JPH05154871A - Manufacture of plastic molded product - Google Patents

Abstract

PURPOSE:To provide a manufacture of a molded product where a rigid material and flexible material are supplied reliably respectively to a part of the molded product for which rigidity is required and a part of the molded product for which only the flexible material is required. CONSTITUTION:The title method is constituted of a process where a gate 12 for exclusive use of a rigid material is provided in a part of a cavity 21 of molds 16, 17 for molding of a mudguard corresponding to a part requiring rigidity for the mudguard and a flexible material is injected within the cavity 21 through a gate 13 for a rigid material and a flexible material provided in the cavity 21, and a process injecting the rigid material within the cavity 21 through the gate 12 for exclusive use of rigid material almost simultaneously with completion of injection of the flexible material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a plastic molded product requiring rigidity, such as a mudguard for automobiles.

[0002]

2. Description of the Related Art A sandwich molding made of plastic which requires rigidity, for example, a mudguard 31 for an automobile shown in FIGS. 10 to 12 has a bolt hole 32 in a mounting portion 31a to a vehicle body of the automobile. Since a bolt is inserted into the bolt hole 32 to apply a torque and load, the mounting portion 31a
Is composed of a core layer 33 made of a hard material and a skin layer 34 made of a soft material covering the core layer 33. 31
Reference numeral b is a flap portion, and 31c is an abutting portion that comes into contact with the vehicle body when the mudguard 31 is attached to the vehicle body, both of which are made of a soft material. Reference numeral 35 is a resin injection gate provided in the mold cavity of the mudguard 31. The arrow P in FIG. 12 indicates the traveling direction of the vehicle.

[0003]

However, as shown in FIG. 12, when the mounting portion 31a is separated from the gate 35, the flap portion 31b, which requires only the soft material, and the contact portion 31c are made of hard material ( The hatched portion in the figure) may be filled, and the end of the mounting portion 31a is difficult to be filled with a hard material.

The present invention is a method for manufacturing a plastic molded product in which a hard material is surely supplied to a molded product portion requiring rigidity and a soft material is surely supplied to a molded product portion requiring only a soft material. Is an issue. As prior art materials of the present application, there are JP-A-1-233178, JP-A-2-206517, and JP-A-2-206519.

[0005]

In order to solve the above problems, the present invention relates to a cavity of a mold for molding a plastic molded product, which corresponds to a region of the plastic molded product requiring rigidity. The step of injecting the soft material into the cavity from the first gate provided in the cavity and the second gate is provided, and the hard material is injected into the cavity from the second gate almost at the same time when the injection of the soft material is completed. And the process of doing.

[0006]

When the soft material is injected from the first gate into the cavity, the soft material reaches the portion of the plastic molded article requiring rigidity. Here, when a hard material is injected from the second cavity, a high-rigidity portion having a hard material as a core layer and a soft material as a skin layer is formed in a portion of a plastic molded product requiring rigidity.

Here, the soft material means a synthetic resin having a relatively large flexibility, such as polypropylene and EPDM.
Blended resin, soft PVC resin, EVA (ethylene vinyl acetate) resin, SEBS (styrene ethylene butadiene styrene) resin, SBS (styrene butadiene styrene) resin, and the like,
Further, the hard material means a hard synthetic resin having a relatively high rigidity, such as AS resin, ABS resin, and hard PVC.
Examples of the resin include polypropylene resin containing a filler such as resin and talc.

[0008]

EXAMPLE An automobile mudguard will be taken up as an example of a plastic molded article, and a molding method of the mudguard will be described below. FIG. 1 shows a front view of the mudguard 1, and FIG. 2 shows a side view thereof. The mudguard 1 is composed of a mounting portion 1a mounted on the vehicle body of an automobile, a flap portion 1b extending downward from the mounting portion 1a, and an abutting portion 1c that abuts on the vehicle body as in the conventional case. In FIGS. 1 and 2, reference numeral 2 is a bolt hole, and its peripheral portion needs to be particularly rigid.

The mudguard 1 is molded by the device shown in FIGS. In the figure, 11 is a float core, 1
2 is a gate for exclusive use of hard material provided on the float core 11, 13
Is a gate for hard and soft materials provided on the float core 11, 14 is a runner for the gates 12 and 13, 15 is a sprue for the runner 14, 16 is a fixed mold, 17 is a movable mold,
18 is a protruding plate, 19 is a soft and hard material injection nozzle, 2
Reference numeral 0 is an injection nozzle dedicated to hard materials. The injection nozzle 19 has a cylinder dedicated to a soft material and a cylinder dedicated to a hard material. In the cavity 21 for molding the mudguard 1, which is formed by the molds 16 and 17, first, to the extent that a soft material is sinked by the soft material cylinder (a short shot is also possible), the sprue 15, runner 14, from the injection nozzle 19 It is injected through the gate 13 for hard material and soft material. Next, at the same time as the injection of the soft material is completed, the hard material dedicated injection nozzle 20 and the sprue 15 are used to provide the hard material dedicated gate 12 provided near the bolt hole 2 as shown in FIGS.
A hard material is injected into the cavity 21 from. If necessary, the hard material is injected from the injection nozzle 19 through the sprue 15, the runner 14, the soft material, and the hard material gate 13 by the hard material cylinder. In addition, FIG. 3 shows the mold 1.
6, showing the cavity 21 in 17 and the mudguard 1
The hard material dedicated gate 12 is attached to the cavity 21 corresponding to the portion requiring the strength and the rigidity.
FIG. 4 shows a state after the soft material R1 is injected into the cavity 21 from the gate 13. Figure 5 shows the left cavity 2
1 shows a state in which the hard material R2 is injected from the gate 13 to form the core layer 5 and the skin layer 6 surrounding the core layer 5, and the hard material R2 is injected into the cavity 21 on the right side from the dedicated gate 12 to form the core. A state in which a layer 5 and a skin layer 6 surrounding the layer 5 are formed is shown. FIG. 6 shows a part of the molded product taken out from the mold. FIG. 9 shows a case where the molding die is a three-plate. Since the structure of this device is almost the same as that of the device of FIG. 7, the same members as those of FIG.

[0010]

[Effect] Since the present invention has the above-mentioned steps, even if the portion requiring rigidity in the plastic molded product is separated from the soft material / hard material injection gate, only the portion requiring rigidity is required. It becomes possible to fill with a hard material, and it is possible to sufficiently enhance the strength and rigidity of the mounting portion of the plastic molded product to the mounted body.

[Brief description of drawings]

FIG. 1 is a front view of a mudguard according to an embodiment.

FIG. 2 is a side view of a mudguard according to an embodiment.

FIG. 3 is a cross-sectional view of a mudguard molding die according to an embodiment.

FIG. 4 is a cross-sectional view after a soft material is injected into the molding die.

FIG. 5 is a cross-sectional view after injecting a hard material into a molding die after injecting a soft material.

FIG. 6 is a sectional view of a main part of a molded product.

FIG. 7 is a front cross-sectional view of a molding die.

8 is a cross-sectional view taken along the line AA of FIG.

FIG. 9 is a front sectional view when a molding die is a three-plate.

FIG. 10 is a front view of a conventional mudguard.

11 is a sectional view taken along the line AA of FIG.

12 is a sectional view taken along line BB of FIG.

[Explanation of symbols]

 1 Mudguard 1a Mounting part 12 Gate for hard material 13 Gate for hard material and soft material 16 Fixed mold 17 Movable mold 21 Cavity

Claims (1)

[Claims] 1. A second gate is provided at a cavity portion of a mold for molding a plastic molded product corresponding to a portion of the plastic molded product where rigidity is required, and the second gate is soft from the first gate provided in the cavity. A method for manufacturing a plastic molded article, which comprises first injecting a material into a cavity and then injecting a hard material into the cavity from a second gate almost at the same time when the injection of the soft material is completed.