JPH02233183A - Film forming method - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a processable part by baking a top coat film composed of a resin having a specific composition on the bottom coat film, which contains an acryl modified polyester resin of a specific composition as main vehicle, baked on a metal plate material. CONSTITUTION:Bottom coat which contains an acryl modified polyester resin wherein glass transition temp. (Tg) is -10-50 deg.C, a number average MW (Mn) is 5000-30000, a ratio of a polyester resin and an acrylic resin is 90/10-50/50 and the MMA content in the whole resin is 10-50% as main vehicle is prepared. This bottom paint is applied to a metal plate material in a dry film thickness of 5-15mum to be baked and dried. Top coat whose vehicle is composed of a resin composition containing a polyvinylidene fluoride and an acrylic resin based on MMA in a wt. ratio of 50/50-85/15 is applied to said bottom coat film in a dry film thickness of 15-30mum to be baked and dried.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a coating film forming method particularly useful in the field of coil coating, and more specifically, to a method for forming a coating film on a metal plate material that is excellent in workability, corrosion resistance of processed parts, and weather resistance. The present invention relates to a coating film forming method.

BACKGROUND OF THE INVENTION In the field of coil coating, polyvinylidene fluoride resin paints are attracting attention as durable paints due to the demand for long-term quality assurance. Although these fluorine-containing resins are stable and durable against light, they have problems with compatibility with other resins and adhesion to substrates, so it is necessary to consider the resins to be blended with, the undercoat, etc. . So, for example,
-11950 etc., an acrylic resin or epoxy resin-based primer is applied to the base coat, and a top coat containing polyvinylidene fluoride resin and acrylic beet mainly composed of methyl methacrylate as a resin vehicle is applied on top of this undercoat. A method has been proposed. In this technology, an acrylic resin mainly composed of methyl methacrylate, which has good compatibility with polyvinylidene fluoride resin, is used as the resin vehicle for the top coat, and an acrylic resin or epoxy resin, which has good adhesion with the top coat, is used as the primer. , aiming to improve the adhesion to the substrate and the adhesion between the eyebrows.

However, since acrylic resin or epoxy resin mainly composed of methyl methacrylate is used for the primer, the coating becomes hard and has poor workability, cracks are likely to occur during processing, and the corrosion resistance of the processed part is poor.

Problems to be Solved by the Invention Therefore, in the field of coil coating, we used a polyvinylidene fluoride resin-based top coat paint, which has excellent durability.
There is a need for the establishment of a vine coating method that has good substrate adhesion and glabella adhesion, and greatly improves workability and corrosion resistance of processed parts, and it is an object of the present invention to meet such problems.

Means for Solving the Problems According to the present invention, the above objects are achieved by: (a) glass transition temperature (Tg) -10 to 50°C (b) number average molecular weight (M n ) 5,000 ~30,0
00(C) Ratio of polyester resin and acrylic resin 90
/10 to 50/ 50 (d) Apply an undercoat paint whose main vehicle is an acrylic modified polyester resin with an MMA content of 10 to 50% in the total resin to a dry film thickness of 5 to 15 μm, and after baking and drying, apply polyvinylidene fluoride resin. and 50% acrylic resin with MMA main component.
This can be achieved by a coating film forming method characterized in that a top coat containing a resin composition in a weight ratio of 50 to 85/15 as a vehicle is applied to a dry film thickness of 15 to 30 microns, and then baked and dried.

The method of the present invention is applied to metal sheet materials such as hot-dip galvanized steel sheets, aluminum galvanized steel sheets, aluminum sheets, stainless steel sheets, etc., which are to be used for high-grade roofing materials, siding materials, and various types of utensils. If desired, these metal plate materials may be subjected to surface treatment in advance to further improve corrosion resistance and adhesion, but this is not necessarily necessary in the method of the present invention.

In the method of the present invention, first, on the above-mentioned metal plate material, (a>glass transition temperature (T g > -10 to 50°C) (b) number average molecular weight (M n ) 5, OOCI-30,00
0(C) Ratio of polyester resin and acrylic resin 90/
10-50/50 (d) An undercoat paint whose main vehicle is an acrylic modified polyester resin having an MMA content of 10-50% in the total resin is applied.

Such acrylic modified polyester resin can be produced by (1) polymerizing an acrylic monomer in the presence of a polyester into which a polymerizable double bond has been introduced; (2) directly reacting a functional group in the polyester resin with a functional group in the acrylic resin. Method; (3) A low molecular weight crosslinkable compound having a reactive functional group (
(4) Transesterification of polyester resin and acrylic resin at high temperature. It can be produced by grafting a polyester resin and an acrylic resin by any method well known to those skilled in the art.

The acrylic modified polyester resin used in the process of the invention must, however, meet the requirements of (a), (b), (c) and (d) above. This is because if the glass transition temperature of the resin is less than -10°C, it will become sticky and will not have enough hardness when formed into a coating, which is undesirable.If it exceeds 50°C, the processability will be poor and the purpose of the present invention will not be achieved. I can't do it. A particularly preferred glass transition temperature range is 10 to 30°C. If the number average molecular weight of the resin is less than 5,000, the workability of the coated plate will be poor and the number average molecular weight of the resin will be 30,0.
The number average molecular weight of the resin should be within the range of 5,000 to 30,000 because if it exceeds 0.00, the fluidity will be poor. The preferred range is 10,000 to 20,
It is 000. Next, for the purpose of the present invention to obtain desirable glabella adhesion and processability, the weight ratio of polyester resin and acrylic resin must be within the range of 90/10 to 50/50, and the acrylic resin must contain the components. The amount of methyl methacrylate included and incorporated into the modified resin is 10-50%, preferably 15-4% in the total resin.
Must be a percentage of 0%. If the amount of methyl methacrylate is less than 10%, the glabella adhesion with the top coat will be poor, and if it exceeds 50%, the processability will be poor, both of which are undesirable for the purposes of the present invention.

Such an undercoat paint is applied to a metal plate material so that the dry film thickness is practically 5 to 15 μm, and is baked and dried. If the film thickness is too thick, wrinkles are likely to occur, which is not preferable. The undercoat paint of the present invention has excellent adhesion to the metal plate material and can be applied directly to the metal plate material as described above, but if desired, a primer for pre-coated metal may be applied to the metal plate material in advance, and then the above-mentioned Of course, it is also possible to use the paint as an intermediate coating (
In this case, it becomes 3C3B). Primers for pre-coated metal include epoxy primers such as Superlac DIF P-70 Primer (manufactured by Nippon Paint Co., Ltd.);
Polyester brimer e.g. Superlac DIF
P-107 Primer (manufactured by Nippon Paint Co., Ltd.) A well-known acrylic primer such as Vinizol 4000 Brimer (manufactured by Nippon Paint Co., Ltd.) is used.
For example, it is applied to a dry film thickness of about 3 to 10μ, and after baking and drying,
The above-mentioned undercoat paint may be applied as an intermediate coat.

In the present invention, in any of the above cases, on the paint layer whose main vehicle is acrylic modified polyester resin,
Next, polyvinylidene fluoride resin and acrylic resin containing methyl methacrylate as main components were mixed at a solid content weight ratio of 85/
A top coat containing a resin composition in a ratio of 15 to 50/50 as a vehicle is applied to a dry film thickness of 15 to 30 μm, and a coated plate is prepared by baking and drying.

The top coat containing polyvinylidene fluoride resin and acrylic resin whose main components are methyl methacrylate used here has already been proposed as a durable coil coating paint in, for example, Japanese Patent Publication No. 6311950. The acrylic resin containing methyl methacrylate as a main component may be either thermoplastic or thermosetting type that is compatible with the polyvinylidene fluoride resin. Regarding the blending ratio of these resins, if the polyvinylidene resin is too large, processability will be poor, and conversely, if the acrylic resin is too large, weather resistance will be poor. ~5
0, preferably at a solid content weight ratio of 75 to 60 to 25 to 40, and the coating method includes general coil coating methods, such as roll coating such as natural roll coating and reverse roll coating. Alternatively, curtain flow coating or the like may be advantageously used.

As mentioned above, the present invention applies an undercoat using a special acrylic modified polyester resin as a vehicle, either directly or after applying a coil coating primer to the metal material.
Alternatively, it includes the 2C2B or 3C3B painting method in which an intermediate coating is applied and a topcoat using an acrylic resin as a vehicle containing polyvinylidene fluoride resin and methyl methacrylate as a vehicle, and the topcoat and acrylic-modified polyester are applied. The acrylic in the resin is thermally fused during baking, exhibiting strong adhesion, and the specific base polyester allows processability to be maintained. It is a way to achieve both.

The present invention will be explained below with reference to Examples. Parts and percentages are by weight unless otherwise specified.

鉦え隨L 664 parts of isophthalic acid, 219 parts of adipic acid, 49 parts of maleic anhydride, 676 parts of neopentyl glycol, 1.
378 parts of 6-hexanediol and 0.3 parts of dibutyltin oxide were charged into a reaction vessel and heated to 220 to 230°C.
After carrying out the esterification reaction for 3 hours at 250°C, 0
．． 1-1. The polycondensation reaction was carried out under a vacuum of OmmHg, the number average molecular weight was 15,000, and the monomer composition ratio isophthalic acid/adipic acid/maleic acid = 67/25/8 (equivalent ratio).
, a polyester resin with neopentyl glycol/1,6-hexanediol=50/50 (equivalent ratio) was obtained, and then cyclohexanone/Solvesso 150 (weight ratio 50/50) was obtained.
50') to obtain a polyester resin face (PE-1) with a non-volatile content of 40%.

175 parts of (PE-1) obtained in Synthesis Example 1, 18 parts of methyl methacrylate, and 12 parts of styrene were charged into a reaction vessel.
Heat to 10°C and add Kayaester O (manufactured by Kayaku Nouri Co., Ltd.)
A mixed solution of 5 parts of xylene and 45 parts of xylene was added dropwise at a constant rate over 3 hours, and then maintained at the same temperature for 2 hours to obtain an acrylic modified polyester resin varnish (PE-AR-1') with a non-volatile content of 40%.

The heptanomer composition ratio isophthalic acid/terephthalic acid/adipic acid = 40/35/25 (
(equivalent ratio), neobentyl glycol/1,6-hexanediol/trimethylolpropane = 50/46/4
(equivalent ratio) to obtain a polyester resin with a number average molecular weight of 10,000, which was then diluted with cyclohexanone/Solvesso 150 (weight ratio 50/50) to have a non-volatile content of 40%.
A polyester resin face (PE-2) was obtained.

1L 175 parts of (PE-2) obtained in Synthesis Example 3,
160 parts of 2-isocyanatoethyl methacrylate was charged into a reaction vessel and reacted at 100°C for 1 hour, then 30 parts of methyl methacrylate was charged and heated to 110°C, and 5 parts of Kayaester 0 (manufactured by Kayaku Nouri ■) and xylene were added. After 51 parts of the mixed solution was added dropwise at a constant rate over 3 hours, the mixture was kept at the same temperature for 2 hours to obtain an acrylic modified polyester resin varnish (PE-AR-2) with a non-volatile content of 40%.

Button-broiled U Monomer composition ratio obtained by the same method as Synthesis Example 1: isophthalic acid/terephthalic acid/adipic acid = 40/35/
25 (equivalent ratio), neobentyl glycol/1,6-
Hexanediol/trimethylolpropane = 50/4
5/5 (equivalent ratio), and the number average molecular weight is 8,000
100 parts of polyester resin, anhydrous trimelit wi2
of cyclohexanone/Solbetsuso 150 (weight ratio 50/5
0) to obtain a polyester resin face (PE-3) with a nonvolatile content of 50%.

420 parts of cyclohexanone/Sobesso 150 (weight ratio 50/50') was charged into a reaction vessel, and the temperature was raised to 120°C. Then, at the same temperature, a mixture consisting of 240 parts of methyl methacrylate, 104 parts of n-butyl acrylate, 56 parts of glycidyl methacrylate, and 20 parts of Kaya Ester O (manufactured by Kayaku Nouri TM) was added dropwise at a constant rate over 3 hours. Furthermore, 8 parts of Kayaester O was added dropwise at a uniform rate over 1 hour, and the mixture was kept at the same temperature for 2 hours to form an acrylic resin face (A) with a non-volatile content of 50%.
R-1> was obtained.

70 parts of (PE-3) obtained in Synthesis Example 5, 30 parts of (AR-1) obtained in Synthesis Example 6, and 25 parts of cyclohexanone/Sobesso 150 (weight ratio 50/50) were charged into a reaction vessel. The reaction was carried out at 120°C for 6 hours, and the non-volatile content was 4.
0% acrylic modified polyester resin face (PE-A
R-3) was obtained.

1E' By the same method as in Shadow Synthesis Example 1, the monomer composition ratio was adjusted to isophthalic acid/terephthalic acid/adipic acid = 40/35/25 (
(equivalent ratio), neobentyl glycol/1,6-hexanediol/trimethylolbroban=50/4g/2
(equivalent ratio) and a number average molecular weight of 12,000 was obtained, and cyclohexanone/Solvesso 15
0 (weight ratio 50/50) to obtain a polyester resin face (PE-4) with a nonvolatile content of 40%.

Pour 412 parts of cyclohexanone/Sobesso 150 (weight ratio 50/50) into one reaction vessel and raise the temperature to 120°C. Then, at the same temperature, 268 parts of methyl methacrylate,
A mixture consisting of 104 parts of n-butyl acrylate, 28 parts of 2-hydroxyethyl methacrylate, and 12 parts of Kayaester ○ (manufactured by Kayaku Nouri ○) was added dropwise at a constant rate over 3 hours. Further, 8 parts of Kaya Ester (○) was added dropwise at a uniform rate over 1 hour, and the mixture was kept at the same temperature for 2 hours to obtain an acrylic resin face (AR-2) with a non-volatile content of 50%.

175 parts of (PE-4) obtained in Synthesis Example 8, 60 parts of (AR-2) obtained in Synthesis Example 9, 1 part of hexamethylene diisocyanate, and 15 parts of cyclohexanone/sobetsuso.
0 (weight ratio 50/50) 16.5 parts were charged into a reaction vessel and reacted at 120°C for 1 hour to obtain an acrylic modified polyester resin varnish (PE-AR-4) with a non-volatile content of 40%.

Using the same method as in Synthesis Example 1, the monomer composition ratio was adjusted to isophthalic acid/terephthalic acid/adipic acid = 40/35/25 (
Neopentyl glycol/1,6-hexanediol=50/50 (equivalent ratio), and 100 parts of a polyester resin having a number average molecular weight of 18,000 was obtained. To this, 30 parts of macromonomer "HA-6"' (manufactured by Toagosei Kagaku Kogyo ■) was added, and the temperature was raised to 240°C.
1-1. Polycondensation reaction was carried out at 0 mmHg for 3 hours, and cyclohexanone/Sobesso 150 (weight ratio 50/50
'') to obtain an acrylic modified polyester resin varnish (PE-AR-5) with a nonvolatile content of 35%.

Gold] Special Yuji L By the same method as in Synthesis Example 1, the monomer composition ratio was adjusted to isophthalic acid/terephthalic acid/adipic acid = 40/35/25 (
100 parts of a polyester resin having an equivalent ratio of neopentyl glycol/16-hexanediol=50/50 (equivalent ratio) and a number average molecular weight of 18.000 was obtained. Polymethyl methacrylate (number average molecular weight 10,000
0) After charging 30 parts and reacting at 230°C for 30 minutes, cyclohexanone/Sobesso 150 (weight ratio 50/50
) to obtain an acrylic modified polyester resin varnish (PE-AR-6) with a nonvolatile content of 40%.

Gold ffi By the same method as in Synthesis Example 1, the monomer composition ratio was adjusted to isophthalic acid/terephthalic acid/adipic acid - 40/35/25 (
(equivalent ratio), neopentyl glycol/1,6-hexanediol/trimethylolpropane = 50/43/7
(equivalence ratio) and a number average molecular weight of 5,000 was obtained, and cyclohexanone/Solbetsuso 15
0 (weight ratio 50/50) Dilute with diluent to obtain a polyester resin face (PE-5) with a non-volatile content of 50%.

90 parts of (PE-5) obtained in Synthesis Example 13 and 1.4 parts of 2-isocyanatoethyl methacrylate were charged into a reaction vessel and reacted at 100°C for 1 hour.
5 parts, cyclohexanone/Sobesso 150 (weight ratio 50
/50) 90 parts were heated to 110°C, a mixed solution of 5 parts of Kayaester O (manufactured by Kayaku Nouri Aji) and 17 parts of xylene was added dropwise at the same rate over 3 hours, and the mixture was kept at the same temperature for 2 hours until it became non-volatile. An acrylic modified polyester resin varnish (PE-AR-7) with a content of 40% was obtained. The monomer composition ratio isophthalic acid/terephthalic acid/adibic acid = 40/35/25 (
(equivalent ratio), neobentyl glycol/1,6-hexanediol/trimethylolbroban = 50/49/1
(equivalence ratio) and a number average molecular weight of 15,000 was obtained, and cyclohexanone/Solvesso 15
0 (weight ratio 50/50) to obtain a polyester resin face (PE-6) with a non-volatile content of 40%.

Gold ffi (PE-6) obtained in Synthesis Example 15 237.
5 parts, 2-isocyanatoethyl methacrylate 1.0
After charging the mixture into a reaction vessel and reacting at 100°C for 1 hour,
5 parts of methyl methacrylate was charged and heated to 110°C, and a mixed solution of 5 parts of Kayaester ○ (manufactured by Kayaku Nouri ○) and 9 parts of xylene was added dropwise at the same rate over 3 hours, and the mixture was kept at the same temperature for 2 hours until it became non-volatile. An acrylic modified polyester resin varnish (PE-AR-8) with a content of 40% was obtained. Gold Ju Special Uni L By the same method as in Synthesis Example 1, the monomer composition ratios were: isophthalic acid/terephthalic acid = 50/50 (equivalent ratio), neopentyl glycol/ethylene glycol/neopentyl glycol hydroxypipate/trimethylolpropane = 40 / 40/ 16/ 4 (equivalent ratio),
Obtaining a polyester resin with a number average molecular weight of 10.000,
Cyclohexanone/Solbetsuso 150 (weight ratio 50/
50') to obtain a polyester resin varnish (PE-7'') with a non-volatile content of 40%.

1.0 parts of 2-isocyanatoethyl methacrylate (P E-7 > 175 parts obtained in Synthesis Example 17) was charged into a reaction vessel and reacted at 100°C for 1 hour, and then 30 parts of methyl methacrylate was added. Preparation: Heat to 110°C, add 5 parts of Kayaester 0 (manufactured by Kayaku Nouri ■), 50 parts of xylene.
A mixed solution of 30% was added dropwise at a constant rate over 3 hours, and the mixture was kept at the same temperature for 2 hours to obtain an acrylic modified polyester resin varnish (PE=AR-9) with a non-volatile content of 40%.

Using the same method as in Synthesis Example 1, the monomer composition ratio was 20/20/60.
(equivalence ratio). A polyester resin with 1.6-hexanediol/trimethylolpropane = 96/4 (equivalent ratio) and a number average molecular weight of 10,000 was obtained, and was diluted with cyclohexanone/Solvesso 150 (weight ratio 50/50) to remove the nonvolatile content. 40% polyester resin face (PE-
8) was obtained.

175 parts of (PE-8) obtained in Button Refinery Example 1 and 1.0 part of 2-isocyanatoethyl methacrylate were charged into a reaction vessel and reacted at 100°C for 1 hour, and then 30 parts of methyl methacrylate was charged. After heating to 110°C, a mixed solution of 5 parts of Kaya Ester 0 (manufactured by Kayaku Nouri Aji) and 50 parts of xylene was added dropwise at a uniform rate over 3 hours, and the mixture was kept at the same temperature for 2 hours to form an acrylic modified polyester with a non-volatile content of 40%. A resin varnish (PE-AR-10) was obtained.

Gold 1 Special λ''L By the same method as in Synthesis Example 1, the heptanomer composition ratio was changed to isophthalic acid/terephthalic acid/adipic acid -40/35/25 (
(equivalent ratio), neopentyl glycol/1,6-hexanediol/trimethylolpropane = 42/42/
16 (equivalence ratio), and the number average molecular weight is 2,00
0 polyester resin was obtained, diluted with cyclohexanone/Solbetsuso 150 (weight ratio 50/50) to make a polyester resin face with a non-volatile content of 50%, and then the varnish 4
00 parts of 2-isocyanatoethyl methacrylate was charged into a reaction vessel and reacted at 100°C for 2 hours to form a mixture of cyclohexanone/Solvesso 150 (weight ratio 50/
50) A polyester resin face (PE-9) having a non-volatile content of 50% was obtained by diluting with 15.9 parts.

Synthesis Example 22 Charge 35 parts of cyclohexanone/Sobesso 150 (weight ratio 50/50) into a reaction vessel and raise the temperature to 110°C.

Then, at the same temperature, the product obtained in Synthesis Example 21 (PE-9>14
0 parts, 30 parts of methyl methacrylate and Kaya ester○
A mixture consisting of 10 parts (manufactured by Kayaku Nouri Aji) was added dropwise at a constant rate over 3 hours. Furthermore, 1 part of Kaya Ester 0 was added dropwise at a uniform rate over 1 hour, and the mixture was kept at the same temperature for 1 hour to create an acrylic modified polyester resin varnish (PE-AR-1 1
') got.

1 to 9 and 1 to 9 A 0.5 mm thick galvanized iron plate was previously treated with zinc phosphate (Nippon Paint Co., Ltd. product, Granodin ZD9200, coating amount 1 g)
/ m”, zinc amount 250 g / m” (both sides)
A test plate was used.

In each example, a varnish having the glass transition temperature, number average molecular weight, polyester resin/acrylic resin solid weight ratio, and methyl methacrylate content indicated solids content of acrylic modified polyester resin was 2C2
It was used as an undercoat paint in the case of B or as an intermediate paint in the case of 3C3B.

Incidentally, as the undercoat paint, one having the following composition was used.

Titanium CR 95 9.4 parts Strontium chromate N 9.4 parts Acrylic modified polyester resin face of each example 66.9 parts Cymel 30
3 4.6 part catalyst 6000
0.3 parts Sorbetso 150
4.7 parts cyclohexanone 4.7
Total 100. 0 parts The above was weighed in a paint shaker and dispersed for 1 hour using glass beads.

When used as an intermediate coating, a coating having the following composition was used.

Titanium CR95 9.0 parts Strontium chromate N 4.5 parts Acrylic modified polyester resin face of each example 72.2 parts Cymel 30
3 5.0 part catalyst 6000
0.3 parts Solvesso 150
4.5 parts cyclohexanone 4.5
Total of 100.0 parts The above was weighed in a paint shaker and dispersed for 1 hour using glass beads.

Furthermore, the following composition was used as the top coat.

Kynar 500 22 parts Paraloid B-44 38 parts NV 25% isophorone solution Titanium CR 95 22 parts Isophorone 18 parts 100 parts The above was weighed in a paint shaker and dispersed for 1 hour using glass beads.

In the case of 2C2B, the undercoat paint was applied directly to the test plate with a bar coat to a dry film thickness of 5μ, and baked in a hot air oven for 50 seconds to reach a maximum plate temperature of 210°C.

In the case of 3C3B, apply the undercoat listed in Table 1 with Barco 1 to a dry film thickness of 5μ, bake in a hot air oven for 50 seconds to reach a maximum board temperature of 200℃, and then apply the above intermediate coat. Apply the paint with a bar coat to a dry film thickness of 10μ, and heat it in a hot air oven for 50℃ to reach a maximum temperature of 210℃.
Baked for seconds. Next, on top of these undercoats or intermediate coats, the above-mentioned top coat paint was applied with a bar coat to a dry film thickness of 20 μm, and each plate was baked in a hot air oven for 60 seconds to reach a maximum plate temperature of 240°C. Ta.

The obtained coated plate was tested according to the following test method and criteria.
Workability, corrosion resistance of processed parts, and coin scratch resistance were investigated, and the results are shown in Table 2. ■ Processability The coated plate is left in a room at 20°C and 75% RH for one day and night, processed in a vise, and indicated by the T number without cracks. (Judgment is done visually using a ×15 magnifying glass) ■ Processed part corrosion resistance salt sobriety tester (according to JISK5400)
Tested for 2000 hours. Processing was performed by OT bending.

◎: No blisters or white rust at all.

○: A small amount of blisters or white rust occurs.

△: Partial blisters or white rust.

×: Blisters or white rust appeared on the entire surface.

■Coin scratch property Fix a 10 yen coin to the tip of a scratch tester, change the charge, and test according to the JISK5400 scratch test method. Displayed with a charge that does not cause the paint film to peel.

1 kg or more is good.

Particularly good for weights of 1.5 kg or more.

(Margin below) 2. 3. Voluntary writing of procedural amendments) October 11, 1999 1999 Patent Application No. 54447 name of invention Paint film formation method person who makes corrections Relationship with the incident

Claims (1)

[Claims] On a metal plate material: (a) Glass transition temperature (Tg) -10 to 50°C (b) Number average molecular weight (Mn) 5,000 to 30,000 (c) Polyester resin and acrylic resin Ratio of 90/10~50
/50 (d) Apply an undercoat with an acrylic modified polyester resin as the main vehicle having an MMA content of 10 to 50% in the total resin to a dry film thickness of 5 to 15 μm, and after baking and drying, polyvinylidene fluoride resin and MMA as the main components are applied. A dry film thickness of 15 to 30μ is obtained by applying a topcoat paint whose vehicle is a resin composition containing acrylic resin in a weight ratio of 50/50 to 85/15.
A coating film forming method characterized by coating and baking drying.