JPS61237611A - In-mold coating method - Google Patents

Abstract

PURPOSE:To prevent the generation of a pin hole by a method wherein a void is formed by separating a mold slightly from a molded article during pressure molding of FRP, IMC paints are cast into a void part by making the inside of the void part into a vacuum state and the pressure molding is performed again. CONSTITUTION:A molded article composed of SMC is obtained by compression molding, a top force 1 is made to ascend by only 0.5mm at a stage when curing is progressed to an extent of about 90% and an in-mold void part 10 corresponding to a coating layer is formed between the top force 1 and a molded article 3. Along with the above process, an opening and closing pin 9 is ascended, air and gas which have been existed within the in-mold void part 10 are discharged out of a mold swiftly by a vacuum pump 8. Then a casting pin 6 is ascended by descending the opening and closing pin 9 and IMC paints are streamed into the in-mold cavity part 10 through a paint hose 5. When casting of the IMC paints 11 into the in-mold void part 10 is completed by a predetermined quantity by descending the casting pin 6, the top force 1 is descended again and IMC coating is formed on the top of the molded article 3 at a uniform thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for injecting an in-mold coating paint into a mold during an FRP molding process.

(Prior art) FRP is processed by molding unsaturated polyester resin, epoxy resin, etc. with reinforcing agents such as glass fibers and carbon fibers. FRP molded products tend to have many minute holes, so-called pinholes, on their surfaces. Therefore, as a pre-process for painting the molded product, it is necessary to fill the surface of the molded product with putty and rework it. If no pinholes are found in this rework process, there is a problem that the pinholes will appear on the surface after the intermediate coating is applied.

In order to solve this problem, we applied in-mold coating paint (IMC paint) to the pinholes on the SMC surface during molding.
It is written as C. ) has been developed and put into practical use.

FIG. 5 shows an example of an IMC molding apparatus used for this purpose. In the figure, l is an upper mold, 2 is a lower mold, and 3 is a molded product.
An IMC paint injection unit 4 for injecting MC paint is installed, and the paint hose 5 of the IMC paint injection unit 4 has a structure that communicates with the inside of the mold by raising the injection pin 6 with an air cylinder 7. There is.

When using this IMC molding equipment, during molding, the -H upper mold 1 is raised approximately 1.0 mm to inject the IMC paint into the mold, and after injection, the upper mold 1 is lowered again to form the molded product 3. Pressure is applied, and the IMC is inserted into the pinhole on the surface of the SMC molded product 3.
Can be filled with paint. As shown in FIG. 6, the molded article 3 thus obtained has an IMC coating film 12 formed on its surface. According to this IMC molding method, SM
Pinholes on the surface of the C molded product 3 can be eliminated, and the inventors have confirmed this result through experiments.

(Problems to be Solved by the Invention) By the way, there is a process in which IMC paint is produced by mixing 1MC resin and various fillers (carbon, calcium carbide, talc, etc.), and a process in which IMC paint and polymerization Air is drawn in during the process of mixing with the initiator (t-butyl perbenzoate, etc.) and remains in the IMC paint.

Furthermore, when the IMC paint is injected into the mold, air remains inside the mold.

When the SMC 3 is pressure-molded again using the upper mold 1, these air cannot be discharged out of the mold quickly enough and remains, so as shown in FIG. Pinholes 13 are formed on the surface, and voids 14 are formed inside the IMC coating 12. And void 14
It has been confirmed through experiments by the present inventors that when the IMC coating film 12 is near the surface of the IMC coating film 12, the surface film is torn and a pinhole 13 is formed when the coating is baked.

Furthermore, FRP materials and IMC coatings generally contain styrene as a crosslinking agent, and the styrene gasifies near the mold temperature (approximately 143°C), and this styrene gas also pins the surface of the IMC coating 12. A hole 13 is created. Note that the reference numeral 15 in FIG. 7 indicates a pinhole on the surface of the SMC 3.

As described above, according to the conventional IMC molding method, even if the problem of pinholes in SMC is solved, a new problem arises in that pinholes are formed on the IMC coating surface. When this IMC molding method is carried out, the original merits of the molding method are significantly lost, and there is a strong demand for improvement in this respect.

The present invention is intended to meet the above-mentioned demands and to provide an in-mold coating method that prevents the occurrence of pinholes in FRP molding.

(Means for solving the problem) In order to achieve this technical problem, the method of the present invention
During the molding process, the IMC paint is injected into the mold by reducing the air remaining in the mold and gases such as styrene generated from the FRP material as much as possible by deaerating the inside of the mold. The gist of this is that That is, in the method of the present invention, during pressure molding of FRP with a mold,
A step is to first separate the mold slightly from the molded product to form a gap corresponding to the coating layer between the mold and the molded product, a step to reduce the pressure inside the mold cavity using a pump to create a vacuum state, and a step to create a vacuum state in the mold. This method is characterized by comprising a step of injecting the IMC paint into the inner cavity, and a step of pressure-molding the molded article again with a mold after injecting the IMC paint.

The timing of separating the mold from the molded product during FRP molding is unfavorable if the adhesive force on the surface of the molded product is large, so the mold should be separated when the molded product has hardened by about 80 to 85% or more. . The gap between the mold and the molded product when the mold is opened is only around 0.5 cm, so the time required for vacuum degassing is extremely short, less than 1.0 to 3.0 seconds. The molding cycle time will not be increased. As means for evacuating the cavity within the mold, a vacuum pump is connected to the cavity, and means is provided between the cavity and the vacuum pump to control on/off communication between the two. It goes without saying that the FRP material according to the present invention is not limited to SMC, but may also be a premix such as BMC.

(Function) In this way, when the cavity inside the mold is evacuated during molding, the residual air inside the mold and the gas generated from the FRP material are almost completely exhausted. Therefore, after this, when IMC paint is injected into the cavity in the mold and the mold is clamped again for molding, there is almost no air or gas in the mold, so the 1MC paint film is generated due to the air or gas. Upper pinholes and voids will be better prevented.

On the other hand, in order to spread the IMC coating over the entire surface of the molded product, it is desirable to extrude the IMC paint over as wide a range of the molded product surface as possible when injecting the IMC paint.
In this regard, in the method of the present invention, in addition to the conventional IMC paint injection pressure, the vacuum pressure inside the mold further promotes the flow of the IMC paint on the surface of the molded product, so that the paint can be sufficiently spread. As a result, the IMC coating film can be uniformly formed over a wide range of areas.

(Example) Hereinafter, one example of the present invention will be described based on the accompanying drawings.

FIG. 1 is a sectional view of the main parts of the 7MC molding apparatus according to this embodiment, where l is the upper mold, 2 is the lower mold, 3 is the molded product, and 3a is the IMC.
This is a tab for injecting paint. Upper mold 1 has IMC
An IMC paint injection unit 4 is mounted to inject paint into the mold, and the paint hose 5 of the IMC paint injection unit 4 is communicated with and disconnected from the inside of the mold by raising and lowering the injection bottle 6 with an air cylinder 7. However, the injection of the IMC paint into the mold is completed by the downward movement of the injection bottle 6. Further, a vacuum pump 8 is mounted on the upper mold l to reduce the pressure and create a vacuum inside the mold, and this vacuum pump 8 communicates with and disconnects from the inside of the mold by raising and lowering an opening/closing pin 9. It is configured.

Next, 7M of the above configuration according to FIGS. 1 to 4.
The IMC method using the C molding device will be explained. First, SMC
A molded article (FRP material) 3 is compression-molded by an upper mold 1 and a lower mold 2 (FIG. 1). Next, when the cure of the molded product (FRP material) 3 has progressed to about 80%, the upper mold 1 is raised by only 0.5 mm+, and a space between the upper mold 1 and the molded product 3 is created in the mold according to the coating layer. A void 10 is formed (FIG. 2). At the same time, the opening/closing pin 9 rises, and the vacuum pump 8 quickly discharges the air and gas present in the mold cavity 10 to the outside of the mold. At this time, the volume of the mold cavity 10 is extremely small, and the mold cavity 10 is already in a reduced pressure state to some extent.
The vacuum state in the mold cavity 10 can be achieved in a very short time of about 3 seconds or less.

Then, as the opening/closing pin 9 descends, the injection bottle 6 rises, and as a result, the paint hose 5 is passed through the cavity lO in the mold.
IMC paint 11 flows into (FIG. 3). In this case, the injection pin 6 may start rising after the opening/closing pin 9 stops at the lowered position, but the injection pin 6 starts rising slightly before the opening/closing pin 9 stops at the lowered position. This setting is advantageous in terms of shortening the molding cycle time.

After that, by lowering the injection pin 6, the IM is injected by the predetermined amount.
The injection of C paint 11 into the mold cavity 1o is completed (4th
figure). When the injection of the IMC paint 11 is completed, the upper mold 1 is finally lowered again, and an IMC paint film is formed on the upper surface of the molded product 3 with a uniform thickness. Here, when the IMC paint 11 flows along the molded product 3 due to the mold clamping force, there is almost no air or gas between the IMC paint 11, the molded product 3, and the upper mold 1, so the IMC paint film is pinned. No holes or voids are formed.

In addition, although the case where compression molding of SMC was demonstrated in the Example, it is applicable also to other molding methods, such as extrusion molding and injection molding.

(Effects of the Invention) As described above, according to the present invention, since the air and gas existing in the mold are degassed under reduced pressure and then the IMC paint is injected, the IMC paint film is damaged due to the presence of these air and gas. Holes can be effectively prevented and the inherent advantages of the IMC molding method can be fully exhibited. Therefore, the IMC coating film can be uniformly formed over a wider range of the surface of the molded article than in the past.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the present invention,
Figure 1 is a sectional view of the main part during pressure molding, Figure 2 is a sectional view of the main part when the pressure is reduced in the mold cavity, Figure 3 is a sectional view of the main part when IMC paint is injected, and Figure 4 is IMC paint. FIG. 3 is a sectional view of a main part when injection is completed. Fig. 5 is a sectional view of a main part showing an example of a conventional IMC molding apparatus, Fig. 6 is a sectional view showing a molded product obtained by the IMC forming apparatus of Fig. 5, and Fig. 7 is a section ``■'' in Fig. 6. It is a detailed view. 1... Upper mold, 3... Molded product (FRP material), 6...
・IMC paint injection unit/), 8...vacuum pump,
10...Mold cavity, 11...IMC paint.

Claims (1)

[Claims] (1) In the process of molding FRP using a mold, the mold is separated from the molded product to form a gap between them that corresponds to the coating layer, and the gap is made into a vacuum state, and then the cavity inside the mold is An in-mold coating method characterized by injecting an in-mold coating paint into the mold and press-molding the molded product using the mold again.