JPH02113908A - Apparatus for molding multilayer parison - Google Patents

Abstract

PURPOSE:To uniformize quality by generating operating force smaller than the reaction accompanied by the movement of the plunger of an auxiliary material resin accumulator in the direction negating said reaction when an auxiliary material resin is supplied to the auxiliary material resin accumulator to be weighed. CONSTITUTION:When at least an auxiliary material resin is supplied to auxiliary material resin accumulators 31, 33 to be weighed, operation force smaller than the reaction accompanied by the movement of plungers 28, 34 acts on the plungers 28, 34 of the auxiliary material resin accumulators 31, 33 in the direction negating said reaction by an operating force generating means. Since the pressure rise of the auxiliary material resin in the accumulators 31, 33 is suppressed small, the leakage of the auxiliary material resin from a nozzle 11 is prevented. Therefore, no expanded part is partially generated in each layer forming a multilayer parison and the multilayer parison where respective resins are respectively laminated in predetermined thicknesses can be certainly formed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves extrusion molding in order to guide a multilayer parison consisting of a main resin layer and an auxiliary resin layer laminated inside the main resin layer into a mold cavity. The present invention relates to a multilayer parison molding device.

[Prior Art] In recent years, plastic containers have been used as containers for storing liquids such as fuel, such as fuel tanks installed in vehicles such as automobiles, in order to reduce the weight of the containers themselves and facilitate molding. New products have been proposed and are being put into practical use. The plastics used to form this type of container include:
High-density polyethylene is often used in consideration of moldability, strength, manufacturing cost, etc.

However, since the above-mentioned high-density polyethylene has the property of being permeable to liquids such as gasoline, if a liquid such as gasoline is left in a container made only of high-density polyethylene for a long period of time, it will not be contained. A problem arises in that liquid such as gasoline gradually penetrates and permeates the peripheral wall of the container.

The problem of permeation of such stored liquids (gasoline, light oil, etc.) has recently become particularly important, and there is now a strong demand for high impermeability in containers such as fuel tanks.

Therefore, as disclosed in Japanese Patent Publication No. 58-23212, for example, a main resin layer made of high-density polyethylene that maintains the strength of the container, and a nylon resin,
A first sub-material resin layer as a so-called barrier layer that prevents the permeation of a contained liquid such as gasoline, and a modified polyethylene, and the main resin layer and the first sub-material resin layer are bonded together.
A multilayer parison is formed by laminating three types of resin layers including a second sub-material resin layer as an adhesive layer, and this multilayer parison is extruded from an extrusion molding device and placed in a mold cavity.
It is well known that -FG can be made to have high impermeability by subsequent blow molding to form a multilayer blow-molded container with a three-layer structure.

The extrusion molding device for forming the above-mentioned multilayer parison, that is, the multilayer parison molding device, consists of a storage chamber and a plunger, an accumulator that stores and measures the resin, and then pressurizes and extrudes it, a drive cylinder that drives the accumulator, and an accumulator. A supply device is provided for each resin.

When extrusion molding a multilayer parison using such a multilayer parison molding apparatus, first, each resin is fed into a storage chamber of an accumulator by a feeding device. At this time, by keeping the drive cylinder in a floating state,
The plunger of the accumulator moves in the direction of pushing back the piston of the drive cylinder, and resin is stored in the storage chamber and measured.

When the plunger reaches a predetermined position, the drive cylinder is activated to move the plunger in the resin extrusion direction, extruding each resin from the nozzle almost simultaneously, so that each resin is laminated to a predetermined thickness. It became possible to form a multi-layered parison.

[Problem to be solved by the invention]

However, in the conventional multilayer parison molding apparatus described above, when the resin is fed into the storage chamber of the accumulator, drag forces such as sliding resistance due to movement and dead weight act on the plunger of the accumulator. Furthermore, even if the drive cylinder is in a floating state, the sliding resistance of the piston of the drive cylinder, its own weight, etc. also act.

Therefore, the pressure of the resin inside the storage chamber of the accumulator increases, and a portion of the resin supplied from the supply device may leak out from the nozzle. In this case, bulges occur partially in each layer forming the multilayer parison, making it difficult to form a multilayer parison in which each resin is laminated to a predetermined thickness. Therefore, there has been a problem in that, for example, the shape and quality of tanks formed by blow molding a multilayer parison tend to vary.

[Means to solve the problem]

In order to solve the above-mentioned problems, the multilayer parison molding apparatus according to the present invention includes a main resin accumulator that measures the main resin and then pressurizes it to extrude it from a nozzle, and a main resin accumulator that measures the secondary resin and then pressurizes it. In a multilayer parison molding device, the apparatus is equipped with an accumulator for an auxiliary resin extruded from a nozzle, and a drive cylinder that drives each of the accumulators, and extrusion molds a multilayer parison in which a main resin layer and an auxiliary resin layer are laminated. At least when the secondary material resin is supplied to the secondary material resin accumulator and measured, an actuation force is generated in a direction that cancels out the drag force caused by the movement of the plunger of the secondary material resin accumulator, and which is smaller than the above-mentioned drag force. It is characterized by being equipped with power generation means.

[Function] With the above configuration, when at least the sub-material resin is supplied to the sub-material resin accumulator and measured, the plunger of the sub-material resin accumulator is subjected to a drag force due to the movement of the plunger by the actuation force generating means. An actuating force acts in a direction that cancels out the above-mentioned drag force and is smaller than the above-mentioned drag force. Therefore,
Since the pressure increase of the secondary material resin inside the accumulator is suppressed to a small level, leakage of the secondary material resin from the nozzle is prevented.

Therefore, no bulges are generated locally in each layer forming the multilayer parison, and a multilayer parison in which each resin is laminated to a predetermined thickness can be reliably formed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 1, an accumulator head 1 constituting a multilayer parison molding apparatus is provided with a cylinder 2 consisting of a concentric cylindrical outer wall 2a and an inner wall 2b. A ring piston 3 that is vertically slidable is provided between the outer wall 2a and the inner wall 2b. This ring piston 3
is adapted to be driven by a first extrusion cylinder 15 consisting of a hydraulic cylinder via a plunger 14.

The cylinder 2 and the ring piston 3 constitute a main resin accumulator 16 that measures a main resin such as high-density polyethylene in a molten state, pressurizes it, and extrudes it from a die slit 11 (described later). .

On the inner peripheral side of the inner wall 2b of the cylinder 2, the cylinder 2
A core 4 fixed to the core 4 is provided, and an annular communication path 7 is formed between the inner wall 2b and the core 4. Further, a resin storage chamber (resin reservoir) 5 is formed by the outer wall 2a and inner wall 2b of the cylinder 2, the ring piston 3, and the core 4. This resin storage chamber 5 is connected to the first
It is communicated with the extruder 6 so that the main resin is continuously supplied. A temperature regulating device (not shown) is provided near the resin storage chamber 5 in the cylinder 2, so that the resin inside the resin storage chamber 5 is maintained at a predetermined temperature.

At the lower end of the outer wall 2a of the cylinder 2, an annular die 8 is provided.
It is fixed concentrically with the cylinder 2.

The lower inner circumferential surface 8a of this die 8 is formed into a conical shape.

On the other hand, a core support 9 is fixed to the lower end of the core 4 concentrically with the cylinder 2. A cylindrical portion 9a is formed at the bottom of this core support 9. core support 9
The cylindrical portion 9a has a core 10 concentric with the cylinder 2.
They are fitted to be slidable in the vertical direction. The lower outer circumferential surface 10a of the core 10 is formed into a conical shape, and an annular die is provided between the lower outer circumferential surface 10a of the core IO and the lower inner circumferential surface 8a of the die 8, which acts as a nozzle through which resin is extruded. A slit 11 is formed. The die slit 11 communicates with the resin storage chamber 5 via a resin passage 12 formed between the outer wall 2a of the cylinder 2 and the die 8, and the core 4 and core support 9.

The core IO is vertically driven by a hydraulic cylinder (not shown) via a rod 13, and the width of the die slit 11 is
That is, the thickness in the radial direction of the parison formed by extruding the resin from the die slit 11 is adjusted.

Inside the resin passage 12, as shown in FIGS. 2 and 3, there is a ring member 17 having a substantially longitudinal hexagonal cross-sectional shape.
is provided concentrically with the resin passage 12. The ring member 17 is supported at a predetermined distance from the inner peripheral surface of the outer wall 2a of the cylinder 2 by four struts 18, and is positioned at a different position in the circumferential direction from the struts 18. The core 4 is
It is supported at a predetermined distance from the outer peripheral surface of. That is, the resin passage 12 is divided by the ring member 17 into an inner annular passage 12a and an outer annular passage 12b.

An annular first auxiliary material resin passage 20 is formed inside the ring member 17 and is located near the center of the longitudinal cross-sectional shape of the ring member 17 . Further, annular second auxiliary material resin passages 21 and 21 are provided on the inner circumferential side and the outer circumferential side of the first auxiliary material resin passage 20 inside the ring member 17, respectively.
is formed. On the other hand, on the lower surface of the ring member 17,
Three concentric annular nozzles 24, 25, and 25 are formed which communicate with the resin passages 20, 21, and 21 via annular slits 22, 23, and 23, respectively.

The first subsidiary resin passage 20 is connected to a second extruder 27 provided outside the accumulator head 1 via a passage 26 formed in one of the struts 18 . This second extruder 27 is configured to continuously supply a first sub-material resin, such as molten nylon resin, which is an impermeable resin as a barrier material that prevents the permeation of liquids such as gasoline. There is.

The second extruder 27 is provided with an accumulator 33 for the auxiliary resin that measures the molten first auxiliary resin, pressurizes it, and extrudes it from the annular nozzle 24 of the ring member 17 . The plunger 28 of the accumulator 33 for secondary material resin is driven by a second extrusion cylinder 32 consisting of a hydraulic cylinder. Further, the secondary material resin accumulator 33 is provided with a temperature adjustment device (not shown), so that the first secondary material resin inside the secondary material resin accumulator 33 is maintained at a predetermined temperature.

On the other hand, the second auxiliary resin passages 21 and 21 are connected to a third resin passage provided outside the accumulator head 1 via passages 29 and 29 formed in a pillar 18 different from the pillar 18 in which the passage 26 is formed. It is connected to an extruder 30. The third extruder 30 is configured to continuously supply a second subsidiary resin as an adhesive, such as molten modified polyethylene.

The third extruder 30 includes an accumulator 3 for measuring the second secondary resin in a molten state, pressurizing it, and extruding it from annular nozzles 25 formed in the ring member 17.
1 is provided. The plunger 34 of the accumulator 31 for secondary material resin is driven by a third extrusion cylinder 35 consisting of a hydraulic cylinder. Also,
The secondary material resin accumulator 31 is provided with a temperature adjustment device (not shown), similar to the secondary material resin accumulator 33, to maintain the second secondary material resin inside the secondary material resin accumulator 31 at a predetermined temperature. It is now possible to

Upper cylinder chamber 1 in the first extrusion cylinder 15
5a and the lower cylinder chamber 15b are each connected to a hydraulic pressure supply device 39 via a first pressure servo valve 36.

Further, the second extrusion cylinder 32 has an upper cylinder chamber 32.
a is the hydraulic pressure supply device 39 via the second pressure servo valve 37
On the other hand, the lower cylinder chamber 32b is connected to a high pressure air source via an air supply device 50. The air supply device 50 includes a solenoid valve 51, an oil separator 52, a check valve 53, and a pressure reducing valve 54 connected in this order, and supplies air at a predetermined pressure to the F-side cylinder chamber 32b of the second extrusion cylinder 32. I'm starting to get it.

Similarly to the second extrusion cylinder 32, the third extrusion cylinder 35 has an upper cylinder chamber 35a connected to the third pressure servo valve 3.
8, the lower cylinder chamber 35b is connected to the hydraulic pressure supply device 39 via the air supply device 6.
0 to a high pressure air source.

Like the air supply device 50, the air supply device 60 includes a solenoid valve 61, an oil separator 62, a check valve 63,
and a pressure reducing valve 64 are connected in this order so that air at a predetermined pressure can be supplied to the lower cylinder chamber 35b of the third extrusion cylinder 35.

The air supply device 50 and the second extrusion cylinder 32 and the air supply device 60 and the third extrusion cylinder 35 supply the first subsidiary resin and the second subsidiary resin to the subsidiary resin accumulators 33 and 31, respectively. In the direction of canceling the drag caused by the movement of the plungers 28 and 34 of the accumulators 33 and 31 for the secondary resin when the resin is supplied to and measured,
Further, an actuation force generating means is configured to generate an actuation force smaller than the above-mentioned drag force.

Solenoids 36a of the first to third pressure servo valves 36 to 38
~38a, and the solenoid 51a of the solenoid valve 51/61
- 61a are each connected to the parison control circuit 40, and are controlled by an excitation signal output from the parison control circuit 40. Parison control circuit 4 (
) also includes first to third extrusion cylinders 15, 32, 3.
The ring piston 3 in the main resin accumulator 16 and the plungers 28 and 3 in the secondary resin accumulators 33 and 31 are connected to the first to third plunger position detection devices 41 to 43 respectively attached to the main resin accumulator 16.
A position detection signal corresponding to the vertical position of No. 4 is inputted.

The parison control circuit 40 further includes a first pressure detector 44 provided in the resin passage 12 of the accumulator head 1 to detect the resin pressure of the main material resin, and a first pressure detector 44 provided in the second extruder 27 to detect the resin pressure of the main material resin. A second pressure detector 4 detects the resin pressure of
5, and a third pressure detector 46 which is provided in the third extruder 30 and detects the resin pressure of the second auxiliary material resin is connected.

In the above configuration, when extruding a multilayer parison, first, the first pressure servo valve 36 is held in the neutral position, and the second pressure servo valve 37 and the third pressure servo valve 38 are respectively moved in the direction of arrow C. Operate in the direction shown.

Further, the solenoid valves 51 and 61 are respectively operated in the directions shown by the arrows.

Then, the first extrusion cylinder 15 becomes in a floating state,
The main resin sent from the first extruder 6 to the main resin accumulator 16 via the communication path 7 is stored in the resin storage chamber 5 and measured while pushing up the ring piston 3.

Further, the hydraulic oil inside the upper cylinder chambers 32a and 35a in the second extrusion cylinder 32 and the third extrusion cylinder 35 is supplied to the second pressure servo valve 37 and the third pressure servo valve 37, respectively.
While being drained via the pressure servo valve 38, air is supplied to the lower cylinder chambers 32b and 35b, respectively, with air reduced to a predetermined pressure by the pressure reducing valves 54 and 64 of the air supply devices 50 and 60, respectively. As a result, the plungers 2B and 34 of the secondary resin accumulators 33 and 31 are acted upon by an actuation force that almost cancels out the drag associated with upward movement, such as sliding resistance and own weight, so the plungers 28 and 34 are free from any external force. While it remains stationary in the non-acting state,
It is maintained in a state where it can easily rise if even the slightest upward external force acts on it.

Therefore, when the first subsidiary resin and the second subsidiary resin are sent from the second extruder 27 and the third extruder 30 to the subsidiary resin accumulators 33 and 31, these subsidiary resins are The liquid pushes up the plungers 28 and 34 without increasing the pressure, and is stored and measured. Since the pressure of the first sub-material resin and the second sub-material resin hardly increases, the annular nozzles 24 and 25
・No leakage from 25.

Eventually, when the ring piston 3 of the main resin accumulator 16 rises to a predetermined position and a predetermined amount of main resin is stored, the parison control circuit 40 starts operating the device comprising the first plunger position detection device 41. Based on the detection signal, the first pressure servo valve 36 is operated in the direction shown by arrow E. Then, the hydraulic oil from the hydraulic supply device 39 is supplied to the upper cylinder chamber 15a of the first extrusion cylinder 15, while the hydraulic oil inside the lower cylinder chamber 15b is supplied to the upper cylinder chamber 15a of the first extrusion cylinder 15.
Drained via pressure servo valve 36.

Therefore, the first extrusion cylinder 15 is driven forward to lower the ring piston 3 of the main resin accumulator 16. As the ring piston 3 descends, the main resin stored in the main resin accumulator 16 is pushed out into the resin passage 12 and, above the ring member 17, is divided into an inner layer and an outer layer. , rejoin below the ring member 17.

The combined main resin is further extruded through the die slint 11 to form a single-layer parison.

At this time, the parison control well circuit 40 controls the first extrusion so that the main resin is extruded at a predetermined rate based on the signals output from the first plunger position detection device 41 and the first pressure detector 44. The driving force generated by the cylinder 15 is controlled.

When the single-layer parison extruded from the die slit 11 reaches a predetermined length, that is, when the ring piston 3 descends by a predetermined amount, the parison control circuit 40 includes a first plunger position detection device 41. The third pressure servo valve 38 is operated in the direction shown by arrow E based on the device detection signal. Further, the solenoid valve 61 is operated in the direction indicated by arrow F.

Then, the upper cylinder chamber 35 of the third extrusion cylinder 35
Hydraulic oil is supplied from the hydraulic pressure supply device 39 to T1.a, while air inside the lower cylinder chamber 35b is supplied to T1. fe
It is drained through the T-valve 61.

At this time, the air supply device 60 includes an oil separator 62.
, and a check valve 63 are provided, so that hydraulic oil does not enter the high pressure air source side.

When hydraulic oil is supplied to the upper cylinder chamber 35a, the third extrusion cylinder 35 is driven forward together with the first extrusion cylinder 15 to lower the plunger 34 of the accumulator 31 for secondary material resin. As the plunger 34 descends, the second subsidiary resin stored in the subsidiary resin accumulator 31 passes through the passages 29, 29, the second subsidiary resin passages 21, 21, and the slits 23, 23. , annular nozzle 25.2
The main resin separated from No. 5 is extruded between the inner layer and the outer layer.

In addition, the parison control circuit 40 also controls the third plunger position detection device 43 as in the case where the main resin is extruded.
, and a signal output from the third pressure detector 46, the driving force generated by the third extrusion cylinder 35 is controlled so that the second auxiliary material resin is extruded in a predetermined position.

After driving the third extrusion cylinder 35 forward, the parison control circuit 40 drives the second extrusion cylinder 32 forward with a slight delay. That is, the second pressure servo valve 37 is operated in the direction shown by arrow E, and the solenoid valve 51 is operated in the direction shown by arrow F.

Then, similarly to the third extrusion cylinder 35, the hydraulic pressure supply device 3 is placed in the upper cylinder chamber 32a of the second extrusion cylinder 32.
While the hydraulic oil from 9 is supplied, the lower cylinder chamber 3
The air inside 2b is drained through ZK1'' through the valve 51. Then, the second extrusion cylinder 32 is driven forward together with the first extrusion cylinder 15 and the third extrusion cylinder 35, and the accumulator for the auxiliary material resin is driven forward. 33 plunger 28 is lowered.As the plunger 28 descends, the first subsidiary resin stored in the subsidiary resin accumulator 33 flows through the passage 26, the first subsidiary resin passage 20, and the slit 72. The second auxiliary resin is extruded through the annular nozzle 24 between the inner layer and the outer layer.

At this time as well, the parison control circuit 40 controls the second plunger position detection device 42 and the second pressure detection device 4 as in the case where the main material resin and the second sub-material resin are extruded.
Based on the signal output from the second extrusion cylinder 32, the driving force generated by the second extrusion cylinder 32 is controlled so that the first subsidiary resin is extruded at a predetermined rate.

In this way, following the middle layer parison consisting of only the main resin layer, the first sub-resin layer is interposed between the two main resin layers, the inner layer and the outer layer, through the second sub-resin layer. A multilayer parison with a five-layer structure of three types is extruded.

When the ring piston 3 further descends by a predetermined amount and the multilayer parison reaches a predetermined length, the parison control circuit 40
The second pressure servo valve 37 is returned to the neutral position based on a device detection signal constituted by the first plunger position detection device 41. Also, after a slight delay, the third pressure servo valve is returned to the neutral position.

Therefore, the second extrusion cylinder 32 and the third extrusion cylinder 35 are locked, and extrusion of the first subsidiary resin and the second subsidiary resin is stopped, and following the multilayer parison, only the main resin layer is A single layer parison is extruded.

When the single layer parison reaches a predetermined length, the parison control circuit 40 returns the first pressure servo valve 36 to the neutral position based on a device detection signal constituted by the first plunger position detection device 41. As a result, the forward drive of the first extrusion cylinder 15 is stopped, the extrusion of the main resin is stopped, and the extrusion molding of the parison in step (2) is completed.

In this way, a parison is extruded which has single layers at both upper and lower ends and multilayers at the center. This parison is introduced into a cavity of a mold (not shown) and blow-molded into a desired shape, such as a fuel tank, by blowing pressurized gas into the parison. Further, the upper and lower single layer parts can be removed as burrs after blow molding and recycled as recycled material for the main resin.

In this way, when supplying the first sub-material resin and the second sub-material resin to the aggulators 33 and 31 for the sub-material resin, the plungers 28 and 34 are provided with drag due to upward movement, such as sliding resistance and their own weight. By applying an almost counteracting actuation force, it is possible to prevent the occurrence of partial bulges in each layer forming the multilayer parison, and to reliably form a multilayer parison in which each resin is laminated to a predetermined thickness. can do.

In addition, in this example, the first sub-material resin and the second
Although the actuation force generating means is provided for the secondary material resin, it is not limited to this, and it may be provided only for one of the secondary material resins, or it may be provided for the main material resin as well. good.

Further, the structure of the multilayer parison is not limited to three types and five layers, but the same effect can be obtained even when extrusion molding multilayer parisons with various structures, such as three types and three layers, for example.

Further, the type of the sub-material resin layer is not limited to a barrier material layer or an adhesive layer, but may also be a resin layer for improving strength, for example.

(Effects of the Invention) As described above, the multilayer parison forming apparatus according to the present invention has the following features:
An accumulator for the main resin that measures the main resin and pressurizes it to push it out from the nozzle, an accumulator for the sub resin that measures the sub resin and then pressurizes it and pushes it out from the nozzle, and a drive that drives each of the above accumulators. In a multilayer parison molding apparatus that extrudes and molds a multilayer parison in which a main resin layer and an auxiliary resin layer are laminated, the multilayer parison molding apparatus includes a cylinder, and when at least the auxiliary resin is supplied to the auxiliary resin accumulator and measured. , the construction includes an actuation force generating means that generates an actuation force in a direction that cancels out the drag force caused by the movement of the plunger of the accumulator for the secondary material resin, and which is smaller than the drag force.

This prevents the secondary resin from leaking out of the nozzle at least when the secondary resin is supplied to the accumulator for secondary resin and is measured, so that each layer forming the multilayer parison is partially bulged. This does not occur, and a multilayer parison in which each resin is laminated to a predetermined thickness is reliably formed.

Therefore, it is possible to easily reduce variations in the shape and quality of tanks formed by blow molding a multilayer parison, for example.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention, in which FIG. 1 is an explanatory diagram showing the configuration of a multilayer parison forming apparatus, and FIG. 2 is a cross section taken along the line A-A in FIG. 1. FIG. 3 is a sectional view taken along the line BB in FIG. 2. 11 is a die slit (nozzle), 15 is a first extrusion cylinder, 16 is an accumulator for main resin, 24 and 25 are annular nozzles, 28 is a plunger, 31 and 33 are accumulators for secondary resin, and 32 is a second extrusion cylinder. (operating force generating means), 34 is a plunger, 35 is a third extrusion cylinder (
50 and 60 are air supply devices (actuation force generation means).

Claims (1)

[Claims] 1. Drives an accumulator for the main resin that measures the main resin and then pressurizes it and pushes it out from the nozzle, an accumulator for the auxiliary resin that measures the sub-material resin and then pressurizes it and pushes it out from the nozzle, and the above-mentioned respective accumulators. In a multilayer parison molding apparatus that extrudes and molds a multilayer parison in which a main resin layer and an auxiliary resin layer are laminated, at least an auxiliary resin is supplied to an accumulator for the auxiliary resin and is measured. A multilayer parison molding apparatus, characterized in that it is equipped with an operating force generating means that generates an operating force in a direction that cancels out the drag force caused by the movement of the plunger of the accumulator for the auxiliary resin and that is smaller than the drag force.