JPH05254007A - Blow molding method - Google Patents

Abstract

PURPOSE:To obtain a blow-molded article having enough strength and rigidity by a method wherein a plurality of heat-treated fiber reinforced resin sheets are piled up each other by pinching heat resistant expansible bag therebetween under the condition that the peripheral edges of the resin sheets are pinched between the mating surfaces of molds and finally air is blown in the heat resistant expansible bag interposed between the resin sheets. CONSTITUTION:Two resin sheets 20, which are fully softened by heat treatment, are piled up each other by pinching heat resistant expansible bag 21 therebetween. At that time, a blowing pin 22, which is bonded to the bag 21, is fitted to the recess 20a of the resin sheet 20. Next, the peripheral edges of the piled-up resin sheets 20 are fitted to the peripheral recesses 23a and 24a, which are provided on the mating surfaces of an top mold 23 and of a bottom mold 24 so as to pinch the resin sheets 20 between the top mold and the bottom mold 24. After that, during the air in the molds are exhausted through exhaust ports 23b and 24b with avacuum pump, air is blown through a blow pin 22 in the heat resistant expansion bag 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for blow molding a resin material containing reinforcing fibers.

[0002]

2. Description of the Related Art In recent years, blow-molded articles of this kind have been used for automobile bumper beams and air spoilers.
FIG. 5 shows an example of an apparatus for molding such parts. In the figure, 1 is an extruder, in which a resin pellet a and a reinforcing fiber b are mixed and charged into a hopper 2. These molding materials a and b are introduced into the cylinder 4 as the screw 3 of the extruder 1 rotates, and the resin pellets a are heated and melted. The molten resin is kneaded by the screw 3 and then extruded into the cylinder 6a of the parison molding machine 6 through the connecting pipe 5 and temporarily stored therein. When the piston 7 is activated, the cylinder 6
The molten resin in a is extruded as parison C from the die 6b. 8 is a blow molding machine. When the parison C extruded from the parison molding machine 6 reaches a predetermined length, the blow pin 9 is inserted into the parison C, the mold 10 is closed, and then the blow pin 9 is inserted into the parison C from the blow pin 9 I try to blow in the air.

[0003]

However, in such a molding apparatus, the reinforcing fiber b is wound into the screw 3 of the extruder 1 together with the resin pellet a, so that the popper 2 having a short fiber length is used. It cannot be charged, and the reinforcing fiber b charged is also cut by the screw 3. Therefore, it was not possible to obtain a product having sufficient strength and rigidity.

[0004]

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and the gist thereof is to put a plurality of heat-treated fiber-reinforced resin sheets in a heat-resistant expansion bag. The blow molding method is characterized in that the peripheral edges of these resin sheets are sandwiched between the divided surfaces of the mold while being overlapped, and then air is blown into a heat resistant expansion bag interposed between the resin sheets.

[0005]

EXAMPLE In the present invention, a fiber reinforced resin sheet is used as a molding material instead of the parison. For this resin sheet, for example, a sheet in which glass fiber is impregnated with a thermoplastic resin, so-called SNC (Sheet Molding Compound) is used.

In molding, first, the two resin sheets 20 are heat-treated to be sufficiently soft, and then the resin sheets 20 are superposed on each other with the heat-resistant expansion bag 21 sandwiched therebetween (see FIG. 1). At that time, the blow pin 22 adhered to the bag 21 is fitted into the recess 20 a of the resin sheet 20. Next, the peripheral edge of the superposed resin sheet 20 is provided with the peripheral recess 23 provided on the dividing surfaces of the upper mold 23 and the lower mold 24.
After being fitted to the a and 24a, the resin sheet 20 is held between the upper mold 23 and the lower mold 24 (see FIG. 2). afterwards,
Air is blown into the heat-resistant expansion bag 21 from the blow pins 22 while the air in the mold is exhausted from the exhaust holes 23b and 24b by a vacuum pump (see FIG. 3). Then, the heat-resistant expansion bag 21
Expand and press the resin sheet 20 against the inner surfaces of the upper mold 23 and the lower mold 24. Finally, after releasing the product 25, the bag 21 attached to the inner surface of the product 25 may be removed (see FIG. 4).

In this embodiment, the heat-resistant expansion bag 21 is used to prevent the air blown from the blow pin 22 from leaking from the gap of the resin sheet 20 and to prevent the resin sheets 20 from being welded to each other. There is. Therefore, the bag 21 should be made of a resin film that does not melt when sandwiched between the heated resin sheets 20.

In this embodiment, the resin sheet 20 is heated and then superposed on each other.
You may heat-process after 0 is piled up. Also,
When molding a thick product, two or more resin sheets 20 may be set in a mold.

[0009]

According to the present invention, a product containing reinforcing fibers having a long fiber length can be obtained.
The rigidity can be increased.

Furthermore, when resin sheets having different kinds and densities of reinforcing fibers are set in a mold, it is possible to obtain a product in which only the strength of a specific portion is increased.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a molding process of the present invention.

FIG. 2 is an explanatory view showing a molding process of the present invention.

FIG. 3 is an explanatory view showing a molding process of the present invention.

FIG. 4 is a cross-sectional view of a product obtained in the molding process.

FIG. 5 is a view showing a conventional blow molding machine.

[Explanation of symbols]

 20 Fiber Reinforced Resin Sheet 20a Recess 21 Heat Resistant Expansion Bag 22 Blow Pin 23 Upper Die 23a Circular Recess 24 Lower Die 24a Circular Recess

Claims (1)

[Claims] 1. A heat-resistant expansion bag is sandwiched between a plurality of heat-treated fiber-reinforced resin sheets to be superposed,
A blow molding method characterized in that the peripheral edges of these resin sheets are sandwiched between the divided surfaces of a mold, and then air is blown into a heat resistant expansion bag interposed between the resin sheets.