JPH08156175A - Antibacterial and antifungal coated steel panel excellent in weldability - Google Patents

Abstract

PURPOSE: To obtain a highly corrosion-resistant steel panel showing excellent antibacterial/antifungal action over a long period of time. CONSTITUTION: A Zn on Zn alloy plating layer is formed on a stainless steel panel being a substrate and a thermosetting coating layer containing an antibacterial/antifungal agent is further applied to the plating layer. The Zn alloy plating layer contains Fe, Ni and Co. As the antibacterial/antifungal agent, an inorg. chemical agent such as Ag, Cu or Zn, a compd. type chemical agent such as zinc phosphate or zinc oxide or an org. chemical agent such as thiazole or imidazole is used. By this constitution, excellent antibacterial/antifungal action can be kept for a long period of time by the antibacterial/antifungal agent and a corrosion product of Zn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated steel sheet that maintains excellent antibacterial and antifungal properties for a long period of time.

[0002]

2. Description of the Related Art With the increasing airtightness of buildings, there is an increasing tendency for molds and germs to be generated on walls and fixtures. For example, in the water around sinks, bathtubs, etc. that are constantly exposed to a moist atmosphere, since the moist atmosphere is maintained for a long time as the building becomes airtight, the generation and propagation of mold and other bacteria cannot be avoided. . If mold, bacteria, etc. adhere to the skin, it will cause slimy skin.
Gives the user an extremely unpleasant impression. In addition, in the fields of food and hygiene, although environmental requirements are strict, generation of mold, germs and the like due to buildings and equipment used cannot be avoided. Therefore, antibacterial and antibacterial
A coated steel sheet coated with a thermosetting paint containing an antifungal agent has come into use. As the antibacterial / antifungal agent added to the thermosetting paint, inorganic agents such as Ag, Cu and Zn, compound agents such as zinc phosphate and zinc oxide,
Organic drugs such as thiazole and imidazole are known. Inorganic drugs have a long-lasting effect, but have the drawback of being inferior in antifungal properties. Therefore, when it is desired to enhance both antibacterial and antifungal properties, a paint containing an organic chemical is used.

[0003]

The antibacterial and antifungal properties show more excellent characteristic values as the amount of the antibacterial and antifungal agent added to the paint increases. However, if the amount of the antibacterial / antifungal agent added is too large, not only the processability of the coating film and the boiling water resistance are deteriorated, but also the human body may be adversely affected. Therefore, it is recommended to use an organic drug that exhibits a large antibacterial / antifungal action even if the same amount is added. However, organic drugs are highly consumed by elution, and there is a problem in sustaining the effects. In addition, a drug with no antibacterial / antifungal action is a nutrient source for various fungi, which may rather promote the growth of fungi and other fungi. In order to obtain a given antibacterial and antifungal property, it is necessary to make the thermosetting coating film water-permeable so that the drug is eluted on the surface. However, when using a coated steel sheet with a permeable coating film in a high humidity environment or an environment where it is immersed in water,
Moisture penetrates into the coating base steel as the organic chemicals elute.

Due to the permeation of water, when the base steel is ordinary steel, corrosion progresses and red rust occurs. As the corrosion progresses, the coating film peels off and a gap is created between the base steel and the original functions such as antibacterial and antifungal properties are impaired. Even if the base steel is a high corrosion resistant steel such as stainless steel, since the base does not have effective antibacterial and antifungal properties, there is a concern that bacteria may be generated from the coating base. In addition, since stainless steel is a passive film on the surface, the coating adhesion is poor. Therefore, a special pretreatment is required at the time of coating in order to form a coating film that adheres to the surface of the base steel so as not to generate a gap where bacteria are generated. The present invention has been devised to solve such a problem, and paying attention to the fact that the corrosion product of the Zn-plated layer exhibits antibacterial / antifungal properties, and by using a Zn-plated stainless steel sheet as a base, , Even when using an organic drug that is quickly consumed as an antibacterial / antifungal agent, it maintains excellent antibacterial / antifungal properties and corrosion resistance for a long period of time without increasing the amount of the drug compounded in the paint. The purpose is to provide a coated steel sheet.

[0005]

In order to achieve the object, an antibacterial / mildewproof coated steel sheet of the present invention has a stainless steel as a base on which a Zn plating layer or a Zn alloy plating layer is formed. It is characterized by having a thermosetting coating containing an antibacterial / antifungal agent. As the stainless steel, one having a Cr content in the range of 12 to 16% by weight is preferable, and either a ferritic type or an austenitic type is used. For the Zn alloy plating layer, Fe, Ni
And one or more of Co are formed.
The content of Fe, Ni, Co or the like is preferably small so that the sacrificial anticorrosive action of Zn can be effectively exhibited and zinc oxide can be produced. However, if the content is too low, the corrosion resistance decreases, so a range of 5 to 30% by weight is preferable. As the antibacterial / antifungal agent, one or more selected from inorganic agents such as Ag, Cu and Zn, compound agents such as zinc phosphate and zinc oxide, and organic agents such as thiazole and imidazole are used. To be done.

[0006]

[Function] When zinc plating or Zn alloy plating is applied to stainless steel, Z which cannot be obtained by the conventional Zn plated steel sheet
n exhibits the anticorrosion action. That is, in the conventional Zn-plated steel sheet, since the corrosion is suppressed by the sacrificial anticorrosion action of Zn, the corrosion of the base steel proceeds when the metal Zn disappears. On the other hand, in the case of Zn-plated stainless steel, JP-A-1-132792 and JP-A-2-4-2
As described in Japanese Patent Publication No. 996, a corrosion protection effect is exhibited by a corrosion product of Zn. Therefore, even after the Zn is consumed by corrosion, the base steel is protected as long as the corrosion product of Zn is present, the generation of red rust is suppressed, and the corrosion under the coating film is not observed. Subsequent studies by the present inventors have revealed that ZnO, Zn (OH) _{2, and the} like, which are corrosion products of Zn, exhibit antibacterial properties. Therefore, if this corrosion product is effectively used, the antibacterial property is maintained for a long period of time, and the deterioration of the antibacterial / antifungal action of the thermosetting coating film with time is suppressed. In addition, since there is a Zn plating layer or a Zn alloy plating layer on the surface of stainless steel, there is no poor adhesion of the coating film due to the passive film, and an antibacterial agent with excellent adhesion even without special pretreatment.・ An antifungal coating film is formed. As a result, even when a coating material containing a small amount of an antibacterial / antifungal agent is used, an excellent antibacterial / antifungal action lasts for a long time, and a coated steel sheet exhibiting an excellent hygiene function can be obtained.

[0007]

EXAMPLE A commercially available stainless steel SUS304 steel plate having a thickness of 0.4 mm was subjected to a nitric acid / hydrofluoric acid pickling finish, and then a Zn plating layer or a Zn alloy plating layer was formed by electroplating at a basis weight of 20 g / m ² per surface. Formed. Next, a coating type chromate treatment was applied, and a polyester resin based undercoat coating having a film thickness of 5 μm was applied thereon. Then, a polyester-based paint containing butylated melamine resin and 2-mercaptobenzimidazole as an antibacterial / antifungal agent is added,
Apply so that the dry film thickness of the coating film is 20 μm, and apply 300
It was baked and dried at ℃. For comparison, a pure stainless steel plate SUS304 and a hot-dip galvanized steel plate were coated with antibacterial and antifungal properties under the same conditions.

(Coating Adhesion Test) A test piece cut out from each coated steel sheet was bent by 180 degrees, and a cellophane tape was attached to the processed portion, and the peeled state of the tape was investigated. In addition, the adhesion of the coating film was investigated by a coin scratch test. As can be seen from Table 1 showing the investigation results, except for the solid SUS304 material, good adhesion was exhibited in the tape peeling test, and no tape peeling was observed. Also in the coin scratch test, peeling occurred in the top coating film except for the solid SUS304 material, and the adhesion between the coating base and the under coating film was good. However, with the solid SUS304 material, peeling occurred at the interface with the base, and good adhesion could not be obtained. From this, it is confirmed that the paint according to the present invention has excellent coating adhesion.

[0009]

[Table 1]

(Corrosion resistance test) A test piece cut out from each coated steel sheet was subjected to a corrosion test, and the rusting state was investigated for the flat portion, the end face and the flaw portion where a cross cut was made with a cutter. The corrosion test is a salt water treatment in which it is immersed in a 5% NaCl aqueous solution for 15 minutes, a drying treatment in which it is kept in an atmosphere of a temperature of 60 ° C. and a relative humidity of 20 to 30% for one hour, and an atmosphere of a temperature of 50 ° C. and a relative humidity of 90 to 95%. Wet treatment to hold for 1
A cycle of 100 cycles was repeated in a salt-wet combined cycle corrosion acceleration test. The surface condition after the corrosion test was observed, and the corrosion resistance was judged by the occurrence of corrosion. As shown in Table 2 showing the investigation results, in the coated steel sheet according to the present invention, no corrosion was detected in the flat portion and white rust was detected in the flaw portion and the end surface. White rust was a corrosion product including zinc oxide, which exhibits antibacterial properties. In the coated steel sheet obtained from the hot-dip galvanized steel sheet, the flat portion was kept in a healthy state, but white rust was observed on the flaw portion and red rust was noticeable on the end surface. In the SUS304 solid material, the flat portion kept a healthy state, and slight red rust was detected on the flaw portion and the end surface. From this comparison, it can be seen that the coated steel sheet according to the present invention is excellent in corrosion resistance after coating.

[0011]

[Table 2]

(Antibacterial test) Escherichia coil IFO 3301 was used for the test pieces cut out from each coated steel sheet.
And Staphylococcus aureus IFO 12732
The antibacterial property was evaluated by the sterilization rate. The antibacterial test was conducted as follows. Prepare a culture solution of Escherichia coli and Staphylococcus aureus that has been shaken in a normal broth medium at 35 ° C for 16 to 20 hours, and drop 1 ml of a culture solution prepared by diluting the culture solution 20,000 times with sterile phosphate buffer solution onto the surface of the test piece. And stored at 25 ° C.
Twenty-four hours after storage, the test pieces were washed out with SCDLP medium, and the number of viable cells of the resulting liquid was measured by the pour plate culture method (culture at 35 ° C. for 2 days) using a standard agar medium. And the sterilization rate was produced according to the following formula. Sterilization rate (%) = [(the number of viable cells at the start of measurement minus the number of viable cells after 24 hours) / (the number of viable cells at the start of measurement)] × 100 As seen in Table 3 showing the results of antibacterial test. The coated steel sheet to which the antibacterial / antifungal agent was added exhibited a good sterilizing action against both Escherichia coli and Staphylococcus aureus. On the other hand, the antibacterial property was not recognized in the solid SUS304 steel plate and the polyester-based coated steel plate to which the antibacterial / antifungal agent was not added.

[0013]

[Table 3]

The antibacterial durability was measured for 5 months under the same test conditions. The sterilization rate of various materials changed as shown in FIG. 1 according to the progress of the test period. The sterilization rate of the stainless steel SUS304, which has only been subjected to antibacterial coating, has decreased with the passage of time, suggesting that the antibacterial / antifungal agent during coating is exhausted. The sterilization rate of the stainless steel SUS304 just plated with Zn increased with the passage of time, which suggests that the corrosion product of Zn produced by the progress of corrosion of the Zn plating layer exhibits an antibacterial action. . On the other hand, in the coated steel sheet according to the present invention, a high antibacterial action is maintained from the beginning to the end of the test period, and it has both the functions of the antibacterial coated stainless steel and the Zn-plated stainless steel. Can be said. The reason why such high antibacterial property is maintained is presumed as follows.

At the initial stage of the test, as shown in FIG. 2 (a), the coating film formed on the surface of the steel sheet contains a required amount of the antibacterial / antifungal agent, so that the effect of the antibacterial / antifungal agent is effective. To be demonstrated. The antibacterial and antifungal agents in the coating film are consumed over the test period, but the coating film is water permeable, so
As shown in (b), the corrosion of the plating layer progresses due to the permeated water. Then, as shown in FIG. 2C, the oxide such as Zn oxide which is a corrosion product penetrates into the coating film, and the antibacterial property caused by the corrosion product is developed. As a result,
As shown in (d), antibacterial properties equivalent to those of Zn-plated stainless steel are obtained. In this way, the coated steel sheet of the present invention maintains excellent antibacterial properties for an extremely long period of time. Moreover, since the Zn-plated or Zn-alloy-plated stainless steel itself exhibits antibacterial properties and high corrosion resistance, it can be used as a solid material, that is, a material as it is as Zn-plated on stainless steel, depending on the use environment.

(Antifungal test) For test pieces cut out from each coated steel sheet, JIS Z 2911 (199)
A test based on the test of the general industrial product of 2) was performed to observe the mold growth condition. As the test solution, a spore suspension was prepared by adding a glucose peptone medium to a spore suspension defined by JIS standard so as to be 1/10 of the normally used concentration in order to promote the growth of mold. When the surface of the test piece after the test was observed, mold growth was detected on the Zn-plated stainless steel plate, the pure stainless steel plate, and the polyester-based coated steel plate. It has been found that the coated steel sheet and the antibacterial / mildewproof coated steel sheet according to the present invention are materials that have no mold growth and exhibit good mildew proofing properties.

[0017]

As described above, in the coated steel sheet of the present invention, a Zn-plated or Zn alloy-plated stainless steel sheet is used as a base, and a coating film to which an antibacterial / antifungal agent is added is formed thereon. . By the combination of the base and the coating film, the properties of the antibacterial / antifungal agent are utilized in the initial stage, and the antibacterial property due to the corrosion product of the Zn plating layer is exhibited after a long time. As a result, excellent antibacterial and antifungal action lasts for an extremely long period of time,
It is a suitable material for members that require antibacterial and antifungal properties such as sanitary equipment. Further, since it is possible to obtain an excellent antibacterial / antifungal action without increasing the amount of the antibacterial / antifungal agent added, there is no adverse effect on the environment or the human body. Moreover, since the base is Zn-plated stainless steel having excellent corrosion resistance, it is used as a material having excellent durability even in a severe corrosive environment where chlorine ions are present.

[Brief description of drawings]

FIG. 1 is a graph showing changes with time of sterilization rates of various steel sheets.

FIG. 2 is a diagram illustrating a synergistic action of an antibacterial / antifungal agent and a corrosion product of Zn, which maintain an excellent antibacterial / antifungal effect for a long period of time.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Waka Dai Harada 4976 Nomura-Minamimachi, Shinnanyo-shi, Yamaguchi Nisshin Steel Co., Ltd.

Claims (3)

[Claims] 1. A stainless steel base material, on which Zn is applied.
Plating layer or Zn alloy plating layer is formed,
An antibacterial and antifungal coated steel sheet with excellent durability that has a thermosetting coating containing an antifungal agent. 2. The Zn alloy plating layer according to claim 1 is F.
An antibacterial / antifungal coated steel sheet having excellent durability, which contains one or more of e, Ni and Co. 3. The antibacterial / antifungal agent according to claim 1 is Ag,
An antibacterial / antifungal agent having excellent durability, which is one or more selected from inorganic agents such as Cu and Zn, compound agents such as zinc phosphate and zinc oxide, and organic agents such as thiazole and imidazole. Coated steel sheet.