JP2002096347A - Method and mold for molding hollow molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molding method for certainly forming a gas channel up to the terminal of a desired thick-walled part even in a relatively large-sized product (molded product) and manufacturing a molded article having no resin flow pattern, sink, warpage or the like and excellent in appearance with good productivity. SOLUTION: A molten thermoplastic resin is injected in the product cavity of a mold to perfectly fill the product cavity and gas is injected in the molten resin to expel a part of the molten thermoplastic resin in the product cavity to a spill-over chamber through an outflow passage to mold a hollow molded article having a hollow part. In this molding method, a mold, wherein the cross- sectional area of the inlet part to the spill-over chamber of the outflow passage is formed into a gently expanded shape, is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molding method capable of producing a high-quality thermoplastic resin hollow molded article having a necessary hollow portion at a desired position of the molded article stably without a trouble and with high productivity. About the method.

[0002]

2. Description of the Related Art A thermoplastic resin molded article having a hollow portion has features such as a reduction in the weight and an increase in rigidity of the molded article. The blow molding method has been mainly adopted as a method for molding these hollow molded articles, because the molding pressure is low, the mold cost and the equipment cost are low, and the production can be performed at low cost. However, the blow molding method has problems such as the shape, dimensional accuracy, hollowness, distribution of hollow portions, raw material yield, and shape limitation of the molded product.

[0003] As another molding method for molding a thermoplastic resin hollow molded article, a gas injection molding method in which a gas is injected into a molten resin injected into a mold cavity to form a hollow portion has recently been used in many fields. Has been adopted. In this gas injection molding method, in order to form a hollow portion in a molded product, a thick portion is provided so that a gas channel is formed in the molded product, so that molding can be performed at a lower pressure than a general injection molding method. it can. For this reason, the mold clamping pressure is low and the production of a large molded product is easy, the residual distortion of the molded product is small, and the occurrence of sink marks and warpage is suppressed, so that a superior molded product is obtained.

However, in forming the hollow portion in the thick portion of the molded product, it is difficult to form the hollow portion by reliably injecting gas into a desired position of the appearance of the molded product and a desired position of the molded product. There is. In some cases, it is necessary to form a hollow portion up to the end of the molded article. In this case, as the injection mold, the molten resin is expelled using a mold having a product cavity and a spillover chamber for expelling the molten resin in the product cavity by gas injection, and a hollow portion is reliably formed at a desired position. That is being done.

For example, in a product provided with a partially thick portion in order to increase the rigidity of a thin-walled molded product such as an instrument panel of an automobile, the surface of the thick portion may have sink marks or warpage due to a difference in heat shrinkage. Deformation easily occurs. As a method for preventing the occurrence of such sink marks, a gas channel is formed by injecting a gas into the thick portion to form a hollow portion. In this case, gas is formed by injecting gas into the thick part of the product to form a gas channel, and this hollow part has a small cross-sectional area and is relatively long. It becomes difficult to form a uniform hollow portion.

Further, in interior parts for automobiles such as an instrument panel, improvement of rigidity by simply forming a hollow portion, prevention of warpage and deformation, and particularly, occurrence of poor appearance due to traces of resin flow are also important problems. I have. The deterioration of the appearance such as the flow pattern of the resin can be solved by completely filling the entire product cavity with the molten resin before injecting the gas, shaping the outer surface of the product, and then injecting the gas. Thus, the resin pressure in the product cavity is relatively high, making it more difficult for the injected gas to reach the tip of the gas channel.

In order to solve these problems, a molten resin is injected into a product cavity, and after a complete filling, a gas is injected to expel the molten resin corresponding to a hollow portion in the product cavity into a spillover chamber to form a hollow. Is preferably adopted. As a result, a molded article having an excellent appearance and having a hollow portion formed by forming a gas channel over the entire length of the thick portion can be formed.

As a product manufactured by such a molding method, the capacity of the spillover chamber has been increased due to the increase in size of products such as automobile interior parts in recent years. Conventionally, the spillover chamber is a part that does not become a product, and it is considered that the function of the spillover chamber should only be the spillover of the molten resin and the injected gas, and no detailed study has been made.

[0009]

However, when the capacity of the spillover chamber becomes large, the resin still melted in the spillover chamber is discharged into the outflow passage when the gas is discharged after the gas is injected and held and shaped. Block the hollow road of
A case occurs in which the gas pressure in the spillover chamber is confined at a high pressure. In such a case, of course, when the mold is opened, the hollow molded product (non-product) corresponding to the spillover chamber swells or, in severe cases, ruptures, and the resin pieces and resin powder are scattered. Will do.

[0010] The scattered pieces or scattered powder of the resin adhere to the inside of the cavity, causing a defective appearance in the next molding shot, or causing damage to the mold by adhering to the contact surface of the mold. appear. In addition, the work environment is deteriorated due to the generation of the popping sound of the resin, and the mental health of the operator is also a problem.

[0011] The present invention provides a method for molding a hollow molded article of a thermoplastic resin, in which even a relatively large product (molded article) is formed without fail in which a gas channel is formed to the end of a desired thick portion. An object of the present invention is to provide a molding method and a metal mold capable of producing a molded product having excellent appearance without resin flow pattern, sink mark, warpage, etc., with high quality and high productivity.

[0012]

Means for Solving the Problems In the method of molding a hollow molded article of a thermoplastic resin, the present inventor stably forms a uniform hollow section especially over the entire length of a thick-walled section of a thin-walled large-sized molded article. The forming method was studied diligently. As a result, after injecting the molten resin into the product cavity of the mold and completely filling,
It has been found preferable to employ a molding method in which a gas is injected to expel a part of the molten resin into a spillover chamber outside the product cavity. In addition, the gas flowing into the spillover chamber may not be able to smoothly depressurize when depressurizing, and the molded product in the spillover part may swell or burst when the mold is released due to the opening of the mold, which greatly increases stable production and product quality. It was found that there was a need for a molding method that had an effect and that depressurization was surely performed, and the present invention was completed.

That is, the present invention provides: (1) a method of injecting a molten thermoplastic resin into a product cavity of a molding die and injecting a gas into the molten resin after complete filling to thereby form a molten thermoplastic resin in the product cavity; Is a method of molding a hollow molded product in which a part of the hollow part is expelled into the spillover chamber through the outflow path, and the cross-sectional area of the entrance part of the outflow path to the spillover chamber is gradually expanded. A method for molding a hollow molded article, characterized by using a mold formed. (2) The method for molding a hollow molded article according to (1), wherein the shape that gradually expands is formed so that a hollow portion communicating between the outflow passage and the spillover chamber is not closed after molding. (3) The method for molding a molded article according to (1) or (2), wherein a hollow portion is formed by forming a gas channel in a thick portion of the molded article. (4) The outflow path is provided with an opening / closing mechanism (1) to (3)
The method for molding a hollow molded article according to any one of the above. (5) A product cavity of a molding die and a spillover chamber communicating from the product cavity via an outflow passage, and a cross-sectional area of an entrance portion of the outflow passage to the spillover chamber is formed so as to gradually expand. An injection mold characterized by the following. (6) An injection mold according to claim 5, wherein the outflow path is provided with an opening / closing mechanism.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The molding method of the thermoplastic resin hollow molded article of the present invention,
By injecting the molten thermoplastic resin into the product cavity of the molding die and injecting gas into the molten resin after complete filling, part of the molten thermoplastic resin in the product cavity is transferred to the spillover chamber via the outflow passage. A method for molding a hollow molded product that is driven out and forms a hollow portion, characterized by using a mold that is formed in a shape in which a cross-sectional area of an entrance portion to a spillover chamber of an outflow passage is gradually expanded. This is a method for molding a molded article, and the injection mold of the present invention is an injection mold suitably used for the method of molding a hollow molded article of the present invention.

The hollow molded article obtained by the method of molding a hollow molded article according to the present invention includes a hollow article such as a molded article in which a hollow portion is formed in the entire molded article, and a molded article in which a hollow section is formed in a part of the molded article. There are no particular restrictions on the shape and location of the. However,
Hollow molded articles to which the molding method of the present invention can be preferably applied include:
It is a long thick molded product or a hollow molded product that is relatively large and requires a large capacity of the spillover chamber.

Further, from the viewpoint of the appearance of the molded product, since the gas is injected after completely (full) filling, the molten resin does not cause an intermittent flow on the product cavity surface of the mold, and furthermore, the mold is formed. This is a gas injection molding method with excellent surface transferability. In other words, after the molten resin is injected and completely filled into the product cavity of the molding die to secure the transfer of the die surface, the surface portion in contact with the die surface is cooled and fixed, and the internal molten resin portion is cooled. The molten resin corresponding to the formation of the hollow portion is expelled into the spillover chamber outside the product cavity.

Therefore, in the method for molding a hollow molded article of the present invention, the ratio of the hollow part to the thick part of the molded article is:
Although it may vary depending on the amorphous resin and the crystalline resin, the volume ratio usually exceeds 10%. This volume ratio is appropriately determined based on the design of the molded article according to the purpose, shape, hollowing purpose, etc. of the molded article.

Hereinafter, the present invention will be described with reference to the drawings. FIG. 1 is a conceptual cross-sectional view illustrating a molding procedure of a method for molding a hollow molded article according to the present invention. In FIG. 1, (A)
Indicates a state after injection filling of a molten resin, and (B) indicates a state after gas injection.
FIG. 2 is an enlarged sectional view of a spillover chamber, which is a main part of a molding die. FIGS. 1A and 1B show a conventional example, and FIG. 1C shows an example of the present invention.

In FIG. 1, a molding die 1 is composed of a fixed die 2 and a movable die 3. The spillover is performed through a product cavity 4 and an outflow path 7 provided at one end of the product cavity 4 by clamping the die. A chamber 9 is formed. The sprue 5 communicates with an injection nozzle of an injection molding machine (not shown). A gas injection (depressurization) mechanism 1 for injecting gas into the molten resin in the product cavity 4 and depressurizing the movable mold 3
1 and an opening / closing mechanism 10 for opening and closing the flow path of the outflow path 7 for closing when injecting the molten resin and opening when injecting gas.

Hereinafter, the molding procedure will be described. The movable mold 3 is advanced with respect to the fixed mold 2 to clamp the mold, and the outflow path 7 is closed. Next, the molten resin injected from the injection nozzle of the injection molding machine is injected and filled into the product cavity 4 through the sprue 5 and the runner gate 6, and the molten resin 12
a fills the product cavity 4. The filled molten resin is pressed against the cavity mold surface by the injection pressure, and cooling of the surface skin layer starts along with transfer and shaping of the mold.

Next, the opening / closing mechanism 10 of the outflow channel 7 is operated, the outflow channel 7 is opened, and gas is injected from the gas injection mechanism 11. The gas injection may be performed simultaneously with or before the opening of the outflow channel 7. A part of the molten resin 12 a in the product cavity 4 is expelled to the spillover chamber 9 through the outflow channel 7 by the gas injection. At the end of expelling the molten resin, the injected gas also flows into the spillover chamber. Thereby, the hollow portion 13 is formed in the product cavity 4.
A hollow molded article (product part) 14 having a is formed in the spillover chamber 9 and a hollow molded article (non-product part) 15 having a hollow part 13b is formed.

Then, after cooling is performed appropriately, the high-pressure gas in the molded product is depressurized and exhausted. Thereafter, the movable mold 3 is retracted, the mold is opened, and the hollow molded articles 14, 15 are formed.
Is taken out. By repeating this molding cycle, a hollow molded article is continuously produced. In order to increase the productivity of the injection molding, the molding cycle is preferably as short as possible, and it is preferable that the molding cycle be shortened within a range where deformation of the molded article does not occur.

By adopting this molding procedure, a hollow molded article having a good appearance without sink marks, warpage or flow pattern can be formed. In a usual method of molding a hollow molded article, molding can be performed with high productivity without any particular problem. However, in the case of an increase in the amount of the molten resin flowing into the spillover chamber due to an increase in the size of the molded product and an increase in the hollow ratio, or a shortening of the molding cycle, the cooling of the molten resin in the spillover chamber causes the hollow in the product cavity to be reduced. The cooling of the molded product may be delayed. That is, while the thickness of the hollow molded product (product part) is small, the thickness of the molded product (non-product part) in the spillover chamber often becomes large.

Such a case will be described with reference to FIG. 2, which is an enlarged view of the spillover chamber. FIG.
(A) shows a state in which a molten resin 12b is placed in a general spillover chamber 9.
And a state in which the hollow portion 22 is formed by the injected gas.
That is, the hollow portion 22 in the spillover chamber communicates with the hollow portion in the product cavity 4 through the outflow channel 7. If the high-pressure gas in the hollow portion is depressurized in this state, no particular problem occurs.

However, when the molten resin 12b in the spillover chamber is not sufficiently cooled, as shown in FIG. 2B, the molten resin becomes
A flow is generated toward the outflow channel 7, and the hollow channel in the outflow channel 7 is closed. That is, in the spillover room,
A molded product (non-product part) 15 having a high-pressure confined hollow portion 23 holding a high pressure is obtained. When this happens,
When the mold is opened and the molded product is taken out, the non-product part 15 in the spillover chamber may swell or may burst.

[0026] The molded product fragments and molded product powder generated by the rupture may damage the surface of the molding die, or the powder may adhere to the mold cavity surface or the mold clamping surface and mix into the molded product.
Adhesion to the surface of the molded product causes poor appearance. In addition, repeated molding may cause burrs due to defective clamping.

For this reason, it is necessary to interrupt the molding operation and clean the mold, which not only makes the automatic operation difficult, but also leads to a drastic decrease in productivity, increases molding costs, increases product quality and product quality. This is a major management problem. Further, the rupture of the non-product occurs rapidly, and a high and loud blasting sound is generated. In addition to the deterioration of the molding environment, there is a great problem on the mental health of the worker.

The present invention is intended to suppress swelling of non-products in the spillover chamber and prevent rupture. FIG.
(C) is an enlarged sectional view of a spillover chamber which is a main part of the present invention. (A) is different from FIG. (A) in that the entrance (8) to the spillover chamber, which is the end of the outflow channel 7, communicates linearly with the spillover chamber. ) Is that the cross-sectional area takes a shape that is gradually enlarged and leads to the spillover chamber.

That is, the gas flow does not disturb the flow of the molten resin during depressurization, and depressurization can be performed without closing the hollow portion of the outflow passage 7. Here, the shape in which the cross-sectional area gradually expands is a shape that allows the product part and the non-product part of the molded product when the mold is opened to substantially communicate with the hollow part in the outflow passage.

Therefore, the shape is as shown in FIG.
The shape is not limited to the partial round shape shown in FIG. 3C, but may be a full round shape (horn shape), a slope shape, or the like. Also, since this part is a non-product part, unlike a general gate, it is not a cut and removal part with a product part like a gate cut, so the gas flow during depressurization should be more smooth Can be.

The method for molding a hollow molded article according to the present invention can be performed using an injection molding apparatus having gas injection equipment. The gas is not particularly limited, but nitrogen gas is generally used from the viewpoints of inertness, safety, low cost, and the like. When the nitrogen gas is directly supplied from a nitrogen cylinder, the nitrogen gas is supplied from the air via a regulating valve from a nitrogen production apparatus using means such as a separation membrane and an adsorption tower. Gas injection equipment
A gas such as nitrogen can be injected at an injection pressure of 30 MPa or less, usually about 5 to 20 MPa, preferably 8 to 15 MPa.

Further, the gas injection control device is configured to control the pressure and time in conjunction with the operation of the injection molding unit. The method of injecting gas into the molten resin in the product cavity of the mold is not particularly limited, and is usually performed using a runner, a gate, a gas injection pin provided on a mold wall, or the like. It is also possible to inject from a nozzle.

The apparatus for controlling gas injection controls the following operations. The injection start signal from the injection molding machine is taken in, and the delay timer is started. After the delay timer expires, the gas controlled at a predetermined pressure by the pressure regulating valve is opened for a set time to inject the gas. After gas injection, the injection valve is closed and held for a certain period of time (the formed hollow portion is kept at a high pressure). Open the depressurizing valve of the depressurizing line to release the pressure (open to the atmosphere). These series of controls are performed by the end of the cooling time.

The injection mold of the present invention is used for molding the hollow molded article of the present invention, and comprises a product cavity of the mold and a spillover chamber communicating from the product cavity via an outflow passage. The cross-sectional area of the entrance to the spillover chamber of the outflow passage is formed to have a shape that gradually expands, and is described in detail in the above-mentioned molding method.

The thermoplastic resin used in the method for molding a hollow molded article of the present invention is not particularly limited, and a resin that can be injection-molded is used. As the thermoplastic resin, for example, polypropylene, propylene-ethylene block copolymer, propylene-ethylene random copolymer, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-α-olefin copolymer elastomer , Polyolefin resins such as unsaturated carboxylic acids or derivatives thereof modified polyolefin resins, polystyrene homopolymers, rubber modified polystyrene, polystyrene resins such as polystyrene containing syndiotactic structure,
AS resin, ABS resin, polyvinyl chloride resin, polyamide resin, polyester resin, polyacetal resin, polycarbonate resin, polyaromatic or thioether resin, polyaromatic ester resin, polysulfone resin, acrylate resin Resins and various thermoplastic elastomers can be employed.

Here, the above-mentioned thermoplastic resins can be used alone or in combination of two or more. These thermoplastic resins may include, if necessary, impact strength improvers such as elastomers, reinforcing agents such as glass fiber, talc and calcium carbonate, fillers, antioxidants, ultraviolet absorbers, antistatic agents, weathering agents, light Additives such as a stabilizer, a nucleating agent, a coloring agent, a foaming agent, and a crosslinking agent can be added.

The method for molding a hollow molded article according to the present invention is preferably such that the injection mold is used to close the outflow path, preferably by an opening / closing mechanism provided in the outflow path, and then melted into the product cavity of the mold. Inject, fill and fill resin. The injected and filled molten resin is surely filled to the end of the product cavity of the mold by the amount of resin, resin temperature, and resin injection pressure. As a result, the fine irregularities of the mold that form the fine ribs, bosses, etc., or the textured surface of the molded product are reliably transferred to the molded product, and the appearance is excellent. The molten resin in the product cavity of the mold starts cooling from the mold surface. After some cooling, gas is injected into the molten resin in the product cavity of the mold, and the resin in the central part of the thick part with melt flowability is expelled to the spillover chamber through the outflow passage, communicating with the so-called thick part A formed gas channel is formed. In addition, the end of the injected gas finally reaches the spillover chamber, and as a result, a hollow portion is surely formed at a desired position of the target molded article, that is, at the end. As a result, the thickness of the hollow body becomes substantially uniform, and no sink marks are generated due to the effect of keeping the pressure of the injected gas. Therefore, it is particularly suitably used for molding molded articles whose appearance is regarded as important, such as automobile interior parts.

Then, the high-pressure gas in the hollow portion including the non-product portion of the spillover chamber which does not become a molded product after being appropriately cooled is depressurized, and if necessary, after auxiliary cooling, the mold is opened to obtain a hollow molded product. Can be In the above description, depressurization has been described in connection with the case of using the gas injection path and the depressurization path together, but it goes without saying that the depressurization can be performed using independent pipes.

[0039]

EXAMPLES Hereinafter, an example of a method for forming a thermoplastic resin hollow molded article of the present invention will be described based on specific examples, but the present invention is not limited to these examples. Injection molding machine equipped with gas injection equipment [Toshiba Machine Co., Ltd .: IS22
00DF], the automobile instrument panel 30 shown in FIG. 3 was continuously formed.

The instrument panel 30 is shown in FIG.
(A) and (B), in order to improve the rigidity of the defroster portion, the defroster portion has a thick portion from the driver seat side to the passenger seat side along the defroster portion. With the formation of 31, a hollow portion is formed. The gas injection position 32 is at the driver's seat end, the spillover setting position is at the passenger's seat gas channel end, and an open / close valve is provided in the resin outflow passage. In addition, injection of molten resin is performed in the center and driver's seat,
The depressurization was performed from the gas pin portion for injecting the gas, from three places substantially at the center of the passenger seat side.

The shape of the entrance from the product cavity to the spillover chamber through the outflow path was a trumpet shape with a 5 mm radius processing over the entire circumference. A molding die having a volume of the spillover chamber of 20 cm ³ was used.

Molding conditions Molding material: polypropylene resin [Idemitsu Petrochemical Co., Ltd.
Made, IDEMITSUPP, MFR (Load: 21.18
(N, temperature: 230 ° C.): 10 g / 10 minutes ・ Molten resin temperature: 220 ° C. ・ Mold temperature: 40 ° C. ・ Injection time: 5 seconds ・ Gas injection timing: 4 seconds later (from the start of injection) ・ Gas injection time: 2.5 seconds ・ Injection gas pressure: 10 MPa ・ Gas holding time after stopping injection: 20 seconds ・ Depressurization time: 10 seconds ・ Cooling time: 40 seconds The spillover chamber is used for molding using the molding die of the present invention. A stable and continuous production was possible without swelling or bursting of the hollow molded product (non-product part) corresponding to the above.

On the other hand, in the case where the die is not formed at the entrance of the spillover chamber and the outflow path is connected at right angles to the spillover chamber, a hollow molded product (non-product part) corresponding to the spillover chamber is used. ) Caused swelling, making it difficult to release the mold, and a phenomenon was observed in which a loud sound was frequently generated and burst. For this reason, it is necessary to interrupt the molding each time and clean the inside of the mold, which is extremely poor in stability and mass productivity. Also, due to the swelling of non-product parts,
Demolding became unstable, and troubles that the take-out robot missed were often observed.

[0044]

According to the present invention, the molten resin is injected, filled, filled, and the mold surface is reliably transferred. Then, a gas is injected into the molten resin, and the molten resin in the product cavity of the mold is injected. Of the product is expelled into the spillover chamber outside the product cavity, and a desired hollow portion can be formed with a desired size and good appearance. Therefore, the obtained hollow molded product is completely filled by injection filling of the molten resin, there is no sink mark on the surface of the molded product, no flow pattern of the resin, etc., and fine irregularities on the mold surface are reliably transferred, and the appearance is excellent. Things. Further, even when the amount of ejection to the spillover chamber is relatively large and the cooling of the molten resin tends to be delayed, the entire hollow portion after cooling can be completely depressurized, which corresponds to the spillover chamber ( The occurrence of abnormalities such as swelling and bursting of the non-product part) can be eliminated. Therefore, it is possible to prevent mold release abnormalities, damage to the molding die due to debris due to rupture, and defective appearance of the product. In addition, productivity is remarkably improved because the mold life, the cooling time is reduced, and there is no molding abnormality. Therefore, it is easy to form a large hollow molded product in which the appearance is particularly important, and it is expected that its application field will be greatly expanded.

[Brief description of the drawings]

FIG. 1 is a conceptual sectional explanatory view for explaining a molding procedure of a method for molding a hollow molded article of the present invention.

FIG. 2 is an enlarged sectional view of a spillover chamber, which is a main part of a molding die.

FIG. 3 is a plan view and a front view of an instrument panel formed by a forming method according to an embodiment.

[Explanation of symbols]

 1: Molding mold 2: Fixed mold 3: Movable mold 4: Product cavity 7: Outflow path 8: Portion to spillover chamber 9: Spillover chamber 10: Outflow path opening / closing mechanism 11: Gas injection (depressurization) mechanism 12: Molten resin 13: Hollow part 14: Hollow molded article (product part) 15: Hollow molded article (non-product part) 22: Hollow part 23: High pressure confined hollow part 30: Instrument panel 31: Gas channel 32: Gas injection position

Claims (6)

[Claims] 1. A molten thermoplastic resin is injected into a product cavity of a molding die, and after complete filling, a gas is injected into the molten resin so that a part of the molten thermoplastic resin in the product cavity is discharged. A method of molding a hollow molded article which drives out to a spillover chamber through and forms a hollow portion,
A method of molding a hollow molded product, comprising using a mold having a shape in which a cross-sectional area of an entrance portion of a flow passage into a spillover chamber is gradually increased. 2. The method of molding a hollow molded article according to claim 1, wherein the shape that gradually expands is formed so that a hollow portion communicating between the outflow passage and the spillover chamber after molding is not closed. 3. The method according to claim 1, wherein a hollow portion is formed by forming a gas channel in a thick portion of the molded product. 4. The outflow path is provided with an opening / closing mechanism.
The method for molding a hollow molded article according to any one of claims 1 to 3. 5. A product cavity of a molding die and a spillover chamber communicated from the product cavity via an outflow passage, wherein a cross-sectional area of an entrance portion of the outflow passage to the spillover chamber is formed in a shape that gradually expands. An injection molding die, characterized in that: 6. The outflow path is provided with an opening / closing mechanism.
2. The injection mold according to 1.