JP2003260753A - Clear-coating metallic sheet excellent in stain resistance and workability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a clear-coating metallic sheet for a kitchen excellent in stain resistance and workability. <P>SOLUTION: A metal surface having a baking type coating film is ≥0.05 μm and ≤0.30 μm in Ra(RaT) in a direction normal to a rolling direction, by average roughness Ra according to JIS B 0601 and ≥0.25 and ≤1.5 in RaL/ RaT, which is a ratio of Ra(RaL) to RaT, and contains a polysiloxane resin of ≤2.0 mass% to a solid resin content. The film contains not less than one kind of a resin selected from a polyester and an urethane resin as a principal component or may contain a fluororesin particle of ≤10 μm in average particle size and ≤5 mass% to the solid resin content. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clear-coated metal plate suitable for use in home appliances and kitchen appliances and having excellent stain resistance and workability.

[0002]

2. Description of the Related Art When assembling a product using a metal plate such as a cold-rolled steel plate or a plated steel plate, the outer plate exposed to human eyes is used with some coating for the purpose of improving corrosion resistance and design. It is almost always done. Conventionally, such coating has been performed by an after-coating method in which the product is assembled after completion of assembly, but recently, the use of a pre-coated steel sheet (pre-coated steel sheet) has been increasing. In the following, a steel plate will be described as an example of the metal plate.

The increase in the usage rate of such coated steel sheets is (1) helping customers to omit processes, and (2) avoiding complicated operations such as degreasing and painting by customers. Yes, (3) The reason is that it is difficult to install painting equipment in the case of an electric appliance factory located near the city.

In addition to these reasons, recently, there are also positive reasons for improving the performance of coated steel sheets, such as (4) special functions can be added and (5) designability can be added. Came.

Among them, plated steel sheets (for example, 55% Al-containing Al-Zn alloy hot dip plated steel sheets) having excellent design and stainless steel sheets have not been conventionally colored with paint in order to make good use of the beauty of the material. It was often used as it is, but due to the demand for functions such as higher corrosion resistance, scratch resistance, and stain resistance, transparent coating (clear coating) is increasingly used. In particular, kitchen panels and wall materials for commercial kitchens, range hoods, outer plates of kitchen appliances, etc. are liable to be spattered with oil stains and foods, so that steel plates with excellent stain resistance are required.

To address these problems, coating compositions and coating films have been proposed in which a polysiloxane resin is added to impart oil repellency to prevent dirt from adhering. For example, in JP-A-9-324142, (a) polyester resin,
(b) a cross-linking material, (c) a polyester-modified polysiloxane compound containing a hydroxyl group or a carboxyl group and / or a polyether-modified polysiloxane compound containing a hydroxyl group or a carboxyl group, and (d) a fluororesin as a main component Stain resistant coating compositions have been proposed. Regarding the mechanism of exhibiting stain resistance in this coating composition, the polysiloxane compound accelerates the crosslinking reaction, and when the coating film is highly crosslinked, the reaction between the pollution source substance and the coating film is suppressed, and It is said that the removability is improved, and the stain resistance is improved by the fluororesin particles having the property of repelling both water and oil.

Japanese Unexamined Patent Publication (Kokai) No. 10-34823 discloses a pre-coated steel sheet having excellent stain resistance and non-adhesiveness, which is obtained by adding an amino-modified silicone oil having a coating solid content of 0.2 to 1.0 mass% and a melamine curing agent to a polyester resin. Japanese Patent Application Laid-Open No. 2000-248227 proposes that a silicone-modified vinyl-based polymer having a silicone group, a hydroxyl group, and a carboxylic acid group in a side chain is contained in an amount of 1 to 20% by mass based on the total solid content, so as to prevent contamination. There has been proposed a surface-treating material which is excellent in removability of a fatty pollutant having a coating layer formed thereon.

In these publications, an excellent effect on the wiping-off property of oily magic stains is recognized. However, there are various types of stains, and no consideration has been given to the effect on stains assuming the actual use environment. Furthermore, the effect of the above non-adhesiveness and oil repellency on the stain resistance has not been examined in an environment in which adhered oil stains and foods are complexly fixed and left for several months.

In the past, cut clear coated metal plates were pasted together or used by bending at 90 °, but recently, clear coated metal plates are also used for forming into complicated shapes by pressing or the like. It is scattered and requires workability. The workability of the clear coated metal plate described here is not only that it can be processed into a predetermined shape,
The adhesion of the coating film is important because the coating film does not peel off due to the processing, nor does it corrode from the processed part during use or corrosion does not proceed.

Regarding the adhesion of the coating film, JP-A-9-141303
There is known a method of improving coating film adhesion by anchoring the surface of a steel sheet with a dull roll as typified by Japanese Patent Publication No. Dull-finished metal plate by these methods,
It is not used as a clear coating metal for home appliances and kitchens, but as a coloring coating base material for roofing materials and exterior materials.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a clear coated metal plate which is mainly used in a general home kitchen, a commercial kitchen, etc. and has excellent stain resistance to oil stains and foods and excellent workability. Is to provide.

[0012]

In order to achieve the above object, the present invention has conducted a study on the stain resistance of various kinds of stain substances (oil, foods) on a clear-coated metal sheet, and as a result, the addition of polysiloxane resin has been investigated. When the amount is increased, oil repellency against highly viscous deteriorated oil is developed,

[0013] Various foods and deteriorated salad oil were applied to various clear-coated metal plates, allowed to stand and washed with a neutral detergent, and the stain resistance was evaluated. As a result, polysiloxane resin was added to most stains. It was removed with or without. However, for stains (such as curry roux) in which fats, solids, and pigments are mixed, a clear coating film with an excess of polysiloxane resin is used as fine pigment particles. Is attached and cannot be removed even with a neutral detergent, resulting in poor stain resistance,

Various clear-painted metal plates were installed in an exhaust duct installed on a commercial fryer in operation, and the samples exposed for 2 months were evaluated. As a result, it became dirty whether or not polysiloxane resin was added. No difference was observed in removability, and no difference was observed in the appearance of the sample after soil removal.

From these results, although the oil repellency due to the addition of the polysiloxane resin has the effect of facilitating the wiping off immediately after the stain adheres, the oil repellency such as the range hood, the kitchen panel, the wall board, etc. Sufficient effect is not recognized for applications where foodstuffs are left with dirt attached for a long period of time and once every few months, for example, after spraying with an alkaline detergent for a range or a ventilation fan and then wiping it off. I found it wasn't.

Then, by changing the way of thinking and limiting the amount of polysiloxane added to 2.0% by mass or less, it was unexpectedly found that effective removal of polysiloxane is possible.

Regarding workability, if the surface shape of the coating base material has a small Ra and the surface is too smooth, it causes peeling of the coating film when severe processing such as press working is performed. In addition, when the difference in roughness between the rolling direction and the direction perpendicular to the rolling direction is large when design is imparted by polishing, etc., when rusting is performed at the broken part of the coating film, the rusting starting point causes It was found that along the line, corrosion is likely to progress in the form of a thread under the coating film.

The present invention has been completed based on these findings, and its gist is as follows. (1) A coated metal plate having a baking type coating film on at least one side of a metal plate, wherein the metal surface having the baking type coating film is JI
The average roughness Ra specified by SB 0601, Ra (RaT) in the direction perpendicular to the rolling direction is 0.05 μm or more and 0.30 μm or less, and the ratio RaL / RaT of Ra (RaL) to RaT in the rolling direction is 0.25 or more, A clear-coated metal plate having a stain resistance and processability of 1.5 or less and containing 2.0% by mass or less of polysiloxane resin based on the resin solid content.

(2) A coated metal plate excellent in stain resistance and workability as described in (1) above, wherein the coating film contains one or more resins selected from polyester and urethane as a main component, A clear coated metal plate with excellent stain resistance and workability, containing 2.0% by mass or less of polysiloxane resin based on the solid content.

(3) A coated metal plate excellent in stain resistance and workability according to (1) or (2) above, having an average particle size of 10 μm.
Hereinafter, a clear-coated metal plate having excellent stain resistance and workability, which contains 5% by mass or less of fluororesin particles with respect to the resin solid content.

(4) The clear-coated metal sheet according to any one of (1) to (3) above, wherein the clear-coated metal sheet is a material for a range hood.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Various conditions limited in the present invention will be described below. Metal substrate The metal plate that is the substrate of the clear-coated metal plate of the present invention is not particularly limited, but examples of suitable materials include:
Examples include stainless steel plates, aluminum plates, and various plated steel plates. The plated steel sheet may be produced by any of hot dipping, electroplating and vapor phase plating, and the plating metal species are zinc, zinc alloy, tin, tin alloy, aluminum,
A typical example is aluminum alloy.

Since the coated metal sheet of the present invention has a clear coating film, a metal sheet substrate having a beautiful appearance, which has been conventionally used without coating, is preferable. Examples of such a metal plate include a stainless steel plate, an aluminum plate, and a galvanized steel plate.

As the stainless steel plate, SUS430, SUS430
LX, SUS304, etc. are exemplified, and preferable aluminum plates are No. 1100, No. 3004, No. 5052 and the like. Examples of the hot-dip galvanized steel sheet include hot-dip galvanized steel sheet and hot-dip Al-Zn alloy-plated steel sheet having a beautiful spangle pattern, and in particular, Al content is about 55 mass% Al-Zn alloy-plated steel sheet. Since the spangle pattern is beautiful, it was often used unpainted, so it is optimal.

Surface Roughness To ensure the workability of a clear coated metal plate, the surface shape of the metal plate serving as the base material is defined as the average roughness Ra specified in JIS B 0601.
Stipulate in. Ra (RaT) in the direction perpendicular to the rolling direction is 0.05 μm
If it is less than the range, the surface is too smooth, which may cause peeling of the coating film during processing. When RaT exceeds 0.30 μm, the design is poor,
Moreover, it is difficult to manufacture with existing equipment except for dull finishing.

The ratio RaL / RaT of Ra (RaL) and RaT in the rolling direction is 0 in order to secure the corrosion resistance of the clear-coated metal sheet after processing.
It was set to 25 or more and 1.5 or less. When RaL / RaT is less than 0.25, rusting of the coating film breaking portion becomes the starting point, and the corrosion progresses like a thread under the coating film. In addition, it is difficult to exceed RaL / RaT of 1.5 in the existing equipment for continuous coiling and coiling.

The surface roughness at this time is the roughness of the surface as a base for the coating film, and in the case of a plated steel sheet, the roughness of the plated surface. Therefore, as means for adjusting the surface roughness in this way, there are rolling and polishing.

Base metal coating is not essential, but it is commonly used in coated metal plates because the base metal can improve corrosion resistance and coating adhesion. However, it is desirable to apply a base treatment.

Chromate treatment is preferred as the base treatment, and coating type chromate treatment is advantageous in terms of workability, but electrolytic type or reactive type chromate treatment is also possible. When chromate treatment is carried out, the amount of chromate attached in terms of metal chromium is preferably in the range of 10 to ²⁰⁰ mg / m ² . If the amount of chromate adhered is small, sufficient adhesion of the coating film cannot be obtained, and if it is too large, the workability is deteriorated.

An example of a commercially available coating type chromate treatment liquid suitable for use in the present invention is NRC300 manufactured by Nippon Paint. The coating-type chromate treatment liquid may be applied by a roll coater or the like according to a conventional method, and heated at 50 to 150 ° C. to be dried to perform the base treatment.

When it is desired to suppress the yellow tint of the chromate film in order to make the best use of the appearance of the material, it is sufficient to perform chromate treatment having a high chromium reduction rate. An example of such a commercially available chromate treatment liquid is NRC500 manufactured by Nippon Paint.

If it is not desired to carry out the chromate treatment using hexavalent chromium due to environmental problems, a chromium-free base treatment can be applied. Although any suitable chromium-free undercoating liquid that has been developed or will be developed in the future can be used, an example of a suitable commercially available product at this time is:
This is a surf coat made by Nippon Paint, which is a silica-based surface treatment liquid.

The clear coating of clear coating present invention can also be only one layer, since corrosion resistance is only one layer may be insufficient, and is commonly employed in the coating of the metal plate As described above, it is desirable to form the undercoating film and the overcoating film by coating at least twice to prevent the coating film from being broken due to pinholes or flaws in the coating film. In the present invention, as described below, by adding an appropriate amount of polysiloxane resin to the top coating film of this clear coating film, and further by adding an appropriate amount of fluororesin particles, excellent stain resistance is exhibited. be able to.

The resin species undercoating film undercoating film is not particularly limited, the main component may be any of thermoplastic and thermoset, epoxy, one or more binder resin selected from polyester and urethane It is preferable to form the undercoat coating film from the baking type coating composition. These resins can form a coating film which has excellent adhesion to an inorganic substrate such as a metal plate and good workability. The paint used may be either water-based or organic solvent-based.

The undercoat coating film can be formed preferably by coating the above-mentioned base-treated metal plate using a roll coater, a sprayer or the like, heating and baking the coating film. . The coating film thickness is 3 to the film thickness after drying.
About 15 μm is desirable, and baking is preferably carried out for about 30 to 60 seconds so that the maximum temperature of the steel sheet reaches about 150 to 250 ° C. For heating, a conventional method such as a conventional hot air blowing type oven, induction heating, or infrared heating can be used.

The topcoat top coating of the resin is not particularly limited, it is possible to use any resin which has been used in the clear coating of the conventionally metal plate. Preferably, the top coat film is formed from a baking type paint containing, as a main component, one or more resins selected from polyester and urethane. In addition, a resin that forms a relatively hard film such as an acrylic resin can be used, but it may not be suitable for severe processing applications.

The top coat film may be formed in the same manner as the undercoat coat film, by heating and baking the coat film. The thickness of the coating film after drying is preferably about 5 to 25 μm, and baking is preferably performed for about 30 to 70 seconds so that the maximum temperature of the steel sheet reaches about 150 to 250 ° C.

Polysiloxane Resin 2.0% by Mass or Less Polysiloxane resin is added in an amount of 2.0% by mass or less with respect to the resin solid content in order to impart stain resistance to the clear coating film.
If it exceeds 2.0% by mass, fine pigment particles adhere to stains (such as curry roux) in which fat, solids and pigments are mixed, and stain resistance deteriorates. . In addition, the paint stability during painting deteriorates. It is preferably 1.0 mass% or less. Further, from the viewpoint of initial stain, 0.5% or more is required to impart oil repellency, and the stain resistance is more preferably 0.5% by mass or more and 1.0% by mass or less.

The polysiloxane resin type is also not particularly limited, and may be dimethylpolysiloxane resin which is a usual silicone oil and its modified product. In the case of a two-layer coating, the polysiloxane resin is added to the top coating film.

Fluororesin Particles In order to impart stain resistance to the clear coating film, 5% by mass or less of fluororesin particles may be added to the resin solid content. The fluororesin particles have the property of repelling both water and oil, and improve the scratch resistance of the coating film as a solid lubricant having a wear-reducing effect, thus facilitating the removal of adhered dirt. The type of fluororesin particles is not particularly limited, and polytetrafluoroethylene (PTFE) or the like is used. If added in excess, the cost will increase and the stability of the coating will decrease, so it is preferably 5% by mass or less, particularly 2% by mass or less.
On the other hand, if the particle size is too large, the stability of the coating film decreases and conversely the stain resistance decreases, so the average particle size is preferably 10 μm or less.

Further, it is possible to add a proper amount of silica or resin particles such as polyester, polyurethane, acryl, melamine and polyamide from the viewpoint of designability. These added particles suppress the gloss of the clear coating film,
It is used to develop a calm appearance. If added excessively, the coating film becomes cloudy and the clear feeling is lost, but addition of an appropriate amount also has the effect of making attached dirt less noticeable.

The clear coating film described above usually forms a two-layer coating film including an undercoat and an overcoat as described above, but it is also possible to provide an intermediate coating to form a three-layer coating film. . The intermediate coating film resin may be the same as the top coating film. Even in this case, it is the uppermost coating film that contains the polysiloxane resin.

The case where each coating film which is a preferred embodiment of the present invention is a clear coating film containing no coloring pigment has been described.
Naturally, it is also possible to make a colored clear-coated metal plate by containing a coloring pigment in an amount of about mass% or less. Further, the coating film according to the present invention may be formed on only one surface of the material, which is an outer plate, but may be formed on both surfaces of the material, if desired. When it is formed on only one side, the unpainted side may be bare or may be subjected to only a base treatment, or may be coated different from the present invention. When forming on both sides, it is not necessary to make the composition of the undercoat and top coat the same on both sides.

[0044]

EXAMPLES Next, the present invention will be described more specifically by way of examples. (Example 1) Manufacturing method of test material Various surface-finished SUS430 (sheet thickness 0.5 mm) stainless steel plates were used as materials, and one side of this material was NRC3 made by Nippon Paint.
00 Coating type Chromate treatment liquid was applied with a bar coater so that the amount of chromium deposited was 30 mg / m ^2, and the maximum temperature reached was 100 ° C.
It was heated for about 10 seconds to form a base chromate film.

On the surface of the chromate film of the stainless steel plate thus treated with the base material, the undercoat paint of polyester resin is applied with a bar coater to a dry film thickness of 5 μm and baked at 215 ° C. for 40 seconds. Apply 1% by weight of polysiloxane resin to the resin solids and apply a top coat paint of polyester resin with a bar coater to a dry coating thickness of 10 μm.
Second baking was performed to produce a clear-coated stainless steel plate by the 2-coat 2-bake method.

Coating film performance evaluation method <Coating film adhesion and corrosion resistance> A clear coated metal plate cut into 100 mm square was formed into a rectangular cylinder with a length of 50 mm and a depth of 20 mm so that the clear coated surface was the convex side. The coating adhesion and corrosion resistance were evaluated by observing the appearance after a complex corrosion test by repeating spraying with 0.5% saline, drying, and wetting. No rusting was rated as ◯, rusting at the scratched portion of the coating was rated as Δ, and peeling of the coating or the progression of corrosion under the coating beyond 1.5 mm starting from rusting was rated as x.

As a comparison, a steel plate of mark E not subjected to clear coating was similarly processed and tested. These results are summarized in Table 1.

(Example 2) Method for preparing sample material The stainless steel plate of mark E of Example 1 was used as a material, and NRC 300 coating type chromate treatment liquid made by Nippon Paint Co., Ltd. was applied to one surface of the material at a chromium adhesion amount of 30 mg / It was coated with a bar coater such that m ^2, about 10 so that the highest temperature reached is 100 ° C.
It was heated for 2 seconds to form an underlying chromate film.

As shown in Table 2, an undercoat paint made of various resin such as polyester, epoxy, and urethane is applied to the surface of the thus-prepared stainless steel plate on which the chromate film is formed so that the dry film thickness becomes 5 μm. On a bar coater and baking at 215 ℃ for 40 seconds, and then dry the top coating with various resin types such as polyester type, acrylic type and urethane type resin with the addition amount of polysiloxane resin shown in Table 2 changed. It was applied by a bar coater so as to have a coating film thickness of 10 μm and baked at 230 ° C. for 50 seconds to prepare a clear-coated stainless steel plate by a 2-coat 2-bake method.

Coating Film Performance Evaluation Method <Magic Contamination Property> A line was drawn on a clear-coated metal plate with an oil-based red marker and allowed to stand at room temperature for 24 hours, after which the dry wiping property with gauze was evaluated. Moreover, it was wiped off with a gauze soaked with ethanol to evaluate the magic stain resistance. Those that could be completely removed were marked with ◯, those that were partially removed but could not be completely removed were marked with Δ, and those that could hardly be removed were marked with x.

<Fouling resistance> The following fouling substances were coated on a clear-coated metal plate in a circle with a diameter of about 30 mm, left for 24 hours, washed with a neutral detergent, and the test piece was observed after washing. Therefore, no stain substance remained, or a slight stain substance remained, the stain resistance was good (○), and the stain substance clearly remained was poor stain resistance (×).

Degraded oil Commercially available salad oil heated in an oven set at 300 ° C. was used. Commercially available soy sauce, ketchup, instant coffee, and curry powder were used, and instant coffee and curry powder were prepared by melting in hot water.

<Oil repellency> 10 cc of the above-mentioned deteriorated oil was applied on a 50 mm square clear-coated metal plate and stretched linearly in the diagonal direction, and the degree of repulsion after 10 minutes was observed. The oil repellency was evaluated as good (∘) when the material was cut into pieces and the coating area was reduced, and Δ was evaluated when there was little change, and the oil repellency was poor (x) when the oil spread and the coating area was increased.

<Exposure test> A 100 mm square clear-coated metal plate test piece attached to a SUS304 stainless steel plate was used. (1) Inside the exhaust duct installed on the fryer in the employee dining room cooking room in operation ( 2) Two months of exposure for each wall plate (the wall is about 30 cm away from the gas port and about 30 cm higher than the gas port) in the side of the gas stove in the employee cafeteria that is in operation. did.

After taking out, oil stains adhering to the stains were removed with gauze impregnated with ethanol, and the presence or absence of stains was observed by observing test pieces. When there was no stain remaining by visual observation, the mark was ◯, and when the stain was stain-like residue, the mark was x. Note that the SUS304 steel plate to which the test piece was attached could not remove the attached oil stain.

Whether or not the stain remained was determined by observing the test piece. When there was no stain remaining by visual observation, the mark was ◯, and when the stain was stain-like residue, the mark was x. The evaluation results are shown in Tables 3 and 4.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

[0060]

[Table 4]

[0061]

INDUSTRIAL APPLICABILITY As described above, the clear-coated metal sheet according to the present invention has excellent oil repellency because the polysiloxane resin is added to the top coating film. Therefore, it is possible to easily remove oil stains and the like at the initial stage of adhesion. further,
By adjusting the amount of polysiloxane resin to an appropriate amount, it exhibits long-term stain resistance against various foods and oils. Also,
From the viewpoint of designability in home appliances and kitchen applications, by responding to the demand for complicated product shapes, by prescribing the surface shape of the coating substrate, it has excellent coating adhesion and corrosion resistance even after molding processing. There is.

The clear-coated metal sheet according to the present invention is suitable for commercial kitchens where various stains are likely to adhere, and for equipment outer panels, kitchen panels, wallboards, range hoods and the like in general household kitchens.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shusuke Kakuchi             4-53 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture             Sumitomo Metal Industries, Ltd. (72) Inventor Naoto Iizaki             Sumitomo Metal Industries, No. 3, Hikari, Oshima, Kashima City, Ibaraki Prefecture             Kashima Steel Works Co., Ltd. F term (reference) 4D075 BB26Z BB91Z CA02 CA06                       CA13 CA33 CA34 CA37 CB06                       DA06 DB02 DB04 DB05 DB07                       DC10 DC18 DC38 EA07 EA43                       EB18 EB22 EB33 EB35 EB38                       EB43 EB56 EB57 EC07 EC53                       EC54                 4F100 AB01A AB04 AK17B AK41B                       AK51B AK52B AL05B BA02                       CC00B DD07A DE01B GB48                       GB81 JL01 JL06 JN01B

Claims (4)

[Claims] 1. A coated metal plate having a baking-type coating film on at least one side of a metal plate, wherein the metal surface having the baking-type coating film has an average roughness Ra defined by JIS B 0601 and is in a rolling direction. Ra (RaT) in the vertical direction is 0.05 μm or more and 0.30 μm or less, and the ratio Ra (RaL) to RaT in the rolling direction RaL / RaT is 0.25 or more and 1.5 or less, and 2.0% by mass or less with respect to the resin solid content. Clear coated metal plate with excellent stain resistance and processability that contains the polysiloxane resin of. 2. The coated metal sheet according to claim 1, which is excellent in stain resistance and workability, wherein the coating film contains at least one resin selected from polyester and urethane as a main component, and has a resin solid content. A clear-coated metal sheet with excellent stain resistance and workability, containing up to 2.0% by weight of polysiloxane resin. 3. A coated metal plate having excellent stain resistance and workability according to claim 1 or 2, wherein the fluororesin particles have an average particle size of 10 μm or less and 5% by mass or less based on the resin solid content. A clear coated metal plate with excellent stain resistance and workability, which is characterized by containing. 4. The clear-coated metal plate according to claim 1, which is a material for a range hood.