Antibacterial material, antibacterial material dispersion, antibacterial material dispersion, and methods for producing the same

Abstract

To provide an antibacterial material that is a stable inorganic matter, and a method for producing the same.SOLUTION: Provided is an antibacterial material containing composite tungsten oxide microparticles characterized by being represented by the general formula MxWyOz.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antibacterial material, an antibacterial material dispersion, an antibacterial material dispersion used for disinfecting various industrial products, household products, etc., and methods for producing the same. [Background technology]

[0002] Cationic disinfectants, biguanide disinfectants, halogenated diphenyl ethers, and similar compounds are widely known as substances with antibacterial effects. Patent Document 1 proposes that one or more mixtures selected from cetylpyridinium hydrochloride, chlorhexidine, triclosan, and Irgasan are preferred as disinfectants.

[0003] On the other hand, heavy metal ions such as zinc, silver, and copper are widely known as substances with antibacterial effects. Patent Document 2 describes an antibacterial agent containing a silver chloro complex salt. Unlike thiosulfate acetate and the like, silver chloro complex salts have the following properties: 2- It has been proposed that since it does not contain ions, it is stable and does not decompose when exposed to heat or acid to generate toxic gases or turn black due to the formation of silver sulfide. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-236914 [Patent Document 2] Japanese Patent Application Publication No. 10-182326 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the inventors' investigation revealed that the descriptions in Patent Documents 1 and 2 have the following problems.

[0006] The disinfectant described in Patent Document 1 is an organic substance. As a result, it is not sufficiently stable under environmental conditions, and it is thought that its applications and methods of use are limited.

[0007] The antibacterial agent containing a silver-chloro complex salt described in Patent Document 2 is more stable than thiosulfate acetate and the like. However, if the silver-chloro complex salt is exposed to the atmosphere for a long period of time, it is thought that it may react with H2S gas, SO2 gas, and the like contained in the atmosphere, and may not be able to exhibit a high antibacterial effect. Furthermore, the reaction with H2S gas, SO2 gas, and the like in the atmosphere may cause the antibacterial agent to turn black.

[0008] The present invention has been made under the above circumstances, and the problem to be solved by the present invention is to provide an antibacterial material, an antibacterial material dispersion, an antibacterial material dispersion that maintain their antibacterial effect and do not discolor even when exposed to the atmosphere for a long period of time, and methods for producing the same. [Means for solving the problem]

[0009] In order to solve the above-mentioned problems, the present inventors conducted research and discovered that inorganic composite tungsten oxide microparticles have antibacterial effects. Furthermore, they discovered that the composite tungsten oxide microparticles maintain their antibacterial effect even when exposed to the atmosphere for a long period of time, are inorganic, do not discolor, and do not discolor even when exposed to H2S gas or SO2 gas in the atmosphere, leading to the completion of the present invention.

[0010] That is, the first invention for solving the above-mentioned problems is: The antibacterial material contains composite tungsten oxide microparticles characterized by being expressed by the general formula MxWyOz (wherein M element is one or more elements selected from alkali metals and alkaline earth metals, W is tungsten, O is oxygen, and 0.01≦x / y≦1.0, 2.2≦z / y≦3.0). The second invention is: The antibacterial material according to the first aspect of the present invention is characterized in that the composite tungsten oxide microparticles have a hexagonal crystal structure. The third invention is The antibacterial material according to the first or second invention is characterized in that the composite tungsten oxide microparticles have an average particle size of 10 nm or more and 200 nm or less. The fourth invention is The antibacterial material dispersion comprises the antibacterial material according to any one of the first to third aspects of the present invention and a solvent. The fifth invention is The antibacterial material dispersion comprises the antibacterial material according to any one of the first to third aspects of the present invention and a solid medium. The sixth invention is a first step of producing a composite tungsten oxide having a hexagonal crystal structure represented by the general formula MxWyOz (wherein M element is one or more elements selected from H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I; W is tungsten; O is oxygen; and 0.01≦x / y≦1.0, 2.2≦z / y≦3.0); and a second step of mechanically pulverizing the composite tungsten oxide obtained in the first step to produce composite tungsten oxide microparticles having a lattice constant in the hexagonal crystal structure of an a-axis of 7.3850 Å or more and 7.4186 Å or less and a c-axis of 7.5600 Å or more and 7.6240 Å or less, and a particle diameter of 100 nm or less. [Effects of the Invention]

[0011] The antibacterial material containing the composite tungsten oxide microparticles of the present invention maintains its antibacterial effect even when exposed to the atmosphere for a long period of time, does not discolor, and does not discolor even when exposed to H2S gas or SO2 gas in the atmosphere. [Brief explanation of the drawings]

[0012] [Figure 1]FIG. 1 is a schematic plan view of a hexagonal crystal structure. DETAILED DESCRIPTION OF THE INVENTION

[0013] The antibacterial material of the present invention contains composite tungsten oxide microparticles represented by the general formula MxWyOz (wherein M element is one or more elements selected from H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I; W is tungsten; O is oxygen; and 0.01≦x / y≦1.0, 2.2≦z / y≦3.0).

[0014] The antibacterial material according to the present invention can be in the form of an antibacterial material dispersion by dispersing the composite tungsten oxide particles in an appropriate solid medium such as an appropriate solvent or resin. The antibacterial material dispersion according to the present invention includes an antibacterial film in which the antibacterial material dispersion is formed on the surface of a substrate or an article, an antibacterial plate in which the antibacterial material dispersion is formed into a plate shape, an antibacterial film in which the antibacterial material dispersion is formed into a film shape, and further, an antibacterial molded body and an antibacterial fiber in which the antibacterial material dispersion is molded into the shape of a container or another article.

[0015] Hereinafter, embodiments of the present invention will be described in detail in the following order: 1. composite tungsten oxide microparticles, 2. method for producing composite tungsten oxide microparticles, 3. antibacterial effect of composite tungsten oxide microparticles, 4. antibacterial material dispersion, and 5. antibacterial material dispersion.

[0016] 1. Composite tungsten oxide particles The composite tungsten oxide microparticles contained in the antibacterial material according to the present invention are known as a material that transmits sunlight in the visible light region with wavelengths of 380 nm to 780 nm, and absorbs light in the near-infrared region with wavelengths of 780 nm or more. The composite tungsten oxide is expressed by the general formula MxWyOz (wherein the M element is one or more elements selected from H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I; W is tungsten; and O is oxygen), and from the viewpoint of stability, the M element is more preferably one or more elements selected from alkali metals and alkaline earth metals, and even more preferably an element belonging to the alkali metals.

[0017] In consideration of the electronic state of the composite tungsten oxide, it is preferable that 2.2≦z / y≦3.0. On the other hand, the ratio of the M element to W is preferably 0.01≦x / y≦1.0. Composite tungsten oxides also have an upper limit on the amount of additive element M added, which is determined by their structure. The maximum amount of additive element M added per mole of tungsten is 1 mole in the case of a cubic crystal and approximately 0.5 moles in the case of a tetragonal crystal (this varies depending on the type of M element, but approximately 0.5 moles is the most suitable for industrial production). The amount of additive element M added is preferably such that the value of x / y is 0.2 or more and 0.5 or less, more preferably 0.22≦x / y≦0.37. When z / y=3, the value of x / y becomes 0.33, which is considered to place the additive element M in all of the hexagonal voids, as shown in Figure 1, resulting in a hexagonal crystal. Note that Figure 1 is a schematic plan view of a hexagonal crystal structure. In FIG. 1, six octahedra formed by WO6 units, indicated by the reference symbol 11, are assembled to form a hexagonal void (tunnel), and an element M, indicated by the reference symbol 12, is placed in the void to form one unit, and many of these units are assembled to form a hexagonal crystal structure.

[0018] Furthermore, when cations of an M element are added to the hexagonal voids, the hexagonal crystal is generally formed when an M element with a large ionic radius is added. Specifically, the hexagonal crystal is easily formed when one or more elements selected from Cs, Rb, K, Ba, Li, Ca, and Sr are added, which is preferable. Furthermore, among these M elements having a large ionic radius, composite tungsten oxide fine particles doped with one or more elements selected from Cs and Rb are preferred because they are chemically stable.

[0019] Composite tungsten oxide microparticles can efficiently absorb infrared rays and improve their antibacterial effect by adopting a tetragonal, cubic, or hexagonal tungsten bronze structure. The absorption position in the near-infrared region tends to change depending on the crystal structure of the composite tungsten oxide microparticles. The absorption position in the near-infrared region tends to shift toward longer wavelengths in the tetragonal crystal compared to the cubic crystal, and further shift toward longer wavelengths in the hexagonal crystal compared to the tetragonal crystal. Furthermore, accompanying this shift in absorption position, absorption in the visible light region is lowest in the hexagonal crystal, followed by the tetragonal crystal, with the cubic crystal having the greatest absorption. Therefore, hexagonal tungsten bronze is preferred from the perspective of improving antibacterial effect while maintaining designability by transmitting more light in the visible light region and absorbing more light in the infrared region.

[0020] Similarly, from the viewpoint of improving antibacterial effect while maintaining designability, it is preferable that the average particle diameter of the composite tungsten oxide microparticles be 800 nm or less. The particle diameter of the composite tungsten oxide microparticles can be determined by measuring the particle diameters of 100 composite tungsten oxide ultrafine particles from a transmission electron microscope image using an image processing device and calculating the average value.

[0021] The composite tungsten oxide microparticles contained in the antibacterial material according to the present invention are preferably single crystals with an amorphous phase volume ratio of 50% or less. When the composite tungsten oxide microparticles are single crystals with an amorphous phase volume ratio of 50% or less, the crystallite diameter can be set to 200 nm or less while maintaining the lattice constant within a predetermined range. By setting the crystallite diameter of the composite tungsten oxide microparticles to 200 nm or less, the dispersed particle diameter can be set to 1 nm or more and 200 nm or less. That is, in the case of ultrafine composite tungsten particles, if the particle diameter is 1 nm or more and 200 nm or less, the volume ratio of the amorphous phase is 50% or less, or the particles are not polycrystalline, the lattice constant can be maintained within a predetermined range, and antibacterial properties can be fully exhibited. The crystallite diameter of the composite tungsten oxide microparticles is more preferably 10 nm or more and 200 nm or less, and even more preferably 100 nm or less and 10 nm or more, because excellent antibacterial properties are exhibited when the crystallite diameter is in the range of 100 nm or less and 10 nm or more.

[0022] The lattice constant of the composite tungsten oxide microparticles in the composite tungsten oxide microparticle dispersion after crushing, pulverization or dispersion described below is maintained in the composite tungsten oxide microparticles obtained by removing volatile components from the composite tungsten oxide microparticle dispersion according to the present invention, and in the lattice constant and crystallite diameter of the composite tungsten oxide microparticles contained in a dispersion obtained from the dispersion. As a result, the effects of the present invention can be achieved as long as the crystalline state, such as the lattice constant and crystallite size, of the composite tungsten oxide microparticles in the composite tungsten oxide microparticle dispersion or the dispersion of composite tungsten ultrafine particles obtained from the dispersion is the crystalline state of the composite tungsten oxide microparticles that can be used in the present invention.

[0023] The fact that composite tungsten oxide microparticles are single crystals can be confirmed by observing, in electron microscope images such as a transmission electron microscope, no crystal grain boundaries within each microparticle, and only uniform lattice fringes. Similarly, the fact that the volume ratio of the amorphous phase in the composite tungsten oxide microparticles is 50% or less can be confirmed by observing, in transmission electron microscope images, uniform lattice fringes throughout the particle, with almost no unclear lattice fringes. Since the amorphous phase is often present on the periphery of the particles, it is often possible to calculate the volume ratio of the amorphous phase by focusing on the periphery of the particles. For example, in spherical composite tungsten oxide microparticles, if an amorphous phase with unclear lattice fringes exists in a layered form on the periphery of the particles, and the thickness is 20% or less of the particle diameter, the volume ratio of the amorphous phase in the composite tungsten oxide microparticles is 50% or less. On the other hand, when composite tungsten oxide microparticles are dispersed in a matrix of a solid medium such as a resin that constitutes an antibacterial material dispersion, if the difference between the average particle size of the dispersed composite tungsten oxide microparticles and the crystallite size is 20% or less, the composite tungsten oxide microparticles can be said to be single crystals with an amorphous phase volume ratio of 50% or less. Furthermore, it is preferable that the lattice constant of the a-axis is 7.3850 Å or more and 7.4186 Å or less, and the c-axis is 7.5600 Å or more and 7.6240 Å or less.

[0024] In the case of Rb tungsten oxide fine particles in which Rb is selected as the M element, the lattice constant of the a-axis is preferably 7.3850 Å or more and 7.3950 Å or less, and the c-axis is preferably 7.5600 Å or more and 7.5700 Å or less. In the case of CsRb tungsten oxide fine particles in which Cs and Rb are selected as the M element, the lattice constants thereof are preferably such that the a-axis is 7.3850 Å or more and 7.4186 Å or less, and the c-axis is 7.5600 Å or more and 7.6240 Å or less. However, the M element is not limited to the above Cs or Rb. The M element may be an element other than Cs or Rb as long as it is present as an added M element in the hexagonal voids formed by the WO6 units.

[0025] The crystal structure of the composite tungsten oxide microparticles can be identified by the X-ray diffraction pattern, and the lattice constant and crystallite size can be calculated using the Rietveld method.

[0026] 2. Manufacturing method of composite tungsten oxide microparticles The method for producing composite tungsten oxide microparticles according to the present invention will be described in the following order: (1) solid-phase reaction method, (2) plasma synthesis method, and (3) microparticulation of composite tungsten oxide.

[0027] (1) Solid-state reaction method The composite tungsten oxide particles according to the present invention, represented by the general formula MxWyOz, can be produced by a solid-state reaction method in which a tungsten compound, which is the starting material for the tungsten oxide microparticles, is heat-treated in a reducing gas atmosphere, or in a mixed gas atmosphere of a reducing gas and an inert gas, or in an inert gas atmosphere. The composite tungsten oxide microparticles obtained by the heat treatment and then pulverizing to a predetermined particle size by a pulverization process or the like have favorable properties as an antibacterial material, as will be described later.

[0028] The starting material for obtaining the composite tungsten oxide particles of the present invention represented by the general formula MxWyOz can be one or more powders selected from tungsten trioxide powder, tungsten dioxide powder, tungsten oxide hydrate, tungsten hexachloride powder, ammonium tungstate powder, tungsten oxide hydrate powder obtained by dissolving tungsten hexachloride in alcohol and then drying, tungsten oxide hydrate powder obtained by dissolving tungsten hexachloride in alcohol and then adding water to precipitate and then drying, tungsten compound powder obtained by drying an aqueous solution of ammonium tungstate, and metallic tungsten powder, and a powder of a simple substance or compound containing the M element can be mixed in a ratio of 0.01≦x / y≦1.0.

[0029] Furthermore, when the tungsten compound that is the starting material for obtaining the composite tungsten oxide particles is in the form of a solution or dispersion, the elements can be easily mixed uniformly. From this viewpoint, it is more preferable that the starting material for the composite tungsten oxide microparticles is a powder obtained by mixing an alcohol solution of tungsten hexachloride or an aqueous solution of ammonium tungstate with a solution of the compound containing the M element, and then drying the mixture. From a similar viewpoint, it is also preferable that the starting material for the composite tungsten oxide microparticles is a powder obtained by mixing a dispersion obtained by dissolving tungsten hexachloride in alcohol, adding water to form a precipitate, with a powder of a simple substance or compound containing the M element, or a solution of a compound containing the M element, and then drying the resulting mixture.

[0030] Examples of compounds containing the element M include, but are not limited to, tungstates, chlorides, nitrates, sulfates, oxalates, oxides, carbonates, and hydroxides of the element M, as long as they are in a solution state. Furthermore, when the composite tungsten oxide microparticles are produced industrially, using a tungsten oxide hydrate powder or tungsten trioxide and a carbonate or hydroxide of the element M is a preferred production method, since no harmful gases are generated during the heat treatment stage or the like.

[0031] Here, the conditions for heat treatment of the composite tungsten oxide particles in a reducing atmosphere or in a mixed gas atmosphere of a reducing gas and an inert gas will be described. First, the starting material is heat-treated in a reducing gas atmosphere or a mixed gas atmosphere of a reducing gas and an inert gas. The heat treatment temperature is preferably higher than the temperature at which the composite tungsten oxide particles crystallize. Specifically, the heat treatment temperature is preferably 500°C or higher and 1000°C or lower, and more preferably 500°C or higher and 800°C or lower. If desired, the material may be further heat-treated in an inert gas atmosphere at a temperature of 500°C or higher and 1200°C or lower.

[0032] The reducing gas is not particularly limited, but H2 is preferred. When H2 is used as the reducing gas, its concentration can be appropriately selected depending on the firing temperature and the amount of the starting materials, and is not particularly limited. For example, it is 20 vol% or less, preferably 10 vol% or less, and more preferably 7 vol% or less. This is because a reducing gas concentration of 20 vol% or less can avoid the generation of WO2, which does not have antibacterial activity, due to rapid reduction. By this heat treatment, the z / y ratio in the composite tungsten oxide is 2.2≦z / y≦3.0.

[0033] (2) Plasma synthesis The composite tungsten oxide particles of the present invention, represented by the general formula MxWyOz, can also be produced by a thermal plasma method by setting appropriate production conditions.The production conditions that should be set appropriately include, for example, the feed rate when feeding raw materials into the thermal plasma, the flow rate of the carrier gas used for feeding raw materials, the flow rate of the plasma gas that maintains the plasma region, and the flow rate of the sheath gas that flows just outside the plasma region.

[0034] The steps up to the heat treatment for obtaining composite tungsten oxide particles, as explained above in "(1) Solid-state reaction method" and "(2) Plasma synthesis method", constitute the first step according to the present invention.

[0035] (3) Microparticulation of composite tungsten oxide The composite tungsten oxide bulk or particles can be made into fine particles by preparing a composite tungsten oxide fine particle dispersion liquid, which will be described later. Specifically, the composite tungsten oxide bulk or particles are mixed with an appropriate solvent, and then loaded into a bead mill, paint shaker, or the like, and subjected to pulverization and mixing, thereby obtaining a composite tungsten oxide fine particle dispersion liquid pulverized to a desired particle size. However, in this microparticulation, the pulverization conditions (microparticulation conditions) are determined so that the desired crystallite size and the desired a-axis length and c-axis length of the lattice constant can be imparted to the resulting composite tungsten oxide. To obtain composite tungsten oxide microparticles from the composite tungsten oxide microparticle dispersion, the solvent may be removed by a known method.

[0036] Furthermore, the composite tungsten oxide bulk or particles can be atomized by dry atomization using a jet mill or the like. However, even in the case of dry microparticulation, it is of course necessary to determine the pulverization conditions (microparticulation conditions) that can give the desired particle size, crystallite size, and lattice constant a-axis length and c-axis length to the obtained composite tungsten oxide. For example, if a jet mill is used, it is sufficient to select a jet mill that provides the appropriate pulverization conditions, such as air volume and processing time.

[0037] The second step according to the present invention is the step of microparticulating the composite tungsten oxide or composite tungsten oxide particles, as explained above in "(3) Microparticulating the composite tungsten oxide."

[0038] 3. Antibacterial effect of composite tungsten oxide particles The composite tungsten oxide microparticles according to the present invention transmit sunlight in the visible light region with wavelengths of 380 nm to 780 nm, and absorb light in the near-infrared region with wavelengths of 780 nm or more. This absorption of light in the near-infrared region is due to plasmon absorption and polaron absorption of the composite tungsten oxide microparticles, and this absorption is caused by the electronic state of the composite tungsten oxide molecules that make up the microparticles. It is presumed that this electronic state is related to the antibacterial and disinfecting effects.

[0039] Since the composite tungsten oxide microparticles are microparticles, they exhibit plasmon absorption and polaron absorption, and therefore have an average particle size of 800 nm or less, preferably 200 nm or less, more preferably 10 nm or more to 200 nm or less, and even more preferably 10 nm or more to 100 nm or less.

[0040] The antibacterial effect of the composite tungsten oxide microparticles according to the present invention was evaluated by carrying out a preservative effectiveness test in accordance with the method prescribed in the Japanese Pharmacopoeia, in which the test target bacterial species was forcibly inoculated and mixed into a composite tungsten oxide microparticle dispersion, and the growth and decline of the test bacteria over time was investigated. In this test, Escherichia coli ATCC8739 (E. coli), Pseudomonas aeruginosa ATCC9027 (Pseudomonas aeruginosa), Staphylococcus aureus ATCC6538 (Staphylococcus aureus), Candida albicans ATCC102313 (Candida), and Aspergillus brasiliensis ATCC16404 (A. koji mold) were used as test strains to evaluate the change in bacterial count and assess the antibacterial effect. Furthermore, the effectiveness of the antibacterial material dispersion according to the present invention can also be confirmed in accordance with JIS L 1902-2015 (Test methods for antibacterial properties and antibacterial effect of textile products) and JIS Z 2801 (Antibacterial processed products - Test methods for antibacterial properties and antibacterial effect).

[0041] 4. Antibacterial material dispersion liquid The antibacterial material dispersion of the present invention is prepared by mixing and dispersing the composite tungsten oxide microparticles of the present invention in an appropriate solvent to form a composite tungsten oxide microparticle dispersion. The solvent is not particularly limited and may be selected appropriately depending on the intended use. For example, various organic solvents can be used, including water; alcohols such as ethanol, propanol, butanol, isopropyl alcohol, isobutyl alcohol, and diacetone alcohol; ethers such as methyl ether, ethyl ether, and propyl ether; esters; ketones such as acetone, methyl ethyl ketone, diethyl ketone, cyclohexanone, and isobutyl ketone; and aromatic hydrocarbons such as toluene.

[0042] If necessary, the pH of the dispersion may be adjusted by adding an acid or alkali to the dispersion. Furthermore, a resin monomer or oligomer may be used as the solvent for the dispersion. On the other hand, in order to further improve the dispersion stability of the fine particles in the dispersion liquid, it is of course possible to add various dispersants, surfactants, coupling agents, etc.

[0043] Suitable commercially available dispersants include Solsperse (registered trademark) 9000, 12000, 17000, 20000, 21000, 24000, 26000, 27000, 28000, 32000, 35100, 54000, and 250 (manufactured by Lubrizol Japan Co., Ltd.), and EFKA (registered trademark). 4008, 4009, 4010, 4015, 4046, 4047, 4060, 4080, 7462, 4020, 4050, 4055, 4400, 4401, 4402, 4403, 4300, 4320, 4330, 4340, 6220, 6225, 6700, 6780, 6782, 8503 (manufactured by Efka Additives), Ajisper (registered trademark) PA111, PB821, PB822, PN411, Famex L-12 (manufactured by Mai-no-moto Fine Techno Co., Ltd.), DisperBYK (registered trademark) 101, 102, 106, 108, 111, 116, 130, 140, 142, 145, 161, 162, 163, 164, 166, 167, 168, 170, 171, 174, 180, 182, 192, 193, 2000, 2001, 2020, 2025, 2050, 2070, 2155, 2164, 220S, 300, 306, 320, 322, 325, 330, 340, 350, 377, 378, 380N, 410, 425, 430 (manufactured by Pick Chemie Japan Co., Ltd.), Dispalyn (registered trademark) Examples of the acrylic acid ester include one or more selected from 1751N, 1831, 1850, 1860, 1934, DA-400N, DA-703-50, DA-725, DA-705, DA-7301, DN-900, NS-5210, NVI-8514L (manufactured by Kusumoto Chemicals Co., Ltd.), Alphon (registered trademark) UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toagosei Co., Ltd.), and the like.

[0044] When water is used as the solvent, it is preferable to add a water-soluble dispersant having an amino group. For example, commercially available dispersants such as Disperbyk 183, Disperbyk 185, Disperbyk 184, Disperbyk 190, Disperbyk 191, and Disperbyk 2010 (manufactured by BYK-Chemie) can be preferably used. Furthermore, amino acids such as serine and phenylalanine may be added as dispersants. Another preferred dispersant is a water-soluble dispersant containing an oxoacid. A preferred example of the oxoacid is a carboxyl group. Examples of commercially available dispersants include Solsperse 41090, Solsperse 43000, Solsperse 44000, Solsperse 46000, Solsperse 47000, and Solsperse 53095 (manufactured by Lubrizol Corporation).

[0045] Furthermore, if the antibacterial material dispersion contains 80 parts by weight or more of solvent per 100 parts by weight of composite tungsten oxide microparticles, the storage stability of the dispersion can be easily ensured, and workability can also be ensured when subsequently producing the antibacterial material dispersion.

[0046] The method of dispersing composite tungsten oxide microparticles in a solvent is a method of uniformly dispersing the microparticles in a dispersion liquid, and the composite tungsten oxide microparticles have a crystal structure in which the a-axis is 7.3850 Å or more and 7.4186 Å or less, and the c-axis is 7.5600 Å or more and 7.6240 Å or less, preferably the a-axis is 7.4031 Å or more and 7.4186 Å or less, and the c-axis is 7.5830 Å or more and 7.6240 Å or less, more preferably the a-axis is 7.4031 Å or more and 7.4111 Å or less, and the c-axis is 7.5891 Å or more and 7.5950 Å or less, while the particle diameter of the composite tungsten oxide microparticles can be adjusted to 800 nm or less, and is not particularly limited. For example, a bead mill, a ball mill, a sand mill, a paint shaker, an ultrasonic homogenizer, etc. can be mentioned.

[0047] The degree of microparticulation of the composite tungsten oxide particles and the variation of the a-axis length and c-axis length, which are the lattice constants in the hexagonal crystal structure, vary depending on the equipment constants of the pulverizer. Therefore, it is important to carry out trial pulverization in advance to determine the pulverizer and pulverization conditions that can impart the desired particle size, crystallite size, and lattice constant a-axis length and c-axis length to the composite tungsten oxide microparticles.

[0048] Even in the case where composite tungsten oxide particles are microparticulated via a composite tungsten oxide particle dispersion and then the solvent is removed to obtain composite tungsten oxide microparticles, it is of course necessary to determine grinding conditions (microparticulation conditions) that can impart particle diameter, crystallite diameter, and a-axis length and c-axis length of the lattice constant. The step of obtaining the composite tungsten oxide microparticle dispersion liquid is the second step according to the present invention.

[0049] The state of the composite tungsten oxide particle dispersion liquid according to the present invention can be confirmed by measuring the dispersion state of the composite tungsten oxide microparticles when the tungsten oxide microparticles are dispersed in a solvent. For example, the composite tungsten oxide microparticles according to the present invention can be confirmed by sampling a sample from a liquid in which the particles and particle aggregates exist in a solvent, and measuring the sample using various commercially available particle size distribution meters. As the particle size distribution meter, for example, a known measuring device such as the ELS-8000 manufactured by Otsuka Electronics Co., Ltd., which is based on the principle of dynamic light scattering, can be used.

[0050] The crystal structure and lattice constant of the composite tungsten oxide microparticles are measured by identifying the crystal structure contained in the composite tungsten oxide microparticles obtained by removing the solvent from the composite tungsten oxide microparticle dispersion using X-ray diffraction, and calculating the a-axis length and c-axis length as lattice constants using the Rietveld method.

[0051] The dispersed particle diameter of the composite tungsten oxide microparticles is preferably 800 nm or less, which is sufficiently fine, and the composite tungsten oxide microparticles are preferably uniformly dispersed. This is because, when the dispersed particle diameter of the composite tungsten oxide microparticles is 800 nm or less, preferably 200 nm or less, more preferably 10 nm or more and 200 nm or less, and even more preferably 10 nm or more and 100 nm or less, the composite tungsten oxide microparticles necessary for exhibiting antibacterial and disinfecting effects are ensured.

[0052] The dispersed particle size in the present invention refers to the particle size of individual composite tungsten oxide microparticles dispersed in the composite tungsten oxide microparticle dispersion liquid, which is an antibacterial material dispersion liquid, or the particle size of aggregated particles formed by aggregation of the composite tungsten oxide microparticles. The dispersed particle size can be measured using various commercially available particle size distribution analyzers. For example, a sample of the antibacterial material dispersion liquid can be collected and measured using a particle size analyzer based on dynamic light scattering (ELS-8000 manufactured by Otsuka Electronics Co., Ltd.). The average particle size of the composite tungsten oxide microparticles in the antibacterial material dispersion can be measured and calculated from a transmission electron microscope image after removing the solvent. The dispersed particle size of the composite tungsten oxide microparticles is 800 nm or less, preferably 200 nm or less, more preferably 10 nm or more and 200 nm or less, and even more preferably 10 nm or more and 100 nm or less. The resulting composite tungsten oxide microparticle dispersion functions as the antibacterial material dispersion according to the present invention.

[0053] 5. Antibacterial material dispersion The antibacterial material dispersion according to the present invention is a dispersion of the composite tungsten oxide microparticles according to the present invention in a medium such as a resin. In the antibacterial material dispersion, the composite tungsten oxide microparticles according to the present invention are maintained in a dispersed state in the medium after being mechanically pulverized under predetermined conditions. The surfaces of the composite tungsten oxide microparticles according to the present invention are exposed on the surface of the antibacterial material dispersion according to the present invention, thereby exhibiting antibacterial activity.

[0054] Examples of antibacterial material dispersions include antibacterial films formed on the surface of a substrate or an article, antibacterial plates formed from the antibacterial material dispersion in the form of a plate, antibacterial films formed from the antibacterial material dispersion in the form of a film, and antibacterial molded articles formed from the antibacterial material dispersion in the shape of a container or other article. Examples also include antibacterial fibers formed from the antibacterial material dispersion in the form of fibers, and antibacterial yarns and antibacterial fabrics obtained from the antibacterial fibers. The antibacterial material dispersion according to the present invention will be described below in the order of (1) a method for producing the antibacterial material dispersion, and (2) an antibacterial film formed by forming the antibacterial material dispersion on the surface of a substrate or an article.

[0055] (1) Method for producing antibacterial material dispersion The antibacterial material of the present invention can be dispersed in a medium by penetrating it from the surface of the medium, or by melting a medium such as a polycarbonate resin by raising the temperature thereof above its melting point and then mixing the antibacterial material of the present invention with the medium to obtain an antibacterial material dispersion of the present invention. The antibacterial material dispersion thus obtained can be formed into a film or plate (board) by a predetermined method to obtain an antibacterial plate.

[0056] For example, a method for dispersing the antibacterial material of the present invention in PET resin involves first mixing the PET resin with the antibacterial material dispersion of the present invention after mechanical pulverization under specified conditions, evaporating the dispersion solvent, heating the mixture to approximately 300°C, the melting temperature of the PET resin, to melt and mix the PET resin, and then stretching the mixture into a film, thereby making it possible to produce an antibacterial film in which the antibacterial material of the present invention is dispersed.

[0057] In addition, the antibacterial material of the present invention can be mixed with resin pellets, the dispersion solvent can be evaporated, the mixture can be heated to the melting temperature of the resin, the resin can be melted and mixed with the antibacterial material, and the mixture can be injection molded to obtain an antibacterial molded body in the shape of a container or other object.

[0058] In addition, the resin that will become the synthetic fiber can be mixed with the antibacterial material of the present invention, molded into a fiber form to make an antibacterial synthetic fiber, and antibacterial yarn (textile product) can be obtained from the antibacterial synthetic fiber, which can then be processed into antibacterial fabric (textile product).

[0059] Applicable synthetic fibers are not particularly limited, but examples thereof include aliphatic polyamide fibers (nylon, nylon 6, nylon 66, nylon 11, nylon 610, nylon 612, etc.), polyester fibers (polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, etc.), acrylic fibers (polyacrylonitrile, acrylonitrile-vinyl chloride copolymer, modacrylic, etc.), polyurethane fibers, aromatic polyamide fibers (aromatic nylon, aramid, etc.), polyvinyl alcohol fibers (vinylon, etc.), polyvinylidene chloride fibers (vinylidene, etc.), polyvinyl chloride fibers (polyvinyl chloride, etc.), polyolefin fibers (polyethylene, polypropylene, polystyrene, etc.), polychlor fibers, and polylactic acid fibers.

[0060] The thickness of the antibacterial synthetic fiber is preferably 1 to 50 μm, more preferably 1 to 20 μm, and even more preferably 1 to 10 μm. The thickness of the antibacterial synthetic fiber affects the flexibility of the antibacterial yarn (textile product) obtained by twisting and bundling (i.e., processing) multiple synthetic fibers, and ultimately affects the flexibility of the antibacterial fabric (textile product) obtained by weaving (i.e., processing) the antibacterial yarn. For this reason, if the thickness of the antibacterial synthetic fiber exceeds 50 μm, the resulting yarn or fabric may become stiff.

[0061] The average particle size of the composite tungsten oxide microparticles, which are the antibacterial material contained in the antibacterial material dispersion, can be calculated by measuring the antibacterial material dispersion with a transmission electron microscope, and is 800 nm or less, preferably 200 nm or less, more preferably 10 nm or more to 200 nm or less, and even more preferably 10 nm or more to 100 nm or less.

[0062] (2) Antibacterial film formed by forming an antibacterial material dispersion on the surface of a substrate or an article A liquid resin or binder is added to the antibacterial material dispersion according to the present invention to obtain a coating liquid, which is then coated onto the surface of a substrate or an article, and the resin or binder in the coating liquid is cured by a predetermined method, thereby forming an antibacterial film on the surface of the substrate or article, in which the antibacterial material according to the present invention is dispersed in the resin or binder. The method for coating the coating liquid is not particularly limited as long as the coating liquid can be uniformly coated on the surface of the substrate or article, and examples thereof include bar coating, gravure coating, spray coating, and dip coating.

[0063] The resin includes not only resin dissolved in a solvent, but also resin monomers and oligomers before curing. Resins can be selected depending on the purpose, such as UV-curable resins, thermosetting resins, electron beam-curable resins, room-temperature-curable resins, and thermoplastic resins. Specific examples include polyethylene resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyvinyl alcohol resins, polystyrene resins, polypropylene resins, ethylene-vinyl acetate copolymers, polyester resins, polyethylene terephthalate resins, fluororesins, polycarbonate resins, acrylic resins, and polyvinyl butyral resins. These resins may be used alone or in combination.

[0064] Examples of such binders include binders using metal alkoxides. Typical examples of such metal alkoxides include alkoxides of Si, Ti, Al, Zr, etc. Binders using these metal alkoxides can form oxide films by hydrolysis and condensation polymerization through heating or other methods.

[0065] The substrate may be a plate-shaped substrate or a film-shaped substrate. Examples of the article include furniture, tools, and other fixtures used in daily life, vehicles, and other mobile machines, as well as electrical and electronic devices such as home appliances, personal computers, and mobile phones.

[0066] Here, if a colorless and transparent resin or binder that transmits visible light is used, the composite tungsten oxide microparticles transmit visible light, so an antibacterial material dispersion that is colorless and transparent to visible light can be obtained. When the colorless and transparent antibacterial material dispersion is formed on the surface of an article, it does not impair the color tone of the article, does not discolor, and does not discolor even when exposed to H2S gas or SO2 gas in the atmosphere, resulting in excellent design properties. [Example]

[0067] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Furthermore, to measure the crystal structure, lattice constant, and crystallite size of the composite tungsten oxide microparticles according to the present invention, composite tungsten oxide microparticles obtained by removing the solvent from the antibacterial material dispersion were used. The X-ray diffraction pattern of the composite tungsten oxide microparticles was measured by powder X-ray diffraction (θ-2θ method) using a powder X-ray diffractometer (X'Pert-PRO / MPD manufactured by PANalytical, Spectris Co., Ltd.). The crystal structure contained in the microparticles was identified from the obtained X-ray diffraction pattern, and the lattice constant and crystallite size were calculated using the Rietveld method.

[0068] Example 1 A solution was obtained by dissolving 7.43 kg of cesium carbonate (CsCO) in 6.70 kg of water. This solution was added to 34.57 kg of tungstic acid (HWO) and thoroughly mixed, then dried with stirring (equivalent to a molar ratio of W to Cs of 1:0.33). The dried product was heated while supplying 5% by volume of H gas with N gas as a carrier, and calcined at 800°C for 5.5 hours. The supply gas was then switched to N gas only, and the temperature was lowered to room temperature to obtain Cs tungsten oxide particles (A1).

[0069] 20% by mass of the Cs tungsten oxide particles (A1), 10% by mass of a cationic surfactant (hereinafter referred to as "additive a"), and 70% by mass of water were weighed out, loaded into a paint shaker (manufactured by Asada Iron Works) containing 0.3 mm diameter ZrO beads, and crushed and dispersed for 20 hours to prepare an antibacterial material dispersion liquid (liquid A) according to Example 1.

[0070] Here, the dispersed particle diameter of the pulverized Cs tungsten oxide microparticles (A2) in the antibacterial material dispersion liquid (Liquid A) was measured using a particle size measuring device (ELS-8000 manufactured by Otsuka Electronics Co., Ltd.) based on dynamic light scattering and was found to be 80 nm. Furthermore, after removing the solvent from the antibacterial material dispersion liquid (Liquid A), the crystal structure of the Cs tungsten oxide microparticles (A2) was confirmed to be hexagonal, and the lattice constants were measured, revealing that the a-axis was 7.4073 Å and the c-axis was 7.6185 Å. The crystallite diameter was 30 nm. The Cs tungsten oxide fine particles (A2) were observed under a transmission electron microscope and the calculated average particle size was 35 nm.

[0071] A preservative effectiveness test was conducted on the antibacterial material dispersion (liquid A) in accordance with the preservative effectiveness test method stipulated in the Japanese Pharmacopoeia. The antibacterial effect was judged by the reduction in bacteria immediately after inoculation and after 28 days of storage at 25°C. After 28 days of storage, bacteria were killed with a ◎, no change in the number of bacteria with a 〇, and an increase in the number of bacteria with an ×. The results are shown in Table 1. The number of bacteria was confirmed on an agar medium.

[0072] Example 2 An antibacterial material dispersion liquid (Liquid B) according to Example 2 was obtained in the same manner as in Example 1, except that 20 mass% of Cs tungsten oxide particles (A1), 10 mass% of anionic surfactant (hereinafter referred to as "additive b"), and 70 mass% of water were weighed. The dispersed particle diameter of the pulverized composite tungsten oxide microparticles (B2) in the antibacterial material dispersion liquid (Liquid B) was 75 nm. After removing the solvent from the antibacterial material dispersion liquid (Liquid B), the crystal structure of the Cs tungsten oxide microparticles (B2) was confirmed to be hexagonal. The lattice constants were measured, and the a-axis was 7.4072 Å and the c-axis was 7.6186 Å. The crystallite diameter was 29 nm. The Cs tungsten oxide microparticles (B2) were observed with a transmission electron microscope and calculated to have an average particle diameter of 35 nm. Next, a preservative effectiveness test was carried out using the antibacterial material dispersion liquid (liquid B) according to Example 2 in the same manner as in Example 1. The results are shown in Table 1.

[0073] Example 3 An antibacterial material dispersion liquid (Liquid C) according to Example 3 was obtained in the same manner as in Example 1, except that 20 mass% of Cs tungsten oxide particles (A1), 10 mass% of a nonionic surfactant (hereinafter referred to as "additive c"), and 70 mass% of water were weighed. The dispersed particle diameter of the pulverized composite tungsten oxide microparticles (C2) in the antibacterial material dispersion liquid (Liquid C) was 80 nm. After removing the solvent from the antibacterial material dispersion liquid (Liquid C), the crystal structure of the Cs tungsten oxide microparticles (C2) was confirmed to be hexagonal. The lattice constants were measured, and the a-axis was 7.4071 Å and the c-axis was 7.6184 Å. The crystallite diameter was 35 nm. The Cs tungsten oxide microparticles (C2) were observed with a transmission electron microscope and calculated to have an average particle diameter of 42 nm. Next, a preservative effectiveness test was carried out using the antibacterial material dispersion liquid (liquid C) according to Example 3 in the same manner as in Example 1. The results are shown in Table 1.

[0074] Example 4 An antibacterial material dispersion liquid (Liquid D) according to Example 4 was obtained in the same manner as in Example 1, except that 20% by mass of the Cs tungsten oxide particles (A1), 10% by mass of a polymer dispersant (amine value 50 mgKOH / g) containing an amine as a functional group (hereinafter referred to as "additive d"), and 70% by mass of water were weighed. The dispersed particle diameter of the pulverized composite tungsten oxide microparticles (D2) in the antibacterial material dispersion liquid (Liquid D) was 85 nm. After removing the solvent from the antibacterial material dispersion liquid (Liquid D), the crystal structure of the Cs tungsten oxide microparticles (D2) was confirmed to be hexagonal. The lattice constants were measured, revealing an a-axis of 7.4074 Å and a c-axis of 7.6179 Å. The crystallite diameter was 35 nm. The Cs tungsten oxide microparticles (D2) were observed with a transmission electron microscope and calculated to have an average particle diameter of 40 nm. Next, a preservative effectiveness test was carried out using the antibacterial material dispersion liquid (liquid D) according to Example 4 in the same manner as in Example 1. The results are shown in Table 1.

[0075] (Comparative Example 1) A mixed solution (solution E) according to Comparative Example 1 was obtained by weighing and mixing 10 mass % of additive a and 90 mass % of water without adding the Cs tungsten oxide particles (A1). Next, a preservative effectiveness test was carried out using the mixed solution (solution E) according to Comparative Example 1 in the same manner as in Example 1. The results are shown in Table 1.

[0076] (Comparative Example 2) A mixed solution (solution F) according to Comparative Example 2 was obtained by weighing and mixing 10 mass % of additive b and 90 mass % of water without adding the Cs tungsten oxide particles (A1). Next, a preservative effectiveness test was carried out using the mixed solution (solution F) according to Comparative Example 2 in the same manner as in Example 1. The results are shown in Table 1.

[0077] (Comparative Example 3) A mixed solution (solution G) according to Comparative Example 3 was obtained by weighing and mixing 10 mass % of additive c and 90 mass % of water without adding the Cs tungsten oxide particles (A1). Next, a preservative effectiveness test was carried out using the mixed solution (solution G) according to Comparative Example 3 in the same manner as in Example 1. The results are shown in Table 1.

[0078] Comparative Example 4 A mixed solution (solution H) according to Comparative Example 4 was obtained by weighing and mixing 10 mass % of additive d and 90 mass % of water without adding the Cs tungsten oxide particles (A1). Next, a preservative effectiveness test was carried out using the mixed solution (solution H) according to Comparative Example 4 in the same manner as in Example 1. The results are shown in Table 1.

[0079] (Comparative Example 5) A preservative effectiveness test was carried out in the same manner as in Example 1, except that pure water was used instead of the antibacterial material dispersion liquid (liquid A). The results are shown in Table 1.

[0080] (summary) As is clear from Table 1, it was found that the antibacterial material dispersions of Examples 1 to 4, in which the antibacterial material of the present invention was dispersed, were able to kill or inhibit the growth of fungi. In contrast, the mixed solutions of Comparative Examples 1 to 4, in which the antibacterial material of the present invention was not dispersed, and the pure water of Comparative Example 5, allowed the growth of fungi. From the above, it has been found that the antibacterial material and the antibacterial material dispersion according to the present invention have an antibacterial effect.

[0081] [Table 1] [Industrial Applicability]

[0082] The composite tungsten oxide according to the present invention can be effectively imparted with antibacterial effects by, for example, applying it to a solid surface or mixing it with other powders or liquids.

Claims

1. An antibacterial material containing composite tungsten oxide microparticles characterized by having a hexagonal crystal structure and represented by the general formula MxWyOz (wherein M element is one or more elements selected from alkali metals, W is tungsten, O is oxygen, and 0.01≦x / y≦1.0, 2.2≦z / y≦3.0).

2. 2. The antibacterial material according to claim 1, wherein the composite tungsten oxide microparticles have a crystalline structure in which the a-axis is 7.3850 Å or more and 7.4186 Å or less and the c-axis is 7.5600 Å or more and 7.6240 Å or less in lattice constant.

3. 3. The antibacterial material according to claim 1, wherein the composite tungsten oxide microparticles have an average particle size of 10 nm or more and 200 nm or less.

4. An antibacterial material dispersion comprising the antibacterial material according to any one of claims 1 to 3 and a solvent.

5. An antibacterial material dispersion comprising the antibacterial material according to any one of claims 1 to 3 and a solid medium.

6. a first step of producing a composite tungsten oxide having a hexagonal crystal structure represented by the general formula MxWyOz (wherein M element is one or more elements selected from alkali metals, W is tungsten, O is oxygen, and 0.01≦x / y≦1.0, 2.2≦z / y≦3.0); and a second step of mechanically pulverizing the composite tungsten oxide obtained in the first step to produce composite tungsten oxide microparticles having a lattice constant in the hexagonal crystal structure of an a-axis of 7.3850 Å or more and 7.4186 Å or less, a c-axis of 7.5600 Å or more and 7.6240 Å or less, and a particle diameter of 100 nm or less.

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