JP2020020075A - Wet sheet and manufacturing method of wet sheet - Google Patents

Abstract

To provide a wet sheet capable of exhibiting excellent deodorant function.SOLUTION: The invention relates to a wet sheet containing a fibrous cellulose having a fiber width of 1,000 nm or less. Moreover, the invention relates to a manufacturing method of the wet sheet including a step of impregnating a chemical solution containing a metal component-loaded fibrous cellulose having a fiber width of 1,000 nm or less into a substrate sheet.SELECTED DRAWING: None

Description

  The present invention relates to a wet sheet and a method for manufacturing the wet sheet.

  Conventionally, cleaning articles such as a cleaning wiper and a wipe for a toilet have been used. As such a cleaning product, a cleaning product in which a nonwoven fabric is impregnated with moisture or a chemical has been put on the market. Some cleaning supplies can be flushed to the flush toilet after use.

  For example, Patent Document 1 discloses a wet wiping sheet obtained by impregnating a nonwoven fabric with a chemical solution. Here, the chemical solution contains cellulose nanofibers, and studies have been made to improve the performance of wiping dirt such as baby's muddy stool by this.

  Patent Document 2 discloses a water-disintegrable wiper including a metal-supported cellulose fiber obtained by supporting predetermined metal particles on an oxidized cellulose fiber having a carboxyl group or a carboxylate group on its surface, and a pulp fiber. I have. Patent Literature 3 discloses a water-disintegrable sheet in which a base paper sheet is impregnated with a water-based drug. In this case, the water-based drug contains cellulose nanofibers.

JP 2018-086203 A JP-A-2017-115277 Japanese Patent No. 6346969

  By the way, the wet sheet may be used for wiping the ass or cleaning the toilet space. In such a case, the wet sheet may be required to have a deodorizing function. However, in the conventional wet sheet, the deodorizing function was not sufficiently exhibited, and improvement was required.

  Therefore, the present inventors have studied to solve such problems of the related art with a view to providing a wet sheet that can exhibit an excellent deodorizing function.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a wet sheet contains fibrous cellulose having a fiber width of 1000 nm or less carrying a metal component, thereby providing an excellent deodorizing function. It has been found that a wet sheet capable of exhibiting the following is obtained.
Specifically, the present invention has the following configuration.

[1] A wet sheet containing fibrous cellulose supporting a metal component and having a fiber width of 1000 nm or less.
[2] The wet sheet according to [1], wherein the fibrous cellulose has an anionic group.
[3] The wet sheet according to [2], wherein the anionic group is at least one selected from a carboxyl group, a substituent derived from a carboxyl group, a phosphate group, and a substituent derived from a phosphate group.
[4] The wet sheet according to [2] or [3], wherein the anionic group is at least one selected from a phosphate group and a substituent derived from the phosphate group.
[5] The wet sheet according to any one of [1] to [4], wherein the metal component is at least one selected from Ag, Au, Pt, Pd, Cu, and Zn.
[6] A method for producing a wet sheet, comprising a step of impregnating a base sheet with a drug solution containing fibrous cellulose having a metal component-supported fiber width of 1000 nm or less,
A method for producing a wet sheet, wherein the concentration of fibrous cellulose in a chemical solution is 0.05 to 20% by mass.

  ADVANTAGE OF THE INVENTION According to this invention, the wet sheet which can exhibit the outstanding deodorizing function can be obtained.

FIG. 1 is a graph showing the relationship between the dropping amount of NaOH and the electric conductivity for a fiber raw material having a phosphate group. FIG. 2 is a graph showing the relationship between the dropping amount of NaOH and the electric conductivity for a fiber raw material having a carboxyl group.

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

(Wet sheet)
The present invention relates to a wet sheet containing fibrous cellulose supporting a metal component and having a fiber width of 1000 nm or less. In the present specification, fibrous cellulose having a fiber width of 1000 nm or less is also referred to as fine fibrous cellulose.

  Since the wet sheet of the present invention has the above configuration, it exhibits an excellent deodorizing function. Specifically, since the wet sheet contains fibrous cellulose having a fiber width of 1000 nm or less, a functional substance exhibiting a deodorizing function can be captured between fibers or carried on fibers. . Thereby, the falling off of the functional substance exhibiting the deodorizing function is suppressed, and the wet sheet can exhibit the excellent deodorizing function over a long period of time.

  Examples of the functional substance that exhibits a deodorizing function include at least one metal component selected from Ag, Au, Pt, Pd, Cu, and Zn. Such a metal component includes Ag, It is preferably at least one selected from Cu and Zn, and particularly preferably Ag. The fibrous cellulose having a fiber width of 1000 nm or less also exerts the deodorizing effect.

  Since the wet sheet of the present invention has the above-described configuration, it can carry other functional substances in addition to the functional substance exhibiting the deodorizing function. Examples of other functional substances further include aromatic substances, antibacterial substances, substances having a virus inactivating effect, substances having a moisturizing effect, and the like. By containing such a functional substance, various functions can be imparted to the wet sheet in addition to the deodorizing function.

  Further, since the wet sheet of the present invention has the above-described configuration, the strength of the wet sheet is enhanced. By containing the fine fibrous cellulose, the tensile strength of the wet sheet can be increased, and further, the tensile strength of the wet sheet when wet can be increased.

  The wet sheet may be a sheet made of fibrous cellulose having a fiber width of 1000 nm or less, but is preferably a layer containing other fibers. Other fibers include at least one selected from natural fibers, synthetic fibers, and regenerated fibers. Examples of natural fibers include pulp, cotton, wool, silk and the like. Examples of the synthetic fibers include polyester fibers, polyolefin fibers, nylon fibers, and acrylic resin fibers. Rayon fibers, acetate fibers, and the like can be given as examples of the recycled fibers. Above all, the wet sheet preferably contains pulp, and preferably contains coarse pulp fibers having a fiber width exceeding 1000 nm.

The content of fine fibrous cellulose in the wet sheet is preferably 0.05 g / ^{m 2} or more, more preferably 0.1 g / ^{m 2} or more, it is 0.5 g / ^{m 2} or more More preferred. Further, the content of the fine fibrous cellulose is preferably 15 g / m ² or less, more preferably 12 g / m ² or less, and further preferably 10 g / m ² or less.

  When the wet sheet contains pulp fibers, the ratio of pulp fibers to fine fibrous cellulose is preferably 1: 0.0001 to 1: 0.1, and is 1: 0.0005 to 1: 0.05. Is more preferable.

  The wet sheet preferably further contains water. The fine fibrous cellulose contained in the wet sheet has high hydrophilicity and can also increase the water retention in the wet sheet. For this reason, the wet sheet of the present invention has sufficient water retention, and the water retention is maintained for a long period of time.

  The sheet forming the wet sheet may further contain other components in addition to the fibrous cellulose having a fiber width of 1000 nm or less and the other fibers described above. Examples of the other components include a binder component and the like. Examples of the binder component include a thermoplastic resin and starch. Examples of the binder component include water-soluble polymers, and specifically, carboxymethyl cellulose, carboxyvinyl polymer, polyvinyl alcohol, alkyl methacrylate / acrylic acid copolymer, polyvinyl pyrrolidone, sodium polyacrylate, polyethylene glycol , Diethylene glycol, triethylene glycol, polyethylene oxide, propylene glycol, dipropylene glycol, polypropylene glycol, isoprene glycol, hexylene glycol, 1,3-butylene glycol, polyacrylamide and the like.

  Other components further include a dry strength agent, a wet strength agent, a softening agent, a wetting agent, an antibacterial agent, an antifungal agent, a fragrance, a drug having a desired medicinal effect, and the like. Examples of the dry paper strength agent include cationized starch, polyacrylamide (PAM), carboxymethyl cellulose (CMC), and the like. Examples of the wet paper strength agent include polyamide epichlorohydrin, urea, melamine, and thermally crosslinkable polyacrylamide. Examples of the softener include an anionic surfactant, a nonionic surfactant, a cationic surfactant, and the like. Examples of the wetting agent include water and propylene glycol. Examples of the antibacterial agent / antifungal agent include alcohol, parabenzoic acid esters, triclosan, cetylpyridinium chloride and the like. Examples of the flavor include essential oils of plants (such as lavender, rosemary, peppermint, spearmint, and eucalyptus), menthol, and citronellol. The above optional components may be used alone or in combination of two or more.

  The thickness of the wet sheet is preferably at least 10 μm, more preferably at least 20 μm, even more preferably at least 30 μm. Further, the thickness of the wet sheet is preferably 3000 μm or less, more preferably 1000 μm or less, and still more preferably 300 μm.

  The wet sheet is used as, for example, a wet tissue, a butt wipe, a wet wiper, or the like. In this case, the wet sheet may be embossed depending on the use of the wet sheet. In this case, the embossing may be applied uniformly over the entire area of the wet sheet, but may be applied unevenly in order to provide designability and functionality. The densities may be different. The emboss pattern (shape) is not particularly limited, and may be a circle, an ellipse, or a polygon (a triangle, a square, a pentagon, a hexagon, or the like).

When the wet sheet is embossed, the diameter of one emboss (the diameter of a circumscribed circle in the case of a polygon and the longest diameter in the case of an ellipse) is preferably 0.5 mm or more and 8 mm or less. , More preferably from 0.7 mm to 5 mm, even more preferably from 0.7 mm to 3 mm, particularly preferably from 1 mm to 3 mm. The embossing density is preferably 0.1 / cm ² or more 50 / cm ² or less, more preferably 0.5 pieces / cm ² or more 30 / cm ² or less, 1 / cm ² More preferably, it is at least 25 particles / cm ² .

  The wet sheet may be a water-disintegrable sheet. In this case, the water disintegration of the wet sheet may be 100 seconds or less, preferably 96 seconds or less, more preferably 90 seconds or less, still more preferably 80 seconds or less, and more preferably 70 seconds or less. Is particularly preferred. The water decomposability of the wet sheet is determined by impregnating the base sheet with pure water so that the mass ratio of the absolutely dry base sheet and the water constituting the wet sheet is 1: 2 (base sheet: water). In this state, it was measured in accordance with JIS P 4501 “4.5 Unravelability”.

(Fine fibrous cellulose)
The wet sheet contains fibrous cellulose (fine fibrous cellulose) having a fiber width of 1000 nm or less.

  The average fiber width of the fibrous cellulose is 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 particularly preferably 2 nm or more and 10 nm or less. preferable. By setting the average fiber width of the fibrous cellulose to 2 nm or more, dissolution in water as cellulose molecules is suppressed, and the effect of improving the strength, rigidity, and dimensional stability of the fibrous cellulose can be more easily exhibited. it can. The fibrous cellulose is, for example, a monofibrous cellulose.

The average fiber width of the fibrous cellulose is measured, for example, using an electron microscope as follows. First, an aqueous suspension of fibrous cellulose having a concentration of 0.05% by mass or more and 0.1% by mass or less was prepared, and this suspension was cast on a carbon film-coated grid that had been subjected to a hydrophilization treatment, and a TEM observation sample was prepared. And In the case of including a wide fiber, an SEM image of a surface cast on glass may be observed. Next, observation with an electron microscope image is performed at a magnification of 1,000 times, 5000 times, 10,000 times, or 50,000 times depending on the width of the fiber to be observed. However, the sample, observation conditions and magnification are adjusted so as to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary position in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y 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 the straight line X and the straight line Y is visually read for an observation image satisfying the above conditions. In this way, at least three or more sets of observation images of the surface portions that do not overlap each other are obtained. Next, the width of the fiber that intersects the straight line X and the straight line Y is read for each image. Thereby, the fiber width of at least 20 fibers × 2 × 3 = 120 fibers is read. Then, the average value of the read fiber width is defined as the average fiber width of the fibrous cellulose.

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

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

  The proportion of the type I crystal structure in the fine fibrous cellulose is, for example, preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. Thereby, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion coefficient. The crystallinity can be determined by measuring the X-ray diffraction profile and using a pattern thereof according to a conventional method (Seagal et al., Textile Research Journal, Vol. 29, p. 786, 1959).

  The axial ratio (fiber length / fiber width) of fibrous cellulose is not particularly limited, but is preferably, for example, 20 or more and 10,000 or less, and more preferably 50 or more and 1000 or less. When the axial ratio is equal to or more than the lower limit, a sheet containing fine fibrous cellulose is easily formed. It is preferable that the axial ratio be equal to or less than the above upper limit, for example, when handling fibrous cellulose as an aqueous dispersion, handling such as dilution becomes easy.

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

  The fibrous cellulose in the present embodiment preferably has an anionic group. Examples of the anionic group include a phosphate group or a substituent derived from a phosphate group (sometimes simply referred to as a phosphate group), a carboxyl group or a substituent derived from a carboxyl group (sometimes simply referred to as a carboxyl group), and It is preferably at least one selected from a sulfone group or a substituent derived from a sulfone group (also simply referred to as a sulfone group), and a carboxyl group, a substituent derived from a carboxyl group, a phosphate group, and a phosphate group. And more preferably at least one selected from a phosphate group and a substituent derived from a phosphate group. A phosphate group has a larger number of anionic groups per molecule than a carboxyl group or the like, and thus can carry more metal components. Thereby, it is considered that a more excellent deodorizing effect is exhibited.

The phosphate group is a divalent functional group corresponding to, for example, a phosphoric acid obtained by removing a hydroxyl group from phosphoric acid. Is specifically a group represented by _-PO 3 _{H 2.} The substituent derived from the phosphate group includes substituents such as a salt of the phosphate group and a phosphate group. The substituent derived from the phosphate group may be contained in the fibrous cellulose as a group in which the phosphate group is condensed (for example, a pyrophosphate group).
The phosphate group or a substituent derived from the phosphate group is, for example, a substituent represented by the following formula (1).

In the formula (1), a, b and n are natural numbers (where a = b × m). a among α ¹ , α ² ,..., α ⁿ and α ′ are O ⁻ , and the rest are either R or OR. Note that all of αn and α ′ may be O ⁻ . R represents a hydrogen atom, a saturated-straight-chain hydrocarbon group, a saturated-branched-chain hydrocarbon group, a saturated-cyclic hydrocarbon group, an unsaturated-straight-chain hydrocarbon group, or an unsaturated-branched-chain hydrocarbon group, respectively. A hydrogen group, an unsaturated-cyclic hydrocarbon group, an aromatic group, or a derivative thereof.

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

  Further, as the deriving group for R, a functional group in which at least one of functional groups such as a carboxyl group, a hydroxyl group, or an amino group is added or substituted to a main chain or a side chain of the above various hydrocarbon groups. Although a group is mentioned, it is not particularly limited. Further, the number of carbon atoms constituting the main chain of R is not particularly limited, but is preferably 20 or less, more preferably 10 or less. By setting the number of carbon atoms constituting the main chain of R to the above range, the molecular weight of the phosphate group can be adjusted to an appropriate range, facilitating penetration into the fiber material, and increasing the yield of fine cellulose fibers. You can also.

β ^{b +} is a monovalent or higher cation composed of an organic or inorganic substance. Examples of the monovalent or higher cation composed of an organic substance include aliphatic ammonium and aromatic ammonium. Examples of the monovalent or higher cation composed of an inorganic substance include sodium, potassium, and ions of an alkali metal such as lithium, Examples thereof include cations of divalent metals such as calcium and magnesium, and hydrogen ions, but are not particularly limited. These can be applied alone or in combination of two or more. The monovalent or higher cation comprising an organic or inorganic substance is preferably a sodium or potassium ion which is less likely to turn yellow when a β-containing fiber material is heated and which is industrially easy to use, but is not particularly limited.

The amount of the anionic group introduced into the fibrous cellulose is, for example, preferably 0.10 mmol / g or more, more preferably 0.20 mmol / g or more, and preferably 0.50 mmol / g per 1 g (mass) of the fibrous cellulose. More preferably, it is more preferably 1.00 mmol / g or more. The amount of anionic group introduced into fibrous cellulose is, for example, preferably 3.65 mmol / g or less, more preferably 3.50 mmol / g or less, and more preferably 3.00 mmol per 1 g (mass) of fibrous cellulose. / G or less. By setting the introduction amount of the anionic group within the above range, it is possible to easily make the fiber raw material fine, and it is possible to increase the stability of the fibrous cellulose.
Here, the unit mmol / g indicates the amount of the substituent per 1 g of the mass of fibrous cellulose when the counter ion of the anionic group is a hydrogen ion (H ⁺ ).

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

  FIG. 1 is a graph showing the relationship between the amount of NaOH added to fibrous cellulose having a phosphate group and the electrical conductivity. The amount of phosphate groups introduced into fibrous cellulose is measured, for example, as follows. First, a slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, before the treatment with the strongly acidic ion exchange resin, a fibrillation treatment similar to the fibrillation treatment step described later may be performed on the measurement target. Next, a change in electric conductivity is observed while adding an aqueous solution of sodium hydroxide, and a titration curve as shown in FIG. 1 is obtained. As shown in FIG. 1, the electrical conductivity sharply decreases at first (hereinafter, referred to as “first region”). Thereafter, the conductivity starts to slightly increase (hereinafter, referred to as “second region”). Thereafter, the increment of the conductivity increases (hereinafter, referred to as “third region”). Note that the boundary point between the second region and the third region is defined as the point at which the amount of change in the conductivity twice (ie, the increment (slope) of the conductivity) becomes maximum. Thus, three regions appear in the titration curve. Of these, the amount of alkali required in the first region is equal to the amount of strongly acidic groups in the slurry used for titration, and the amount of alkali required in the second region is equal to the amount of weakly acidic groups in the slurry used for titration. Become equal. When the phosphate group causes condensation, the weakly acidic group is apparently lost, and the amount of alkali required in the second region is smaller than the amount of alkali required in the first region. On the other hand, the amount of the strongly acidic group matches the amount of the phosphorus atom regardless of the presence or absence of condensation. For this reason, simply referring to the phosphate group introduction amount (or phosphate group amount) or the substituent group introduction amount (or substituent amount) indicates a strongly acidic group amount. Therefore, the value obtained by dividing the alkali amount (mmol) required in the first region of the titration curve obtained above by the solid content (g) in the slurry to be titrated is the phosphate group introduction amount (mmol / mmol). g).

  FIG. 2 is a graph showing the relationship between the amount of NaOH added to fibrous cellulose having a carboxyl group and the electrical conductivity. The amount of carboxyl groups introduced into fibrous cellulose is measured, for example, as follows. First, a slurry containing fibrous cellulose is treated with a strongly acidic ion exchange resin. If necessary, before the treatment with the strongly acidic ion exchange resin, a fibrillation treatment similar to the fibrillation treatment step described later may be performed on the measurement target. Next, a change in electric conductivity is observed while adding an aqueous solution of sodium hydroxide, and a titration curve as shown in FIG. 2 is obtained. As shown in FIG. 2, the titration curve shows a first region where the increment (slope) of the conductivity becomes substantially constant after the decrease in the electric conductivity, and thereafter, the increment (slope) of the conductivity increases. It is divided into a second area. Note that the boundary point between the first region and the second region is defined as a point at which the amount of change in the conductivity twice (in other words, the increment (slope) of the conductivity becomes maximum). Then, the value obtained by dividing the amount of alkali (mmol) required in the first region of the titration curve by the solid content (g) in the slurry containing fine fibrous cellulose to be titrated is the amount of carboxyl group introduced ( mmol / g).

The amount of carboxyl group introduced (mmol / g) refers to the amount of substituent per mass of fibrous cellulose when the counter ion of the carboxyl group is hydrogen ion (H ⁺ ) (hereinafter, the amount of carboxyl group (acid Type). On the other hand, when the counter ion of the carboxyl group is substituted with an arbitrary cation C so as to have a charge equivalent, the denominator is converted into the mass of fibrous cellulose when the cation C is a counter ion. Then, the amount of carboxyl groups of the fibrous cellulose having the cation C as a counter ion (hereinafter, the amount of carboxyl groups (C type)) can be determined.
That is, the carboxyl group introduction amount is calculated by the following formula.
Carboxyl group introduction amount (C type) = Carboxyl group amount (acid type) / {1+ (W-1) × (carboxyl group amount (acid type)) / 1000}
W: Formula weight per valence of cation C (eg, 23 for Na, 9 for Al)

<Manufacturing process of fine fibrous cellulose>
Fine fibrous cellulose is produced from a fiber raw material containing cellulose. The fiber material containing cellulose is not particularly limited, but pulp is preferably used because it is easily available and inexpensive. Pulp includes, for example, wood pulp, non-wood pulp, and deinked pulp. Examples of the wood pulp include, but are not limited to, hardwood kraft pulp (LBKP), softwood kraft pulp (NBKP), sulfite pulp (SP), dissolved pulp (DP), soda pulp (AP), and unbleached kraft pulp (UKP). And oxygen bleached kraft pulp (OKP); semi-chemical pulp such as semi-chemical pulp (SCP) and chemical ground wood pulp (CGP); groundwood pulp (GP); and thermomechanical pulp (TMP, BCTMP). And mechanical pulp. Non-wood pulp includes, but is not limited to, cotton pulp such as cotton linter and cotton lint, and non-wood pulp such as hemp, straw and bagasse. Examples of the deinked pulp include, but are not particularly limited to, deinked pulp made from waste paper. As the pulp of this embodiment, one of the above-mentioned types may be used alone, or two or more types may be used in combination.
Among the above pulp, for example, wood pulp and deinked pulp are preferable from the viewpoint of availability. In addition, among wood pulp, a viewpoint that the cellulose ratio is large and the yield of fine fibrous cellulose at the time of defibration treatment is high, and the decomposition of cellulose in pulp is small, and fine fibrous cellulose of long fibers having a large axial ratio can be obtained From the viewpoint, for example, chemical pulp is more preferable, and kraft pulp and sulfite pulp are more preferable.

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

<Phosphate group introduction step>
When the fine fibrous cellulose has a phosphate group, the step of producing the fine fibrous cellulose includes a step of introducing a phosphate group. In the phosphate group introduction step, at least one compound selected from compounds capable of introducing a phosphate group by reacting with a hydroxyl group of a cellulose-containing fiber material (hereinafter, also referred to as “compound A”) is converted into cellulose. This is a step of acting on a fiber raw material containing. By this step, a phosphate group-introduced fiber is obtained.

  In the phosphate group introduction step according to the present embodiment, the reaction between the fiber material containing cellulose and the compound A is performed in the presence of at least one selected from urea and its derivatives (hereinafter, also referred to as “compound B”). You may. On the other hand, the reaction between the fiber raw material containing cellulose and the compound A may be performed in a state where the compound B is not present.

  As an example of a method of causing the compound A to act on the fiber material in the presence of the compound B, a method of mixing the compound A and the compound B with the fiber material in a dry state, a wet state, or a slurry state can be mentioned. Among them, it is preferable to use a fiber material in a dry state or a wet state, and particularly to use a fiber material in a dry state, because of high uniformity of the reaction. The form of the fiber raw material is not particularly limited, but is preferably, for example, cotton or a thin sheet. The compound A and the compound B may be added to the fiber material in the form of a powder, a solution dissolved in a solvent, or a state in which the compound A and the compound B are heated to a melting point or higher and melted. Among these, it is preferable to add in the form of a solution dissolved in a solvent, particularly in the form of an aqueous solution, because of high reaction uniformity. Further, the compound A and the compound B may be added simultaneously to the fiber raw material, may be added separately, or may be added as a mixture. The method of adding the compound A and the compound B is not particularly limited, but when the compound A and the compound B are in a solution state, the fiber raw material may be immersed in the solution, absorbed and then taken out. May be added dropwise to the solution. In addition, the necessary amount of compound A and compound B may be added to the fiber raw material, or the excessive amount of compound A and compound B may be added to the fiber raw material, respectively, and then the excess compound A and compound B may be squeezed or filtered. It may be removed.

  The compound A used in the present embodiment includes, but is not particularly limited to, phosphoric acid or a salt thereof, dehydrated condensed phosphoric acid or a salt thereof, and phosphoric anhydride (diphosphorus pentoxide). As phosphoric acid, those having various purities can be used. For example, 100% phosphoric acid (normal phosphoric acid) and 85% phosphoric acid can be used. The dehydrated condensed phosphoric acid is obtained by condensing two or more molecules of phosphoric acid by a dehydration reaction, and examples thereof include pyrophosphoric acid and polyphosphoric acid. Examples of the phosphate and the dehydrated condensed phosphate include lithium salt, sodium salt, potassium salt, and ammonium salt of phosphoric acid or dehydrated condensed phosphoric acid, and these can have various degrees of neutralization. Among these, phosphoric acid, phosphoric acid, phosphoric acid, from the viewpoint of high efficiency of introduction of the phosphate group, easier to improve the defibration efficiency in the defibration step described later, low cost, and industrially applicable A sodium salt, a potassium salt of phosphoric acid, or an ammonium salt of phosphoric acid is preferable, and phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, or ammonium dihydrogen phosphate is more preferable.

  The amount of the compound A added to the fiber raw material is not particularly limited. For example, when the amount of the compound A added is converted into the phosphorus atomic weight, the amount of the 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, further preferably 2% by mass or more and 30% by mass or less. By setting the amount of the phosphorus atom added to the fiber raw material within the above range, the yield of fine fibrous cellulose can be further improved. On the other hand, by setting the amount of phosphorus atoms added to the fiber raw material to be equal to or less than the above upper limit, the effect of improving the yield and the cost can be balanced.

The compound B used in this embodiment is at least one selected from urea and its derivatives as described above. Compound B includes, for example, urea, biuret, 1-phenylurea, 1-benzylurea, 1-methylurea, 1-ethylurea and the like.
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 the compound A and the compound B are dissolved.

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

  In the reaction between the fiber material containing cellulose and the compound A, for example, an amide or an amine may be included in the reaction system in addition to the compound B. Examples of the amide include formamide, dimethylformamide, acetamide, dimethylacetamide and the like. Examples of the amines include methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, hexamethylenediamine, and the like. Among these, it is known that triethylamine particularly works as a good reaction catalyst.

  In the phosphoric acid group introduction step, it is preferable that after the compound A or the like is added to or mixed with the fiber raw material, the fiber raw material is subjected to a heat treatment. As the heat treatment temperature, it is preferable to select a temperature at which a phosphate group can be efficiently introduced while suppressing the thermal decomposition and hydrolysis of the fiber. The heat treatment temperature is, for example, preferably from 50 ° C. to 300 ° C., more preferably from 100 ° C. to 250 ° C., and even more preferably from 130 ° C. to 200 ° C. In addition, equipment having various heat media can be used for the heat treatment, for example, a stirring dryer, a rotary dryer, a disk dryer, a roll heater, a plate heater, a fluidized bed dryer, an airflow A drying device, a reduced-pressure drying device, an infrared heating device, a far-infrared heating device, and a microwave heating device can be used.

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

  In addition, the heating device used for the heat treatment always generates, for example, the water retained by the slurry and the water generated by the dehydration condensation (phosphate esterification) reaction between compound A and the hydroxyl group contained in cellulose or the like in the fiber material. It is preferable that the device can be discharged outside the device system. As such a heating device, for example, an air-blowing oven or the like can be mentioned. By constantly discharging the water in the system, it is possible to suppress the hydrolysis reaction of the phosphate ester bond, which is the reverse reaction of the phosphorylation, and also to suppress the acid hydrolysis of the 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 of the heat treatment is, for example, preferably from 1 second to 300 minutes after water 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. Is more preferable. In the present embodiment, by setting the heating temperature and the heating time in an appropriate range, the amount of the phosphate group introduced can be set in a preferable range.

  The phosphoric acid group introduction step may be performed at least once, but may be repeated twice or more. By performing the phosphate group introduction step twice or more, a large number of phosphate groups can be introduced into the fiber raw material. In the present embodiment, as an example of a preferred embodiment, a case where the phosphate group introduction step is performed twice is exemplified.

<Carboxyl group introduction step>
When the fine fibrous cellulose has a carboxyl group, the step of producing the fine fibrous cellulose includes a step of introducing a carboxyl group. The carboxyl group introduction step has a compound having a carboxylic acid-derived group or a derivative having a carboxylic acid-derived group, or a carboxylic acid-derived group, for a fiber raw material containing cellulose, such as ozone oxidation or oxidation by the Fenton method, or TEMPO oxidation treatment. It is carried out by treating with an acid anhydride of a compound or a derivative thereof.

  The compound having a group derived from a carboxylic acid is not particularly limited. Tricarboxylic acid compounds. The derivative of the compound having a group derived from a carboxylic acid is not particularly limited, and examples thereof include an imidized product of an acid anhydride of a compound having a carboxyl group and a derivative of an acid anhydride of a compound having a carboxyl group. The imidized product of the acid anhydride of the compound having a carboxyl group is not particularly limited, and examples thereof include imidized products of dicarboxylic acid compounds such as maleimide, succinimide, and phthalimide.

  Examples of the acid anhydride of the compound having a group derived from a carboxylic acid include, but are not particularly limited to, maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, dicarboxylic acid compounds such as Acid anhydrides. The derivative of the acid anhydride of the compound having a group derived from a carboxylic acid is not particularly limited. For example, dimethyl maleic anhydride, diethyl maleic anhydride, and a compound having a carboxyl group such as diphenylmaleic anhydride can be used. An acid anhydride in which at least a part of hydrogen atoms are substituted with a substituent such as an alkyl group or a phenyl group is exemplified.

  In the case where the TEMPO oxidation treatment is performed in the carboxyl group introduction step, it is preferable that the treatment be performed, for example, at a pH of 6 to 8. Such a process is also called a neutral TEMPO oxidation process. Neutral TEMPO oxidation treatment is performed, for example, by adding sodium phosphate buffer (pH = 6.8), pulp as a fiber raw material, and TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl) as a catalyst. It can be performed by adding nitroxy radical and sodium hypochlorite as a sacrificial reagent. Further, by allowing sodium chlorite to coexist, aldehyde generated in the course of oxidation can be efficiently oxidized to a carboxyl group.

  Further, the TEMPO oxidation treatment may be performed under the condition that the pH is 10 or more and 11 or less. Such a treatment is also called an alkaline TEMPO oxidation treatment. The alkali TEMPO oxidation treatment can be performed, for example, by adding a nitroxy radical such as TEMPO as a catalyst, sodium bromide as a cocatalyst, and sodium hypochlorite as an oxidizing agent to pulp as a fiber raw material. .

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

<Alkali treatment step (neutralization step)>
In the case of producing fine fibrous cellulose, an alkali treatment may be performed on the fiber raw material between the anion group introduction step and the defibration treatment step described below. The method of the alkali treatment is not particularly limited, and includes, for example, a method of immersing the phosphate group-introduced fiber in an alkaline solution.

  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 the present embodiment, it is preferable to use, for example, sodium hydroxide or potassium hydroxide as the alkali compound because of high versatility. The solvent contained in the alkaline solution may be either water or an organic solvent. Above all, the solvent contained in the alkaline solution is preferably a polar solvent containing water or a polar organic solvent exemplified by alcohol, and more preferably an aqueous solvent containing at least water. As the alkali solution, for example, an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide is preferable because of high versatility.

  The temperature of the alkali solution in the alkali treatment step is not particularly limited, but is preferably, for example, 5 ° C or more and 80 ° C or less, more preferably 10 ° C or more and 60 ° C or less. The immersion time of the phosphate group-introduced fiber in the alkali solution in the alkali treatment step is not particularly limited, but is preferably, for example, 5 minutes or more and 30 minutes or less, and more preferably 10 minutes or more and 20 minutes or less. The amount of the alkali solution used in the alkali treatment is not particularly limited. For example, it is preferably from 100% by mass to 100,000% by mass, and preferably from 1,000% by mass to 10,000% by mass, based on the absolute dry mass of the phosphate group-introduced fiber. Is more preferable.

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

<Fibrillation processing>
By fibrillating the anionic group-introduced fiber in the fibrillation treatment step, fine fibrous cellulose is obtained. In the defibrating process, for example, a defibrating device can be used. The defibrating apparatus is not particularly limited, but includes, for example, a high-speed defibrillator, a grinder (stone mill type crusher), a high-pressure homogenizer or an ultra-high-pressure homogenizer, a high-pressure collision type crusher, a ball mill, a bead mill, a disc refiner, a conical refiner, and a twin-screw. A kneader, a vibration mill, a homomixer under high-speed rotation, an ultrasonic disperser, a beater, or the like can be used. Among the above defibration apparatuses, it is more preferable to use a high-speed defibrator, a high-pressure homogenizer, or an ultra-high-pressure homogenizer, which is less affected by the pulverized media and is less likely to cause contamination.

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

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

(Metal components)
It is preferable that the fine fibrous cellulose supports at least one metal component selected from Ag, Au, Pt, Pd, Cu and Zn. Such a metal component is preferably at least one selected from Ag, Cu and Zn, and particularly preferably Ag. The above-described metal component is supported, for example, by forming a coordination bond, a hydrogen bond, or an ionic bond with a phosphate group contained in the microfibrous cellulose having a phosphate group. Such a bonding state can be analyzed by, for example, X-ray photoelectron spectroscopy or infrared spectroscopy.

  The content of metal ions contained in 1 g of the fine fibrous cellulose is preferably from 1.0 to 100 mg, more preferably from 5.0 to 80 mg.

<Support of metal component>
Examples of a method for supporting the metal component on the fine fibrous cellulose include a method in which an aqueous metal compound solution is brought into contact with the fine fibrous cellulose having an anionic group. For example, an aqueous solution of a metal compound may be added to a dispersion of fine fibrous cellulose having an anionic group, and an aqueous solution of a metal compound may be added dropwise to a fiber layer containing fine fibrous cellulose having an anionic group. It may be impregnated. As the aqueous solution of the metal compound, for example, an aqueous solution of a metal salt or an organic metal compound can be used. Examples of the metal salt include a metal component complex (complex ion), a halide, a nitrate, a sulfate, and an acetate. The metal salt is preferably water-soluble.

  The concentration of the aqueous metal compound solution is not particularly limited, but is preferably from 10 parts by mass to 80 parts by mass, more preferably from 30 parts by mass to 60 parts by mass, per 100 parts by mass of the fine fibrous cellulose having an anionic group. The time for contacting the metal compound may be appropriately adjusted. The temperature at the time of contact is not particularly limited, but is preferably from 20 ° C to 40 ° C. The pH of the solution at the time of contact is preferably 2.5 or more and 13 or less.

  After contacting the aqueous metal compound solution with the fine fibrous cellulose having an anionic group, a step of reducing the metal compound bound to the fine fibrous cellulose having an anionic group may be provided. As a result, metal components such as metal particles obtained by reduction are supported on the surface of the cellulose fiber. The reduction reaction may be performed by a known method, but is preferably performed while reducing the metal compound so as not to cleave the bond between the metal compound and the anion group. In the present embodiment, for example, the reduction treatment can be performed by a gas phase reduction method using hydrogen and a liquid phase reduction method using a reducing agent such as an aqueous solution of sodium borohydride. Conditions such as time and temperature in the gas phase reduction are appropriately adjusted. For example, the reaction can be performed at 50 ° C. or more and 60 ° C. or less for about 1 hour or more and 3 hours or less. The reaction temperature in the liquid phase reduction is preferably, for example, 4 ° C. or more and 40 ° C. or less, and more preferably room temperature. In addition, in this embodiment, it is not necessary to perform the process of reducing the metal compound.

  After contacting the aqueous metal compound solution with the fine fibrous cellulose having an anionic group, a washing step may be provided. For example, when a nitrate aqueous solution is used as the metal compound aqueous solution, nitrate ions and the like can be removed by providing a washing step.

The wet sheet may contain, as an optional component, a metal compound or an inorganic compound that is not supported on the fine fibrous cellulose. Such optional components include, for example, silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O), yttrium oxide (Y ₂ O ₃ ), indium trioxide (InO), Magnesium oxide (MgO), titanium dioxide (TiO ₂ ), cerium dioxide (CeO ₂ ), trimanganese tetroxide (Mn ₃ O ₄ ), niobium pentoxide (Nb ₂ O ₅ ), silicon carbide (SiC), boron carbide ( B ₄ C), aluminum nitride (AlN), titanium boride _(TiB 2), zeolite, hydroxyapatite, and silica nano metal nanoparticles are bonded to platinum - can be exemplified silica particles. Examples of the metal nanoparticles include gold, silver, copper, aluminum, nickel, cobalt, iron, platinum, ruthenium, zinc, panadium, rhodium, palladium, osmium, and iridium.

(Method of manufacturing wet sheet)
The method for producing a wet sheet preferably includes a step of obtaining a wet sheet containing fine fibrous cellulose supporting a metal component.

  The step of obtaining a wet sheet containing the fine fibrous cellulose supporting the metal component includes the step of obtaining a base sheet serving as a base paper of the wet sheet, and contacting the base sheet with the fine fibrous cellulose-containing slurry supporting the metal component. It is preferable to include a step of performing the following. Such steps include, for example, a step of spraying a fine fibrous cellulose-containing slurry supporting a metal component on a base sheet, a step of applying the slurry to a base sheet, and a step of impregnating the base sheet with the slurry. Can be included. Above all, the step of contacting the fine fibrous cellulose-containing slurry carrying the metal component is preferably a step of impregnating the base sheet with the fine fibrous cellulose-containing slurry carrying the metal component. That is, the method for producing a wet sheet preferably includes a step of impregnating the base sheet with a chemical solution containing fibrous cellulose having a metal component-supporting fiber width of 1000 nm or less.

The basis weight of the substrate sheet is preferably 15~200g / ^{m 2,} more preferably from 20 to 150 g / ^{m 2,} further preferably 25~100g / ^{m 2.} By setting the basis weight of the base sheet within the above range, the deodorizing function can be more effectively exerted. In addition, it is preferable that a base material sheet is a nonwoven fabric.

  When the base sheet is impregnated with the fine fibrous cellulose-containing slurry supporting the metal component, the concentration of the fine fibrous cellulose contained in the impregnating chemical is preferably 0.05% by mass or more, and is preferably 0.1% by mass or more. It is more preferably at least 0.5% by mass, further preferably at least 0.5% by mass, further preferably at least 1% by mass, particularly preferably at least 2% by mass. The upper limit of the concentration of the fine fibrous cellulose contained in the drug solution is not particularly limited, but is, for example, preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 12% by mass or less. .

  The wet sheet preferably contains an additive such as carboxymethyl cellulose in addition to the fine fibrous cellulose supporting the metal component. Thereby, the wettability of the sheet can be maintained in a more preferable state. In addition, since it functions as a binder that enhances the bonding between cellulose fibers, the strength of the sheet in a wet state can be increased. Additives such as carboxymethylcellulose are preferably added, for example, to the slurry for impregnation. In this case, the content of carboxymethylcellulose should be 0.1% by mass or more based on the total mass of the slurry for impregnation. Is more preferable, and it is more preferable that it is 0.5 mass% or more. Further, the content of carboxymethyl cellulose is preferably 10% by mass or less based on the total mass of the slurry for impregnation.

  After the above steps (spraying, coating or impregnating steps), it is preferable to provide a drying step, and the drying method is not particularly limited. The drying step can be performed, for example, by allowing to stand for 1 hour or more in an environment of 23 ° C. and a relative humidity of 50%.

  It is preferable that the step of obtaining the base sheet serving as the base paper of the wet sheet includes the step of obtaining a slurry containing pulp fibers. In this case, the slurry preferably contains other fibers such as regenerated cellulose fibers. Then, the slurry is subjected to wet papermaking using a known paper machine such as a round paper machine, a short net paper machine, an inclined wire paper machine, a fourdrinier paper machine, etc. to form a base sheet. The fiber orientation of the substrate sheet can be controlled by adding a thickener such as polyethylene oxide to the slurry or adjusting the ratio of the papermaking liquid speed to the wire speed in the wire part of the papermaking process. Further, by subjecting the obtained base sheet to a high-pressure water jet treatment, it is possible to promote the entanglement of the fibers.

  In the step of obtaining the above-mentioned base sheet, fine fibrous cellulose may be mixed into the base sheet. For example, the base sheet may be made from a slurry containing pulp fibers and fine fibrous cellulose. In this case, the fine fibrous cellulose to be mixed with the pulp fiber may carry the metal component in advance, or after the base sheet is obtained, the base sheet and the aqueous metal compound solution may be brought into contact. In this way, by making a base sheet containing fine fibrous cellulose, a wet sheet having higher strength can be obtained.

  In the wet sheet manufacturing process, embossing may be further performed as necessary. The embossing is preferably provided before the fine fibrous cellulose-containing slurry supporting the metal component is brought into contact with the base sheet. The embossing is performed by passing a base material sheet between an embossing roll provided with a convex structure constituting the embossing pattern and a rubber roll, and embossing the embossing pattern. By changing the embossing height, the amount of pressing, and the pressing pressure of the embossing roll, an emboss having a desired embossing height can be formed.

  The wet sheet thus obtained may be folded after being cut into a predetermined size. The laminate of a plurality of such wet sheets is accommodated in an outer container. It is preferable that the exterior container has a property that does not transmit moisture. For example, it is preferable that the wet sheet is accommodated in a container made of a resin film or the like.

  Hereinafter, the features of the present invention will be described more specifically with reference to production examples. Materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following production examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples described below.

(Example 1)
<Preparation of fine fibrous cellulose>
[Phosphorylation]
As a raw material pulp, a softwood kraft pulp made by Oji Paper (solid content: 93% by mass, basis weight: 208 g / m ² , defibrated; Canadian Standard Freeness (CSF) 700 ml measured according to JIS P 8121) It was used. This raw material pulp was subjected to a phosphorylation treatment as follows. First, a mixed aqueous solution of ammonium dihydrogen phosphate and urea is added to 100 parts by mass (absolute dry mass) of the raw material pulp to obtain 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water. To obtain a chemical-impregnated pulp. Next, the obtained chemical-impregnated pulp was dried with a dryer at 105 ° C., and the water was evaporated and pre-dried. Thereafter, the mixture was heated for 10 minutes with a blow dryer set at 140 ° C. to introduce a phosphate group into cellulose in the pulp to obtain a phosphorylated pulp.
Next, the obtained phosphorylated pulp was subjected to a washing treatment. The washing treatment is performed by repeating the operation of pulverizing a pulp dispersion obtained by pouring 10 L of ion-exchanged water into 100 g of phosphorylated pulp (absolute dry mass) so that the pulp is uniformly dispersed, and then filtering and dewatering. went. When the electric conductivity of the filtrate became 100 μS / cm or less, it was regarded as the washing end point.
The phosphorylated pulp after washing was further subjected to the above phosphorylation treatment and the above washing treatment once in this order.

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

Next, the above-mentioned washing treatment was performed on the phosphorylated pulp after the neutralization treatment.
The infrared absorption spectrum of the phosphorylated pulp thus obtained was measured using FT-IR. As a result, absorption based on a phosphate group was observed at around 1230 cm ⁻¹ , confirming that a phosphate group was added to the pulp.
Further, the obtained phosphorylated pulp was tested and analyzed by an X-ray diffractometer. As a result, it was found that two points, 2θ = around 14 ° to 17 ° and 2θ = around 22 ° to 23 °, were located at two positions. A typical peak was confirmed, and it was confirmed to have cellulose type I crystals.

[Fibrillation processing]
Ion-exchanged water was added to the obtained phosphorylated pulp to prepare a slurry having a solid content of 2% by mass. This slurry was treated twice with a wet atomizer (Starburst, manufactured by Sugino Machine Co., Ltd.) at a pressure of 200 MPa to obtain a fine fibrous cellulose dispersion liquid (1) containing fine fibrous cellulose. X-ray diffraction confirmed that the fine fibrous cellulose maintained cellulose type I crystals. Further, the fiber width of the fine fibrous cellulose was measured using a transmission electron microscope, and was 4 nm. In addition, the amount of phosphate groups (the amount of strongly acidic groups) measured by the measurement method described later was 1.00 mmol / g.

[Measurement of fiber width]
The fiber width of the fine fibrous cellulose was measured by the following method.
The supernatant liquid of the fine fibrous cellulose dispersion liquid (1) obtained by the treatment with the wet type atomization device is adjusted so that the concentration of the fine fibrous cellulose becomes 0.01% by mass or more and 0.1% by mass or less. The resultant was diluted with water and dropped on a carbon grid film subjected to a hydrophilic treatment. After drying, it was stained with uranyl acetate and observed with a transmission electron microscope (JEOL-2000EX, manufactured by JEOL Ltd.).

[Measurement of phosphate group content]
The phosphate group content of the fine fibrous cellulose is prepared by diluting the fine fibrous cellulose dispersion (1) containing the target fine fibrous cellulose with ion-exchanged water so that the content becomes 0.2% by mass. After the treatment with the ion-exchange resin was performed on the fibrous cellulose-containing slurry thus obtained, the measurement was performed by performing titration using an alkali.
The treatment with the ion-exchange resin is performed by adding 1/10 by volume of a strongly acidic ion-exchange resin (Amberjet 1024; Organo, Inc., conditioned) to the fibrous cellulose-containing slurry and shaking for 1 hour. The resin and the slurry were separated by pouring on a mesh having a mesh size of 90 μm.
In addition, titration using an alkali is performed by adding an aqueous 0.1 N sodium hydroxide solution to a fibrous cellulose-containing slurry after treatment with an ion-exchange resin at a rate of 50 μL once every 30 seconds while maintaining the electrical conductivity of the slurry. The measurement was performed by measuring the change in the value. The amount of phosphoric acid groups (mmol / g) is obtained by dividing the amount of alkali (mmol) required in a region corresponding to the first region shown in FIG. 1 in the measurement results by the solid content (g) in the slurry to be titrated. Was calculated.

[Ion exchange treatment and metal ion loading]
The obtained fine fibrous cellulose dispersion liquid (1) was diluted with ion-exchanged water so as to have a content of 0.2% by mass, and then treated with an ion-exchange resin. In the treatment with the ion-exchange resin, 1/10 by volume ratio of a strongly acidic ion-exchange resin (Amberjet 1024: Organo Corporation, conditioned) was added to 0.2% by mass of the fine fibrous cellulose dispersion, and the mixture was added for 1 hour. Shaking was performed. Thereafter, the mixture was poured onto a mesh having openings of 90 μm to separate the resin and the slurry. Next, silver nitrate (I) was added so as to be twice the amount of the phosphate group introduced, and the mixture was stirred for 30 minutes to obtain a slurry (1) containing fine fibrous cellulose supporting silver ions as a metal component. .

[Washing and preparation of slurry]
Next, the obtained slurry (1) was filtered and washed to remove nitrate ions remaining in the system. Specifically, a PTFE membrane filter having a pore diameter of 1.0 μm is placed on a glass filter, and the filter is moistened with IPA, and then the slurry is poured, and the pressure is reduced at a reduced pressure of −0.09 MPa (absolute vacuum 10 kPa). Filtration was performed. After confirming that a deposit of fine fibrous cellulose supporting silver ions was formed on the PTFE membrane filter, the same amount of water as that of the original slurry was poured, and the step of filtration under reduced pressure was repeated twice. . The obtained deposit of fine fibrous cellulose supporting silver ions was diluted with ion-exchanged water so as to have a content of 1.0% by mass, and a washed fine fibrous cellulose-containing slurry supporting silver ions ( 1) was obtained.

<Preparation of wet sheet>
A base material sheet (basis weight 45 g / m ² ) was manufactured by papermaking and drying a slurry in which the raw materials were blended so that rayon fiber was 20% by mass and softwood bleached kraft pulp was 80% by mass. On the other hand, a slurry (1) containing fine fibrous cellulose supporting silver ions and a carboxymethylcellulose solution were mixed with water to prepare a chemical solution for impregnation (hereinafter, referred to as "chemical solution"). When a chemical solution was prepared, the concentration of fine fibrous cellulose was adjusted to 0.1% by mass, and the concentration of carboxymethyl cellulose (binder) was adjusted to 3% by mass. A wet sheet was prepared by impregnating 200 parts by mass of the chemical solution with respect to 100 parts by mass of the base sheet.

(Example 2)
A wet sheet was prepared in the same manner as in Example 1, except that the concentration of the fine fibrous cellulose was adjusted to 0.5% by mass when preparing the drug solution.

(Example 3)
A wet sheet was prepared in the same manner as in Example 1, except that the concentration of the fine fibrous cellulose was adjusted to be 1.0% by mass when preparing the drug solution.

(Example 4)
A wet sheet was prepared in the same manner as in Example 1 except that the concentration of the fine fibrous cellulose was adjusted to be 5.0% by mass when preparing the chemical solution.

(Example 5)
A wet sheet was prepared in the same manner as in Example 1, except that the concentration of the fine fibrous cellulose was adjusted to 10.0% by mass when preparing the chemical solution.

(Example 6)
A wet sheet was prepared in the same manner as in Example 1 except that fine fibrous cellulose was not added when preparing a chemical solution.

(Evaluation)
(Odor)
The filter paper was placed in a plastic bag (10 L), and the filter paper was impregnated with 1 ml of 10% aqueous ammonia. Next, a wet sheet (100 mm in width and 100 mm in length) was placed in a plastic bag so as not to come into contact with the filter paper in the odor bag, and the odor bag was sealed. Five minutes after sealing, the odor bag was opened, and the odor in the odor bag was evaluated according to the following five steps. Evaluation was performed by 10 test subjects, and the average value of the 10 test subjects was used as the evaluation value. Table 1 shows the results.
5: Smell was not felt at all 4: Slightly smell was not felt 3: Slight smell was felt 2: Smell was felt 1: Strong smell was felt

(Example 7)
[TEMPO oxidation]
100 parts by mass of dry mass of bleached softwood bleached kraft pulp, 1.6 parts by mass of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), and 10 parts by mass of sodium bromide in water 10,000 Dispersed in parts by mass. Next, a 13% by mass aqueous sodium hypochlorite solution was added to 3.8 g of 1.0 g of pulp to start the reaction. During the reaction, a 0.5 M aqueous sodium hydroxide solution was added dropwise to keep the pH at 10 or more and 10.5 or less, and the reaction was considered completed when no change in pH was observed.

  Next, a washing treatment was performed on the obtained TEMPO oxidized pulp. The washing treatment is carried out by dehydrating the pulp slurry after TEMPO oxidation, obtaining a dehydrated sheet, pouring 5,000 parts by mass of ion-exchanged water, stirring and uniformly dispersing, and then repeating filtration and dehydration. Was. When the electric conductivity of the filtrate became 100 μS / cm or less, it was regarded as the washing end point. Using the obtained carboxyl group-modified cellulose fiber, a mechanical treatment was performed in the same manner as in Example 1 to obtain a fine fibrous cellulose (2). The average fiber width of the fine fibrous cellulose contained in the fine fibrous cellulose dispersion (2) was 4 nm. In addition, the amount of carboxyl groups measured by the measurement method described later was 1.01 mmol / g.

[Measurement of carboxyl group content]
The carboxyl group content of the fine fibrous cellulose was prepared by diluting the fine fibrous cellulose dispersion (2) containing the target fine fibrous cellulose with ion-exchanged water so as to have a content of 0.2% by mass. The fibrous cellulose-containing slurry was subjected to a treatment with an ion-exchange resin, and then subjected to titration using an alkali to measure.
The treatment with the ion-exchange resin is performed by adding 1/10 by volume of a strongly acidic ion-exchange resin (Amberjet 1024; Organo, Inc., conditioned) to the fibrous cellulose-containing slurry and shaking for 1 hour. The resin and the slurry were separated by pouring on a mesh having a mesh size of 90 μm.
In addition, titration using an alkali is performed by adding 50 μL of a 0.1N aqueous sodium hydroxide solution once every 30 seconds to a fibrous cellulose-containing slurry after treatment with an ion-exchange resin while maintaining the electric conductivity of the slurry. This was done by measuring the change in value. The amount of carboxyl group (mmol / g) is obtained by dividing the amount of alkali (mmol) required in the region corresponding to the first region shown in FIG. 2 by the solid content (g) in the slurry to be titrated. Calculated.

[Ion exchange treatment and metal ion loading]
The obtained fine fibrous cellulose dispersion (2) was subjected to ion exchange treatment and metal ion loading in the same manner as in Example 1. Washing was performed in the same manner as in Example 1 to prepare a slurry (2) containing fine fibrous cellulose supporting silver ions.

<Preparation of wet sheet>
A base material sheet (basis weight 45 g / m ² ) was manufactured by papermaking and drying a slurry in which the raw materials were blended so that rayon fiber was 20% by mass and softwood bleached kraft pulp was 80% by mass. On the other hand, a fine fibrous cellulose-containing slurry (2) supporting silver ions and a carboxymethylcellulose solution were mixed with water to prepare a chemical for impregnation (hereinafter, referred to as "chemical"). When a chemical solution was prepared, the concentration of fine fibrous cellulose was adjusted to 0.1% by mass, and the concentration of carboxymethyl cellulose (binder) was adjusted to 3% by mass. A wet sheet was prepared by impregnating 200 parts by mass of the chemical solution with respect to 100 parts by mass of the base sheet.

(Example 8)
A wet sheet was prepared in the same manner as in Example 7, except that the concentration of the fine fibrous cellulose was adjusted to 0.5% by mass when preparing the chemical solution.

(Example 9)
A wet sheet was prepared in the same manner as in Example 7, except that the concentration of the fine fibrous cellulose was adjusted to be 1.0% by mass when preparing the drug solution.

(Example 10)
A wet sheet was prepared in the same manner as in Example 7, except that the concentration of the fine fibrous cellulose was adjusted to be 5.0% by mass when preparing the drug solution.

(Example 11)
A wet sheet was prepared in the same manner as in Example 7, except that the concentration of the fine fibrous cellulose was adjusted to be 10.0% by mass when preparing the chemical solution.

(Evaluation)
Examples 7 to 11 were evaluated by the above-described odor evaluation method.

  It was confirmed that a wet sheet containing fine fibrous cellulose (a sheet impregnated with a chemical solution containing fine fibrous cellulose) exhibited a deodorizing effect. In particular, in Examples 1 to 5, the wet sheet containing fine fibrous cellulose having a phosphate group exhibited a high deodorizing effect.

Claims (6)

  A wet sheet containing fibrous cellulose supporting a metal component and having a fiber width of 1000 nm or less.   The wet sheet according to claim 1, wherein the fibrous cellulose has an anionic group.   The wet sheet according to claim 2, wherein the anion group is at least one selected from a carboxyl group, a substituent derived from a carboxyl group, a phosphate group, and a substituent derived from a phosphate group.   4. The wet sheet according to claim 2, wherein the anion group is at least one selected from a phosphate group and a substituent derived from the phosphate group. 5.   The wet sheet according to any one of claims 1 to 4, wherein the metal component is at least one selected from Ag, Au, Pt, Pd, Cu, and Zn. A method for producing a wet sheet including a step of impregnating a base sheet with a chemical solution containing fibrous cellulose having a fiber width of 1000 nm or less carrying a metal component,
A method for producing a wet sheet, wherein the concentration of fibrous cellulose in the chemical solution is 0.05 to 20% by mass.

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