Field of the Invention:
[0001] The present invention relates to draft beer dispensing systems and related beer packaging,
in particular although not necessarily limited to small volume dispense systems such
as home draft dispense appliances.
Background of the invention:
[0002] Low volume throughput beverage dispense systems - ( for example, but also especially
"at home" dispense systems for draft beer), typically employ relatively small kegs
with, in general, lower turnover rates than might be expected in installations typical
of commercial enterprises, such as bar or restaurant keg dispense systems. Both of
these factors leave the beer more predisposed to risks associated with more and more
rapid loss of CO2, and to oxidation of the beer through gas infiltration. (Small volume
containers almost necessarily have larger packaging surface area to contained volume
ratios - increasing the volumetric rate of loss and infiltration respectively - and
compounding the keeping quality problem on both fronts).
[0003] Taking it as a given that home draft dispense carries with it both consumer expectations
of a premium experience, as well as the collateral system and beer packaging cost
premiums necessarily incurred in delivering that experience to a consumer's home:
the viability of the value proposition becomes particularly precarious. If the system's
packaging integrity fails, the quality of the beer and the draft experience will degrade
rapidly. Marketing prospects for sustaining consumer interest in such circumstances
is contraindicated. The entire commercial opportunity is susceptible to failure as
a direct result of packaging performance.
[0004] From an appliance design and logistical convenience point of view, liner-in-keg dispense
systems are particularly suited to this general class of dispense systems. In this
context, however, the entire home draft opportunity can be critically dependent on
the efficacy of gas barrier liners employed in the liner-in-keg combination.
[0005] Due at least in part to their ability to be fabricated into packaging articles of
various sizes and shapes (e.g., their design flexibility), plastic materials based
on organic polymers, are becoming increasingly important in the packaging industry.
More particularly, the use of organic polymers in films, has become widespread in
packaging applications. However, the barrier properties of available organic polymers
have not been able to approach the barrier properties of traditional packaging materials,
such as glass and metal. In particular, virtually all plastics having oxygen barrier
characteristics that might otherwise be suitable for liner-in-keg purposes fail dramatically
in that very connection under the high relative humidity that conditions prevail in
a liner-in-keg environment.
[0006] Inorganic-organic "alloys" (nanocomposites) have been produced which comprise gas
impermeable inorganic fillers dispersed in an organic polymer matrix. This technology
has resulted in enhanced gas barrier performance as the result of the "tortuous path
effect," however these approaches have had limited commercial acceptance due to the
cost associated with the additional fabrication steps involved.
[0007] Another approach to providing packaging for oxygen sensitive products involves inorganic
and/or organic oxygen scavengers being used in packaging structures to eliminate or
reduce the oxygen inside a package. Oxygen scavengers that can be used include iron
powders and unsaturated olefinic polymers. In oxygen scavenging packaging, oxygen
within the package or that diffuses through the packaging wall from the outside environment
is removed by the irreversible reaction of the oxygen scavenger with the oxygen. In
the case of polymeric oxygen scavengers, the oxygen scavenging functionality can be
an unsaturated olefinic moiety, which can be incorporated into or grafted onto a polymer.
Because these polymers were developed to aid in the removal of headspace oxygen from
a package, they typically have relatively high oxygen transmission rates, so that
the oxygen within the headspace can easily reach the reactive site (scavenging site)
and so that it is reacted at a sufficiently rapid rate. Therefore, most oxygen scavenging
polymers used in packaging, such as polyolefins and acrylate polymers, have relatively
high oxygen transmission rates and/or relatively low oxygen barrier properties. These
advances have therefore not materially addressed the requirements for liner-in-keg
applications.
[0008] The overall shortcomings of oxygen barrier performance of polymers in general, has
resulted in their being ignored for liner-in-keg applications, in favor of specialty,
modified polymer films that are intended to more closely approximate the oxygen barrier
performance associated with traditional glass and metal packaging materials.
[0009] Instead, the packaging arts has pursued a materials "hybridization" - which has been
demonstrated to deliver improved gas barrier performance. This approach has, for example,
included thin-layer surface coating/deposition of metals, silica or graphite over
an organic polymer substrate. Metallized PET is widely employed.
[0010] From a simple barrier perspective, the use of foil or metal coated barrier films
as liner materials is unequivocally preferred - their properties are unmatched by
the currently available alternative materials in this respect. However, and despite
their demonstrable superiority as gas barrier materials, per se, their use remains
problematic for liner-in-keg packaging applications. The problem is "two-fold": involving
as it does, both the folding that is typically employed in installing the liner in
the keg, and the unfolding of the liner within the keg that occurs during or as a
preamble to filling. Both such operations can and often do result in an unacceptable
physical compromise of the gas barrier integrity of foil and metallized film packaging.
However, un-hybridized polymers to such foil and metallized flexible liners offer
little hope of a viable alternative. Virtually all such gas barrier polymer's performance
degrades unacceptably in liner-in-keg applications. The problem of such polymeric
alternatives is that their gas barrier properties are, virtually without exception,
significantly or even radically compromised in the presence of moisture (including
elevated relative humidity) that is trapped and/or accumulates in the space between
the liner and the keg. This problem is particularly acute in liner-in-keg dispense
systems in which unconditioned air, (i.e. with its often high ambient relative humidity),
is utilized to pressurize the keg - and so results in condensation forming between
the keg and the liner when the keg is refrigerated within the dispense system.
[0011] Heretofore, the industry has continued to use foil or metallized films for this reason,
notwithstanding the quality problems that they continue to face, and in spite of the
fact that the market for these products and the related dispense appliances is "fragile"
in the sense elaborated upon above. These liner materials continue to fail to reliably
deliver their essential performance, for the reasons set forth above. Since consumer
quality demands high and consistent quality, the superior gas barrier properties of
these hybrid materials boarders on being useless when challenged by marketplace expectations.
[0012] Accordingly, there remains an unsatisfied need in the art for a liner which:
- overcomes the shortcomings of foil and metallized films
- is not subject to the general shortcomings of most known gas barrier polymers with
regard to moisture, and
- can reliably support consumer expectations and the related value proposition for these
dispense systems.
Summary of the Invention:
[0013] The present invention relates to a liner adapted for a "liner-in-keg" packaging wherein
the liner comprises a vinylidene chloride based polymeric gas barrier, to be deployed
internally of the keg and adapted to provide a gas diffusion barrier between a gas-sensitive
liquid to be contained within the liner and the liner-surrounding keg surfaces. The
gas barrier performance of the vinylidene chloride moieties is largely indifferent
to high relative humidity, at least in comparison to almost all other generally known
plastics.
[0014] Of course the use of vinylidene chloride based polymers (PVDC) and copolymers are
generally well known, and continue to be among the most widely used "high oxygen barrier"
resins. Among the more familiar domestic examples of the vinylidene chloride based
polymers that used in packaging, are the Saran® cling film products. Other uses of
PVDC are variously described in the prior art, as indicated below.
[0015] US patent 2,713,543 discloses the use of vinylidene chloride in beverage bulbs useful for packaging carbonated
beverages.
[0016] US patent 2,721,691 discloses drum liners comprised of multilayer plastic films that can be based on
suitable materials such as vinyl resin.
[0017] US 3,248,040 discloses double wall flexible film packaging using vinylidene chloride copolymers
- all in connection with the production of bags and pouches.
[0019] US patent 3,620,774 discloses a tubular container for beer, made using vinylidene chloride, and especially
copolymers of vinylidene chloride and lesser amounts of acrylonitrile.
[0020] US patent 3,630,759 discloses yet another use of vinylidene chloride pouches, for use in packaging perishable
vegetables.
[0021] US patent 4,172,152 discloses a double walled film container structure to provide insulation space there
between, in which beer can be sold. The outer wall of this packaging construction
can employ vinylidene chloride polymers.
[0022] In accordance with the present invention , the package's keg may be a metal or plastic
keg that substantially encloses the liner and provides an opening that extends into
the kegs interior through which the liner is adapted to be filled and emptied.
[0023] In a preferred form of the present invention the package is a flexible liner. In
particular, the liner is a folded liner adapted to be initially deployed into unfolded
relation within the keg, by inflation. The barrier properties of the packaging according
to the present invention is particularly well suited (i.e. is particularly resistant
to problems associated with folding/folding in other barrier packaging). This can
be done by filling the liner with the gas-sensitive liquid content that it is designed
to hold and dispense; or, the liner can be inflated by pre-filling with a liner-interior
flushing gas. This is an intermediate filling step and is performed to aid in displacing
oxygen from the interior and interior surface of the liner, that might otherwise prejudice
the shelf-life of the gas-sensitive liquid that is subsequently introduced into the
liner.
[0024] The present invention is particularly applicable to packaging wherein the keg is:
- predisposed towards accumulation/retention of exogenous moisture in between said liner's
exterior and said keg's interior; and,
- adapted to hold and dispense a gas-in-liquid solution, which is sensitive either to
the ingress of oxygen or to release of solubilized gas from said solution or both.
[0025] Moisture can be accumulated within the keg prior to insertion of the liner into the
keg during the assembly of the package, e.g. by way of atmospheric water vapor prior
to sealing of the keg. The problem manifests most acutely then, in packages that are
adapted to be cooled to temperatures at which the water vapor condenses as liquid
water between the keg and the liner.
[0026] Preferably, the liner according to the present invention is a flexible liner and
the liquid contents are dispensed from the package in response to the introduction
of fluid between the liner and the keg. This too is problematic in that the introduction
of fluid can collaterally introduce either or both of liquid water or water vapor
between said liner and said keg.
[0027] In accordance with the present invention, the liner functions as a passive gas barrier
and preferably it is a gas-barrier vinylidene chloride based polymer comprised of
polyvinylidene chloride homopolymer. However, PVDC homopolymer has a narrow melt processing
temperature that makes its processing difficult. Alternatively therefore, the gas-barrier
vinylidene chloride based polymer comprises one or more polyvinylidene chloride copolymers..
Note however, that various PVDC copolymers that comprise small amounts of a comonomer,
such as vinyl chloride, methylacrylate or acrylonitrile have had some commercial success.
While these copolymers offer the desired melt process capability due to their reduced
melting points, their gas barrier performance is compromised due to their decreased
crystallinity and due to dilution of the vinylidene chloride moieties.
[0028] With this in mind, it is preferred in connection with the present invention, to employ
a chemically modified PVDC polymer structure that achieves both enhanced oxygen barrier
performance and good processability (due to decreased melting point). To this end
an oxygen-scavenging vinyl cycloalkenylacrylate monomer can be successfully incorporated
into the polymer structure of PVDC by free radical polymerization. The oxygen scavenging
vinyl cycloalkenylacrylate monomer has two carbon-carbon double bonds, one in the
vinyl moiety of the monomer and the other in the cycloalkenyl moiety of the monomer.
The polymerization of vinylidene chloride with the cycloalkenyl acrylate monomer apparently
proceeds primarily through reaction of the vinyl double bond of the oxygen scavenging
monomer with the carbon-carbon double bond of the vinylidene chloride. Reaction of
vinylidene chloride with the double bond of the cycloalkenyl moiety of the oxygen
scavenging monomer is believed to be minimal during the polymerization reaction. See
in this connection,
US patent 6,818,151. Thus, in accordance with this aspect of the present invention, the liner provides
both passive and active gas barrier properties, with the latter in particular being
related advantages associated with managing to the ingress of oxygen and the problems
of oxidation that would otherwise be manifest through the exposure of an oxygen sensitive
liquid contained in the liner.
[0029] The packaging according to the present invention is especially well suited for liquids
that are sensitive to loss of solubilized gas selected from the group consisting of:
carbon dioxide; nitrogen; or mixtures thereof.
[0030] Comestible products that have various sensitivities to gas loss or oxygen ingress
include liquids such as edible oils; or a beverage such as beer or wine are particularly
notable in this respect.
[0031] In a particularly preferred form of the present invention there is provided a (folded)
liner and spear assembly adapted to be deployed in a keg. The liner is folded to facilitate
insertion into a keg, and to deploy on inflation thereof during some aspect of the
filling process. The assembly in question comprises a spear (or dip tube), an a bung
to seal the opening into the keg. The bung includes integral valve means for filing
and dispensing operations.
[0032] The present invention also relates to a liner-in-keg package assembly, and especially
although not necessarily the one in which the afore-mentioned liner and spear assembly
are employed. In this liner in keg assembly the bung is positioned in engaged relation
sealing the opening into the keg and holding the liner and spear in relatively fixed
relation within the kegs interior.
[0033] In an especially preferred form of the present invention, of course, there is provided
a beer-filled liner-in-keg package assembly. As previously indicated, the present
invention extends to a beer dispensing system comprising a liner-in-keg package assembly,
with an air pump to pressurize space between keg and liner, to thereby facilitate
the dispense of said beer from said package. In systems of this type that make provision
for refrigeration of the contents (again, preferably a comestible, and in particular
a beverage such as wine or especially a carbonated beverages such as beer) of the
liner-in-keg packaging, the advantages manifest in the combination when humid air
is driven by the pump into the space between the liner and the keg. In accordance
with the present invention the high relative humidity that results in the interior
of this package in this combination with an appliance does not radically degrade the
gas-barrier properties of the liner material.
Introduction to the Drawing:
[0034] The figure of the drawing appended to this specification illustrates a cross-sectional
view through a keg enclosing a liner, according to the present invention;
Detailed Description of the Invention:
[0035] In the preferred form of the present invention the packaging described herein is
a dispensing keg - and in particular, a keg that is used in combination with a "draft"
beverage dispensing appliance.
[0036] "Draft" or draught have been variously used in the beer business to describe beer
that is served using taps from a large multi-serving container, or even beer that
is not heat pasteurized. In the context of the preferred form of the present invention
detailed herein, the term is a reference to dispense from a multi-serving packaging
in a dispense system which is reminiscent of traditional bar taps.
[0037] In any case, under preferred practice in accordance with the present invention, there
is provided a combination of a keg and a (e.g. draft beverage) dispensing appliance.
The dispensing keg is preferably adapted to dispense a comestible, which could be,
for example, an edible oil. In the preferred embodiment, however, the keg is adapted
to dispense a beverage, such as wine.
[0038] The invention however, is particularly advantageous in relation to the packaging
and dispense of carbonated, oxygen-sensitive beverages such as beer. These latter
mentioned comestibles are sensitive to loss of solubilized gas (typically selected
from the group consisting of: carbon dioxide; nitrogen; or mixtures thereof). As is
also the cases with edible oils and wines, beer for example is also susceptible to
exposure to gas infiltration (i.e. oxygen) that occurs through the liner into its
interior.
[0039] Accordingly, the liner 1 according to the present invention is adapted for a "liner-in-keg"
package 2 as illustrated generally in The figure hereof. More particularly, the liner
1 comprises a vinylidene chloride based polymeric gas barrier, to be deployed internally
of a keg 3 and adapted to provide a the diffusion barrier between a gas-sensitive
liquid to be contained within the liner 1 and the liner-surrounding interior surfaces
of keg 3. The selection of the liner material has a bearing on whether the gas barrier
is a passive gas barrier (such as polyvinylidene chloride homopolymers) or an active
barrier such as active oxygen scavenging polyvinylidene chloride copolymers.
[0040] As illustrated the liner 1 resides within a (metal or plastic) keg 3 that substantially
encloses the liner. The keg 3 circumscribes an opening 4 into its interior through
which the liner 1 (and any associated dispensing apparatus such as valve body 5 and
spear 6) is adapted to be inserted, and through which the liner 1 is subsequently
filled and emptied.
[0041] In operation, of the illustrated packaging, the liner is a folded flexible liner
that is adapted to be inserted into keg 3 and then initially deployed into unfolded
relation within the keg, by inflation. The pattern in which the liner is folded orders
the sequence in which it unfolds during inflation, so as to ensure that it expands
properly so that it can receive a full charge of beer without damaging the liner.
In a preferred practice, the liner is deployed by inflation by one of the group selected
from: filling with said gas-sensitive liquid or, pre-filling with a liner-interior
flushing gas. This is done to reduce the carry-over of oxygen from the liner interior
into the beer when it is subsequently introduced into the packaging. Note that the
liner according to the present invention is less sensitive to folding/unfolding problems
associated with prior art liner materials and is also less sensitive to positioning
(which if not perfectly accomplished can result in damaging deformation of the liner
to which other liner materials are generally more susceptible).
[0042] Note too, that although moisture can be accumulated within the keg prior to insertion
of said liner into the keg during the assembly of the package, ( as by way of its
introduction as atmospheric water vapor prior to sealing of the keg), - it is also
through the operation the appliance/package combination that the problem is compounded.
When liquid (e.g. beer) is dispensed from the package in response to the introduction
of fluid between the liner and the keg introduction of that fluid collaterally introduces
either or both of liquid water or water vapor between the liner and the keg. In this
way, the keg is predisposed towards accumulation/retention of exogenous moisture in
between the liner's exterior and the keg's interior. The problem is further exacerbated
in the illustrated appliance wherein the package is adapted to be cooled to temperatures
at which the water vapor introduced by way of the fluid (e.g. air) condenses as liquid
water between the keg and the liner.
[0043] In the dispensing operation, air is introduced through into the space between the
liner 1 and the interior surfaces of keg 3 through an opening in the valve body that
is segregated from the opening through which beer is introduced/dispensed. Pressure
exerted by the air acts against the exterior of liner 1, and upon selective operation
of a dispense tap (not shown), beer is forced from the liner 1 by that applied pressure.
[0044] Optionally, the package 2 includes a supporting shell 7 having upper and lower chimes
8 and 9 respectively, with shell 7 enclosing keg 3 therein.
1. A liner adapted for a "liner-in-keg" package wherein said liner comprises a vinylidene
chloride based polymeric gas barrier, to be deployed internally of said keg and adapted
to provide a gas diffusion barrier between a gas-sensitive liquid to be contained
within said liner and the liner-surrounding keg surfaces.
2. The liner according to claim 1, wherein said package's keg is a metal or plastic keg
substantially enclosing said liner around an opening there through that circumscribes
an opening into said liner though which said liner is adapted to be filled and emptied.
3. The package according to claim 1, wherein said liner is a flexible liner.
4. The packaging according to claim 3, wherein said liner is a folded liner adapted to
be initially deployed into unfolded relation within the keg, by inflation.
5. The packaging according to claim 4, wherein said liner is adapted to be deployed by
inflation by one of the group selected from: filling with said gas-sensitive liquid
or, pre-filling with a liner-interior flushing gas.
6. The package according to claim 1, wherein said keg is predisposed towards accumulation/retention
of exogenous moisture in between said liner's exterior and said keg's interior.
7. The package according to claim 6, wherein said liquid is a gas-in-liquid solution,
which is sensitive to release of solubilized gas from said solution.
8. The package according to claim 6, wherein said liquid is susceptible to exposure to
gas infiltration into said liner.
9. The package according to claim 6, wherein moisture is accumulated within said keg
prior to insertion of said liner into said keg during the assembly of said package.
10. The package according to claim 6, wherein said moisture is introduced as atmospheric
water vapor prior to sealing of said keg.
11. The package according to claim 10, wherein said package is adapted to be cooled to
temperatures at which said water vapor condenses as liquid water between said keg
and said liner.
12. The package according to claim 6, wherein said liner is a flexible liner.
13. The package according to claim 12, wherein said liquid is dispensed from said package
in response to the introduction of fluid between said liner and said keg.
14. The package according to claim 13 wherein said introduction of fluid collaterally
introduces either or both of liquid water or water vapor between said liner and said
keg.
15. The package according to claim 6 wherein said gas barrier is a passive gas barrier.
16. The package according to claim 15 wherein said gas-barrier vinylidene chloride based
polymer comprises polyvinylidene chloride homopolymer.
17. The package according to claim 15 wherein said gas-barrier vinylidene chloride based
polymer comprises one or more polyvinylidene chloride copolymers.
18. The package according to claim 17, wherein said copolymer(s) is/are active oxygen
scavenging polymers.
19. The package according to claim 7, wherein said liquid is sensitive to loss of solubilized
gas selected from the group consisting of: carbon dioxide; nitrogen; or mixtures thereof.
20. The package according to claim 6, wherein said liquid is a comestible.
21. The package according to claim 6, wherein said liquid is and edible oil.
22. The package according to claim 6, wherein said liquid is a beverage.
23. The package according to claim 22, wherein said beverage is beer or wine.
24. The package according to claim 6, wherein said package is a dispensing keg.
25. The package according to claim 24, wherein said keg is adapted to be used in combination
with a draft beverage dispensing appliance.