Antibacterial photocatalyst material

Abstract

To provide an antibacterial photocatalyst material that exhibits superior antibacterial performance in light conditions.SOLUTION: An antibacterial photocatalyst material according to the present invention includes a first resin layer and a second resin layer that covers the surface of the first resin layer, the first resin layer incorporating an antibacterial agent, and the second resin layer incorporating a photocatalyst material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antibacterial photocatalytic material. [Background technology]

[0002] In recent years, with growing awareness of public health, efforts have been made to impart antibacterial properties to a variety of products. For example, melt-spun fibers containing antibacterial agents are known (see, for example, Patent Document 1). Also, photocatalytic materials in which a photocatalyst is kneaded with a resin are known (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-191801 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-314509 Summary of the Invention [Problem to be solved by the invention]

[0004] When conventional antibacterial agent-containing fibers become wet, the antibacterial agent elutes from the fibers, causing the fibers to lose their antibacterial properties. Furthermore, when photocatalysts are kneaded with resin, the surface of the photocatalyst is covered with resin, preventing the photocatalytic activity from being fully utilized. The present invention has been made in view of the above circumstances, and provides an antibacterial photocatalytic material that has excellent antibacterial properties in bright light. [Means for solving the problem]

[0005] The present invention provides an antibacterial photocatalytic material having a first resin layer and a second resin layer covering the surface of the first resin layer, the first resin layer containing an antibacterial agent, and the second resin layer containing a photocatalytic substance. [Effects of the Invention]

[0006] The antibacterial photocatalytic material of the present invention can have excellent antibacterial properties in bright light, as demonstrated by experiments conducted by the inventors of the present application. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic perspective view of an antibacterial photocatalytic material according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view of the antibacterial photocatalytic material shown in FIG. 1. [Figure 3] 1 is a schematic cross-sectional view of a resin-coated member including an antibacterial photocatalytic material according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] The antibacterial photocatalytic material of the present invention has a first resin layer and a second resin layer covering the surface of the first resin layer, the first resin layer containing an antibacterial agent, and the second resin layer containing a photocatalytic substance.

[0009] The photocatalytic substance preferably includes a visible light responsive photocatalytic substance. The visible light responsive photocatalytic material preferably contains tungsten oxide. The content of the visible light responsive photocatalytic substance in the second resin layer is preferably 0.001 wt % or more and 3.0 wt % or less. The content of the antibacterial agent in the first resin layer is preferably 0.01 wt % or more and 5.0 wt % or less.

[0010] The antibacterial agent is preferably a compound containing divalent copper. The first resin layer is preferably fibrous. Preferably, the antibacterial photocatalytic material has a core-sheath structure, the first resin layer being the core of the core-sheath structure, and the second resin layer being the sheath of the core-sheath structure.

[0011] The present invention will be described in more detail below with reference to several embodiments. The configurations shown in the drawings and the following description are examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

[0012] First embodiment FIG. 1 is a schematic perspective view of the antibacterial photocatalytic material of this embodiment, and FIG. 2 is a schematic cross-sectional view of the antibacterial photocatalytic material shown in FIG. The antibacterial photocatalytic material 10 of this embodiment has a first resin layer 2 and a second resin layer 3 covering the surface of the first resin layer 2, the first resin layer 2 containing an antibacterial agent, and the second resin layer 3 containing a photocatalytic substance. The antibacterial photocatalytic material 10 is a fiber having a core-sheath structure, with the first resin layer 2 being the core of the core-sheath structure and the second resin layer 3 being the sheath of the core-sheath structure.

[0013] The antibacterial photocatalytic material 10 is a material that has antibacterial properties and contains a photocatalyst, and is a fiber with a core-sheath structure. The antibacterial photocatalytic material 10 may be a fiber that constitutes fabric (woven fabric, nonwoven fabric, knitted fabric, etc.), a fiber that constitutes thread, string, or rope, a fiber that constitutes paper, a fiber that constitutes netting, or a fiber contained in a composite material. The antibacterial photocatalytic material 10 may also be a thermoplastic synthetic fiber.

[0014] The first resin layer 2 is a layer of resin containing an antibacterial agent, and is the core of a core-sheath structure. The first resin layer 2 is fibrous. The resin contained in the first resin layer 2 is the main component of the first resin layer 2, and is, for example, a polyolefin resin such as polyethylene or polypropylene, polyester, nylon, acrylic resin, PET, polyacrylonitrile, polyvinyl chloride, aromatic polyamide resin, polyvinyl alcohol resin, polyvinylidene chloride, polyurethane, polychlor, polylactic acid, etc. The resin contained in the first resin layer 2 is preferably a thermoplastic resin. This makes it possible to produce the antibacterial photocatalyst material 10 by melt spinning.

[0015] The antibacterial agent contained in the first resin layer 2 is an antibacterial agent contained in a resin, and is, for example, a water-soluble compound containing divalent copper, a water-soluble compound containing silver, a substance from which copper ions elute, or a substance from which silver ions elute. Examples of water-soluble compounds containing divalent copper include copper gluconate, copper chlorophyll, and copper stearate. When an organic copper complex such as copper chlorophyll is used as the antibacterial agent and the antibacterial photocatalyst material 10 is produced by melt spinning, the resin contained in the first resin layer 2 is preferably a low-melting-point resin (for example, a polyolefin resin such as polyethylene) in consideration of the heat resistance of the antibacterial agent. The content of the antibacterial agent in the first resin layer 2 is, for example, 0.01 wt% to 5.0 wt%, preferably 0.1 wt% to 3.0 wt%, and more preferably 0.1 wt% to 1.0 wt%.

[0016] The second resin layer 3 is a layer of resin containing a photocatalytic substance, and is the sheath portion of the core-sheath structure. The second resin layer 3 can be provided so as to coat the first resin layer 2. The second resin layer 3 can also be provided so as to be in contact with the first resin layer 2. The second resin layer 3 can also be provided so as to cover the entire periphery of the first resin layer 2 (excluding the ends in the longitudinal direction). By covering the surface of the first resin layer 2 with the second resin layer 3, it is possible to prevent the antibacterial agent contained in the first resin layer 2 from leaching out when it gets wet, etc., and the antibacterial photocatalytic material 10 can maintain antibacterial properties for a long period of time.

[0017] The resin contained in the second resin layer 3 is the main component of the second resin layer 3, and is, for example, a polyolefin resin such as polyethylene or polypropylene, polyester, nylon, polyvinyl chloride, acrylic resin, or polyvinyl alcohol resin. The resin contained in the second resin layer 3 may be the same type of resin as the resin contained in the first resin layer 2. The resin contained in the second resin layer 3 is preferably a thermoplastic resin. This makes it possible to produce the antibacterial photocatalyst material 10 by melt spinning.

[0018] The photocatalytic substance contained in the second resin layer 3 is a photocatalytic substance kneaded into the resin, and is, for example, a visible light responsive photocatalytic substance. The visible light responsive photocatalytic substance may contain tungsten oxide particles (WO3 particles). The tungsten oxide particles may have a composition deviating from the stoichiometric composition as long as they have photocatalytic activity. Furthermore, the tungsten oxide particles may contain impurity atoms or additive atoms to the extent that the photocatalytic activity is not lost. Furthermore, the visible light responsive photocatalytic substance may have a co-catalyst on the surface of the tungsten oxide particles. The co-catalyst may include, for example, a platinum group metal such as Pt, Pd, Rh, Ru, Os, or Ir. The proportion of the photocatalytic substance in the second resin layer 3 is, for example, 0.001 wt% or more and 3.0 wt% or less, and preferably 0.01 wt% or more and 1.0 wt% or less.

[0019] The inclusion of a photocatalytic substance in the second resin layer 3 allows the antibacterial photocatalytic material 10 to have excellent antibacterial properties in bright places. It is thought that the photocatalytic substance contained in the second resin layer 3 receives light, and excited electrons and holes are generated, which act on the nearby antibacterial agent, resulting in antibacterial components (such as copper ions), which diffuse within the second resin layer 3 and reach the surface of the antibacterial photocatalytic material 10.

[0020] The antibacterial photocatalytic material 10 may be produced by using a melt spinning method, or by coating a fibrous first resin layer 2 with a second resin layer 3 using a known coating method. When producing the antibacterial photocatalytic material 10 by the melt spinning method, a core-sheath type fiber spinning nozzle can be used.

[0021] Second embodiment FIG. 3 is a schematic cross-sectional view of a resin-coated member 15 including the antibacterial photocatalytic material 10 of this embodiment. The resin-coated member 15 includes a substrate 4 and an antibacterial photocatalytic material 10 covering the surface of the substrate 4. The antibacterial photocatalytic material 10 includes a first resin layer 2 covering the surface of the substrate 4, and a second resin layer 3 covering the surface of the first resin layer 2. The antibacterial photocatalytic material 10 can have a layered coating structure in which the first resin layer 2 and the second resin layer 3 are provided in this order on the surface of the substrate 4. The first resin layer 2 contains an antibacterial agent, and the second resin layer 3 contains a photocatalytic substance.

[0022] The substrate 4 is, for example, wallpaper, curtains, interior walls of buildings, exterior walls of buildings, ceilings of rooms, floors of buildings, furniture, windows, glass, plastics, metals, ceramics, wood, stone, cement, concrete, fibers, filters, fabrics, paper, leather, etc.

[0023] In the first embodiment, the first resin layer 2 is fibrous, but in the second embodiment, the first resin layer 2 is a coating layer of the substrate 4. The resin contained in the first resin layer 2 is the main component of the first resin layer 2, and is, for example, a polyolefin resin such as polyethylene or polypropylene, polyester, nylon, polyvinyl chloride, an acrylic resin, or a polyvinyl alcohol resin.

[0024] The antibacterial agent contained in the first resin layer 2 is an antibacterial agent contained in the resin, such as a water-soluble compound containing divalent copper, a water-soluble compound containing silver, a substance that elutes copper ions, or a substance that elutes silver ions. The content of the antibacterial agent in the first resin layer 2 is, for example, 0.01 wt% to 5.0 wt%, preferably 0.1 wt% to 3 wt%, and more preferably 0.1 wt% to 1.0 wt%.

[0025] The second resin layer 3 is a layer of a resin containing a photocatalytic substance, and is a layer that coats the substrate 4 together with the first resin layer 2. The second resin layer 3 can be provided so as to be in contact with the first resin layer 2. By covering the surface of the first resin layer 2 with the second resin layer 3, it is possible to prevent the antibacterial agent contained in the first resin layer 2 from leaching out when it gets wet, etc., and the antibacterial photocatalytic material 10 can maintain antibacterial properties for a long period of time.

[0026] The resin contained in the second resin layer 3 is the main component of the second resin layer 3 and is, for example, a polyolefin resin such as polyethylene or polypropylene, polyester, nylon, polyvinyl chloride, an acrylic resin, a polyvinyl alcohol resin, etc. The resin contained in the second resin layer 3 may be the same type of resin as the resin contained in the first resin layer 2.

[0027] The photocatalytic substance contained in the second resin layer 3 has been explained in the first embodiment, and therefore will not be explained here. The inclusion of a photocatalytic substance in the second resin layer 3 allows the antibacterial photocatalytic material 10, which is a coating layer on the substrate 4, to have excellent antibacterial properties in bright places. It is thought that the photocatalytic substance contained in the second resin layer 3 receives light, and excited electrons and holes are generated, which act on the nearby antibacterial agent, resulting in antibacterial components (such as copper ions), which diffuse within the second resin layer 3 and reach the surface of the antibacterial photocatalytic material 10.

[0028] Preparation of antibacterial agent-containing resin pellets Three types of antibacterial-containing resin pellets were prepared with different antibacterial concentrations, with the proportion of copper gluconate in the resin pellets being 0.01 wt%, 0.1 wt%, or 1.0 wt%. Specifically, copper gluconate powder (antibacterial agent) was mixed with polyethylene powder (resin), and the resulting mixed powder was pelletized using a twin-screw kneading extruder to produce antibacterial-containing resin pellets.

[0029] Preparation of photocatalyst-containing resin pellets First, a photocatalyst dispersion (Pt-WO3 dispersion) was prepared as follows. Specifically, 200 g of tungsten oxide powder (Kishida Chemical Co., Ltd.) was mixed with 1000 mL of pure water and then dispersed under ultrasonic irradiation to obtain tungsten oxide particle suspension A. Platinum(VI) hexachlorohydrate (Kishida Chemical Co., Ltd., purity 98.5%) was dissolved in suspension A to obtain tungsten oxide particle suspension B. The amount of hexachloroplatinum(VI) hexahydrate added was adjusted so that the ratio of the weight of platinum to the weight of the tungsten oxide particles was 0.05 wt%. Suspension B was heated to 100°C to evaporate the water and then calcined at 500°C to obtain platinum-loaded tungsten oxide powder (Pt-WO3). The average particle diameter of the platinum-loaded tungsten oxide particles contained in the powder obtained after the crushing process was 175 nm (measured by the BET method). Platinum-supported tungsten oxide powder (Pt-WO3) was mixed with pure water to a solid concentration of 20 wt%, and the mixture was dispersed under ultrasonic irradiation to prepare a 20 wt% photocatalyst dispersion. This 20 wt% photocatalyst dispersion was dried and powdered to prepare a photocatalyst powder.

[0030] Using the prepared photocatalyst powder, three types of photocatalyst-containing resin pellets with different photocatalyst concentrations were produced, with the photocatalyst ratio in the resin pellets being 0.01 wt%, 0.1 wt%, or 1.0 wt%. Specifically, the photocatalyst powder was mixed with polyethylene powder (resin), and the resulting mixed powder was pelletized using a twin-screw kneading extruder to produce photocatalyst-containing resin pellets.

[0031] Preparation of resin pellets containing antibacterial agents and photocatalysts Antibacterial and photocatalyst-containing pellets were prepared by setting the ratio of copper gluconate in the resin pellets to 0.1 wt% and the ratio of photocatalyst to 0.1 wt%. Additionally, antibacterial and photocatalyst-containing resin pellets were prepared by setting the ratio of copper gluconate in the resin pellets to 1.0 wt% and the ratio of photocatalyst to 1.0 wt%. Specifically, the prepared photocatalyst powder, copper gluconate powder (antibacterial agent), and polyethylene powder (resin) were mixed, and the resulting mixed powder was pelletized using a twin-screw kneading extruder to produce antibacterial and photocatalyst-containing resin pellets.

[0032] Production of nonwoven fabrics of Examples 1 to 5 and Comparative Examples 1 and 2 The nonwoven fabrics of Examples 1 to 5 and Comparative Examples 1 and 2 were produced using the melt-blowing method. Specifically, an antibacterial-containing resin obtained by melting antibacterial-containing resin pellets and a photocatalyst-containing resin obtained by melting photocatalyst-containing resin pellets were supplied to a sheath-core fiber spinning nozzle, and a resin filament having a sheath-core structure (two-layer structure) in which one of the antibacterial-containing resin and the photocatalyst-containing resin was the core and the other was the sheath was extruded. The continuously extruded resin filaments were blown off with high-temperature, high-pressure air, and the blown-off resin filaments (sheath-core fibers) were deposited. The deposited sheath-core fibers were pressed to produce a nonwoven fabric. Table 1 shows the type of additive (antibacterial agent or photocatalyst) and its content in the core of the fiber contained in the nonwoven fabrics of Examples 1 to 5 and Comparative Examples 1 and 2, and the type of additive (antibacterial agent or photocatalyst) and its content in the sheath.

[0033] [Table 1]

[0034] Manufacture of nonwoven fabrics of Comparative Examples 3 to 8 The nonwoven fabrics of Comparative Examples 3 to 8 were produced using the melt-blowing method. Specifically, one of the following was supplied to a spinning nozzle: an antibacterial-containing resin obtained by melting antibacterial-containing resin pellets; a photocatalyst-containing resin obtained by melting photocatalyst-containing resin pellets; and an antibacterial-photocatalyst-containing resin obtained by melting antibacterial-photocatalyst-containing resin pellets. The resin was extruded in the form of filaments, and the continuously extruded resin filaments were blown off with high-temperature, high-pressure air, and the blown-off resin filaments (single-layer fibers) were deposited. The deposited fibers were pressed to produce nonwoven fabrics. Table 1 shows the types of additives (antibacterial agent, photocatalyst, or both) contained in the fibers (core in Table 1) of the nonwoven fabrics of Comparative Examples 3 to 8, and the proportions thereof.

[0035] Antibacterial Testing Antibacterial tests were conducted in a lighted place and in a dark place according to Japanese Industrial Standard JIS L 1902 (bacterial liquid absorption method) using the nonwoven fabrics of Examples 1 to 5 and Comparative Examples 1 to 8, and antibacterial activity values ​​were calculated. Table 1 shows the antibacterial activity values ​​calculated in the antibacterial test in a lighted place and in a dark place for each nonwoven fabric. Table 1 also shows the difference (light-dark difference) between the antibacterial activity value calculated in the antibacterial test in a lighted place and the antibacterial activity value calculated in the antibacterial test in a dark place.

[0036] The core-sheath fibers contained in the nonwoven fabrics of Examples 1 to 5 have a core made of a resin containing an antibacterial agent and a sheath made of a resin containing a photocatalyst. The antibacterial activity values ​​calculated in antibacterial tests using these nonwoven fabrics were high in bright places and low in dark places. The difference between the light and dark values ​​of the antibacterial activity values ​​was 1.1 or more. The antibacterial activity values ​​of the nonwoven fabrics of Examples 1 to 5 in the test in a dark place were 0.2 or less, and the nonwoven fabrics of Examples 1 to 5 showed only low antibacterial activity in a dark place. Since the core of the fibers contained in the nonwoven fabrics of Examples 1 to 5 contains the antibacterial agent, it is thought that the photocatalyst did not act on the antibacterial agent in a dark place, and the antibacterial component did not diffuse from the core to the surface of the fiber.

[0037] On the other hand, the antibacterial activity values ​​in the antibacterial test in a dark place for the nonwoven fabrics of Comparative Examples 1 and 2, whose sheaths have fibers containing an antibacterial agent, and the antibacterial activity values ​​in the antibacterial test in a dark place for the nonwoven fabrics of Comparative Examples 5 to 8, whose sheaths have single-layer fibers containing an antibacterial agent, were 2.0 or higher, and the nonwoven fabrics of Comparative Examples 1, 2, and 5 to 8 exhibited high antibacterial activity in a dark place. It is believed that the antibacterial agent is present near the surface of these nonwoven fabrics, and therefore the antibacterial agent near the surface directly acts on the bacteria.

[0038] The antibacterial activity values ​​of the nonwoven fabrics of Examples 1 to 5 in the test in a bright place were 1.2 or more, and the nonwoven fabrics of Examples 1 to 5 exhibited high antibacterial properties in a bright place. In particular, the antibacterial activity values ​​of the nonwoven fabrics of Examples 1, 2, 4, and 5 in the test in a bright place were 3.3 or more.

[0039] When comparing the antibacterial activity values ​​of the nonwoven fabrics of Examples 1 and 5, which have fibers containing 1.0 wt% of photocatalyst in the sheath portion, in an antibacterial test conducted in a bright place with the nonwoven fabric of Comparative Example 3, which has single-layer fibers containing 1.0 wt% of photocatalyst, the antibacterial activity value of Comparative Example 3 was 1.2, while the antibacterial activity values ​​of Examples 1 and 5 were 3.4 or more. Furthermore, when comparing the antibacterial activity values ​​of the nonwoven fabrics of Examples 2 and 4, which have fibers containing 0.1 wt% of photocatalyst in the sheath portion, in an antibacterial test conducted in a bright place with the nonwoven fabric of Comparative Example 4, which has single-layer fibers containing 0.1 wt% of photocatalyst, the antibacterial activity value of Comparative Example 4 was 0.8, while the antibacterial activity values ​​of Examples 2 and 4 were 3.3. Furthermore, the antibacterial activity value of the nonwoven fabric of Example 3, which has fibers containing 0.01 wt% of photocatalyst in the sheath portion, in an antibacterial test conducted in a bright place was 1.2, which was greater than the antibacterial activity value of the nonwoven fabric of Comparative Example 4, which has single-layer fibers containing 0.1 wt% of photocatalyst, in an antibacterial test conducted in a bright place.

[0040] From these findings, it is believed that the antibacterial properties of the nonwoven fabrics of Examples 1 to 5 in bright light are not due solely to photocatalytic activity, but that both the photocatalytic activity and the antibacterial agent contribute to the antibacterial properties. Therefore, it was suggested that in the core-sheath fibers contained in the nonwoven fabrics of Examples 1 to 5, the antibacterial agent contained in the core diffuses to the sheath in bright light and reaches the fiber surface. It is believed that the photocatalytic substance contained in the sheath absorbs light, generating excited electrons and holes that act on the nearby antibacterial agent, resulting in antibacterial components (such as copper ions) that diffuse within the sheath.

[0041] From the above, in the nonwoven fabrics of Examples 1 to 5, the photocatalyst is hardly soluble in water and therefore is difficult to dissolve, and the core containing the antibacterial agent is covered with the sheath containing the photocatalyst, which prevents the water-soluble antibacterial agent from dissolving. Therefore, it is believed that even if the nonwoven fabric is washed with water, dirt on the nonwoven fabric can be removed without significantly impairing the antibacterial properties. [Explanation of symbols]

[0042] 2: First resin layer 3: Second resin layer 4: Base material 10: Antibacterial photocatalytic material 15: Resin-coated member

Claims

1. a first resin layer and a second resin layer covering the surface of the first resin layer; the first resin layer contains an antibacterial agent, The second resin layer is an antibacterial photocatalytic material containing a photocatalytic substance.

2. The antibacterial photocatalytic material according to claim 1 , wherein the photocatalytic substance comprises a visible light responsive photocatalytic substance.

3. The antibacterial photocatalytic material according to claim 2 , wherein the visible light responsive photocatalytic substance contains tungsten oxide.

4. 4. The antibacterial photocatalytic material according to claim 2, wherein the content of the visible light responsive photocatalytic substance in the second resin layer is 0.001 wt % or more and 3.0 wt % or less.

5. 4. The antibacterial photocatalytic material according to claim 1, wherein the content of the antibacterial agent in the first resin layer is 0.01 wt % or more and 5.0 wt % or less.

6. 4. The antibacterial photocatalytic material according to claim 1, wherein the antibacterial agent is a compound containing divalent copper.

7. 4. The antibacterial photocatalytic material according to claim 1, wherein the first resin layer is fibrous.

8. The antibacterial photocatalytic material has a core-sheath structure, the first resin layer is a core of the core-sheath structure, The antibacterial photocatalytic material according to claim 7 , wherein the second resin layer is a sheath portion of the core-sheath structure.

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