Note: Descriptions are shown in the official language in which they were submitted.
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MULTILAYERED PLASTIC CONTAINER
BACKGROUND OF THE INVENTION
The present invention relates to multi-layered containers. More particularly,
the
present invention relates to blow molded multi-layered plastic containers.
Multi-layered plastic containers are commonly used for packaging items in a
wide range of fields, including food and beverage, medicine, health and
beauty, and
home products. Plastic containers are known for being easily molded, cost
competitive,
lightweight, and generally suitable for many applications. Multi-layered
containers
provide the added benefit of being able to use different materials in each of
the layers,
wherein each material has a specific property adapted to perform a desired
function.
Because plastic containers may permit low molecular gases, such as oxygen and
carbon dioxide, to slowly permeate through their physical configurations, the
use of
plastic containers sometimes proves to be less desirable when compared to
containers
fonned from other less permeable materials, such as metal or glass. In most
applications,
the shelf life of the product contents is directly related to the package's
ability to
effectively address such molecular permeation. In the case of carbonated
beverages, such
as beer, oxygen in the atmosphere surrounding the container can gradually
permeate
inwardly through the plastic walls of the container to reach inside of the
container and
deteriorate the contents. Likewise, carbon dioxide gas associated with the
contents may
permeate outwardly through the plastic walls of the container until eventually
being
released on the outside, causing the carbonated beverage to lose some of its
flavor and
possibly become "flat".
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To address some of the foregoing concerns, plastic container manufacturers
have
utilized various techniques to reduce or eliminate the absorption and/or
permeability of
such gases. Some of the more common techniques include: increasing the
thickness of
all or portions of the walls of the container; incorporating one or more
barrier layers into
the wall structure; including oxygen-scavenging or reacting materials within
the walls of
the containers; and applying various coatings to the internal and/or external
surface of the
container. However, a number of conventional barrier and/or scavenger
materials will
not effectively curtail the permeation of both oxygen and carbon dioxide over
extended
periods of time. Moreover, there are usually other practical concerns
associated with
most conventional techniques, most commonly, increased material costs and/or
production inefficiencies.
In recent times, the use of plastics has become a significant social issue.
Recycling has become an increasingly important environmental concern and a
number of
governments and regulatory authorities continue to address the matter. In a
number of
jurisdictions, legislation pertaining to minimum recycled plastic content and
the
collection, return, and reuse of plastic containers has either been considered
or has
already been enacted. For example, in the case of plastic containers used to
hold
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consumable items, such as food items or beverages, regulations often require a
certain
content and minimum thickness of FDA approved material for the innermost layer
that
comes in contact with the contents. Conventional processes, such as co- or
multiple-
injection molding, are often limited as to the amount of recycled plastic that
can be
effectively incorporated into the structure of the container due to process
limitations.
Commonly, the amount of recycled content that can be effectively incorporated
into
conventional co-injection molded containers that are suitable for food
contents is less
than 40% of the total weight of the container.
Therefore, a need exists in the industry for, and it is an object of the
present
invention to provide, an improved multi-layered plastic container including
oxygen
scavenging materials suitable for holding products such as carbonated
beverages or other
food products, and having a long shelf life.
It is a further objective of the present invention to provide a multi-layered
plastic
container as aforesaid which may include desired levels of recycled material.
It is a still further object of the present invention to provide a multi-
layered plastic
container as aforesaid which may be readily and conveniently prepared at a
moderate
cost.
Further objects and advantages of the present invention will appear
hereinbelow.
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SUMMARY OF THE INVENTION
In accordance with the present invention, the foregoing objects and advantages
are readily obtained.
It is desirable for multi-layered plastic containers to effectively utilize an
oxygen-
scavenging material. However, these materials may not be approved to come into
contact
with food or beverage if the container is used to hold these items. In a multi-
layered
container the innermost plastic layer would be a plastic material that is
approved for
contact with the food or beverage contents of the container.
Moreover, after a container is manufactured, it often is not filled with food
or
beverage immediately. Naturally, one desires the oxygen scavenger material to
begin
working only after the container is filled. Disadvantageously, an oxygen
scavenger may
start to react prior to filling of the container, limiting the storage life of
empty containers
in inventory (not filled).
In accordance with the present invention, a three or more layered plastic
container
is provided, wherein
an innermost first layer is a plastic material, preferably approved for
contact with food or beverage products,
an intermediate second layer is a plastic material adjacent the first layer
containing an oxygen scavenger material; and
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- an outermost third layer is a plastic material, desirably containing
recycled
plastic,
wherein the thickness of the innermost layer is in the range of 0.1 to 3 mils
and is
controlled based on the desired shelf life of the container in the unfilled
condition, i.e.,
the thicker the innermost layer in this range the greater the protection
afforded the oxygen
scavenger material.
Thus, for example, it has been found that a three layered plastic container
with an
innermost layer of polyethylene terephthalate (PET) that is 0.5 mils thick,
and with an
intermediate plastic layer containing an oxygen scavenging material, can be
stored in a
warehouse in the unfilled condition for at least six (6) weeks without the
oxygen
scavenging material beginning to react with oxygen. When the container is
thereafter
filled with product, as for example, a beverage, the oxygen scavenging
material will be
fully effective to protect the product. Naturally, the innermost layer may be
thicker if
longer protection times are desired in the unfilled condition, and thinner if
shorter
protection times are desired.
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In accordance with one aspect of the present invention, there is provided a
multilayered container, comprising: an upper wall portion, an intermediate
sidewall
portion and a self-supporting base portion, said portions formed from at least
an
innermost first layer of a plastic material approved for contact with food or
beverage
products, an intermediate second layer and an outermost third layer; wherein
said
innermost first layer is a plastic material having a thickness of from 0.1 to
3 mils, said
intermediate second layer is a plastic material containing at least one oxygen
scavenging
material that reacts with oxygen, wherein the oxygen scavenging material
contains
polyolefin oligomer segments, plus at least one oxygen barrier material, and
having a
thickness of from 0.1 to 3 mils, and said outermost third layer is a plastic
material having
a thickness of from 3 to 23 mils and comprising at least 40% by weight of the
total weight
of the container, wherein the thickness of the innermost layer is controlled
to provide that
the thicker innermost layer the greater the protection afforded to the oxygen
scavenging
material, and wherein the innermost layer varies in thickness along the
vertical length
thereof, with the upper wall portion thereof being the thinnest and the base
thereof being
the thickest, and wherein said container is blow molded and has extrusion
molded
innermost and intermediate layers and an injection molded outermost layer.
There is also provided, in accordance with another aspect of the present
invention, a process which comprises: forming a blow molded, multi-layered
plastic
container having an upper wall portion, an intermediate sidewall portion and a
self-
supporting base portion, said portions formed to have at least an innermost
first layer, an
intermediate second layer and an outermost third layer; wherein said innermost
first layer
is formed from a plastic material to have a thickness of from 0.1 to 3 mils,
said
intermediate second layer is formed from a single layer of plastic material
having a
constant thickness and containing at least one oxygen scavenging material that
reacts with
oxygen, wherein the oxygen scavenging material contains polyolefin oligomer
segments,
plus at least one oxygen barrier material, and to have a thickness of from 0.1
to 3 mils,
and said outermost third layer is formed from a plastic material to have a
thickness of
from 3 to 23 mils and comprising at least 40% by weight of the total weight of
the
container; wherein the thickness of the innermost layer is controlled to
provide that the
thicker the innermost layer the greater the protection afforded to the oxygen
scavenging
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material, and wherein the thickness of the innermost layer is varied along the
vertical
length thereof, the intermediate second layer is in direct surface contact
with the
innermost first layer and the outermost third layer along the vertical length;
and wherein
the oxygen barrier material contains at least one of vinyl alcohol, vinyl
chloride and
vinylidene chloride.
There is further provided, in accordance with another aspect of the present
invention, a process comprising: forming a blow molded, multi-layered plastic
container
having an upper wall portion, an intermediate sidewall portion and a self-
supporting base
portion, said portions formed to have at least an innermost first layer, an
intermediate
second layer and an outermost third layer; wherein said innermost first layer
is formed
from a plastic material to have a thickness of from 0.1 to 3 mils, said
intermediate second
layer is formed from a single layer of plastic material having a constant
thickness and
containing at least one oxygen scavenging material that reacts with oxygen,
wherein the
oxygen scavenging material contains polyolefin oligomer segments, plus at
least one
oxygen barrier material, and to have a thickness of from 0.1 to 3 mils, and
said outermost
third layer is formed from a plastic material to have a thickness of from 3 to
23 mils and
comprising at least 40% by weight of the total weight of the container;
wherein the
thickness of the innermost layer is controlled to provide that the thicker the
innermost
layer the greater the protection afforded to the oxygen scavenging material,
and wherein
the thickness of the innermost layer is varied along the vertical length
thereof; the
intermediate second layer is in direct surface contact with the innermost
first layer and the
outermost third layer along the vertical length; and wherein the oxygen
barrier material is
comprised of PEN, saran and ethylene vinyl alcohol copolymers (EVOH), or
acrylonitrile copolymers.
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The process of the present invention comprises:
- forming a plastic container with three or more layers of plastic, with
- the innermost first layer being a plastic layer preferably approved for
contact with food or beverage products,
- the intermediate second layer is a plastic layer adjacent the first layer
containing at least one oxygen scavenger material, and
- the outermost third layer is a plastic layer, preferably containing recycled
plastic,
including the step of controlling the thickness of the innermost layer in the
range of 0.1 to
3 mils based on the desired shelf life of the container in the unfilled
condition.
Further features of the present invention will appear hereinbelow.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more readily understandable from the following
illustrative drawings, wherein:
Figure 1 is an elevational view of a preform for forming a container in
accordance
with the present invention;
Figures 1 A, 1B and 1C are enlarged cross-sectional views of various areas of
the
preform of Figure 1;
Figure 2 is an elevational view of a container of the present invention; and
Figures 2A, 2B and 2C are enlarged cross-sectional views of various areas of
the
container of Figure 2.
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DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The molded innermost plastic layer is comprised of a thermoplastic material.
The
following resins are representative of resins that may be used as plastic
materials for the
innermost layer: polyethylene, polypropylene, polystyrene, cycloolefin
copolymer,
polyethylene terephthalate, polyethylene naphthalate, ethylene-(vinyl alcohol)
copolymer, poly-4-methylpentene- 1, poly (methyl methacrylate), acrylonitrile,
polyvinyl
chloride, polyvinylidene chloride, styrene-acrylo nitrile, acrylonitrile-
butadiene-styrene,
polyamide, polyacetal, polycarbonate, polybutylene terephthalate, ionomer,
polysulfone,
polytetra-fluoroethylene, and the like. When food product contents are
involved, the
innermost layer should be formed from resins approved for contact with food
products, as
virgin polyethylene terephthalate (PET), polyethylene naphthalate (PEN),
and/or blends
of polyethylene terephthalate or polyethylene naphthalate. However, other
thermoplastic
resins approved for contact with food products may also be used.
The molded outermost layer may be any desired plastic material, such as those
set
out hereinabove.
Desirably, the molded outermost layer includes recycled plastic material,
including the plastics set forth above, but is preferably formed from recycled
polyethylene terephthalate.
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However, the invention is not limited to a particular type of recycled plastic
and
other recycled plastic materials may be used. Moreover, any desired amount of
recycled
plastic material may be used in the outermost layer, for example, at least
five (5) percent,
at least forty (40) percent, or at least ninety (90) percent. Further, the
outermost layer
desirably comprises at least 40% by weight of the total weight of the
container, but can
comprise at least 85% by weight of the total weight of the container. The
outermost layer
generally has a wall thickness, taken along its vertical length, that is in
the range of 3 to
23 mils (0.1524 mm to 0.5842 min). Moreover, the thicknesses of each layer can
be
separately and independently varied along their vertical length, as desired.
The intermediate layer is a plastic layer that contains an oxygen scavenging
material. Oxygen scavenging materials are well known and include materials
marketed
for such a purpose by several large oil companies and resin manufacturers. A
specific
example of such a material is marketed under the trade name AMOSORB and is
commercially available from the Amoco Corporation. Polyolefin oligomer
segments are
prepared for copolycondensation by first functionalizing the polyolefin
oligomer
segments with end groups capable of entering into polycondensation reactions
The
polyolefin oligomers are, in effect, addition polymers. Functionalization of
the
polyolefin oligomers with end groups affords a convenient method for
incorporation of
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addition polymer segments into a copolycondensate. A preferred polyolefin
oligomer as
an oxygen scavenger in the present invention is polybutadiene because it has
good
oxygen scavenging capacity and reacts quickly with oxygen especially in the
presence of
a transition metal catalyst, such as cobalt, and in the presence of
benzophenone, or both
cobalt and benzophenone. Desirably, the intermediate layer can be made of or
include a
barrier material. The barrier material or layer is desirably an oxygen barrier
and is
preferably formed from PEN, saran and ethylene vinyl alcohol copolymers (EVOH)
or
acrylonitrile copolymers, such as Barex. The term saran is used in its normal
commercial
sense to contemplate polymers made for example by polymerizing vinylidene
chloride
and vinyl chloride or methyl acrylate. Additional monomers may be included as
is well
known. Vinylidene chloride polymers are the most commonly used, but other
oxygen
barrier materials are will known.
Naturally, other layers may be provided as desired.
The container of the present invention may be formed by any of several known
processing techniques which permit the manufacture of a multi-layered blow
molded
plastic container having a plastic molded inner layer and a relatively thick
molded plastic
outer layer which may include recycled plastic, and an intermediate plastic
layer, all as
aforesaid. In a preferred embodiment, the multi-layered container is formed
via a blow
molding operation involving a multi-layered preform. Although not a required
feature,
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the preform may include a neck flange, which is convenient for handling
purposes, and
outer threads to secure a closure. In a preferred embodiment, the preform may
be
produced by extrusion molding an inner and intermediate layer and injection
molding an
outer layer. Extrusion of the preform allows the manufacturer to produce
thinner inner
and/or intermediate layers of controlled thicknesses. Further, an extrusion or
co-
extrusion process permits the manufacturer to readily vary the thickness of
material being
extruded along the length of the extrudate. The multi-layered container can
then be blow
molded using conventional blow molding operations.
Referring now to the drawings in detail, there is shown in FIG. 1 an
elevational
view of a preform, in accordance with the present invention, designated
generally as 10.
Preform 10 preferably includes a threaded and flanged upper portion 12, an
angled
intermediate portion 14, a vertical intermediate portion 16 and a base portion
18. In the
configuration shown in FIG. 1, preform 10 is adapted to be blow molded into a
container
in accordance with the present invention.
Referring now to FIGS. 1A, 1B & 1C, which show enlarged cross-sectional views
of areas 1A, 1B and 1C, respectively of FIG. 1, preform 10 is preferably
formed from
three layers of material. These clearly show encircling innermost first layer
20,
encircling second intermediate layer 22, and the third outermost layer of the
preform,
encircling outer layer 24. As can be seen from FIGS. lA-1C, the thicknesses of
the
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layers may if desired vary in accordance with specific portions of preform 10.
Outer
layer 24 desirably has increased thickness at threaded and flanged upper
portion 12.
Innermost layer 20 also desirably may vary in thickness depending upon the
portion of
the bottle, i.e., threaded and flanged upper portion 12, angled and vertical
intermediate
portions 14 and 16, and base portion 18.
Innermost layer 20 and intermediate layer 22 are preferably coextruded via an
extrusion process, and outer layer 24 is preferably formed onto the extruded
layers via an
injection molding process, which allows the formation of the threaded upper
portion 12.
As a result of the extrusion process, innermost layer 20 can be readily
controllably
adjusted in thickness based upon the functions to be performed by the various
portions
and especially to provide a desired degree of protection to the oxygen
scavenger material
in the intermediate layer.
The intermediate layer 22 is preferably maintained at a constant thickness,
but this
also can be varied in thickness if desired.
Variations in thickness of the inner layer are also desirable for reasons
which
include aesthetics, efficient material use and reduced costs, and variable
strength
requirements. Efficient material use is evident in innermost layer 20 at upper
portion 12,
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where innermost layer 20 is thinnest. Strength considerations are evident in
base portion
18, where additional support is required and as a result, innermost layer 20
may be
thickest.
With reference now to FIG. 2, a container 58 is shown which is formed from
preform 10 of FIG. 1 via a blow molding operation. Similar to the preform,
container 58
desirably includes a threaded upper portion 60, an angled intermediate portion
62, a
substantially vertical intermediate portion 64 and a base portion 66, which is
shown in the
embodiment of FIG. 2 as a self-supporting base. Naturally, other base
configurations
may be used, as a footed base for example. As shown in FIGS. 2A - 2C,
container 58
also has three layers of material, each of which may have differing properties
and relative
thickness relationships.
Referring to FIGS. 2A - 2C , which represent enlarged cross-sectional views of
areas 2A, 2B and 2C, respectively, of FIG. 2, container 58 includes innermost
layer 68,
central layer 70 and outer layer 72. Because innermost layer 68 is not subject
to blowing
at the neck region in forming the container shape, the thickness ratios
between the
various portions of the container may differ from those of preform 10.
However, the
thicknesses of the layers of the container may if desired vary in accordance
with specific
portions of the container in a manner after the thickness variations of the
preform.
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Self-supporting base portion 66 is preferably comprised of a circumferential
encircling member 74, particularly a ring defining an annulus and an indented
center
positioned wall 75, whose function is to sturdily support container 58 on a
flat surface.
Encircling member 74 forms the lower circumference of the container at the
lower end 76
thereof. Indented wall 75 joins the inside portions of encircling member 74
and is located
in the center of encircling member 74. Encircling member 74 starts at the
bottom 77 of
container 58 and extends upwardly forming lower end 76 and is continuous with
the inner
and outer diameters of the container wall defined by layers 68, 70 and 72 of
container 58.
Due to the increased thickness of innermost layer 68 at the self-supporting
base 66, base
66 including encircling member 74 is substantially harder and less flexible
than
intermediate portions 62 and 64 providing increased support.
The shape and parts of container 58, shown in FIG. 2 are by way of example
only
and accordingly, a plurality of shapes with varying parts are contemplated,
all of which
have a layered structure similar to as discussed above. For example, the
container may
contain greater than three layers if desired and the shape shown in FIG. 2 is
exemplificative only.
It is to be understood that the invention is not limited to the illustrations
described
and shown herein, which are deemed to be merely illustrative of the best modes
of
carrying out the invention, and which are susceptible of modification of form,
size,
arrangement of parts and details of operation. The invention rather is
intended to
encompass all such modifications which are within its spirit and scope.
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