Note: Descriptions are shown in the official language in which they were submitted.
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ASEPTIC AND LIQUID FOOD PACKAGING WITH AQUEOUS MULTIBARRIER
COATINGS AND METHODS OF MAKING SAME
FIELD OF THE INVENTION
The present invention is directed to coatings for a variety of aseptic and
liquid food
packaging materials that provide improved total barrier properties for long-
term storage. More
specifically, the present invention is directed to aqueous coatings for
packaging for foods and
liquids and methods of applying the coatings. The aqueous coatings may include
light blocking
particles.
BACKGROUND OF THE INVENTION
Various materials have been used for the packaging of foods, liquids, and
other materials
that need protection from handling, moisture, water (liquid and vapor) oxygen,
and light.
Conventional barrier layers or films that are intended to reduce or inhibit
the permeation of vapor
typically include polyolefins, polyesters, polyvinylidene chloride, acrylic
polymers, styrene
acrylate, styrene butadiene, polyurethanes, polyamides, and metallic foils
(aluminum). Polyvinyl
alcohol (PVOH) and copolymers such as ethylene vinyl alcohol copolymer (EVOH)
are known
to have good oxygen barrier properties, but the performance is highly
dependent on ambient
relative humidity. Indeed, while a thin dispersion coated layer of PVOH or
EVOH or a similar
polymer may be suitable for packaging of dry products in a dry environment,
such a layer is not
ideal for liquid packaging unless encapsulated by water-vapor and liquid
impervious layers. As
such, a barrier layer including polyvinyl alcohol or copolymers thereof
typically include
additives, cross-linking agents, multivalent cations, and/or platy fillers;
however, even with such
additives, the oxygen barrier performance about 75 percent relative humidity
is generally poor.
In addition, crosslinking the polymer or including additives to improve the
moisture resistance
makes processing more difficult and more expensive and also may run afoul of
existing food
safety regulations for food packaging. Moreover, the crosslinking and
inclusion of additives
may affect pot life and therefore manufacturability.
Water-based polyurethanes can also have good oxygen barrier properties, but
lack high
gas and moisture vapor barrier under high humidity conditions. As such, a
barrier layer
including water-based polyurethane typically includes an inorganic filler or
requires pre-
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treatment of the underlying substrate with a metal oxide layer or the use of a
metallized film.
For example, U.S. Patent Publication No. 2005/0084686 generally discloses
aqueous gas barrier
coatings that include dispersed polyurethane resins and layered inorganic
materials, but the
disclosure is limited to a one-coat system on the surface of the substrate or
within a laminate
system. U.S. Patent Publication No. 2008/0070043 generally discloses aqueous
gas barrier
coatings that include a polyurethane, but uses a metal oxide layer applied to
the base film, i.e.,
underneath the coating, to achieve the desired gas water vapor barrier
properties.
Metallized substrates have also been independently employed to provide a gas
barrier.
However, such metallized substrates are typically expensive and, because of
their low flexibility,
are commonly used as an intermediate layer of a laminated structure.
Indeed, as a result of the shortcomings of the conventional coatings used in
packaging
materials for food and liquid materials, the packaging material is generally
always coated with a
laminate, i.e., a bulk core layer of paper or paperboard and an outer laminate
layer that includes
multiple liquid barrier layers of thermoplastics. And, in order to ensure that
the packaging for
liquids and aseptic packaging has both water vapor barrier properties and
oxygen barrier
properties, the outer laminate layer generally includes at least one foil
layer, e.g., aluminum foil.
As long as the aluminum foil is not damaged, the presence in the laminate
effectively prevents
any molecules existing in the environment around the package or in the
packaged product from
migrating in any direction through the foil. In fact, there are few known
aseptic packaging
materials or liquid packaging materials that do not include a foil laminate
and those known are
typically difficult to process because they require expensive co-extruded
layers or are much
thicker than foil laminates and, thus, more expensive to produce.
In addition to the use of laminates to provide barrier properties to packaging
materials,
conventional barrier layers or films for liquid packaging materials and those
materials intended
for aseptic packaging are also commonly applied via melt extrusion coating.
However, as
generally discussed above, melt extrusion coating complicates processing of
the packaging and
increases the expense. European Patent Publication No. 2 199 077 generally
describes aseptic
packaging for liquid or wet food that includes a core substrate, a first heat
sealable polyolefin
layer applied to the outside of the core substrate, an oxygen gas barrier
layer formed by liquid
film coating and applied to the inner side of the core substrate, a water
vapor barrier layer
disposed on the oxygen gas barrier layer, and a second heat sealable
polyolefin layer applied on
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to the water vapor barrier layer. The water vapor barrier layer is laminated
to the oxygen gas
barrier layer via direct extrusion or co-extrusion coating of the polyolefin-
based water vapor
barrier layer. The second heat sealable polyolefin layer is also directly
extruded onto the water
vapor barrier layer or co-extrusion coated together with the water vapor
barrier layer. As such,
.. even though this reference teaches a non-foil paper or paperboard packaging
laminate for aseptic
packaging, the formation of the packaging requires laminates and extrusion
coating.
It has been recognized that barrier layers applied by liquid film or aqueous
coating may
help to reduce complexity in converting operations. In addition, such liquid
film coating may
reduce overall material usage and eliminate manufacturing steps. However, as
discussed above,
such liquid film coating applications only exist in single water-based barrier
layer coatings in
combination with melt extruded or laminated layers.
Moreover, while light shielding is typically accomplished through the
paperboard itself,
manufacturers currently use an additional metal foil lamination layer to
further block light from
transmitting through the packaging. It would be advantageous to eliminate the
need for the
additional lamination step and accomplish the light shielding trait through
aqueous coating.
As such, there remains a need in the art for aqueous multi-barrier coatings
and methods
of application that reduce the need for or completely eliminate additional
extrusion or lamination
steps but still achieve the desired moisture resistance, water vapor barrier
properties, and light
shielding.
SUMMARY OF THE INVENTION
The present invention is directed to aqueous coating compositions for use in
packaging
materials for aseptic and liquid packaging, the packaging materials derived
therefrom, and
methods of making the packaging materials. In an aspect, the invention is
directed to a
packaging material having a substrate comprising at least two layers thereon,
wherein the at least
two layers comprise a first layer and a second layer disposed on the first
layer, wherein the first
and second layers each comprise a composition comprising an aqueous polymeric
solution or
dispersion, and wherein the composition is dried to form a continuous film to
provide distinct
barrier functions. In an aspect, the substrate can include treated or
untreated paper and/or
paperboard.
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The first and second layers can be different compositions from one another. In
an aspect,
the first layer composition, coated onto the substrate, can be used to form an
oxygen gas barrier
and the second layer, coated on the first layer, can form a water liquid and
vapor barrier. In such
instances, the first layer composition can include an acrylic latex dispersion
and the second layer
composition can include a polyvinyl alcohol. In other embodiments, the first
and second layers
can form gas barriers and barriers to light. In one aspect, the layers can be
coated on the inside
side of a substrate (i.e., the side intended for contact with the packaged
liquid or food). If only
one side of the substrate is to be coated, it is preferable that the inside
side of the substrate be
coated. In some instances, compositions are applied at a wet thickness to the
substrate of about
100 g/m2 or less. In another instances, the compositions are applied at a dry
thickness of about 30
g/m2 or less.
The substrate can also include a third layer composition comprising an aqueous
polymeric solution or dispersion. In such instances, the first layer and the
third layer can be same
composition, or different compositions. In other embodiments, the substrate
can include six
layers, where the fourth, fifth, and sixth layers are placed on a side of the
substrate exposed to a
product contained in the packaging. In such aspects, the first and fourth
layers can have the same
composition. In other aspects, the substrate can include four layers of an
aqueous polymeric
solution or dispersion compositions. In such aspects, the third and fourth
layers can be placed on
a side of the substrate that is exposed to the atmosphere.
In an aspect, the food packaging material can include least two barrier
providing layers,
with the first layer forming a liquid and water vapor barrier. In such
aspects, the composition can
include an acrylic latex dispersion. In an aspect, the composition of the
second layer forms an
oxygen gas barrier, and can be made of a polyvinyl alcohol. In an embodiment,
the liquid barrier
layer can be between the outer layer and the substrate. In other embodiments,
the oxygen barrier
can between the substrate and the outer layer. In instances where the
substrate includes three
layers, the second layer can be between the first and third layers, with the
first layer adjacent the
substrate and the third layer being the topmost layer. In an aspect, the
first, second, and third
layers are coated on the inside of the substrate. In an aspect, the third
layer can comprise an
acrylic latex dispersion.
In an aspect, the compositions of the first and second layers of the substrate
of the food
packaging product can vary. For example, in one embodiment, the first layer
comprises a
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polyurethane latex dispersion and the composition of the second layer
comprises an acrylic latex
dispersion. In such an embodiment, the second layer can be the topmost layer,
adjacent to the
first layer opposite the substrate, and vice versa. Further, the first and
second layers can be
coated on the side of the substrate intended for the interior of the
container. In another aspect, the
composition of the first layer can include a mixture of polyvinyl acetate
dispersion and a carbon-
black dispersion and the composition of the second layer can include a
polyolefin dispersion.
In another embodiment, the compositions of the layers coated on the substrate
can
include additives. For example, any of the compositions of the layers can
include additives. In
such aspects, the additives can include fillers designed to enhance barrier
characteristics,
manufacturability, or other functions. For example, the fillers can include
light absorbing fillers,
odor control additives, light scattering particles (e.g., applied in a
polymeric matrix), scavengers
(oxygen, CO2, ethylene, etc.), thickeners, surfactants, inorganics,
antimicrobials, preservatives,
friction control, anti-blocking, and the like.
In another aspect, the invention is directed at a method of manufacturing
aseptic
packaging. The method can include the steps of providing a substrate,
providing a first and
second coating composition, and forming a plurality of barrier layers on a
first side of the
substrate by forming a first barrier layer by coating and drying the first
coating composition as a
film onto the substrate, and forming a second barrier layer by coating and
drying the second
coating as a film on top of the first barrier layer. In one embodiment, the
plurality of barrier
layers can be coated simultaneously. In an aspect, the substrate can include a
layer of paper or
paperboard. In another aspect, the first composition can include an acrylic
latex dispersion. The
second composition can include a polyvinyl alcohol. The method can also
include forming a
third barrier layer by coating and drying a third coating composition on top
of the second barrier
layer. In such aspects, the first and third compositions can be the same or
different. In some
aspects, the first and second barrier layers are formed to block oxygen and
water vapor. In other
aspect, the second layer can form a barrier to light.
This summary does not limit the scope of the claimed subject matter.
Furthermore, the
claimed subject matter is not constrained to the limitations that solve any or
all disadvantages
noted in any part of this disclosure. Features, aspects and advantages of the
present invention are
understood with reference to the following description, appended claims and
accompanying
figures.
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BRIEF DESCRIPTION OF THE DRAWINGS
Further features and advantages of the invention can be ascertained from the
following
detailed description that is provided in connection with the drawing(s)
described below:
FIG. 1 is a cross-section of an embodiment of a packaging material produced
according
to the invention;
FIG. 2 is a cross-section of another embodiment of a packaging material
produced
according to the invention;
FIG. 3 is a cross-section of another embodiment of a packaging material
produced
according to the invention; and
FIG. 4 is a cross-section of another embodiment of a packaging material
produced
according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to aqueous coating compositions for use in
packaging
.. materials for aseptic and liquid packaging, the packaging materials derived
therefrom, and
methods of making the packaging materials. As used herein, "aseptic packaging"
refers to
packaging in which a previously sterilized food is packed in a similarly
previously sterilized
package under aseptic conditions. An aseptic package is distinguishable from
other types of
liquid packaging in that the contents of the package may be stored in the
package for up to
months and even longer at ambient temperature, without the contents
deteriorating or being
ruined. However, packaging in which the food must, throughout its entire
storage time in the
package, be kept refrigerated (at most approx. 8 C) in order not to
deteriorate or be completely
ruined is also contemplated for use with the present invention. Moreover,
retortable packages
that are intended to be filled with food and, after sealing, be subjected to a
heat treatment for the
.. purposes of extending shelf-life at elevated temperature in an atmosphere
of high relative
humidity are also contemplated for use with the present invention. The aqueous
coating
compositions described herein may be applied to suitable substrates to achieve
improved
moisture resistance, water vapor barrier, oxygen barrier, and light shielding.
The packaging materials of the present invention may include multiple barrier
layers
.. applied via aqueous coating onto an untreated or pre-treated substrate. For
example, according
to some aspects of the invention, a packaging material of the present
invention may include a
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substrate and at least two aqueous coating barrier layers disposed thereon. In
other aspects, a
packaging material of the present invention may include a substrate and at
least three aqueous
coating barrier layers disposed thereon. In an aspect, such coatings are
applied in-line on the
same machine forming the paper base. The coating compositions, packaging, and
methods of
making are described in greater detail below.
Aqueous Coating Compositions
The aqueous coating compositions may vary depending on the objective of the
barrier
layer formed therefrom and the placement of the particular barrier layer in
the multi-barrier layer
coating system.
Polymeric Dispersions and Solutions
The aqueous coating compositions described herein may be in the form of a
continuous
phase solution. That is, the barrier-forming polymeric components of the
aqueous formulation
are completely dissolved in the base solvent (e.g., water). In this aspect,
the polymer resin is
dissolved in an aqueous medium, for example, water. In another embodiment, the
aqueous
coating compositions described herein may be in the form of a dispersion. That
is, the polymer
resin is dispersed (for example, is present as small particles) in an aqueous
medium such as
water.
In one aspect, the aqueous coating compositions may include acrylic latex
dispersions.
Without being bound by any particular theory, it is believed that the use of
acrylics in the
aqueous coating composition of the invention may provide superior liquid and
water vapor
barrier properties. For instance, an aqueous coating layer including the use
of one or more
acrylic latex dispersions is resistant to aqueous liquids and provides a
moisture vapor barrier.
Additionally, the use of one or more acrylics in the aqueous coating
composition of the invention
provides superior heat sealing characteristics. Suitable examples of acrylic
polymers useful in
forming acrylic latex dispersions for use with the present invention include,
but are not limited
to, acrylic polymers, styrene-acrylic copolymers, styrene-acrylic
acrylonitrile terpolymers, and
derivatives thereof. Examples of commercially available acrylic latex
dispersions for use with
the present invention include JONCRYL 74, 89, 537, and 538 from BASF
Corporation,
ACRONAL dispersions from BASF Corporation, RHOPLEXTM dispersions from The Dow
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Chemical Company, and dispersions from Mallard Creek Polymers, Trinseo,
Archroma, and
Synthomer.
In another embodiment, the aqueous coating composition of the invention
includes a
polyvinyl alcohol (PVOH) solution, an ethyl vinyl alcohol (EVOH) solution, or
combinations
thereof. Without being bound by any particular theory, since PVOH and EVOH
have high
oxygen gas barrier properties, are relatively easy to use as a liquid film
coating, and have high
odor barrier properties, it is believed that the use of an aqueous coating
including PVOH, EVOH,
or a combination thereof in at least one coating layer will improve overall
barrier properties of
packaging material for aseptic and liquid packaging. One example of a
commercially available
PVOH for use in this aspect of the invention includes SELVOLTM Polyvinyl
Alcohol 21-205
Solution from Sekisui Specialty Chemicals America, LLC. An example of a
commercially
available EVOH for use in this aspect of the invention includes EXCEVALTM RS-
2117 from
Kuraray.
In this aspect, the coating composition may include, along with the PVOH,
EVOH, or
combination thereof, a polymer or compound with functional carboxylic acid
groups. Suitable
examples of such a polymer with functional carboxylic acid groups include, but
are not limited to
ethylene acrylic acid copolymer (EAA), ethylene methacrylic acid copolymers
(EMAA), or
mixtures thereof. If included, this polymer may be present in an amount of
about 1 percent to
about 20 percent by weight of the dry coating, preferably about 5 percent to
about 15 percent by
weight of the dry coating. The coating composition may also include inorganic
compounds such
as metal oxides.
In yet another embodiment, the aqueous coating composition of the invention
includes a
polyurethane latex dispersion. As used herein, the term "polyurethane" refers
to a polymer
including multiple urethane (-NH-C(0)-0-) linkages within the backbone and,
optionally, urea
linkages (NH-C(0)-NH-) within the backbone. As used herein, a "polyurethane
latex
dispersion" refers to a polyurethane resin that, when neutralized, forms a
stable dispersion in
water or a water-miscible solvent. In this regard, the water-miscible solvent
may be a single
solvent or a blend of solvents, e.g., methanol, ethanol, propanol, and
combinations thereof. The
water-miscible solvent may also be a mixture of water and at least one water-
miscible solvent.
Without being bound to any particular theory, the use of certain polyurethane
latices in
the aqueous coating composition of the invention confers an array of
beneficial properties to the
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packaging material. For example, the polyurethane latex dispersion can provide
good oxygen-
barrier properties, high flexibility, and good adhesion with various
substrates. In this aspect, the
polyurethane latex dispersion may incorporate a neutralizable acid group or
other anionic
hydrophilic group that may be neutralized with a neutralizing agent. Suitable
polyurethanes
generally include the reaction product of at least one isocyanate-containing
component, a
polyisocyanate, and at least one isocyanate-reactive component, e.g., a
hydroxy-terminated
component or an amine-terminated component. Any isocyanate-containing
component available
to one of ordinary skill in the art is suitable for use according to the
present invention including,
but not limited to, 4,4'-diphenylmethane diisocyanate (MDI); polymeric MDI;
carbodiimide-
modified liquid MDI; 4,4'-dicyclohexylmethane diisocyanate (H12MDI); p-
phenylene
diisocyanate (PPDI); m-phenylene diisocyanate (MPDI); toluene diisocyanate
(TDI); 3,3'-
dimethy1-4,4'-biphenylene diisocyanate (TODI); isophoronediisocyanate (IPDI);
hexamethylene
diisocyanate (HDI); naphthalene diisocyanate (NDI); xylene diisocyanate (XDI);
p-
tetramethylxylene diisocyanate (p-TMXDI); m-tetramethylxylene diisocyanate (m-
TMXDI);
ethylene diisocyanate; propylene-1,2-diisocyanate; tetramethylene-1,4-
diisocyanate; cyclohexyl
diisocyanate; 1,6-hexamethylene-diisocyanate (HDI); dodecane-1,12-
diisocyanate; cyclobutane-
1,3-diisocyanate; cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate;
1-isocyanato-
3,3,5-trimethy1-5-isocyanatomethylcyclohexane; methyl cyclohexylene
diisocyanate;
triisocyanate of HDI; triisocyanate of 2,4,4-trimethy1-1,6-hexane diisocyanate
(TMDI); tetracene
.. diisocyanate; napthalene diisocyanate; anthracene diisocyanate;
isocyanurate of toluene
diisocyanate; uretdione of hexamethylene diisocyanate; and mixtures thereof
Any hydroxy-terminated component available to one of ordinary skill in the art
is suitable
for use in forming the polyurethane latex dispersion including, but not
limited to, polyether
polyols, hydroxy-terminated polybutadiene (including partially/fully
hydrogenated derivatives),
.. polyester polyols, polycaprolactone polyols, and polycarbonate polyols. Any
amine-terminated
component available to one of ordinary skill in the art is suitable for use in
forming the
polyurethane latex dispersion including, but not limited to, 3,5-dimethylthio-
2,4-toluenediamine
and isomers thereof 3,5-diethyltoluene-2,4-diamine and isomers thereof, such
as 3,5-
diethyltoluene-2,6-diamine; 4,4'-bis-(sec-butylamino)-diphenylmethane; 1,4-bis-
(sec-
butylamino)-benzene, 4,4'-methylene-bis-(2-chloroaniline); 4,4'-methylene-bis-
(3-chloro-2,6-
diethylaniline); polytetramethyleneoxide-di-p-aminobenzoate; N,N'-
dialkyldiamino diphenyl
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methane; p,p'-methylene dianiline; m-phenylenediamine; 4,4'-methylene-bis-(2-
chloroaniline);
4,4'-methylene-bis-(2,6-diethylaniline); 4,4'-methylene-bis-(2,3-
dichloroaniline); 4,4'-diamino-
3,3'-diethy1-5,5'-dimethyl diphenylmethane; 2,2',3,3'-tetrachloro diamino
diphenylmethane;
trimethylene glycol di-p-aminobenzoate; and mixtures thereof. The polyurethane
latex
dispersion may also include a curative that is an amine-terminated component
or a hydroxy-
terminated component. The polyurethane may be saturated or unsaturated.
The polyurethane latex dispersion may be formed according to any method known
in the
art including the one-shot technique or the prepolymer technique. In
particular, in the one-shot
technique, the isocyanate-containing component, isocyanate-reactive component,
and curing
agent are reacted in one step. The prepolymer technique involves a first
reaction between an
isocyanate-containing component and an isocyanate-reactive component to
produce a
prepolymer, and a subsequent reaction between the prepolymer and hydroxy
and/or amine-
terminated curing agent. In one embodiment, the polyurethane latex dispersion
includes a
prepolymer formed from the reaction product of an isocyanate and a polyol or a
polyamine,
which is then emulsified and reacted with an amine-terminated or hydroxy-
terminated
component. A particularly suitable commercially available polyurethane latex
dispersion is
TAKELACTmWPB-341 from Mitsui Chemicals. Other examples of suitable
commercially
available polyurethane dispersions include, but are not limited to, BAYHYDROL
polyurethane
dispersions from Covestro, SANCURETM from Lubrizol, LUPHEN , EPOTAL , and
EMULDUR from the BASF Corporation, and polyurethane dispersions from
Alberdinck
Boley.
In still another embodiment, the aqueous coating composition includes a
chlorinated
polymer. For example, the aqueous coating composition may include a
polyvinylidene chloride
(PVdC) based latex. More specifically, the PVdC may be a homopolymer of PVDC
and its
copolymers and blends. Examples of copolymers suitable for use in this aspect
of the invention
include those with polyvinyl chloride (PVC) and chlorinated PVC (CPVC) and
other copolymers
containing any moiety derived from copolymerization with an active double bond
such as an
alkene, haloalkene or any of the acrylic containing monomers. Most commonly,
in a latex
dispersion, VdC is copolymerized with methyl methacrylate, methyl acrylate,
butyl acrylate
and/or acrylonitrile. One example of a commercially available family of PVdC
copolymers for
use with the present invention is DIOFAN from Solvay Specialty Polymers.
Another example
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of a commercially available PVdC for use with the present invention is DARAN
PVdC
dispersions available from Owensboro Specialty Polymers, Inc.
In yet another embodiment, the aqueous coating composition includes a
polyolefin
dispersion. The polyolefin dispersion may be made by polymerizing olefins such
as ethylene,
propylene, butene-1, pentene-1,4-methylpent-1-ene, and the like, in any
conventional manner. In
an aspect, using mechanical dispersion technology developed by Dow (commonly
practiced
under the BLUEWAVETM mark), large polyolefin pellets are processed with a
specially designed
high-temperature polymer dispersant system. Water and neutralizer are added,
resulting in a
High Internal-Phase Emulsion (HIPE) that locks in the particle size needed for
thin-film
coatings. The emulsion is then diluted with water to create a stable
suspension of polymer
particles that are approximately 1 micron in diameter. These particles remain
suspended in water
until applied to a surface. Non-limiting examples of polyolefins suitable for
use in this aspect of
the invention include high-density polyethylene (HDPE), polypropylene, low-
density
polyethylene (LDPE), very low-density polyethylene (VLDPE), linear low-density
polyethylene
(LLDPE), polybutylene (PB), and blends thereof Examples of commercially
available
polyolefin dispersions for use with the present invention include HYPODTM
polyolefin
dispersions from The Dow Chemical Company or Aquaseal dispersions available
from Paramelt.
In still another embodiment, the aqueous coating composition may include a
polyester
aqueous dispersion. The present invention contemplates the use of any
aliphatic, semi-aromatic,
or aromatic polyester. Non-limiting examples of polyesters suitable for use in
this aspect of the
invention include polyethylene terephthalate, polybutylene terephthalate,
polytrimethylene
terephthalate, polyethylene terephthalate, vectran, and their derivatives.
Examples of
commercially available polyester aqueous dispersions for use with the present
invention include
EvCoteTM polyester aqueous dispersions from AkzoNobel and EastekTM polyester
aqueous
dispersions from Eastman Chemical Company. The aqueous coating composition may
also
include aqueous dispersions of biodegradable polyesters. Biodegradable
polyesters are
advantageous in that such polyesters are biocompatible and have short
degradation times. In one
embodiment, the biodegradable polyester is an aliphatic polyester. Examples of
aqueous
dispersions of biodegradable polyesters for use with the aqueous coating
systems of the present
invention include, but are not limited to, polylactic acid,
polyhydroxyalkanoate, polyglycolic
acid, poly-c-caprolactone, polyhydroxybutyrate, and poly(3-hydroxy valerate).
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In another embodiment, the aqueous coating composition may include styrene
butadiene.
Examples of commercially available styrene butadiene products include GenFlo
from Omnova
Solutions as well as products from BASF, Trinseo and Synthomer. In still
another embodiment,
the aqueous coating composition includes vinyl polymers or copolymers derived
from moieties
such as ethylene (for example, ethylene vinyl acetate), polystyrene,
polyacrylonitrile, and
polyvinyl acetate. One example of a commercially available polyvinyl acetate
dispersion for use
with the present invention is SUINBONIDTM 3410 from Omnova Solutions.
The polymeric solutions and dispersions discussed above may be present in the
aqueous
coating composition in varying weight and volume percentages. The weight and
volume percent
of the polymeric solutions and dispersions will depend on the other components
present in the
composition. However, the volume percentage should be selected so that the
barrier-providing
polymeric solution or dispersion component forms a continuous and contiguous
arrangement, in
order to form an interconnected network. In addition, the volume percentage of
the polymeric
component should be selected so as to maintain the mechanical integrity of the
substrate to be
coated. In one embodiment, the polymeric component is present in the aqueous
coating
composition, on a dry volume basis, in an amount of about 35 volume percent to
about 100
volume percent. In another embodiment, the polymeric component is present in
the aqueous
coating composition, on a dry volume basis, in an amount of about 50 volume
percent to about
99 volume percent. In still another embodiment, the polymeric component is
present in the
aqueous coating composition, on a dry volume basis, in an amount of about 75
volume percent to
about 95 volume percent.
In each of the coating compositions discussed above, the coating composition
includes
about 99 percent to about 60 percent of the dispersion, latex, or mixture by
weight of the dry
coating composition. In one embodiment, the coating composition includes about
99 percent to
about 70 percent of the dispersion, latex, or mixture by weight of the dry
coating composition.
In another embodiment, the coating composition includes about 99 percent to
about 75 percent of
the dispersion, latex, or mixture by weight of the dry coating composition. In
still another
embodiment, the coating composition includes about 95 percent to about 80
percent of the
dispersion, latex, or mixture by weight of the dry coating composition.
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Additives
Any of the coating systems discussed herein may include one or more additives.
In one
embodiment, the polymeric solutions and dispersions of the present invention
may include one or
more light absorbing or scattering fillers. As used herein, the term "light
absorbing filler" refers
to an additive that is capable of absorbing light and providing opacity to the
substrate after
application of the aqueous coating composition., for example, the packaging
material ultimately
formed using the aqueous coating composition. Non-limiting examples of light
absorbing fillers
contemplated for use with the present invention include metal flakes, metal
paste, metal
nanoparticles, carbon black, dyes, pigmented colorants, titanium dioxide, and
hollow sphere
particles such as the commercially available ROPAQUETM hollow sphere polymeric
pigments
from The Dow Chemical Company and Expancel Microspheres from AkzoNobel.
In one embodiment, the polymeric solutions and dispersions of the present
invention may
include aluminum flakes, paste, or nanoparticles as a light reflecting filler.
For example, the
aqueous coating composition may include a polyolefin dispersion and aluminum
flakes or paste.
One example of a commercially available aluminum paste for use with the
present invention is
STAPA IL HYDROLAN 801 55900/G from Eckart GmbH. The aluminum flakes may be
present in the aqueous coating composition, on a dry weight basis, in an
amount of about 10
percent to about 90 percent by weight of the coating composition. In another
embodiment, the
aluminum flakes may be present in the aqueous coating composition, on a dry
weight basis, in an
amount of about 12 percent to about 83 percent by weight of the coating
composition. In still
another embodiment, the aluminum flakes may be present in the aqueous coating
composition,
on a dry weight basis, in an amount of about 25 percent to about 75 percent by
weight of the
coating composition. In yet another embodiment, the aluminum flakes may be
present in the
aqueous coating composition, on a dry weight basis, in an amount of about 35
percent to about
65 percent by weight of the coating composition. The aluminum flakes may also
be present in
the aqueous coating composition, on a dry volume basis, in an amount of about
2 volume percent
to about 65 volume percent. In another embodiment, the aluminum flakes may be
present in the
aqueous coating composition, on a dry volume basis, in an amount of about 10
volume percent to
about 50 volume percent. In still another embodiment, the aluminum flakes may
be present in
the aqueous coating composition, on a dry volume basis, in an amount of about
15 volume
percent to about 40 volume percent.
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In another embodiment, any of the polymeric solutions and dispersions of the
present
invention may include carbon black, for example, a carbon black dispersion, as
a light absorbing
filler. For example, the aqueous coating composition may include a mixture of
a polyvinyl
acetate dispersion and a carbon-black dispersion. One example of a
commercially available
carbon black dispersion for use with the present invention is AQUABLAK 8328
from Solution
Dispersions. The carbon black may be present in the aqueous coating
composition, on a dry
weight basis, in an amount of about 5 percent to about 80 percent by weight of
the coating
composition. In another embodiment, the carbon black may be present in the
aqueous coating
composition, on a dry weight basis, in an amount of about 9 percent to about
77 percent by
weight of the coating composition. In still another embodiment, the carbon
black may be present
in the aqueous coating composition, on a dry weight basis, in an amount of
about 15 percent to
about 65 percent by weight of the coating composition. In yet another
embodiment, the carbon
black may be present in the aqueous coating composition, on a dry weight
basis, in an amount of
about 20 percent to about 55 percent by weight of the coating composition. The
carbon black
may also be present in the aqueous coating composition, on a dry volume basis,
in an amount of
about 2 volume percent to about 65 volume percent. In another embodiment, the
carbon black
may be present in the aqueous coating composition, on a dry volume basis, in
an amount of
about 10 volume percent to about 50 volume percent. In still another
embodiment, the carbon
black may be present in the aqueous coating composition, on a dry volume
basis, in an amount of
about 15 volume percent to about 40 volume percent.
The coating compositions may also include additives such as thickeners,
surfactants,
inorganics, oxygen scavengers, scavengers for other gases such as carbon
dioxide or ethylene,
antimicrobials, preservatives, friction control, anti-blocking, colorants,
dispersion stabilizers, and
combinations thereof
Inorganic additives are also contemplated for use in the aqueous coating
compositions of
the invention. Examples of inorganic additives suitable for use with the
present invention
include, but are not limited to, calcium carbonate, talc, clays, and
nanoparticulates such as
nanoparticulate clays. In one embodiment, the inorganic additive is a platy
nanoparticulate, i.e.,
a particulate with a high aspect ratio and a low particle size. In this
aspect, the aspect ratio of the
inorganic additive may be greater than about 20 in its exfoliated form. In one
embodiment, the
aspect ratio of the inorganic additive ranges from about 50 to about 10,000.
In another
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embodiment, the aspect ratio of the inorganic additive ranges from about 50 to
about 5,000. In
yet another embodiment, the nanoparticulate preferably has a particle size in
at least one
dimension of less than about 100 nm. In one embodiment, the nanoparticulate
has a particle size
of about 50 nm or less. In another embodiment, the nanoparticulate has a
particle size of about
20 nm or less. For example, the nanoparticulate may have a particle size of
about 51.tm or less.
Without being bound by any particular theory, it is believed that the use of
such play
nanoparticulates improve the barrier properties by creating a more difficult
path for gas
molecules to traverse the barrier coating.
Suitable nanoparticulates include, but are not limited to, kaolin, kaolinite,
antigorite,
smectite, vermiculite, bentonite, illite, mica, laponite, dickite, nacrite,
halloysite, antigorite,
chrysotile, pyrophyllite, montmorillonite, hectorite, saponite, sauconite,
sodium tetrasilicic mica,
sodium taeniolite, margarite, vermiculite, phlogopite, xanthophyllite,
atapulgite, zeolite,
boehmite, diatomaceous and fuller's earth, calcined aluminium silicate,
hydrated aluminium
silicate, magnesium aluminium silicate, sodium silicate, magnesium silicate,
and combinations
thereof.
When included, the inorganic additive may be present in an amount of about 5
percent to
about 40 percent by weight of the dry coating composition. In one embodiment,
the inorganic
additive is present in an amount of about 10 percent to about 40 percent by
weight of the dry
coating composition. The inorganic additive may also be present in the aqueous
coating
composition, on a dry volume basis, in an amount of about 2 volume percent to
about 65 volume
percent. In another embodiment, the inorganic additive may be present in the
aqueous coating
composition, on a dry volume basis, in an amount of about 10 volume percent to
about 50
volume percent. In still another embodiment, the inorganic additive may be
present in the
aqueous coating composition, on a dry volume basis, in an amount of about 15
volume percent to
about 40 volume percent.
When included, the dispersion stabilizer may be present in an amount of about
1 percent
or less by weight of the dry coating composition.
Packaging Materials Formed According to the Invention
The packaging materials formed according to the invention may include multiple
barrier
layers formed from the coating compositions of the invention. For example, in
one embodiment,
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the packaging material may include at least two barrier layers formed from the
aqueous coating
compositions of the invention. In another embodiment, the packaging material
may include at
least three barrier layers formed from the aqueous coating compositions of the
invention. The
multiple barrier layers may be coated on a single side of the substrate or may
be coated on both
sides of the substrate. Various embodiments are described below.
The underlying substrate may be paper, paperboard, or any fibrous board base
conventionally used in aseptic packaging, liquid packaging, or retortable
packaging. As such,
the term "substrate" includes, without limitation, materials such as packaging
films (including
antiseptic, corrosion protective, vacuum and controlled atmosphere packages),
paper,
paperboard, carton, and other fibrous board bases used for packaging. The
substrate may have a
thickness of from about 100 p.m up to about 600 p.m. For instance, in the case
of aseptic
packaging, the substrate may have a caliper from about 9 pt. to about 20 pt.
In the case of gable
top cartons, the substrate may have a caliper from about 14 pt. to about 22
pt. The surface
weight of the substrate may vary depending on factors such as the machine
design and
manufacturing conditions. However, in one embodiment, the surface weight of
the substrate
may be about 50 g/m2 to about 500 g/m2. In one embodiment, the surface weight
of the substrate
is about 200 g/m2 to about 300 g/m2. In another embodiment, the surface weight
of the substrate
is about 50 g/m2 to about 150 g/m2. For example, the surface weight of the
substrate may be
about 75 g/m2 to about 125 g/m2.
The substrate may be untreated or pre-treated. However, as used herein, when
the
substrate is pre-treated, the pre-treatment will be considered part of the
substrate. A variety of
pre-treatments may be used depending upon the identity and utility of the
substrate. In one
embodiment, a size press application may be applied in order to improve the
holdout properties
of the substrate. In another embodiment, the substrate may be coated with clay
and/or calcium
carbonate and a styrene-acrylate binder. In another embodiment, a pigmented
smoothing layer
and/or other pre-coats can be applied in the substrate. In still another
embodiment, the
paperboard may be calendared to improve smoothness. The substrate can be
treated and/or
selected to have other characteristics, including, but not limited to,
flexibility (resistance to score
cracking), brightness, and anti-wicking properties. In yet another embodiment,
an adhesion
promoter may be applied to the substrate.
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In an aspect, the packaging material includes a substrate that has a first
layer coated on a
first side of the substrate, and a second layer coated on the first layer,
placing the first layer
between the substrate and the second layer. In an aspect, the second layer is
oriented to be in
contact with the contents that the packaging material is used to contain. In
such aspects, the
second layer can be configured to be a liquid and vapor barrier and the first
layer is an oxygen
gas barrier. In such instances, the barriers are placed closest to the most
likely occurrence of
exposure in which they are trying to block, protecting the adjacent layers to
potential exposure to
which they could be sensitive too. For example, when the packaging material is
used to contain a
food item, which can include liquid and other vapors, the second layer, acting
as a vapor and
liquid barrier, can operate more efficiently to block the adjacent materials
from crossing into the
first layer. Likewise, the first layer, being adjacent the substrate and hence
oxygen from exterior
exposure, can prevent oxygen from entering or reaching the second layer and
the food items.
In one embodiment, as shown in FIG. 1, the packaging material 10 has barriers
layers 14,
16, 18 on only one side of the substrate 12. However, in other aspects, the
substrate 12 can be
surrounded by three barrier layers on each side. As shown, the packaging
material 10 includes a
first aqueous coating layer 14 formed from a first aqueous coating
composition, a second
aqueous coating layer 16 formed from a second aqueous coating composition, and
a third
aqueous coating layer 18 formed from a third aqueous coating composition. In
this aspect, the
third aqueous coating layer 18 is the topmost layer, i.e., the layer exposed
to the atmosphere or
packaged food, the second aqueous coating layer 16 is located in between the
third aqueous
coating layer 18 and the first aqueous coating layer 14, and the first aqueous
coating layer 14 is
the bottommost layer, i.e., the layer disposed directly on the substrate 12.
The first, second, and
third aqueous coating compositions 14, 16, 18 respectively may be the same or
different. For
example, in one embodiment, the first aqueous coating composition 14 is the
same as the third
.. aqueous coating composition 18, but different from the second aqueous
coating composition 16.
In another embodiment, as shown in FIG. 2, the packaging material 20 includes
a first
aqueous coating layer 24 formed from a first aqueous coating composition and a
second aqueous
coating layer 26 formed from a second aqueous coating composition. In this
aspect, the second
aqueous coating layer 26 is the topmost layer, i.e., the layer exposed to the
atmosphere or the
packaged food or liquid, and the first aqueous coating layer 24 is the
bottommost layer, i.e., the
layer disposed directly on the substrate 22. The first and second aqueous
coating compositions
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may be the same or different. For example, in one embodiment, the first
aqueous coating
composition is different from the second aqueous coating composition.
In one embodiment, the packaging material 10 includes a first aqueous coating
layer 14
formed from a coating composition including an acrylic latex dispersion, a
second aqueous
coating layer 16 formed from a coating composition including PVOH, EVOH, or a
combination
thereof, and a third aqueous coating layer 18 formed from a coating
composition including the
acrylic latex dispersion. In this aspect, as shown in FIG. 1, the third
aqueous coating layer 18 is
the topmost layer, i.e., the layer exposed to the atmosphere and/or the
packaged food or liquid,
and the first aqueous coating layer 14 is the bottommost layer, i.e., the
layer disposed directly on
the substrate 12. Without being bound to any particular theory, since PVOH,
EVOH, or a
combination thereof has good oxygen barrier properties but poor moisture vapor
barrier
properties and moisture resistance and acrylics have good liquid barrier and
heat seal properties,
the second aqueous coating layer 16 resides between coating layers 14 and 18
that each include
an acrylic latex dispersion. Indeed, the PVOH, EVOH, or combination thereof is
encapsulated
with a moisture-resistant coating (i.e., the acrylic latex dispersion) in
order to minimize or mask
the humidity-dependence of the internal PVOH/EVOH oxygen barrier performance.
This three-
layer coating configuration may also be applied to the inside of a substrate,
i.e., the third aqueous
coating layer 18 is exposed to the contents of the packaging rather than the
atmosphere.
In another embodiment, the packaging material 20 includes a first aqueous
coating layer
24 formed from a coating composition including a polyurethane latex dispersion
and a second
aqueous coating layer 26 formed from a coating composition including an
acrylic latex
dispersion. In this aspect, as shown in FIG. 2, the second aqueous coating
layer 26 is the
topmost layer, i.e., the layer exposed to the atmosphere, and the first
aqueous coating layer 24 is
the bottommost layer, i.e., the layer disposed directly on the substrate 22.
Without being bound
to any particular theory, since water-based polyurethanes have high oxygen
resistance but are
often limited to non-direct-contact food packaging applications from a health
and safety
perspective, a second (top) layer formed from the acrylic dispersion is
sufficient to achieve the
desired overall oxygen barrier properties, liquid barrier, and heat seal
properties. This two-layer
coating configuration may also be applied to the inside of a substrate, i.e.,
the second aqueous
coating layer 26 is exposed to the contents of the packaging rather than the
atmosphere.
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In yet another embodiment, the packaging material 20 includes a first aqueous
coating
layer 24 formed from a coating composition including a polyvinylidene chloride-
based latex and
a second aqueous coating layer 26 formed from a coating composition including
a polyolefin
dispersion. Without being bound to any particular theory, since polyvinylidene
chloride-based
polymers have high oxygen and moisture vapor barrier properties and polyolefin
dispersions
have desirable liquid barrier and heat seal properties, this two-layer coating
system will provide
the desired overall barrier properties. This two-layer coating configuration
may also be applied
to the inside of a substrate, i.e., the second aqueous coating layer 26 is
exposed to the contents of
the packaging rather than the atmosphere.
In still another embodiment, the packaging material 20 includes a first
aqueous coating
layer 24 formed from a coating composition including a mixture of a polyvinyl
acetate dispersion
and a carbon-black dispersion and a second aqueous coating layer 26 formed
from a coating
composition including a polyolefin dispersion. Without being bound to any
particular theory,
since polyvinyl acetate has desirable heat seal and oxygen barrier properties,
carbon-black
provides light shielding properties, and polyolefin dispersions have desirable
liquid barrier and
heat seal properties, this two-layer coating system will provide the desired
overall barrier and
light shielding properties. This two-layer coating configuration may also be
applied to the inside
of a substrate, i.e., the second aqueous coating layer 26 is exposed to the
contents of the
packaging rather than the atmosphere.
In yet another embodiment, the packaging material 20 includes a first aqueous
coating
layer 24 formed from a coating composition including a polyvinylidene chloride-
based latex and
a second aqueous coating layer 26 formed from a coating composition including
a polyolefin
dispersion and aluminum flake. Without being bound to any particular theory,
since
polyvinylidene chloride-based polymers have high oxygen and moisture vapor
barrier properties,
polyolefin dispersions have desirable liquid barrier and heat seal properties,
and aluminum flake
provides light shielding properties, this two-layer coating system will
provide the desired overall
barrier properties. This two-layer coating configuration may also be applied
to the inside of a
substrate, i.e., the second aqueous coating layer 26 is exposed to the
contents of the packaging
rather than the atmosphere.
In another embodiment, as shown in FIG. 3, the packaging material 30 includes
a first
aqueous coating layer 34a formed from a first aqueous coating composition, a
second aqueous
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coating layer 36a formed from a second aqueous coating composition, and a
third aqueous
coating layer 38a formed from a third aqueous coating composition. In this
aspect, the third
aqueous coating layer 38a is the topmost layer, i.e., the layer exposed to the
atmosphere, and the
first aqueous coating layer 34a is the bottommost layer, i.e., the layer
disposed directly on the
.. substrate 32. The packaging material also includes a fourth aqueous coating
layer 34b formed
from a fourth aqueous coating composition, a fifth aqueous coating layer 36b
formed from a fifth
aqueous coating composition, and a sixth aqueous coating layer 38b formed from
a sixth aqueous
coating composition. In this aspect, the sixth aqueous coating layer 38b is
the topmost layer, i.e.,
the layer exposed to the packaged product, and the fourth aqueous coating
layer 34b is the
bottommost layer, i.e., the layer disposed directly on the substrate 32. The
various coating layers
may be formed of the same or different aqueous coating compositions. For
example, in one
embodiment, the first and third aqueous coating compositions are the same as
the fourth and
sixth aqueous coating compositions and the second and fifth aqueous coating
compositions are
the same. However, other configurations are contemplated. For example, while
not shown, the
substrate 32 may have only two aqueous coating layers on the inside of the
packaging, i.e., the
side of the substrate that contacts the packaged contents. The aqueous coating
compositions
layered on the inside of the substrate may differ from the aqueous coating
compositions layered
on the outside of the substrate. In the alternative, only one of the aqueous
coating compositions
layered on the inside of the substrate may differ from the aqueous coating
compositions layered
on the outside of the substrate.
In another embodiment, the packaging material 40 includes a first aqueous
coating layer
44a formed from a first aqueous coating composition and a second aqueous
coating layer 46a
formed from a second aqueous coating composition. In this aspect, as shown in
FIG. 4, the
second aqueous coating layer 46a is the topmost layer, i.e., the layer exposed
to the atmosphere,
and the first aqueous coating layer 44a is the bottommost layer, i.e., the
layer disposed directly
on the substrate 42. The packaging material also includes a third aqueous
coating layer 44b
formed from a third aqueous coating composition and a fourth aqueous coating
layer 46b formed
from a fourth aqueous coating composition. In this aspect, as shown in FIG. 4,
the fourth
aqueous coating layer 46b is the topmost layer, i.e., the layer exposed to the
packaged product,
.. and the third aqueous coating layer 44b is the bottommost layer, i.e., the
layer disposed directly
on the substrate 42. The various coating layers may be formed of the same or
different aqueous
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coating compositions. For example, in one embodiment, the first aqueous
coating composition is
the same as the third aqueous coating composition. In another embodiment, the
fourth aqueous
coating composition may be a different aqueous coating composition than any of
the first,
second, or third aqueous coating compositions.
Wet Thickness
The aqueous coating compositions may be applied to the untreated or pre-
treated
substrates at a wet thickness of about 100 g/m2 or less for each layer. In one
embodiment, the
aqueous coating compositions may be applied to the untreated or pre-treated
substrates at a wet
thickness of about 50 g/m2 or less. In another embodiment, the aqueous coating
compositions
may be applied to the untreated or pre-treated substrates at a thickness of
about 10 g/m2 to about
50 g/m2. In yet another embodiment, the aqueous coating compositions may be
applied to the
untreated or pre-treated substrates at a wet thickness of about 2 g/m2 to
about 25 g/m2.
Dry Thickness
The aqueous coating compositions may be applied to the untreated or pre-
treated
substrates at a dry thickness of about 30 g/m2 or less for each layer. In one
embodiment, the
aqueous coating compositions may be applied to the untreated or pre-treated
substrates at a dry
thickness of about 20 g/m2 or less. In another embodiment, the aqueous coating
compositions
may be applied to the untreated or pre-treated substrates at a thickness of
about 2 g/m2 to about
20 g/m2. In yet another embodiment, the aqueous coating compositions may be
applied to the
untreated or pre-treated substrates at a dry thickness of about 5 g/m2 to
about 15 g/m2.
Coating Method
The aqueous coating compositions may be applied to the substrate using a
variety of
known techniques, including but not limited to spraying, rod coating, roll
coating, blade coating,
slot die coating, gravure coating (direct, reverse, and offset), flexographic
coating, size press
(puddle and metered), slide hopper, and curtain-coating. In one embodiment,
the barrier layers
are formed by applying the aqueous coating compositions by rod coating. In
another
embodiment, the barrier layers are formed by applying the aqueous coating
compositions with a
technique that allows for the deposition of multiple layers simultaneously.
For example, the
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barrier layers may be formed by applying the aqueous coating compositions via
curtain-coating
or slide hopper coating. However, it is also contemplated that not all barrier
layers are applied to
the substrate using the same technique, e.g., a first barrier layer may be
applied via rod coating, a
second barrier layer may be applied via curtain-coating, etc.
Properties
Once applied to the underlying packaging material, the coating systems
described herein
provide packaging containers for aseptic packaging and liquid packaging with
improved total
barrier properties for long-term storage as well improved recyclability. The
coating systems of
the invention may also reduce costs associated with manufacturing. In one
embodiment, the
packaging containers are able to preserve the qualities of the packaged
contents, i.e., nutritional
value, hygienic safety and taste, at ambient conditions for at least 3 months.
In another
embodiment, the packaging containers are able to preserve the qualities of the
packaged
contents, i.e., nutritional value, hygienic safety and taste, at ambient
conditions for at least 4
months. In most aseptic cases, however, the packaging is able to preserve the
contents for longer
periods than that. In addition, the coating systems of the invention are
moisture- resistant and
provide superior oxygen barrier properties and heat sealing characteristics.
Suitable Uses
As previously discussed, the multiple barrier layers described herein are
intended for use
in aseptic packaging, liquid packaging, and retortable packaging. Indeed,
packaging containers
of the single use disposable type for liquid foods such as milk, fruit juices,
and the like intended
for long term ambient storage are contemplated. Similarly, packaging of liquid
food products
intended for chilled storage and distribution are also contemplated. Likewise,
packaging
intended to be durable for sterilization of filled packages in autoclave of
retort treatment such as
for soups, pastes and semi-solid food are also contemplated.
EXAMPLES
The following non-limiting examples are merely illustrative of the preferred
embodiments of the present invention, and are not to be construed as limiting
the invention, the
scope of which is defined by the appended claims.
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In each of the examples, various coating systems of the present invention were
applied to
a substrate, for example, paperboard. Table 1 below provides the wet and dry
thicknesses of
each of the coating layers applied in the examples.
TABLE 1
Example or Coating material Meyer Rod Approximate wet Approximate dry
Comparative thickness, 1.1
thickness, 1.1
Example
1, C, 2, E ALD 15 34 16
1,B PVA 25 57 12
2,D PUL 15 34 10
3,5 DIOFAN B204 15 34 17
3,5 HYPODTm 9105 15 34 15
and
9105/Aluminum
4 SUINBONDTM 12 27 14
3410/C-black
Example 1: Three Layer Coating System
A solid bleached sulfate pre-coated with a composition including calcium
carbonate and
styrene-acrylate binder was used as the underlying substrate. The substrate
was coated with an
aqueous dispersion as shown in Table 2 below. Each coating layer was applied
using a Meyer
rod having the size designated in Table 2. After each coating, the layer was
dried by forced air
in a box oven at 200 F.
Moisture vapor transmission rate (MVTR) was measured via the wet cup technique
with
the coated layers (if present) oriented toward the liquid-filled water
receptacle and placed in
standard Tappi conditions.
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TABLE 2
Example 1 Comp. Ex. A Comp. Ex. B
Comp. Ex. C
Bottom Layer ALD1 PVA2 ALD1
Meyer Rod Size 15 25 15
Middle Layer PVA2 ALD
Meyer Rod Size 25 15
Top Layer ALD1
Meyer Rod Size 15
MVTR (g/m2/day) 60 644 635 57
1 Joncryl 74-A from BASF Corporation.
2 Selvolg Polyvinyl Alcohol 21-205 Solution from Sekisui Specialty Chemicals
America, LLC.
As shown above, the composition and method of the present invention resulted
in a
MVTR an order of magnitude less than Comparative Examples A and B. In
addition, when
comparing the results of Example 1 and the results of Comparative Example C,
it can be seen
that a middle PVA layer, which is resistant to oxygen transmission, does not
disrupt or change
the MVTR.
Example 2: Two Layer Coating System
A solid bleached sulfate pre-coated with a composition including calcium
carbonate and
styrene-acrylate binder was again used as the underlying substrate. The
substrate was coated
with an aqueous dispersion as shown in Table 3 below. Each coating layer was
applied using a
Meyer rod having the size as designated in Table 3. After each coating, the
layer was dried by
forced air in a box oven at 200 F.
Moisture vapor transmission rate (MVTR) was measured via the wet cup technique
with
the coated layers (if present) oriented toward the liquid-filled water
receptacle and placed in
standard Tappi conditions. Oxygen Transmission Rate (OTR) was measured in
accordance with
ASTM D3985.
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TABLE 3
Example 2 Comp. Ex. D Comp. Ex. E
Bottom Layer PUL1 PUL1
ALD2
Meyer Rod Size 15 15 15
Top Layer ALD2
Meyer Rod Size 25
MVTR (g/m2/day) 99 180 95
OTR (cc/m2/day) 185 6400
8900
1 Takelac WPB-341 from Mitsui Chemicals America, Inc.
2 Joncryl 74-A from BASF Corporation.
As shown above, the composition and method of the present invention resulted
in a
MVTR an order of magnitude less than Comparative Example D. In addition, when
comparing
the results of Example 2 and the results of Comparative Example E, it can be
seen that an
additional layer of PUL does not degrade the MVTR. Moreover, the two-layer
system of
Example 2 resulted in a large improvement in OTR.
Example 3: Two Layer Coating System with Heat-sealable Layer Over Oxygen
Barrier
An uncoated paper substrate was used as the underlying substrate. A first
layer of
polyvinylidene chloride (Diofan B 204 from Solvay Specialty Polymers USA,
LLC) was
applied to the substrate with the wet and dry thicknesses shown in Table 1 via
a Meyer rod
having a size of 15. The layer was then dried by forced air in a box oven at
200 F. A second
layer including a polyolefin dispersion (Hypod 9105 from Dow Chemical
Company) was then
applied over the first layer with a wet and dry thickness of shown in Table 1
via a Meyer rod
having a size of 15 and dried in the same manner as the first layer. The
resulting coated substrate
was visually inspected and found to be defect-free and smooth.
Example 4: Two Layer Coating System with Heat-sealable Layer Over Light-
Blocking
Layer
A solid bleached sulfate pre-coated with a composition including calcium
carbonate and
styrene-acrylate binder was used as the underlying substrate. The substrate
was then coated with
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a mixture of a polyvinyl acetate dispersion and a carbon-black dispersion as
shown in Table 4
below. The mixture was applied at the wet and dry thicknesses shown in Table 1
using a Meyer
rod having a size of 12. After coating, the light-blocking layer was dried by
forced air in a box
oven at 200 F. A polyolefin dispersion was then applied over the first layer
at the wet and dry
thicknesses shown in Table 1 using a Meyer rod having a size of 15 and dried
in the same
manner as the first layer.
TABLE 4
Example 4
Bottom Layer
Polyvinyl Acetate Disperson1 20 g
Carbon-Black Dispersion2 4.5 g
Meyer Rod Size 12
Top Layer
Polyolefin dispersion'
Meyer Rod Size 15
1 SUNBONDTm 3410 from Omnova Solutions, Inc.
2 Aquablak 8328 from Solution Dispersions
Hypod 9105TM from The Dow Chemical Company.
The resulting coated substrate was visually inspected and found to be defect-
free and
smooth.
Example 5: Two Layer Coating System with Light-Blocking Layer Over
Oxygen/lVloisture
Vapor Layer
A polyvinylidene chloride-based latex dispersion was applied to an uncoated
paper
substrate at the wet and dry thicknesses shown in Table 1 using a Meyer rod
having a size of 15.
After coating, the layer was dried by forced air in a box oven at 200 F. A
mixture of a polyolefin
dispersion and aluminum flake (as shown in Table 5 below) was then applied
over the first layer
at the wet and dry thicknesses shown in Table 1 using a Meyer rod having a
size of 15 and dried
in the same manner as the first layer.
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TABLE 5
Example 5
Bottom Layer
Polyvinylidene Chloride-
based Dispersonl
Meyer Rod Size 15
Top Layer
Polyolefin Dispersion2 20 g
Aluminum Flake3 1.7 g
1 Diofang B 204 from Solvay Specialty Polymers USA, LLC.
2 Hypod 9105TM from The Dow Chemical Company.
3STAPA IL HYDROLAN 801 5590/G Aluminum Paste from Eckart GmbH.
The resulting coated substrate was visually inspected and found to be defect-
free with a
metallic appearance (like a foil), smooth, and having improved opacity as
compared with the
uncoated paper substrate.
Notwithstanding that the numerical ranges and parameters setting forth the
broad scope
of the invention are approximations, the numerical values set forth in the
specific examples are
reported as precisely as possible. Any numerical value, however, inherently
contain certain
errors necessarily resulting from the standard deviation found in their
respective testing
measurements. Furthermore, when numerical ranges of varying scope are set
forth herein, it is
contemplated that any combination of these values inclusive of the recited
values may be used.
The invention described and claimed herein is not to be limited in scope by
the specific
embodiments herein disclosed, since these embodiments are intended as
illustrations of several
aspects of the invention. Any equivalent embodiments are intended to be within
the scope of this
invention. Indeed, various modifications of the invention in addition to those
shown and
described herein will become apparent to those skilled in the art from the
foregoing description.
Such modifications are also intended to fall within the scope of the appended
claims. All patents
and patent applications cited in the foregoing text are expressly incorporated
herein by reference
in their entirety.
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