Stock material or miscellaneous articles – Composite – Of metal
Utility Patent
1998-05-06
2001-01-02
Speer, Timothy M. (Department: 1775)
Stock material or miscellaneous articles
Composite
Of metal
C428S472200, C428S907000, C428S472000, C424S414000, C424S618000, C424S630000, C424S641000, C424S711000, C427S419200, C427S435000, C205S324000
Utility Patent
active
06168869
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an aluminum product having an improved anodic oxide coating and a method for producing the same.
In the past, aluminum had widely been used as table wares. Nowadays, it has also been applied to architectural materials ranging from interior components including door knobs to window sashes, and are indispensable as the architectural materials and items. In addition, aluminum is also applied to heat-transfer fins of air conditioners and the like due to an advantage of high heat-conductivity.
In general, in order to prevent an aluminum product from corrosion, there is formed an anodic aluminum oxide coating (known as the registered trade name “ALUMITE”) made of aluminum oxide on surfaces of the aluminum product. The anodic oxide coating has a high hydrophilic property and thus a microbial accompanying water is easy to adhere to the coating.
The architectural components are frequently touched by hands of unspecified number of persons. Furthermore, they have little occasion to be washed because they are hard to be detached. Therefore, when aluminum is applied to the architectural material, the microbials adhered to the surface of the material are liable to propagate thereon.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to solve the above-mentioned problems and provides an aluminum product which has a constantly clean anodic oxide coating.
The present invention provides an anti-microbial aluminum product that has a porous anodic oxide coating carrying an inorganic bacteria controlling ingredient in the micropores.
The present invention also provides a method for producing an anti-microbial aluminum product comprising the steps of:
forming an oxide coating on a surface of an aluminum core for the product by anodically polarizing the aluminum core in an electrolyte solution; and
making an inorganic bacteria controlling ingredient be carried in micropores of the oxide coating by immersing the aluminum core in a solution containing an inorganic bacteria controlling ingredient.
In a preferred mode of the method for producing an anti-microbial aluminum product, the method further comprises the step of sealing the surface of the oxide coating.
The present invention makes the inorganic bacteria controlling ingredient be carried in the micropores with a diameter of 10 to 20 nm existing in the anodic oxide coating of the aluminum product. For an aluminum product to be applied to use accompanying a contact with water, the aluminum core is further subjected to the sealing treatment of the anodic oxide coating so as to prevent the bacteria controlling ingredient from falling off. By this treatment, the anti-microbial property of the aluminum product can be maintained for a long period.
This sealing of the anodic oxide coating does not mean a complete occlusion of the micropores containing the bacteria controlling ingredient. The bacteria controlling ingredient is gradually released from the micropores through minute gaps remaining after the sealing, and the released bacteria controlling ingredient demonstrates a performance of preventing the propagation of the microbials. For a product with no occasion of coming in contact with water, the above-mentioned sealing treatment is not necessarily required.
In another preferred mode of the present invention, a compound of at least one metal selected from the group consisting of silver, copper and zinc is used as the bacteria controlling ingredient which gives the anti-microbial property to the anodic oxide coating of the aluminum product. Among the compounds, a thiosulfato complex, in particular silver thiosulfato complex, is preferable. A solution of silver thiosulfato complex is preferably prepared by adding potassium sulfite to a saturated aqueous solution of silver acetate, then adding potassium thiosulfate to the aqueous solution. Here, silver acetate, potassium sulfite and potassium thiosulfate may be mixed in a molar ratio of 1:3:3.
The silver thiosulfato complex is absorbed to the surface of the anodic oxide coating and firmly adhered thereon since the anodic oxide coating is charged positively and the silver thiosulfato complex is an anion. In addition, since the silver thiosulfato complex is an anion, it has a low reactivity with chlorine and hardly reacts with a chlorine bleaching agent, sweat on the hands, other chemicals such as an invert soap (benzalkonium chloride) which is frequently used in medical institution, or the like. Therefore, the anti-microbial property is maintained for a long period when the silver thiosulfato complex is employed as the bacteria controlling ingredient.
Furthermore, the silver thiosulfato complex has advantages of colorlessness and of a higher stability against light as compared with the other silver salts, and another advantage of being stabilized still more in color change on aging when it is once adsorbed on the anodic oxide coating.
The silver thiosulfatocomplex has another advantage of high safety. It has a low acute toxicity with LD
50
of larger than 2,000 mg/kg, and shows negativity to both primary skin irritation test and mutagenicity test. Further, it requires less care in environmental pollution. Thus, a great value is brought to the industry, in a case of applying the silver thiosulfato complex to the bacteria controlling ingredient.
Therefore, the silver tiosulfatocomplex is particularly suited for the bacteria controlling ingredient.
In another preferred mode of the present invention, the anti-microbial aluminum product further comprises an organic anti-fungal agent of low molecular weight carried in said micropores.
In still another preferred mode of the present invention, an organic anti-fungal agent of low molecular weight such as 2-(4-thiazolyl)-benzimidazole (hereinafter referred to as “TBZ”) is also used in addition to the bacteria controlling ingredient. It is preferable to immerse the anodic oxide coating into a polar solvent solution of TBZ or an aqueous dispersion thereof to give the oxide coating an anti-fungal property.
Further, a dye may be contained in the solution of the bacteria controlling ingredient.
In one of the methods for sealing the anodic oxide coating carrying the bacteria controlling ingredient, the anodic oxide coating is immersed in the above-mentioned aqueous solution of silver thiosulfato complex at a temperature of not less than 80° C. for about 10 minutes. The sealing treatment may also be carried out by immersing the anodic oxide coating in a hot water. However, in order to prevent the complex once adsorbed in the micropores from diffusing into the water, it is preferable to carry the sealing treatment by using an aqueous solution of silver thiosulfato complex at a higher temperature of not less than 80° C. which is higher than that of the aqueous solution of silver thiosulfato complex used in the previous step of making the complex be carried.
In another method for sealing the anodic oxide coating, the anodic oxide coating is immersed in a solution containing at least one member selected from the group consisting of an acetate of nickel, acetate of cobalt and chromates thereof at not less than 80° C. for not less than 3 minutes.
In still another method for sealing the anodic oxide coating, the anodic oxide coating is immersed in a reactive organic silicone compound such as tetraethoxysilane or the like, and the reactive organic silicone compound is hydrolyzed on the surface of the anodic oxide coating thereby to produce silicon dioxide. As the reactive organic silicone compound used here, an alcohol solution of tetraethoxysilane is suitable.
Usually, the anodic oxide coating is industrially produced by a series of treatments of degreasing, anodizing, sealing, washing with water and painting, after the substrate plate of aluminum has been worked to have a desired shape. Any of a sulfuric acid method, oxalic acid method, chromic acid method, organic acid-added sulfuric acid method or the like known as a method for forming the anodic oxide coating can be applied to the present inv
Tomioka Toshikazu
Yoshida Akihiko
Matsushita Electric - Industrial Co., Ltd.
McDermott & Will & Emery
Speer Timothy M.
Young Bryant
LandOfFree
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