Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-07-14
2001-09-18
Berman, Susan W. (Department: 1711)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S378000, C428S380000, C428S384000, C502S208000, C502S350000, C502S402000, C502S522000, C523S125000
Reexamination Certificate
active
06291067
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a photocatalytic powder, and a process for producing the powder, which is used as an environmental clarification material for removing malodors, decomposition-removing harmful substances or pollutants in air, effecting drainage or water purification, or killing bacteria or algae in water, which is particularly suitably used in the form such that the powder is incorporated in organic fibers or plastics by kneading or embedding. The invention further relates to a polymer composition comprising the photocatalytic powder, a shaped article made from the composition, and a process for making the shaped article.
(2) Description of the Related Art
For preventing or removing malodors or removing harmful substances in air, a method of absorbing these by an acid or alkali solution or adsorbent has heretofore been widely used in many fields. However, this method has a problem in the treatment of a waste solution or an adsorbent used which may cause secondary pollution. A method of concealing malodors using a fragrance may also be used, however, the odor of fragrance may soak into food, thus, this method has a fear of damages by the order of fragrance itself (see, for example, Konosuke Nishida,
Daihyakka
-
jiten
(
Encyclopedia
), Vol. 1, p. 136, published by Heibon Sha (1984)).
When titanium oxide is irradiated with light, an electron having a strong reducing action and a positive hole having a strong oxidizing action are generated and a molecular seed coming into contact therewith is decomposed by the oxidation-reduction action. Using such an action, namely, photocatalytic action of titanium oxide, organic solvents dissolved in water, environmental pollutants such as agricultural chemicals and surface active agents, or harmful substances in air or malodors can be decomposition-removed. This method utilizes only titanium oxide and light and can be repeatedly used, and moreover, the resulting reaction product is a harmless carbon dioxide or the like. Furthermore, this method is more free of restriction on the reaction conditions such as temperature, pH, gas atmosphere and toxicity, as compared with the biological treatment using microorganisms, and is advantageous in that those, which are difficult to decompose or remove by the biological treatment, such as organic halogen-containing compounds or organophosphorus compounds, can be easily decomposed and removed.
However, in conventional researches on decomposition and removal of organic materials using photocatalysis of titanium dioxide, a titanium dioxide powder as it is has been used as the photocatalyst (see, for example, A. L. Pruden and D. F. Ollis,
Journal of Catalysis,
Vol. 82, 404 (1983); H. Hidaka, H. Jou, K. Nohara and J. Zhao,
Chemosphere,
Vol. 25, 1589 (1992); and Teruaki Kubo, Kenji Harada and Kei-ichi Tanaka,
Kogyo Yosui
(
Industrial Water
), No. 379, 12 (1990)). Accordingly, there are difficulties in the handling or use, for example, the used photocatalyst is difficult to recover. Due to this, use of a titanium dioxide photocatalyst has been not easily realized in practice. To overcome this problem, use of a titanium dioxide catalyst by kneading it into fibers or plastics which are easy to handle has been attempted. However, not only the harmful organic materials or environmental pollutants but also the fibers or plastics themselves are readily decomposed by the strong photocatalytic action of titanium dioxide to cause serious deterioration. Thus, use of titanium dioxide photocatalyst by kneading it into fibers or plastics cannot be actually employed.
JP-A-9-239277 (the term “JP-A” as used herein means an “unexamined Japanese patent publication”) has proposed a photocatalyst carrier comprising a titanium dioxide particle on which surface an optically inactive compound such as aluminum, silicon or zirconium is island-like supported. This proposed technique of treating the surface of a titanium dioxide particle with an optically inactive compound such as aluminum, silicon or zirconium to support the compound is a technique originally developed in the field of cosmetics or pigments so as to greatly reduce the catalytic activity of titanium dioxide. However, this method suffers from a contradiction such that when the reaction of titanium oxide with fibers or plastics is intended to prevent, the photocatalytic action is in turn greatly reduced at the same time. Furthermore, when the surface-treated titanium dioxide is used as a photocatalyst for a bactericidal or fungicidal material, since fungi scarcely adhere to the photocatalyst, for example, under running water, the photocatalytic effect is difficult to bring out, the efficiency is poor and the durability is inferior.
DISCLOSURE OF THE INVENTION
By taking account of the above-mentioned problems of conventional techniques, the first object of the present invention is to provide an environmental clarification powder which can effectively, economically and safely perform the environmental clarification such as removal of malodors, decomposition-removal of harmful substances or pollutants in air, drainage or water purification, and killing of fungi or molds, particularly when the powder is used after it is supported by kneading with or embedding in an organic polymer medium such as organic fibers or plastics, the powder can exhibit a photocatalytic action superior in view of durability without causing any deterioration of the organic polymer medium.
The second object of the present invention is to provide a process for producing such a photocatalytic powder for environmental clarification.
The third object of the present invention is to provide an organic polymer composition having incorporated therein such a photocatalytic powder for environmental clarification.
The fourth object of the present invention is to provide a polymer shaped article produced from the said organic polymer composition, and a process for making the polymer shaped article.
As a result of extensive researches for achieving the above-described objects, the present inventors have found that, when finely divided titanium dioxide particles are dispersion-treated in an aqueous slurry containing an anionic surface active agent, and then a coating of calcium phosphate is formed on at least part of the surface of each titanium dioxide particle, a calcium phosphate coating having enhanced durability can be obtained, and further that, since this coating is porous and has a property of adsorbing miscellaneous fungi, the photocatalytic function of the titanium dioxide particles is not impaired and, when the titanium dioxide particles are supported on an organic polymer medium, the durability of the medium is remarkably improved. The present invention has been accomplished based on these findings.
Thus, in one aspect of the present invention, there is provided a photocatalytic powder for environmental clarification, comprising finely divided titanium dioxide particles having a coating of porous calcium phosphate formed on at least part of the surface of each finely divided titanium dioxide particle, wherein an anionic surface active agent is present at least on the interface between said coating of porous calcium phosphate and the finely divided titanium dioxide particle.
In another aspect of the present invention, there is provided a process for producing a photocatalytic powder for environmental clarification, comprising dispersing finely divided titanium dioxide particles in an aqueous slurry containing an anionic surface active agent, and then forming a coating of porous calcium phosphate on at least part of the surface of each finely divided titanium dioxide particle.
In still another aspect of the present invention, there is provided a polymer composition comprising an organic polymer and about 0.01% to about 80% by weight, based on the weight of the polymer composition, of the above-mentioned photocatalytic powder for environmental clarification.
In a further aspect of the present invention, there is provided a process for mak
Hagihara Hiroyuki
Ito Katsura
Nonami Toru
Taoda Hiroshi
Berman Susan W.
Japan as represented by Director General of the Agency of Indust
Sughrue Mion Zinn Macpeak & Seas, PLLC
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