JP3208240B2 - Injection blow molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection hollow molding method for molding a hollow molded product by injecting a pressurized fluid such as air or nitrogen gas into a molten resin injected into a mold cavity. It is about.

[0002]

2. Description of the Related Art Conventionally, the following method has been proposed as this kind of injection blow molding method.

(A) As shown in FIG. 6A, a slide core 104 is projected into a cavity 103 of a clamped mold 101, 102, and an insufficient amount of the slide core 104 fills the cavity 103. After injecting the molten resin, as shown in FIG. 6B, a gas G is injected and the slide core 104 is retracted before the molten resin is solidified to form a hollow portion. (C) A method of molding a hollow molded article (see JP-A-1-168425).

(B) As shown in FIG. 7 (a), a molten resin 208 is injected from an injection nozzle 206 into a cavity 203 of a clamped mold 201, 202 to form a cavity 20.
3 is filled with the molten resin 208, and then a pressurized fluid is pressed into the interior of the molten resin 208 from the nozzle 207, as shown in FIG.
(B), a hollow part 209 is formed, and when the hollow part 209 is formed, the molten resin 20 in the cavity 203 is formed.
8 is pushed into the auxiliary chamber 204 which is communicated with the cavity 203 by the communication passage 205 so as to be shown in FIG.
(Japanese Patent Laid-Open No. 3-1)
No. 21820).

[0005]

However, of the above prior arts, the method (a) involves injecting an insufficient amount of molten resin into the cavity and then injecting gas into the cavity. When the hollow core is formed in the molten resin by retreating the slide core, before the molten resin expands to the entire cavity, before the molten resin flows by the pressure of the gas pressed into the molten resin, There is a problem that a pinhole is generated at the tip portion, and at the stage when the pinhole is generated, the expansion of the molten resin is stopped to cause a molding failure.

In (b), since the hollow portion is formed by extruding the molten resin into the auxiliary chamber, the gas pressure must be set to a high pressure, and the fluidity of the molten resin is increased. Molding must be carried out at high temperatures in order to be kept good. For this reason, the gas cannot flow into the molten resin extruded into the auxiliary chamber, and the hollow rate of the molded product itself cannot be increased due to the occurrence of a hollow portion in this portion. Therefore, there is a problem that the molding cycle becomes long.

The present invention has been made in view of the above-mentioned problems of the prior art, and is a hollow molded article which can increase the hollow ratio and does not cause molding failure due to generation of pinholes. It is an object of the present invention to realize a manufacturing method.

[0008]

In order to achieve the above object, an injection blow molding method according to the present invention is directed to a hollow double molding method comprising a frame portion and a double wall body surrounded by the frame portion. A cavity for regulating the outer surface of the hollow molded article having a wall structure, a frame-shaped portion forming portion for forming the frame-shaped portion, and a double-walled body forming portion for forming the double-walled body. Using a mold having a slide member capable of moving back and forth into the cavity for partitioning, moving the slide member into the cavity of the mold with the mold clamped, and forming the frame-shaped portion forming portion and the double wall body After forming a gap between the part forming part and the molten resin, the molten resin is injected into the frame part forming part to fill the same and press-fit a pressurized fluid into the inside of the molten resin. To form a small hollow, and pressurized fluid Rui while injecting replenish molten resin to further the frame-like portion forming part together with the press-fitting of the pressurized fluid,
By retreating the slide member, the compartment in the cavity is released, and the small hollow portion is enlarged to form the hollow molded product along the entire cavity.

Further, the slide member may be formed of an annular body disposed between the frame-shaped portion forming portion and the double wall body portion forming portion, or the slide member may be disposed inside the annular body. And a slide core for making the cavity volume of the double wall body forming portion variable.

[0010]

Since the molten resin is injected into the divided frame-shaped portion at the initial stage, the molten resin moves to a portion far from the injection port. The pressurized fluid is filled into the frame-shaped portion forming portion because the pressurized fluid is pressed into the molten resin filled in the frame-shaped portion forming portion in the cavity defined by moving the slide core into the cavity. After forming the small hollow portion inside the molten resin, when the slide member is retracted to release the partition in the cavity and expand the small hollow portion to a shape along the entire cavity, the pressurized fluid Is uniformly applied to the entire inner wall surface of the small hollow portion, and there is no possibility that pinholes are generated. In addition, since the small hollow portion inside the molten resin is enlarged in the cavity in which the compartments are released as described above, molding of a hollow molded article having a high hollow ratio without maintaining the molten resin at an excessively high temperature can be performed. Since it is possible, the time required for the cooling step is short.

[0011]

An embodiment of the present invention will be described with reference to the drawings.

First, an example of a hollow molded product as a door member constituting a housing of an electric device manufactured by the injection blow molding method of the present invention will be described.

As shown in FIGS. 1 and 2, the hollow molded article 1 has one wall 1a and the other wall 1b (shown in FIG. 3) opposed to each other at an interval, and the periphery of both walls is an end wall. 1c
A double wall body 8a, 8b having a hollow double wall structure closed by a double wall body 8a. Surrounding frame 7
Are integrally formed. Needless to say, the double-walled body can be made of only a flat body or a bent body, or three or more body parts can be arranged side by side.

The frame-like portion 7 of the wall 1a has a pair of plate-like hinge portions 2, which are convex portions provided on the wall surface, a plate-like bracket portion 3, and a concave portion which is a concave portion provided on the wall surface. In particular, the plate-shaped bracket portion 3 and the recessed portion 4 are provided on the enlarged portion 7a of the frame-shaped portion 7 protruding toward the one double wall body 8a side. The frame portion 7 and the double-walled body portion 8
A continuous or partially cut-out intermittent boundary portion 5 is formed between a and 8b.

(First Embodiment) As shown in FIG. 3A, one mold 11 and the other mold 12 are clamped and one mold 11 is closed.
The slide member 13 which is movable forward and backward into the cavity 15 slidably fitted in the guide hole 11d is advanced toward the other mold 12 by driving means (not shown),
By forming a gap portion 14 between the tip end surface of the slide member 13 and the cavity surface 12a of the other mold 12 to prevent intrusion of the molten resin 16, the inside of the cavity 15 forms a frame-like portion 7. It is divided into a double wall body forming part 15b which forms the double wall body parts 8a and 8b (however, the other double wall body part 8b is not shown).

After the above, recess 1 for plate-like hinge portion
The molten resin 16 is injected into the frame-shaped portion forming portion 15a including the recesses 1c and the plate-shaped bracket portion recessed portions 13c so that the molten resin 16 is filled in the frame-shaped portion forming portion 15a and the leading end thereof flows into the gap portion 14 slightly. An injection nozzle 9 (shown in FIG. 2) is brought into contact with 9a to perform injection. Thereby, the plate-shaped hinge part 2, the plate-shaped bracket part 3, and the concave part 4 are formed.

After the above, as shown in FIG. 3B, the pressurized fluid pressurizing nozzle 10 is inserted into the molten resin 16 filled in the frame-shaped portion forming portion 15a through the press-in hole 10a.
(Shown in FIG. 2) pressurizes the pressurized fluid.

A small amount of the molten resin 26 extruded by the start of the pressurization of the pressurized fluid flows into the gap 14, and its tip advances toward the center of the cavity 15 to form a small hollow portion 17. .

After the above, as shown in FIG. 3 (c), while continuously pressurizing the pressurized fluid or while additionally injecting and replenishing the molten resin 16 with the pressurization of the pressurized fluid, the slide member 13 is moved to its front end surface. Is retreated so as to be flush with the cavity surface 11a of one of the molds 11 to release the compartment in the cavity 15, and to enlarge the small hollow portion 17 to form a hollow having a hollow portion 1d shaped along the cavity 15. The molded article 1 is molded. At this time, the molten resin 16
Has flowed into the gap 14 in advance, so that the cavity 1
5, the time required for the small hollow portion 17 to expand toward the center portion of the small hollow portion 17 to form a hollow portion 1d by merging at the center portion and the flow distance are shortened, so that the molten resin 16 cannot be maintained at a high temperature. Molded product of uniform thickness with high hollow ratio
Can be molded. Note that a rib 1f is formed at a portion where the molten resin 16 is united.

After the above, the hollow molded article 1 is cooled in a mold, then opened and removed.

Usually, a pressurized fluid has excellent flow characteristics, and its flow characteristics are not substantially changed by a change in temperature.
On the other hand, molten resin is inferior in flow characteristics to pressurized fluid,
Also, the flow characteristics are extremely impaired due to the decrease in temperature.
Therefore, when the temperature of the surface resin portion at the front end in the flow direction of the injected molten resin is high, the pressurized fluid breaks through the portion and pinholes are generated. According to an experiment conducted by the present inventor, in the case of the first embodiment, it has been found that pinholes can be prevented from being generated due to a decrease in the temperature of the front surface resin portion of the molten resin 16 which has flowed into the gap portion 14 in advance.

In this connection, a boundary portion 5 as shown in FIG. 2 is formed in the gap portion 14, and a plurality of portions of the boundary portion 5 are pierced by the pressure of the pressurized fluid that is press-fitted. Each of the passage portions 6 is opened, and the pressure of the pressurized fluid acts on the entire inner wall of the hollow portion.

(Second Embodiment) As shown in FIG. 4A, one mold 21 and the other mold 22 are clamped and one mold 21 is closed.
The slide member 23 which can slide forward and backward into the cavity 25 which is slidably fitted in the guide hole 21d is advanced toward the other mold 22 by driving means (not shown),
At the same time, a gap 24 is formed between the tip end surface of the slide member 23 and the cavity surface 22a of the other mold 22 to prevent the molten resin 26 from entering, and at the same time, the slide core slidably fitted into the slide member 23. 28 is advanced toward the other mold 22 by driving means (not shown), and a space slightly larger than the gap 24 is formed between the tip surface 28a of the slide core 28 and the cavity surface 22a of the other mold 22. Let it form.

Thus, the inside of the cavity 25 is divided into a frame-shaped portion forming portion 25a for forming the frame-shaped portion 7 and a double-wall body forming portion 25b having a variable cavity volume.

After the above, the recess 2 for the plate-shaped hinge portion
The molten resin 26 is filled in the frame-shaped portion forming portion 25a including the recesses 1c and the plate-shaped bracket portion recesses 21c, and the molten resin 26 has such an amount that the tip portion slightly flows into the gap portion 24. Is implanted in the same manner as in the first embodiment. Thereby, the plate-shaped hinge part 2, the plate-shaped bracket part 3, and the concave part 4 are formed.

After the above, as shown in FIG. 4B, a pressurized fluid is press-fitted into the molten resin 26 filled in the frame-shaped portion forming portion 25a as in the first embodiment.

A small amount of the molten resin 26 extruded when the pressurized fluid starts to be injected flows into the gap 24, and the tip of the molten resin 26 is connected to the tip surface 28a of the slide core 28 and the cavity surface 2
2a to the center of the space between
Is formed.

After the above, as shown in FIG. 4C, the slide core 28 and the slide member 23 are continuously pressed in with the pressurized fluid or while the molten resin 26 is further injected and replenished together with the pressurized fluid. Is retreated so that the front end surfaces of the two molds are flush with the cavity surface 21a of one of the molds 21 to release the compartment in the cavity 25, and the small hollow portion 27 is enlarged to form a hollow along the cavity 25. The hollow molded article 1 having the portion 1e is formed.

After the above, the hollow molded article 1 is cooled in a mold, then opened and removed.

In this embodiment, since the volume of the double-walled body forming portion 25b in the cavity 25 is variable by the slide core 28, the retreating position is slightly shifted to the inside of the cavity 25 in the above process. By changing to a projecting position or a position retracted from the cavity surface 21a, the cavity volume of the double-walled body forming portion is changed to form a hollow mold having a double-walled body having the same shape but different shapes. It is possible to mold the article.

(Third Embodiment) In this embodiment, as shown in FIG. 5, instead of the slide member 23 and the slide core 28 of the second embodiment, a projecting portion is formed on the peripheral edge of the distal end surface of the slide core 38. 38b are provided integrally, and are substantially the same as the steps from the second embodiment. Therefore, description thereof will be omitted, and portions different from the second embodiment will be described.

In this embodiment, as shown in FIG. 5A, the gap portion 34 is formed between the tip surface of the protruding portion 38b and the cavity surface 32a of the other mold 32. Further, as shown in FIG.
a is protruded into the cavity 35 when it is retracted so that a is the same as the cavity surface 31a of the one mold 31.
Is projected, so that a boundary groove 1e is formed at the boundary between the frame portion 7 of the hollow molded article 1 and the double wall body portions 8a, 8b.

In the present invention, the pressurized fluid may be nitrogen gas, air, water or a vaporizable liquid, and the resin may be ABS resin, polypropylene, polystyrene, polyethylene, modified polyphenylene oxide, polycarbonate, polyamide, polyethylene. Thermoplastic synthetic resin materials such as terephthalate, polybutylene terephthalate, and other resins having elastomeric properties can be used. In addition, a known filler, a flame retardant, a pigment, a foaming agent, and the like can be added to the above-described materials as needed.

The hollow molded product obtained by the present invention is used for electric equipment such as copying machines, computers, printers, and electronic musical instruments, housing equipment such as cabinets, wagons, desks, and partitions, and automobiles such as dashboards, seat backs, and soundproof covers. It can be used as a plate material, a frame material, and other members constituting parts.

[0035]

Since the present invention is configured as described above, it has the following effects.

Since the cavity into which the molten resin is injected is partitioned at the initial stage, the molten resin moves earlier to a portion farther from the injection port, and short molding can be prevented. In addition, since the internal pressure of the pressurized pressurized fluid acts on the entire small hollow portion formed inside the molten resin to expand the small hollow portion, pinholes may be generated in the molten resin. And good moldability.

In addition, since the molding can be performed without maintaining the molten resin at a high temperature, the time required for the cooling step is short, and the molding cycle is shortened accordingly.

Further, since the functional portion is integrally molded with the frame portion when the molten resin is injected, short molding can be prevented, and a hollow molded product having a highly accurate shape and dimensional accuracy of the functional portion can be formed. .

[Brief description of the drawings]

FIG. 1 is a perspective view of a door member showing an example of a hollow molded product manufactured by an injection blow molding method according to the present invention, as viewed from a back surface.

FIG. 2 is a plan view showing a part of the hollow molded article shown in FIG.

FIG. 3 is a schematic cross-sectional view of the mold taken along the line AA of FIG. 1, showing the steps of the first embodiment.

FIG. 4 is a schematic cross-sectional view of a mold taken along the line AA of FIG. 1, showing the steps of the second embodiment.

FIG. 5 is a schematic cross-sectional view of the mold taken along the line AA of FIG. 1, showing the steps of the third embodiment.

FIG. 6 is a schematic cross-sectional view of a mold showing steps of an example of a conventional method for manufacturing a hollow molded article.

FIG. 7 is a schematic cross-sectional view of a mold, illustrating a process of another example of the conventional method for manufacturing a hollow molded product.

[Explanation of symbols]

Reference Signs List 1 hollow molded product 1a one wall 1b other wall 1c end wall 1d hollow portion 1e boundary groove 1f rib 2 plate-shaped hinge portion 3 plate-shaped bracket portion 4 recessed portion 5 boundary portion 6 passage portion 7 frame-shaped portion 8a, 8b Double wall body 9 Injection nozzle 10 Pressurized fluid press-fit nozzle 11, 11, 31 One mold 11a, 12a, 21a, 22a, 31a, 32a
Cavity surface 12,22,32 The other mold 14,24,34 Gap portion 15,25,35 Cavity 15a, 25a, 35a Frame portion forming portion 15b, 25b, 35b Double wall body forming portion 16,26, 36 Molten resin 17, 27, 37 Small hollow part

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/37 B29C 49/00-49/80 B29D 24/00 B29L 24:00

Claims (4)

(57) [Claims] 1. A cavity for regulating the outer surface of a hollow molded product having a hollow double-wall structure having a frame-shaped portion and a double-walled body surrounded by the frame-shaped portion; Using a mold having a slide member that can be advanced and retracted into the cavity for partitioning into a frame-shaped portion forming portion that forms a shape portion and a double wall body forming portion that forms the double wall body portion, After the slide member is advanced into the cavity of the mold in which the mold is clamped, a gap is formed between the frame-shaped portion forming portion and the double-walled body portion forming portion to prevent intrusion of the molten resin, The molten resin is injected and filled into the frame-shaped portion forming portion, and a small hollow portion is formed by press-fitting a pressurized fluid into the molten resin. With the press-fitting, the molten resin is further Injection, wherein the slide member is retracted, the partition in the cavity is released, and the small hollow portion is enlarged to form the hollow molded product along the entire cavity. Hollow molding method. 2. The injection blow molding method according to claim 1, wherein the slide member is an annular body disposed between the frame-shaped portion forming portion and the double wall body portion forming portion. 3. The injection blow molding according to claim 2, wherein the slide member has a slide core for changing the cavity volume of the double wall body forming portion disposed inside the annular body. Method. 4. The frame-shaped part has a function part formed integrally therewith, and the function part is a projection or a depression provided on a wall surface. Injection blow molding method.