Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2000-09-08
2002-05-07
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S159000, C502S242000, C502S250000, C502S252000, C502S350000, C502S341000, C502S342000, C502S343000, C502S527130, C502S328000, C502S329000, C502S330000, C502S331000, C502S527120, C428S403000, C428S405000, C428S328000, C106S287130, C106S287160
Reexamination Certificate
active
06383980
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a photocatalytic titanium dioxide powder, process for producing the same and applications thereof. More particularly, it relates to a photocatalytic powder comprising finely divided titanium dioxide particles having a first calcium oxide layer and a second substantially water-insoluble substance layer; a process for producing the photocatalytic titanium dioxide powder; a polymer composition comprising the photocatalytic titanium dioxide powder; a shaped article made of the polymer composition; and a structure having a coating of the polymer composition.
The photocatalytic titanium dioxide powder of the present invention is used as an environmental clarification material for removing malodor, decomposition-removing harmful substances or pollutants in air, treating drainage, purifying waste water, or performing sterilization or algicidal treatment of water. In particular, the photocatalytic titanium dioxide powder of the present invention is suitably used as an environmental clarification material by coating it on the surface of textile fiber, paper or plastic article, or incorporating it into textile fiber or plastic article, or used in the form of a coating material.
(2) Description of the Related Art
In recent years, photocatalysts using finely divided titanium dioxide particles are attracting attention as an environmental clarification material used for the purpose of antibacterial effect, deodorization, anti-staining or air or water clarification. The photocatalytic mechanism of the titanium dioxide is considered as follows. An electron and a hole generated inside the finely divided titanium dioxide particles convert water and oxygen present in the vicinity of the surface of the titanium dioxide particles into hydroxyl radical or hydrogen peroxide, and by virtue of the strong oxidation-reduction function of hydroxyl radical or hydrogen peroxide, harmful substances are converted into a harmless substance such as carbon dioxide gas, thereby attaining clarification. This photocatalytlc action of finely divided titanium dioxide particles is said to permanently lasts as long as finely divided titanium dioxide particles, light, water and oxygen are present.
As applications of the titanium dioxide photocatalyst attempts are being made wherein the photocatalyst is incorporated in a medium having a shape suitable for handling such as fiber and plastic molded article, or a the surface of a substrate such as cloth and paper is coated with the photocatalyst. However, the strong photocatalytic action of titanium dioxide causes decomposition or degradation not only of harmful organic materials or environmental pollutants but also of the medium itself such as textile fiber, plastic and paper. This stands as an obstacle to the practical use of titanium dioxide photocatalyst. A coating material obtained by mixing finely divided titanium dioxide particles and a binder is drawing attention because of its good handling properties. However, an inexpensive binder exhibiting no adverse effect on the above-described medium has not yet been found out.
A process of allowing a photocatalytically inactive compound to be supported in the form of islands on the surface of titanium dioxide particles thereby suppressing the photocatalytic activity thereof so as to prevent or minimizing degradation of a plastic medium or a binder attributable to the activity of titanium dioxide particles is proposed in Japanese Unexamined Patent Application No. H9-225319 and H9-239277 (the term “Japanese unexamined patent publication” is hereinafter abbreviated to “JP-A”). According to this process, the degradation of a plastic medium or a binder is reduced, but, the photocatalytically inactive compound directly adheres to the active site on the surface of titanium dioxide particles, therefore, it reduces the activity of the titanium dioxide particles as a photocatalyst, namely, it counteracts the photocatalytic activity thereof.
A photocatalyst comprising titanium dioxide particle, the surface of which is coated with porous calcium phosphate is proposed in JP-A H10-244166. This coated titanium dioxide particle has durability which is still poor under irradiation of a strong ultraviolet ray such as sunlight.
SUMMARY OF THE INVENTION
In view of the foregoing problems of the heretofore proposed techniques, an object of the present invention is to provide a photocatalytic titanium dioxide powder which can effectively and advantageously perform the environmental clarification, for example, which can remove malodor, decomposition-remove harmful substances or pollutants in air, treat drainage, purify waste water and impart bactericidal or antifungal properties, in particular, which deteriorates mediums such as textile fiber, paper or plastic shaped article only to a negligible extent and exhibits excellent durability for a long period of time when it is coated on textile fiber, paper of plastic shaped article, incorporated into fiber or plastic shaped article, or used in the form of a coating material.
Other objects of the present invention are to provide a process for producing the above-mentioned photocatalytic titanium dioxide powder, a polymer composition comprising an organic polymer and the photocatalytic titanium dioxide powder, a shaped article made of the polymer composition, and a structure having a coating formed from the polymer composition.
To sum up, the objects of the present invention are to provide a photocatalytic titanium dioxide powder capable of exhibiting durable photocatalytic activity in the environment irradiated with strong light such as sunlight, a polymer composition comprising the photocatalytic powder, a shaped article made of the polymer composition, and a structure having a coating of the polymer composition.
As a result of extensive researches to attain the above-described objects, the present inventors have found that when a first supported layer composed of a calcium compound is formed on the surface of finely divided titanium dioxide particle, and further, a porous second supported layer composed of a photocatalytically inactive and substantially water-insoluble substance is formed on the surface of the first supported layer-formed titanium dioxide particle, the photocatalytic activity of finely divided titanium dioxide particle can be maintained for a long time without substantial deterioration of mediums such as textile fiber, paper and plastic material, i.e., the two supported layer-formed titanium dioxide particle exhibits durable photocatalytic activity.
In one aspect of the present invention, there is provided a photocatalytic titanium dioxide powder comprising finely divided titanium dioxide particles each having supported on the surface thereof a first supported layer comprising a calcium compound, and further having supported on the surface of said first supported layer-formed titanium dioxide particle a porous second supported layer comprising a photocatalytically inactive and substantially water-insoluble substance. The substantially water-insoluble substance preferably has a solubility product in water as measured at 25° C. of not larger than about 10
−25
.
In other aspects of the present invention, there are provided processes for producing the above-mentioned titanium dioxide powder, which include:
(1) a process for producing a photocatalytic titanium dioxide powder, comprising the steps of:
allowing a calcium compound to be supported on the surface of finely divided titanium dioxide particles to form a first supported layer; and then,
allowing a material capable of forming a photocatalytically inactive and substantially water-insoluble substance to be supported on the surface of said first supported layer-formed titanium dioxide particles, followed by drying or burning said material-supported titanium dioxide particles to form a porous second supported layer comprising the photocatalytically inactive and substantially water-insoluble substance;
(2) a process for producing a photocatalytic tit
Hagihara Hiroyuki
Ito Katsura
Bell Mark L.
Hailey Patricia L.
Showa Denko Kabushiki Kaisha
Sughrue & Mion, PLLC
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