JPH01257018A - Simultaneous monolithic molding method for different kind of foam - Google Patents

Abstract

PURPOSE:To obtain a bumper which is light in weight due to a simple structure and possesses sufficient shock absorbing capacity by a method wherein molding is performed by injecting a plurality of resins whose foaming properties are different from each other at a time to a molding die through different injection holes. CONSTITUTION:Molten high molecular resin (such as polypropylene) 2 is injected into a space A to be formed by being surrounded with a recessed part 10a of a die 10 and a protrusion 11a of a die 11 and a bumper 3 is molded. The highest shock absorbing capacity is required on a part to be formed with the bottom of the recessed part 10a of the die 10 at the time of fitting of the part to an automobile, in the bumper 3. Therefore, resin of a low bubble rate is used as beads 6 to be injected to this part by passing through an injection hole 8b and beads 7 of a high bubble rate is injected to the remaining part through an injection hole 9b. The beads 6 or 7 is injected into the space A through the injection hole 8b or 9b and filled into the space A as the resin 2 which has indwelled bubble 4a or 5a grown up somewhat large. The bubbles 4a, 5a are gown up large by heating a mold 1 and the bumper 3 is molded by solidifying the resin 2.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an injection molding method using resin.

[Conventional technology]

Currently, various products are manufactured by injection molding resin. Recently, many shock absorbing bumpers (hereinafter referred to as bumpers) for automobiles have been manufactured using this injection molding method. As long as the bumpers used in automobiles can exhibit sufficient shock absorption performance, it is desirable that the weight be as light as possible in order to improve fuel efficiency. Therefore, it was decided that if the entire bumper was made of a dense material such as rubber, it would be too heavy.
In Publication No. 14129, the bumper is divided into a part that requires high shock absorption performance and the remaining part that does not, and the part that requires high shock absorption performance uses a member that emphasizes performance even if it is somewhat heavy. A technique has been proposed for reducing the weight of the entire bumper by using lighter members for the parts. However, Jikko Sho 58-141
In the technique of Publication No. 29, the bumper is divided into several parts, which increases the number of parts and complicates the structure, resulting in longer assembly time and a significant increase in manufacturing costs. Even in the method of molding the bumper by injection molding, a problem arises in that if the bumper is densely molded, it becomes too heavy. For this reason, resin is foamed and molded, but the conventional injection molding method, which molds the entire part uniformly, has a relatively low foaming rate that meets the highest impact absorption performance required for bumper performance. However, since the entire bumper had to be molded, the weight reduction effect was not that great.

[Problem to be solved by the invention]

As mentioned above, there was no conventional automobile bumper that was light in weight and had high impact absorption performance, so we invented a method for manufacturing a bumper with a simple structure, light weight, and sufficient impact absorption performance. was desired.

[Means to solve the problem]

The present invention has been made in order to solve the above-mentioned problems of the prior art, and is a method of producing a heterogeneous foam material by simultaneously injecting a plurality of resins with different foaming characteristics into a molding die through different injection holes. This provides a simultaneous integral molding method.

[Effect]

Since the simultaneous integral molding method of different types of foams according to the present invention has the above-described structure, a plurality of molten resins having different foaming properties are simultaneously injected into the space of the injection mold through a plurality of injection holes, and the foams have different cell ratios. Solidify the resin and mold it.

【Example】

Next, the present invention will be explained in detail based on examples. In the figure, reference numeral 1 denotes an injection mold that includes a mold 10 having a concave portion 10a at the center of the recess, and a mold 11 having a circumferentially small protrusion 11a corresponding to the concave portion 10a of the mold 10. The concave portion 11a of the mold 10 and the mold 11
In the space A surrounded and formed by the protrusion 11a,
A molten polymer resin (for example, polypropylene) 2 is injected to form a breadboard 3. As the resin 2, beads 6 or 7 containing minute bubbles 4 or 5 in a molten state are heated by an appropriate heating means (e.g. steam) and are used as direct raw materials, respectively. 9, and each conveyor vibrator 8a or 9a is individually moved by a compression pump (not shown)
% and are simultaneously injected into the space A described above through a plurality of injection holes 8b or 9b formed in the mold 10 or 11. The bumper 3 is required to have the highest impact absorption performance since the portion formed at the bottom of the concave portion 10a of the mold 10 is on the front side when mounted on an automobile. Therefore, beads 6 are injected into this area through the injection hole 8b.
A resin with a low bubble rate is used for the remaining part, and beads 7 with a high bubble rate are injected from the injection hole 9b for the remaining part. beads 6
or 7 is simultaneously injected into the space A from the injection hole 8b or 9b, filling the space A with the resin 2 containing somewhat enlarged air bubbles 4a or 5a. The boundary between the beads 6 and 7 constituting the resin 2 is wavy and partially mixed with each other. When the space A is filled with the molten resin 2 containing the air bubbles 4a or 5a, the mold 1 is heated to cause the air bubbles 4a and 5a to grow larger, and the resin 2 is solidified to form the bumper 3. The solidified bunba 3 can be taken out by expanding the molds 10 and 11 in the direction of the arrow. As shown in FIG. 2, the cross section of the solidified bumper 3 containing air bubbles is the front part 3 formed at the bottom of the concave part 10a of the mold 10, which becomes the front side when installed in an automobile.
In case a, the bubbles 4b are small and few, and in the rear part 3b, many large bubbles 5b are formed, but in the front part 3a and the rear part 3.
b is completely integrated. Therefore, the front part 3a
Although the sides are heavy, their shock absorption performance as a bumper is high.
Since the remaining portion 3b has a low density, it has a large effect of reducing the weight of the bumper 3. In addition to using the resin 2 by changing the material itself, as shown in the examples, even if the same material is used, the initial cell ratio may be changed, or the type of gas may be changed to change the foaming characteristics. It is also possible to simultaneously mold different types of foams by changing the number of foams. Furthermore, although the boundary between the beads 6 and 7 of the resin 2 filled in the space A is wavy, it can be made flat by appropriately increasing the number of injection holes 8b or 9b.

【Effect of the invention】

As explained above, in the simultaneous integral molding method of different types of foams according to the present invention, multiple resins with different foaming characteristics are simultaneously injected into the mold through different injection holes, so the cell ratio changes depending on the part of the injection molded product. I can do it. Therefore, it is possible to impart different characteristics to different parts of the molded body, so that, like an automobile impact-absorbing bumper, only the front part requires high impact-absorbing performance, while the remaining parts require high impact-absorbing performance. In the case of parts with no foam, only the front part is molded with high density, and the remaining parts are made by increasing the bubble rate.
It is also possible to reduce the weight of parts and the amount of raw materials used. As described above, according to the present invention, the strict performance required for the parts, weight reduction, and amount of raw materials used can be easily minimized by integrally molded products, which has a great effect on reducing the manufacturing cost of each plate member. are expected to demonstrate their abilities.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing, in cross section, an example of a device for carrying out the present invention;
FIG. 2 is an explanatory diagram illustrating a cross section of an automobile bumper molded in one embodiment. 1... Mold, 2... Resin, 3... Bumper, 4.5... Air bubbles, 6.7... Beads,
8.9...Tank. Patent applicant: 1 person other than Fuji Heavy Industries, Ltd.

Claims (1)

[Claims] A simultaneous integral molding method for different types of foam, characterized by simultaneously injecting multiple resins with different foaming characteristics into a molding die through different injection holes.