JPH0550356B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method of painting an automobile body, and particularly to a method of integrally painting an automobile body and resin parts. (Prior Art) Conventionally, in a method of painting an automobile equipped with resin parts, as shown in FIG. 3, a car body steel plate 1 is degreased and chemically treated to form a chemical conversion layer 2, and then Undercoat film 3 by electrodeposition coating.
Next, a chipping primer or stone guard coating layer 7 is formed, an intermediate coating film 5 is applied thereon, and a top coating film 6 is further applied thereon, followed by baking and curing treatment. On the other hand, for resin parts such as bumpers and lower aprons, as shown in FIG. 4, a molded body 11 of the desired shape is formed from a resin material, and the surface to be painted of this molded body 11 is purified by degreasing and cleaning or physical treatment. , a primer is applied to form a coating film 12, and an intermediate coating film 13 is applied thereon.
Further, a top coat 14 is applied thereon, baked and hardened, and then assembled into the painted vehicle body as shown in FIG. Note that the intermediate coating film 13 may be omitted when painting resin parts. Another method is to apply an undercoat to the resin parts and then paint them all together on an automobile painting line. (Problems to be Solved by the Invention) However, according to such conventional painting methods, the coating film composition on the car body panel and the coating film composition on the resin parts are different, so ( 1) In a painting method where car body panels and resin parts are processed on separate painting lines until the assembly process, at least the undercoating is done in a separate workshop using painting equipment for resin parts that is separate from the car body painting equipment. (2) Painting of the car body and resin parts is also done by applying a primer coat to the resin parts and then painting them simultaneously with the car body panels on the car painting line. It is difficult to make the later colors the same, making color matching difficult; (3) the paint film composition of the car body panel and resin parts are different, so the durability quality of each is different; and (4) the paint film composition is different from the resin parts. If it is adapted for use on a car body, the performance of the weather-resistant coating on car body panels will be sacrificed, and if it is adapted for use on the car body, the adhesion of the coating on resin parts will be sacrificed. There was a problem. (Means for Solving the Problems) This invention provides an ethylene-vinyl acetate copolymer having a glass transition temperature (Tg) of -20°C or lower and an elongation rate of 900% or more at 20°C and 100% or more at -20°C. The above-mentioned problems are solved by applying a paint containing a polymeric resin as a main component as a universal primer to the electrodeposited film, which is the undercoat film, for car body panels, and as a resin primer for resin parts. The paint used in this invention, whose main component is an ethylene-vinyl acetate copolymer resin, which has a glass transition temperature (Tg) of -20°C or lower and a breaking elongation of 900% at 20°C and 100% or more at -20°C, is In the painting of car body panels, it is used as a primer for the intermediate coat (or top coat if no intermediate coat is applied) on the electrocoated film, while in the painting of resin parts it is used as a primer for the resin. , which is referred to as a universal primer in this invention. If the glass transition temperature of the resin component of this universal primer is higher than -20℃, and if the elongation at break is lower than 900% at room temperature and lower than 100% at -20℃, the physical performance of the formed coating film This is not desirable because it does not satisfy the following. The paint used as the universal primer may contain a pigment. As pigments that can be used, inorganic and organic coloring pigments, inorganic extender pigments, and conductive pigments can all be used. It is preferable to impart electrical conductivity to the formed coating film, and in this case, it is preferable to add electrically conductive carbon black. The surface resistivity value of a coating film is usually 10 ¹⁰ Ω-cm or less. The organic solvent that can be used may be any organic solvent as long as it can be uniformly dissolved in the resin, and examples thereof include ester, alcohol, ketone, aromatic, and aliphatic solvents used in ordinary paints. In addition, paint additives such as surface conditioners, anti-settling agents, photo/thermal deterioration inhibitors, etc. may be added as necessary. The method for producing a paint as a universal primer is to mix the necessary components among the above components, and if it does not contain pigments, it can be produced as a uniform solution using a known stirring device, but if it does not contain pigments, it can be produced as a uniform solution. In this case, the pigment can be produced by dispersing it with a known pigment dispersing machine and adjusting the viscosity to an appropriate value. Any known coating method can be used as the coating method. In this invention, when painting a car body panel, a steel plate 1 is degreased and subjected to chemical conversion treatment to form a chemical conversion treatment layer 2, as shown in FIG. A universal primer coating film 4 is formed, an intermediate coating film 5 is applied thereon, and a topcoat coating film 6 is coated thereon according to a known method, followed by baking and curing treatment. The universal primer can also be used as an intermediate coat, and in this case, a top coat can be applied immediately without further intermediate coat. On the other hand, for resin parts, the surface to be painted of the resin part molded body 11 is purified in the same manner as explained with reference to FIG. The coating film 5 is further coated with a top coating film 6, which is then subjected to baking and curing treatment. According to the method of this invention, after coating and forming an undercoat film on a car body panel, resin parts are assembled, and at the same time, a universal primer is applied using the same booth and drying oven, and then an intermediate coat film and a top coat film are applied. Can be formed by coating. (Function) In this invention, the universal primer coating film acts as an energy absorption layer or stress relaxation film for the coating quality on the car body panel, so (a) the chipping resistance is improved, and (b) the intermediate coating Since the coating film can be made harder, the finish (image clarity) is improved; (c) it is possible to increase the amount of pigment added to the electrodeposited coating, resulting in better edge coverage; and (d) the durability is improved. Improves skibability and yarn rust resistance. In addition, regarding the quality of the coating film on resin parts, (a) the adhesion mechanism uses heat fusion, so it can adhere to all resins, (b) chipping resistance is improved, and (c) intermediate coating The film or topcoat can be made harder, improving the finish (sharpness), (d) improving low-temperature impact resistance, and (e) filling pinholes on the surface of the resin material and giving a smooth finish. . In addition to the above, since vehicle body panels and resin parts can be painted at the same time, (a) color matching is possible, (b) durability is improved, and (c) painting costs are significantly reduced. (Effects of the Invention) As explained above, the method for painting an automobile body of the present invention involves applying an undercoat to the automobile body, then attaching resin parts, and achieving a glass transition temperature of 900% at a glass transition temperature of -20°C or lower and at room temperature. A universal primer is a paint whose main component is an ethylene-vinyl acetate copolymer resin that has an elongation at break of 100% or more at -20℃, and is applied to car bodies with an undercoat film and resins without an undercoat film. Coat the universal primer on the material surface of the parts at the same time,
Next, a top coat is applied on the paint film, or an intermediate coat is applied, and then a top coat is applied, thereby improving the chipping resistance, finish quality, and skib resistance of the paint film on the vehicle body panel. , the chipping resistance, low-temperature impact resistance, finish quality, and pinhole covering properties of the coating film on resin parts have been improved, and by performing simultaneous painting,
The effects of color matching, uniformity of durability quality, and significant reduction in painting costs can be obtained. (Examples) Next, the present invention will be explained by examples and comparative examples. Example 1 and Comparative Examples 1 to 6 (Manufacture of Universal Primer) 100 g of each of the blended compositions of Examples 1 to 6 and Comparative Examples 1 to 6 shown in Table 1 were thoroughly kneaded with a dissolver, and then mixed with a paint primer. Kneaded in Acre for 1 hour. A mixed solvent of equal weights of Solbetsuso #100 (manufactured by Exxon, trade name), methyl isobutyl ketone, and butyl acetate was added to the resulting composition, and the spray viscosity was adjusted to 14 seconds (20°C) using a #4 food cup. , produced a universal primer. Details of each component in Table 1 are as follows. Urethane resin varnish: Nipporan 2301, manufactured by Nippon Polyurethane Industries Co., Ltd. (product name, elongation at break)
A urethane resin solution with a solid content of 15% by adding a 1:1 mixed solvent of xylene and methyl isobutyl ketone (20℃ 600%, glass transition temperature -20℃). Ethylene-vinyl acetate copolymer resin varnish: Everex 150, manufactured by Mitsui Polychemical Co., Ltd.
(Product name, elongation at break 20℃ 900%, glass transition temperature -30℃) was added with a 2:1 mixed solvent of xylene and Solbetsuso #100 (manufactured by Exsan, product name) to reduce the solid content.
20% ethylene-vinyl acetate copolymer resin solution. Titanium dioxide: JR-602 (manufactured by Teikoku Kako Co., Ltd.,
Product name). Barium sulfate: Precipitated burr SS-50 (manufactured by Sakai Kagaku Co., Ltd., trade name). Carbon black: Raven 420 (manufactured by Columbia Carbon, trade name). Talc: TALC SH2 (manufactured by Toho Chemical Industry Co., Ltd.,
Product name). Conductive carbon: Vulcan XC-72 (manufactured by Cabot Co., Ltd., trade name). (Painting on steel plate) A cold rolled steel plate of 0.8 mm x 70 mm x 150 mm was coated with Bonderite #3004 (manufactured by Nippon Parkerizing Co., Ltd.).
The surface was treated with zinc phosphate using cationic electrodeposition paint Aqua No. 4100 (manufactured by Nippon Oil & Fats Co., Ltd., trade name), and then baked and dried at 175°C for 20 minutes. The dry film thickness of the obtained electrodeposition coating film was 15 μm. Next, each of the primers was applied using an air atomization method, and then Epico No. 1500 Sealer TX, an amino/oil-free polyester resin intermediate coating, was applied using a wet-on-wet method.
-100 (manufactured by Nippon Oil & Fats Co., Ltd., trade name) was applied using an air atomization coating method, and baked and dried at 140°C for 30 minutes. The dry film thickness of the obtained primer is 5~
The dry film thickness of the intermediate coating was 30 to 35 μm. Next, Melami No. 1 Red (manufactured by NOF Corporation, trade name), which is an amino/alkyd resin solid color, was applied as a top coat using an air atomization method, and was baked at 140° C. for 30 minutes to dry. The dry film thickness of the resulting top coat was 40 μm. (Painting on resin board) Resin material (A) Polyamide (PA) Resin material Based on 6-nylon or 6,6-nylon, inorganic materials such as glass fiber and talc are used alone or in combination with 5 to 40 % filling to improve rigidity, and 5 to 20% elastomer blended to improve impact resistance. 1014RX-109 (manufactured by Ube Industries, Ltd., product name). (B) Polybutyl terephthalate (PBT) resin material Modified PBT blended with 5 to 20% elastomer such as polybutadiene and ethylene propylene rubber (EPR) as a means of improving impact resistance.
resin. 5201X11 (manufactured by Toray Industries, Inc., product name). (C) Unsaturated polyester (SMC) resin material Polyester resin filled with glass fiber, calcium carbonate, talc, etc. to strengthen it, and molded using a heated mold.
N12 (trade name, manufactured by Takeda Pharmaceutical Co., Ltd.) (D) Polyurethane (PU) resin material It is called this because it is a reaction product of isocyanate and polyol and has urethane bonds. C1056/FA720 (Japan Polyurethane) (manufactured by Co., Ltd., product name). Painting method: Wash each of the above resin plates of 70 x 150 mm with 1,1,1-trichlorothane vapor (74°C) for 60 seconds.
After degreasing and drying, the primers are respectively applied by air atomization coating method, and then,
Amino/
The Epico No. 1500 Sealer TX-100, which is an oil-free polyester resin intermediate coating, was applied by air atomization and baked at 140° C. for 30 minutes to dry. The dry film thickness of the obtained primer is 5 to 8 μm, and the dry film thickness of the intermediate coat is 30 μm.
It was ~35 μm. Next, the above-mentioned Melami No. 1 red, which is an amino/alkyd resin-based sonic color, was applied as an image coating using an air atomization method.
It was baked and dried at 140°C for 30 minutes. The dry film thickness of the resulting top coat was 40 μm. Note that (a) The plate thickness used in the high rate impact tester (low temperature impact test) was 3.0 mm. (b)PP
and PU were set in a special jig during baking to prevent thermal deformation. Comparative Example 7 In this example, a urethane resin primer: Flexene #60 (manufactured by Nippon B Chemical Co., Ltd., trade name, elongation rate 100, glass transition temperature 34°C) was used as the primer. For painting steel plates, use the above primer as a universal primer.
The same procedure was carried out except that the primer was used instead of the primer. Next, the resin plate was painted as follows. Each of the 70 x 150 mm PA, PBT, SMC, and PU resin plates was washed with 1,1,1-trichloroethane vapor (74°C) for 60 seconds, degreased, dried, and then coated with the primer. Painting was performed using an air atomization method, and then a polyester urethane resin topcoat paint, Flexene 101 Red (manufactured by Nippon B Chemical Co., Ltd., trade name), was applied using an air atomization method, followed by a wet-on-wet coating at 120°C. Bake and dry for 20 minutes. The dry film thickness of the obtained primer was 5 to 8 μm, and the dry film thickness of the top coat was 30 to 40 μm. Comparative Example 8 A steel plate was painted in the same manner as in Example 1, except that the universal primer was not applied. The dry film thickness of the obtained intermediate coating is 30 to 35 μm,
The dry film thickness of the top coat was 40 μm. The steel plates and resin plates painted as described above were evaluated for appearance, chemical performance, etc. according to the following evaluation method.
The physical performance and electrostatic performance were evaluated and shown in Tables 2 to 7. However, Table 2 shows steel plate, Table 3 shows PA, and Table 4 shows steel plate.
The table shows the results of PBT, Table 5 shows the results of SMC, and Table 6 shows the results of PU. Evaluation method Appearance A. Paint film appearance Perform an appearance inspection indoors under conditions of daylight color fluorescent lighting of 500 lux or more and from a position approximately 50 cm away from the surface to be inspected with normal visual acuity. However, painting defects such as blisters and pinholes may be removed from close range or diagonally. ○: No change at all B Glossiness Measured in accordance with 6.7 of JIS K 5400-1979. The higher the number, the better. C. Sharpness Angle sharpness Measured using a gloss meter (manufactured by Suga Test Instruments Co., Ltd.). The higher the number, the better. D. Adhesion Using a multi-cross cutter, draw parallel lines of 1 mm at equal intervals that touch the substrate at right angles to each other on the coated surface of the test piece, and cut 100 squares of 1 mm square.
Make one. In this state, adhere a cellophane adhesive tape with ample width and peel it upwards at once.The number of squares where the painted surface does not peel off is determined and evaluated as a percentage of the total number (100 pieces). E. Paint film hardness Measured in accordance with 6.14 of JIS K 5400-1979. Chemical performance (a) Humidity resistance Use a sealed box where both temperature and humidity can be adjusted, and place the test piece horizontally in the sealed box adjusted to a temperature of 50 ± 1°C and a relative temperature of 98% or higher. Check the state of change and continue for up to 240 hours. ○: No blistering or change at all △: Slight blistering or dullness ×: Minute blisters all over or large blisters B Cap resistance Chipping resistance test on a 70 mm x 150 mm test piece Salt water spray (2 hours)
→ Dry (60℃, 2 hours) → Wet (50℃,
After 24 hours, apply a cellophane adhesive tape approximately 18 mm wide to the painted surface where the skip rust has occurred, and peel it upward at once to remove the paint film. Check the diameter and display the maximum skib diameter in mm. The higher the number, the better. C Heat resistance The test piece was placed in a constant temperature bath at 90℃ for 500 hours.
After leaving it at room temperature for 24 hours, examine the appearance of the paint film and any changes to the paint surface caused by heat, such as discoloration or shrinkage. ○: No change at all D. Gasoline resistance Approximately 0.3 to 0.5 ml of gasoline was dropped onto the surface of the test piece, and after leaving it in the test chamber for 4 hours, it was wiped off with a cloth. Check for peeling and cracking. ○: No change at all △: Softening Physical performance (a) Low-temperature impact resistance (high-rate impact test) Using a high-speed impact tester manufactured by Rheometrics Inc. in the United States, the impact energy value when the center of impact punches through the test plate is measured. The test conditions are striking core tip diameter 1.6cm (5/8
Inch) holder 5.1cm (2 inches), impact speed 11.1m/sec, yield energy value at -40℃ is 10 joules or more to pass. (b) Low-temperature impact resistance (DuPont test) In an atmosphere of −40°C, the radius of a DuPont impact tester (manufactured by Uejima Seisakusho Co., Ltd.)
Sandwich the test piece between the 6.4 mm firing die and the pedestal with the painted side facing upward. Next, a weight weighing 500g is dropped onto the shooting mold from a specified height, and at the same time the paint surface is checked for damage, and at the same time, the height of the weight at which no abnormality is detected in the paint film is checked. The evaluation standard is 50 cm (excellent) to 0 cm (poor). C. Chipping resistance The phenomenon of pebbles, sand, etc. hitting the paint film is artificially reproduced, and the abrasion resistance is measured using a gravelometer (manufactured by Suga Test Instruments Co., Ltd.). Measurement conditions are as follows: 250 g of No. 6 crushed stone specified in JIS A 5001-77 is measured at an air pressure of 4 kg/cm ² ; a blowing angle of 90 degrees; and a test piece temperature of 20°C. ○: The number of scratches is small and the peeling area is small. △ The number of scratches is large and the peeling area is small. × The number of scratches is large and the peeling area is large. Electrostatic performance a. Appearance Visually compare the external finish. ○ (Excellent) ~ △ ~ × (Poor) B Efficiency Wrap saran wrap around the surface of the test piece, calculate the weight of the attached coating film from the difference in weight before and after electrostatic coating (measured after baking) (W ₁ : solid content), and discharge. Measure the paint weight ( _W2 : solid) or efficiency. Efficiency = W ₁ / W ₂ × 100 (%)

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[Table] As is clear from Table 2, after coating the universal primer of the present invention on a steel plate on which an undercoat film had been formed, an intermediate coat film and a top coat film were formed (in the coating film composition of Example 1, Scab resistance, low-temperature impact resistance, and chipping resistance are improved.In contrast, resins with a glass transition temperature of -15℃, elongation at break of 350% at 20℃, and elongation at -20℃ of 10% or less (comparison) Examples 1, 3, 4), elongation at break at 20℃ is 300
%, and the elongation at break at -20°C of 10% or less (Comparative Examples 2, 5, 6) and urethane resin paint (Comparative Example 7) are used as universal primers to improve skib resistance, low-temperature impact resistance, and chipping resistance. inferior in sex. In addition, the coating film configuration (Comparative Example 8) in which the universal primer of the present invention is not applied has poor skib resistance, low-temperature impact resistance, and chipping resistance. On the other hand, as is clear from Tables 3 to 6, when various resin parts are coated with the same paint as the steel plate on which the undercoat is applied, the universal primer of the present invention is applied after the intermediate coat and topcoat are applied. A film was formed (Example 1) In the coating film structure, low temperature impact resistance,
Improves chipping resistance. On the other hand, resins with glass transition temperature of -15℃, elongation at break of 350% at 20℃, and elongation at break of -20℃ of 10% or less (Comparative Examples 1, 3, and 4), elongation at break at 20℃ When using resins (Comparative Examples 2, 5, 6) and urethane resin paints (Comparative Example 7) with 300% and -20℃ elongation at break of 10% or less as universal primers, low-temperature impact resistance and chipping resistance are improved. Inferior.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view of a steel plate having a coating film applied by the method of the present invention, FIG. 2 is a partial cross-sectional view of a resin molded body having a coating film applied by the method of the present invention, and FIG. FIG. 4 is a partial sectional view of a steel plate having a coating film applied according to a conventional method. FIG. 4 is a partial sectional view of a resin molded body having a coating film applied according to a conventional method. 1... Steel plate, 2... Chemical conversion treatment layer, 3... Undercoat film (or electrodeposition coating film), 4... Universal primer coating film, 5, 13... Intermediate coating film, 6, 14
...Top coat film, 7...Chipping primer,
Stone guard coat layer, 11...Resin molded body, 1
2... Primer coating film.

Claims (1)

[Claims] 1 After applying a primer coat to the car body, attach the resin parts and maintain the glass transition temperature (Tg) of -20℃ or less.
A paint whose main component is an ethylene-vinyl acetate copolymer resin with a breaking elongation of 900% or more at 20℃ and 100% or more at -20℃ is used as a universal primer to coat the car body with an undercoat film and the undercoat. An automobile characterized in that the universal primer is simultaneously applied to the surface material surface of a resin part that is not coated with a film, and then a top coat is applied on the coating film, or an intermediate coat is applied, and then a top coat is applied. How to paint a car body.