JPH08311687A - Antifungal plated product - Google Patents

Abstract

PURPOSE: To impart an excellent antifungal property to instruments while maintaining an initial color tone of a cobalt-based plated layer as it is by preventing a discoloring and corrosion of a cobalt alloy-plated layer on the instruments requiring the antifungal property. CONSTITUTION: 1. In an antifungal plated product, an chromium-cobalt alloy- plated layer containing 2-6wt.% chromium is provided on a metal or a plastic. 2. In the antifungal plated product, (1) the cobalt-plated layer or the cobalt alloy-plated layer and (2) the chromium-cobalt alloy-plated layer containing 22-88wt.% chromium are provided in order on the metal or the plastic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for imparting antibacterial properties to metal materials and metal products, and plastic materials and plastic products.

[0002]

2. Description of the Related Art In recent years, complications caused by methicillin-resistant Staphylococcus aureus have led to various materials used in hospitals, nursing homes, general households, recreation facilities, etc. Also, efforts are being made to prevent various harmful bacteria from adhering to the product or from developing or proliferating. In particular, equipment, equipment, facilities, etc. in places where unspecified large numbers of people's hands such as hospitals, public toilets, public baths, hotels, department stores, supermarkets, companies, playgrounds, trains, buses, ships, etc. For example, even in faucets for hand-washing, cocks, valves, flush toilet levers, door knobs, bed legs, elevator touch panels, telephones, automated teller machines or transfer machines at financial institutions, harmful bacteria may adhere. Since it is considered that they are proliferating, it is necessary for hygiene to impart antibacterial properties to these instruments, devices, facilities (hereinafter simply referred to as instruments).

As a means for imparting antibacterial properties to these instruments, it is known to form a cobalt plating layer, a cobalt alloy plating layer or the like having excellent antibacterial properties. However, when these cobalt-based plating layers are formed on the outermost surface of instruments, they are likely to be discolored by contact with the outside air.
For example, cobalt plating and cobalt-nickel alloy plating change color from yellow to gray, and cobalt-tungsten alloy plating is more likely to change to grayish black, and these plating may take 2 to 3 months depending on environmental conditions. In some cases, discoloration occurs remarkably, corrosion further progresses, and the appearance may deteriorate significantly.

For this reason, it has been proposed to further apply a chromium plating layer on the cobalt plating layer or the cobalt alloy plating layer on the surface of the equipment in a thickness of 0.2 to 0.5 μm (JP-A-5-78861). Issue). This method is intended to prevent discoloration and corrosion of the above-mentioned cobalt plating layer or cobalt alloy plating layer, and also to maintain the antibacterial property of these plating layers. However, since the chromium plating layer on the surface is excellent in corrosion resistance, it has a drawback that the antibacterial effect is not sufficiently exhibited. That is, the antibacterial effect is exerted by the chemical species involved in antibacterial contact with fungi. The antibacterial chemical species here are cobalt ions or their compound ions, and the antibacterial effect is exhibited only when these diffuse to the outside (surface) through cracks, defects, etc. of the chromium plating layer. However, since the above-mentioned chromium plating layer has too high corrosion resistance, it interferes with the diffusion of the antibacterial chemical species to the surface of the plating layer and prevents the manifestation of the antibacterial effect of cobalt ions.

[0005]

Accordingly, the present invention prevents the discoloration and corrosion of the cobalt alloy plating layer on the equipment requiring antibacterial properties, thereby maintaining the aesthetic appearance of the cobalt plating layer. At the same time, its main purpose is to impart a high degree of antibacterial property to instruments.

[0006]

As a result of conducting research in view of the current state of the art as described above, the present inventor has found that chromium 6 is formed on the cobalt plating layer or the cobalt alloy plating layer formed on the surface of the equipment. Chromium containing 0.5-29% by weight
It has been found that the above object can be achieved when a cobalt alloy plating layer is formed.

Further, in the equipment which does not require decorativeness, the above object can be achieved by directly forming a thick chromium-cobalt alloy plating layer containing a specific amount of chromium on the surface of the equipment. I also found As a result, the present inventors have already applied for a patent based on these findings (Japanese Patent Application No. 6-258045; hereinafter, the invention of this application is referred to as a prior invention).

In the course of subsequent research, the inventor of the present invention has found that the invention of the prior application exhibits excellent effects, but there is room for improvement. That is, when the thickness of the chromium-cobalt alloy plating layer is about 3 μm or less, the gloss is high and the decorative plating is excellent, but the corrosion resistance is poor. In kitchen baskets that are in a state where vegetables, leftover food, etc. are collected, the color tone will change significantly from the initial state due to the elution of Co ²⁺ ions and the surface being oxidized, which will reduce the product value. It may decrease.

Under these circumstances, the present inventor has conducted further research and found that when a chromium-black chromium-cobalt alloy plating layer having a chromium content of 2 to 6% by weight is formed on the surface of appliances. Even if corrosion of the plating layer due to oxygen, water, chlorine compounds, sulfurous acid gas, nitrogen oxides, etc. in the air progresses, the gray-black color tone itself does not change, so it does not reduce the commercial value. I found it.

That is, the present invention provides the following antibacterial plating products: An antibacterial plating product in which a chromium-cobalt alloy plating layer containing 2 to 6% by weight of chromium is provided on metal or plastic.

2. Metal or plastic with (1) cobalt plating layer or cobalt alloy plating layer and (2)
An antibacterial plating product in which a chromium-cobalt alloy plating layer containing 2 to 6% by weight of chromium is sequentially provided.

In the present invention, a chromium-cobalt alloy containing a cobalt plating layer or a cobalt alloy plating layer (hereinafter sometimes referred to as a base plating layer) on the surface of metal or plastic, and further containing a specific amount of chromium on the surface. Plating layer (hereinafter sometimes referred to as surface plating layer)
To form. The chromium-cobalt alloy plating layer as the surface plating layer is antibacterial because it is slightly corroded by oxygen, moisture, chlorine compounds, sulfur dioxide, nitrogen oxides in the natural environment, as compared with the chromium single plating layer. Cobalt ions, which are a chemical species, are easily eluted on the surface, and the compound is easily generated. On the other hand, from the cobalt plating layer or the cobalt alloy plating layer which is the base plating layer,
Through microscopic defects such as pinholes, pits, and cracks in the chromium-cobalt alloy plating layer on the surface, cobalt ions or their compound ions, etc. come out on the surface and also exert an antibacterial effect. That is, since the cobalt ions from the surface plating layer and the cobalt ions from the base plating layer synergistically exert an antibacterial effect, the antibacterial property is remarkably improved as compared with the case where the chromium single plating layer is formed on the surface. It

The chromium-cobalt alloy layer, which is the surface plating layer, is superior to the cobalt plating layer and its alloy plating layer also in terms of corrosion resistance, and effectively prevents corrosion of these underlying plating layers. Therefore, the beautiful appearance of the cobalt plating layer or the cobalt alloy plating layer, which is the base plating layer, is maintained for a long period of time.

In the present invention, the metal or plastic as the material for forming the plating layer may be in the state of the material before being processed into a product, or may be in the state of being processed into a product.

The cobalt plating layer or the cobalt alloy plating layer as the underlying plating layer on the metal or the plastic can be formed by the usual electroplating method and / or chemical plating (electroless plating) method. The thickness of the base plating layer is not particularly limited, but is usually
It may be about 1 to 25 μm.

Then, a chromium-cobalt alloy plating layer is formed on the underlying plating layer by an electroplating method using an acidic plating bath containing trivalent chromium and divalent cobalt. The thickness of the chromium-cobalt alloy plating layer is not particularly limited, but is usually in the range of about 0.3 to 1 μm.

In the present invention, a nickel plating layer, a cobalt plating layer, a copper plating layer, a nickel-cobalt alloy plating layer, a copper plating layer and a nickel plating layer, etc., in order to improve the adhesion between the base plating layer and the material. May be formed.

The structure and method of forming the plating layer in the present invention will be described in detail below.

In order to form a plating layer of cobalt or its alloy on a metal or plastic substrate, various pretreatment steps (degreasing step, washing step, catalyst applying step, activation step, etc.), plating layer forming method (electroplating) Method, chemical plating method or electroless plating method, etc. are adopted. In the present invention, these known steps, methods and the like can be adopted as they are. Further, known plating bath compositions and plating conditions can be used as they are. For example, for metal substrates, (a) degreasing-water washing-immersing in acidic aqueous solution-water washing-nickel plating-water washing-cobalt / nickel alloy plating layer formation, (b) degreasing-water washing-immersing acidic aqueous solution-water washing-cobalt plating. The plating layer of cobalt or cobalt alloy can be formed by known steps such as layer formation, (c) degreasing-water washing-immersing in acidic aqueous solution-water washing-copper plating-water washing-cobalt / nickel alloy plating layer formation.

A cobalt plating layer or a cobalt alloy plating layer can be formed on plastics by a known process as in the case of metal. As a matter of course, in the case of plastic, an appropriate pretreatment process according to the type is adopted. For example, for ABS resin, degreasing-water washing-etching (chromic anhydride / sulfuric acid mixed aqueous solution) -neutralization (hydrochloric acid) -water washing-catalyst applying step (stannous chloride / palladium chloride) -water washing-activation. Step (sulfuric acid aqueous solution) -electroless nickel plating layer formation-sulfuric acid aqueous solution immersion-water washing-nickel plating layer formation-cobalt / nickel alloy plating layer formation, a cobalt or cobalt alloy plating layer can be formed by known steps. it can.

There are various types of alloy plating containing cobalt, and specific examples thereof include cobalt-phosphorus, cobalt-nickel-phosphorus, cobalt-tungsten and cobalt-molybdenum.

In the present invention, the chromium-cobalt alloy plating itself has antibacterial properties regardless of the antibacterial plating of the base. That is, the cobalt content of the alloy is 94-
As much as 98%, since cobalt has a lower potential than chromium, cobalt elutes from the alloy and exhibits an antibacterial effect. In order to maintain the excellent gloss and luster of grayish black as decorative plating, the plating thickness is preferably up to about 1 μm. Further, the hardness of this chromium plating is about Vvs hardness of about Hv500 to 700, which is lower than the hardness of the conventional chromium plating using a hexavalent chromium bath (about Hv880 to about 1000), so that it has poor wear resistance. As a result, when plating having excellent antibacterial properties is not applied as the base, the antibacterial effect is lost with the passage of time when the chromium-cobalt alloy plating is almost lost due to corrosion or wear. Therefore, considering antibacterial property retention and social safety, it is desirable to provide antibacterial cobalt plating or cobalt alloy plating on the base.

When the base is cobalt-plated or cobalt-alloy-plated, oxygen, water, chlorine compounds, and sulfurous acid in the natural environment are passed through defects (pin poles, pits, cracks, etc.) of the chromium-cobalt alloy plating. Chromium-cobalt alloy plating is the cathode (anode in batteries) as a result of corrosion due to gas, nitrogen oxides, etc.
Then, the cobalt or cobalt alloy plating serves as an anode (cathode in a battery), corrosion progresses, and cobalt ions, their compounds, etc. come out from the base to the surface, which has the effect of enhancing the antibacterial effect. However, as described above, since the surface chromium-cobalt alloy plating layer itself has an antibacterial action, the cobalt content in the underlying cobalt alloy plating is not particularly limited and is 25% by weight or more (this value Is the minimum value at which the antibacterial effect can be sufficiently exerted only with a cobalt alloy), or a plating layer of cobalt alone may be used.

Further, since the chromium-cobalt alloy plating itself has an antibacterial action, when the surface of the equipment does not require decorative properties, the thickness of the chromium-cobalt alloy plating layer can be increased. Since the long-term antibacterial property can be ensured, the antibacterial plating layer made of cobalt plating or cobalt alloy plating as a base is not essential. When the undercoat plating layer is not formed, the thickness of the chromium-cobalt alloy plating layer may be, for example, about 2 μm or more, although not particularly limited.

The chromium-cobalt alloy plating layer can be formed by an electroplating method from an acidic solution containing a trivalent chromium salt and a divalent cobalt salt according to a conventional method. For example, a desired chromium-cobalt alloy plating layer can be formed by an electroplating method using a mixed aqueous solution containing cobalt sulfate, chromium sulfate, oxalic acid, ammonium sulfate, boric acid and the like.

As a more specific example, cobalt sulfate 15-
35g / l, chromium sulfate 65-110g / l, oxalic acid 30-65g / l, ammonium sulfate 40-65g / l, boric acid 20-35g / l Electroplating can be performed under the conditions of pH 1.8 to 3.5 and cathode current density of 10 to 30 A / dm ² . When the cathode current density is too high, the degree of blackness is high, so the color tone is excellent, but the chromium content is too high and the antibacterial property is reduced. When the object to be plated is large, it is preferable to gently stir or move the object to be plated in the bath in order to make the composition of the entire bath uniform.

The chromium content (Cr / Cr + Co) in the chromium-cobalt alloy plating may be in the range of 2 to 6% by weight. When the ratio of Cr / Cr + Co is in the range of 2 to 6% by weight, a chrome-cobalt alloy which is grayish black, does not discolor even when corroded by oxidation and has excellent antibacterial properties is obtained.

The degree of blackness of the gray-black chrome-cobalt alloy plating layer according to the present invention depends on the visible light region (wavelength).
Light absorption of 85% or more (reflectance 15
% Or less).

Although the reason why the chromium-cobalt alloy according to the present invention exhibits a grayish black color is not clear, the chemical state in the plated layer is measured by an x-ray photoelectron spectroscopy analyzer (ESCA).
Since oxides of both metals are observed, it is presumed that the alloy plating contains these oxides.

The antibacterial effect in the present invention is exhibited by contacting cobalt ions, which is an antibacterial chemical species, or a compound easily soluble in water, with a bacterium existing together with water. The practical antibacterial effect varies depending on the growth rate of bacteria, the production and diffusion rates of antibacterial chemical species, environmental conditions, etc.For example, in a nourishing environment, the growth rate of fungi is higher than in a non-nutritive environment. fast.

[0031]

EFFECTS OF THE INVENTION According to the present invention, metal and plastic products provided with a cobalt-based plating layer are provided with an excellent aesthetic appearance of grayish black color, while at the same time imparting a high antibacterial property based on the presence of Co. You can

[0032]

EXAMPLES Reference examples, examples and comparative examples are shown below,
The features of the present invention will be further clarified.

Various tests in Examples and Comparative Examples were conducted as follows.

1. Antibacterial test 1-1) Type and concentration of bacteria used in the test Escherichia coli IFO 3301 and Staphylococcus aureus IFO 12732 were used.

1-2) Preparation of test bacterial solution The test bacterial solution was subcultured three times in a normal broth medium at 35 ° C. for 18 hours for three times, and appropriately diluted with a sterile phosphate buffer solution to prepare a test bacterial solution. did.

1-3) Measuring medium: SCDLP agar medium (Eiken) 1-4) Measuring method: Test bacterial solution of each test strain is placed on each sample.
Smear a 3 cm x 3 cm area, and immediately after smearing and at 35 ° C 4
After holding for a period of time, wipe it off with a normal wiping method, and
(cm × 3 cm), the number of remaining bacteria of each test strain was measured. The measurement result is shown as an average value of three times.

The number of bacteria immediately after smearing was 7.9 × 10 ⁵ for Escherichia coli and 5.2 × 10 ^{5 for} Staphylococcus aureus.
Met.

Comparative Example 1 A stainless steel test piece (SUS304; 50 mm × 50 mm × 0.3 mm) was electrolytically degreased, washed with water and then immersed in 1% sulfuric acid for 5 minutes.
It was washed with water and dried.

The antibacterial test results were 2.9 × 10 ⁵ for E. coli and 2.0 × 10 ⁵ for Staphylococcus aureus. From this, it is clear that stainless steel itself has almost no antibacterial property.

Comparative Example 2 A stainless steel test piece (SUS304; 50 mm × 50 mm × 0.3 mm) was electrolytically degreased, washed with water, then immersed in 10% hydrochloric acid for about 3 minutes, washed with water, and then subjected to a Cr plating bath (sergeant bath). : Bath composition is CrO ₃ 250 g / l, H ₂ SO ₄ 2.8 g / l; plating conditions are bath temperature 50 ° C., cathode current density 25 A / dm ² ) and hexavalent Cr plating is performed, followed by washing with water and drying. did. Plating thickness is 0.25 μm
Met.

The antibacterial test results were 3.2 × 10 ⁵ for Escherichia coli and 2.2 × 10 ⁵ for Staphylococcus aureus. From this, it is clear that Cr plating itself on stainless steel has almost no antibacterial property.

Comparative Example 3 A plain steel test piece (50 mm × 50 mm × 0.3 mm) was electrolytically degreased, washed with water, then immersed in 10% hydrochloric acid for 2 minutes, washed with water, and
Value Cr plating bath (Sergent bath: composition is CrO ₃ 250
g / l, H ₂ SO ₄ 2.8 g / l; plating conditions are bath temperature 50 ° C., cathode current density 25 A / dm ² ), Cr plating, and rinsing with water.
Dried. The plating thickness was 10 μm.

The antibacterial test results were 2.7 × 10 ⁵ for E. coli and 1.8 × 10 ⁵ for Staphylococcus aureus. From this, it is clear that Cr plating on ordinary steel itself has almost no antibacterial property.

Comparative Example 4 A stainless steel test piece (SUS304; 50 mm × 50 mm × 0.3 mm) was electrolytically degreased, washed with water, then immersed in 10% hydrochloric acid for 3 minutes and washed with water.

Next, a Ni plating bath (bath composition is NiC
L ₂ · 6H ₂ O 240 g / l, concHCl 120 ml / l; plating conditions are bath temperature 25 ° C., cathode current density 15 A / dm ² for 2 minutes)
It was plated with Ni and washed with water.

Then, using a bright Co plating bath (cobalt sulfate 120 g / l, cobalt chloride 30 g / l, boric acid 30 g / l, and sodium saccharin 3 g / l as a brightener) were added to the above test pieces and air was used. Co plating was performed at a bath temperature of 62 ° C. and a cathode current density of 4 A / dm ² for 22 minutes with stirring, washed with water, and dried. The Co plating layer had a thickness of about 13 μm.

Then, hexavalent Cr was added to the above test piece.
Plating bath (Sergent bath: composition: CrO ₃ 250 g / l, H ₂
SO ₄ 2.8g / l; plating conditions: bath temperature 50 ℃, cathode current density 25A
/ dm ² ), followed by Cr plating, followed by washing with water and drying.
The thickness of the Cr plating layer was about 0.25 μm.

The antibacterial test results were 600 for E. coli and 1400 for S. aureus. Antibacterial effect is recognized, but not sufficient.

Comparative Example 5 A stainless steel test piece (SUS304; 50 mm × 50 mm × 0.3 mm) was electrolytically degreased, washed with water, then immersed in 10% hydrochloric acid for 3 minutes and washed with water.

Then, for the above test piece, a Ni plating bath (the bath composition was NiCl ₂ .6H ₂ O 240 g / l, concHCl
120ml / l; plating conditions: bath temperature 25 ℃, cathode current density 15A
/ dm ² for 3 minutes), followed by Ni plating and washing with water.

Then, using a bright Co plating bath (cobalt sulfate 120 g / l, cobalt chloride 30 g / l, boric acid 30 g / l, and sodium saccharin 3 g / l as a brightener were added) to the above test pieces, and air was used. Co plating was performed for 22 minutes at a bath temperature of 60 ° C. under agitation and a cathode current density of 4 A / dm ² , washed with water, and dried. The Co plating layer had a thickness of 13 μm.

Then, Cr--Co was applied to the above test pieces.
Plating bath (Chromium chloride 150g / l, Cobalt chloride 12g / l
l, formic acid 70ml / l, potassium bromide 17g / l, ammonium chloride
50g / l, sodium citrate 70g / l, boric acid 30g / l; plating conditions are bath temperature 25 ℃, pH about 0.6, cathode current density 30A / dm ² )
Cr-Co plating was performed for 5 minutes, followed by washing with water and drying. The plating thickness was about 1.2 μm (Cr / Cr + Co = 9% by weight).

The results of the antibacterial test were 300 or less for Escherichia coli and 650 for Staphylococcus aureus, and a good antibacterial effect was recognized.

However, in this test piece, corrosion progressed with the passage of time, and first, the metallic luster portion was partially changed to grayish yellow, and then was changed to nonuniform grayish yellow as a whole, and further corrosion was progressed. Then, it partially changed to gray-black, and finally became a non-uniform gray-black.

Example 1 A stainless steel test piece (SUS304; 50 mm × 50 mm × 0.3 mm) was electrolytically degreased, washed with water, then immersed in 10% hydrochloric acid for 3 minutes and washed with water.

Then, for this stainless steel test piece,
Using a nickel plating bath containing nickel chloride 240 g / l and concentrated hydrochloric acid 120 ml / l, after electrolytic plating for 3 minutes at a cathode current density of 15 A / dm ² , washed with water, and further cobalt sulfate 120 g / l,
Using a bright cobalt plating bath containing 30 g / l of cobalt chloride, 30 g / l of boric acid and 3 g / l of sodium saccharin as a brightening agent, electrolytic plating was performed for 22 minutes under air agitation at a cathodic electrolytic density of 4 A / dm ² , A bright cobalt plating layer having a thickness of about 13 μm was formed.

Then, the stainless steel test piece on which the cobalt plating layer was formed was washed with water, and then a carbon plate was used as an anode material, cobalt sulfate 20 g / l, chromium sulfate 80 g / l, oxalic acid 50 g / l, ammonium sulfate 55 g. Using a chromium-cobalt alloy plating bath of 1 / l and sodium borate 30g / l,
Under conditions of bath temperature of 30 ℃, pH of about 2.5, and cathode current density of 20A / dm ² .
It was electrolyzed for 5 minutes, washed with water and dried. The obtained gray-black C
The thickness of the r / Co alloy plating layer is about 0.5 μm (Cr / C
r + Co = 5% by weight).

The results of the antibacterial test were 300 or less for Escherichia coli and 690 for Staphylococcus aureus. It was confirmed that the plating layer according to the present invention exhibits an excellent antibacterial effect.

Further, the color tone of the obtained Cr / Co alloy plated layer hardly changed even after a long time.

Example 2 A plain steel test piece (50 mm × 50 mm × 0.3 mm) was electrolytically degreased, washed with water, then immersed in 10% hydrochloric acid for 2 minutes and washed with water,
Nickel sulfate 240g / l, nickel chloride 45g / l and boric acid 3
Using 0g / l matte nickel plating bath (Watt bath),
Electrolysis was performed for 5 minutes at a bath temperature of 48 to 53 ° C. and a cathode current density of 4 A / dm ² , followed by washing with water to form a nickel plating layer (about 3 μm).

Then, nickel sulfate was applied to this test piece.
240 g / l, nickel chloride 45 g / l, boric acid 30 g / l, sodium saccharin 3 g / l, 2-butyne-1,4-diol 0.3 g / l
Using a bright nickel plating bath of 50
Electrolysis was carried out for 20 minutes at a cathode current density of 4 A / dm ² at ℃ and washed with water to form a bright nickel plating layer (about 12 μm).

Then, using the bright cobalt plating bath containing 120 g / l of cobalt sulfate, 30 g / l of cobalt chloride, 30 g / l of boric acid and 2.7 g / l of sodium saccharin as a brightening agent, cathodic electrolysis was performed on the above test piece. Electrolytic plating was carried out at a density of 5 A / dm ² for 20 minutes while stirring in air to form a bright cobalt plating layer having a thickness of about 15 μm.

Next, the plain steel test piece on which the cobalt plating layer was formed was washed with water, and then a carbon plate was used as an anode material, and cobalt sulfate 20 g / l, chromium sulfate 80 g / l, and oxalic acid 50
g / l, ammonium sulfate 55 g / l and boric acid 30 g / l chrome-cobalt alloy plating bath, bath temperature 30 ℃, pH
Electrolyze for 6 minutes under the conditions of about 2.5, cathode current density 18 A / dm ² ,
It was washed with water and dried. The resulting gray-black Cr / Co alloy plating layer had a thickness of about 0.5 μm (Cr / Cr + Co = 4.5% by weight).

The antibacterial test results were 300 or less for Escherichia coli and 670 for Staphylococcus aureus. It was confirmed that the plated layer according to the present invention exhibits an excellent antibacterial effect.

The color tone of the Cr / Co alloy plated layer obtained in the present example hardly changed even after a long time.

Example 3 A stainless steel test piece (SUS304; 60 mm × 50 mm × 0.3 mm) was electrolytically degreased, washed with water, then immersed in 10% hydrochloric acid for 3 minutes and washed with water to form a dull Ni plating layer. Let The bath composition used was nickel chloride 240 g / l and concentrated hydrochloric acid 120 ml / l.
The plating layer was formed at a bath temperature of 25 ° C and a cathode current density of 20A /
It was electrolyzed with dm ² for 2 minutes.

Next, the above stainless steel test piece was washed with water and plated with bright Co-Ni. The composition of the plating bath was 180 g / l cobalt sulfate, 120 g / l nickel sulfate, 45 g / l nickel chloride, 30 g / l boric acid, 3 g / l sodium saccharin as a brightener and 2-butyne-1,4-diol.
Electrolysis was carried out at a bath temperature of 28 to 30 ° C. and a cathode current density of 4 A / dm ² under air agitation for 10 minutes to form a Co—Ni alloy plating layer having a thickness of about 6 μm.

Next, the test piece on which the above Co-Ni alloy plating layer was formed was washed with water and then subjected to Cr-Co alloy plating. Bath composition: cobalt sulfate 25g / l, chromium sulfate 80g
/ l, oxalic acid 50 g / l, ammonium sulfate 55 g / l and boric acid 30 g / l. The plating conditions are carbon plate as the anode,
Bath temperature 30 ° C, pH 2.2, cathode current density 15A / dm ² under air stirring
Electrolyzed for 4 minutes. The obtained gray-black Cr-Co plating layer had a thickness of about 0.5 μm, and its composition was Cr / Cr.
+ Co = 4% by weight.

The results of the antibacterial test were 300 or less for Escherichia coli and 620 for Staphylococcus aureus. It is clear that the plated layer according to the present invention exhibits an excellent antibacterial effect.

The color tone of the Cr / Co alloy plating layer obtained in this example also changed little after a long time.

Example 4 A brass plate test piece (50 mm × 50 mm × 0.3 mm) was electrolytically degreased, washed with water, then immersed in 10% hydrochloric acid for 2 minutes and washed with water to form a dull Ni plating layer. . The bath used was a Watts bath, the composition of which was 240 g / l nickel sulphate, 45 g / l nickel chloride and 30 g / l boric acid. The plating layer was formed by electrolysis for 5 minutes at a bath temperature of 48 to 53 ° C. and a cathode current density of 4 A / dm ² , and the thickness of the matte Ni plating layer was about 3 μm.

Then, the brass plate test piece on which the matte Ni plating layer was formed was washed with water and plated with glossy Ni. Gloss N
An i plating bath was prepared by adding 3 g / l of sodium saccharin and 0.3 g / l of 2-butyne-1,4-diol as a brightening agent to the Watt bath. Plating bath temperature 50
Electrolysis was carried out at a temperature of 4 ° C. and a cathode current density of 4 A / dm ² for 15 minutes while stirring with air. The thickness of the bright Ni plating layer was about 12 μm.

Next, the brass plate test piece on which the above-mentioned bright Ni plating layer was formed was washed with water and then plated with bright Co. Bath composition: cobalt sulfate 120g / l, cobalt chloride 30g / l
1 and 30 g / l boric acid, and 3 g / l sodium satsukaline was added as a brightener. The plating conditions were such that the bath temperature was 60 ° C., the cathode current density was 5 A / dm ² , and the electrolysis was performed for 15 minutes while stirring with air. The thickness of the obtained bright Co plating layer was about 12 μm.

Next, the brass plate test piece on which the bright Co plating layer was formed was washed with water and then plated with Cr / Co alloy. Bath composition is cobalt sulfate 20g / l, chromium sulfate 80g
/ l, oxalic acid 50g / l, ammonium sulfate 55g / l and boric acid 30g / l. Plating uses a carbon plate as the anode for the test piece, bath temperature about 30 ° C, pH about 2.5, cathode current density After electrolysis for 3 minutes at 15 A / dm ² , it was washed with water and dried. Cr
/ Co alloy plating layer has a thickness of about 0.2μm (Cr content 4
% By weight).

The antibacterial test result in this case was 300 for E. coli.
Below was 630 for S. aureus. It is clear that the plated layer according to the present invention exhibits an excellent antibacterial effect.

The color tone of the Cr / Co alloy plated layer obtained in this example also changed little after a long time.

Example 5 ABS resin test pieces (50 mm × 50 mm × 5 mm) were treated with 10 g / l of sodium carbonate, 20 g / l of sodium phosphate and 2 ml / l of surfactant.
Immersed in a cleaning solution having the composition of 50 ° C. for 4 minutes and washed with water, and then immersed in a mixed aqueous solution of chromic anhydride 400 g / l and sulfuric acid 400 g / l for 10 minutes at a temperature of 67 ° C.
It was immersed in a mixed solution of 50 ml / l and 5 g / l of acidic sodium sulfite for 2 minutes, washed with water and washed.

Next, the ABS resin test piece washed as described above was added to a mixed solution of 10 g / l of stannous chloride and 8 ml / l of concentrated hydrochloric acid.
After soaking for 5 minutes and washing with water, it was immersed in a mixed aqueous solution of 0.3 g / l of palladium chloride and 3 ml / l of concentrated hydrochloric acid for 4 minutes and washed with water to activate and apply a catalyst.

Next, the ABS resin test piece pretreated as described above was electroless Ni plated with nickel sulfate 21 g / l, lactic acid 28 g / l, propionic acid 2.3 g / l and hypophosphorous acid 21 g / l. Using a bath, electroless Ni plating was performed under the conditions of temperature 90 ° C., pH 5.2, and immersion time 10 minutes.

Next, ABS after Ni electroless plating treatment
After washing the resin test piece with water, dip it in an aqueous solution of sulfuric acid 100 g / l, wash it with water, then nickel sulfate 240 g / l, nickel chloride
Electrolytic plating was performed using a nickel electrolytic plating bath having a composition of 45 g / l and boric acid of 30 g / l. In the electrolytic plating treatment, electrolysis was carried out for 7 minutes at a bath temperature of 35 ° C. and a cathode electrolytic density of 1 A / dm ² , followed by washing with water. As a result, a nickel plating layer having a total thickness of about 1 μm was formed.

Next, the ABS resin test piece plated with electrolytic Ni was plated with bright Co / Ni alloy. Bath _{composition, CoSO 4 · 7H 2 O230g /} l, NiSO 4 · 6H 2 O70
g / l, NiCl ₂ .6H ₂ O 45 g / l and H ₃ BO ₄ 30 g / l, sodium saccharin 3 g / l and 2 as brightener
-Butyne-1,4-diol 0.12 g / l was added. At the time of plating, electrolysis was carried out for 10 minutes with stirring at air with a bath temperature of 28 to 30 ° C. and a cathode current density of 4 A / dm ² . The thickness of the bright Co / Ni plating layer was about 6 μm.

After completion of electrolysis, the gloss Co / N is obtained as described above.
The ABS resin test piece on which the i plating layer was formed was washed with water to form a gray-black Cr / Co alloy plating layer. The composition of the Cr / Co alloy plating bath is cobalt sulfate 25 g / l, chromium sulfate 8
0 g / l, oxalic acid 50 g / l, ammonium sulfate 55 g / l and boric acid 30 g / l. When plating, use a carbon plate as the anode, bath temperature 30 ° C under agitation, pH about 2.5, cathode It was electrolyzed for 5 minutes under the condition of current density of 15 A / dm ² , washed with water and dried. The thickness of the obtained Cr / Co alloy plating layer is about 0.4.
μm (Cr content 4% by weight).

The antibacterial test results were 300 or less for Escherichia coli and 660 for Staphylococcus aureus. It is clear that the plated layer according to the present invention exhibits an excellent antibacterial effect.

The color tone of the Cr / Co alloy plated layer obtained in this example also changed little after a long time.

Example 6 A polyamide test piece (50 mm × 50 mm × 5 mm) was immersed in an aqueous solution having a composition of 100 g / l of sodium hydroxide and 2 ml / l of a surfactant at a temperature of 60 ° C. for 10 minutes, washed with water, and then concentrated. Hydrochloric acid 80
It was immersed in an aqueous solution of ml / l at a temperature of 25 ° C. for 3 minutes and washed with water.

Next, the polyamide test piece treated as described above was placed in a mixed solution of 10 g / l stannous chloride and 8 ml / l concentrated hydrochloric acid.
After soaking for 5 minutes and washing with water, it was immersed in a mixed aqueous solution of 0.3 g / l of palladium chloride and 3 ml / l of concentrated hydrochloric acid for 4 minutes and washed with water to activate and apply a catalyst.

Next, the polyamide test piece pretreated as described above was applied to an electroless Ni plating bath containing nickel sulfate 21 g / l, lactic acid 28 g / l, propionic acid 2.3 g / l and hypophosphorous acid 21 g / l. Was used to perform electroless Ni plating under the conditions of temperature 90 ° C., pH 5.2, and immersion time 10 minutes.

Then, the polyamide test piece after the Ni electroless plating treatment was washed with water, immersed in an aqueous solution of sulfuric acid 100 g / l and washed with water, and then nickel sulfate 240 g / l, nickel chloride
Electrolytic plating was performed using a nickel electrolytic plating bath having a composition of 45 g / l and boric acid of 30 g / l. In the electrolytic plating treatment, electrolysis was performed for 7 minutes at a bath temperature of 35 ° C. and a cathode current density of 1 A / dm ² , followed by washing with water. As a result, a nickel plating layer having a total thickness of about 1 μm was formed.

Then, the polyamide test piece subjected to the electrolytic Ni plating treatment was subjected to bright cobalt plating. Bath composition is cobalt sulfate 120g / l, cobalt chloride 30g / l, boric acid 30g / l and sodium saccharin (brightener) 3g / l
Met. The plating operation was carried out at a bath temperature of 60 ° C. and a cathode current density of 5 A / dm ² for 15 minutes while stirring with air.
A plating layer was formed.

Next, the polyamide test piece on which the bright Co plating layer was formed as described above was washed with water to obtain a gray / black Cr /
A Co alloy plating layer was formed. The composition of the Cr / Co alloy plating bath is chromium sulfate 80 g / l, cobalt sulfate 20 g / l, oxalic acid 50 g / l, ammonium sulfate 60 g / l and boric acid 30 g / l.
Therefore, at the time of plating, using a carbon plate as the anode material,
Electrolysis was carried out for 5 minutes under conditions of bath temperature of 33 ° C., pH of about 2.7, and cathode current density of 20 A / dm ² , washed with water and dried. The thickness of the obtained Cr / Co alloy plating layer is about 0.5 μm (Cr content 3.8% by weight)
Met.

The antibacterial test result in this case was 300 for E. coli.
Below was 680 for S. aureus. It is clear that the plated layer according to the present invention exhibits an excellent antibacterial effect.

The color tone of the Cr / Co alloy plated layer obtained in the present example hardly changed even after a long time.

Claims (2)

[Claims] 1. Chromium 2-6 in metal or plastic
An antibacterial plating product provided with a chromium-cobalt alloy plating layer containing 50% by weight. 2. An antibacterial plating product in which (1) a cobalt plating layer or a cobalt alloy plating layer and (2) a chromium-cobalt alloy plating layer containing 2 to 6% by weight of chromium are sequentially provided on a metal or a plastic.