JPH11181596A - Antibacterial anodic oxidation treated aluminum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain antibacterial properties in aluminum even without depending on antibacterial coating by allowing antibacterial metal or the compd. thereof to be adsorbed an sealrd into the fine pores of anodically oxidized coating. SOLUTION: Prepd. Alumite(R) is immersed into an aq. soln. of antibacterial metal salt, antibacterial metal 20 is adhered to the insides of the fines pores 15 of anodically oxidized coating 18, and furthermore, sealing 22 is execute by sealing treatment. As for the form of the antibacterial metal 20, it is the one of metal salt or oxide in the case the metallic ions of metal salt is not subjected to reducing operation, and it is the form of metal in the case it is subjected to reducing operation. The sealing 22 is executed by transforming aluminum forming the anodically oxidized coating 8 into aluminum hydroxide. As the antibacterial metal 20, silver, copper, zinc and the compds. thereof are given, and among these, silver salt, particularly silver nitrate is preferable since it is excellent in antibacterial propeties and solubility to water. In the case the Alumite(R) is simultaneously subjected to electrolytic pigmentation, it is possible that it is added with alkyl sulfonic acid, and AC. electrolysis is simultaneously executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to anodized aluminum having antibacterial properties (hereinafter commonly referred to as "alumite").

[0002]

BACKGROUND ART In recent years, aluminum products have been used for building materials (particularly, interior materials and sashes), housing equipment, electric equipment, and the like because of their light weight, excellent corrosion resistance, and ease of colorization. It is frequently used for transportation equipment, medical equipment, stationery and the like.

[0003] On the other hand, due to the growing trend toward cleanliness and safety in the market in recent years, and furthermore, the social problem of food poisoning caused by pathogenic Escherichia coli, the demand for "antibacterial" treatment of aluminum products is increasing.

[0004] The conventional antibacterial treatment of aluminum products is the same as that of other metal products in that a resin-based paint (usually heat-treated) in which an antibacterial metal ion is immobilized on ceramic and a finely divided inorganic antibacterial agent is mixed. (Curable type) The anti-bacterial coating was formed (Summary of the 3rd Aluminum Technology Lecture "The latest attention aluminum" antibacterial and antifungal technology "edited by the Japan Light Metal Association Development Theme Committee) Shu "(October 1997), pp. 1-18).

[0005]

However, inorganic antibacterial agents are generally expensive, and the antibacterial coating is a resin coating, and the antibacterial properties may be attenuated over time due to abrasion or the like.

[0006] In view of the above, an object of the present invention is to provide an antibacterial alumite having antibacterial properties without using an antibacterial coating film and a method for producing the same.

Another object of the present invention is to provide an antibacterial alumite which hardly loses its antibacterial properties due to abrasion and the like, and a method for producing the same.

[0008]

The antibacterial alumite according to the present invention solves the above problems by the following constitution.

In the alumite having an anodized film and having an antibacterial property, an antibacterial metal (including the form of a compound; the same applies hereinafter) is adsorbed and enclosed in pores of the anodized film.

Here, as the antibacterial metal, silver or a silver compound is preferable because of its excellent antibacterial action as compared with other antibacterial metals.

The alumite having the above structure can be easily produced by the following method.

[0012] Aluminum (alumite) provided with an anodized film is immersed in a solution of an antibacterial metal salt to adsorb the antibacterial metal into the pores of the anodized film, and then subjected to sealing treatment. Alternatively, aluminum (alumite) provided with an anodized film is immersed in a solution of an antibacterial metal salt to perform a sealing treatment simultaneously with adsorption of the antibacterial metal into the pores of the anodized film.

Further, the aluminum provided with the anodic oxide film is subjected to alternating current electrolysis in a solution of an antibacterial metal salt, thereby electrolytically coloring and simultaneously adsorbing the antibacterial metal into the pores of the anodic oxide film. It can also be manufactured by performing a sealing treatment. Usually, it is desirable that the above solution contains an alkylsulfonic acid in order to improve the electrolytic property.

In each of the above cases, silver nitrate is desirable as the antibacterial metal salt because of its excellent solubility in water and antibacterial effect of silver.

[0015]

The antimicrobial alumite of the present invention or the antimicrobial alumite produced by the method of the present invention has antimicrobial ions carrying antimicrobial metal such as silver directly in the pores of the anodic oxide film. It is sealed in the form.

[0016] For this reason, it is possible to impart antibacterial properties to the alumite without forming a special antibacterial coating film on the alumite. In addition, since the antimicrobial metal service ions are encapsulated in the pores of the anodized film, which has excellent wear resistance and excellent adhesion, the antibacterial properties may be attenuated due to wear of the surface film. Absent.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (1) A method for producing an antibacterial alumite of the present invention will be described (see FIG. 1).

First, pretreatment such as degreasing, causticity, and neutralization is performed on aluminum or aluminum alloy (base), and then anodization is performed.

Specifically, in the degreasing treatment, fats and oils adhering to the surface of the substrate are removed with a detergent. In caustic treatment,
A 5 to 8 wt% aqueous solution of caustic soda is heated to 50 to 60 ° C. to remove oxides on the surface of the substrate and to clean the substrate. In the neutralization process,
10-15% nitric acid or sulfuric acid neutralizes the remaining caustic soda and removes contaminant metals or their compounds remaining on the substrate surface. After each treatment, all are usually washed with water.

The anodic oxidation treatment is a treatment in which a substrate is used as an anode, oxygen is generated by electrolysis, and aluminum is oxidized to form an aluminum oxide layer. At this time, a direct current or an alternating current flows through the cathode using carbon, lead, aluminum or the like as an electrode.

That is, the aluminum base 12 serving as the anode
Then, anions (for example, SO ₄ ^-2 ) are sucked to generate oxygen to form a thin barrier layer 14 having a thickness of 10 to 50 nm, and at the same time, a hexagonal column-shaped cell having a pore 15 in the center (about 80 nm in diameter). 16 are formed, the anions reach the bottom of the cell through the holes of the cell, and oxidation is performed through the barrier layer 14 to grow the cell 16 (see FIG. 2). Along with the growth of the cell 16, the growth rate is suppressed, and the growth of the cell 16 is substantially stopped by dissolution of the oxide film by the sulfuric acid electrolytic solution, and a porous film (frost column-shaped film) 18 of alumina (aluminum oxide) is formed. Is formed.

As the electrolytic solution used at this time, an electrolyte containing sulfuric acid, oxalic acid, chromic acid, sulfamic acid, tartaric acid, or the like is used so that the porous coating (frosted column-shaped coating) 18 is formed. Usually, an aqueous solution of sulfuric acid is used. This is because the conductivity is good, the cost is low, and the management is simple. Furthermore, since the coating is transparent, the post-treatment of electrolytic coloring is easy.

At this time, the current density is 0.5 to 5 A / d
m ² , preferably 0.5 to 3.0 A / dm ² . The film thickness is usually 6 μm or more for indoor use and 6 to 15 μm for outdoor use. Further, in the case of hard alumite, the thickness is 30 to 60 μm.

(2) The alumite prepared as described above is immersed in an aqueous solution of an antibacterial metal salt,
0 in the pores of the anodized metal coating 18,
Sealing 22 is performed by sealing processing. At this time, the form of the antibacterial metal 20 is a form of a metal salt or an oxide when the metal ions of the metal salt are not reduced, and a form of the metal when the metal ions are reduced. In addition, the sealing is usually performed by converting alumina forming the anodized metal coating into aluminum hydroxide.

Here, examples of the antibacterial metal include silver, copper, zinc and their compounds (oxides, salts).
Among them, silver salts, particularly silver nitrate, are preferable because they have excellent antibacterial properties and also have excellent solubility in water (high ionization degree).

The concentration of the metal salt is 0.5 to 10 g /
L, preferably 1 to 5 g / L.

The bath temperature is 50 to 95 ° C., preferably 80 to 90 ° C. when the sealing treatment is performed later, and 70 to 95 ° C., preferably 85 to 90 ° C. when the sealing treatment is performed simultaneously. ~ 95 ° C. If the bath temperature is too low, the treatment time will be prolonged, and if the bath temperature is too high, it will be difficult to control the bath temperature to prevent boiling.

The treatment time is 3 to 10 min when the sealing treatment is performed later, and 7 to 15 mi when the sealing treatment is performed.
Let n.

When electrolytic coloring (coloring treatment) is simultaneously performed on the alumite, an alternating current electrolysis may be performed simultaneously with addition of an alkylsulfonic acid. The concentration of the alkylsulfonic acid is usually 5 to 30 g / L.

For example, when the treatment is performed at 1.0 V for 2 minutes in a treatment bath containing 3 g / L of silver nitrate and 15 g / L of methanesulfonic acid, the anodic oxide film becomes golden and becomes light brown in 5 minutes. Also, 1.
The anodic oxide film turns brown when the operation is performed at 5 V for 2 minutes.

After the antibacterial metal salt adsorption treatment,
Perform a sealing process. The sealing treatment is performed, for example, in hot water of nickel acetate or triethanolamine at 90 ° C. or higher.

[0032]

EXAMPLES (1) Next, examples performed to confirm the effects of the present invention will be described.

The alumite used was an aluminum base (50 mm × 50 mm × 1 mmt) in an anodizing bath (15 wt.
% Sulfuric acid, bath temperature: 20 ° C), 1 A / dm ² × 30 min
Anodized (voltage: 17 V, cathode: lead electrode) was used under the conditions described above.

<Example 1> Antibacterial treatment bath (silver nitrate concentration: 3)
g / L, bath temperature: 85 ° C.) for 5 minutes to perform antibacterial treatment.

Thereafter, sealing treatment was performed for 10 minutes in boiling water of a sealing treatment bath (triethanolamine: 3 g / L).

Example 2 Antibacterial treatment bath (silver nitrate concentration: 3)
g / L, bath temperature: 90 ° C.) for 10 minutes to perform antibacterial treatment and sealing treatment.

<Comparative Example 3> Only the sealing treatment was performed for 10 minutes in boiling water of a sealing bath (triethanolamine: 3 g / L).

(2) An antibacterial test was carried out on each of the sealed alumites prepared as described above (film adhesion method). In addition, Staphylococcus aureus (Stap
hylococcus aureus (IFO 123272)) was used.

From Table 1 showing the test results, it can be seen that the antibacterial alumite of each example has good antibacterial properties.

[0040]

[Table 1]

[0041]

The antimicrobial alumite of the present invention is provided with an anodized film, and in the alumite having antimicrobial properties, an antimicrobial metal salt is adsorbed and enclosed in pores of the anodized film. The following operations and effects are achieved.

The antibacterial property is imparted to the pores by directly attaching the antibacterial metal to the pores without depending on the antibacterial coating, so that it is not necessary to use an antibacterial paint containing an expensive antibacterial agent. Further, since the antibacterial metal is adsorbed in the pores of alumina having much higher hardness than the resin, the antibacterial metal is not lost due to abrasion or the like. Therefore, the antibacterial action can be maintained semipermanently.

[Brief description of the drawings]

FIG. 1 is a process chart showing a method for producing an antibacterial alumite of the present invention.

FIG. 2 is a cross-sectional view of a model of the antibacterial alumite of the present invention.

[Explanation of symbols]

 12 Aluminum base 15 Anodized coating pores 18 Anodized coating 20 Antibacterial metal 22 Sealing

Claims (7)

[Claims] 1. An anodized aluminum having an anodized film and having an antibacterial property, wherein an antibacterial metal (including a compound form; the same applies hereinafter) in pores of the anodized film.
Is an antibacterial anodized aluminum characterized by being adsorbed and sealed. 2. The antibacterial anodized aluminum according to claim 1, wherein the antibacterial metal is silver or a silver compound. 3. An aluminum having an anodized film,
A method for producing an antibacterial anodized aluminum, comprising immersing in an antibacterial metal salt solution to adsorb the antibacterial metal in the pores of the anodic oxide coating, and then performing a sealing treatment. 4. An aluminum having an anodized film,
A method for producing an antibacterial anodized aluminum, which comprises immersing in an antibacterial metal salt solution and adsorbing the antibacterial metal into the pores of the anodic oxide film and simultaneously performing a sealing treatment. 5. An aluminum having an anodized film,
AC electrolysis in a solution of an antibacterial metal salt causes the antibacterial metal to be adsorbed in the pores of the anodic oxide film at the same time as electrolytic coloring, and further, a pore sealing treatment is performed. Manufacturing method of treated aluminum. 6. The method according to claim 5, wherein the solution of the antibacterial metal salt is an alkylsulfonic acid-containing material. 7. The method for producing an antibacterial anodized aluminum according to claim 3, wherein the antibacterial metal salt is silver nitrate.