JP2000117818A - Method and apparatus for molding composite parison - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control a thickness ratio altering unit of each resin layer of a parison to be discharged from an annular slit of an extrusion head in a short range by extruding one molten resin to a resin supply passage, and sucking molten resin left in other resin supply passage. SOLUTION: In the molding step of a thickness ratio altering unit of a parison to be discharged from an annular slit 18 of a boundary between a rigid part and a soft part, in the molding of the rigid part, a large quantity of a molten hard resin is fed to a second resin supply passage 14 by a plunger 24, and an infinitesimal amount of a molten soft resin is fed to a first resin supply passage 13 by a plunger 20. Then, the plunger 24 starts to suck at a starting position of the altering unit of the parison, and stops at an ending position. The plunger 20 is advanced at the starting position of the altering unit of the parison, passed through the ending position of the altering unit, advanced to molding of the soft part, and a large quantity of the molten soft resin is fed to the passage 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forming a composite parison for blow molding an air duct used in, for example, an engine intake system of an automobile.

[0002]

2. Description of the Related Art Conventionally, a blow-molded air duct of this type has a single multi-layer parison having different material distributions in a longitudinal direction, for example, a laminated structure of a hard resin layer and a soft resin layer. There is known a blow molding of a parison in which a rigid portion having a high thickness ratio and a flexible portion having a high thickness ratio of a soft resin layer are formed in series in the length direction.

[0003]

However, in the above-mentioned parison, a strong internal pressure is generated in the resin remaining in each resin supply passage in the parison extrusion head, and one of the resins is discharged from the extrusion head outlet. It is difficult to quickly adjust the extrusion amount of each resin due to the so-called resin back-drawing phenomenon in which the other resin is also dragged and discharged.
The thickness ratio of the hard synthetic resin layer and the soft synthetic resin layer can be changed only gradually, and the hard resin adversely affects the flexible parts (bellows part of the duct and connecting parts at both ends) where excellent flexibility is required. On the other hand, there is a problem that the soft resin adversely affects the rigid portion to be provided with sufficient rigidity for maintaining the shape.

The present invention has been made in view of the above problems, and in forming parisons having different material distributions in the length direction while adjusting the extrusion amount of different resin materials, the resin switching is performed sharply by changing the resin. It is an object of the present invention to provide a method and an apparatus for forming a composite parison in which the wall thickness ratio of the composite parison can be sufficiently exhibited without deteriorating the quality of the material-allocated parison.

[0005]

Means for Solving the Problems The present invention has the following means to solve the above-mentioned problems.

(1) At least two types of molten resins melted in separate extruders are merged in a common extrusion head through respective resin supply paths, and are extruded from an annular slit of the extrusion head to form a single parison. A method of molding, in which each molten resin sent from the extruder is temporarily stored in each accumulator type injection machine,
In the step of adjusting the extrusion amount of each molten resin to each resin supply path by advancing each plunger, the forward movement of one plunger and the control of the suck-back operation of the other plunger corresponding to this are performed, and By extruding the resin into the resin supply path and sucking the molten resin remaining in the other resin supply path, the thickness ratio of each resin layer of the parison discharged from the annular slit of the extrusion head can be changed rapidly. A composite parison molding method.

(2) At least two annular resin supply paths communicating with the annular slits provided in the extrusion head, an accumulator type injector connected to each resin supply path, and different accumulator type injectors connected to each accumulator type injector. An extruder for supplying a molten resin, and a control device for controlling the mutual advance and suck-back operation of the plungers of the accumulator-type injection machine in accordance with the material distribution of the parison to be formed. .

[0008]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a sectional view of a composite parison according to the present invention, FIG. 2 is a sectional view showing another embodiment of the composite parison, FIG. 3 is a sectional view of an air duct in which the composite parison shown in FIG. 2 is blow-molded, and FIG. FIG. 5 is a schematic diagram illustrating an example of an apparatus in which a molding method according to the present invention is performed, and FIG. 5 is an explanatory diagram illustrating a molding state of a thickness ratio changing unit.

In FIG. 1, a parison P is a multilayer single parison in which a soft resin layer 1 and a hard resin layer 2 are partially laminated, and a thickness ratio of the hard resin layer 2 to the soft resin layer 1 is shown. The rigid portions 3 and 3 which make up a large part of the parison thickness and the flexible portions 4 and 4 where the soft resin layer 1 makes up the entire parison thickness are formed at the boundary between the two with the resin switching. Are connected alternately along the longitudinal direction via the thickness ratio changing portions 5 and 5. In this embodiment, a soft resin layer 1 made of a thermoplastic elastomer (TPE) or the like is provided in an inner layer, and a hard resin layer 2 made of an HDPE resin or a polypropylene resin is provided in an outer layer.

The switching of the resin from the rigid portion 3 to the flexible portion 4 and from the flexible portion 4 to the rigid portion 3 is sharp, and the length d of the thickness ratio changing portions 5 and 5 along the parison longitudinal direction is extremely large. And the thickness t of the parison P is 0.5, for example.
The thickness t of the parison P
Is 8 mm, the length d of the thickness ratio changing portions 5, 5 is approximately 4-1.
It is formed in a range of 2 mm.

FIG. 2 shows a parison P formed by laminating a thin hard resin layer 2 on the outside of a soft resin layer 1 constituting a large part of the parison thickness in the flexible portions 4 and 4 to form a multilayer over the entire length of the parison. ', And other structures are the same as those of the parison P shown in FIG.

FIG. 3 shows that the parison P is sandwiched between a pair of molds (not shown), and pressurized air is blown into the parison while both ends of the parison are squeezed, thereby inflating the parison and pressing the parison against the inner surface of the mold. This shows an air duct T formed by molding, and the flexible portions 4 and 4 of the parison P have a bellows portion 6 that requires bending and a joint portion 7 that requires sealing, and rigid portions 3 and 3 have shape holding portions 8. , 8 are formed. In the air duct T, the boundary 9 between the bellows portion 6 and the joint portion 7, which are rich in flexibility, and the shape holding portions 8, 8, which require rigidity for holding the shape, is extremely sharp, and the flexibility of the soft resin is improved. Is hardly adversely affected by the presence of the hard resin, and conversely, the rigidity of the hard resin is adversely affected by the presence of the soft resin.

FIG. 4 shows an apparatus in which the method of the present invention is carried out. A mandrel 12 is disposed substantially at the center of the extrusion head 11 of the composite parison molding apparatus, and an annular first resin supply is provided around the mandrel 12. A passage 13 is formed along the axial direction, and an annular second resin supply passage 14 partitioned by an inner pipe member 15 is formed outside the first resin supply passage 13. Is separated by an outer pipe member 16 so that its flow path extends along the axial direction of the mandrel 12. First
The second resin supply passages 13 and 14 join at their lower ends, and communicate with an annular slit 18 formed between the nozzle 17 and the mandrel 12, and a parison is discharged from the annular slit 18.

The upper portions of the first resin supply path 13 and the second resin supply path 14 are bent in the side direction of the head 11,
An accumulator type injection machine 21 having a plunger 20 driven by a cylinder 19 is connected to the first resin supply path 13,
An extruder 22 for flowing a first molten resin is connected to the accumulator-type injector 21, and an accumulator-type injector 25 having a plunger 24 driven by a cylinder 23 is connected to the first resin supply path 14. An extruder 26 for flowing the second molten resin is connected to the type injection machine 25.

The extruder 22 has a low density polyethylene (LDPE) or a thermoplastic elastomer (TP).
E) or the like, and the other extruder 26 is supplied with a hard resin such as high-density polyethylene (HDPE) or polypropylene (PP) and is melted, and the corresponding accumulator-type injectors 21 and 25 are supplied. At this time, each accumulator type injection machine 21,
The on-off valve (not shown) provided at the end of the nozzle 25 is closed to temporarily store the molten resin, and the plungers 20, which allow the stored molten resin to flow toward the resin supply passages 13 and 14. There is provided a control device 27 for controlling the forward and suckback operations of the motor 24.

When a composite parison P in which the flexible part 4 and the rigid part 3 shown in FIG. 1 are connected along the length direction by the composite parison molding apparatus as described above is molded, one resin supply path (the inner layer) is used. The resin supply passage (for forming the outer layer) 14 is used as a passage for the hard resin, and the accumulator type injection machines 21 and 25 communicating with the resin supply passages 13 and 14 are used. As described above, a predetermined amount of molten resin is fed from each of the extruders 22 and 26 and temporarily stored therein. Then, the on-off valve of one accumulator-type injection machine 21 is opened, and the plunger 20 is opened.
Is advanced by a predetermined dimension, and the soft resin in the molten state is extruded from the annular slit 18 through the first resin supply path 13, and the portion corresponding to the soft resin layer 1 of the parison P, mainly the flexible portion 4 having a high wall thickness ratio is removed. Molding. Next, after the advance of the plunger 20 is stopped while the on-off valve is open, the on-off valve of the other accumulator-type injection machine 21 is opened, the plunger 24 is advanced by a predetermined dimension, and the molten hard resin is removed. 2 Extruded from the annular slit 18 through the resin supply passage 14 to form the hard resin layer 2 of the parison P, mainly the portion corresponding to the rigid portion 3 having a high wall thickness ratio, and then the on-off valve is opened. After stopping the advance of the plunger 24 as it is, one of the plungers 20 is advanced to form the flexible portion 4, and the parison P in which the rigid portions 3 and the flexible portions 4 are connected alternately in a series to form an integrated parison P is formed. You. After that, both the on-off valves are closed and each molten resin is injected into each accumulator type injection machine 21, 21.
Basically, the parison P is intermittently continuously formed by repeating the above-described steps, such as storing the parison P5.

However, according to the present invention, in the molding process of the wall thickness ratio changing portion 5 of the parison P formed by switching between the resins at the boundary portion between the rigid portion 3 and the flexible portion 4, as one plunger starts to advance. The other plunger is controlled so as to perform a suck-back operation, retreat a predetermined dimension, and stop. That is, FIG. 5 schematically shows the control of the stroke amount between the plungers 20 and 24 when the parison P is switched from the rigid portion 3 to the flexible portion 4 via the thickness ratio changing portion 5. In forming the rigid portion 3, the plunger 24 moves forward to feed a large amount of molten hard resin into the second resin supply path 14 in accordance with the thickness ratio of each resin layer, whereas the plunger 20 A small amount of molten soft resin is fed into the first resin supply path 13. Next, when reaching the start position 5a of the thickness ratio changing unit 5 of the parison P, the plunger 24 starts a suck-back operation, retreats to reach the end position 5b of the thickness ratio changing unit 5, and stops at that position. On the other hand, when the plunger 20 reaches the start position 5a of the thickness ratio changing unit 5 of the parison P, it starts to move forward by a predetermined distance, passes through the end position 5b of the thickness ratio changing unit 5, and passes through the flexible unit 4. And a large amount of molten soft resin is fed into the first resin supply path 13. Therefore, the sucked-back operation of the plunger 24 causes the molten hard resin in the second resin supply path 14 communicating therewith to be sucked in vacuum backward, and the molten soft resin fed into the first resin supply path by the plunger 20. Is rapidly discharged from the annular slit 18, and the resin is switched from the rigid portion 3 to the flexible portion 4 with the very short thickness ratio changing portion 5. Conversely, from the flexible part 4 to the rigid part 3
Although not shown, resin switching is similarly performed by controlling the stroke of the plunger.

The stroke control between the plungers 20 and 24 is performed by sensors 28 and 2 for detecting the positions of the plungers provided in the cylinders 19 and 23 as the plungers move forward and backward.
9 is connected to the control unit 27, and the detected position from the sensors 25 and 26 is fed back to the control unit 27 in which an appropriate operation pattern is stored as a program, and a hydraulic work valve (not shown) is controlled under the control. This is done by sending a signal to take a predetermined stroke.

The molding operation of the parison P ′ shown in FIG. 2 is performed in substantially the same manner as described above, except that the plunger 24 is advanced at a very low speed during the molding of the flexible portion 4 so that the thin hard resin layer 2 is formed.
Is formed.

[0020]

According to the present invention, there is provided a parison for blow molding in which a rigid portion having a high thickness ratio of a hard resin layer and a flexible portion having a high thickness ratio of a soft resin layer are connected in the longitudinal direction. In addition, the thickness ratio changing portion formed at the boundary between the rigid portion and the flexible portion can be suppressed to a remarkably short range, and the quality can be improved by distributing the parison material.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a composite parison according to the present invention.

FIG. 2 is a sectional view showing another embodiment of the composite parison.

FIG. 3 is a sectional view of an air duct in which the composite parison shown in FIG. 1 is blow molded.

FIG. 4 is a schematic view showing an example of a molding apparatus according to the present invention.

FIG. 5 is an explanatory diagram showing a molding state of a parison thickness ratio changing portion.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Soft resin layer 2 Hard resin layer 3 Rigid layer 4 Flexible layer 5 Thickness ratio change part 6 Bellows part 7 Connecting part 8 Shape holding part 9 Boundary surface 11 Head 12 Mandrel 13 First resin supply path 14 Second resin supply path 15 Inner pipe member 16 Outer pipe member 17 Nozzle 18 Annular slit 19 Cylinder 20 Plunger 21 Accumulator-type injection machine 22 Extruder 23 Cylinder 24 Plunger 25 Accumulator-type injection machine 26 Extruder 27 Control device 28 Position detection sensor 29 Position detection sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29L 9:00 23:00 (72) Inventor Nobuhide Tanaka 1-4-4 Shinsenri Higashicho, Toyonaka City, Osaka No.1 Tigers Polymer Co., Ltd. F term (reference) 4F207 AH17 AR12 KA01 KA17 KB22 KF14 KK04 KK12 KK36 4F208 AH17 AR12 LA01 LA08 LB01 LD14 LG24 LG25 LG26

Claims (2)

[Claims] At least two kinds of molten resins melted in separate extruders are merged in a common extrusion head through respective resin supply paths and extruded from an annular slit of the extrusion head to form a single parison. In this method, each molten resin sent from the extruder is temporarily stored in each accumulator-type injection machine, and then each plunger is advanced to determine the amount of each molten resin extruded into each resin supply path. In the adjusting step, the forward movement of one plunger and the corresponding suck-back operation of the other plunger are controlled, and one molten resin is pushed out to the resin supply path and the molten resin remaining in the other resin supply path is removed. By suction, the thickness ratio of each resin layer of the parison discharged from the annular slit of the extrusion head can be changed rapidly. A composite parison molding method, characterized in that: 2. An at least two annular resin supply path communicating with an annular slit provided in an extrusion head, an accumulator type injector connected to each resin supply path, and a different type of molten resin connected to each accumulator type injector. An extruder for supplying a resin, and a control device for controlling the mutual advance and suckback operation of the plungers of the accumulator-type injection machine in accordance with the material distribution of the parison to be molded.