JPH0249154B2 - JIDOSHASHATAINOTOSOHOHO - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a coating method for integrally coating an automobile body and resin parts. (Prior Art) Conventionally, as shown in Fig. 2, the painting method for automobiles equipped with resin parts includes degreasing, degreasing,
After chemical conversion treatment, an undercoat is applied, which is baked and hardened at a temperature of 120 to 180℃, then an intermediate coat is applied, and the
Baked and hardened at 150℃, then topcoated on top of this,
Baking and hardening at 120-170℃. On the other hand, regarding resin parts such as bumpers and lower aprons, the third
As shown in the figure, a molded body of a desired shape is molded from a resin material such as urethane resin, nylon resin, etc., this molded body is purified by degreasing and cleaning or physical treatment, and is undercoated with a polyurethane resin paint. A method has been used in which the material is baked and cured, then top coated with a polyurethane resin paint, baked and cured, and then assembled into the vehicle body which has been subjected to the treatment shown in FIG. As such a painting method, a method of combining metal parts and organic material parts into one and then painting each part separately to avoid color difference is disclosed in JP-A-58-17866 and JP-A-58-119379. Disclosed in the official gazette. Another method is to apply an undercoat to the resin parts and then paint them all together on an automobile painting line. In this method, polyurethane resin paint is used as a primer for resin parts, and fatty acid-modified polyester resin, oil-free polyester resin, which is used for polyamide resin, polybutylene terephthalate resin, polycarbonate resin, etc.
Intermediate paints for car bodies (for example, JP-A-57-98575) whose main composition is epoxy-modified polyester resin, melamine resin, or aminoalkyd resin are used.
Separate baking is performed, and a coating film is formed by further applying (intermediate and/or top coat) paint containing amino alkyd resin or amino acrylic resin as a main component. In this case, the following top coating compositions are used: (a) aminoalkyd resin-based one-coat, one-bake type solid color, (b) aminoacrylic resin-based two-coat, one-bake type solid color, (c) amino (d) Aminoacrylic resin-based 2-coat, 1-bake merik color. (Problems to be Solved by the Invention) In such conventional painting methods, (a) the method described in the above-mentioned Japanese Patent Application Laid-open Nos. 58-17866 and 58-119379 does not coat the metal until before the assembly process. Just as parts and organic parts are processed on separate painting lines, at least the undercoat painting must be done in a separate workshop using painting equipment for resin parts that is separate from the car body painting equipment, which improves work efficiency. The coating process is poor, and equipment such as coating and ovens are required. (b) Also, even with the method of applying a primer coat to resin parts and then painting them simultaneously on an automobile painting line, it is difficult to make the color of the car body and the resin parts the same after painting, resulting in color discrepancies. It was hot. (Means for Solving the Problems) This invention uses a conductive primer as a primer for resin parts, and its composition has good compatibility with the electrocoating paint, intermediate coat paint, and top coat paint of the car body, and the appearance finish is conductive. By stipulating that the problem does not occur regardless of the presence or absence of a primer, it is possible to coat the resin parts and the vehicle body as one body, thereby solving the above-mentioned problems. Therefore, the method of painting an automobile body according to the present invention involves applying an undercoat to the car body, attaching resin parts, applying a conductive primer mainly to the resin parts, then applying an intermediate coat and then applying a top coat, or applying a top coat. It is characterized by the fact that the resin parts and the car body are painted together. As the resin constituting the resin parts used in this invention, resins such as polybutylene terephthalate (PBT), polyamide (PA), and SMC that do not deform even at the baking temperature (12°C or higher) of the car body intermediate coating and top coating are used. . In addition, the conductive primer that is mainly applied to resin parts must have the following properties: (a) Even if hard resins such as car body top coats are used, the low-temperature physical properties of the resin parts will not deteriorate. (b) It is compatible with the base coat, intermediate coat, and top coat for car bodies, and the physical properties of the paint film are the same as current products. (c) The appearance finish of the top coat is the same as the current one, and there is no difference in the appearance of the paint film on the resin parts and on the car body. In the present invention, a conductive primer containing an ethylene-propylene copolymer (anhydrous) maleic acid graft copolymer and a conductive material is used as a primer that satisfies the above-mentioned required characteristics. Resin made by graft copolymerization of maleic acid or Freicic anhydride 50~
Preferably, a composition containing 99% by weight of the conductive material and 50 to 1% by weight of the conductive material in the solid content is used as the primer. Plug loss is suitable for this type of primer.
1100 (manufactured by Nippon Oil & Fats Co., Ltd.). Next, as the intermediate coating, it is preferable to use a coating mainly composed of aminoalkyd-based resin or preester-based resin, and as the top coating, it is preferable to use a coating mainly composed of aminoalkyd-based or aminoacrylic-based resin. . Next, this invention will be explained with reference to the drawings. FIG. 1A shows a process diagram of the coating method of the present invention, and FIG. 1B shows an explanatory diagram of the undercoating process 1, the intermediate coating process 2, and the top coating process 3. As shown in FIG. 1A, a resin part is molded according to a conventional method, and the surface is treated with resin, cleaned or physically treated (plasma treatment, sanding, etc.). On the other hand, the car body is degreased and chemically treated according to conventional methods, then an undercoat is applied (electrodeposition, etc.) and baked to harden. Next, after the pretreated resin parts are attached to the vehicle body before the intermediate coating process, a conductive primer is applied mainly to the resin parts, but it may also be applied to the vehicle body. The installation of this plastic part is shown more clearly in FIG. 1B. That is, after electrocoating the car body 4 in the primer coating process 1 and before entering the intermediate coating process 2, resin parts 5 such as bumpers are put in and attached to the car body, and then the primer 6 is applied. It is preferable to apply this conductive primer in an amount of 1 to 20μ, preferably 2 to 8μ; if it is less than 1μ, it will not form a continuous film;
If it exceeds 20μ, not only will local flow occur during painting, but it will also be disadvantageous in terms of cost. Next, after some setting time shown in 7, an intermediate coat is applied according to the conventional method in intermediate coating step 2,
The resin parts are baked and cured as shown in 9, and then a top coat is applied in a top coating step 3 according to a conventional method, and the resin parts and the car body are baked and cured as shown in 9 to complete the car body color painting of the resin parts and the car body. (Function) Because of the painting process described above, (a) work efficiency can be greatly improved compared to conventional separate painting. (b) Color matching is easier compared to conventional separate painting. (c) Compared to conventional separate painting, there is no need for painting equipment for resin parts, reducing equipment costs. (Examples) Next, the present invention will be explained with reference to Examples and Test Examples. Example 1 Primers Nos. 1 to 8 shown in Table 1 and No. 9 were intermediate coatings for car bodies (manufactured by Nippon Oil & Fats Co., Ltd., trade name: Melami No. 1 Sealer, oil-free polyester resin, epoxy resin, melamine resin). ) was used as a primer. However, Nos. 5 to 9 are primers for comparison.

[Creation of painted board for testing]

After degreasing the following A polyamide resin material, B polybutylene terephthalate resin material, and C polycarbonate resin material with 1,1,1-trichloroethane, each primer No. 1 to 9 was applied by air atomization, and then left for 5 minutes. After that, the top coat was applied with electrostatic air atomization, and baked at 140℃ for 30 minutes to dry.
A painted board for testing was created. The following experiments were conducted on these painted boards, and the results obtained are shown in Table 2 for the case where Material A was used, Table 3 for the case where Material B was used, and Table 4 for the case where Material C was used. Each is shown in the table. In addition, Nos. 1 to 8 in Tables 2 to 4 correspond to those in Table 1, respectively.
The results are shown for the test coated plates prepared using the primers No. 1 to 8, and for the test coated plate prepared using the car body intermediate coating No. 9 as the primer. The symbols in the table are as follows: ◎: Excellent with no abnormalities in appearance or performance. 〇: There are some abnormalities, but only an expert can distinguish between ◎ and 〇. △: Deterioration occurs, but the same level as normal paint film.
Does not cause any practical problems. (a) Low-temperature impact resistance (b) Paint film performance (a) Paint film appearance (b) Adhesion (c) Moisture resistance (d) Heat resistance (e) Gasoline resistance (c) Electrostatic coating properties In addition, the above materials The following was used: (A) Polyamide (PA) resin material Based on nylon 6 or 6-6 nylon, it is filled with 5-40% of inorganic materials such as glass fiber and talc alone or in combination to improve rigidity and impact resistance. A blend of 5 to 20% elastomer. (B) Polybutylene terephthalate (PBT) resin material Polybutadiene,
Modified PBT resin blended with 5 to 20% elastomer such as ethylene propylene rubber (EPR). (C) Polycarbonate (PC) resin material Modified PC resin that is based on PC resin and modified by blending 5 to 40% PBT resin etc. to improve heat resistance and chemical resistance.

[Table] No. 1 to 4 and No. 6 to 8 are conductive primers.
(b) ◎ is excellent, ○ is good, △ is practically acceptable,
× means fail

【table】

[Table] Note: ◎ is excellent, ○ is good, △ is practically passed, × is failed

[Table] Notes: ◎ is excellent, ○ is good, △ is practically passed, × is failed Evaluation method (a) Low temperature impact resistance High rate impact test
Impact Test) Using a RIT testing machine manufactured by American Rheomerik, the impact energy is measured when the impact center punches the sample (the moving speed of the impact center is always kept at a constant speed without changing before and after punching). In this test (-40°C and impact velocity of 11.1 m/sec), the yield energy must be 10 Joul or more. (b) Paint film performance (a) Paint film appearance Carry out the visual inspection with normal visual acuity from a position approximately 50 cm away from the surface to be inspected, indoors under conditions of 500 Lux or more under daylight color fluorescent lighting. However, it swells,
Painting defects such as pinholes may be detected from close range or diagonally. (b) Adhesion Using a multi-cross cutter, draw parallel lines at equal intervals of 1 mm that lightly reach the substrate, perpendicular to each other, on the coated surface of the test piece to create 100 1 mm squares.
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). (c) Moisture resistance Use a sealed box where both temperature and humidity can be adjusted. Place the test piece horizontally in a sealed box adjusted to a temperature of 50 ± 1°C and a relative humidity of 98% or higher, and check for blistering and humidity every 24 hours. Check the state of change and continue for up to 240 hours. (iv) Heat resistance Place the test piece in a constant temperature bath at 90°C for 500 hours, and after leaving it at room temperature for 24 hours, examine the appearance of the paint film and changes in the painted surface due to heat, such as discoloration and gloss shrinkage. (e) Gasoline resistance Approximately 0.3 to 0.5 ml of gasoline was dropped on the surface of the test piece, and after leaving it in the test chamber for 4 hours, it was wiped off with a cloth and the coating film was immediately checked for gloss, fading, staining, discoloration, softening, peeling, and cracking. Check to see if there are any. (c) Electrostatic coating properties (a) Transfer efficiency measurement (TE) Wrap Saran wrap around the surface of the test piece, calculate the weight of the adhered paint from the difference in weight before and after electrostatic coating (measured after baking), and calculate the weight of the ejected paint (solid). Efficiency is measured from (calculated from minutes). (b) Coating quality confirmation (appearance measurement) Visually compare the appearance finish with a standard plate (air spray) and measure the film thickness from the cut cross section.
From the results in Tables 2 to 4, by using a primer that satisfies the above-mentioned required properties, it becomes possible to perform electrostatic top coating on resin parts, and the resulting coating film does not deteriorate in low-temperature impact resistance. It can also be seen that it is possible to replace the intermediate coating, and it is possible to form a coating film by integrally coating the automobile body and resin parts. Example 2 Prepare 12 test pieces of steel plates for automobile bodies,
For each test piece, ED (manufactured by Nippon Paint Co., Ltd., Power Top) was applied as an undercoat to a film thickness of 15 μm.
Baked at 175℃ for 30 minutes, and then coated with Plugloss 1100 (manufactured by Nippon Oil & Fats Co., Ltd.) as a conductive primer with a film thickness of 5μ.
The coating was divided into four types: 10μ, 15μ, and dust, and a 30μ film thickness of Melami No. 1 Sealer Gray T (manufactured by Nippon Oil & Fats Co., Ltd.) was applied as an intermediate coating to each test piece.
Bake at 140℃ for 30 minutes to harden, and then apply #002 (manufactured by Kansai Paint Co., Ltd.) and #006 (manufactured by Nippon Oil & Fats Co., Ltd.) as top coats.
#013 (manufactured by Nippon Oil & Fats Co., Ltd.) was repeatedly applied twice (film thickness 35 μm) and baked at 140° C. for 30 minutes to harden. For comparison, 12 test pieces were prepared in the same manner except that no conductive primer was applied. For the 24 test pieces produced as described above, the appearance finish was evaluated using the same method as described in Example 1. Next, the difference between the presence and absence of primer was evaluated visually, and the color difference between the presence and absence of primer was further evaluated. The results obtained by evaluating ΔE (measured using a color difference meter) are shown in Table 5 below.

[Table] (Effects of the Invention) As explained above, in the automobile painting method of the present invention, the resin parts are attached to the car body before the intermediate coating process of the car body, and after the conductive primer is applied, the intermediate coating is applied. Because we adopted a painting method that paints the car body color through a process and a top coat process, (a) electrostatic painting can be done at the same time as the car body, (b) it is possible to color match the car body and resin parts, and (c) the resin parts can be colored. There is no need to install separate painting equipment for parts, and the painting cost can be significantly reduced, among other effects.

[Brief explanation of drawings]

FIG. 1A is a process diagram of the coating method of this invention.
Figure B is an explanatory diagram of the undercoating process, intermediate coating process, and top coating process of the painting method of this invention, Figure 2 is a process diagram of the conventional car body painting method, and Figure 3 is a process diagram of the conventional painting method for automotive resin parts. It is. 1...Undercoating process, 2...Intermediate coating process, 3...Top coating process, 4...Car body, 5...Resin parts, 6...Primer, 7...Setting, 8...Intermediate coating, 9...
Baking, hardening, 10...top coating.

Claims (1)

[Claims] 1. In a method of continuously painting an automobile body, after applying an undercoat to the vehicle body, resin parts are attached, and an ethylene-propylene copolymer (anhydrous) maleic acid graft copolymer and a conductive material are applied. A method for painting an automobile body, characterized in that a conductive primer contained therein is applied mainly to resin parts, and then an intermediate coat is applied and then a top coat is applied or a top coat is applied to paint the resin parts and the car body as one body.