the like.
From the viewpoint of improving the uniformity of the reaction, compound B is preferably used as an aqueous solution. Further, from the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.
The amount of Compound B added to the fiber raw material (absolute dry mass) is not particularly limited, but is, for example, 1% by mass or more, more preferably 10% by mass or more, still more preferably 100% by mass or more, and preferably 500% by mass or more. % Or less, more preferably 400% by mass or less, still more preferably 350% by mass or less.

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

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

In the heat treatment according to the present embodiment, for example, compound A is added to a thin sheet-shaped fiber raw material by a method such as impregnation and then heated, or the fiber raw material and compound A are heated while kneading or stirring with a kneader or the like. A drying method can be adopted. This makes it possible to suppress uneven concentration of compound A in the fiber raw material and more uniformly introduce the phosphorous acid group onto the surface of the cellulose fiber contained in the fiber raw material. This is because when the water molecules move to the surface of the fiber raw material due to drying, the dissolved compound A is attracted to the water molecules by the surface tension and also moves to the surface of the fiber raw material (that is, the concentration unevenness of the compound A is caused. It is considered that this is due to the fact that it can be suppressed.
Further, the heating device used for the heat treatment always keeps the water content retained by the slurry and the water content generated by the dehydration condensation (phosphite esterification) reaction between the compound A and the hydroxyl group contained in the cellulose in the fiber raw material. It is preferable that the device can be discharged to the outside of the system. Examples of such a heating device include a ventilation type oven and the like. By constantly discharging the water in the apparatus system, in addition to being able to suppress the hydrolysis reaction of the phosphite ester bond, which is the reverse reaction of phosphite esterification, the acid hydrolysis of sugar chains in the fiber is suppressed. You can also do it. Therefore, it is possible to obtain fine fibrous cellulose having a high axial ratio.

The time of the heat treatment is preferably 1 second or longer, more preferably 10 seconds or longer, and preferably 300 minutes or shorter, more preferably 1000 seconds or shorter, after substantially removing water from the fiber raw material, for example. More preferably, it is 800 seconds or less. In the present embodiment, the amount of phosphite group introduced can be within a preferable range by setting the heating temperature and the heating time within appropriate ranges.

The phosphorous acid group introduction step may be performed at least once, but may be repeated twice or more. By performing the phosphite group introduction step two or more times, many phosphorous acid groups can be introduced into the fiber raw material. In the present embodiment, as an example of a preferable embodiment, there is a case where the phosphite group introduction step is performed twice.

The amount of the phosphorous acid group introduced into the fiber raw material is, for example, 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and 0.50 mmol / g per 1 g (mass) of fine fibrous cellulose. It is more preferably / g or more, further preferably 0.60 mmol / g or more, and particularly preferably 1.00 mmol / g or more. Further, the amount of the phosphorous acid group introduced into the fiber raw material is preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less per 1 g (mass) of fine fibrous cellulose, for example, 3 It is more preferably 0.00 mmol / g or less. By setting the amount of the phosphorous acid group introduced within the above range, it is possible to facilitate the miniaturization of the fiber raw material and enhance the stability of the fine fibrous cellulose.

(Washing process)
In the method for producing fine fibrous cellulose in the present embodiment, a washing step can be performed on the phosphite group-introduced fiber as needed. The washing step is performed, for example, by washing the phosphite group-introduced fibers with water or an organic solvent. Further, the cleaning step may be performed after each step described later, and the number of cleanings performed in each cleaning step is not particularly limited.
In the washing step, it is preferable to repeat the operation of dispersing the phosphorous acid group-introduced fibers in water or an organic solvent and then filtering, and controlling the progress of the washing step by setting the electrical conductivity of the filtrate to a desired range. be able to. The washing step is performed so that the electrical conductivity of the filtrate is preferably 10,000 μS / cm or less, more preferably 1,000 μS / cm or less, still more preferably 300 μS / cm or less, and even more preferably 150 μS / cm. Is preferable.

(Alkaline treatment process (neutralization process))
In the case of producing fine fibrous cellulose, an alkali treatment is performed on the fiber raw material between the phosphite group introduction step and the defibration treatment step described later to neutralize the phosphite groups. It may have a step (neutralization step). The alkaline treatment method is not particularly limited, and examples thereof include a method of immersing the phosphite group-introduced fiber in an alkaline solution.
The alkaline compound contained in the alkaline solution is not particularly limited, and may be an inorganic alkaline compound or an organic alkaline compound. In the present embodiment, for example, sodium hydroxide or potassium hydroxide is preferably used as the alkaline compound because of its high versatility. Further, the solvent contained in the alkaline solution may be either water or an organic solvent. Among them, the solvent contained in the alkaline solution is preferably a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. As the alkaline solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of its high versatility.

The temperature of the alkaline solution in the alkaline treatment step is not particularly limited, but is, for example, 5 ° C. or higher, more preferably 10 ° C. or higher, and preferably 80 ° C. or lower, more preferably 60 ° C. or lower. The immersion time of the phosphite group-introduced fiber in the alkaline solution in the alkali treatment step is not particularly limited, but is preferably, for example, preferably 5 minutes or more, more preferably 10 minutes or more, and preferably 30 minutes or less, more preferably. Is less than 20 minutes. The amount of the alkaline solution used in the alkaline treatment is not particularly limited, but is preferably 100% by mass or more, more preferably 1000% by mass or more, and preferably 1000% by mass or more, based on the absolute dry mass of the phosphorous acid group-introduced fiber, for example. It is 100,000% by mass or less, more preferably 10,000% by mass or less.

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

In the alkaline treatment, an alkaline solution is gradually added to the dispersion liquid in which the phosphorous acid group-introduced fibers are dispersed, and the pH in the system is preferably 10 or more, more preferably 11 or more, still more preferably 12 or more, and It is preferable to add the alkaline solution so that the amount is preferably 14 or less, more preferably 13.5 or less, and even more preferably 13 or less.
By setting the amount of the alkaline solution added in the above range, the defibration treatment can be performed more easily, and fine fibrous cellulose having a small fiber width can be easily obtained.

(Acid treatment process)
In the case of producing fine fibrous cellulose, the fiber raw material may be subjected to acid treatment between the step of introducing a phosphorous acid group and the defibration treatment step described later. For example, the phosphite group introduction step, acid treatment, alkali treatment and defibration treatment may be performed in this order.
The acid treatment method is not particularly limited, and examples thereof include a method of immersing the fiber raw material in an acidic liquid containing an acid. The concentration of the acidic liquid used is not particularly limited, but is preferably, for example, 10% by mass or less, and more preferably 5% by mass or less. The pH of the acidic solution used is not particularly limited, but is preferably 0 or more, more preferably 1 or more, and preferably 4 or less, more preferably 3 or less, for example. As the acid contained in the acidic solution, for example, an inorganic acid, a sulfonic acid, a carboxylic acid or the like can be used. Examples of the inorganic acid include sulfuric acid, nitric acid, hydrochloric acid, hydrobromic acid, hydroiodic acid, hypochlorous acid, chloric acid, chloric acid, perchloric acid, phosphoric acid, boric acid and the like. Examples of the sulfonic acid include methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, trifluoromethanesulfonic acid and the like. Examples of the carboxylic acid include formic acid, acetic acid, citric acid, gluconic acid, lactic acid, oxalic acid, tartaric acid and the like. Among these, it is particularly preferable to use hydrochloric acid or sulfuric acid.

The temperature of the acid solution in the acid treatment is not particularly limited, but is, for example, preferably 5 ° C. or higher, more preferably 20 ° C. or higher, and preferably 100 ° C. or lower, more preferably 90 ° C. or lower. The immersion time in the acid solution in the acid treatment is not particularly limited, but is preferably, for example, preferably 5 minutes or more, more preferably 10 minutes or more, and preferably 120 minutes or less, more preferably 60 minutes or less. The amount of the acid solution used in the acid treatment is not particularly limited, but is preferably 100 parts by mass or more, more preferably 1000 parts by mass or more, and preferably 100,000 parts by mass with respect to 100 parts by mass of the absolute dry mass of the fiber raw material. It is less than a part by mass, more preferably 10000 parts by mass or less.

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

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

The solid content concentration of the fibrous cellulose during the defibration treatment can be appropriately set. Further, the slurry obtained by dispersing the phosphorous acid group-introduced fiber in a dispersion medium may contain a solid content other than the phosphorous acid group-introduced fiber such as urea having a hydrogen bond property.

<Protease or protein derived from protease>
The fine fibrous cellulose-containing composition of the present invention contains a protease or a protein derived from the protease. In the present invention, the fine fibrous cellulose-containing composition may contain both a protease and a protein derived from the protease.
Here, the "protein derived from protease" means a protein in a state in which the protease is inactivated by heat, light, acid, base or the like and loses the protease activity. That is, the fine fibrous cellulose-containing composition of the present invention treats the fine fibrous cellulose dispersion with a protease, and it is not necessary to inactivate the protease after the protease treatment, but the protease is not inactivated by the subsequent treatment. It also includes the case where it contains a protein derived from a protease that has been inactivated.

The protease used in the present invention is not particularly limited, and may be an exopeptidase that cleaves 1 to 2 amino residues from the end of the sequence of the protein or peptide chain, and may be an endopeptidase that cleaves the center of the sequence of the protein or peptide chain. Although it may be peptidase, it is preferably endopeptidase from the viewpoint of effectively suppressing yellowing.
Casein, hemoglobin, fibrin and the like can be used as the substrate for the protease.
The optimum pH of the protease used in the present invention is preferably 3 or more and 12 or less, more preferably 4 or more and 11 or less, and further preferably 5 or more and 10 or less because of the ease of treatment with the protease.
The optimum temperature of the protease used in the present invention is preferably 10 ° C. or higher and 80 ° C. or lower, more preferably from the viewpoint of ease of treatment with the protease and suppression of deterioration of the fine fibrous cellulose-containing composition due to heating. It is 15 ° C. or higher and 70 ° C. or lower, more preferably 20 ° C. or higher and 60 ° C. or lower.

From the viewpoint of effectively suppressing yellowing, the amount of protease added is preferably 0.001 U or more, more preferably 0.005 U or more, still more preferably 0.01 U or more, based on 1 mg of fine fibrous cellulose. From the viewpoint of economy and suppression of excessive addition of protease, which is a protein, it is preferably 10 U or less, more preferably 1 U or less, still more preferably 0.5 U or less.
U is an international unit of enzyme and is defined by the amount of enzyme activity that converts 1 μmol of substrate into a product per minute.

<Composition containing fine fibrous cellulose>
In the present invention, the fine fibrous cellulose-containing composition contains fine fibrous cellulose and a protease or a protein derived from a protease, and may further contain other components other than the above. Examples of other components include water-soluble polymers and surfactants.
Examples of the water-soluble polymer include carboxyvinyl polymer, polyvinyl alcohol, alkyl methacrylate / acrylic acid copolymer, polyvinylpyrrolidone, sodium polyacrylate, polyethylene glycol, diethylene glycol, triethylene glycol, polyethylene oxide, propylene glycol and dipropylene glycol. Synthetic water-soluble polymers such as polypropylene glycol, isoprene glycol, hexylene glycol, 1,3-butylene glycol, and polyacrylamide; xanthan gum, guar gum, tamarind gum, carrageenan, locust bean gum, quince seed, alginic acid, purulan , And thickening polymers such as pectin; cellulose derivatives such as carboxymethyl cellulose, methyl cellulose, and hirodoxyethyl cellulose; cationized starch, raw starch, oxidized starch, etherified starch, esterified starch, and Examples of starches such as amylose; glycerins such as glycerin, diglycerin, and polyglycerin; hyaluronic acid, metal salts of hyaluronic acid, and the like can be mentioned.
The content of the water-soluble polymer in the fine fibrous cellulose-containing composition is preferably 0.05 parts by mass or more, preferably 0.1 parts by mass or more, with respect to 100 parts by mass of fine fibrous cellulose, for example. More preferably, it is more preferably 0.5 parts by mass or more. On the other hand, the content of the water-soluble polymer in the fine fibrous cellulose-containing composition is preferably 500 parts by mass or less and 200 parts by mass or less with respect to 100 parts by mass of fine fibrous cellulose, for example. Is more preferable, and 100 parts by mass or less is further preferable. By setting the content of the water-soluble polymer in the above range, both the characteristics of the fine fibrous cellulose and the characteristics of the water-soluble polymer can be exhibited.

As the surfactant, a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant can be used. Examples of the nonionic surfactant include polyoxyalkylene alkyl ether, polyglycerin fatty acid ester, glycerin mono fatty acid ester, glycerin di fatty acid ester, purulonic, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, sucrose fatty acid ester, and poly. Examples thereof include oxyethylene acyl ester, alkyl polyglycoside, fatty acid methyl glycoside ester, alkyl methyl glucamide, and fatty acid alkanolamide. Examples of anionic surfactants include sodium oleate, potassium oleate, sodium laurate, sodium todecylbenzene sulfonate, sodium alkylnaphthalene sulfonate, sodium dialkyl sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, and polyoxy. Examples thereof include sodium ethylenealkylallyl ether sulfate, sodium polyoxyethylene dialkylsulfate, polyoxyethylene alkyl ether phosphoric acid ester, and polyoxyethylene alkyl allyl ether phosphoric acid ester. Examples of the cationic surfactant include alkyltrimethylammonium salt, dialkyldimethylammonium salt, alkyldimethylbenzylammonium salt, acylaminoethyldiethylammonium salt, acylaminoethyldiethylamine salt, alkylamidepropyldimethylbenzylammonium salt, and alkylpyridinium salt. , Alkylpyridinium sulfate, stearamide methylpyridinium salt, alkylquinolinium salt, alkylisoquinolinium salt, fatty acid polyethylene polyamide, acylaminoethylpyridinium salt, acylcholaminoformylmethylpyridinium salt and other quaternary ammonium salts, Ester-bonded amines such as stearooxymethylpyridinium salt, fatty acid triethanolamine, fatty acid triethanolamine formate, trioxyethylene fatty acid triethanolamine, cetyloxymethylpyridinium salt, p-isooctylphenoxyethoxyethyldimethylbenzylammonium salt Complex return amines such as ether-bonded quaternary ammonium salt, alkyl imidazoline, 1-hydroxyethyl-2-alkyl imidazoline, 1-acetylaminoethyl-2-alkyl imidazoline, 2-alkyl-4-methyl-4-hydroxymethyloxazoline. , Polyoxyethylene alkylamine, N-alkylpropylenediamine, N-alkylpolyethylenepolyamine, N-alkylpolyethylenepolyaminedimethylsulfate, alkylbiguanide, long-chain amine oxides and other amine derivatives. Examples of the amphoteric surfactant include lauryldimethylaminoacetic acid betaine, cocamidopropyl betaine, lauramidepropyl betaine, sodium cocoamphoacetate and the like.
The content of the surfactant in the fine fibrous cellulose-containing composition is preferably 0.01 part by mass or more, and 0.05 part by mass or more with respect to 100 parts by mass of fine fibrous cellulose, for example. Is more preferable, and 0.1 parts by mass or more is further preferable. On the other hand, the content of the surfactant in the fine fibrous cellulose-containing composition is preferably 5 parts by mass or less and 3 parts by mass or less with respect to 100 parts by mass of fine fibrous cellulose, for example. More preferably, it is 2 parts by mass or less. By setting the content of the surfactant in the above range, both the characteristics of the fine fibrous cellulose and the characteristics of the surfactant can be exhibited.
The fine fibrous cellulose-containing composition includes fine fibrous cellulose, a water-soluble polymer, and a surfactant, as well as, for example, organic ions, coupling agents, inorganic layered compounds, inorganic compounds, leveling agents, preservatives, and antifoaming agents. , Organic particles, lubricants, antistatic agents, UV protectants, dyes, pigments, stabilizers, magnetic powders, orientation promoters, plasticizers, dispersants, and cross-linking agents. It may be included.

The fine fibrous cellulose-containing composition may contain a solvent. The solvent may include, for example, one or both of water and an organic solvent. Examples of the organic solvent include alcohols, polyhydric alcohols, ketones, ethers, esters, hydrocarbons, halogens, aprotonic polar solvents and the like. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, isobutyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of ketones include acetone, methyl ethyl ketone (MEK) and the like. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of hydrocarbons include n-hexane, toluene, xylene and the like. Examples of halogens include methylene chloride, trichlorethylene, chloroform and the like. Examples of the aprotonic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

Measured at 23 ° C. using a glass cell having an optical path length of 1 cm in accordance with JIS K 7136: 2000, which is a slurry of a fine fibrous cellulose-containing composition adjusted to a solid content concentration of fine fibrous cellulose of 0.2% by mass. The haze is preferably 2.0% or less. Further, the haze is more preferably 1.5% or less, still more preferably 1.0% or less. On the other hand, the lower limit of the haze is not particularly limited and may be, for example, 0%. By setting the haze of the slurry of the fine fibrous cellulose-containing composition in such a range, it becomes possible to form a sheet or the like having higher transparency.
In the present embodiment, the haze can be measured using, for example, a haze meter (HM-150, manufactured by Murakami Color Technology Laboratory Co., Ltd.). Further, as the glass cell having an optical path length of 1 cm, for example, a glass cell for liquid having an optical path length of 1 cm (manufactured by Fujiwara Seisakusho Co., Ltd., MG-40, backlit path) can be used. The zero point measurement is performed with ion-exchanged water contained in the glass cell.
The solvent at the time of haze measurement preferably contains at least water, and the content of water in the entire solvent is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90% by mass. % Or more, particularly preferably 95% by mass or more, and may be 100% by mass.
When the fine fibrous cellulose-containing composition is used for applications where transparency is not required, the haze may be, for example, 30% or more, 60% or more, 90% or more. It may be.

In the present invention, a glass cell in which a fine fibrous cellulose-containing composition is prepared by adjusting the solid content concentration of the fine fibrous cellulose to 0.2% by mass according to JIS K 7361-1: 1997 and has an optical path length of 1 cm is provided. The total light transmittance measured in use is preferably 90% or more. Further, the total light transmittance is more preferably 93% or more, and further preferably 95% or more. On the other hand, the upper limit of the total light transmittance is not particularly limited and may be, for example, 100%. By setting the total light transmittance of the slurry of the fine fibrous cellulose-containing composition in such a range, it is possible to form a sheet or the like having higher transparency.
In the present embodiment, the total light transmittance can be measured using, for example, a haze meter (HM-150, manufactured by Murakami Color Technology Laboratory Co., Ltd.). Further, as the glass cell having an optical path length of 1 cm, for example, a glass cell for liquid having an optical path length of 1 cm (manufactured by Fujiwara Seisakusho Co., Ltd., MG-40, backlit path) can be used. The zero point measurement is performed with ion-exchanged water contained in the glass cell.
The solvent at the time of measuring the total light transmittance is preferably at least water, and the content of water in the whole solvent is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferable. Is 90% by mass or more, particularly preferably 95% by mass or more, and may be 100% by mass.
When the fine fibrous cellulose-containing composition is used for applications where transparency is not required, the transmittance may be, for example, 60% or less, 30% or less, or 10%. It may be as follows.

The viscosity of the slurry prepared by adjusting the fine fibrous cellulose-containing composition to a solid content concentration of 0.4% by mass of the fine fibrous cellulose is preferably measured at 23 ° C. and a rotation speed of 3 rpm using a B-type viscometer. 3.0 × 10 ⁴ mPa · s or less, more preferably 2.5 × 10 ⁴ mPa · s or less, still more preferably 2.0 × 10 ⁴ mPa · s or less, still more preferably 1.5 × 10 ⁴ mPa · s or less. -S or less. The lower limit of the viscosity is not particularly limited, but is preferably 1.0 × 10 ³ mPa · s or more, more preferably 1.5 × 10 ³ mPa · s or more, and further preferably 5.0 × 10 ³ or more. It is mPa · s or more.
Here, for the measurement of the viscosity, for example, an analog viscometer T-LVT manufactured by BLOOKFIELD, which is a B-type viscometer, can be used. The measurement conditions are, for example, a liquid temperature of 23 ° C. and a viscometer rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of measurement is taken as the viscosity of the dispersion liquid.
The solvent at the time of measuring the viscosity preferably contains at least water, and the content of water in the whole solvent is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90% by mass. % Or more, particularly preferably 95% by mass or more, and may be 100% by mass.

The change in the yellow index of the fine fibrous cellulose-containing composition before and after heating is preferably 30 or less, more preferably 27 or less, still more preferably 25 or less, from the viewpoint of effectively suppressing yellowing. Further, the lower limit is not particularly limited, but from the viewpoint of design ease, it is preferably 1 or more, more preferably 3 or more, and further preferably 5 or more.
Here, the yellow index of the fine fibrous cellulose-containing composition is measured according to JIS K 7373: 2006 by diluting the fine fibrous cellulose to a solid content of 0.2% by mass when the fine fibrous cellulose is in the form of a slurry. .. After 24 hours or more have passed after diluting the fine cellulose-containing composition, heating is performed by heating at 95 ° C. for 1 hour, and the change in yellow index before and after heating is measured.
The solvent at the time of measuring the yellow index preferably contains at least water, and the content of water in the entire solvent is preferably 50% by mass or more, more preferably 70% by mass or more, and further preferably 90. It is 5% by mass or more, particularly preferably 95% by mass or more, and may be 100% by mass.
When the fine fibrous cellulose-containing composition is in the form of a sheet, the sheet-like fine fibrous cellulose-containing composition is heated at 200 ° C. for 4 hours, and in accordance with JIS K 7373: 2006, yellow before and after heating. Measure the change in the index.
Further, when the fine fibrous cellulose-containing composition is in the form of powder, a tablet molding compressor (BRE-30, manufactured by Maekawa Testing Machine Mfg. Co., Ltd.) is used so that the powder has a basis weight of 3000 g / m ^2. It is press-molded at a surface pressure of 600 MPa for 1 minute to obtain pellets for measuring yellowness. The obtained pellets are heated at 200 ° C. for 4 hours, and the yellowness before and after heating the pellets is measured by reflected light measurement using a spectrophotometer (Spectroeye, manufactured by Gretag Macbeth) in accordance with ASTM E313. ..

The form of the fine fibrous cellulose-containing composition is not particularly limited, and examples thereof include liquid substances such as slurries, solid substances such as powders and granules, and gel-like substances.
(Slurry)
When the fine fibrous cellulose-containing composition is a slurry, the content of the fine fibrous cellulose contained in the fine fibrous cellulose-containing composition is 0.1% by mass with respect to the total mass of the fine fibrous cellulose-containing composition. It is preferably 5.0% by mass or more, more preferably 0.3% by mass or more and 3.0% by mass or less, and further preferably 0.5% by mass or more and 3.0% by mass or less. .. By setting the content of the fine fibrous cellulose in the above range, the characteristics of the fine fibrous cellulose can be easily exhibited.
When the fine fibrous cellulose-containing composition is a slurry and the solvent contained in the fine fibrous cellulose-containing composition is water, the content of the solvent is preferable with respect to the total mass of the fine fibrous cellulose-containing composition. Is 60% by mass or more, more preferably 90% by mass or more, still more preferably 97% by mass or more, and preferably 99.9% by mass or less, more preferably 99.7% by mass or less, still more preferably 99.5% by mass. It is mass% or less. By setting the content of the solvent in the above range, a suitable viscosity can be obtained.

(Solid or gel)
When the fine fibrous cellulose-containing composition is a solid or gel, the content of the fine fibrous cellulose contained in the fine fibrous cellulose-containing composition is, for example, the total mass of the fine fibrous cellulose-containing composition. On the other hand, it is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and particularly preferably 20% by mass or more. When the fine fibrous cellulose-containing composition is a solid or gel, the upper limit of the content of the fine fibrous cellulose contained in the fine fibrous cellulose-containing composition is not particularly limited, but is, for example, 99. It can be 5.5% by mass. By setting the content of the fine fibrous cellulose in the above range, a fine fibrous cellulose-containing composition having more excellent handleability can be obtained.

When the fine fibrous cellulose-containing composition is a solid or gel, the content of the solvent contained in the fine fibrous cellulose-containing composition is, for example, 90 with respect to the total mass of the fine fibrous cellulose-containing composition. It is preferably 5% by mass or less, more preferably 85% by mass or less, further preferably 80% by mass or less, and particularly preferably 70% by mass or less. By setting the upper limit of the content of the solvent contained in the fine fibrous cellulose-containing composition within the above range, a fine fibrous cellulose-containing composition having excellent handleability can be obtained. On the other hand, the lower limit of the content of the solvent contained in the fine fibrous cellulose-containing composition is not particularly limited and may be, for example, 0% by mass. In the present embodiment, the content of the solvent contained in the fine fibrous cellulose-containing composition can be, for example, 0.5% by mass or more with respect to the total mass of the fine fibrous cellulose-containing composition.
When the fine fibrous cellulose-containing composition is a solid substance or a gel-like substance, the fine fibrous cellulose-containing composition may contain, for example, a concentrating agent used in a concentration step described later. For example, when the concentrating agent is a metal component, the content of the metal component in the fine fibrous cellulose-containing composition is preferably 1.0% by mass or less, more preferably 0.3% by mass or less. , 0.15% by mass or less, and particularly preferably 0.1% by mass or less. When the concentrating agent is a metal component, the lower limit of the content of the metal component in the fine fibrous cellulose-containing composition is not particularly limited, but can be, for example, 0.0001% by mass. By setting the content of the metal component in the above range, a fine fibrous cellulose-containing composition having excellent redispersibility in a predetermined dispersion medium such as water can be obtained.

When the fine fibrous cellulose-containing composition is in the form of powder (powder or granular material), the fine fibrous cellulose-containing composition contains one or both of the powdery material and the granular material. Here, the powdery substance is smaller than the granular substance. Generally, the powdery substance refers to fine particles having a particle diameter of 1 nm or more and less than 0.1 mm. Further, the granular material refers to particles having a particle diameter of 0.1 mm or more and 10 mm or less. The particle size of the powder or granular material can be measured and calculated using, for example, a laser diffraction method. The measurement by the laser diffraction method can be performed using, for example, a laser diffraction / scattering type particle size distribution measuring device (Microtrac 3300EXII, Nikkiso Co., Ltd.).

The fine fibrous cellulose-containing composition, which is a solid or gel, can be used as a redispersion slurry redispersed in a solvent such as water. The type of solvent used to obtain such a redispersion slurry is not particularly limited, and examples thereof include water, an organic solvent, and a mixture of water and an organic solvent. Examples of the organic solvent include alcohols, polyhydric alcohols, ketones, ethers, esters, hydrocarbons, halogens, aprotonic polar solvents and the like. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, isobutyl alcohol and the like. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of ketones include acetone, methyl ethyl ketone (MEK) and the like. Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether and the like. Examples of the esters include ethyl acetate, butyl acetate and the like. Examples of hydrocarbons include n-hexane, toluene, xylene and the like. Examples of halogens include methylene chloride, trichlorethylene, chloroform and the like. Examples of the aprotonic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

(Sheet)
In the present invention, the fine fibrous cellulose-containing composition may be in the form of a sheet.
In the present embodiment, for example, a sheet can be obtained by carrying out the sheet forming step described later using the above-mentioned liquid material fine fibrous cellulose-containing composition.
The content of the fine fibrous cellulose in the sheet is, for example, preferably 0.5% by mass or more, more preferably 1% by mass or more, and 5% by mass or more, based on the total mass of the sheet. It is more preferable, and it is particularly preferable that it is 10% by mass or more. On the other hand, the upper limit of the content of the fine fibrous cellulose in the sheet is not particularly limited, and may be 100% by mass or 95% by mass with respect to the total mass of the sheet.
In particular, from the viewpoint of obtaining a sheet having excellent mechanical strength, the content of the fine fibrous cellulose in the sheet is preferably, for example, 60% by mass or more, more preferably 70% by mass or more, and 80% by mass. It is more preferably% or more, and particularly preferably 90% by mass or more.
Further, from the viewpoint of including a large amount of other materials such as a water-soluble polymer in the sheet, the content of the fine fibrous cellulose in the sheet is preferably 50% by mass or less, for example.

The sheet may contain, for example, a water-soluble polymer. As a result, the transparency and mechanical strength of the sheet can be further improved. As the water-soluble polymer, for example, those described above can be used.
The content of the water-soluble polymer in the sheet is, for example, preferably 1% by mass or more, more preferably 5% by mass or more, and preferably 10% by mass or more, based on the total mass of the sheet. More preferred. As a result, a sheet having excellent transparency and mechanical properties can be obtained. On the other hand, the content of the water-soluble polymer in the sheet is preferably, for example, 99.5% by mass or less, and more preferably 95% by mass or less, based on the total mass of the sheet.

In addition to fine fibrous cellulose, proteases or proteins derived from proteases, and water-soluble polymers, the sheets include, for example, surfactants, organic ions, coupling agents, inorganic layered compounds, inorganic compounds, leveling agents, preservatives, etc. One or two selected from defoaming agents, organic particles, lubricants, antistatic agents, UV protection agents, dyes, pigments, stabilizers, magnetic powders, orientation promoters, plasticizers, dispersants, and cross-linking agents. It may contain more than a seed.
The sheet may contain a solvent. As the solvent, for example, those described above can be used.
The content of the solvent in the sheet is, for example, preferably 0.5% by mass or more, more preferably 1% by mass or more, and further preferably 5% by mass or more, based on the total mass of the sheet. preferable. This makes it possible to impart flexibility to the sheet. On the other hand, the content of the solvent in the sheet is, for example, preferably 25% by mass or less, and more preferably 15% by mass or less, based on the total mass of the sheet. Thereby, a sheet having good flexibility can be obtained.
The content of the solvent in the sheet can be calculated, for example, by the following procedure. First, a 100 mm square sheet is humidity-controlled for 24 hours under the conditions of a temperature of 23 ° C. and a relative humidity of 50%, and then the mass W ₀ of the sheet is measured. Then, after the sheet is dried for 16 hours at 105 ° C. in a constant temperature dryer, measuring the mass W ₁ of the sheet. From the measured mass, the content of the solvent in the sheet is calculated according to the following formula (4).
Solvent content in the sheet = 100 × (1-W ₁ / W ₀ ) Equation (4)

The tensile elastic modulus of the sheet is, for example, preferably 2.5 GPa or more, more preferably 3.0 GPa or more, and further preferably 3.5 GPa or more. The upper limit of the tensile elastic modulus of the sheet is not particularly limited, but may be, for example, 50 GPa or less.
Here, the tensile elastic modulus of the sheet is, for example, a value measured using a tensile tester Tensilon (manufactured by A & D Co., Ltd.) in accordance with JIS P 8113: 2006. When measuring the tensile elastic modulus, a test piece prepared at 23 ° C. and 50% relative humidity for 24 hours is used as a test piece for measurement, and the measurement is performed under the conditions of 23 ° C. and 50% relative humidity.
The haze of the sheet is, for example, preferably 2% or less, more preferably 1.5% or less, and even more preferably 1% or less. On the other hand, the lower limit of the haze of the sheet is not particularly limited and may be, for example, 0%. Here, the haze of the sheet is, for example, a value measured using a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute Co., Ltd.) in accordance with JIS K 7136: 2000.
The total light transmittance of the sheet is, for example, preferably 85% or more, more preferably 90% or more, and further preferably 91% or more. On the other hand, the upper limit of the total light transmittance of the sheet is not particularly limited and may be, for example, 100%. Here, the total light transmittance of the sheet is a value measured using, for example, JIS K 7361-1: 1997 and a haze meter (HM-150, manufactured by Murakami Color Technology Research Institute Co., Ltd.).

The thickness of the sheet is not particularly limited, but is preferably, for example, 5 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more. The upper limit of the thickness of the sheet is not particularly limited, but may be, for example, 1000 μm. The thickness of the sheet can be measured, for example, with a stylus type thickness gauge (Millitron 1202D manufactured by Marl).
The basis weight of the sheet is not particularly limited, but is preferably 10 g / m ² or more, more preferably 20 g / m ² or more, and further preferably 30 g / m ² or more. The basis weight of the sheet is not particularly limited, but is preferably 100 g / m ² or less, more preferably 80 g / m ² or less, for example. Here, the basis weight of the sheet can be calculated in accordance with, for example, JIS P 8124: 2011.
The density of the sheet is not particularly limited, but is preferably 0.1 g / cm ³ or more, more preferably 0.5 g / cm ³ or more, and further preferably 1.0 g / cm ³ or more. preferable. The density of the sheet is not particularly limited, but is preferably 5.0 g / cm ³ or less, and more preferably 3.0 g / cm ³ or less, for example. Here, the density of the sheet can be calculated by measuring the thickness and mass of the sheet after adjusting the humidity of a 50 mm square sheet under the conditions of 23 ° C. and 50% RH for 24 hours.

[Method for producing fine fibrous cellulose-containing composition]
In the present invention, the above-mentioned fine fibrous cellulose-containing composition having a phosphorous acid group is preferably produced by a method having the following steps 1 and 2 in this order.
Step 1: A step of defibrating the fibrous cellulose in the solvent to obtain a dispersion liquid containing the fine fibrous cellulose, and a step 2: a step of adding a protease to the dispersion liquid containing the fine fibrous cellulose. In the present invention, the protease added in step 2 is preferably endopeptidase as described above. The amount of the enzyme to be added is preferably 0.001 U or more, more preferably 0.005 U or more, more preferably 0.005 U or more, relative to 1 mg of the fine fibrous cellulose, from the viewpoint of suppressing yellowing of the fine fibrous cellulose-containing composition. It is preferably 0.01 U or more, and is preferably 10 U or less, more preferably 1 U or less, still more preferably 0.5 U or less, from the viewpoint of economy and suppression of excessive addition of the protein protease.

In step 1, the step of obtaining a dispersion liquid containing fine fibrous cellulose is a step of introducing a phosphite group into a fiber raw material containing cellulose, as described in the method for producing fine fibrous cellulose. , The cleaning step, the alkali treatment step (neutralization step), and the defibration treatment step are preferably provided in this order, and an acid treatment step may be provided instead of or in addition to the cleaning step. Further, a pretreatment step may be provided before the phosphite group introduction step. Therefore, in the present invention, the fine fibrous cellulose in the dispersion liquid containing the fine fibrous cellulose obtained in step 1 has a phosphite group.

In step 2, a protease is added to the dispersion containing the fine fibrous cellulose. The pH at the time of addition is not particularly limited, but from the viewpoint of obtaining high enzymatic activity, the optimum pH of the protease to be added is preferably ± 3, more preferably the optimum pH of the protease to be added ± 2, and more preferably the protease to be added. The optimum pH is ± 1.
The pH of the dispersion to which the protease is added is preferably 3 or more, more preferably 4 or more, still more preferably 5 or more, and preferably 12 or less, more preferably 11 or less, still more preferably 10 or less.
Further, the temperature of the dispersion liquid at the time of treatment with protease in step 2 depends on the optimum temperature of the enzyme, but for example, from the viewpoint of obtaining high enzyme activity, it is preferably 10 ° C. or higher, more preferably 15 ° C. or higher. It is more preferably 20 ° C. or higher, and preferably 80 ° C. or lower, more preferably 70 ° C. or lower, still more preferably 60 ° C. or lower.
The treatment time with the protease in the step 2 may be appropriately selected depending on the temperature, the amount of the enzyme added, and the like, but is preferably 3 minutes or longer, more preferably 10 minutes or longer, and further preferably 15 minutes or longer. As described above, the protease does not need to be inactivated, and the upper limit of the treatment time is not particularly limited.

The fine fibrous cellulose-containing composition of the present invention can be used for various purposes, for example, as a thickener. Further, it can be mixed with a resin or an emulsion and used as a reinforcing material, or a film may be formed using a slurry of a fine fibrous cellulose-containing composition to prepare various sheets. Sheets are suitable for applications of light transmissive substrates such as various display devices, various solar cells, and the like. It is also suitable for applications such as substrates for electronic devices, materials for home appliances, window materials for various vehicles and buildings, interior materials, exterior materials, and packaging materials. Further, it is suitable for applications where the sheet itself is used as a reinforcing material in addition to threads, filters, woven fabrics, cushioning materials, sponges, and abrasives.

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

<Manufacturing example 1>
As raw material pulp, softwood kraft pulp manufactured by Oji Paper Co., Ltd. (solid content 93% by mass, basis weight 245 g / m ² sheets, disintegrated and measured according to JIS P 811-2: 2012 Canadian standard drainage degree (CSF) is 700 mL) was used. Subphosphorylation treatment was carried out on this raw material pulp as follows. First, a mixed aqueous solution of phosphorous acid (phosphonic acid) and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to add 33 parts by mass of phosphorous acid (phosphonic acid), 120 parts by mass of urea, and 150 parts of water. The amount was adjusted to be parts by mass, and a chemical-impregnated pulp was obtained. Next, the obtained chemical-impregnated pulp was heated in a hot air dryer at 165 ° C. for 250 seconds to introduce a phosphorous acid group into the cellulose in the pulp to obtain a phosphorylated pulp.

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

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

Next, the subphosphorylated pulp after the neutralization treatment was subjected to the above washing treatment. The infrared absorption spectrum of the obtained subphosphorylated pulp was measured using FT-IR. As a result, absorption of the phosphonic acid group, which is a tautomer of the phosphite group, based on P = O was observed around 1210 cm- ¹ , and it was confirmed that the phosphite group was added to the pulp. Further, when the obtained subphosphorylated pulp was tested and analyzed by an X-ray diffractometer, two positions were found: 2θ = 14 ° or more and 17 ° or less and 2θ = 22 ° or more and 23 ° or less. A typical peak was confirmed in the cellulose type I crystal, and it was confirmed that the cellulose type I crystal was present.

(Defibration treatment)
Ion-exchanged water was added to the subphosphorylated pulp obtained through the above alkali treatment step and stirred to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated four times at a pressure of 200 MPa with a wet atomizing device (manufactured by Sugino Machine Limited, Starburst) to obtain a fine fibrous cellulose dispersion (A) containing fine fibrous cellulose.

By X-ray diffraction, it was confirmed that this fine fibrous cellulose maintained the cellulose type I crystal. Moreover, when the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, it was 3 to 5 nm. Further, the amount of phosphite group (first dissociated acid amount) measured by the measuring method described later was 1.51 mmol / g. The total amount of dissociated acid was 1.54 mmol / g.

(Measurement of phosphorus oxo acid group amount)
The amount of phosphite groups in the fine fibrous cellulose is a fine particle prepared by diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion exchange water so that the content is 0.2% by mass. The fibrous cellulose-containing slurry was treated with an ion exchange resin and then titrated with an alkali for measurement.
For the treatment with the ion exchange resin, a strongly acidic ion exchange resin (Amberjet 1024; manufactured by Organo Co., Ltd., conditioned) having a volume of 1/10 was added to the fine fibrous cellulose-containing slurry, and the mixture was shaken for 1 hour. After that, it was poured onto a mesh having a mesh size of 90 μm to separate the resin and the slurry, and the phosphoroxo acid group was converted into an acid type.
In the titration using alkali, the pH value indicated by the slurry is changed while adding 10 μL of 0.1 N sodium hydroxide aqueous solution to the fine fibrous cellulose-containing slurry treated with the ion exchange resin every 5 seconds. Was performed by measuring. The titration was carried out while blowing nitrogen gas into the slurry from 15 minutes before the start of the titration.
In this neutralization titration, two points were given where the increment (differential value of pH with respect to the amount of alkali dropped) was maximized in the curve plotting the measured pH with respect to the amount of alkali added. Of these, the maximum point of the increment obtained first when alkali is added is called the first end point, and the maximum point of the increment obtained next is called the second end point. The amount of alkali required from the start of the titration to the first end point is equal to the amount of the first dissociated acid in the slurry used for the titration. Further, the amount of alkali required from the start of titration to the second end point becomes equal to the total amount of dissociated acid in the slurry used for titration. The amount of alkali (mmol) required from the start to the first end point of titration divided by the solid content (g) in the slurry to be titrated is the amount of first dissociated acid (mmol / g) of the phosphite group. The amount was (mmol / g). Further, the value obtained by dividing the amount of alkali (mmol) required from the start of titration to the second end point by the solid content (g) in the slurry to be titrated was defined as the total amount of dissociated acid (mmol / g).

(Measurement of fiber width of fine fibrous cellulose)
The fiber width of the fine fibrous cellulose was measured by the following method.
The supernatant of the fine fibrous cellulose dispersion obtained by treatment with a wet atomizing device is mixed with water so that the concentration of the fine fibrous cellulose is 0.01% by mass or more and 0.1% by mass or less. It was added dropwise to the diluted and hydrophilized carbon grid film. This was dried, stained with uranyl acetate, and observed with a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.).

<Example 1>
The solid content concentration of the fine fibrous cellulose dispersion (A) was adjusted to 2% by mass. Protease was added to this dispersion so as to be 0.01 U per 1 mg of fine fibrous cellulose, and the mixture was stirred to obtain a composition containing fine fibrous cellulose and protease.

<Example 2>
A composition containing the fine fibrous cellulose and the protease was obtained in the same manner as in Example 1 except that the amount of the protease added was changed to 0.5 U per 1 mg of the fine fibrous cellulose.

<Example 3>
The dispersion liquid containing the fine fibrous cellulose and protease obtained in Example 1 was applied to a polycarbonate plate using a film applicator so that the coating amount was 3750 g / m ^2, and dried at 100 ° C. for about 1 hour. .. As a result, a sheet composed of fine fibrous cellulose and protease having a basis weight of 75 g / m ² and a thickness of 50 μm was obtained.

<Comparative example 1>
In Example 1, a composition containing fine fibrous cellulose was obtained in the same manner as in Example 1 except that no protease was added.

<Comparative example 2>
In Example 3, all of the same as in Example 3 except that the composition containing the fine fibrous cellulose obtained in Comparative Example 1 was used instead of the composition containing the fine fibrous cellulose obtained in Example 1 and the protease. A sheet made of fine fibrous cellulose was obtained in the same manner.

(Measurement of viscosity of fine fibrous cellulose-containing composition)
The viscosity of the fine fibrous cellulose-containing composition was measured as follows. First, the fine fibrous cellulose-containing composition is diluted with ion-exchanged water so that the solid content concentration becomes 0.4% by mass, and then stirred at 1500 rpm for 5 minutes with a disperser at 23 ° C. and relative humidity before measurement. It was allowed to stand in a 50% environment for 24 hours. Next, the viscosity of the fine fibrous cellulose-containing composition thus obtained was measured using a B-type viscometer (analog viscometer T-LVT manufactured by BLOOKFIELD). The measurement conditions were a rotation speed of 3 rpm, and the viscosity value 3 minutes after the start of measurement was taken as the viscosity of the composition. The liquid temperature of the composition at the time of measurement was 23 ° C.

(Measurement of specific viscosity of fine fibrous cellulose-containing composition)
The specific viscosity of the fine fibrous cellulose-containing composition was measured according to Tappi T230. That is, the viscosity of the fine fibrous cellulose-containing composition to be measured (η ₁ (unit: cP)) and the blank viscosity measured only with the medium excluding the fine fibrous cellulose (η ₀ (unit: cP)). ) Was measured, and then the specific viscosity (η _sp ) and the intrinsic viscosity ([η] (unit: mL / g)) were measured according to the following formulas.
η _sp = (η ₁ / η ₀ ) -1
[Η] = η _{sp / (} c (1 + 0.28 × η _sp ))
Here, c in the formula indicates the concentration (g / mL) of fine fibrous cellulose at the time of viscosity measurement.

(Measurement of polymerization degree of fine fibrous cellulose)
The degree of polymerization of the fine fibrous cellulose was measured according to Tappi T230. The degree of polymerization (DP) of the fine fibrous cellulose was calculated from the following formula.
DP = 1.75 x [η]
Since this degree of polymerization is the average degree of polymerization measured by the viscosity method, it is sometimes called "viscosity average degree of polymerization".

(Change in yellowness (yellow index) before and after heating of fine fibrous cellulose-containing composition)
The fine fibrous cellulose-containing composition was diluted with ion-exchanged water so that the solid content concentration was 0.2% by mass, and adjusted by appropriately stirring with a magnetic stirrer. After that, the diluted solution was placed in a glass cell for liquid with an optical path length of 1 cm (manufactured by Fujiwara Seisakusho Co., Ltd., MC-40, backlit path), measured in accordance with JIS K 7373: 2006, and Color Cutei (Suga Test Instruments Co., Ltd.) Measured by company). The change in yellowness ΔYI before and after heating was calculated by the following equation.
ΔYI = YI ₂ -YI ₁
Here, YI ₁ is the yellowness of the fine fibrous cellulose dispersion immediately after production, and YI ₂ is 95 ° C. after preparing the fine fibrous cellulose-containing compositions described in Examples and Comparative Examples and allowing at least 24 hours to elapse. Shows the yellowness after heating for 1 hour.

(Yellowness before and after heating the sheet)
In accordance with JIS K 7373: 2006, the yellowness of the sheet before and after heating was measured using Color Cutei (manufactured by Suga Test Instruments Co., Ltd.). The yellowness after heating was the yellowness of the sheet vacuum-dried at 200 ° C. for 4 hours. Further, ΔYI was calculated as the amount of change in yellowness from the following formula.
ΔYI = YI ₄ -YI ₃
Here, YI ₃ represents the yellowness of the sheet before heating, and YI ₄ represents the yellowness of the sheet after heating.

In Examples 1 and 2 to which an appropriate amount of protease, which is a substance degrading a protein, was added, the numerical value of ΔYI decreased as compared with Comparative Example 1 (Comparative Example 1:47, Example 1:12, Example 2:24). .. It is considered that this is because the protein mixed in the production process of the fine fibrous cellulose was decomposed by the protease and the cause of yellowing was eliminated. Furthermore, the amount of protease added in Examples 1 and 2 was not large enough to increase the YI of the fine fibrous cellulose dispersion, and it is presumed that the increase in YI by the protease itself was slight.
In Examples 1 to 3, ΔYI was 30 or less. On the other hand, in Comparative Examples 1 and 2 to which no protease was added, the value of ΔYI exceeded 30. This is thought to be due to the protein mixed in the fine fibrous cellulose.
Further, in Example 3, the composition composed of the fine fibrous cellulose obtained in Example 1 and the protease was used as a raw material, and the composition was dried to obtain a sheet containing the fine fibrous cellulose. When YI was measured before and after heating the sheet and ΔYI was determined, ΔYI remained at 30 or less.
Comparative Example 2 is obtained by preparing a film using the fine fibrous cellulose of Comparative Example 1 as a raw material and measuring YI. In Comparative Example 2, ΔYI exceeded 30. Similar to Comparative Example 1, the protein mixed in the fine fibrous cellulose is considered to be the cause of the coloring.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a fine fibrous cellulose-containing composition in which the degree of coloring due to heating is suppressed. Conventional fine fibrous cellulose may cause yellowing due to, for example, heating when mixed with the composition or exposure to high temperature during hot pressing, which may spoil the appearance of the final product. It was an issue.
The present invention solves these problems, and is expected to be used in various applications such as screens for inks, cosmetics, foods, and electronic devices in which good color development and appearance are particularly important.

Claims (9)

It contains fine fibrous cellulose having a phosphite group having a fiber width of 1,000 nm or less, and a protease or a protein derived from the protease.
Fine fibrous cellulose-containing composition. The fine fibrous cellulose-containing composition according to claim 1, wherein the degree of polymerization of the fine fibrous cellulose is 505 or more and 700 or less. The viscosity of fine fibrous cellulose is 1.5 x 10 ³ mPa · s or more 3.0 × 10 ⁴ The fine fibrous cellulose-containing composition according to claim 1 or 2, which is mPa · s or less. The fine fibrous cellulose-containing composition according to any one of claims 1 to 3 , wherein the change in the yellow index upon heating is 30 or less. The fine fibrous cellulose-containing composition according to any one of claims 1 to 4 , which is in the form of a slurry. The fine fibrous cellulose-containing composition according to any one of claims 1 to 4 , which is in the form of a powder. The fine fibrous cellulose-containing composition according to any one of claims 1 to 4 , which is in the form of a sheet. The step of defibrating the fibrous cellulose having a phosphite group in the solvent to obtain a dispersion liquid containing the fine fibrous cellulose and the step of adding a protease to the dispersion liquid containing the fine fibrous cellulose are performed. Have in order,
A method for producing a fine fibrous cellulose-containing composition. The method for producing a fine fibrous cellulose-containing composition according to claim 8 , wherein the amount of protease added to 1 mg of fine fibrous cellulose is 0.001 U or more and 10 U or less.