JP3487924B2 - Paint composition for painted metal sheet and method for producing painted metal sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition for coated metal sheets having excellent hardness, workability, stain resistance and weather resistance, and a method for producing coated metal sheets.

[0002]

2. Description of the Related Art Conventionally, painting of home electric appliances and the like has been performed after processing and forming steel plates, but the amount of coated metal plates used is increasing due to pollution problems and work environment problems. Since the painted metal plate is premised to be processed after painting, it is required to have a high degree of workability, and further, to have hardness, stain resistance, and weather resistance comparable to those of conventional post painting.

However, since workability and these properties are contradictory, it is difficult to make them compatible with each other to a high degree.
For example, in JP-B-61-32351, a high molecular weight polyester resin is mixed with an alkyl etherified amino resin,
Further, an example in which a sulfonic acid-based catalyst was added was shown, but the stain resistance was insufficient.

Further, Japanese Patent Application Laid-Open No. 2-269168 discloses a method for achieving both processability and hardness / stain resistance of a coating film by using a combination of a specific polyester resin, a methylated melamine resin and an amine-blocked acid catalyst. Has been done. However, in recent years, users of coated metal sheets are increasingly required to have higher contamination resistance, and chemical resistance and weather resistance are insufficient. In order to further improve the stain resistance, it is possible to increase the amount of the melamine resin and the catalyst, but this not only lowers the processability but also improves the crosslink density of the coating surface and causes wrinkles on the coating surface. However, the appearance is impaired and the gloss is significantly reduced. Further, when the dry film thickness becomes thin, the stain resistance tends to be slightly lowered, and the degree of freedom in designing the coating film is narrowed.

On the other hand, for example, Journal of Coloring Materials, Vol. 64 (1991)
(Year) When the butylated melamine resin is combined with the polyester resin shown on pages 780 to 786, the butylated melamine resin is concentrated on the surface of the coating film even if the addition amount of the butylated melamine resin is small, and the stain resistance is improved. However, in this case, the workability and gloss tend to decrease with an increase in the amount, and since the compatibility of both resins is not always good, a large amount cannot be blended and there is a limit to the improvement of stain resistance.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a coating composition for a coated metal sheet which is further high in hardness and excellent in stain resistance, chemical resistance and weather resistance, and a method for producing a coated metal sheet. To do.

[0007]

[Means for Solving the Problems] Coating for a coated metal plate of the present invention
The composition is Is the street.

Polyester resin (A) having an average number of functional groups of 2.1 to 2.6, a number average molecular weight of 8000 to 22000, and a glass transition temperature of 0 to 30 ° C., a methylated methylolmelamine resin
(B), butylated methylol melamine resin (C), acid catalyst
(D), and a coating composition for a coated metal plate containing an amine compound (E) as an essential component , wherein the polyester resin (A)
However, as the glycol component, butylene glycol, penta
Type selected from benzenediol and hexanediol
Or a combination of two or more types and trimethylol
Including lopan, ethylene glycol, diethylene
Paint for metal plates characterized by not containing glycol
Composition .

Regarding the solid content weight ratio of the polyester resin (A), the methylated methylolmelamine resin (B), and the butylated methylolmelamine resin (C), A / (B + C) = 100/30
100/50, B / C = 30/70 to 70/30, D = (A + B + C) × 0.005 to (A + B + C) × 0.03 for the weight of the acid catalyst (D). The coating composition for a coated metal plate as described above, which is characterized.

[0010]   The acid catalyst (D) is dodecylbenzene sulfone.
Acid or paratoluene sulfonic acid, one or two
Characterized in that it is a typeOrPainted metal plate
Coating composition.

The method for producing a coated metal plate of the present invention is as follows.

[0012]   Butylene glyco as a glycol component
Alcohol, pentanediol, hexanediol
One type or a combination of two or more types
Contains methylolpropane and ethylene glycol
Polyester resin not containing diethylene glycol
AndThe average number of functional groups is 2.1 to 2.6, and the number average molecular weight is
8000 ~ 22000, glass transition temperature 0 ~ 30 ℃ Polyester
Resin (A), methylated methylol melamine resin (B),
Cylated methylol melamine resin (C), acid catalyst (D), and
Paint set for painted metal plates containing amine compound (E) as an essential component
Characterized by coating the product on a metal plate and curing and drying
A method for producing a coated metal plate.

[0013]   Polyester resin (A), methylated methyl
Roll melamine resin (B), butylated methylol melamine
Regarding the solid content weight ratio of resin (C), A / (B + C) = 100 / 30〜
100/50, B / C = 30/70 ~ 70/30, for the weight of acid catalyst (D)
D = (A + B + C) × 0.005 ~ (A + B + C) × 0.03
Characterized by the above Manufacturing method of painted metal plate.

[0014]   The acid catalyst (D) is dodecylbenzene sulfone.
Acid or paratoluene sulfonic acid, one or two
Characterized in that it is a typeOrPainted metal plate
Manufacturing method.

[0015]   Characterized by hardening and drying by induction heating
And saidOne ofManufacturing method of painted metal plate.

[0016]

[Function] When a specific polyester resin is used in combination with a methylated methylol melamine resin and a butylated methylol melamine resin, and an amine-blocked acid catalyst is used, the coating film surface that tends to occur when a methylated methylol melamine resin is used Shrinkage and gloss, and a large decrease in processability that tends to occur when using a butylated methylolmelamine resin, and stain resistance without impairing processability, which is unexpected from the individual blends. It is possible to improve. Further, the influence of the film thickness on the stain resistance is less than that in the case where only the methylated melamine resin is used, and the stain resistance can be secured even with a thinner film thickness.

The present invention will be described in detail below.

First, the polyester resin (A) is a saturated polyester resin having an average number of functional groups of 2.1 to 2.6 and a molecular weight of 800.
The one having a glass transition temperature of 0 to 22000 and a glass transition temperature of 0 to 30 ° C. is used. If the average number of functional groups is less than 2.1, the stain resistance becomes poor, and if it exceeds 2.6, the processability deteriorates, and the crosslink density becomes too high, so that the surface of the coating film has many defects such as wrinkles and the gloss decreases. The average number of functional groups can be calculated from the amount charged at the time of resin design. The molecular weight is the number average molecular weight, measured by gel permeation chromatography using a standard polystyrene calibration curve. For example, due to problems in polyester resin synthesis such as gelation during synthesis and insolubility in solvents, it is difficult to obtain more than 25,000 with functional groups of 2.1 or more,
If it exceeds 22000, the compatibility with melamine resin deteriorates and the appearance of the coating film is impaired, so the upper limit is 22000. If the glass transition temperature is less than 0 ° C, it is difficult to obtain hardness and stain resistance, and if it exceeds 30 ° C, workability becomes poor. In the present invention, the glass transition temperature is TMA (Thermal mechanical a
nalysis, thermomechanical analysis method) was used.

The polyester resin (A) is synthesized from a polybasic acid and a polyhydric alcohol. Polybasic acids that can be used include terephthalic acid, inphthalic acid, orthophthalic acid, adipic acid, succinic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, cyclohexanedicarboxylic acid, etc., or their lower alkyl esters, acid anhydrides, etc. And one or more of these can be used.

[0020] Examples of polyhydric alcohol that can be used, 1, 2
Propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methylpentanediol, 1,6-hexanediol , 1 , There are 4-cyclohexanedimethanol, butylene glycol, etc., and one or more of these can be used , in particular, one or more selected from butylene glycol, pentanediol, hexanediol and trimethylolpropane are included. ,
In addition, those that do not contain ethylene glycol or diethylene glycol have excellent stain resistance, chemical resistance, and weather resistance.

Polyester resin (A) such as trivalent or higher polybasic acid, trimellitic acid, pyromellitic acid, or trivalent or higher polyhydric alcohol, pentaerythritol, trimethylolpropane, trimethylolethane, glycerin, etc.
Can be used to synthesize

Next, as the methylated methylolmelamine resin (B) to be blended in the paint, it is possible to use one or more methylated methylolmelamine resins containing 60% or more of hexamethoxymethylolmelamine. Examples of the methylated methylol melamine resin corresponding to this include Cymel 303, Cymel 301, Cymel 300 and the like.

As the butylated methylol melamine resin (C) blended in the paint, Uban 128, Uban 225, Uban 134, Uban 62, Super Beckamine J830, Super Beckamine G821 and the like can be used. Also, a methyl / butyl mixed alkylated melamine resin such as Cymel 266 or Cymel 267 can be used as a part of or instead of the butylated methylolmelamine resin.

Polyester resin (A), methylated methylol melamine resin (B), butylated methylol melamine resin
The blending amount of (C) is A / (B + C) = 100/30 to 100/50, and B / C =
It is preferably 70/30 to 30/70. Melamine resin amount B +
If the C content is low, good stain resistance cannot be obtained, and if the melamine resin content B + C is high, the processability and gloss decrease. In particular
When A / (B + C) = 100/30 to 100/40 and B / C = 60/40 to 30/70, the balance between workability, stain resistance and hardness is good.

The coating composition of the present invention may be blended with a resin other than the polyester resin and a crosslinking agent resin other than the melamine resin. For example, a polyester resin may be mixed with an acrylic resin, an epoxy resin, a urethane resin, an amide resin, a fluororesin, or the like to provide the required performance. However, in this case, the addition amount of these resins is preferably 100 parts by weight or less with respect to 100 parts by weight of the polyester resin. As the cross-linking agent resin other than the melamine resin that can be mixed, for example, a carboxylic acid contained in the polyester resin, an isocyanate group that reacts with a hydroxyl group, a hydroxyl group, an amino group, an epoxy group,
Examples thereof include those having an amide group, a carboxyl group and the like.
The amount of these cross-linking agent components added is preferably 100 parts by weight or less with respect to 100 parts by weight of the melamine resin. If the amount of these added resins is too large, the workability, stain resistance and the like are deteriorated.

The coating composition of the present invention contains an acid catalyst (D) and an amine compound (E) in addition to the above resins. The acid catalyst (D) is not particularly limited, but it is possible to use dodecylbenzene sulfonic acid, paratoluene sulfonic acid, benzene sulfonic acid and the like which are usually used for polyester resin / melamine-based paints. The amount of catalyst (D) added is D = (A
+ B + C) × 0.005 to (A + B + C) × 0.025 is preferable. When the acid catalyst amount D is small, the curing is insufficient and the solvent resistance and stain resistance are poor, and when it is too large, the processability and gloss are deteriorated. In particular, when either or both of dodecylbenzene sulfonic acid and paratoluene sulfonic acid are used in combination, the stain resistance is improved.

Amine compound that blocks the acid catalyst (D)
(E) is not particularly limited, and examples thereof include triethylamine, dimethylethanolamine, monoethanolamine, and isopropanolamine. A boiling point of 150 ° C or less is particularly desirable. The amine compound (E) was previously acid-catalyzed (D).
It may be added to the resin after being added therein, or may be added to the resin separately from the catalyst. The amount added is arbitrary,
It is desirable to add 0.3 to 1.2 times the equivalent amount of the acid catalyst (D).

Although it is not clear why the processability and other properties, particularly hardness and stain resistance, can be highly compatible by combining these, when a methylated methylolmelamine resin or a butylated methylolmelamine resin is used alone. It is considered that, due to a synergistic effect of the two, the concentration of the melamine resin on the surface layer is more likely to proceed and the volume shrinkage due to the crosslinking of the outer surface layer is suppressed, for some reason.

The coating composition of the present invention may contain additives such as various solvents, pigments, aggregates, defoaming agents and leveling agents, if necessary. The type of the solvent is not particularly limited, and those generally used in paints can be used, for example, cyclohexanone, ketones such as isophorone, butyl acetate, ester such as ethyl acetate, xylene, aromatic such as toluene, Solvesso 100, Examples include hydrocarbons such as Solvesso 150 and alcohols such as butanol and ethanol. The type of pigment is not particularly limited, and inorganic pigments such as titanium white, silica, calcium carbonate, barium sulfate, and alumina used in general paints, and organic pigments such as cyanine blue and indigo red may be used as necessary. You can use it. As the additive, a commercially available antifoaming agent, leveling agent, etc. may be used if necessary. The form of the paint is solvent-soluble, solvent-dispersed, water-soluble, water-dispersed,
Either powder or the like may be used.

The method for producing the coating composition of the present invention is not particularly limited. For example, after adding a necessary amount of a solvent to a polyester resin and a pigment, dispersion is performed by a sand mill or a roll.
After mixing, the remaining polyester resin and melamine resin may be added, and then additives and the like may be added.

Next, the method for producing a coated metal plate of the present invention is as follows.
The coating composition of the present invention may be applied to a metal plate, and the composition may be baked to cure and dry. The type of metal plate and the number of layers of the coating film formed are not limited.

Examples of the metal plate include a steel plate, an aluminum plate, a stainless plate, a titanium plate and a copper plate. Of these, examples of steel sheets include cold rolled steel sheets, hot rolled steel sheets, galvanized steel sheets, galvannealed steel sheets, zinc-iron alloy plated steel sheets, zinc-aluminum alloy plated steel sheets, aluminized steel sheets,
Examples thereof include chrome-plated steel sheet, nickel-plated steel sheet, zinc-nickel alloy-plated steel sheet, tin-plated steel sheet and the like.

The metal plate can be subjected to a pretreatment if necessary. Examples of the pretreatment include washing with water, washing with hot water, pickling, alkaline degreasing, grinding, polishing, chromate treatment, zinc phosphate treatment, and complex oxide film treatment. These pretreatments are performed alone or in combination. The conditions for the pretreatment for coating may be appropriately selected.

If necessary, an undercoat paint may be applied on a metal plate and cured and dried to form an undercoat film layer. As the undercoat paint, there are polyester-based, epoxy-based, urethane-based, etc., which have a required film thickness with a roll coater, curtain flow coater, roller curtain coater, electrostatic coater, brush, blade coater, die coater, etc. Thus, the undercoating film layer is obtained by leaving it to stand at room temperature or curing and drying in a hot air oven, an induction heating oven, a near infrared ray oven, a far infrared ray oven, an energy ray curing oven, or the like. Although the film thickness is arbitrary, a dry film thickness of about 1 to 30 μm, particularly 3 to 12 μm is generally used for a coated metal plate. The drying conditions may be appropriately selected according to the content of the paint and the desired performance, but the maximum plate temperature of 150 to 240 ℃ and the arrival time of 10 to 200 seconds in a hot air oven, induction heating furnace, near infrared furnace, etc. Is common.

Next, the coating composition of the present invention is applied onto a metal plate,
Alternatively, it is applied on the undercoat film and cured and dried.

As the coating method and the curing / drying method, those described as the method for forming the undercoat film can be used. The film thickness is not particularly limited, but it is 5 to 60 μm, of which 10 to 25 μm.
μm is common. The curing and drying conditions are the same as those for forming the undercoat coating film.

The effect of the present invention becomes particularly remarkable when induction heating is used as the curing and baking method. In the hot stove,
In order to raise the plate temperature to about 150 to 240 ° C in a short time of about 10 to 200 seconds during baking, the temperature of hot air must be fairly high. For example, in order to raise the plate temperature to 230 ° C in about 45 seconds, it is generally necessary to have a hot air temperature of 270 to 300 ° C, although it depends on the conditions of the line. This means that the very surface of the coating is exposed to temperatures above the plate temperature. When forming a coating film having a high crosslinking density as in the present invention, the temperature of the coating film surface is important, and when the temperature of the coating film surface becomes too high as in a hot air oven, the crosslinking density of the surface increases. If it is too small, shrinkage may occur or the gloss may be reduced. On the other hand, in the induction heating furnace, the plate temperature is raised by an induced current, so the temperature of the coating film surface is basically the same as the plate temperature, and the temperature of the coating film surface can be controlled. The range of choices is widened, and the design becomes easier. Note that another coating layer may be formed between the undercoat coating and the coating layer essential to the invention.

[0038]

EXAMPLES Examples will be described below.

Terephthalic acid, isophthalic acid, adipic acid, butylene glycol, neopentyl glycol,
After the esterification reaction of dibutyltin oxide (catalyst) and 250 ° C for 2 hours in the presence of an inert gas, 1mmHg
Further reaction is carried out at 270 ° C under reduced pressure to obtain a number average molecular weight of 1300.
A polyester resin having a glass transition temperature of 11 ° C. was obtained. Thereafter, polyester resins having the compositions and characteristics shown in Table 1 were synthesized in the same manner.

[0040]

[Table 1]

As shown in Tables 2 and 3, the polyester resin was mixed with titanium oxide (Taipaque CR-95, manufactured by Ishihara Sangyo) and the required amount of solvent (Solvesso 150 / cyclohexanone = 1/1 (weight ratio)). Then, glass beads were added and dispersed by a disperser, and then a methylated methylolmelamine resin, a butylated methylolmelamine resin, an acid catalyst, a leveling agent and, if necessary, a solvent were added to obtain a coating composition.

[0042]

[Table 2]

[0043]

[Table 3]

The molecular weight is TSK-G3000 as a column in gel permeation chromatography manufactured by JASCO Corporation.
H, TSK-G4000H, and TSK-GMH (all of which are Tosoh Corporation) were used in series connection, and after developing with tetrohydrofuran to obtain a chromatogram, it was calculated based on standard polystyrene. The glass transition temperature was measured by TMA penetration method using a Shimadzu thermal analyzer.

[0045] An electrogalvanized steel sheet having a thickness of 0.6 mm and a zinc adhesion amount of 20 g / m ^{2 on} one side was alkali degreased, and a coating type chromate solution was used.
(ZM-1300 manufactured by Nihon Parkerizing Co., Ltd.) was dried with a roll coater, and then applied as chromium so that the amount of adhesion was 50 mg / m ² , and dried in a hot air drying oven so that the plate temperature was 70 ° C. On this steel plate, a highly workable polyester base coat P185 (
Nihon Paint Co., Ltd.) was applied with a roll coater to a dry film thickness of 5 μm, and then baked and cured in an induction heating furnace so that the reached plate temperature was 220 ° C. in 35 seconds. In addition, apply the coating composition shown in Tables 2 and 3 on this undercoat coating to dry film thickness.
After coating with a roll coater so as to have a thickness of 18 μm, it was baked and cured in an induction heating furnace so that the reached plate temperature was 230 ° C. in 45 seconds. Some steel plates reach a temperature of 230 ° C in a hot stove in 45 seconds.
It was baked and cured so that Regarding the obtained coated steel sheet, the following various evaluation tests were performed in addition to the appearance.

1) Gloss: According to JIS K 5400, the measurement was performed at an incident angle of 60 degrees.

2) Pencil hardness: Measured using Mitsubishi Uni. Tests were carried out by the method of JIS K 5400, and the scratches on the coating film surface were evaluated, and the hardness at the limit without scratches was displayed.

3) Workability: The coated steel sheet was bent 180 degrees, and the cracks in the bent portion were observed with a magnifying glass of 20 times.
Displayed the number of T's. For example, 2T is a case where two plates with the same plate thickness are sandwiched in the bent portion, and 0T is a case where the plate is folded 180 degrees without sandwiching the plate. The workability was evaluated at temperatures of 20 ° C and 0 ° C.

4) Contamination resistance: After the red magic ink was applied to the surface of the coating film, it was allowed to stand at 20 ° C. for 24 hours and wiped off with ethanol, and the trace residue was evaluated. A score of 7 indicates that no trace was left, and a score of 1 indicates that the trace did not disappear at all, and a score of 2 to 6 was evaluated during this period. Score
6 shows a slight trace, a score of 5 has a slight trace, a score of 4 has a trace, a score of 3 has a noticeable trace, and a score of 2 shows almost no disappearance.

5) Alkali resistance: The appearance of the coating film after immersion in a 5% NaOH aqueous solution for 24 hours and 72 hours was evaluated. A rating of 7 indicates a gloss retention of 90% or more without blistering, and a rating of 6 indicates a gloss retention of 80% or more without blistering, a rating.
5 is gloss retention of 70% or more without blistering, rating 4 is gloss retention of 50% or more without blistering, rating 3 is less than 50% gloss but no blistering, rating 2 is spotted blistering, rating 1 is rating 1 Blisters appear on the entire surface.

6) Acid resistance: Appearance was evaluated after immersion in a 5% sulfuric acid aqueous solution for 24 hours and 72 hours. A rating of 7 indicates a gloss retention rate of 90 or higher and a color difference of 2 or less from before the test indicates no blistering. A rating of 6 indicates a gloss retention rate of 80% or higher and a color difference of 2
No blistering below, rating 5 is 70% or more gloss retention, color difference
2 or less, no blistering, score 4 was spotted blistering, less than 10% blistering area, rating 3 was less than 30% blistering area, rating 2 was no peeling at more than 30% blistering area, and rating 1 was film peeling. Indicates what is present.

7) Weather resistance: A JIS D 0205 sunshine carbon arc lamp type weather resistance tester with the black panel temperature set at 63 ± 3 ° C.
After the test for 0 hours, the gloss was measured and the gloss retention was calculated and displayed.

8) Solvent resistance: Xylene was dipped in gauze, and the appearance of the coating film surface after rubbing with a load of 1 kg was evaluated. A rating of 7 is 100 times back and forth and there are no abnormalities other than slight scratches, a rating of 6 is a slight loss of gloss after 100 cycles, a rating of 5 is a loss of gloss after 100 cycles, and a rating of 4 is slightly after 100 cycles. Substrate is exposed, with a score of 3 showing a large exposure of the substrate after 100 reciprocations, a score of 2 shows a large exposure of the substrate at 50 to 100 reciprocations, and a score of 1 shows a large exposure of the substrate at less than 50 reciprocations.

The test results are shown in Tables 4 and 5. Table 4 shows examples of the present invention, and Table 5 shows comparative examples.

[0055]

[Table 4]

[0056]

[Table 5]

Examples of the present invention include workability, pencil hardness, stain resistance,
The gloss was very good. In particular, in Examples 1 and 2 of the present invention containing butylene glycol and not using ethylene glycol as a component, the polyester resin was excellent in weather resistance and chemical resistance.

In Examples 5 and 10 of the present invention and 6 and 11 , there was a difference between when the paint was baked in the induction heating furnace and when it was baked in the hot air furnace. All of them have workability, pencil hardness, stain resistance,
It was found that the gloss was good, but the gloss and workability tended to be slightly inferior when baked in a hot air oven, and the performance was particularly excellent when baked in an induction heating oven.

In Comparative Example 12, the pencil hardness and the stain resistance were poor in Comparative Example 12 containing a small amount of the melamine resin. On the contrary, in Comparative Example 13 in which the amount of melamine resin was too large, the workability was poor. When only the methylated methylol melamine resin was used, Comparative Example 14 with a film thickness of 18 μm showed good performance, but when the film thickness was as thin as 12 μm as in Comparative Example 22 , the stain resistance was significantly reduced. did. Further, in the case of blending only the methylated methylol melamine resin, when the amount of the melamine resin was small as in Comparative Example 15 , the stain resistance was lowered. When only the butylated methylol melamine resin was added, the processability was poor and the gloss was reduced as in Comparative Example 16 . As in Comparative Example 17 , when the amount of the acid catalyst is small, the pencil hardness and the stain resistance are lowered, and on the contrary, Comparative Example 18
When the amount is too large, the workability and the gloss are significantly deteriorated.
As in Comparative Example 19 , using a low molecular weight polyester resin has poor processability, and using a polyester resin having a too high molecular weight as in Comparative Example 20 has poor compatibility with the melamine resin, resulting in poor appearance. . Further, when a polyester resin having a glass transition temperature exceeding 30 ° C. was used as in Comparative Example 21 , workability was poor. When a polyester resin having an average number of functional groups of 2.0 as in Comparative Example 23 was used, stain resistance was poor, and when a polyester resin having an average number of functional groups of more than 2.6 was used as in Comparative Example 24 , the processability was significantly deteriorated.

[0060]

INDUSTRIAL APPLICABILITY The present invention makes it possible to manufacture a coated metal sheet having a high degree of workability, gloss, hardness, and stain resistance, and it is possible to greatly improve chemical resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B05D 7/14 B05D 7/14 A C D G 101 101A 7/24 302 7/24 302S 302V B32B 15/08 104 B32B 15/08 104Z C09D 161/28 C09D 161/28 (56) Reference JP 59-210977 (JP, A) JP 4-370172 (JP, A) JP 4-180869 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09D 1/00-10/00 C09D 101/00-201/10

Claims (7)

(57) [Claims] 1. A polyester resin (A) having an average number of functional groups of 2.1 to 2.6, a number average molecular weight of 8000 to 22000, and a glass transition temperature of 0 to 30 ° C., a methylated methylolmelamine resin (B).
, Butylated methylol melamine resin (C), acid catalyst (D)
, And a coating composition for a coated metal plate containing an amine compound (E) as an essential component , wherein the polyester resin (A) is
Butylene glycol as a glycol component, pentane
1 type selected from all or hexanediol or
A combination of two or more types and trimethylolpropan
And ethylene glycol, diethylene glycol
Paint set for painted metal plates characterized by not containing coal
A product . 2. The solid content weight ratio of the polyester resin (A), the methylated methylolmelamine resin (B) and the butylated methylolmelamine resin (C) is A / (B + C) = 100/3 to 10
0/50, B / C = 30/70 ~ 70/30, weight of acid catalyst (D)
The coating composition for a coated metal plate according to claim 1, wherein D = (A + B + C) × 0.005 to (A + B + C) × 0.03 is satisfied. Wherein the acid catalyst (D) is dodecylbenzene sulfonic acid, one or two coated metal plate for a coating composition according to claim 1 or 2, characterized in that it is of the p-toluenesulfonic acid . 4. Butylene glycol as a glycol component
Selected from the group consisting of phenol, pentanediol, and hexanediol
One or a combination of two or more types
Including tyrole propane, and ethylene glycol,
Polyester resin that does not contain diethylene glycol
The average number of functional groups is 2.1 to 2.6, and the number average molecular weight is 8000.
~ 22000, glass transition temperature 0 ~ 30 ℃ polyester resin (A), methylated methylol melamine resin (B), butylated methylol melamine resin (C), acid catalyst (D), and amine compound (E) are essential A method for producing a coated metal sheet, which comprises applying a coating composition for a coated metal sheet as a component onto a metal sheet and curing and drying the composition. 5. The solid content weight ratio of the polyester resin (A), the methylated methylolmelamine resin (B), and the butylated methylolmelamine resin (C) is A / (B + C) = 100/3 to 10
0/50, B / C = 30/70 ~ 70/30, weight of acid catalyst (D)
5. The method for producing a coated metal sheet according to claim 4, wherein D = (A + B + C) × 0.005 to (A + B + C) × 0.03 is satisfied. 6. The method for producing a coated metal sheet according to claim 4, wherein the acid catalyst (D) is one or two of dodecylbenzenesulfonic acid and paratoluenesulfonic acid. 7. The method for producing a coated metal plate according to claim 4 , wherein the curing and drying are performed by induction heating .