Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1999-08-10
2002-09-24
Bell, Mark L. (Department: 1755)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S439000, C502S527140, C502S527150, C502S527160, C502S523000, C428S472000, C428S472100, C428S325000, C428S701000, C428S702000, C427S427000, C427S190000, C427S453000
Reexamination Certificate
active
06455465
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photocatalyst coated products and a process for coating with titania (TiO
2
) as a photocatalyst having a decomposing function including deodorizing, antibacterial and soil-resisting actions, and also a hydrophilic function, more particularly to a photocatalyst coated product comprising a titania layer formed on a surface of a product to be treated made of a metal, a ceramic or a mixture thereof by injecting a titanium or titanium alloy-containing powder against the surface of the product to be treated, and also to a method for producing a photocatalyst layer as a process for forming or coating the titania layer.
Photocatalysts containing as the major component titania having excellent decomposing and hydrophilic functions have been utilized conventionally in many fields. The decomposing function will now be described. Irradiation of ultraviolet light contained in the sunlight or fluorescent light upon titania causes generation of electrons and positive holes on the titania surface, and the electrons reduce the atmospheric oxygen into super oxide ions (O
2
), whereas the positive holes oxidize the moisture deposited on the titania surface into hydroxyl group radicals (OH). These superoxide ions and hydroxyl group radicals carry out oxidative decomposition of organic compounds including soil and the like present on the titania surface.
To describe now the hydrophilic function, the superoxide ions and hydroxyl groups generated by the ultraviolet irradiation as described above decompose hydrophobic molecules present on the titania surface to produce hydroxyl groups, and the atmospheric moisture is adsorbed by the hydroxyl groups thus produced to form a thin water film, thus imparting hydrophilicity to the titania surface. Accordingly, photocatalysts are frequently utilized in lenses, interior materials and furniture, such as mirrors, wall papers and curtains for the purpose of imparting deodorizing, antibacterial and soil-preventing actions, because of their hydrophilic function as well as the decomposing function.
When these photocatalytic functions are to be utilized in products such as interior materials and furniture, the product is impregnated with titania as a major component of the photocatalyst and is irradiated well with ultraviolet light. As a technique of achieving this, it is practiced to form a titania layer on the surface of a product to be treated.
2. Description of the Prior Art
As one method of forming a titania layer, a product to be treated made of titanium or titanium alloy is oxidized on the surface to form an oxide layer or a titania layer utilizing its liability to undergo oxidation reactions, since titanium per se is an active metal and have particularly great affinity with oxygen.
As other methods for forming a titania layer, a sol-gel method and a binder method are employed.
According to the sol-gel method, an organic titanium sol such as of titanium alkoxide and titanium chelates, which are precursors of titania, is applied onto the surface of a product to be treated having heat resistance, such as glass and ceramics by means of spray coating and the like, and then dried to cause gelation, followed by heating to 500° C. or higher and form a stiff titania layer. Since titania particles are distributed over the entire surface of the product to be treated, the titania layer thus formed has high decomposition power and high hardness.
Meanwhile, according to the binder method, titania particles are immobilized on the surface of a product to be treated using a binder, for example, an inorganic binder such as silica or an organic binder such as silicone. The difference of the binder method from the sol-gel method is that the heating temperature may be the hardening temperature of the binder, so that the former requires a heat treatment at about 100° C. or lower and no high-temperature treatment.
The conventional photocatalyst coating methods described above involve the following problems.
(1) The method of forming a titania layer by surface-oxidizing a product to be treated made of titanium or titanium alloy involves problems in that titanium per se is expensive to cause cost elevation and that titanium has poor processability and the fields of its application are limited.
(2) The sol-gel method also involves a problem in that it requires a heat treatment at about 500° C. or higher for converting the organic titanium such as titanium alkoxide and titanium chelates, which are precursors of titania, into a titania layer, so that the product to be treated should have heat resistance, and that the product to be treated is limited to glass, ceramics and the like. If a titania layer is to be formed on the surface of a metal according to the sol-gel method, the metal surface is oxidized by the high-temperature heat treatment to cause reduction of commercial value due to deterioration and reduced luster.
The sol-gel method further involves a problem in that it requires much time and labor since the organic titanium is applied many times, that it requires an expensive equipment to cause cost elevation, and that harmful waste is by-produced.
(3) Meanwhile, the binder method can solve the problems inherent in the sol-gel method and enjoys merits in that it can treat various kinds of products and that it is relatively inexpensive. However, it involves a problem in that it is necessary to use as the binder a material which has high adhesion with the product to be treated and which is not susceptible to the decomposing function of the photocatalyst, and that selection of binder influences the effect of the catalyst.
Further, the titania layer formed according to the binder method has a hardness lower than that of the layer formed according to the sol-gel method, disadvantageously. In order to increase the hardness of the titania layer to be obtained according to the binder method, the amount of binder is increased to enhance adhesion. In this case, however, the amount of titania is reduced relative to the binder, and the titania layer shows poor decomposing power. On the contrary, if the amount of binder is reduced, the amount of titania to be exposed on the surface of the product to be treated is increased to show enhanced decomposing power, but the adhesion is reduced to readily cause peeling of the titania layer, resulting in the reduced hardness, disadvantageously.
SUMMARY OF THE INVENTION
The present invention was developed with a view to solving the problems described above, and it is an objective of the present invention to provide a photocatalyst coated product having excellent photocatalytic functions including the decomposing and hydrophilic functions which were imparted by forming by using a simple blasting treatment a titania powder as a photocatalyst having high hardness and high adhesion with products to be treated and a method for producing the photocatalyst layer.
In order to attain the above objective, the photocatalyst coated product according to the present invention comprises a titania layer formed on a surface of a product to be treated which is a metal product, a ceramic or a mixture of them; wherein a titanium or titanium alloy-containing powder is diffused, penetrated and oxidized into the surface of the product to be treated.
Meanwhile, the method for producing a photocatalyst layer as described above comprises injecting a titanium or titanium alloy-containing powder against a surface of a product to be treated which is a metal product, or against a ceramic or a mixture of them to effect diffusion of the titanium contained in the titanium or titanium alloy-containing powder over the surface of the product to be treated mentioned above and also oxidation of the titanium to form a titania layer.
Incidentally, the titanium or titanium alloy-containing powder is injected at an injection velocity of 80 m/sec or higher and under an injection pressure of 0.29 MPa or higher.
Further, the titanium or titanium alloy-containing powder has an average particle size of 20 to
Bell Mark L.
Fuji Kihan Co., Ltd.
Hailey Patricia L.
LaPointe Dennis G.
Mason & Associates P.A.
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