PRESSURIZED REFILL CONTAINER RESISTANT TO STANDING RING CRACKING

Abstract

Refillable plastic container includes a top portion, a sidewall portion defining an interior and a longitudinal axis and a base portion extending downwardly of the sidewall portion and defining a closed bottom. The base portion has a heel extending downwardly and inwardly of the sidewall portion at an angle relative the longitudinal axis and having a substantially frustoconical shape. A standing ring extends from heel and defines a support surface of the container. A central dome projects upwardly of the standing ring toward the interior. The central dome portion has a convex surface relative the interior.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International Patent Application No. PCT/US2019/029267, filed Apr. 26, 2019, which claims priority to U.S. Provisional Patent Application Ser. No. 62/663,065, filed on Apr. 26, 2018, which are hereby incorporated by reference in their entireties.

BACKGROUND

Field of the Disclosed Subject Matter

The present disclosed subject matter relates to pressurized containers, such as returnable and/or refillable PET carbonated beverage containers, including such containers having a base structure with increased resistance to deformation.

Description of Related Art

Many polymer containers, such as refillable PET containers, are repeatedly exposed to caustic washing to clean the container prior to repeated uses. Such caustic washing can involve exposure to caustic cleaning agents at elevated temperatures. Additionally, refilling of the containers can involve exposure to elevated internal pressures during the refilling process. As such, repeated caustic washing and refilling of such containers over time can cause various deformations, such as stress cracking, including in the standing ring of the base portion. Standing ring cracking can allow contaminants to infiltrate the cracks and thus inhibit or prevent thorough cleaning of the container. Additionally, such cracks can grow to create loss of pressurization and leakage of the bottle contents, which can result in complete bottle failure. Furthermore, cracking can cause whitening or opacity of the standing ring, which can be aesthetically undesirable and can interfere with contaminant inspection machinery, which can consider a whitened or opacified region to be a contaminant and reject the bottle.

A refillable container must go through a processing “loop” each time the container is reused. The loop generally is comprised of (1) an empty caustic wash followed by (2) contaminant inspection and product filling/capping, (3) warehouse storage, (4) distribution to wholesale and retail locations, and (5) purchase, use and empty storage by the consumer followed by eventual return to the bottler. The hot caustic wash is particularly detrimental to the reuse of a blow molded polyester container. Certain refillable container base geometries have a longer linear length due at least in part to the hemispherical shape of the heel, which can result in increased stretching of the preform during blow molding to form the standing ring portion container. As such, the wall thickness of the standing ring can be thinner, and thus more susceptible to stress cracking due to caustic washing. It therefore is desirable to provide a container having a standing ring which can increase resistance to caustic washing yet flexible enough to withstand the internal pressures from refilling.

SUMMARY

The purpose and advantages of the disclosed subject matter will be set forth in and are apparent from the description that follows, as well as will be learned by practice of the disclosed subject matter. Additional advantages of the disclosed subject matter will be realized and attained by the devices particularly pointed out in the written description and claims hereof, as well as from the appended drawings.

To achieve these and other advantages and in accordance with the purpose of the disclosed subject matter, as embodied and broadly described, the disclosed subject matter includes a container having a top portion defining an opening, a sidewall portion extending downwardly of the top portion and defining an interior and a longitudinal axis, and a base portion extending downwardly of the sidewall portion and defining a closed bottom. The base portion includes a heel extending downwardly and inwardly of the sidewall portion at an angle relative the longitudinal axis and having a substantially frustoconical shape, a standing ring extending from the heel and defining a support surface of the container, and a central dome extending upwardly of the standing ring toward the interior, the central dome having a convex surface relative the interior.

In accordance with another aspect of the disclosed subject matter, a base portion for a container includes a heel extending downwardly and inwardly of the sidewall portion at an angle relative the longitudinal axis and having a substantially frustoconical shape, a standing ring extending from heel and defining a support surface of the container, and a central dome extending upwardly of the standing ring toward the interior, the central dome having a convex surface relative the interior.

It is to be understood that both the foregoing general description and the following detailed description and drawings are examples and are provided for purpose of illustration and not intended to limit the scope of the disclosed subject matter in any manner.

The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the devices of the disclosed subject matter. Together with the description, the drawings serve to explain the principles of the disclosed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the application will be more readily understood from the following detailed description when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a side view of an exemplary embodiment of a container having an exemplary base in accordance with the disclosed subject matter.

FIG. 2 is a cross-sectional side profile view of the container taken along line 2-2 in FIG. 1.

FIG. 3 is a detailed view of region 3 of FIG. 2, showing the exemplary base of the container.

FIG. 4 is a cross-sectional side view of the base of FIG. 3 overlaid with a conventional base of a conventional container shown in dashed lines for purpose of illustration and comparison with the disclosed subject matter.

FIG. 5 is the side view of the conventional base of a conventional container of FIG. 4, illustrating selected reference locations in brackets for purpose of illustration and comparison with the disclosed subject matter.

FIG. 6 is a cross-sectional side profile view of the base of FIG. 3, illustrating selected reference locations in brackets.

FIG. 7 is a diagram illustrating the wall thickness at the various reference locations illustrated in FIGS. 5-6 for purpose of illustration and confirmation of the disclosed subject matter.

FIG. 8A is a side view image of a finite element model of the conventional base of a conventional container for purpose of illustration and comparison with the disclosed subject matter.

FIG. 8B is a bottom perspective view image of the finite element model of FIG. 8A of the conventional base of a conventional container for purpose of illustration and comparison with the disclosed subject matter.

FIG. 9A is a side view image of a finite element model of an exemplary base in accordance with the disclosed subject matter.

FIG. 9B is a bottom perspective view image of the finite element model of the exemplary base of FIG. 9A in accordance with the disclosed subject matter.

FIG. 10 is a diagram illustrating the stress concentration in the heel over a range of increasing pressures for a container in accordance with the disclosed subject matter as compared with a conventional base for a conventional container.

FIG. 11 is a diagram illustrating the stress concentration in the standing ring over a range of increasing pressure for a container in accordance with the disclosed subject matter as compared with a conventional base for a conventional container.

FIG. 12 is a diagram illustrating standing ring movement over a range of increasing pressure for a container in accordance with the disclosed subject matter as compared with a conventional base for a conventional container.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the disclosed subject matter, an example of which is illustrated in the accompanying drawings. The disclosed subject matter will be described in conjunction with the detailed description of the system.

The apparatus and methods presented herein can be used for transporting and refilling of perishable or nonperishable liquids. The disclosed subject matter is particularly suited for packaging, storing, and dispensing beverages, including fruit and vegetable juices, soft drinks or tea or the like.

In accordance with the disclosed subject matter, a container includes a top portion defining an opening, a sidewall portion extending downwardly of the top portion and defining an interior and a longitudinal axis, and a base portion extending downwardly of the sidewall portion and defining a closed bottom. The base portion includes a heel extending downwardly and inwardly of the sidewall portion at an angle relative the longitudinal axis and having a substantially frustoconical shape, a standing ring extending from the heel and defining a support surface of the container, and a central dome extending upwardly of the standing ring toward the interior, the central dome having a convex surface relative the interior.

In accordance with another aspect of the disclosed subject matter, a base portion for a container includes a heel extending downwardly and inwardly of the sidewall portion at an angle relative the longitudinal axis and having a substantially frustoconical shape, a standing ring extending from heel and defining a support surface of the container, and a central dome extending upwardly of the standing ring toward the interior, the central dome having a convex surface relative the interior.

The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the disclosed subject matter. For purpose of illustration, and not limitation, exemplary embodiments of the base and container with the disclosed subject matter are shown in the accompanying FIGS. FIGS. 1-4 and 6. The base and container are suitable for use with a wide variety of liquids. For purpose of illustration only, reference is made to a container for a carbonated beverage. As used herein, the terms “front,” “rear,” “side,” “top,” and “bottom” are used for the purpose of illustration only, and not limitation.

For purpose of illustration, reference will be made to one representative embodiment of a container having a generally cylindrical shape. FIGS. 1-2 illustrate exemplary embodiments of a representative container having the base of the disclosed subject matter. The examples herein are not intended to limit the scope of the disclosed subject matter in any manner. For the purposes of illustration and not limitation, reference is made to the exemplary embodiment of a container 100 as shown in FIGS. 1-2.

With reference to FIGS. 1-2, for example and as embodied herein, the container 100 generally includes a top portion 101 defining an opening 102, a sidewall portion 103 extending downwardly from the top portion 101 and defining an interior and a longitudinal axis 107, and a base portion 111 extending downwardly from the sidewall portion 103 and defining a closed bottom. The opening 102 can be formed of any suitable or desired configuration. The top portion can further include an unexpanded and substantially amorphous neck finish 104, with external screw threads and retaining flange 105. A tapered shoulder 106 can increase radially in diameter going down towards a sidewall portion 103. The sidewall portion 103 can define an interior and a longitudinal axis 107. The base portion 111 of the container 100 includes a heel 108 extending downwardly and inwardly from sidewall portion 103 at an angle A relative the longitudinal axis 107, the heel 108 having a substantially frustoconical shape and reducing in diameter towards a standing ring 109. The heel 108 can extend directly or indirectly from sidewall portion 103. For example, and as embodied herein, the heel 108 can extend directly from the sidewall portion 103.

With continued reference to FIGS. 1-2, the standing ring 109 extends inwardly from the heel 108 and defines a support surface 110 of the container 100. In some embodiments, the base portion further includes an outer support wall 113 extending between the sidewall portion 103 and the heel 108. Extending upwardly of the standing ring 109 towards the interior is a central dome 112 having a convex surface relative the interior.

As shown in FIGS. 1-2, for example and as embodied herein the container 100 generally includes a cylindrical shape with an initial height H, sidewall portion diameter D[SW], a maximum base portion diameter D[BP], and a standing ring diameter D[SR]. The base of the disclosed subject matter can be used with containers of a wide variety of shapes and configurations. For example, containers according to the disclosed subject matter can have any suitable shape, including but without limitation, square, rectangular, and elliptical shapes, and can be used with the base disclosed herein. For example, and not limitation, as embodied herein, an exemplary container for approximately 2.5 liters of carbonated beverage can have an initial height H of approximately 14 to approximately 15 inches; a sidewall portion diameter D[SW] of approximately 4 to approximately 5 inches; a maximum base portion diameter of approximately 4 to approximately 5 inches and a standing ring diameter D[SR] of approximately 2.5 inches to approximately 3 inches.

Referring now to FIG. 3, for example and as embodied herein, the container 100 includes a heel 108 extending downwardly and inwardly from sidewall portion 103 at an angle A relative the longitudinal axis 107. The heel can have any suitable shape. For example, and as depicted in FIG. 3, the heel 108 can have a substantially frustoconical shape, and can taper in diameter towards a standing ring 109. The angle A can be any suitable angle capable of achieving the desired purpose of the disclosed subject matter. For example, the angle A can be within the range of about 35 degree to about 45 degrees and in some embodiments, the angle A can be about 40 degrees. In this manner, angle A can reduce or minimize the distance the preform must stretch to reach the standing ring 109 of the container 100, which can allow for a greater wall thickness in the standing ring 109 of the container 100. As shown for example in FIG. 3, and as embodied herein, the standing ring 109 can be concave relative the interior in transverse cross-section.

With continued reference to FIG. 3, and as noted above, the base portion 111 as depicted has a central dome 112 extending upwardly from the standing ring 109 toward the interior, the central dome 112 having a convex surface relative the interior. The central dome 112 can extend directly or indirectly from the standing ring 109. For example, and as embodied herein, the central dome 112 can extend directly from the standing ring 109. Additionally or alternatively, the central dome 112 can have a substantially hemispherical shape.

For purpose of illustration and comparison with the disclosed subject matter, FIG. 4 shows a cross-sectional view of base portion 111 overlaid onto a cross-sectional view of a conventional base portion 111O of similar volume and material of construction. As shown in FIG. 4, and as embodied herein, base portion 111 can have a central dome 112 having a radius of curvature R4, a standing ring 109 having a radius of curvature R5, and a heel transition portion 114 having a radius of curvature R6. By contrast, the conventional base portion 111O in cross section has a central dome 112O having a radius of curvature R3, a standing ring 109O having a radius of curvature R2, and a heel 108O having a radius of curvature R1. The conventional base portion 111O further includes an external gate (not shown in FIG. 4 for the purpose of comparison only). Further, as depicted in FIG. 4, the standing ring 109 of the base portion 111 can have a radius in plan view of L[N1], while the standing ring 109O of the conventional base has a radius in plan view of L[O1]. The central dome 112 of the base portion 111 can have depth of L[N2], while the central dome 112O of the conventional base 111O has a depth of L[O2]. Additional details of an exemplary container base according to the disclosed subject matter as compared to a conventional base portion for a container of similar volume and material of construction are set forth in Table 1, below.

	TABLE 1
	Base Portion 111		Conventional Base Portion 111O
	R3 (inches)	1.654	R4 (inches)	1.372
	R2 (inches)	0.14	R5 (inches)	0.10
	R1 (inches)	1.52	R6 (inches)	0.50
	L[O1] (inches)	1.436	L[N1] (inches)	1.35
	L[O2] (inches)	0.760	L[N2] (inches)	0.850

FIGS. 5-7 together illustrate exemplary wall thicknesses of an exemplary base 111 for a container in accordance with the disclosed subject matter as compared with a conventional base 111O for a conventional container of similar volume and material of construction for purpose of illustration and comparison of the disclosed subject matter. FIG. 5 shows reference locations [1]-[8] along the center line of a conventional container base portion 111O having a hemispherical heel. FIG. 6 shows reference locations [1]-[8] along container base portion 111 in accordance with the disclosed subject matter having a frustoconical heel extending downwardly and inwardly at an angle relative the longitudinal axis. For purpose of comparison, the containers having the base portions of FIG. 5 and FIG. 6, respectively, were made using substantially similar preforms with substantially the same amount of material and substantially similar blow molding techniques. As shown in FIG. 7, for purpose of illustration and not limitation, the base portion 111 in accordance with the disclosed subject matter results in a wall thickness in the standing ring 109 (shown at reference point 4.5 in FIG. 6) that is greater than the wall thickness in the standing ring 109O (shown at reference point 4.5 in FIG. 5) of the conventional base 111O.

Hence, in accordance with the disclosed subject matter, the configuration of the base portion 111 provides for a greater wall thickness at the standing ring 109 as compared to the wall thickness of the standing ring of a conventional container formed using a substantially similar preform with substantially the same amount of material and a substantially similar blow molding technique as used to form the container having base portion 111. For example and not limitation, the wall thickness in the standing ring 109 of the base portion 111 in accordance with the disclosed subject matter results in at least 10% greater than the standing ring 109O of a substantially similar bottle having a conventional base 111O. In certain embodiments, the thickness in the standing ring 109 of the base portion 111 for a container 110 weighing 106 grams can be within a range of 2.4 mm to 2.5 mm. In certain embodiments, the thickness in the standing ring 109 of the base portion 111 for a container 110 weighing 112 grams can be within a range of 2.5 mm to 2.6 mm. The increased thickness of the standing ring 109 of the base portion 111 for a container 110 as compared to the standing ring 109O of the base portion 111O for a container 110O having a substantially similar weight can prevent or inhibit deformation due to increased pressure, such as stress cracking due to caustic washing and/or refilling. Thereby, the resulting increased thickness of the standing ring 109 of the base portion 111 for a container 110, as discussed herein, can also allow for a container 110 to be made lighter or with less material while maintaining the performance of a container 110O having a heavier weight.

FIGS. 8A-9B together illustrate the stress due to internal pressure at various locations on an exemplary base 111 for a container in accordance with the disclosed subject matter as compared with a conventional base 111O for a conventional container for purpose of illustration of the disclosed subject matter. FIG. 8A is a side view of a finite element model of a conventional container base portion 111O having a hemispherical heel and FIG. 8B is a bottom perspective view of the base portion of FIG. 8A, each illustrating the stress due to internal pressure at various locations. FIG. 9A is a side view of a finite element model of an exemplary embodiment of container base portion 111 in accordance with the disclosed subject matter having a frustoconical heel extending downwardly and inwardly at an angle relative the longitudinal axis and FIG. 9B is a bottom perspective view of the base portion of FIG. 9A, each illustrating the stress due to internal pressure at various locations. The respective containers of these figures are otherwise substantially the same. As demonstrated in FIGS. 9A-9B, for purpose of illustration and not limitation, the heel 108 of the base portion 111 of the disclosed subject matter distributes the stress upwardly along the heel as compared to the conventional base 111O.

FIG. 10 depicts a graph of the stress concentration in the heel over a range of increasing pressures for a container in accordance with the disclosed subject matter as compared with a conventional base for a conventional container for purpose of illustration of the disclosed subject matter. Particularly, conventional bases of this type are most prone to failure due to internal pressure along the radiused heel, such as stress cracking due to caustic washing and/or refilling. As shown in FIG. 10, the embodiment of the disclosed subject generally exhibits less stress concentration in the heel compared to the conventional base.

FIG. 11 depicts a graph of the stress concentration in the standing ring over a range of increasing pressures for a container in accordance with the disclosed subject matter as compared with a conventional base for a conventional container for purpose of illustration of the disclosed subject matter. As shown in FIG. 11, the embodiment of the disclosed subject matter generally exhibits less stress concentration in the standing ring compared to the conventional base.

FIG. 12 depicts a graph of the standing ring movement over a range of increasing pressures for a container in accordance with the disclosed subject matter as compared with a conventional base for a conventional container for purpose of illustration of the disclosed subject matter. As shown in FIG. 12, the embodiment of the disclosed subject matter generally exhibits less standing ring movement compared to the conventional base.

Bases and containers according to the disclose subject matter can particularly useful as a refillable carbonated beverage container able to withstand repeated refill cycles while maintaining aesthetic and functional features. For the purpose comparison, samples each of a container having an exemplary base in accordance with the disclosed subject matter and a container having a conventional base for a conventional container were produced. The containers were made using a substantially similar preform with substantially the same amount of material and a substantially similar blow molding technique, and each were substantially the same weight. For purpose of illustration and confirmation of the disclosed subject matter, a test procedure for simulating and repeating such cycles without crack failure was performed on the produced sample containers, as further discussed below.

Generally, the containers were subjected to a known commercial acceptable caustic wash solution, which was maintained at a desired wash temperature. The containers were submerged uncapped in the wash for a desired amount of time to approximate the time/temperature conditions of a commercial bottle wash system. After removal from the wash solution, the bottles were rinsed in tap water and then filled with a carbonated water solution at a desired pressure to approximate the pressure of a carbonated soft drink container. The containers were then depressurized and subjected to the same refill cycle (i.e. a loop) until failure. For purpose of this test, initial failure was defined as any visual crack observed in the container wall, and final failure was defined any crack propagating through the container wall resulting in leakage and pressure loss, such that the container was no longer usable.

It was determined through the aforementioned testing of a number of samples of each type of container that the unique base configuration of the disclosed subject matter results in an improved and desirable processing cycle performance as compared to a substantially identical container of the same weight and material but with a conventional base. For example, at certain container weights, such as 119 grams, a conventional container withstood an average of 10 refill cycles (i.e. loops) before initial failure when initial failure occurred in the neck, and an average of 17 loops before initial failure when initial failure occurred in the base. In contrast, the container of the disclosed subject matter withstood an average of 12.2 loops before initial failure when initial failure occurred in the neck, and no failure ever occurred in the base portion. Further, a conventional container withstood an average 15.67 refill cycles before final failure when final failure occurred in the neck, and an average of about 21.25 loops before final failure when final failure occurred in the base. In contrast, the container of the disclosed subject matter withstood an average of 19.4 loops before final failure when final failure occurred in the neck, and no failure ever occurred in the base portion. Hence, these test results demonstrate that the frustoconical heel as disclosed and as generally embodied herein can improve resulting container performance by reducing failure due to internal pressure, e.g., from caustic washing; specifically, the unique base configuration of the disclosed subject results in no failure in the base portion before failure of the container as a whole (e.g., failure in the neck portion), as well as an increased average life or number of loops in the processing cycle before initial and final failures in the neck portion as compared to a conventional container.

The container of the disclosed subject matter can be manufactured by any number of suitable methods, as known in the art. For example, and as embodied herein, the container and integral base can be manufactured by conventional blow molding. Exemplary techniques for blow molding a container in accordance with the disclosed subject matter are shown and described in U.S. Pat. No. 5,989,661, which is incorporated by reference herein in its entirety. As is appreciated by one having skill in the art, a variety of known manufacturing and process variations can be used in accordance with the disclosed subject matter. Additional techniques for manufacturing refillable beverage containers are shown and described in U.S. Pat. Nos. 4,334,627; 4,725,464; and 5,066,528; each of which is incorporated by reference herein in its entirety.

The container and the base can be formed from any suitable materials. For example and as embodied herein, the container and base can be formed of a polymeric material, such as and not limited to, polyethylene terephthalate (PET). Additionally or alternatively, for example and without limitation, the container and base can be formed from polyethylene naphthalate (PEN) and PEN-blends, polypropylene (PP), high-density polyethylene (HDPE), and can also include monolayer blended scavengers or other catalytic scavengers as well as multi-layer structures including discrete layers of a barrier material, such as nylon or ethylene vinyl alcohol (EVOH) or other oxygen scavengers.

While the disclosed subject matter is described herein in terms of certain preferred embodiments, those skilled in the art will recognize that various modifications and improvements can be made to the disclosed subject matter without departing from the scope thereof. Moreover, although individual features of one embodiment of the disclosed subject matter can be discussed herein or shown in the drawings of the one embodiment and not in other embodiments, it should be apparent that individual features of one embodiment can be combined with one or more features of another embodiment or features from a plurality of embodiments.

In addition to the various embodiments depicted and claimed, the disclosed subject matter is also directed to other embodiments having any other possible combination of the features disclosed and claimed herein. As such, the particular features presented herein can be combined with each other in other manners within the scope of the disclosed subject matter such that the disclosed subject matter includes any suitable combination of the features disclosed herein. Thus, the foregoing description of specific embodiments of the disclosed subject matter has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosed subject matter to those embodiments disclosed.

It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed subject matter without departing from the spirit or scope of the disclosed subject matter. Thus, it is intended that the disclosed subject matter include modifications and variations that are within the scope of the appended claims and their equivalents.

Claims

1. A refillable plastic container comprising:

a top portion defining an opening;

a sidewall portion extending downwardly of the top portion, the sidewall portion defining an interior and a longitudinal axis; and

a base portion extending downwardly of the sidewall portion and defining a closed bottom, the base portion comprising: a heel extending downwardly and inwardly of the sidewall portion at an angle relative the longitudinal axis, the heel having a substantially frustoconical shape, a standing ring extending from the heel and defining a support surface of the container, a central dome extending upwardly of the standing ring toward the interior, the dome having a convex surface relative the interior.

2. The container of claim 1, wherein the sidewall portion is cylindrical and generally circular in plan view.

3. The container of claim 1, wherein the base portion further comprises an outer support wall extending between the sidewall portion and the heel.

4. The container of claim 1, wherein the angle of the heel relative the longitudinal axis is within a range of about 35 degrees to about 45 degrees.

5. The container of claim 1, wherein the angle of the heel relative the longitudinal axis is about 40 degrees.

6. The container of claim 1, wherein the standing ring is concave relative the interior in transverse cross-section.

7. The container of claim 1, wherein the standing ring is arcuate in transverse cross-section.

8. The container of claim 1, wherein the standing ring has a radius of less than about 1.5 inches in transverse cross-section.

9. The container of claim 1, wherein the standing ring has a wall thickness configured to resist flexing of the standing ring during a sterilization and refill process.

10. The container of claim 1, wherein the standing ring has a wall thickness at least 10 percent greater than a wall thickness of the standing ring of a substantially similar bottle having a radiused heel in transverse cross section.

11. The container of claim 9, wherein the wall thickness of the standing ring is within a range of about 2.4 mm to about 2.6 mm.

12. The container of claim 1, wherein the standing ring extends directly from the heel.

13. The container of claim 1, wherein the central dome extends directly from the standing ring.

14. The container of claim 1, wherein the central dome has a substantially hemispherical shape.

15. The container of claim 1, wherein the container can withstand at least 20 refill cycles in a commercially acceptable caustic wash without failure in the standing ring portion.

16. The container of claim 1, wherein the container comprises polyester.

17. The container of claim 15, wherein the container comprises a polyester comprising polyethylene terephthalate (PET).

18. A base portion for a refillable plastic container having a top portion, sidewall portion, and the base portion, the base portion comprising:

a heel extending downwardly and inwardly of the sidewall portion at an angle relative the longitudinal axis, the heel having a substantially frustoconical shape;

a standing ring extending from the heel and defining a support surface of the container;

a central dome extending upwardly of the standing ring toward the interior, the central dome having a convex surface relative the interior.

19. The base portion of claim 18, wherein the sidewall portion is cylindrical and generally circular in plan view.

20. The base portion of claim 18, wherein the base portion further comprises an outer support wall extending between the sidewall portion and the heel.

21. The base portion of claim 18, wherein the angle of the heel relative the longitudinal axis is within a range of about 35 degrees to about 45 degrees.

22. The base portion of claim 18, wherein the angle of the heel relative the longitudinal axis is about 40 degrees.

23. The base portion of claim 18, wherein the standing ring is concave relative the interior in transverse cross-section.

24. The base portion of claim 18, wherein the standing ring is arcuate in transverse cross-section.

25. The base portion of claim 18, wherein the standing ring has a radius of less than about 1.5 inches in transverse cross-section.

26. The base portion of any of claim 18, wherein the standing ring has a wall thickness configured to resist flexing of the standing ring during a sterilization and refill process.

27. The base portion of claim 18, wherein the standing ring has a wall thickness of at least 10 percent greater than a wall thickness of a standing ring of a substantially similar bottle having a radiused heel in transverse cross section.

28. The base portion of claim 26, wherein the wall thickness of the standing ring is within a range of about 2.4 mm to about 2.6 mm.

29. The base portion of claim 18, wherein the standing ring extends directly from the heel.

30. The base portion of claim 18, wherein the central dome extends directly from the standing ring.

31. The base portion of claim 18, wherein the central dome has a substantially hemispherical shape.

32. The base portion of claim 18, wherein the container can withstand at 20 refill cycles in a commercially acceptable caustic wash without failure in the standing ring.

33. The base portion of claim 18, wherein the container comprises polyester.

34. The base portion of claim 32, wherein the container comprises a polyester comprising polyethylene terephthalate (PET).