JP6370698B2 - Antimicrobial agent - Google Patents

Description

  The present invention relates to an antimicrobial agent comprising crystalline rutile-type titanium oxide and exhibiting excellent antimicrobial activity in bright and dark places.

  Since titanium oxide particles can exhibit a strong oxidizing action when absorbing ultraviolet rays, they are used to suppress the growth of microorganisms, kill them or inactivate them. However, although titanium oxide particles exert a strong oxidizing action under outdoor ultraviolet irradiation, the oxidizing action is not sufficiently exhibited indoors and in the dark, and the problem is that the growth of bacteria cannot be suppressed. It was.

  As titanium oxide particles that exhibit antimicrobial activity in the dark, Patent Document 1 proposes a compound in which fluorine is chemically bonded by reacting anatase-type titanium oxide with hydrofluoric acid. However, this compound needs to be made from difficult-to-handle hydrofluoric acid as a raw material, and was not industrially advantageous.

  Patent Document 2 describes silver or copper-supported anatase-type titanium oxide. However, this compound was not satisfactory in terms of antimicrobial activity in the dark and antibacterial spectrum.

JP 2010-222266 A JP2013-724

  Accordingly, an object of the present invention is to provide an antimicrobial agent comprising crystalline rutile-type titanium oxide and exhibiting excellent antimicrobial activity in light and dark places.

  As a result of intensive studies to achieve the above object, the present inventors have conducted a hydrothermal treatment of the titanium compound in an aqueous medium, thereby producing a rod shape [specifically, the average minor axis is 50 nm or less, the average aspect ratio (major axis / The crystalline rutile-type titanium oxide having a minor axis of 1.5 or more] can be easily and inexpensively manufactured, and the rod-like crystalline rutile-type titanium oxide has a charge separated between the tip portion and the side portion. In addition, it has excellent separation between excited electrons and holes, and can suppress the recombination of excited electrons and holes and the progress of reverse reaction. In addition, it was found that excellent antimicrobial activity can be exhibited. The present invention has been completed based on these findings.

  That is, the present invention is an antimicrobial agent containing a titanium compound, which is a crystalline rutile-type titanium oxide having an average minor axis of 50 nm or less and an average aspect ratio (major axis / minor axis) of 1.5 or more. The present invention provides an antimicrobial agent comprising more than 50% by weight of the total titanium compound contained in the antimicrobial agent (excluding titanium oxide doped with anions and titanium oxide supporting a transition metal compound).

  The present invention also provides a rutile type titanium oxide in which the crystalline rutile type titanium oxide has a crystal face (110) and a crystal face (111) and / or a crystal face (110), a crystal face (111) and a crystal face (001). The antimicrobial agent is a rutile-type titanium oxide having the following.

The present invention also provides the antimicrobial agent described above, wherein the crystalline rutile-type titanium oxide has a specific surface area of 10 m ² / g or more.

  The present invention also relates to an antimicrobial agent for coating containing a titanium compound and a dispersion medium. As a titanium compound, the crystallinity having an average minor axis of 50 nm or less and an average aspect ratio (major axis / minor axis) of 1.5 or more. Rutile-type titanium oxide (excluding anion-doped titanium oxide and transition metal compound-supported titanium oxide) containing more than 50% by weight of the total titanium compound contained in the coating antimicrobial agent An antimicrobial agent is provided.

  The antimicrobial agent of the present invention contains, as a titanium compound, crystalline rutile titanium oxide having an average minor axis of 50 nm or less and an average aspect ratio (major axis / minor axis) of 1.5 or more. A superior range of oxidative activity compared to the case of containing type titanium oxide, and a wide range of microorganisms from bacteria to viruses under a wide wavelength light source from the ultraviolet range to the visible light range and even in the dark. Can exhibit antimicrobial activity against. For this reason, the antimicrobial activity has been sufficient in the past, such as in a car or indoors, where there is no light or light, or where there is a long light non-irradiation state even if there is a lighting facility. It can be suitably used for environmental purification of a space that has been difficult to exhibit.

Schematic diagram (a) of rod-shaped rutile titanium oxide having crystal plane (110) and crystal plane (111), and rod-shaped rutile having crystal plane (110), crystal plane (111), and crystal plane (001) It is a schematic diagram (b) of type titanium oxide.

[Antimicrobial agent]
The antimicrobial agent of the present invention is an antimicrobial agent containing a titanium compound, which is a crystalline rutile titanium oxide having an average minor axis of 50 nm or less and an average aspect ratio (major axis / minor axis) of 1.5 or more. It is characterized by including. The crystalline rutile-type titanium oxide of the present invention does not include titanium oxide doped with anions such as nitrogen and sulfur and titanium oxide carrying a transition metal compound such as an iron compound.

(Crystalline rutile titanium oxide)
The average minor axis of the crystalline rutile type titanium oxide of the present invention is 50 nm or less (for example, 5 to 50 nm, preferably 5 to 30 nm, particularly preferably 5 to 20 nm).

  The crystalline rutile titanium oxide of the present invention has a rod shape (that is, a rod shape or a needle shape) and an average aspect ratio (major axis / minor axis) of 1.5 or more (for example, 1.5 to 40). The lower limit is preferably 2, particularly preferably 3, and most preferably 5. The upper limit is preferably 30, particularly preferably 20, and most preferably 15. Therefore, the separation between excited electrons and holes is high, the recombination of excited electrons and holes and the progress of reverse reaction can be suppressed very low, and excellent antimicrobial activity can be exhibited.

  Furthermore, the crystalline rutile type titanium oxide of the present invention comprises a rutile type titanium oxide having a crystal face (110) and a crystal face (111) and / or a crystal face (110), a crystal face (111) and a crystal face (001). Is a rutile type titanium oxide having a separation between charges at the tip and side portions, excellent separation between excited electrons and holes, and suppression of recombination of excited electrons and holes and progress of reverse reaction Therefore, it is preferable in that it can exhibit excellent antimicrobial activity under a light source having a wide wavelength from the ultraviolet region to the visible light region, and even in a dark place.

Furthermore, the specific surface area (by the BET multipoint method) of the crystalline rutile type titanium oxide is, for example, 10 m ² / g or more, preferably 10 to ²⁰⁰ m ² / g, more preferably 10 to 150 m ² / g, still more preferably. Is 30 to 150 m ² / g, particularly preferably 50 to 100 m ² / g, and most preferably 60 to 100 m ² / g. When the specific surface area of the crystalline rutile type titanium oxide is less than the above range, the ability to adsorb the reactant tends to be reduced, and the antimicrobial activity tends to be reduced. On the other hand, if the specific surface area of the crystalline rutile-type titanium oxide exceeds the above range, the separability between excited electrons and holes decreases, so that the antimicrobial activity also tends to decrease.

The specific surface area of a sample obtained by degassing crystalline rutile-type titanium oxide at 100 ° C. (under vacuum) for 60 minutes was measured using a high-speed specific surface area / pore size distribution device (trade name “NOVA-1200”, Quantachtome. It is the average of the values obtained by measuring the sample twice under the following conditions using Co).
<Specific surface area measurement conditions>
Measuring principle: Constant volume method (blank correction type)
Detection method: Relative pressure (Calculates the amount of injected gas in the ideal gas from pressure detection using a pressure transducer and manifold temperature detection using a thermistor)
Adsorption gas: Nitrogen gas Cell size: Small pellet cell (cell capacity: 1.8 cm ³ , stem outer diameter: 9 mm)
Measurement item: P / P ₀ (relative pressure, P ₀ : saturated vapor pressure) = 0.1, 0.2, 0.3 adsorption side 3 points

  As the crystalline rutile-type titanium oxide of the present invention, those produced by a known method can be used.

  Among crystalline rutile type titanium oxides, rutile type titanium oxide having crystal face (110) and crystal face (111), and rutile type oxide having crystal face (110), crystal face (111) and crystal face (001). For example, titanium is hydrothermally treated in an aqueous medium (for example, water or a mixture of water and a water-soluble organic solvent) [for example, 100 to 200 ° C., 3 to 48 hours (preferably 6 to 12 hours). ] Can be synthesized.

Further, in the case of hydrothermal treatment, stirring [required stirring power (Pv value) is, for example, about 0.1 to 1500 W / m ³ ] is preferable because the size and surface area of the particles to be obtained can be adjusted.

  Examples of the titanium compound include trivalent or tetravalent titanium compounds.

Examples of the trivalent titanium compound include titanium trihalides such as titanium trichloride and titanium tribromide. As the trivalent titanium compound, titanium trichloride (TiCl ₃ ) is preferable because it is inexpensive and easily available.

Moreover, as a tetravalent titanium compound, the compound etc. which are represented by following formula (1) can be mentioned, for example.
Ti (OR ¹ ) _t X _4-t (1)
(Wherein R ¹ represents a hydrocarbon group, X represents a halogen atom, t represents an integer of 0 to 3)

Examples of the hydrocarbon group for R ¹ include C _1-4 aliphatic hydrocarbon groups such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl (preferably linear or branched). Chain C _1-4 alkyl group) and the like.

  Examples of the halogen atom in X include chlorine, bromine, iodine atom and the like.

Examples of such tetravalent titanium compounds include titanium tetrahalides such as TiCl ₄ , TiBr ₄ , and TiI ₄ ; Ti (OCH ₃ ) Cl ₃ , Ti (OC ₂ H ₅ ) Cl ₃ , and Ti (OC _{4). H 9) Cl 3, Ti (} OC 2 H 5) Br 3, Ti (OC 4 H 9) trihalide alkoxy titanium Br _{3 such; Ti (OCH 3) 2 Cl} 2, Ti (OC 2 H 5) 2 Dihalogenated dialkoxytitanium such as Cl ₂ , Ti (OC ₄ H ₉ ) ₂ Cl ₂ , Ti (OC ₂ H ₅ ) ₂ Br ₂ ; Ti (OCH ₃ ) ₃ Cl, Ti (OC ₂ H ₅ ) ₃ Cl, Examples thereof include monohalogenated trialkoxytitanium such as Ti (OC ₄ H ₉ ) ₃ Cl and Ti (OC ₂ H ₅ ) ₃ Br. As the tetravalent titanium compound in the present invention, titanium tetrahalide is preferable, and titanium tetrachloride (TiCl ₄ ) is particularly preferable because it is inexpensive and easily available.

  In particular, when a tetravalent titanium compound is used as the titanium compound, the reaction temperature is 110 to 220 ° C. (preferably 130 to 220 ° C.), and the reaction temperature is higher than the saturated vapor pressure for 2 hours in an aqueous medium. Rutile type titanium oxide having crystal face (110) and crystal face (111) and / or crystal face (110), crystal face (111) and crystal face by hydrothermal treatment as above (preferably 5 to 15 hours) A rutile-type titanium oxide having (001) can be synthesized.

  The rutile type titanium oxide having the crystal plane (110), the crystal plane (111), and the crystal plane (001) is obtained by converting the rutile type titanium oxide having the crystal plane (110) and the crystal plane (111) into sulfuric acid (preferably 50 It is put into sulfuric acid having a high concentration of not less than% by weight, particularly preferably concentrated sulfuric acid), and is stirred under heating to synthesize (dissolve) the ridge or apex of the crystalline rutile titanium oxide. You can also.

  The crude crystalline rutile type titanium oxide (= crystalline rutile type titanium oxide containing impurities) obtained by the above method is separated from impurities by, for example, separation means such as filtration, concentration, distillation, etc., or a separation means combining these. Thus, purified crystalline rutile-type titanium oxide can be obtained.

  In the present invention, among them, the pH of the supernatant of the aqueous suspension of crystalline rutile-type titanium oxide is 1 or more (preferably 1 to 7, particularly preferably 2 to 6, most preferably 2 to 5.5). It is preferable to repeatedly wash with water until it becomes, and in particular, membrane filtration by the cross flow method maintains ionic impurities (for example, hydrogen ions, chlorine ions, titanium ions while maintaining the crystal structure of crystalline rutile titanium oxide) (The chloride ion content can be reduced to, for example, 1000 ppm or less, and preferably 850 ppm or less), and a crystalline rutile-type titanium oxide having excellent dispersibility can be obtained. preferable.

  Moreover, it is preferable that the crystalline rutile-type titanium oxide to be subjected to the water washing treatment is in a wet state (that is, to be subjected to the water washing treatment without performing evaporation / drying after hydrothermal treatment). Thereby, aggregation of crystalline rutile type titanium oxide can be prevented, and crystalline rutile type titanium oxide having high dispersibility can be obtained.

  Examples of water used for the water washing include purified water, distilled water, ion exchange water, and pure water.

  Membrane filtration by the cross flow method means that water to be treated flows parallel to the surface of the filtration membrane, and a part of the water to be treated is moved to the side of the flow of the water to be treated while preventing filtration membrane contamination due to deposition of filter cake. It is a method of filtering. By subjecting the aqueous suspension of crude crystalline rutile-type titanium oxide to membrane filtration by the cross flow method, ionic impurities can be efficiently removed without forming a compacted filter cake on the filtration membrane surface, While maintaining the crystal structure of the crystalline rutile-type titanium oxide, the content of ionic impurities can be reduced extremely low.

  The concentration of the aqueous suspension of the crude crystalline rutile-type titanium oxide subjected to membrane filtration by the crossflow method is, for example, about 0.1 to 40% by weight (preferably 0.1 to 30% by weight). When the concentration of the coarse crystalline rutile-type titanium oxide is out of the above range, the removal efficiency of ionic impurities tends to decrease. Moreover, when the density | concentration of a coarse crystalline rutile type titanium oxide exceeds the said range, a viscosity will become high too much and it will become easy to clog a filtration membrane.

  When an aqueous suspension of crude crystalline rutile-type titanium oxide is subjected to membrane filtration by a cross flow method, ionic impurities are separated and removed together with the permeate, and a concentrated aqueous suspension of crystalline rutile-type titanium oxide is obtained. It is done.

  The concentration ratio is preferably adjusted to about 1 to 400 times (in particular, 1 to 20 times, particularly 1 to 10 times). When the concentration ratio exceeds the above range, it is difficult to suppress the deposition of the adhering substance on the film surface, and it tends to be difficult to prevent consolidation of the crystalline rutile-type titanium oxide. In addition, clogging of the filtration membrane due to the deposition of adhering substances on the membrane surface tends to reduce the membrane life, often necessitating frequent backwashing, or the filtration process becoming inoperable. There exists a tendency for the filtration rate to fall by such. On the other hand, when the concentration factor is below the above range, the separation efficiency of ionic impurities tends to decrease and the amount of washing water used tends to increase.

  The concentration ratio can be adjusted, for example, by controlling the filtration pressure, the film surface linear velocity (cross flow velocity) of the aqueous suspension of the coarse crystalline rutile-type titanium oxide, and the like. The filtration pressure is, for example, about 0.001 to 5.0 MPa, preferably 0.005 to 3 MPa, and particularly preferably 0.01 to 2.0 MPa.

  Further, the larger the film surface linear velocity of the supply liquid containing the aqueous suspension of the crude crystalline rutile-type titanium oxide, the more the deposition of adhering substances on the film surface is suppressed, and a higher filtration flux (flux) is obtained. The film surface linear velocity (cross flow velocity) is, for example, 0.02 m / s or more and less than 3 m / s, preferably 0.05 m / s or more and less than 1.5 m / s.

  The concentrated crystalline rutile-type titanium oxide aqueous suspension obtained through membrane filtration by the cross-flow method is diluted by adding water so that the concentration of the crystalline rutile-type titanium oxide falls within the above range, and then cross-linked again. It is preferable to repeat the operation of membrane filtration by the flow method. Thereby, the load of the filtration membrane such as clogging can be reduced, and the content of ionic impurities in the crystalline rutile-type titanium oxide can be reduced extremely low while suppressing the decrease in the lifetime of the filtration membrane.

  Examples of the filtration membrane used for membrane filtration by the crossflow method include an ultrafiltration membrane, a microfiltration membrane, a nanofilter, and a reverse osmosis membrane. In the present invention, it is particularly preferable to use an ultrafiltration membrane in terms of excellent separation performance.

  The ultrafiltration membrane has an average pore diameter of about 1 to 20 nm (preferably 1 to 10 nm), and can separate and remove substances having a molecular weight of 1000 or less and an average minor axis of less than 1 nm.

  The membrane shape of the ultrafiltration membrane may be, for example, any of a hollow fiber type filtration membrane, a tubular membrane, a spiral membrane, a flat membrane, etc. It is preferable to use a mold filtration membrane or a tubular membrane.

  The inner diameter of the hollow fiber membrane in the hollow fiber membrane is about 0.1 to 2.0 mm (preferably, 0.5 to 2.0 mm) from the viewpoint of preventing clogging with contaminants and improving the hollow fiber filling rate of the membrane module. 1.5 mm).

  Examples of the material of the filtration membrane include general cellulose acetate, polyacrylonitrile, polysulfone, polyethersulfone (PES), polyacrylonitrile, aromatic polyamide, polyvinylidene fluoride, polyvinyl chloride, polyethylene, polypropylene, polyimide, ceramic and the like. Can be mentioned. In the present invention, among them, cellulose acetate, polysulfone, polyethersulfone (PES), polyacrylonitrile, and aromatic polyamide are preferable.

  When using a hollow fiber type filtration membrane, as a method of flowing an aqueous suspension of coarse crystalline rutile type titanium oxide (filtration method), water of the coarse crystalline rutile type titanium oxide is provided on the inner side (inside the hollow fiber membrane). A feed liquid containing a suspension is flowed and permeate flows toward the outside (outside of the hollow fiber membrane) (internal pressure filtration system), and vice versa. A system (external pressure filtration system) in which permeated water flows toward the inside is allowed to flow. In the present invention, the internal pressure filtration method is preferable because the membrane surface flow rate can be kept high.

  In membrane filtration by the cross flow method, the deposition on the filtration membrane surface is prevented to reduce the burden on the filtration membrane and the membrane filtration operation is performed for a long time. It is preferable to perform back washing. The reverse cleaning is preferably performed at a predetermined cycle while controlling the pressure and flow rate.

The pressure for back washing is, for example, about 0.01 to 3.0 MPa, preferably 0.01 to 2.0 MPa, particularly preferably 0.01 to 1.0 MPa, and most preferably 0.01 to 0.5 MPa. More preferably, it is 0.05 to 0.5 MPa. The flow rate of backwashing is, for example, about 0.01 to 10 kg / mim, preferably 0.05 to 5 kg / mim, particularly preferably 0.1 to 5 kg / mim [or, for example, 1 × 10 ⁻⁷ to 2. × 10 ⁻⁴ m / sec, preferably 8 × 10 ^{−7 to} 9 × 10 ⁻⁵ m / sec, and particularly preferably 1 × 10 ^{−6 to} 9 × 10 ⁻⁵ m / sec. The frequency of back washing is preferably about once every 0.5 to 3 hours, for example. The back washing time is preferably about 0.5 to 10 minutes.

  In addition, it is preferable to use water (for example, purified water, distilled water, pure water, ion-exchanged water, etc.) as washing water used for back washing. Further, the washing water that has passed through the membrane by back washing may be reused as water for diluting the concentrated aqueous suspension of crystalline rutile-type titanium oxide.

  The antimicrobial agent of the present invention is an antimicrobial agent containing a titanium compound, which resists the crystalline rutile-type titanium oxide (excluding titanium oxide doped with an anion and titanium oxide supporting a transition metal compound) as the titanium compound. More than 50 wt% (preferably 70 wt% or more, particularly preferably 80 wt% or more, most preferably 90 wt% or more) of the total titanium compound contained in the microbial agent is characterized. The upper limit of the content of the crystalline rutile-type titanium oxide is 100% by weight.

  The antimicrobial agent of the present invention may contain other components in addition to the titanium compound. For example, a titanium compound (particularly, crystalline rutile titanium oxide) is suspended in a dispersion medium. Also good. Examples of the dispersion medium include water, water-soluble organic solvents such as alcohol, and mixtures thereof. That is, the dispersion medium is preferably water and / or a water-soluble organic solvent.

  When the antimicrobial agent of the present invention contains a titanium compound and a dispersion medium, and the titanium compound is suspended in the dispersion medium, the method of spraying with a spray or the method of applying with a roller, etc. By applying to a place where death or inactivation is required, antimicrobial activity can be imparted to the place. Therefore, it is useful as an antimicrobial agent for coating.

  The content of titanium compound in the total amount (100% by weight) of the antimicrobial agent of the present invention (the total amount when containing two or more) is particularly limited as long as it is a concentration that can exhibit antimicrobial activity. For example, it is 0.001% by weight or more. The upper limit is, for example, 100% by weight, preferably 95% by weight, more preferably 80% by weight, further preferably 70% by weight, particularly preferably 50% by weight, most preferably 30% by weight, particularly preferably 10% by weight. . The lower limit is preferably 0.01% by weight, more preferably 0.05% by weight, still more preferably 0.1% by weight, particularly preferably 0.5% by weight, most preferably 1.0% by weight, particularly preferably 5.0% by weight.

  In addition to the dispersion medium, the antimicrobial agent of the present invention may further contain additives such as a water-insoluble organic solvent, a dispersant, a surfactant, a binder, a fragrance, and a colorant as necessary. it can. The content of the additive is, for example, 70% by weight or less, preferably 50% by weight or less, more preferably 30% by weight or less, particularly preferably 10% by weight or less, and most preferably 5% by weight or less of the total amount of the antimicrobial agent. .

  Conventional titanium compounds did not sufficiently exhibit antimicrobial activity in an environment with a low amount of ultraviolet light or in a dark place, so application to indoor and in-car applications did not progress very easily. Excellent antimicrobial activity can be exhibited under a light source having a wide wavelength from a visible light region to a visible light region, and even in a dark place. Therefore, not only outdoors, but also in an environment where the amount of ultraviolet rays is low, such as indoors or in a car, and even in a place where there is a long light non-irradiation state or a place where light does not reach or where there is no light even if there is a lighting facility. It can exert microbial activity, and can suppress the growth, kill or inactivate a wide range of microorganisms from bacteria to viruses. The antibacterial activity value is, for example, 2 or more, and the antiviral activity value is, for example, 2 or more. The antibacterial activity value and antiviral activity value can be measured by the methods described in the Examples. Therefore, the antimicrobial agent of this invention can be used conveniently also as an antimicrobial agent for dark places.

  The application location of the antimicrobial agent of the present invention is not particularly limited as long as it is a place where suppression of growth, killing or inactivation of microorganisms is required. For example, homes and public facilities (hospitals, schools, care facilities) Etc.), toilets, waste disposal rooms, kitchens, bathrooms, washrooms, warehouses, meeting rooms, waiting rooms, floors (especially operating room floors), walls, ceilings, curtains, furniture, electrical appliances, air conditioning equipment, hygiene Equipment: Car seats, air conditioner filters, floors, wall surfaces, etc. By applying the antimicrobial agent of the present invention to the place, the growth of microorganisms such as bacteria and viruses existing there can be suppressed, or can be killed or inactivated. Especially in areas where light is hardly irradiated, such as inside refrigerators (storage rooms), inside machines such as washing machines and bathroom dryers, water pipes, water pipes, coolers, humidifier water tanks, air conditioner drain pans, etc. Bacteria and virus growth can be effectively suppressed.

  In addition, as an application method of the antimicrobial agent of the present invention, it may be applied to a place where growth suppression, killing or inactivation of the microorganism is required. For example, a method of spraying the place with a spray, a roller The method of coating etc. are mentioned. The application amount is not particularly limited as long as the effect is exhibited.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

The average minor axis and average aspect ratio were determined by the following method (image analysis method).
<Sample preparation method>
1. Put a small amount (about half of the earpick size spatula) crystalline rutile titanium oxide into a 9 mL glass sample bottle, add 7 mL of ethanol, and disperse the ultrasonic wave in ethanol over 5 minutes with an ultrasonic cleaner. An ethanol dispersion is obtained.
2. One drop of the obtained ethanol dispersion is taken with a glass spoid, dropped on a sample stage for SEM and allowed to dry naturally, and then platinum deposition is performed for 30 seconds.
<Measurement method>
Use a field emission scanning electron microscope (trade name “FE-SEM JSM-6700F”, manufactured by JEOL Ltd., acceleration voltage: 15 kV, WD: about 3 mm, magnification: 200,000 times) to randomly crystallize particles Observe, extract three representative points, and 30 particles that are not extremely large or small in appearance in the entire extracted SEM photograph and have a clear outline centered on average-sized particles Extracted and copied to OHP sheet, and for each of these particles, find each short diameter (width orthogonal to the maximum long diameter) using image analysis software (trade name “WinROOF Version5.6”, manufactured by Mitani Corp.) These values were averaged to obtain an average minor axis. Further, the average major axis (maximum major axis) was determined by the same method, and the ratio (average major axis / average minor axis) was taken as the average aspect ratio.

Example 1
(Preparation of crude titanium oxide suspension)
At room temperature (25 ° C.), titanium tetrachloride aqueous solution (Ti concentration: 16.5 wt% ± 0.5 wt%, chloride ion concentration: 31 wt% ± 2 wt%, manufactured by Toho Titanium Co., Ltd.) Ti concentration Was diluted with pure water so as to be 5.6% by weight. The diluted titanium tetrachloride aqueous solution 5650 g was placed in a 10 L tantalum-lined autoclave and sealed. Using a heat medium, the temperature inside the autoclave was raised to 140 ° C. over 2 hours. Then, while stirring at a required power for stirring (Pv value) of 220 W / m ³ , the temperature was maintained at 140 ° C., pressure: vapor pressure at that temperature for 10 hours, and then the heat medium was cooled to cool the autoclave. It cooled to 40 degrees C or less. After confirming that the temperature inside the autoclave was 40 ° C. or less, 5650 g of a crude titanium oxide suspension was taken out.

(Cross flow membrane filtration)
The obtained crude titanium oxide suspension was diluted three-fold with pure water, stirred and mixed at a stirring speed of 300 rpm, and hollow fiber type ultrafiltration membrane (trade name “FS03-FC-FUS03C1”, material: PES , Nominal molecular weight cut off: 30,000, manufactured by Daisen Membrane Systems Co., Ltd.) at room temperature (25 ° C.) and filtration pressure of 0.02 MPa while adding pure water in the same amount as the permeated liquid. Filtration treatment by the method was performed. The concentrate obtained through the filtration treatment was circulated again into the charging tank, and repeatedly subjected to the filtration treatment until the pH of the permeate became 4.0. The pH was measured using a pH test paper.
During this time, backwashing was performed once a hour at a pressure of 0.1 MPa and a flow rate of 2 kg / min for 1 minute. The washing water that passed through the membrane by this reverse washing was circulated to the charging tank. Thereafter, the preparation of pure water was stopped and the titanium oxide concentration was concentrated to obtain a titanium oxide suspension (rod-like crystalline rutile-type titanium oxide content: 10% by weight), which was used as an antimicrobial agent.

When the obtained titanium oxide suspension was dried at 105 ° C. for 1 hour under normal pressure, rod-shaped rutile titanium oxide having crystal face (110) and crystal face (111), crystal face (110), crystal face (111) and crystalline rutile type titanium oxide which is a mixture of rod-like rutile type titanium oxide having crystal plane (001) (average minor axis: 15 nm, average aspect ratio: 5, specific surface area: 80.2 m ² / g) 533 g was obtained. Chlorine ion remaining on the surface of the obtained crystalline rutile type titanium oxide was 830 ppm (mg / kg).

(Antimicrobial activity evaluation)
The obtained antimicrobial agent was evaluated for antibacterial activity against Escherichia coli by the following method. The antibacterial activity value was 4.7 after 4 hours of storage in the dark. Further, the antiviral property against bacteriophage Qβ was an antiviral activity value of 5.2 after 2 hours in the dark.

<Antimicrobial activity and antiviral activity test>
An antimicrobial agent layer was formed by applying an antimicrobial agent to a glass plate (50 mm x 50 mm x 1 mm) surface using a spray gun so that the titanium compound was 25 mg / 25 cm ² and drying it naturally. Antibacterial and antiviral tests were carried out using a piece (= antimicrobial agent-coated glass plate).

(Measurement method of antibacterial activity)
Using the above test piece, the test was conducted only in the dark by a method based on Japanese Industrial Standard JIS R 1752: 2013 “Fine Ceramics-Antibacterial Test Method / Antimicrobial Effect of Visible Light Responsive Photocatalyst Antibacterial Products”. Evaluation was made by measuring the number of viable bacteria.
First, on the antimicrobial agent layer, the UV light intensity is 1 mW / cm ² (measured by attaching the UV receiver “UD-36” to Topcon UV intensity meter “UVR-2”) and the black light. The sample was irradiated with ultraviolet rays for 17 hours.
Next, the antimicrobial agent layer is inoculated with Escherichia coli NBRC3972 bacterial solution (viable cell count: 2.0 × 10 ⁵ ), and a coated film is placed on top of it to allow it to come to room temperature (25 ± 5 ° C.). ), Stored in the dark for 4 hours, and the number of viable bacteria per test piece was measured. The measurement was performed simultaneously using three test pieces, and the evaluation was performed using the average value of the number of these three viable bacteria.
The same operation was performed on the glass plate not coated with the antimicrobial agent, and the viable cell count was measured.
The antibacterial activity value was determined by the following formula. If the antibacterial activity value is 2 or more, it can be said that the antibacterial activity is generally expressed.
Antibacterial activity value = log (N _b0 / N _b )
N _b0 : Average number of viable cells on glass plate not coated with antimicrobial agent N _b : Average value of viable cells on glass plate coated with antimicrobial agent Low number of viable cells after 4 hours storage in dark place It can be said that the antibacterial properties of Escherichia coli are high.

(Measurement method of antiviral activity)
Using the above test piece, a test based on Japanese Industrial Standard JIS R 1756: 2013 “Fine Ceramics—Antiviral Test Method for Visible Light Responsive Photocatalyst Material—Bacteriophage Qβ” was performed only in the dark, and bacteriophage Evaluation was made by measuring the infectious titer.
First, on the antimicrobial agent layer, the UV light intensity is 1 mW / cm ² (measured by attaching the UV receiver “UD-36” to Topcon UV intensity meter “UVR-2”) and the black light. Used and irradiated with ultraviolet rays for 24 hours.
Next, the antimicrobial agent layer is inoculated with a test solution of bacteriophage Qβ (Escherichia coli phage Qβ NBRC20012) (bacteriophage infectivity titer: 1.0 × 10 ⁶ pfu), and a coated film is placed on the layer, and this is allowed to come to room temperature. After storage for 2 hours in the dark (25 ± 5 ° C.), the infectivity phage was infected with E. coli to measure the bacteriophage infectivity per test piece. In addition, it performed simultaneously using three test pieces, and evaluated by the average value of these three bacteriophage infectious titers.
The same operation was performed on the glass plate not coated with the antimicrobial agent, and the bacteriophage infectivity titer was measured.
The antiviral activity value was determined by the following formula. If the antiviral activity value is 2 or more, it can be said that the antiviral activity is generally expressed.
Antiviral activity value = log (N _v0 / N _v )
N _v0 : Average value of bacteriophage infectious titer on glass plate not coated with antimicrobial agent N _v : Average value of bacteriophage infectious titer on glass plate coated with antimicrobial agent _Nb0 : Bacteriophage infectious titer after 2 hours storage in dark place It can be said that the smaller the amount, the higher the antiviral property, that is, the photocatalytic activity.

Claims (3)

The antimicrobial agent for dark places containing the following titanium compound .
Titanium compound : crystalline rutile-type titanium oxide (anion-doped titanium oxide and transition metal) having an average minor axis of 50 nm or less, an average aspect ratio (major axis / minor axis) of 1.5 or more , and a specific surface area of 60 m ² / g or more (Excluding titanium oxide supporting the compound) in excess of 50% by weight of the total titanium compound contained in the antimicrobial agent for dark places A rutile titanium oxide in which the crystalline rutile type titanium oxide has a crystal face (110) and a crystal face (111) and / or a rutile type titanium oxide in which the crystal face (110), the crystal face (111) and the crystal face (001) are present. The antimicrobial agent for dark places according to claim 1. An antimicrobial agent for coating in the dark containing the following titanium compound and dispersion medium.
Titanium compound : crystalline rutile-type titanium oxide (anion-doped titanium oxide and transition metal) having an average minor axis of 50 nm or less, an average aspect ratio (major axis / minor axis) of 1.5 or more , and a specific surface area of 60 m ² / g or more (Excluding titanium oxide supporting the compound) in excess of 50% by weight of the total titanium compound contained in the antimicrobial agent for dark coating

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