JPS60250924A - Painting of thick rim product - Google Patents

Abstract

PURPOSE:To obtain a thick RIM product without pinhole by a method wherein an undercoat film is applied into a mold to be transferred onto a reaction injection molding and after the washing away of a mold release agent from the molding released from the mold and cured, an undercoat and a topcoat are applied thereto again. CONSTITUTION:A mold release agent is sprayed on the surface of a mold 6 for the molding of a spoiler and then, a 2-liquid type urethane coat is applied and dried thereon as an undercoat 7. Then, after a steel plate reinforcement 9 is arranged in the mold 6, a urethane resin containing a foaming agent is injection molded and an undercoat film 11 is transferred onto the foamed urethane resin 10. The mold release agent attached to the coat film 11 hardened by a post-cure is washed away from the molding released from the mold using an organic solvent and dried and then, an undercoat 12 and a topcoat 13 are applied thereon again to finish a spoiler 8. This permits the inhibiting of bubbles generated near a skin layer of a thick RIMMED product thereby producing a product without pinhole.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to reaction injection molding (RIM).
JECTION MOLDING) It is a method of applying a paint film to a product, especially a thick -fluttering IM product. There are many different types depending on the purpose. Among them, urethane IM products have minute air bubbles,
And because it is highly elastic, it has higher impact resistance and elastic recovery rate than, for example, polypropylene molded products, so it has excellent functions as a bumper, and there is no need to provide a reinforcing lip on the back side like with propylene molded products. Therefore, it is preferable from the design point of view as it gives a high-grade feel. Initially, these products were installed on vehicles unpainted, that is, as molded products, but due to the market demand for a sense of unity with the vehicle and the resulting sense of luxury, they were installed in the same color as the exterior of the vehicle. Usually, RIM products removed from the mold are thoroughly washed with a solvent or hot water to remove the mold release agent, then an undercoat is applied, and after heat treatment, a topcoat is applied. The conventional RIM product coated with paint and then heat-treated to harden the coating film has the cross section shown in Figure 5, and regardless of the wall thickness, the coating film is hardened by heat treatment. An undercoat film 2 and a topcoat film 5 are formed on the surface of a foamed molded product 1 consisting of an integral skin layer A and a foam layer B of tens to hundreds of microns.

However, as shown in FIG. 6, bubbles 4 existing inside the skin layer A or in the outermost layer are the cause of defects in the appearance quality (pinholes) 5 of the coating film, and how can these be kept to a minimum number? This was the key to improving finishing quality and productivity.

By the way, in RIM products with relatively thin wall thickness (2 to 5 cm) such as Bamba, the monomer is flowed in a film form along the surface of the cavity by adjusting the mold temperature, the injection speed of the raw monomer, the shape of the injection port, etc. This made it possible to avoid the inclusion of air bubbles as described above, and therefore prevent the occurrence of pinholes, but the wall thickness was thick (approximately 50101 mm) and the shape was complicated, so reinforcement was required within the foam layer. For molded products that require the insertion of material, the injected monomer causes turbulence and air bubbles tend to flow into the skin layer (conventional molding technology has not been able to eliminate coating film defects (pinholes).

Figure 7 shows a cross-sectional view of a thick-walled RIM product as described above after being demolded and then coated with an undercoat and topcoat.
It can be seen that μ) 4 is the cause and trap for the occurrence of pinholes 50 [Object of the Invention] The object of the present invention is to provide a coating method for thick-walled IM products to solve the above-mentioned problem of pinholes. ○ [Structure of the Invention] The present inventors coated the inner surface of a foam mold with an undercoat paint prior to molding, and transferred this coating layer to the molded product during IM molding. By suppressing the air bubbles that occur near the layer, the number of air bubbles that appear on the surface of the R, IM molded product is reduced.

Furthermore, by fully curing the undercoat film during post-curing after molding,
It has been confirmed that the undercoat film is not damaged by the solvent used when removing the mold release agent.In other words, the coating method for thick-walled IM products of the present invention involves applying the undercoat paint to the inner surface of the mold. After drying, reaction injection molding is carried out.
After transferring the above-mentioned undercoat film to the molded product and curing the above-mentioned film by post-curing after demolding, cleaning the mold release agent adhering to the undercoat film using an organic solvent,
It is characterized by drying and then applying another primer coat and top coat.

The undercoat used in the present invention has the disadvantage of a short pot life when used internally, but on the other hand, this shortens the setting time from painting on one side to RIM molding, so in the present invention two-component urethane is used. Although paint is used, it is not limited to this. When these undercoat films are dried or semi-cured and then injection molded, the unreacted groups in the paint film and the unreacted groups in the foam layer cause a urethane reaction, and bond through chemical bonds. The mold has a large heat capacity, so it is always heated at 40 to 60 degrees Celsius.Normally, after drying the undercoat film, it is directly put into the molding process, but if the mold has been cooled, it must be heated to the above temperature in advance. It needs to be heated to.

The undercoat film transferred to the molded body during molding has the effect of suppressing air bubbles from entering the vicinity of the skin layer.
% is difficult to suppress, and depending on the variation in the molding properties, there is still a risk of pinholes occurring after topcoating.On the other hand, the film thickness of the mold coating described above must be sufficiently increased, for example, from 50 to 6
Furthermore, if the mold is closed and injection molding is performed after sufficiently accelerating the curing of the coating film, the pinholes will disappear, but the curing of the coating film will take too long, which will cause problems in terms of productivity. . Therefore, the purpose of the second undercoat in the present invention is to correct small pinholes that could not be eliminated by the first undercoat (1).

Therefore, before applying the second undercoat, it is necessary to wash and remove the mold release agent using a solvent.To do this, the molded product is placed in the solvent vapor for several minutes, and the mold release agent is removed along with the vapor. It depends on the method of removing the base coat or wiping it off with gauze soaked in a solvent.
The coating film has already been cured to a certain extent in the dry state before molding, but the method of the present invention is characterized by performing post-curing on the molded product that has been removed from the mold after further molding.The degree of post-curing is determined by the subsequent process. As shown in the example,
80 to 100% based on the uncured state of the paint
, preferably 90 to 100 inches.

Next, the solvent used for cleaning the mold release agent on the cured undercoat (1) coating film is appropriately selected from trichloroethane, trichloroethylene, xylene, alcohol, thinner, etc., depending on the type of mold release agent.

Since the solvent is adsorbed on the surface of the molded product after cleaning, if you apply the undercoat #12), the solvent will remain in the undercoat (2) coating and this solvent will evaporate. Undercoating (2) There is a risk of blistering on the coating film.Therefore, after washing, apply the molded product again at 80 to 12 cm.
The solvent is evaporated and dried by heating at 0° C. for 15 to 60 minutes.

In this way, after washing and drying, the undercoat (2) and top coat are applied. 〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇〇Example Fig. 1 shows the present invention in detail with reference to Examples and Comparative Examples. After spraying a mold release agent on the surface of the mold 6 for spoiler molding shown in FIG. Next, a steel plate reinforcement material with a thickness of 1+a+ was inserted into the mold 6, which was left to dry for 2 minutes, and then a mixed liquid with the following mixing ratio was used, and the raw material temperature was adjusted using a mold equipped with a mixing head. Injection molding was carried out at 32°C, mold temperature 60°C, and injection pressure 170°C.

Component distribution ratio A liquid polypropylene glycol 90 parts Polyethylene glycol 20 parts Dibutyl laurate (catalyst) α2 parts Freon R-11 (blowing agent) 5 parts B liquid isocyanate 115 parts After keeping the mold temperature above for several minutes, mold 4 was opened and removed from the mold, and heat was applied to correct the distortion of the product and a base coat was applied.

Undercoat (1) The degree of curing of the coating film is 80% as shown in the table below.
A hardness of 100 to 100% is necessary, and if the curing is insufficient, mulch will occur in the coating film. In addition, as the curing conditions for obtaining the following samples, the temperature was varied in the range of 80 to 120°C and the time was varied in the range of 60 to 60 minutes, and the residual NCO amount in the coating film was measured, and four types having the NCO amount in the table were selected from the results. 1.1.1 Sample of
-) Wrinkles on the paint film after immersing it in IJ chloroethane vapor for 2 minutes Note 1 = Measurement of NCO amount was based on infrared absorption analysis method O Absorbance of 3CH in paint state (frequency: 290
Absorbance of >NCO (frequency: 225
The NCO amount was set as 100% based on the ratio of 0 m ).

Note 2 Second visual evaluation ×: Large degree of wrinkles in the paint film △: Medium @: If you don't look carefully, you won't be able to find the wrinkles in the paint film.

O: No wrinkles in the coating film. In other words, if the coating film is not cured by at least 80 inches as in sample 3 above, the coating film will wrinkle when washed.

Next, the molded product of the example was kept at 120°C for 30 minutes, and the undercoat (1) (1) residual 1.1.1-) IJ dichlorothane in the coating film was volatilized and dried. Undercoat with primer paint! 7 (21 coating was applied and baked at 100℃ for 20 minutes.Finally, it was coated with a top coat white paint made by Nihon Pikemi, which is usually used for painting urethane molded products, and baked at 120℃ for 40 minutes. Figure 2 is a cross-sectional view of the spoiler 8 that was baked in this way, where 9 is the reinforcing material, 10 is the foamed urethane resin, 11 is the undercoat (1) paint film, and 12 is the undercoat (2).
A coating film, 13 is a top coating film, and 14 is a mounting surface to a trunk room. No wrinkles or pinholes were observed on the surface of the above product.

Comparative Example The process up to cleaning with trichloroethane liquid was carried out in the same manner as in the example, and then the undercoat (2) was applied immediately after which the top coat was applied. The surface of the spoiler 8 was observed, as shown in the plan view of Fig. 5 and Fig. 4. A small pinhole 5 as shown in the cross-sectional view of the figure
was occurring.

〔Effect of the invention〕

As is clear from the above description, the thick-walled IM product of the present invention suppresses air bubbles from entering the skin layer by the F coating (1), and also prevents air bubbles from penetrating into the skin layer by the F coating (1). Since pinholes can be corrected with the undercoat (2), the thickness of the undercoat (1) can be made thinner, and it does not take a long time to cure the boss.And since the paint film is sufficiently cured, The coating film is not damaged by the organic solvent used in the subsequent mold release agent removal step. As described above, the method of the present invention can provide thick-walled RIM products with no defects in appearance and can be used for automobile parts such as the aforementioned spoilers.

[Brief explanation of the drawings] Figure 1 shows a cross-sectional view of the undercoating (1) step, Figure 2 shows a cross-sectional view of a spoiler according to an example, and Figure 3 shows an external view of a product of a comparative example. , Fig. 4 shows a cross-sectional view of a comparative example product, and Fig. 5 shows a conventional thin-walled RIM.
Figure 6 shows a schematic cross-sectional view of a pinhole that occurred in a thin-walled IM product, and Figure 7 shows a pinhole that occurred in a conventional thick-walled IM product. represents a cross-sectional view of In the figure, 1... Foamed molded body 2... Undercoat film 3... Top coat film 4... Bubbles 5... Pinhole 6... Mold 7... Undercoat (1) Paint 8... Spoiler 9...
Reinforcement material 10... Urethane foam resin 11... Undercoat (1) Paint film 12... Undercoat (2) Paint film 13... Top coat paint film 14... Mounting surface fang 1 figure 3 figure

Claims (1)

[Claims] (11) Apply an undercoat to the inner surface of the mold, dry it, transfer the undercoat film to the molded product by reaction injection molding, and then post-cure to transfer the above-mentioned paint film to the molded product. After curing, the release agent adhering to the undercoat film is washed with an organic solvent, dried, and then another undercoat and topcoat are applied. Coating method for Meat RIM products. (2) Bost cure to apply an undercoat film of 80 to 1
The method according to claim 1, wherein the method is 00% cured.