Deodorant cardboard

Abstract

To provide a cardboard having excellent deodorant property.SOLUTION: An antiviral cardboard including a cellulose fiber is presented by this invention. A deodorant cardboard according to this invention has an offensive odor absorption rate after one hour of use of 7.5% or over. Also, a paper container using the deodorant cardboard of this invention has an offensive odor leakage degree calculated by [offensive odor index of a paper-made container outer part / offensive odor index of a paper-made container inner part] after one hour of use is 85% or under, hence leakage of an offensive odor to around the paper container can be suppressed.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an odor-eliminating paperboard, and more particularly to an odor-eliminating paperboard having multiple paper layers. [Background technology]

[0002] Functional sheets, which are sheet-like substrates to which functionalizing agents have been added, are used in a variety of industrial fields. Specific examples of functional properties include deodorizing, antibacterial, heat-resistant, moisture-resistant, weather-resistant, solvent-resistant, abrasion-resistant, and electromagnetic wave-blocking. They are used in packaging materials (paper containers, cardboard, plastic films, etc.), building materials (wallpaper, decorative paper, floor coverings, etc.), household goods (deodorizers, fragrances), industrial products (filters, wipers, etc.), medical products (masks, etc.), clothing, and other paper products (calendars, etc.). Deodorizing and antibacterial properties are particularly important in many industrial fields. Depending on the application, functional sheets are also required to have mechanical properties such as tensile strength, tear strength, and burst strength.

[0003] Various techniques have been proposed for imparting deodorizing and antibacterial properties to sheet-like substrates. For example, Patent Documents 1 and 2 propose an inorganic porous crystal-hydrophilic polymer composite impregnated with zeolite, and disclose that the zeolite can be imparted with antibacterial and deodorizing effects by supporting a metal. Patent Document 3 discloses a cellulose fiber structure in which a silicon compound and an aluminum compound are reacted inside cellulose fibers to produce zeolite, a porous silica-alumina material. Patent Document 4 discloses antibacterial cellulose fibers containing a silver-based antibacterial agent. Patent Document 5 discloses a paper substrate containing oxidized pulp. Patent Document 6 discloses an antiviral paperboard containing cellulose fibers containing metal ions and / or metal particles. [Prior art documents] [Patent documents]

[0004] [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 [Patent Document 6] Japanese Patent Publication No. 2023-075561 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventions described in Patent Documents 1 to 3 use a simple mixture of cellulose fibers and inorganic compounds containing metal components, and the cellulose fibers and inorganic compounds containing metal components are not strongly chemically bonded. In other words, inorganic compounds containing metal components do not form a physical or chemical network like fibers. Therefore, when functional sheets are produced using these 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 the substrate. Furthermore, the inventions described in Patent Documents 4 and 5 focus on antibacterial and antiviral properties, but do not specifically mention deodorizing properties.

[0006] In view of the above circumstances, an object of the present invention is to provide an odor-eliminating paperboard that can improve odor absorption rate one hour after the start of use. [Means for solving the problem]

[0007] The present invention includes, but is not limited to, the following aspects. [1] A deodorizing paperboard having multiple paper layers, in which at least one of the surface layers of the paperboard contains 2.0% or more cellulose fibers containing at least one metal ion and / or metal particle selected from the group consisting of Cu, Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, and Zn, and has an odor absorption rate of 7.5% or more after one hour of use. [2] The deodorizing paperboard according to [1], wherein the cellulose fibers are contained in the deodorizing paperboard in an amount of 0.3 to 2.0%. [3] The deodorizing paperboard according to [1] or [2], wherein the cellulose fibers contain Cu and / or Ag. [4] The deodorizing paperboard according to any one of [1] to [3], wherein the cellulose fibers contain Cu. [5] The deodorizing paperboard according to any one of [1] to [4], wherein the paperboard has a paper layer that does not contain cellulose fibers containing metal ions and / or metal particles. [6] A paper container using the deodorizing paperboard described in any one of [1] to [5], characterized in that the odor leakage rate calculated as [odor index outside the paper container / odor index inside the paper container] after one hour of use is 85% or less. [7] Paper furniture using the deodorizing paperboard according to any one of [1] to [5]. [8] Paper bedding using the deodorizing paperboard according to any one of [1] to [5]. [Effects of the Invention]

[0008] The present invention can provide a deodorizing paperboard having an odor absorption rate of 15% or more by containing metal ions and / or metal particles. The present invention also can provide a method for producing the deodorizing paperboard. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention relates to an odor-eliminating paperboard comprising multiple paper layers. The odor-eliminating paperboard according to the present invention has an odor absorption rate of 7.5% or more after one hour of use, and contains 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.

[0010] The deodorizing paperboard of the present invention has a multilayer structure in which multiple paper layers are laminated, preferably 2 to 10 layers, and more preferably 3 to 9 layers. In the case of a multilayer structure, at least one layer must contain the metal-containing cellulose fiber. The deodorizing paperboard of the present invention may also have three or more paper layers. In this case, the inner layer may contain the metal-containing cellulose fiber, but it is preferable that the outer layer other than the inner layer contains the metal-containing cellulose fiber.

[0011] The basis weight of the deodorizing paperboard is not particularly limited, but is preferably 50 to 1000 g / m 2 The range is preferably 80 to 700 g / m 2 or 100-500g / m 2 It is more preferable that the basis weight of each layer is in the range of 10 g / m 2 It is preferable that the thickness is 15 to 200 g / m or more in order to produce a uniform paperboard that has a minimum strength when handled during production, and 2 or 20-100g / m 2 It is more preferable that the basis weight of the deodorizing paperboard in the present invention is in the range of 0.05 m 2 After drying the sample at 105°C until it reached a constant mass, it was left in a constant temperature room at 20°C and 65% RH for 16 hours or more, and its mass was measured. 2 Simply calculate the mass (g) per unit.

[0012] The thickness of the deodorizing paperboard is not particularly limited, but is preferably in the range of 50 to 1500 μm, more preferably in the range of 100 to 1000 μm or 140 to 500 μm. From the viewpoint of producing a uniform paperboard, the thickness of each layer constituting the deodorizing paperboard is preferably in the range of 20 to 500 μm, more preferably in the range of 30 to 100 μm.

[0013] The deodorizing paperboard of the present invention can be produced by papermaking in the same manner as for ordinary paperboard, i.e., by making paper from a pulp slurry (stock) containing metal-containing cellulose fibers using a known papermaking machine such as a Fourdrinier papermaking machine, a twin-wire papermaking machine, or a cylinder papermaking machine, and the papermaking conditions are not limited.

[0014] The deodorizing paperboard according to the present invention can be made using pulp, which is a cellulose fiber. Examples of cellulose fibers other than metal-containing cellulose fibers (also called ordinary cellulose fibers) include wood pulp; non-wood pulps such as bamboo, cotton, hemp, jute, kenaf, agricultural waste, animal (e.g., sea squirts), algae, and microbial (e.g., acetic acid bacteria such as Acetobacter); regenerated cellulose, and rayon. Wood pulp is preferred as the ordinary cellulose fiber, and one or more types of ordinary cellulose fibers can be mixed and used. The content of ordinary cellulose fibers in the deodorizing paperboard is preferably 99% by mass or less.

[0015] The papermaking pulp used in the present invention may be, for example, deinked pulp (DIP), softwood or hardwood kraft pulp (NKP or LKP), mechanical pulp made from softwood or hardwood, such as groundwood pulp (GP), refined groundwood pulp (RGP), thermomechanical pulp (TMP), chemi-thermomechanical pulp (CTMP), chemi-ground pulp (CGP), semi-chemical pulp (SCP), etc., recycled paper pulp made by disintegrating cardboard, coated broken paper made by disintegrating broken paper including coated paper, coated base paper, and other papers, or a mixture of two or more of these pulps.

[0016] The number-average fiber diameter and number-average fiber length of the cellulose fibers are not particularly limited, and any values ​​can be used depending on the required mechanical properties such as tensile strength and tear strength, breathability, texture, etc. Two or more types of fibers with different number-average fiber diameters and number-average fiber lengths may be mixed in any ratio. In one embodiment, softwood kraft pulp (NBKP), which is one of the natural cellulose fibers, has a number-average fiber diameter of about 30 to 60 μm and a number-average fiber length of about 2 to 5 mm, while hardwood bleached kraft pulp (LBKP) has a number-average fiber diameter of about 10 to 30 μm and a number-average fiber length of about 1 to 2 mm.

[0017] The cellulose fibers may be subjected to a beating treatment one or more times. Here, beating refers to a treatment that applies mechanical shear force to the fibers. The beating treatment fibrillates or converts some of the cellulose fibers into nanofibers, improving mechanical properties such as tensile strength. The freeness of general cellulose fibers is not particularly limited and can be freely selected from a general freeness range, for example, a range of 5 to 950 ml, depending on the desired quality.

[0018] 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.

[0019] In the present invention, chemicals may be added during papermaking, such as sizing agents such as rosin emulsion, neutral rosin, alkyl ketene dimer, alkenyl succinic anhydride, and styrene / acrylic copolymer, dry strength agents such as cationic, amphoteric, and anionic polyacrylamides, polyvinylamines, and resins containing polyacrylic acid, and guar gum, wet strength agents such as cationic, amphoteric, and anionic modified starches, polyamidoamine epichlorohydrin, and carboxymethyl cellulose, drainage aids, colorants, dyes, fluorescent dyes, coagulants, bulking agents, and retention aids.

[0020] The base paper of the present invention may contain a filler. Such fillers are not particularly limited, but examples include inorganic fillers such as diatomaceous earth, talc, kaolin, calcined kaolin, delaminated kaolin, heavy calcium carbonate, light calcium carbonate, magnesium carbonate, barium carbonate, titanium dioxide, zinc oxide, silicon oxide, amorphous silica, calcium sulfite, gypsum, white carbon, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, papermaking sludge, and inorganic particles recycled from deinking froth; organic fillers such as urea-formalin resin, polystyrene resin, vinyl chloride resin, melamine resin, phenolic resin, and plastic microhollow particles; and fillers contained in recycled paper or broken paper, used alone or in combination of two or more. The blending ratio of the above fillers to the base paper (base paper ash content) is preferably 10% by weight or more.

[0021] In the present invention, the method for drying the multilayer paperboard is not limited, and various methods such as a steam heating cylinder, a heated hot air dryer, a gas heater dryer, an electric heater dryer, and an infrared heater dryer can be used alone or in combination.

[0022] The deodorizing paperboard of the present invention may be used as is, or may be laminated with other substrates as needed, or may be subjected to various processes such as embossing or pleating, and then used suitably for various applications.

[0023] The deodorizing paperboard of the present invention can be used for any purpose requiring deodorizing functionality, but is not particularly limited thereto. That is, the deodorizing paperboard can be used as is, or after various processing steps as necessary, for a variety of purposes. Examples include packaging materials (paper containers, cardboard, resin films, wrapping paper, etc.), building materials (wallpaper, decorative paper, floor coverings, etc.), household goods (partitions, deodorizing agents, fragrances, potholders, disposable slippers, carpet base materials, shoe insoles, carrier bags, etc.), gardening and agricultural materials (gardening sheets, agricultural sheets, seedbed sheets, fruit bags, etc.), and disaster prevention and outdoor products (paper beds, paper tents, etc.).

[0024] In a preferred embodiment, the deodorizing paperboard of the present invention is used in paper containers for transporting odor-generating items such as onions, and it is more preferable to use the deodorizing paperboard of the present invention on the inner surface of a paper container. Furthermore, when the deodorizing paperboard of the present invention is used as a paper container, it is preferable that the paper container have an odor leakage rate calculated as [odor index outside the paper container / odor index inside the paper container] after 1 hour of use of 85% or less, more preferably 82.5% or less, even more preferably 80% or less, and most preferably 75% or less.

[0025] In a preferred embodiment, the odor absorption rate of the deodorizing paperboard of the present invention after 1 hour of use is 7.5% or more, more preferably 10% or more, even more preferably 12.5% ​​or more, and most preferably 15% or more. The odor index can be measured using an odor measuring device or the like.

[0026] In a preferred embodiment, the deodorizing paperboard of the present invention is used for paper furniture such as cardboard beds, pet cages, and paper tents, as well as paper bedding such as paper sleeping bags. When used in these paper furniture and bedding applications, the deodorizing paperboard of the present invention effectively absorbs sweat and other body odors emitted by the human body, providing a comfortable environment. Body odor is primarily composed of organic compounds such as ammonia, acetaldehyde, isovaleric acid, and propionic acid. These compounds are produced when bacteria on the skin decompose proteins and lipids in sweat, resulting in a distinctive, unpleasant odor. The deodorizing paperboard of the present invention can efficiently absorb and decompose these organic compounds, resulting in a significant reduction in the odor index, thereby providing a more comfortable space for users. In particular, the use of paperboard with deodorizing properties is extremely effective for bedding and furniture, which are often in direct contact with the human body and are prone to permeating the materials with sweat and body odor.

[0027] Because cardboard beds and pet cages are places where animals and people come into contact for long periods of time, the deodorizing paperboard used in these places has the effect of keeping the environment clean and improving comfort. Similarly, paper tents and paper sleeping bags used in camping and outdoor activities are expected to be significantly more convenient if they utilize this function. Based on the above, the deodorizing paperboard of the present invention can be used in a wide range of applications due to its high odor absorption rate, and its value is expected to increase not only in everyday life but also in specific environments.

[0028] Metal-containing cellulose fibers The metal-containing cellulose fibers of the present invention include 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. As will be described later, the metal-containing cellulose fibers are preferably metal-containing anion-modified cellulose fibers.

[0029] The metal-containing cellulose fibers do not need to be contained in all paper layers constituting the paperboard, but may be contained in at least one paper layer. In a preferred embodiment, the metal-containing cellulose fibers are preferably contained in one or both surface layers of the paperboard. The content of the metal-containing cellulose fibers in the paper layer containing the metal-containing cellulose fibers is preferably 1% by weight or more, more preferably 2% by weight or more. If the content is too low, a sufficient deodorizing effect may not be imparted. The upper limit of the content is not particularly limited and can be adjusted appropriately depending on the desired level of deodorizing effect, but may be 100% by weight, 50% by weight or less, or 30% by weight or less. In a preferred embodiment, the content of the metal-containing cellulose fibers in the paper layer containing the metal-containing cellulose fibers is 1.5 to 10% by weight, more preferably 2.0 to 8.0% by weight or 2.5 to 6.0% by weight.

[0030] The content of the metal-containing cellulose fibers is preferably 0.01% by mass or more relative to the paperboard. If the content is too low, it may not be possible to provide a sufficient deodorizing effect. The upper limit of the content is not particularly limited and can be adjusted appropriately depending on the desired level of deodorizing, antibacterial, and antiviral effect, but it may be 100% by mass. In a preferred embodiment, the content of the metal-containing cellulose fibers is 0.01 to 30% by mass of the paperboard, more preferably 0.1 to 10% by mass, and even more preferably 0.2 to 5.0% by mass or 0.3 to 2.0% by mass.

[0031] In the case of metal-containing cellulose fibers, beating can further enhance the deodorizing effect after the metal ions and / or metal particles are loaded. Freeness (Canadian Standard Freeness: CSF) is generally used as an indicator of the degree of beating. The freeness of metal-containing cellulose fibers is preferably in the range of 30 to 800 ml. If the freeness is too low, the yield in the paperboard manufacturing process decreases, while if the freeness is too high, fibrillation is insufficient, resulting in a low specific surface area, which reduces the exposure of metal ions to the surface and may result in insufficient antiviral effect.

[0032] The metal-containing cellulose fibers are preferably metal-containing anion-modified cellulose fibers in which metal ions are ionically bonded to cellulose fibers having anionic groups. Examples of anion-modified cellulose fibers include oxidized cellulose, etherified cellulose (e.g., carboxymethylated cellulose), and esterified cellulose (e.g., phosphate-esterified cellulose).

[0033] The amount of anionic groups in oxidized cellulose fibers having carboxyl groups, carboxylate groups, phosphate groups, or sulfonic acid groups can be measured by the following method. Note that the above functional groups are collectively referred to as "acid groups." (Amount of anionic groups) 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 amount of anionic groups is calculated using the following formula from the amount of sodium hydroxide (a) consumed in the neutralization stage of a 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) 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.

[0034] The amount of anionic groups in the cellulose 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 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.

[0035] The metal-containing anion-modified cellulose fibers can be produced by chemically modifying ordinary cellulose fibers as follows to introduce anion-modifying groups into the glucose units on the surface, and then further supporting metal ions and / or metal particles.

[0036] Hereinafter, a method for introducing anion-modified groups into glucose units on the surface of cellulose fibers and a method for subsequently supporting metal ions and / or metal particles will be described.

[0037] (1) Modification of cellulose fibers Cellulose has three hydroxyl groups per glucose unit and can be chemically modified in various ways. Oxidized cellulose is obtained by modifying cellulose 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.

[0038] 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."

[0039] The method of modification to introduce carboxyl groups or carboxylate groups is not particularly limited as long as the cellulose fibers after modification contain carboxyl groups or carboxylate groups.

[0040] (1-1) Oxidation In the present invention, the method for oxidizing cellulose 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.

[0041] 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.

[0042] The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of oxidizing cellulose fibers. For example, it 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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 or more. 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:

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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. 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.

[0058] 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.

[0059] (1-2) Etherification For the etherification, any method that results in a carboxyl group or a carboxylate group being present in the functional group after the reaction can be used, and any known method can be used, so long as it allows for the convenient introduction of metal ions into the cellulose fibers in a subsequent step. Examples include carboxyalkyl etherification such as carboxymethyl (etherification), carboxyethyl (etherification), carboxypropyl (etherification), and carboxybutyl (etherification), as well as carboxyphenyl (etherification). Among these, the carboxymethylation method will be described below as an example.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] During the carboxymethylation reaction, the reaction mixture may be stirred as needed. 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.

[0067] The degree of carboxymethyl substitution per glucose unit of carboxymethylated cellulose fiber 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-form carboxymethyl cellulose with 15 mL of 80% methanol, add 100 mL of 0.1 N NaOH, and shake at room temperature for 3 hours. 5) Back-titrate excess NaOH with 0.1N H2SO4 using phenolphthalein as an indicator. 6) The degree of carboxymethyl substitution (DS) is calculated by 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 of 1N NaOH (mL) required to neutralize 1 g of hydrogen-type carboxymethyl cellulose F´: Factor of 0.1N NaOH F: Factor of 0.1N H2SO4 (1-3) Esterification 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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. 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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. (1-4) Sulfonation 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.

[0078] 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.

[0079] 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.

[0080] (2) Supporting metal ions and / or metal particles A high deodorizing effect is achieved 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 the cellulose fibers. The use of Ag and Cu in particular further improves the deodorizing function.

[0081] In particular, anion-modified cellulose fibers have the metal and cellulose fibers chemically bonded together, so when the fibers are made into a sheet, the metal components are less likely to be released from the sheet, and the fibers also have good mechanical properties such as tensile strength.

[0082] The method for loading the metal ions onto the cellulose fibers is not particularly limited, and may involve, for example, mixing a previously prepared dispersion of the cellulose fibers with an aqueous solution of a metal compound, or applying the dispersion containing the cellulose fibers onto a substrate to form a film, and then dripping the aqueous solution of the 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.

[0083] These methods allow metal ions derived from metal compounds to be added to cellulose 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.

[0084] 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.

[0085] 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.

[0086] In the present invention, metal ions can be introduced into cellulose 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 cellulose fibers can be reduced by adding a reducing agent or the like, thereby forming metal particles partially on the surface of the cellulose fibers.

[0087] However, it is preferable from the viewpoint of deodorizing effect to use the entire amount of the metal compound in the form of metal ions without carrying out any special reduction treatment. The mechanism by which metal particles are generated in the cellulose fibers by reducing the metal compounds in the metal-containing cellulose fibers obtained above is not clear, but is presumed as follows. The metal compounds or ions derived from the metal compounds in the metal compound-containing cellulose fibers are reduced to metal through a reduction reaction. The generated metal is then supported on the surface of the cellulose fibers. Similarly, neighboring metals generated combine with each other, causing the particles to grow and form nanoparticles. Meanwhile, metal compounds present near the cellulose fibers but not bonded to the cellulose 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.

[0088] 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; for example, the reaction may be carried out 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 fibers do 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.

[0089] The presence of metal ions or particles in cellulose fibers can be confirmed by scanning electron microscope images and ICP atomic emission spectrometry of strong acid extracts. In other words, the presence of metal ions cannot be confirmed by scanning electron microscope images, but the presence of metals can be confirmed by ICP atomic emission spectrometry. 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.

[0090] In the step of supporting metal ions or metal particles, the metal content relative to the cellulose fibers 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 the metal content is less than 10 mg / g, the antiviral, deodorizing, and antibacterial functions may be impaired. On the other hand, if the metal content exceeds 100 mg / g, the metal ions are more likely to elute during production, increasing the burden on wastewater treatment.

[0091] 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 deodorizing effect of the metal-containing cellulose fibers. The freeness factor (CSF) can be used as an indicator of the degree of beating. Specifically, if the freeness is too low, the yield will be low and the deodorizing effect of the paperboard will be reduced, while if the freeness is too high, fibrillation will be insufficient, reducing the deodorizing effect of the metal-containing cellulose fibers.

[0092] 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.

[0093] 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).

[0094] The metal ion-containing cellulose fibers may be nanofiberized. The nanofiberized 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.

[0095] Other ingredients The deodorizing paperboard of the present invention may contain one or more other materials, if necessary, in addition to the metal-containing cellulose fibers and general cellulose 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 paperboard.

[0096] 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.

[0097] 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.

[0098] Examples of colorants include inorganic colorants such as titanium oxide and calcium carbonate, and organic colorants such as phthalocyanine. Examples of the lubricant include oleic acid amide, erucic acid amide, and stearic acid amide. [Example]

[0099] The present invention will be described in more detail based on specific examples, but the present invention is not limited to the following examples. Unless otherwise specified, concentrations and the like in this specification are based on mass, and numerical ranges are stated as including their endpoints.

[0100] Experiment 1. Production of metal-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 (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.

[0101] 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 of 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 of the system no longer changed.

[0102] The reaction mixture was filtered through a glass filter, washed with sufficient amounts of water, and filtered twice to obtain oxidized cellulose fibers. The pulp yield was 90%, the oxidation reaction took 90 minutes, and the carboxyl group content was 1.68 mmol / g.

[0103] Water was added to the above oxidized cellulose fibers to prepare a dispersion with a solids concentration of 2%. The pH was then adjusted to 9.0, after which CuCl2 (Fujifilm Wako Pure Chemical Industries, Ltd.) was 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.

[0104] The unreacted metal salts were removed by washing with sufficient amounts of water and filtering twice to obtain Cu ion-loaded oxidized cellulose fibers (metal-containing cellulose fibers). The metal ion content of the oxidized cellulose fibers was 40 mg / g, and the freeness (CSF) of the metal ion-loaded cellulose fibers was 500 ml.

[0105] Experiment 2: Manufacturing deodorizing paperboard

[0106] Pulp slurries were prepared by mixing softwood unbleached kraft pulp (NUKP, CSF: 400 ml) and metal-containing cellulose fiber at various weight ratios. Two weight percent aluminum sulfate, 0.2 weight percent polyacrylamide-based strength agent, and 0.2 weight percent rosin-based sizing agent were then added to the pulp slurry solids, and the mixture was diluted to a solids concentration of 1 weight percent to prepare stock slurries A1, A2, A3, and A4 for the surface layer. The weight ratio of NUKP to metal-containing cellulose fiber was varied from 100:0 to 95:5, and the Canadian Standard Freeness (CSF) of the mixed pulp slurries was 390 ml.

[0107] In addition, 2% by weight of aluminum sulfate, 0.2% by weight of a polyacrylamide-based strength agent, and 0.2% by weight of a rosin-based sizing agent were mixed into a pulp slurry of recycled paper pulp, in that order based on the solid content of the pulp slurry, and then diluted to a solid content concentration of 1% by weight to prepare paper stock slurry B for use in making paper other than the surface layer.

[0108] Next, in the paper machine, pulp slurry B was applied to the back layer, back middle layer, middle layer, and top bottom layer in the order of bone dry basis weight of about 45 g / m 2 After laminating the sheets so that the surface layer had a bone dry basis weight of about 40 g / m, pulp slurries A1 to A4 were applied. 2 After lamination, the sheets were pressed and dried to obtain a paperboard having five paper layers (Samples 1 and 2: Comparative Examples, Samples 3 and 4: Examples, bone dry basis weight: about 167 g / m 2 ).

[0109] Experiment 3: Evaluation of deodorizing paperboard The deodorizing function and other properties were evaluated by the following methods. 3-1. Copper content The contents (mg / g) of metal ions and metal particles per gram of sample were measured by inductively coupled plasma optical emission spectroscopy (ICP-OES) according to the following procedure. (1) Dry the sample (50°C, 1 day) before measurement. (2) Weigh out 0.1 g of the dried sample for measurement and place it in a 50 ml beaker. (3) Take 10 ml of concentrated nitric acid with a whole pipette and add it to the beaker containing the measurement sample to create a measurement sample solution (10 times dilution). (4) Leave the sample to stand for 30 minutes, then filter it through a syringe filter to remove any fibrous matter from the sample. (5) Take 1 ml of the filtered sample liquid with a micropipette and add it to a test tube containing 49 ml of distilled water (50 times dilution). (6) Close the test tube tightly and shake to mix. (7) Measure (quantify) the content of metal ions and metal particles using ICP-OES (Agilent Technology, ICP-OES 5110). (8) From the quantitative results (ppb) obtained by ICP-OES, calculate the content (mg / g) of metal ions and metal particles per gram of sample using the following formula: (ICP-OES quantitative result (ppb) x 10 x 50) / (measurement sample weight (g)) x 1000 / 1000000000

[0110] 3-2. Deodorizing properties The deodorizing function test was carried out in the following manner. (1) Sample 1 was used as the inner core and back liner of a cardboard sheet, and the surface of each sample was pasted together using a corrugator so that it became the surface of the cardboard sheet, to produce a cardboard sheet sample (A flute, sheet thickness: approximately 5 mm). (2) Using the prepared cardboard sheet sample, a type A (JIS Z 1507 0201 format) cardboard box with a lid was made (external dimensions of the box: width 18.6 cm x depth 18.2 cm x height 9.5 cm). (3) A disposable cup containing 40 g of onion that had been thoroughly mashed in a blender was placed in a box with a lid, and the box was then sealed with packing tape. (4) The sealed cardboard box was stored in a polystyrene foam (internal dimensions: width 22 cm x depth 22 cm x height 16 cm). After leaving it for 24 hours, a sensory evaluation of the odor inside the polystyrene foam was conducted, and the odor inside the polystyrene foam was also measured using an odor measuring device (portable odor sensor model XP-329IIIR, manufactured by New Cosmos Electric Co., Ltd.). The sensory evaluation was carried out based on the following criteria. 〇: Almost no smell △: Slight odor ×: Strong odor The odor absorption rate and odor leakage rate were calculated using the following formulas. Odor absorption rate (%) = 1 - [Odor index when using each sample / Odor index when using sample 1 (blank)] x 100 Odor leakage rate (%) = [Odor index when each sample is used / Odor index when no box is used (onion itself)] x 100

[0111] [Table 1]

[0112] As is clear from the table above, the paperboard having a paper layer containing metal-containing cellulose fibers in the surface layer exhibited high deodorizing properties. Furthermore, the deodorizing properties increased as the amount of metal-containing cellulose fibers in the surface layer of the paperboard increased.

Claims

1. A deodorizing paperboard having a plurality of paper layers, at least one of the surface layers of the paperboard contains 2.0% or more of cellulose fibers containing at least one metal ion and / or metal particle selected from the group consisting of Cu, Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, and Zn, and has an odor absorption rate of 7.5% or more after 1 hour of use.

2. 2. The deodorizing paperboard according to claim 1, wherein the cellulose fibers are contained in the deodorizing paperboard in an amount of 0.3 to 2.0%.

3. The deodorizing paperboard according to claim 1 or 2, wherein the cellulose fibers contain Cu and / or Ag.

4. The deodorizing paperboard according to claim 1 or 2, wherein the cellulose fibers contain Cu.

5. 3. The deodorizing paperboard according to claim 1 or 2, wherein the paperboard has a paper layer that does not contain cellulose fibers containing metal ions and / or metal particles.

6. A paper container using the deodorizing paperboard according to claim 1 or 2, characterized in that the odor leakage rate calculated by [odor index outside the paper container / odor index inside the paper container] is 85% or less one hour after the start of use.

7. 3. Paper furniture using the deodorizing paperboard according to claim 1 or 2.

8. 3. Paper bedding using the deodorizing paperboard according to claim 1 or 2.

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