JPH03114707A - Manufacture for cylindrical molded body - Google Patents

Abstract

PURPOSE:To make an intermediate layer of a molded body moldable at appropriate positions in parts each in a vertical direction of the molded body, by a method wherein a feed rate of surface layer forming resin through the second resin discharge port is varied at the first and second processes. CONSTITUTION:An intermediate layer forming resin is fed through an extruding machine 19 and enters into a process discharging oxygen barrier layer forming resin through the third resin discharge port 14a. The process possesses the first process forming a part corresponding to a belly part of a preform and the second process forming a part corresponding to the bottom part of the preform. A flow control valve 20 is opened to its full width and a flow rate QS1 of resin flowing through an inner surface layer resin feed passage 15 is increased more than a flow rate QS2 of the resin flowing through an outer surface layer resin feed passage 13, in the first process. A ratio Qr between the flow rates QS1, QS2 of the resin is set up at about 1.6. The ratio Qr is set up at about 0.3 and a position of an oxygen barrier layer is positioned at an inner side of a vessel than the center line of a thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a cylindrical molded body having an intermediate layer.

(Prior Art) Conventionally, plastic bottles are known in which a resin with excellent gas barrier properties, a resin with excellent heat resistance, or the like is provided in the intermediate layer of the wall portion of the container.

In the stretch blow molding method, which is one of the methods for molding plastic bottles, the bottle is formed through a process of forming a preform for forming the plastic bottle, and a process of stretch blowing the preform while it is in a softened state. A method using a mold for forming a preform and a co-injection nozzle having three layers of concentric resin discharge ports is known.

That is, in manufacturing such plastic bottles, first, the mold is closed to form a cavity for the preform.
The resin discharge ports of the co-injection nozzle are communicated with this cavity, and the resin that forms the surface layer of the bottle, such as polyethylene terephthalate or polypropylene, is injected from the resin discharge ports located in the center of the concentric circle and the resin discharge ports located outside the concentric circle. Then, a resin for forming an intermediate layer is discharged from a resin discharge port located in the middle of the concentric circles to form a preform as a first cylindrical molded body within the cavity.

Then, while the molten resin in the cavity is at a temperature that allows stretch blow molding, the preform is carried into the blow mold and stretch blow molding is performed to produce the final cylindrical molded plastic bottle. Form. In such conventional plastic bottle manufacturing methods, since the amount of resin supplied from the three layers of resin discharge ports is constant,
The intermediate layer of the plastic bottle to be molded is formed at a certain position in the thickness direction of the container wall that constitutes the bottle.

(Problem to be Solved by the Invention) However, the oxygen barrier layer of plastic bottles for storing drinks etc. deteriorates due to moisture permeating from the inside of the bottle to the constituent walls of the bottle. If you want to place the oxygen barrier layer on the outside of the container, you want to place it on the outside of the component wall.
There is a problem in that the strength of the bottle against dropping is reduced, and the oxygen barrier layer is more likely to peel off from the surface layer when the bottle is dropped.

Furthermore, when a preform having a multilayer structure is molded by the hot parison method, a resin whose suitable stretching temperature is higher than that of the surface layer is often used for the intermediate layer. Moreover, when the temperature is compared at the same height after cooling the parison, the highest temperature is maintained on the wall thickness center line.

Therefore, when a parison in which the intermediate layer is located away from the thickness center line is cooled for stretch blow molding, although the surface layer maintains the appropriate stretching temperature, the intermediate layer is at a temperature below the appropriate stretching temperature. Something like this happens.

In view of the above problems, the present invention provides a method for manufacturing a cylindrical molded body comprising inner and outer surface layers and an intermediate layer, in which the position of the intermediate layer in the thickness direction can be changed in the process of injecting a parison. The purpose is to provide a method for manufacturing the body.

(Means for Solving the Problems) In order to solve the above problems, the method for manufacturing a multilayer molded body according to the present invention includes a co-injection nozzle in which at least three layers of annular resin discharge ports are opened concentrically. A cylinder is brought into contact with a resin injection hole of a mold in which a cavity for forming a cylindrical molded body is formed, and a cylindrical body is inserted from a first resin discharge port on the inside of the concentric circle and a second resin discharge port on the outside of the concentric circle. In the method for manufacturing a cylindrical molded body, the resin for forming the surface layer of the molded body is discharged, and the resin for forming the intermediate layer is discharged from a third resin discharge port located in the middle of the concentric circles. The step of forming a cylindrical molded body in the cavity by discharging the surface layer forming resin from the second resin discharge port and discharging the intermediate layer forming resin from the third resin supply port includes a first step of forming a portion corresponding to the body of the cylindrical molded body; a second step of forming a portion corresponding to the bottom of the cylindrical molded body;
The first step and the second step are characterized in that the amount of surface layer forming resin supplied from the second resin discharge port is changed.

(Function) According to the method for manufacturing a cylindrical molded body according to the present invention, in the first step and the second step, the surface layer forming resin is discharged from the first resin discharge port and the second resin discharge port. Since the ratio with the supply amount changes, the position of the intermediate layer forming resin from the third resin discharge port changes in the thickness direction of the cylindrical molded body. Therefore, the intermediate layer of the cylindrical molded body can be formed at the most appropriate position in the vertical direction of the cylindrical molded body.

(Example) Hereinafter, an example of the method for manufacturing a cylindrical molded body according to the present invention will be described with reference to the drawings.

(Configuration of Injection Molding Apparatus) FIG. 3 shows the partial configuration of the injection molding apparatus used in this example. When tightened, a cavity 3 is formed. A sprue communicating with the cavity 3 is opened in the fixed mold 2, and a nozzle part 6 of the hot runner 5 is inserted into the sprue bush part 4 (resin injection hole part) in which the sprue is opened.
The tip of the holder is brought into contact with the tip of the holder.

The hot runner 5 has a nozzle part 6 and a nozzle holding part 7 that holds the nozzle part 6. The nozzle portion 6 is a co-injection nozzle and includes first to third cylindrical portions 8,9°10. The first cylindrical portion 8 is formed with a recess 11 having a conical tip and a cylindrical rear end. A second cylindrical portion 9 is disposed within this recess 11 . Similarly, the second cylindrical portion 9 is also formed with a cylindrical recess 12 whose tip end has a slightly smaller diameter. A third cylindrical portion 10 is further inserted into this recessed portion 12 . The tip of the third cylindrical portion 10 protrudes from a third resin discharge 014a opened at the tip of the second cylindrical portion 9, and forms an orifice opened at the tip of the first cylindrical portion 8. We are facing 8a. A first resin discharge port 15a is opened at the tip of the third cylindrical portion 10.

A surface layer resin supply passage 13 is formed between the first cylindrical portion 8 and the second cylindrical portion 9 to supply a surface layer forming resin made of an injection moldable thermoplastic resin.

An elongated passage 13 is provided at the rear end of the surface layer resin supply passage 13.
b is communicating. Further, between the second cylindrical part 9 and the third cylindrical part 10, there is an intermediate layer resin supply passage 14 for supplying a resin forming an oxygen barrier layer (gas barrier layer) as an intermediate layer. It is formed. Intermediate layer resin supply passage 1
A communication path 14b that extends at right angles is connected to the rear end of 4. A surface layer resin supply passage 15 is formed in the third cylindrical portion 11 . A flow control valve 20 is provided at the rear end of the surface layer resin supply passage 15, as shown in FIG. This flow rate control valve 20 is located at the middle part 7 of the nozzle holding part 7.
The surface layer resin supply passage 15 is opened and closed by forward and backward movement of an operating section 20a that is provided in the recess 7b of the intermediate section 7a and is operated from outside the intermediate section 7a.

Both the surface layer resin supply passage 13 and the intermediate layer resin supply passage 14 are formed in an annular shape. Further, the surface layer resin supply passage 15 has a circular cross section. Surface layer resin supply passage 15
The intermediate layer resin supply passage 14 and the surface layer resin supply passage 13 are arranged concentrically, and the surface layer resin supply passage 1
A first resin discharge port 15 a is opened at the tip of the intermediate layer resin supply passage 14 , and a second resin discharge port 14 is opened at the tip of the intermediate layer resin supply passage 14 .
a is open, and a third resin discharge port 13 a is opened at the tip of the surface layer resin supply passage 13 .

A resin supply passage 16 formed in the nozzle holding part 7 communicates with the communication passage 13 b between the surface layer resin supply passage 15 and the surface layer resin supply passage 13 , and the communication passage 14 of the intermediate layer resin supply passage 14 communicates with the communication passage 13 b of the surface layer resin supply passage 15 and the surface layer resin supply passage 13 .
A resin supply path 17 of the nozzle holding portion 7 is in communication with b. An extruder 18 is connected to the resin supply passage 16 that communicates with the surface layer resin supply passage 15 and the surface layer resin supply passage 13, and an extruder 19 is connected to the resin supply passage 17 that communicates with the intermediate layer resin supply passage 14. It looks like this.

From the extruder 18, for example, polyester resin, polyolefin resin, polyamide resin, PVC resin, P
Resin such as S resin and ABS resin is supplied, and the flow control valve 2
The supply amount of resin flowing through the surface layer resin supply passage 15 is controlled by opening and closing of the resin supply passage 15. From the extruder 19, for example, barrier nylon, EvOHl barrier polyester,
Resins with gas barrier properties such as isophthalic group-containing polyesters and polyacrylonitrile, or resins with excellent heat resistance such as polyarylates and polycarbonates are supplied.

(Method for Molding a Cylindrical Molded Body) Next, a method for manufacturing a cylindrical molded body according to this example will be explained using the above injection molding machine.

In this example, the cylindrical molded body is a preform for performing injection stretch blow molding, and after molding this preform with an injection molding machine, it is carried into a blow molding machine and blow molding is performed. Form a plastic bottle. When a plastic bottle is molded by injection molding, this plastic bottle corresponds to a cylindrical molded body.

FIGS. 1 and 2 illustrate the process of supplying resin in the injection molding apparatus according to this embodiment.

First, the fixed mold 2, the movable mold 1, and the core 2a are clamped together to form a cavity 3 for injection molding a preform. Next, the tip of the nozzle part 6 of the hot runner 5 is brought into close contact with the sprue bush part 4, the flow control valve 20 is set in a half-open state, and the surface layer forming resin is supplied from the extruder 18 into the resin supply path 16. and the first resin discharge port 15a and the second resin discharge port 15a.
The surface layer forming resin is discharged into the cavity 3 from the resin discharge port 13a.

Next, as shown in FIG. 4, a step is started in which the intermediate layer forming resin is supplied from the extruder 19 and the oxygen barrier layer forming resin is discharged from the third resin discharge port 14a. This step consists of a first step of forming a body portion P2 of the preform P, and a second step of forming a bottom portion P3 of the preform P.
It has the following steps. In the first step of forming the body portion P2 of the preform P, the flow rate control valve 20 is fully opened and the flow rate QS+ of the resin flowing through the inner surface layer resin supply passage 15 is controlled to flow through the outer surface layer resin supply passage 13. Increase the resin flow rate from QS2. The ratio Qr between the resin flow rate QS+ and the resin flow rate QS2 is Qr=QS+/Q
32, the ratio Qr when forming the mouth P1 of the preform P is approximately 1, but in the first step, the ratio Qr is set to approximately 1.6. In the second step, the ratio Qr is set to about 0.3, and the position of the oxygen barrier layer pb in the bottom portion P3 of the preform P is aligned with the thickness center line P1.
Position it closer to the inside of the container. When the oxygen barrier layer Pb is formed in the bottom portion P3, the supply of the intermediate layer forming resin from the extruder 19 is stopped, and the flow control valve 20 is fully opened to separate the inner surface layer forming resin and the outer surface layer forming resin. The flow rate ratio Qr is returned to approximately 1 again, and the nozzle bushing portion 4a of the cavity 3 is filled with the surface layer forming resin.

When the cavity 3 is filled with resin, the supply of resin from the extruder 18 is stopped and pressure retention is started, and the hot runner 5 is separated from the nozzle bushing part 4, so that the preform P can be stretched and blown. At some point, the preform P is removed and blow molding is performed using a blow molding machine (not shown). As a result, a plastic bottle 21 as shown in FIG. 7 is molded.

In the body 21a of this plastic bottle 21, the oxygen barrier layer 22a is located along the wall thickness center line 23a of the body 21a.
Since it is located on the outside of the container, it takes longer than before for moisture to reach the oxygen barrier layer 22a even if it is filled with a secret substance containing moisture, and the deterioration time of the oxygen barrier layer 22a becomes longer. Moreover, the bottom part 2 of the plastic bottle 21
In case 1b, the oxygen barrier layer 22a is located inside the container from the wall thickness center line 23b of the bottom part 21b, so that the strength against dropping of the bottle is improved compared to the conventional case.

(Effects of the Invention) Since the method for manufacturing a cylindrical molded body according to the present invention is configured as described above, the formation position of the intermediate layer in the thickness direction can be changed in the vertical direction of the cylindrical molded body,
By having the intermediate layer in each part of the molded body in the vertical direction, the molded body can be molded at appropriate positions.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the resin flow rate adjustment state when manufacturing a preform according to an embodiment of the present invention, and FIG. 2 shows a supply process of the surface layer-forming resin and the intermediate layer-forming resin of the present embodiment. 3 is a configuration diagram of the injection molding machine used in this example, FIG. 4 is a partially enlarged view of the state in which resin is injected into the cavity, FIG. 5 is a sectional view of the flow control valve, and FIG. The figure is a cross-sectional view of a preform as a cylindrical molded body of this example, and FIG. 7 is a cross-sectional view of a plastic bottle formed from the preform. DESCRIPTION OF SYMBOLS 1... Movable mold, 2... Fixed mold, 3... Cavity, 5... Hot runner 6... Co-injection nozzle 1
3...Outer surface layer resin supply passage 13a...Second resin discharge port, 14...Middle layer resin supply passage 14a...Third resin discharge port, 15...Inner surface layer resin supply Passage, 15a... First resin discharge port, 18.19... Extruder, 20... Flow rate control valve, 2
DESCRIPTION OF SYMBOLS 1...Plastic bottle, 22a...Oxygen barrier layer, 23a, 23b...Thickness center line, P...Preform, P2...Body equivalent part P3...Bottom equivalent part

Claims (1)

[Scope of Claims] A co-injection nozzle having at least three layers of annular resin discharge ports concentrically opened is brought into contact with a resin injection hole of a mold in which a cavity for forming a cylindrical molded body is formed, The surface layer forming resin of the cylindrical molded body is discharged from a first resin discharge port on the inside of the concentric circle and a second resin discharge port on the outside of the concentric circle, and a third resin discharge port located in the middle of the concentric circle is discharged. In a method for manufacturing a cylindrical molded body in which an intermediate layer-forming resin is discharged from a resin discharge port, while the surface layer-forming resin is discharged from the first and second resin discharge ports, the intermediate layer-forming resin is discharged from the third resin supply port. The step of discharging the intermediate layer forming resin to form a cylindrical molded body in the cavity includes a first step of forming a portion corresponding to the body of the cylindrical molded body, and a portion corresponding to the bottom of the cylindrical molded body. the second forming
A method for manufacturing a cylindrical molded body, characterized in that the amount of surface layer forming resin supplied from the second resin discharge port is changed in the first step and the second step. .