JPH0328309B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for molding a molded article having a sandwich structure.

The Sanderutsch structure is made by sandwiching and joining the core material between the upper and lower surface materials, and it is lightweight and has a high bending rigidity.
Widely used as roofing or other structural materials. The core material used is paper honeycomb, aluminum honeycomb, fiber reinforced thermosetting resin (FRP) honeycomb, or foamed plastic.
Metals, various plastics, FRP, etc. are known as surface materials. Forming methods for sand German structure include bonding the surface material and core material with adhesive, stacking uncured FRP on the core material and curing them together, or forming a space surrounded by surface material and mold. A method is known in which a liquid foamed plastic raw material such as polyurethane is injected and solidified. This injection foaming method is said to be suitable for cases where the shape of the sandwich structure is relatively complex, such as in the case of vehicle roof materials or the outer walls of electric refrigerators, where the thickness of the core material varies.

According to the studies conducted by the inventors, the injection foaming method is a highly productive method, but when the core material is 10 mm or less thick and a large molded product is produced, voids are unavoidable during injection foaming. It has been found. Therefore,
We investigated a method for forming a sanderch structure that has productivity equal to or higher than that of injection foaming and does not have the drawbacks mentioned above, and found that it is possible to mold the synthetic resin foam into a predetermined shape by aligning it with the surface shape of the surface material. They discovered a method of pressurized integral molding.
That is, in the present invention, a synthetic resin foam having a bending elastic modulus, a heat deformation temperature, and a compressive strength up to 10% compression are larger than the foam, and is placed between molded bodies previously molded into a predetermined shape. The present invention relates to a method for molding a sandwich structure, characterized in that the foam and the molded body are solidified together by applying pressure until the foam conforms to the surface shape of the molded body.

The synthetic resin foam used as the core material is preferably a closed-cell foam from the viewpoint of heat insulation, but it may be an open-cell foam. Further, a plate-shaped body having a thickness of about 5 to 15 mm before pressurization that can constitute a sanderch structure is suitable for the method of the present invention. The more complex the final shape of the sanderch structure becomes, the lower the density of the foam may be to make it easier to conform the foam to the surface shape of the surface material during pressurization. Of course, the foam may be preformed to the final shape of the sandwich structure. The density of the foam before pressure molding is 0.02
-0.2, and from the viewpoint of achieving a lightweight structure, it is preferable to select a foam whose density after pressure molding is 0.4 or less on average. Examples of the material of the synthetic resin foam include, but are not limited to, polyurethane foam, polystyrene foam, polyvinyl chloride foam, phenol resin foam, and polyolefin foam such as polypropylene.

The surface material made of a molded body pre-formed into a predetermined shape is not limited in any way as long as its bending elastic modulus, heat distortion temperature, and compressive strength up to 10% compression are higher than those of the foam as the core material, and iron, aluminum, etc. metals, various plastics, or fiber-reinforced thermoplastic resins (hereinafter referred to as
FRTP) or fiber-reinforced thermosetting resin (hereinafter referred to as FRP) is preferable. It is preferable that these be preformed to the final shape of the sanderch structure, or nearly so, but this is not necessarily necessary in the case of FRTP and the like. The thickness of the surface material may be 1 to 5 mm as the average thickness of the final shape. Normally, the thickness of the surface material should be smaller than the thickness of the core material. Resins used for FRTP include polyamide resin, polyimide resin, polycarbonate resin, polysulfone resin, polyacetal resin, polyphenylene oxide resin, polypropylene resin, polyethylene resin, polyvinyl chloride resin, cellulose resin, acrylic resin, methacrylic resin, and styrene resin. , thermoplastic polyurethane resin, fluororesin, etc. Resins used for FRP include epoxy resin, phenolic resin, unsaturated polyester resin, furan resin, alkyd resin, allyl resin, melamine resin, silicone resin,
There are thermosetting polyurethane resins, vinyl ester resins, urea resins, etc.

FRTP and FRP are resins reinforced with various fibers, including glass fiber,
Carbon fiber, carbon fiber, boron fiber, fused silica fiber, silica fiber, alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron carbide fiber, silicon carbide fiber, asbestos fiber,
Inorganic fibers such as metal fibers, hemp, vinylon,
Mention may be made of natural or synthetic fibers such as polyamide and polyester. As a surface material, it is advantageous to use a resin reinforced with these reinforcing fibers rather than using one of the above-mentioned various resins alone, as it is more durable and requires a thinner surface material.

For joining the core material and the surface material, a method using an adhesive or a method using the adhesive force of the surface material melted during heating and pressing or the thermoplastic resin itself used for the core material, etc. can be adopted. When molding complex sanderch structures, it is sufficient to preform the core material and surface material.
In addition, the pressure mold used for preforming the surface material may be used as it is as a mold for the sanderch structure. For example, using the same preformed surface material,
The core material may be placed in the upper and lower molds of the preform, the core material inserted between these surface materials, and pressure molded. In the method of the present invention, the core material is compressed under pressure until it matches the surface shape of the surface material and is integrated with the surface material. However, in cases where the core material has a high compressive strength, etc. A shape in which there is a large difference in thickness is not preferable. The method of the present invention is effective when molding a relatively thin sandwich structure, which is difficult with conventional injection foaming methods. Can be molded.

Examples of the present invention will be described below.

Example 2 mm with a concave part on the surface as shown in Figure 1
Thick glass fiber reinforced unsaturated polyester resin molded plate 1 (flexural modulus 1200Kg/mm ² , maximum compressive stress 20Kg/
mm ² , heat deformation temperature > 180℃), and apply an epoxy resin adhesive 2 to the opposing surfaces of the 8.5mm thick 30x foamed polystyrene plate 3 (flexural elasticity rate 2Kg/mm ² , compressive strength up to 10% compression 0.03Kg/mm ² , heat distortion temperature 75℃),
Pressure set at 3Kg/ ^cm2 between hot plates at 80℃, 12mm
When a thick insulation panel was manufactured, a good closed-cell sandwich structure was obtained without any voids.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an example of a sandwich structure including a surface material and a core material. 1...Glass fiber reinforced unsaturated polyester resin molded plate (surface material), 2...Adhesive, 3...Polystyrene plate (core material).

Claims (1)

[Scope of Claims] 1. A synthetic resin foam having a higher bending modulus, heat deformation temperature, and compressive strength up to 10% compression than the foam and arranged between molded bodies pre-molded into a predetermined shape,
A method for molding a sandwich structure, characterized by applying pressure until the foam matches the surface shape of the molding material, thereby solidifying the foam and the molded product together. 2. The molding method according to claim 1, wherein the molded body pre-molded into a predetermined shape is a fiber-reinforced thermosetting resin.