JP6575700B1 - Sheet - Google Patents

Abstract

An object of the present invention is to provide a wet sheet containing fine fibrous cellulose that is easy to handle during use and has excellent adhesion to the skin. The present invention is a sheet containing fibrous cellulose having a fiber width of 1000 nm or less and water, the sheet is in a gel form, and the fibrous cellulose is a phosphite group or a phosphite group. The content of moisture is related to a sheet having a moisture content of 70% by mass or more and a tensile strength of 0.08 MPa or more with respect to the total mass of the sheet. [Selection figure] None

Description

  The present invention relates to a sheet. Specifically, the present invention relates to a wet sheet containing fine fibrous cellulose.

  Conventionally, a beauty sheet in which a nonwoven fabric containing cellulose fibers is impregnated with a cosmetic ingredient or the like is known. Such a beauty sheet is mounted along, for example, the unevenness of a human face, and is used to enhance the skin beauty effect. Generally, a beauty sheet is commercially available in a form packaged in a packaging container in a state in which a cosmetic material such as a cosmetic liquid is impregnated into a sheet made of a nonwoven fabric or the like.

  When using a beauty sheet, it is preferable that the sheet is in close contact with the skin and that the cosmetic component can be permeated. For example, Patent Document 1 discloses a cellulose fiber nonwoven fabric for a face mask having a Sin curve pattern and having a ratio of wavelength to amplitude and a formation index within a predetermined range. Here, the ratio of wavelength and amplitude and the formation index are adjusted by applying pure water and high-pressure water entanglement in the process of manufacturing the nonwoven fabric for face masks, which makes the adhesion between the skin and the nonwoven fabric high and makes the chemical solution uniform. It is said that a non-woven fabric for face mask that can be transferred to the skin is obtained. Patent Document 2 discloses a sheet-like cosmetic containing biocellulose and a water component having a high refractive index. Here, it is said that by using biocellulose and a high refractive index water-soluble component, a cosmetic sheet that is transparent in appearance and can visually recognize the effect of improving the skin condition during use is obtained.

  In addition, cosmetic sheets are also required to have a characteristic that the cosmetic components impregnated during use are less likely to evaporate. For example, Patent Document 3 discloses a laminated nonwoven fabric obtained by laminating an ultrafine synthetic fiber layer containing ultrafine fibers and a hydrophilic fiber layer. Patent Document 4 discloses a chemical liquid-impregnated sheet in which a fine cellulose fiber nonwoven fabric layer is laminated on one surface or both surfaces of a nonwoven fabric containing cellulosic fibers. Thus, improving the liquid retention performance of cosmetic ingredients by adjusting the fiber type and fiber diameter of each layer constituting the beauty sheet has been studied.

JP 2017-150110 A JP 2014-1111639 A JP 2005-124916 A JP 2014-205924 A

For example, a wet sheet such as a beauty sheet is desired to be easy to handle without tearing. Further, depending on the use of the wet sheet, it is also required to flexibly follow the unevenness of the face and to exhibit excellent adhesion. As described above, the wet sheet is required to satisfy both ease of handling and excellent adhesion, but the wet sheet of the prior art has room for improvement in these performances.
Therefore, in order to solve such problems of the prior art, the present inventors have studied for the purpose of providing a wet sheet that is easy to handle at the time of use and has excellent adhesion to the skin.

As a result of intensive studies to solve the above problems, the present inventors have used fine fibrous cellulose as a constituent material of the wet sheet, and the moisture content and tensile strength of the wet sheet are not less than a predetermined value. As a result, it was found that a gel-like wet sheet that is easy to handle during use and excellent in adhesion to the skin can be obtained.
Specifically, the present invention has the following configuration.

[1] A sheet comprising fibrous cellulose having a fiber width of 1000 nm or less and water,
The sheet is gel-like,
Fibrous cellulose has a substituent derived from a phosphite group or a phosphite group,
The moisture content is 70% by mass or more based on the total mass of the sheet,
A sheet having a tensile strength of 0.08 MPa or more.
[2] The sheet according to [1], wherein the fibrous cellulose has a fiber width of 8 nm or less.
[3] The sheet according to [1] or [2], wherein the tensile elastic modulus is 0.5 MPa or more.
[4] The sheet according to any one of [1] to [3], wherein the elongation is 5.0% or more.
[5] The sheet according to any one of [1] to [4], wherein the haze is 20.0% or less.
[6] The sheet according to any one of [1] to [5], wherein the density of the sheet in an absolutely dry state is 0.5 g / cm ³ or more.
[7] The sheet according to any one of [1] to [6], further containing a resin component.
[8] The sheet according to any one of [1] to [7], further containing an external preparation for skin.
[9] The sheet according to any one of [1] to [8], which is for a beauty sheet.

  ADVANTAGE OF THE INVENTION According to this invention, the gel-like wet sheet which is easy to handle at the time of use, and was excellent in the adhesiveness with respect to skin is obtained.

FIG. 1 is a graph showing the relationship between the amount of NaOH dropped and the pH with respect to a fibrous cellulose-containing slurry having a phosphorus oxo acid group.

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

(Wet sheet containing fine fibrous cellulose)
The present invention relates to a gel-like sheet containing fibrous cellulose having a fiber width of 1000 nm or less and water. Here, fibrous cellulose has a phosphite group or a substituent derived from a phosphite group. Further, the moisture content of the sheet is 70% by mass or more with respect to the total mass of the sheet, and the tensile strength of the sheet is 0.08 MPa or more.
In the present specification, fibrous cellulose having a fiber width of 1000 nm or less may be referred to as fine fibrous cellulose. Moreover, in this specification, a gel-like sheet | seat may be called a wet sheet or a fine fibrous cellulose containing wet sheet.

  Since the sheet | seat of this invention has the said structure, it is easy to handle at the time of use and is excellent also in the adhesiveness with respect to skin. Specifically, since the sheet of the present invention is a sheet having appropriate elongation and strength, it can be easily mounted along an uneven structure such as a face. Further, in the sheet of the present invention, it is easy to visually recognize the air bubbles entrained between the sheet and the object to be adhered, and the air entrained air bubbles can be easily removed, so that the sheet is brought into close contact with the object to be adhered. Cheap. Furthermore, since the sheet of the present invention is kept in close contact with the object to be adhered after being mounted, even if the concavo-convex structure moves, a part of the sheet does not float or peel off. Thus, the sheet of the present invention combines ease of handling and excellent adhesion. In the present specification, the state of excellent adhesion means that the initial adhesion that allows adhesion between the sheet and the adherend without interposing bubbles is good, and that the state of adhesion after attachment can be maintained. This refers to a state where adhesion durability can be exhibited.

  In order to obtain a wet sheet having the above-described configuration, for example, it is preferable to appropriately select the sheet composition and manufacturing process. For example, obtaining a wet sheet by applying water to a fine fibrous cellulose-containing sheet once dried is one aspect of a process capable of realizing the above-described configuration. It is considered that this is because once the fine fibrous cellulose-containing sheet is dried to a wet state, water can be uniformly distributed in the sheet, and the above-described configuration is satisfied.

  In one embodiment of the present invention, it is also preferable to obtain a wet sheet in which fine fibrous cellulose is crosslinked with a metal salt. In this case, in order to obtain a wet sheet having the above-described configuration, it is preferable to adjust the degree of crosslinking to an appropriate range by adjusting the crosslinking reaction time with the metal salt. For example, it is preferable to obtain a wet sheet with a low degree of cross-linking by shortening the immersion time in a solution containing a metal salt. In the wet sheet in which the fine fibrous cellulose is cross-linked with the metal salt, it is possible to suppress the water absorption rate. Therefore, when water is applied to the dried fine fibrous cellulose-containing sheet, The immersion time can be made relatively long. Thus, when the dried fine fibrous cellulose-containing sheet is immersed in water, the immersion time can be given a wide range, and the process management becomes easy.

  The sheet of the present invention is further excellent in transparency. Specifically, the haze of the sheet of the present invention is preferably 20.0% or less, more preferably 15.0% or less, still more preferably 10.0% or less, and 7.5 % Or less, more preferably 6.7% or less, particularly preferably 6.5% or less, and most preferably 6.0% or less. The haze of the sheet is a value measured using, for example, a haze meter (manufactured by Murakami Color Research Laboratory Co., Ltd., HM-150) in accordance with JIS K 7136. Thus, since the sheet of the present invention is also excellent in transparency, even when air bubbles enter between the object to be adhered and the sheet at the time of mounting, the entry of air bubbles can be visually recognized from the sheet side. . As a result, the user of the sheet can perform an operation of bringing the sheet into close contact so as to remove air bubbles, or can be reattached, and as a result, the adhesion between the sheet and the adherend can be more effectively improved. it can.

  The total light transmittance of the sheet of the present invention is preferably 70% or more, more preferably 80% or more, and further preferably 85% or more. In addition, the total light transmittance of a sheet | seat is a value measured using a haze meter (Murakami Color Research Laboratory company make, HM-150) based on JISK7361.

  The sheet of the present invention is a gel sheet. In the present specification, whether a sheet is in a gel form is determined by not dripping from the sheet even when the sheet is pressurized in a state where the moisture content of the wet sheet is 70% by mass or more. Can do. The rubber hardness of the sheet is preferably E1 / 30 or more, and more preferably E5 / 30 or more. The rubber hardness of the sheet is preferably E90 / 30 or less. In general, rubber hardness cannot be measured in a nonwoven fabric sheet. For this reason, when the rubber hardness of the wet sheet is within the above range, the wet sheet and the non-woven sheet of the present invention are distinguished.

  The moisture content of the sheet of the present invention may be 70% by mass or more with respect to the total mass of the sheet, preferably 75% by mass or more, more preferably 80% by mass or more, 85 More preferably, it is at least mass%. Moreover, it is preferable that the moisture content of a sheet | seat is 95 mass% or less with respect to the total mass of a sheet | seat. By setting the moisture content of the sheet within the above range, the adhesion of the wet sheet to the skin can be enhanced.

  The solid content contained in the sheet of the present invention is preferably 5% by mass or more, and more preferably 10% by mass or more with respect to the total mass of the sheet. The solid content is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, and more preferably 15% by mass with respect to the total mass of the sheet. It is particularly preferred that The adhesiveness with respect to the skin of a wet sheet can be improved by making solid content of a sheet into the said range.

  In addition, the moisture content of the sheet of the present invention is preferably 233% by mass or more, more preferably 300% by mass or more, and 400% by mass or more with respect to 100% by mass of the solid content. Is more preferable, and it is especially preferable that it is 565 mass% or more. Moreover, it is preferable that the content rate of a water | moisture content is 1920 mass% or less with respect to 100 mass% of solid content mass. By setting the moisture content of the sheet within the above range, a wet sheet having excellent adhesion to the skin can be obtained.

  The tensile strength of the sheet (wet sheet) of the present invention may be 0.08 MPa or more, preferably 0.1 MPa or more, more preferably 0.2 MPa or more, and 0.4 MPa or more. Is more preferable, and 0.5 MPa or more is particularly preferable. Further, the tensile strength of the sheet (wet sheet) is preferably 10.0 MPa or less, more preferably 8.0 MPa or less, and even more preferably 6.0 MPa or less. By setting the tensile strength of the sheet (wet sheet) within the above range, it becomes easy to attach the sheet to an object to be adhered such as a face at the time of use, and the handleability is improved.

  The tensile elastic modulus of the sheet (wet sheet) of the present invention is preferably 0.5 MPa or more, more preferably 0.8 MPa or more, and further preferably 1.0 MPa or more. Further, the tensile modulus of the sheet (wet sheet) is preferably 50.0 MPa or less, more preferably 40.0 MPa or less, and further preferably 30.0 MPa or less. By setting the tensile elastic modulus of the sheet (wet sheet) within the above range, it becomes easy to attach the sheet to an adherend such as the face during use, and the handleability is improved. Moreover, the adhesiveness to a to-be-adhered object can also be improved more effectively by making the tensile elasticity modulus of a sheet | seat (wet sheet | seat) into the said range.

  The elongation of the sheet (wet sheet) of the present invention is preferably 5.0% or more, more preferably 6.0% or more, still more preferably 7.0% or more. It is particularly preferably 0% or more. Further, the elongation of the sheet (wet sheet) is preferably 50.0% or less, more preferably 40.0% or less, and even more preferably 30.0% or less. By setting the elongation of the sheet (wet sheet) within the above range, it becomes easy to attach the sheet to an adherend such as the face during use, and the handleability is improved. Moreover, the adhesiveness to a to-be-adhered object can also be improved more effectively by making the tensile elasticity modulus of a sheet | seat (wet sheet | seat) into the said range.

  Here, the tensile strength, tensile elastic modulus, and elongation of the sheet are the tensile strength, tensile elastic modulus, and elongation of the gel-like wet sheet. Specifically, the tensile strength, tensile modulus, and elongation of the sheet are measured in accordance with JIS P 8135 with the distance between the grips set to 100 mm after the wet sheet is cut into a width of 25 mm and a length of 150 mm. Value. For the measurement, for example, a tensile tester Tensilon (manufactured by A & D) can be used.

  The content of fibrous cellulose with respect to the solid mass in the sheet of the present invention is preferably 1% by mass or more, more preferably 10% by mass or more, and further preferably 20% by mass or more. Moreover, it is preferable that content of the fibrous cellulose with respect to the solid content mass in a sheet | seat is 90 mass% or less.

  The thickness of the sheet (wet sheet) of the present invention is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more. Further, the thickness of the wet sheet is preferably 2000 μm or less. The thickness of the wet sheet can be measured, for example, by a constant pressure thickness measuring instrument (PG-02J, manufactured by Teflock).

  The thickness of the absolutely dry sheet (dry sheet) obtained by drying the sheet of the present invention is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, More preferably, it is 20 μm or more. Moreover, it is preferable that the thickness of a dry sheet is 1000 micrometers or less. The thickness of the dry sheet can be measured, for example, with a constant pressure thickness measuring instrument (PG-02J, manufactured by Teflock).

The basis weight of the absolutely dry sheet (dried sheet) is preferably 5 g / m ² or more, more preferably 10 g / m ² or more, and further preferably 20 g / m ² or more. The basis weight of the dry sheet is preferably 300 g / m ² or less. Here, the basis weight of the sheet can be calculated in accordance with, for example, JIS P 8124.

The density of the absolutely dry sheet (dry sheet) is preferably 0.5 g / cm ³ or more, more preferably 0.7 g / cm ³ or more, and 1.0 g / cm ³ or more. Is more preferable. Moreover, it is preferable that the density of a dry sheet is 2.0 g / cm < ³ > or less. In addition, the density of a dry sheet is a value calculated from the thickness and basic weight of the dry sheet mentioned above.

(Fine fibrous cellulose)
The sheet of the present invention contains fibrous cellulose having a fiber width of 1000 nm or less and having a phosphite group or a substituent derived from a phosphite group. The fiber width of the fibrous cellulose is preferably 100 nm or less, more preferably 50 nm or less, still more preferably 10 nm or less, and particularly preferably 8 nm or less. The fiber width of the fibrous cellulose can be measured, for example, by observation with an electron microscope.

  The average fiber width of fibrous cellulose is, for example, 1000 nm or less. The average fiber width of the fibrous cellulose is, for example, preferably 2 nm or more and 1000 nm or less, more preferably 2 nm or more and 100 nm or less, further preferably 2 nm or more and 50 nm or less, and more preferably 2 nm or more and 10 nm or less. More preferably, it is particularly preferably 2 nm or more and 8 nm or less. By making the average fiber width of fibrous cellulose 2 nm or more, it is possible to suppress dissolution in water as cellulose molecules, and to more easily express the effects of improving strength, rigidity, and dimensional stability due to fibrous cellulose. it can. The fibrous cellulose is, for example, monofilamentous cellulose.

The average fiber width of fibrous cellulose is measured as follows using, for example, an electron microscope. First, an aqueous suspension of fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less is prepared, and this suspension is cast on a carbon film-coated grid subjected to a hydrophilization treatment, and a sample for TEM observation. And When a wide fiber is included, an SEM image of the surface cast on glass may be observed. Next, observation with an electron microscope image is performed at a magnification of 1000 times, 5000 times, 10000 times, or 50000 times depending on the width of the fiber to be observed. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicular to the straight line is drawn in the same image, and 20 or more fibers intersect the straight line Y.
The width of the fiber that intersects with the straight line X and the straight line Y is visually read from the observation image that satisfies 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. Thereby, at least 20 fibers × 2 × 3 = 120 fiber widths are read. And let the average value of the read fiber width be an average fiber width of fibrous cellulose.

  The fiber length of the fibrous cellulose is not particularly limited, but is preferably 0.1 μm or more and 1000 μm or less, more preferably 0.1 μm or more and 800 μm or less, and further preferably 0.1 μm or more and 600 μm or less. preferable. By setting the fiber length within the above range, the destruction of the crystalline region of fibrous cellulose can be suppressed. Moreover, it becomes possible to make the slurry viscosity of fibrous cellulose into an appropriate range. In addition, the fiber length of fibrous cellulose can be calculated | required by the image analysis by TEM, SEM, and AFM, for example.

  The fibrous cellulose preferably has an I-type crystal structure. Here, it can be identified in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418Å) monochromatized with graphite that the fibrous cellulose has an I-type crystal structure. Specifically, it can be identified by having typical peaks at two positions of 2θ = 14 ° to 17 ° and 2θ = 22 ° to 23 °.

  The proportion of the I-type crystal structure in the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and further preferably 50% or more. Thereby, further superior performance can be expected in terms of heat resistance and low coefficient of thermal expansion. The degree of crystallinity is obtained by measuring an X-ray diffraction profile and determining the crystallinity by a conventional method (Seagal et al., Textile Research Journal, 29, 786, 1959).

  The axial ratio (fiber length / fiber width) of fibrous cellulose is not particularly limited, but is preferably 20 or more and 10000 or less, and more preferably 50 or more and 1000 or less. By setting the axial ratio to be equal to or more than the above lower limit value, it is easy to form a sheet containing fine fibrous cellulose. In addition, sufficient viscosity is easily obtained when a solvent dispersion is produced. By setting the axial ratio to be equal to or less than the above upper limit value, for example, when handling fibrous cellulose as an aqueous dispersion, it is preferable in terms of easy handling such as dilution.

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

  Fibrous cellulose has a phosphite group or a substituent derived from a phosphite group (also simply referred to as a phosphite group). When the fibrous cellulose has a phosphite group, a highly transparent sheet is easily obtained.

In the present invention, the phosphite group or the substituent derived from the phosphite group is, for example, a substituent represented by the following formula (2).

  In Formula (2), b is a natural number, m is an arbitrary number, and b × m = 1. α is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched hydrocarbon group. An unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative group thereof. Among these, α is particularly preferably a hydrogen atom. Note that α in the formula (2) does not include a group derived from a cellulose molecular chain.

  Examples of the saturated-linear hydrocarbon group represented by α in Formula (2) include, but are not particularly limited to, a methyl group, an ethyl group, an n-propyl group, and an n-butyl group. Examples of the saturated-branched hydrocarbon group include i-propyl group and t-butyl group, but are not particularly limited. Examples of the saturated-cyclic hydrocarbon group include a cyclopentyl group and a cyclohexyl group, but are not particularly limited. Examples of the unsaturated-linear hydrocarbon group include, but are not particularly limited to, a vinyl group or an allyl group. Examples of the unsaturated-branched hydrocarbon group include i-propenyl group and 3-butenyl group, but are not particularly limited. Examples of the unsaturated-cyclic hydrocarbon group include, but are not limited to, a cyclopentenyl group and a cyclohexenyl group. Examples of the aromatic group include, but are not limited to, a phenyl group or a naphthyl group.

  In addition, the derivative group in α is a functional group in which at least one of functional groups such as a carboxy group, a hydroxy group, or an amino group is added or substituted to the main chain or side chain of the above-mentioned various hydrocarbon groups. Although group is mentioned, it is not specifically limited. Further, the number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, and more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R within the above range, the molecular weight of the phosphite group can be set within an appropriate range, and the penetration into the fiber raw material can be facilitated, and the yield of fine cellulose fibers can be reduced. It can also be increased.

Β ^{b +} in the formula (2) is a monovalent or higher cation composed of an organic substance or an inorganic substance. Examples of the monovalent or higher cation made of an organic substance include aliphatic ammonium or aromatic ammonium. Examples of the monovalent or higher cation made of an inorganic substance include ions of alkali metals such as sodium, potassium, or lithium, Examples include, but are not particularly limited to, a cation of a divalent metal such as calcium or magnesium, or a hydrogen ion. These can 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 a sodium ion or potassium ion which is not easily yellowed when heated to a fiber raw material containing β and is industrially useful, but is not particularly limited.

  In addition to the phosphite group or the substituent derived from the phosphite group, the fine fibrous cellulose may further have a phosphate group or a group derived from the phosphate group. The group derived from a phosphoric acid group or a phosphoric acid group is, for example, a substituent represented by the following formula (1) or (3). The phosphoric acid group or the group derived from the phosphoric acid group may be a condensed phosphorus oxo acid group represented by the following formula (3).

In formula (1), a and b are natural numbers, and m is an arbitrary number (provided that a = b × m). Of α and α ′, a is O ⁻ and the rest is OR. Here, R is a hydrogen atom, a saturated-linear hydrocarbon group, a saturated-branched hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched chain. It is a hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative group thereof. In addition, α in the formula (1) may be a group derived from a cellulose molecular chain.

In formula (3), a and b are natural numbers, m is an arbitrary number, and n is a natural number of 2 or more (provided that a = b × m). Of α ¹ , α ² ,..., α ⁿ and α ′, 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 hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-linear hydrocarbon group, an unsaturated-branched chain. It is a hydrocarbon group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative group thereof. In addition, α in the formula (3) may be a group derived from a cellulose molecular chain.

Specific examples of each group in formulas (1) and (3) are the same as the specific examples of each group in formula (2). Further, the formula (1) and specific examples beta ^{b +} a in (3) are the same as specific examples of beta ^{b +} in equation (2).

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

The amount of phosphite groups introduced into the fibrous cellulose is, for example, preferably 0.10 mmol / g or more per gram (mass) of fibrous cellulose, more preferably 0.20 mmol / g or more, and 0.50 mmol. / G or more is more preferable, and 1.00 mmol / g or more is particularly preferable. The amount of phosphite groups introduced into the fibrous cellulose is preferably 3.65 mmol / g or less, more preferably 3.50 mmol / g or less, for example, per 1 g (mass) of fibrous cellulose. More preferably, it is 0.000 mmol / g or less. By making the introduction amount of the phosphorous acid group within the above range, the fiber raw material can be easily refined, and the stability of the fibrous cellulose can be enhanced. Moreover, when the amount of the phosphite group introduced is within the above range, good characteristics can be exhibited in a sheet containing fibrous cellulose.
Here, the denominator in the unit mmol / g indicates the mass of the fibrous cellulose when the counter ion of the phosphite group is a hydrogen ion (H ⁺ ).

  The amount of phosphorus oxo acid groups (including phosphite groups) introduced into the fibrous cellulose can be measured, for example, by a neutralization titration method. In the measurement by the neutralization titration method, the introduction amount is measured by determining the change in pH while adding an alkali such as an aqueous sodium hydroxide solution to the obtained slurry containing fibrous cellulose.

FIG. 1 is a graph showing the relationship between the amount of NaOH dropped and the pH with respect to a fibrous cellulose-containing slurry having a phosphorus oxo acid group. For example, the introduction amount of the phosphorus oxo acid group into the fibrous cellulose is measured as follows.
First, the slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. In addition, you may implement the fibrillation process similar to the fibrillation process mentioned later with respect to a measuring object before the process by strong acidic ion exchange resin as needed.
Next, the pH change is observed while adding an aqueous sodium hydroxide solution to obtain a titration curve as shown in the upper part of FIG. In the titration curve shown in the upper part of FIG. 1, the measured pH is plotted against the amount of added alkali, and in the titration curve shown in the lower part of FIG. The increment (derivative value) (1 / mmol) is plotted. In this neutralization titration, two points where the increment (differential value of pH with respect to the amount of alkali dropped) is maximized in the curve plotting the measured pH against the amount of alkali added. Among these, the maximum point of increment obtained first after adding alkali is called the first end point, and the maximum point of increment obtained next is called the second end point. The alkali amount required from the start of titration to the first end point is equal to the first dissociated acid amount of fibrous cellulose contained in the slurry used for titration, and the alkali required from the first end point to the second end point Fibrous cellulose whose amount is equal to the second dissociated acid amount of fibrous cellulose contained in the slurry used for titration, and whose alkali amount required from the start of titration to the second end point is contained in the slurry used for titration Is equal to the total dissociated acid amount. Then, the value obtained by dividing the alkali amount required from the start of titration to the first end point by the solid content (g) in the titration target slurry is the amount of introduction of the phosphorus oxo acid group (mmol / g). In addition, when it is simply referred to as a phosphorus oxo acid group introduction amount (or a phosphorus oxo acid group amount), it represents the first dissociated acid amount.
In FIG. 1, a region from the start of titration to the first end point is referred to as a first region, and a region from the first end point to the second end point is referred to as a second region. For example, when the phosphorus oxo acid group is a phosphoric acid group and this phosphate group undergoes condensation, the amount of the weakly acidic group in the phosphorus oxo acid group (also referred to as the second dissociated acid amount in this specification) apparently appears. The amount of alkali required for the second region is reduced compared to the amount of alkali required for the first region. On the other hand, the strongly acidic group amount (also referred to as the first dissociated acid amount in the present specification) in the phosphorus oxo acid group coincides with the amount of phosphorus atoms regardless of the presence or absence of condensation. Further, when the phosphorus oxo acid group is a phosphite group, the weakly acidic group does not exist in the phosphorus oxo acid group, so that the alkali amount required for the second region is reduced or the alkali amount required for the second region is reduced. May be zero. In this case, in the titration curve, there is one point where the increment of pH becomes maximum.

The above-mentioned introduction amount (mmol / g) of the phosphorus oxo acid group indicates the mass of the acid type fibrous cellulose in the denominator, so that the amount of the phosphorus oxo acid group possessed by the acid type fibrous cellulose (hereinafter, the amount of the phosphorus oxo acid group) (Referred to as (acid type)). On the other hand, when an arbitrary cation C is substituted so that the counter ion of the phosphorus oxo acid group has a charge equivalent, the denominator is converted to the mass of fibrous cellulose when the cation C is the counter ion. Thus, the amount of the phosphorus oxo acid group (hereinafter, the amount of the phosphorus oxo acid group (C type)) possessed by the fibrous cellulose whose cation C is the counter ion can be determined.
That is, it calculates with the following formula.
Phosphooxo acid group amount (C type) = Phosphooxo acid group amount (acid type) / {1+ (W−1) × A / 1000}
A [mmol / g]: A total amount of anion derived from a phosphorus oxo acid group in fibrous cellulose (total amount of dissociated acid of a phosphorus oxo acid group)
W: Formula weight per cation C (for example, Na is 23, Al is 9)

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

  In addition to phosphorous acid group, whether phosphorous oxoacid detected when it contains either phosphoric acid group or condensed phosphoric acid group or both is derived from phosphorous acid, phosphoric acid or condensed phosphoric acid As a method of distinguishing, for example, a method of performing the above-mentioned titration operation after performing a treatment of cutting a condensed structure such as acid hydrolysis, or a method of converting a phosphite group to a phosphate group such as an oxidation treatment Examples thereof include a method of performing the above-described titration operation.

<Production process of fine fibrous cellulose>
<Fiber raw material>
The fine fibrous cellulose is produced from a fiber raw material containing cellulose. Although it does not specifically limit as a fiber raw material containing a cellulose, It is preferable to use a pulp from the point of being easy to acquire and cheap. Examples of the pulp include wood pulp, non-wood pulp, and deinked pulp. Although it does not specifically limit as wood pulp, For example, hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolution pulp (DP), soda pulp (AP), unbleached kraft pulp (UKP) ) And oxygen bleached kraft pulp (OKP) and other chemical pulp, semichemical pulp (SCP) and semi-chemical pulp such as Chemi-groundwood pulp (CGP), groundwood pulp (GP) and thermomechanical pulp (TMP, BCTMP) and the like Examples thereof include mechanical pulp. The non-wood pulp is not particularly limited, and examples thereof include cotton-based pulp such as cotton linter and cotton lint, and non-wood-based pulp such as hemp, straw and bagasse. Although it does not specifically limit as a deinking pulp, For example, the deinking pulp which uses a waste paper as a raw material is mentioned. The pulp of this embodiment may be used alone or in combination of two or more.
Among the above pulps, for example, wood pulp and deinked pulp are preferable from the viewpoint of easy availability. In addition, among wood pulps, it is possible to obtain a fine fiber cellulose having a large cellulose ratio and a high yield of fine fibrous cellulose at the time of defibrating treatment, and a long fiber fine fibrous cellulose having a small degradation of cellulose in the pulp and a large axial ratio. From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are more preferable.

  As a fiber raw material containing cellulose, for example, cellulose contained in ascidians or bacterial cellulose produced by acetic acid bacteria can be used. Moreover, it can replace with the fiber raw material containing cellulose, and the fiber which linear nitrogen-containing polysaccharide polymer | macromolecules, such as chitin and chitosan form, can also be used.

<Phosphorous acid group introduction process>
In the phosphite group introduction step, at least one compound selected from compounds capable of introducing a phosphite group by reacting with a hydroxyl group of a fiber raw material containing cellulose (hereinafter also referred to as “compound A”) is used. It is the process of making it act on the fiber raw material containing a cellulose. By this step, a phosphite group-introduced fiber is obtained.

  In the phosphite group introduction step according to this 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, in the state where compound B does not exist, the fiber raw material containing cellulose and compound A may be reacted.

  As an example of a method for causing compound A to act on a fiber raw material in the presence of compound B, a method of mixing compound A and compound B with a dry, wet, or slurry fiber raw material can be mentioned. Among these, since the uniformity of the reaction 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. Although the form of a fiber raw material is not specifically limited, For example, it is preferable that it is a cotton form or a thin sheet form. The compound A and the compound B may be added to the fiber raw material in the form of a powder or a solution dissolved in a solvent, or heated to a melting point or higher and melted. Among these, since the uniformity of the reaction is high, it is preferable to add in the form of a solution dissolved in a solvent, particularly in an aqueous solution state. Compound A and Compound B may be added simultaneously to the fiber raw material, may be added separately, or may be added as a mixture. The method for adding compound A and compound B is not particularly limited, but when compound A and compound B are in solution, they may be taken out after dipping the fiber raw material in the solution and absorbing the fiber raw material. The solution may be added dropwise. In addition, a necessary amount of Compound A and Compound B may be added to the fiber raw material, or after adding an excessive amount of Compound A and Compound B to the fiber raw material, respectively, excess compound A and Compound B may be added by pressing or filtration. It may be removed.

  Compound A used in this embodiment is at least one selected from a compound having a phosphite group and a salt thereof. Examples of the compound having a phosphite group include phosphorous acid, and examples of phosphorous acid include 99% phosphorous acid (phosphonic acid). Examples of the salt of the compound having a phosphite group include lithium salt, sodium salt, potassium salt, and ammonium salt of phosphorous acid, and these can have various degrees of neutralization. Of these, phosphorous acid and phosphorous acid are introduced from the viewpoint that the introduction efficiency of the phosphorus oxo acid group is high, the fibrillation efficiency is easily improved in the fibrillation process described later, the cost is low, and the industrial application is easy. The sodium salt of acid, the potassium salt of phosphorous acid, or the ammonium salt of phosphorous acid is preferably used.

  The amount of compound A added to the fiber raw material is not particularly limited. For example, when the amount of compound A added is converted to phosphorus atomic weight, the amount of phosphorus atom added to the fiber raw material (absolute dry mass) is 0.5% by mass or more. It is preferably 100% by mass or less, more preferably 1% by mass or more and 50% by mass or less, and further preferably 2% by mass or more and 30% by mass or less. By making the addition amount of the phosphorus atom with respect to the fiber raw material within the above range, the yield of the fine fibrous cellulose can be further improved. On the other hand, when the amount of phosphorus atoms added to the fiber raw material is set to the upper limit value or less, the effect of improving the yield and the cost can be balanced.

Compound B used in this embodiment is at least one selected from urea and derivatives thereof as described above. Examples of compound B include urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, and 1-ethylurea.
From the viewpoint of improving the uniformity of the reaction, the compound B is preferably used as an aqueous solution. From the viewpoint of further improving the uniformity of the reaction, it is preferable to use an aqueous solution in which both compound A and compound B are dissolved.

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

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

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

  In the heat treatment according to this embodiment, for example, compound A is added to a thin sheet-like fiber raw material by a method such as impregnation, and then heated, or heated while kneading or stirring the fiber raw material and compound A with a kneader or the like. The method to do can be adopted. Thereby, it is possible to suppress the concentration unevenness of the compound A in the fiber raw material and introduce the phosphite group more uniformly on the surface of the cellulose fiber contained in the fiber raw material. This is because when the water molecules move to the fiber raw material surface with drying, the dissolved compound A is attracted to the water molecules by the surface tension and similarly moves to the fiber raw material surface (that is, the concentration unevenness of the compound A is reduced). This can be attributed to the fact that it can be suppressed.

  In addition, the heating device used for the heat treatment, for example, always retains the moisture retained by the slurry and the moisture generated in the dehydration condensation (phosphate esterification) reaction between the compound A and the hydroxyl group contained in the cellulose or the like in the fiber raw material. It is preferable that the apparatus can be discharged out of the apparatus system. As such a heating device, for example, a blower type oven or the like can be cited. In addition to being able to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of phosphate esterification, by constantly discharging the water in the apparatus system, it is also possible to suppress the acid hydrolysis of sugar chains in the fiber. it can. For this reason, it becomes possible to obtain fine fibrous cellulose having a high axial ratio.

  The time for the heat treatment is, for example, preferably from 1 second to 300 minutes after moisture is substantially removed from the fiber raw material, more preferably from 1 second to 1000 seconds, and more preferably from 10 seconds to 800 seconds. More preferably. In the present embodiment, the amount of phosphite groups introduced can be within a preferred range by setting the heating temperature and the heating time to appropriate ranges.

  The phosphite group introduction step may be performed at least once, but may be repeated twice or more. By performing the phosphite group introduction step twice or more, a large number of phosphite groups can be introduced into the fiber raw material. In this embodiment, the case where a phosphorous acid group introduction | transduction process is performed twice as an example of a preferable aspect is mentioned.

  The amount of phosphite groups introduced into the fiber raw material is, for example, preferably 0.10 mmol / g or more per 1 g (mass) of fine fibrous cellulose, more preferably 0.20 mmol / g or more, and 0.50 mmol. / G or more is more preferable, and 1.00 mmol / g or more is particularly preferable. The amount of phosphite groups introduced into the fiber raw material is, for example, preferably 5.20 mmol / g or less, more preferably 3.65 mmol / g or less, per 1 g (mass) of fine fibrous cellulose. More preferably, it is 0.000 mmol / g or less. By making the introduction amount of the phosphite group within the above range, the fiber raw material can be easily refined and the stability of the fine fibrous cellulose can be enhanced.

<Washing process>
In the manufacturing method of the fine fibrous cellulose in this embodiment, a washing | cleaning process can be performed with respect to a phosphite group introduction | transduction fiber as needed. The washing step is performed, for example, by washing the phosphite group-introduced fiber with water or an organic solvent. In addition, the cleaning process may be performed after each process described later, and the number of times of cleaning performed in each cleaning process is not particularly limited.

<Alkali treatment process>
When manufacturing a fine fibrous cellulose, you may perform an alkali process with respect to a fiber raw material between a phosphite group introduction | transduction process and the fibrillation process mentioned later. Although it does not specifically limit as a method of an alkali treatment, For example, the method of immersing a phosphite group introduction | transduction fiber in an alkaline solution is mentioned.

  The alkali compound contained in the alkali solution is not particularly limited, and may be an inorganic alkali compound or an organic alkali compound. In this embodiment, since versatility is high, it is preferable to use sodium hydroxide or potassium hydroxide as an alkali compound, for example. Moreover, 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. The alkaline solution is preferably a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution because of its high versatility.

  Although the temperature of the alkali solution in an alkali treatment process is not specifically limited, For example, it is preferable that it is 5 to 80 degreeC, and it is more preferable that it is 10 to 60 degreeC. Although the immersion time of the phosphite group-introduced fiber in the alkali solution in the alkali treatment step is not particularly limited, it is preferably, for example, from 5 minutes to 30 minutes, and more preferably from 10 minutes to 20 minutes. The amount of the alkali solution used in the alkali treatment is not particularly limited. For example, it is preferably 100% by mass or more and 100000% by mass or less, and 1000% by mass or more and 10000% by mass with respect to the absolute dry mass of the phosphite group-introduced fiber. The following is more preferable.

  In order to reduce the amount of the alkaline solution used in the alkali treatment step, the phosphite group introduction 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 phosphite group-introduced fiber subjected to the alkali treatment with water or an organic solvent from the viewpoint of improving the handleability.

<Acid treatment process>
When manufacturing a fine fibrous cellulose, you may acid-treat with respect to a fiber raw material between the process of introduce | transducing a phosphorous acid group, and the fibrillation process process mentioned later. For example, the phosphite group introduction step, acid treatment, alkali treatment, and defibration treatment may be performed in this order.

  Although it does not specifically limit as a method of an acid treatment, For example, the method of immersing a fiber raw material in the acidic liquid containing an acid is mentioned. Although the density | concentration of the acidic liquid to be used is not specifically limited, For example, it is preferable that it is 10 mass% or less, and it is more preferable that it is 5 mass% or less. Further, the pH of the acidic liquid to be used is not particularly limited, but is preferably 0 or more and 4 or less, and more preferably 1 or more and 3 or less. As the acid contained in the acidic liquid, 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, chlorous 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, and tartaric acid. Among these, it is particularly preferable to use hydrochloric acid or sulfuric acid.

  Although the temperature of the acid solution in an acid treatment is not specifically limited, For example, 5 to 100 degreeC is preferable and 20 to 90 degreeC is more preferable. Although the immersion time in the acid solution in acid treatment is not specifically limited, For example, 5 minutes or more and 120 minutes or less are preferable, and 10 minutes or more and 60 minutes or less are more preferable. Although the usage-amount of the acid solution in an acid treatment is not specifically limited, For example, it is preferable that it is 100 mass% or more and 100,000 mass% or less with respect to the absolute dry mass of a fiber raw material, and it is 1000 mass% or more and 10000 mass% or less. Is more preferable.

<Defibration processing>
Fine fibrous cellulose is obtained by defibrating the phosphite group-introduced fiber in the defibrating process. In the defibrating process, for example, a defibrating apparatus can be used. The defibrating apparatus is not particularly limited, but for example, a high-speed defibrator, a grinder (stone mortar grinder), a high-pressure homogenizer or an ultra-high pressure homogenizer, a high-pressure collision grinder, a ball mill, a bead mill, a disk refiner, a conical refiner, biaxial A kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, or a beater can be used. Among the above-described defibrating apparatuses, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, or an ultrahigh-pressure homogenizer that is less affected by the pulverizing media and has less risk of contamination.

  In the defibrating process, for example, it is preferable to dilute the phosphite group-introduced fiber with a dispersion medium to form a slurry. As a dispersion medium, 1 type, or 2 or more types selected from water and organic solvents, such as a polar organic solvent, can be used. The polar organic solvent is not particularly limited, but alcohols, polyhydric alcohols, ketones, ethers, esters, aprotic polar solvents, and the like are preferable. Examples of alcohols include methanol, ethanol, isopropanol, n-butanol, and isobutyl alcohol. Examples of the polyhydric alcohols include ethylene glycol, propylene glycol, glycerin and the like. Examples of ketones include acetone and methyl ethyl ketone (MEK). Examples of ethers include diethyl ether, tetrahydrofuran, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono n-butyl ether, propylene glycol monomethyl ether, and the like. Examples of the esters include ethyl acetate and butyl acetate. Examples of the aprotic polar solvent include dimethyl sulfoxide (DMSO), dimethylformamide (DMF), dimethylacetamide (DMAc), N-methyl-2-pyrrolidinone (NMP) and the like.

  The solid content concentration of the fine fibrous cellulose during the defibrating treatment can be set as appropriate. The slurry obtained by dispersing the phosphite group-introduced fiber in the dispersion medium may contain solids other than the phosphite group-introduced fiber such as urea having hydrogen bonding properties.

  As described above, a slurry containing fine fibrous cellulose is obtained. The solid content concentration in the slurry can be appropriately adjusted. For example, the solid content concentration is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. Moreover, it is preferable that solid content concentration is 50 mass% or less, and it is more preferable that it is 40 mass% or less.

(Resin component)
The sheet of the present invention preferably further contains a resin component. The resin component is preferably a water-soluble polymer. Examples of the water-soluble polymer include carboxyvinyl polymer, polyvinyl alcohol, alkyl methacrylate / acrylic acid copolymer, polyvinyl pyrrolidone, sodium polyacrylate, polyethylene glycol, diethylene glycol, Synthetic water-soluble polymers exemplified by triethylene glycol, polyethylene oxide, propylene glycol, dipropylene glycol, polypropylene glycol, isoprene glycol, hexylene glycol, 1,3-butylene glycol, polyacrylamide, polyamine polyamide epihalohydrin, etc .; xanthan gum, Guar gum, tamarind gum, carrageenan, locust bean gum, quince seed, alginic acid, pullulan, cara -Nan and thickening polysaccharides exemplified by pectin and the like; cellulose derivatives exemplified by carboxymethylcellulose, methylcellulose, and hydroxyethylcellulose; cationized starch, raw starch, oxidized starch, etherified starch, esterified starch, And starches exemplified by amylose; glycerols exemplified by glycerin, diglycerin, and polyglycerin; hyaluronic acid, metal salts of hyaluronic acid, and the like.
Among these, the water-soluble polymer is preferably polyvinyl alcohol, polyethylene oxide, or polyamine polyamide epihalohydrin, and more preferably polyethylene oxide. The polyvinyl alcohol is also preferably modified polyvinyl alcohol, and examples of the modified polyvinyl alcohol include acetoacetyl group-modified polyvinyl alcohol. Examples of the polyamine polyamide epihalohydrin include polyamine polyamide epichlorohydrin, polyamine polyamide epibromohydrin, polyamine polyamide epiiohydrin, and the like. Among these, polyamine polyamide epichlorohydrin is preferably used. The sheet of the present invention may contain one or more of the above resin components.

  The sheet | seat of this invention may contain resin components other than the said water-soluble polymer as a resin component. Examples of such resin components include polypropylene resins, acrylic resins, polycarbonate resins, polyester resins, polyamide resins, silicone resins, fluorine resins, chlorine resins, epoxy resins, melamine resins, Examples thereof include a phenol resin, a polyurethane resin, a diallyl phthalate resin, a polyol resin, a polyether resin, a cellulose derivative, and a polyethylene resin. Among these, polypropylene resins and the like are preferably used, and such resins are also preferably used in combination with the water-soluble polymer described above. The resin component may be added as an emulsion.

  The content of the resin component contained in the sheet is preferably 1 part by mass or more, more preferably 5 parts by mass or more, with respect to 100 parts by mass of the fine fibrous cellulose in the sheet. More preferably. Further, the content of the resin contained in the sheet is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and 60 parts by mass or less with respect to 100 parts by mass of the fine fibrous cellulose. More preferably. By setting the content of the resin component contained in the sheet within the above range, the strength of the sheet can be increased. Moreover, it becomes easy to adjust the moisture content of a sheet | seat to a desired range by making content of the resin component contained in a sheet into the said range. Specifically, since the water absorption amount of water can be suppressed by making the content of the resin component within the above range, for example, when impregnating a sheet base paper into a solution containing water in the sheet manufacturing process described below, It is not necessary to strictly control the impregnation time in the solution, and handling in production can be improved.

(External preparation for skin)
The sheet of the present invention preferably further contains an external preparation for skin. As external preparations for skin, oily bases, surfactants, alcohols, moisturizers, polymers / thickening / gelling agents, antioxidants, preservatives, bactericides, chelating agents, pH adjusters, acids, Alkali, UV absorber, whitening agent, exfoliating / dissolving agent, antipruritic agent, anti-inflammatory agent, antiperspirant, cooling agent, reducing agent / oxidizing agent, vitamins and derivatives thereof, saccharides and derivatives thereof, organic acids, Inorganic powders, fragrances, dyes, pigments and the like can be mentioned. Among these, the external preparation for skin is preferably a cosmetic component or a medicinal component, and more preferably a moisturizer, whitening agent, exfoliating / dissolving agent, antipruritic agent, anti-inflammatory agent, vitamins and derivatives thereof. The sheet of the present invention may contain one or more of the above components.

  The content of the external preparation for skin contained in the sheet is preferably 0.0001% by mass or more, more preferably 0.001% by mass or more, and 0.01% by mass with respect to the total mass of the sheet. % Or more is more preferable. In addition, the content of the external preparation for skin is preferably 29% by mass or less, more preferably 25% by mass or less, and further preferably 20% by mass or less with respect to the total mass of the sheet. By setting the content of the external preparation for skin within the above range, a wet sheet excellent in cosmetic effect and medicinal effect can be easily obtained. Moreover, it becomes easy to obtain the wet sheet | seat excellent in the handleability and adhesiveness by making content of the external preparation for skin into the said range.

(Other optional ingredients)
The sheet of the present invention may contain a polyvalent metal salt. Examples of the polyvalent metal salt include aluminum sulfate, magnesium sulfate, potassium aluminum sulfate, ammonium aluminum sulfate, and ferric chloride. Among them, the polyvalent metal salt is selected from aluminum sulfate and magnesium sulfate. It is preferable that it is at least one kind. By including the polyvalent metal salt, a crosslinked structure is formed between the fine fibrous celluloses in the sheet, and the strength of the sheet can be increased. Thereby, the handleability of the sheet can be further improved.

  The sheet of the present invention may contain a solvent other than water. Examples of the solvent include organic solvents. Examples of the organic solvent include methanol, ethanol, n-propyl alcohol, isopropyl alcohol (IPA), 1-butanol, m-cresol, glycerin, acetic acid, pyridine, tetrahydrofuran (THF), acetone, methyl ethyl ketone (MEK), and ethyl acetate. Aniline, N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), N, N-dimethylformamide (DMF), hexane, cyclohexane, benzene, toluene, p-xylene, diethyl ether chloroform, phenoxyethanol, butylene glycol Etc. The content of the solvent other than water in the sheet is preferably 10% by mass or less, more preferably 5% by mass or less, and further preferably 1% by mass or less based on the total mass of the sheet. preferable.

  Other optional components include, for example, organic ions, coupling agents, inorganic layered compounds, inorganic compounds, leveling agents, antifoaming agents, organic particles, lubricants, antistatic magnetic powders, alignment accelerators, plasticizers, A dispersing agent, a crosslinking agent, etc. can be mentioned, The sheet | seat of this invention may contain the 1 type (s) or 2 or more types of the said component.

  The content of the above components contained in the sheet is preferably 10% by mass or less, more preferably 5% by mass or less, and more preferably 1% by mass or less, based on the total solid content in the sheet. More preferably.

(Sheet manufacturing process)
The production process of the sheet of the present invention includes a step of obtaining a slurry containing fine fibrous cellulose having a phosphite group or a substituent derived from a phosphite group, and a coating step of coating the slurry on a substrate. Alternatively, it is preferable to include a paper making process for making the slurry, and a process of adding moisture to the sheet base paper obtained through the coating process or the paper making process. Thereby, the wet sheet | seat whose water content rate is 70 mass% or more is obtained. Among them, the sheet manufacturing process includes a process of obtaining a slurry containing fine fibrous cellulose, a coating process of coating the slurry on a substrate, and a sheet base paper obtained through the coating process containing moisture. Preferably including a step.

  It is preferable that the sheet | seat of this invention includes the process of containing a water | moisture content in the sheet | seat base paper obtained through the coating process or the papermaking process. In the coating process or the papermaking process, it is preferable to provide a process for drying the sheet base paper. In the subsequent step of containing moisture, it is preferable to contain moisture in an absolutely dry or humidity-controlled sheet, and it is more preferable to impregnate a solution containing water in an absolutely dry or humidity-conditioned sheet. As a result, a wet sheet having a moisture content equal to or higher than a predetermined value and uniformly holding moisture can be obtained. In the production process of the sheet of the present invention, it is preferable to impregnate the sheet with water after processing the dried or dried sheet into a desired shape. As described above, in the sheet manufacturing process of the present invention, an absolutely dry sheet or a dried sheet can be processed, and therefore, for example, the sheet can be easily cut (punched) into a desired shape. For this reason, the production efficiency of a sheet | seat can be improved and the manufacturing cost of a sheet | seat etc. can also be suppressed as a result. The completely dry sheet is a sheet obtained by drying a sheet base paper obtained through the coating process or the paper making process at 105 ° C. for 24 hours, and is a sheet having a moisture content of 0% by mass. . In addition, a humidity-conditioned sheet is a sheet obtained by allowing a sheet base paper obtained through a coating process or a papermaking process to stand for 24 hours at 23 ° C. and a relative humidity of 50%, and contains moisture. It is a sheet having a rate of 15% by mass or less.

  A wet sheet is obtained in the step of adding moisture to the sheet base paper obtained through the coating step or the paper making step. In this step, the amount of water provided, the impregnation time, and the like may be adjusted so that the moisture content of the wet sheet falls within a desired range. For example, when the step of containing water is a step of impregnating a solution containing water, the immersion time of the sheet base paper can be 1 second or more and 60 minutes or less. As described above, the moisture content can be controlled by adding a resin component to the sheet. In this case, the immersion time and the like can be further increased.

  The step of adding moisture may be a step of spraying moisture on the sheet base paper obtained through the coating step or the papermaking step. In this case, it is preferable to spray-apply a solution containing water on the entire surface or part of the sheet base paper. Further, the step of adding moisture may be a step of applying moisture to the sheet base paper obtained through the coating step or the paper making step.

  In addition, the solution containing water used in the step of containing water may contain an external preparation for skin and other optional components as necessary.

  The manufacturing process of the sheet of the present invention may include a step of impregnating a sheet base paper obtained through the coating process or the papermaking process with an aqueous solution containing a polyvalent metal salt. The step of impregnating the aqueous solution containing the polyvalent metal salt is preferably provided before the step of containing water, and after the step of impregnating the aqueous solution containing the polyvalent metal salt, the sheet base paper is completely dried or It is preferable to provide the process of making it a dry sheet | seat and making it contain a water | moisture content after that. By further providing a step of impregnating an aqueous solution containing a polyvalent metal in the sheet production process, a crosslinked structure is formed between the fine fibrous celluloses in the sheet, and the strength of the sheet can be increased. Thereby, the handleability of the sheet can be further improved.

  In the step of impregnating the aqueous solution containing the polyvalent metal salt, it is preferable to adjust the concentration of polyvalent metal and the immersion time according to the amount of the crosslinked structure to be formed. For example, when the concentration of the polyvalent metal in the aqueous solution containing the polyvalent metal is 1 to 10% by mass, the immersion time of the sheet base paper is preferably 10 seconds to 10 minutes. The aqueous solution containing a polyvalent metal salt is preferably water-soluble in a salt derived from a strong acid of a divalent or higher metal. Examples of the polyvalent metal salt include aluminum sulfate, magnesium sulfate, aluminum potassium sulfate, aluminum ammonium sulfate, and ferric chloride. At least one selected from aluminum sulfate and magnesium sulfate is used. Is preferred.

  A washing step is preferably provided after the step of impregnating the aqueous solution containing the polyvalent metal. Thereby, an unnecessary polyvalent metal can be removed. Moreover, it is preferable to provide the process of drying a sheet | seat after a washing | cleaning process. In the drying step, it is preferable to dry the sheet by standing in a dry environment of 20 to 100 ° C. (for example, relative humidity is 30% or less).

  When the resin component is contained in the sheet, the resin component is preferably added in the step of obtaining a slurry containing fine fibrous cellulose. The resin component is preferably added as a resin solution, and such a resin solution is preferably an aqueous solution in which a resin and water are mixed. In addition, after adding a resin solution, you may heat a slurry and may improve the dispersibility of a resin component.

<Coating process>
In the coating step, for example, a sheet base paper can be obtained by coating a slurry containing fine fibrous cellulose on a base material and drying the slurry to release the base paper sheet formed from the base material. Moreover, a sheet | seat base paper can be continuously manufactured by using a coating device and a elongate base material.

  The material of the base material used in the coating process is not particularly limited, but the one with higher wettability to the slurry may be able to suppress the shrinkage of the sheet base paper during drying, but the sheet base paper formed after drying It is preferable to select one that can be easily peeled off. Among them, a resin film or plate or a metal film or plate is preferable, but is not particularly limited. For example, resin films and plates of acrylic, polyethylene terephthalate, vinyl chloride, polystyrene, polyvinylidene chloride, etc., metal films and plates of aluminum, zinc, copper, and iron plates, and their surfaces oxidized, stainless steel films A metal plate, a brass film or a plate can be used.

  In the coating process, when the slurry has a low viscosity and spreads on the base material, a damming frame is fixed on the base material to obtain a sheet base paper of a predetermined thickness and basis weight. May be. The damming frame is not particularly limited. For example, it is preferable to select a frame that can easily peel off the edge of the sheet base paper that adheres after drying. From such a viewpoint, a molded resin plate or metal plate is more preferable. In the present embodiment, for example, resin plates such as acrylic plates, polyethylene terephthalate plates, vinyl chloride plates, polystyrene plates, polyvinylidene chloride plates, metal plates such as aluminum plates, zinc plates, copper plates, iron plates, and the surfaces thereof. An oxidation-treated one, a stainless plate, a brass plate or the like can be used.

  Although it does not specifically limit as a coating machine which coats a slurry on a base material, For example, a roll coater, a gravure coater, a die coater, a curtain coater, an air doctor coater etc. can be used. A die coater, a curtain coater, and a spray coater are particularly preferable because the thickness of the sheet base paper can be made more uniform.

  The slurry temperature and the atmospheric temperature when the slurry is applied to the substrate are not particularly limited, but are preferably 5 ° C. or more and 80 ° C. or less, more preferably 10 ° C. or more and 60 ° C. or less, and more preferably 15 ° C. The temperature is more preferably 50 ° C. or lower and particularly preferably 20 ° C. or higher and 40 ° C. or lower. If the coating temperature is equal to or higher than the lower limit, the slurry can be applied more easily. If coating temperature is below the said upper limit, volatilization of the dispersion medium during coating can be suppressed.

In the coating process, the slurry is adjusted so that the finished basis weight of the sheet base paper is preferably 10 g / m ² or more and 200 g / m ² or less, more preferably 20 g / m ² or more and 150 g / m ² or less. It is preferable to apply to the substrate. By coating so that the basis weight is within the above range, a sheet base paper having excellent strength can be obtained.

  A coating process includes the process of drying the slurry coated on the base material as above-mentioned. The step of drying the slurry is not particularly limited, and is performed by, for example, a non-contact drying method, a method of drying while restraining the sheet base paper, or a combination thereof. The non-contact drying method is not particularly limited. For example, a method of drying by heating with hot air, infrared rays, far infrared rays or near infrared rays (heating drying method), or a method of drying in vacuum (vacuum drying method) is applied. can do. Although the heat drying method and the vacuum drying method may be combined, the heat drying method is usually applied. Although drying by infrared rays, far-infrared rays, or near-infrared rays is not specifically limited, For example, it can carry out using an infrared device, a far-infrared device, or a near-infrared device. The heating temperature in the heat drying method is not particularly limited, but is preferably 20 ° C. or higher and 150 ° C. or lower, and more preferably 25 ° C. or higher and 105 ° C. or lower. If the heating temperature is at least the above lower limit, the dispersion medium can be volatilized quickly. Moreover, if heating temperature is below the said upper limit, the suppression of the cost required for a heating and the discoloration by the heat | fever of a fibrous cellulose are realizable.

<Paper making process>
The papermaking process is performed by making a slurry with a papermaking machine. The paper machine used in the paper making process is not particularly limited, and examples thereof include a continuous paper machine such as a long net type, a circular net type, and an inclined type, or a multi-layered paper machine combining these. In the paper making process, a known paper making method such as hand making may be employed.

  The paper making process is performed by filtering and dewatering the slurry with a wire to obtain a wet base paper sheet, and then pressing and drying the base paper. The filter cloth used when the slurry is filtered and dehydrated is not particularly limited. For example, it is more preferable that the fibrous cellulose does not pass through and the filtration rate does not become too slow. Such a filter cloth is not particularly limited, but for example, a sheet made of an organic polymer, a woven fabric, and a porous film are preferable. The organic polymer is not particularly limited, but non-cellulosic organic polymers such as polyethylene terephthalate, polyethylene, polypropylene, polytetrafluoroethylene (PTFE) and the like are preferable. In this embodiment, for example, a porous film of polytetrafluoroethylene having a pore diameter of 0.1 μm or more and 20 μm or less, a polyethylene terephthalate or polyethylene fabric having a pore diameter of 0.1 μm or more and 20 μm or less, and the like can be mentioned.

  In the sheet forming step, a method for producing a sheet base paper from the slurry is, for example, discharging the slurry containing fine fibrous cellulose onto the upper surface of the endless belt and squeezing the dispersion medium from the discharged slurry to generate a web. It can be carried out using a production device comprising a section and a drying section for drying the web to produce a sheet stock. An endless belt is disposed from the squeezing section to the drying section, and the web generated in the squeezing section is conveyed to the drying section while being placed on the endless belt.

  The dehydration method used in the papermaking process is not particularly limited, and examples thereof include a dehydration method usually used in paper production. Among these, the method of dehydrating with a roll press after dehydrating with a long net, a circular net, an inclined wire or the like is preferable. The drying method used in the paper making process is not particularly limited, and examples thereof include a method used in paper manufacture. Among these, a drying method using a cylinder dryer, a Yankee dryer, hot air drying, a near infrared heater, an infrared heater or the like is more preferable.

(Use)
Although the use of the sheet | seat of this invention is not specifically limited, For example, it is preferable to be used as a beauty sheet. Examples of the beauty sheet include a face mask. In particular, when the sheet of the present invention is used as a face mask, it may be brought into close contact with the face by pulling the sheet during use. Since the sheet of the present invention can exhibit sufficient strength and elongation even in such a usage mode, the sheet does not break during use and is easy to handle.

  Moreover, the sheet | seat of this invention can also be used for the sheet | seat for culture | cultivation of a wound site | part bonding sheet | seat, a medical sheet | seat, a cooling sheet | seat, a shock absorption sheet | seat, bacteria, a cell, a structure | tissue, etc.

  The present invention will be described more specifically with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

[Example 1]
[Production of subphosphorylated pulp]
Oji Paper's softwood kraft pulp as raw material pulp (solid content 93% by weight, basis weight 245g / m ² sheet, disaggregated and measured according to JIS P 8121, Canadian standard freeness (CSF) 700ml) It was used.

  The raw material pulp was subjected to phosphorus oxo oxidation treatment as follows. First, a mixed aqueous solution of phosphorous acid (phosphonic acid) and urea is added to 100 parts by mass (absolute dry mass) of the above raw pulp, and 33 parts by mass of phosphorous acid (phosphonic acid), 120 parts by mass of urea, and 150 parts of water. It prepared so that it might become a mass part, and obtained the chemical | medical solution impregnation pulp. Next, the obtained chemical-impregnated pulp was heated with a hot air dryer at 165 ° C. for 250 seconds to introduce a phosphite group into cellulose in the pulp to obtain a phosphorylated pulp.

  Next, the obtained phosphorylated pulp was washed. In the washing treatment, the pulp dispersion obtained by pouring 10 L of ion-exchanged water with respect to 100 g (absolute dry mass) of phosphorylated pulp is stirred so that the pulp is uniformly dispersed, and then the operation of filtration and dehydration is repeated. It went by. When the electrical conductivity of the filtrate reached 100 μS / cm or less, the end point of washing was determined.

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

An infrared absorption spectrum was measured using FT-IR for the phosphite pulp thus obtained. As a result, absorption based on P = O of a phosphonic acid group, which is a tautomer of a phosphorous acid group, was observed near 1210 cm ⁻¹ , and a phosphorous acid group (phosphonic acid group) was added to the pulp. Was confirmed. Moreover, when the obtained phosphorylated pulp was tested and analyzed with an X-ray diffractometer, two positions of 2θ = 14 ° to 17 ° and 2θ = 22 ° to 23 ° were found. A typical peak was confirmed, and it was confirmed to have cellulose type I crystals. In addition, about the obtained phosphorous-ized pulp, the amount of phosphite groups (1st dissociated acid amount) measured by the measuring method as described in [Measurement of the amount of phosphite groups] described later was 1.51 mmol / g. It was. The total dissociated acid amount was 1.54 mmol / g.

[Defibration processing]
Ion exchanged water was added to the obtained phosphorylated pulp to prepare a slurry having a solid content concentration of 2% by mass. This slurry was treated twice with a wet atomizer (Sugino Machine, Starburst) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion A containing fine fibrous cellulose. X-ray diffraction confirmed that the fine fibrous cellulose maintained the cellulose I-type crystals. Moreover, it was 3-5 nm when the fiber width of the fine fibrous cellulose was measured using the transmission electron microscope.

<Measurement of phosphorous acid group amount>
The amount of phosphorous acid group of the fine fibrous cellulose is a fiber prepared by diluting a fine fibrous cellulose dispersion containing the target fine fibrous cellulose with ion-exchanged water so that the content becomes 0.2% by mass. It measured by performing the titration using an alkali, after processing with an ion exchange resin with respect to the slurry containing a cellulose.
In the treatment with the ion exchange resin, 1/10 by volume of the strongly acidic ion exchange resin (Amberjet 1024; Organo Corporation, conditioned) is added to the fibrous cellulose-containing slurry, and the mixture is shaken for 1 hour. The mixture was poured onto a mesh having an opening of 90 μm to separate the resin and the slurry.
In addition, titration using an alkali measures the change in the pH value of the slurry while adding 10 μL of a 0.1 N sodium hydroxide aqueous solution every 5 seconds to the fibrous cellulose-containing slurry after treatment with an ion exchange resin. It was done by doing. The titration was performed while blowing nitrogen gas into the slurry 15 minutes before the start of titration. In this neutralization titration, two points at which the increment (differential value of pH with respect to the amount of alkali dropped) is maximized in a curve plotting the measured pH against the amount of alkali added. Among these, the maximum point of increment obtained first after adding alkali is called the first end point, and the maximum point of increment obtained next is called the second end point (FIG. 1). The amount of alkali required from the start of titration to the first end point is equal to the amount of first dissociated acid in the slurry used for titration. Further, the amount of alkali required from the start of titration to the second end point becomes equal to the total amount of dissociated acid in the slurry used for titration. In addition, the value which remove | divided the alkali amount (mmol) required from the titration start to the 1st end point by the solid content (g) in a titration object slurry was made into the amount of phosphite groups (mmol / g).

<Measurement of fiber width>
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 atomizer is water so that the concentration of fine fibrous cellulose is 0.01% by mass or more and 0.1% by mass or less. It diluted and dripped at the carbon grid membrane hydrophilized. After drying, this was stained with uranyl acetate and observed with a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.).

<Sheet>
The resulting fine fibrous cellulose dispersion A was subjected to concentration adjustment by adding ion-exchanged water so that the solid content concentration was 0.5% by mass. Next, a 0.5% by mass aqueous solution of polyethylene oxide (manufactured by Sumitomo Seika Co., Ltd., PEO-18) is added to the fine fibrous cellulose dispersion A so as to be 20 parts by mass with respect to 100 parts by mass of the fine fibrous cellulose. Thus, a coating solution was obtained. Next, the coating liquid is weighed so that the basis weight in the absolutely dry state of the obtained sheet (layer composed of the solid content of the coating liquid) is 50 g / m ² and applied to a commercially available acrylic board. And dried in a constant temperature dryer at 50 ° C. A damming metal frame (inner size 180 mm × 180 mm, height 5 cm) was placed on the acrylic plate so as to have a predetermined basis weight. Next, the dried sheet was peeled from the acrylic plate to obtain a fine fibrous cellulose-containing sheet 1.
The moisture content after the dried fine fibrous cellulose-containing sheet 1 was allowed to stand for 24 hours at 23 ° C. and 50% relative humidity was 9.6% by mass. The moisture content of the post-humidity-controlled sheet after being allowed to stand for 24 hours at 23 ° C. and 50% relative humidity was measured by measuring the mass of the sheet that was allowed to stand for 24 hours under the conditions of 23 ° C. and 50% relative humidity. Thereafter, the sheet was dried with a hot air drier at 105 ° C. for 24 hours, the mass in the absolutely dry state was measured, and calculated from the following formula.
Moisture content after humidity conditioning [% by mass] = (sheet mass after humidity conditioning−sheet mass in an absolutely dry state) / sheet mass after humidity conditioning × 100

<Wetting treatment>
The obtained fine fibrous cellulose-containing sheet 1 was immersed in ion exchange water at 23 ° C. for 30 seconds to obtain a wet sheet containing fine fibrous cellulose. In addition, the moisture content of the fine fibrous cellulose-containing wet sheet is determined by immersing a 50 mm square fine fibrous cellulose-containing wet sheet in 23 ° C. ion exchange water for 30 seconds and measuring the mass after the immersion. Was measured for 24 hours with a hot air dryer at 105 ° C., and the mass was measured and calculated from the following formula. The measurement was repeated 5 times, and the average value was the moisture content of the wet sheet containing fine fibrous cellulose.
Moisture content of wet sheet [% by mass] = (mass of wet sheet after immersion in ion exchange water−absolute dry mass of sheet) / mass of wet sheet after immersion in ion exchange water × 100
In addition, the moisture content in the solid content mass of the fine fibrous cellulose-containing wet sheet was calculated from the following formula.
Moisture content of wet sheet (based on solid content) [% by mass] = (mass of wet sheet after immersion in ion-exchanged water−absolute dry mass of sheet) / absolute dry mass of sheet × 100

[Example 2]
A wet sheet containing fine fibrous cellulose was obtained in the same manner as in Example 1 except that the immersion time in <wet treatment> was 60 seconds.

[Example 3]
A wet sheet containing fine fibrous cellulose was obtained in the same manner as in Example 1 except that the immersion time in <wet treatment> was 120 seconds.

[Example 4]
To ion-exchanged water, acetoacetyl group-modified polyvinyl alcohol (Nippon Gosei Co., Ltd., Gohsenx Z200, degree of polymerization: 1200, degree of saponification: 99 mol% or more) was added to 10% by mass, and stirred at 95 ° C. for 1 hour. Dissolved.
Example 2 except that the fine fibrous cellulose dispersion A and the acetoacetyl group-modified polyvinyl alcohol solution were mixed so that the acetoacetyl group-modified polyvinyl alcohol was 40 parts by mass with respect to 100 parts by mass of the fine fibrous cellulose. Similarly, a fine fibrous cellulose-containing sheet 2 and a fine fibrous cellulose-containing wet sheet were obtained.

[Example 5]
20 parts by mass of a 0.5% by mass aqueous solution of polyethylene oxide (manufactured by Sumitomo Seika Co., Ltd., PEO-18) was added to 100 parts by mass of the fine fibrous cellulose dispersion A having a solid content concentration of 0.5% by mass. Thereafter, an emulsion of polypropylene resin (Toho Chemical Co., Ltd., HYTEC P-5060P, particle size 30 nm) was added to the dispersion so as to be 10 parts by mass with respect to 100 parts by mass of fine fibrous cellulose.
Thirty seconds after the addition of the polypropylene resin emulsion, polyamine polyamide epichlorohydrin (manufactured by Seiko PMC Co., Ltd., wet paper strength agent WS4030) is 0.4 parts by mass with respect to 100 parts by mass of fine fibrous cellulose. Added. A fine fibrous cellulose-containing sheet 3 was obtained in the same manner as in Example 1 except that this dispersion was formed into a sheet. The obtained fine fibrous cellulose-containing sheet 3 in a dry state was immersed in ion exchange water at 23 ° C. for 5 minutes to obtain a wet sheet containing fine fibrous cellulose.

[Example 6]
The fine fibrous cellulose-containing sheet 4 and the fine fibrous cellulose contained in the same manner as in Example 5 except that the amount of polyamine polyamide epichlorohydrin added was 0.2 parts by mass with respect to 100 parts by mass of the fine fibrous cellulose. A wet sheet was obtained.

[Example 7]
The dried fine fibrous cellulose-containing sheet 1 obtained in the same manner as in Example 1 was subjected to a crosslinking treatment by the following method. First, water was added to magnesium sulfate heptahydrate (manufactured by Kanto Chemical Co., Ltd.) to prepare an aqueous solution containing 5% by mass of magnesium sulfate. The fine fibrous cellulose-containing sheet 1 was immersed in this aqueous solution for 8 minutes and subjected to a crosslinking treatment with magnesium. Next, this sheet was immersed in ion exchange water for 15 minutes and washed. After repeating this washing twice, the sheet was affixed to an acrylic plate and dried in a chamber at 35 ° C. and a relative humidity of 15% to obtain a dried fine fibrous cellulose-containing sheet 5.
The obtained fine fibrous cellulose-containing sheet 5 was immersed in ion exchange water at 23 ° C. for 5 minutes to obtain a wet sheet containing fine fibrous cellulose.

[Example 8]
A fine fibrous cellulose-containing sheet 6 and a fine fibrous cellulose-containing wet sheet were obtained in the same manner as in Example 7 except that the immersion time in the magnesium sulfate aqueous solution was 3 minutes.

[Comparative Example 1]
A wet sheet containing fine fibrous cellulose was obtained in the same manner as in Example 5 except that the immersion time in the wet treatment was 30 seconds.

[Comparative Example 2]
The sheet in the middle of drying in the <sheeting> step in Example 1 was a fine fibrous cellulose-containing wet sheet. The water content of the fine fibrous cellulose-containing wet sheet obtained in Comparative Example 2 was calculated using the following equation.
Moisture content [mass%] = (mass of wet sheet during drying−absolute dry mass of sheet) / mass of wet sheet during drying × 100
In addition, the mass of the wet sheet in the middle of drying is based on the total mass of the sheet preparation tool (a metal frame for damming on the acrylic plate) and the sheet installed in a constant temperature dryer at 50 ° C. in the <sheeting> step. The mass was obtained by subtracting the mass of the sheet making tool. In addition, the absolutely dry mass of the sheet was the mass of the sheet after the fine fibrous cellulose-containing wet sheet obtained during drying was dried at 105 ° C. for 24 hours.

[Comparative Example 3]
In the <sheeting> step in Comparative Example 2, the drying time was stopped at a shorter position, and a wet sheet containing fine fibrous cellulose with a uniform moisture distribution was obtained visually. The moisture content of the wet sheet was calculated by the same method as in Comparative Example 2.

[Comparative Example 4]
A pulp sheet made of Oji Paper's softwood kraft pulp was defibrated using a swirling jet airflow defibrating apparatus, and then a fiber sheet was formed using an airlaid web forming apparatus. An aqueous binder liquid of an ethylene-vinyl acetate copolymer resin emulsion (Sumitomo Chemtech, Sumikaflex 755, Tg-15 ° C.) is sprayed on the fiber sheet so that the solid content adheres to 4.5 g / m ^2. After spraying, hot air (atmosphere temperature 150 ° C.) was passed to bond the fibers to each other. Further, the fiber sheet was inverted, and the aqueous binder liquid was sprayed on the opposite side of the surface on which the aqueous binder liquid was first sprayed so that the solid content was 44.5 g / m ^2. Atmospheric temperature 150 ° C.) was passed to obtain a dry nonwoven fabric. The basis weight of the obtained nonwoven fabric was 48 g / m ² .

[Evaluation]
[Evaluation of sheet containing fine fibrous cellulose before wetting]
<Punching workability evaluation>
After cutting the sheet containing fine fibrous cellulose before wetting into 100 mm square and leaving it at 23 ° C. and 50% relative humidity for 24 hours, using a punching machine (FUJI SHOKO MACHINERY CORPORATION, UD-5000), A punch test was performed. Here, as a punching blade, an outer frame punching blade having a rectangular shape of 60 mm long × 80 mm wide and having four corners curved to R = 10 mm, and an elliptical inner through-hole blade having a short diameter of 20 mm × long diameter of 40 mm The provided pinnacle blade was used. This punching blade was arranged so that the short side of the outer frame punching blade was perpendicular to the traveling direction of the sheet.
The punching test was performed 5 times, and the sheet after punching and the pinnacle blade were observed and evaluated according to the following criteria. When both sheet cracking and pinnacle blade contamination occurred during one test, one set was counted as “one time”.
○: Chips and cracks do not occur in all five tests, and the pinnacle blade is free of dirt and other deposits.
(Triangle | delta): During the test of 5 times, a crack of a sheet | seat and / or the stain | pollution | contamination of a pinnacle blade generate | occur | produced once.
X: During 5 tests, sheet cracking and / or pinnacle blade contamination occurred twice or more.

[Evaluation of wet fine fibrous cellulose-containing sheet]
<Density>
The 50-mm square wet microfiber cellulose-containing sheet was dried in a hot air dryer at 105 ° C. for 24 hours to be in an absolutely dry state, then the thickness and basis weight of the sheet were measured, and the sheet density (g / cm ³ ) Was calculated.

<Tensile properties>
After cutting the sheet containing fine fibrous cellulose before wetting to a width of 25 mm and a length of 150 mm, wetting is performed in accordance with “7.2 Partial Soaking Method” of JIS P 8135 except that the dipping time is set to the time of each wetting condition. The tensile strength (unit: N / m) and tension using a tensile tester Tensilon (manufactured by A & D Co.) according to JIS P 8113, except that the distance between the grips is 100 mm. Elastic modulus and elongation were measured. In addition, the immersion time of the sample used for the tensile property test was the same as the immersion time in each Example and Comparative Example. The tensile strength (unit: MPa) was calculated by dividing the tensile strength by the thickness of the test piece.

<Rubber hardness>
Rubber hardness in accordance with JIS K 6253-3, except that the wet microfibrous cellulose-containing sheet is cut to a width of 25 mm and a length of 50 mm, the test pieces are stacked to a thickness of 2 mm, and the measurement time is 30 seconds. Was measured. For the measurement, an Asker rubber hardness meter E type (manufactured by Kobunshi Keiki Co., Ltd.) was used.

<Haze>
In accordance with JIS K 7136, the haze of the wet sheet containing fine fibrous cellulose was measured using a haze meter (manufactured by Murakami Color Research Laboratory Co., Ltd., HM-150).

<Ease of seating>
The wet sheet containing fine fibrous cellulose is cut into a 100 mm square, and this wet sheet is pasted along the unevenness of the middle phalangeal joint of the fist of a human hand. The ease of handling of the wet sheet at the time of pasting is shown below. Evaluated by criteria.
○: It has moderate elongation and strength and is easy to wear.
Δ: Too much force breaks or stretches, making it difficult to wear.
X: It is difficult to wear because it is easily torn, or it is strong but has poor elongation and is difficult to wear.

<Visibility of bubbles (evaluation of initial contact state)>
A 100 mm square wet sheet was affixed to the unevenness of the metacarpophalangeal joint of the fist of a human hand, and the ease of air bubbles between the skin and the sheet was evaluated according to the following criteria.
○: The bubbles can be visually confirmed from a distance of 30 cm or more, and the bubbles can be easily removed and adhered to the skin.
X: Visual confirmation of bubbles cannot be made unless the distance is within 10 cm. Or there are many air bubbles derived from the unevenness of the sheet, and all the air bubbles cannot be removed and adhered to the skin.

<Degree of sticking to skin (adhesion durability evaluation)>
A 100 mm square wet sheet was attached to the unevenness of the metacarpophalangeal joint of the fist of a human hand, and then the palm was opened and closed once. The degree of sticking of the sheet at that time was evaluated according to the following criteria.
○: Cannot be peeled off.
Δ: A part of the sheet is lifted.
X: More than half peel off.

  The fine fibrous cellulose-containing wet sheet obtained in the examples can be easily mounted and has excellent adhesion to the skin (initial adhesion and adhesion persistence). Furthermore, the fine fibrous cellulose-containing wet sheet obtained in the examples was excellent in transparency.

  The fine fibrous cellulose-containing wet sheets obtained in the examples were excellent in processability in a dry state, and particularly excellent in punching processability. Such an effect is, for example, an effect that cannot be obtained with a biocellulose-based fine fibrous cellulose-containing wet sheet.

  In addition, the fine fibrous cellulose-containing wet sheet obtained in Comparative Example 1 had a low moisture content, was not easily mounted, and had poor adhesion. In the wet sheet containing fine fibrous cellulose obtained in Comparative Example 2, there are a dried portion and a portion where water is collected, and the water distribution is clearly uneven even visually, and a sample suitable for evaluation is obtained. I couldn't. In Comparative Example 3, the sheet was very fragile and the sheet could not be peeled off from the acrylic plate. For this reason, a sample suitable for evaluation was not obtained. When the sheet obtained in Comparative Example 4 was attached to the skin surface, a large number of bubbles were generated, the bubbles could not be removed, and could not be adhered to the skin.

Claims (9)

A sheet containing fibrous cellulose having a fiber width of 1000 nm or less and water,
The sheet is in gel form,
The fibrous cellulose has a substituent derived from a phosphite group or a phosphite group,
The moisture content is 70% by mass or more based on the total mass of the sheet,
A sheet having a tensile strength of 0.08 MPa or more.   The sheet according to claim 1, wherein the fibrous cellulose has a fiber width of 8 nm or less.   The sheet according to claim 1 or 2, wherein the tensile elastic modulus is 0.5 MPa or more.   The sheet according to any one of claims 1 to 3, which has an elongation of 5.0% or more.   The sheet according to any one of claims 1 to 4, wherein the haze is 20.0% or less. The sheet according to claim 1, wherein the density of the sheet in an absolutely dry state is 0.5 g / cm ³ or more.   The sheet according to any one of claims 1 to 6, further comprising a resin component.   The sheet according to any one of claims 1 to 7, further comprising an external preparation for skin.   The sheet according to any one of claims 1 to 8, which is for a beauty sheet.

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