JP2017141531A - Functional sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a functional sheet having excellent deodorant and antibacterial properties and also excellent mechanical properties such as tensile strength.SOLUTION: A functional sheet comprises a cellulose fiber. At least part of the cellulose fiber has, on its surface, a carboxyl group or a carboxylate group. The cellulose fiber comprises at least one metal ion or metal nanoparticle selected from the element group of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn and Cu.SELECTED DRAWING: None

Description

  The present invention relates to a functional sheet. More specifically, the present invention relates to a functional sheet having a deodorizing function and an antibacterial function.

Functional sheets obtained by adding a functionality-imparting agent to a sheet-like base material are used in various industrial fields. Examples of functions generally include deodorization, antibacterial, heat resistance, moisture resistance, weather resistance, solvent resistance, abrasion resistance, electromagnetic wave blocking, etc. Examples of applications include packaging materials (paper containers, cardboard, resin films) Etc.), building materials (wallpaper, decorative paper, laying paper, etc.), daily necessities (deodorizing materials, aromatic materials), industrial products (filters, wipers, etc.), medical products (masks, etc.), clothing, other paper products (calendars, etc.) Etc. In particular, deodorant and antibacterial functions are often required in many industrial fields.

  As performance required for the functional sheet, in addition to the above functions, the mechanical properties of the sheet include tensile strength, tear strength, burst strength, and if necessary, air permeability and printability.

  Various methods have been proposed for imparting a deodorant / antibacterial function to a sheet-like substrate. For example, in Patent Document 1, an aqueous solution of either a silicon compound or an aluminum compound, which is a constituent component of zeolite, is impregnated into a hydrophilic polymer substrate such as cellulose fiber, and a basic substance and the other aqueous solution are mixed. Further, an inorganic porous crystal-hydrophilic polymer composite in which zeolite is further impregnated and zeolite is supported inside the cellulose fiber has been proposed, and by further supporting the metal on the zeolite, antibacterial effect and deodorizing effect are proposed. Is disclosed.

  Patent Document 2 discloses a method for producing an antibacterial cellulose fiber containing one or more silver antibacterial agents selected from silver zeolite, silver zirconium phosphate, silver calcium phosphate and silver soluble glass. Has been.

  Moreover, in patent document 3, it is a paper base material containing oxidized pulp, Comprising: The quantity of the carboxyl group of this oxidized pulp is 1.0 mmol / g-2.0 mmol / g with respect to the absolute dry weight of oxidized pulp. There is disclosed a method for producing a paper base material for a functional sheet having deodorizing properties, which is characterized in that it exists.

JP 11-315492 A Japanese Patent Laid-Open No. 11-107033 WO2014 / 097929 A1 publication

However, the method described in Patent Document 1 or 2 is a method in which cellulose and an inorganic substance containing a metal component are mixed, and the cellulose and the metal component are not firmly bonded as in, for example, ionic bonding. Therefore, when a substrate such as paper is produced using this, the deodorizing and antibacterial effects are not sufficient. In addition, since inorganic materials containing metal components do not form a physical or chemical network like fibers, when manufacturing a substrate using this, the yield is poor and the mechanical properties of the substrate such as tensile strength are also low. There was a problem that may decrease.
Moreover, although the method described in Patent Document 3 has a deodorizing effect, it is not sufficient, and further improvement has been desired.
Therefore, an object of the present invention is to provide a functional sheet that has good deodorant properties and antibacterial properties and good mechanical properties such as tensile strength.

The present invention provides the following.
[1] A functional sheet containing cellulose fiber, wherein at least a part of the cellulose fiber contains a carboxyl group or a carboxylate group on the surface, and the cellulose fiber is Ag, Au, Pt, Pd, Ni A functional sheet containing one or more metal ions or metal nanoparticles selected from the group consisting of elements of Mn, Fe, Ti, Al, Zn and Cu.
[2] The cellulose fiber according to claim 1, wherein the cellulose fiber containing a carboxyl group or a carboxylate group on the surface is an oxidized cellulose fiber in which a part of the hydroxyl group at the C6 position in the glucose unit of cellulose is oxidized to a carboxyl group. The functional sheet according to claim 1, wherein the functional sheet is provided.
[3] The functional sheet according to claim 1 or 2, wherein the metal ion or metal nanoparticle according to claim 1 or 2 contains either Ag or Cu.

  According to the present invention, it is possible to provide a functional sheet that has good deodorizing properties and antibacterial properties and good mechanical properties such as tensile strength.

In the present invention, the functional sheet refers to a sheet having a single layer or multilayer structure having at least one function. Examples of functions generally include deodorization, antibacterial, heat resistance, moisture resistance, weather resistance, solvent resistance, abrasion resistance, electromagnetic wave shielding, etc., but the functional sheet of the present invention is particularly deodorant / It has an antibacterial function. The application is not particularly limited, and can be used for any application that requires a deodorant / antibacterial function. Examples include packaging materials (paper containers, cardboard, resin films, etc.), building materials (wallpaper, decorative paper, laying paper, etc.), household items (deodorizing materials, aromatic materials), industrial products (filters, wipers, etc.), medical products ( Mask, etc.), clothing, and other paper products (calendar etc.).
The functional sheet of the present invention is a single-layer or multilayer-structured sheet containing at least one layer containing cellulose fibers, and the cellulose fibers in at least one of the layers containing cellulose fibers are on the surface. One or more kinds of metal ions or metal containing a carboxyl group or a carboxylate group, and the cellulose fiber is selected from the element group of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn and Cu It is characterized by containing nanoparticles. Hereinafter, these will be described in detail.

<1. Cellulose fiber>
There is no limitation in particular in the kind of cellulose fiber in this invention, Arbitrary kinds can be used as needed. Moreover, you may mix and use 2 or more types of cellulose fibers in arbitrary ratios among them. Examples include plant-derived raw materials (eg, wood, bamboo, hemp, jute, kenaf, farmland waste, cloth, pulp (conifer unbleached kraft pulp (NUKP), conifer bleach kraft pulp (NBKP), hardwood unbleached kraft) Pulp (LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (eg, squirts) ) -Derived raw materials, algae-derived raw materials, microorganisms (for example, acetic acid bacteria (Acetobacter))-derived raw materials, microbial products, etc. Among them, plants or microorganism-derived cellulose fibers are preferable, and plant-derived cellulose Fiber is particularly preferred.

  The number average fiber diameter and the number average fiber length of the cellulose raw material used in the present invention are not particularly limited, and those having any number average fiber diameter and number average fiber length can be used as necessary. Further, two or more types of cellulose fibers having different number average fiber diameters and number average fiber lengths may be mixed and used at an arbitrary ratio. As an example, in the case of softwood kraft pulp (NBKP), which is one of the common pulps, in the case of hardwood bleached kraft pulp (LBKP), the number average fiber diameter is about 30-60 μm, the number average fiber length is about 3-5 mm. The number average fiber diameter is about 10 to 30 μm and the number average fiber length is about 1 to 2 mm.

<1-1. Modification of cellulose fiber>
Cellulose fibers have three hydroxyl groups per glucose unit and can be subjected to various chemical modification treatments. In this invention, in order to introduce | transduce a metal ion or a metal nanoparticle into at least one part of a cellulose fiber in the process mentioned later, the modification | denaturation which introduce | transduces a carboxyl group or a carboxylate group with respect to at least one part of a cellulose fiber is performed.

  Here, the carboxyl group refers to a group represented by —COOH, and the carboxylate group refers to a group represented by —COO—. The counter ion of the carboxylate group is not particularly limited. As will be described later, when metal nanoparticles are formed through ionic bonds with carboxylate groups, these metal ions serve as a counter. The carboxyl group or carboxylate group is also referred to as an “acid group”.

The content of acid groups can be measured by the method disclosed in paragraph 0021 of JP2008-001728A. That is, using a precisely weighed dry cellulose sample, 60 mL of a 0.5 to 1 mass% slurry is prepared, and the pH is adjusted to about 2.5 with a 0.1 mol / L hydrochloric acid aqueous solution. Then, 0.05 mol / L sodium hydroxide aqueous solution is dripped and electrical conductivity measurement is performed. The measurement is continued until the pH is about 11. From the amount (V) of sodium hydroxide consumed until the neutralization step of the weak acid, where the change in electrical conductivity shows a gradual change, the acid group amount X1 is determined using the following equation.

X1 (mmol / g) = V (mL) × 0.05 / mass of cellulose fiber (g)
The amount of acid groups of the cellulose fiber is preferably 0.2 to 2.2 mmol / g. When the amount of acid groups is less than 0.2 mmol / g, the amount of metal particles present on the surface of the cellulose fiber is not sufficient in the step of supporting metal ions or metal nanoparticles on the cellulose fiber, which will be described later. May have inferior antibacterial function. On the other hand, when the amount of acid groups exceeds 2.2 mmol / g, the metal particles may aggregate and may have poor deodorization and antibacterial functions as well.

  The modification method for introducing a carboxyl group or a carboxylate group is not particularly limited as long as the modified cellulose fiber contains a carboxyl group or a carboxylate group. Examples include oxidation (carboxylation) and etherification. , Phosphorylation, esterification, silane coupling, fluorination, and cationization. Of these, oxidation (carboxylation) and etherification are preferable. Hereinafter, these will be described in detail.

<1-1-1. Oxidation>
In the present invention, the method for oxidizing the cellulose fiber is not particularly limited, and a known method can be used. As an example, there may be mentioned a method of oxidizing a cellulose raw material in water using an oxidizing agent in the presence of a substance selected from the group consisting of an N-oxyl compound and bromide, iodide or a mixture thereof. According to this method, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized to produce a group selected from the group consisting of an aldehyde group, a carboxyl group, and a carboxylate group. Although the density | concentration of the cellulose raw material at the time of reaction is not specifically limited, 5 weight% or less is preferable.

  The N-oxyl compound refers to a compound that can generate a nitroxy radical. Examples of the nitroxyl radical include 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO). As the N-oxyl compound, any compound can be used as long as it promotes the target oxidation reaction.

  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, 0.01 mmol or more is preferable and 0.02 mmol or more is more preferable with respect to 1 g of absolutely dry cellulose. The upper limit is preferably 10 mmol or less, more preferably 1 mmol or less, and still more preferably 0.5 mmol or less. Accordingly, the amount of N-oxyl compound used is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and still more preferably 0.02 to 0.5 mmol with respect to 1 g of absolutely dry cellulose.

  The bromide is a compound containing bromine, and examples thereof include alkali metal bromide that can be dissociated and ionized in water, such as sodium bromide. Further, the iodide is a compound containing iodine, and examples thereof include alkali metal iodide. What is necessary is just to select the usage-amount of a bromide or iodide in the range which can accelerate | stimulate an oxidation reaction. The total amount of bromide and iodide is preferably 0.1 mmol or more, more preferably 0.5 mmol or more, with respect to 1 g of absolutely dry cellulose. The upper limit is preferably 100 mmol or less, more preferably 10 mmol or less, and still 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 still more preferably 0.5 to 5 mmol with respect to 1 g of absolutely dry cellulose.

  The oxidizing agent is not particularly limited, and examples thereof include halogen, hypohalous acid, halous acid, perhalogen acid, salts thereof, halogen oxide, and peroxide. Among them, hypohalous acid or a salt thereof is preferable because it is inexpensive and has a low environmental burden, hypochlorous acid or a salt thereof is more preferable, and sodium hypochlorite is still more preferable. The amount of the oxidizing agent used is preferably 0.5 mmol or more, more preferably 1 mmol or more, and still more preferably 3 mmol or more with respect to 1 g of absolutely 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. Therefore, the amount of the oxidizing agent used is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, further preferably 1 to 25 mmol, and most preferably 3 to 10 mmol with respect to 1 g of absolutely dry cellulose. When the N-oxyl compound is used, the amount of the oxidizing agent used is preferably 1 mol or more with respect to 1 mol of the N-oxyl compound. The upper limit is preferably 40 mol. Therefore, the amount of the oxidizing agent used is preferably 1 to 40 mol with respect to 1 mol of the N-oxyl compound.

  Conditions such as pH and temperature during the oxidation reaction are not particularly limited, and in general, 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, and more preferably 30 ° C. or lower. Accordingly, the temperature is preferably 4 to 40 ° C, and may be about 15 to 30 ° C, that is, room temperature. The pH of the reaction solution is preferably 8 or more, and more preferably 10 or more. The upper limit is preferably 12 or less, and more preferably 11 or less. Therefore, the pH of the reaction solution is preferably about 8 to 12, more preferably about 10 to 11. Usually, a carboxyl group is generated in cellulose as the oxidation reaction proceeds, and therefore the pH of the reaction solution tends to decrease. Therefore, in order to advance the oxidation reaction efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution in the above range. The reaction medium for the oxidation is preferably water for reasons such as ease of handling and the difficulty of side reactions.

  The reaction time in the oxidation can be appropriately set according to the progress of the oxidation, and is usually 0.5 hours or longer. The upper limit is usually 6 hours or less, preferably 4 hours or less. Therefore, the reaction time in oxidation is usually 0.5 to 6 hours, for example, about 0.5 to 4 hours.

  Oxidation may be carried out in two or more stages. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first stage reaction again under the same or different reaction conditions, the efficiency is not affected by the reaction inhibition by the salt generated as a by-product in the first stage reaction. Can be oxidized well.

  Another example of the carboxylation (oxidation) method is a method of oxidizing by ozone treatment. By this oxidation reaction, at least the 2- and 6-position hydroxyl groups of the glucopyranose ring constituting cellulose are oxidized, and the cellulose chain is decomposed. The ozone treatment is usually performed by bringing a gas containing ozone and a cellulose raw material into contact with each other. The ozone concentration in the gas is preferably 50 g / m 3 or more. The upper limit is preferably 250 g / m 3 or less, and more preferably 220 g / m 3 or less. Therefore, the ozone concentration in the gas is preferably 50 to 250 g / m 3, and more preferably 50 to 220 g / m 3. The amount of ozone added is preferably 0.1 parts by weight or more and more preferably 5% by weight or more with respect to 100% by weight of the solid content of the cellulose raw material. The upper limit is usually 30% by weight or less. Therefore, the amount of ozone added is preferably 0.1 to 30% by weight and more preferably 5 to 30% by weight with respect to 100% by weight of the solid content of the cellulose raw material. The ozone treatment temperature is usually 0 ° C. or higher, 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. The ozone treatment time is usually 1 minute or longer, preferably 30 minutes or longer. The upper limit is usually 360 minutes or less. Therefore, the ozone treatment time is usually about 1 to 360 minutes, and preferably about 30 to 360 minutes. When the condition of the ozone treatment is within the above range, it is possible to prevent the cellulose from being excessively oxidized and decomposed, and the yield of oxidized cellulose is improved.

  Further, the resulting product obtained after the ozone treatment may be further oxidized using an oxidizing agent. The oxidizing agent used for the additional oxidation treatment is not particularly limited, and examples thereof include chlorine compounds such as chlorine dioxide and sodium chlorite; oxygen, hydrogen peroxide, persulfuric acid, peracetic acid and the like. Examples of the oxidation treatment method include a method in which these oxidizing agents are dissolved in a polar organic solvent such as water or alcohol to prepare an oxidizing agent solution, and the cellulose raw material is immersed in the oxidizing agent solution.

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

<1-1-2. Etherification>
For the etherification, any method may be used as long as it contains a carboxyl group or a carboxylate group in the functional group after the reaction for the purpose of introducing metal ions into the cellulose fiber in the subsequent step, and a known method should be used. Can do. Examples include carboxymethyl (ether), carboxyethyl (ether), carboxypropyl (ether), carboxybutyl (ether) and other carboxyalkyl etherification, and carboxyphenyl (ether). . As an example, a carboxymethylation method will be described below.

  The method of carboxymethylation is not specifically limited, A well-known method can be used. For example, a cellulose raw material as a bottoming raw material is mercerized and then etherified. A common solvent is used in the carboxymethylation reaction. Examples of the solvent include water, alcohol (for example, lower alcohol), and a mixed solvent thereof. Examples of the lower alcohol include methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, and tertiary butanol. The mixing ratio of the lower alcohol in the mixed solvent is usually 60% by weight or more and 95% by weight or less, and preferably 60 to 95% by weight. The amount of the solvent is usually 3 times the weight of the cellulose raw material. Although an upper limit is not specifically limited, It is 20 weight times. Therefore, the amount of the solvent is preferably 3 to 20 times by weight.

  Mercerization is usually performed by mixing a bottoming raw material and a mercerizing agent. Examples of mercerizing agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The amount of the mercerizing agent used is preferably 0.5 times mol or more, more preferably 1.0 mol or more, and further preferably 1.5 times mol or more per anhydroglucose residue of the starting material. The upper limit is usually 20 moles or less, preferably 10 moles or less, more preferably 5 moles or less, and more preferably 0.5 to 20 moles, more preferably 1.0 to 10 moles. More preferably 5 to 5 moles.

  The mercerization reaction temperature 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 less, preferably 7 hours or less. Therefore, it is usually 15 minutes to 8 hours, preferably 30 minutes to 7 hours.

  The etherification reaction is usually performed by adding a carboxymethylating agent to the reaction system after mercerization. Examples of the carboxymethylating agent include sodium monochloroacetate. The addition amount of the carboxymethylating agent is usually preferably 0.05 times mol or more, more preferably 0.5 times mol or more, and further preferably 0.8 times mol or more per glucose residue of the cellulose raw material. The upper limit is usually 10.0 times mole or less, preferably 5 moles or less, more preferably 3 times mole or less, and therefore preferably 0.05 to 10.0 times mole, more preferably 0.5 to 5, more preferably 0.8 to 3 times mol. The reaction temperature is usually 30 ° C. or higher, preferably 40 ° C. or higher, and the upper limit is usually 90 ° C. or lower, preferably 80 ° C. or lower. Accordingly, 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 less, preferably 4 hours or less. Therefore, the reaction time is usually 30 minutes to 10 hours, preferably 1 hour to 4 hours. The reaction solution may be stirred as necessary during the carboxymethylation reaction.

  When the cellulose raw material is modified by carboxymethylation, the degree of carboxymethyl substitution per anhydroglucose unit in the obtained carboxymethylated cellulose fiber is preferably 0.01 or more, more preferably 0.05 or more, and 0.10 or more. More preferably. The upper limit is preferably 0.50 or less, more preferably 0.40 or less, and still more preferably 0.35 or less. Accordingly, the degree of carboxymethyl group substitution is preferably 0.01 to 0.50, more preferably 0.05 to 0.40, and still more preferably 0.10 to 0.30.

The degree of carboxymethyl substitution per glucose unit of the carboxymethylated cellulose fiber can be measured, for example, by the following method. That is, 1) About 2.0 g of carboxymethylated cellulose (absolutely dry) is precisely weighed and put into a 300 mL conical stoppered Erlenmeyer flask. 2) 100 mL of nitric acid methanol solution obtained by adding 100 mL of special grade concentrated nitric acid to 1000 mL of methanol is added and shaken for 3 hours to convert the carboxymethyl cellulose salt (carboxymethylated cellulose) into hydrogen-type carboxymethylated cellulose. 3) 1.5-2.0 g of hydrogen-type carboxymethylated cellulose (absolutely dry) is precisely weighed and placed in a 300 mL Erlenmeyer flask with a stopper. 4) Wet the hydrogen-type carboxymethylated cellulose with 15 mL of 80% methanol, add 100 mL of 0.1N NaOH, and shake at room temperature for 3 hours. 5) Back titrate excess NaOH with 0.1 N H2SO4 using phenolphthalein as indicator. 6) The degree of carboxymethyl substitution (DS) is calculated by the following formula:
A = [(100 × F ′ − (0.1 N H 2 SO 4) (mL) × F) × 0.1] / (absolute dry mass of hydrogenated carboxymethylated cellulose (g))
DS = 0.162 × A / (1-0.058 × A)
A: 1N NaOH amount (mL) required for neutralizing 1 g of hydrogen-type carboxymethylated cellulose
F ′: 0.1N NaOH factor F: 0.1N H 2 SO 4 factor

<1-2. Loading of metal ions on cellulose fiber>
In the present invention, one or more metals selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn and Cu are further added to the cellulose fiber containing a carboxyl group or a carboxylate group. By containing metal ions containing elemental ions, a high deodorizing effect is exhibited. In particular, by using one or more ions selected from the group of Ag and Cu, an antibacterial function is further imparted in addition to the deodorizing effect. In the present invention, the metal ions having the deodorizing ability are supported on the fiber, but the fiber form is maintained, so that there is no detachment when the paper is used, and the performance and strength are not lowered.

  Regarding the contact method of the cellulose fiber and the metal compound, a cellulose fiber dispersion prepared in advance and a metal compound aqueous solution may be mixed, and a dispersion containing the cellulose fiber is applied onto a substrate to form a film. The film may be impregnated with a metal compound aqueous solution dropwise. At this time, the film may remain fixed on the substrate or may be peeled from the substrate. Although the detailed mechanism is unknown, by these methods, metal ions derived from the metal compound form or coordinate with carboxylate groups to add metal ions to the cellulose fiber. It is guessed.

  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.

  Although the density | concentration of metal compound aqueous solution is not specifically limited, It is preferable that it is the range of 10-80 mass% with respect to 100 mass parts of cellulose fibers, and it is more preferable that it is the range of 30-60 weight%.

  You may adjust suitably the time which a metal compound is made to contact. Although the temperature at the time of making it contact is not specifically limited, It is preferable that it is the range of 2-50 degreeC. Further, the pH of the liquid at the time of contacting is not particularly limited. However, when the pH is low, it is difficult for the metal ions to bind to the carboxyl group, and therefore it is preferably in the range of 7 to 13, and in the range of pH 8 to 12. It is particularly preferred.

The fact that the oxidized cellulose fiber contains metal ions can be confirmed by a scanning electron microscope image and ICP emission analysis of the extract with a strong acid. That is, the presence of metal ions cannot be confirmed in the scanning electron microscope image, while it can be confirmed that the metal ions are contained in the ICP emission analysis. On the other hand, for example, when the metal is reduced from ions and exists as metal particles, the metal particles can be confirmed by a scanning electron microscope image, so the presence or absence of metal ions can be determined. The presence or absence of metal ions can also be determined by scanning electron microscope images and element mapping. That is, metal ions cannot be confirmed in a scanning electron microscope image, but the presence of metal ions can be confirmed by elemental mapping.
In the present invention, the effect is exhibited by introducing metal ions into the cellulose fiber as described above. If necessary, the metal compound bonded to the obtained metal ion-containing cellulose fiber is reduced to reduce the cellulose fiber. Metal nanoparticles may be partially formed on the surface.

  Although this mechanism is not clear, it is guessed as follows. The metal compound or the ion derived from the metal compound that has been bonded to the acid group by the reduction reaction is reduced to a metal. At this time, the produced metal is supported on the surface of the oxidized cellulose fiber. Similarly, the generated neighboring metals are integrated with each other, so that the particles grow to form nanoparticles. On the other hand, a metal compound or the like that exists in the vicinity of the cellulose fiber but does not bind to the acid group is also reduced to generate a metal. This metal quickly integrates with the metal on the surface of the cellulose fiber to form metal nanoparticles.

  The reduction reaction may be performed by a known method, but it is preferable to perform the reduction reaction so as not to cleave the bond between the metal compound and the acid group while reducing the metal compound. Examples of such a reduction method include a gas phase reduction method using hydrogen and a liquid phase reduction method using a reducing agent such as an aqueous sodium borohydride solution. Conditions such as time and temperature in the gas phase reduction are appropriately adjusted. For example, the reaction may be performed at 50 to 60 ° C. for about 1 to 3 hours. The gas phase reduction reaction is preferably performed in a state where the oxidized cellulose fiber does not contain water or a 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 can be obtained from the above dispersion and subjected to a reduction reaction with or without drying. Further, the dispersion can be subjected to a liquid phase reduction reaction without drying. The reaction temperature in the liquid phase reduction is preferably 4 to 40 ° C., more preferably room temperature.

  The metal nanoparticles are supported on the surface of the cellulose fiber by using an acid group present on the surface of the cellulose fiber as a contact. That is, the metal nanoparticles are fixed to the surface of the cellulose fiber via acid groups present on the surface of the cellulose fiber. The chemical bond for immobilization is preferably a coordination bond, a hydrogen bond, or an ionic bond. The bonding state can be analyzed by X-ray photoelectron spectroscopy or infrared spectroscopy.

The average particle diameter of the metal nanoparticles is determined from a transmission electron microscope image or X-ray diffraction. In the present invention, the average particle diameter of the metal nanoparticles is preferably in the range of 1 to 50 nm when determined from a transmission electron microscope image. Specifically, the average particle diameter is obtained by preparing a transmission electron microscope image of cellulose fibers, obtaining the equivalent-circle diameter of primary particles of a plurality of metal nanoparticles from the image, and averaging these values.
In the step of supporting the metal ions or metal nanoparticles, the content of the metal ions with respect to the cellulose fiber is preferably in the range of 10 to 60 mg / g. If it is less than 10 mg / g, the deodorizing and antibacterial functions may be inferior. On the other hand, when the amount of acid groups exceeds 2.2 mmol / g, the metal particles may aggregate and may have poor deodorization and antibacterial functions as well.

<1-3. Beating>
The metal-supporting cellulose fiber in the present invention may be subjected to a beating treatment at least once before the modification treatment and after the metal support treatment. Here, the beating process is a process for applying a mechanical shearing force to the fiber. By the beating treatment, part of the cellulose fiber is fibrillated and the surface area is increased. In general, the fiber-to-fiber bond can be strengthened during drying. In the present invention, the deodorizing effect and the antibacterial effect are further improved. Can be increased. In particular, the deodorizing effect in a wet state is improved. On the other hand, if the beating process is excessively performed and the cellulose fibers are excessively refined, the yield decreases when blended with pulp to make paper, and does not remain in the paper (there is no residue), metal ions or metal nanoparticles. Since the deodorizing and antibacterial effects of the contained cellulose fiber are lowered, it is not preferable. The freeness (CSF) can be used as an index of the beating degree. Specifically, if the freeness (CSF) is less than 30 ml, the deodorization / antibacterial effect is reduced due to the decrease in yield on the sheet, and if the freeness (CSF) exceeds 600 ml, the fibrillation is insufficient. Deodorant and antibacterial effects are reduced. As described above, by setting the freeness (CSF) of the cellulose fibers containing metal ions or metal nanoparticles to 30 to 600 ml, the deodorizing effect and the antibacterial effect are improved, and in particular, the deodorizing effect in a wet state is improved. To do.

  The apparatus used for beating is not specifically limited, A well-known apparatus can be used arbitrarily. Examples of beating devices include refiners, beaters, PFI mills, kneaders, dispersers, etc., which operate metal or blade and pulp fibers around the rotation axis, those caused by friction between pulp fibers, high pressure homogenizers, and ultra high pressure homogenizers , Nanomizers, various mills, stone mills and the like.

  Further, preliminary processing may be performed as necessary prior to beating or, if necessary, distributed processing performed before beating. Examples of the pretreatment include mixing, stirring, emulsification, and dispersion, and a known apparatus (eg, high-speed shear mixer) may be used.

<2. Production of sheet>
The functional sheet in the present invention is a sheet having a single layer structure or a multilayer structure having at least one layer containing the metal ions or cellulose fibers supporting metal nanoparticles. In the case of the multilayer structure, it is preferable that the outermost layer contains the metal ions or the metal nanoparticle-supporting cellulose fibers because the deodorizing and antibacterial effects are more easily exhibited.

The raw material other than the metal ion or metal nanoparticle-supporting cellulose fiber is not particularly limited, and a known raw material can be used. Examples include normal cellulose fibers, synthetic fibers, resins, inorganic substances, etc. that do not carry metal ions or metal nanoparticles. When using these, it is preferable that content of a metal ion and a metal nanoparticle with respect to 1g of layers containing a metal ion or a metal nanoparticle carrying | support cellulose fiber is 0.5 mg / g or more. If it is less than 0.5 mg / g, the deodorizing and antibacterial functions may be inferior.
It does not specifically limit as a manufacturing method of a sheet | seat, A well-known method can be used. For example, a so-called wet method in which water in which a raw material is dispersed is discharged and dehydrated by pressure or heat may be used, or a so-called dry method in which the raw material is discharged in a dry state and similarly formed into a sheet by pressure or heat may be used. . Since the metal ion or metal nanoparticle-supporting cellulose fiber is hydrophilic, it is preferably wet.

The basis weight of the layer containing the metal ions or the metal nanoparticle-supporting cellulose fibers is not particularly limited, and a general range can be set as necessary. Here, the general basis weight is about 10 to 400 g / m2. In the case of a multilayer structure, the basis weight of other layers is not particularly limited as well. The basis weight of the entire functional sheet is not particularly limited, but is preferably in the range of 10 to 1000 g / m2. If it is greater than 1000 g / m 2, the sheet is likely to be inferior in its ease of bending and cutting.
When the functional sheet has a multilayer structure, after each layer is manufactured one layer at a time, they may be laminated by a known method, or a multilayer is formed at a time while simultaneously discharging the raw materials of each layer. A multilayer type may be used. The method for adhering the layers is not particularly limited, and a known method can be used. For example, a method using an adhesive, a method of passing layers between hot rolls, or a method of fusing layers by applying hot air can be used.
When the functional sheet has a multilayer structure, the outermost layer may be laminated one or more layers, and has an adhesive layer for adhering to another base material, such as a so-called adhesive label sheet. It may be. Further, a single layer sheet may be simply laminated, and one or more layers may have a three-dimensional structure like a cardboard.

  The functional sheet of the present invention may be printed on the outermost layer as necessary. In that case, the outermost layer to be printed is preferably a coating layer made of a pigment and an adhesive because printing reproducibility is improved.

  Hereinafter, although an example is given and the present invention is explained still in detail, the present invention is not limited to these.

<Example 1>
[Manufacture of oxidized cellulose fiber]
Bleached unbeaten kraft pulp derived from conifers (whiteness 85%), 5.00 g (absolutely dry), 39 mg of TEMPO (Sigma Aldrich) and 0.05 mmol of sodium bromide (absolutely dry) The solution was added to 500 ml of an aqueous solution in which 1.0 mmol) was dissolved in 1 g of cellulose, and stirred until the pulp was uniformly dispersed.
An aqueous sodium hypochlorite solution was added to the reaction system so that sodium hypochlorite was 5.5 mmol / g, and the oxidation reaction was started at room temperature. During the reaction, the pH in the system was lowered, but a 3M sodium hydroxide aqueous solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system no longer changed.
After the reaction mixture was filtered through a glass filter, washing with a sufficient amount of water and filtration were repeated twice to obtain oxidized cellulose fibers impregnated with water having a solid content of 10% by mass. The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.68 mmol / g.

[Production of metal ion-containing cellulose fibers]
To the oxidized cellulose fiber, water is added to obtain a dispersion having a solid content concentration of 2%, pH is adjusted to 9.0, CuCl2 (manufactured by Wako Pure Chemical Industries, Ltd.) is added, and the concentration relative to 1 g of oxidized cellulose fiber is increased. Was added with stirring so as to be 1.0 mmol / g, and further stirred for 30 minutes, so that the oxidized cellulose fiber contained Cu ions. On the other hand, washing with a sufficient amount of water and filtration were repeated twice to remove unreacted metal salts and obtain water-impregnated Cu ion-containing cellulose fibers having a solid content of 30% by mass. The metal ion content relative to the cellulose fiber was 31.9 mg / g, and the freeness was 500 ml.

[Manufacture of functional sheets]
4.0 g of the metal ion-containing cellulose fiber (20% by mass with respect to the whole cellulose fiber), 16.0 g of pulp (NBKP, manufactured by Nippon Paper Industries Co., Ltd., solid content concentration 30%, freeness 600 ml) (80% by mass with respect to the whole cellulose fiber) %), Wet paper strength enhancer (product name: WS4020, manufactured by Seiko PMC Co., Ltd., active ingredient 25%) 7.0 g (0.3% by mass with respect to the whole cellulose fiber), and 1179 g of water are mixed and stirred. An aqueous dispersion having a solid content concentration of 0.5% by mass was prepared. Using this aqueous dispersion, paper was made with a round hand machine, dehydrated with a press, and further dried at 85 ° C. with a cylinder dryer (105 ° C.) to produce a sheet having a diameter of about 16 cm. . The basis weight was 100 g / m2.

  About the obtained functional sheet, tensile strength, deodorizing property, antibacterial property, and lint were evaluated by the following methods.

[Tensile strength]
The tensile strength in the MD direction and CD direction during drying of the obtained sheet was measured according to JIS P8113 “Paper and paperboard—Testing method of tensile properties”. The sample width was 25 mm. The measured value was compared with Comparative Example 1 to be described later.

[Deodorization]
A gas bag with a cock containing four 5 cm × 5 cm test pieces was filled with 1.5 L of ammonia gas with a humidity of 70% adjusted to 100 ppm with an air pump. Next, the suction tube and the rubber tube were connected to the detection tube, and the rubber tube was connected to the gas bag. And the ammonia gas concentration in the gas bag 50 minutes after filling with air was measured.

◎: Very good residual concentration is 1/5 or less of the initial value ○: Good Residual concentration exceeds 1/5 of the initial value and 1/4 or less △: Normal Residual concentration exceeds 1/4 of the initial value and 1/3 or less ×: Poor residual concentration exceeds 1/3 of initial level

[Antimicrobial]
In accordance with JIS L1902, “Antibacterial test method and antibacterial effect of textile products”, a qualitative test by the halo method was performed. Specifically, an agar medium containing Escherichia coli was prepared, a test piece of 5 cm × 5 cm was placed thereon, cultured at 37 ° C. for 17 hours, and the “growth inhibition zone” of the test bacteria formed around the sample. The presence or absence was confirmed. Evaluation was made according to the following criteria.
○: Growth inhibition zone is recognized and has antibacterial properties.
X: No growth inhibition zone was observed and no antibacterial activity was observed.

<Lint (dropping fine powder such as paper powder)>
The dust generation test of the sheet was performed according to JIS B9923 (tumbling method), and the measurement was performed with a particle counter (product name “KC-01D1” manufactured by Rion). The measurement result was compared with Comparative Example 1 to be described later. When the numerical value was smaller than Comparative Example 1, ◎, when equal, ◯, and when larger, ×. It shows that there are few fallen fine powders, such as paper powder, so that evaluation is good. If the evaluation is ◎ or ○, there is no practical problem.

<Example 2>
In the process for producing the metal ion-supported oxidized cellulose fiber of Example 1, the same solution as in Example 1 except that the aqueous solution of CuCl2 was changed to an aqueous solution of AgNO3 (concentration per gram of oxidized cellulose fiber: 1.0 mmol / g). The method was carried out. The content of Ag ions relative to the cellulose fiber was 20.0 mg / g, and the freeness was 500 ml.

<Example 3>
In the process for producing the functional sheet of Example 1, the blending ratio of the Cu ion-supported oxidized cellulose fibers to the total cellulose fibers is changed from 20% by mass to 50% by mass, and the blending ratio of the pulp to the total fibers is 80% by mass. The procedure was the same as in Example 1 except that the content was changed from% to 50% by mass.

<Comparative Example 1>
In the process of producing the functional sheet of Example 1, the same procedure as in Example 1 was carried out except that the Cu-supported oxidized cellulose fiber was replaced with the same amount of pulp (NBKP, manufactured by Nippon Paper Industries Co., Ltd., freeness 600 ml). did.

<Comparative example 2>
In the process of producing the functional sheet of Example 1, it was carried out in the same manner as in Example 1 except that the Cu ion-containing oxidized cellulose fiber was changed to the oxidized cellulose fiber (before supporting Cu ions). .

<Comparative Example 3>
In the process of producing the functional sheet of Example 1, the Cu ion-containing oxidized cellulose fiber was changed to a commercially available metal (Cu) ion-supported zeolite high-density crystallized pulp (trade name: Copper Cellgaia, manufactured by Rengo Co., Ltd.). Except for this, the same method as in Example 1 was used.

As is clear from the results in Table 1, in Examples 1 to 3 containing metal ion-containing cellulose fibers, deodorant properties, antibacterial properties, and tensile strength compared to Comparative Examples 1 to 3 not containing metal ion-containing cellulose fibers. Both are high, and the lint is also good with respect to Comparative Example 3, and it can be seen that these are compatible at a high level.

Claims (3)

  A functional sheet containing cellulose fibers, wherein at least a part of the cellulose fibers contains a carboxyl group or a carboxylate group on the surface, and the cellulose fibers are Ag, Au, Pt, Pd, Ni, Mn, A functional sheet comprising one or more metal ions or metal nanoparticles selected from the group of elements Fe, Ti, Al, Zn, and Cu.   The cellulose fiber containing a carboxyl group or a carboxylate group on the surface according to claim 1 is an oxidized cellulose fiber in which a part of the hydroxyl group at the C6 position in the glucose unit of cellulose is oxidized to a carboxyl group. The functional sheet according to claim 1, which is characterized.   The functional sheet according to claim 1 or 2, wherein the metal ions or metal nanoparticles according to claim 1 or 2 contain either Ag or Cu.