JPH11227734A - Self-standing pressure-resistant plastic bottle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent occurrence of environmental stress cracking caused by internal pressure, deterioration of self-stranding stability caused by indefinite deformation at leg parts and occurrence of breaking arising from drop impulse. SOLUTION: In a self-supporting pressure-resistant plastic bottle wherein a plurality of hollow leg parts 2 that project almost radially toward the peripheral downside from the center 10 of the bottom part in a pressure-resistive shape projecting downward approximately in a hemispherical surface are formed with a grounding part 21 provided at the outer lower end of each of the leg parts 2 and troughs 3 extending almost radially from the center 10 of the bottom part are formed respectively between the adjoining leg parts 2, a small uneven part 4 is formed at the internal surface in an area where orientation is insufficient at the center 10 of the bottom part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of filling a content liquid having a high internal pressure, such as a juice-containing gas-containing beverage, having heat resistance and pressure resistance to withstand heat sterilization, and integrally forming legs for self-supporting. Self-standing pressure-resistant plastic bottle.

[0002]

2. Description of the Related Art In recent years, plastic bottles obtained by stretch blow molding plastics such as polyethylene terephthalate and polyethylene naphthalate are extremely superior in impact resistance and lighter weight than glass, so that they can be filled with various beverages. It has been widely used as a container.

[0003] Utilizing strength enhancement by stretch blow molding, it is also used for beverages that generate internal pressure, such as carbonated beverages and beer. In this case, in order to cope with the internal pressure, the bottom of the main body is formed downward, the bottom of the pressure-resistant shape protruding in a substantially hemispherical shape, and the hollow legs having the grounding portion are arranged at equal intervals in the outer peripheral direction of the bottom. A pressure-resistant plastic bottle which is self-supporting by integrally forming a plurality of radially-integrated bottles, so-called one-piece bottles, is also widely used.

[0004] These self-standing pressure-resistant plastic bottles
Due to the fact that the center of the bottom is difficult to stretch, and because it has a complex shape with multiple hollow legs formed on the almost hemispherical bottom, depending on the severe environment such as summer heat,
There is a possibility that environmental stress cracking due to internal pressure or cracking due to drop impact may occur.

Therefore, focusing on these points, conventionally, for example, Japanese Patent No. 2604499 discloses that a large number of stresses that cause a local thickness change, such as fine unevenness, on the outer surface of a stretch-deficient region at the bottom. The invention of shaping the concentration reduction function is described.

[0006]

However, the above conventional self-standing pressure-resistant plastic bottle has an effect of preventing environmental stress cracking and cracking due to internal pressure and the like by forming a large number of stress concentration reducing portions on the outer surface. Although recognized, there was a problem that it was still insufficient to prevent environmental stress cracking and cracking, especially at the center of the bottom.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and to provide a self-supporting pressure-resistant plastic bottle which is less likely to cause an environmental stress crack due to an internal pressure or a crack due to a drop impact, especially in the center of the bottom. It is.

[0008]

According to the present invention, there are provided a plurality of hollow legs, which project downward from the center of a pressure-resistant shape projecting substantially in a hemispherical shape and radiate substantially radially downward from the center of the bottom. A self-standing pressure-resistant plastic bottle having a ground contact portion at an outer lower end of a leg portion and a valley portion extending substantially radially from the center of the bottom portion between the leg portions. A self-standing pressure-resistant plastic bottle characterized by having small irregularities formed on the surface.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a partially sectional front view showing an example of a self-standing pressure-resistant plastic bottle of the present invention, and FIG.
Sectional views, FIGS. 3 and 4 are bottom inner surface views showing another example of the self-standing pressure-resistant plastic bottle of the present invention, and FIG. 5 is a perspective view showing an example of a preform.

According to the present invention, as shown in FIGS. 1 to 4, a plurality of hollow legs 2 projecting substantially radially downward from the center 10 of the pressure-resistant shape projecting downward in a substantially hemispherical shape. In a self-standing pressure-resistant plastic bottle, which is formed individually and has a ground contact portion 21 at the outer lower end of each leg portion 2 and a valley portion 3 extending substantially radially from the bottom center 10 between the leg portions 2, A self-standing pressure-resistant plastic bottle, wherein small irregularities 4 are formed on the inner surface of the insufficiently stretched region at the bottom center 10.

As shown in FIG. 1, for example, the self-standing pressure-resistant plastic bottle of the present invention has a plug portion 11 at an upper end, a shoulder portion 12 extending circumferentially below the plug portion 11, and a cylinder below the shoulder portion 12. It consists of a torso 13 and a bottom 14 below the torso.

In the present invention, the bottom portion 14 often has a bottom portion 1 which protrudes downward in a substantially hemispherical shape. If the bottom portion 1 has a pressure-resistant shape, the curvature may change. The center may be recessed upward.

The bottom 1 has a center 10 and is formed with a plurality of hollow legs 2 projecting substantially radially downward from the center 10 of the bottom.

The hollow leg 2 has a ground contact portion 21 at the outer lower end, and a leg lower surface 22 extending inward and upward from the ground contact portion 21;
It has a leg outer surface 23 extending outwardly from the ground contact portion 21 at a steep slope and continuing to the trunk portion 12, and a leg side surface 24 extending upward from both sides of the ground contact portion 21 and continuing to the valley bottom 31 of the valley portion 3.

The valley 3 is formed so as to be sandwiched between the two legs 2, and the leg side surface 24 also serves as a side surface of the valley 3,
The valley bottom 31 forms a part of the pressure-resistant bottom portion 1 that protrudes in a substantially hemispherical shape, which is the basic shape of the bottom portion 14, extends outwardly upward from the bottom center 1 in a substantially curved shape, and is continuous with the trunk portion 13. ing. The valley bottom 31 may have a linear shape or a wide planar shape.

In the present invention, when the preform is heated and blow-molded, the stretch-deficient region near the bottom center 10 is located at the center of stretching, so that the circumferential magnification cannot be gained. Therefore, although the thickness is larger than other portions, it is a portion where it is difficult to improve mechanical strength by stretching orientation and resistance to moisture and chemical substances.

In addition, when the bottom center 10 is added, the stress exerted by the internal pressure and the drop impact on the hollow leg 2 and the valley 3 extending substantially radially is the radial shape center. It is also a unique point that it is easy to concentrate on the bottom center 10.

In the present invention, the formation of the small irregularities 4 on the inner surface of the understretched region at the bottom center 10 surprisingly results in environmental stress cracking on the bottom 1 even by long-term stress due to internal pressure. This has the effect that cracking is unlikely to occur even if a sudden stress occurs due to a drop impact.

Although the reason is not clear, micro defects, which are thought to trigger environmental stress cracking and cracking, so-called crazing, rather occur on the outer surface. Irregularities have insufficient effect, whereas small irregularities 4 according to the present invention.
The effect of increasing the surface area of the inner surface of the understretched region of the bottom center 10 and the buffering action based on the uneven shape disperses the stress applied to the bottom at the inner surface, thereby preventing the concentration on the outer surface. It is considered that the generation itself can be suppressed, and even if there is crazing, it is unlikely to lead to environmental stress cracking or cracking.

In the example of FIGS. 1 and 2, each of the small irregularities 4 has a substantially spherical concave portion 41 having a depth from the inner surface of 0.1 to 1 mm and an opening of 0.2 to 2 mm. As a unit, a number of closely arranged units are employed.

In the example shown in FIG. 3, as the configuration of the small unevenness 4, a plurality of small concave grooves 42 are arranged so as to form a radial pattern from the center.
However, it has a curved shape that gradually increases clockwise as it goes outward.

The small unevenness 4 in this example not only disperses the stress applied to the bottom on the inner surface but also arranges the small unevenness 4 in a slanted radial pattern so that the stress tending toward the bottom center 10 is changed in the rotational direction. Concentration can be prevented by flowing, so that environmental stress cracks near the center of the bottom and cracks due to impact can be more effectively prevented.

The fine concave grooves 42 constituting the small irregularities 4 include:
A range of 0.1 to 1.0 mm, a width of 0.2 to 2 mm, and a length of 2 to 15 mm from the inner surface of the bottom whose depth or height is a reference can be suitably adopted.

In the example of FIG. 4, a large number of narrow grooves 42 are formed on the inner surface near the bottom center 10 and are inclined clockwise from the bottom center 10 toward the periphery with respect to the virtual radiation line L. Not only on the outer surface as shown by the dotted line,
With respect to the virtual radiation straight line L, a narrow concave groove 43 inclined in a counterclockwise direction from the bottom center 10 toward the periphery is formed. The narrow concave groove 42 is branched outward to form a denser small unevenness 4.

Thus, by forming the small irregularities 4 on both the inner and outer surfaces, cracks due to environmental stress cracks and impacts near the center of the bottom can be more effectively prevented.

In order to produce the self-standing pressure-resistant plastic bottle of the present invention, for example, polyethylene terephthalate,
A test tube preform is made by injection molding plastic such as polyethylene naphthalate, and heated to a stretching temperature above the glass transition temperature and below the melting point, and biaxially stretched by blowing high-pressure fluid in a blow mold. A method of blow molding can be adopted.

In order to form the small irregularities 4, a shape corresponding to the small irregularities 4 is dug into the tip of a stretch rod for extending in the axial direction during blow molding, and is formed between the bottom die of the blow molding die. It may be formed by pinching. In this case, if the small irregularities 4 are formed in a radial shape that matches the stretching direction as shown in FIG. 3, there is an effect that the resistance is small and the film is easily stretched.

Further, as shown in FIG. 5, by embedding small irregularities 50 in the male mold 5 of the preform injection mold, small irregularities 40 are formed in advance on the bottom of the preform 6 itself. This may be blow molded. In this case, although the final small irregularities 4 are somewhat stretched during blow molding and lose their shape as they move away from the center 10 of the bottom, no matter what the shape of the small irregularities 40, the shape of the small irregularities 40 is caused by contact with the blow mold. Since there is no physical resistance, there is an effect that the design is free.

[0030]

According to the present invention, a plurality of hollow legs protruding substantially radially downward from the center of the bottom of the pressure-resistant shape protruding downward in a substantially hemispherical shape and substantially downward toward the periphery are formed. A self-standing pressure-resistant plastic bottle that has a grounding portion at the lower end and a valley extending almost radially from the center of the bottom between the legs, and has small irregularities on the inner surface of the insufficiently stretched region at the center of the bottom. Because it is a self-standing pressure-resistant plastic bottle characterized by the formation of, it is difficult to cause environmental stress cracking due to long-term stress due to internal pressure even near the center of the bottom, and hard to crack due to sudden stress due to drop impact This has the effect.

[Brief description of the drawings]

FIG. 1 is a partially sectional front view showing an example of a self-standing pressure-resistant plastic bottle of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a bottom inner surface view showing another example of the self-standing pressure-resistant plastic bottle of the present invention.

FIG. 4 is a bottom inner surface view showing another example of the self-standing pressure-resistant plastic bottle of the present invention.

FIG. 5 is a perspective view showing an example of a preform.

[Explanation of symbols]

 10 Bottom center 2 Legs 21 Ground contact 3 Valley 4 Small irregularities

Claims (1)

[Claims] 1. A plurality of hollow legs protruding substantially radially downward from the center of the bottom of a pressure-resistant shape protruding substantially hemispherically downward from the center of the bottom, and grounding at the outer lower end of each leg. In the self-standing pressure-resistant plastic bottle having a valley extending substantially radially from the center of the bottom between the legs, small irregularities were formed on the inner surface of the insufficiently stretched region near the center of the bottom. A self-standing pressure-resistant plastic bottle characterized by the following: