JP2835976B2 - Manufacturing method of hollow molded body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a large-sized hollow molded article having a large hollow portion. More specifically, in addition to automobile parts such as air spoilers, bumpers, dashboards, console boxes, seat backs, rear parcel shells, etc., they are also used as fishing buoys, surf boards, and office drawers, chairs, bench parts, etc. The present invention relates to a method for producing a hollow molded article.

[Prior Art] Conventionally, the following method is known as a method for producing a molded article having a large and large hollow portion as described above.

(1) Joined article and joining method A method for manufacturing a hollow molded article in which a pair of molded articles is molded and joined by bonding or the like.

(2) Blow Molded Body and Blow Molding Method A method for producing a hollow molded body in which a tubular resin is sandwiched between molds and a gas is press-fitted into the tubular resin.

(3) Gas injection molding and gas injection molding method By injecting a pressurized gas into a cavity and injecting a pressurized gas after injection of a smaller amount of molten resin than an amount that fills the cavity, or by injecting a pressurized gas together with the molten resin. Manufacturing method of molded hollow molded article (Japanese Patent Publication No. 57-14968).

[Problems to be Solved by the Invention] However, the following problems remain in the conventional method for producing a hollow molded article.

In the case of the joining method, not only the presence of the joined portion causes the appearance to be deteriorated, but also since the joined portion is inferior in strength, there is a problem that the joint is liable to peel off during use. In addition to the need for a joining step in addition to the molding step, there is also a problem that productivity is poor because a step is likely to occur in the joined portion and post-processing is required for this correction.

In the case of the blow molding method, there is a problem that the strength of the pinch-off fusion-bonded portion is low, so that the portion is easily damaged. In addition, since appearance defects such as pinholes and die lines are unavoidable, in applications where importance is attached to appearance, complicated post-processing such as polishing is required, and there is a problem that productivity is significantly deteriorated.

In the case of the gas injection molding method, if a large and large hollow portion is formed, there is a problem that the strength of the surfaces opposed to each other across the hollow portion tends to be insufficient, and the portion is easily deformed or damaged.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a method in which a molten resin and a hollow part forming fluid are pressed into a cavity from a plurality of positions,
In manufacturing an integrally molded hollow molded body having a plurality of hollow portions separated by partition walls, after injecting a part of the required molten resin into the cavity, the hollow portion forming fluid is injected together with the injection of the remaining molten resin. And a method for producing a hollow molded article characterized by press-fitting.

[Examples and Functions] The present invention will be further described below.

The hollow molded article 1 manufactured by the present invention has a plurality of hollow portions 2 partitioned by partition walls 3, as shown in FIGS. 1 and 2, for example. The volume ratio of the hollow part 2 refers to the ratio of the volume of the hollow part 2 to the total volume of the hollow molded body 1 including the plurality of hollow parts 2. 5 to 50% is good. Incidentally, reference numeral 4 in FIG. 1 denotes a press-in place of the fluid.

First, as shown in FIG.
The injection nozzle 5 is pressed into contact with the sprue 12, and a part of the molten resin 7 is injected from two or more resin injection ports 9. The total injection amount of the molten resin 7 required for molding the molded body is determined by the cavity
Insufficient amount to satisfy 11.

As the molten resin, a thermoplastic resin that can be injection-molded, a thermoplastic elastomer, a thermosetting resin, any of these and a compound of a conventionally known additive and a filler may be used, but a thermoplastic resin, a thermoplastic elastomer, and And a combination of a conventionally known additive, stabilizer, filler, and reinforcing material such as glass fiber.

The injection conditions of the molten resin are the same as in the case of general injection molding. The injection of the molten resin may be performed by injection of a single resin (non-foamable or foamable) or multi-component resin (non-foamable only, foamable only or non-foamable and foamable) conventionally known as a sandwich molding method. (Combination of the same or different resins).

After injecting a part of the necessary molten resin 7 into the cavity 11, a hollow molding fluid is injected from two or more fluid pressure inlets 10 together with the injection of the remaining molten resin, and the partition wall 3 is inserted between the hollow portions 2.
Are formed in the molten resin 7 in the cavities 11 having a plurality of cavities 11. Each hollow portion 2 is separately enlarged, and the molten resin 7 is left between the plurality of hollow portions 2 to form the partition walls 3. The volume ratio of the hollow portion 2 can be adjusted by adjusting the injection amount of a part of the molten resin performed in advance and the injection amount of the remaining molten resin thereafter.

As shown in FIG. 3 (b), the injection molding of the hollow part forming fluid is performed by incorporating the fluid nozzle 8 in the injection nozzle 5, bringing the injection nozzle 5 into close contact with the sprue 12, and It can be performed into the sprue 12 of the mold 6. In addition, for example, as shown in FIG.
This can be provided separately, and can be directly brought into the cavity 11 by closely contacting the receiving portion 13 of the mold 6.

As the hollow molding fluid, a gas that is harmless and does not liquefy at the molding temperature and injection pressure, such as nitrogen, carbon dioxide gas, and air, is generally used, but a solution or oligomer that is not compatible with the molten resin is used. You can also.

As shown in FIG. 3 (c), the cooling and solidification of the molten resin 7 is performed in a state where the pressure of the above-mentioned hollow portion forming fluid in the mold 6 is maintained. That is, the injection nozzle 5 is in close contact with the sprue 12, and when a separate fluid nozzle 8 is provided as shown in FIG. After the molten resin 7 is cooled and solidified, the hollow portion forming 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 10 of the fluid nozzle 8.
The molding fluid in the mold 6 is discharged through the fluid pressure inlet 10 while maintaining the sealed state between the mold and the mold.

That is, the injection nozzle 5 and the sprue 12 containing the fluid nozzle 8 or the fluid nozzle 8 and the receiving portion 13 maintain the same state as at the time of the hollow part forming fluid press-fitting and cooling and solidification. 5 prevents the molding fluid from being released into the atmosphere directly from the mold 6 by separating the sprue 12 from the sprue 12 and the fluid nozzle 8 from the receiving portion 13, while preventing the molding fluid from being built into the injection nozzle 5 or Is performed through a fluid pressure inlet 10 of a separate fluid nozzle 8.

Further, the fluid discharged through the fluid pressure inlet 10 may be released to the atmosphere, or may be collected in a collection container and reused. In the case of performing the collection, the number of the collection containers may be two or more, and each of the collection containers may be sequentially switched at a different pressure to perform the collection. Also, during the injection of the hollow part forming fluid, the collected hollow part forming fluid is recompressed by the pressurizing device 17 (for example, a multi-stage reciprocating compression cylinder or the like), and the collected container is placed in the hollow part forming fluid for reuse. Is preferably connected to the suction side of the booster 17.

After the discharge of the hollow part forming fluid, as shown in FIG. 3 (e), the mold 6 is opened to take out the hollow molded body 1, and the take-out is performed through the injection nozzle 5 and the fluid nozzle 8 through the mold 6. The pressing may be performed while the pressure is kept in contact with the mold 6 or after the two are separated from the mold 6. When taking out with both being pressed against the mold 6, the mold 6 is closed and the process returns to the injection step again. When taking both of them away from the mold 6, the mold 6 is closed and Before or after the two are pressed against the mold 6, the process returns to the injection step again.

Next, an apparatus used in the manufacturing method of the present invention will be described with reference to FIG.

Reference numeral 5 denotes an injection nozzle for injecting the molten resin 7 by the screw 14 and connected to the mold 6 at two points. Further, a resin injection port 9 is provided at the tip, and a fluid nozzle 8 is built in the resin injection port 9. The injection nozzle 5 can advance and retreat with respect to the mold 6. When the tip is pressed against the sprue 12 of the mold 6, the injection nozzle 5 moves between the resin injection port 9 and the mold 6 and between the mold 6 and the fluid. The space between the fluid pressure inlets 10 of the nozzle 8 is simultaneously sealed.

The fluid nozzle 8 built in the injection nozzle 5 is arranged with a gap around which the molten resin 7 passes,
At the time of press-fitting the hollow portion forming fluid described above, the hollow portion forming fluid is press-fitted into the mold 6 through the resin injection port 9 from the fluid pressure inlet 10 provided at the tip thereof.

The fluid nozzle 8 is connected to a pressure increasing device 17 including a cylinder 15 and a piston 16. Also, this booster
17 has a fluid source 19 via an on-off valve 18 and a check valve 20.
Is connected.

At the time of the above-described fluid injection, the fluid supplied from the fluid source 19 enters the pressurizing device 17, is pressurized by the advance of the piston 16, and is then sent out to the mold 6. At the time of discharging the fluid, the piston 16
Retreats to receive the pressurized fluid in the hollow molded body 1 formed in the mold 6, and at the time of the next fluid injection, receives the insufficient fluid from the fluid source 19, and then moves the piston 16 forward. To press-fit the pressurized fluid.

In addition, a second pressure increasing device (not shown) is provided between the pressure increasing device 17 and the check valve 18 in front of the fluid source 19, and the pressure increasing device 17 is provided.
After the piston 16 moves backward to collect the pressurized fluid in the hollow molded body formed in the mold 6, the piston of the second pressure increasing device is similarly retracted to lower the fluid pressure at the time of collection. You can also.

[Effects of the Invention] The present invention is as described above, and is a hollow molded body having a partition wall between a plurality of hollow parts. Therefore, even if the volume ratio of the hollow part of the obtained hollow molded body is increased. A hollow molded article excellent in strength can be obtained. Also, joints,
Since the hollow molded body can be manufactured as an integrated injection-molded product having a good surface condition without a fused portion pinhole or a die line, labor such as finishing can be omitted, and productivity can be improved. Things.

[Brief description of the drawings]

FIG. 1 is an overall view of a hollow molded body. FIG. 2 is an AA ′ cross-sectional view of the hollow molded body. 3 (a) to 3 (e) are explanatory views of the molding method of the present invention. FIG. 4 is an explanatory diagram of a case where an injection nozzle and a fluid nozzle are separately provided. FIG. 5 is an explanatory view of an apparatus used for the manufacturing method of the present invention. DESCRIPTION OF SYMBOLS 1 ... Hollow molded object, 2 ... Hollow part 3 ... Partition wall, 4 ... Fluid press-in place 5 ... Injection nozzle, 6 ... Mold 7 ... Molten resin, 8 ... Fluid nozzle 9 ... Resin Injection port, 10 Fluid pressure inlet 11 Gavity, 12 Sprue 13 Receptor, 14 Screw 15 Cylinder, 16 Piston 17 Pressure booster, 18 Opening / closing valve 19 ... fluid source, 20 ... check valve

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-108510 (JP, A) JP-A-3-268913 (JP, A) JP-A-2-295714 (JP, A) 505851 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 45/00-45/17 B29C 45/46-45/84

Claims (1)

(57) [Claims] When a molten resin and a hollow part forming fluid are press-fitted from a plurality of locations into a cavity to produce an integrally formed hollow molded body having a plurality of hollow parts partitioned by partition walls, the cavity is formed into a cavity. A method for manufacturing a hollow molded body, comprising injecting a part of a required molten resin, and then press-in a hollow molding fluid together with injection of the remaining molten resin.