JP2801847B2 - Heat and pressure resistant free-standing container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched blow-molded saturated polyester free-standing container suitable for filling carbonated beverages, soft drinks, and the like.
The present invention relates to a self-standing container having improved heat resistance and pressure resistance at the time of heat sterilization of contents and excellent in impact resistance.

[0002]

2. Description of the Related Art Conventionally, as a heat-resistant and pressure-resistant container, in order to enhance the pressure resistance of the container body, a bottom portion is bulged and formed into a hemispherical shell shape, and a base cup formed into a cylindrical shape with a bottom is attached thereto. Thus, the mainstream was to provide a container with a self-supporting function. However, the use of the base cup requires that the base cup be separately formed and fixed, the weight of the container increases, the size of the container increases, and the hot water is sufficiently supplied to the bottom of the container in the heat sterilization process. Therefore, there are various problems such as that the contents cannot be heat-sterilized smoothly, and that water is accumulated in the base cup and it is difficult to quickly drain the contents.

[0003] Further, from the viewpoint of resource saving and environmental issues, it is desired to effectively reuse used empty containers.
For containers equipped with a base cup, the container body and the base are usually
Since the materials of the scoop and the adhesive are different, when they are reused, they must be separated, and there is a problem that the cost is increased in terms of process.

[0004] Because of these problems, a heat-resistant and pressure-resistant container that does not require a base cup is desired. There have been several proposals for pressure-resistant containers that do not require a base cup. Generally, a plurality of legs are radially bulged around a center of a bottom, and a valley is formed between the legs. Either a structure having a line wall or a champagne type structure. These are described, for example, in JP-B-48-570.
No. 8, No. 59-40693, No. 61-9170, JP-A-63-202424, and JP-A-3-43342.
No., etc.

[0005]

However, although the containers described in each of these items can provide satisfactory performance as a pressure-resistant container, they are not suitable for use as a heat-resistant and pressure-resistant container for performing a heat sterilization step. Cannot get enough performance. That is, the container described in each of the above items has a bottom central portion and a low stretching region existing around the central portion, and the temperature of the contents is 50 ° C. during heat sterilization.
When the temperature rises to about 70 ° C., the internal pressure increases and the container material itself easily undergoes creep deformation, so that the center of the bottom protrudes and the container loses its self-standing stability.

As a method for solving this problem, for example,
It is conceivable to use the container described in JP-A-5-85535. Since this container is a container in which the central portion of the bottom is crystallized and the periphery of the central portion is sufficiently stretched, it is considered that the container has sufficient pressure resistance against an increase in internal pressure during heat sterilization. However, when a part of the bottom is crystallized with high density as in this container, the crystallized portion becomes brittle, and the impact resistance when a drop impact is applied to the container is extremely poor, losing practicality. Problems arise.

The present invention has solved such a problem, and (A) the center of the container bottom and / or (B)
The low stretch area existing around the center part has a density of 1.337 g / c.
By crystallization half such that the m ³ ~1.360g / cm ^3,
An object of the present invention is to provide a heat-resistant and pressure-resistant self-standing container which does not lose its self-standing stability due to creep deformation at the bottom during heat sterilization of the container and has excellent impact resistance and chemical resistance.

[0008]

SUMMARY OF THE INVENTION The present invention is directed to a biaxially stretch blow-molded saturated polyester container having a self-supporting bottom structure, comprising: (A) a central portion of the container bottom and / or (B) A heat-resistant and pressure-resistant self-supporting container characterized in that a low-stretched region existing around the central portion is semi-crystallized so that the density becomes 1.337 g / cm ^{3 to} 1.360 g / cm ^3. Is what you do.

As the saturated polyester resin used in the present invention, polyethylene terephthalate resin is suitable from the viewpoints of strength, transparency and gas barrier properties.

As the container bottom structure in the present invention, there are a structure in which a plurality of legs are radially bulged around the center of the bottom and a champagne type structure.

In the present invention, (A) the central portion of the bottom of the container and / or (B) the low stretching region existing around the central portion is adjusted so that the density is 1.337 g / cm ^{3 to} 1.360 g / cm ^3. The semi-crystallized region preferably occupies 50% or more of each part. Further, the low-stretched region adjacent to the center portion of the valley line may be partially semi-crystallized. In addition, the low stretching in the present invention means that the stretching ratio is less than 1.5 times. Biaxial stretching means a stretching ratio of 1.5 times or more, preferably 2 to 6 times.

In the present invention, as a method for semi-crystallizing the (A) central portion of the container bottom and / or (B) the low-stretched region existing around the central portion, a reheated preform is biaxially stretched. When blow molding, the bottom should be 100 ° C
Heat fixing at ~ 150 ° C for 3-15 seconds, or
There is a method in which the bottom of the container after the biaxial stretch blow molding is heated by hot air or an infrared heater. These two methods are easier to control the semi-crystalline state than the method in which the bottom of the preform is preliminarily semi-crystallized and then subjected to biaxial stretch blow molding, and the semi-crystallization is performed without leaving a low stretching area. It can be crystallized.

The density of the polyethylene terephthalate resin in the translucent and semi-crystallized low-stretching region at the bottom of the container is 1.
337 g / cm ^{3 to} 1.360 g / cm ³ , preferably 1.340 g / cm ^{3 to} 1.35
The range of 0 g / cm ³ is good.

If the density of the low-stretched area is 1.337 g / cm ³ or less, the container bottom easily undergoes creep deformation during heat sterilization, and the container loses its self-standing stability. Also, 1.360 g / c
If it is at least m ³ , the impact resistance will be reduced, and the portion will be easily broken when a drop impact is applied to the container.

Further, by semi-crystallizing the low-stretched portion, it is possible to improve the chemical resistance to the lubricant on the conveyor line of the filling factory, and to suppress the occurrence of stress cracks.

[0016]

The present invention will be described below in more detail with reference to examples. The preform obtained by injection molding polyethylene terephthalate resin is reheated, then placed in a blow mold, stretched in the circumferential direction by air blow while stretching in the axial direction with a stretch rod, and biaxial stretch blow molding Was done.
At this time, while the bottom of the mold is heated to 120 ° C., heat setting is performed for 5 seconds. Subsequently, the molded body is cooled by circulating air at normal temperature in the blow mold, and is taken out.
A 5 liter container 1 was obtained (FIG. 1). As shown in FIG. 2, the bottom portion 2 of the container 1 has five leg pieces 5 bulging radially around the central portion at equal intervals, and a valley portion 6 is formed between the leg pieces 5. The low-stretched region existing in the center 3, the center periphery 4, and the valley 6 is semi-crystallized. This container 1 was filled with carbonated water of 2.5 gas volume at 5 ° C. to a fill line of 43 mm, capped, and then subjected to a hot water shower at 70 ° C. for 30 minutes, and then allowed to cool naturally to room temperature. However, the bottom of the container did not lose its independence stability from beginning to end. Next, the filled container was dropped from a height of 1.5 meters in an upright state, and as a result, there was no breakage at the bottom of the container. The density of the semi-crystallized portion at the bottom of the container was measured by a density gradient tube method to be 1.340 g / cm ^{3 to} 1.347 g / cm ³ .

[0017]

As described above, according to the present invention, it is possible to provide a heat-resistant and pressure-resistant self-standing container which prevents the bottom portion from protruding at the time of heat sterilization and has excellent impact resistance and chemical resistance. Further, since the container according to the present invention does not require a base cup, the hot water during the heat sterilization treatment sufficiently reaches the bottom of the container, and the contents can be heat sterilized smoothly.

[Brief description of the drawings]

FIG. 1 is a sectional view of a self-standing container of the present invention.

FIG. 2 is a bottom view of the self-standing container of the present invention.

FIG. 3 is a sectional view of the bottom of the self-standing container of the present invention.

[Explanation of symbols]

 1. Independent container 2. Bottom 3. Central part 4. 4. Around the center Leg piece 6. Valley line

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-305620 (JP, A) JP-A-2-98536 (JP, A) JP-A-55-163137 (JP, A) JP-A-4- 144731 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B29C 49/02-49/14 B29C 49/64-49/68 B65D 1/00 B29K 67:00 B29L 22:00

Claims (1)

(57) [Claims] 1. A biaxially stretched blow molded saturated polyester container having a self-supporting bottom structure, comprising:
(A) The central portion of the bottom of the container and / or (B) the low-stretched region existing around the central portion has a density of 1.337 g / cm ³ to 1.37 g / cm ³ .
A heat-resistant and pressure-resistant self-standing container characterized by being semi-crystallized to 360 g / cm ³ .