JPH04296539A - Core material for molding fiber-reinforced resin - Google Patents

Abstract

PURPOSE:To prevent thermal deformation of a molded product free from melting and deforming at RTM molding, by forming a core material for molding fiber- reinforced resin by placing a foamed thermoplastic resin core material between reinforcing fiber mats. CONSTITUTION:Foamed thermoplastic resins of polypropylene resin and polyethylene/polystylene resin are molded for a core material 3 to be used. In the resin transfer molding(RTM) using the core material 3, the core material 3 is only required not to be deformed by a molten resin injected. A molded product having a large cross-sectional coefficient due to impregnated FRP (glass fiber reinforced resin) layers 2, 4 has an enough rigidity without additional rigidity of the core material 3. The foamed core material 3 contributes to the light weight of the molded product to which a high-temperature baking finish can be applied without causing deformation of the molded product.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core material used for molding fiber-reinforced resin products.

0002

2. Description of the Related Art Recently, FRP (glass fiber reinforced resin) products have come to be used for various molded products such as automobile outer panels. In the case of the engine hood W shown in FIG. 1, for example, in the case of the engine hood W shown in FIG. As shown in FIG. 2, which is a cross-sectional view, a hard urethane foam is inserted as a core material 3 and integrally molded. By using the core material in this manner, the weight of the product can be reduced and the surface quality can be improved compared to when molding is performed using only reinforcing fibers such as glass fibers and resin.

Conventional molding of FRP engine hoods is carried out by resin transfer molding (hereinafter referred to as RTM), similar to the molding method described in, for example, Japanese Patent Laid-Open No. 2-130115. . That is, a core material 3 of urethane foam is placed between the front and back reinforcing glass fiber mats 1 and 2, set between the upper and lower molds, and molten resin such as polyester is injected to form the resin 4 into the reinforcing glass. It is formed by impregnating and curing the fiber mats 1 and 2, and covering the core material 3 with an FRP layer.

0004

[Problem to be Solved by the Invention] However, when the molded engine hood W is heated to 120°C in the next baking painting process, the uncured portion of the urethane foam of the core material 3 inside the engine hood reacts. Gas is released, stress is generated inside the FRP molded body, and distortion, sink marks, etc. occur in the product. This is because urethane is a two-component thermosetting resin, so inside the core material, which is a foam molded product, there is always a part where the reaction has not been completed, and the reaction in the unreacted part progresses at high temperatures. This is an unavoidable phenomenon because gas is released and volumetric expansion occurs. Since the heat resistance of urethane is 120℃,
Painting at higher temperatures is no longer possible.

[0005] Even in the case of low-medium temperature painting which is heated to 80°C to 120°C, it is necessary to perform an annealing treatment in advance to heat the urethane core 3 to the same temperature as the paint baking temperature and degas it. This annealing treatment requires about 8 hours, so the pretreatment is time-consuming.

The present invention solves the above problems by using thermoplastic resin foam as the core material of the molded article, without using urethane.

[0007]

[Means for Solving the Problems] The present invention uses a thermoplastic resin foam as a core material disposed between reinforcing fiber mats during fiber-reinforced resin molding.

[0008]

[Action] The thermoplastic resin foam used as the core material is
It does not melt or deform during RTM molding, and molded products using this core material are free from thermal deformation, making it possible to bake and paint at a high temperature of 120°C or higher.

[0009]

[Example] For example, in the case of the engine hood W shown in Fig. 1,
The role of the core material 3 shown in Fig. 2 is that when resin is injected in RTM molding, it is sufficient to have enough rigidity to withstand the injected molten resin and not deform. The sections 2 and 4 have a large section modulus to maintain rigidity, and the rigidity provided by the core material 3 is not required. therefore,
For the core material, it is sufficient to use a material that does not generate gas or deform at high temperatures, and does not generate unnecessary pressure or stress on the molded product.

Polypropylene resin (thermoplastic resin)
PP), polyethylene/polystyrene resin (PE/PS
) was used as the core material 3 to perform RTM molding. As a result, the core material did not melt or deform during RTM molding. It was confirmed that there was no thermal deformation of the molded product even during high-temperature baking painting at temperatures above ℃.

In addition to the above-mentioned resins, polyethylene (PE), polymethyl methacrylate (PMMA), and the like can be used as the thermoplastic resin used as the core material.

[0012] Foams using the above resin are lighter than conventional urethane foams, making it possible to reduce the weight of molded products.Also, even when high-temperature baking paint is applied, the molded products do not undergo thermal deformation, so they can be easily molded. This makes it possible to incorporate parts such as engine hoods into the car body and paint them online. The present invention is also applicable to the molding of architectural structures other than automobile parts such as engine hoods and outer panels.

[0013]

[Effects of the Invention] According to the present invention, a lightweight fiber-reinforced resin molded article with high heat resistance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a plan view of an engine hood to which the present invention is applied.

FIG. 2 is a sectional view taken along the Y-Y line in FIG. 1;

[Explanation of symbols]

1, 2 Reinforcing fiber mat 3 Core material 4 Resin

Claims (1)

[Claims] 1. A core material for fiber-reinforced resin molding, characterized in that the core material disposed between reinforcing fiber mats is a thermoplastic resin foam.