JPS59159834A - Formation of coating film on rim for use in automobile outside plate - Google Patents

Abstract

PURPOSE:To form a coating film excellent in weather resistance and clearness on an RIM (reaction injection molding resin) base without detriment to the toughness of the RIM, by coating the base with a specified priming paint having an elongation corresponding to that of the RIM and then applying thereto top coat. CONSTITUTION:In the formation of a coating film on an automobile outside plate RIM base with a tensile elongation at room temperature in the direction normal to that of orientation of added glass fiber of 40-80%, the coating film is formed by performing priming coating with a paint satisfying the relationship of formula I (e.g., Plagloss No.1000-YE 100, a product of Nippon Yushi, Ltd.) at room temperature, (ii) performing top coating with a paint satisfying the relationship of formula II (for elongations of primer coats <=30%) or the relationship of formula III (for elongations of primer coats >30%) at room temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a coating film on a reaction injection molded resin (RIM) reinforced with fibers or the like, particularly on a urethane RI'M or a nylon RIM.

The conventional method for forming automobile exterior coatings is to apply a chemical conversion coating treatment to the surface of a steel plate, and then apply electrocoating paint, chipping primer, intermediate coat paint, and top coat paint over this in that order. ing. As for the inner top coat and intermediate coat, the paints shown in Table 1 below are mainly used.

Table 1 However, in this conventional method for forming coating films for automobile exterior panels, the object to be coated is a steel plate, and its stiffness is significantly larger than that of the coating film, so the coating film is difficult to coat. There was no need to consider the effect on the physical properties of the material.

However, with the aim of reducing the weight of automobiles, there is a movement to change the exterior panels from steel plates to lightweight plastic RIMs such as urethane RIM and nylon RI'M. If you apply a plastic paint, the problem arises that it reduces the toughness, which is a characteristic of plastics. For example, as shown in Figure 1, RI
When a steel plate intermediate coat (elongation 4) 2 and a steel plate top coat (elongation 4) 8 are applied to the 'M outer panel' and it is pulled in the direction of the arrow, the crack in the coating film due to the tension becomes notch 4, and the part Stress concentrates on the R work M1, causing it to crack as well. On the other hand, to solve this problem, applying a stretchy paint such as that used for automobile urethane bumpers reduces toughness. However, there are problems in that the gloss decreases due to outdoor exposure and the color difference is inferior to that of conventional automobile exterior paints.The present invention solves these conventional problems. It was made with a focus on urethane RIM, nylon RIM? These R
Ax aims to solve the above problems by applying a specific paint that has an elongation corresponding to the elongation of IM as an undercoat and then applying a topcoat on top of this.

RIM for plastics for exterior panels on which a coating film is formed by the method of the present invention includes urethane RIM and nylon RIM, which exhibit an elongation rate (δR) of 40 to 80φ when pulled perpendicularly to the orientation direction of added glass fibers at room temperature. In order to meet the above objective, a paint that satisfies the following condition = (elongation rate of base material Under the following conditions: If the elongation rate of the undercoat film is 30% or less, 10 inches ≦ The elongation rate of the top coat film ≦ 15φ If the elongation rate of the undercoat film is greater than 80 inches, 1 inch ≦ The elongation rate of the top coat film 〈〈〈〈It is necessary to use a paint that satisfies 8.

In the method of the present invention, R of the plastic for outer panels is
First, an undercoat is applied over the IM base coat, and this undercoat guarantees initial adhesion with the RIM and secondary adhesion after drought resistance, and also protects against stress caused by cracks in the topcoat when the RIM is deformed from the outside. In other words, as shown in Figure 2, the undercoat plays the role of alleviating the stress concentration that occurs when the coating film cracks due to tension, thereby preventing the RIM from cracking. In particular, urethane paints that are stretchable and have excellent adhesion to the base material, such as polyether urethane paints (for example, Nippon Oil & Oil Co., Ltd., Plaglos/161'0O
O1YE-100), polyester urethane paint (e.g. Nippon Oil & Fats Co., Ltd., Pragloss Sho 1000, YE-100)
, polyester urethane paint (e.g. Nippon Oil & Fats Co., Ltd., Plaglos YE-500), acrylic urethane paint (Nippon Oil & Fats Co., Ltd., Plaglos Kuzu 2000, YE'-550')
) etc. 0 Note that it is preferable to use 20% (°minimum (
40%) Although the cross-mesh adhesion was satisfactory, the secondary adhesion after the hot water resistance test was poor.

In addition, Fig. 2 shows that, whereas in Fig. 1, the RIM was directly coated with the intermediate coat and top coat for steel plates, the method of the present invention was used to apply the RIM.
Apply 5 coats of RIM urethane paint that satisfies the above conditions as an undercoat to the M outer panel 1, and apply a topcoat for steel plates (4% elongation) on top of this.
When 3 is applied and it is pulled in the direction of the arrow G, a notch 4 is generated due to the tension as shown in the figure. This shows that this does not lead to cracking of the RIM as in the case of FIG.

Next, in the method of the present invention, a top coat is applied directly onto the coated film. This top coat paint has the effect of maintaining weather resistance for automobile exterior panels. Therefore, a paint that satisfies the above conditions and has excellent weather resistance is used. In addition to paint, urethane paint (
For example, Nippon Oil & Fats, Plugloss A40.0O1HI'-
100), and an appropriate one may be selected from these to suit the base material and undercoat.

As described above, according to the method of the present invention, the urethane RIM of the plastic base material for automobile exterior panels is made of a two-layer coating film.
, the weather resistance, physical properties of the coating film, and sharpness are excellent without reducing the toughness of RIMs such as nylon RIMs, and it is possible to obtain a coating film equivalent to that of current automobile exterior paints.

Next, the present invention will be explained with reference to Examples and Comparative Examples.Example 1 A urethane paint M for exterior panels having an elongation rate of 40% was degreased using white gasoline.Then, this urethane paint M was coated with an elongation blade of 20%. Acrylic urethane paint with
) was spray-painted with a coating of about 30μ, allowed to set for 10 minutes, and then baked in an oven at 80°C for 30 minutes. After baking, add about 80% of acrylic urethane paint with an elongation rate of 15q6.
After 0μ spray painting and setting for 10 minutes,
Bake and heat at 0℃ for 30 minutes. The thus prepared test piece (size: 1 t"lrL x 6cIr) was subjected to a hot water resistance test, a chemical resistance test, and a weather resistance test (sunshine weather) in accordance with JIs K5400.
In addition to checking whether the performance of the paint film satisfies the performance required for current exterior paints, test pieces (using a No. 8 dumbbell χ at 25°C with a universal tensile tester The elongation of RIM was measured at 300 mm/min using a graph), and the test piece was tested using a universal tensile testing machine (Tensiro,
The elongation of the coating film was measured under the conditions of 5 am/min (span: 40 mm) using a 300° C. test method, and the results are shown in Table 3.

The rate of change in elongation (correspondence) in the table was calculated by blowing.

Example 2~]0. Comparative Examples 1 to 1 1 Same as Example 1 (20 types of tests of Examples 2 to 20 and Comparative Examples 1 to 11 Pieces were prepared and then tested in the same manner as in Example 1, and the results obtained are shown in Table 8G.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the deterioration of RIM's physical properties when RIM is coated with a steel plate intermediate coat and top coat, and Figure 2 is an explanatory diagram showing the state in which deterioration of RIM's physical properties is prevented by the method of the present invention. . ]...RIM outer plate 2...Intermediate coat 8...Top coat 4...Crack notches formed in the coating film 5...Undercoat Patent applicant Nissan Motor Co., Ltd. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. When forming a coating film on a RIM substrate for automobile exterior panels that has an elongation rate of 40 to 80 inches when pulled perpendicularly to the orientation direction of the added fibers at room temperature, the undercoat is coated at room temperature. The following conditions: Use a paint that satisfies (base material elongation rate If the elongation rate of the undercoat film is greater than 30%, use a paint that satisfies the following: 10%≦Elongation rate of the topcoat film is 515%.If the elongation rate of the undercoat film is greater than 30%, use a paint that satisfies the following: A method for forming a coating film of R-work M for automobile exterior panels, characterized in that the coating is applied in the following order: , top coat paint.