JPH0524063A - Manufacture of injection molded product - Google Patents

Abstract

PURPOSE:To obtain a molded product having a rationalized hollow part at a desired part, by constituting the subject method so that molten resin of high- viscosity fluid and a gaseous body of a low-viscosity fluid flow simultaneously at the time of compression of a mold cavity. CONSTITUTION:Molten resin 11 of a high-viscosity fluid is injected to a mold cavity 10 and a gaseous body of a low-viscosity fluid is cast into the same by an appropriate quantity. Simultaneously with this or by delaying timing properly, the whole or a part of the mold cavity 10 is compressed and controlled so that capacity of the mold cavity 10 is reduced. In contents of the mold cavity 10 which has received compression like this, the low-viscosity fluid is removed from a pressurizing part. Therefore, though a hollow part 12 is obtained when the low-viscosity fluid is injected into molten resin 11 within the mold cavity 10 by making the low-viscosity fluid into gas such as nitrogen or carbonic acid gas, the hollow part 12 can be rationalized so that the same is distributed to a desirous position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic resin mold by injection molding.

In order to obtain a molding of a thermoplastic resin, a method of feeding a gaseous fluid into the flow of a molten resin to obtain a hollow portion is being adopted at present. Such a molding method has many advantages such as sink prevention, molding distortion reduction, and weight reduction, and is suitable for a reinforcing member and a structural member. However, FIG.
As described above, the distribution of the hollow portion 2 due to the gaseous fluid in the resin portion 1 of the molded product does not go as designed or is not constant, and there are many portions that must rely on experience.

When molding is performed in such a state, it is often impossible to control the distribution of other kinds of fluids in the molded product as ideal. In the worst case, the resin layer may be penetrated, resulting in a poor product yield.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks of the prior art and to provide a method for producing an injection-molded article capable of obtaining the expected fluid distribution.

[0005]

According to the present invention, while injecting another kind of fluid into a flow of a molten resin, the whole or a part of the mold cavity is compressed to fill the mold cavity with the molten resin. The method is characterized by a method for manufacturing an injection-molded mold that optimizes the distribution of the seed fluid.

In the present invention, the desired fluid distribution can be obtained by appropriately adjusting the timing of compressing the whole or a part of the mold cavity.

[0007]

The present invention is based on the fact that when a mixture of a high-viscosity fluid and a low-viscosity fluid is compressed, the low-viscosity fluid is first preferentially excluded from the pressurizing site. According to the present invention, the molten resin, which is a high-viscosity fluid, is injected into the mold cavity, and an appropriate amount of a gas body, which is a low-viscosity fluid, is injected. At the same time or with an appropriate timing delay, the whole or a part of the mold cavity is compressed, and the volume of the mold cavity is controlled to be reduced.

The contents of the mold cavity that have undergone such compression have the low viscosity fluid removed from the pressurizing section. Therefore, if a low-viscosity fluid is used as a gas such as nitrogen or carbon dioxide and injected into the molten resin in the mold cavity, a hollow portion can be obtained, but this hollow portion can be optimized so as to be distributed at desired positions. .

That is, among the constituent parts of the molding die, the part to be solid and the part to be hollow are clarified, and pressure is applied to the former part and not applied to the latter part so that a low viscosity is obtained. The distribution of the gaseous fluid, which is a fluid, can be controlled arbitrarily. It is natural that such compression must be performed before solidification of the molten resin, which is a high-viscosity fluid, but many modifications can be considered. For example, by changing the rate of pressure rise, or by dividing the time and / or place into a plurality of stages, and further by performing compression at each adjusted pressure, etc.,
A more desirable hollow and solid distribution can be achieved.

[0010]

The present invention will be disclosed below with reference to the accompanying drawings showing the embodiments. FIG. 1 is a conceptual diagram showing the principle of the method for producing an injection-molded article according to the present invention. The left side (I) of the figure shows a state where the molten resin 11 is injected into the mold cavity 10. Part (II) in the center shows a state in which the gaseous fluid is injected into the molten resin 11 to form the hollow portion 12. At the same time or with an appropriate timing delay, pressure is applied to the whole or part of the mold cavity as indicated by the arrow to compress the contents. As a result, as shown in the right side (III) of the figure, a strong compressive force is exerted on the horizontal portion of the molding die, and it becomes a reliable solid state. On the other hand, a hollow portion is formed from the base of the vertical portion where the compression force is restrained to the vertical portion.

The present embodiment shows a state in which the left and right horizontal portions are evenly compressed, but the position, shape and other states of the hollow portion 3 are changed by appropriately changing the compression force or changing the compression timing. It is also possible.

FIG. 2 shows an example of an apparatus suitable for implementing the present invention. The positional relationship between the mold 15 and the heating cylinder of the injection molding machine and the injection nozzle 16 is similar to the relationship in the molding machine according to the related art.

The mold 15 has a sprue 17 and a runner 18, which communicate with the mold cavity 10 via these. Behind the mold cavity 10 are compression bodies 19 and 21.
Is provided. These compression bodies 19 and 21 are
Pressure is applied by a pressure system including a pressure gauge and a variable valve connected via a solenoid valve 23. Although a pressurizing cylinder 20 is provided in the mold for the compression body 19, a fluid cylinder 22 is provided outside as shown in the lower part of the figure, and only the mechanical action force is transmitted to the compression body 21. It can also be configured as follows.

In carrying out the present invention, a means for injecting a gaseous fluid as a low viscosity fluid into the molten resin is required. As such means, the injection nozzle 24 from the injection nozzle 16 can be used. Other,
It can be injected from one or more locations such as the sprue 17, runner 18, mold cavity 10, etc., either simultaneously or at different times.

FIGS. 3 to 6 separately explain the steps for carrying out the manufacturing method according to the present invention. FIG. 3 shows a state in which the molten resin stored at the tip of the injection molding machine heating cylinder 16 is injected into the sprue 17 of the mold 15. In this case, the compression bodies 19 and 21 behind the mold cavity 10 are retracted.

In FIG. 4, a predetermined amount of molten resin sprues 17,
It shows a state of being injected into the mold cavity 10 via the runner 18. Also in this case, the compression bodies 19 and 21 behind the mold cavity 10 remain retracted.

FIG. 5 shows a fluid nozzle 24 provided in the injection nozzle for the molten resin injected into the mold cavity 10.
FIG. 3 shows a state in which a gaseous fluid is injected from the above to form a hollow portion inside the molten resin and to extend into the mold cavity 10.

In FIG. 6, the compression bodies 19 and 21 behind the mold cavity 10 are actuated during or at the same time as the injection of the gaseous fluid or at the end of the injection to pressurize the whole or a part of the molded product. As a result, the molten resin reaches the end of the mold cavity 10, and the gas body, which is a low-viscosity fluid, is driven away from the pressurizing portion to other portions, forming a hollow portion at a predetermined portion. Therefore, the shape and arrangement of the contact surfaces of the compression bodies 19 and 21 as well as the compression stroke and the like are extremely important for obtaining a desired molded product, and should be appropriately set according to the desired molded product shape.

By controlling the pressure of the gas body, controlling the number of pressurizations and the like, it is possible to obtain a molded product having a good appearance and a distribution of hollow portions optimized for a desired portion.

Examples of the resin suitable for the production method according to the present invention include many plastics. For example, so-called engineering plastics such as modified polyphenylene ether, polycarbonate, polyethylene terephthalate, polybutylene terephthalate and the like, or It can be applied to a plurality of blended resins.

[0021]

EFFECTS OF THE INVENTION According to the method for producing an injection-molded article according to the present invention, the molten resin, which is a high-viscosity fluid, and the gas body, which is a low-viscosity fluid, simultaneously flow when the die cavity is compressed, so that the gas body is The inconvenient phenomenon of penetrating the resin layer is unlikely to occur. Furthermore, if the portion that should be solid is solid up to the end and the portion that should be hollow is not compressed, it can be almost certainly made hollow. As a result, it is possible to obtain a molding product having a hollow portion optimized at a desired portion.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a method for manufacturing an injection-molded article according to the present invention.

FIG. 2 is an explanatory view showing a configuration of a main part of an apparatus suitable for carrying out a method for manufacturing an injection-molded article according to the present invention.

FIG. 3 is an explanatory diagram showing a main step 1 of a method for manufacturing an injection-molded article according to the present invention.

FIG. 4 is an explanatory view showing the main step 2 of the method for producing an injection-molded article according to the present invention.

FIG. 5 is an explanatory view showing the main step 3 of the method for producing an injection-molded article according to the present invention.

FIG. 6 is an explanatory view showing the main step 4 of the method for producing an injection-molded article according to the present invention.

FIG. 7 is a sectional view of a structural model of an injection-molded mold according to a conventional technique.

[Explanation of symbols]

10 type cavity 11 Molten resin 12 Hollow part

Claims (2)

[Claims] 1. A method of manufacturing a molding tool for injecting a molten resin into a mold cavity for molding, injecting another kind of fluid into the flow of the molten resin, and A method for producing an injection-molded mold, comprising compressing and filling a mold cavity with a molten resin. 2. The manufacturing method according to claim 1, wherein the injection of the other type of fluid and the compression operation of the mold cavity that fills the mold cavity are performed with a predetermined timing delay.