JPS6138665A - Coating method of reinforced reaction injection molded article - Google Patents

Abstract

PURPOSE:To prevent generation of wrinkled surface in a top-coated film in the coating of a reinforced reaction injection molded (R-RIM) article by forming an undercoated or intermediate coated film having high Young's modulus. CONSTITUTION:In an R-RIM article contg. a reinforcing material such as glass fiber, or mica, an undercoating or intermediate coating film comprised of urethane paint is formed on the material 1. In this case, a urethane paint forming a coating film of a different Young's modulus to the top coating film is selected, and the under-coating or intermediate coating film 3 having 180- 4,000kg/cm<2> Young's modulus is formed. By this method, wrinkles on the surface of the top-coating film 3 can be vanished.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to so-called reinforced reaction injection molding, which is performed by reaction injection molding by mixing a reinforcing material.
action injection molding)
This relates to a method for coating molded products.

[Prior art]

Boliureta, which is used for automobile parts such as bumpers, is generally molded using IM molding, that is, two or more chemically active liquid components with relatively low viscosity that react with each other are molded into a sealed mold using a high-pressure injection machine. Although the mixture is injected into the mold to cause a chemical reaction and is then molded at the same time, it has the disadvantage of large dimensional changes due to heat and water absorption. Therefore, exterior parts such as bumpers, which have become larger in recent years, and seven-enders, which are being made of resin to reduce body weight, are required to have dimensional stability close to that of steel.

For this reason, IM molded products containing reinforcing materials such as glass fiber and mica are attracting attention, but Rf
- One of the problems with IM molded products is that when a conventional two-coat coating for IM molded products is applied, the surface of the top coat has minute irregularities (hereinafter referred to as ``chirichiri'') due to the inclusion of the reinforcing material. (referred to as "skin"), resulting in a loss of appearance.

[Problems that the invention attempts to solve]

The problem faced by the present invention is to provide a method for coating IM molded products without causing the above-mentioned rough skin.

[Means for solving problems]

When painting an R-IM molded product, the present inventors have determined that the Young's modulus of the undercoat film or intermediate coating film applied directly to the R-IM molded product as a raw material is 180 to 400011.
By providing a high Young's modulus coating of /cl/I and then applying a topcoat, it was possible to prevent the occurrence of dusty skin in the topcoat.

[Effect]

In general, IM molded products are removed from the mold, the release agent is washed and removed, and then an undercoat (so-called primer coating) is applied, followed by heat drying to harden the coating film.

It was coated with topcoat IIItllj, and further heat-treated to harden the coating film. Urethane paints are mainly used for the above primers (conventional undercoat paints) because they are the same as the material, have good adhesion, and can be cured at low temperatures. The paint film has a low Young's modulus of about 16Q/cm4, which makes it easy to stretch, and when applied to IM molded products, it is difficult to create unevenness due to the reinforcing material on the surface of the material when the top coat is heated and dried. Because it is transmitted directly to the coating surface (overcoat),
Causes unevenness in the topcoat film.

However, the physical properties of polyurethane vary greatly depending on the ratio and properties of the starting materials. The present inventors selected from commercially available polyurethane paints those that form coating films with different Young's moduli. We have found that by using these paints as base paints or Nakatsu paints, those that can form a film with a Young's modulus of 180 to 4000 hP/cd are effective in eliminating irritated skin. . In addition, as described in the later examples.

There is no effect if it is less than x801 [p/- (,4000 kyu/-
There is no change in the effect even if the amount is exceeded.

〔Example〕

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

Example 1 Short glass fiber reinforcement material I was added to 90 pieces of polyurethane raw material consisting of polyol, organic isocyanate, chain extender, and catalyst.
Part O was 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, it has a length of 10aR and a width of 110mm.
11 test pieces (1 to NILll) obtained by cutting into 0.3 small pieces with a thickness of 5I were coated with 11 types of paint selected from commercially available two-component urethane paints, each with a film thickness of 20 to 25 μm.
The mixture was applied to M and allowed to stand at 100°C for 30 minutes. Next, a white paint (top coat) commonly used for painting polyurethane molded products was applied to a thickness of 30 to 35 μm, and then baked at 120° C. for 40 minutes. These test pieces were then tested using a Gloss Tester TI (DC-2, manufactured by Toyota Central Research Institute).
The cross value was measured using a 50 to 60 μm thick coating film obtained by pouring the above 11 types of paint onto a flat plate and peeling it off after curing. The results of measuring the rate are shown in Table 1 together with the above-mentioned cross values.

Young's modulus measurement conditions Measuring device: Tensilon UTM-2-8g-105D-
B (manufactured by Toyo Bold Twin Co., Ltd.) Sample length: 10cm x 40mm Sample film thickness: 50 to 60μm Tensile speed: 50cm/IIk Measurement temperature: 20℃ #c1 table note O: Smooth Coating film Δ: Coating film that is not completely smooth ×: Coating film with scratchy skin From the above results, the Young's modulus is 180 to 4ooo? It has been found that by forming a coating film with a high Young's modulus of /cd, it is possible to eliminate the dusty skin from the top coating film.

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

Example 2 A conventionally used two-component urethane paint for primer was applied to the surface of a test piece similar to that obtained in Example 1 (mlz ~ 22) to a thickness of 20 to 25 μmK, and baked at 100°C for 30 minutes. After that, a two-coat coating similar to that in Example 2 was applied to obtain a three-coat coating as shown in FIG. Table 2 shows the results of a test similar to that of Example 1 performed on this three-coat film. Note that 4 indicates a primer coating film.

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

Example 3 Primer coating film 4 and high Young's modulus coating film 2 in Example 2
Same as Example 2 except that the order of 0 stacking was changed,
A 3-coat coating was applied to the test piece (N123 to Team 33).
Table 3 shows the results of a test similar to Example 2.

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

Next, when the test results shown in Tables 1 to 3 above are combined into one graph K and shown in the graph of FIG.
By applying the above coating film as a base coat film or a small amount of intermediate coat film, the rippled skin disappears and the coating is approximately 4000Kt/-
It is observed that the cross value reaches an equilibrium state at .

〔Effect of the invention〕

As mentioned above, when painting a B-几■ molded product, a Young's modulus of 180 to 4000 Ky/
By providing all coating films, it is possible to eliminate the rough skin of the top coating film and improve the appearance quality. Furthermore, if the above-mentioned high Young's modulus coating is provided in place of the conventional primer coating, a high-quality product can be obtained with the same two-coat coating as in the conventional method, which is advantageous in terms of manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 shows a schematic sectional view of the coating film of Example 1, and FIG. 2 shows a schematic sectional view of the coating film of Example 2. 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 coat coating film. In the figure, l...Material 2...High Young's modulus coating film 3...
・Top coat) Paint film 4...Primer paint film patent applicant
Toyota Motor Corporation (and 1 other person) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] By providing a high Young's modulus coating film with a Young's modulus of 180 to 4000 kg/cm^2 as an undercoat film or intermediate coating film that is applied directly to the material, and then applying a top coat, it is possible to eliminate the dusty skin in the top coat film. A method for coating reinforced reaction injection molded products characterized by preventing the occurrence of such occurrence.