JPH03286814A - Hollow molded body and its manufacture - Google Patents

Abstract

PURPOSE:To eliminate peeling and damage and increase the strength by forming an integral injection molded body provided with a plurality of hollow sections parted by partitions. CONSTITUTION:An injection nozzle 5 is brought into contact with a sprue 12 of a closed mold 6, and a part of molten resin 7 is injected out of two resin injection holes 9 or more. A part of required molten resin 7 is injected into a cavity 11, and then a hollow section forming fluid is forced in from two or more fluid forcing inlets 10 together with residual molten resin, and a plurality of hollow sections 2 provided with partitions 3 among themselves are formed. Cooling and solidifying of molten resin 7 are carried out in the state of retaining the pressure of hollow section forming fluid in the mold 6. Discharge of the hollow section forming fluid is carried out after cooling and solidifying the molten resin 7, and for instance, the hollow section forming fluid in the mold 6 is discharged through a fluid forcing inlet 10 of an injection nozzle 8, while retaining the sealed state between the resin injection hole 9 of the injection nozzle 5 and the mold 6 and also between the fluid forcing inlet 10. The mold 6 is opened and a hollow molded body 1 is released after discharging the hollow section forming fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a large-sized hollow molded body having a large hollow portion and a method for manufacturing the same. For example, in addition to automobile parts such as air spoilers, bumpers, dash boards, console boxes, jet nocks, and glossy base shells, we also manufacture surfboards for fishing, as well as office drawers, chairs, This invention relates to a hollow molded body used as a bench component, etc., and a method for manufacturing the same.

[Prior Art] Conventionally, the following types of molded bodies that are large and have large hollow portions as described above and methods for manufacturing the same have been known.

(1) Joined product and joining method A hollow molded product in which a set of two molded products are molded and joined by adhesive or the like, and a method for manufacturing the same.

(2) Blow molded object and blow molding method A hollow molded object formed by sandwiching a tube-shaped resin between molds and pressurizing gas into the tube-shaped resin, and a method for manufacturing the same.

(3) Gas injection molded product and gas injection molding method By injecting a pressurized gas into the cavity after injecting a smaller amount of molten resin than the amount that fills the cavity, or by pressurizing the pressurized gas together with the molten resin. Molded hollow molded body and its manufacturing method (Japanese Patent Publication No. 14968/1983).

[Problems to be Solved by the Invention] However, the following problems remain with the above-mentioned conventional hollow molded body and its manufacturing method.

In the case of bonded products and bonding methods, the presence of a bonded portion not only causes a deterioration in appearance, but also has a problem in that the bonded portion tends to peel off during use because the bonded portion has poor strength. Further, not only is a joining process required in addition to the molding process, but also steps are likely to occur at the joint, and post-processing is required to correct this, resulting in poor productivity.

In the case of blow-molded bodies and blow-molding methods, the strength of the pinch-off fused portion is low, so there is a problem that this portion is easily damaged. In addition, since appearance defects such as pinholes and green lines are unavoidable, in applications where appearance is important, time-consuming post-processing such as polishing is required, which poses the problem of significantly decreasing productivity.

In the case of gas injection molded products and gas injection molding methods, when large and large hollow parts are formed, the strength of the surfaces facing each other across the hollow part tends to be insufficient, and there is a problem that the parts are easily deformed or damaged. .

[Means for Solving the Problems] In order to solve the above problems, in the invention of claim 1, as shown in FIGS. 1 and 2, a plurality of hollow portions partitioned by partition walls 3 are provided. 2 is an integrally molded injection molded body.

In addition, in the invention as claimed in claim 2, as shown in FIG. 3, a measure is taken in which the molten resin and the hollow molding fluid are press-fitted into the cavity 11 from a plurality of locations.

The present invention will be further explained below.

The volume ratio of the hollow part refers to the proportion of the volume of the hollow part in the total volume of the hollow molded body including the plurality of hollow parts 2, and the volume ratio of the hollow part is preferably 5 to 50% of the total volume of the hollow molded body. .

Next, the molding method of the present invention will be explained.

First, as shown in FIG. 3(a), the injection nozzle 5 is pressed against the sprue 12 of the closed mold 6, and a portion of the molten resin 7 is injected from two or more resin injection ports 9. The total injection amount of the molten resin 7 necessary to mold the molded body is set to be an amount insufficient to fill the cavity 11.

The molten resin may be injection moldable thermoplastic resins, thermoplastic elastomers, thermosetting resins, or blends of these with conventionally known additives and fillers; Blends with conventionally known additives, stabilizers, fillers, and reinforcing materials such as glass fibers are preferred.

The injection conditions for the above molten resin are the same as those for general injection molding. The injection of this molten resin can be either the injection of a single resin (non-foaming or foaming) or the injection of multi-component resins (non-foaming only, foaming only or non-foaming and foaming or Either composite injection (a combination of the same type of resin or a combination of different types of resin) may be used.

After injecting a part of the necessary molten resin 7 into the cavity 1, the remaining molten resin is injected and the hollow part forming fluid is compressed from two or more fluid pressure inlets 10, and a partition wall 3 is formed between the hollow parts 2. A plurality of hollow portions 2 are formed. As shown in FIG. 3(b), the injection of the molding fluid into the hollow part is carried out by incorporating a fluid nozzle 8 into the injection nozzle 5, bringing the injection nozzle 5 into close contact with the sprue 12, and then passing it through the resin injection port 10. It can be made into the sprue 12 of the mold 6. Alternatively, for example, as shown in FIG. 4, a fluid nozzle 8 can be provided separately from the injection nozzle 5, and this can be brought into close contact with the receiving part 13 of the mold 6, so that the fluid nozzle 8 can be inserted directly into the cavity 11.

As the hollow part molding fluid, for example, nitrogen, carbon dioxide, air, etc., are harmless and can be used under the molding temperature and injection pressure. ! Generally, a gas that does not oxidize is used, but it is also possible to use a solution or oligomer that is incompatible with the molten resin.

As shown in FIG. 3(c), the molten resin 7 is cooled and solidified while the pressure of the hollow molding fluid in the mold 6 is maintained. That is, the injection nozzle 5 is closely attached to the sprue 12, and when a separate fluid nozzle 8 is provided as shown in FIG.
Further, the fluid nozzle 8 is held in close contact with the portion 13. After the molten resin 7 is cooled and solidified, the hollow molding fluid is discharged, for example, by the following method.

As shown in FIG. 3(d), between the resin injection port 9 of the injection nozzle 5 and the mold 6, and the fluid pressure inlet lO of the fluid nozzle 8.
The molding fluid in the hollow part of the mold 6 is discharged through the fluid pressure inlet 10 while maintaining the sealing state between the mold 6 and the mold 6.

That is, the injection nozzle 5 containing the fluid nozzle 8 and the sprue 12, or the fluid nozzle 8 and the receiving part 13 maintain the same state as when the fluid was press-fitted into the hollow part and when it was cooled and solidified. While preventing the hollow molding fluid from being directly released into the atmosphere from the mold 6 due to the nozzle 5 separating from the sprue 12 or the fluid nozzle 8 separating from the receiver 13, 5 is carried out through a fluid pressure inlet 10 of a fluid nozzle 8 which is separate from the fluid nozzle 8.

Furthermore, the fluid discharged through the fluid pressure inlet IO may be released into the atmosphere or may be collected in a collection container and reused. When performing recovery, there may be two or more recovery containers, and each recovery container may be sequentially switched to recover at different pressures. In addition, during the injection of the hollow molding fluid, the collected hollow molding fluid is recompressed by the pressure booster 17 (for example, a multi-stage reciprocating compression cylinder, etc.), and in order to reuse the hollow molding fluid, the recovery container is moved into the hollow molding fluid. It is preferable to connect it to the suction side of the pressure booster 17.

After the hollow molding fluid is discharged, as shown in FIG. 3(e), the mold 6 is opened and the hollow molded body 1 is taken out. The process may be performed while they are in pressure contact with each other, or may be performed after separating both from the mold 6.

If both are pressed against the mold 6 and taken out,
If the mold 6 is closed and the injection process is performed again, and both are removed from the mold 6, the mold 6 is closed and both are brought into pressure contact with the mold 6 before or after that, and then the injection process is resumed. will return to.

[Function] In the present invention as claimed in claim 1, since it is an integrally molded injection molded product that does not require joining or fusing after molding, there is no peeling or damage of the part and it has excellent strength. .

In addition, the adjacent parts between the plurality of hollow parts 2 that make up the large hollow part of the molded product are partition walls 3 that cross the opposing surfaces with the hollow parts in between, so the rigidity of the molded product is improved. do.

In the second aspect of the present invention, not only the joining step is not required, but also post-processing of the joining portion is not required, so that the number of manufacturing steps can be reduced.

Furthermore, since a good appearance without via holes or die lines can be obtained, post-processing such as polishing is not required.

[Example] The apparatus used in the example will be explained with reference to FIG.

Reference numeral 5 denotes an injection nozzle for injecting the molten resin 7 by means of a screw 14, and is connected to the mold 6 at two points.

Further, it has a resin injection port 9 at its tip, and a fluid nozzle 8 is built inside the resin injection port 9. This injection nozzle 5 is connected to the mold 6
When it moves forward and its tip comes into pressure contact with the sprue 12 of the mold 6, the gap between the resin injection port 9 and the mold 6 and between the mold 6 and the fluid pressure inlet 10 of the fluid nozzle 8 is It is supposed to be sealed at the same time.

A fluid nozzle 8 built into the injection nozzle 5 is arranged around the fluid nozzle 8 with a gap through which the molten resin 7 passes. The hollow molding fluid is press-fitted into the mold 6 through the resin injection port 9.

A pressure booster 17 consisting of a cylinder 15 and a piston 16 is connected to the fluid nozzle 8 . Further, a fluid source 19 is connected to this pressure increase device 17 via an on-off valve 18 and a check valve 20.

During the above-described fluid injection, the fluid supplied from the fluid source 19 enters the pressure increasing device 17, is pressurized by the movement of the piston 16, and is then sent to the mold 6. Furthermore, when discharging the fluid as described above, the piston 16 of the pressure booster 17 retreats and the hollow molded body 1 formed in the mold 6
The pressurized fluid in the piston 1 is input into the piston 1, and when the next fluid is pressurized, after receiving the insufficient fluid supply from the fluid source 19, the piston 1
6 advances to inject pressurized fluid.

Note that a second pressure increase device (not shown) is provided between the pressure increase device 17 and the check valve 18 in front of the fluid source 19, so that the piston 16 of the pressure increase device F retreats and molds into the mold 6. After recovering the pressurized fluid inside the hollow molded body, the piston of the second pressurizing device can be similarly retracted to lower the fluid pressure at the time of recovery.

Example 1 Using the equipment shown in Fig. 5, a length of 1200 m+ and a width of 1
50 sm+, thickness 15-35ED! A large rectangular hollow molded body 1 was injection molded.

As a synthetic resin, polystyrene ["Styron #47
0J manufactured by Asahi Kasei Kogyo Co., Ltd. was heated and plasticized at 200°C,
The tip of the injection nozzle 5 is brought into close contact with the sprue 12 of the mold 6, and 2000 g of the molten resin 7 is injected into the mold 6, and then nitrogen is injected as a pressurized fluid into the mold 6 at a pressure of 150 kg/cm. did.

After the injection nozzle 5 is maintained as it is and the molten resin 7 in the mold 6 is cooled and solidified, the piston 16 of the pressure booster 17 is retreated to discharge the pressurized fluid in the mold 6. Ta. Thereafter, the mold 6 was opened and the hollow molded body 1 was taken out.

The dimensions of the hollow molded body 1 are length 1190 mm and width 149 mm.
IIm and a thickness of 15 to 35 mm, which was the expected size, and the surface had a smooth appearance with no sink marks.

Further, the number of hollow parts 2 was two, and the volume ratio of the two hollow parts 2 was 35%.

[Effects of the Invention] Since the structure has a plurality of partition walls crossing opposing surfaces of the molded object with a large hollow portion in between, the molded object has excellent strength and eliminates deformation such as sagging of the opposing surfaces of the molded object.

Furthermore, as the rigidity of the molded body is improved, the wall pressure of the molded body can be reduced, resulting in weight reduction.

Since the injection molded body is integrally formed, a hollow molded body with excellent dimensional accuracy can be easily obtained.

Since a hollow molded body with a good surface condition free of joints, fused parts, pinholes, die lines, etc. can be obtained, the labor of finishing processing etc. can be saved and productivity can be improved.

[Brief explanation of drawings]

FIG. 1 is an overall view of the hollow molded body. FIG. 2 is a sectional view taken along line AA' of the hollow molded body. FIGS. 3(a) to 3(e) are explanatory diagrams of the molding method of the present invention. FIG. 4 is an explanatory diagram when an injection nozzle and a fluid nozzle are provided separately. FIG. 5 is an explanatory diagram of the apparatus used in the example. i-m-hollow molded body 3-m-partition wall 5-m-injection nozzle 7--molten resin 9-m-resin injection port 11-m-cavity 13--one receiving part 15--cylinder 17- --- Boosting device 19 -- Fluid source --- --- --- --- --- o--- 2--- 4--- 6--- 0--- Hollow part fluid press-in place mold Fluid nozzle fluid pressure inlet spruce screw piston open/close valve check valve Keisuke Watanabe

Claims (1)

[Scope of Claims] 1) A hollow molded article characterized in that it is an integrally molded injection molded article having a plurality of hollow parts partitioned by partition walls. 2) A method for manufacturing a hollow injection molded article, which comprises pressurizing molten resin and hollow molding fluid into the cavity from multiple locations.