Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
1999-06-25
2001-11-06
Griffin, Steven P. (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S350000, C502S337000, C502S331000
Reexamination Certificate
active
06313064
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an alloy having antibacterial effect and sterilizing effect, and a process for producing the same.
It is known that when oxides of titanium are irradiated with ultraviolet rays, the oxides exhibit antibacterial effect and hydrophilicity by their optical catalyst action. Antibacterial materials to which this principle is applied include a tile on which a thin TiO
2
film is formed (Japanese Patent Application Laid-Open No. 8-66635). As metallic materials containing TiO
2
and having optical catalyst function, there are developed antibacterial materials containing, as a matrix, titanium or titanium alloy (Japanese Patent Application Laid-Open No. 8-252461) or nickel or nickel alloy (Japanese Patent Application Laid-Open No. 10-18095). The Japanese Patent Application Laid-Open No. 8-252461 describes a method of pickling an titanium alloy containing 0-20% of a transition metal as an auxiliary component with an inorganic acid and heat-treating the alloy, thereby forming an oxide film on its surface. The Japanese Patent Application Laid-Open No. 10-18095 states that a composite metal plating-film in which titanium oxide is dispersed is formed on the surface of nickel or a nickel-chromium alloy, and this antibacterial material is effective in spots wherein unwanted bacteria propagate easily, such as a sink in kitchen equipment in a hospital institution or other institutions.
It is known that copper is a metal exhibiting sterilizing effect. Since early times, therefore, alloy containing copper has been used for coins, ornaments, tableware and the like. Copper exhibits its sterilizing effect when target bacteria contact the copper directly or the ion of the copper is produced in an aqueous solution.
As sterilizing metallic materials containing copper, the following are proposed: a Cu-containing stainless steel (Japanese Patent Application Laid-Open No. 8-229107), a stainless steel wherein the concentration of Cu is heightened in its surface layer, and a process for producing the same (Japanese Patent Application Laid-Open Nos. 8-60301, 8-60302 and 8-60303), a material having sterilizing effect by addition of Cu to a stainless steel, whereby prevention of infection, such as periodical sterilization, is unnecessary (Japanese Patent Application Laid-Open No. 9-170053) and the like. All of them are brought into direct contact with bacteria, to sterilize the bacteria.
Titanium and materials comprising as their main component titanium, among metallic materials having antibacterial effect based on optical catalyst function, belong to metallic materials which are relatively difficult to work. Nickel or nickel alloy wherein on its surface a composite metal plating-film in which titanium oxide is dispersed is formed has problems that a complicated plating step is necessary and that if the titanium oxide content in the plating layer increases, the adhesion of the plating onto the base metal decreases.
Furthermore, metallic materials having both antibacterial effect based on optical catalyst function and sterilizing effect cannot be found in the prior art. Metallic materials having only the sterilizing effect based on optical catalyst function do not exhibit any effect when they are not irradiated with light.
BRIEF SUMMARY OF THE INVENTION
In the light of such problems in the prior art, an object of the present invention is to provide a material which has both of sterilizing effect and antibacterial effect based on optical catalyst function and has excellent workability. Another object of the present invention is to provide a material which has excellent sterilizing effect and antibacterial effect in humid air containing water vapor and in liquid, as well as in the atmosphere.
The present invention is a copper alloy comprising 0.1-7.3% (the symbol “%” means percent(s) by weight in the specification) of titanium, wherein its surface layer contains an oxide containing titanium, thereby having both of sterilizing effect and antibacterial effect based on optical catalyst function. Examples of the copper alloy of the present invention comprising 0.1-7.3% of titanium include a copper alloy which comprises 0.1-7.3% of titanium and, as its balance, copper and inevitable impurities, and a copper alloy which further comprises one or more of the following:
Zn: 0.001-10%, Si: 0.001-3%, and silver: 0.001-1%.
A further aspect of the present invention is a nickel alloy comprising 0.1-13% of titanium and 0.1-15% of copper and, as its balance, nickel and inevitable impurities, wherein its surface layer contains an oxide containing titanium.
In the present invention, copper imparts sterilizing effect, and dispersion of the oxide containing titanium having optical catalyst function in the copper alloy provides antibacterial effect. The sterilizing effect is further improved by dispersing an oxide containing zinc. Moreover, the sterilizing effect and the antibacterial effect can be effectively used in humid atmosphere containing water vapor and in liquid by dispersing an oxide containing silicon exhibiting hydrophilicity. Silver has effect of enhancing the sterilizing effect.
The alloy of the present invention can be made up into a form of a plate, a strip, a foil, a wire, an expanded metal or a tube. In order to produce the oxide containing the above-mentioned elements in the surface layer of the copper or nickel alloy of the present invention, heat treatment is conducted in the atmosphere or in vacuum in such a manner that its real temperature is set up to 200-800° C. and 200-1000° C. in the case of the copper alloy and the nickel alloy, respectively, by a heating furnace, corona discharge, glow discharge, laser rays, plasma, infrared rays, or the like. Titanium, zinc and silicon are preferentially oxidized to produce oxides. Before the treatment for producing the oxides, anodic oxidization may be performed.
When the alloy of the present invention is allowed to stand in a gas or liquid, the sterilizing effect and the antibacterial effect of its surface cause organic materials contacting the alloy to be decomposed and extinguished. Therefore, it has an effect of causing extinction, reduction, decomposition, or removal of a lot of organic materials, for example, colon bacilli and house dusts such as smoke of a cigarette, formalin, ammonia, spores of mold, pollen allergens (antigens) and ticks.
Since the alloy of the present invention is excellent in workability, it can be molded or worked into various shapes to be integrated into a required site as an antibacterial member. In the case that the alloy is a copper alloy, the alloy can be used as articles for which high electrical conductivity, thermal conductivity and corrosion resistance are made use of. In the case that the alloy is a nickel alloy, the alloy can be used as articles for which corrosion resistance in various atmospheres and strength are made good use of.
Furthermore, the alloy can be caused to have characteristics such as lightness, higher strength, higher heat resistance by cladding, adhesion or coating of the alloy onto other metallic materials, ceramics, glass, resins or the like, or mixing of the alloy with the same.
For this reason, the alloy of he present invention can be applied to the field for which sterilized or antibacterial atmosphere is necessary, such as manufacture of medicinal supplies, medical facilities, manufacture and sale of foods, and eating houses, or can be applied as building materials of interiors of places where clean environment is desired to be kept, such as halls and meeting rooms where many people meet or pass. Furthermore, the alloy can be applied to various articles, for examples, parts used in an air cleaner, or an air conditioner, and means of transport such as automobiles, ships and airplanes.
REFERENCES:
patent: 4005243 (1977-01-01), Baba et al.
patent: 5147686 (1992-09-01), Ichimura et al.
patent: 5454886 (1995-10-01), Burrell et al.
patent: 5595750 (1997-01-01), Jacbson et al.
patent: 5635439 (1997-06-01), Fukui et al.
patent: 5643436 (1997-07-01), Oga
Miyafuji Motohisa
Nakayama Takenori
Tsuzaki Yoshinobu
Urushihara Wataru
Yamada Sadako
Griffin Steven P.
Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel Ltd).
Nguyen Cam N.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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