Antibacterial material, antibacterial material liquid dispersion, antibacterial material dispersion, and method for producing the same

Abstract

To provide antibacterial materials having stability as inorganic substances and methods for producing the antibacterial materials.SOLUTION: Provided is an antibacterial material containing composite tungsten oxide fine particles, represented by a 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 body, and methods for producing the same, which are used for sterilizing various industrial products, household goods, and the like.

Background Art

[0002] As substances having antibacterial effects, cationic bactericides, biguanide bactericides, halogenated diphenyl ethers or compounds similar thereto are widely known. In Patent Document 1, it is proposed that one or more mixtures selected from cetylpyridinium hydrochloride, chlorhexidine, triclosan, and Irgasan are preferable as bactericides.

[0003] On the other hand, heavy metal ions such as zinc, silver, and copper are widely known as substances having antibacterial effects. Patent Document 2 describes an antibacterial agent containing a silver chloro complex salt. And the silver chloro complex salt is proposed to be stable because it does not contain S 2- ions, does not decompose by heat or acid to generate toxic gases, and does not blacken due to the formation of silver sulfide.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, according to the study by the present inventors, it has been found that the descriptions in Patent Documents 1 and 2 have the following problems.

[0006] The bactericide described in Patent Document 1 is an organic substance. As a result, its stability in the environment is not sufficient, so its uses and methods of use were considered to be limited.

[0007] The antibacterial agent containing silver chloro complex salt described in Patent Document 2 is more stable than thiosulfuric acetate and the like. However, when the silver chloro complex salt is exposed to the atmosphere for a long period of time, it is considered to react with H2S gas, SO2 gas, etc. contained in the atmosphere, and there may be cases where it cannot exhibit a high antibacterial effect. In addition, it may turn black by reacting with H2S gas, SO2 gas, etc. in the atmosphere.

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

Means for Solving the Problems

[0009] As a result of research to solve the above problems, the present inventors have found that composite tungsten oxide fine particles, which are inorganic fine particles, have an antibacterial effect. And the composite tungsten oxide fine particles are inorganic substances that maintain the antibacterial effect even when exposed to the atmosphere for a long period of time and do not discolor, and are also not discolored by H2S gas and SO2 gas in the atmosphere, and the present invention has been completed.

[0010] That is, the first invention for solving the above problems is An antibacterial material containing composite tungsten oxide fine particles represented by the general formula MxWyOz (where 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 invention, wherein the composite tungsten oxide fine particles have a hexagonal crystal structure. The third invention is the antibacterial material according to the first or second invention, wherein the average particle diameter of the composite tungsten oxide fine particles is 10 nm or more and 200 nm or less. The fourth invention is an antibacterial material dispersion characterized by containing the antibacterial material according to any one of the first to third inventions and a solvent. The fifth invention is an antibacterial material dispersion characterized by containing the antibacterial material according to any one of the first to third inventions and a solid medium. The sixth invention is a first step of producing a composite tungsten oxide containing a hexagonal crystal structure represented by the general formula MxWyOz (wherein the M element is one or more elements selected from H, He, an alkali metal, an alkaline earth metal, a rare earth element, 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, 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 fine particles having a lattice constant in the hexagonal crystal structure of 7.3850 Å or more and 7.4186 Å or less for the a-axis and 7.5600 Å or more and 7.6240 Å or less for the c-axis and a particle diameter of 100 nm or less. The method for producing an antibacterial material is characterized by having these steps.

Advantages of the Invention

[0011] The antibacterial material containing the composite tungsten oxide fine particles according to 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 by H2S gas or SO2 gas in the atmosphere.

Brief Description of the Drawings

[0012]

Figure 1

Embodiments for Carrying Out the Invention

[0013] The antibacterial material according to the present invention contains composite tungsten oxide fine particles represented 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, 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 fine particles in an appropriate solid medium such as an appropriate solvent or resin. And the antibacterial material dispersion according to the present invention includes an antibacterial film formed by forming the antibacterial material dispersion on the surface of a substrate or an article, an antibacterial plate formed by forming the antibacterial material dispersion into a plate shape, an antibacterial film formed by forming the antibacterial material dispersion into a film shape, and further, an antibacterial molded body formed by molding the antibacterial material dispersion into the shape of a container or other articles, and antibacterial fibers.

[0015] Hereinafter, the embodiments for carrying out the present invention will be described in detail in the order of 1. Composite tungsten oxide fine particles, 2. Method for producing composite tungsten oxide fine particles, 3. Antibacterial effect of composite tungsten oxide fine particles, 4. Antibacterial material dispersion liquid, 5. Antibacterial material dispersion.

[0016] 1. Composite tungsten oxide fine particles The composite tungsten oxide fine particles contained in the antibacterial material according to the present invention are known as materials that transmit light in the visible light region with wavelengths of 380 nm to 780 nm in sunlight and absorb light in the near-infrared region with wavelengths of 780 nm or more. The composite tungsten oxide is represented by the general formula MxWyOz (where 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, I, W is tungsten, and O is oxygen). From the perspective of stability, it is more preferable that the M element is one or more elements selected from alkali metals and alkaline earth metals, and those belonging to alkali metals are even more preferable.

[0017] Considering 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. There is also an upper limit to the addition amount of the added element M derived from the structure in the composite tungstate. The maximum addition amount of the added element M with respect to 1 mol of tungsten is 1 mol in the case of cubic crystals and about 0.5 mol in the case of tetragonal crystals (although it varies depending on the type of the M element, about 0.5 mol is easy for industrial production). The addition amount of the added element M is preferably 0.2 or more and 0.5 or less in terms of the value of x / y, and more preferably 0.22 ≦ x / y ≦ 0.37. When z / y = 3, when the value of x / y becomes 0.33, as shown in FIG. 1, it is considered that the added element M is arranged in all the hexagonal voids, resulting in a hexagonal crystal. Note that FIG. 1 is a schematic plan view of the crystal structure of a hexagonal crystal. In FIG. 1, octahedrons formed by WO6 units indicated by reference numeral 11 gather in 6 to form a hexagonal void (tunnel), and the element M indicated by reference numeral 12 is arranged in the void to form one unit, and a large number of these units gather to form a hexagonal crystal structure.

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

[0019] The composite tungsten oxide fine particles efficiently absorb infrared rays by adopting the structures of tetragonal, cubic, and hexagonal tungsten bronzes, and the antibacterial effect is improved. Depending on the crystal structure adopted by the composite tungsten oxide fine particles, the absorption position in the near-infrared region tends to change. This absorption position in the near-infrared region moves to the longer wavelength side in the case of tetragonal crystals compared to cubic crystals, and further moves to the longer wavelength side in the case of hexagonal crystals compared to tetragonal crystals. Also, accompanying the variation in the absorption position, the absorption in the visible light region is the least in hexagonal crystals, followed by tetragonal crystals, and the largest in cubic crystals among these. Therefore, from the viewpoint of improving the antibacterial effect while ensuring designability by transmitting more light in the visible light region and absorbing more light in the infrared region, it is preferable to use hexagonal tungsten bronzes.

[0020] Similarly, from the viewpoint of improving the antibacterial effect while ensuring designability, the average particle size of the composite tungsten oxide fine particles is preferably 800 nm or less. The particle size of the composite tungsten oxide fine particles can be determined by measuring the particle sizes of 100 composite tungsten oxide ultrafine particles using an image processing device from a transmission electron microscope image and calculating their average value.

[0021] And in the composite tungsten oxide fine particles contained in the antibacterial material according to the present invention, it is preferable that they are single crystals with an amorphous phase volume ratio of 50% or less. When the composite tungsten oxide fine particles are single crystals with an amorphous phase volume ratio of 50% or less, the crystallite size can be reduced to 200 nm or less while maintaining the lattice constant within a predetermined range. By setting the crystallite size of the composite tungsten oxide fine particles to 200 nm or less, the dispersed particle size can be set to 1 nm or more and 200 nm or less. That is, in the case of composite tungsten ultrafine particles, when the particle size is 1 nm or more and 200 nm or less and the amorphous phase is 50% or less by volume ratio, or when it is not polycrystalline, the lattice constant can be maintained within a predetermined range, and the expression of antibacterial properties can be sufficiently exhibited. It is more preferable that the crystallite size of the composite tungsten oxide fine particles is 200 nm or less and 10 nm or more, and even more preferably 100 nm or less and 10 nm or more. This is because excellent antibacterial properties are exhibited when the crystallite size is in the range of 100 nm or less and 10 nm or more.

[0022] Incidentally, the lattice constant of the composite tungsten oxide fine particles in the composite tungsten oxide fine particle dispersion after disintegration, pulverization, or dispersion described later is the lattice constant of the composite tungsten oxide fine particles obtained by removing the volatile components in the composite tungsten oxide fine particle dispersion according to the present invention, or the lattice constant and crystallite size of the composite tungsten oxide fine particles contained in the dispersion obtained from the dispersion liquid are also maintained. As a result, as long as the crystal state such as the lattice constant and crystallite size of the composite tungsten oxide fine particles in the composite tungsten oxide fine particle dispersion or the dispersion of the composite tungsten ultrafine particles obtained from the dispersion liquid is the crystal state of the composite tungsten oxide fine particles that can be used in the present invention, the effects of the present invention are exhibited.

[0023] Whether the composite tungsten oxide fine particles are single crystals can be confirmed from the fact that in an electron microscope image such as a transmission electron microscope, no grain boundaries are observed inside each fine particle, and only uniform lattice fringes are observed. Further, the fact that the volume ratio of the amorphous phase in the composite tungsten oxide fine particles is 50% or less can be confirmed from the fact that in the same transmission electron microscope image, uniform lattice fringes are observed throughout the particles and almost no unclear lattice fringe portions are observed. Since the amorphous phase often exists in the outer peripheral portion of the particles, the volume ratio of the amorphous phase can often be calculated by paying attention to the outer peripheral portion of the particles. For example, in the case of spherical composite tungsten oxide fine particles, if an amorphous phase with unclear lattice fringes exists in a layered manner in the outer peripheral portion 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 fine particles is 50% or less. On the other hand, when the composite tungsten oxide fine particles are dispersed in the matrix of a solid medium such as a resin constituting the antibacterial material dispersion, if the difference obtained by subtracting the crystallite size from the average particle size of the dispersed composite tungsten oxide fine particles is 20% or less, it can be said that the composite tungsten oxide fine particles are single crystals with a volume ratio of the amorphous phase of 50% or less. Furthermore, it is preferable that the lattice constant is 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.

[0024] In the case of Rb tungsten oxide fine particles in which Rb is selected as the M element, it is preferable that the lattice constant is such that the a-axis is 7.3850 Å or more and 7.3950 or less, and the c-axis is 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, it is preferable that the lattice constant is 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 Cs or Rb. Even if the M element is an element other than Cs or Rb, it may exist as an added M element in the hexagonal voids formed by WO6 units.

[0025] Furthermore, the crystal structure of the composite tungsten oxide fine particles can be specified by an X-ray diffraction pattern, and the lattice constant and crystallite size can be calculated using the Rietveld method.

[0026] 2. Method for producing composite tungsten oxide fine particles The method for producing the composite tungsten oxide fine particles according to the present invention will be described in the order of (1) solid-phase reaction method, (2) plasma synthesis method, and (3) micronization of composite tungsten oxide.

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

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

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

[0030] Examples of the compound containing the M element include tungstates, chlorides, nitrates, sulfates, oxalates, oxides, carbonates, hydroxides, etc. of the M element, but are not limited thereto, as long as they can be in a solution state. Furthermore, when the composite tungsten oxide fine particles are industrially produced, using a hydrated powder of tungsten oxide or tungsten trioxide and a carbonate or hydroxide of the M element is a preferable production method because no harmful gases are generated during heat treatment or other steps.

[0031] Here, the heat treatment conditions in a reducing atmosphere or a mixed gas atmosphere of a reducing gas and an inert gas for the composite tungsten oxide particles 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. This heat treatment temperature is preferably higher than the temperature at which the composite tungsten oxide particles crystallize. Specifically, it is preferably 500°C or higher and 1000°C or lower, more preferably 500°C or higher and 800°C or lower. If desired, it 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 may be appropriately selected according to the firing temperature and the amount of starting materials, and is not particularly limited. For example, it is 20 vol% or less, preferably 10 vol% or less, more preferably 7 vol% or less. This is because if the concentration of the reducing gas is 20 vol% or less, generation of WO2 having no antibacterial action due to rapid reduction can be avoided. By the heat treatment, 2.2 ≦ z / y ≦ 3.0 is achieved in the composite tungsten oxide.

[0033] (2) Plasma synthesis method The composite tungsten oxide particles represented by the general formula MxWyOz according to the present invention can also be produced by the thermal plasma method by setting appropriate production conditions. Examples of the production conditions to be appropriately set include the supply rate when supplying raw materials into the thermal plasma, the flow rate of the carrier gas used for raw material supply, the flow rate of the plasma gas that holds the plasma region, and the flow rate of the sheath gas that flows immediately outside the plasma region.

[0034] The steps until heat treatment to obtain the composite tungsten oxide particles described in the above-mentioned "(1) Solid-phase reaction method" and "(2) Plasma synthesis method" are the first step according to the present invention.

[0035] (3) Microparticulation of composite tungsten oxide Microparticulation of the bulk or particles of the composite tungsten oxide can be carried out through the composite tungsten oxide fine particle dispersion liquid described later. Specifically, the bulk or particles of the composite tungsten oxide are mixed with an appropriate solvent, loaded into a bead mill, a paint shaker, etc., and pulverization and mixing are carried out to obtain a composite tungsten oxide fine particle dispersion liquid pulverized to a desired particle size. However, in the microparticulation, pulverization conditions (microparticulation conditions) are determined that can impart a desired crystallite size, a-axis length, and c-axis length of the lattice constant to the obtained composite tungsten oxide. To obtain the composite tungsten oxide fine particles from the composite tungsten oxide fine particle dispersion, the solvent may be removed by a known method.

[0036] Also, the micronization of the bulk or particles of the composite tungsten oxide can be achieved by dry micronization using a jet mill or the like. However, even in the case of dry micronization, it is of course necessary to determine the grinding conditions (micronization conditions) that can impart the desired particle size, crystallite size, a-axis length, and c-axis length of the lattice constant to the obtained composite tungsten oxide. For example, if a jet mill is used, a jet mill with appropriate air volume and processing time that will result in appropriate grinding conditions may be selected.

[0037] The micronization of the composite tungsten oxide or the composite tungsten oxide particles described in the above "(3) Micronization of Composite Tungsten Oxide" is the second step according to the present invention.

[0038] 3. Antibacterial Effect of Composite Tungsten Oxide Fine Particles The composite tungsten oxide fine particles according to the present invention transmit light in the visible light region with a wavelength of 380 nm to 780 nm in sunlight and absorb light in the near-infrared region with a wavelength of 780 nm or more. This absorption of light in the near-infrared region is due to the plasmon absorption or polariton absorption of the composite tungsten oxide fine particles, and the electronic state of the composite tungsten oxide molecules constituting the fine particles causes these absorptions. Such an electronic state is presumed to be related to the antibacterial and sterilizing effects.

[0039] Since the composite tungsten oxide fine particles are fine particles, they exhibit plasmon absorption and polariton absorption. Therefore, the average particle size of the composite tungsten oxide fine particles is 800 nm or less, preferably 200 nm or less, more preferably 10 nm or more and 200 nm or less, and still more preferably 10 nm or more and 100 nm or less.

[0040] The antibacterial effect of the composite tungsten oxide fine particles according to the present invention was evaluated by conducting a preservation efficacy test in accordance with the method specified in the Japanese Pharmacopoeia, forcibly inoculating and mixing the test bacterial species into the composite tungsten oxide fine particle dispersion, and tracking the growth and decline of the test bacteria over time. In this test, the changes in the number of bacteria were evaluated using Escherichia coli ATCC8739 (E. coli), Pseudomonas aeruginosa ATCC9027 (P. aeruginosa), Staphylococcus aureus ATCC6538 (S. aureus), Candida albicans ATCC102313 (C. albicans), and Aspergillus brasiliensis ATCC16404 (A. brasiliensis) as the test strains, and the antibacterial effect was evaluated. In addition, the antibacterial material dispersion according to the present invention can also confirm the effect by JIS L 1902-2015 (Test method for antibacterial properties and antibacterial effect of textile products) and JIS Z 2801 (Antibacterial processed products - Antibacterial test method - Antibacterial effect).

[0041] 4. Antibacterial material dispersion The antibacterial material dispersion according to the present invention is a composite tungsten oxide fine particle dispersion obtained by mixing and dispersing the composite tungsten oxide fine particles according to the present invention in an appropriate solvent. The solvent is not particularly limited and may be appropriately selected according to the use. For example, various organic solvents such as 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 can be used.

[0042] Also, if necessary, an acid or an alkali may be added to the dispersion to adjust the pH. Furthermore, monomers or oligomers of resins may be used as the solvent of 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] Commercially available dispersants that can be preferably used include Solsperse (registered trademark) 9000, 12000, 17000, 20000, 21000, 24000, 26000, 27000, 28000, 32000, 35100, 54000, 250 (manufactured by Nippon Lubrizol Corporation), 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, Faimex L-12 (manufactured by Ajinomoto 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 BYK-Chemie Japan Co., Ltd.), Disperpon (registered trademark) 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, Ltd.), Alphon (registered trademark) UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toagosei Co., Ltd.), etc. One or more selected therefrom may be mentioned.

[0044] When water is used as the solvent, it is preferable to add a water-soluble dispersant having an amino group. For example, as commercially available dispersants, Disperbyk183, Disperbyk185, Disperbyk184, Disperbyk190, Disperbyk191, Disperbyk2010 (manufactured by BYK Chemie) and the like can be preferably mentioned. In addition, amino acids such as serine and phenylalanine may be added as a dispersant. In addition, as a preferable dispersant, a water-soluble dispersant having an oxo acid can also be mentioned. Here, as the oxo acid, a carboxyl group can be preferably mentioned. For example, as commercially available dispersants, Solsperse 41090, Solsperse 43000, Solsperse 44000, Solsperse 46000, Solsperse 47000, Solsperse 53095 (manufactured by Lubrizol) and the like can be preferably mentioned.

[0045] In the antibacterial material dispersion, if the solvent is contained in an amount of 80 parts by weight or more with respect to 100 parts by weight of the composite tungsten oxide fine particles, it is easy to ensure the storage stability of the dispersion, and the workability in producing the subsequent antibacterial material dispersion can also be ensured.

[0046] The method for dispersing the composite tungsten oxide fine particles in the solvent is a method for uniformly dispersing the fine particles in the dispersion liquid. In the crystal structure of the composite tungsten oxide fine particles, the a-axis is in the range of 7.3850 Å or more and 7.4186 Å or less, and the c-axis is in the range of 7.5600 Å or more and 7.6240 Å or less. Preferably, the a-axis is in the range of 7.4031 Å or more and 7.4186 Å or less, and the c-axis is in the range of 7.5830 Å or more and 7.6240 Å or less. More preferably, as long as the particle size of the composite tungsten oxide fine particles can be adjusted to 800 nm or less while ensuring the range where the a-axis is in the range of 7.4031 Å or more and 7.4111 Å or less, and the c-axis is in the range of 7.5891 Å or more and 7.5950 Å or less, it is not particularly limited. For example, bead mills, ball mills, sand mills, paint shakers, ultrasonic homogenizers, etc. can be mentioned.

[0047] Furthermore, the micronization of the composite tungsten oxide particles and the fluctuations in the a-axis length and c-axis length, which are lattice constants in the hexagonal crystal structure, vary depending on the equipment constants of the grinding equipment. Therefore, it is important to perform preliminary test grinding to determine the grinding equipment and grinding conditions that can impart a predetermined particle size, crystallite size, a-axis length, and c-axis length of the lattice constant to the composite tungsten oxide fine particles.

[0048] In addition, even when micronizing the composite tungsten oxide particles through a composite tungsten oxide particle dispersion liquid and then removing the solvent to obtain the composite tungsten oxide fine particles, it is of course necessary to determine the grinding conditions (micronization conditions) that can impart the particle size, crystallite size, a-axis length, and c-axis length of the lattice constant. The step of obtaining the composite tungsten oxide fine particle 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 fine particles when the tungsten oxide fine particles are dispersed in the solvent. For example, a sample can be sampled from a liquid in which the composite tungsten oxide fine particles according to the present invention exist as particles and an aggregated state of the particles in the solvent and measured with various commercially available particle size distribution meters. As the particle size distribution meter, for example, a known measuring device such as ELS-8000 manufactured by Otsuka Electronics Co., Ltd. based on the dynamic light scattering method can be used.

[0050] In addition, for the measurement of the crystal structure and lattice constant of the composite tungsten oxide fine particles, the crystal structure contained in the fine particles is specified by X-ray diffraction for the composite tungsten oxide fine particles obtained by removing the solvent of the composite tungsten oxide fine particle dispersion liquid, and the a-axis length and c-axis length are calculated as lattice constants by using the Rietveld method.

[0051] The dispersed particle size of the composite tungsten oxide fine particles is preferably 800 nm or less and sufficiently fine. Furthermore, the composite tungsten oxide fine particles are preferably uniformly dispersed. If the dispersed particle diameter of the composite tungsten oxide fine particles 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 fine particles necessary for the expression of the antibacterial effect and the sterilization effect are ensured.

[0052] Incidentally, the dispersed particle diameter according to the present invention means the particle diameter of the single particles of the composite tungsten oxide fine particles dispersed in the composite tungsten oxide fine particle dispersion which is an antibacterial material dispersion, or the aggregated particles formed by the aggregation of the composite tungsten oxide fine particles. The dispersed particle diameter can be measured with various commercially available particle size distribution meters. For example, a sample of the antibacterial material dispersion can be collected and measured using a particle size measuring device (ELS-8000 manufactured by Otsuka Electronics Co., Ltd.) based on the dynamic light scattering method. In addition, the average particle diameter of the composite tungsten oxide fine particles in the antibacterial material dispersion can be measured and calculated from a transmission electron microscope image after removing the solvent. The dispersed particle diameter of the composite tungsten oxide fine particles 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 obtained composite tungsten oxide fine particle 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 one in which the composite tungsten oxide fine particles according to the present invention are dispersed in a medium such as a resin. In the antibacterial material dispersion, the composite tungsten oxide fine particles according to the present invention maintain a dispersed state in the medium after mechanical grinding under predetermined conditions. And on the surface of the antibacterial material dispersion according to the present invention, the surface of the composite tungsten oxide fine particles according to the present invention is exposed and exhibits an antibacterial action.

[0054] As the antibacterial material dispersion, there are included an antibacterial film formed by forming the antibacterial material dispersion on the surface of a base material, article, etc., an antibacterial plate formed by forming the antibacterial material dispersion in a plate shape, an antibacterial film formed by forming the antibacterial material dispersion in a film shape, and further an antibacterial molded article formed by molding the antibacterial material dispersion into the shape of a container or other article. Also included are antibacterial fibers obtained by processing the antibacterial material dispersion into a fibrous form, and antibacterial yarns and antibacterial fabrics obtained from the antibacterial fibers. Hereinafter, the antibacterial material dispersion according to the present invention will be described 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 base material or article.

[0055] (1) Method for producing the antibacterial material dispersion To disperse the antibacterial material according to the present invention in a medium, it may be infiltrated from the surface of the medium. However, after melting a medium such as a polycarbonate resin by raising the temperature above its melting temperature, the antibacterial material according to the present invention and the medium are mixed to obtain the antibacterial material dispersion according to the present invention. The antibacterial material dispersion thus obtained can be formed into a film or a plate (board) shape by a predetermined method to obtain an antibacterial plate.

[0056] For example, as a method for dispersing the antibacterial material according to the present invention in a PET resin, first, the PET resin and the antibacterial material dispersion liquid after mechanical pulverization under predetermined conditions according to the present invention are mixed, the dispersion solvent is evaporated, and then heated to about 300°C which is the melting temperature of the PET resin to melt and mix the PET resin, and further stretched into a film shape, whereby it is possible to produce an antibacterial film in which the antibacterial material according to the present invention is dispersed.

[0057] Also, the antibacterial material according to the present invention and resin pellets are mixed, the dispersion solvent is evaporated, then heated to the melting temperature of the resin to melt the resin and mix it with the antibacterial material, and injection molding is performed to obtain an antibacterial molded article formed into the shape of a container or other article.

[0058] Also, a resin to be a synthetic fiber and the antibacterial material according to the present invention are mixed, formed into a fibrous shape to obtain antibacterial synthetic fibers, and an antibacterial yarn (fiber product) can be obtained from the antibacterial synthetic fibers, and further processed into an antibacterial fabric (fiber product) from the antibacterial yarn.

[0059] The synthetic fibers to be applied are not particularly limited. For example, 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 (aramid, etc.), polyvinyl alcohol fibers (vinylon, etc.), polyvinylidene chloride fibers (vinylidene, etc.), polyvinyl chloride fibers (polyvinyl chloride, etc.), polyolefin fibers (polyethylene, polypropylene, polystyrene, etc.), polyvinyl chloride fibers, polylactic acid fibers, and the like can be mentioned.

[0060] The thickness of the above antibacterial synthetic fiber is preferably 1 to 50 μm, more preferably 1 to 20 μm, and still more preferably 1 to 10 μm. The thickness of the antibacterial synthetic fiber affects the flexibility of the antibacterial yarn (fiber product) obtained by twisting and bundling (i.e., processing) a plurality of synthetic fibers, and ultimately affects the flexibility of the antibacterial fabric (fiber product) obtained by weaving (i.e., processing) the antibacterial yarn. Therefore, when the thickness of the antibacterial synthetic fiber exceeds 50 μm, the resulting yarn or fabric may become hard.

[0061] The average particle diameter of the composite tungsten oxide fine particles, which are the antibacterial materials contained in the antibacterial material dispersion, can be measured and calculated by a transmission electron microscope for the antibacterial material dispersion. The average particle diameter is 800 nm or less, preferably 200 nm or less, more preferably 10 nm or more and 200 nm or less, and still more preferably 10 nm or more and 100 nm or less.

[0062] (2) An 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. Then, after coating the surface of the base material or article with the coating liquid, if the resin or binder in the coating liquid is cured by a predetermined method, an antibacterial film in which the antibacterial material according to the present invention is dispersed in the resin or binder is formed on the surface of the base material or article. The method of coating the coating liquid is not particularly limited as long as the coating liquid can be uniformly coated on the surface of the base material or article. For example, a bar coating method, a gravure coating method, a spray coating method, a dip coating method, etc. can be mentioned.

[0063] The resin includes not only the resin dissolved in the solvent but also the resin monomer or oligomer before curing. As the resin, a UV curable resin, a thermosetting resin, an electron beam curable resin, a room temperature curable resin, a thermoplastic resin, etc. can be selected according to the purpose. Specifically, polyethylene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol resin, polystyrene resin, polypropylene resin, ethylene vinyl acetate copolymer, polyester resin, polyethylene terephthalate resin, fluororesin, polycarbonate resin, acrylic resin, polyvinyl butyral resin can be mentioned. These resins may be used alone or in combination.

[0064] Examples of the binder include a binder using a metal alkoxide. Representative examples of the metal alkoxide include alkoxides of Si, Ti, Al, Zr, etc. The binder using these metal alkoxides can form an oxide film by hydrolysis and polycondensation by heating or the like.

[0065] In addition, as the base material, a plate-shaped base material or a film-shaped base material can be used. Furthermore, examples of the article include articles such as furniture and utensils used in daily life, articles such as mobile machines such as vehicles, and 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, since the composite tungsten oxide fine particles transmit visible light, an antibacterial material dispersion that is colorless and transparent with respect to visible light can be obtained. If a colorless and transparent antibacterial material dispersion is formed on the surface of an article, the color tone of the article is not impaired, it does not discolor, and it does not discolor even by H2S gas or SO2 gas in the atmosphere, so it has excellent design properties.

Example

[0067] Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In addition, for the measurement of the crystal structure, lattice constant, and crystallite size of the composite tungsten oxide fine particles according to the present invention, the composite tungsten oxide fine particles obtained by removing the solvent from the antibacterial material dispersion were used. Then, the X-ray diffraction pattern of the composite tungsten oxide fine particles was measured by the powder X-ray diffraction method (θ-2θ method) using a powder X-ray diffractometer (X‘Pert-PRO / MPD manufactured by PANalytical Co., Ltd.). The crystal structure contained in the fine particles was specified from the obtained X-ray diffraction pattern, and the lattice constant and crystallite size were calculated using the Rietveld method.

[0068] (Example 1) 7.43 kg of cesium carbonate (Cs2CO3) was dissolved in 6.70 kg of water to obtain a solution. The solution was added to 34.57 kg of tungstic acid (H2WO4) and sufficiently stirred and mixed, and then dried while stirring (the molar ratio of W to Cs is equivalent to 1:0.33). The dried product was heated while supplying 5% by volume of H2 gas with N2 gas as a carrier, fired at a temperature of 800 ° C for 5.5 hours, and then the supply gas was switched to N2 gas only and cooled to room temperature to obtain Cs tungsten oxide particles (A1).

[0069] Weighed 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, loaded them into a paint shaker (manufactured by Asada Iron Works Co., Ltd.) containing 0.3 mmφ ZrO2 beads, and carried out a pulverization and dispersion treatment for 20 hours to prepare an antibacterial material dispersion (A liquid) according to Example 1.

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

[0071] A storage efficacy test was carried out on the antibacterial material dispersion (A liquid) in accordance with the storage efficacy test method defined in the Japanese Pharmacopoeia. The determination was based on the situation of the decrease in bacteria after storing at 25°C immediately after inoculation of the bacterial species and 28 days after inoculation, and the antibacterial action was judged by the decrease in the number of bacteria. Those in which the bacteria had died after 28 days of storage were marked as ◎, those in which there was no change in the number of bacteria were marked as 〇, and those in which the number of bacteria had increased were marked as ×. The results are shown in Table 1. The number of bacteria was confirmed on an agar medium.

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

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

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

[0075] (Comparative Example 1) Without adding the Cs tungsten oxide particles (A1), 10% by mass of additive a and 90% by mass of water were weighed and mixed to obtain a mixed liquid (E liquid) according to Comparative Example 1. Next, using the mixed liquid (E liquid) according to Comparative Example 1, a storage efficacy test was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0076] (Comparative Example 2) Without adding the Cs tungsten oxide particles (A1), 10% by mass of additive b and 90% by mass of water were weighed and mixed to obtain a mixed liquid (F liquid) according to Comparative Example 2. Next, using the mixed liquid (F liquid) according to Comparative Example 2, a storage efficacy test was carried out in the same manner as in Example 1. The results are shown in Table 1.

[0077] (Comparative Example 3) Without adding the Cs tungsten oxide particles (A1), 10% by mass of additive c and 90% by mass of water were weighed and mixed to obtain a mixed liquid (G liquid) according to Comparative Example 3. Next, using the mixed solution (Solution G) according to Comparative Example 3, a storage efficacy test was conducted in the same manner as in Example 1. The results are shown in Table 1.

[0078] (Comparative Example 4) Without adding Cs tungsten oxide particles (A1), 10% by mass of additive d10 and 90% by mass of water were weighed and mixed to obtain a mixed solution (Solution H) according to Comparative Example 4. Next, using the mixed solution (Solution H) according to Comparative Example 4, a storage efficacy test was conducted in the same manner as in Example 1. The results are shown in Table 1.

[0079] (Comparative Example 5) A storage efficacy test was conducted in the same manner as in Example 1, except that pure water was used instead of the antibacterial material dispersion (Solution A). The results are shown in Table 1.

[0080] (Summary) As is clear from Table 1, it was found that the antibacterial material dispersions according to Examples 1 to 4 in which the antibacterial material according to the present invention was dispersed were able to kill fungi or suppress the increase of fungi. On the other hand, in the mixed solutions according to Comparative Examples 1 to 4 in which the antibacterial material according to the present invention was not dispersed and the pure water according to Comparative Example 5, the fungi increased. From the above, it was 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] By applying the composite tungsten oxide according to the present invention to, for example, a solid surface or mixing it with other powders or liquids, an antibacterial effect can be preferably imparted.

Claims

1. An antibacterial material which is a composite tungsten oxide fine particle represented by the general formula MxWyOz (wherein the 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).

2. The antibacterial material according to Claim 1, wherein the composite tungsten oxide fine particle contains a hexagonal crystal structure.

3. The antibacterial material according to Claim 1 or 2, wherein the average particle diameter of the composite tungsten oxide fine particle is 10 nm or more and 200 nm or less.

4. An antibacterial material dispersion liquid characterized by containing the antibacterial material according to any one of Claims 1 to 3 and a solvent.

5. An antibacterial material dispersion characterized by containing 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 containing a hexagonal crystal structure, represented 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, 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 fine particles having 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 in the lattice constant of the hexagonal crystal structure and a particle diameter of 100 nm or less. A method for producing an antibacterial material, characterized by comprising the above steps.

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