US20120091149A1

US20120091149A1 - Retort-resistant plastic container

Info

Publication number: US20120091149A1
Application number: US13/274,874
Authority: US
Inventors: Marc A. Pedmo
Original assignee: Plastipak Packaging Inc
Current assignee: Plastipak Packaging Inc
Priority date: 2010-10-18
Filing date: 2011-10-17
Publication date: 2012-04-19
Also published as: CA2815075A1; MX2013004273A; EP2630047A4; WO2012054398A3; EP2630047A2; WO2012054398A2; AU2011317279A1; CN103429498A

Abstract

A retort-resistant plastic container includes a base portion, a sidewall portion, and a neck portion. The base portion includes a domed portion and a lower annular portion. The sidewall portion extends upwardly from the base portion, and typically has a minimum thickness of 0.020 inches. The neck portion extends upwardly from the sidewall portion and includes an annular flange. In embodiments, the outer diameter of the lower annular portion is less than the inner diameter of the annular flange. Further, in some embodiments, the sidewall is substantially smooth absent various sidewall structural reinforcements (e.g., vacuum panels or reinforcement ribs). Moreover, for embodiments, the sidewall portion is at least 0.80 of the total vertical length of the container.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/394,248, filed Oct. 18, 2010, which is hereby incorporated by reference as though fully set forth herein.

TECHNICAL FIELD

The present invention relates in general to retort-resistant plastic containers, including molded plastic containers with improved structural characteristics for resisting retort.

BACKGROUND

Metal cans have been used to hold product contents for some time. More recently, with increases in the costs of metals, such as steel, there has been an interest in providing cans and other forms of containers made of plastic. However, plastic cans and containers have been commonly considered less suitable for some applications due to the physical stresses placed on the material, which for some applications may be significantly greater than those encountered in common plastic container “hot-fill” applications. Retort processes provide an example of applications in which, due to high temperatures and internal pressures, plastic containers have been considered to be undesirable. A common industry objective is to provide a plastic container that can practically withstand such processing with minimal or sufficiently recoverable deformation.
Consequently, there exists a desire to, among other things, provide plastic, retort-resistant containers that are capable of serving as replacements for applications involving relatively higher physical stresses, such as microwave applications or other retort processes.

SUMMARY

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective illustration of an embodiment of a plastic container generally illustrating certain teachings of the present invention;

FIG. 2 is perspective illustration of an embodiment of a plastic container similar to that generally illustrated in FIG. 1;

FIG. 3 is a top view of the container generally illustrated in FIG. 2;

FIG. 4 is a side elevation view of the container generally illustrated in FIG. 2;

FIG. 5 is a side cross-sectional elevation view of the container taken along lines A-A in FIG. 4;

FIG. 6 is a side elevation view of a container similar to that shown in FIG. 2, generally illustrating split lines for the container;

FIG. 7 is a cross-sectional view of the container taken along lines B-B in FIG. 6;

FIG. 8 is a cross-sectional view of an embodiment of a base portion for a container, the view generally illustrating aspects of the inventive concept;

FIG. 8A is a cross-sectional view of another embodiment of a base portion for a container;

FIG. 8B is a cross-sectional view of an embodiment of a base portion similar to that shown in FIG. 8A, generally showing a base portion in a different configuration;

FIG. 9 is a cross-sectional view of a portion of the neck of a container;

FIG. 10 is perspective view of two containers generally shown in a stacked configuration;

FIG. 11 is an elevation view of two containers generally shown in a stacked configuration; and

FIG. 12 is an enlarged sectional view of an annular flange and closure.

DETAILED DESCRIPTION

Reference will now be made in detail to embodiments of the present invention, examples of which are described herein and illustrated in the accompanying drawings. While the invention will be described in conjunction with embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.
FIGS. 1 and 2 generally illustrate embodiments of plastic containers 10, 20 including teachings and aspects of the present invention. As generally illustrated, the container 20 may include a base portion 30, a sidewall portion 40 that extends upwardly from the base portion 30, and a neck portion 50 that may include an annular flange 60. A top view of the container 20 is generally illustrated in FIG. 2.
In an embodiment, the plastic container 20 may be comprised of polypropylene (PP). However, the container is not limited as such, and other plastic materials, such as polyethylene terephthalate (PET), high density polyethylene (HDPE), and various plastic monomers, may also be employed for some applications. The container may also, if desired include one or more barrier materials/layers and/or oxygen scavengers, including conventional oxygen scavengers that do not haze, provide a clear appearance, and do not have a negative impact on recyclability. It is noted that the container according to the disclosure may be monolayer. However, if desired such containers can instead be provided in the form of a multi-layer construction. For example and without limitation, in an embodiment, a container may be provided with two polymer layers (e.g., two polypropylene (PP) layers) separated, for instance, by a barrier/scavenger layer (e.g., ethylene vinyl alcohol (EVOH)), and, if desired, the layers may be held together by some form of adhesive.
Further, while various molding techniques may be employed to form the container, in embodiments, the plastic container may be injection molded. With injection molded embodiments, the plastic container 20 may comprise an amorphous plastic, as opposed to a biaxially oriented plastic that may be produced by a different process, such as injection stretch blow molding (ISBM). Notably, for embodiments of the container, the wall thicknesses at the majority of portions of the container will exceed 0.020 inches, for other embodiments the wall thicknesses at the majority of portions of the container will exceed 0.030 inches, and for some embodiments, the minimum wall thickness for all portions of the container may be 0.030 inches. Moreover, and without limitation, for some embodiments, the average wall thickness may be 0.070 inches or more.
FIG. 4 generally illustrates a side view of the container 20. The base portion 30 is shown including a lower angular portion 70 and a lower annular portion 80. As generally depicted in the illustrated embodiment, in embodiments, the sidewall portion 40 may comprise a substantial portion of the vertical length of the container 20. In embodiments, without limitation, the sidewall may comprise at least 0.80 of the total vertical length of the container, and for some embodiments may comprise at least about 0.89 of the total vertical length. Moreover, for comparison purposes, and without limitation, in an embodiment the total vertical length L₁of the container 20 may be approximately 3.35 inches, L₂may be approximately 3.19 inches, and L₃may be approximately 3.09 inches. Further, also for comparative purposes, and without limitation, the diameter of the container 20 at or about D₁may be, for example, about 2.69 inches; while the diameter at the position labeled D₂may have about a 0.25° inward taper moving toward the base portion 30.
FIG. 5 includes a cross-sectional view of the container 20 viewed along lines A-A in FIG. 4. For illustration and comparison purposes, and without limitation, in an embodiment the thickness of the sidewall portion 40 at T₁may be, for example, about 0.070 inches; the diameter at D₃may be about 2.52 inches; the diameter at D₄may be about 2.97 inches; and the diameter at D₅may be about 2.37 inches. Moreover, as additionally depicted, vertical lengths L₄and L₅may, for example, be about 3.18 and 3.07, respectively. Further, the illustrated angle θ may, for example, be about 35°±10°. It is noted that the container is not limited to the aforementioned dimensions, which merely illustrate aspects and features of the inventive concept in an illustrative context. It is noted that FIG. 5 also identifies two regions, generally identified as C and CDS (custom double seam), which are discussed further hereinafter in connection with FIGS. 8 and 9. For some embodiments, D₅will not be less than 0.75 the diameter of D₃. For example, without limitation D₅may be about 0.89 times D₃.
FIG. 6 generally includes other dimensions of container 20 in an illustrative context, generally illustrating possible mold split lines. For example, without limitation, L₆, which may generally represent a vertical length for a stripper ring, may be about 0.022 inches; L₇, which may generally represent a vertical length for a cavity (top), may be about 2.49 inches; and L₈, which may generally represent a vertical length for a cavity (bottom), may be about 0.085 inches. It is noted that the invention is not limited to the split lines illustrated, and other and/or more split lines may be employed as known to persons skilled in the field.
FIG. 7 includes a cross-sectional view of the container 20 viewed along lines B-B in FIG. 6. For illustration and comparison purposes, and without limitation, vertical lengths L₉and L₁₀may, for example, be about 3.33 and 0.64, respectively.
The base portion region generally identified as region C in FIG. 5 is illustrated in additional detail in FIG. 8. In addition to the lower angular portion 70 and the lower annular portion 80, the figure also generally illustrates a domed portion 90, which is shown comprising an upward angular portion 100, a curved portion 110, and a dimpled portion 120. It is noted that, the base portion 30 of the container may, if desired, be configured to facilitate container-on-container stackability. That is, portions of the base portion 30 may be configured to receive and/or retain upper portions associated with similarly configured containers. For illustration and comparison purposes, and without limitation, the diameter at D₆may be about 1.77 inches; the diameter at D₇may be about 2.53 inches; and the diameter at D_gmay be about 2.66 inches. Further, the vertical length L₁₁may be, for example, about 0.47 inches; and the illustrated thicknesses at T₂, T₃, T₄, T₅, T₆, and T₇may be about 0.070, 0.070, 0.079, 0.069, and 0.070 inches, respectively. Upward angular portion 100 may have an angle, as measured from the standing surface, of about 15°. For some embodiments, the angle between the upward angular portion 100 and the standing surface may be at least 5°. However, for some embodiments, the angle may be between about 5° and about 45°, and may further be between about 5° and 25°. The upward angular portion 100 provides space for stacking with respect to features of a container stacked vertically below it. For example, a clearance (or head space) may be created by lower annular portion 80, which may, for example, have a vertical height H₁of at least about 0.030 inches, and for some embodiments may have a vertical height H₁of at least about 0.100 inches. The clearance may provide sufficient room for a raised formation, e.g., a raised tab, or pull tab, that can extend vertically upward from a lower container. The clearance, or head space, may further be increased at portions vis-à-vis an associated upward angular portion 100. An upward angular portion, for example and without limitation as generally illustrated in FIG. 8, may provide a further increased vertical height H₂. Additionally, for some embodiments, D₇may not be less than 0.85 the diameter of D_g. For example, without limitation D₇may be about 0.95 times D₈.
Turning to FIG. 8A, another embodiment of a base portion region is shown. The illustrated embodiment of a base portion 30′ includes a lower angular portion 70′, a lower annular portion 80′, and a domed portion 90′. With some embodiments, such as that illustrated, the base portion 30′ may include wall portions, or at least segments thereof, that are comparatively thinner than other portions of the base portion, and/or in comparison to a container with a base portion that is intended to be substantially rigid in service. If desired, the domed portion 90′ may include an upward angular portion 100′, a curved portion 110′, and a dimpled portion 120′. Further, the base portion 30′ can also be configured to facilitate container-on-container stackability.
While some embodiments of the base portion may be substantially “fixed,” in that there is little or no intended flexing, embodiments of a base portion, such as base portion 30′, may instead include portions that are configured to be flexible and/or to promote movement (e.g., in response to internal pressure or a vacuum) as a filled container takes commercial form. That is, in embodiments, portions of base portion 30′ may, for instance, be formed to be comparatively thinner than surrounding portions, and such thinner portions may be configured to move or flex between inward and outward positions. To illustrate the point, and without limitation, FIG. 8B generally illustrates a base portion 30′ similar to the base portion shown in FIG. 8A. As shown in FIG. 8B, the base portion can have portions that, at least at a point in time (e.g., prior to contents cooling and creating a vacuum force), extend downwardly. As shown in the illustrated embodiment, a portion of the base portion—e.g., the segment where the upward angular portion 100′ and curved portion 110′ generally come together—can extend downward to a vertical height/level that is at or near the same vertical height/level as the lowermost height/level of the lower annular portion 80′ (which may be a lower resting plane or standing surface for the container). Then upon sufficient internal force, the aforementioned portion of the base portion can flex or translate to an upward position, such as generally illustrated in FIG. 8A. The intentional reduction in internal volume of the container provided by the upward flexing of a portion of the base portion can accommodate internal pressure (e.g., vacuum pressure) associated with the container, such as in connection with the cooling of contents in a retort or hot-fill application.
For example, and without limitation, a wall thickness of a “flex” base portion may have wall portions with a thickness of about 0.025 inches, while the wall thickness for a comparable portion of a “fixed” base portion might have a thickness several times thicker (e.g., about 0.100 inches). For illustration and comparison purposes, and without limitation, the illustrated thicknesses at T₉, T₁₀, T₁₁, and T₁₂may for instance be about 0.069, 0.025, 0.070, and 0.070 inches, respectively.
The upper region generally identified as region CDS in FIG. 5 is illustrated in additional detail in FIG. 9. For illustration and comparison purposes, and without limitation, thickness T8 may be about 0.022 inches; lengths L₁₂, L₁₃, and L₁₄may be about 0.040, 0.128, and 0.217 inches, respectively; and diameters D₉, D₁₀, D₁₁, D₁₂, and D₁₃may be about 2.85, 2.61, 2.61, 2.58, and 2.55 inches, respectively.
FIGS. 10 and 11 generally illustrate an embodiment of plastic containers 20 shown in a stacked configuration.
In embodiments, the neck portion 50 may include a finish with flange configured to accept a double seam closure. Such a finish may be configured with respect to desired closure features. For a number of applications, metallic seals and closures are envisioned. For some embodiments, such as generally illustrated in FIG. 12, the annular flange 60, which serves as a sealing flange, may be sealed via a double-seemed closure 130. Further, for some embodiments the neck portion will be configured to be compatible with a metal closure having a pull tab, and may be sealed to the neck portion 50 using induction or other known processes. While easy-open pull tab closures may be employed, other closures, including standard metallic closures without a pull tab may also be used.
Plastic containers provided in accordance with the teachings of the present concept may, for example, have a minimum top load strength of 100 pounds. However, some embodiments provide for a plastic container having a minimum top load strength of 200 pounds or more, with some embodiments providing a minimum top load strength of 400 pounds or more. Embodiments of the invention may be employed with a number of different retort-related processes. By way of example, without limitation, embodiments of containers provided in accordance with teachings of the present concept may be used in connection with low-acid foods, such as those having has an initial temperature of 140° F., a retort temperature of 250° F., with 25 minutes circulating in a rotary cooker at 28 psig. Such containers may also be employed with another process that would ramp up the temperature to 265° F. over a 20 minute time frame before ramping down for 20 minutes. Embodiments of plastic containers constructed in accordance with the teachings of the present invention may be cylindrical and are rigid—even when provided with smooth sidewall portions that are absent various sidewall structural reinforcements (e.g., vacuum panels or reinforcement ribs)—and such plastic containers may exhibit little or no deformation. That is, such plastic containers may be provided so that, under normal retort conditions, the container will exhibit no more than 5% deformation, and preferably less than 1-2% deformation.
It is noted that embodiments of containers provided in accordance with the teachings disclosed herein may balance a number of design considerations. For instance, if the diameter of the base is too large, the container may not rest on a surface properly; if the wall thickness of the base portion is made too thick, it will not fit between a tab and a sidewall properly; and if the height of the base portion is made too short, the base portion will not clear tabs or other formations associated with the closure of a similar container stacked below it.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and various modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to explain the principles of the invention and its practical application, to thereby enable others skilled in the art to utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims and their equivalents.

Claims

1. A retort-resistant plastic container comprising:

a base portion, the base portion including a domed portion and a lower annular portion;

a sidewall portion extending upwardly from the base portion, the sidewall portion having a minimum thickness of 0.020 inches; and

a neck portion that extends upwardly from the sidewall portion, the neck portion including an annular flange;

wherein the outer diameter of the lower annular portion is less than the inner diameter of the annular flange, whereby at least part of the base portion is configured to be received or retained within a neck portion of a similarly configured container.

2. The container of claim 1, wherein the minimum wall thickness for the base portion, sidewall portion, and neck portion of the container are all at least about 0.030 inches.

3. The container of claim 1, wherein the average wall thickness of the container for the base portion, sidewall portion, and neck portion of the container are all at least about 0.070 inches.

4. The container of claim 1, wherein the height of the sidewall portion is at least about 0.80 the total vertical height of the container.

5. The container of claim 1, wherein the height of the sidewall portion is at least about 0.89 the total vertical height of the container.

6. The container of claim 1, wherein the base portion includes a lower angular portion.

7. The container of claim 1, wherein the lower angular portion is provided at an angle within the range of about 25 degrees to about 45 degrees relative to a central vertical axis of the container.

8. The container of claim 1, wherein the lower annular portion is substantially cylindrical and substantially parallel to a central vertical axis of the container.

9. The container of claim 1, wherein the domed portion includes an upward angular portion.

10. The container of claim 9, wherein the upward angular portion is provided at an angle of at least 5 degrees relative to a standing surface of the container.

11. The container of claim 9, wherein the upward angular portion is provided at an angle of between about 5 degrees and about 45 degrees relative to a standing surface of the container.

12. The container of claim 9, wherein the domed portion further includes a curved portion and a dimpled portion.

13. The container of claim 9, wherein the domed portion is substantially rigid.

14. The container of claim 9, wherein the upward angular portion is thinner than other portions of the domed portion and the upward angular portion is configured to flex from a downward position to an upward position in response to an internal force.

15. The container of claim 1, wherein the lower annular portion has a vertical height of at least about 0.030 inch.

16. The container of claim 1, wherein the lower annular portion has a vertical height of at least about 0.100 inch.

17. The container of claim 1, wherein at least a segment of the sidewall portion has an inward taper moving in the direction toward the base portion.

18. The container of claim 1, wherein the base portion is configured to receive or retain an upper portion of a similarly configured container.

19. The container of claim 1, wherein the container is comprised of polypropylene.

20. The container of claim 1, wherein the flange is configured to accept a double seam closure or an easy-open pull tab.

21. The container of claim 1, wherein the container has a minimum top load strength of at least one hundred pounds.

22. The container of claim 1, wherein the sidewall is substantially smooth.

23. The container of claim 1, wherein under retort conditions, the container exhibits no more than 5% deformation.