JPH0139896B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for molding a bottle made of polyethylene terephthalate resin, and in particular, a method for molding a bottle made of polyethylene terephthalate resin.
The present invention relates to a biaxial stretch blow molding method for a bottle that improves the physical properties of the neck and shoulder.

Conventional technology Polyethylene terephthalate resin (hereinafter simply referred to as
PET) is widely used in large quantities due to its excellent properties and physical properties. this
Some of the excellent physical properties of a PET bottle are exhibited only when the bottle is biaxially stretched and molded.

Normally, PET bottles are molded by injection molding a piece, which is a primary molded product, and then performing biaxial stretch blow molding on the piece, and the mouth part that is assembled into the blow mold is completely removed. It will be molded into the final shape without being stretched. Further, the neck and shoulder portions connected to the mouth barrel portion are also molded into the final shape without being sufficiently stretched. For this reason, if the bottle is formed by simply biaxially stretching the piece as it is, the mouth, neck, and shoulders will be exposed to the biaxially stretching.
The excellent physical properties of PET will not be exhibited.

Thus, if the piece is simply biaxially stretch blow molded, the mouthpiece, neck and shoulders will be formed into their final shape without being stretched or sufficiently stretched. As a result, for example, high-temperature alcohol may penetrate and cause crazing, various deformations including elongation may occur because the hardness is not sufficient, and furthermore, when the liquid is filled at high temperature for purposes such as sterilization. This can easily cause thermal deformation, resulting in low heat resistance.In particular, when high internal pressure is applied, such as when fruit juice carbonated beverage liquid is stored as an inner liquid, the molding process may not be sufficiently stretched. The thin-walled neck and shoulders have the disadvantage that they extend and deform in the axial direction under the influence of this internal pressure.

Problems to be Solved by the Present Invention The present invention improves the physical properties of the mouth tube portion, which is not subjected to any stretching, and the neck portion, which is not sufficiently stretched. To provide a method for forming a bottle which has excellent physical properties that allow stretching to be carried out and thereby prevent the shoulder from deforming due to internal pressure even when carbonated beverage liquid is stored as the content liquid. The purpose is to

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention provides an outer circumferential surface of the prime minister's abutment directly below the mouth tube equivalent part in a tapered surface shape that expands downward so that the wall thickness of the prime minister's abutment is equal to that of the body's equivalent part. A piece that is thinner than the thickness is injection molded, and the entire mouth part of the piece is crystallized by heat treatment, and at the same time, the outer part of the prime minister's part except for the boundary part between the prime minister's part and the body equivalent part is After the piece is crystallized by heat treatment, the thin inner part of the prime minister's part that is not crystallized is stretched and flowed to form a shoulder between the prime minister's part and the body part, which is then biaxially stretched and blow molded. The structure is such that it is then molded into a bottle.

Effect The present invention prevents crazing of the mouth part and the neck by crystallizing the mouth part that does not receive stretching and the outer part of the neck part that does not receive sufficient stretching.
It also has increased hardness to better tighten caps, etc., and the shoulder part is formed by stretching and flowing the uncrystallized thin wall part of the inner part of the prime area that does not crystallize, so it can be stretched sufficiently. can.

Embodiment The present invention relates to a method for forming a bottle 1 by biaxial stretch blow molding from a piece P that has been injection molded as a primary molded product. The outer circumferential surface of the prime minister part 4' located directly below the mouthpiece equivalent part 5' corresponding to the cylinder part is formed into a tapered surface shape that expands downward, and the wall thickness of this prime minister part 4' is equal to that of the barrel equivalent part. The structure is formed to have a thickness thinner than that of 2'. The outer circumferential surface of the tapered prime portion 4' is molded into exactly the same shape as the outer circumferential surface of the neck portion 4 of the bottle 1 which is biaxially stretch blow molded from the piece P.

Prior to the biaxial stretch blow molding of the piece P formed into the shape described above, the entire area corresponding to the mouth tube 5' and the outer part of the prime portion 4' are heat-treated to crystallize. The crystallized portion of the outer portion of the prime minister portion 4' is arranged such that the boundary portion with the end crystallized portion of the inner portion approximately follows the taper of the outer circumferential surface of the prime minister portion 4', that is, the mouthpiece portion 5'. It is crystallized so that it slopes inward. As a result, the uncrystallized part inside the prime part 4' becomes thin, and when the piece is biaxially stretched, the crystallized part inside the prime part 4' receives sufficient stretching flow. Bottle 1
The shoulder portion 3 will be formed.

Further, when crystallizing the outer part of the prime minister part 4', it is made so that it does not reach the boundary part 6 formed on the curved surface with the trunk corresponding part 2' connected to the prime minister part 4'. This is because if the crystallization reaches the boundary portion 6, this boundary portion 6 becomes a portion that is not deformed by stretching.

As described above, after crystallizing the entire area of the part corresponding to the mouthpiece 5' and the outer part of the prime part 4', this piece P is heated to a temperature that produces a stretching effect, and the part corresponding to the mouthpiece 5 is placed in a blow mold. ' and then biaxially stretched blow molded into bottle 1.

The biaxial stretch blow molding operation itself of this piece P into the bottle body 1 is exactly the same as the conventional operation, but the deformation of each part, especially the deformation of the neck part 4 and shoulder part 3, by the biaxial stretch blow molding. This differs greatly from the conventional case because the outer part of the prime minister part 4' is crystallized and the wall thickness of the prime minister part 4' itself is smaller than that of the body equivalent part 2'. are doing.

That is, as is well known, stretching deformation occurs concentrated in thinner parts, and this thinner part is deformed to a predetermined amount of stretching more quickly. Therefore, piece P is formed by biaxial stretch blow molding. When it is attempted to form the bottle 1, at the initial stage of the stretching process, stretching deformation tends to concentrate on the thinner prime portion 4'.

However, since the outer part of the prime minister part 4' is crystallized and does not undergo stretching deformation, only the inner part of the prime minister part 4' that is not crystallized is subject to the stretching deformation of the trunk corresponding part 2'. At the same time, it is sufficiently stretched and deformed in a manner that it flows toward the body-corresponding portion 2', thereby forming the shoulder portion 3 of the bottle body 1.

When the inner part of the prime abutment part 4' of this piece P is subjected to stretching flow deformation, only the outer part of the mouth tube equivalent part 5' and the outer part of the prime abutment part 4', that is, the crystallized part, are exposed to the blow mold. Since the inner part of the prime part 4' is in contact with the other parts and not in contact with each other, the cooling force from the blow mold has almost no effect on the inner part of the prime part 4' which does not cause crystallization, and therefore the cooling force from the blow mold does not cause crystallization. Stretch flow deformation of the inner portion of the prime minister portion 4' is carried out extremely smoothly.

In this way, the inner portion of the prime minister section 4' that is not crystallized is sufficiently stretched and deformed, so that the second
As is clear from the figure, when the bottle body 1 is stretch-formed, the neck portion 4 is formed by the crystallized outer part of the prime portion 4', and the shoulder portion 3 following this neck portion 4 is formed by the crystallized outer portion of the prime portion 4'. Since the inner portion of the body 2 which is not crystallized is formed by stretching and flowing deformation, it can be formed with a thickness equivalent to that of the body 2 which has been sufficiently stretched.

Therefore, the biaxial stretch blow molded bottle 1
crystallizes the mouth part which forms a part of the bottle body without being stretched at all from the piece P, and the neck part 4 which forms a part of the bottle body 1 without being subjected to almost any stretching deformation. The shoulder portion, which was conventionally formed without being sufficiently stretched, is now formed with sufficient stretching deformation.

Effects According to the bottle forming method of the present invention, since the inner part of the prime area has a thin wall that does not crystallize, the shoulder part can be formed with sufficient stretching, and the same stretching effect as the body part can be applied to the shoulder part. In addition, it is possible to prevent the occurrence of crazing caused by high concentration of alcohol in the mouth barrel and neck, and it is also possible to provide sufficient hardness.
There is no risk of permanent deformation due to tightening of the cap, etc., and it can withstand high heat for sterilizing showers when the content is carbonated fruit juice, and even under the high internal pressure generated by this. This has many effects such as being able to prevent the shoulder from deforming.

[Brief explanation of drawings]

Fig. 1 is a longitudinal cross-sectional view of a main part of a piece molded by the method of the present invention, and Fig. 2 is a longitudinal cross-sectional view of a main part of a bottle formed by biaxial stretch blow molding of the piece in Fig. 1. be. 1: Bottle, P: Piece, 2: Body, 2': Body equivalent, 3: Shoulder, 4: Neck, 4': Prime Minister's Department,
5: Mouth tube part, 5': Mouth tube equivalent part, 6: Boundary part.

Claims (1)

[Claims] 1. In a method of molding a bottle made of polyethylene terephthalate resin, the outer circumferential surface of the prime minister part immediately below the neck equivalent part is shaped into a tapered surface that expands downward, so that the wall thickness of the prime minister part is thinner than the wall thickness of the body equivalent part. The piece is injection-molded, and the entire mouth tube part of the piece is crystallized by heat treatment, and at the same time, the outer part of the prime minister part except for the boundary part between the prime minister part and the trunk corresponding part is crystallized by heat treatment. After this, the thin inner part of the prime area that does not crystallize the piece is stretched and flowed to form a shoulder between the prime area and the body part, and the piece is biaxially stretched and blow-molded into a bottle. How to form a bottle.