Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Halogen or compound containing same
Patent
1998-04-03
2000-06-13
Wood, Elizabeth D.
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Halogen or compound containing same
502226, 502227, 502228, 502229, 502230, 502231, B01J 2706, B01J 27135
Patent
active
060749814
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a photocatalyst, and more particularly to a highly reactive photocatalyst or a photocatalyst bearing material, and its manufacturing method, that can be applied to window glass and interior wall materials used in hospitals, offices, and automobiles. The photocatalyst provides various functions, such as indoor air cleaning, antibacterial, anti-fouling, and defogging action. Furthermore, it demonstrates excellent indoor air cleaning performance when used as an interior wall material and in air filters for super clean enclosed spaces and conveyance enclosed spaces for semiconductor production, clean rooms for various other purposes, and office buildings and residential homes.
BACKGROUND OF THE INVENTION
Antibacterial oxide semiconductors, such as titanium oxides, zinc oxides, tungsten oxides, and iron oxides, which have high photocatalytic activity and excellent durability, have been introduced as various fixed-type photoreactors that are immobilized on fixed supporters. For instance, Japanese Laid-Open Patent No. 63-97234/1988 discloses an immobilized photocatalyst comprised of particle-, flake-, or fiber-shaped clear material coated with a platinum- or palladium-doped titanium oxide thin film.
The development of a product bearing a photocatalyst with a higher photoreactivity is greatly desired because it broadens the possibility of using such a product as an antipollution material, besides acting as an antibacterial agent.
Among various photocatalytic materials, titanium oxide, which has the highest photocatalytic activity and excellent durability, already has been actually used as an antibacterial agent in a particulate form. Titanium oxide, however, can be excited only by ultraviolet light, the amount of which is limited under actual usage conditions. Accordingly, it can be said that the window glass application for indoor use is best suited for the product, as both artificial illumination and sunlight can be utilized.
However, as the window glass application also requires high clarity of photocatalyst film, titanium oxide particulate-based material has not be utilized. Thus, achieving a photocatalytic film with both high photocatalytic activity and clarity can maximize its performance and significantly broaden potential applications.
Another serious problem with photocatalytic film in window glass application is its significantly reduced reactivity due to Na ion diffusion from the soda-lime glass base material. As a solution to this problem, the use of a Na diffusion-preventing silica undercoat for glass surfaces has been proposed (Paz, et al., J. Mater. Res., Vol. 10, p2842, 1995). It has been reported that this method can achieve photocatalytic activity similar to that of a titanium oxide film coating on a quartz substrate.
Recently, in the field of semiconductors, reduced yield caused by trace organic gases in clean rooms being deposited on substrates has become a serious problem as the density of elements increases. In addition, even in a residential setting, allergic reactions to various plasticizers that may be in construction materials, such as formaldehyde and acetaldehyde, have become a serious concern.
The aforementioned photocatalysts, such as titanium oxide, effectively oxidize organic materials, and can decompose various organic gases existing indoors. Therefore, the photocatalysts have the potential of becoming a key material to solve the above-mentioned reduced semiconductor yield and allergy problems.
However, for a photocatalyst to decompose organic gases, it is essential to improve its reactivity and expand its surface area because the concentration of gases is extremely small.
In the past, various attempts were made to make shoji-screen paper- or glass fiber cloth-based material bear a photocatalyst to decompose organic gases of extremely low concentration (for instance, Japanese Laid-Open Patent No. 1-139139/1989). Although the surface area is large, shoji-screen paper is an organic material itself that, over time, inevitably deteri
REFERENCES:
patent: 5183656 (1993-02-01), Uesaka et al.
patent: 5472593 (1995-12-01), Gosling et al.
patent: 5690922 (1997-11-01), Mouri et al.
Hattori Akihiko
Ito Toshiya
Shimoda Koji
Tada Hiroaki
Nippon Sheet Glass Co. Ltd.
NSG Techno-Research Co., Ltd.
Wood Elizabeth D.
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