JP2021066459A - Synthetic resin container - Google Patents

Abstract

To provide a container 1 including a bottom 5 having a recess 50 positioned at the center and a ground part 51 provided in the periphery of the recess which improves a longitudinal compression strength by suppressing generation of buckling deformation with the ground part as a starting point when being compressed in an axial direction.SOLUTION: A ground part 51 has an inner peripheral side ground part 51a extending in a circumferential direction, and an outer peripheral side ground part arranged concentrically with the inner peripheral side ground part, and has an annular groove part 55 having an arc-shaped groove bottom whose a longitudinal cross section is convex inward of the container provided between the inner peripheral side ground part 51a and the outer peripheral side ground part 51b.SELECTED DRAWING: Figure 4

Description

The present invention relates to a synthetic resin container having improved longitudinal compressive strength.

Conventionally, a container made of synthetic resin, which is formed by forming a bottomed tubular preform using a thermoplastic resin such as polyethylene terephthalate and then molding this preform into a bottle shape by biaxial stretching blow molding or the like. It is used in a wide range of fields as a container containing various beverages and various seasonings.

In addition, the sales form of bottles for beverages using such synthetic resin containers is also diversifying, and in the cold season of winter, they are displayed on hot warmers in stores to warm the contents to an appropriate temperature. Being sold has also become familiar as a general sales form (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-25559

By the way, the container disclosed in Patent Document 1 includes a bottom having a recessed portion located at the center and a ground contact portion provided around the recessed portion. Such a bottom shape is a well-known shape not only in containers used for heated sales but also in this type of synthetic resin container, and the ground contact portion provided around the depressed portion is relatively large. It tends to be molded thin.

That is, in the case of blow molding, in general, the preform set in the blow molding mold is stretched in the axial direction by the stretching rod, and is stretched in the axial direction and the circumferential direction by the blow air, and blow molding is performed on the stretched portion. By shaping the inner surface shape of the mold, it is molded into a predetermined container shape. At this time, the bottom side of the stretched preform first contacts the portion forming the depressed portion located in the center of the bottom, and then sequentially contacts the periphery of the portion while being further stretched. The bottom shape is shaped. For this reason, the ground contact portion provided around the depressed portion is in a more stretched state, and it is easy to form a thin wall by that amount.

According to the study by the present inventors, in the container disclosed in Patent Document 1, the overall height is lowered so that it can be displayed on a hot warmer, but the body diameter is increased so that a predetermined capacity can be secured. However, it was found that the larger the body diameter, the stronger the tendency for the ground contact portion to be formed thinner. Then, for example, when the contents are filled and sealed and supplied to the market, when the contents are compressed in the axial direction by the load pressure applied when the contents are packed and sealed during transportation and storage, the buckling starts from the ground contact portion. It has been found that deformation may occur.

The present invention has been made in view of the above circumstances, and is a synthetic resin container having a bottom portion having a recessed portion located at the center and a ground contact portion provided around the depressed portion. To provide a synthetic resin container with improved longitudinal compressive strength (axial load strength) by suppressing buckling deformation starting from the ground contact portion when compressed in the axial direction. The purpose.

The synthetic resin container according to the present invention is a synthetic resin container having a bottom portion having a recessed portion located at the center and a grounding portion provided around the depressed portion, and the grounding portion is a peripheral portion. It has an inner peripheral side grounding portion extending along the direction and an outer peripheral side grounding portion concentrically arranged with the inner peripheral side grounding portion, and the inner peripheral side grounding portion and the outer peripheral side grounding portion. An annular groove portion having an arcuate groove bottom whose vertical cross section is convex inward of the container is provided between the two.

According to the present invention, in a synthetic resin container having a bottom portion having a recessed portion located at the center and a grounding portion provided around the depressed portion, the grounding portion is provided when compressed in the axial direction. The longitudinal compressive strength can be improved by suppressing the occurrence of buckling deformation as the starting point.

It is a front view which shows the outline of the synthetic resin container which concerns on embodiment of this invention. It is a bottom view which shows the outline of the synthetic resin container which concerns on embodiment of this invention. It is a perspective view which shows the outline of the synthetic resin container which concerns on embodiment of this invention. It is the AA end view of FIG. It is an enlarged end view of the main part of Comparative Example 1. It is an enlarged end view of the main part of Comparative Example 2.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a front view showing an outline of a synthetic resin container according to the present embodiment, FIG. 2 is a bottom view thereof, and FIG. 3 is a perspective view showing a perspective view from diagonally below.

The container 1 shown in these figures includes a mouth portion 2, a shoulder portion 3, a body portion 4, and a bottom portion 5, and the body portion 4 is formed in a substantially cylindrical shape, and is generally referred to as a round bottle. It has a container shape.

In addition, the container 1 shown in these figures has a capacity of about 527 mL, a height H of about 171.5 mm, and a body diameter D of about 73 mm, and should be displayed on a hot warmer in a store so as to be suitable for heated sales. In consideration of the above, a predetermined capacity can be secured while lowering the overall height.

In such a container 1, a bottomed tubular preform is formed by injection molding, compression molding, or the like using a thermoplastic resin, and this preform is formed into a predetermined container shape by biaxial stretching blow molding or the like. Manufactured by

As the thermoplastic resin to be used, any resin capable of blow molding can be used. Specifically, thermoplastic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, amorphous polyarylate, polylactic acid, polyethylene furanoate or copolymers thereof can be used, and in particular, ethylene terephthalate such as polyethylene terephthalate can be used. Polyplastic polyesters are preferably used. Two or more of these resins may be mixed, or other resins may be blended. Polycarbonate, acrylonitrile resin, polypropylene, propylene-ethylene copolymer, polyethylene, etc. can also be used. The preform is not limited to being molded into a single layer, but can also be molded into multiple layers including a gas barrier layer and the like, depending on the characteristics required for the container 1.

The mouth portion 2 is a cylindrical portion that serves as a spout for the contents. A screw thread for attaching a lid (not shown) is provided on the side surface of the mouth portion 2 on the opening end side.
The shoulder portion 3 is a portion that connects to the lower end of the mouth portion 2 and expands in diameter toward the body portion 4 to connect the mouth portion 2 and the body portion 4. In the illustrated example, the shoulder portion 3 is formed in a substantially truncated cone shape.
The body portion 4 occupies most of the height direction of the container 1, and the upper end is connected to the shoulder portion 3 and the lower end is connected to the bottom portion 5.

Here, the height direction means a direction orthogonal to the horizontal plane when the container 1 is upright on the horizontal plane with the mouth portion 2 facing up, and the container 1 is in this state (the state shown in FIG. 1). The vertical and horizontal directions and the vertical and horizontal directions of the above shall be specified.
Further, although the central axis is indicated by reference numeral C in FIG. 1, the cross section cut by the surface including the central axis C is referred to as a vertical cross section unless otherwise specified.

Six-sided pressure adjusting panels 40 for adjusting the pressure inside the container by deforming according to the change in pressure inside the container are arranged on the body 4 at predetermined intervals along the circumferential direction. The specific configuration of the pressure adjusting panel 40 is not particularly limited, and the container is deformed inward as the pressure inside the container decreases, while deformed outward in the container as the pressure inside the container increases. It suffices if it is configured so as to absorb the pressure change in the container 1 and thereby suppress the non-uniform deformation of the container 1.

Further, in order to increase the load-bearing strength against a load from the lateral direction (direction orthogonal to the height direction), the body portion 4 is annularly formed along the circumferential direction on each of the upper end side and the lower end side thereof, for example. Although extending peripheral groove portions 41 and 42 are provided, the specific configuration of the body portion 4 is not limited to the illustrated example.

In the present embodiment, the bottom portion 5 has a recessed portion 50 located at the center and a ground contact portion 51 provided around the depressed portion 50.

The depressed portion 50 can be formed as a portion in which the central portion of the bottom portion 5 is recessed inward in the container in a substantially truncated cone shape. In the illustrated example, eight reinforcing ribs 50a projecting outward from the container are radially provided on the side surface of the recessed portion 50 in order to increase the rigidity of the depressed portion 50, but the independence of the container 1 is impaired. As long as the deformation of the recessed portion 50 can be suppressed, the example is not limited to the illustrated example.

The ground contact portion 51 provided around the recessed portion 50 is a portion that comes into contact with the horizontal plane when the container 1 is erected on the horizontal plane, and has an inner peripheral side ground contact portion 51a extending along the circumferential direction. It has an inner peripheral side grounding portion 51a and an outer peripheral side grounding portion 51b arranged concentrically. The width (grounding width) and outer diameter (grounding diameter) of the grounding portion 51 can be appropriately designed so that the container 1 can be stably self-supported.
The outer peripheral edge of the ground contact portion 51 is connected to a heel portion formed of an outwardly convex curved surface of the container whose diameter gradually increases upward.

Further, as shown in FIG. 4, at the central portion in the width direction of the ground contact portion 51, an annular groove portion 55 having the portion raised inward in the container is provided, and an arcuate groove bottom having a vertical cross section convex inward in the container. It is provided in a ring shape along the circumferential direction so as to have. The annular groove portion 55 is provided between the inner peripheral side grounding portion 51a and the outer peripheral side grounding portion 51b, and the vertical cross section is outward of the container at each connecting portion between the inner peripheral side grounding portion 51a and the outer peripheral side grounding portion 51b. It is preferable that they are smoothly connected so as to form a convex arc shape.
Note that FIG. 4 is an end view of AA of FIG. 2, in which the wall thickness appearing on the end face is omitted and the end face of the main part of the bottom 5 is enlarged and shown.

In the container 1 having a bottom portion 5 having a recessed portion 50 located at the center and a grounding portion 51 provided around the depressed portion 50, when compressed in the axial direction, the grounding portion 51 is used as a starting point. Buckling deformation may occur. As a countermeasure in such a case, according to the present embodiment, by providing the annular groove portion 55 between the inner peripheral side grounding portion 51a and the outer peripheral side grounding portion 51b, the rigidity of the grounding portion 51 is improved and the rigidity thereof is improved. The vertical cross section of the groove bottom is formed in an arc shape that is convex inward of the container so that the stress is dispersed. As a result, buckling deformation starting from the ground contact portion 51 can be suppressed, and the longitudinal compressive strength of the container 1 is improved.

In addition, when the product is sold by heating, the air in the contents and head space expands due to the heating, and the pressure inside the container increases. As a result, if the ground contact portion 51 is deformed so as to bulge unevenly to the outside of the container, the self-sustaining stability of the container 1 is impaired, but according to the present embodiment, such a defect is also effective. Can be avoided.

In order to exert these effects more effectively, an annular shape is provided between the ground contact portion 51 and the depressed portion 50 so as to include a peripheral surface 52a rising along the axial direction from the inner peripheral edge of the inner peripheral side ground contact portion 51a. It is preferable that the step portion 52 is provided. The annular step portion 52 can be provided so as to include a first step surface 52b located on the ground contact portion 51 side and a second step surface 52c located above the first step surface 52b. It is preferable that the first stepped surface 52b and the second stepped surface 52c are on a plane orthogonal to the central axis C, respectively.

In order to avoid stress concentration, the peripheral surface 52a rising from the inner peripheral edge of the inner peripheral side ground contact portion 51a is connected to the first stepped surface 52b via an arcuate connecting portion whose vertical cross section is convex inward of the container. It is preferable that the first stepped surface 52b and the second stepped surface 52c are connected to each other via an arc-shaped connecting portion 52d whose vertical cross section is convex outward of the container.
Further, considering the shapeability at the time of blow molding, it is preferable that the annular groove portion 55 is formed so that the groove depth thereof is equal to the height of the first stepped surface 52b.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

[Example 1]
A preform weighing about 24 g was injection-molded using a polyethylene terephthalate resin. After the molded preform was heated and softened, it was set in a blow molding mold, and the container 1 was prepared so as to have the container shape shown in FIGS. 1 to 4 by biaxial stretching blow molding.
The capacity of the container 1 is about 527 mL, the height H is about 171.5 mm, the body diameter D is about 73 mm, and the average wall thickness of the container 1 calculated from the weight of the preform is about 0.3 mm. It was. The average wall thickness of the container 1 calculated from the weight of the preform was about 0.23 mm.

A presser is pressed against the obtained container 1 (empty container 1 filled with contents and not sealed) from above the mouth portion 2 downward in the axial direction, and the container 1 is pressed at a compression speed of 50 mm / min. The load (longitudinal compressive strength) when compressed and buckled was measured. The result was about 280 N (average value of N number 5; the same applies hereinafter), and the buckling location was the peripheral groove portion 42 provided on the lower end side of the body portion 4.
An air escape groove was provided on the lower surface of the presser so that the presser would not block the mouth 2.

Next, the obtained container 1 was filled with about 515 mL of water at about 85 ° C. as a content, and a lid (not shown) was attached to the mouth 2 and sealed. The volume of headspace was about 12 mL. Then, when the same compressive strength test as above was carried out, deformation was observed in the peripheral groove portion 42 provided on the lower end side of the body portion 4 from around 300 N, but after confirming the deformation, the load was applied. When released, it was restored to its original shape.
Further, when the container 1 was compressed until buckling occurred, the container 1 buckled so that the vicinity of the connecting portion between the mouth portion 2 and the shoulder portion 3 was depressed. The load at that time was about 473N.

[Comparative Example 1]
As shown in FIG. 5, a container similar to that of Example 1 was prepared except that the ground contact portion 51C was not provided with an annular groove portion, and a compressive strength test was carried out in the same manner as in Example 1.
Note that FIG. 5 is an enlarged end view of a main part of Comparative Example 2 showing a portion corresponding to the end face shown in FIG. 4 of Example 1.

The longitudinal compressive strength under the condition that the container was empty was about 271N, and the ground contact portion and the peripheral groove portion provided on the lower end side of the body portion buckled at the same time.
The longitudinal compressive strength under the condition that the contents were filled and sealed in the same manner as in Example 1 was about 283N, and the ground contact portion and the peripheral groove portion provided on the lower end side of the body portion buckled at the same time.

[Comparative Example 2]
As shown in FIG. 6, a container similar to that of the first embodiment was prepared except that the cross section of the annular groove portion 55C orthogonal to the extending direction was rectangular.
Note that FIG. 6 is an enlarged end view of a main part of Comparative Example 2 showing a portion corresponding to the end face shown in FIG. 4 of Example 1.

When the compressive strength test was carried out under the condition that the contents were filled and sealed in the same manner as in Example 1, the deformation started from around about 300 N, and after confirming the deformation, it was restored to some extent when the load was released. However, when the ground contact portion after restoration was observed, wrinkle-like traces which were considered to have been caused by deformation were observed, and as in Example 1, the restoration was not completely performed.

Although the present invention has been described above with reference to preferred embodiments, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. Nor.

For example, in the above-described embodiment, an example suitable for heated sales is shown, but the present invention is not limited to this. In this type of synthetic resin container, the location where buckling occurs when compressed in the axial direction differs depending on the shape of the container, but the present invention provides the recessed portion located in the center and the periphery of the recessed portion. In a synthetic resin container having a bottom having a grounded portion, it can be effectively applied as a countermeasure against buckling deformation starting from the grounded portion when compressed in the axial direction. it can.

1 Container 5 Bottom 50 Depressed part 51 Grounding part 51a Inner peripheral side grounding part 51b Outer peripheral side grounding part 52 Circular stepped part 52a Peripheral surface 52b First stepped surface 52c Second stepped surface 52d Connecting part 55 Circular groove part

Claims (3)

A synthetic resin container having a bottom portion having a recessed portion located in the center and a ground contact portion provided around the depressed portion.
The grounding portion has an inner peripheral side grounding portion extending along the circumferential direction and an outer peripheral side grounding portion arranged concentrically with the inner peripheral side grounding portion.
A synthetic resin container characterized in that an annular groove portion having an arcuate groove bottom whose vertical cross section is convex inward in the container is provided between the inner peripheral side grounding portion and the outer peripheral side grounding portion. The synthetic resin container according to claim 1, wherein an annular step portion including a peripheral surface rising along the axial direction from the inner peripheral edge of the inner peripheral side grounding portion is provided between the grounding portion and the depressed portion. .. The annular step portion includes a first step surface located on the ground contact portion side and a second step surface located above the first step surface, and includes the first step surface and the second step surface. However, the synthetic resin container according to claim 2, wherein the container is connected via an arcuate connecting portion whose vertical cross-sectional shape is convex outward from the container.

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