JPS62110779A - Method for overcoating automobile body - Google Patents

Abstract

PURPOSE:To prevent the generation of a defective overcoated film by forming an UV curing clear coated film on the surface of the overcoated film on a wet-on-wet basis, passing the material through a drying furnace and an UV ray irradiation region, and simultaneously baking and curing both coated films. CONSTITUTION:An overcoated film 5 or an undercoated film 3 and an intermediate coated film 4 are successively formed on the surface of an automobile body 1, an overcoat paint is coated thereon, and an UV curing clear paint 6 is coated on the surface on a wet-on-wet basis without baking and curing the overcoated film. Then the body 1 is passed through the drying furnace 24 and the UV ray irradiation region 25 in the drying furnace to simultaneously bake and cure the overcoated film 5 and the clear coated film 6. Consequently, the generation of a defective overcoated film is prevented, and the generation of flaws on the clear coated film is prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a top coating V for four automobiles and a charging method. After applying UV-curable clear paint in a wet-on-wet state to the surface of the top coat, the four automobiles were passed through a drying oven and an ultraviolet irradiation area to simultaneously bake and cure both coatings. This relates to a method of painting an automatic JLJ width body.

[Conventional technology]

Conventionally, the painting methods used on four automobiles are as follows:
After performing pre-treatment such as degreasing and chemical conversion treatment,
An undercoat is applied using electrodeposition paint, and an intermediate coat is applied to the surface.

Furthermore, the surface is coated with a one-coat paint as shown in FIGS. 3 and 4, a partially enlarged sectional view of FIG.

That is, in FIG. 3, reference numeral 30 indicates four automobile bodies made of steel plates, and after the surfaces of these four automobile bodies 30 have been subjected to pretreatment such as degreasing, water washing, and chemical conversion treatment, the surfaces have been coated with electrodeposition paint. An undercoat film 31 is formed, and after washing with water, the undercoat film 31 is baked and cured. Next, undercoat film 3
An intermediate coating film 32 is formed on the surface of the intermediate coating 1ii32 by intermediate coating paint, and the intermediate coating 1ii32 is baked and hardened. Subsequently, a top coat 33 is formed on the surface of the intermediate coat 32 using a top coat, and the top coat 33 is baked and cured.

Further, in FIG. 4, after the surface of the automobile body 40 has been subjected to pre-treatments such as degreasing, washing with water, and chemical conversion treatment, an undercoat #') coating film 41 is applied in the same manner as the painting process explained in FIG. and intermediate coat 111ti42 are sequentially formed. after that,
The surface of the intermediate coat HfJ42 is coated with a top coat and a clear paint to form a top coat 43 and a clear coat 44 in sequence, and both coats 43 and 44 are baked and cured at the same time.

[Problem that the invention seeks to solve]

However, in the former partial coating method (the coating method shown in Figure 3), since the -1-coating film 33 is a one-coat system, it cannot be attacked by external factors such as ultraviolet rays, dustfall, and photochemical smog. There are problems such as paint film defects such as chalking, bronzing, color bleeding, and discoloration.

Also, the latter -1 = painting method (painting method in Figure 4)
Since this is a two-coat system in which a transparent rear coating film 44 is formed on the surface of the -F coating film 43, the occurrence of top coating film defects in the top coating film 43 does not directly occur, but the hardness of the clear coating film 44 It is easy to get scratches because of the low coating color, and the scratches with clear coating 1IIji 44 are easy to get on the solid coating film where the coating color of topcoat 43 is 1 color.
There is a problem that looks like a scratch on Q43.

Therefore, this invention was made to solve the above-mentioned problems, and involves forming a wet-on-wet ultraviolet-curable clear coating film on the surface of the top coating film, and applying this to a drying oven and an ultraviolet irradiation area. By simultaneously baking and curing both coating films, it is possible to prevent the occurrence of coating defects in the top coating film and also to prevent the occurrence of scratches on the clear coating film.

[Means for solving problems]

That is, in the method for top-coating an automobile body according to the present invention, -1-coating paint is applied to the surface of the automobile body on which a coating film or an undercoating film and an intermediate coating film have been sequentially formed. , top coat it! Without baking or curing the surface of the vehicle, UV-curing clear paint is applied to the surface of the vehicle in a wet state, and then the car body is exposed to ultraviolet rays in a drying oven. It is made to pass through the irradiation area to bake and harden the top coat and clear coat at the same time.

In the present invention, the undercoat or intermediate coating film formed on the automobile body can be formed using commonly used undercoating paints or intermediate coating paints. For example, the undercoat can be formed by anionic and cationic electrodeposition paints, organic solvent-based paints, water-based paints, powder paints, etc., and the intermediate paint can be formed by any of the above-mentioned electrocoating paints. It can be formed using a paint other than the adhesive paint. Furthermore, these coating methods are carried out using coating equipment and coating conditions suitable for each paint. Furthermore, the undercoat film and intermediate coat film formed on the automobile body can be replaced with only the undercoat film, if necessary. Furthermore, as the top coat formed on the surface of the undercoat or intermediate coat, a commonly used top coat can be used. For example, top coat paints such as organic solvent paints and water-based paints can be mentioned, and these top coat paints may be either solid type or metallic type. Furthermore, each top coat can be applied using a coating device and coating conditions suitable for each paint.

In addition, as the UV-curable clear paint that is applied to the surface of the top coat, the UV-curable clear paint that is commonly used for painting plastics, wood, etc. can be used as is, and its coating method The coating can also be carried out by an appropriate coating method such as electrostatic coating, airless coating, air spray coating, etc., which are commonly used.

The thickness of the top coat I formed on the surface of the undercoat or intermediate coat is suitably in the range of 35 to 40 μm after baking and curing. Furthermore, the thickness of the ultraviolet curable clear coating film formed on the surface of the top coating film after baking and curing is suitably in the range of 5 to 10 μm.

Further, in the drying oven C=, a drying oven that is generally used for baking and curing paint films on automobile bodies can be used as is, and there is no need to specify any special baking conditions. Further, in the ultraviolet irradiation area, any furnace equipped with equipment for irradiating ultraviolet rays may be used, such as a tunnel-shaped furnace body with ultraviolet irradiation lamps attached to the ceiling and side walls inside the furnace body. .

〔Example〕

Hereinafter, one embodiment of the present invention will be explained in detail based on the drawings.

FIG. 1 is a cross-sectional view illustrating the method for top-coating an automobile body according to the present invention, and FIG. 2 is a schematic process diagram illustrating the method for top-coating an automobile body according to the present invention.
□ In Figures 1 and 2, l represents a car body, and this car body l is sequentially treated with a pretreatment process consisting of alkaline degreasing, water washing, zinc phosphate treatment, and water washing. Drain and dry in a drying oven for 10 minutes at ℃.
A zinc phosphate film H9!2 with an average thickness of 3 g/rrl was formed on the surface of an automobile body 1.

Next, this automobile body 1 was passed through an electrodeposition coating process 20 consisting of the electrodeposition paint Ma and coating conditions shown below to form an undercoat film 3 consisting of an electrodeposition coating film.

(1) Electrodeposition paint: Cationic electrodeposition paint Ma (a) Resin used: Polyamide-modified epoxy resin (b) Residue on heating: 20% by weight (c) Color of paint: Black (2) Coating conditions (a) Paint temperature: 29℃ (b) Anode: Stainless steel (c) Cathode: Automobile body (d) Distance between electrodes: 300 1 (e) Voltage between electrodes: 250V (f) Total immersion time = 5 minutes (3 ) Coating film thickness: 20 μm After removing drips from each car body for 5 minutes and washing with water, it was baked and cured for 30 minutes in a drying oven with an internal temperature of 170 tons.

Subsequently, the entire automobile body 1 was air-sprayed in an intermediate coating process 21 consisting of the intermediate coating Mb and coating conditions shown below to form an intermediate coating film 4.
・ (1) Intermediate paint Mb' □(
a) Composition (parts are parts by weight) ゛(i) Epoxy resin: 30 parts゛゛゛゛゛゛〉rti titanium pigment 30 parts □(c) Petroleum solvent = 20 parts □(d) Aromatic solvent
: 20 parts '(e) Carbon: Trace amount (b) Viscosity: 22 to '23 seconds (Food cuff 23°C) (e) Paint color: Gray (2) Coating conditions (a) Painting machine: Devilbiss JGS-572 spray gun (b) Paint discharge amount + 300 mJ/lll1n
(°C) Paint pressure: 1.5kg/c+J(d)
Air pressure: 5. Okg/cIa (e) Pattern width: 30cm/φ(3') Paint film thickness: 30μm Intermediate coating-II 4'A<The formed automobile body 1,
Thirty parts were baked and cured in a drying oven with an internal temperature of 140°C.

The entire obtained automobile body l was subjected to a top coating process consisting of the top coating MC and coating conditions shown below.
□Apply one coat of Aspre, and examine the top coat 5i.'
-□ ``< 1) ``Hanging coating'' 6 coatings Mc (a) Composition (parts are parts by weight) ゛(□)
Polyester resin: 30 parts (°) 4 parts Red pigment: 30 parts (c) Inorganic pigment 2 parts' 2) Petroleum solvent 25 parts (most i'□ Aromatic solvent 25 parts (b) Viscosity:
22 to 23 seconds (Ford cassode'/23°C) (c, ) Paint color: Red (2) Painting conditions Same as the painting conditions of intermediate coating Mb 3) Paint film thickness: 30 μm Car with top coat 5 formed 4 bodies 1 at room temperature 30℃
After setting for 10 minutes in the setting room, without baking or curing the topcoat M*5, air spray painting is performed in the clear coating process 23, which consists of the UV-curable clear paint Md and the coating conditions shown below. A UV-curable clear coating film 6 was formed.

(1) Ultraviolet curable clear paint Md (a) Composition (parts are weight parts) (a) Acrylic resin: 35 parts (b) Reactive diluent: trace amount (iii) Photopolymerization initiator: trace amount (d) Additives: Trace amount (e) Hydrocarbon solvent = 10 parts (f) Ester solvent = 35 parts (g) Alcohol solvent: 20 parts (b) Viscosity = 12 to 13 seconds (Ford Casodene 23°C) (c ) Paint color: Colorless and transparent (2) Painting conditions Same as painting conditions for intermediate coating Mb.

(3) Paint film IW: After setting the four automobiles 1 on which the ultraviolet curable clear coating 6 of 5 to 10 μm has been formed in a setting room at a room temperature of 30° C. for 10 minutes, the four automobiles 1 were placed in an oven. The top coat film 5 was baked and semi-cured for 20 to 25 minutes in a drying oven 24 whose internal temperature was set to 140°C. Thereafter, in an ultraviolet irradiation area 25 provided on the downstream side of the drying oven 24, ultraviolet rays were continuously irradiated for 5 minutes to simultaneously cure the top coat 5 and the ultraviolet curable clear coating 6.

As a result, the undercoat film 3,
Intermediate coating film 4, top coating film 5, and clear coating film 6 were formed in sequence, and a coating film could be formed without causing poor adhesion or poor coating.

By the way, clear coating film 6 obtained in Example and conventional 2
Coat system 1 - clear coating film 4 formed from coating
4 (see FIG. 4), the clear coating film 6 of the example was 4H, and the conventional clear coating film 44 was F. As a result, the clear coating film 6 of the example is less likely to be scratched, and the occurrence of grasshoppers can be suppressed.

〔Effect of the invention〕

As explained above-1-, in the top coating method for four automobiles according to the present invention, an ultraviolet curable clear coating film is formed wet-on-wet on the surface of the top coating film, and then this is dried in a drying oven. Since both coatings are baked and cured at the same time by passing through the ultraviolet irradiation range, it is possible to increase the hardness of the coating compared to conventional clear coatings, which prevents scratches on the clear coating. This has the effect of preventing the occurrence of scratches and suppressing the appearance of scratches on the top coat.

In addition, in the top coating method for four automobiles according to the present invention, by increasing the hardness of the clear coating H-,
It is less susceptible to external factors such as air pollutants, and has the effect of preventing paint defects such as chalking and bronzing.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view illustrating the top coating method for four automobile bodies according to the present invention. FIG. 2 is a schematic process diagram illustrating the top coating method for four automobile bodies according to the present invention. FIG. 3 is a cross-sectional view illustrating a conventional one-coat top coating method. FIG. 4 is a sectional view illustrating a conventional two-coat top coating method. 1---Car body 2--Zinc phosphate film 3--Undercoat 4--1 Intermediate coat 5--1 Top coat 6-- ---Clear coating film 24--1--Drying oven 25-1 Ultraviolet irradiation area

Claims (1)

[Claims] A top coat is applied to the surface of the automobile body on which the top coat, undercoat, and intermediate coat have been sequentially formed,
An ultraviolet-curable clear paint is applied to the surface in a wet-on-wet state without baking or curing the top coat, and then the car body is exposed to ultraviolet rays in a drying oven. A method for topcoating an automobile body, characterized in that the topcoat film and the clear paint film are simultaneously baked and cured by passing the topcoat through a clear coating.