Antimicrobial fibers

Abstract

To provide an antimicrobial fiber that is superior in outer appearance, washing durability, and antimicrobial properties.SOLUTION: An antimicrobial fiber includes titania nanoparticles supported thereon. The titania nanoparticles have acyloxy groups combined with at least some titanium atoms present on their surfaces. When a temperature of the titania nanoparticles is increased to 600°C with a differential thermal and thermogravimetric analyzer, mass reduction of 5 mass% or more is observed at temperatures of 200°C or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to antimicrobial fibers. [Background technology]

[0002] In recent years, infectious diseases caused by microorganisms such as the novel coronavirus and multidrug-resistant bacteria have not only threatened human life but also significantly impacted social activities, making countermeasures against them an urgent issue.

[0003] Processing to impart antimicrobial properties to fibers has been practiced for a long time. Specifically, it is common to apply organic antimicrobial agents such as quaternary ammonium salts, metallic antimicrobial agents such as silver, and photocatalysts such as titanium dioxide.

[0004] When these antimicrobial agents are fixed to fibers to impart both antimicrobial properties and durability against washing, it is common practice to use a binder, such as resin or silica, to fix the antimicrobial agent to the fiber, as described in Patent Document 1. However, when antimicrobial agents are fixed to fibers using a binder, the antimicrobial agent is covered by the binder, which has the problem that the antimicrobial agent's functions are not fully exhibited.

[0005] To address the above problem, for example, Patent Document 2 describes a method in which a binder layer containing a fixing resin and an antimicrobial agent layer are laminated in that order to suppress the reduction in antimicrobial activity due to the binder. However, forming a multilayer structure requires multiple processing steps, making it complicated, and the antimicrobial agent slides off the binder layer, resulting in insufficient wash durability. Furthermore, while it is possible to improve wash durability by increasing the amount of antimicrobial agent fixed to the fibers and increasing the amount of antimicrobial agent remaining on the fibers after washing, this increases the amount of agent carried, which impairs the texture and color of the fibers.

[0006] Thus, there was a demand for fibers that excelled in aesthetics, such as feel and texture, as well as in wash durability and antimicrobial properties. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Patent No. 3761248 [Patent Document 2] Patent No. 4827031 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] This invention was made in view of the above background, and its purpose is to provide a fiber that is excellent in aesthetics, wash durability, and antimicrobial properties. [Means for solving the problem]

[0009] In light of the above objectives, and after diligent research, the inventors have found that an antimicrobial fiber having titania nanoparticles on its surface, in which at least some of the titanium atoms present on the surface are bonded to acyloxy groups and exhibits a mass loss of 5% or more at temperatures above 200°C when heated to 600°C using a differential thermogravimetric analyzer, can solve all of the above problems. Further research has led to the completion of the present invention. That is, the present invention encompasses the following configuration.

[0010] Item 1. An antimicrobial fiber on which titania nanoparticles are supported, The titania nanoparticles have acyloxy groups bonded to at least some of the titanium atoms present on their surface. An antimicrobial fiber wherein the titania nanoparticles exhibit a mass loss of 5% by mass or more at temperatures above 200°C when heated to 600°C using a differential thermogravimetric analyzer.

[0011] Item 2. The titania nanoparticles are supported with an antimicrobial compound, as described in Item 1, for the antimicrobial fiber.

[0012] Item 3. The antimicrobial fiber according to Item 2, wherein the antimicrobial compound contains an antimicrobial metal compound.

[0013] Item 4. The antimicrobial fiber according to Item 3, wherein the antimicrobial metal compound contains at least one selected from the group consisting of silver, copper, and platinum.

[0014] Item 5. The antimicrobial fiber according to Item 3 or 4, wherein the antimicrobial metal compound contains silver.

[0015] Item 6. The antimicrobial fiber according to any one of Items 3 to 5, wherein the antimicrobial metal compound is silver nanoparticles.

[0016] Item 7. The antimicrobial fiber according to any one of Items 2 to 6, wherein the loading amount of the antimicrobial compound is 0.0001 to 50% by mass with respect to 100% by mass of the titanium oxide mass in the titania nanoparticles.

[0017] Item 8. The antimicrobial fiber according to any one of Items 1 to 7, wherein the acyloxy group is bonded to the titanium atom by a group represented by -OCOR (wherein R represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, or a hydroxyalkyl group having 1 to 2 carbon atoms).

[0018] Item 9. The antimicrobial fiber according to any one of Items 1 to 8, wherein the acyloxy group is an acyloxy group derived from at least one organic acid selected from the group consisting of monocarboxylic acids having 1 to 4 carbon atoms and hydroxycarboxylic acids having 2 to 3 carbon atoms.

[0019] Item 10. The antimicrobial fiber according to Item 9, wherein the organic acid is acetic acid and / or lactic acid.

[0020] Item 11. The antimicrobial fiber according to Item 9 or 10, wherein the organic acid is acetic acid.

[0021] Item 12. The antimicrobial fiber according to any one of Items 1 to 11, wherein the titania nanoparticles are composed of anatase type.

[0022] Item 13. The specific surface area of ​​the titania nanoparticles is 150 to 500 m². 2 An antimicrobial fiber as described in any one of items 1 to 12, wherein the amount is / g.

[0023] Item 14. An antimicrobial fiber according to any one of items 1 to 13, wherein the average particle size of the titania nanoparticles is 1 to 5 nm.

[0024] Item 15. The amount of titania nanoparticles supported is 0.01 to 5000 mg / m² as solid content. 2 The antimicrobial fiber described in any one of items 1 to 14. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide antimicrobial fibers that are excellent in aesthetics, wash durability, and antimicrobial properties. [Modes for carrying out the invention]

[0026] In this specification, "contains" is a concept that encompasses all of the following: "contains," "consist essentially of," and "consist of."

[0027] In this specification, when a numerical range is expressed as A to B, it means A or greater and B or less.

[0028] In this specification, "titanium dioxide" or "titania" does not refer only to titanium dioxide (TiO2), but also includes titanium trioxide (Ti2O3), titanium monoxide (TiO), and compositions in which titanium dioxide has been deficient in oxygen, such as Ti4O7 and Ti5O9. Furthermore, it may also include groups other than Ti-O-Ti, which are partly due to the synthesis of titanium dioxide, such as terminal OH groups. In addition, it may also include compositions in which organic acids, etc., are bonded to terminal OH groups.

[0029] 1. Antimicrobial fiber supported with titania nanoparticles The antimicrobial fiber of the present invention is an antimicrobial fiber on which titania nanoparticles are supported, wherein at least some of the titanium atoms on the surface of the titania nanoparticles have acyloxy groups bonded to them, and when the titania nanoparticles are heated to 600°C using a differential thermogravimetric analyzer, the mass loss at 200°C or higher is 5% by mass or more.

[0030] By adopting this configuration, the antimicrobial fiber of the present invention can support titania nanoparticles on the fiber without using a binder, thereby suppressing the reduction in antimicrobial properties caused by binders and the deterioration of the fiber's aesthetic appearance, such as its feel and texture. Furthermore, in bright light, the antimicrobial activity can be achieved through the photocatalytic activity of the titania nanoparticles, while in dark light, the antimicrobial activity can be achieved through the action of the antimicrobial compound supported on the titania nanoparticles. Moreover, in the antimicrobial fiber of the present invention, the titania nanoparticles and the fiber, and the titania nanoparticles and the antimicrobial compound, are firmly adhered to each other, resulting in high resistance to physical impacts such as abrasion. Therefore, it has high durability against washing and can maintain excellent aesthetic appearance and antimicrobial properties over time.

[0031] (1-1) Titania nanoparticles Normally, water, inorganic acids, and free organic acids almost completely volatilize below 200°C. On the other hand, the titania nanoparticles constituting the antimicrobial fibers of the present invention have acyloxy groups bonded to at least some of the titanium atoms on their surface, so they gradually detach in the range of 200 to 600°C. For example, in the case of acetoxy groups, they gradually detach in the range of 200 to 600°C, peaking at approximately 260°C. Thus, because the titania nanoparticles constituting the antimicrobial fibers of the present invention have acyloxy groups bonded to at least some of the titanium atoms on their surface, aggregation of titania nanoparticles during drying or firing is suppressed, making them less prone to cracking and peeling, and resulting in particularly excellent coatability, transparency, and texture. Furthermore, they can suppress cracking and peeling, and as a result, they easily support the antimicrobial compounds described later, resulting in excellent visible photocatalytic activity. Normally, it is common technical knowledge that the presence of acyloxy groups on the surface reduces visible photocatalytic activity, which in turn reduces antimicrobial activity. However, in the present invention, as described above, aggregation of titania nanoparticles can be suppressed during drying or calcination, resulting in particularly excellent suppression of cracks, peeling, etc. Furthermore, it is easy to firmly support the antimicrobial compounds described later, so even though acyloxy groups are present, visible photocatalytic activity can be improved, and consequently, antimicrobial activity can also be improved.

[0032] Furthermore, it is preferable that the titania nanoparticles have a large number of acyloxy groups bonded to the titanium atoms present on their surface. When acyloxy groups are present on at least some of the titanium atoms on the surface, they gradually detach in the range of 200 to 600°C as described above, resulting in a large mass loss above 200°C when heated using a differential thermogravimetric analyzer (TG-DTA). In other words, in the present invention, the mass loss above 200°C when heated using a differential thermogravimetric analyzer (TG-DTA) is an indicator of the number of acetoxy groups bonded to the titanium atoms present on the surface. For this reason, the mass loss above 200°C when heated to 600°C using a differential thermogravimetric analyzer (TG-DTA) is 5% by mass or more, preferably 7 to 20% by mass. In this case, the detailed conditions for the differential thermogravimetric analyzer (TG-DTA) are: atmosphere: air, heating rate: 3°C / min.

[0033] As described above, the titania nanoparticles have acyloxy groups bonded to at least some of the titanium atoms present on their surface. Preferably, these acyloxy groups are bonded to the titanium atoms by groups represented as -OCOR (wherein R represents a hydrogen atom, a C1-C3 alkyl group, or a C1-C2 hydroxyalkyl group). In other words, it is preferable that these acyloxy groups are derived from organic acids such as C1-C4 monocarboxylic acids or C2-C3 hydroxycarboxylic acids.

[0034] Examples of alkyl groups in R above include methyl group, ethyl group, n-propyl group, etc., and examples of hydroxyalkyl groups include hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, etc. In other words, examples of monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, etc., and examples of hydroxycarboxylic acids include glycolic acid, lactic acid, etc.

[0035] From the viewpoint of volatility, toxicity, and decomposability, R is preferably a hydrogen atom or a methyl group, hydroxymethyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, etc. From the viewpoint of water solubility and odor, a methyl group, 1-hydroxyethyl group, 2-hydroxyethyl group, etc., is preferred. In other words, from the viewpoint of volatility, toxicity, and decomposability, formic acid, acetic acid, etc. are preferred as monocarboxylic acids, and glycolic acid, lactic acid, etc. are preferred as hydroxycarboxylic acids. Furthermore, from the viewpoint of water solubility and odor, acetic acid, glycolic acid, lactic acid, etc., are particularly preferred. These organic acids can be used individually or in combination of two or more.

[0036] The average particle size of the titania nanoparticles described above is preferably 1 to 5 nm, and more preferably 2 to 4 nm. By setting the average particle size of the titania nanoparticles within this range, it is easier to appropriately and firmly support the antimicrobial compound, resulting in excellent aesthetics and wash durability when supported on fibers, and it is easier to increase visible photocatalytic activity. Furthermore, when the average particle size is small, shrinkage during heating is large, which can easily lead to cracking and delamination from the substrate, but the titania nanoparticles used in this invention are materials that exhibit excellent coatability even when the average particle size is small. In this invention, the average particle size of the titania nanoparticles is measured by electron microscope (TEM) observation.

[0037] The specific surface area of ​​the above titania nanoparticles is 150-500 m². 2 / g is preferred, and 200-400m 2 A value of / g is more preferable. By setting the specific surface area of ​​the titania nanoparticles within this range, it is easier to appropriately and more firmly support the antimicrobial compound, resulting in excellent aesthetics and wash durability when supported on fibers, and making it easier to increase visible photocatalytic activity. The specific surface area of ​​the titania nanoparticles is measured by the BET method.

[0038] Furthermore, the concentrations of N, Cl, and S in the titania nanoparticles can be set to 0-5000 ppm, particularly 0-1000 ppm. By setting the concentrations of N, Cl, and S in the titania nanoparticles within this range, corrosion of the substrate is easily suppressed. This condition means that impurities derived from acidic titania precursors such as TiCl4 and TiOSO4 are absent or present in very small amounts. The concentrations of N, Cl, and S in the titania nanoparticles are measured by WDX (X-ray fluorescence).

[0039] Furthermore, the anatase crystal form of the titania nanoparticles is preferred. By having the titania nanoparticles composed of the anatase crystal form, the visible photocatalytic activity can be particularly improved.

[0040] (1-2) Antimicrobial compounds The antimicrobial compound used in the present invention is not particularly limited, and for example, either an antimicrobial metal compound or an antimicrobial organic compound can be used. However, from the viewpoint of aesthetics, stability of the antimicrobial compound, and wash durability, an antimicrobial metal compound is preferred. The antimicrobial fiber of the present invention can have antimicrobial activity in bright light due to the photocatalytic activity of titania nanoparticles, and in dark light due to the action of the antimicrobial compound supported on the titania nanoparticles.

[0041] (1-2-1) Antimicrobial metal compounds The antimicrobial metal compounds used in the present invention are not particularly limited, and for example, any metal compound having antimicrobial properties can be used. However, from the viewpoint of aesthetics, stability of the metal compound, and antimicrobial activity in light and dark places (especially dark places), it is preferable to include at least one selected from the group consisting of silver, copper, and platinum. These antimicrobial metal compounds can be used individually or in combination of two or more.

[0042] In particular, while the form of silver is not particularly limited, silver nanoparticles and / or monovalent silver ions are preferred, and silver nanoparticles are more preferred, from the viewpoint of aesthetics, wash durability, stability of silver, and antimicrobial activity in light and dark places (especially dark places).

[0043] Furthermore, while the form of copper is not particularly limited, from the viewpoint of aesthetics, washing durability, copper stability, and antimicrobial activity in light and dark places (especially dark places), at least one selected from the group consisting of copper nanoparticles, monovalent copper ions, and divalent copper ions is preferred, with copper nanoparticles being more preferred.

[0044] Furthermore, while the form of platinum is not particularly limited, from the viewpoint of aesthetics, wash durability, stability of platinum, and antimicrobial activity in light and dark places (especially dark places), at least one selected from the group consisting of platinum nanoparticles, divalent platinum ions, and tetravalent platinum ions is preferred, with platinum nanoparticles being more preferred.

[0045] Normally, when metal ions or metal nanoparticles are added to titanium dioxide, regardless of the specific surface area of ​​titanium dioxide or the concentration of metal ions, the metal ions are reduced over time, generating metal nanoparticles, and these metal nanoparticles undergo thermal agglomeration over time, often resulting in metal precipitation. On the other hand, the titania nanoparticles used in this invention have acyloxy groups bonded to at least some of the titanium atoms on their surface, which stabilizes the metal ions and metal nanoparticles on the titania nanoparticles, suppressing reduction and thermal agglomeration over time.

[0046] When using silver nanoparticles, the particle size growth of the silver nanoparticles is easily suppressed from the above viewpoint, and the average particle size of the silver nanoparticles is preferably 500 nm or less, and more preferably 10 to 200 nm. By setting the average particle size of the supported silver nanoparticles within this range, it is easier to form a film with improved visible photocatalytic activity and improved transparency. The average particle size of the silver nanoparticles is measured by electron microscopy observation.

[0047] When using copper nanoparticles, the particle size growth of the copper nanoparticles is easily suppressed from the above viewpoint, and the average particle size of the copper nanoparticles is preferably 500 nm or less, and more preferably 1 to 100 nm. By setting the average particle size of the supported copper nanoparticles within this range, it is easier to form a film with improved visible photocatalytic activity and improved transparency. The average particle size of the copper nanoparticles is measured by electron microscopy observation.

[0048] When using platinum nanoparticles, the particle size growth of the platinum nanoparticles is easily suppressed from the above viewpoint, and the average particle size of the platinum nanoparticles is preferably 500 nm or less, and more preferably 0.1 to 50 nm. By setting the average particle size of the supported platinum nanoparticles within this range, it is easier to form a film with improved visible photocatalytic activity and improved transparency. The average particle size of the platinum nanoparticles is measured by electron microscopy observation.

[0049] In the present invention, the amount of silver supported on the titania nanoparticles is preferably 200% by mass or less relative to the titanium dioxide in the titania nanoparticles, more preferably 0.0001 to 50% by mass, and even more preferably 0.01 to 10% by mass, from the viewpoint of aesthetics, washing durability, antimicrobial activity, and stability of the titania nanoparticles. By keeping it within this range, it is easy to maintain coatability and transparency, and it is particularly easy to improve antimicrobial activity and photocatalytic activity in the dark.

[0050] In the present invention, the amount of copper supported on the titania nanoparticles is preferably 100% by mass or less relative to the titanium dioxide in the titania nanoparticles, more preferably 0.0001 to 50% by mass, and even more preferably 0.01 to 10% by mass, from the viewpoint of antimicrobial activity and the stability of the titania nanoparticles. By keeping it within this range, it is easy to maintain coatability and transparency, and it is particularly easy to improve antimicrobial activity and photocatalytic activity in the dark.

[0051] In the present invention, the amount of platinum supported on the titania nanoparticles is preferably 100% by mass or less relative to the titanium dioxide in the titania nanoparticles, more preferably 0.0001 to 50% by mass, and even more preferably 0.01 to 10% by mass, from the viewpoint of aesthetics, washing durability, antimicrobial activity, and stability of the titania nanoparticles. By keeping it within this range, it is easy to maintain coatability and transparency, and it is particularly easy to improve antimicrobial activity and photocatalytic activity in the dark.

[0052] In the present invention, the ratio of the amount of silver supported on the titania nanoparticles to the amount of copper supported (amount of silver / amount of copper) is not particularly limited, but from the viewpoint of antimicrobial activity and the stability of the titania nanoparticles, 0.0001 to 2,000,000 is preferred, 0.001 to 10,000 is more preferred, and 0.01 to 100 is even more preferred.

[0053] In the present invention, the ratio of the amount of silver supported on the titania nanoparticles to the amount of platinum supported (amount of silver / amount of platinum) is not particularly limited, but from the viewpoint of antimicrobial activity and the stability of the titania nanoparticles, 0.0001 to 2,000,000 is preferred, 0.001 to 10,000 is more preferred, and 0.01 to 100 is even more preferred.

[0054] (1-2-2) Other antimicrobial compounds In addition to the antimicrobial metal compounds mentioned above, the antimicrobial compounds used in this invention can also include, for example, antimicrobial organic compounds. Examples of such antimicrobial organic compounds include synthetic organic antimicrobial agents such as quaternary ammonium salt compounds, isothiazolin compounds, pyridine compounds, phenol compounds, phthalimide compounds, benzalkonium chloride, and iodine compounds; natural antimicrobial agents such as chitosan, chitin, tea catechins, tannic acid, and persimmon tannin; and inorganic antimicrobial agents such as metal-containing zeolites. From the viewpoint of aesthetics, wash durability, and stability of antimicrobial activity, synthetic organic antimicrobial agents and natural antimicrobial agents are preferred, with benzalkonium chloride, tea catechins, and tannic acid being more preferred. These antimicrobial organic compounds can be used individually or in combination of two or more.

[0055] In the present invention, the amount of antimicrobial organic compound supported on the titania nanoparticles is preferably 100% by mass or less relative to the titanium dioxide in the titania nanoparticles, more preferably 0.0001 to 50% by mass, and even more preferably 0.01 to 10% by mass, from the viewpoint of aesthetics, wash durability, antimicrobial activity, and stability of the titania nanoparticles. By keeping it within this range, it is easy to maintain coatability and transparency, and it is particularly easy to improve antimicrobial activity and photocatalytic activity in the dark.

[0056] (1-3) Fibers In the present invention, "fiber" refers to any structure composed of fibers, regardless of whether it is a yarn, woven fabric, knitted fabric, nonwoven fabric, or sewn textile product. Furthermore, there are no particular restrictions on the fiber material that can be used. The fibers constituting the antimicrobial fibers of the present invention are not particularly limited, but examples include natural fibers such as cotton, linen, silk, and wool; recycled and semi-synthetic fibers such as rayon, cupro, acetate, and triacetate; synthetic fibers such as nylon, polyester, acrylic, and polyurethane; inorganic fibers such as glass, carbon, and metal; and mixtures thereof.

[0057] In addition to general clothing, the above-mentioned textile products include disposable diapers, sanitary napkins, incontinence pads, masks and other hygiene products, underarm pads, stockings, gloves, caps, dishcloths, wipers, cooking sheets, drip sheets, wet wipes, bedding (bed sheets, pillowcases, etc.), tote bags, slippers, tissues, nursing care supplies, towels, oral care sheets, food preservation sheets, dust collection filters, filtration filters, mops, bath mats, and clothing for hospitals and nursing homes.

[0058] 2. Method for producing antimicrobial fibers supported with titania nanoparticles The antimicrobial fiber of the present invention can be manufactured by supporting the titania nanoparticles on the fiber.

[0059] Specifically, the antimicrobial fiber of the present invention is (A) A step of mixing a titanium-containing substance, an organic acid, and water to obtain a dispersion, (B) A step of heating the dispersion obtained in step (A) at a temperature higher than 80°C for 1 hour or more, (C1) Optionally, a step of irradiating ultraviolet light onto a dispersion obtained by mixing the dispersion obtained in step (B) with an antimicrobial compound. (C2) Optionally, a step of mixing the dispersion obtained in step (B) with an antimicrobial compound, or (C3) Optionally, add an antimicrobial compound to the dispersion obtained in step (B) and allow it to stand. (D) A step to make the dispersion obtained in step (B), (C1), (C2), or (C3) into a more uniform dispersion, (E) A step of applying the dispersion obtained in step (D) to the fiber surface and drying it. It can be manufactured by a method that includes the following:

[0060] (2-1) Process (A) In step (A), a titanium-containing substance, an organic acid, and water are mixed to obtain a dispersion.

[0061] There are no particular restrictions on the titanium-containing substance used, as long as it becomes titanium oxide upon heating. In other words, titanium oxide and / or titanium oxide precursors are preferred as titanium-containing substances, specifically including titanium oxide; titanium hydroxide; titanium alkoxide; titanium halides such as titanium trichloride and titanium tetrachloride (especially those neutralized with a base); and metallic titanium. These titanium-containing substances can be used individually or in combination of two or more. Among these, titanium alkoxide, titanium hydroxide, or titanium halides (especially those neutralized with a base) are preferred from the viewpoint of the dispersibility, coating properties, and visible photocatalytic properties of the resulting titania, and titanium alkoxide is more preferred from the viewpoint of purity, dispersibility, coating properties, transparency, and visible photocatalytic properties.

[0062] Examples of titanium alkoxides include titanium tetraisopropoxide, titanium tetra-n-butoxide, titanium tetra-n-propoxide, and titanium tetraethoxide. From the viewpoint of cost, water solubility of by-products, applicability, and visible photocatalytic properties, titanium tetraisopropoxide is preferred.

[0063] In addition, depending on the combination of titanium alkoxide and organic acid, the resulting titania may act as a catalyst to release ester compounds that are poorly soluble in water. However, titania itself does not pose a problem (for example, in the combination of titanium tetra-n-butoxide and acetic acid, butyl acetate is formed and released when mixed and heated). However, from the viewpoint of obtaining a homogeneous dispersion, it is preferable to use a combination of organic acid and titanium alkoxide that yields an organic acid alkoxide with excellent water solubility.

[0064] For titanium halides (titanium tetrachloride, titanium trichloride, etc.), it is preferable to neutralize them with a base and wash the precipitate before use, from the viewpoint of impurities (halogens), corrosion of reactors during mass production, crystallinity control, coatability, transparency, and visible photocatalytic properties. In that case, it is preferable to use the resulting titania without drying it, from the viewpoint of its dispersibility.

[0065] When using solid materials containing titanium, such as titanium oxide or metallic titanium, the average particle size is preferably 100 nm or less, and more preferably 50 nm or less. While no lower limit is specifically set, it is typically around 1 nm. If the particle size is large, it can be used after being pulverized dry or wet using a planetary ball mill, paint shaker, etc. The average particle size of solid materials such as titanium oxide and metallic titanium is measured by electron microscopy (TEM).

[0066] The concentration of the titanium-containing substance in the dispersion produced in step (A) is preferably 0.01 to 5 mol / L, and more preferably 0.05 to 3 mol / L, from the viewpoint of productivity, viscosity of the reaction solution, coatability, transparency, and visible photocatalytic properties.

[0067] The acid used in the reaction is an organic acid, and a volatile acid is preferred, hence the chemical formula Cn H 2n+1 Examples include monocarboxylic acids represented by COOH(n=0~3) (monocarboxylic acids with 1 to 4 carbon atoms) and hydroxycarboxylic acids with 2 to 3 carbon atoms.

[0068] From the viewpoint of volatility, toxicity, and decomposability, n=0 formic acid and n=1 acetic acid are preferred as monocarboxylic acids, glycolic acid and lactic acid are preferred as hydroxycarboxylic acids, and acetic acid, glycolic acid, and lactic acid are particularly preferred from the viewpoint of water solubility and odor. These organic acids can be used individually or in combination of two or more.

[0069] From the viewpoints of dispersibility, coating properties, transparency, wash durability, antimicrobial properties, and cost, it is preferable to adjust the amount of organic acid used so that the number of moles of acyloxy groups per mole of titanium in the titanium-containing material is 1.5 moles or more, particularly 2 moles or more. The more organic acid is used, the easier it is to improve stability over time, coating properties, transparency, etc. Although there is no particular upper limit, it is generally preferable to adjust the number of moles of acyloxy groups per mole of titanium in the titanium-containing material so that it is 10 moles or less.

[0070] The concentration of the organic acid in the dispersion obtained in step (A) is preferably 0.02 to 10 mol / L, and more preferably 0.1 to 7 mol / L, from the viewpoint of dispersibility, coatability, transparency, wash durability, antimicrobial properties, and cost.

[0071] As the reaction solvent, it is preferable to use an aqueous solvent such as water as the main component (specifically, for example, 50% by mass or more), but it may also contain alcohol or ester during the reaction.

[0072] For example, when titanium tetraisopropoxide is used as a raw material, isopropyl alcohol is produced by reaction with organic acids. In addition, isopropyl esters of organic acids may be produced by heating. In other words, alcohol or ester may be added to the dispersion obtained in step (A), or it may be generated in the system. This alcohol or ester may be removed by heating in an open system below 100°C, by reducing the pressure, or it may remain in the reaction solution.

[0073] Furthermore, if alcohol is present in the dispersion, the average particle size of the resulting titania nanoparticles tends to decrease. Therefore, alcohol may be intentionally added to control the average particle size.

[0074] In this invention, inorganic acids (especially strong inorganic acids) such as nitric acid, hydrochloric acid, and sulfuric acid, which are commonly used in the hydrothermal synthesis reaction of titania nanoparticles, are generally not used. This is because the resulting titania nanoparticles will contain both anatase and brookite crystal forms, and also because of concerns regarding the storage stability of the resulting dispersion, corrosion of the equipment, impurities, and wastewater. However, if the dispersibility, transparency, and uniformity of the raw materials are to be improved and handling is facilitated, they may be used auxiliaryly in a range of, for example, 0.01 mol / L or less, as long as the effect is not impaired. In this case, the concentrations of N, Cl, and S elements in the dispersion obtained in step (A) will all be 0.01 mol / L or less.

[0075] The pH of the dispersion obtained in such a process (A) is preferably 2 or more and less than 6, and more preferably 2.1 to 5, from the viewpoint of preventing corrosion of the equipment, safety of handling, and dispersibility.

[0076] In step (A), there are no particular restrictions on the method of preparing the dispersion; the titanium-containing substance, organic acid, and water (solvent) may be mixed simultaneously or sequentially. In particular, on a mass production scale, it is preferable to add the titanium-containing substance while stirring after mixing the organic acid and water (solvent) to prevent aggregation and the formation of large clumps, and to facilitate continuous stirring. On the other hand, on a laboratory scale, it is preferable to add water while stirring after mixing the titanium-containing substance and organic acid.

[0077] (2-2) Process (B) In step (B), the dispersion obtained in step (A) is heated at a temperature higher than 80°C for at least one hour.

[0078] Step (B) may be carried out under normal pressure or under pressure in a sealed container. From the viewpoint of reducing the average particle size of the titania nanoparticles used in the present invention, it is preferable to carry out the step under normal pressure, specifically 0.09 to 0.11 MPa. When carrying out the step under pressure, from the viewpoint of forming a film with high visible photocatalytic activity and high transparency, it is preferable to carry out the reaction for a short time (for example, about 5 to 30 minutes) at 0.2 MPa or less (0.11 to 0.2 MPa).

[0079] During heating, stirring is preferable to ensure a sufficient reaction between the titanium-containing substance, the organic acid, and the water. There are no particular restrictions on the method of stirring; conventional methods can be used. Furthermore, the stirring time is preferably 1 hour or more, and more preferably 1.5 hours or more, from the viewpoint of ensuring a sufficient reaction between the titanium-containing substance, the organic acid, and the water. There is no particular upper limit on the stirring time, but it is usually 240 hours.

[0080] The heating temperature should be higher than 80°C, preferably 82°C or higher. Below 80°C, cracks are likely to occur, resulting in poor coatability and rapid detachment, making it difficult to form a coating. There is no particular upper limit on the heating temperature, but it is usually 120°C when reacting at atmospheric pressure.

[0081] The pH of the dispersion obtained in such a process (B) is preferably 2 or more and less than 6, and more preferably 2.1 to 5, from the viewpoint of preventing corrosion of the equipment, safety of handling, and dispersibility.

[0082] (2-3) Process (C1) In step (C1), the dispersion obtained by mixing the dispersion obtained in step (B) with an antimicrobial compound is irradiated with ultraviolet light.

[0083] When using silver nanoparticles as an antimicrobial compound, known or commercially available silver nanoparticles may be used. When synthesizing silver nanoparticles, for example, they can be synthesized based on the method described in "Silver Nanoparticles," Journal of the Adhesion Society of Japan, 2008, Vol. 44, No. 11, pp. 414-419.

[0084] There are no particular restrictions on the average particle size of the silver nanoparticles that can be used in this process, but from the viewpoint of antimicrobial activity and dispersion stability of the nanoparticles, 0.1 to 500 nm is preferred, and 1 to 100 nm is more preferred.

[0085] When using silver salts as antimicrobial compounds, it is preferable to avoid the dispersion (sol) obtained in steps (A) and (B) being acidic, and thus the dispersion after step (C1) becoming basic. For this reason, silver salts whose aqueous solutions are acidic or neutral are preferred. Specific examples of such silver salts include silver(I) chloride, silver(I) nitrate, silver organic acids (silver(I) lactate, silver(I) acetate, silver(I) citrate, silver(I) myristate, etc.), silver(I) sulfide, silver(I) oxide, silver(I) phosphate, silver(I) carbonate, silver(I) bromide, and silver(I) iodide. These silver salts can also be used as silver nanoparticle precursors that become silver nanoparticles upon reduction.

[0086] The silver nanoparticles and silver compounds described above can be used individually or in combination of two or more types.

[0087] When copper nanoparticles are used as antimicrobial compounds, known or commercially available copper nanoparticles may be used. When synthesizing copper nanoparticles, for example, they can be synthesized based on the method described in Cu and Cu-Based Nanoparticles: Synthesis and Applications in Catalysis Chemical Reviews, 2016, 116 (6), 3722-3811.

[0088] There are no particular restrictions on the average particle size of the copper nanoparticles that can be used in this process, but from the viewpoint of antimicrobial activity and dispersion stability of the nanoparticles, 0.1 to 200 nm is preferred, and 1 to 50 nm is more preferred.

[0089] When using copper salts as antimicrobial compounds, it is preferable to avoid the dispersion (sol) obtained in steps (A) and (B) being acidic, and thus the dispersion after step (C1) becoming basic. For this reason, copper salts whose aqueous solutions are acidic or neutral are preferred. Specific examples of such copper salts include organic copper acids (copper(II) acetate, copper(II) lactate, copper(II) citrate, copper(II) myristate, etc.), copper(II) sulfate, copper(II) nitrate, copper(II) phosphate, copper(I) oxide, copper(II) oxide, and copper(II) carbonate. These copper salts can also be used as copper nanoparticle precursors that become copper nanoparticles upon reduction.

[0090] The copper nanoparticles and copper compounds described above can be used individually or in combination of two or more types.

[0091] In particular, although not particularly limited, copper nanoparticles, copper nanoparticle precursors, monovalent copper salts, divalent copper salts, etc. are preferred from the viewpoint of the stability of copper in the resulting antimicrobial compound-supported titania nanoparticles and antimicrobial activity in light and dark (especially dark). Monovalent copper salts, divalent copper salts, etc. are more preferred, and divalent copper salts are even more preferred.

[0092] When using platinum nanoparticles as an antimicrobial compound, known or commercially available platinum nanoparticles can be used. When synthesizing platinum nanoparticles, for example, they can be synthesized based on the method described in "A Comprehensive Review on the Synthesis, Characterization, and Biomedical Application of Platinum Nanoparticles: Nanomaterials, 2019, 9(12), 1719".

[0093] There are no particular restrictions on the average particle size of the platinum nanoparticles that can be used in this process, but from the viewpoint of aesthetics, wash durability, antimicrobial properties, and dispersion stability of the nanoparticles, 0.1 to 500 nm is preferred, and 0.1 to 50 nm is more preferred.

[0094] When using platinum salts as antimicrobial compounds, it is preferable to avoid the dispersion (sol) obtained in steps (A) and (B) being acidic, and thus the dispersion after step (C1) becoming basic. For this reason, platinum salts whose aqueous solutions are acidic or neutral are preferred. Specific examples of such platinum salts include organic platinum acids (platinum(IV) oxalate, platinum(II) acetate, etc.), platinum(II) sulfate, platinum(II) nitrate, platinum(II) oxide, platinum(IV) oxide, platinum(II) cyanide, platinum(IV) chloride, platinum(II) chloride, platinum(IV) fluoride, platinum(IV) bromide, platinum(IV) iodide, etc. These platinum salts can also be used as platinum nanoparticle precursors that become platinum nanoparticles upon reduction.

[0095] The platinum nanoparticles and platinum compounds described above can be used individually or in combination of two or more types.

[0096] In particular, although not particularly limited, platinum nanoparticles, platinum nanoparticle precursors, divalent platinum salts, tetravalent platinum salts, etc. are preferred from the viewpoint of the stability of platinum in the resulting titania nanoparticles carrying the antimicrobial compound, and antimicrobial activity in light and dark (especially dark), and platinum nanoparticles are even more preferred.

[0097] In step (C1), the amount of the antimicrobial compound used is preferably 200% by mass or less, more preferably 0.0001 to 25% by mass, and even more preferably 0.01 to 10% by mass, based on the solid content when the dispersion obtained in step (B) is heated at 200°C, from the viewpoints of dispersibility, transparency, antimicrobial activity, stability of titania nanoparticles, etc. By setting it within this range, it is easy to maintain coatability and transparency, and particularly easy to improve the antimicrobial activity and photocatalytic activity in the dark.

[0098] In step (C1), the irradiation intensity of ultraviolet light is preferably 10 μW / cm 2 or more, more preferably 100 μW / cm 2 or more, and even more preferably 1 mW / cm 2 or more, from the viewpoints of the ease of loading the antimicrobial compound onto the titania nanoparticles, visible-light photocatalytic activity, reaction rate, productivity, etc. The upper limit value of the irradiation intensity of ultraviolet light is not particularly limited, but is usually 2 W / cm 2 .

[0099] In step (C1), it is easy to generate the antimicrobial metal compound on the surface of the titania nanoparticles by irradiating with ultraviolet light for 5 minutes or more, but from the viewpoints of visible-light photocatalytic activity, etc., it is preferably irradiated for 10 minutes or more, and more preferably irradiated for 20 minutes or more. The upper limit value of the irradiation time of ultraviolet light is not particularly limited, but is usually 5 hours.

[0100] In step (C1), the ultraviolet light irradiation may be pulse irradiation in which the ultraviolet light is pulsed and repeatedly irradiated at a predetermined time interval, or continuous irradiation in which the irradiation is continuously performed without interruption, and can be appropriately set according to the required characteristics.

[0101] In step (C1), the ultraviolet light irradiation is preferably performed at room temperature (20°C) or higher, and more preferably at 50°C or higher, from the viewpoints of the ease of loading the antimicrobial compound onto the titania nanoparticles, visible-light photocatalytic activity, reaction rate, productivity, etc. The upper limit value of the temperature is not particularly limited, but is usually 100°C when reacting under normal pressure.

[0102] In step (C1), when irradiating with ultraviolet light, it is preferable to stir the mixture to ensure that the dispersion obtained in step (B) and the antimicrobial compound react thoroughly. There are no particular restrictions on the method of stirring, and conventional methods can be used.

[0103] Process (C1) may be carried out under an air atmosphere or under anaerobics. Specifically, anaerobic conditions include inert gas atmospheres such as a nitrogen atmosphere or an argon atmosphere.

[0104] The pH of the dispersion obtained in this way varies depending on the type and amount of antimicrobial compound added, but 1 to 3 is preferred.

[0105] Subsequently, the titania nanoparticles supporting the antimicrobial compound can be recovered by conventional methods, such as precipitation and centrifugation. In other words, titania nanoparticles on which a large number of acyloxy groups are bonded to titanium atoms present on the surface, thereby supporting the antimicrobial compound, can be obtained.

[0106] (2-4) Processes (C2) and (C3) In the present invention, instead of the above-described step (C1), a step (C2) may be adopted in which the dispersion obtained in step (B) is mixed with an antimicrobial compound, or a step (C3) may be adopted in which an antimicrobial compound is added to the dispersion obtained in step (B) and allowed to stand.

[0107] The antimicrobial compound used is the same as in step (C1) described above. The amount of antimicrobial compound used is also the same as in step (C1) described above.

[0108] In step (C2), there are no particular restrictions on the method of mixing the dispersion obtained in step (B) with the antimicrobial compound, and any conventional method may be used. For example, the antimicrobial compound can be added to the dispersion obtained in step (B) and stirred. There are no particular restrictions on the method of stirring, and any conventional method may be used.

[0109] In step (C2), the mixing of the dispersion obtained in step (B) with the antimicrobial compound is preferably carried out at room temperature (20°C) or higher, and more preferably at 50°C or higher, from the viewpoint of ease of loading the antimicrobial compound onto titania nanoparticles, visible photocatalytic activity, reaction rate, and productivity. There is no particular upper limit on the temperature, but it is usually 100°C when reacting at atmospheric pressure.

[0110] Processes (C2) and (C3) may be carried out under an air atmosphere or under anaerobic conditions. Specifically, anaerobic conditions include inert gas atmospheres such as a nitrogen atmosphere or an argon atmosphere.

[0111] The pH of the dispersion obtained in this way varies depending on the type and amount of antimicrobial compound added, but 1 to 3 is preferred.

[0112] Of processes (C1), (C2), and (C3), process (C1) makes it easier to improve the loading efficiency by applying energy from the outside, while adopting process (C2) not only prevents the titania nanoparticle dispersion from becoming highly viscous but also makes it easier to obtain uniform particles.

[0113] Furthermore, in steps (C1), (C2), and (C3), heating can be used to further improve the loading efficiency of the antimicrobial compound.

[0114] Subsequently, the titania nanoparticles supported by the antimicrobial compound can be recovered by conventional methods, such as precipitation and centrifugation. In other words, a large number of acyloxy groups bond to the titanium atoms present on the surface, and the antimicrobial compound is supported, resulting in titania nanoparticles that are firmly attached.

[0115] (2-5) Process (D) The titania nanoparticle dispersion used in this invention is obtained by using the reaction solution obtained through steps (A), (B), (C1), (C2), or (C3) above, and by adding a dispersion step such as ultrasonic dispersion as needed to produce an even more uniform dispersion. In this case, since a uniform dispersion could not be obtained without using a dispersant in conventional visible light-responsive photocatalyst dispersions, a dispersant may also be added in this invention. However, even without adding a dispersant, a dispersion with far better dispersibility than that of ordinary visible light-responsive photocatalysts can be obtained. As a result of the good dispersibility, the crack resistance of the coating is also excellent. Furthermore, as a result of not needing to add a dispersant, a dense titania coating becomes possible, and it is excellent in terms of coatability and transparency, as well as visible light photocatalytic activity.

[0116] In this case, in the titania nanoparticle dispersion used in the present invention, the total amount of the titania nanoparticle dispersion is set to 100% by mass, and the content of water, which is the main solvent, is preferably 50% by mass or more, and particularly 60% by mass or more, from the viewpoint of ease of coating and film properties of the coating.

[0117] Furthermore, it is possible to remove the titania nanoparticles used in this invention from the reaction solution and change the solvent. Water may be removed from the reaction solution by centrifugation or filtration membrane and replaced with an organic solvent. In this case, it is preferable not to dry the titania nanoparticles used in this invention from the viewpoint of dispersibility, transparency, etc.

[0118] Organic solvents used in dispersions include alcohols. These alcohols include aliphatic alcohols with 1 to 6 carbon atoms such as methanol, ethanol, and isopropanol, as well as non-aliphatic alcohols such as α-terpineol; glycol solvents such as butyl carbitol (diethylene glycol monobutyl ether), hexylene glycol (2-methyl-2,4-pentanediol), ethylene glycol-2-ethylhexyl ether, ethylene glycol monomethyl ether, and propylene glycol monomethyl ether; and diols such as 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol.

[0119] Furthermore, even if the solvent does not have an OH group, it is sufficient if it has affinity for titania and other solvents (water, alcohol, etc.), and examples include diethylene glycol butyl methyl ether, tripropylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol diacetate, triethylene glycol diacetate, and tetraethylene glycol diacetate. Among these, diethylene glycol monobutyl ether acetate and tetraethylene glycol dimethyl ether are preferred from the viewpoint of boiling point, etc.

[0120] The titania nanoparticle dispersion used in this invention can be made into a coating by adjusting its viscosity according to the application. For example, it is preferable to use a low viscosity when used for spin coating, dip coating, spraying, etc., to adjust the viscosity to a higher level when used for brush coating, squeegeeing, etc., and to adjust the viscosity to an even higher level when used for screen printing to suppress fluidity. The coating film obtained in this way is a dense coating as described above.

[0121] (2-6) Process (E) In step (E), the dispersion obtained in step (D) is applied to the fiber surface and dried.

[0122] In step (E), there are no particular restrictions on the method of applying the dispersion obtained in step (D) to the fiber surface, and any conventional method may be used. For example, fibers can be added to the dispersion obtained in step (D) and stirred. There are no particular restrictions on the method of stirring, and any conventional method may be used. Alternatively, in addition to the immersion method described above, other methods for applying the dispersion obtained in step (D) to the fiber surface include the roller touch method, spray method, shower method, impregnation method, etc.

[0123] In step (E), the solid content concentration of the dispersion to be attached to the fiber surface is preferably less than 50% by mass, more preferably 0.00001 to 40% by mass, and even more preferably 0.001 to 5% by mass, from the viewpoint of titania nanoparticle loading efficiency, ease of coating, and coating film properties. In order to achieve the above solid content concentration within this range, the dispersion obtained in step (D) can be appropriately diluted with the above solvent.

[0124] In step (E), the amount of dispersion liquid to be attached to the fiber surface is preferably 1 to 10,000% by mass relative to the fiber, more preferably 10 to 1,000% by mass, and even more preferably 20 to 500% by mass, from the viewpoint of the load-bearing efficiency of titania nanoparticles, ease of coating, and film properties of the coating.

[0125] In step (E), the drying temperature is preferably 0 to 200°C, more preferably 5 to 160°C, and even more preferably 10 to 100°C, from the viewpoint of the stability of the fibers and the antimicrobial compound.

[0126] In step (E), the drying time is preferably 48 hours or less, more preferably 24 hours or less, and even more preferably 0.1 seconds to 6 hours, from the viewpoint of the stability of the fibers and the antimicrobial compound.

[0127] The drying in process (E) may be carried out under normal pressure or under reduced pressure.

[0128] After process (E), the amount of titania nanoparticles supported on the fibers should be 0.001 to 5000 mg / m² in solid content, from the viewpoint of fiber aesthetics, wash durability, and antimicrobial activity. 2 Preferably, 0.01 to 1000 mg / m² 2 More preferably, 0.1 to 100 mg / m² 2 That is even more preferable. [Examples]

[0129] The present invention will be specifically described based on the examples, but the present invention is not limited to these examples. Furthermore, antibacterial activity was determined to be extremely high when the activity value is 3 or higher, and to be inactive when the activity value is 2 or lower.

[0130] [Example 1] 142.1 g (0.5 mol) of titanium tetraisopropoxide was mixed with 120 g (2 mol) of acetic acid and stirred for 60 minutes, then 538 g of water was added. The resulting dispersion had a titanium tetraisopropoxide concentration of 0.625 mol / L, an acetic acid concentration of 2.5 mol / L, and a pH of 2.2. A large amount of translucent precipitate formed, but after stirring for 60 minutes and then heating, the precipitate completely dissolved at 70°C. In this dispersion, the concentrations of inorganic acid, and the concentrations of elements N, Cl, and S were all 0 mol / L.

[0131] Subsequently, the mixture was stirred at atmospheric pressure (0.10 MPa) and 85°C for 3 hours, yielding a translucent, homogeneous titania dispersion without the use of organic dispersants. When ultrasonic dispersion was applied to this dispersion, the viscosity decreased and the transparency increased. This dispersion had a water content of 67% by mass and a pH of 2.3.

[0132] This dispersion was dried to obtain titania nanoparticles. The BET specific surface area of ​​these titania nanoparticles was measured to be 250 m². 2 The particle size was [value missing] / g. TEM observation revealed an average particle size of approximately 3 nm. X-ray diffraction analysis of the obtained titania nanoparticles showed that 100% were of the anatase type (no other crystalline forms were present).

[0133] The TG-DTA titania nanoparticles, which were dried using a moisture meter at 200°C until no further mass loss occurred, were then heated to 600°C under an air atmosphere at a rate of 3°C / min. The mass loss above 200°C was 10% by mass. This mass loss above 200°C corresponds to the loss due to the elimination of acetic acid, an organic acid. Since liberated acetic acid almost completely volatilizes below 200°C, a mass loss of 10% by mass above 200°C suggests that a large number of acetyl groups, which are acyloxy groups, are bonded to the titanium atoms on the surface of the titania nanoparticles in the form of -OCOCH3.

[0134] Next, the dispersion was diluted to a solid content concentration of 2.5 wt%, and fibers (100% cotton rags) were immersed in the solution. The fibers coated with the solution at a weight ratio of 100% to the fibers were dried at 80°C for 2 hours. At this time, the dried fibers had no roughness on the surface, and no powder slipped off or adhered when the surface was traced with a cotton swab. An antibacterial test targeting photocatalysts was conducted on the dried fibers. In this test, the antibacterial test was conducted referencing the glass contact method of JIS R1702, with Escherichia coli (K-12) as the bacterial species in contact with the liquid, a contact time of 4 hours, and an ultraviolet irradiation intensity of 0.25 mW / cm² during contact with the liquid. 2 The obtained antibacterial activity value was very high, at 3 or higher.

[0135] [Example 2] 30 g (5.9% by mass) of a dispersion containing titania nanoparticles, obtained by the same method as in Example 1 except for a change in the amount of water, was mixed with 137.5 mg of silver(I) acetate, and irradiated at an intensity of 1.5 mW / cm² under an air atmosphere. 2 A dispersion was obtained by continuously irradiating the material with ultraviolet light (continuous irradiation) while stirring and mixing at room temperature (20°C) for 30 minutes. In other words, the supported silver was added so that it amounted to 5% by mass relative to the weight of titanium oxide. This dispersion had a water content of approximately 95% by mass and a pH of 2.3.

[0136] Next, the dispersion was diluted to a solid content concentration of 2.5 wt%, and fibers (100% cotton rags) were immersed in the solution. The fibers coated with the solution at a weight ratio of 100% to the fibers were dried at 80°C for 2 hours. At this time, the dried fibers had no roughness on the surface, and no powder slipped off or adhered when the surface was traced with a cotton swab. An antibacterial test was conducted on the dried fibers targeting substances that exhibit antibacterial properties even in the dark. In this test, the antibacterial test was conducted in accordance with JIS L1902, with Escherichia coli (K-12) as the bacterial species in contact with the liquid and a contact time of 2 hours. A very high antibacterial activity value of 3 or higher was obtained.

[0137] [Example 3] In the same manner as in Example 2, 30 g of a dispersion containing silver nanoparticle-supported titania nanoparticles with a solid content of 2.5 wt% was obtained, and 270 g of water was added to the dispersion to dilute it 100-fold. A fiber (100% cotton rag) was immersed in this dispersion, and the fiber coated with the dispersion at a weight ratio of 100% relative to the fiber was dried at 80°C. At this time, the fiber after drying had no roughness on the surface, and no powder slippage or adhesion was observed when the surface was traced with a cotton swab or the like. An antibacterial test was performed on the dried fiber targeting substances that exhibit antibacterial properties even in the dark. In this test, the antibacterial test was conducted in accordance with JIS L1902, with Escherichia coli (K-12) as the bacterial species in contact with the liquid and a contact time of 2 hours. A very high antibacterial activity value of 3 or higher was obtained.

[0138] [Example 4] A dispersion was obtained by adding 137.5 mg of silver(I) nitrate to 30 g (5.9% by mass) of a dispersion containing titania nanoparticles, obtained in the same manner as in Example 1 except for a change in the amount of water, and stirring at room temperature (20°C) for 30 minutes. In other words, the silver ions were added so that the supported silver ions amounted to 5% by mass relative to the weight of titanium dioxide. This dispersion had a water content of approximately 95% by mass and a pH of 2.3.

[0139] Next, the dispersion was diluted to a solid content concentration of 2.5 wt%, and fibers (100% cotton rags) were immersed in the solution. The fibers coated with the solution at a weight ratio of 100% to the fibers were dried at 80°C for 2 hours. At this time, the dried fibers had no roughness on the surface, and no powder slipped off or adhered when the surface was traced with a cotton swab. An antibacterial test was conducted on the dried fibers targeting substances that exhibit antibacterial properties even in the dark. In this test, the antibacterial test was conducted in accordance with JIS L1902, with Escherichia coli (K-12) as the bacterial species in contact with the liquid and a contact time of 2 hours. A very high antibacterial activity value of 3 or higher was obtained.

[0140] [Example 5] 30 g (5.9% by mass) of a dispersion containing titania nanoparticles, obtained by the same method as in Example 1 except for a change in the amount of water, was mixed with 137.5 mg of silver(I) acetate, and irradiated at an intensity of 1.5 mW / cm² under an air atmosphere. 2 A dispersion was obtained by continuously irradiating the material with ultraviolet light (continuous irradiation) while stirring and mixing at room temperature (20°C) for 30 minutes. In other words, the supported silver was added so that it amounted to 5% by mass relative to the weight of titanium oxide. This dispersion had a water content of approximately 95% by mass and a pH of 2.3.

[0141] Next, the dispersion was diluted to a solid content concentration of 2.5 wt%, and fibers (100% polypropylene nonwoven fabric) were immersed in the solution. The fibers coated with the solution at a weight ratio of 100% to the fibers were dried at 80°C for 2 hours. At this time, the dried fibers had no roughness on the surface, and no powder slipped off or adhered when the surface was traced with a cotton swab. An antibacterial test was conducted on the dried fibers targeting substances that exhibit antibacterial properties even in the dark. At this time, since the polypropylene nonwoven fabric is water-repellent, it was considered unsuitable to apply JIS L1902, and the antibacterial test was conducted in the dark, using Escherichia coli (K-12) as the contact bacterium, and the contact time was 2 hours, based on JIS R1702. The obtained antibacterial activity value was very high, above 3.

[0142] [Example 6] An aqueous solution was prepared by adding 2 g of Clean Ace to 100 g of deionized water and stirring. 2 g of the fibers obtained in Example 1 were immersed in this solution, heated to 80°C, for 2 hours. After immersion, the fibers were thoroughly rinsed with tap water and dried at 80°C for 2 hours. An antibacterial test targeting photocatalysis was conducted on the dried fibers. The antibacterial test followed the glass contact method of JIS R1702, using Escherichia coli (K-12) as the bacterial species in contact with the liquid, a contact time of 4 hours, and an ultraviolet irradiation intensity of 0.25 mW / cm² during contact. 2 The obtained antibacterial activity value was very high, at 3 or higher.

[0143] [Example 7] An aqueous solution was prepared by adding 2 g of Clean Ace to 100 g of deionized water and stirring. 2 g of the fibers obtained in Example 2 were immersed in this solution, heated to 80°C, for 2 hours. After immersion, the fibers were rinsed thoroughly with tap water and dried at 80°C for 2 hours. An antibacterial test was conducted on the dried fibers, targeting substances that exhibit antibacterial properties even in the dark. The antibacterial test was conducted in accordance with JIS 1902, using Escherichia coli (K-12) as the liquid-contacting bacterium and a contact time of 2 hours. The obtained antibacterial activity value was very high, above 3.

[0144] [Example 8] An aqueous solution was prepared by adding 2 g of Clean Ace to 100 g of deionized water and stirring. 2 g of the fibers obtained in Example 4 were immersed in this solution, heated to 80°C, for 2 hours. After immersion, the fibers were thoroughly rinsed with tap water and dried at 80°C for 2 hours. An antibacterial test was conducted on the dried fibers, targeting substances that exhibit antibacterial properties even in the dark. The antibacterial test was conducted in accordance with JIS L1902, with Escherichia coli (K-12) as the bacterial species in contact with the liquid and a contact time of 2 hours. The obtained antibacterial activity value was very high, above 3.

[0145] [Example 9] An aqueous solution was prepared by adding 2 g of Clean Ace to 100 g of deionized water and stirring. 2 g of the fibers obtained in Example 5 were immersed in this solution, heated to 80°C, for 2 hours. After immersion, the fibers were thoroughly rinsed with tap water and dried at 80°C for 2 hours. An antibacterial test was conducted on the dried fibers targeting substances that exhibit antibacterial properties even in the dark. At this time, since the polypropylene nonwoven fabric is water-repellent, the application of JIS L1902 was considered unsuitable. Therefore, the antibacterial test was conducted in the dark, using Escherichia coli (K-12) as the contact bacterium, and the contact time was 2 hours, based on JIS R1702. A very high antibacterial activity value of 3 or higher was obtained.

[0146] [Comparative Example 1] Titania nanoparticles P-25 (manufactured by Evonik Degussa, specific surface area 50 m²) 2 10 g of titania nanoparticles (average particle size 21 nm, no acyl groups on the surface) were mixed with 30 g of acetic acid and 160 g of water, and after stirring and mixing at room temperature (20°C) for 30 minutes, ultrasonic dispersion was performed to obtain a suspension. Even after stirring and mixing, a uniform solution was not obtained. Next, fibers were immersed in a solution diluted with this dispersion to a solid content concentration of 2.5 wt%, and fibers coated with the solution at a weight ratio of 100% to the fibers (100% cotton rags) were dried at 80°C for 2 hours. At this time, the dried fibers had a rough surface, and when the surface was traced with a cotton swab, white powder adhered to the cotton swab. From this, it can be understood that Comparative Example 1 had lower adhesion between titania nanoparticles and fiber samples compared to Example 1. An antibacterial test was performed on the dried fibers targeting substances that have antibacterial properties even in the dark. At this time, the antibacterial test was performed referring to JIS L1902, with Escherichia coli (K-12) as the liquid-contacting bacterium species and a liquid contact time of 2 hours. The obtained antibacterial activity value was very high, at 3 or higher.

[0147] [Comparative Example 2] 30 g (5.9% by mass) of the suspension obtained in Comparative Example 1 was mixed with 137.5 mg of silver(I) acetate, and the mixture was irradiated at an intensity of 1.5 mW / cm² under an air atmosphere. 2A suspension containing silver nanoparticles was obtained by continuously irradiating the sample with ultraviolet light (continuous irradiation) while stirring and mixing at room temperature (20°C) for 30 minutes. Even after stirring and mixing, a uniform solution was not obtained. Next, a fiber (100% cotton rag) was immersed in a solution diluted with this dispersion to a solid content concentration of 2.5 wt%, and the fiber coated with the solution at a weight ratio of 100% to the fiber was dried at 80°C for 2 hours. At this time, the fiber had a rough surface after drying, and when the surface was traced with a cotton swab, brown powder adhered to the swab. From this, it can be understood that the adhesion between the titania nanoparticles and the fiber sample in Comparative Example 2 was lower than that in Example 2. An antibacterial test was performed on the dried fiber targeting substances that have antibacterial properties even in the dark. At this time, the antibacterial test was conducted with reference to JIS L1902, with Escherichia coli (K-12) as the bacterium species in contact with the liquid and a contact time of 2 hours. A very high antibacterial activity value of 3 or higher was obtained.

[0148] [Comparative Example 3] 30 g (5.9% by mass) of the suspension obtained in Comparative Example 1 was mixed with 137.5 mg of silver(I) acetate, and the mixture was irradiated at an intensity of 1.5 mW / cm² under an air atmosphere. 2A suspension containing silver nanoparticles was obtained by continuously irradiating the material with ultraviolet light (continuous irradiation) while stirring and mixing at room temperature (20°C) for 30 minutes. Next, 90g of the silane coupling agent KR-516 was added as a binder to 10g of the suspension containing silver nanoparticles to obtain a suspension containing silver nanoparticles and the binder. Then, a fiber (100% cotton rag) was immersed in this suspension, and the fiber coated with the suspension at a weight ratio of 100% to the fiber was dried at 80°C to obtain a fiber sample. At this time, the fiber surface was rough after drying, but no powder adhered to the cotton swab when the surface was traced. From this, it can be understood that Comparative Example 3 has higher adhesion between the titania nanoparticles and the fiber sample compared to Comparative Example 1. An antibacterial test was performed on the dried fiber targeting substances that have antibacterial properties even in the dark. At this time, the antibacterial test was performed referring to JIS L1902, with Escherichia coli (K-12) as the bacterium species in contact with the liquid and a contact time of 2 hours. The obtained antibacterial activity value was 2.1, and although antibacterial activity was observed, it was weaker compared to Examples 2 and 3 and Comparative Example 2. From this, it can be understood that in Comparative Example 3, the adhesion between titania nanoparticles and fibers was improved compared to Comparative Example 2 due to the binder, but at the same time, the antibacterial activity decreased.

[0149] [Comparative Example 4] An aqueous solution was prepared by adding 2 g of Clean Ace to 100 g of deionized water and stirring. 2 g of the fibers obtained in Comparative Example 1 were immersed in this solution, heated to 80°C, for 2 hours. After immersion, the fibers were thoroughly rinsed with tap water and dried at 80°C for 2 hours. An antibacterial test was conducted on the dried fibers, targeting substances that exhibit antibacterial properties even in the dark. The antibacterial test was conducted in accordance with JIS L1902, using Escherichia coli (K-12) as the contact bacterium and a contact time of 2 hours. The obtained antibacterial activity value was 2 or less, indicating no antibacterial activity. From this, it can be understood that Comparative Example 4 showed a greater decrease in antibacterial activity after washing compared to Example 6.

[0150] [Comparative Example 5] An aqueous solution was prepared by adding 2 g of Clean Ace to 100 g of deionized water and stirring. 2 g of the fibers obtained in Comparative Example 2 were immersed in this solution, heated to 80°C, for 2 hours. After immersion, the fibers were thoroughly rinsed with tap water and dried at 80°C for 2 hours. An antibacterial test was conducted on the dried fibers, targeting substances that exhibit antibacterial properties even in the dark. The antibacterial test was conducted in accordance with JIS L1902, using Escherichia coli (K-12) as the contacting bacterium and a contact time of 2 hours. The obtained antibacterial activity value was 2 or less, indicating no antibacterial activity. From this, it can be understood that Comparative Example 5 showed a greater decrease in antibacterial activity after washing compared to Example 7.

[0151] [Table 1]

Claims

1. An antimicrobial fiber on which titania nanoparticles are supported, The titania nanoparticles have acyloxy groups bonded to at least some of the titanium atoms present on their surface. When the titania nanoparticles are heated to 600°C using a differential thermogravimetric analyzer, the mass loss at temperatures above 200°C is 5% by mass or more. The amount of titania nanoparticles supported is 0.01 to 5000 mg / m² as solid content. Binder-free, Antimicrobial fiber.

2. The titania nanoparticles are supported with an antimicrobial compound, as described in claim 1, for the antimicrobial fiber.

3. The antimicrobial fiber according to claim 2, wherein the antimicrobial compound comprises an antimicrobial metal compound.

4. The antimicrobial fiber according to claim 3, wherein the antimicrobial metal compound comprises at least one selected from the group consisting of silver, copper, and platinum.

5. The antimicrobial fiber according to claim 3 or 4, wherein the antimicrobial metal compound contains silver.

6. The antimicrobial fiber according to any one of claims 3 to 5, wherein the antimicrobial metal compound is silver nanoparticles.

7. The antimicrobial fiber according to any one of claims 2 to 6, wherein the amount of the antimicrobial compound supported is 0.0001 to 50% by mass, with the mass of titanium oxide in the titania nanoparticles being 100% by mass.

8. The antimicrobial fiber according to any one of claims 1 to 7, wherein the acyloxy group is a group represented by -OCOR (wherein R represents a hydrogen atom, a C1-C3 alkyl group, or a C1-C2 hydroxyalkyl group) and is bonded to a titanium atom.

9. The antimicrobial fiber according to any one of claims 1 to 8, wherein the acyloxy group is an acyloxy group derived from at least one organic acid selected from the group consisting of monocarboxylic acids having 1 to 4 carbon atoms and hydroxycarboxylic acids having 2 to 3 carbon atoms.

10. The antimicrobial fiber according to claim 9, wherein the organic acid is acetic acid and / or lactic acid.

11. The antimicrobial fiber according to claim 9 or 10, wherein the organic acid is acetic acid.

12. The antimicrobial fiber according to any one of claims 1 to 11, wherein the titania nanoparticles are composed of anatase type.

13. The specific surface area of ​​the titania nanoparticles is 150 to 500 m². ２ The antimicrobial fiber according to any one of claims 1 to 12, wherein the amount is / g.

14. The antimicrobial fiber according to any one of claims 1 to 13, wherein the average particle size of the titania nanoparticles is 1 to 5 nm.

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