U.S. patent application number 10/188216 was filed with the patent office on 2004-01-01 for method for extending the effective life of an oxygen scavenger in a container wall.
Invention is credited to Joshi, Prasad, Rost, John M., Schmidt, Frank J..
Application Number | 20040000127 10/188216 |
Document ID | / |
Family ID | 29780100 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040000127 |
Kind Code |
A1 |
Joshi, Prasad ; et
al. |
January 1, 2004 |
Method for extending the effective life of an oxygen scavenger in a
container wall
Abstract
A method of filling a container, and thereby extending the
effective life of an oxygen scavenger, includes providing a
container having an oxygen scavenger material, introducing product
contents and a liquefied gas into the container to displace at
least a portion of the air within the headspace, and capping or
otherwise sealing the container. Displacing oxygen from the
headspace diminishes the available oxygen within the container that
can permeate into the container sidewall, thereby extending the
effective life of the scavenger.
Inventors: |
Joshi, Prasad; (Woodridge,
IL) ; Schmidt, Frank J.; (Lisle, IL) ; Rost,
John M.; (Oak Forest, IL) |
Correspondence
Address: |
WOODCOCK WASHBURN LLP
ONE LIBERTY PLACE, 46TH FLOOR
1650 MARKET STREET
PHILADELPHIA
PA
19103
US
|
Family ID: |
29780100 |
Appl. No.: |
10/188216 |
Filed: |
July 1, 2002 |
Current U.S.
Class: |
53/431 ;
53/485 |
Current CPC
Class: |
B65D 81/266 20130101;
B65D 23/102 20130101; B67C 3/222 20130101; B65D 81/2076
20130101 |
Class at
Publication: |
53/431 ;
53/485 |
International
Class: |
B65B 055/18 |
Claims
We claim:
1. A method for extending effective life of an oxygen scavenger
that is disposed in the wall of a container, comprising the steps
of: a. providing the container formed of a material comprising the
oxygen scavenger; b. introducing a comestible product into the
container, thereby forming a headspace between a product fill line
a rim of the container; c. introducing a quantity of liquefied gas
into the container; d. enabling vaporized liquefied gas to displace
at least a portion of air in the headspace; and e. capping the
container so as to maintain low oxygen partial pressure within the
headspace relative to ambient atmospheric pressure, thereby
diminishing the amount of oxygen available to permeate from inside
the container into the oxygen scavenger.
2. The method of claim 1 wherein the container wall includes an
outer layer of PET, an interior layer of an oxygen scavenging
compound comprising nylon, and an inner layer of PET for contacting
the product.
3. The method of claim 1 wherein the container wall includes a
single layer comprising a blend of an oxidizable polymer and a
non-oxidizable polymer.
4. The method of claim 1 wherein the container wall includes a
blend of an oxygen scavenger material and polyethylene
terephthalate.
5. The method of claim 1 wherein the oxygen scavenger is an
oxidizable organic component and a metal catalyst.
6. The method of claim 5 wherein the organic component is a
polymer.
7. The method of claim 5 wherein the organic component is a
polyamide.
8. The method of claim 5 wherein the organic component a
condensation polymer of m-xylylenediamine and adipic acid.
9. The method of claim 1 wherein the liquefied gas forms a positive
total pressure inside the container after the capping step (e).
10. The method of claim 9 wherein the introducing step (b) includes
introducing the comestible product into the container at an
elevated temperature.
11. The method of claim 10 wherein the oxygen partial pressure
within the headspace is below about 3.1 psi.
12. The method of claim 1 wherein the oxygen partial pressure
within the headspace is below about 2.75 psi upon capping.
13. The method of claim 1 wherein the oxygen partial pressure
within the headspace is below about 2.3 psi upon capping.
14. The method of claim 1 wherein the oxygen partial pressure
within the headspace is below about 1.54 psi upon capping.
15. The method of claim 1 wherein the oxygen partial pressure
within the headspace is below about 0.77 psi upon capping.
16. The method of claim 1 wherein capping step (e) thereby forms an
oxygen partial pressure gradient across the container wall.
17. The method of claim 1 wherein the quantity of liquefied gas is
sufficient to maintain a positive total pressure within the
container upon cooling to ambient temperature.
18. The method of claim 1 wherein the quantity of liquefied gas is
sufficient to maintain a positive total pressure within the
container upon cooling to approximately 50 degrees F.
19. The method of claim 1 wherein the quantity of liquefied gas is
sufficient to maintain a positive total pressure within the
container upon cooling to approximately 40 degrees F.
20. The method of claim 1 wherein the quantity of liquefied gas is
such that the container has a substantially atmospheric pressure
upon cooling to ambient temperature.
21. The method of claim 1 wherein the liquefied gas comprises
liquefied nitrogen.
22. The method of claim 1 wherein the liquefied gas is an inert
gas.
23. The method of claim 1 wherein the liquefied gas is liquefied
nitrogen.
Description
BACKGROUND
[0001] This invention relates to processing and filling containers,
and more particularly to processing and/or filling containers
having an oxygen scavenging material.
[0002] Polyethylene terephthalate ("PET"), polypropylene, or other
thermoplastic materials are often employed for forming containers
for comestible products, such as food and beverages--especially
beer, juices, and the like. Containers suitable for filling
processes at which elevated temperatures are employed (including
for example filling a container with a product that is at an
elevated temperature, pasteurizing a container after filling, and
the like) will be referred to herein as "hot-fillable."
Hot-fillable containers generally are blow molded and a heat set
process during which the containers are subjected to elevated
temperatures for predetermined time periods in order to increase
crystallization and decrease orientation of the polymer. Heat
setting, which increases crystallinity, is beneficial, among other
things, to reduce shrinkage of the container at elevated
temperature. Container configurations, blow molding techniques, and
heat setting techniques for both hot-fillable containers are well
known.
[0003] Typically, hot-fillable containers are not designed to
withstand positive internal pressures, but rather such designs
focus on maintaining an appropriate and desirable shape during
vacuum deformation upon cooling of the contents after capping.
Thus, collapsible or deformable portions are often formed in the
container wall, and the hot-fillable base is typically designed to
withstand only negative pressure. U.S. Pat. No. 5,251,424, entitled
"Method Of Packaging Products In Plastic Containers," which is
incorporated herein in its entirety, describes a method of hot
filling a plastic container that includes introducing liquid
nitrogen into the container prior to capping for providing a
positive internal pressure. The '424 patent states that advantages
of such a technique include eliminating vacuum panels, enabling
reduction of container thickness, and control of the headspace
volume. Numerous references disclose introducing nitrogen into
metal cans prior to application of a can end.
[0004] PET and many other plastics suitable for containers are
permeable to oxygen, whether the container is hot-fillable or is
suitable for another filling process. Thus, the shelf life of
comestible products in PET or other plastic containers is limited
or decreased by oxygen permeation through the container surfaces,
and comestible products packaged in such containers are subject to
spoilage. Pressurizing a container formed entirely of PET with
liquid nitrogen would likely have little effect on product shelf
life. Thus, in efforts to reduce oxygen permeation, an oxygen
barrier may be employed. For example, a multilayer container may
include an outermost and an innermost layer (that is, forming the
container chamber surface) of virgin PET, with an oxygen barrier
material, such as EVOH, therebetween. Often, tie layers are
employed between EVOH and PET.
[0005] The commercial acceptance of containers employing
conventional barrier layers has been limited at least in part
because the effectiveness of the oxygen barrier is less than
commercially desired, even if additional coatings or layers are
employed. Oxygen scavenging compounds in a container wall are often
employed rather than barrier layers described above. For example,
U.S. Pat. Nos. 5,955,527; 5,639,815; 5,049,624; and/or 5,021,515
(which will be referred to as the "Packaging" patents) disclose an
oxygen scavenging material that is suitable for use in bottles in
hot-fillable and other containers. Oxygen scavenging compounds have
a finite effective life (that is, useful life) because eventually
the oxidizable material oxidizes to a degree that enables oxygen to
permeate through the container wall (that is, the oxidizable
material is essentially used up).
[0006] Thus, there is a need for container technology that extends
the effective life of an oxygen scavenger or the shelf life of a
product in a container.
SUMMARY OF THE INVENTION
[0007] In a conventional container that includes an oxygen
scavenging material in the container wall, oxygen is available to
permeate both from outside the container (that is, from the ambient
atmosphere) into the oxygen scavenging material and from within the
container (that is, from the enclosed chamber) into the oxygen
scavenging material. Oxygen is typically available from inside the
container because it is present in the container headspace upon
capping, and also possibly because it is dissolved in the product.
The oxidizable material in the container wall portion surrounding
the headspace may have a diminished effective life compared with
other portions of the container wall because of the oxygen
permeation from both inside and outside the container in
circumstances in which the concentration of oxygen (and/or the mass
transfer rate of the oxygen into the container wall) is greater in
the headspace than in the product
[0008] Displacing oxygen from within the container headspace prior
to capping diminishes the (molar) quantity and/or partial pressure
of oxygen inside the container, thereby diminishing the amount of
oxygen that is available to permeate from inside the container into
the container wall. We have found that displacing some oxygen from
the headspace increases the effective life of the oxygen scavenger
in the container wall in the region of the headspace.
[0009] Diminishing the oxygen partial pressure within the container
has little effect on the gross rate of oxygen permeation from
outside the container into the oxidizable material in the container
wall, yet it diminishes the oxygen available within the container
for permeating in an outward direction into the oxidizable material
of the container wall. Thus, the effective life of the oxidizable
material, especially in the portion defining or proximate to the
headspace, is extended by the degree of decrease in oxygen
permeation from within the container into the container wall.
[0010] A method of extending effective life of an oxygen scavenging
material disposed in a container wall employs the phenomenon
described above. The method includes providing a container that has
a wall comprising an oxygen scavenging material. The container wall
may be formed either of multiple layers or a monolayer. The
multiple layers preferably include a discrete layer that includes
an oxidizable compound sandwiched between layers that substantially
lack oxygen scavenging capabilities, such as polyethylene
terephthalate ("PET"), polypropylene, or other suitable material.
The monolayer preferably is a blend of an oxidizable material with
a conventional plastic.
[0011] The container is filled with a product and a dose of
liquefied gas up to a fill line, which is spaced apart from the rim
of the container to form a headspace. Upon introducing the
liquefied gas into the container, at least a portion of the
liquefied gas vaporizes and displaces at least a portion of the air
in the container headspace. Upon the displacement of at least some
of the air from the headspace, a closure or liner is applied to the
container to seal the container. The liquefied gas within the
container then continues to vaporize to form a positive total
pressure within the container. U.S. patent application Ser.
No.______ (Attorney Docket Number CC-3412), entitled "Method For
Diminishing Delamination of A Multilayer Plastic Container," which
discloses related or complimentary technology, is incorporated
herein by reference in its entirety.
[0012] In hot-fill applications that would otherwise be subject to
vacuum deformation upon cooling of the contents, providing a
positive pressure within the container by liquefied gas dosing
enables the elimination or diminished size of vacuum panels or
other collapsible or deformable portions of the container, and may
also enable a lighter-weight container and control over the
headspace. Further, the combination of an oxygen scavenger in the
container wall with liquefied gas dosing is beneficial for product
shelf life. In this regard, displacing a portion of the air present
in the headspace by introducing a dose of liquefied gas extends the
life of the oxygen scavenger in the container wall in the region of
the headspace. Extending the effective life of the oxygen
scavenger, and thus likely extending the product shelf life,
applies to hot-filling and non-hot-filling applications.
BRIEF DESCRIPTION OF THE FIGURES
[0013] FIG. 1 is a flow chart illustrating steps according to the
present invention;
[0014] FIG. 2 is a diagrammatic view of a monolayer container
wall;
[0015] FIG. 3 is a diagrammatic view of a three layer container
wall;
[0016] FIG. 4 is a view of a portion of a container package with
which the present invention may be employed; and
[0017] FIG. 5 is a perspective view of the container shown in FIG.
4.
DESCRIPTION OF A PREFERRED EMBODIMENT
[0018] A method of extending the effective life of a container that
includes an oxygen scavenging material is provided. The present
invention may be employed with any type of container, including:
injection blow-molded bottles, extrusion blow-molded bottles, and
bottles formed by any other process; heat set bottles suitable for
hot-fillable applications and non-heat set bottles; and jars or
containers suitable for foods, sauces, and the like.
[0019] FIGS. 4 and 5 illustrate merely one embodiment of a
container 9 with which the present invention may be employed.
Container 9 preferably is a heat set container capable of
withstanding filling with a beverage at hot-fill temperatures,
which typically is about 190 degrees F., with volumetric shrinkage
of only a few percent. Heat set processes for forming containers
are well known by persons familiar with plastic container
manufacturing and design.
[0020] Container 9 is capable of withstanding internal positive
pressures contemplated to be encountered in liquefied gas dosing
applications, as well as in pressure filling applications. The
particular internal pressure rating or design point of a container
may be chosen according to the particular parameters of the
application, such as desired internal pressure at a given
temperature, carbonization of the product, container configuration,
container wall material properties, resistance to abuse, and the
like. Such parameters will be understood by persons familiar with
container design and technology.
[0021] Container 9 includes a base 12, a body 14, a dome 16, a neck
18, and a finish 20. Base 12 preferably has a substantially
continuous contact ring or standing ring on which the container
rests. Body 14 extends upwardly from base 12, and is preferably
substantially continuous. Because the liquefied gas pressurizes
container 9, as explained more fully below, vacuum panels or other
features that flex upon internal vacuum are unnecessary. Thus, body
14 preferably is substantially cylindrical. Body 14 may optionally
grip portions. In this regard, finger indentations 22 may be formed
in body 14 to aid gripping.
[0022] Dome 16 extends upwardly from body 14, and yields to neck
18. Preferably, neck 18 is substantially cylindrical or slightly
tapered. Preferably, neck 18 is sufficient long to provide an
adequate headspace such that spilling of the product is unlikely
upon initial opening of the closure. Finish 20 is disposed at the
top of neck 18. Further description of container 9 is described in
co-pending, concurrently filed U.S. patent application Ser. No.
______ , entitled "Pressurizable Container With Contact Ring"
(Attorney Docket Number CC-3438), which is incorporated by
reference herein in its entirety.
[0023] Container 9 may be formed of any material comprising any
oxygen scavenger. The wall of container 9 may be formed in any
configuration, including multiple layers or a single layer. In this
regard, FIG. 2 illustrates a container wall 30 that is formed of a
single, substantially uniform composition that includes an oxygen
scavenger. FIG. 3 illustrates a container wall formed in multiple
layers 32, 34, and 36. Outer and inner layers 32 and 36 preferably
are a virgin plastic material, such a polyethylene terephthalate,
polypropylene, or other suitable material. Sandwich between outer
and inner layers 32 and 36 is an intermediate layer 34, which
preferably includes an oxygen scavenger. The present invention
encompasses any combination of layers, including walls formed of
more than three layers and walls having additional coatings.
[0024] Preferably, the oxygen scavenger includes an oxidizable
organic component and a metal catalyst for the oxidation of the
oxidizable organic component. The oxidizable organic component
preferably is a polymer, such as a polyamide and especially MXD6,
which is a condensation polymer of m-xylylenediamine and adipic
acid. The metal catalyst may include cobalt, copper, rhodium
compounds and/or other suitable substances. A suitable material for
the oxygen scavenger layer is OXBAR.TM., which is available from
Crown Cork & Seal Company, Philadelphia, Pa. U.S. Pat. Nos.
5,955,527; 5,639,815; 5,049,624; and/or 5,021,515, each of which is
incorporated by reference in its entirety, disclose technology
relating to such a scavenger. The present invention is not limited
to the preferred oxygen scavenger, but rather encompasses employing
any such substance capable of such oxidation.
[0025] Further, particular features or configuration of container 9
are employed to illustrate an embodiment of a container on which
the present invention may be employed. The present invention,
however, is not limited to the particular features or configuration
of the container. Rather, the invention encompasses a container of
any configuration, including without limitation cylindrical and
non-cylindrical containers, containers of any dome shape or lacking
a dome, containers of any neck configuration or lacking a neck, and
containers having any standing ring configuration, a footed
configuration, and the like.
[0026] Referring again to the figures to illustrate the present
method, a container, such as container 9, is provided to a filling
station for filling a comestible product, such as juice, sauces,
and/or the like. The product is filled up to a predetermined fill
line, which is illustrated by reference numeral 24 in FIGS. 4 and
5. Preferably, the product is introduced at conventional hot-fill
temperatures, such as 180 to 190 degrees F. The product may be
filled by any type of gravity filling process in which the product
is allowed to flow into container 9 under atmospheric conditions or
at a low head pressure, a pressure filling process in which the
product is pumped into container such that the container encounters
a positive internal pressure (typically a few pounds per square
inch), or other filling method.
[0027] A predetermined dose of liquefied gas is introduced into
container 9 either just prior to, concurrently with, or after
introduction of the product into container 9. The liquefied gas
preferably is an inert gas, and even more preferably is liquefied
nitrogen. The liquefied gas may be introduced into the container
prior to, concurrently with, or after the product in introduced
into the container. The product filling system and liquefied gas
delivery system are schematically represented by reference numerals
42 and 44, respectively, in FIG. 5. Equipment and systems for
filling plastic containers is well known. Similarly, equipment and
systems for introducing liquefied nitrogen or other inert gas into
containers, especially metal cans, is well known. Any conventional
equipment and systems may be employed to accomplish such steps.
[0028] Upon filling the container up to fill line 24, a headspace
28 is formed between fill line 24 and the top lip of container 9.
The gas in the headspace upon filling in a conventional process
typically has a composition like that of the atmosphere. In this
regard, under gravity filling conditions, container 9 is
essentially open (or at least not sealed air-tight) during the
filling process. Similarly, under pressure filling conditions, the
container is open to the atmosphere prior to filling and prior to
capping.
[0029] According to the present invention, the liquefied gas, which
vaporizes upon being introduced into container 9, displaces at
least some of the oxygen in headspace 28. Closure 26, which is
diagrammatically shown in dashed lines in FIG. 4, is applied to
finish 20 while at least some of the oxygen is displaced to seal
container 9. Similarly, a liner, which may also be represented by
reference numeral 26, may be applied. Upon application of closure
(and/or liner) 26, container 9 is sealed. Because at least some of
the oxygen was displaced from headspace 28 upon sealing, the
composition of the gas in headspace 28 includes an elevated partial
pressure or concentration of nitrogen (or other gas making up the
liquefied gas) and a diminished partial pressure or concentration
of oxygen, compared with ambient conditions.
[0030] The diminished oxygen partial pressure within headspace 28
provides fewer molecules that may migrate into the container wall
11 or 36 compared with an oxygen partial pressure in the headspace
of conventionally filled containers or filling by other means.
Similarly, the diminished quantity of available oxygen in the
headspace will also extend the life of an oxygen scavenger that is
formed as part of the liner.
[0031] The present invention encompasses any oxygen partial
pressure in the sealed headspace below ambient (that is, about 3.1
psi) when the contents reach equilibrium, ambient temperature. Each
of the exemplary pressures provided below are the pressure in the
headspace immediately upon capping, regardless of the headspace gas
or product temperature, although it is understood that such
pressures will vary upon cooling of the product. Vaporization of
any liquefied gas in the product after capping may increase the
total pressure in the headspace. Preferably, the oxygen partial
pressure in the sealed headspace is below about 2.75 psi, which
provides a measurable increase in the effective life of the oxygen
scavenger, or even more preferably below about 2.3 psi, even more
preferably below about 1.54 psi, and even more preferably below
about 0.77 psi.
[0032] The present invention is illustrated with respect to a
particular container, although the present invention is not limited
to the particular container configuration or materials described
herein. Rather, the present invention encompasses employing any
container configuration, container material, or container
manufacturing method. Further, the present invention encompasses
any filling technique. Even though the present invention provides
advantages in hot-filling applications, the present invention also
encompass including filling at any temperature in any type of
process. Reference should be made to the claims to ascertain the
scope of the present invention.
* * * * *