JPH08290459A - Method and machine for blow molding - Google Patents

Abstract

PURPOSE: To obtain a panel-shaped blow molded product which has high transfer and surface properties of both inside and outside surfaces of a parison surely in a short time by transferring the surface of a heating plate to the inner surface of a parison, clamping a mold by heating, injecting hot air into the parison, and cooling the parison after holding it. CONSTITUTION: A heating plate 20 the surface of which is mirror-finished, has a vent 20a, and heated at molding temperature is pressed on the inner surface of a parison P before mold clamping which is discharged from a blow molding machine 1 and is hanging, air existing between the inner surface of the parison P and the heating plate 20 is discharged through the vent 20a, and the surface of the heating plate 20 is transferred to the inner surface of the parison P to improve a surface property. The lower end of the parison P is prepinched, a mold 8 is clamped in a condition in which the mold 8 is heated with the parison P sandwiched, hot air is injected into the parison P, the parison P is held for a specified time, the mold 8 is cooled, cooling air is circulated in the parison P to cool the parison P, and the blow molded product is removed after the finish of the cooling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a blow molding method and a blow molding machine, and in particular, it is an object of the present invention to obtain a panel-like blow molded article having improved transparency in the inner and outer surfaces of a parison in a short time. I am trying.

[0002]

2. Description of the Related Art In blow molding in which a hollow resin product is made from a parison that is cylindrically injected or extruded from a die head, the parison is injected or extruded from the die head and pre-blown into a parison that is formed into a bag by a parison pinch. After inflating slightly, put it in an open mold and close the mold, and after removing the gas in the cavity formed by the mold and parison, a vacuum pump device from a small air vent hole that communicates with the mold surface After suctioning air through the parison, high-pressure air is blown into the parison to form the parison into a predetermined shape based on the cavity and then cooled by a mold to complete the molding. In this way, the molded resin product is taken out by opening the mold. The thing shown in FIG. 10 shows the conventional blow molding machine. 10 shows a so-called side-feed type blow molding machine 1 in which molten resin is supplied from one side of the die head 2, and the resin in a high temperature molten state pressed by the extruder 4 is the resin supply port 2a. And passes through an annular passage provided between the die head 2 and the mandrel 3 and is discharged from the annular space passage 7 at the lowermost end to form a parison P. And the core 3a
Is connected to a rod 6a for Parison penetrating the mandrel 3 and is slightly moved up and down in the vertical direction by the operation of the Parison cylinder 6. The gap of the annular space passage 7 can be adjusted to control the wall thickness of the parison P. It is like this.

On the other hand, as shown in FIG. 11, a resin is molded into a panel shape having a bag-shaped air space therein to be used as a building material such as a door (gate) or a simple wall material (partition wall). However, it has come to be considered to use it for floors such as formwork for concrete pouring and simple piers, but these molded products have considerable structural strength despite their light weight,
It has the feature of being strong against deformation. In addition to using these panel-shaped blow-molded products as the above-mentioned structural members, they may be molded with a see-through resin material and used as a partition wall for furniture and houses. It was necessary to use a transparent resin material and to finish the inner and outer surfaces of the parison to be smooth.

[0004]

In order to form a transparent panel-shaped blow-molded article in this manner, for example, heating and cooling of a mold for obtaining high transfer and high surface property using a light-transmissive resin material. If the outer surface of the molded product, which is in contact with the mold cavity surface even in the conventional method, can be made to have a high gloss and high transferability, the blow molding can be performed. Since the inner surface of the parison is a light-transmitting resin, it cannot be a high-transfer or high-gloss surface because it remains extruded from the die, and the surface quality is poor and the surface quality of the outer surface of the molded product is poor. The result is similar to that in a bad state, and there is a problem that the advantage of high transfer and high gloss on the outer surface of the corner cannot be fully utilized. In the present invention, both the inner and outer surfaces of the parison have high transferability,
An object of the present invention is to provide a blow molding method and a blow molding machine that can reliably obtain a panel-shaped blow molded product having high surface properties in a short time.

[0005]

In order to solve the above-mentioned problems and obtain a panel-shaped blow-molded article having excellent transparency, in the present invention, in the first invention, the discharge is carried out from the blow-molding machine. The inner surface of the hanging parison before mold clamping is mirror-finished and the surface has a through hole for deaeration, and the surface presses a heating plate heated to the molding temperature, and is interposed between the inner surface of the parison and the heating plate. Air is discharged through the degassing through hole, the surface of the heating plate is transferred to the inner surface of the parison to improve the surface property of the inner surface of the parison, and the lower end of the parison is pre-pinched, and then the parison is sandwiched. The mold is clamped in a heated state, heated air is injected into the parison and held for a certain period of time, and then the mold is cooled and cooling air is circulated into the parison to cool the parison. It was cooled, it was decided to take out cooling after completion blow-molded article. Further, in the second invention, in order to enhance the transparency, the first invention is implemented as a resin material and a light-transmissive resin material. Further, according to a third aspect of the present invention, there is provided a blow molding machine for molding a panel-shaped molded product, wherein the blow molding machine includes a pair of left and right molds, and the mold is supplied by a hot oil unit. A heat medium for heating the heating medium or a cooling medium supplied by a cooling oil unit for cooling the mold, or a passage for conducting blow air for air purging both of the heating medium and the cooling medium at the time of switching between the heating medium and the cooling medium. The mold is equipped with a blow pin for switching and injecting heated air and cooled air into the parison of
A pair of left and right heating plates with a smooth surface and mirror finish and a plurality of degassing through holes on the surface and a plate heater for heating the surface on the back surface and both heating plates are moved up and down inside the parison The inner surface of the parison is provided with an elevating means for moving the heating plate and a forward / backward moving means for expanding / contracting the two heating plates in the left-right direction, and connecting an intake / exhaust system for sucking air and injecting air into the degassing through hole. And a device.

[0006]

In the blow molding method of the first invention, a heating plate having a mirror-finished surface and a heated surface is put into the hanging parison and pressed against the inner surface of the parison, and at the same time, degassing provided on the heating plate surface. The intervening air is sucked through the through hole, the surface of the heating plate is transferred to the inner surface of the parison, a smooth inner surface of the parison is formed, and then the heating plate is retracted from the inside of the parison to pre-pinch the lower end of the parison and preheated. The parison is sandwiched between a pair of left and right molds, and hot air is injected into the parison via blow pins and held for a certain period of time.
After that, the mold is cooled by passing a cooling medium through the mold, and the cool air is injected into the parison, and the cool air is circulated between the outside to cool the parison from the inner surface as well. After completion, the blow-molded product molded is opened and taken out. In this way, a panel-shaped blow-molded article having excellent surface properties with high transferability on both the inner and outer surfaces can be obtained. Further, in order to obtain a panel-shaped blow-molded article having particularly high transparency, it is desirable to use the above-mentioned method to produce the resin material having high light transmittance such as polycarbonate. In the third invention, a blow molding machine suitable for carrying out the blow molding method of the first invention is configured, and a panel-shaped blow molded article having a desired surface property improved smoothly in order and automatically. Can be produced.

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 9 relate to an embodiment of the present invention,
1 is an overall vertical sectional view of the blow molding machine, FIG. 2 is a front view of the heating plate, FIG. 3 is a side sectional view of the heating plate, FIG. 4 is a rear view of the heating plate, and FIGS. FIG. 8 is an operation explanatory view, FIG. 8 is a heating / cooling system diagram of the blow molding machine, and FIG. 9 is a process diagram of the blow molding method.

As shown in FIGS. 1 to 4, a blow molding machine 1
Below the pair of left and right dies 8, the heating plate 20
A parison circular surface transfer device 100 including the plate arm 30, the forward / backward moving cylinder 40, and the elevating / lowering cylinder 50 on the inner surface of the parison is provided. That is, the heating plate 2
0 is fixedly installed on the head side of a forward / backward traveling cylinder 40 that is horizontally arranged via a plate arm 30 connected to the lower end edge, while the piston rod 40 of the forward / backward traveling cylinder 40 is fixed.
The tip of a is connected to the tip block 50b at the tip of the piston rod 50a of the elevating cylinder 50 standing upright on the ground, and is configured to be able to move up and down and move back and forth and left and right. Heating plate 2
0, the plate arm 30, and the forward / backward moving cylinder 40 are arranged in a pair of left and right in the opening / closing direction of the molds 8, 8.

On the other hand, as shown in FIGS. 2 to 4, the heating plate 20 has a plurality of rear surfaces each formed of a copper plate and having a mirror-finished flat surface and arranged in a grid pattern in a direction orthogonal to the front surface. The deaeration through hole 20a is formed. Degassing through hole 20
a has a small diameter of about 0.1 to 0.5 mm, has an area on the back surface of the heating plate 20 that is slightly smaller than the heating plate 20, and forms a space having a thickness of about 20 to 30 mm. Is connected to the collecting pipe 20
It is connected to c and is connected via a hose 22 to a supply / exhaust device (not shown) so as to be capable of performing air intake or air injection. Further, as shown in FIG. 4, a plate heater 20e is provided behind the closed cavity 20b via a flat back plate 20d so that the surface of the heating plate 20 can be heated. ing. The panel-shaped blow-molded product targeted in the present invention is a blow-molded product whose front and back surfaces are both flat and smooth.

Next, the heating / cooling system in the molds 8 and 8 and the parison will be described. As shown in FIG. 8, in the blow molding machine 1 of the present invention, a mold heating / cooling system 200 for heating or cooling the pair of left and right molds 8 and a blow pin (blowing nozzle) 9 into the parison. A parison blow air heating / cooling system 300 that heats or cools the air to be sent is provided, and the mold heating / cooling system 200 includes a hot oil unit 210 that supplies hot oil that is a heat medium and a cold oil that is a refrigerant body. A medium in which the hot oil or the cold oil up to that time is previously provided in the mold 8 when switching the cold oil to the cold oil unit 220 and the hot oil for supplying the cold oil, or vice versa. Route (not shown)
A mold blow air system 230 for injecting air for more air purging, and a hydraulic unit and a pneumatic unit each having a hydraulic control device (hydraulic pump, pressure adjusting valve, direction switching valve, check valve, etc.). Has become. Meanwhile, the parison blow air heating and cooling system 300
Is a line for supplying compressed air supplied from an air source 301 to a blow pin 9 of a mold 8 by heating with a heater to a predetermined temperature, and a vaporizing chamber for cooling the compressed air by vaporizing liquid nitrogen. The cool air supply line has a switching system with a two-way switching valve that injects hot air or cool air into the parison, and when hot air is supplied, the circulation nozzle 9a is closed and the parison retains the hot air and keeps it cool. In this case, the circulation nozzle 9a is in a communicating state, and the system is such that cool air is constantly flowed into the parison during cooling.

The operation of the blow molding machine of the present invention constructed as above and the operation of the blow molding method of the present invention will be described. First, after the discharge of the parison P by the blow molding machine 1 is finished and the parison P is in a hanging state, the elevating cylinder 50 is operated to operate the heating plate 20 as shown in FIG.
Is moved to the inside of the parison P. After this,
Before or after the forward / reverse cylinder 40 is operated, or at the same time as the operation, an unillustrated air supply / exhaust device is operated to degas the through hole 20a.
Air is sucked in via the air to suck air existing between the surface of the heating plate 20 and the inner surface of the parison facing the heating plate 20. Operate the forward / backward movement cylinder 40 to move both heating plates 2
At the forward limit position where 0 and 20 are most distant from each other, as shown in FIG. 6, the surface of the heating plate 20 whose surface is heated to the same temperature as the molding temperature and the inner surface of the parison P are almost in close contact with each other, and this state is maintained for a while. By continuing the suction while remelting the inner surface of the parison, the inner surface of the parison is transferred to a smooth mirror-finished state of the heating plate 20,
The surface property is improved. As described above, after the transfer and the surface property are improved, the intake by the air supply / exhaust device is stopped, and conversely, the low pressure (0.2 to 0.5 kg / cm ² G) compressed air is degassed from the heating plate 20. It is sprayed from the through hole 20a for use to release the close contact between the surface of the heating plate 20 and the inner surface of the parison P, and the forward / backward moving cylinder 40 is operated in reverse to reduce the distance between the heating plates 20 and 20 and to set the backward limit. Then, the heating plate 20 is lowered by the elevating cylinder 50. As described above, by pressing the surface of the heating plate 20 against the inner surface of the parison, only the resin surface on the inner surface of the parison is re-melted, and die lines and wrinkles generated when extruded from the die 2 can be eliminated.

In this way, after the heating plate 20 is completely retracted from the lowering of the parison, the lower end of the parison P is tightly bound and sealed by the pre-pinch device 60, and then both molds are closed and blow molding is performed. Mold the product.

Next, the blow molding process after the mold clamping process will be described. As shown in FIG. 9, the parison whose lower end is pre-pinched is clamped with both molds 8 and 8 in close proximity to each other to mold the parison. At this time, the molds 8 and 8 are blown by the mold blow air system 230 in advance and heated to 150 ° C. to 250 ° C. through the heat medium from the hot oil unit 210, and the parison blow air heating and cooling system through the blow pins 9 inside the parison. 150 supplied from 300
Compressed air (hot air) heated to ℃ to 250 ℃ is enclosed. In this way, a fixed time (for example, 30 seconds to 6
After holding for 0 seconds), in order to cool the mold 8 this time, first, a mold air blow is performed to purge the heat medium in the mold, and the cooling medium of the cold oil unit 220 is flown into the mold. The mold 8 is circulated to cool the mold 8 and hot air in the parison is discharged, and then the two-way switching valve 330 is switched to allow cool air of −30 ° C. to −50 ° C. to flow into the parison. After completing the cooling process in this manner, the mold is opened and the molded blow-molded product is taken out.

In the present invention, the transfer of the inner surface of the parison to the smooth surface, which has not been carried out up to now, by the above-described procedure, the surface properties of not only the outer surface of the parison but also the inner surface of the parison are significantly improved. It is possible to obtain a favorable panel-shaped blow-molded product suitable for see-through.
Also, by heating or cooling the mold during blow molding after mold clamping, the surface quality of the parison outer surface is improved, and the blow air inside the parison is switched between hot air and cool air. In addition, the molding process can be completed in a short time, the productivity can be improved by shortening the cycle, and a panel-shaped blow-molded article having excellent surface properties on the inner and outer surfaces of the parison can be produced.
Furthermore, the air initially enclosed in the parison is hot air, which prevents the parison from being rapidly cooled and promotes the expansion of the parison into the product shape smoothly. Further, in the present invention, by applying this method to a light-transmissive resin such as polycarbonate, a panel-like molded article with high transparency which has not been conceived in the past can be obtained. Expanded.

[0015]

As described above, in the blow molding method and the blow molding machine of the present invention, the surface property is improved by heating and cooling the mold and the smooth and high transfer of the parison inner surface as well as the parison outer surface. It is possible to obtain a panel-shaped blow-molded product having excellent surface properties, and shorten the molding process to improve productivity. Further, by using the light-transmissive resin material in the method of the present invention, it becomes possible to produce a resin product having a further excellent transparency, and the use of the blow molded product is expanded.

[Brief description of drawings]

FIG. 1 is an overall vertical sectional view of a blow molding machine according to an embodiment of the present invention.

FIG. 2 is a front view of a heating plate of the blow molding machine according to the embodiment of the present invention.

FIG. 3 is a side sectional view of a heating plate of the blow molding machine according to the embodiment of the present invention.

FIG. 4 is a rear view of the heating plate of the blow molding machine according to the embodiment of the present invention.

FIG. 5 is an operation explanatory view of the heating plate of the blow molding machine according to the embodiment of the present invention.

FIG. 6 is an operation explanatory view of the heating plate of the blow molding machine according to the embodiment of the present invention.

FIG. 7 is an operation explanatory view of the heating plate of the blow molding machine according to the embodiment of the present invention.

FIG. 8 is a heating / cooling system diagram of the blow molding machine according to the embodiment of the present invention.

FIG. 9 is a process drawing of the blow molding method according to the embodiment of the present invention.

FIG. 10 is an overall vertical sectional view of a conventional blow molding machine.

FIG. 11 is a perspective view showing an example of a panel-shaped blow-molded product.

[Explanation of symbols]

 1 Blow Molding Machine 2 Dies (Dice Head) 2a Resin Supply Port 3 Mandrel 3a Core 4 Extruder 6 Paricon Cylinder 6a Paricon Rod 7 Annular Space Passage 8 Mold 9 Blow Pin (Blow Nozzle) 9a Circulation Nozzle 10 Panel Blow Molded product 12 Panel back surface 14 Panel surface 20 Heating plate 20a Degassing through hole 20b Cavity portion 20c Collecting pipe 20d Rear plate 20e Plate heater 22 Hose 30 Plate arm 40 Forward / backward moving cylinder 40a Piston rod 50 Lifting cylinder 50a Piston rod 50b Tip Block 60 Pre-pinch device 100 Parison inner surface transfer device P Parison 200 Mold heating / cooling system 210 Hot oil unit 220 Cold oil unit 230 Mold blow air system 300 Parison blow air Heating / cooling The stem 301 air source 302 liquid nitrogen cylinder 310 vaporizing chamber 320 heater 330 two-way switching valve

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area // B29K 101: 12 105: 32

Claims (3)

[Claims] 1. A heating plate whose surface is mirror-finished on the inner surface of the parison before being clamped and hung down from a blow molding machine and which has through holes for deaeration and which is heated to the molding temperature is pressed against the heating plate. Air existing between the inner surface of the parison and the heating plate is discharged through the degassing through hole, and
After the surface of the heating plate is transferred to the inner surface of the parison to improve the surface property of the inner surface of the parison, the lower end of the parison is pre-pinched, and the mold is clamped while sandwiching the parison and heating is performed. A blow molding method in which air is injected into the parison and held for a certain period of time, then the mold is cooled and cooling air is circulated in the parison to cool the parison, and a blow molded product is taken out after completion of cooling. 2. The blow molding method according to claim 1, wherein the resin material is a light transmissive resin material. 3. A blow molding machine for molding a panel-shaped molded product, wherein the blow molding machine comprises a pair of left and right dies, and the dies are supplied by a hot oil unit to heat the dies. The interior of the parison after the mold is clamped is equipped with a passage through which a refrigerant body supplied by a heat medium or a cooling oil unit for cooling the mold or a blow air for air purging of both the heat medium and the refrigerant body is switched at the switching timing. The mold is equipped with a blow pin for switching and injecting heated air and cooling air into the mold, and the surface is smooth and mirror-finished, and a plurality of degassing through holes are provided on the surface to heat the surface on the back side. A pair of left and right heating plates having plate heaters for heating, a raising and lowering means for raising and lowering the both heating plates inside the parison, and a forward and backward moving means for expanding and contracting the both heating plates in the left and right direction, A blow molding machine, comprising: a parison inner surface transfer device, which is connected to an intake / exhaust system for inhaling air and injecting air into the air through hole.