JP2000051334A - Air permeable photocatalyst sheet and air cleaning unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve air cleaning effect of a photocatalyst sheet and peeling resistance of a photocatalyst layer and to purify the air efficiently in a compact- sized device by providing a fluororesin sintered layer on the surface of a mesh- like support substrate material, and providing a fluororesin sintered layer containing photocatalyst particles on the surface of the fluororesin sintered layer. SOLUTION: A polytetrafluoroethylene sintered layer 121 is formed by heating dispersion of polytetrafluoroethylene powder applied to a mesh-like support substrate 11 to evaporate and remove a solvent in the coat layer, and heating and sintering to sinter between the powder particles. A polytetrafluoroethylene sintered layer 122 containing photocatalyst particles is formed by heating dispersion containing polytetrafluoroethylene powder and photocatalyst particles applied to the sintered layer 121 to evaporate and remove a solvent in the coat layer, and heating and sintering to sinter between the powder partiles. Accordingly, the contact area between the photocatalyst particles and the air in the photocatalyst layer 12 can be increased so as to efficiently perform oxide decomposition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas permeable photocatalyst sheet and an air purification unit using the gas permeable photocatalyst sheet. It is useful for air purification.

[0002]

2. Description of the Related Art As is well known, in a metal oxide semiconductor such as titanium oxide, electrons of a valence band jump up to a conduction band by irradiation of ultraviolet rays to generate holes, and contact with the surface under this excited state. Active species (radicals) from oxygen and moisture
The active species oxidize and decompose organic substances and microorganisms attached to the surface, and also oxidize nitrogen oxides and sulfur oxides to final oxides.

[0003] Therefore, by utilizing the oxidative decomposition of metal oxide semiconductors such as titanium oxide, ie, photocatalytic particles, odors such as tobacco odor in living spaces and workplaces, and harmful gases such as nitrogen oxides and sulfur oxides, Alternatively, it has been known to perform concentration reduction / removal of volatile organic compounds (VOC) or air purification such as antibacterial in a newly built house or the like.

[0004] As an air purifying apparatus using the photocatalyst, a photocatalyst sheet (photocatalyst particles are bound to a support base material by a binder) is used.
(Japanese Unexamined Patent Publication No. 7-25) has been proposed in which an ultraviolet lamp is disposed in the cylindrical body and air is circulated through the cylindrical body by a fan.
No. 1028), it is difficult to effectively use the outer surface side of the cylindrical body for air purification by a photocatalyst, the arrangement direction of the ultraviolet lamp is restricted to the longitudinal direction in the cylindrical body, and the air flow in contact with the inner surface of the cylindrical body is limited. There is a problem that the flow tends to flow and high contact efficiency between the air and the photocatalyst layer cannot be expected.

Conventionally, as a photocatalyst sheet, a gas permeable photocatalyst sheet in which photocatalyst particles are supported on a net-like supporting substrate has been known (Japanese Patent Application Laid-Open No. 3-106420). If this air permeable photocatalyst sheet is bent and formed into a multi-layer structure, the air flow resistance can be kept sufficiently low to make the flowing air turbulent, and the ultraviolet light passing through the air holes can be reflected by a reflecting mirror. The outer surface of the photocatalyst sheet can also be used sufficiently efficiently for air purification,
Further, by appropriately bending the photocatalyst sheet, it is possible to dispose the ultraviolet lamp in a desired direction.

[0006]

However, when the above air-permeable photocatalyst sheet is bent, a shear stress acts on the interface between the supporting substrate and the photocatalyst layer (layer of a mixture of the photocatalyst particles and the binder). However, there is a concern that the separation of the photocatalyst layer is promoted. That is, in addition to the decrease in interfacial adhesive strength due to the degradation of the binder due to the photocatalytic particles and the low initial interfacial adhesive strength due to the photocatalytic particles inhibiting adhesion at the interface, as a result of the shear stress due to bending acting on the same interface, It is feared that interfacial peeling is promoted.

Further, in order to guarantee a sufficiently low flow resistance even under a multi-layer structure of a gas permeable photocatalyst sheet, it is necessary to increase the mesh or pores to some extent. Therefore, there is also a problem that the air purification efficiency decreases due to a decrease in the contact area between the air and the photocatalyst layer.

Conventionally, various proposals have been made to suppress the decomposition and degradation of the binder due to photocatalyst particles. For example, fluorine-based polymers such as vinyl ether-fluoroolefin copolymer and vinyl ester-fluoroolefin copolymer and isocyanate have been proposed. A coating solution of a photo-catalyst fine particle and a cross-linking agent such as a photo-curing agent is coated on a support, and the coated layer is cured by a cross-linking reaction (JP-A-7-171408).
) Or rolling a mixture of polytetrafluoroethylene particles, titanium dioxide and activated carbon into a sheet (JP-A-6-315614) is known. However, in these conventional examples, only a part of the surface of the photocatalyst particles is exposed from the binder and comes into contact with the air, and the contact area is small, so that it is difficult to expect a high-efficiency air purification effect.

By the way, the present inventors have found that a photocatalyst layer obtained by applying a dispersion of polytetrafluoroethylene powder and photocatalyst fine particles and firing the applied layer exhibits remarkably excellent air purification performance. Knew. In order to investigate the cause of this high purification performance, when the structure of the photocatalyst layer was observed with a microscope, a void layer was present between the photocatalyst fine particles and the resin, and the void layer was connected to form a communication passage. I knew that In this photocatalyst layer, the voids are formed at the interface between the photocatalyst fine particles and the polytetrafluoroethylene resin because of the remarkable difference in the heat shrinkage between polytetrafluoroethylene and the photocatalytic titanium oxide fine particles and the non-adhesion of polytetrafluoroethylene. It is presumed that large heat shrinkage stress is generated at the interface at the time of cooling during baking heating, and interface separation occurs due to the large tensile stress due to the non-adhesiveness of the interface.

An object of the present invention is to improve the air purification efficiency of a photocatalyst sheet having a photocatalyst layer provided on a mesh-like or perforated support base material and to improve the peeling resistance of the photocatalyst layer, thereby efficiently and mechanically using a compact device. An object of the present invention is to provide a gas permeable photocatalyst sheet and an air purifying unit capable of stably purifying air.

[0011]

A gas permeable photocatalyst sheet according to the present invention is provided with a polytetrafluoroethylene fired layer on the surface of a mesh-like or perforated support substrate, and the surface of the polytetrafluoroethylene fired layer is provided. Is provided with a photocatalyst particle-containing polytetrafluoroethylene fired layer.

[0012] An air purification unit according to the present invention is characterized by comprising an ultraviolet ray generating source and the above-mentioned air-permeable photocatalyst sheet which is disposed by bending in a light receiving region for the ultraviolet ray generating source. The configuration is as follows.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a drawing showing a gas permeable photocatalyst sheet according to the present invention, and FIG. 1B is a cross-sectional view of FIG. In FIG. 1, reference numeral 11 denotes a mesh-like supporting substrate, for example, a plain-woven glass cloth can be used. 121 is a mesh-like support substrate 1
1 is a fired polytetrafluoroethylene layer applied to the substrate 1. A dispersion of polytetrafluoroethylene powder is applied to a mesh-like support base material, the solvent in the applied layer is removed by heating, and the fired polytetrafluoroethylene is further fired. It is provided by sintering between tetrafluoroethylene particles and then cooling. Reference numeral 122 denotes a photocatalyst particle-containing polytetrafluoroethylene fired layer adhered to the polytetrafluoroethylene fired layer 121. A dispersion containing polytetrafluoroethylene powder and photocatalyst particles is applied to the polytetrafluoroethylene fired layer 121. Apply,
The solvent in the coating layer is removed by evaporation by heating, and the polytetrafluoroethylene particles are sintered by heating and sintering, followed by cooling. During this cooling, a void layer is formed between the photocatalyst particles and the polytetrafluoroethylene resin due to heat shrinkage larger than that of the photocatalyst particles of the polytetrafluoroethylene resin and the non-fusion property of the polytetrafluoroethylene resin to the photocatalyst particles. Is generated. Therefore, in the photocatalyst particle-containing polytetrafluoroethylene fired layer 122, the photocatalyst particles are dispersed in the fired layer of sintered polytetrafluoroethylene powder, and minute voids are formed between the resin and the photocatalyst particles, These are connected to form a chain structure. The thickness of this gap is a fine gap of several nanometers to several micrometers, and air can sufficiently enter and leave due to the chain structure.

Therefore, the contact area between the photocatalyst particles and air per unit area of the photocatalyst layer (indicated by 12) is large due to the chain gap at the interface between the photocatalyst particles and the polytetrafluoroethylene resin binder. Thus, even if the mesh of the mesh-like supporting base material is considerably large, the oxidative decomposition of organic substances and microorganisms contained in the air by contact with the photocatalyst particles can be efficiently performed, and the relatively high permeability of the air-permeable photocatalyst sheet can be achieved. Because of the large mesh, air can be circulated with low flow resistance, and air can be efficiently purified under smooth air circulation.

In the gas permeable photocatalyst sheet 1 according to the present invention, since there is a chain gap at the interface between the photocatalyst particles and the polytetrafluoroethylene resin as a binder, the contact area between the air and the photocatalyst particles can be sufficiently increased. Can be wide. Also,
Photocatalyst particle-containing polytetrafluoroethylene fired layer 12
2, the polytetrafluoroethylene resin has a strong molecular chain structure so that it can well withstand the oxidative decomposition of the photocatalyst particles, and the photocatalyst particle-containing polytetrafluoroethylene fired layer 122 and the polytetrafluoroethylene fired layer 121 Are firmly integrated by sintering of polytetrafluoroethylene, and between the polytetrafluoroethylene fired layer 121 and the mesh-shaped support substrate 11 are firmly bound in the absence of photocatalyst particles. Therefore, the photocatalyst layer 12 can be stably held against bending or the like.

Therefore, the photocatalyst sheet can be severely bent and disposed in a light receiving region for an ultraviolet light source such as an ultraviolet lamp, so that the size of the air purification device can be reduced.

In the present invention, as the mesh-shaped or perforated support substrate 11, any material can be used as long as it satisfies requirements such as flexibility, heat resistance, and high strength. (For example, aluminum wire mesh),
It is also possible to use a heat-resistant plastic sheet (for example, polyimide or polytetrafluoroethylene) punched sheet, a heat-resistant organic fiber (for example, polyamide fiber) woven fabric, or the like.

The photocatalyst particles include titanium oxide, strontium titanate, tungsten oxide, zinc oxide,
Tin oxide, cadmium sulfide and the like can be mentioned,
It is preferable to use an anatase type titanium oxide fine particle exhibiting the most excellent photocatalytic activity. Further, in order to enhance the activity of the photocatalyst particles, an alkali metal ion can be supported.

The polytetrafluoroethylene powder has a particle size of 0.2 to 0.3 μm, and the photocatalyst particles have a particle size of 0.1 to 0.3 μm.
The porosity of the chain void structure of the polytetrafluoroethylene fired layer containing photocatalyst particles is usually 5 to 30%.

If the content of the photocatalyst particles in the photocatalyst particle-containing polytetrafluoroethylene fired layer 122 is too large, the photocatalyst particle-containing polytetrafluoroethylene fired layer 12
2 and the calcined layer 121 of polytetrafluoroethylene are insufficient, and if the amount is too small, the air purification efficiency becomes insufficient. Therefore, the mixing ratio of polytetrafluoroethylene powder / photocatalyst particles is 1/9 to 7 / 3, preferably 3/7
６6/4.

The above-mentioned respective dispersions are usually applied by a dipping method, but a method of applying with a roll coater, a method of spraying the dispersion, a method of brush-coating the dispersion, -A method of casting John can also be used. The concentration of the dispersion is set in accordance with the coating method, and is usually 40% to 60%.

In the gas permeable photocatalyst sheet according to the present invention, it is also possible to add at least one of activated carbon particles, zeolite particles and silica gel particles together with the photocatalyst particles to the photocatalyst particle-containing polytetrafluoroethylene fired layer 122. is there. In the present invention, polychlorotrifluoroethylene may be used instead of the above polytetrafluoroethylene.

The air-permeable photocatalyst sheet according to the present invention is specifically disposed in an air purifying apparatus, and is used for odors such as tobacco odors, harmful gases such as nitrogen oxides and sulfur oxides, or for newly built houses. In addition to being used for reducing or removing the concentration of volatile organic compounds (VOCs) or for antibacterial activity, it can be used for decomposing and removing ethylene, which is arranged in a refrigerator to accelerate the ripening of fruits and crops.

In the air purifying apparatus described above, the ultraviolet light source and the air-permeable photocatalyst sheet of the present invention are provided in the light receiving region for the ultraviolet light source in a columnar, elliptical column, arc, spiral, umbrella, or yellow. An air purifying unit, which is bent and formed into a tube shape, a wave shape, a spiral shape, etc., is accommodated in a case (a case having a filter at an air inlet and a fan at an air outlet); Anything can be used.

As the ultraviolet ray generator, a fluorescent lamp, a black light bull lamp, a halogen lamp, a xenon flash lamp, a mercury lamp, a germicidal lamp, etc., which generate ultraviolet rays having a wavelength of 400 nm or less can be used.

FIGS. 2A to 2D and FIGS. 3A to 3D show different examples of the air purification unit according to the present invention. Excellent air purification efficiency based on the chain void structure of the photocatalyst particle-containing polytetrafluoroethylene fired layer 122 in the gas permeable photocatalyst sheet 1 and excellent resistance of the photocatalyst layer 12 to bending of the gas permeable photocatalyst sheet 1. High efficiency for peelability
Safe air purification becomes possible.

In the air purifying unit shown in FIG. 2A, the air permeable photocatalyst sheet 1 according to the present invention is bent into a double column concentric with the ultraviolet irradiation lamp 2, and the photocatalyst sheet and The structure is such that the distance between the lamps is constant and the irradiation is uniform, suitable for miniaturization, and the outer surface side of the photocatalyst sheet 1 can be used for air purification by being surrounded by a cylindrical reflecting mirror (for example, made of an aluminum plate). . The flow direction of the air can correspond to either a parallel direction or a perpendicular direction to the ultraviolet irradiation lamp.

In the air purifying unit shown in FIG. 2B, the air-permeable photocatalyst sheet 1 according to the present invention has a U-shaped ultraviolet irradiation lamp or two ultraviolet irradiation lamps 2 as focal points. It is bent into an elliptical column shape, and is suitable for miniaturization as in FIG. 2A. The outer surface of the photocatalyst sheet 1 is also surrounded by a cylindrical reflector (for example, made of an aluminum plate). It can be used for air purification, and the flow direction of air can be either parallel or perpendicular to the ultraviolet irradiation lamp. In particular, in the case of a U-shaped ultraviolet irradiation lamp, since the lamp is fixedly supported at one end, replacement of the photocatalyst sheet,
Easy to attach and detach during washing.

In the air purifying unit shown in FIG. 2C, the air permeable photocatalyst sheet 1 according to the present invention is bent into a large and small semicircular dome shape and disposed on the reflecting plate 3. The ultraviolet irradiation lamp 2 is covered with these dome.

The air purifying unit shown in FIG. 2D has a structure in which a gas permeable photocatalyst sheet 1 according to the present invention is spirally bent around an ultraviolet irradiation lamp 2 so as to form one air vent. The performance similar to that of the air purification unit shown in FIG.

The air purifying unit shown in FIG. 3A has a structure in which the air-permeable photocatalyst sheet 1 according to the present invention is attached to an ultraviolet irradiation lamp 2 by bending it into a multistage umbrella shape. The air can be purified in multiple stages for the air flow in the direction parallel to.

The air purifying unit shown in FIG. 3 (b) has a configuration in which the air-permeable photocatalyst sheet 1 according to the present invention is bent and arranged on an ultraviolet irradiation lamp 2 in a beam shape. It is planar and can be used in combination with sunlight. FIG.
It is also possible to use a reflector in combination as in the embodiment (c).

The air purifying unit shown in FIG. 3C has a configuration in which the air-permeable photocatalyst sheet according to the present invention is disposed in a wave shape on an ultraviolet irradiation lamp. As in the embodiment shown in FIG. 3 (b), it is planar and can be used together with sunlight, and it can also be used together with a reflector as in the embodiment shown in FIG. 2 (c). It is possible.

The air purifying unit shown in FIG. 3D has a structure in which the air-permeable photocatalyst sheet 1 according to the present invention is spirally bent and attached to the ultraviolet irradiation lamp 2 and is parallel to the lamp. Multi-stage air purification can be performed for the directional air flow.

[0035]

Example [Example] Yarn thickness 0.5 mm, mesh size 2.
5 mm x 2.5 mm plain woven glass cloth (porosity is about 3
0%) was used as a mesh-like support substrate, and this was used as a polytetrafluoroethylene disperser having a resin amount of 40% by weight.
After immersion in John (resin particle diameter approximately 0.25 μm), 11
After removing water at 0 ° C × 60 seconds, 370 ° C × 100
Firing was performed in seconds to form a polytetrafluoroethylene fired layer. Further, it is immersed in a dispersion containing a polytetrafluoroethylene powder (particle diameter approximately 0.25 μm) and anatase type titanium oxide fine particles (particle diameter 0.007 μm) at a weight ratio of 6: 4 and having a solid content concentration of 40%. After, 110 ° C
After removing water for 60 seconds, calcination was performed at 370 ° C. for 100 seconds to form a baked layer of polytetrafluoroethylene containing photocatalyst particles to obtain a gas permeable photocatalyst sheet. The thickness of the gas permeable photocatalyst sheet was 0.55 mm, and the adhesion amount of titanium oxide fine particles was 90 g / m ² .

Comparative Example 1 The procedure was the same as that of the example except that the formation of the polytetrafluoroethylene fired layer was omitted.

Comparative Example 2 Comparative Example 1 was the same as Comparative Example 1 except that the polytetrafluoroethylene in the dispersion was replaced with a perfluoroalkylvinyl ether-tetrafluoroethylene copolymer. did.

For each of these examples and comparative examples, a 10 W black light and a breathable photocatalyst sheet cut into a sample area of 200 mm × 300 mm and formed into an arc were placed in a closed container having an internal volume of 2 m ^3. Was set at a distance of 10 cm, acetaldehyde was injected into the container so as to have a concentration of 10 ppm, and a test was performed in which the aldehyde concentration after black light was turned on was measured by gas chromatography (on the sheet). UV intensity of 1m
(W / cm ² ), and the aldehyde concentration after 180 minutes was 3 ppm in the case of the example and comparative example 1, but was about 3 times higher in the case of comparative example 2 than in the example.

The cross section of the photocatalyst layer was observed with an electron microscope at a magnification of 25,000 for each of Example and Comparative Example 1.2. In Example and Comparative Example 1, a chain gap was formed at the interface between the photocatalyst particles and the binder. Was formed,
In Comparative Example 2, the formation of chain voids was hardly observed, and it is presumed that the difference in the above decomposition results depends on the presence or absence of the chain voids.

Further, the photocatalytic layer was subjected to repeated bending to inspect the peelability of the photocatalyst layer in each of Example and Comparative Example 1.2. In Comparative Example 1, the photocatalytic layer was peeled 20 times. No abnormalities were observed in the number of times.

[0041]

In the gas permeable photocatalyst sheet according to the present invention, fine chain voids exist between the photocatalyst particles and the binder resin (polytetrafluoroethylene).
External air can be flowed in contact with almost the entire surface of the photocatalyst particles. Further, since the polytetrafluoroethylene fired layer is provided as an intermediate layer between the photocatalyst particle-containing polytetrafluoroethylene fired layer and the mesh or perforated base material, the peeling resistance of the photocatalyst layer can be improved.

Therefore, even if the gas permeable photocatalyst sheet according to the present invention is compactly bent in the light receiving region for the ultraviolet irradiation lamp, the photocatalyst layer can be stably held, and the air purification device can be downsized. Due to the high contact between the photocatalyst particles and the flowing air, highly efficient air purification becomes possible.

[Brief description of the drawings]

FIG. 1 is a view showing a gas permeable photocatalyst sheet according to the present invention.

FIG. 2 is a view showing another example of the air purification unit according to the present invention.

FIG. 3 is a drawing showing another example of the air purification unit according to the present invention, which is different from the above.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Air-permeable photocatalyst sheet 11 Mesh-like support base material 12 Photocatalyst layer 121 Polytetrafluoroethylene fired layer 122 Photocatalyst particle-containing polytetrafluoroethylene fired layer 2 Ultraviolet light generation lamp

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Tadanori Michimoto 1-2-1 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 4C080 AA07 AA10 BB02 BB05 CC12 JJ06 KK08 MM02 NN27 QQ03 QQ11 QQ17 QQ20 4F100 AA21 AK18B AT00A BA03 BA07 DC11A DC16A DE01 EJ28 EJ48B GB56 JC00 JD01 JL06 JL08C 4G069 AA01 AA03 AA08 AA09 BA04A BA04B BA17 BA22A BA22B BA48A BB04A BC12A CA13ABC13ABC BC12A BC36A BC35A BC30A BC36A

Claims (4)

[Claims] An air-permeable material characterized in that a fluororesin sintering layer is provided on the surface of a mesh-shaped or perforated support substrate, and a fluorinated resin sintering layer containing photocatalyst particles is provided on the surface of the fluororesin sintering layer. Photocatalyst sheet. 2. The gas permeable photocatalyst sheet according to claim 1, wherein the fluororesin is polytetrafluoroethylene. 3. An air purifying apparatus comprising: an ultraviolet ray generating source; and a gas permeable photocatalyst sheet according to claim 1, which is disposed in a light receiving region for said ultraviolet ray generating source by bending. unit. 4. The air purifying unit according to claim 3, wherein the fluororesin is polytetrafluoroethylene.