JPH08206590A - Coated metallic plate excellent in resistance to uv rays and production of coated metallic plate - Google Patents

Abstract

PURPOSE: To provide a coated metallic plate excellent in resistance to UV rays by incorporating a ketone based solvent composition having a specified range b.p. in a specified ratio in a polyester resin based coating film containing a titanium pigment. CONSTITUTION: The coated metallic plate used to an appliance, a building material, etc., and excellent in resistance to UV rays is provided with the polyester resin based coating film containing a titanium pigment and the polyester resin based coating film is formed from a material in which 10-50% ketone based solvent composition having 150-250 deg.C b.p. is incorporated in total solvent. In such a case, a content of the solvent except cyclohexanone is <=10%. And at the time of forming the coating film, a high-frequency inductive heating device is used together with a hot air heating device as a heating and baking method, and the solvent in an upper layer coating film on the coated metallic plate is evaporated at <=150 deg.C in the preceding inductive heating furnace, and the film is formed at <=250 deg.C in the post stage inductive heating furnace after setting for several second in a holding furnace of 150-250 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated metal plate which is used in home appliances, building materials, automobiles and the like and has excellent ultraviolet resistance on the surface of a coating film by irradiation with light rays such as ultraviolet rays and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, painted products that have been painted after processing are precoated metal sheets (hereinafter referred to as painted metal) to meet the needs of improving the working environment, preventing pollution problems, and omitting processes with low production efficiency. The use of coated metal plates has been increasing as the conversion to plates has progressed. Since it is essential that the coated metal sheet be formed and processed, it must have a high level of workability, while it must also satisfy the performance that has been required in the past, and its coating film design is difficult. there were. For UV resistance, which is an important performance other than processability,
A method of improving the resin composition as in JP-A-61-32351 and JP-A-62-21830, addition of an ultraviolet absorber, and the like correspond.

[0003]

In the prior art, as a result, the number of kinds of paints is increased, and it takes time and trouble to change paints.
There is a problem that the performance other than the object of improvement is affected and that the addition of additives such as an ultraviolet absorber is expensive. Further, in recent years, the required level for various performances such as workability and light resistance has become extremely high, and it is the current situation that the conventional technology cannot meet this requirement.

Further, addition of an ultraviolet absorber and modification of a resin, which have been conventionally taken to suppress a decrease in gloss due to irradiation with ultraviolet rays, have an effect on coating film performance other than ultraviolet resistance, and also increase in cost. There is a point.

The present invention provides a coated metal plate having excellent UV resistance and a method for producing a coated metal plate, which does not affect the coating film performance other than the UV resistance and easily improves the UV resistance. To aim.

[0006]

The gist of the present invention is as follows. A coated metal plate having a polyester resin-based coating film containing a titanium pigment, characterized in that it has a polyester resin-based coating film having a boiling point of 150 to 250 ° C. and a ketone solvent composition of 10 to 50% of all solvents. Painted metal plate with excellent UV resistance. The coated metal sheet excellent in ultraviolet resistance according to claim 1, which has a polyester resin coating film in which the content of a solvent other than cyclohexanone in the ketone solvent is 10% or less. When forming the upper coating film on the metal plate, a high frequency induction heating device and a hot air heating device are used together as a heating and baking method, and the solvent of the upper coating film of the coating metal plate is volatilized in the pre-stage induction heating furnace to retain it. After being put in the furnace for several seconds, baking is performed with a heat pattern for forming a film in the latter-stage induction heating furnace, and the temperature of the first-stage induction heating furnace is 150 ° C. or lower,
The temperature of the holding furnace is 150 to 250 ° C, the temperature of the latter stage induction heating furnace is 250 ° C or less, and the average heating rate is 8 to 15 ° C / sec.
The method for producing a coated metal plate excellent in ultraviolet resistance according to claim 1 or 2, characterized in that.

[0007]

According to the present invention, it is possible to produce a coated metal plate having excellent ultraviolet resistance without adding an ultraviolet absorber or changing the resin. The manufacturing process is shown below.

Examples of the metal plate include a steel plate, an aluminum plate,
A stainless steel plate, a titanium plate, a copper plate etc. are mentioned. Of these, examples of steel sheets include cold-rolled steel sheets, hot-rolled steel sheets, hot-dip galvanized steel sheets, galvannealed steel sheets, electrogalvanized steel sheets, zinc-iron alloy plated steel sheets, zinc-aluminum alloy plated steel sheets, aluminized steel sheets. , Chromium-plated steel sheet, nickel-plated steel sheet, zinc-nickel alloy-plated steel sheet, tin-plated steel sheet and the like.

Further, the metal plate can be subjected to a pretreatment if necessary. As pretreatment, washing with water, washing with hot water, pickling,
Alkali degreasing, grinding, polishing, chromate treatment, zinc phosphate treatment, complex oxide film treatment, etc. are available, and these are used alone or in combination to perform pretreatment for coating. The conditions of the pretreatment may be appropriately selected.

Then, an undercoat paint film layer can be formed by applying the undercoat paint on the metal plate and curing and drying. There is no particular designation as the undercoat paint,
For example, polyester type, epoxy type, urethane type, etc. are available, and roll coater, curtain flow coater,
Roller curtain flow coater, electrostatic coating machine, brush,
The undercoat coating film layer is obtained by coating with a blade coater, a die coater or the like to a required film thickness, and curing and drying with a hot air heating furnace, an induction heating furnace, a near infrared furnace or the like. In addition, the undercoat may be a curing catalyst, if necessary,
Depending on the application, extender pigments, rust preventive pigments, coloring pigments, aggregates, defoamers, leveling agents, coupling agents and the like may be added. Although the film thickness is arbitrary, the coated metal plate has a thickness of 1 to 30.
It is generally about μm, particularly 3 to 12 μm. When the thickness is 1 μm or less, it is difficult to secure the corrosion resistance, and when the thickness is 30 μm or more, the cost becomes high and defects such as cracks are likely to occur during drying. The drying conditions may be appropriately selected according to the content of the coating material and the required performance, but the maximum attainable plate temperature of 1 in a hot air stove, induction heating stove, etc.
The conditions are generally 50 to 230 ° C. and arrival time of about 10 to 200 seconds.

In the present invention, the number of coating film layers formed is not limited in any way, and after forming several coating films as necessary, top coating is performed. For top coating, a polyester resin coating is used as the coating. The polyester resin-based coating film means a coating film containing polyester resin and amidoplast resin as essential components.

The polyester resin is a resin having an ester group in the resin, and is an oiful-polyester resin,
It is called an alkyd resin, a linear high molecular weight polyester resin, or a branched high molecular weight polyester resin.

The polyester resin may further contain another resin, for example, an epoxy resin, a urethane resin, an acrylic resin, a fluororesin, a silicone resin, an amide resin or an imide resin, or a mixture of two or more thereof.

The amidoplast resin is a melamine resin,
Examples thereof include benzoquanamine resin, and examples of the melamine resin include methylated melamine resin and mixed etherified melamine resin such as butyl-melamine.

In addition to the amidoplast resin, a crosslinking agent component having a group capable of reacting with a component added to the coating film such as an isocyanate group, an epoxy group, an amino group, or a polyester resin may be added.

In addition to titanium oxide as a titanium pigment, a polyester resin film has a valve stem, barium sulfate,
Coloring pigments or extender pigments such as silica and cyanine blue, additives such as resin beads, aluminum flakes, mica, etc., and additives such as defoaming agents for improving paintability, leveling agents, etc. should be contained as necessary. You can

The solvent has a boiling point of 150 to 250.
Anone-based solvents such as isophorone and cyclohexanone at ℃ are preferable. The mixed solvent is added at 10 to 50% of the total solvent. The content of the solvent other than cyclohexanone in the anone-based solvent is 10% or less.

If it is less than 10%, the resin will not dissolve, and if it is more than 50%, the solvent will not be completely volatilized in the baking furnace in the actual machine line, resulting in poor appearance, so 10 to 50% is suitable.

The coating method is not particularly specified and may be the same as the coating method shown in the undercoat coating method. The film thickness is arbitrary,
About 1 to 50 μm, especially 5 to 30 μm for coated metal plate
A dry film thickness of m is common. As the baking conditions, an induction heating furnace and a hot-air heating furnace are used together, and a predetermined heat pattern as shown in FIG. 2 is used, t ₁ is 150 to 250 ° C., and t ₂ is 200 to 200 ° C.
Baking is performed at 250 ° C. and an average heating rate of 8 to 15 ° C./sec.

The formed coating film is analyzed by high frequency GDS. The measurement condition of the high frequency GDS is not particularly limited, but for example, the discharge power is 20 to 60 W and the argon flow rate is 1
50-350 mL / min, Photomalt voltage for carbon detection is 400-500V, Photomalt voltage for titanium detection is 700-900V, sampling interval 300-250
Measure at 0 msec. Note that these values are constant during one measurement and are not changed during the measurement.

From the spectrum obtained by the measurement of high frequency GDS, the intensity of the Ti / C spectrum peak, which is found within 0.5 μm from the surface of the polyester resin coating film in contact with air, was measured.
Calculate C.

[0022]

[Example] 0.6 mm hot-dip galvanized steel sheet (60 g /
m ² ) is degreased, then coating chromate treatment (ZM1300, manufactured by Nippon Parkerizing Co., Ltd.) is applied, and the undercoat paint shown in Table 1 is applied to a steel plate having a chromate film of 50 g / m ² by a roll coater, followed by induction heating Was baked (shown in Table 1) to form an undercoat coating film layer.

For the top coating, a paint containing 44% of PWC as a pigment (TiO ₂ ) was used. As shown in Table 1, the paint composition excluding the pigment and the setting time until baking after coating were changed, and after coating with a roll coater. Then, it was baked using an induction heating furnace to form a top coating film.

As the evaluation method, a sterilizing lamp of 100V-15W was used as a light source, and the gloss retention rate after irradiation for 72 hours at an irradiation distance of 10 cm was measured. A gloss meter manufactured by Suga Test Co., Ltd. was used.

FIG. 1 shows the results of the gloss retention rate when the anone (cyclohexanone, isophorone) ratio in the solvent was changed. The solvent is a mixed solution of Solvesso 100, Solvesso 150, cyclohexanone and isophorone,
Isophorone was 5% in the anone type solvent (isophorone, cyclohexanone). As a result, when the content of the anone solvent was 10% to 50% in all the solvents, a good gloss retention of 70% or more was exhibited, and when the content of the anone solvent was 10% or less, the resin did not dissolve.
%, The gloss retention shows 70% or more, but since the appearance of the coating film is poor, 10 to 50% is suitable as the content.

[0026]

[Table 1]

[0027]

As described above, according to the present invention, it is possible to obtain a coated metal plate having excellent ultraviolet resistance without adding a resin or an ultraviolet absorber.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between anone content in a solvent and a gloss retention rate in an example of the present invention.

FIG. 2 is a diagram showing a heat pattern in a pre-stage induction heating furnace, a holding furnace and a post-stage induction heating furnace which are examples of the present invention.

Claims (3)

[Claims] 1. A coated metal plate having a polyester resin coating film containing a titanium pigment, having a boiling point of 150 to 2
A coated metal plate excellent in ultraviolet resistance, which has a polyester resin coating film having a ketone solvent composition at 50 ° C of 10 to 50% of all solvents. 2. A coated metal sheet excellent in ultraviolet resistance according to claim 1, which has a polyester resin coating film containing 10% or less of a solvent other than cyclohexanone among ketone solvents. . 3. When forming an upper coating film on a metal plate, a high frequency induction heating device and a hot air heating device are used together as a heating and baking method, and a solvent for the upper coating film of the coating metal plate is placed in a pre-stage induction heating furnace. It is volatilized, put in a holding furnace for a few seconds, and then baked in a heat pattern for forming a film in a second-stage induction heating furnace.
50 ° C or less, the temperature of the retaining furnace is 150 to 250 ° C, the temperature of the latter-stage induction heating furnace is 250 ° C or less, and the average heating rate is 8 to 1
3. The method according to claim 1, wherein the temperature is 5 ° C./sec.
A method for producing a coated metal sheet having excellent UV resistance as described in the above.