Antiviral Sheet

Abstract

To provide an antiviral sheet that has good mechanical properties, is capable of suppressing the separation of antiviral / deodorant / antibacterial ingredients, and also has good antiviral / deodorant / antibacterial effects.SOLUTION: The antiviral sheet has an antiviral activity value (Mv) of at least 2.0 against influenza viruses or feline caliciviruses in an antiviral test method for textile products according to JIS L 1922:2016, and comprises a metal-containing cellulosic fiber containing one or more metal ions and / or metal particles selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and Cu.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an antiviral sheet, more specifically to an antiviral sheet having antiviral, deodorizing, and antibacterial functions. [Background technology]

[0002] Functional sheets, which are sheet-like substrates to which functional agents have been added, are used in a variety of industrial fields. Examples of functions generally include deodorizing, antibacterial, heat resistance, moisture resistance, weather resistance, solvent resistance, abrasion resistance, and electromagnetic wave blocking. Examples of applications include packaging materials (paper containers, cardboard, resin films, etc.), building materials (wallpaper, decorative paper, floor coverings, etc.), household goods (deodorizing agents, fragrances), industrial products (filters, wipers, etc.), medical products (masks, etc.), clothing, and other paper products (calendars, etc.).

[0003] The functional sheets mentioned above are often required to have deodorizing and / or antibacterial properties, such as the ability to effectively and continuously suppress the so-called four major odors, including ammonia, trimethylamine, hydrogen sulfide, and methyl mercaptan (such as the odor of urine, feces, and putrefaction).

[0004] Various methods have been proposed for imparting these deodorizing and antibacterial functions. Patent Documents 1 and 2 propose an inorganic porous crystal-hydrophilic polymer composite in which a hydrophilic polymer substrate such as cellulosic fibers is impregnated with an aqueous solution of one of the silicon compounds or aluminum compounds that are components of zeolite, and the resulting substrate is further impregnated with a mixture of a basic substance and an aqueous solution of the other compound, thereby supporting zeolite inside the cellulosic fibers. Furthermore, they disclose that by supporting a metal on this zeolite, antibacterial and deodorizing effects can be imparted.

[0005] Patent Document 3 discloses a cellulose-based fiber structure in which a fiber structure is impregnated with an aqueous solution containing a silicon compound and a basic substance, and an aqueous solution containing an aluminum compound and a basic substance, and then the fiber structure is heated with moist heat to react the silicon compound and the aluminum compound inside the cellulose-based fiber to produce zeolite, a porous silica-alumina material. It also discloses that the introduction of metal ions into this porous silica-alumina material can impart antibacterial and antifungal properties.

[0006] Patent Document 4 discloses an antibacterial cellulosic fiber containing one or more silver-based antibacterial agents selected from silver zeolite, silver zirconium phosphate, silver calcium phosphate, and silver-soluble glass, and further discloses a nonwoven fabric using this antibacterial cellulosic fiber.

[0007] Patent Document 5 also discloses a paper base material containing oxidized pulp, in which the amount of carboxyl groups in the oxidized pulp is 1.0 mmol / g to 2.0 mmol / g based on the bone dry weight of the oxidized pulp, and also describes that this paper base material contains a certain range of fibers made from synthetic resin. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 10-120923 [Patent Document 2] Japanese Patent Application Publication No. 11-315492 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-031591 [Patent Document 4] Japanese Patent Application Publication No. 11-107033 [Patent Document 5] International Publication No. 2014 / 097929 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0009] However, Patent Documents 1 to 4 only describe a simple mixture of cellulosic fibers and inorganic compounds containing metal components, and the cellulosic fibers and inorganic compounds containing metal components are not strongly chemically bonded to each other. In other words, inorganic compounds containing metal components do not form a physical or chemical network like fibers. Therefore, when nonwoven fabrics are produced using such inorganic compounds, the mechanical properties of the substrate, such as tensile strength and tear strength, are reduced, and the inorganic compounds containing metal components tend to fall off from the substrate.

[0010] Furthermore, there is a problem that the antiviral, deodorizing, and antibacterial effects of the functional sheet decrease when it is placed in a high-humidity environment or when it becomes wet. Here, "wet" refers to a state in which the nonwoven fabric contains more than 100% moisture by mass relative to a certain mass after drying.

[0011] Furthermore, the paper substrate described in Patent Document 5 does not have sufficient antiviral and deodorizing effects.

[0012] Therefore, an object of the present invention is to provide an antiviral sheet that has good mechanical properties, can prevent the antiviral, deodorizing, and antibacterial components from falling off, and maintains its antiviral, deodorizing, and antibacterial effects regardless of humidity, even when wet. [Means for solving the problem]

[0013] To achieve the above object, the antiviral sheet of the present invention comprises metal-containing cellulosic fibers containing one or more metal ions and / or metal particles selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and Cu.

[0014] In the metal-containing cellulosic fibers, it is preferable that metal ions are ionically bonded to the cellulosic fibers having anionic groups.

[0015] The present invention includes, but is not limited to, the following aspects. (1) An antiviral sheet having an antiviral activity value (Mv) of 2.0 or more against influenza virus or feline calicivirus according to JIS L 1922:2016, Testing Methods for Antiviral Activity of Textile Products, which comprises metal-containing cellulose fibers containing one or more metal ions and / or metal particles selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and Cu. (2) The antiviral sheet according to (1), wherein the content of the metal ions and / or metal particles in the metal-containing cellulose fiber is 10 to 100 mg / g of the cellulose fiber. (3) The antiviral sheet according to (1) or (2), wherein the metal-containing cellulosic fiber is a cellulosic fiber in which a metal ion is ionically bonded to a cellulosic fiber having an anionic group. (4) The antiviral sheet according to any one of (1) to (3), wherein the amount of anionic groups in the cellulose fibers having anionic groups is 0.01 to 3.0 mmol / g. (5) The antiviral sheet according to (3) or (4), wherein the cellulose-based fiber having an anionic group is an oxidized cellulose-based fiber having a carboxyl group or a carboxylate group. (6) The antiviral sheet according to (3), wherein the cellulose-based fiber having an anionic group is a carboxyalkylated cellulose-based fiber having a carboxyalkyl group. (7) The antiviral sheet according to (3), wherein the cellulose-based fiber having an anionic group is a phosphated cellulose-based fiber having a phosphate group. (8) The antiviral sheet according to (3), wherein the cellulose-based fiber having an anionic group is a phosphite-esterified cellulose-based fiber having a phosphite group. (9) The antiviral sheet according to (3), wherein the cellulose-based fiber having an anionic group is a sulfonated cellulose-based fiber having a sulfate group. (10) The antiviral sheet according to any one of (1) to (9), wherein the antiviral sheet contains cellulosic fibers that do not contain metal. (11) The antiviral sheet according to any one of (1) to (10), which contains synthetic fibers. (12) The antiviral sheet according to any one of (1) to (11), wherein the antiviral sheet is a sheet of two or more layers, at least one of which contains the metal-containing cellulose fiber. (13) The antiviral sheet according to any one of claims 1 to 10, wherein the content of metal ions and / or metal particles in the antiviral sheet is 0.2 to 50% by mass. (14) Metal-containing cellulose-based fibers that have antiviral activity against influenza virus or feline calicivirus with an antiviral activity value (Mv) of 2.0 or more according to JIS L 1922:2016 Testing methods for antiviral activity of textile products, and that contain one or more metal ions and / or metal particles selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and Cu. (15) The metal-containing cellulose fiber according to (14), wherein the content of the metal ions and / or metal particles in the metal-containing cellulose fiber is 10 to 100 mg / g of the cellulose fiber. (16) The metal-containing cellulose fiber according to (14) or (15), characterized in that the metal-containing cellulose fiber is a cellulose fiber having an anionic group to which a metal ion is ionically bonded. (17) The metal-containing cellulose fiber according to any one of (14) to (16), characterized in that the amount of anionic groups in the cellulose fiber having anionic groups is 0.01 to 3.0 mmol / g. (18) The metal-containing cellulose fiber according to (16) or (17), wherein the cellulose fiber having an anionic group is an oxidized cellulose fiber having a carboxyl group or a carboxylate group. (19) The metal-containing cellulose fiber according to (16) or (17), wherein the cellulose fiber having an anionic group is a carboxyalkylated cellulose fiber having a carboxyalkyl group. (20) The metal-containing cellulose fiber according to (16) or (17), wherein the cellulose fiber having an anionic group is a phosphated cellulose fiber having a phosphate group. (21) The metal-containing cellulose fiber according to (16) or (17), wherein the cellulose fiber having an anionic group is a phosphite-esterified cellulose fiber having a phosphite group. (22) The metal-containing cellulose fiber according to (16) or (17), wherein the cellulose fiber having an anionic group is a sulfonated cellulose fiber having a sulfate group. [Effects of the Invention]

[0016] According to the present invention, it is possible to obtain an antiviral sheet that can suppress the shedding of antiviral, deodorizing, and antibacterial components and has excellent antiviral properties. DETAILED DESCRIPTION OF THE INVENTION

[0017] An antiviral sheet according to an embodiment of the present invention has an antiviral activity value (Mv) of 2.0 or more against influenza virus or feline calicivirus according to JIS L 1922:2016, Testing Methods for Antiviral Activity of Textile Products, and is an antiviral sheet comprising metal-containing cellulosic fibers containing one or more metal ions and / or metal particles selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and Cu. This will be described in detail below.

[0018] <1. Metal-containing cellulose-based fibers> The metal-containing cellulose fiber of the present invention includes a metal-containing cellulose fiber containing one or more metal ions and / or metal particles selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and Cu. As will be described later, the metal-containing cellulose fiber is preferably a metal-containing anion-modified cellulose fiber.

[0019] The content of metal-containing cellulose fibers is preferably 1% by mass or more relative to the sheet. If the content is less than 1% by mass, sufficient antiviral, deodorizing, and antibacterial effects may not be achieved. There is no upper limit to the content, which can be adjusted as appropriate depending on the desired level of deodorizing, antibacterial, and antiviral effects, but it may also be 100% by mass.

[0020] <2. Metal-free cellulose-based fibers> In addition to the metal-containing cellulosic fibers, the antiviral sheet according to the embodiments of the present invention may also contain metal-free cellulosic fibers (hereinafter referred to as "general cellulosic fibers") depending on the desired functions, such as moisture absorption, water absorption, and texture.

[0021] Examples of common cellulosic fibers include wood pulp; non-wood pulp such as bamboo, cotton, hemp, jute, kenaf, agricultural waste, animal (e.g., sea squirts), algae, and microbial (e.g., acetic acid bacteria (Acetobacter)) products; regenerated cellulose, and rayon.

[0022] As the general cellulosic fiber, wood pulp is preferred, and one or more types of general cellulosic fibers can be used in combination.

[0023] As described above, since the content of metal-containing cellulosic fibers is preferably 1% by mass or more, the content of general cellulosic fibers in the antiviral sheet is preferably 99% by mass or less. There is no particular lower limit for the content of general cellulosic fibers, and the antiviral sheet does not necessarily need to contain general cellulosic fibers.

[0024] The number average fiber diameter and number average fiber length of the metal-containing cellulose fiber and the general cellulose fiber are not particularly limited, and any value can be used depending on the required mechanical properties such as tensile strength and tear strength, breathability, texture, etc. Furthermore, two or more types of fibers having different number average fiber diameters and number average fiber lengths may be mixed in any ratio.

[0025] For example, softwood kraft pulp (NBKP), a type of natural cellulose fiber, has a number average fiber diameter of approximately 30 to 60 μm and a number average fiber length of approximately 2 to 5 mm, while hardwood bleached kraft pulp (LBKP) has a number average fiber diameter of approximately 10 to 30 μm and a number average fiber length of approximately 1 to 2 mm.

[0026] The metal-containing cellulose fibers and general cellulose fibers may be subjected to a beating treatment one or more times during the manufacturing process before being incorporated into a sheet. Here, beating refers to a treatment that applies mechanical shear force to the fibers. The beating treatment fibrillates or nanofibers part of the cellulose fibers, improving their mechanical properties such as tensile strength.

[0027] In particular, in the case of metal-containing cellulose fibers, beating can further enhance the antiviral, deodorizing and antibacterial effects after the metal ions and / or metal particles are supported.

[0028] The freeness factor (CSF) is generally used as an index of the degree of beating. The freeness factor of the metal-containing cellulose fiber is preferably in the range of 30 to 800 ml.

[0029] If the freeness is lower than 30 ml, the yield in the sheet will decrease during the sheet manufacturing process, and if the freeness is higher than 800 ml, fibrillation will be insufficient, resulting in a low specific surface area and reduced exposure of metal ions to the sheet surface, which may result in reduced deodorizing, antibacterial, and antiviral effects.

[0030] The freeness of general cellulosic fibers is not particularly limited, and can be freely selected from a general freeness range, for example, from 5 to 950 ml, depending on the desired quality.

[0031] The apparatus used for beating is not particularly limited, and any known apparatus can be used. Examples of beating apparatuses include refiners, beaters, PFI mills, kneaders, dispersers, and other apparatuses that act on pulp fibers with metal or blades around a rotating shaft, apparatuses that use friction between pulp fibers, and apparatuses such as high-pressure homogenizers, ultra-high-pressure homogenizers, nanomizers, various mills, and stone mills.

[0032] <3. Production of metal-containing anion-modified cellulose-based fibers> The metal-containing cellulose fiber is preferably a metal-containing anion-modified cellulose fiber in which a metal ion is ionically bonded to a cellulose fiber having an anionic group. Examples of anion-modified cellulose fiber include oxidized cellulose, etherified cellulose (carboxymethyl cellulose, etc.), and esterified cellulose (phosphate esterified cellulose, etc.).

[0033] The amount of anionic groups in oxidized cellulose fibers containing carboxyl groups, carboxylate groups, phosphate groups, or sulfonic acid groups can be measured by the following method. Note that these functional groups are also collectively referred to as "acid groups."

[0034] 60 ml of a 0.5% by mass slurry (aqueous dispersion) of an oxidized cellulose fiber sample having acid groups is prepared, and a 0.1 M aqueous hydrochloric acid solution is added to adjust the pH to 2.5. After that, a 0.05 N aqueous sodium hydroxide solution is added dropwise, and the electrical conductivity is measured until the pH reaches 11. The electrical conductivity is calculated using the following formula from the amount of sodium hydroxide (a) consumed in the neutralization stage of the weak acid, where the change in electrical conductivity is gradual. Amount of anionic groups in oxidized cellulose fiber with acid groups [mmol / g] = a [ml] × 0.05 / mass of oxidized cellulose fiber with acid groups [g] / x. x: Value corresponding to the valence of the acid group (carboxyl group, carboxylate group, sulfonic acid group: 1, phosphate group: 2)

[0035] The amount of anionic groups resulting from the carboxyalkylation treatment was quantified using the following method. Approximately 2.0 g of carboxyalkylated cellulose fiber (bone dry) was weighed and placed in a 300 mL Erlenmeyer flask with a stopper. 100 mL of a solution of 1000 mL of nitric acid / methanol and 100 mL of special-grade concentrated nitric acid was added and the mixture was shaken for 3 hours to convert the carboxyalkyl cellulose salt (carboxymethylated cellulose) into hydrogenated carboxymethylated cellulose. 1.5-2.0 g of hydrogenated carboxymethylated cellulose (bone dry) was weighed and placed in a 300 mL Erlenmeyer flask with a stopper. The hydrogenated carboxymethylated cellulose was moistened with 15 mL of 80% methanol, 100 mL of 0.1 N NaOH was added, and the mixture was shaken at room temperature for 3 hours. Using phenolphthalein as an indicator, excess NaOH was back-titrated with 0.1 N H2SO4. The degree of carboxyalkyl substitution (DS) was calculated using the following formula: A = [(100 × F' - (0.1N H2SO4) (mL) × F) × 0.1] / (bone-dry mass of hydrogen-type carboxyalkylated cellulose (g)) DS=0.162×A / (1-0.058×A) A: Amount (mL) of 1N NaOH required to neutralize 1 g of hydrogen-type carboxyalkylated cellulose F': Factor of 0.1N H2SO4 F: Factor of 0.1N NaOH.

[0036] The amount of anionic groups in the cellulose-based fibers is preferably 0.01 to 3.0 mmol / g. If the amount of acid groups is less than 0.01 mmol / g, the amount of metal ions present on the surface of the cellulose-based fibers may be insufficient in the metal ion-immobilizing step described below, resulting in poor deodorizing, antibacterial, and antiviral functions. On the other hand, if the amount of acid groups exceeds 3.0 mmol / g, cellulose cleavage is more likely to occur as a side reaction during the oxidation reaction, resulting in a reduced yield.

[0037] The metal-containing anion-modified cellulose fiber can be produced by chemically modifying a general cellulose fiber as follows to introduce anion-modifying groups into the glucose units on the surface, and then further supporting metal ions and / or metal particles.

[0038] Hereinafter, a method for introducing anion-modified groups into glucose units on the surface of cellulosic fibers and a method for subsequently supporting metal ions and / or metal particles will be described.

[0039] <3-1. Oxidized Cellulose> Cellulose has three hydroxyl groups per glucose unit and can be chemically modified in various ways. Oxidized cellulose is obtained by modifying cellulosic fibers in such a way that carboxyl or carboxylate groups are introduced into at least a portion of the fibers in a process described below.

[0040] Here, a carboxyl group refers to a group represented by -COOH, and a carboxylate group refers to a group represented by -COO-. The counter ion of the carboxylate group is not particularly limited. Note that a carboxyl group and a carboxylate group are collectively referred to as an "acid group."

[0041] The method for introducing carboxyl or carboxylate groups into the cellulosic fiber is not particularly limited as long as the modified cellulosic fiber contains carboxyl or carboxylate groups. These methods will be described in detail below.

[0042] (3-1-1. Oxidation of cellulosic fibers) In the present invention, the method for oxidizing cellulosic fibers is not particularly limited, and known methods can be used. One example is a method in which a cellulose raw material is oxidized in water using an oxidizing agent in the presence of a substance selected from the group consisting of N-oxyl compounds, bromides, iodides, and mixtures thereof. This method selectively oxidizes the primary hydroxyl group at C6 of the glucopyranose ring on the cellulose surface, generating a group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group. The concentration of the cellulose raw material during the reaction is not particularly limited, but is preferably 5% by mass or less.

[0043] An N-oxyl compound refers to a compound that can generate a nitroxy radical. An example of a nitroxy radical is 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). Any compound that promotes the target oxidation reaction can be used as the N-oxyl compound.

[0044] The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulosic fibers. For example, the amount is preferably 0.01 mmol or more, more preferably 0.02 mmol or more, per 1 g of bone-dry cellulose. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and even more preferably 0.5 mmol or less. Therefore, the amount of the N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and even more preferably 0.02 to 0.5 mmol, per 1 g of bone-dry cellulose.

[0045] Bromides are compounds containing bromine, such as alkali metal bromides that can dissociate and ionize in water, such as sodium bromide. Iodides are compounds containing iodine, such as alkali metal iodides. The amount of bromide or iodide used may be selected within a range that can promote the oxidation reaction. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, per 1 g of bone-dry cellulose. The upper limit is preferably 100 mmol or less, more preferably 10 mmol or less, and even more preferably 5 mmol or less. Therefore, the total amount of bromide and iodide is preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and even more preferably 0.5 to 5 mmol, per 1 g of bone-dry cellulose.

[0046] The oxidizing agent is not particularly limited, but examples thereof include halogen, hypohalous acid, hypohalous acid, perhalogen acid, salts thereof, halogen oxides, peroxides, etc. In particular, hypohalous acid or a salt thereof is preferred because it is inexpensive and has a low environmental impact, hypochlorous acid or a salt thereof is more preferred, and sodium hypochlorite is even more preferred.

[0047] The amount of the oxidizing agent used is preferably 0.1 mmol or more, more preferably 1 mmol or more, and even more preferably 3 mmol or more, relative to 1 g of bone-dry cellulose. The upper limit is preferably 500 mmol or less, more preferably 50 mmol or less, and even more preferably 25 mmol or less.

[0048] When an N-oxyl compound is used, the amount of the oxidizing agent used is preferably 1 mol or more per mol of the N-oxyl compound, with the upper limit being preferably 40 mol. Therefore, the amount of the oxidizing agent used is preferably 1 to 40 mol per mol of the N-oxyl compound.

[0049] Conditions such as pH and temperature during the oxidation reaction are not particularly limited, and generally, the oxidation reaction proceeds efficiently even under relatively mild conditions. The reaction temperature is preferably 4°C or higher, more preferably 15°C or higher. The upper limit is preferably 40°C or lower, more preferably 30°C or lower. Therefore, the temperature is preferably 4 to 40°C, and may be about 15 to 30°C, i.e., room temperature.

[0050] The pH of the reaction solution is preferably 8 or higher, more preferably 10 or higher. The upper limit is preferably 12 or lower, more preferably 11 or lower. Therefore, the pH of the reaction solution is preferably 8 to 12, more preferably about 10 to 11.

[0051] Usually, as the oxidation reaction proceeds, carboxyl groups are generated in the cellulose, and the pH of the reaction solution tends to decrease. Therefore, in order to efficiently proceed with the oxidation reaction, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution within the above range. Water is preferred as the reaction medium during oxidation because it is easy to handle and does not easily cause side reactions.

[0052] The reaction time for oxidation can be set appropriately depending on the degree of progress of the oxidation, and is usually 0.5 hours or more. The upper limit is usually 6 hours or less, preferably 4 hours or less. Therefore, the reaction time for oxidation is usually 0.5 to 6 hours, for example, about 0.5 to 4 hours.

[0053] The oxidation may be carried out in two or more separate reaction stages. For example, the oxidized cellulose obtained by filtration after the completion of the first reaction stage can be oxidized again under the same or different reaction conditions, thereby enabling efficient oxidation without reaction inhibition by sodium chloride produced as a by-product in the first reaction stage. Another example of an oxidation method is oxidation by ozone treatment, which oxidizes at least the hydroxyl groups at positions 2 and 6 of the glucopyranose ring that constitutes cellulose, and decomposes the cellulose chain.

[0054] Ozone treatment is usually carried out by contacting the cellulose raw material with a gas containing ozone. The ozone concentration in the gas is 50 g / m 3 The upper limit is 250 g / m 3 Preferably, it is 220 g / m or less. 3 Therefore, the ozone concentration in the gas is preferably 50 to 250 g / m or less. 3 It is preferable that the thickness is 50 to 220 g / m 3 It is more preferable that:

[0055] The amount of ozone added is preferably 0.1 part by mass or more, more preferably 5% by mass or more, relative to 100% by mass of the solid content of the cellulose raw material. The upper limit is usually 30% by mass or less. Therefore, the amount of ozone added is preferably 0.1 to 30% by mass, more preferably 5 to 30% by mass, relative to 100% by mass of the solid content of the cellulose raw material.

[0056] The ozone treatment temperature is usually 0° C. or higher, and preferably 20° C. or higher. The upper limit is usually 50° C. or lower. Therefore, the ozone treatment temperature is preferably 0 to 50° C., and more preferably 20 to 50° C.

[0057] The ozone treatment time is usually 1 minute or more, preferably 30 minutes or more. The upper limit is usually 360 minutes or less. Therefore, the ozone treatment time is usually about 1 to 360 minutes, preferably about 30 to 360 minutes.

[0058] When the ozone treatment conditions are within the above-mentioned ranges, excessive oxidation and decomposition of cellulose can be prevented, resulting in a good yield of oxidized cellulose.

[0059] The product obtained after the ozone treatment may be further subjected to a post-oxidation treatment using an oxidizing agent. The oxidizing agent used in the post-oxidation treatment is not particularly limited, but examples thereof include chlorine compounds such as chlorine dioxide and sodium chlorite; oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. Examples of methods for the post-oxidation treatment include dissolving these oxidizing agents in water or a polar organic solvent such as alcohol to prepare an oxidizing agent solution, and immersing the cellulose raw material in the oxidizing agent solution.

[0060] The amounts of carboxyl groups, carboxylate groups, and aldehyde groups contained in the oxidized cellulose fibers can be adjusted by controlling the oxidation conditions, such as the amount of oxidizing agent added and the reaction time.

[0061] (3-1-2. Etherification of cellulosic fibers) For the etherification, any method that results in a carboxyl group or a carboxylate group in the functional group after the reaction can be used, and known methods can be used, so long as it allows for the convenient introduction of metal ions into the cellulosic fibers in a subsequent step. Examples include carboxyalkyl etherification such as carboxymethyl (etherification), carboxyethyl (etherification), carboxypropyl (etherification), and carboxybutyl (etherification), and carboxyphenyl (etherification). Among these, the carboxymethylation method will be described below as an example.

[0062] The carboxymethylation method is not particularly limited, and known methods can be used. For example, a method in which the cellulose raw material as the starting material is mercerized and then etherified can be used. A common solvent is used in the carboxymethylation reaction. Examples of the solvent include water, alcohol (e.g., lower alcohol), and mixed solvents thereof. Examples of lower alcohol include methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, and tertiary butanol.

[0063] The mixing ratio of the lower alcohol in the mixed solvent is usually 60% by mass or more or 95% by mass or less, and preferably 60 to 95% by mass. The amount of the solvent is usually 3 times by mass relative to the cellulose raw material. The upper limit is not particularly limited, but is 20 times by mass. Therefore, the amount of the solvent is preferably 3 to 20 times by mass.

[0064] Mercerization is typically carried out by mixing the cellulose raw material with a mercerizing agent. Examples of mercerizing agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The amount of mercerizing agent used is preferably 0.5 times or more by mole, more preferably 1.0 mole or more, and even more preferably 1.5 times or more by mole, per anhydrous glucose residue of the raw material. The upper limit is typically 20 times or less by mole, preferably 10 times or less by mole, and more preferably 5 times or less by mole. Therefore, 0.5 to 20 times by mole is preferred, more preferably 1.0 to 10 times by mole, and even more preferably 1.5 to 5 times by mole.

[0065] The reaction temperature for mercerization is usually 0°C or higher, preferably 10°C or higher. The upper limit is usually 70°C or lower, preferably 60°C or lower. Therefore, the reaction temperature is usually 0 to 70°C, preferably 10 to 60°C. The reaction time is usually 15 minutes or longer, preferably 30 minutes or longer. The upper limit is usually 8 hours or shorter, preferably 7 hours or shorter. Therefore, the reaction time is usually 15 minutes to 8 hours, preferably 30 minutes to 7 hours.

[0066] The etherification reaction is usually carried out by adding a carboxymethylating agent to the reaction system after mercerization. Examples of the carboxymethylating agent include sodium monochloroacetate. The amount of the carboxymethylating agent added is usually preferably 0.05 times or more by mole, more preferably 0.5 times or more by mole, and even more preferably 0.8 times or more by mole, per glucose residue of the cellulose raw material. The upper limit is usually 10.0 times or less by mole, preferably 5 moles or less, and more preferably 3 times or less by mole. Therefore, the amount is preferably 0.05 to 10.0 times by mole, more preferably 0.5 to 5, and even more preferably 0.8 to 3 times by mole.

[0067] The reaction temperature is usually 30°C or higher, preferably 40°C or higher, with the upper limit usually being 90°C or lower, preferably 80°C or lower. Therefore, the reaction temperature is usually 30 to 90°C, preferably 40 to 80°C. The reaction time is usually 30 minutes or longer, preferably 1 hour or longer. The upper limit is usually 10 hours or shorter, preferably 4 hours or shorter. Therefore, the reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours. During the carboxymethylation reaction, the reaction mixture may be stirred as needed.

[0068] When a cellulose raw material is modified by carboxymethylation, the degree of carboxymethyl substitution per anhydroglucose unit in the resulting carboxymethylated cellulose fiber is preferably 0.01 or more, more preferably 0.05 or more, and even more preferably 0.10 or more. The upper limit is preferably 0.50 or less, more preferably 0.40 or less, and even more preferably 0.35 or less. Therefore, the degree of carboxymethyl group substitution is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, and even more preferably 0.10 to 0.30.

[0069] The degree of carboxymethyl substitution per glucose unit of carboxymethylated cellulose-based fibers can be measured, for example, by the following method: 1) Accurately weigh out approximately 2.0 g of carboxymethylated cellulose (bone dry) and place it in a 300 mL Erlenmeyer flask with a stopper. 2) Add 100 mL of concentrated nitric acid to 1000 mL of methanol, add 100 mL of the resulting nitric acid-methanol solution, and shake for 3 hours to convert the carboxymethyl cellulose salt (carboxymethylated cellulose) into hydrogen-type carboxymethyl cellulose. 3) Accurately weigh out 1.5 to 2.0 g of hydrogen-type carboxymethyl cellulose (bone dry) and place it in a 300 mL Erlenmeyer flask with a stopper. 4) Wet the hydrogen-type carboxymethyl cellulose with 15 mL of 80% methanol, add 100 mL of 0.1 N NaOH, and shake for 3 hours at room temperature. 5) Using phenolphthalein as an indicator, back-titrate the excess NaOH with 0.1 N H2SO4. 6) Calculate the degree of carboxymethyl substitution (DS) using the following formula: A = [(100 × F' - (0.1N H2SO4) (mL) × F) × 0.1] / (bone-dry mass of hydrogen-form carboxymethyl cellulose (g)) DS=0.162×A / (1-0.058×A) A: The amount required to neutralize 1 g of hydrogen-type carboxymethyl cellulose Amount of 1N NaOH (mL) F': Factor of 0.1N NaOH F: Factor of 0.1N H2SO4

[0070] (3-1-3. Esterification of cellulosic fibers) The esterification may be any method that introduces an anionic functional group, and known methods can be used. Examples include phosphate esterification and sulfate esterification. Among these, the phosphate esterification and sulfate esterification methods are described below as examples.

[0071] (Cellulose phosphate, cellulose phosphite) Phosphated cellulose is cellulose that has been phosphorylated with a compound having a phosphate group or a phosphite group. Examples of compounds having a phosphate group or a phosphite group include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, polyphosphonic acid, and esters and salts thereof. These compounds are low-cost and easy to handle.

[0072] Examples of compounds having a phosphate group or a phosphite group include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, sodium pyrophosphate, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, ammonium pyrophosphate, ammonium metaphosphate, phosphorous acid, sodium hydrogen phosphite, ammonium hydrogen phosphite, potassium hydrogen phosphite, sodium dihydrogen phosphite, sodium phosphite, lithium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite, triethyl phosphite, triphenyl phosphite, pyrophosphorous acid, etc. Among these, phosphoric acid, sodium salt of phosphoric acid, potassium salt of phosphoric acid, ammonium salt of phosphoric acid, phosphorous acid, sodium salt of phosphorous acid, potassium salt of phosphorous acid, and ammonium salt of phosphorous acid are preferred because of their high efficiency in phosphite or phosphite formation and ease of industrial application, and sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium hydrogen phosphite, and sodium dihydrogen phosphite are more preferred. The compounds having a phosphate group or a phosphite group may be used singly or in combination of two or more.

[0073] In cellulose phosphate or cellulose phosphite, the lower limit of the amount of phosphate or phosphite groups introduced per 1 g (weight) of cellulose phosphate or cellulose phosphite is preferably 0.1 mmol / g or more. If it exceeds 3.5 mmol / g, the desired physical properties may not be obtained. The amount of phosphate or phosphite groups introduced per 1 g (weight) of cellulose phosphate or cellulose phosphite is preferably 0.1 to 3.5 mmol.

[0074] The phosphate esterification reaction or phosphite esterification reaction is carried out, for example, by reacting a cellulose raw material with a compound having a phosphate group or a phosphite group. Methods for reacting a cellulose raw material with a compound having a phosphate group or a phosphite group include, for example, mixing a powder or an aqueous solution of the compound having a phosphate group or a phosphite group with the cellulose raw material, and adding an aqueous solution of the compound having a phosphate group or a phosphite group to a slurry of the cellulose raw material. Among these, the method of mixing an aqueous solution of the compound having a phosphate group or a phosphite group with the cellulose raw material or a slurry thereof is preferred because it increases the uniformity of the reaction and the efficiency of phosphate esterification and phosphite esterification. The pH of the aqueous solution of the compound having a phosphate group or a phosphite group is preferably 7 or less from the viewpoint of increasing the efficiency of introduction of phosphate groups or phosphite groups, and more preferably 3 to 7 from the viewpoint of suppressing hydrolysis.

[0075] The lower limit of the amount of the compound having a phosphate group or a phosphite group added is preferably 0.2 parts by mass or more, more preferably 1 part by mass or more, calculated as phosphorus atoms, per 100 parts by mass of the cellulose raw material. This range can improve the yield of cellulose phosphate and cellulose phosphite. On the other hand, the upper limit is preferably 500 parts by mass or less, more preferably 400 parts by mass or less. This range allows for efficient production of a yield commensurate with the amount of the compound having a phosphate group or a phosphite group added.

[0076] The amount of the compound having a phosphate group or a phosphite group added is preferably 0.2 to 500 parts by mass, more preferably 1 to 400 parts by mass.

[0077] When reacting a cellulose raw material with a compound having a phosphate group or a phosphite group, a basic compound may be further added to the reaction system. Examples of methods for adding the basic compound to the reaction system include adding it to a slurry of the cellulose raw material, an aqueous solution of the compound having a phosphate group or a phosphite group, or a slurry of the cellulose raw material and the compound having a phosphate group or a phosphite group. The basic compound is not particularly limited, but a nitrogen-containing compound that exhibits basicity is preferred. "Exhibiting basicity" usually means that an aqueous solution of the basic compound exhibits a pink to red color in the presence of a phenolphthalein indicator, or that the pH of the aqueous solution of the basic compound is greater than 7.

[0078] The basic nitrogen-containing compound is not particularly limited as long as it can achieve the effects of the present invention. Among them, compounds having an amino group are preferred. Examples include urea, methylamine, ethylamine, trimethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, pyridine, ethylenediamine, and hexamethylenediamine. Among these, urea is preferred because of its low cost and ease of handling.

[0079] The amount of basic compound added is preferably 2 to 1,000 parts by mass, more preferably 100 to 700 parts by mass. The reaction temperature is preferably 0 to 95°C, more preferably 30 to 90°C. The reaction time is not particularly limited, but is usually about 1 to 600 minutes, preferably 30 to 480 minutes. When the reaction conditions are within any of these ranges, it is possible to prevent cellulose from becoming easily soluble due to excessive introduction of phosphate groups or phosphite groups, and the yield of phosphated cellulose and phosphite cellulose can be improved.

[0080] After reacting a compound having a phosphate group or a phosphite group with a cellulose raw material, a suspension is usually obtained. The suspension is dehydrated as needed. After dehydration, it is preferable to carry out a heat treatment, which can suppress hydrolysis of the cellulose raw material. The heating temperature is preferably 100 to 170°C, and it is more preferable to heat the material at 130°C or less (more preferably 110°C or less) while it contains water during the heat treatment, and then heat it at 100 to 170°C after removing the water.

[0081] It is preferable that the cellulose phosphate and cellulose phosphite be subjected to a washing treatment such as boiling and then washing with cold water.

[0082] (sulfonated cellulose) Sulfonated cellulose is cellulose sulfonated with a compound having a sulfate group. Examples of compounds having a sulfate group include sulfuric acid, sulfamic acid, chlorosulfonic acid, sulfur trioxide, and esters and salts thereof. These compounds are low-cost and easy to handle.

[0083] Sulfamic acid is preferably used as the sulfonating reagent. Sulfamic acid not only has a lower cellulose solubility than sulfuric anhydride or aqueous sulfuric acid solutions, but also has low acidity, making it possible to maintain the degree of polymerization. Furthermore, unlike sulfuric anhydride and aqueous sulfuric acid solutions, which are highly acidic and corrosive, there are no restrictions on how to handle sulfamic acid, and it is not designated as a specified substance under the Air Pollution Control Act, so it has a low environmental impact.

[0084] The amount of sulfamic acid used can be adjusted appropriately taking into consideration the amount of substituents introduced into the cellulose fiber. For example, sulfamic acid can be used in an amount of preferably 0.01 to 50 mol, more preferably 0.1 to 30 mol, per mol of glucose unit in the cellulose molecule. <3-2. Supporting of metal ions and / or metal particles> By further supporting ions or particles of one or more metal elements selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and Cu on cellulosic fibers, high antiviral, antibacterial, and deodorizing effects are achieved.The use of Ag and Cu in particular further improves the antiviral, antibacterial, and deodorizing functions.

[0085] In particular, anion-modified cellulose fibers have the metal and cellulose fibers chemically bonded together, so when the fibers are incorporated into a sheet, the metal components are less likely to be released from the sheet, and the sheet also has good mechanical properties such as tensile strength.

[0086] The method for loading the metal ions onto the cellulosic fibers is not particularly limited, and may involve, for example, mixing a previously prepared cellulosic fiber dispersion with an aqueous solution of a metal compound, or applying the cellulosic fiber-containing dispersion onto a substrate to form a film, and then dripping the aqueous solution of a metal compound onto the film to impregnate it. In this case, the film may remain fixed on the substrate, or may be peeled off from the substrate.

[0087] These methods allow metal ions derived from metal compounds to be added to cellulosic fibers by counterion exchange with sodium ions already ionically bonded to anion-modified groups such as carboxylate groups. This counterion exchange is thought to occur due to the difference in ionization tendency between the metal ions.

[0088] Here, the metal compound aqueous solution is an aqueous solution of a metal salt. Examples of metal salts include complexes (complex ions), halides, nitrates, sulfates, and acetates. The concentration of the metal compound aqueous solution is not particularly limited, but is preferably 0.2 to 2.2 mmol, more preferably 0.4 to 1.8 mmol, per 1 g of cellulose fiber. The time for contacting the metal compound may be adjusted as appropriate.

[0089] The temperature during contact is not particularly limited, but is preferably in the range of 2 to 50° C. Furthermore, the pH of the liquid during contact is not particularly limited, but if the pH is low, it becomes difficult for metal ions to bind to the anion-modified group, so the pH is preferably in the range of 7 to 13, and particularly preferably in the range of 8 to 12.

[0090] In the present invention, metal ions can be introduced into cellulosic fibers as described above, but some of the metal ions may be reduced to form metal particles. Furthermore, if necessary, some of the metal ions bound to the metal ion-supported cellulosic fibers can be reduced by adding a reducing agent or the like, thereby partially forming metal particles on the surface of the cellulosic fibers.

[0091] However, it is preferable to use the entire amount of the metal compound in the form of metal ions without carrying out any special reduction treatment, from the viewpoint of antiviral, antibacterial and deodorizing effects.

[0092] The mechanism by which metal particles are generated in the cellulosic fibers by reducing the metal compounds in the metal-containing cellulosic fibers obtained above is unclear, but is presumed to be as follows: The metal compounds or ions derived from the metal compounds in the metal compound-containing cellulosic fibers are reduced to metal by a reduction reaction. At this time, the generated metal is supported on the surface of the cellulosic fibers. Similarly, neighboring metals generated combine with each other, causing the particles to grow and form nanoparticles. Meanwhile, metal compounds present near the cellulosic fibers but not bonded to the cellulosic fibers are also reduced to generate metal. This metal quickly combines with the metal on the surface of the cellulose fibers to form metal particles.

[0093] The reduction reaction may be carried out by a known method, but is preferably carried out while reducing the metal compound without cleaving the bond between the metal compound and the acid group. Examples of such reduction methods include gas-phase reduction using hydrogen and liquid-phase reduction using a reducing agent such as an aqueous solution of sodium borohydride. Conditions such as time and temperature during gas-phase reduction are appropriately adjusted, but the reaction may be carried out, for example, at 50 to 60°C for approximately 1 to 3 hours. The gas-phase reduction reaction is preferably carried out in a state in which the metal-containing cellulose-based fiber does not contain water or solvent. In the reduction reaction, the film may remain fixed on the substrate or may be peeled from the substrate. In the case of liquid-phase reduction, a film is obtained from the dispersion and can be subjected to the reduction reaction with or without drying. Alternatively, the dispersion can be subjected to the liquid-phase reduction reaction without drying. The reaction temperature during liquid-phase reduction is preferably 4 to 40°C, more preferably room temperature.

[0094] The presence of metal ions or particles in cellulosic fibers can be confirmed by scanning electron microscope images and ICP atomic emission spectrometry of extracts prepared with strong acids. In other words, the presence of metal ions cannot be confirmed by scanning electron microscope images, whereas ICP atomic emission spectrometry can confirm the presence of metals. In contrast, if the metals are reduced from ions and exist as metal particles, the metal particles can be confirmed by scanning electron microscope images, allowing the presence or absence of metal ions to be determined. The presence or absence of metal ions can also be determined by elemental mapping using scanning electron microscope images and energy dispersive X-ray analysis (EDS). In other words, the presence of metal ions cannot be confirmed by scanning electron microscope images, but the presence of metal ions can be confirmed by elemental mapping.

[0095] In the step of supporting metal ions or metal particles, the metal content relative to the cellulosic fiber is preferably in the range of 10 to 100 mg / g, more preferably 15 to 80 mg / g, and particularly preferably 20 to 60 mg / g. If it is less than 10 mg / g, the antiviral, deodorizing, and antibacterial functions may be impaired. On the other hand, if it exceeds 100 mg / g, metal ions are more likely to elute during production, increasing the burden on wastewater treatment.

[0096] The metal-containing cellulose fibers of the present invention may be beaten at least once between the time before the modification treatment and the time after the metal-loading treatment. Here, beating refers to a treatment that applies mechanical shear force to the fibers. Beating fibrillates a portion of the cellulose fibers, increasing their surface area. This generally strengthens interfiber bonds during drying and also increases the specific surface area, allowing metal ions to be exposed to the surface. This further enhances the antiviral, deodorizing, and antibacterial effects of the present invention. On the other hand, excessive beating, resulting in excessively fine cellulose fibers, is undesirable because it reduces the yield when blended with pulp for production, or the fibers do not remain in paper, thereby reducing the antiviral, deodorizing, and antibacterial effects of the metal-containing cellulose fibers. The freeness factor (CSF) can be used as an indicator of the degree of beating. Specifically, if the CSF is less than 30 ml, the yield of the material in the sheet decreases, resulting in a reduced antiviral, deodorizing, and antibacterial effect, while if the CSF is more than 600 ml, fibrillation is insufficient, resulting in a reduced antiviral, deodorizing, and antibacterial effect.In this way, by adjusting the CSF of cellulose fibers containing metal ions or metal nanoparticles to 30 to 600 ml, the antiviral, deodorizing, and antibacterial effects can be improved.

[0097] The apparatus used for beating is not particularly limited, and any known apparatus can be used. Examples of beating apparatuses include refiners, beaters, PFI mills, kneaders, dispersers, and other apparatuses that act on pulp fibers with a metal or blade around a rotating shaft, apparatuses that use friction between pulp fibers, and apparatuses such as high-pressure homogenizers, ultra-high-pressure homogenizers, nanomizers, various mills, and stone mills.

[0098] Furthermore, prior to beating or, if necessary, prior to the dispersion treatment carried out before beating, a pretreatment may be carried out as necessary. Examples of the pretreatment include mixing, stirring, emulsification, and dispersion, and the pretreatment may be carried out using a known device (e.g., a high-speed shear mixer).

[0099] The metal ion-containing cellulose fibers may be nanofiberized. The nanofibered areas have an increased surface area, which can enhance the antiviral, deodorizing, and antibacterial effects. On the other hand, if the fibers are completely nanofiberized, the fibers will be completely disintegrated, which can reduce the yield when blended with pulp to produce paper, or they will not remain in the paper, thereby reducing the effects of the metal ion-containing cellulose fibers. Here, nanofiberization refers to the process of defibrating metal ion-containing cellulose fibers to fibers with a fiber diameter of 100 nm or less. To nanofiberize, any known device similar to that used for beating can be used.

[0100] <4. Synthetic Fibers> The antiviral sheet of the present invention may be a nonwoven fabric and contains at least one type of synthetic fiber, i.e., fiber made from a synthetic resin obtained by polymerizing low-molecular-weight organic materials such as petroleum. Generally, synthetic fibers are inferior to the above-mentioned cellulose-based fibers in terms of hygroscopicity, water absorption, and flexibility, but are superior in terms of dimensional stability and light resistance.

[0101] The synthetic fiber content is preferably 5% by mass or more relative to the nonwoven fabric from the viewpoint of dimensional stability. Also, since the metal ion-containing cellulosic fiber content is preferably 1% by mass or more relative to the nonwoven fabric, the synthetic fiber content is preferably 99% by mass or less relative to the nonwoven fabric.

[0102] The type of synthetic fiber is not particularly limited, and examples thereof include polyester fibers such as polyethylene terephthalate (PET) fibers, polybutylene terephthalate (PBT) fibers, polyethylene naphthalate (PEN), and polyethylene isophthalate (PEI) fibers; polyolefin fibers such as polypropylene (PP) fibers, polyethylene (PE) fibers, ethylene-vinyl alcohol copolymer fibers, and ethylene-vinyl acetate copolymer fibers; polyacrylic fibers, polyamide fibers, polyvinyl alcohol (PVA) fibers, polylactic acid (PLA) fibers, and composite fibers such as polyester copolymer resin-polyester resin, polyethylene resin-polyester resin, ethylene-vinyl alcohol copolymer resin-polyester resin, polyester copolymer resin-polypropylene resin, polyethylene resin-polypropylene resin, ethylene-vinyl alcohol copolymer resin-polypropylene resin, and ethylene-vinyl acetate copolymer resin-polypropylene resin.

[0103] The synthetic fibers may be either primary fibers having a single concentric structure or sheath-core fibers having different melting points for the core and sheath. In a preferred embodiment, the synthetic fibers have a fineness of 0.5 to 4.5 dtex and a fiber length of 3 to 30 mm (preferably 5 to 20 mm, and more preferably 5 to 15 mm) from the viewpoint of fiber dispersion. The fineness and fiber length of the synthetic fibers are measured in accordance with JIS L 1015:2010. The melting point of the synthetic fibers is, for example, in the range of 110 to 300°C, preferably 110 to 280°C, and more preferably 200 to 260°C, considering the stability and high-temperature processing such as embossing at high temperatures in the subsequent stage. If the melting point is lower than 110°C, synthetic fiber-derived stains (fuzzing) are likely to occur on the papermaking dryer during the production of base paper for wetlaid nonwoven fabrics. On the other hand, blending synthetic fibers with melting points exceeding 300°C is not only technically meaningless but also uneconomical. When using a core-sheath type synthetic fiber, select one whose sheath melting point is within the above range. The melting point of synthetic fiber is measured in accordance with JIS K 7121:2012.

[0104] Examples of sheath-core fibers include those in which the core / sheath is polypropylene (PP) / polyethylene (PE), polyethylene terephthalate (PET) / polyethylene (PE), polyethylene terephthalate (PET) / low-melting-point polyethylene terephthalate (PET), or polypropylene (PP) / polypropylene (PP). Examples of sheath-core polyester composite fibers include composite fibers (sheath-core fibers) in which the sheath (low-melting-point component) is made of modified polyester and the core (high-melting-point component) is made of polyethylene terephthalate. Examples of sheath-core polyolefin composite fibers include composite fibers (sheath-core fibers) in which the sheath (low-melting-point component) is made of polyethylene and the core (high-melting-point component) is made of polypropylene.

[0105] A binder may be used if necessary. Examples of binders include heat-fusible fibers, hot-water-soluble fibers, and water-based adhesives. Examples of heat-fusible fibers include the aforementioned core-sheath polyester composite fibers, polyethylene terephthalate (PET) fibers, core-sheath polyolefin composite fibers, and hydrophilic pulp-like hyperbranched fibers. Hydrophilic pulp-like hyperbranched fibers are also known as polyolefin synthetic pulp, and an example of this is the product commercially available from Mitsui Chemicals, Inc. under the trade name SWP. Hot-water-soluble fibers are fibers that are virtually insoluble in water at room temperature and maintain their fibrous form, but readily dissolve when heated on the dryer surface after papermaking. They then resolidify during dehydration and drying to form strong paper layer constituent fibers. Examples of hot-water-soluble fibers include polyvinyl alcohol-based fibrous binders. These are typically short-cut polyvinyl alcohol fibers that swell but do not dissolve in water at room temperature, but dissolve in warm water at 60–90°C and function as a binder. Examples of water-based adhesives that can be used include water-soluble adhesives such as casein, sodium alginate, hydroxyethyl cellulose, carboxymethyl cellulose sodium salt, polyvinyl alcohol (PVA), and sodium polyacrylate, as well as emulsion adhesives such as polyacrylic esters, acrylic-styrene copolymers, polyvinyl acetate, ethylene-vinyl acetate copolymers, acrylonitrile-butadiene copolymers, methyl methacrylate-butadiene copolymers, and styrene-butadiene copolymers.

[0106] <5. Other ingredients> The antiviral sheet of the present invention may contain one or more other materials as needed in addition to the metal-containing cellulose fibers, general cellulose fibers, and synthetic fibers. The types of other materials are not particularly limited, but examples include stabilizers such as heat stabilizers and weather stabilizers, fillers, antistatic agents, slip agents, antiblocking agents, antifogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, waxes, etc. These materials may be used alone or in combination. The total content of these materials is preferably within a range not exceeding 10% by mass of the sheet.

[0107] Examples of stabilizers include antioxidants such as 2,6-di-t-butyl-4-methyl-phenol (BHT); tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, β-(3,5-di-t-butyl-4-hydroxyphenyl)propionic acid alkyl ester, 2,2'-oxamidobis[ethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], and phenolic antioxidants; fatty acid metal salts such as zinc stearate, calcium stearate, and calcium 1,2-hydroxystearate; and polyhydric alcohol fatty acid esters such as glycerin monostearate, glycerin distearate, pentaerythritol monostearate, pentaerythritol distearate, and pentaerythritol tristearate.

[0108] Examples of fillers include silica, diatomaceous earth, alumina, titanium oxide, magnesium oxide, pumice powder, pumice balloons, aluminum hydroxide, magnesium hydroxide, basic magnesium carbonate, dolomite, calcium sulfate, potassium titanate, barium sulfate, calcium sulfite, talc, clay, mica, asbestos, calcium silicate, montmorillonite, bentonite, graphite, aluminum powder, and molybdenum sulfide.

[0109] Examples of colorants include inorganic colorants such as titanium oxide and calcium carbonate, and organic colorants such as phthalocyanine.

[0110] Examples of the lubricant include oleic acid amide, erucic acid amide, and stearic acid amide. <6. Antiviral Sheet> The antiviral sheet of the present invention can be produced by mixing the metal-containing cellulose fibers with a pulp slurry (stock) in the same manner as for ordinary paper sheets, and then making paper using the resulting sample. For papermaking, a known papermaking machine such as a Fourdrinier papermaking machine, a twin-wire papermaking machine, or a cylinder papermaking machine can be used, and the papermaking conditions are not limited.

[0111] The antiviral sheet of the present invention can be produced by forming a layer of fibers called fleece from the above-mentioned metal-containing cellulosic fibers, and optionally synthetic fibers, general cellulosic fibers, and other materials, bonding the fibers together, and optionally dyeing, laminating, coating, or other processes.

[0112] The method for forming the fleece is not particularly limited, and any known method can be used. Examples include a dry method in which dried fibers are arranged in a certain direction or randomly using a machine called a card or an air flow called an air laying method; a wet method in which fibers are dispersed in water and combed onto a mesh net, similar to the method used in paper production; and a spunbond method in which a molten raw resin is directly eluted and spun from the tip of a nozzle to form a fleece from continuous long fibers.

[0113] In particular, a wet process is preferred because cellulose-based fibers are hydrophilic. In the case of a wet process, conventional papermaking methods can be used for production. As the papermaking machine, various types of conventionally known machines can be used, such as a cylinder papermaking machine, an inclined short-wire papermaking machine, a Fourdrinier papermaking machine, a short-wire papermaking machine, etc., and papermaking machines can be combined appropriately depending on the required properties. Examples of the drying process in the papermaking method include a Yankee dryer type, a multi-cylinder type, a hot air type, and an infrared heating type.

[0114] The method for bonding fibers together is not particularly limited, and known methods can be used. Examples include a chemical bonding method in which an emulsion adhesive resin is applied to a fleece by impregnation or spraying, and then heated and dried to bond the intersections of the fibers; a thermal bonding method in which a fleece containing low-melting-point heat-fusible fibers is thermally bonded between heated rolls or by applying hot air to bond the fibers together; a needle punch method in which a fleece is repeatedly pierced with a needle that moves up and down at high speed, entangling the fibers with the barbs engraved on the needle; and a hydroentanglement method in which a high-pressure water stream is sprayed in a columnar shape onto the fleece to entangle the fibers. Chemical bonding methods are particularly preferred.

[0115] In the production of drylaid nonwoven fabrics, synthetic fibers, paper strength agents, binders, fillers, etc. may be further added as needed. Drylaid methods include carding and air-laying for web formation, and chemical bonding, thermal bonding, spunlace, and needle punching for web bonding.

[0116] The carding method involves feeding the composite and thermoplastic synthetic fibers into a carding machine to form a fiber accumulation layer (nonwoven web), which is then heat-treated at a temperature equal to or higher than the melting point of the thermoplastic fibers to melt some of the thermoplastic synthetic fibers and bond the fibers together (thermal bonding method), or by hydroentangling the nonwoven web and then heat-treating it. Examples of webs produced by the carding method include parallel webs, cross webs, random webs, crisscross webs, and semi-random webs.

[0117] The air-laying method involves transporting defibrated raw fibers in an air current to form a web, applying a binder to the web, and then carrying out a drying and heating process (drying process) to bond the fibers of the fiber web together with the binder.Air-laying methods include the Honshu Paper Method (Kinocloth Method), Karl Kroyer Method, Scanweb Method (Dunweb Method), J&J Method, KC Method, and Scott Paper Method.

[0118] When the dry nonwoven fabric of the present invention is produced by air-laying, a binder may be used to bond the fibers together. The binder can be selected appropriately as needed, and examples include aqueous binders such as casein, sodium alginate, hydroxyethyl cellulose, carboxymethyl cellulose sodium salt, polyvinyl alcohol (PVA), and sodium polyacrylate, as well as emulsions of polyacrylic esters, acrylic-styrene copolymers, polyvinyl acetate, ethylene-vinyl acetate copolymers, acrylonitrile-butadiene copolymers, and methyl methacrylate-butadiene copolymers, and emulsion binders such as styrene-butadiene copolymer latex.

[0119] The nonwoven antiviral sheet of the present invention may have a single-layer structure or a multi-layer structure. In the case of a multi-layer structure, at least one layer must contain the metal-containing cellulose fiber.

[0120] The content of metal ions and / or metal particles in the antiviral sheet of the present invention is preferably 0.2 to 50 mass%. If the content of metal ions and / or metal particles is less than 0.2 mass%, the antiviral, antibacterial, and deodorizing effects will be insufficient, and if it exceeds 50 mass%, the improvement in the antiviral, antibacterial, and deodorizing effects will plateau.

[0121] The basis weight of the antiviral sheet is not particularly limited, but is preferably 10 to 300 g / m 2 The range is preferably 15 to 200 g / m 2 When the nonwoven fabric has a multi-layer structure, the basis weight of each layer is more preferably in the range of 10 g / m. 2 It is preferable that the antiviral sheet has a minimum strength when handled during production, and that the basis weight of the antiviral sheet in the present invention is 0.05 m 2 The nonwoven fabric having an area of ​​above 1000 mm was dried at 105°C until it reached a constant mass, and then left in a constant temperature room at 20°C and 65% RH for 16 hours or more, after which the mass was measured. 2 This is the mass (g) per unit.

[0122] The thickness of the antiviral sheet is preferably in the range of 20 to 500 μm, more preferably in the range of 30 to 100 μm. When the nonwoven fabric has a multilayer structure, it is preferable that the thickness of each layer is 20 μm or more in order to produce a uniform sheet. There are no particular restrictions on the density of the nonwoven fabric.

[0123] The antiviral sheet of the present invention can be used as is, or can be laminated with other substrates such as nonwoven fabrics as needed and / or subjected to various processes such as embossing and pleating, and then suitably used for various applications such as filters for filtering gases or liquids.

[0124] The antiviral sheet of the present invention may include three or more nonwoven fabric layers. In this case, it is preferable that the inner layer is a nonwoven fabric layer containing metal ion-containing cellulose fibers. The outer layers other than the inner layer can be nonwoven fabrics used in known mask substrates.

[0125] In the present invention, the antiviral sheet may be subjected to a mesh treatment. Specific examples of the mesh shape include, but are not limited to, a lattice shape, a polka dot shape, and a polygonal shape.

[0126] In the present invention, the antiviral sheet and the antiviral metal-containing cellulose fiber can be used for any purpose requiring antiviral, deodorizing, or antibacterial functions, without any particular limitations. Furthermore, when the antiviral sheet is made into a nonwoven fabric, it can be used as is, or, if necessary, laminated with a substrate such as another nonwoven fabric and / or subjected to various processes such as embossing or pleating, and then suitably used for various purposes such as gas or liquid filtration filters. Examples include packaging materials (paper containers, cardboard, plastic film, wrapping paper, etc.), building materials (wallpaper, decorative paper, floor coverings, etc.), hygiene products (diapers, sanitary products, wipers, masks, wet towels, gauze, cotton swabs, etc.), daily necessities (deodorizing materials, fragrances, food filters, clean filters, lunch mats, tray masks, tablecloths, draining nets, cooking paper, cooking sheets, lye removal sheets, kitchen towels, dish towels, aprons, pot holders, toilet seat covers, splash-proof sheets for toilet floors, foot mats, wet tissues, disposable slippers, carpet base materials, shoe insoles, suitcases, etc.). Examples include: bars, carrier bags, condensation sheets, book covers, vacuum cleaner bags, sticky notes, bookmarks, notebooks, planner covers, pet sheets, disposable sheets, pillowcases, futon covers, cleaning sheets, etc.), industrial goods (industrial filters, industrial wipers, automotive interior materials, etc.), medical supplies (masks, protective clothing, surgical attire (caps, aprons, upper and lower garments), antibacterial mats, cleaning cloths, medical tape, etc.), clothing (disposable underwear, etc.), gardening and agricultural supplies (gardening sheets, agricultural sheets, seedbed sheets, fruit bags, etc.), headrest covers (for bullet trains and automobiles), and other paper products (calendars, etc.). [Example]

[0127] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0128] [Example 1] <Production of oxidized cellulose fibers> 5.00 g (bone dry) of bleached, unbeaten kraft pulp (brightness 85%) derived from softwood was added to 500 ml of an aqueous solution containing 39 mg (0.05 mmol per 1 g of bone dry cellulose) of TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl; Sigma-Aldrich) and 514 mg (1.0 mmol per 1 g of bone dry cellulose) of sodium bromide, and the mixture was stirred until the pulp was uniformly dispersed. Aqueous sodium hypochlorite solution was added to the reaction system so that the sodium hypochlorite concentration was 5.5 mmol / g, and the oxidation reaction was initiated at room temperature. The pH in the system decreased during the reaction, but 3M aqueous sodium hydroxide solution was gradually added to adjust the pH to 10. The reaction was terminated when the sodium hypochlorite was consumed and the pH in the system no longer changed. The reaction mixture was filtered through a glass filter, washed with sufficient amounts of water, and filtered twice to obtain oxidized cellulose fibers impregnated with water to a solid content of 10% by mass. The pulp yield was 90%, the oxidation reaction took 90 minutes, and the carboxyl group content was 1.68 mmol / g.

[0129] <Supporting metal ions on oxidized cellulose fibers> Water was added to the above oxidized cellulose fibers to prepare a dispersion with a solids concentration of 2%, and the pH was adjusted to 9.0. CuCl2 (manufactured by Wako Pure Chemical Industries, Ltd.) was then added with stirring to a concentration of 1.0 mmol / g per 1 g of oxidized cellulose fibers, and the mixture was further stirred for 30 minutes to incorporate Cu ions into the oxidized cellulose fibers. The unreacted metal salts were removed by washing with a sufficient amount of water and filtering twice, and water-impregnated Cu ion-loaded cellulose fibers (metal ion-containing cellulose fibers) with a solid content of 30% by mass were obtained. The metal ion content in the oxidized cellulose fiber was 40 mg / g, and the freeness of the metal ion-containing cellulose fiber was 500 ml.

[0130] <Manufacturing of antiviral sheets> A mixture of 5% of the above-mentioned metal ion-containing cellulose fiber and 95% hardwood bleached kraft pulp (LBKP with a freeness of 600 ml; manufactured by Nippon Paper Industries Co., Ltd.) as a cellulose fiber not containing metal ions (general cellulose fiber) was used, and water was further added to prepare an aqueous dispersion with a solids concentration of 0.5% by mass. This is made into paper with a round hand-made papermaking machine, with a basis weight of 30 g / m 2 The paper was made into a round antiviral sheet with a diameter of approximately 16 cm, which was then dehydrated in a press and dried at 85°C in a cylinder dryer.

[0131] [Comparative Example 1] An antiviral sheet was produced in the same manner as in Example 1, except that in the process of producing the antiviral sheet, no metal-containing cellulosic fibers were added, and the blending ratio of hardwood bleached kraft pulp (LBKP with a freeness of 600 ml; manufactured by Nippon Paper Industries Co., Ltd.) as cellulosic fibers not containing metal ions was 100%.

[0132] [Example 2] <Production of carboxymethyl cellulose-based fibers> 200 g of pulp (NBKP (softwood bleached kraft pulp), manufactured by Nippon Paper Industries Co., Ltd.) in dry mass and 111 g of sodium hydroxide in dry mass were added to a mixer capable of mixing pulp, and water was added so that the pulp solids content was 20% (w / v). After stirring for 30 minutes at 30°C, 216 g of sodium monochloroacetate (active ingredient equivalent) was added. After stirring for 30 minutes, the temperature was raised to 70°C and stirred for 1 hour. The reaction product was then removed, neutralized, and washed to obtain carboxymethylated cellulose-based fibers with a carboxymethyl substitution degree per glucose unit of 0.25.

[0133] <Carboxymethylated cellulose fiber loaded with metal ions> The pH of the carboxymethylated cellulose fiber (carboxymethylated cellulose fiber) dispersion obtained above was adjusted to 8.5, and a CuCl aqueous solution was added to a concentration of 1.0 mmol / g (per gram of carboxymethylated cellulose fiber) and stirred for 15 minutes. This allowed the carboxymethylated cellulose fiber to contain Cu ions. The fibers were then washed to remove unreacted metal salts, yielding Cu ion-supported cellulose fiber (metal ion-containing cellulose fiber). The metal ion (Cu) content of the resulting metal ion-containing cellulose fiber was 31.3 mg / g.

[0134] <Manufacturing of antiviral sheets> An antiviral sheet was produced in the same manner as in Example 1, except that the metal ion-containing cellulose fiber was replaced with the above-mentioned carboxylated cellulose fiber containing metal ions.

[0135] [Example 3] <Production of cellulose phosphate> A reaction solution was prepared by dissolving 6.75 g of sodium dihydrogen phosphate dihydrate and 4.83 g of disodium hydrogen phosphate in 19.62 g of water. Water was added to bleached, unbeaten kraft pulp (85% brightness) derived from softwood to a 4% consistency. The pulp was then refined using a double-disc refiner to a CSF of 200 ml and an average fiber length of 0.7 mm. The resulting cellulose suspension was diluted to 0.3% to obtain a pulp sheet with a moisture content of 90% and a solids content (bone dry mass) of 3 g. The pulp sheet was immersed in 31.2 g of the reaction solution, heated in a fan dryer at 105 °C for 1 hour, and then further heated at 150 °C for 1 hour to introduce phosphate groups into the cellulosic fibers. Next, 500 ml of ion-exchanged water was added to the pulp sheet containing the introduced phosphate groups into the cellulosic fibers, washed by stirring, and then dehydrated. The dehydrated sheet was diluted with 300 ml of ion-exchanged water, and 5 ml of 1N aqueous sodium hydroxide solution was added little by little while stirring to obtain a cellulose suspension with a pH of 12-13. This cellulose suspension was then dehydrated and washed with 500 ml of ion-exchanged water. Furthermore, infrared absorption spectroscopy using FT-IR revealed absorption at 1230-1290 cm-1 due to phosphate groups, confirming the addition of phosphate groups. The amount of phosphate groups introduced was 2.1 mmol / g per 1 g (mass) of fine fibrous cellulose.

[0136] <Supporting metal ions on phosphate-esterified cellulose fibers> Water was added to the above phosphated cellulose fibers to prepare a dispersion with a solids concentration of 2%, and the pH was adjusted to 9.0. CuCl2 (manufactured by Wako Pure Chemical Industries, Ltd.) was then added with stirring to a concentration of 1.0 mmol / g per 1 g of phosphated cellulose fibers, and the mixture was further stirred for 30 minutes to incorporate Cu ions into the phosphated cellulose fibers. The unreacted metal salts were removed by washing with a sufficient amount of water and filtering twice, and water-impregnated cellulose fibers carrying Cu ions (cellulose fibers containing metal ions) with a solid content of 30% by mass were obtained. The metal ion content in the phosphated cellulose fiber was 41 mg / g.

[0137] <Manufacturing of antiviral sheets> An antiviral sheet was produced in the same manner as in Example 1, except that the metal ion-containing cellulose fiber was replaced with the above-mentioned metal ion-containing phosphated cellulose fiber.

[0138] [Example 4] <Production of phosphite esterified cellulose fiber> A reaction solution was prepared by mixing 13 g of sodium hydrogen phosphite pentahydrate, 10.8 g of urea, and 76.2 g of water. 100 g of the reaction solution was mixed with 10 g of bleached, unbeaten kraft pulp (85% brightness, dry weight) derived from softwood and dried at 105°C. The dried pulp was reacted at 170°C for 2 hours, then washed with water and filtered twice to obtain phosphite-esterified cellulose fibers incorporating phosphate esters containing inorganic cations. The amount of phosphite groups introduced was 1.2 mmol / g per 1 g (mass) of fine fibrous cellulose.

[0139] <Supporting metal ions on phosphite-esterified cellulose fibers> Water was added to the above phosphite-esterified cellulose-based fibers to prepare a dispersion with a solids concentration of 2%, and the pH was adjusted to 9.0. CuCl2 (manufactured by Wako Pure Chemical Industries, Ltd.) was then added with stirring to a concentration of 1.0 mmol / g per 1 g of phosphite-esterified cellulose-based fibers, and the mixture was further stirred for 30 minutes to incorporate Cu ions into the phosphite-esterified cellulose-based fibers. The unreacted metal salts were removed by washing with a sufficient amount of water and filtering twice, and water-impregnated cellulose fibers carrying Cu ions (cellulose fibers containing metal ions) with a solid content of 30% by mass were obtained. The metal ion content in the phosphite-esterified cellulose fiber was 42 mg / g.

[0140] <Manufacturing of antiviral sheets> An antiviral sheet was produced in the same manner as in Example 1, except that the metal ion-containing cellulose fiber was replaced with the above-mentioned metal ion-containing phosphite-esterified cellulose fiber.

[0141] [Example 5] <Production of sulfonated cellulose-based fibers> A reaction solution was prepared by mixing 20 g of sulfamic acid, 10 g of urea, and 100 ml of water. 2 g (dry weight) of bleached, unbeaten kraft pulp (85% brightness) derived from softwood was added to 130 g of this reaction solution, and the resulting slurry was stirred for 10 minutes. After stirring, the slurry was suction filtered using filter paper to produce a pulp sheet. The pulp sheet was placed in a dryer set at 50°C and dried until the moisture content reached equilibrium. The dried pulp was heated at 120°C for 30 minutes. After the heating reaction, the reacted pulp was washed with pure water until neutral, producing sulfamic acid / urea-treated sulfonated cellulose-based fibers. The amount of sulfonic groups introduced was 0.9 mmol / g.

[0142] <Supporting metal ions on sulfonated cellulose fibers> Water was added to the sulfonated cellulose fiber to prepare a dispersion with a solids concentration of 2%. The pH was adjusted to 9.0, and then CuCl2 (manufactured by Wako Pure Chemical Industries, Ltd.) was added with stirring to a concentration of 0.5 mmol / g per 1 g of sulfonated cellulose fiber. The mixture was further stirred for 30 minutes to incorporate Cu ions into the sulfonated cellulose fiber.

[0143] The unreacted metal salts were removed by washing with a sufficient amount of water and filtering twice, and water-impregnated cellulose fibers carrying Cu ions (cellulose fibers containing metal ions) with a solid content of 30% by mass were obtained. The metal ion content of the sulfonated cellulose fiber was 21 mg / g.

[0144] <Manufacturing of antiviral sheets> An antiviral sheet was produced in the same manner as in Example 1, except that the metal ion-containing cellulose fiber was replaced with the above-mentioned metal ion-containing sulfonated cellulose fiber.

[0145] The antiviral properties of the antiviral sheets obtained in the Examples and Comparative Examples were evaluated as follows. Evaluation of antiviral properties The antiviral properties of the samples produced in Example 1 and Comparative Example 1 were evaluated. The amount of sample used in the antiviral test was 0.4 g. The antiviral test was performed in accordance with JIS L 1922:2016, and the antiviral activity value was calculated. The following two types of viruses were used as test viruses. Influenza virus (H3N2, ATCC VR-1679) Feline calicivirus (Strain: F-9 ATCC VR-782)

[0146] [Table 1]

[0147] As is clear from Table 1, Examples 1 to 5, which contained metal-containing cellulose fibers, exhibited high antiviral properties. On the other hand, Comparative Example 1, which did not contain metal-containing cellulose fibers, exhibited low antiviral properties.

[0148] [Example 6] <Production of metal ion-containing cellulose fibers> 5.00 g (bone dry) of bleached, unbeaten kraft pulp (brightness 85%) derived from softwood was added to 500 ml of an aqueous solution containing 39 mg (0.05 mmol per 1 g of bone dry cellulose) of TEMPO (Sigma Aldrich) and 514 mg (1.0 mmol per 1 g of bone dry cellulose) of sodium bromide, and the mixture was stirred until the pulp was uniformly dispersed. Next, sodium hypochlorite aqueous solution was added to the reaction system so that the sodium hypochlorite concentration was 5.5 mmol / g, and the oxidation reaction was initiated at room temperature. The pH in the system decreased during the reaction, but 3 M sodium hydroxide aqueous solution was gradually added to adjust the pH to 10. The reaction was terminated when the sodium hypochlorite was consumed and the pH in the system no longer changed (time required for the oxidation reaction: 90 minutes). After the reaction, the mixture was filtered through a glass filter, and then washed with a sufficient amount of water and filtered twice to obtain water-impregnated oxidized cellulose fibers (solid content: 10% by mass, pulp yield: 90%, carboxyl group content: 1.68 mmol / g). Water was added to the resulting oxidized cellulose fibers to prepare a dispersion with a solids concentration of 2%, and the pH was adjusted to 9.0. Next, CuCl2 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added with stirring to a concentration of 1.6 mmol / g per 1 g of oxidized cellulose fibers, and the mixture was stirred for a further 30 minutes to incorporate Cu ions into the oxidized cellulose fibers. The resulting mixture was washed twice with sufficient water and filtered to remove unreacted metal salts, yielding water-impregnated Cu ion-loaded cellulose fibers (solid content: 30% by mass). The metal ion content of the resulting metal ion-loaded cellulose fibers was 50 mg / g, and the freeness of the metal ion-loaded cellulose fibers was 500 ml. <Nonwoven fabric manufacturing> An aqueous dispersion with a solids concentration of 0.5% by mass was prepared by adding water to a mixture of 10% of the above-mentioned metal ion-containing cellulose fiber, 20% softwood bleached kraft pulp (NBKP with a freeness of 600 ml; manufactured by Nippon Paper Industries Co., Ltd.) as a cellulose fiber not containing metal ions (general cellulose fiber), 30% synthetic PET fiber (Teijin Frontier, Ecopet) cut to a fiber length of 5 mm, and 40% binder fiber (core-sheath polyester composite fiber, melting point of the sheath: 100-160°C, core: polyethylene terephthalate). This is made into paper with a round hand-made papermaking machine, with a basis weight of 30 g / m 2The paper was dewatered in a press and further dried at 85°C in a cylinder dryer to produce a round nonwoven fabric with a diameter of about 16 cm.

[0149] Comparative Example 2 A nonwoven fabric was produced in the same manner as in Example 6, except that in the process of producing the nonwoven fabric, no metal-containing cellulosic fiber was blended, and the blending ratio of cellulosic fiber not containing metal ions (NBKP pulp with a freeness of 600 ml, manufactured by Nippon Paper Industries Co., Ltd.) was set to 30%. <Evaluation of nonwoven fabrics> The antiviral properties of the obtained nonwoven fabric were evaluated in the same manner as in Example 1. [Table 2] As is clear from the above results, the nonwoven fabrics containing metal-containing cellulosic fibers and synthetic fibers exhibited high antiviral properties, while the nonwoven fabrics that did not contain metal-containing cellulosic fibers did not exhibit antiviral properties.

Claims

1. A method for producing an antiviral sheet, comprising the step of wet-laid papermaking from a slurry containing metal-containing cellulosic fibers, The metal-containing cellulose fiber is a cellulose fiber having an anionic group to which Cu is ionically bonded, and the metal-containing cellulose fiber has a freeness of 30 to 800 mL. The cellulose fiber having an anionic group includes a phosphate-esterified cellulose fiber having a phosphate group, a phosphite-esterified cellulose fiber having a phosphite group, or a sulfonated cellulose fiber having a sulfate group. The above method, wherein the antiviral sheet has an antiviral activity value (Mv) against influenza virus or feline calicivirus of 2.0 or more in accordance with the antiviral activity test method for textile products (JIS L 1922:2016), and the content of metal-containing cellulose fibers in the antiviral sheet is 10 mass% or less.

2. 2. The method according to claim 1, wherein the metal-containing cellulosic fiber has a Cu ion content of 10 to 100 mg / g of cellulosic fiber.

3. The method according to claim 1 or 2, wherein the content of Cu ions is 10 to 60 mg / g of the cellulosic fiber.

4. The method according to any one of claims 1 to 3, wherein the amount of anionic groups in the cellulose fibers having anionic groups is 0.01 to 3.0 mmol / g.

5. The method according to any one of claims 1 to 4, wherein the antiviral sheet contains cellulosic fibers that do not contain metal.

6. The method according to any one of claims 1 to 5, wherein the antiviral sheet contains synthetic fibers.

7. The method according to any one of claims 1 to 6, wherein the antiviral sheet contains binder fibers.

8. The method according to any one of claims 1 to 7, wherein the antiviral sheet is a sheet of two or more layers, at least one of which contains the metal-containing cellulosic fiber.

9. The method according to any one of claims 1 to 8, wherein the content of Cu ions in the antiviral sheet is 0.2 to 50 mass%.

Images