JP2003301273A - Metal sheet with hydrophilic coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal sheet which makes the adhering oil stain easily removed, makes the adhering fingerprint unnoticeable, and has also superior rain-streak stain resistance and weldability. <P>SOLUTION: The metal sheet with a hydrophilic coating has a 0.5 μm or thinner hydrophilic film formed on the surface of a metal sheet with a sol-gel method, of which the composition is expressed by a chemical formula: Li<SB>a</SB>Na<SB>b</SB>K<SB>c</SB>(SiO<SB>m</SB>)<SB>x</SB>(ZrO<SB>n</SB>)<SB>y</SB>(H<SB>2</SB>O)<SB>z</SB>(wherein, a, b, c, and z are arbitrary numbers; m and n are arbitrary numbers among 1-4; and x+y=1). The hydrophilic coating can include aluminum ions or one or more bivalent metal ions selected among alkaline earth metals, zinc and copper, and further may include polyacrylic acid or a copolymer containing an acrylic acid monomer. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is capable of easily removing stains such as oil, is very invisible even if fingerprints are attached thereto, is resistant to rain streak stains even when installed outdoors, and can be spot welded. Hydrophilic coated metal plate.

[0002]

2. Description of the Related Art Stainless steel sheets are widely used in kitchen facilities and equipment because of their excellent corrosion resistance and cleanliness. Galvanized steel sheets and the like are widely used as inner members of kitchen equipment such as range hoods because they are superior in cost resistance to stainless steel sheets but have excellent cost performance. However, a drawback of stainless steel plates, galvanized steel plates, etc. is that it is difficult to remove the attached oil stains. Further, stainless steel sheets are used for various building materials, articles and the like by taking advantage of their beautiful appearance, and galvanized steel sheets and the like are also frequently used for equipment, housings and the like. In this type of application, if fingerprints are attached, they are easily noticeable and it is difficult to remove the attached fingerprints. A stainless steel plate may be used as the exterior material, but in this case, it is disadvantageous that rain streaks are likely to be attached.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have conducted various investigations on the surface characteristics of metal plates such as stainless steel plates, galvanized steel plates, and aluminum plates in order to eliminate defects such as oil stains, fingerprint adherence, and rain streak stains. ·investigated. Regarding oil stains,
By forming a fluorine coating that easily repels oil on the surface of the metal plate, it becomes easy to remove oil stains. For the fluorine coating, a method of coating various resins containing a tetrafluororesin or a fluorine resin component is adopted. Although it is possible to wipe off the attached oil with a rag with a fluorine coating to some extent, it is difficult to clean the surface beautifully with a wet rag containing water. A fluorine coating is formed with a film thickness of 5 μm or more due to oil stain resistance, but a fluorine-coated metal plate cannot be welded like an uncoated metal plate.

By applying a resin coating to the metal plate, the adhesion of fingerprints is suppressed and the partial corrosion caused by fingerprints is also suppressed. Fingerprints attached on the resin coating can be easily removed by dry wiping. However, the attached fingerprints are easily noticeable on the surface of the resin-coated metal plate. The resin coating is effective against rain streaks because it hydrophilizes the surface of the film to increase the action of draining rainwater. However, like the fluorine coating, the resin coating is inferior in weldability to an uncoated metal plate, and there is room for improvement in applications where an assembly process involving welding is planned.

[0005]

SUMMARY OF THE INVENTION The present invention has been devised to solve such a problem, and by forming a sol-gel film of a predetermined component system on the surface of a metal plate, it is resistant to oil stains. An object of the present invention is to provide a hydrophilic coated metal plate which has excellent rain line stain resistance, is hard to be noticed even when fingerprints are attached, and has excellent weldability.

In order to achieve the object, the hydrophilic coated metal plate of the present invention has a film thickness of 0.1 as represented by the following chemical formula.
A hydrophilic film having a thickness of 5 μm or less is provided on the surface of the metal plate. Chemical formula: Li _a Na _b K _c (SiO _m ) _x (ZrO _n ) _y (H ₂ O) _z where a, b, c, z: arbitrary number m, n: 1 to 4
Any number of x + y = 1

The hydrophilic film may contain aluminum ions or one or more divalent metal ions selected from alkaline earth metals, zinc and copper, and further contains polyacrylic acid or acrylic acid monomer. A copolymer may be blended and formed on the surface of the metal plate by the sol-gel method.

[0008]

The present inventors have conducted various investigations and studies on a material that is easy to remove oil stains, has less noticeable fingerprints, is less likely to be stained with rain streak when installed outdoors, and is easy to weld. As a result, they have found that it is effective to form a hydrophilic film having a thickness of 0.5 μm or less on the surface of the metal plate. The hydrophilic film formed on the surface of the metal plate is not compatible with the oil component. Even if oil stains adhere to the surface of the metal plate, when the surface of the metal plate is wiped with a wet cloth containing water, water is spread at the interface of the hydrophilic film / oil component. Therefore, the oil component is removed so as to be peeled off from the surface of the metal plate.

In a general resin coating based on a water repellent resin, microscopically raised fingerprints adhere to the surface of the film. The tendency of the adhered fingerprint to stand out is due to microscopic swelling, but most of the body fluid that comes out of the fingertip is water, and it is thought that the fingerprint rises as a result of being repelled by the resin film. In this respect, on the surface of the metal plate to which hydrophilicity is imparted by the hydrophilic film, the water content of the fingerprint spreads widely and spreads, so that the attached fingerprint becomes difficult to be visually recognized. In addition, the attached fingerprint does not diffuse into the hydrophilic film and can be easily wiped off the metal plate surface.

The rain streak stains that tend to occur on the exterior materials constructed outdoors are due to the strong affinity between the stains containing oil components and the surface of the metal plate. Some of the dirt is washed away by rainwater when it rains, but due to its strong affinity, it remains as rain streaks. In this respect, on the surface of the hydrophilized metal plate, rainwater spreads at the interface of the hydrophilic film / oil component-containing stain at the time of rainfall and lifts the oil component-containing stain. As a result, the oil component-containing dirt is washed away by rainwater, and the occurrence of rain streaks is suppressed.

Further, the hydrophilic film is a thin film formed by the sol-gel method and having a film thickness of 0.5 μm or less. Therefore, the influence of the film on welding is small, and welding under the same welding conditions as the uncoated metal sheet becomes possible. When a hydrophilic film having a thickness of 0.5 μm or less is formed on the surface of the metal plate by the sol-gel method as described above, the adhered oil stains can be easily wiped off with a moist cloth, and the adhered fingerprints are inconspicuous and can be exposed outdoors. Even when installed, rain streaks are less likely to get dirty and can be welded similarly to uncoated metal plates.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The metal plate on which the hydrophilic film is formed is not particularly limited by the material, and is a plain steel plate, a zinc plated steel plate, an aluminum plated steel plate, a Zn-Al alloy plated steel plate, a chemical conversion treated steel plate, a stainless steel plate, Aluminum plate,
Various metal plates such as aluminum alloy plate and copper plate can be used. Prior to the formation of the hydrophilic film, polishing according to a conventional method,
Pretreatment such as degreasing and pickling is appropriately applied to the metal plate. Furthermore,
It is also possible to apply pretreatments such as phosphate treatment, chromate treatment, and Cr-free treatment.

The hydrophilic film can be formed by applying a liquid paint to the surface of the metal plate and baking it. The paint component is preferably prepared as a raw material dissolved or dispersed in an aqueous solvent. The hydrophilic film formed by coating and baking has the following chemical formula. H ₂ O in the chemical formula represents water of crystallization or the like which is solidified by the hydration reaction. Chemical formula: Li _a Na _b K _c (SiO _m ) _x (ZrO _n ) _y (H ₂ O) _z where a, b, c, z: arbitrary number m, n: 1 to 4
Any number of x + y = 1

The complex oxide represented by the above chemical formula is amorphous, and excellent hydrophilicity is exhibited by the alkali metal ion and H ₂ O which have an action of attracting external water molecules.
As a silicon oxide raw material which is a source of SiO _m forming the chemical formula, various alkali silicate aqueous solutions, colloidal silica (silica sol), and various silicic acid alkoxides represented by ethyl silicate are suitable. When an alkoxide is used, a good quality hydrophilic film can be formed by using a sol which is once hydrolyzed in the presence of water and an acid or alkali catalyst. Sufficient hydrophilicity is exhibited when the proportion of silicon oxide in the entire hydrophilic film is 1% by mass or more.
If the silicon oxide is contained in excess of more than mass%, the film strength tends to decrease.

As the zirconium oxide raw material serving as the source of ZrO _n constituting the chemical formula, an aqueous solution of zirconium oxychloride or zirconium oxynitrate, a hydrolyzate of an alkoxide such as zirconium tetrabutoxide, and zirconia sol are suitable. Sufficient coating strength can be obtained when the proportion of zirconium oxide in the entire hydrophilic coating is 1% by mass or more, but hydrophilicity tends to decrease when an excess amount of zirconium oxide exceeding 90% by mass is contained.

The alkali metal ion sources such as Li, Na and K, which are the sources of Li _a Na _b K _c forming the chemical formula, include
Water-soluble salts such as nitrates, chlorides and organic acid salts can be used. When the proportion of the alkali metal ion in the hydrophilic film is 0.1% by mass or more, hydrophilicity is exhibited,
If the excess amount exceeds 10% by mass, sufficient film strength cannot be obtained. Li, Na, and K may be used alone or in combination of two or more, and there is no particular limitation on the ratio of Li, Na, and K.

H ₂ O, which constitutes the chemical formula, is not a liquid phase that easily evaporates, but water of crystallization or the like bound by a chemical hydration reaction. This H ₂ O is an aqueous solvent in which each component is dissolved or dispersed, water used for hydrolysis of alkoxide,
It is replenished from water in the air. H in hydrophilic film
The proportion of ₂ O is preferably in the range of 1 to 70% by mass. When aluminum ions are contained in the hydrophilic film, the film strength and durability are improved. The effect of aluminum ions is 0.
It can be seen at 1% by mass or more, but an excessive amount of aluminum ions exceeding 10% by mass reduces hydrophilicity and is not preferred. Examples of the aluminum ion source include water-soluble salts such as nitrates and chlorides, alkoxide hydrolysates typified by aluminum isopropoxide, and alumina sol.

The film strength and durability are Mg, Ca, S
It is also improved by blending 0.1 to 10% by mass of alkaline earth metals such as r and Ba and water-soluble salts such as nitrates and chlorides such as Zn and Cu. It is considered that the improvement of the film strength and durability is due to the fact that the network structure consisting of silicate oxide, zirconium oxide or their composite oxide, alkali ion and H ₂ O is crosslinked by the metal component. Furthermore, when a copolymer containing polyacrylic acid or an acrylic acid monomer is blended in the hydrophilic film, the adhesion of the hydrophilic film to the surface of the metal plate is improved. Adhesion improving effect can be seen in copolymers containing 1% by mass or more of polyacrylic acid or acrylic acid monomer, but 10% by mass
If the blending amount exceeds the above range, the film strength tends to decrease.

The above raw materials are weighed and various solvents are used to prepare a hydrophilic coating liquid having a predetermined composition. In addition to water, organic solvents such as alcohols and ketones that are compatible with water can be used. In the preparation of the hydrophilic coating liquid, pH adjustment by addition of acid or alkali and adjustment of water content are adopted as necessary in order to prevent instability of the liquid composition such as precipitation and separation. The solid content concentration in the hydrophilic coating solution is not particularly limited, but is 0.1
The range of 10 to 10 mass% is preferable.

After the hydrophilic coating liquid is applied to the surface of the metal plate by a roll coating method, a curtain flow method, a spray method or the like, a hydrophilic film is formed by heating and baking.
The coating amount of the hydrophilic coating liquid is determined so that the film thickness of the hydrophilic film is 0.5 μm or less (preferably 0.3 μm or less). When the film thickness is 0.5 μm or less, the same weldability as that of the uncoated metal plate is secured. When laminating a hydrophilic film, the application of the hydrophilic coating solution, heating and baking are repeated. The temperature range of 100 to 300 ° C. is preferable for heating and baking. If the baking temperature is less than 100 ° C., the hydrophilic film is not sufficiently formed and the film strength is reduced. vice versa,
If the baking temperature is higher than 300 ° C., an oxide film is likely to be formed on the surface of the metal plate, and the adhesion of the hydrophilic film to the surface of the metal plate may be reduced.

[0021]

Example To 10 g of tetraethoxysilane, 80 g of ethanol, 9 g of butoxyethanol: 1 g of a 1% by mass nitric acid aqueous solution were added, and a hydrolysis reaction was allowed to proceed with stirring at 60 ° C. for 24 hours to prepare a silica sol solution. Zirconium oxynitrate: 1 g, aluminum nitrate: 0.1 g, zinc nitrate: 0.1 g, lithium nitrate: 1
g, polyacrylic acid: 1 g, dissolved in water, aqueous solution: 10
0 g was prepared. 50 g of the silica sol solution was mixed with 50 g of the aqueous solution to obtain a hydrophilic coating solution whose pH was adjusted to 1 with nitric acid. This hydrophilic coating liquid has a solid content concentration of about 5% by mass, and has a chemical composition when heated to 200 ° C. (in other words, a chemical composition of the hydrophilic film) of SiO ₂ : 5.
8% by mass, ZrO ₂ : 11% by mass, Al ₂ O ₃ : 0.4% by mass, ZnO: 0.8% by mass, Li ₂ O: 4% by mass, H
₂ O: 7% by mass, polyacrylic acid: 19% by mass. Since there is no evaporation of water even after heating at 200 ° C, H ₂
It is considered that O is solidified in the hydrophilic film by the hydration reaction.

[Hydrophilic treatment I] SUS having a plate thickness of 0.5 mm
After degreasing and drying the 430 stainless steel plate, a hydrophilic coating solution was applied, heated and baked at 210 ° C. for 60 seconds, and cooled with water to form a hydrophilic film having a dry film thickness of 0.2 μm. [Hydrophilic treatment II] After degreasing and drying a SUS430 stainless steel plate with a plate thickness of 0.3 mm, apply a hydrophilic coating solution, heat and bake at 250 ° C for 40 seconds, and cool with water to obtain a dry film thickness of 0.3 μm. To form a hydrophilic film.

[Hydrophilic treatment III] After degreasing and drying an aluminum plate having a thickness of 1.0 mm, a hydrophilic coating solution is applied, heated and baked at 250 ° C. for 40 seconds, and cooled with water to obtain a dry film thickness of 0. A hydrophilic film of 0.3 μm was formed. [Hydrophilic treatment IV] After degreasing and drying a 55% Al-Zn alloy-plated steel sheet with a plate thickness of 0.5 mm, apply a hydrophilic coating solution, heat and bake at 210 ° C for 60 seconds, and dry by cooling with water. A hydrophilic film having a film thickness of 0.1 μm was formed.

[Comparative Treatment I] SUS4 having a plate thickness of 0.5 mm
After degreasing and drying the 30 stainless steel plate, coating type chromate treatment is applied, fluororesin-containing thermosetting polyester resin clear paint is applied, heating and baking is performed at 210 ° C. for 60 seconds, and water cooling is performed to obtain a dry film thickness of 10 μm. A clear coating film was formed. [Comparative Treatment II] A clear coating film formed by Comparative Treatment I was further coated with a polytetrafluoroethylene resin / polyethersulfone resin clear paint and baked at 400 ° C. for 60 seconds to give a dry film thickness of 7 μm. A coating film was formed. [Comparative Treatment III] A hydrophilic film was formed on the surface of a stainless steel sheet under the same conditions as in the hydrophilic treatment I except that the dry film thickness was 1.2 μm.

Each metal plate on which a hydrophilic coating or a clear coating was formed was subjected to a contact bending test under an environment of 20 ° C. and 65% RH, and a DuPont impact processing tester (500 g × 50 cm).
The impact processing test was conducted with and the coating film after the test was visually observed and cracked,
The coating film abnormality such as peeling was investigated. In addition, the contact angle with water was measured, and the following tests were conducted to examine the ease of wiping off oil stains, the visibility of adhered fingerprints, the stain resistance to rain streaks, and the weldability. Regarding the ease with which oil stains can be wiped off, 1 ml of salad oil prepared by dissolving red paint on the surface of a metal plate provided with a hydrophilic coating or a clear coating is dropped with a dropper and heated at 50 ° C for 24 hours, followed by a wet tissue. It was wiped twice and the state of oil remaining on the surface of the metal plate was investigated.

Regarding the visibility of the adhered fingerprint, a fingerprint was adhered to a hydrophilic film or a clear coating film on the surface of the metal plate, and a sensory test was conducted on the visibility of the adhered fingerprint. Rain streak resistance is
A metal plate provided with a hydrophilic film or a clear coating film was placed on a portion of the aluminum sash corner through which rainwater passes, exposed to the outdoors for 3 months, and visually evaluated on the surface of the metal plate. Regarding the weldability, an uncoated metal plate is superposed on the surface of a metal plate provided with a hydrophilic coating or a clear coating, and a single-phase AC stationary welder is used to achieve an electrode diameter of 6 mm and a pressing force of 400 mm.
Spot welding was performed under the conditions of kgf, initial pressurization time of 30 cycles, energization time of 20 cycles, and holding time of 30 cycles. The weldability and the tensile shear strength were measured to evaluate the weldability.

As can be seen from the survey results in Table 1, all the metal plates provided with the hydrophilic coating according to the present invention have excellent hydrophilicity, oil stain resistance and rain streak stain resistance, and the adhered fingerprints are It was hard to stand out. Moreover, a tensile shear strength of 15 kN was obtained with a welding current of 8 A, and the weldability was excellent.
On the other hand, in the metal plates provided with the clear coating film or the hydrophilic film in Comparative Treatments I to III, the hydrophilicity was low, the oil stain resistance and the rain line stain resistance were poor, and the fingerprints were easily noticeable or spot welding was not possible.

[0028]

[0029]

As described above, the film thickness is 0.5 μm.
By providing the following hydrophilic film on the surface of the metal plate, even if oil stains are attached, it can be easily removed with a wet rag, and even if fingerprints are attached it is not conspicuous. Difficult and can be welded like uncoated metal plates. Utilizing these advantages, it is used in a wide range of fields as interior materials with beautiful appearance, equipment / equipment for kitchens, exterior materials, etc.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshio Nagatomo             7-1 Takaya Shinmachi, Ichikawa City, Chiba Prefecture Nisshin Steel             Technical Research Institute Co., Ltd. (72) Inventor Hirokazu Yano             7-1 Takaya Shinmachi, Ichikawa City, Chiba Prefecture Nisshin Steel             Technical Research Institute Co., Ltd. (72) Inventor Keijiro Shige             28 Sumitomo Osaka, 6-6 Rokubancho, Chiyoda-ku, Tokyo             Inside Cement Co., Ltd. F-term (reference) 4D075 CA34 CA37 DA03 DB01 DC10                       EB22 EC10                 4F100 AA20B AA27B AB01A AB04                       AB09B AB10B AB17B AB18B                       AK25B AL01B BA02 BA07                       GB90 JB05B JL06 YY00B                 4K026 AA02 AA04 AA06 AA07 AA09                       AA11 AA22 BA01 BB02 CA13                       CA18 CA32 CA38 CA41 DA02                       DA11 EA08 EB11

Claims (4)

[Claims] 1. A hydrophilic coated metal plate, wherein a hydrophilic film having a film thickness of 0.5 μm or less represented by the following chemical formula is provided on the surface of the metal plate. Chemical formula: Li _a Na _b K _c (SiO _m ) _x (ZrO _n ) _y (H ₂ O) _z where a, b, c, z: arbitrary number m, n: 1 to 4
Any number of x + y = 1 2. The hydrophilic coated metal plate according to claim 1, wherein the hydrophilic film contains aluminum ions or one or more divalent metal ions selected from alkaline earth metals, zinc and copper. 3. A hydrophilic film is blended with a copolymer containing polyacrylic acid or an acrylic acid monomer.
The hydrophilic coated metal plate described. 4. The hydrophilic coated metal plate according to claim 1, wherein a hydrophilic film is formed by a sol-gel method.