JPH0811155A - Molding of hollow molded product - Google Patents

Abstract

PURPOSE:To prevent the leakage of a resin to a hollow part by inserting an insert part in a gate part or weld part or providing a projection structure to a divided member only at the gate part or weld part in order not only to control the flow of a molten resin but also to provide rigidity against injection pressure. CONSTITUTION:Respective divided members 31, 32 are left in respective female molds to be opposed each other and respective molds are registered to allow the respective divided members 31, 32 to abut each other. Next, a molten resin 34 is injected into the peripheral edge part of the abutted surface to mutually weld the divided members. When the molten resin 34 is injected into the peripheral edge part after the divided members are allowed to abut each other, a reinforcing plate 42 being an insert part is inserted in a gate part or weld part in order not only to control the flow of the molten resin but also to provide rigidity against injection pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a hollow molded article made of synthetic resin. In particular, the present invention relates to improvement of a method for molding a synthetic resin hollow molded product by an injection molding machine.

[0002]

2. Description of the Related Art As a method for manufacturing a hollow molded article made of synthetic resin, there are a molding method using a hollow molding machine and a molding method using an injection molding machine. Among them, the molding method using a hollow molding machine is one in which a molten resin is extruded and molded as a cylindrical parison by an accumulator head, the parison is sandwiched by dies from both sides, and air is blown into the parison. Liquid containers such as bottles can be easily produced by such a molding method.

However, in this method, since the parison is sandwiched between the molds, it is inevitable that relatively large burrs are left on the top and bottom of the product, and the work of removing the burrs is troublesome. Further, since a nozzle hole for blowing air into the product always remains in the product, it is not possible to obtain a completely sealed hollow molded product. Further, it is difficult to obtain a product having a uniform thickness, and the thickness of the obtained product is limited.

Therefore, in the case of producing a completely sealed hollow molded product, a thick hollow molded product, or a hollow molded product having a complicated shape having a thick portion and a thin portion,
A molding method using an injection molding machine is used. In this method, first, an injection molding machine is used to mold each of the divided bodies obtained by dividing the hollow molded product into two. Remove the split bodies from the mold and butt each other. Then, the abutting surfaces are welded to each other by heating or the like or are adhered with an adhesive to obtain a hollow molded article.

However, in such a molding method,
A step of welding or adhering the two divided bodies to each other is required, but it is extremely difficult to automate such a step. Therefore, the method for molding a hollow molded product by such an injection molding machine is not suitable for mass production. Further, particularly when the divided bodies are adhered to each other with an adhesive, the obtained hollow molded article is
There is also a problem that the strength of the joint becomes weak.

To solve these problems, Japanese Patent Publication No.
In Japanese Patent No. 38377, an improvement regarding a molding method of a hollow molded article and a mold used for the method is proposed. In this method, one mold is provided with a male mold and a female mold for molding a divided body of a hollow molded product into two parts, and the other mold is provided with a female mold that faces the male mold and the female mold, respectively. A set of molds provided with a mold and a male mold is used, and molten resin is injected into a pair of cavities formed between the male mold and the female mold that face each other, and each divided body By molding (primary molding), then sliding one mold so that the divided bodies remaining in each female mold face each other, and by matching the respective molds, After abutting against each other, a molten resin is injected (secondary molding) to the peripheral edge of the abutting surface to weld each divided body to each other.

Further, the mold is composed of a fixed mold having a single sprue and a movable mold matched with a slide mold moved along the fixed mold. The slide mold is provided with a male mold for molding one of the two split bodies and a female mold for molding the other. The movable mold is provided with a female mold and a male mold corresponding to the male mold and the female mold. The slide mold is designed so that the male mold and the female mold are moved between two positions, that is, a position where the male mold and the female mold face the movable female mold and the position where the female mold faces the movable female mold, respectively. Has become. And
The slide type is provided with a sub-sprue which is continuous between the fixed type sprue between the two positions. The sub-sprue is adapted to communicate with the edge portions of the slide type and movable type female dies. Further, each male die is provided with a projection that forms a groove on the peripheral edge of the butting surface of each divided body.

[0008]

However, in the above-described injection molding method for hollow molded articles, the molten resin leaks into the hollow portion during injection (secondary molding) of the molten resin to the peripheral edge of the abutting surface of each divided body. The phenomenon is sometimes seen. If the resin leaks into the hollow portion, the weight balance of the hollow molded product may be lost, and the product specifications may not be satisfied. Moreover, since the injection amount of the molten resin is not constant, stable injection molding cannot be performed. Further, when a large amount of resin leaks, if those resins come into contact with the wall, there is a problem that a large sink mark is generated and a poor appearance is exhibited. In consideration of these problems, in the above-mentioned injection molding method of a hollow molded product, a projection is formed on the periphery of the abutting surface of each divided body, but the injection pressure is adjusted so that resin leakage into the hollow portion does not occur. Under the reduced molding conditions, the flow length of the molten resin at the peripheral portion cannot be sufficiently obtained, which is a problem.

The present invention has been made in view of the above problems, and an object thereof is to prevent resin leakage into the hollow portion at the time of injecting molten resin into the peripheral portion in injection molding of the hollow molded article. Is intended.

[0010]

In order to achieve the above object, according to the present invention, when performing the method for molding a hollow molded article, when injecting a molten resin into a peripheral portion after abutment of each divided body, , In order to control the flow of molten resin and to have rigidity against injection pressure, insert parts are inserted in the gate part or the weld part, or only the gate part or the weld part has a protruding structure in the divided body. Is. Of course, the slide or displacement of the mold after the temporary molding is not limited to one, and may be performed for both molds.

That is, according to the present invention, one mold is provided with a male mold and a female mold for molding a split body of a hollow molded product, and the other mold is provided with the male mold and the female mold. Using a pair of molds each having a female mold and a male mold facing each other, and injecting the molten resin into a pair of cavities formed between the male mold and the female mold facing each other. hand,
Molding each split, then displacing one or both molds to leave each split in each female mold,
And, facing each divided body left in each female mold,
A method for molding a hollow molded product in which, after matching the respective molds with each other, the respective divided bodies are butted to each other, a molten resin is injected to the peripheral edge of the butted surface, and the respective divided bodies are welded to each other. In order to control the flow of the molten resin and to provide rigidity to the injection pressure when injecting the molten resin into the peripheral portion after the butting of each divided body, insert the insert part into the gate part or the weld part, or It is intended to provide a method for molding a hollow body molded article, characterized in that only a gate portion or a weld portion has a protruding structure in a divided body.

[0012]

Embodiments of the present invention will be described below with reference to the accompanying drawings. For better understanding of the present invention, prior to the description of the embodiments of the present invention, Japanese Patent Publication No. 2-383.
The injection molding method of the hollow molded article described in Japanese Patent No. 77 will be briefly described. 2 to 9 are sectional views of a mold for explaining the injection molding method of this hollow molded product. The molding die 1 is composed of a fixed die 2, a slide die 3 and a movable die 4. An arm 8 for holding a slide cylinder 9 is attached to the fixed die 2, and a piston rod of the cylinder 9 is connected to the slide die 3. Thus, the slide die 3 is adapted to slide vertically by the cylinder 9.

An injection device 11 for injecting molten resin in the mold clamping state shown in FIG.
When injection is performed from the above, each of the divided bodies 31 and 32 of the hollow molded product is obtained in the state shown in FIG. After the divided bodies 31 and 32 are cooled and solidified, the mold opening and closing device (not shown) opens the mold, and the sprue 33 is removed as shown in FIG. At this time, the respective divided bodies 31, 32 have their respective female dies 16, 1
It remains in the 7 side.

Next, as shown in FIG. 5, the cylinder 9 is contracted, and the slide die 3 is moved upward so that the divided bodies 31 and 32 are located at opposite positions. At this time, the sub-sprue 14 of the slide die 3 is in communication with the sprue 12 of the fixed die 2. Next, in this state, the movable mold 4 is moved to the slide mold 3 side, and these molds are aligned as shown in FIG. As a result, the abutting surfaces 31a, 32a of the respective divided bodies 31, 32 are abutted against each other, and the grooves 31b, 32 are provided around the abutting portions.
The space by b is formed. This space communicates with the sub-sprue 14 via the gate 22 and the runner 21.

Next, as shown in FIG. 7, after injecting the molten resin into the peripheral portion of each divided body, the mold is opened as shown in FIG. 8 and the hollow molded product 30 and the sprue 35 are taken out. After that, when the slide die 3 is slid and the mold is clamped from the state of FIG. 9, the state returns to the state of FIG. In this way, the molding process for the next molded product is performed. Therefore, in this method, as described above, when the molten resin 34 is injected into the peripheral portion in FIG. 7, the resin leak 41 into the hollow portion 40 occurs as shown in FIG. This is the butt section 31
Although a and 32a are phenomena caused by insufficient strength, the cooling time must be shortened to some extent in order to improve the efficiency of the molding cycle. However, at this time,
The temperature of each of the divided bodies 31, 32 is high, and the abutting portion 31
The rigidity of a and 32a is not sufficient. On the other hand, each divided body 3
As the peripheral edge resin 34 is injected with the temperature of 1 and 32 being higher, the adhesion strength between the divided bodies 31 and 32 and the peripheral edge resin 34 is improved. Therefore, it is difficult to balance the improvement of the adhesion strength and the reduction of the resin leakage 41. further,
Although the peripheral edge resin 34 needs to flow over the entire circumference,
When the injection pressure is increased to increase the flow distance, resin leakage 41 occurs, and when the injection pressure is set low so that the resin leakage 41 does not occur, the peripheral resin 34 has a short shot phenomenon. Therefore, it has been known that the resin leakage 41 occurs only at the place where the pressure of the molten peripheral edge resin 34 is highest, that is, at the gate portion or the weld portion where the molten resin joins.

The present invention has been made to solve the above problems, and is characterized in that a reinforcing portion 42 is provided at a portion where resin leakage occurs, as shown in FIG. Since the location where the resin leaks is the gate portion or the weld portion as described above, the reinforcing portion 42 may be installed according to the number of gate points at the time of the peripheral edge resin injection. However, because the structure of various hollow molded products limits the places where rigidity is weak such that resin leakage occurs, it is not necessary to install it on all gates or welds. It should be installed. The material of the reinforcing portion 42 may be the same material as each of the divided bodies 31, 32, but is reinforced with glass fiber, carbon fiber, or the like.
A material having high rigidity is preferable. Also, the same effect can be obtained by using a metal material. The shape of the reinforcing portion 42 may be determined according to the injection pressure, but not limited to a flat plate, a holed shape or a notched shape may be used. When insert-molding these reinforcing members 42, the reinforcing member 42 is inserted into either of the grooves 31b, 32b of the peripheral edge portion to form the peripheral edge portion in the state shown in FIG. 5 of the molding process of the hollow molded article. Just go. In addition, the reinforcing portion 42
Is a protrusion structure of a part of the divided body,
One of them may be integrally molded, and in that case, the divided bodies 31 and 32 have an interlocking structure.

[0017]

As is apparent from the above description, according to the present invention, when a hollow molded article is manufactured by injection molding, when a molten resin is injected into the peripheral portion of each divided body after abutting, Since insert parts are inserted in the welded portion or the welded portion or the divided body is provided with the protruding structure only in the gate portion or the welded portion, there is no resin leakage into the hollow portion and stable molding can be performed. Further, since the injection pressure of the molten resin to the peripheral portion can be set high, the flow length can be extended and the number of gates can be reduced. Further, since there is also a structural reinforcing effect at the joint portion, it is possible to prevent a phenomenon that the resin is covered on the outside when the molten resin is injected to the peripheral portion. Furthermore, since it has a reinforcing effect as a hollow structure, it is possible to reduce the amount of deformation and improve reliability. Furthermore, by using a reinforcing material having a perforated shape or a cutout shape, the adhesion strength of the joint portion can be improved.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a hollow molded article obtained by the method of the present invention.

FIG. 2 is a cross-sectional view of a mold for explaining a structure of a mold used for molding a hollow molded product and a molding process of the hollow molded product.

FIG. 3 is a cross-sectional view of a mold for explaining a configuration of a mold used for molding a hollow molded product and a molding process of the hollow molded product.

FIG. 4 is a cross-sectional view of a mold for explaining a structure of a mold used for molding the hollow molded product and a molding process of the hollow molded product.

FIG. 5 is a cross-sectional view of a mold for explaining a configuration of a mold used for molding a hollow molded product and a molding process of the hollow molded product.

FIG. 6 is a cross-sectional view of a mold for explaining a configuration of a mold used for molding the hollow molded product and a molding process of the hollow molded product.

FIG. 7 is a cross-sectional view of a mold for explaining a structure of a mold used for molding a hollow molded product and a molding process of the hollow molded product.

FIG. 8 is a cross-sectional view of a mold for explaining a structure of a mold used to mold the hollow molded product and a molding process of the hollow molded product.

FIG. 9 is a cross-sectional view of a mold for explaining a configuration of a mold used for molding a hollow molded product and a molding process of the hollow molded product.

FIG. 10 is a partial cross-sectional view of a hollow molded product showing resin leakage into the hollow portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Mold 2 ... Fixed type 3 ... Slide type 4 ... Movable type 5 ... Injection molding machine 9 ... Sliding cylinder 11 ... Injection device 12 ... Sprue 13, 14 ... Sub-sprue 15, 18 ... Male type 16, 17 ... Female type 19, 20 ... Cavity 30 ... Hollow molded article 31, 32 ... Divided body 31a, 32a ... Butt face 31b, 32b ... Groove 34 ... Peripheral part resin 40 ... Hollow part 41 ... Resin leak 42 ... Reinforcement part

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area B29K 105: 20 B29L 22:00

Claims (1)

[Claims] 1. A male mold and a female mold for respectively molding a split body of a hollow molded product into two pieces are provided in one mold,
A pair of molds in which a female mold and a male mold that face the male mold and the female mold are provided in the other mold, and the mold is formed between the male mold and the female mold that face each other. Molten resin is injected into a pair of cavities to mold each divided body, and then one or both molds are displaced so that each divided body remains in each female mold, and each female body is kept. The divided bodies remaining in the mold are made to face each other, and the respective molds are matched with each other, so that these divided bodies are butted against each other, and then the molten resin is injected to the periphery of the butted surface to make each divided body. In a method of forming a hollow molded product in which the bodies are welded to each other, in order to control the flow of the molten resin and to provide rigidity against the injection pressure when injecting the molten resin into the peripheral portion after the butting of each divided body. Insert in gate or weld A method for molding a hollow body molded article, characterized in that a component is inserted or the divided body is provided with a protruding structure only in a gate portion or a weld portion.