Solar irradiation system air cleaning element and cleaning of air

[Technical field to which the invention belongs] The present invention is of the sunlight irradiation type.<u style="single">Air purifying sheet</u>And its<u style="single">Air purifying sheet</u>It is particularly useful for deodorizing the inside of an automobile with respect to the method of purifying air using the above.

[0002] When photocatalytic fine particles such as titanium oxide, which is an oxide semiconductor, are irradiated with light having an energy equal to or larger than a band gap, electrons and holes are generated by excitation, and organic substances and microorganisms close to the surface are generated. Is decomposed by oxidation, and in the case of inorganic oxides, it is oxidized to the final oxide. Therefore, it has been proposed to bring indoor air into contact with a photocatalyst body on which these photocatalyst fine particles are supported by a binder to decompose odorous components in the air to perform deodorization or air purification. In this case, as an ultraviolet source for exciting (activating) the photocatalytic fine particles, there are a case using sunlight and a case using an ultraviolet generator such as a black light, but they are exposed to sunlight. It is convenient to use sunlight to purify the air in the room.

[0003] In order to support the photocatalytic fine particles on the support, a method of fixing the photocatalytic fine particles to the support via a binder is usually used, and the binder is made of activated photocatalytic fine particles. Stability that does not decompose and deteriorate is required. Therefore, many prior arts have been presented, for example, as a binder, a fluoropolymer such as a silicone-based polymer, a vinyl ether-fluoroolefin polymer, or a vinyl ester-fluoroolefin polymer is used. It has been proposed (Japanese Patent Laid-Open No. 7-171408). Further, since the above air purification is due to a contact reaction on the surface of the photocatalyst, it is required to make the contact area as wide as possible. For example, sheet-shaped photocatalysts may be laminated with a gap between them. It has been proposed to focus a tubular photocatalyst and use the gap as an air passage (Japanese Patent Laid-Open No. 7-251028).

[0004] [Problems to be Solved by the Invention] In the case of a new car, the so-called new car odor caused by the volatile gas from the interior material is disliked, and in the case of a car in use, the interior material and the like. The odor of cigarettes adsorbed inside the air conditioner is a problem. Conventionally, a deodorizing material containing an adsorbent such as activated carbon, zeolite, silica gel, or alumina as a main component has been used for deodorizing the interior of an automobile, but the life of the deodorizing material is short and it is necessary to replace it considerably frequently. It is troublesome. Therefore, it has been proposed to deodorize the tobacco odor with the above photocatalyst (Japanese Patent Laid-Open No. 7-251028), but the conventional photocatalyst has a small air contact area per unit volume, and as described above, -It is necessary to stack g-shaped photocatalysts with a gap between them, or to focus tubular photocatalysts and use the gap as an air passage. In such a gap structure, in order to allow air to flow through the gap. Juan etc. are required, and it is inevitable that the equipment cost will increase.

[0005] Further, when sunlight is used to activate the photocatalyst, the arrangement of the photocatalyst is limited to the vicinity of the window, and therefore the installation space is inevitably limited. For example, in the case of an automobile, the space is limited to the space between the windshield and the back mirror, near the rear window, and does not substantially obstruct the view, and the space that can be used is a vertical flat area of at most 200 mm x 200 mm. It is within the range. However, with a conventional photocatalyst, it is difficult to satisfactorily deodorize the inside of a vehicle under sunlight irradiation at such a limited space.

[0006] Therefore, as a result of diligent studies to enable the deodorization of the inside of the automobile by the photocatalyst under the use of sunlight, the present inventor has made a disspa of the polytetrafluoroethylene powder and the photocatalyst fine particles. -I learned that the photocatalyst layer obtained by applying John and firing this coating layer exhibits remarkably excellent deodorizing performance, and can effectively deodorize the inside of the vehicle even with the above-mentioned small installation space. In order to clarify the cause of this high deodorizing performance, the structure of the photocatalyst layer was observed with a microscope. As a result, an air layer was present between the photocatalyst fine particles and the resin, and the air layers were connected to form a continuous passage. I knew that I was there. In this photocatalyst layer, the reason why voids are formed at the interface between the photocatalyst fine particles and the polytetrafluoroethylene resin is the remarkable difference in the heat shrinkage between the polytetrafluoroethylene and the photocatalyst titanium oxide fine particles and the non-adhesion of the polytetrafluoroethylene. It is presumed that this is due to the fact that a large heat shrinkage stress is generated at the interface when the firing heating is cooled, and the interface is peeled off due to the large tensile stress due to the non-adhesiveness of the interface.

[0007] Conventionally, as a method for producing a photocatalyst, a fluoropolymer such as vinyl ether-fluoroolefin copolymer or vinyl ester-fluoroolefin copolymer, a cross-linking agent such as an isocyanate-based curing agent, and photocatalyst fine particles are used. A solvent solution is applied onto the support, and this coating layer is cured by a cross-linking reaction (Japanese Patent Laid-Open No. 7-171408), or a mixture of polytetrafluoroethylene particles, titanium dioxide, and activated charcoal is rolled into a sheet. It is known that (Japanese Patent Laid-Open No. 6-3156), but in these, there is no process of generating shrinkage stress at the interface between the photocatalyst fine particles and the resin, and the generation of voids at the interface cannot be expected at all.

[0008] An object of the present invention is to use sunlight as a photocatalyst in the interior of an automobile based on the findings of the above study results so that the sun can be satisfactorily deodorized without obstructing the visibility of a driver or the like. It is an object of the present invention to provide a light irradiation type air purifying element and a method for purifying air.

[Means for Solving the Problems] The present invention.<u style="single">The solar irradiation type air cleaning sheet is a porous photocatalyst layer formed by coating and firing a dispersion containing polytetrafluoroethylene powder and photocatalyst fine particles on a supporting base material and sintering the polytetrafluoroethylene powder. It is said that the void ratio of the porous photocatalyst layer is 7% or more by the interfacial peeling at the time of firing based on the difference in the thermal expansion / contraction ratio between the polytetrafluoroethylene powder and the photocatalyst fine particles.</u>It is a characteristic structure, and a deodorizing sheet containing one or more kinds of activated carbon, zeolite, or copper carboxylmethylcellulos as a main component can be laminated. The air purification method according to the present invention is characterized in that these sunlight irradiation type air purification sheets are arranged indoors and irradiated with sunlight.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the air purifier according to the present invention.<u style="single">Sheet</u>A cross-sectional view of A is shown. In FIG. 1, 1 is a supporting base material. Reference numeral 2 denotes a photocatalyst layer provided on the support base material 1, in which the photocatalyst fine particles are dispersed in the fired layer of the sintered polytetrafluoroethylene powder, and fine voids are formed between the resin and the photocatalyst fine particles, resulting in firing. The gaps between the tied polytetrafluoroethylene powders are connected to the air layer to form a multi-gap communication structure. The thickness of the voids between the polytetrafluoroethylene resin and the photocatalytic fine particles is a fine gap of several nanometers to several microns, and due to the hydrophobicity of polytetrafluoroethylene, water or the like does not pass through. , Air can fully flow in and out.

[0011] For air purification according to the present invention.<u style="single">Sheet</u>In order to produce the above, a dispersion containing polytetrafluoroethylene powder and photocatalytic fine particles is applied to a supporting base material, the solvent in the coating layer is evaporated and removed by heating, and further heating and firing (heating temperature is 330 ° C). Sinter between polytetrafluoroethylene particles by C or higher). During cooling after sintering, the photocatalytic fine particles and the polytetrafluoroethylene resin are separated from each other due to heat shrinkage larger than that of the photocatalytic fine particles of the polytetrafluoroethylene resin and the non-fusion property of the polytetrafluoroethylene resin to the photocatalytic fine particles. An air layer is formed between them. In addition, since the melt viscosity of the polytetrafluoroethylene powder at the time of firing is high (10 poise or more), the grain shape is maintained without flowing, and the firing is performed without pressure, the sintered polytetrafluoroethylene is obtained. Sufficient gaps remain between the powders. Therefore, the photocatalyst layer has a breathable multi-gap structure. The particle size of the polytetrafluoroethylene powder is 0.1 to 1 μm, and the particle size of the photocatalytic fine particles is 200 nm or less, preferably 50 nm or less. The porosity of the photocatalyst layer is 7% or more, preferably 10% or more. For this porosity x, if the true specific gravity of the photocatalyst layer is ρ and the weight of the volume v of the photocatalyst layer is w, x = 1-Given by [w / (vρ)]. When the porosity is less than 7%, the effect of improving the contact degree between the air and the photocatalytic fine particles by the multi-gap structure is low, and as is clear from the comparative examples described later, it is difficult to satisfactorily deodorize the interior of the automobile. However, it is preferably 30% or less in terms of mechanical strength. The thickness of the photocatalyst layer is preferably 3 μm to 30 μm. If it is less than 3 μm, the volume of the photocatalyst layer is small and the deodorizing performance is low, and if it exceeds 30 μm, the gas diffusion efficiency is lowered and the layer thickness becomes thicker than necessary. If the amount of the photocatalytic fine particles in the dispersion is too large, the binding strength between the photocatalytic fine particles by polytetrafluoroethylene becomes insufficient, so the content of the photocatalytic fine particles is preferably 5 to 60%.

[0012] As the photocatalytic fine particles, it is preferable to use anatase-type titanium oxide fine particles exhibiting excellent photocatalytic activity. In addition, alkali metal ions can be supported in order to increase the activity of the photocatalytic fine particles. As the supporting base material, a material having heat resistance that does not cause deformation or the like even when heated during firing is used. For example, metal foils such as aluminum and stainless steel, ceramic plates, inorganic plates such as glass plates, polyimide, and poly Fiberglass and polyamide fiber woven fabrics impregnated with heat-resistant plastic films such as tetrafluoroethylene and heat-resistant plastics such as polytetrafluoroethylene, and feld-like products of glass fibers, ceramic fibers, metal fibers, carbon fibers alone or in admixture. A net of glass fiber, ceramic fiber, metal fiber, carbon fiber alone or a mixture can be used. To apply the dispersion to the above supporting base material, a method of applying with a roll coater, a method of immersing the supporting base material in the dispersion and pulling it up, a method of spraying the dispersion, and a method of spreading the dispersion. A method of brushing John, a method of spreading the dispersion, etc. can be used. The concentration of the dispersion is set according to the coating method, but is usually 40% to 60%. It is also possible to appropriately add an additive for increasing the porosity of the fired layer, an additive for improving the strength, and a gas adsorbent capable of withstanding the firing temperature to the dispersion.

[0013] The present invention.<u style="single">Air purifying sheet</u>In, there is a gap between the photocatalyst fine particles and the resin binder, and air diffuses and circulates through the gap. Therefore, air passes through the outer surface of the photocatalyst fine particles in contact with almost the entire surface and deodorizes in the air. The components are efficiently oxidatively deodorized with activated photocatalytic fine particles. Further, since the polytetrafluoroethylene supporting the photocatalyst fine particles is persistent, the resin binder can be stably held for a long period of time without disintegration, and the photocatalyst fine particles are wrapped through the voids of the resin layer. , Photocatalyst fine particles can be stably supported for a long period of time. Therefore, the deodorizing component in the air can be efficiently oxidatively deodorized for a long period of time. The present invention<u style="single">Air purifying sheet</u>Can be used by attaching fasteners such as hooks to both ends of a flat plate shape such as a rectangle or an ellipse, and in order to increase the surface area, it should be used by bleaching or honeycombing as shown in Fig. 2. You can also. In FIG. 2, 3 indicates a hook. It can also be used by laminating with a deodorizing sheet containing one or more of activated carbon, zeolite, or copper carboxylmethylcellulos as a main component.

[0014] For air purification according to the present invention.<u style="single">Sheet</u>Can be suitably used for deodorizing the interior of a car (deodorizing a new car odor, deodorizing a cigarette odor), and as shown in Fig. 3, drive the air purifying sheet A between the windshield 41 of the car and the back mirror-42. The photocatalyst layer of the air cleaning sheet A is arranged in a size that does not substantially obstruct the view of the hand, or is arranged in the vicinity of the rear window 43 in a size that does not substantially obstruct the view of passengers, and is irradiated with sunlight. Can be activated to deodorize the room.

[Example 1] [Example 1] Polytetrafluoroethylene powder having a content of 40% by weight of photocatalytic titanium oxide fine particles (particle size 7 nm, specific gravity 3.84) (particle size 0.3 μm, specific gravity 2.20) is contained in the dispersion. The aqueous dispersion of No. 1 was used, and an aluminum foil having a thickness of 60 μm was used as the supporting base material. This aluminum foil is immersed in a dispersion, pulled up, dried at 100 ° C, and fired at 390 ° C x 2 minutes to form a sheet with a porosity of 12.2% and a thickness of 7 μm. A photocatalyst was obtained. This sheet-shaped photocatalyst is cut into 10 cm x 100 cm, processed into 10 cm x 10 cm outer size bullets, and hooks are attached to both ends.<u style="single">Air purifying sheet</u>And said. This air purifying element was placed between the windshield and the back mirror of a new passenger car (2000cc class sedan type) and parked outdoors in the sunlight to deodorize it. For air purification<u style="single">Sheet</u>The new car odor was deodorized 5 hours after the arrangement. When I removed the air purifying sheet on the third day, the smell of the new car was detected again after a day and night, so it was used again for air cleaning.<u style="single">Sheet</u>The new car odor disappeared 5 hours after the rearrangement, and no new car odor was detected thereafter.

[Example 2] The supporting base material has a thickness of 0.6 mm and a basis weight of 30 g / m.²A sheet-like photocatalyst was obtained in the same manner as in Example 1 except that the carbon fiber felt of the above was used, and a deodorizing sheet containing copper carboxymethyl cellulosic as a main component was added to the sheet-like photocatalyst. Kojinsha Clean Sky) is laminated, cut into 10 cm x 100 cm, processed into 10 cm x 10 cm outer size fibers, and hooks are attached to both ends for air purification.<u style="single">Sheet</u>And said. For this air purifier<u style="single">Sheet</u>Is placed between the windshield and back mirror of a passenger car (2000cc class sedan type) in which the odor of cigarettes is adsorbed inside the car interior materials and air conditioners, and parked outdoors in sunlight to deodorize. It was. After 6 hours had passed after the air purifying sheet was placed, the tobacco odor disappeared, and thereafter the permanent odor due to desorption of the tobacco odor from the adsorbent was completely deodorized.

[Comparative Example 1] Compared to Example 1, a sheet-like photocatalyst having a porosity of 3.1% and a thickness of 7 μm was obtained, and the others were used for air purification in the same manner as in Example 1.<u style="single">Sheet</u>Was produced. When an attempt was made to deodorize the new car odor in the same manner as in Example 1, a satisfactory deodorization could not be achieved. [Comparative Example 2] Example 1 except that polytetrafluoroethylene in water dispersion was replaced with a perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer having a melt viscosity of 10 poise. Same as 1. The porosity of the photocatalyst layer was 1%. When an attempt was made to deodorize the new car odor in the same manner as in Example 1, a satisfactory deodorization could not be achieved.

[0018] Comparative Example 2 is inferior in deodorizing performance to Example 1 because the perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer is well heat-sealed to the photocatalyst fine particles, and the photocatalyst fine particles are heat-fused. Most of the surface is covered with a perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer, and the melt viscosity of the perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer is low, resulting in a powder form during firing. It is presumed that this is because it is difficult to hold and it is difficult for gaps to remain between the sintered powders.

[Effect of the Invention] For air purification according to the present invention.<u style="single">Sheet</u>In, there are fine voids between the photocatalyst fine particles and the binder-resin, and the outside air circulates in contact with almost the entire surface of the photocatalyst fine particles through the voids. Oxidation deodorization efficiency can be improved. Further, since the photocatalyst fine particles are embraced in the resin binder and the resin itself is persistently decomposable, the photocatalyst fine particles can be stably supported. Therefore, it can be deodorized for a long period of time with a relatively small outer size, and it is arranged between the windshield and back mirror of an automobile or near the rear window without substantially obstructing the visibility, and the activity of photocatalytic particles by irradiation with sunlight. It is possible to satisfactorily deodorize new car odors and cigarette odors.

BRIEF DESCRIPTION OF THE DRAWINGS [FIG. 1] For sunlight irradiation type air purifier according to the present invention.<u style="single">Sheet</u>It is a cross-sectional view of.

FIG. 2 is for sunlight irradiation type air purifying according to the present invention.<u style="single">Sheet</u>It is a drawing which shows an example.

FIG. 3 is for sunlight irradiation type air purifying according to the present invention.<u style="single">Sheet</u>It is a drawing which shows the usage state of.

[Description of code] 1 Support base material 2 Photocatalyst layer A For solar irradiation type air purification<u style="single">Sheet</u>