JPH0681699B2 - Molding method for deformed hollow container - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of stretch blow molding a parison of an injection-molded thermoplastic synthetic resin into a deformable hollow container.

[Prior Art] A packaging container made of a thermoplastic resin such as polyethylene terephthalate is formed by axially stretching an injection-molded bottomed parison and blowing air into it.

[Problems to be Solved by the Invention] In general, injection molding of a parison is carried out by using a cavity mold and a core mold which is positioned at the center of the cavity, and the core mold is removed from the parison after molding.

In consideration of the removal after molding, the peripheral side surface of the core mold is inwardly inclined from the mouth molding part of the parison to the tip where the inner bottom end of the parison is molded. Even if the parison is attached, the core mold can be easily pulled out.

For this reason, the shape of the parison formed by injection molding is limited to those having no bend in the center line, and inevitably the hollow container molded from the parison is also limited to the shape in which the mouth is located at the center of the container. Further, even if it is possible to form a deformed parison with a bent side portion, it is difficult to axially stretch such a parison, and from this point also, it is difficult to form a deformed hollow container by stretch blow molding. .

The present invention was conceived in order to solve the above-mentioned problems in injection stretch blow molding, and its object is a deformed hollow container in which the mouth is largely displaced from the center of the container or inclined from the center of the container from the injection molded parison as usual. It is an object of the present invention to provide a new molding method capable of stretch-blow molding.

[Means for Solving the Problems] The present invention according to the above-mentioned object is to perform injection molding of a bottomed parison having a straight center line, stretch the pariso in the axial direction, and then apply external pressure to the side of the parison to form a barrel. Is formed into a deformed deformed parison from a required location, and a deformed hollow container whose mouth center is displaced from the center of the main body is blow-molded from the deformed parison, so that a deformed hollow container can be formed even by injection stretch blow molding. Become.

Axial stretching of the parison may be carried out during temperature control in some cases, and the deformed parison is pre-blended once in a temperature-controlled mold before blow molding, and the preform molded therein is deformed into a deformable hollow container. It can also be blow molded.

[Operation] In the above method, an injection-molded parison is bent to form a deformed parison. Therefore, there is no hindrance to the injection molding of the parison, and the axial direction before molding into the deformed parison. Since stretching is performed, stretching can be performed easily, and a biaxially oriented hollow container having a deformed mouth can be molded even though a parison is injection-molded.

[Examples] FIG. 1 First, a bottomed parison 1 having a straight center line made of a thermoplastic resin such as polyethylene terephthalate is injection-molded in an injection mold having a normal structure.

FIG. 2 The mouth portion 2 of the parison 1 is held by a lip die 3, and a core 5 having a stretching rod 4 movably in the center is inserted into the mouth portion 2 from inside the rib die. At this time, the parison temperature is maintained within the range of 105 ° to 110 ° C except for the mouth portion 2. In this state, the stretching rod 4 is stretched and the trunk of the parison 1 is
It is stretched about 1.3 times in the axial direction.

FIG. 3 Next, the stretching rod 4 is returned to its original position, and the molding member 6, which has been previously installed so as to be vertically movable below the stretching position, is moved upward to press the parison body laterally.

The molding member 6 is formed by a block whose side surface facing the parison is inclined at about 35 degrees, and is heated to a temperature of about 90 ° C. so that the parison temperature is not partially lowered when the parison is pressed.

The parison body, which is sequentially pressed laterally from the bottom to the upper side along the inclined side surface of the molding member 6, is bent at an angle of 35 degrees to form the modified parison 7.

When the molding of such a modified parison 7 is completed, the core 5
Is drawn from the lip mold 3 together with the drawing rod 4, and the molding member 6 is lowered to return it to its original position. With the removal of the molding member 6, the bent portion of the deformed parison 7 also returns to the original shape, but this return angle is settled at about 5 degrees, and the deformed parison 7 in which the body portion is inclined at about 30 degrees is formed. .

FIG. 4 The modified parison 7 is transferred to the blow mold 8 while the mouth 2 is held by the rib mold 3. The blow mold 8 is composed of a split mold that opens and closes in the lateral direction, and a bottom mold 10 is provided at the bottom of the cavity 9. The cavities 9 are provided so as to be inclined at an angle of about 30 degrees except for the mouth portion, and the modified parison 7 is positioned at the center of the cavities 9 and then the mold is closed.

A blow core 11 is inserted into the mouth portion 2 through the rib mold 3, and after the mold is clamped, air is blown from the blow core 11 into the deformed parison at high pressure. The deformed parison 7 expands to the full cavity as shown by the chain line by the air pressure and becomes a hollow container 12.

After the blow molding, the mold is opened, and the blow core 9 is extracted, and then the hollow container 12 is transferred to the take-out position together with the lip mold 3.

Fig. 5 In the above hollow container 12, the mouth 2 of the parison serves as the mouth of the container as it is, and the hollow container 12 is formed at a position largely deviated from the center of the flat container body and by the mouth 2 inclined outward. It becomes a deformed hollow container.

When temperature control of the parison is required in the above step, the temperature control is preferably performed at the time of stretching the parison.

FIG. 6 shows the state, in which the temperature control pot 13 is preliminarily arranged at the stretching position so that it can be moved up and down, and the temperature control pot 13 is stretched at the time of stretching.
Raise 13 to store parison 1 in pot. In the stretching under the temperature controlled state, the temperature decrease due to the thinning is prevented, and the temperature difference is leveled by the heat from the outside.
Therefore, the temperature control drop is improved more than when the temperature control is performed before and after the stretching.

The stretched and temperature-controlled parison 1 is secondarily molded into the deformed parison 7 at the next position. The molding member 6 is movably arranged laterally of the parison so as not to interfere with the temperature-controlled pot 13. If it can be provided, after the temperature control, the secondary molding to the deformed parison 7 can also be performed at that position.

A hollow container after pre-blowing the modified parison 7
It is also possible to perform 12 blow moldings.

FIGS. 7 and 8 show the case where both the secondary molding of the parison and the pre-blowing are performed at the same location, in which the pre-blow mold 14 which opens and closes in the lateral direction is arranged at the stretching position, and the molding is performed below. The member 6 is arranged so that it can be raised and lowered.

Molding into the modified parison 7 is performed as shown in FIG.
At the center of the pre-blow mold 14 in the mold open state, the molding member 6 is lifted after stretching. When the molding is completed, lower the molding member 6 and adjust the temperature to 80 ° -110 ° C.
The mold is closed.

Fig. 8 After mold clamping, air is blown from the air passage 15 formed between the core 3 and the stretch rod 4 to the deformed parison 7 located in the center of the cavity 16 to pre-blow to form the preform 17. To do.

After opening the mold, the preform 17 is transferred to the blow mold to blow mold the hollow container 12 from the preform 17 as shown in FIG.

Molding of such a deformed hollow container is a hot parison method in which injection molding of a parison is continuously performed and stretch blow molding is performed. Cold injection is performed by temporarily stocking the injection-molded parison and then adjusting the heating temperature of the parison. It can be applied to any of the parison methods.

Further, the shape of the container is not limited to that shown in the figures, and various shapes can be formed under the same process.

[Effects of the Invention] As described above, according to the present invention, an injection-molded bottomed parison is axially stretched and then secondary-molded into a deformed parison, and the deformed parison causes the mouth portion to largely deviate from the center of the container. Or, since a deformed hollow container that is inclined is blow-molded, the parison can be injection-molded in the same manner as when molding a normal parison without requiring a special mold or technique for injection-molding the parison. . In addition, since the modified parison has already been stretched in the axial direction, even if the hollow container is formed by blow molding, the resin forming the container body is biaxially oriented, which is different from the usual biaxially oriented container. It has similar strength and transparency.

Furthermore, in the usual molding method, the wall thickness of the hollow container (molded product) far away from the central axis of the parison is considerably thinned, and stress whitening or rupture may occur. In the present invention, a substantially uniform wall thickness distribution can be obtained as a whole, the temperature of the parison and the pre-blow can be easily performed, and the preform can be molded to form a hollow container having a shape difficult to mold from the modified parison. It has the advantage that it can be molded.

[Brief description of drawings]

The drawings illustrate a method for forming a deformed hollow container according to the present invention. FIGS. 1 to 4 are partial cross-sectional views for sequentially explaining a forming process, and FIG. 5 is a cross-sectional view of a formed deformed hollow container,
FIG. 6 is a sectional view during temperature control, and FIGS. 7 and 8 are sectional views showing the pre-blow molding process. 1 ... Parison, 2 ... Port 3 ... Lip type, 4 ... Extension rod 5 ... Core, 6 ... Molding member 7 ... Modified parison, 8 ... Blowing type 9 ... Cavity, 11 ... Blow core 12 …… Deformed hollow container, 13 …… Temperature control pot 14 …… Pre-blow type, 16 …… Cavity 17 …… Preform

Claims (3)

[Claims] 1. A bottomed parison having a straight center line is injection-molded, the parison is stretched in the axial direction, and then external pressure is applied to the side of the parison to form a deformed parison in which the body is bent from a required location. Then, the method for forming a deformed hollow container is characterized in that the deformed hollow container is blow-molded from the deformed parison with the center of the mouth largely displaced or inclined from the center of the main body. 2. The method for molding a deformed hollow container according to claim 1, wherein temperature control is performed when the parison is stretched in the axial direction. 3. The method for molding a deformed hollow container according to claim 1, wherein the deformed parison is pre-blown in a temperature-controlled mold before the blow molding.