JPH07132926A - Pressure-resistant self-standing container - Google Patents

Abstract

PURPOSE:To provide a pressure-resistant self-standing plastic container with legs provided at the bottom of a petaloid form reinforced. CONSTITUTION:A pressure-resistant self-standing container 1 formed with a plurality of legs 12 forming a grounding part with equal intervals in a peripheral direction and having a recess 11 at the center of the bottom includes recessed ribs 14, 15 respectively formed at a radial inner part of each leg 12 and a radial inner part of a valley between the legs. The center recess 11 is formed by raising a protruding member at the time of biaxial orientation blow-molding to stretch the bottom center to 1.5 times or longer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic container having good self-supporting property, and more particularly to a pressure resistant self-supporting plastic container in which legs provided on the bottom of a so-called petaloid shape are reinforced.

[0002]

A biaxially stretched blow molded container made of a saturated polyester resin represented by polyethylene terephthalate has a very excellent transparency and surface gloss, and is beautiful and has a gas barrier. Excellent in water resistance, moisture impermeability, content resistance and storage stability. In addition, it has many advantages such as low heat generation during combustion and easy disposal because it does not damage the furnace.
Therefore, it is widely used for various drinking water, seasonings, containers for liquor and other foods.

Such a biaxially stretch blow-molded container (bottle) is used as a container for contents such as carbonated drinks having a high internal pressure, or weak carbonated drinks containing fruit juice that require a post-past sterilization step after low temperature filling. When used, the bottom portion is made spherical and a so-called base cup is attached to it in order to improve resistance to internal pressure. The container with a base cup has excellent self-sustaining stability, and the bottom portion is reinforced, but the cost increases because the step of manufacturing the base cup in a separate step and then attaching the base cup to the container body increases. In addition, since the base cup is usually molded with a resin different from that of the container body, the container equipped with the base cup is inferior in recyclability.

Therefore, various irregularities are formed on the bottom of the container to reinforce the bottom of the container and at the same time, the container has a structure which ensures self-standing without a base cup (for example, Japanese Patent Laid-Open No. 61-91).
70, JP-A-2-57545, etc.) have been developed and put to practical use.

However, these pressure-resistant self-supporting containers have a problem that the strength is not sufficient because the center portion of the bottom is hardly stretched. Therefore, it is conceivable to extend the container by forming a recess in the center of the bottom of the container to reinforce the center of the bottom, but then there is a problem that the strength in the vicinity of the center of the bottom where the radially inner part touches becomes insufficient. Occurs.

Accordingly, it is an object of the present invention to provide a pressure resistant self-supporting plastic biaxially stretch blow molded container with a reinforced bottom.

[0007]

As a result of earnest research in view of the above-mentioned object, the inventors of the present invention formed a recess in the center of the bottom part, and formed radially inward parts of a plurality of legs forming ground contact parts, and If concave ribs are formed in the radial inner part of the valley between each leg, the central part of the bottom is reinforced, and swelling etc. does not occur even after filling the contents and after the post-pass sterilization process. And found the present invention.

That is, in the pressure resistant self-supporting container of the present invention, a plurality of legs forming the ground portion are formed at equal intervals in the circumferential direction, and have a recess in the center of the bottom, and each leg has a recess. It is characterized in that concave-shaped ribs are respectively formed on the radially inner portion and the radially inner portion of the valley portion between the respective leg portions.

[0009]

The present invention will be described in detail below.

[1] Pressure Resistant Freestanding Container FIG. 1 shows a bottom structure of a pressure resistant freestanding container 1 according to an embodiment of the present invention, (a) is a bottom view, and (b) is A of (a).
FIG. In addition, in FIG. 1 (b), the broken line is
The cross section along line OB in (a) is shown, and the leg portion 12 ′ in this cross section is shown.

Although only the bottom structure of the container 1 is shown in FIG. 1, the shape of parts other than the bottom, such as the mouth, shoulders, and body of the container 1, depends on the purpose of use of the container. It may be appropriately set to various shapes found in conventional plastic biaxially stretch blow molded containers. A feature of the container of the present invention is its bottom shape.

In the embodiment shown in FIG. 1, the bottom of the container 1 is provided with a central concave portion 11, leg portions 12 formed at equal intervals in the circumferential direction, and valley portions 13 existing between the leg portions. Has been done. In such a pressure-resistant self-standing container, the diameter of the central recess is preferably 5 to 70% of the diameter of the container. Also,
The draw ratio of this central recess is 1.5 times or more, especially 1.8-3.
It is preferably double.

Concave ribs 14 and 15 are formed on the inner side of the bottom leg 12 in the radial direction and on the inner side of the valley 13 between the legs in the radial direction. Although the concave ribs 14 and 15 are elongated in the radial direction in this embodiment,
The shape is not necessarily limited to this. Concave ribs 14, 15
The radial length of is preferably about 1/20 to 1 / 1.25 of the bottom radius, and the degree of depression is 1/20 to about the radial length.
About 1/8 is preferable. By forming the concave ribs on the radially inner portion of the leg portion and the radially inner portion of the valley portion in this manner, it is possible to prevent the portions from bulging due to the pressure of the contents or the like.

A polyester resin is suitable as the resin forming the pressure resistant self-supporting container of the present invention as described above.
As the polyester resin, a thermoplastic resin composed of saturated dicarboxylic acid and saturated dihydric alcohol can be used. Saturated dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, naphthalene-1,4- or 2,6-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, diphenyldicarboxylic acids, diphenoxyethanediethanedicarboxylic acids And the like, aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, decane-1,10-dicarboxylic acid and the like, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and the like can be used. As the saturated dihydric alcohol, aliphatic glycols such as ethylene glycol, propylene glycol, trimethylene glycol, tetramethylene glycol, diethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, hexamethylene glycol, dodecamethylene glycol and neopentyl glycol are used. Glycols, alicyclic glycols such as cyclohexanedimethanol, 2,2-bis (4'-β-hydroxyethoxyphenyl) propane, and other aromatic diols can be used. A preferred polyester is polyethylene terephthalate consisting of terephthalic acid and ethylene glycol.

Polyester resin has an intrinsic viscosity of 0.5 to 1.5.
, Preferably having a value in the range 0.55 to 0.8. In addition, such polyester is produced by melt polymerization,
Those that have been subjected to reduced pressure treatment or heat treatment in an inert gas atmosphere at a temperature of 250 ° C., or those that have reduced the content of oligomers and acetaldehyde which are low molecular weight polymers by solid-phase polymerization are suitable.

In the polyester resin, additives such as stabilizers, pigments, antioxidants, heat deterioration preventing agents, UV deterioration preventing agents, antistatic agents, antibacterial agents, etc. may be added to the polyester resin within the range not impairing the object of the present invention. An appropriate amount of resin can be added.

[2] Manufacturing Method Next, a method of manufacturing the pressure resistant self-supporting container of the present invention as described above will be described.

(1) Preform FIG. 2 is a sectional view schematically showing an example of a preform that can be used in the present invention.

The preform 20 comprises a mouth 21 having a support ring 24, a substantially cylindrical body 22 and a bottom 23. In the preformed body 20, the bottom portion 23 is preferably thicker (particularly 10 to 90% thicker) than the body portion 22. By making the bottom portion 23 of the preformed body thick, the bottom portion (especially the outer wall surface portion 1 of the leg portion 1) can be obtained even if the stretching ratios of the bottom portion and the body portion are substantially the same.
The thickness of 2a) can be made about 10 to 90% thicker than that of the body portion, so that the bottom portion of the obtained container, especially the leg portion can be prevented from bulging.

(2) Biaxial Stretch Blow Molding For the biaxial stretch blow molding of the preform, a molding die having a cavity having a shape corresponding to the leg shape is used. In addition, in order to form the recess 11 at the center of the bottom, it is preferable to use a molding die having a member protruding to the center of the bottom. Such a molding die includes a bottom die 30 having a projecting member 31 at the center of the bottom and a body die 40 as illustrated in FIG.
It is preferable to have and.

The bottom part mold 30 is fixed to the body part mold 40 so as to be sandwiched from the lateral direction at the lower part of the body part mold 40 which is divided into two parts in the lateral direction. In addition, the bottom mold 30 includes
Three hole portions 32 are formed in the vertical direction, and curved surface portions 33 are formed alternately with the hole portions 32. The hole portion 32 and the curved surface portion 33 are provided with ridges 32 'and 33' corresponding to the concave ribs 14 and 15, respectively. Also bottom type 3
A projecting member 31 is movably mounted in the vertical direction at the center of 0.

The biaxially stretch blow-molded container of the present invention can be manufactured by the following method using such a mold.

First, the above-mentioned preform is placed in the above-mentioned molding die, and then biaxially stretch blow molding is performed. This biaxial stretch blow molding may be performed according to a known method. At this time,
The protruding member 31 is set at the retracted limit position (broken line in the figure).

When the parison is blown in the cavity of the biaxially stretched blow mold, the bottom of the molded body immediately after blowing (hereinafter referred to as an intermediate molded body) is in a state where the central recess is not formed. If this intermediate compact 50 is obtained,
While the intermediate molded body 50 is still hot, the protruding member 31 is pressed from below and moved upward to form the recess 11 in the center of the bottom.

Thereafter, if necessary, each part of the molded body is heat set in the biaxially stretched blow molding die, and the die is opened to obtain the pressure resistant self-supporting container of the present invention.

When the container is manufactured by the method described above, it is easy to form the concave portion 11 at the center of the bottom portion at a draw ratio of 1.5 times or more, and the radially inner portion of each leg portion and the space between the leg portions. Ribs 14, 1 on the radially inner side of the valley
5 can be clearly formed.

Although the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to this and various modifications can be made without departing from the concept of the present invention. For example, the shape and the number of legs are appropriately set in consideration of the intended use and design of the container.

[0028]

As described above in detail, in the pressure-resistant self-supporting container of the present invention, a plurality of legs forming the ground portion are formed at equal intervals in the circumferential direction, and a pressure-resistant self-supporting container having a recess in the central portion is formed. In the container, ribs are formed on the radially inner part of each leg and on the radially inner part of the valley between each leg, so that the leg is reinforced and swelling etc. occurs even when the contents are filled. Never.

The container of the present invention as described above is suitable for containers (bottles) of various foods and drinks such as carbonated drinks.

[Brief description of drawings]

FIG. 1 shows a bottom structure of a container according to an embodiment of the present invention, (a) is a bottom view of the container, and (b) is a vertical cross-sectional view of the bottom of the container.

FIG. 2 is a cross-sectional view schematically showing an example of a preformed body forming the container shown in FIG.

FIG. 3 is a partial cross-sectional view showing a molding die for manufacturing the pressure resistant self-supporting container of the present invention.

[Explanation of symbols]

 1 ... Pressure resistant self-supporting container 11 ... Central recess 12 ... Legs 13 ... Bottom part 14, 15 ... Recessed rib 20 ... Preform 21 ... Mouth 22 ... Body 23 ... Bottom 24 ... Support ring 30 ... Bottom mold 31 ... Projection member 32 ... Hole 32 ', 33' ... Ridge 33 ... Curved section 40 ...・ Body 50: Intermediate molding

Claims (3)

[Claims] 1. A pressure-resistant self-supporting container having a plurality of leg portions forming a ground contact portion at equal intervals in the circumferential direction and having a recess in the central portion of the bottom portion. A pressure resistant self-supporting container, characterized in that recessed ribs are respectively formed in radially inner portions of the valleys between the legs. 2. The pressure resistant self-supporting container according to claim 1, wherein the stretching ratio of the central recess is 1.5 times or more. 3. The pressure-resistant self-supporting container according to claim 1, wherein the bottom portion is crystallized to impart pressure resistance and heat resistance.