JP2006239517A - Coating film forming method and coated article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated article which is obtained in compliance with required performance (such as finishing property and anti-corrosive property) to components in the coating line conveyed together with at least two or more components different in shape and size. <P>SOLUTION: The coating film forming method comprises the steps 1 of immersing a material to be coated in an ionic coating composition (A), the step 2 of applying at least one process selected from a setting, air blowing and pre-heating; the step 3 of conducting heat drying at a drying furnace and the step 4 of further applying one or more layers of an aqueous or organic solvent type top coating (B) and to conduct baking/drying. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a coating film forming method capable of obtaining a coated article excellent in finish and corrosion resistance at a low price.

In the industrial coating field, various efforts are being made to provide inexpensive products to users. For example, production such as thinning, process saving, energy saving, space saving, tact-up, material cost reduction, etc. Efficiency is improved and manufacturing costs are reduced.
At present, industrial parts are subjected to a chemical conversion treatment such as zinc phosphate for anticorrosion, and then the film is immersed in a bath of cationic electrodeposition paint and electrodeposition is applied to form a dry film thickness of 5 μm to 30 μm. In order to form a thickness, and then remove excess paint, it is washed with UF filtrate or pure water, baked and dried to form a coating film.

If the dry film thickness is less than 5 μm using an electrodeposition coating facility as described in JP-A-11-350194, the finish and corrosion resistance deteriorate due to gas generation accompanying electrodeposition coating. Moreover, since the cost of electricity is generated with the operation of the equipment, the cost has not been reduced.
Conventionally, the invention relates to a paint for dip coating, containing 12 to 40 parts by weight of a silicon dioxide pigment having an oil absorption of 200 or more with respect to 100 parts by weight of the resin, and the total oil absorption of the pigment per 100 g is 4000 to 15000. There is an invention relating to the anticorrosion properties of edge edges using a paint for dip coating, which is characterized (Patent Document 1). The coating material for dip coating according to Patent Document 1 contains a certain amount of pigment that defines the amount of oil absorption, so that it has excellent anticorrosion properties at the edge end portion, but the finishing performance is degraded due to the accumulation of the pigment in the horizontal portion. In addition, it takes time to control the viscosity of the paint in order to increase the film thickness beyond a certain level, and if the viscosity of the paint is increased to increase the film thickness, a reservoir will be formed in the object to be coated and the finish will be impaired. was there.

In addition, there is an invention relating to a room-temperature dry paint for metals, the main component of which is a cationic epoxy resin, and a coating method characterized in that the paint is applied to a metal by spray coating or immersion coating and dried at room temperature (patent) Reference 2). Since the coating film by the coating method of patent document 2 is a normal temperature curing type, the fusion | melting and bridge | crosslinking of the coating film by heat flow were not enough, and corrosion resistance was inadequate.
From such a background, there has been a demand for a method for forming a coating film using an existing coating facility and obtaining a product at a low price in a mixed loading line for industrial parts.

  In addition, the production of an organic monomolecular thin film in which an oxidized compound semiconductor is immersed in a solution or melt containing an amphiphilic organic molecule, and the organic molecule is chemically adsorbed on a semiconductor substrate to form an organic monomolecular film. There is an invention relating to a method (Patent Document 3). Even when the organic monomolecular film related to Patent Document 3 is applied to automobile parts, it is not possible to sufficiently ensure finish and corrosion resistance.

Japanese Patent Laid-Open No. 1-261467 JP-A-8-48936 Japanese Patent Laid-Open No. 11-112061

  In a painting line in which at least two types of parts with different shapes and sizes are mixed, a coated article corresponding to the coating film performance (for example, finish and corrosion resistance) required for the parts is obtained, and cost reduction is achieved. thing.

  The present invention is a coating line in which electrodeposition coating is usually performed, so that the object to be coated is immersed in an ionic coating composition (for example, a cationic coating or an anionic coating) and appropriately washed with a UF filtrate. It discovered that it could achieve by the coating-film formation method which coats a top coat after heat-drying and heat-drys.

  According to the coating film forming method of the present invention, in the electrodeposition coating line, particularly in a coating line in which at least two kinds of parts having different shapes and sizes are mixedly mounted, the performance (finishability, corrosion resistance) required for the parts is improved. Corresponding coated articles can be obtained. The coating film forming method of the present invention does not generate gas holes generated during electrodeposition coating, and can ensure finish and corrosion resistance even when the dry film thickness is less than 5 μm. Thus, a coated article can be obtained at a low cost. Further, after being immersed in the ionic coating composition, washing with a UF filtrate further contributes to improvement in finish and corrosion resistance.

  The present invention is a method for forming a coating film according to the following steps 1 to 4. “Step 1: Step of immersing the article to be coated in the ionic coating composition (A), Step 2: Step of applying at least one selected from setting, air blowing, and preheating, Step 3: Heat drying in a drying furnace Steps to be performed, Step 4: Steps in which one or more layers of the top coat paint (B) are further applied and baked and dried.

Step 1: A step of immersing the article to be coated in the ionic coating composition (A). The material to be coated is not limited as long as it is a material having a metal surface, such as iron, aluminum, tin, zinc, and alloys containing these metals. Examples include parts, electrical products, and building materials. These coated materials are preferably subjected to a surface treatment such as zinc phosphate before being immersed in the ionic coating composition (A) in order to improve corrosion resistance.
As a tank in which the ionic paint composition (A) is placed, an electrodeposition paint tank generally used for painting industrial parts and the like as shown in FIG. 1 can be applied.
As the ionic coating composition (A), for example, a resin obtained by introducing a hydroxyl group and an ionic group such as an epoxy resin, an acrylic resin, and a polyester resin, and emulsifying by neutralization and water dispersion can be used. The emulsion may or may not contain a curing agent. Furthermore, a pigment paste obtained by dispersing a pigment, a catalyst, or the like using a dispersing resin can also be blended.

  As the ionic coating composition (A), a cationic coating composition using an amine-added epoxy resin obtained by adding an amine compound using an epoxy resin as a starting material because of its excellent anticorrosion properties is preferable. . The epoxy resin used as the starting material is particularly preferably an epoxy resin obtained by a reaction between a polyphenol compound and epichlorohydrin, for example, epichlorohydrin, from the viewpoint of anticorrosion properties of the coating film.

  As the polyphenol compound that can be used for the formation of the epoxy resin, those similar to the conventional ones can be used. Bis (4-hydroxyphenyl) -2,2-propane (bisphenol A), 4,4-dihydroxybenzophenone Bis (4-hydroxyphenyl) methane (bisphenol F), bis (4-hydroxyphenyl) -1,1-ethane, bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert- Butyl-phenyl) -2,2-propane, bis (2-hydroxynaphthyl) methane, tetra (4-hydroxyphenyl) -1,1,2,2-ethane, 4,4-dihydroxydiphenylsulfone (bisphenol S), A phenol novolak, a cresol novolak, etc. can be mentioned.

  Moreover, as an epoxy resin obtained by reaction of a polyphenol compound and epichlorohydrin, the following formula induced | guided | derived from bisphenol A is mentioned especially,

Here, those represented by n = 0 to 8 are preferred.
The epoxy resin is generally from 180 to 2,500, preferably from 200 to 2,000, more preferably having an epoxy equivalent weight in the range from 400 to 1,500, and is generally at least 200, in particular from 400 to Those having a number average molecular weight in the range of 4,000, more particularly 800 to 2,500 are suitable.

  Examples of such commercially available epoxy resins include those sold by Japan Epoxy Resins Co., Ltd. under the trade names of Epicoat 828EL, 1002 on the left, 1004 on the left, and 1007 on the left.

  The average molecular weight of the epoxy resin is not particularly different from usual, and the average molecular weight is preferably 1,000 to 10,000, more preferably 2,000 to 5,000. Next, as the amine compound, primary mono- and polyamines, secondary mono- and polyamines, or 1,2 mixed polyamines, secondary mono- and polyamines having a ketimized primary amino group, ketiminated 1 Examples thereof include hydroxy compounds having a secondary amino group. Specifically, it is preferable to use a ketimine product of diethylamine, diethanolamine, diethylenetriamine or the like.

  The amine-added epoxy resin may be used as it is, but of course, a plasticized and modified epoxy resin may be used. The plasticizing modifier for the epoxy resin is preferably compatible with the epoxy resin and hydrophobic, and as a modification method, the terminal epoxy group is preferably reacted in the same manner as the above amine compound.

  The amount of modification needs to be kept to the minimum amount necessary for plasticization, and is preferably 5 to 50 parts by weight, more preferably 10 to 30 parts by weight with respect to 100 parts by weight of the epoxy resin. Examples of preferred modifiers include xylene formaldehyde resin and polycaprolactone having reactivity with epoxy groups.

  The amine-added epoxy resin is cationized by neutralization with an organic acid. The organic acid is preferably a lower carboxylic acid, particularly acetic acid, formic acid or a mixture thereof, and the use of these acids improves the finish, anticorrosion, and paint stability.

In order to cure the above cationic coating composition integrally with a sealer or a top coat film, for example, as a curing agent, an aromatic polyisocyanate blocked with alcohols, or an aliphatic polyisocyanate or oxime blocked with oxime. It is desirable to contain a blocked polyisocyanate compound such as an alicyclic polyisocyanate blocked with.
Any pigment that has been used in the past can be incorporated into the cationic coating composition without any particular limitation. For example, colored pigments such as titanium oxide, carbon black, and bengara; clay, mica, barita, calcium carbonate And extender pigments such as silica; rust preventive pigments such as basic lead silicate, aluminum phosphomolybdate, aluminum tripolyphosphate, and antimony pentoxide;

  Furthermore, a bismuth compound can be contained as a corrosion inhibitor, and examples thereof include bismuth oxide, bismuth hydroxide, basic bismuth carbonate, bismuth nitrate, and bismuth lactate. The blending amount of these pigments is preferably in the range of 1 to 100 parts by weight, particularly 5 to 30 parts by weight per 100 parts by weight of the total solid content of the base resin and the curing agent.

  The cationic coating composition is generally diluted with deionized water or the like so that the solid content concentration is about 5 to 40% by weight, preferably 15 to 25% by weight, and the pH is further adjusted to 5.5 to 9.0. The bath temperature is adjusted to 15 to 35 ° C. In the present invention, an object to be coated is immersed in a cationic coating composition. The immersion time is 1 second to 60 minutes, preferably 1 minute to 10 minutes, and more preferably 2 minutes to 5 minutes. As a dry film thickness of the obtained coating film, it is less than 5 micrometers based on a cured coating film, Furthermore, it is the range of 0.01-3 micrometers, especially 0.1-2 micrometers.

  When immersing the coating in the cationic coating composition, the coating is swung back and forth or the coating is swung up and down to penetrate into the bag and clearance of the coating. It is also possible to give.

Step 2: A step of applying at least one selected from setting, air blow, and preheating. In addition, after at least one kind selected from setting, air blow, and preheating is performed, at least one UF filtrate cleaning of spray cleaning with the recovered liquid and / or immersion cleaning with the recovered liquid is performed, and further setting is performed. At least one selected from air blowing and preheating can also be applied. As setting and air blowing, the temperature is from room temperature to less than 40 ° C. for 10 seconds to 120 minutes, preferably 1 minute to 30 minutes, and as preheating, the temperature is from 40 ° C. to 100 ° C. for 10 seconds to 120 minutes, preferably 1 It can be performed in a range of from 30 minutes to 30 minutes.
By immersing in the ionic coating composition (A) and then washing with the UF filtrate, the solvent contained in the UF filtrate contributes to the leveling of the coating film, thereby further contributing to the improvement of finish and corrosion resistance.

  Step 3: The coating film obtained in Step 2 is heated to cure the coating film. The heating temperature is about 120 to 200 ° C, preferably about 150 to 180 ° C, and the heating time is 1 to 120 minutes, preferably 20 to 60 minutes. Examples of the heating means include, but are not limited to, direct or indirect hot air drying methods such as electric furnaces and gas furnaces, heating methods using infrared rays or far infrared rays, and induction heating methods using high frequencies. Alternatively, a hot air drying method can be performed after a heating method using far infrared rays.

  Process 4: It is a process formed by further applying one or more layers of an aqueous or organic solvent type top coating (B) and baking and drying. Examples of the top coat (B) include water-based or organic solvent-type top coats, which are water-based paints composed of an aqueous dispersion such as an emulsion, a carboxyl group, or a hydroxyl group-containing acrylic resin for environmental protection. It is preferable.

  The top coating is applied by a method such as airless spraying, air spraying, and rotary atomization coating (which may be applied electrostatically) to a layer of colored coating so that the dry film thickness is about 10 to 50 μm. 1-coat 1-bake method (1C1B), which is applied and dried by heating at about 100 to 180 ° C., preferably about 120 to 160 ° C. for about 10 to 40 minutes; airless spray, air spray, It is applied so as to have a dry film thickness of about 10 to 50 μm by a method such as rotary atomization coating (which may be electrostatically applied), and about 100 to 180 ° C., preferably about 120 to 160 ° C. After curing by heating for 10 to 40 minutes, or after standing or preheating at room temperature for several minutes without curing, then the uncured or one or more clear paints on the cured surface are dried 2 coat 1 bake method (2C1B) or 2 coat 2 bake, which is applied by heating to about 60 to 160 ° C., preferably about 80 to 140 ° C. and dried for about 10 to 90 minutes. Examples thereof include a method (2C2B), a 3 coat 1 bake method (3C1B), a 3 coat 2 bake method (3C2B), and a 3 coat 3 bake method (3C3B).

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited thereby. “Parts” and “%” indicate “parts by weight” and “% by weight”.

Production Example 1 Production of amine-added epoxy resin 1000 parts of Epicoat 828EL (epoxy resin manufactured by Japan Epoxy Resin Co., Ltd.), 390 parts of bisphenol A, and 0.2 part of dimethylbenzylamino were added and reacted at 130 ° C. until the epoxy equivalent was 755. .
Next, 260 parts of ε-caprolactone and 0.03 part of tetrabutoxytitanium are added, the temperature is raised to 170 ° C., sampling is performed over time while keeping this temperature, and the amount of unreacted ε-caprolactone is tracked in the infrared absorption spectrum measurement. When the reaction rate reached 98% by mass or more, the temperature was lowered to 120 ° C. Next, 160 parts of diethanolamine and 65 parts of methyl isobutyl diketiminate of diethylenetriamine were added and reacted at 120 ° C. for 4 hours, and 470 parts of ethylene glycol monobutyl ether was added to obtain an amine-added epoxy resin having a resin solid content of 80% by mass.

Production Example 2
In the reaction vessel, 270 parts of “Cosmonate M-200” (trade name, Crude MDI, manufactured by Mitsui Chemicals) and 4 parts of methyl isobutyl ketone were added and heated to 70 ° C. In this, 15 parts of 2,2-dimethylolbutanoic acid was gradually added and reacted at 70 ° C. for 1 hour, then cooled to 60 ° C., 270 parts of propylene glycol was added, and this temperature was maintained over time. Sampling was performed, and it was confirmed by infrared absorption spectrum measurement that there was no absorption of unreacted isocyanato groups, and a curing agent having a solid content of 75% was obtained.

Production Example 3 Production Example of Emulsion for Cationic Paint Amine-added epoxy resin No. 1 obtained in Production Example 1 above. 1 is 87.5 parts (70 parts by resin solid content), 40 parts of the curing agent obtained in Production Example 2 (30 parts by resin solid content), SANNICS PP-1000 (manufactured by Sanyo Chemical Co., Ltd., trade name, surface Adjuster) 1 part, 1.5 parts of acetic acid (corresponding to a neutralization value of 14) as a neutralizing agent, 167 parts of deionized water was added dropwise over about 15 minutes with vigorous stirring, and the solid content was 34%. An emulsion for cationic paint was obtained.

Production Example 4 Production of pigment dispersion paste 60% quaternary ammonium salt type epoxy pigment dispersion resin 5.8 parts (solid content 3.5 parts), bismuth hydroxide 2.0 parts, aluminum tripolyphosphate 2 parts, Add hydride PXN (Note 1) 10.0 parts, carbon MA-7 (Note 2) 3 parts, dioctyltin oxide 1.0 part, deionized water 15.3 parts and disperse, pigment dispersion of 55% solids A paste was obtained.
(Note 1) Hydride PXN: Georgia Kaolin, trade name, kaolin (Note 2) Carbon MA-7: Mitsubishi Kasei, trade name, carbon black.

Production Example 5 Production of Cationic Paint A 34% of the emulsion for cationic paint obtained in Production Example 3 297 parts (101 parts solids) and 39.6 parts of 55% pigment dispersion paste (solids 21 0.5 part) and 275.9 parts of deionized water were added to obtain a cationic paint A having a solid content of 20%.

Production Example 6 Manufacture of water-based topcoat paint Hydroxyl-containing polyester resin (Note 3) 60 parts, Hydroxyl-containing acrylic resin (Note 4) 15 parts,
Mix and disperse 25 parts of Cymel 303 (Note 5), 5 parts of dimethylaminoethanol, 100 parts of JR701 (Note 6), 2 parts of TINUVIN 292 (Note 7) and 2 parts of TINUVIN 571 (Note 8) in deionized water. For 10 seconds (Ford Cup # 4/20 ° C.), the solid content was adjusted to 15% to obtain an aqueous top coat.

  (Note 3) Hydroxyl-containing polyester resin: 756 parts of neopentyl glycol, 109 parts of trimethylolpropane, 370 parts of hexahydrophthalic acid, 292 parts of adipic acid and 398 parts of isophthalic acid are placed in a reaction vessel and reacted at 220 ° C. for 6 hours. Then, 45 parts of trimellitic anhydride was added and reacted at 170 ° C. for 30 minutes to obtain a polyester resin having a number average molecular weight of about 8,000, an acid value of 20 mgKOH / g, and a hydroxyl value of 95 mgKOH / g.

  (Note 4) Hydroxyl group-containing acrylic resin: In a reaction vessel, 10 parts of styrene, 60 parts of methacrylic acrylate, 13.7 parts of n-butyl acrylate, 10 parts of hydroxyethyl acrylate, 6.3 parts of acrylic acid, and azobisisobutyronitrile Three parts were added and reacted at 120 ° C. for 6 hours to obtain a hydroxyl group-containing acrylic resin having a number average molecular weight of about 10,000, an acid value of 50 mgKOH / g and a hydroxyl value of 50 mgKOH / g.

(Note 5) Cymel 303: Nihon Cytec Industries, Inc., trade name, melamine resin (Note 6) JR701: Teika, trade name, titanium white (Note 7) TINUVIN292: Ciba Specialty Chemicals, trade name, Hindered amine light stabilizer (Note 8) TINUVIN571: Ciba Specialty Chemicals, trade name, liquid benzotriazole ultraviolet absorber.

The test plate was manufactured by subjecting a cold-rolled steel plate (70 × 150 × 0.8 mm) to chemical conversion treatment using Palbond # 3020 (trade name, zinc phosphate treatment, manufactured by Nihon Parkerizing Co., Ltd.). A coating film was formed according to the following steps using the paint obtained in the production example.

Example 1
Step 1: The test plate was immersed in the cationic paint A (28 ° C.) obtained in Production Example 5 for 3 minutes.
Step 2: Setting was performed at 25 ° C. for 10 minutes.
Process 3: The coating film obtained by the process 1 and the process 2 was heat-dried at 170 degreeC-20 minutes using the hot air dryer. The dry film thickness of the cationic paint A was 1 μm.
Step 4: The aqueous top coating obtained in Production Example 6 was applied with a dry film thickness of 30 μm, and dried by heating in a hot air drying oven at 140 ° C. for 20 minutes. 1 was obtained.

Example 2
Step 1: The test plate was immersed in the cationic paint A (28 ° C.) obtained in Production Example 5 for 2 minutes.
Step 2: Preheating was performed at 50 ° C. for 20 minutes.
Process 3: The coating film obtained by the process 1 and the process 2 was heat-dried at 170 degreeC-20 minutes using the hot air dryer. The dry film thickness of the cationic paint A was 0.5 μm.
Step 4: Amirac 1000 (Note 9) was applied with a dry film thickness of 30 μm and dried by heating in a hot air drying oven at 140 ° C. for 20 minutes. 2 was obtained.

  (Note 9) Amirac 1000: product name, alkyd resin / amino resin top coat, manufactured by Kansai Paint Co., Ltd.

Example 3
Step 1: The test plate was immersed in the cationic paint A (26 ° C.) obtained in Production Example 5 for 2 minutes.
Step 2: Setting was performed at 25 ° C. for 20 minutes. Spray-washed with UF filtrate. Setting was performed at 25 ° C. for 10 minutes.
Process 3: The coating film obtained by the process 1 and the process 2 was heat-dried at 170 degreeC-20 minutes using the hot air dryer. The dry film thickness of the cationic paint A was 0.5 μm.
Step 4: Amilac 1000 was coated with 30 μm and dried by heating in a hot air drying oven at 170 ° C. for 20 minutes. 3 was obtained.

Example 4
Step 1: The test plate was immersed in the cationic paint A (30 ° C.) obtained in Production Example 5 for 5 minutes.
Process 2: Preheating was performed at 80 ° C. for 10 minutes.
Process 3: The coating film obtained by the process 1 and the process 2 was heat-dried at 170 degreeC-20 minutes using the hot air dryer. The dry film thickness of the cationic paint A was 2 μm.
Step 4: The aqueous topcoat obtained in Production Example 6 was applied with a thickness of 30 μm and dried by heating in a hot air drying oven at 140 ° C. for 20 minutes. 4 was obtained.

Comparative Example 1
Step 1: Cationic paint A (28 ° C.) obtained in Production Example 5 was electrodeposited at 80 V for 30 seconds.
Process 2: Spray water washing and pure water water washing were performed with the UF filtrate. Thereafter, setting was performed at 25 ° C. for 10 minutes.
Process 3: The coating film obtained in Process 1 and Process 2 was heat-dried at 170 ° C. for 20 minutes using a hot air dryer. The dry film thickness of the cationic paint A was 2 μm.
Step 4: The aqueous topcoat obtained in Production Example 6 was applied with a thickness of 30 μm and dried by heating in a hot air drying oven at 140 ° C. for 20 minutes. 5 was obtained.

Comparative Example 2
Step 1: Cationic paint A (28 ° C.) obtained in Production Example 5 was electrodeposited at 60 V for 30 seconds.
Process 2: Spray water washing and pure water water washing were performed with the UF filtrate. Thereafter, setting was performed at 25 ° C. for 10 minutes.
Process 3: The coating film obtained in Process 1 and Process 2 was heat-dried at 170 ° C. for 20 minutes using a hot air dryer. The dry film thickness of the cationic paint A was 1 μm.
Step 4: Amilac 1000 was coated with 30 μm and dried by heating in a hot air drying oven at 170 ° C. for 20 minutes. 6 was obtained.

Comparative Example 3
The test plate was coated with 30 μm of Amirac 1000 and dried by heating in a hot air drying oven at 140 ° C. for 20 minutes. 7 was obtained.

  Table 1 shows the steps and test results of Examples 1 to 4, and Table 2 shows the steps and test results of Comparative Examples 1 to 3.

(Note 10) Finishability:
○ is good without any decrease in armpit, buttocks, dents and round feeling △ is a decrease in either armpit, buttocks, dents and round feeling × means armpit, buttocks, dents and round Any decrease in feeling is significant.

(Note 11) Anticorrosion: The coated plate obtained in Steps 1 to 4 is cross-cut with a knife so as to reach the substrate, and this is subjected to a salt water resistance test for 720 hours according to JIS Z-2371. Evaluation was made according to the following criteria based on rust from knife scratches and blister width.
○: The maximum width of rust and blisters is less than 3mm from the cut part (one side)
△ indicates that the maximum width of rust and blisters is 3mm or more and less than 4mm from the cut part (one side)
×: The maximum width of rust and blisters is 4 mm or more from the cut part (one side)
(Note 12) Water resistance: A coated plate coated up to the top coat is placed in a blister box at 50 ° C. and taken out after 240 hours. After drying for 2 hours at room temperature, 100 2 mm square gobangs were cut. Next, a vinyl tape was attached, and the number of pieces remaining after peeling was counted.
○ is 100/100 remaining △ is in the range of 90 to 99/100 × is less than 90/100

It is a model figure of an electrodeposition (immersion) tank.

According to the present invention, a coated article excellent in finish and corrosion resistance can be obtained at low cost.

Claims (5)

The coating-film formation method by the following processes 1-process 4.
Step 1: The object to be coated is immersed in the ionic coating composition (A).
Step 2: Apply at least one selected from setting, air blow, and preheating.
Step 3: Heat and dry in a drying furnace.
Step 4: One or more layers of an aqueous or organic solvent type top coat (B) are applied and baked and dried. The coating film forming method according to claim 1, wherein step 2 has the following contents.
Step 2: Apply at least one selected from setting, air blow, and preheating, and after washing with at least one UF filtrate, apply at least one selected from setting, air blow, and preheating. The method for forming a coating film according to claim 1 or 2, wherein the dry film thickness of the coating film obtained by immersing the article to be coated in the ionic coating composition (A) is less than 5 µm. The coating film according to any one of claims 1 to 3, wherein the ionic coating composition (A) is a cationic coating composition containing an amino group-containing epoxy resin as a base resin and a blocked isocyanate compound as a curing agent. Forming method. The coated article obtained by the coating-film formation method of any one of Claims 1-4.

Images