JPS6157630A - Method of coating molded article of reinforcing reaction injection molding - Google Patents

Abstract

PURPOSE:To improve evenness of film of topcoating, by setting a film of coating having high Young's modulus as a film of coating of undercoating or middle coating of a molded article of reinforcing reaction injection molding, carrying out topcoating, baking it at <= a specific temperature. CONSTITUTION:A polyurethane raw material is blended with a reinforcing material, subjected to reaction injection molding to give a molded article of reinforcing reaction injection molding, from which a releasing agent is removed. A urethane coating compound having 180-4,000kg/cm<2> Young's modulus is applied to the molded article, baked, a topcoating compound is applied to the molded article, baked at <=80 deg.C for 60min, dried, so that a rough surface of film of topcoating is eliminated, and coating is done to provide the same evenness as that of outer plate of steel body or more improved evenness than it.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to so-called reinforced reaction injection molding, R-RIM (Reinforced Reinforced
action
) relates to a method of painting molded products.

[Prior art]

Polyurethane used in bumpers, etc., which are lower parts of automobiles, is generally produced by RIM molding, that is, by mixing and injecting relatively low-viscosity chemically active liquid components of 2 m or more that react with each other into a closed mold using a high-pressure injection machine. However, it has the disadvantage of large dimensional changes due to heat and water absorption. As bumpers have become larger in recent years, it has become difficult to use conventional RIM urethane due to its dimensional stability. In addition, outer panel parts such as fenders, which are being made of resin to reduce body weight, are expected to have dimensional stability close to that of steel.

For this reason, R-RIM molded products containing reinforcing materials such as glass fiber and mica are gaining attention, but R-
2 for conventional RIM molded products as a labor point for RIM molded products
When a coating is applied, fine irregularities (hereinafter referred to as dusty skin) occur on the surface of the top coat due to the inclusion of the reinforcing material, which impairs the appearance.

(Problems to be solved by the invention) What are the problems faced by the present invention? , -RIΔ It is an object of the present invention to provide a coating method capable of obtaining a coated product having a smoothness equal to or better than that of a steel body outer panel using a castle-shaped product as a material.

[Means for Solving Problem 1] The present inventors have developed R-RIMIil! When painting molded parts, use an undercoat film or intermediate paint film that is applied directly to the R-RIM molded part as a raw material with a Young's modulus of 180 to 4000.
By applying a high Young's modulus coating with a thickness of 197 cm, and then applying a topcoat and drying it at 80C or less, the smoothness of the topcoat can be made equal to or higher than that of a steel body outer panel. Ta.

[Effect]

Generally, RIM molded products are shipped from the mold, the release agent is washed and removed, and then an undercoat (so-called primer coating) is applied, the coating is cured by heating and drying, and then covered with a top eardrum and roughly heat treated. The paint film is hardened. Urethane paints are mainly used for the above-mentioned primers (conventional undercoat materials) because they are the same as the material, have good adhesion, and can be cured at low temperatures. The Young's modulus of the coating film is approximately 16Kq/(7
) 2, and as a result, the coating film stretches easily, and when applied to RIM molded products, when the topcoat film is heated and dried, the unevenness caused by the reinforcing material on the topcoat surface is directly transmitted to the topcoat midway surface ( The film becomes uneven.

However, since the Young's modulus of a polyurethane coating varies greatly depending on the ratio and properties of the starting materials, the inventors selected commercially available polyurethane coatings that form a coating with a specific Young's modulus. It was found that when these paints are used as undercoat or intermediate paint and can form a coating film with a Young's modulus of 180 to 4000 Kq/cm", they are effective in eliminating dusty skin. As described in the example, 180KV' Tan 2
There is no effect if it exceeds 4000 to 9/cm", and there is no change in effectiveness even if it exceeds 4000 to 9/cm".And after forming the undercoat or intermediate coat film having the above-mentioned high Young's modulus, the top coat film, which is usually applied at about 120C. If the heating is carried out at a temperature of 80° C. or lower, the movement of the metal during heating is suppressed, the reinforcing material does not come out on the surface, and a coating film as smooth as or better than that of a steel body shell is obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 One piece of short glass fiber reinforcement was added to 90 pieces of polyurethane raw material consisting of polyol, organic incyanate, chain extender, and catalyst.
0 parts were added, mixed using a high-pressure injection machine, and injected into a flat plate type sealed mold to obtain a polyurethane molded product. After removing the mold release agent from the obtained molded product, the length is 10tM1 and the width is 10
The sample was cut into small pieces with a thickness of 0.3 mm to prepare test pieces.

Next, 6'Pf1 paints with different Young's modulus of the coating film were selected from commercially available two-component urethane paints, and VC was applied to the above test piece to a film thickness of 20 to 25 μm, followed by baking at 100C for 30 minutes. Further, a white top paint commonly used for painting polyurethane molded products was applied to a film thickness of 30 to 35 μm, and then baked for 40 to 60 minutes at varying temperatures. The cross value of these test pieces was measured using a gloss tester TRDC-2 manufactured by Toyota Central Research Institute, and visual evaluation was performed. The results are shown in Table 1 along with the Young's modulus of the coating film.

In addition to the above-mentioned test, the Young's modulus of the coating film was measured separately from the above-mentioned test on prepared coating films of N150 to 60 μm obtained by pouring each coating onto a flat plate and peeling it off after curing.

Young's modulus measurement conditions Measuring device: Tensilon UTM-2-88-105D
-B (manufactured by Toyo Baldwin Co., Ltd.) Sample length: 10 x 40 Sample film thickness: 50 to 60 μm Tensile speed: 50 strips/min Measurement temperature: 20°C Table 1: Made by Oni Steel A coating film that is as smooth as or better than the body outer panel 0: Smooth coating film Δ: A coating film that is not completely smooth By forming a coating film with a high Young's modulus of 180 to 4000 kg/cm and baking the topcoat at a temperature below 80°C, it is possible to not only eliminate the textured skin from the topcoat film, but also to make it smoother than steel body skins. It was found that it was possible to obtain a coating film.

FIG. 1 shows a schematic cross-sectional view of such a two-coat coating film, where 1 shows the R-RIM material, 2 shows the high Young's modulus coating film, and 3 shows the top coated tympanic membrane.

Example 2 A conventionally used two-component cretan paint for primer (Young's modulus: 16Vc1ft) was applied to the surface of a test piece similar to that obtained in Example 1 to a thickness of 20 to 25 μm, and heated at 100°C for 30 minutes. After baking, a two-coat coating similar to that in Example 1 was applied to obtain a three-coat coating as shown in FIG.

Table 2 shows the results of a similar test. Note that 4 indicates a primer coating film.

From the results shown in Table 2, it can be seen that there is no difference in the effect even if the primer coating film 4 is provided under the vX2 in the high Young car.

Example 3 Primer coating film 4 and high Young's modulus coating film 2 in Example 2
In the same manner as in Example 2 except that the order of stacking was changed,
Table 3 shows the results of applying 3 coats to the test piece and conducting the same test as in Example 1.

Table 3 From the above results, it can be seen that even if the primer coating film 4 is superimposed on the high Young's modulus coating film 2, there is no change in the effect.

Next, among the test results shown in Tables 1 to 3 above, the cross values of the coating films baked at 80°C are summarized in one graph and shown in the graph of Figure 4. Young's modulus to 180 through 39/cWt'' to 4
It is recognized that the cross value reached 86 to 87 by providing a coating film of 000 Ky/c- as an undercoat film or intermediate coat film.

〔Effect of the invention〕

As mentioned above (when painting R-RIM molded products, by providing a coating film with a Young's modulus of 180 to 4000 Ky/sub2 between the topcoat film and the material, the rough skin of the topcoat film can be eliminated, and the topcoat can be applied to By baking the film at a temperature below 80°C, it is possible to obtain a coating film that is equivalent to or better than that of a steel body skin. Furthermore, if the above-mentioned high Young's modulus coating is provided in place of the conventional primer coating, a product that can be used as a body exterior panel can be obtained with the same two-coat coating as before, which will increase the cost of expanding the uses of R-RIM molded products. can do.

[Brief explanation of the drawing]

FIG. 1 shows a schematic front view of the coating film of Example 1, FIG. 2 shows a schematic cross-sectional view of the coating film of Example 2, and FIG. 3 shows a schematic cross-sectional view of the coating film of Example 3. FIG. 4 is a graph showing the relationship between the Young's modulus of the high Young's modulus coating film and the cross value and visual evaluation of the top coating film. In the figure, 1...Material 2...High Young's modulus coating 3.
・・Top coating film 4・・Primer coating material
Applicant Toyota Motor Corporation Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A high Young's modulus coating film with a Young's modulus of 180 to 4000 Kg/cm^2 is provided as an undercoat film or intermediate coating film that is applied directly to the material, and then a top coat is applied at 80°C.
A method for painting a reinforced reaction injection molded product, characterized by baking and drying the product as follows: