Solar irradiation system air cleaning element and cleaning of air

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a sunlight irradiation type air purifying element and an air purifying method using the air purifying element, and is particularly useful for deodorizing the inside of an automobile.

【0002】

[Conventional technology]

When photocatalytic fine particles such as titanium oxide, which is an oxide semiconductor, are irradiated with light having an energy equal to or higher than the band gap, electrons and holes are generated by excitation, organic substances and microorganisms close to the surface are decomposed by oxidation, and inorganic oxidation occurs. In the case of a product, 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 photocatalyst fine particles on the support, a method of fixing the photocatalyst fine particles to the support via a binder is usually used, and the binder is decomposed and deteriorated by the activated photocatalyst fine particles. Unprecedented stability 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 automobiles, the so-called new car odor caused by volatile gas from interior materials is disliked in the case of new cars, and in the case of cars in use, the odor of cigarettes adsorbed on the interior materials and the inside of air conditioners is a problem. ing. 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】

Also, when sunlight is used to activate the photocatalyst, the arrangement of the photocatalyst is restricted to the vicinity of the window, and thus 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, the present inventor has made a diligent study to enable deodorization in an automobile by a photocatalyst under the use of sunlight, and as a result, has determined the dispersion of polytetrafluoroethylene powder and photocatalyst fine particles. It was found that the photocatalyst layer obtained by coating and firing this coating layer exhibited remarkably excellent deodorizing performance, and the inside of the vehicle could be effectively deodorized even with the small installation space described above. 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 peeling occurs due to the large tensile stress due to the non-adhesiveness of the interface.

【0007】

Conventionally, as a method for producing a photocatalyst, a solvent solution of a fluoropolymer such as vinyl ether-fluoroolefin copolymer or vinyl ester-fluoroolefin copolymer, a cross-linking agent such as an isocyanate curing agent, and photocatalyst fine particles is used. It is applied on a support and the 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 (special feature). Kaihei 6-3156) is known, 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 a solar irradiation type that uses sunlight as a photocatalyst in the interior of an automobile based on the findings of the above study results so that the driver can satisfactorily deodorize without obstructing the visibility of the driver or the like. To provide an air purifying element and a method for purifying air.

【0009】

[Means for solving problems]

In the solar irradiation type air cleaning element according to the present invention, the photocatalytic fine particles are dispersed in the fired layer of the polytetrafluoroethylene resin, and fine voids are formed between the resin and the photocatalytic fine particles, and the porosity is 7% or more. The structure is characterized by having a photocatalyst layer formed on a supporting base material, and a deodorizing sheet containing one or more of activated carbon, zeolite, or copper carboxylmethylcellulos as a main component is laminated. Can be done. The air purification method according to the present invention is characterized in that these solar irradiation type air purification elements are arranged indoors and irradiated with sunlight.

【0010】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional view of the air purifying element A according to the present invention. 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】

In order to manufacture the air cleaning element according to the present invention, a dispersion containing polytetrafluoroethylene powder and photocatalytic fine particles is applied to a supporting base material, and the solvent in the coating layer is evaporated and removed by heating, and further. The polytetrafluoroethylene particles are sintered by heating and firing (heating temperature is 330 ° C or higher). During cooling after sintering, the photocatalytic fine particles and the polytetrafluoroethylene resin are separated 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, the melt viscosity of the polytetrafluoroethylene powder at the time of firing is high (10).⁸(Poise or more) Since the grain shape is maintained without flowing and the firing is performed without pressure, a sufficient gap remains between the sintered polytetrafluoroethylene 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. This porosity x is obtained 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-[w / (vρ)] Given in. 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 support base material, apply with a roll coater, immerse the support base material in the dispersion and pull it up, spray the dispersion, and disperse. You can use a method of brushing John, a method of spreading the dispersion, and so on. 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】

In the air purifying element according to the present invention, a gap exists between the photocatalyst fine particles and the resin binder, and air diffuses and circulates through the gap, so that the air comes into contact with the outer surface of the photocatalyst fine particles on almost the entire surface. After passing through, the deodorizing component in the air is efficiently oxidatively deodorized by the 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 air purifying element according to the present invention has a flat plate shape such as a rectangle or an ellipse, and can be used by attaching fasteners such as hooks to both ends thereof. It can also be used after being processed into a honeycomb. 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】

The air purifying element according to the present invention can be suitably used for deodorizing the interior of an automobile (deodorizing a new car odor, deodorizing a cigarette odor), and as shown in FIG. Arranged with the back mirror-42 in a size that does not substantially obstruct the driver's view, or placed in the vicinity of the rear window 43 in a size that does not substantially obstruct the passenger's view, by irradiation with sunlight. The photocatalyst layer of the air purifying element A can be activated to deodorize the room.

【0015】

[Example]

[Example 1] An aqueous dispersion of polytetrafluoroethylene powder (particle size 0.3 μm, specific gravity 2.20) containing 40% by weight of photocatalytic titanium oxide fine particles (particle size 7 nm, specific gravity 3.84) was used for dispersion. , An aluminum foil with 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 was cut into 10 cm x 100 cm, processed into 10 cm x 10 cm outer size bullets, and hooks were attached to both ends to make an air purifying element. 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. After arranging the air purifying element, the new car odor was deodorized 5 hours later. When the air purifying element was removed on the third day, the new car odor was detected again after a day and night, so when the air purifying element was placed again, the new car odor disappeared 5 hours after the rearrangement, and then the new car odor disappeared. Was not detected.

【0016】

[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. (Clean Sky made by Kojin Co., Ltd.) was laminated, cut into 10 cm x 100 cm, processed into 10 cm x 10 cm outer size fibers, and hooks were attached to both ends to make an air purifying element. This air purifying element is placed between the windshield and back mirror of a passenger car (2000cc class sedan type) in which the odor of cigarettes is adsorbed on the interior materials of the car and the inside of the air conditioner, and parked outdoors in the sunlight. And deodorized. After 6 hours had passed after the air purifying element was placed, the tobacco odor disappeared, and thereafter the permanent odor due to desorption of the tobacco odor from the adsorbent was completely deodorized.

【0017】

[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 an air cleaning element was manufactured in the same manner as in Example 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. [Comparative Example 2] Compared to Example 1, the melt viscosity of polytetrafluoroethylene in water dispersion is 10.⁴It was the same as in Example 1 except that it was replaced with a poise perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer. 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】

In this way, Comparative Example 2 is inferior in deodorizing performance to Example 1 because the perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer is well heat-fused to the photocatalyst fine particles, and the surface of the photocatalyst fine particles is large. The part is covered with a perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer, and the melt viscosity of the perfluoroalkyl vinyl ether-tetrafluoroethylene copolymer is low, making it difficult to maintain the powder form during firing. , It is presumed that it is difficult for gaps to remain between the sintered powders.

【0019】

[Effect of the invention]

In the air purifying element according to the present invention, there are fine voids between the photocatalyst fine particles and the binder resin, and the outside air passes through the voids in contact with almost the entire surface of the photocatalyst fine particles. The oxidative deodorization efficiency of the active photocatalyst fine particles with respect to the medium deodorizing component can be improved. Further, since the photocatalyst fine particles are embraced in the resin binder and the resin itself is persistent, 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.

[Simple explanation of drawings]

[Figure 1]

It is sectional drawing of the sun irradiation type air cleaning element which concerns on this invention.

[Figure 2]

It is a drawing which shows an example of the solar irradiation type air cleaning element which concerns on this invention.

[Fig. 3]

It is a drawing which shows the use state of the solar irradiation type air cleaning element which concerns on this invention.

[Explanation of symbols]

1 Support base material 2 Photocatalytic layer A Sun-irradiated air purifying element