JPH08142170A - Container made of polyester resin and molding thereof - Google Patents

Abstract

PURPOSE: To obtain a container made of a polyester resin made hard to generate the softening of the region just below the mouth cylindrical part of the shoulder part thereof to be made hard to deform as compared with a conventional polyester resin container at the time of heating, for example, at a time when the content in the container is heated and sterilized by hot water. CONSTITUTION: The mouth cylindrical part of a preform 1 is heat-treated to be crystallized. Next, the region just below the mouth cylindrical part of the preform 1 is locally stretched to be formed into a thin-walled region 4. Finally, the non-crystallized part 3 other than the mouth cylindrical part of the preform 1 is subjected to biaxial stretching blow molding to form a container made of a polyester resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin container formed by biaxially stretch blow-molding a preform and an improvement in its molding method.

[0002]

2. Description of the Related Art A conventional polyester resin container a shown in FIG. 5 has a mouth tube portion b which is milky white due to crystallization by heat treatment, a shoulder portion c following the mouth tube portion b, A polyester resin container a is provided with a body portion d following the shoulder portion c and a hemispherical shell-shaped bottom portion e continuing from the body portion d. The preform A is biaxially stretch blow-molded after heat-treating the mouth tube portion B in A to crystallize it.

In this polyester resin container a, the uncrystallized portion C of the preform A other than the mouth tube portion B is stretched in two directions, the axial direction and the radial direction of the preform A, and the container a shown in FIG. Since the shoulder portion c / body portion d and the bottom portion e of the container a are formed, the shoulder portion c / body portion d and the bottom portion e of the container a are formed.
Has improved mechanical properties such as pressure resistance and heat resistance as compared with the polyester resin before stretching.

Since the mouth tube portion b of the polyester resin container a is crystallized by heat treatment instead of being unstretched, it has a mechanical property such as pressure resistance and heat resistance as compared with the polyester resin before crystallization. The physical properties are improved.

However, since the shoulder portion c following the mouth tube portion b is a transition portion from the mouth tube portion b which is a crystallized region to the stretched region which is an uncrystallized region, the conventional polyester resin container a is used.
Then, as shown in FIG. 6, the thickness of the region c1 immediately below the mouth tube portion b in the shoulder portion c is thicker than the other portions of the container a, and the thin portion of the extending region from the mouth tube portion b. Is gradually decreasing.

That is, in the conventional polyester resin container a, a region c1 of the shoulder portion c immediately below the mouth tube portion b is an uncrystallized and low stretched region. In this region c1, the pressure resistance due to stretching and The degree of improvement in mechanical properties such as heat resistance was smaller than that in the stretched region other than the region c1, and the mechanical strength was sharply reduced at a temperature near 65 ° C.

By the way, since the polyester resin container a has excellent gas barrier properties, chemical resistance, transparency, etc., it is widely used as a container for liquid beverages, liquid seasonings and the like. For example, when used as a container for carbonated drinks, the container a is filled with carbonated drink, the mouth tube portion b of the container a is capped to seal the carbonated drink in the container a, and then hot water is poured into the container a. The carbonated beverage in the container a is subjected to heat sterilization by pouring it over the entire container a from above.

However, in the conventional polyester resin container a, since the mechanical strength of the region c1 of the shoulder portion c just below the mouth tube portion b sharply decreases at a temperature near 65 ° C., for example, the contents in the container a When the container is heat-sterilized with hot water, the region c immediately below the mouth cylinder b in the shoulder c of the container a
1 may soften due to heating, and the mouth tube portion b above the area c1 may be tilted, or the area c1 may swell due to an increase in pressure inside the container a due to heating.

That is, in the conventional polyester resin container a, the region c1 of the shoulder portion c immediately below the mouth tube portion b is softened by heating during heat sterilization, and the container a is opened during heating during heat sterilization. There was a risk of deformation.

[0010]

In view of the above-mentioned dangers of the prior art, in the present invention, when heating during heat sterilization or the like, as compared with a conventional polyester resin container, a container immediately below the mouth tube part in the shoulder part is provided. It is an object of the present invention to provide a polyester resin container in which the region is not easily softened and thus the container is not easily deformed, and a molding method thereof.

[0011]

As a means for solving the above-mentioned problems, in the invention of claim 1, two preforms are provided.
In a polyester resin container that is formed by axial stretch blow molding and the mouth tube is crystallized by heat treatment, the region immediately below the mouth tube in the shoulder portion that follows the mouth tube is shaped into the preform. It employs a configuration in which a thin portion that has been locally stretched is formed by biaxial stretch blow molding.

According to the second aspect of the present invention, a method for molding a polyester resin container, in which the mouth tube of the preform is heat-treated to crystallize and then the preform is biaxially stretch blow molded to form a polyester resin container In the preform after crystallization of the mouthpiece of the preform,
Prior to axial stretch blow molding, a part of the preform immediately below the mouth tube part is locally stretched to a thin part.

[0013]

In the invention of claim 1, the region 12a immediately below the mouth tube portion 11 in the shoulder 12 following the mouth tube portion 11 of the polyester resin container 10 shown in FIGS. 1 and 2 is shown in FIG. It is formed by biaxially stretch-blow molding the thin-walled portion 4 by local stretching that has been shaped on the preform 1. Since it has already been stretched slightly at the stage of the preform 1, the shoulder portion of the container 10 Mouth tube part 1 at 12
The region 12a immediately below 1 is the mouth cylinder part b in the shoulder part c of the conventional polyester resin container a shown in FIGS.
As compared with the region c1 immediately below, it is stretched more, and mechanical properties such as heat resistance and pressure resistance are improved.

According to the second aspect of the present invention, as shown in FIG. 3, the preform 1 is formed after the mouth tube portion 2 of the preform 1 is crystallized and before the biaxial stretch blow molding of the preform 1. Since the portion immediately below the mouth tube portion 2 is locally stretched to form the thin portion 4, when the preform 1 having the thin portion 4 is biaxially stretch blow molded, the preform 1 except the mouth tube portion 2 in the preform 1 is formed. The crystallized portion 3 is stretched in the axial direction and the radial direction of the preform 1, and the thin portion 4 located immediately below the mouth tube portion 2 of the preform 1 is a polyester resin container shown in FIGS. 1 and 2. A region 12a immediately below the mouth tube portion 11 in the shoulder portion 12 following the mouth tube portion 11 of 10 is formed.

Therefore, in the polyester resin container 10 formed by the molding method according to the second aspect of the present invention, the region 12a of the shoulder portion 12 immediately below the mouth tube portion 11 is already slightly stretched at the stage of the preform 1. Figure 5,
Since the shoulder portion c of the polyester resin container a formed by the conventional molding method shown in FIG. 6 is stretched more than the region c1 immediately below the mouth tube portion b, the shoulder of the polyester resin container 10 is formed. The region 12a of the portion 12 immediately below the mouth tube 11 has improved mechanical properties such as heat resistance and pressure resistance as compared with the region c1 of the shoulder c of the conventional polyester resin container a immediately below the mouth tube b. .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A polyester resin container 10 shown in FIGS. 1 and 2 is an example of an embodiment of the invention of claim 1,
A preform 1 shown in FIG. 3 is formed by biaxial stretch blow molding, and has a mouth tube portion 11 that is milky white due to crystallization by heat treatment, a shoulder portion 12 following the mouth tube portion 11, and this shoulder. The mouth tube portion 1 in the shoulder portion 12 is provided with a body portion 13 following the portion 12 and a hemispherical shell-shaped bottom portion 14 continuing from the body portion 13.
The region 12a immediately below 1 is formed by biaxially stretch blow-molding the thin-walled portion 4 that has been shaped in the preform 1 by local stretching.

The molding of the polyester resin container 10 is performed as follows. That is, as shown in FIG. 4A, the bottomed tubular preform 1 is attached to the holder 6.
And heats only the mouth tube portion 2 of the preform 1 to crystallize, and immediately after this crystallization, before the temperature of the boundary region with the mouth tube portion 2 in the uncrystallized portion 3 of the preform 1 decreases. Then, the pressing rod 7 is inserted into the preform 1, and the pressing rod 7 presses the bottom portion 5 of the preform 1 downward with a predetermined force P, as shown in FIG. A portion of the uncrystallized portion 3 of the preform 1 immediately below the mouth tube portion 2 is locally stretched by 1 to 5 mm to form a thin portion 4 immediately below the mouth tube portion 2.

As shown in FIG. 4A, the preform 1 has a relatively high temperature when only the mouth tube portion 2 of the preform 1 is heated and crystallized.
The region of the uncrystallized portion 3 near the mouth tube portion 2 gradually becomes thicker from the mouth tube portion 2 side of the preform 1 toward the bottom portion 5 side.

Therefore, when the bottom portion 5 of the preform 1 is pressed downward by the pressing rod 7 with a predetermined force P, the uncrystallized portion 3 of the preform 1 near the mouth tube portion 2 where the temperature becomes relatively high. The tensile stress per unit cross-sectional area generated by the action of the force P becomes maximum at the portion immediately below the mouth tube portion 2, which is the minimum cross-sectional area portion in the area near the mouth tube portion 2, and as a result, as shown in FIG. As shown in (b), the portion of the preform 1 immediately below the mouth tube portion 2 is stretched to become the thin portion 4.

After forming the thin portion 4 just below the mouth tube portion 2 of the preform 1, the preform 1 having the crystallized mouth tube portion 2 is biaxially stretch blow molded to obtain the mouth tube of the preform 1. The uncrystallized portion 3 other than the portion 2 is stretched in two directions of the preform 1 in the axial direction and the radial direction,
As shown in FIG. 1, a polyester resin container 10 in which the mouth tube portion 11 is crystallized by heat treatment is formed.

The uncrystallized portion 3 of the preform 1 shown in FIG. 3 other than the mouth tube portion 2 is stretched in two directions of the preform 1 in the axial direction and the radial direction, and the polyester resin container shown in FIG. Since the shoulder portion 12, the body portion 13 and the bottom portion 14 of the container 10 are molded, the shoulder portion 12, the body portion 13 and the bottom portion 14 of the container 10 have a mechanical property such as pressure resistance and heat resistance as compared with the polyester resin before stretching. The physical properties are improved.

Moreover, FIG. 2 shows the shoulder portion 12 of the container 10.
The region 12a immediately below the illustrated mouth tube part 11 is formed by biaxially stretch blow molding the thin portion 4 by local stretching which was formed on the preform 1 shown in FIG. In the conventional polyester resin container a shown in the figure, a region c immediately below the mouth tube portion b of the shoulder c shown in FIG.
Compared with No. 1, it is more stretched and thinner, and mechanical properties such as pressure resistance and heat resistance are further improved.

By the way, in the method of molding the polyester resin container 10 described above, the mouth tube portion 2 of the preform 1 is used.
Immediately after heating and crystallizing the preform 1, a portion of the uncrystallized portion 3 of the preform 1 immediately below the mouth tube portion 2 is locally stretched to form a thin portion 4 immediately below the mouth tube portion 2 of the preform 1. Although it is formed, the timing of forming the thin portion 4 just below the mouth tube portion 2 of the preform 1 is not limited to immediately after heating and crystallizing the mouth tube portion 2 of the preform 1. After the crystallization of the mouth tube part 2 and before the biaxial stretch blow molding of the preform 1, it may be performed at any time.

However, if the time is allowed from the crystallization of the mouth tube portion 2 of the preform 1 to the formation of the thin portion 4 directly below the mouth tube portion 2, the mouth tube heated at the time of crystallization of the mouth tube portion 2 Since the portion immediately below the portion 2 becomes cold and it is necessary to reheat this portion at the time when the thin portion 4 is formed, it is necessary to reheat the portion immediately below the mouth tube portion 2 of the preform 1. Immediately after heating and crystallizing the mouth tube part 2 of 1 is preferable to the case where it is not so.

Further, in the method of molding the polyester resin container 10 described above, the portion of the uncrystallized portion 3 of the preform 1 immediately below the mouth tube portion 2 is stretched downward so that the thin wall portion immediately below the mouth tube portion 2. 4 is formed, the stretching direction when forming the thin portion 4 directly below the mouth tube portion 2 is not limited to the downward direction, and may be the radial direction of the preform 1.

[0026]

The polyester resin container according to the first aspect of the present invention has the following advantages over conventional polyester resin containers.
Since mechanical properties such as pressure resistance and heat resistance are improved in the region of the shoulder immediately below the mouth tube, when heating during heat sterilization, etc.
The area is less likely to soften and therefore the container is less likely to deform.

In the polyester resin container formed by the molding method according to the second aspect of the present invention, compared with the polyester resin container formed by the conventional molding method,
Since mechanical properties such as pressure resistance and heat resistance are improved in the region of the shoulder immediately below the mouth tube, when heating during heat sterilization, etc.
The area is less likely to soften and therefore the container is less likely to deform.

[Brief description of drawings]

FIG. 1 is a front view showing an example of implementation of the invention of claim 1.

FIG. 2 is an enlarged end view of a section taken along line YY of the one shown in FIG.

FIG. 3 is a front view showing the preform of the one shown in FIG. 1 before molding in a half section.

FIG. 4 is an explanatory diagram showing a manufacturing method of the one shown in FIG.

FIG. 5 is a front view showing an example of a conventional product.

6 is an enlarged end view of a cross section taken along line XX of the one shown in FIG.

7 is a front view showing the preform of FIG. 5 before molding in a half section.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Preform 2 Preform mouth cylinder part 4 Thin part 10 Polyester resin container 11 Polyester resin container mouth cylinder part 12 Shoulder part 12a Region immediately below the mouth cylinder part in the shoulder

Claims (2)

[Claims] 1. A polyester resin container (1) which is formed by biaxially stretch blow molding a preform (1) and whose mouthpiece (11) is crystallized by heat treatment.
0), the shoulder portion (12) following the mouth tube portion (11)
The region (12a) immediately below the mouth tube part (11) is formed by biaxially stretch blow-molding the thin portion (4) formed by local stretching that was formed on the preform (1). A polyester resin container characterized in that 2. A polyester resin container (10) is formed by subjecting the mouth tube (2) of the preform (1) to heat treatment for crystallization and then biaxially stretch blow molding the preform (1). In the method of molding a polyester resin container (10), after the preform (1) is crystallized in the mouth tube portion (2) and before the preform (1) is biaxially stretch blow molded, the preform (1 (3) A method for molding a polyester resin container (10), characterized in that a portion immediately below the mouth tube portion (2) is locally stretched to form a thin portion (4).