JPH01206012A - Manufacture of thin-wall resin product - Google Patents

Abstract

PURPOSE:To make it possible to easily manufacture a molded item, which has neither extra parting line nor flash developed and consequently is fine in appearance, in a short molding cycle by a method wherein a two-layer molded item, the outer layer of which is made of one of two kinds of incompatible resin materials and the inner layer of which is made of the other soft resin material, is produced and, after that, the inner layer is removed. CONSTITUTION:A part of soft polyvinyl chloride-based resin R2, for example, which is to serve as an outer layer 1, is injected from an injection cylinder 3 through a nozzle part 8 in the cavity 7 of a mold. In succession, soft resin R1 made of rubber-containing PP, for example, which is to serve as an inner layer 2, is injected from an injection cylinder 4 through the nozzle part 8 is the same cavity 7. At this time, the soft resin R1 and the soft resin R2 are incompatible with each other. The soft two-layer molded item produced as mentioned above is drawn downward out of the extracting port 13 of a fixed mold 5. Next, the soft resin R1 in the extracted two-layer molded item is pulled out of a pulling-out port 9, which communicates with the nozzle part 8 at the right end of the two-layer molded item, in order to remove the inner layer 2. Thus, a hollow thin-wall resin product is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing thin-walled resin products used as automobile interior parts and the like.

[Prior Art 1] Conventionally, for thin, bag-shaped resin products or products with undercuts that prevent them from being released from the mold, Sura Nosh molding method, injection molding method, blow molding method, etc. have been adopted.

For example, in the injection molding method, as shown in FIG. A cavity 23 of a predetermined shape is formed from these three molds.

After the injection molding is completed, the molded product is taken out by moving the movable mold 21 upward and then moving the slide core 22 to the right.

[Problem to be solved by the invention] In the conventional injection molding method described above, a movable mold 21 is attached to the molded product.
and the line at the boundary between the slide core 22 and the fixed mold 20
There was a problem in that a line appeared at the boundary between the movable mold 21 and the movable mold 21, and also cracks were generated, resulting in a poor appearance. Furthermore, both the slush molding method and the blow molding method have a problem in that the molding cycle is long.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a method for manufacturing thin-walled resin products that has a short molding cycle, does not include unnecessary lines in the molded product, and does not generate flakes.

[Means for Solving the Problems] In order to achieve the above object, the present invention injects a predetermined amount of one of two incompatible resin materials into the cavity of a mold, and then injects the other resin material into the cavity of a mold. After injecting soft resin material to form a two-layer molded product, the inner layer soft resin material is removed.

[Operation] By adopting the above configuration, when a predetermined amount of one of the two types of resin materials is injected into the cavity of the mold, and then the other soft resin material is injected, one resin material forms the outer layer. At the same time, the other soft resin material forms an inner layer to obtain a two-layer molded product, and by subsequently removing the inner layer soft resin material, a thin resin product with a hollow interior can be easily obtained.

[First Embodiment] An embodiment embodying the present invention will be described below with reference to FIGS. 1 to 9.

In this example, the two-layer molded product in the preliminary stage for producing a thin-walled resin product with a hollow interior is molded by a so-called sandwich molding method. The sandwich molding method refers to a molding method in which two types of resin are divided into an outer layer and an inner layer and molded into a sandwich shape using an injection molding method.

Specifically, as shown in FIG. 1, a molding device that performs the sandwich molding method includes an injection cylinder 3 for injecting the soft vinyl chloride resin R2 that forms the outer layer 1, and an injection cylinder 3 for injecting the soft vinyl chloride resin R2 that forms the outer layer 1. An injection cylinder 4 that injects a soft resin R1 made of rubber-containing polypropylene (hereinafter referred to as PP), and both resins R supplied from these injection ratio cylinders 3.4.
, , a nozzle part 8 for injecting R2.

The mold consists of an upper fixed mold 5 with a concave cross-section and a lower movable mold 6 with a convex cross-section. A cavity 7 is provided. Both resins R1 and R2 are injected from the nozzle portion 8 into the cavity 7. The concave portion at the bottom of the fixed mold 5 serves as an extraction hole 13 for extracting the two-layer molded product.

Next, a method for manufacturing thin-walled resin products using the molding apparatus configured as described above will be described.

First, as shown in FIG. 2, the soft vinyl chloride resin R passes from the injection cylinder 3 through the nozzle part 8 to form the outer layer l.
2 is injected into the cavity 7 of the mold. continue,
As shown in FIG. 3, the soft resin R1 forming the inner layer 2 is also injected into the cavity 7 from the injection cylinder 4 through the nozzle part 8. At this time, since the soft resin R1 made of rubber-filled PP and the soft vinyl chloride resin R2 are not compatible with each other, the soft vinyl chloride resin R2 injected first
is extruded by the subsequently injected soft resin R1 and is pressed against the inner wall surface of the cavity 7. At this time, the soft vinyl chloride resin R2 may be simultaneously injected. When the injection of the soft resin R1 is further continued, the state shown in FIG. 4 is reached. That is, the inner layer 2 made of soft resin R1 is soft chlorinated,
It is completely covered with an outer layer l made of vinyl resin R2.

After lowering the movable mold 6 in FIG. 4, the soft two-layer molded product thus formed is extracted downward from the extraction hole 13 of the fixed mold 5. Since the two-layer molded product is soft and elastic as a whole, it can be extracted from the extraction hole 13.

Next, as shown in FIG. 5, the soft resin R1 of the two-layer molded product that has been pulled out is pulled out from the pull-out hole 9 at the right end of the two-layer molded product that communicates with the nozzle part 8, and the inner layer 2 is removed. Remove. The soft resin R1 of the inner layer 2 and the soft vinyl chloride resin R2 of the outer layer 1 are not compatible and have different viscosities, and the soft resin R1 has good elasticity, so that they can be easily pulled out.

When the inner layer 2 of the two-layer molded product is pulled out, the state shown in FIG. 6 is obtained, and a thin resin product with a hollow interior is obtained.

The thickness of the thin resin product is about 0.61.

Next, in this embodiment, a foamed urethane resin is injected and filled into the hollow thin-walled resin product.

As shown in FIG. 7, a tubular injection port 1 is provided in the extraction hole 9
0, and inject a predetermined amount of foamed urethane resin U from the same injection port 1o. Thereafter, as shown in FIG. 8, the injection port 10 is moved back and the extraction hole 9 is covered. Then, as shown in FIG. 9, the foamed urethane resin is foamed by allowing it to stand at room temperature for a predetermined period of time, and a foamed body F is obtained. The foaming ratio of this foam F is 2 times or more. Further, its density is 0.03 to 0.5 g/cd. In this way, a soft-touch two-layer molded product is obtained in which the inside of the hollow thin-walled resin product is filled with the foam F having a high expansion ratio. This two-layer molded product has a higher expansion ratio of the foam F than a foam molded product made by a normal injection molding method, so that a softer feel can be obtained. Furthermore, since the foamed resin is injected later, the foaming ratio can be set freely and the feel can be changed as appropriate.

As mentioned above, according to this example, the molding cycle can be shortened, especially by using the sand inch molding method, and since a slide core unlike the conventional injection molding method is not used, there is no need to add unnecessary parts to the molded product. The appearance is good because there are no lines or cracks.

Note that the soft resin R1 of the inner layer 2 of the thin resin product is
As a method for extracting the soft resin R1, it is also possible to make a large extraction hole 9 in the upper or lower surface in FIG. 5 and extract the entire soft resin R1 from the extraction hole 9.

[Second Example] In this example as well, a two-layer molded product having a core material as a reinforcing material is molded by the sandwich molding method as in the first example.

As shown in FIG. 10, a movable mold 6 is first placed in a cavity 7 having a U-shaped cross section formed by a fixed mold 5 and a movable mold 6.
A core material 11 made of PP and having a U-shaped cross section is attached to surround the convex portion of the fixed mold 5, and a support member 12 made of silicone rubber and having a U-shaped cross section is attached to cover the inner surface of the concave portion of the fixed mold 5. is attached. Thereafter, a predetermined amount of the soft vinyl chloride resin R2 that forms the outer layer 1 is injected, and then a soft resin R1 made of rubber-containing PP that forms the inner layer 2 is injected.

After molding is completed, when the mold is opened, as shown in Figure 11,
A two-layer molded product whose upper and side parts are covered with the supporting member 12 and whose lower part is covered with the core material 11 is taken out.

Subsequently, the support member 12 at the right end is bent and lifted. Next, the enclosed two-layer molded product is taken out in that state. In this way, a two-layer molded product with PP as the core material 11 fixed to the lower surface is obtained. This two-layer molded product is
After the soft resin of the inner layer 2 is pulled out as in the first embodiment, the foamed resin can be injected.

As described above, according to this embodiment, a two-layer molded product including a core material can be obtained in a short molding cycle by the sandwich molding method, and a line formed by the mold crack surface between the fixed mold 5 and the movable mold 6 can be obtained in a short molding cycle. The two-layer molded product does not have any cracks or flakes, and the product has a good appearance.

Incidentally, after the core material 11 is molded, it may be joined by adhesion with an adhesive or heat fusion.

The present invention is not limited to the above embodiments, but can also be configured as follows.

(1) The soft vinyl chloride resin R2 forming the outer layer 1 and the soft resin R made of rubber-containing PP forming the inner layer N2 in the first embodiment can be replaced. Moreover, a soft urethane resin can also be used instead of these.

(2) In each of the above Examples, the soft vinyl chloride resin R2, which is a soft resin material, was used as the outer layer 1, but instead of this, a hard resin material such as ordinary PP or hard urethane resin may be used. It is also possible.

(3) The thin-walled resin products obtained by the manufacturing method of the present invention are particularly suitable for use in products with simple shapes such as console box lids and glove box doors.

[Effects of the Invention] The method for manufacturing thin-walled resin products of the present invention has the excellent effect of easily obtaining a molded product with a good appearance without unnecessary lines or flakes in a short molding cycle. play.

[Brief explanation of the drawing]

1 to 9 are diagrams showing a first embodiment of the present invention, in which FIG. 1 is a cross-sectional view of an apparatus showing the sandwich molding method, and FIG. 2 shows a state in which a predetermined amount of resin for the outer layer is injected. FIG. 3 is a cross-sectional view of the mold showing a state in which the inner layer resin has been injected, FIG. 4 is a cross-sectional view of the mold showing a state in which sand inch molding has been completed, and FIG. A cross-sectional view showing a state in which the inner layer soft resin material is pulled out from a layer molded product, Fig. 6 is a cross-sectional view showing a hollow thin-walled resin product, and Fig. 7 shows injecting foamed urethane resin into the inside of the hollow thin-walled resin product. Figure 8 is a cross-sectional view showing the state in which the injection of foamed urethane resin is completed; Figure 9 is a cross-sectional view showing the two-layer molded product in a state where the foamed urethane resin is foamed; Figure 1O. and 11th
The figure shows a second embodiment of the present invention, and FIG. 10 is a sectional view of the mold showing a state in which a two-layer molded product is molded.
FIG. 1 is a cross-sectional view showing a two-layer molded product taken out from the mold, and FIG. 12 is a cross-sectional view of the mold in a conventional injection molding method. 1... Outer layer, 2... Inner layer, 7... Cavity, R
1... Soft resin as resin material, R2... Soft vinyl chloride resin as resin material

Claims (1)

[Claims] 1. One of the two incompatible resin materials (R_1, R_2) inside the mold cavity (7)
_2) is injected in a predetermined amount, and then the other soft resin material (R
After injecting _1) to form a two-layer molded product, the inner layer (2)
A method for manufacturing a thin-walled resin product, characterized by removing a soft resin material (R_1).