JPH0623775A - Compression molding method - Google Patents

Abstract

PURPOSE:To obtain an SMC molded piece having no pores or pin hole on its surface by a method wherein a metallic foil and an SMC are set between an upper mold and a lower mold so that the metallic foil is disposed on a surface of a molded piece, and these are compressed under heat. CONSTITUTION:In forming, for example, an automobile body outer plate, an SMC 4 is placed on a lower mold 1 of a mold, which consists of the projected lower mold 1 and a recessed upper mold 2. A stainless foil 5 is clamped from the both sides to be set between the lower mold 1 and the upper mold 2 longitudinally movable to a certain extent. Next, these are compression molded by closing the lower mold 1 and the upper mold 2. In this manner, an SMC molded piece covered with the metallic foil is obtained without a surface defect, such as pores and pin holes, on the surface thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compression molding method for a sheet molding compound, and more particularly to a compression molding method for a sheet molding compound, the surface of which is coated with a metal foil.

[0002]

2. Description of the Related Art In recent years, automobiles have been required to be lighter due to energy saving and the like, and in particular, a body outer plate considering lightness is lightweight and has high strength, does not rust, and has a large degree of freedom in shape design. A sheet molding compound (hereinafter abbreviated as SMC) having characteristics such as excellent dimensional stability and heat resistance is used. The SMC is a sheet-shaped molded composite in which a reinforcing fiber such as glass fiber is contained in a resin such as an unsaturated polyester resin in an amount of about 20 to 50%, and an SMC molded body is obtained by compression molding the SMC. However, since the molded body is porous, burrows and pinholes are generated on the surface of the molded body, which causes a problem that the appearance is not good and S
When the paint is baked after forming the MC, there is a problem that the air trapped in the holes expands and a popping phenomenon that breaks the paint film occurs. Therefore, in order to prevent this, Japanese Patent Application Laid-Open No. 62-44414 discloses
A technique of coating the surface of a molded article with a thermosetting resin film having no surface defects is disclosed.

[0003]

When molding an SMC, the resin in the SMC is melted by heating and flows to fill the corners of the mold. Therefore, S
When the surface of the MC molded body is covered with a resin film, the SMC is set between the upper mold and the lower mold, and compression molding is performed with the resin film simply placed on the SMC. There is a problem that the resin film is locally stretched by the fluid pressure, that is, the shear stress, and is torn. Therefore, when the SMC molded product is covered with the resin film, the resin film must be vacuum-molded in advance in close contact with the mold in order to reduce the shear stress generated in the resin film, resulting in poor productivity. There was a problem. Therefore, the present invention enables efficient production of SMC molded products without defects such as burrows and pinholes on the surface by using a material that can withstand shear stress generated during compression molding, that is, a coating material that has excellent elongation and strength. The purpose is to

[0004]

The compression molding method of the present invention for solving the above problems is a metal foil and an SMC between an upper mold and a lower mold, and an SMC molded product intended for the metal foil. It is characterized in that it is set so as to be positioned on the surface side of, and while the metal foil is clamped, the upper die and the lower die are combined, and heated and pressure-bonded.

The SMC that can be used in the present invention is a SM with low shrinkage.
It is C, and conventionally used one can be used. A typical example is SMC having a composition of 30% glass fiber, 20% unsaturated polyester, 40% calcium carbonate, and 10% other components, and other reinforcing fibers include, for example, carbon fiber and boron fiber. . Examples of the base material resin include phenol resin, unsaturated polyester resin, and epoxy resin, and the amount thereof is 20
~ 50%. The metal foil covering the surface of the SMC is not particularly limited, but, for example, stainless foil, aluminum foil, pure copper foil, Fe-based metal foil, amorphous foil, ultra low carbon steel, etc. can be used. The thickness of the foil may be selected according to need, but a thickness of 0.1 to 0.02 mm is preferable in terms of strength, wrinkle resistance, and tear resistance.
In addition, the surface of the metal foil can be washed with an acid in order to improve the adhesion with the SMC. As molding conditions, a temperature range of 80 to 140 ° C. and a pressure range of 15 to 120 atm are preferable.

[0006]

According to the compression molding method of the present invention, a metal foil having a strength and elongation sufficient to withstand shear stress during compression molding is used as a coating material for SMC. Since it has a so-called work hardening characteristic that the deformation resistance increases with the above, it is not necessary to bring the resin into close contact with the mold by vacuum forming in advance unlike the case of the resin film. Therefore, compared with the case of coating with a resin film, an SMC molded body having no cavities or pinholes on the surface can be obtained by a molding process that is one process less.

[0007]

EXAMPLES The present invention will be specifically described below with reference to examples. First, the mold will be described. As shown in FIG. 4, it is a mold for molding a body outer plate, which is composed of a convex lower mold 1 and a concave upper mold 2. The upper mold 2 and the lower mold 1 are combined. At times, both molds are sealed, and a seal member 3 for preventing resin from flowing out is provided around the lower mold 1 or the upper mold 2. Although not shown, a support member for clamping the metal foil is provided outside the mold. Next, the molding method will be described. As shown in FIG. 1, first, an SMC 4 containing glass fiber as a reinforcing fiber and an unsaturated polyester resin as a base resin is placed on the lower mold 1. Then, between the lower mold 1 on which the SMC 4 is mounted and the upper mold 2 facing the lower mold 1,
The stainless steel foil 5 whose surface has been subjected to acid cleaning is clamped from both sides by a supporting member and set so that it can be moved left and right to some extent. Next, as shown in FIG.
The lower die 1 and the upper die 2 are combined and compression-molded at 100 ° C. at 100 ° C., and the stainless foil 5 is cut at the end of the SMC molded body so that the surface shown in FIG. A coated SMC molding is obtained. Further, a body skin is obtained by applying a coating on the stainless steel foil and baking it. As another embodiment, stainless steel foil is clamped and set directly from both sides by a supporting member on the concave upper mold 2, SMC is placed on the stainless steel foil, and 140 ° C. is set in the same manner as the above method. A method of heating and compressing at 100 atm to obtain an SMC molded body may be used.

The SMC molded product obtained by these methods has a good appearance because it is covered with a metal foil having no surface defects such as burrows and pinholes on the surface.
Furthermore, the popping phenomenon did not occur even after painting and baking after molding, and the body skin had a clean painted surface.
Further, unlike the case of the resin film, the vacuum forming step for bringing the film into close contact with the mold is not required, and the film can be efficiently obtained. From the viewpoint of appearance quality, the appearance of the metal foil itself such as stainless steel foil may be used as it is without coating, or it may be subjected to clear coating for the purpose of preventing surface contamination. Even if the coating is applied, since it is integrally molded at the time of molding, conductivity is imparted, and there is an effect that a conductive primer is not necessary.

[0009]

According to the compression molding method of the present invention, SMC
By covering the surface with a metal foil, it is possible to efficiently produce an SMC molded body having no surface defects such as burrows and pinholes on the surface. Further, since the obtained SMC molded product has the metal foil on the surface, it has an excellent electromagnetic shielding property and further has an effect that the surface is not easily scratched.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a metal foil and SMC according to an embodiment of the present invention before compression molding.

FIG. 2 is a cross-sectional view of a metal foil and SMC according to an embodiment of the present invention during compression molding.

FIG. 3 is a cross-sectional view of a metal skinned body skin molded in accordance with one embodiment of the present invention.

FIG. 4 is a sectional view of a mold used in an embodiment of the present invention.

[Explanation of symbols]

 1 ・ ・ ・ Lower mold 2 ・ ・ ・ Upper mold 3 ・ ・ ・ Sealing member 4 ・ ・ ・ SMC 5 ・ ・ ・ Stainless foil

Claims (1)

[Claims] 1. A metal foil and an SMC are set between an upper mold and a lower mold so that the metal foil is located on the surface side of an intended SMC molded body, and the metal foil is clamped. A compression molding method comprising heating and compressing the upper mold and the lower mold together.