Note: Descriptions are shown in the official language in which they were submitted.
CA 02817292 2013-05-30
. ,
1
PACKAGING FILM AND METHOD OF MANUFACTURE
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. provisional patent
application
Serial No. 61/653,917 filed May 31, 2012. The aforementioned provisional
application is
incorporated by reference in its entirety.
BACKGROUND
[0002] 1. Field
[0003] Embodiments of the present inventive concept relate to packaging and,
in
particularly, to a packaging film having enhanced barrier, sealability, and
flex-crack
resistance characteristics and is ideal for use with food products, such as
cheese and meat,
to increase shelf life thereof.
100041 2. Related Art
[0005] Flexible packaging, particularly for food, is subject to many demands.
The packaging needs to be workable in such a way that the packaging material
may be
quickly placed around the item to be packaged using machinery. The packaging
material
must also be of such a quality that it adequately stores the product before
the packaging is
open. In the case of food products, this typically means that the packaging
materials
provide an oxygen barrier to maintain freshness.
[0006] Ethylene vinyl alcohol (EVOH) is an extrudable resin that has excellent
oxygen, flavor, and aroma barrier properties. EVOH resins and packaging
materials have
been used for several decades as meat and cheese film wrappers and the barrier
properties
CA 02817292 2013-05-30
2
of EVOH with respect to oxygen, grease, oil, flavor additives, and aroma is
well
understood.
[0007] However, when exposed to humidity levels of 85% or higher, the barrier
properties of EVOH degrade. To avoid this degradation, the EVOH is typically
extruded
in a multi-layer symmetrical coextrusion in which specialized tie resins are
used to
adhere the EVOH to outer polyolefin layers that protect the EVOH from
humidity. For
example, a three resin, five layer coextrusion of EVOH may include LDPE-Tie
Resin-
EVOH-Tie Resin-LDPE. In this five layer structure, the LDPE (low density
polyethylene) layers protect the EVOH layer from exposure to moisture. Also,
the LDPE
and Tie Resin are extruded each from one extruder where they are split into
two layers
and directed to either side of the EVOH layer by a feedblock device. The LDPE
and Tie
Resin are exactly the same material on both sides of the EVOH, thus it is
called a
symmetrical coextrusion.
[0008] It should be further understood that, when melted, EVOH becomes fluid
very quickly with very low melt strength and cannot be extruded as a separate
thin film.
In extrusion coating, a melt curtain is formed between the exit of the
extruder die and the
extruder nip. The melt curtain is completely unsupported in this air gap
between the die
and the extruder nip. Therefore, the melt curtain needs to have enough
viscosity and melt
strength to keep from tearing apart. Thus, EVOH has traditionally required the
above-
described five layer structure not only to maintain its barrier properties,
but also to
provide adjacent structural layers (such as polyethylene) that physically
support the
coextruded layer of the EVOH. Thus, while EVOH has excellent oxygen barrier
properties, EVOH has been considered unsuitable as a barrier layer in some
applications
for a number of reasons. For one, production of EVOH has required extrusion
machines
capable of coextruding more than two resins. Such machines are very expensive
and not
as common as those extruding only two resins. Further, dual tie resin and
polyolefin
layers are provided on both sides of the EVOH coextrusion to protect the EVOH
layer
from humidity; however, these multiple layers can increase the material cost
of the
packaging and increase the thickness of the packaging. This has made EVOH-
based
packaging less competitive for certain packaging applications.
CA 02817292 2013-05-30
3
[0009] Accordingly, there is a continuing need for improved and lower cost
packaging and a method of making the same that maintains product freshness
without
presenting cost, processing, or post-use concerns.
SUMMARY
[0010] The following brief summary is provided to indicate the nature of the
subject matter disclosed herein. While certain aspects of the present
inventive concept
are described below, the summary is not intended to limit the scope of the
present
inventive concept. Embodiments of the present inventive concept provide a
packaging
film and method that does not suffer from the problems and limitations of
conventional
packaging such as those previously discussed.
[0011] Embodiments of the present inventive concept provide a packaging film
having enhanced barrier, sealability, and flex-crack resistance
characteristics, and is ideal
for use with food products, such as cheese and meat, to increase shelf life
thereof.
[0012] In more detail, embodiments of the present inventive concept provide a
packaging film having an innermost sealant layer disposed on a multilayer core
structure.
The innermost sealant layer and the multilayer core structure may be
configured to
cooperatively provide a sealant layer comprising a thickness ratio of at least
60% of a
total thickness of the packaging film.
[0013] The core structure may be co-extruded and may include an outer layer
and
inner layer on either side of a middle barrier layer. The outer and inner
layers may
contain a same material. The outer and/or inner layers may contain
polyolefins.
[0014] The middle barrier layer may contain one of ethylene vinyl alcohol and
polyamide.
[0015] The packaging film may include an abuse layer disposed on a side of the
core structure opposite to the outermost sealant layer. This layer may contain
one of
biaxially oriented polyethylene terephthalate and nylon.
[0016] The packaging film may include an adhesion layer formed within the core
structure. The adhesion layer may contain a tie resin and may be formed
directly
between the inner layer and/or the middle barrier layer.
CA 02817292 2013-05-30
4
[0017] Embodiments of the present inventive concept may provide a method of
manufacturing a packaging film, which may include the step of forming an
innermost
sealant layer disposed on a multilayer core structure. The innermost sealant
layer and the
multilayer core structure may be configured to cooperatively provide a sealant
layer
comprising a thickness ratio of at least 60% of a total thickness of the
packaging film.
The core structure may be co-extruded and may include an outer layer and inner
layer on
either side of a middle sealant layer.
[0018] The method may include the step of forming an abuse layer on a side of
the core structure opposite to the innermost sealant layer. The abuse layer
may contain
one of biaxially oriented polyethylene terephthalate and nylon.
[0019] Additional aspects, advantages, and utilities of the present inventive
concept will be set forth in part in the description which follows and, in
part, will be
obvious from the description, or may be learned by practice of the present
inventive
concept.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Embodiments of the present inventive concept are described in detail
below with reference to the attached drawing figures, wherein:
[0021] FIG. 1 is a schematic illustrating a film with a layer structure, in
accordance with first exemplary embodiment of the present inventive concept;
and
[0022] FIGS. 2 is a schematic illustrating a film with a layer structure, in
accordance with second exemplary embodiments of the present inventive concept.
[0023] The drawing figures do not limit the present inventive concept to the
specific embodiments disclosed and described herein. The drawings are not
necessarily
to scale, emphasis instead being placed upon clearly illustrating the
principles of the
present inventive concept.
DETAILED DESCRIPTION
[0024] Detailed embodiments of the present inventive concept are disclosed
herein; however, it is to be understood that the disclosed embodiments are
merely
exemplary of the invention, which may be embodied in various forms. Therefore,
CA 02817292 2013-05-30
specific structural and functional details disclosed herein are not to be
interpreted as
limiting but merely as a basis for the claims and as a representative basis
for teaching one
skilled in the art to variously employ the present inventive concept in
virtually any
appropriately detailed structure. Further, the terms and phrases used herein
are not
intended to be limiting but rather to provide an understandable description of
the present
inventive concept.
[0025] The terms "a" or "an," as used herein, are defined as one or more than
one.
The term "another," as used herein, is defined as at least a second or more.
The terms
"including" and/or "having" as used herein, are defined as comprising (i.e.,
open
transition). The term "coupled" or "operatively coupled," as used herein, is
defined as
indirectly or directly connected.
[0026] Turning now to the drawings, and particularly FIGS. 1-2, a packaging
film
manufactured in accordance with embodiments of the preset inventive concept is
illustrated. The packaging film 10 is configured to be utilized to package
food products,
e.g., cheese and/or meat. The packaging film has enhanced barrier,
sealability, and flex-
crack resistance characteristics and is particularly ideal for use in
packaging the food
products and to increase shelf life of the food products relative to
conventional
packaging. Embodiments of the present inventive concept will be discussed in
use with
respect to cheese, although it is to be understood that the present inventive
concept is
equally useable with other food products.
[0027] In FIGS. 1-2, two structures of the packaging film 10 are illustrated
including:
(1) PET-LDPE/EVOH/Tie/LDPE-Sealant
(2) BON-LDPE/EVOH/Tie/LDPE-S ealant
[0028] Each of these structures (1) and (2) for packaging film 10 contains
sealant
layers that comprise at least 60% of the entirety of the packaging film 20.
[0029] As used herein, a "2 is used to indicate layers that are separately
formed
and attached and "I" is used to indicate layers that are coextruded with one
another.
[0030] In FIG. 1, the packaging film 10 includes a primary sealant layer 12
formed on an innermost portion of the packaging film 10 relative to a food
product 14.
The primary sealant layer 12 is made of linear-low-density polyethylene
(LLDPE) having
CA 02817292 2013-05-30
6
a thickness of approximately 1.5 mil. In this manner, the thickness of the
primary sealant
layer 12 comprises at least a fraction of the thickness of the packaging film
20 in its
entirety. It is foreseen that the primary sealant layer 12 may be made of any
like material
without deviating from the scope of the present inventive concept.
[0031] On the primary sealant layer 12 is a multilayer core structure 16
having an
inner layer 18, a middle barrier layer 20, and an outer layer 22. The
thickness of the core
structure 16 is a fraction of the thickness of the packaging film 10 in its
entirety, and
provides a variety of advantages to the packaging film 10, as discussed
herein.
[0032] The inner layer 18 is made of low-density polyethylene (LDPE) and has a
thickness of a fraction of the thickness of the packaging film 20 in its
entirety. It is
foreseen, however, that the inner layer 18 may be made of any LDPE material or
the like
without deviating from the scope of the present inventive concept. The
thickness of the
inner layer 18 is a fraction of the thickness of the packaging film 10 in its
entirety. The
inner layer 18 directly abuts the primary sealant layer 12. The layers 12, 18
complement
each other by supplementing weaker characteristics of the other. For instance,
the inner
layer 18 is susceptible to stress cracking in some environments. The primary
sealant
layer 12, on the other hand, has enhanced seal properties that is
significantly higher than
that of the inner layer 18.
[0033] The middle layer 20 provides an oxygen barrier for the packaging film
10
to the surrounding environment. The middle layer 20 is made of one of ethylene
vinyl
alcohol (EVOH) or polyamide and has a thickness of a fraction of the thickness
of the
packaging film 20 in its entirety. It is foreseen, however, that the middle
layer 20 may be
made of any EVOH or polyamide material or the like without deviating from the
scope of
the present inventive concept. The thickness of the middle layer 20 is a
fraction of the
thickness of the packaging film 10 in its entirety.
[0034] The outer layer 22 is made of polyolefin and has a thickness of a
fraction
of the thickness of the packaging film 20 in its entirety. It is foreseen,
however, that the
outer layer 22 may be made of any polyolefin or the like without deviating
from the
scope of the present inventive concept. The thickness of the outer layer 22 is
a fraction of
the thickness of the packaging film 10 in its entirety. The outer layer 22 and
the inner
layer 18 are made of the same material and sandwich the middle layer 20.
CA 02817292 2013-05-30
7
[0035] A bonding or adhesion layer 24 is disposed within the core structure 16
during co-extrusion of the layers 18, 20 so that the adhesion layer 24 is in
direct connect
with and between the inner layer 18 and the middle layer 20, as illustrated in
FIG. 1. The
adhesion layer 24 is made of one or more specialized tie resins and is
operable to
increased adhesion between the inner layer 18 and the middle barrier layer 20.
In this
manner, the inner layer 18 and the middle layer 20 are adhered together. It is
foreseen,
however, that the adhesion layer 24 may be made of any specialized tie
resin(s) without
deviating from the scope of the present inventive concept.
[0036] On an outermost portion of the packaging film 10 opposite to the
primary
sealant layer 12 and in non-contact with the food product 14 is an abuse layer
26 to
provide a moisture barrier to the packaging film 10. The abuse layer 26 is
made of
polyethylene terephthalate (PET) and has a thickness of a fraction of the
thickness of the
packaging film 20 in its entirety. It is foreseen, however, that the abuse
layer 26 may be
made of any PET material or the like without deviating from the scope of the
present
inventive concept. For instance, abuse layer 26 of the packaging film 10
illustrated in
FIG. 2 is made of biaxially oriented nylon (BON) instead of PET. The thickness
of the
abuse layer 26 is a fraction of the thickness of the packaging film 10 in its
entirety.
[0037] In this manner, the packaging film 10 of the present inventive concept
has
enhanced barrier, sealability, and flex-crack resistance characteristics.
Additionally, the
packaging film 10 of the present inventive concept has exceptional seal
strength, hot tack,
and caulkability. It has been discovered via testing of the packaging film 10
of the present
inventive concept that such yields almost zero pin holes in both machine and
transverse
directions due to the location of layers 12, 14, 16 and low thickness of the
abuse layer.
Thus, the packaging film 10 is particularly ideal for use with and to store
the food
product 14, which may be meat and/or cheese, e.g., retail shredded cheese,
institutional
shredded cheese, chunk cheese, and/or sliced cheese. Although the present
inventive
concept has been described with reference to the preferred embodiments
illustrated in the
attached drawing figures, it is noted that equivalents may be employed and
substitutions
made herein without departing from the scope of the present inventive concept
as recited
in the claims.
CA 02817292 2013-05-30
8
[0038] Related patent applications include PCT/US2011/021533 to Knout and
PCT/US2011/021535 to Knauf, the disclosures of which are incorporated herein
by
reference in their entireties.
