The present invention relates to a polymer composition containing
oxygen scavenging compounds therein, for use in packaging beverages, foods, pharmaceuticals
and the like. In particular, these polymer compositions have utility as liners
or gasketing materials for crowns, closures, lids or caps of various containers
such as bottles or cans to prevent oxygen ingress and to scavenge oxygen which
is present inside the container, or contained in outside air leaking past or permeating
through the polymer composition. These polymer compositions may also be used in
the construction of the container, as the container material itself, as a component
of a container, or as a barrier layer thereupon or therein, to prevent oxygen ingress
therethrough or to scavenge oxygen therein.
In packaging oxygen sensitive materials such as foodstuffs, beverages,
and pharamceuticals (collectively "products") oxygen contamination can be particularly
troublesome. Care is generally taken to minimize the introduction of oxygen or
to reduce the detrimental or undesirable effects of oxygen on the foodstuff or
Molecular oxygen (02) can be reduced to a variety of intermediate
species by the addition of one to four electrons; these species are superoxide,
hydroxy radical, hydrogen peroxide, and water. 02 and water are relatively
unreactive: the three intermediate species are very reactive. Also, 02
can be activated to singlet electron state oxygen (which can undergo subsequent
reduction to the more reactive oxygen species) by irradiation, or by the presence
of catalytic agents. These reactive oxygen species are free radical in nature,
and the oxidative reactions in which they participate are therefore autocatalytic.
Carbon-carbon double bonds are particularly susceptible to reaction
with the intermediate species. Such carbon-carbon bonds are often found in foods
and beverages, pharmaceuticals, dyes, photochemicals, adhesives, and polymer precursors.
Virtually any product which has complex organic constituents will contain such
carbon-carbon double bonds or other oxygen reactive components, and hence can
undergo oxidative reactions. Thus, if the oxidation products adversely affect the
performance, odor or flavor of the product, then removing the oxygen which is present
(either dissolved in or trapped with the product), preventing oxygen ingress,
or inhibiting the reactions of oxygen will benefit the product.
A number of strategies exist to deal with oxygen as a contaminant.
The most basic is simply to remove oxygen from the product by vacuum or by inert
gas sparging, or both. Such systems are used in boiler water treatment, the orange
juice and brewing industries, and in modified-atmosphere packaging of food products.
This technology, while somewhat equipment intensive, can remove about 90-95% of
the oxygen present in air from the product (or its container) prior to or during
packaging. However, the removal of the remaining 5-10% of oxygen using this approach
requires longer times for vacuum treatment and/or sparging and increasingly larger
volumes of higher and higher purity inert gas which must not itself be contaminated
with trace levels of oxygen. This makes the removal (by such methods) of the last
traces of oxygen expensive. A further disadvantage of these methods is a tendency
to remove volatile product components. This is a particular problem with foods
and beverages, wherein such components are often responsible for some or all of
the aroma and flavor.
Herein, the term "oxygen scavenger' means materials or chemical compounds
a) remove oxygen from the interior of a closed package by reacting or combining
with entrapped oxygen or with oxygen that is leaking into the package interior
past the package/closure sealant or gasket;
b) prevent or reduce the perfusion of oxygen through the gasketing/sealant
materials between container and closure;
c) prevent or reduce the perfusion of oxygen through the materials of the package/closure
itself by incorporation of the oxygen scavenger into the materials of which the
container/closure is/are made;
d) prevent or reduce the perfusion of oxygen through the material of the package/closure
itself by incorporation of the oxygen scavenger into one or more layers of a multilayer
The term "antioxidants" as used herein means materials or compounds
which, when added to the foodstuff or beverage itself, slow the rate of oxidation
or otherwise reduce the undesirable effects of oxidation upon the foodstuff or
For example, it has been known since the 1930's that oxygen in beer
adversely affects its flavor and stability. Amounts of oxygen as low as 0.1 to
0.2 ml per 355 ml container will, over time, cause darkening of the beer, an increase
in chill-haze values and significant taste changes. Oxygen's effect on beer is
so strongly detrimental that many brewers go to great lengths to remove it from
the bottle during the filling process. One usual technique is to (1) remove the
air (via vacuum) from a clean bottle; (2) fill the bottle with C02;
(3) flow the beer down the bottle wall into the bottle thus displacing the C02;
and (4) finally, to squirt a jet of high-pressure deoxygenated water into the
bottle to cause the beer to over-foam just as the cap is put on (attempting thereby
to displace the remaining headspace gases with the beer's own C02).
In addition, to minimize introduction of air (21% 02) into the headspace
just before capping, production lines are run more slowly than otherwise necessary.
All this is expensive, and usually reduces the total 02 concentration
in the headspace to only about 200-400 parts per billion: the desired level is
as close to zero as possible, but certainly below about 50 ppb. The 200-400 ppb
achieved in the packaged product by careful brewers corresponds to approximately
50-100 microliters of oxygen per 355 ml bottle. Even this small quantity of oxygen
is still considered to be one of the major limitations on quality and shelf life
of beer today.
Many other food products suffer similar oxygen-mediated degradation;
for example, individual portions of prepared foods are marketed in containers made
of plastics, and air entrapped therein, and leaking or perfusing into the package
after processing, is an acknowledged industry problem. This leakage a perfusion
is often especially true for packages made entirely of plastics, because many
plastics with otherwise desirable properties are relatively permeable to oxygen.
Incorporation of the present invention into the bulk of such plastics, or into
one or more layers of a multilayer package, could be beneficial in reducing or
eliminating such perfusion. Among obvious benefits of such applications of the
invention is extended shelf life.
None of the above techniques remove or control (a) oxygen dissolved
in the product (which will outgas into the headspace as the enclosed system comes
to equilibrium), or (b) oxygen leakage into the package past the gasket/container
interface, or (c) oxygen permeating through the gasket into the interior of the
package, or (d) oxygen permeating through the container itself into the package.
The present invention also aids in removal of 02 from these other three
sources. Furthermore, it is known that free oxygen inside a package may yield very
rapid degradation of the product, consequently a desired property of any scavenger
is to remove most of the free oxygen as quickly as possible (i.e., ultimate 02
absorption capability is subordinate to fast uptake kinetics).
Antioxidants (such as sulfur dioxide, trihydroxy butyrophenone, butylated
hydroxy toluene and butylated hydroxy anisole) and oxygen scavengers (such as ascorbic
acid, isoascorbic acid and glucose oxidase-catalase) have been used in an attempt
to reduce the effects of oxygen contamination on beer (See e.g., Reinke
etal., "Effect of Antioxidants and Oxygen Scavengers on the Shelf-life
of Canned Beer, "A.S.B.C. Proceedings, 1963, pp. 175-180, Thomson, "Practical
Control of Air in Beer", Brewer's Guild Journal, Vol. 38, No. 451, May 1952, pp.
167-184, and von Hodenberg, "Removal of Oxygen from Brewing Liquor," Brauwelt
International, III, 1988, pp. 243-4). The direct addition of such agents into beer
has several disadvantages. Both sulfur dioxide and ascorbates, when added to beer,
can result in production of off-flavors thus negating the intended purpose of
the addition. Many studies have been conducted on the effect of such agents on
the flavor of beer. (See e.g., Klimowitz etal., "The impact of Various
Antioxidants on Flavor Stability," MBAA Technical Quarterly, Vol. 26, pp. 70-74,
1989 and Gray etal., "Systematic Study of the Influence of Oxidation
on Beer Flavor," A.S.B.C. Proceedings, 1948, pp. 101-112.) Also, direct addition
of such compounds to a food or beverage requires stating on the label that the
product contains the additive. This is somewhat undesirable in today's era of "fresh"
and "all-natural" products.
It is also known in the art to prepare plastic containers (e.g.,
for beer, other beverages and various foods) wherein a wall comprises, or includes
a layer which comprises, a polymer, an oxidizable component having oxygen-scavenging
properties, and a metal catalyst, for binding any oxygen penetrating the container
wall (see, e.g., Folland, the OXBAR Super-Barrier System: A Total Oxygen Barrier
System for PET Packaging, "EUROPAK '89, Oct. 30-Nov. 1, 1989, and European Patent
Application 301,719). Also, U.S. Patent 4,048,361 discloses a food container having
at least one barrier layer which contains an oxygen "getter," while U.S. Patent
3,586,514 discloses a thin wall polyvinyl chloride container wherein the plastic
contains a quantity of an antioxidizing agent to reduce oxygen permeability therethrough,
and Japanese patent application 58-160,344 discloses hollow moldings of a polyethylene
terephthalate ("PET") with a meta-xylene group containing polyamide resin. The
containers described in these references are described as oxygen barriers which
prevent or reduce the transmission of oxygen through the wall and into the container.
Such products are generally more expensive than glass containers and are less
likely to be recycled than glass or aluminum containers.
Attempts have been made to incorporate oxygen scavenging systems
in a container crown or closure. For example, U.S. Patent 4,279,350 discloses a
closure liner which incorporates a catalyst disposed between an oxygen permeable
barrier and a water absorbent backing layer. Another closure is disclosed in UK
Patent Application 2,040,889. This closure is in the form of a stopper molded
from ethylene vinyl acetate ("EVA") having a closed-cell foamed core (which may
contain water and sulfur dioxide to act as an oxygen scavenger) and a liquid impervious
skin. Also, European Patent Application 328,336 discloses a preformed container
closure element, such as a cap, removable panel or liner, formed of a polymeric
matrix containing an oxygen scavenger therein. Preferred scavengers include ascorbates
or isoascorbates, and their scavenging properties are activated by pasteurizing
or sterilizing the element after it has been fitted onto a filled container. Similarly,
European Patent Application 328,337 discloses a sealing composition for a container
closure comprising a polymeric matrix material which is modified by the inclusion
therein of an oxygen scavenger. These compositions may be in fluid or meltable
form for application to a closure or to be present as a deposit on the closure
in the form of a closure gasket. Ascorbates or isoascorbates, alone or in combination
with sulfites, are preferred oxygen scavengers. Again, the scavenging properties
of these compounds are activated by pasteurizing or sterilizing the deposit when
sealing a container with the gasket on a closure or metal cap.
Ferrous oxide has been used commercially as an oxygen scavenger for
food applications. It is currently manufactured in sachets or packets by a number
of firms including Mitsubishi Gas Chemical, Inc., which markets it in a product
known as AGELESS™. (See, e.g., European Packaging Newsletter and World Report,
Vol. 21, No. 7, July, 1988.) Such products may also contain ascorbates as an oxygen
scavenging agent, per U.S. Patent 4,752,002. Also, Patent 4,524,015 discloses
the use of a granular mixture of an ascorbate or ascorbic acid, an alkali metal
carbonate, an iron compound, carbon black, and water, and U.S. Patent 4,384,972
discloses a foodstuff freshness keeping agent of a particulate composition that
contains a salt of a metal, an alkali substance, a sulfite or other deliquescent
compound, and optionally, ascorbic acid or a salt thereof.
While such products are effective at removing oxygen from within
packages of breads, cookies, pasta, coffee and other relatively dry foodstuffs,
they have significant drawbacks. They (a) are hygroscopic and water soluble to
some extent, (b) function less effectively in high CO2 environments,
(e.g., beer containers), (c) in order to preserve their activity, they must be
carefully sequestered from air (or other oxygen-containing environments) until
use, and (d) they require a sachet or packet, often of multilayer construction,
for proper storage and handling of the oxygen scavenger.
U.S. Patents 4,536,409 and 4,702,966 each disclose a multilayer wall
construction for a polymeric container to be used to pack comestibles, wherein
outer and inner layers are structural and protective layers: positioned therebetween
are materials designed to control the unwanted permeation of oxygen. Preferably,
the outer and inner layers are olefinic and resistant to the transmission of water
vapor at room temperature, but at elevated temperatures, they permit water vapor
to permeate into the oxygen absorbing system to trigger such system to an active
state which is capable of absorbing oxygen. While this construction is useful
from the standpoint of retaining the oxygen absorbing system in a dormant state
until it is needed, such construction requires heat to render the inner and outer
layers permeable to water vapor which can trigger or activate the oxygen absorbing
Consequently, there is a need for a material or product which can
rapidly reduce oxygen levels inside a package of products which are wet or moist
(or which are capable of generating moisture inside their packaging) without adversely
changing taste, aroma, or functionality of such packaged foodstuffs, beverages
and pharmaceuticals. Persons skilled in the art have considered the addition of
various agents into the packaging of such products in an attempt to meet this
Japanese patent application 61-238,836 discloses a packaging film
made from a thermoplastic such as low density polyethylene ("PE"), which includes
ascorbic acid alone or in combination with an aliphatic polycarboxylic acid. This
film is disclosed as having good gas barrier properties.
Japanese patent application 54-022,281 discloses a fruit tray made
of a thermoplastic foam base having a thin layer of ascorbic acid or erythorbic
acid (or one of their alkali metal salts) on the face of indentations in the tray
upon which the fruit is to be placed.
New oxygen absorbing and scavenging materials are also being developed
by Aquanautics, Inc., Alameda, California. (See Packaging Technology, "Oxygen Eliminator
Extends Shelf Life," 1989 and "Extending the Life of a Bottle of Beer," New York
Times, 3/29/89). These materials are transition metal complexes, particularly (but
not exclusively) those complexes formed between transition metals and "polyalkylamines"
(as disclosed in U.S. Patent No. 4,959,135, which is expressly incorporated herein
by reference thereto), as well as those complexes formed between transition metals
and "macrocyclic amines" (as disclosed in U.S. Patent No. 4,952,289, which is expressly
incorporated herein by reference thereto).
These "amine + metal" complexes can bind ligands such as oxygen and
can be used as oxygen scavengers in packaging. The complexes either do not form
or do not become activated (i.e., cannot, or do not, bind oxygen) until the amine
and metal are together exposed to water or water vapor. The ingredients of the
complex can be mixed and used either free, or immobilized on or within a support
inter alia, on or mixed with silicone rubber or with a polymer such as
polyvinyl chloride ("PVC"), EVA, polypropylene ("PP"), PE or polyurethane (see
e.g., U.S. Patent Application Serial No. 07/317,172, filed February 28, 1989,
the content of which is expressly incorporated herein by reference thereto, wherein
one use for such complexes is as an oxygen scavenger in sealing compositions and
structures for beer bottle crowns).
Salicylic acid complexes and their reactivities towards oxygen are
generally known and are described in Zanello etal., Inorganica
Chim. Acta 1983, Vol. 74, pp. 89-95 and Cini etal.,
Inorganica Chim. Acta 1984, Vol. 88, pp. 105-113.
U.S. Patent 4,287,995 discloses a sealing member for a container
which is used to preserve aqueous liquids therein. This sealing member is mounted
on the cap or stopper of the container on the portion facing the contents. The
sealing member contains an oxygen absorbent which is separated from contacting
the contents of the container by a film which has a plurality of fine openings
such that it is gas-permeable but water-impermeable at one atmosphere pressure.
U.S. Patent 4,510,162 discloses an oxygen absorbent composition comprising
iron particles, yeast and moisture, which mounted on a suitable carrier and adapted
to be mounted in a closable container for removing oxygen therefrom.
U.S. Patent 4,756,436 discloses a construction for an oxygen scavenging
composition to be installed in a cap upon a liquid substance containing vessel.
This construction includes an upper, vacant compartment, a lower compartment containing
the oxygen scavenger, and a partition therebetween. The partition is made of single
or plural sheets of gas permeable liquid-proof material to provide a barrier between
the oxygen scavenger and the liquid substance.
Current crown liner technology includes the insitu
of a thermoplastic liner material directly in the crown which will later be used
for bottling beer or other beverages. Such liners are primarily made of PVC in
the United States and of thermoplastics which do not contain chlorine (such as
EVA or PE) in Europe and Japan.
PVC compositions, with or without additives as stabilizers or for
imparting certain properties, are known in the art. For example, U.S. Patent 4,380,597
discloses a stabilized thermoplastic composition of PVC (or mixed polymers) which
may include ascorbates or gluconates as stabilizer additives. These stabilizers
are added not to absorb oxygen from inside packages made of the polymer, but to
prevent breakdown of the polymer itself. U.S. Patent 4,211,681 discloses shaped
articles (e.g., films or tubes) which include high molecular weight poly (ethylene
oxide) polymers with stabilizers of ascorbic acid, 2,3-butyl hydroxyanisoles,
and the like.
Japanese patent application 62-215,010 discloses a deodorizing fiber
obtained by treating thermoplastic fibers with inorganic particles of divalent
ferrous iron and L-ascorbic acid. U.S. patent 4,278,718 discloses a sealing composition
for beverage containers consisting essentially of a vinyl chloride resin, a plasticizer,
and a metal oxide.
Today there is a need for oxygen-scavenging thermoplastic compositions
for use in oxygen-scavenging systems for packaging beverages, foods, pharmaceuticals
and other products. The oxygen-scavengers in such systems should rapidly reduce
oxygen levels within the package (and/or in the goods themselves), as well as prevent
oxygen ingress into the package. There is a particular need for such systems where
the internal environment of the package is (or can become) wet or moist. Most advantageously,
the oxygen-scavengers of such systems would remain inactive until after the product
is packaged. One particular need for such a composition is a liner for beer bottle
crowns wherein the oxygen-scavenging properties of the liner do not become active
until after the bottle is crowned.
Other particular uses of such a composition may involve dry products
packaged under low relative humidity. In such cases, the compositions of this invention
may be activated by application of water or water vapor to the composition itself
immediately prior to sealing of the container. For example, in the case of a dry
product to be sealed in a container by means of a screw-on lid with a gasket comprising
a composition of this invention, activation moisture might be provided by a water-mist
spray, by dipping in water, by exposure of the lid to a water-vapor-saturated
atmosphere, or by incidental exposure to steam during pre-capping sterilization.
The present invention provides certain compositions and formulations as solutions
to these general needs, and specifically for bottled beverages including beer.
Summary of the Invention
This invention teaches the preparation and use of certain oxygen
scavenging materials dispersed in various carriers, such as polymers or plastics,
and used in packaging as oxygen scavenging compositions. These compositions, by
virtue of novel and unexpected increases in oxygen uptake rates of the oxygen scavenging
material, are useful in preventing deterioration or reaction of the packaged substances
due to exposure to oxygen in the package.
In one aspect of the invention, the oxygen scavenging composition
comprises a polymeric carrier which is permeable to both oxygen and water or water
vapor; an organic compound which is dispersed relatively uniformly throughout the
polymeric carrier in an amount ranging from 10 to 50% by weight of the concentrate,
the organic compound only being reactive with oxygen after activation with water
or water vapor which permeates the polymeric carrier; and a catalyzing agent in
an amount effective to increase the rate of reaction of the organic compound with
oxygen which is present in or permeates through or into the polymeric carrier.
Preferred organic compounds include D- or L-ascorbic acid or a salt
or fatty acid derivative thereof (i.e., D- or L-ascorbates). Isoascorbates or erythrobates
may also be used, but most preferably, the organic compound is sodium L-ascorbate,
since it is readily available and known to be safe for contact with foodstuffs
The catalyzing agents for these ascorbates includes any transition
metal, compound, complex or chelate. The transition metal is preferably chosen
from the group comprising iron, copper, cobalt, or nickel, and most preferably
it is either iron or copper. The transition metal may preferably be supplied either
(1) as a compound such an ordinary salt, or (2) as a polyalkylpolyamine ("PAPA")
chelate, macrocyclic amine ("macrocycle") chelate, an amino polycarboxylate chelate,
or a salicylate chelate of a transition metal ion. It is also possible to instead
utilize other transition metal chelates or complexes which contain one or more
amine, hydroxyl, carboxylate or sulfhydryl groups, or combinations thereof.
Simple transition metal salts such as ferrous or ferric chloride,
cuprous or cupric chloride, ferrous or cupric sulfate, ferrous gluconate, nickel
sulfate, or cobalt chloride, are suitable as catalyzing agents for the ascorbates,
and of these salts, cupric or ferric sulfates are preferred. The transition metal
chelates are particularly useful because, when utilized in the appropriate amounts,
they possess oxygen scavenging properties which augment the oxygen scavenging properties
of the ascorbate compound, thus making the transition metal chelate a secondary
scavenging compound, while the transition metal ion in the chelate or complex can
catalyze the oxygen scavenging activity of the ascorbate compound.
Of the chelated ion complexes, transition metal chelates of ethylene
diamine tetracetic acid ("EDTA") are advantageous, with monoferrous disodium EDTA
[Fe++/EDTA/2Na+] being the most preferred. Transition metal
chelates of polyalkylpolyamines are also useful, with those amines having symmetrical-length
carbon chains between adjacent nitrogen atoms being preferred. The most preferable
of those amines have symmetric carbon chains which each comprises between one
and four, and optimally two, carbon atoms. Transition metal chelates of salicylates
or salicylate salts can also be used in practicing this invention. As noted above,
each of these chelates provides oxygen scavenging activity to augment that of the
ascorbate, while the transition metal ion catalyzes the ascorbate compound when
exposed to moisture.
In an embodiment of the invention, the oxygen scavenging composition
includes an organic compound as defined above and a transition metal complex or
chelate of a polycarboxylic or salicylic acid dispersed relatively uniformly through
the carrier. The polycarboxylic acid is preferably an amino polycarboxylic acid,
and most preferably EDTA. Other useful polycarboxylic acids include ethylene diamine
triacetic acid, hydroxyethylene diamine triacetic acid, diethylene triamine pentaacetic
acid or trans-1,2-diamino cyclohexane tetraacetic acid.
It is also possible to utilize other polycarboxylic acids, such as
citric and oxalic acids, which are capable of forming a chelate with the transition
metal. Such polycarboxylic acids may also contain one or more amine hydroxyl,
carboxylate or sulfhydryl groups, or combinations thereof. Alternatively, transition
metal chelates or complexes of salicylic acid or salicylates, whether or not substituted,
can also be used instead of the amino polycarboxylic compounds. Salts of any of
these acids are also suitable.
It is also possible, and in some cases preferred, to include a reducing
agent, such as an ascorbate compound, in the polymer in an amount sufficient to
enhance, preserve or augment the oxygen scavenging properties of the transition
metal chelate or complex. The ascorbate reduces the oxidation state of the transition
metal ion of the chelate so that the ion can be oxidized when the chelate contacts
oxygen. This enhances the oxygen scavenging properties of the chelate. A particularly,
preferred combination illustrates this embodiment of the invention is monoferric
monosodium EDTA [Fe+++/EDTA/Na+] in combination with sodium
ascorbate as a reducing agent. Ascorbic acid, in its D- or L- form, or a derivative,
analog or salt thereof, as described above, may be used as a preferred reducing
agent, since it has oxygen scavenging properties.
Preferred polymers for use as carriers include polyolefins, PVC,
polyurethanes, polyamides and elastomers. PVC, EVA and PE are typically utilized,
but PET, PP, and other olefins, ethylene/alpha-olefin copolymers, ethyl octene
copolymers, various thermoplastic (or other) polyurethanes, elastomers, such as
isoprene rubber, nitrile rubber, chloroprene rubber, silicone rubber, or other
rubber analogs, and other thermoplastic materials such as chlorinated polyethylene
("CPE"), SURLYN™, or various combinations or mixtures thereof, are acceptable.
In addition, sprayed or dipped coatings of epoxies, polyesters or other conventional
coating materials are useful as carriers for the oxygen scavenging compositions
of the invention.
The most preferred polymers or other materials which may be used
as the carrier are those which are pervious to water vapor at room temperature,
so that exposure to elevated temperatures is not necessary to activate the oxygen
scavenging capabilities of the composition. The oxygen scavenging material is uniformly
dispersed in and throughout the carrier by a direct mixing technique. Advantageously,
the oxygen scavenging material is mixed or blended into the carrier in a dry state.
The oxygen scavenging capabilities of these compositions are later activated by
contact with water or water vapor which permeates into or through the carrier.
The water vapor may be provided by the package contents or, for dry contents,
may be introduced separately before sealing the package.
One use of the invention includes use as a package (for, e.g., a
foodstuff, beverage, or pharmaceutical product) comprising means for supporting
or retaining the product, and an oxygen scavenging composition material as described
above in contact with the product (or in contact with the environment between
the product and the package) for scavenging oxygen therefrom so as to avoid detrimental
effects to the performance, odor or flavor properties of the product.
The oxygen scavenging composition may be present on an inside surface
of the product supporting or retaining means. This means can be in the form of
a carrier film, with the oxygen scavenging composition being dispersed relatively
uniformly throughout the carrier film. If desired, one or a plurality of polymer
films may be used, with at least one layer of adhesive or binder therebetween,
with the oxygen scavenging composition being present in at least one of the polymer
films or layers. Also, the oxygen scavenging composition can be applied as a coating
or lining upon the inside surface of the product supporting or retaining means
to function as a barrier to oxygen permeation.
The invention is also useful in containers for water-containing foodstuff,
beverage, chemical or pharmaceutical products comprising means for retaining the
product and having at least one opening therein for tilling or dispensing of the
product; a member for closing the opening and preventing escape of the liquid product
when not desired; and a liner or gasket comprising one of the oxygen scavenging
compositions described above and being positioned adjacent the closing member.
Preferably, the retaining means is a can, jar or bottle, the closing member is
a crown or closure, and the polymer of the liner or gasket comprises a polyurethane,
PVC, EVA or PE. The retaining means may also be a metal can or glass jar, with
the closing member being a lid therefore. In this variation, the oxygen scavenging
composition may be applied to the lid in the form of a ring, a spot, or coating.
Also, the oxygen scavenging composition may be applied to the interior of the can
as a coating, generally of an epoxy or polyester carrier. When a metal can is
used, it is usually provided with a seam. Thus, it is possible to apply the oxygen
scavenging compositions of the invention as a sealant in or upon the seam to prevent
oxygen ingress into the can through the seam.
Another use of the invention includes use in an oxygen scavenging
container which may be made from any one of the compositions of the invention described
above. Yet another use includes a multilayer container or closure where one or
more layers comprise the oxygen scavenging compositions of the invention. Also,
these compositions may be used as a sealant for, or in an article trapped by the
closure methodology for packaging which does not include an identifiable closure
which is differentiable from the material of the container itself.
In preferred embodiments, the concentrates of this invention contain
about 10 to 50% oxygen scavenging material and about 0.3 to 8% catalyzing agent,
depending, of course, on the desired use of the concentrate and the particular
components employed. In one specific embodiment, the concentrate includes about
10 to 50% by weight sodium ascorbate and about 0.3 to 8% by weight copper sulfate
in a polyethylene carrier. Of course, other carriers such as ethylene vinyl acetate
or polyvinyl chloride are suitable for many embodiments.
In a further aspect of the invention, a two-part composition and
method for using such composition is provided. The two-part system includes separate
oxygen scavenger and catalyst concentrates which are combined to obtain the final
reactive composition. In some embodiments, additional base resin is added to dilute
the concentrates during the combination step. Each concentrate includes a carrier
that is typically a resin or other material described in connection with the embodiments
described above. The concentrates also include either an oxygen scavenging material
or catalyzing agent (as described above), but not both. Thus, the oxygen scavenger
concentrate includes an oxygen scavenging material dispersed throughout a carrier
that is substantially free of catalyst. Likewise, the catalyst concentrate includes
a catalyst dispersed throughout a carrier that is substantially free of oxygen
scavengers. In this context, a composition is "substantially free" of a component
when that component is present in a sufficiently small quantity that it has no
effect on the desired activity of the composition. Thus, for example, an oxygen
scavenger concentrate that is substantially free of catalyst can be extruded and
quenched in water without undergoing reactions that consume the oxygen scavenger.
A further understanding of the nature and advantages of the inventions
herein may be realized by reference to the remaining portions of the specification
and the attached drawings.
Detailed Description of the Invention
The oxygen scavenging compositions of the invention include certain
preferred combinations of oxygen scavenging and catalyzing agents which are added
to and dispersed in and throughout a carrier for these agents.
The most preferred oxygen scavenging agent of the invention is an
ascorbate compound which is used in combination with a transition metal chelate
of EDTA. The term "ascorbate compound" is used to include ascorbic acid in either
its D or L form and any derivative, analog or salt thereof, including erythorbic
acid. In particular, D- or L-ascorbic acid, and their sodium, potassium or calcium
salts, or fatty acid derivatives may be used in this invention. Certain of the
above, especially the sodium ascorbate salts, are particularly preferred since
these materials are widely accepted for contact with food and have achieved "Generally
Recognized As Safe" (or "GRAS") status with the U.S. Food and Drug Administration
for such applications.
An advantage in practicing this invention is that the oxygen scavenging
compositions do not become active for scavenging oxygen until they contact water
or water vapor. Thus, the selected composition or compound is dispersed relatively
uniformly throughout a carrier which is permeable both to oxygen and water or water
vapor. Thereafter, when the carrier is used in an application adjacent to or in
the vicinity of a water bearing foodstuff, pharmaceutical, chemical, or beverage,
water or water vapor will permeate into the carrier and thus activate the ascorbate
compound for removal of oxygen. By retaining the carrier in a dry environment
prior to use, the oxygen scavenging compound will remain essentially dormant until
activated. For dry products, the oxygen scavenging ability of the compound or
composition may be activated by exposure to non-product water or water vapor before
sealing the container.
The inclusion of a catalyzing agent with the ascorbate compound greatly
enhances the rate of oxygen scavenging after the ascorbate compound is activated
by exposure to water or water vapor. It has been found that a transition metal
compound, in the form of an organic or inorganic salt, or as a complex or chelate,
is useful in accelerating (i.e., catalyzing) the rate of oxygen scavenging by
an ascorbate compound. The preferred catalysts include the transition metal chelates
of EDTA. The most preferred catalysts are the iron complexes of EDTA or sodium
salts thereof. Monoferrous disodium EDTA [Fe++/EDTA/2Na+]
and monoferric monosodium EDTA [Fe+++/EDTA/Na+] are the most
preferred chelate. It is also suitable to use a simple iron or copper salt, such
as iron chloride or sulfate or copper chloride or sulfate. Typically, the carrier
is mixed with the ascorbate compound for uniform dispersion throughout the carrier.
Subsequently the catalyst is added to form the desired composition which is activated
by contact with water or water vapor which permeates the carrier. The combination
of an ascorbate and transition metal compound enables the ascorbate compound to
be oxidized rapidly at low pH values (e.g., at pH values between 4 and 5) which
are typically encountered in many foods including bottled beer and many fruit juices.
The catalyzing agent may also act as an additional oxygen scavenger
Amino polycarboxylates, such as EDTA, and other polycarboxylates, optionally containing
hydroxyl moieties, as well as their salts or other derivatives, are representative
examples of preferred compounds which can be complexed with lower oxidation states
of transition metal ions and used in this invention. Transition metal chelates
of hydroxyethylene diamine triacetic acid, diethylene triamine pentacetic acid,
or trans-1, 2-diamino cyclohexane tetracetic acid can also be used as suitable
catalyzing agents and oxygen-scavenging compounds. Other transition metal chelates
containing one or more amine, hydroxyl, carboxylate or sulfhydryl groups, or combinations
thereof, may also be used.
These chelates are effective oxygen scavengers because the transition
metal ion of the chelate becomes oxidized when the chelate contacts oxygen. It
is well known that elements such as the transition metals can exist in any one
of a number of oxidation states. Thus, the use of lower oxidation of transition-metal
ions is necessary for an appropriate degree of oxygen scavenging. This lower oxidation
state can be achieved in two ways: one is to utilize chelates state transition
metals in their lowest oxidation state (e.g., ferrous, cuprous, etc) Alternatively,
when the transition metals are present in the chelate in their higher oxidation
states (e.g., ferric, cupric, etc.), a reducing agent can be used to covert the
metal ion to a lower oxidation state thus imparting oxygen scavenging properties
to the chelate. As noted above, the preferred reducing agents are the ascorbates.
In a further embodiment of the invention, a transition metal (preferably
iron) chelate of a particular salicylate salt, in particular Fe+++/Sal3/3Na+3NaCl
where Sal =
can be used as the oxygen-scavenging material. Instead of this material, a wide
variety of other salicylates can be used, including
where M is a transition metal, Y is an alkali metal such as Na, K, Ca or H, and
R1 and R2 are carbon atoms or part of a benzene ring, or
where M is a transition metal, X is (CH2)m Z(CH2)m
with m being an integer, Z is N or C=C with the proviso that if Z is N then N
is also bonded to M, and R1 and R2 are carbon atoms or part
of a benzene ring.
These salicylates are effective as oxygen scavengers because they
react with oxygen to become oxidized. In addition, selection of a transition metal
in its lower oxidation state enhances the oxygen scavenging performance of these
chelates. As noted above, if transition metals in their higher oxidation state
are utilized in these chelates, the oxygen scavenging properties of the chelate
can be further enhanced by the incorporation of a reducing agent into the composition.
Again, the ascorbates are preferred reducing agents for the reasons given above.
A wide variety of carriers (or mixtures thereof) may be used in accordance
with the teachings of the present invention. For use in applications such as crown
or closure liners, the carrier is preferably a polymeric thermoplastic, such as
PVC, EVA, PET, PE or PP, or polyurethane. As noted above, PVC liners are well known
for use in crowns. There is also well-known technology for making aluminum or plastic
closures containing EVA liners. Thus, one of the preferred uses of the compositions
of the invention is a liner or gasket in a crown or closure for capping a beverage
bottle. Entire closures may also be made of plastics containing the compositions
of the invention (e.g., all-plastic screw-on threaded caps for soft-drink bottles,
and the like).
In addition to its use as a crown or closure liner, the compositions
of the invention may also be used in the form of a film for packaging materials.
Such films are preferably made of PE, PP, PVC, or SURYLYN™, a DuPont Corporation
polymer. The oxygen scavenging compositions of the invention could also be used
for forming containers; in this situation the polymer is preferably PET, PVC, or
PE. Other polymers which are contemplated by the invention include silicones as
well as elastomers such as isoprene rubber and its rubber-like analogs: nitrile
rubber, chloroprene, EPDM, etc. Silicone rubber can also be used in some situations.
The only requirements of the polymer are that it can be processed in a manner which
allows the oxygen-scavenging composition to be dispersed relatively uniformly
throughout and that the polymer be permeable to oxygen and water or water vapor.
Another application of the compositions of the invention would be
as a sachet, packet or pellet which is mounted on a support and then attached to
a crown or other container lid or to the container itself in the form of an article,
such as a ring or spot, or as a coating. Thus, the compositions can be applied
to a wide variety of jar lids and caps which are used for retaining food substances
therein. Again, however, one preferred use of the compositions of the invention
is in connection with foodstuffs which contain water so that the oxygen-absorbing
compounds is activated by contact with water or water vapor which permeates into
the polymer. The compositions may also be used with dry products by pre-activating
the composition via exposure to water or water vapor shortly before sealing the
Other uses for the compositions of the invention will be readily
apparent to those of skill in the art. By way of example, the uses include metal
(i.e., aluminum or tinplate) cans for beverages. It is also contemplated to prepare
plastic bottles or other styles of containers (e.g., tubs, cans, etc.) from or
incorporating the compositions of the invention. Another preferred use of the composition
of the invention is as a gasket or liner applied to an aluminum or plastic closure
or metal crown for plastic or glass bottles. The oxygen scavenging composition
of the invention may also be incorporated into the materials used as an adhesive
between adjacent layers of plastic or incorporated into the adhesive which holds
adjacent layers together.
Other embodiments of the present invention are readily apparent to
those skilled in the packaging arts, all of which embodiments fall within the scope
of the invention and are intended to be included therein. For instance:
1) Many packages are constructed of transparent plastic films so that the product
may be seen by the purchaser. Such packages usually have printed decoration incorporated
therein, often actually printed on a central layer of a multi-layer film so as
to avoid the possibilities of both ink-contamination of package contents and rubbing
off of the printing during handling. An oxygen-scavenging composition of the present
invention might be unobtrusively incorporated into such a package by being printed
onto the central layer underneath the decorative or informative printing.
2) For other packages which do not comprise a separate closure (e.g., sterile
or refrigerated "brick-packs" such as often used for fruit juices and the like;
gable-top packages such as milk cartons; containers made to have the contents
expressed therefrom and not be resealed, such as individual portions of condiments;
or various film or foil bags made to be torn open and not resealed, such as potato
chip bags) a composition of the present invention may be incorporated into the
sealant or gasketing material used to hold the package closed. For example, oxygen-scavenging
compositions of this invention can be printed onto the head space region of the
package. Alternatively, the compositions can form a laminated insert in the package.
3) Likewise, the composition of this invention might be applied as a paint
or coating attached to the interior of the container, or as a tape or similar item
protruding into or exposed to the interior of the package and mechanically held
in place by the closing mechanism or technique.
4) There may be instances in which the oxygen scavenger compositions of the
present invention must be separated from the product: in such cases the compositions
may again be incorporated into an interior layer of a multilayer container.
5) The compositions of this invention may conveniently be combined with solutions
to other manufacturing problems. For example, a common problem in plastics manufacturing
today is to safely recycle previously-used plastic plastics into food-safe containers.
Much recycled plastic may have been used as containers for random unknown materials,
and the recycled plastics may therefore contain traces of materials not acceptable
for food contact, and may also be composed of an admixture of plastics highly
and minimally pervious to oxygen. Use of such recycled materials, combined with
the compositions of this invention, as an inner layer in multiple-layer container
construction would allow much easier use of mixed-recycle materials.
In the plastics manufacturing art, "master batches" or concentrates
of various sorts are sometimes used in the preparation of final mixtures of materials
for eventual use in manufacturing finished articles. In the present invention,
preparation and use of highly concentrated forms of oxygen control chemicals in
carrier (e.g., PVC, plastisol, epoxy can coatings, gasketing, spray, roll-on,
and dip coatings, and the like) is convenient in the manufacture of the composition
which will eventually be used as final oxygen-scavenging compositions. The present
invention lends itself readily to such practices, which are fully within the scope
contemplated for the invention.
The resin concentrate form of this invention is particularly useful
for shipping and storing oxygen scavenging compositions. It is much easier to handle
than the uncombined oxygen scavenger and catalyst powders, and it is lighter and
therefore more convenient to ship and store than the final diluted compositions.
Further, it is easier to protect concentrates against humidity conditions which
could prematurely inactivate component ingredients. For example, the concentrate
can be shipped in sealed 55 pound bags. When the final fitment, film, or other
form of the composition is to be produced, the concentrate is diluted with a base
resin to obtain an oxygen scavenging composition having the concentration and form
required for the end product. For example, the end user can combine the concentrate
with a base resin in appropriate processing machinery.
Preferably, the concentrate is diluted in a ratio of between about
1:38 and 1:1, and more preferably between about 1:13 and 1:1 concentrate to base
resin. In these concentrate formulations, it is preferred to use an amount of
oxygen scavenging compound ranging from about 10 to 50% by weight and more preferably
from about 20 to 40% by weight (i.e., between about 500 and 2500, and preferably
between 1000 and 2000 micromoles of scavenger compound per gram of polymer for
compounds having molecular weights of between 200 and 500 grams per mole). When
an ascorbate is used as the scavenger, the catalyzing agent of the transition
metal element compound or complex may be used in an amount of about 0.3 to 8% by
weight (i.e., between 40 and 200 micromoles per gram of polymer). More preferably,
the catalyzing agent is used in an amount of about 0.6 to 2% by weight.
In some preferred embodiments, two separate concentrates are employed,
one containing the oxygen scavenging compound and the other containing the catalyst.
The oxygen scavenging compound is preferably present at a concentration ranging
from about 10 to 50% by weight and more preferably from about 20 to 40% by weight
in the first concentrate. The catalyzing agent is preferably present at a concentration
ranging from about 0.3 to 8% by weight and more preferably from about 0.6 to 2%
by weight in the second concentrate. The carrier resin in the two concentrates
may be different but they should be compatible with each other in the final oxygen
scavenging composition. The two concentrates are combined in a ratio that depends
upon the particular application. By providing separate concentrates, a master
batch is provided that is not oxygen reactive and can be diluted to a lower concentration
at the time a film, part, or fitment is made. This allows the master batches to
be water quenched without loss of activity during a processing step such as twin
screw compound extrusion. It also allows flexible control of the ratio of oxygen
scavenger to catalytic agent. Generally, the ingredients for the concentrates
are well mixed, using low sheer and good temperature control. In subsequent processing,
storage or transport, the concentrate should not be exposed to moisture. In some
cases, drying of the master batch prior to extrusion as well as storage of the
resulting pellets in high moisture barrier bags is necessary.
When a PAPA chelate, macrocyclic chelate or amino polycarboxylic
acid or salicylic acid chelate of a transition metal ion is used as the catalyzing
agent in the compositions of this invention, these chelates may also be used to
augment the oxygen scavenging properties of the ascorbate compounds. To do so,
such chelates should include a lower oxidation state transition metal ion and be
used in an amount of between about 0.3 and 33 and preferably, 2.5 to 15 parts
per weight based on 100 parts by weight of the polymer (i.e., between 10 and 500,
and preferably 50 to 300 micromoles per gram of polymer). Preferred transition
metal chelates include polyalkyl polyamines or macrocyclic amine chelates of transition
metal ions such as iron, copper, nickel or cobalt. In these polyalkyl polyamine
chelates, equal length carbon chains are utilized between adjacent nitrogen atoms,
preferably those chains having between 1 and 4, and optimally 2, carbon atoms.
Other transition metal chelates containing one or more amine, hydroxyl,
carboxylate or sulfhydryl groups, or combinations thereof, may also be used to
augment the oxygen absorbing properties of the composition. Transition metal chelates
of salicylates or salicylate salts; amino polycarboxylates, such as EDTA; and other
polycarboxylates, optionally containing hydroxyl moieties, are representative
examples of suitable compounds. Hydroxyethylene diamine triacetic acid, diethylene
triamine pentaacetic acid, or trans-1,2-diamino cyclohexane tetraacetic acid can
be used. As noted above, however, the transition metal ion should be in a lower
oxidation state. Thus, monoferrous disodium EDTA [Fe++/EDTA/2Na+] would
be preferred, while monoferric monosodium EDTA [Fe+++/EDTA/Na+] would
be used in combination with a reducing agent, such as sodium ascorbate.
In another embodiment of the invention, the oxygen scavenging compositions
may be treated to maintain these agents in a dry state before they are dispersed
relatively uniformly throughout the polymer. Numerous methods are known for maintaining
this dry state, and freeze drying, spray drying, or microencapsulation are preferred
due to simplicity of processing. Thereafter, the oxygen scavenging composition
will be activated by contact with water or water vapor which permeates into the
polymer. Techniques for freeze drying and microencapsulation are well known in
the art, and one skilled in the art can select the appropriate encapsulant for
the intended application. By such appropriate selection of the encapsulating material,
one may protect the enclosed oxygen scavenging compound from the oxygen in air;
this would allow longer storage of the prepared oxygen scavenger. After freeze
drying, spray drying, or microencapsulation, the materials are then blended with
the appropriate carrier and manufactured into the final composition, form and configuration
for use in, on or as the product packaging.
By way of example, one way of distributing the oxygen scavenging
material throughout a carrier is by preparing direct blend polymers as "master
batch" concentrates. As noted above, such concentrates are often preferred because
they contain less inert material and are therefore less expensive to manufacture,
store and ship. For preparation of a concentrate or "master batch" which will be
diluted during manufacture of the final compositions, very high weight percentages
of oxygen scavenging ingredients (up to, e.g., greater than 40% and even up to
50%) may be used. Beads of a polymer carrier, such as polyvinyl chloride, low density
polyethylene, or ethylene vinyl acetate, are placed between the rollers of a polymer
forming mill operating at about 300°F. The back roller of the mill operates at
a higher velocity than the front roller. The rollers spin in opposite directions,
so that the beads are sheared downward therebetween. As the polymer beads become
fluid they spread across the front roller at the thickness set between the rollers.
After the PVC has become heated and softened, the oxygen scavenging
compounds to be blended into the polymer are slowly poured into the space between
the rollers. The mixing of PVC, LDPE, or EVA and compound is then achieved by
cutting the polymer to the center of the mill and then allowing it to spread back
out over the roller. This is done 20-30 times until the compounds are well mixed.
The mixing may also be done in the standard ways of commercial preparation of
various plastic formulations, e.g., by simple addition of oxygen absorbing materials
of the invention as an additional ingredient during bulk "dry mixing" of PVC,
plasticizer, and other components. In some preferred embodiments, a Banbury style
batch mixer or a twin screw continuous mixer of the type commonly used in the resin
industry is used to combine the base resin with oxygen scavenging ingredients.
The following examples illustrate preferred embodiments of the invention.
In each example, the formulation components are designated in parts by weight
unless otherwise indicated.
Crown liners were prepared from PVC resin containing the oxygen scavenging
and catalyzing agents shown in Table I. These liners were placed in bottle crowns
which were then used to cap fresh bottled beer. Oxygen measurements were made
in six replicate samples immediately after sealing and pasteurizing the bottles,
and again after seven days of storage at room temperature. These oxygen measurements
were made using a polarographic oxygen probe device from Orbisphere, Inc. Results
are shown below in Table I.
Samples (µ moles) Component Initial Control F G H I Sodium Ascorbate----50112.5250250 FeCl2----555-- CuSO4----------5 Oxygen Content* (ppb)415.4229.1135.1106.683.2121.4
* The control and samples F-I were measured after seven days.
These data show that beer, itself, consumes oxygen, which is one
cause for the normal limited shelf life of this product. The use of a crown liner
made of one of the polymer compositions of the invention results in removal of
oxygen over and above that which is normally consumed by the beer. Moreover, the
greater the amount of ascorbate used for a particular catalyst, the greater the
amount of oxygen that is removed.
A standard PVC lining compound was heated and mixed on a two roller
mill via standard practice.
When the proper degree of fluidity was reached, the oxygen scavenging
ingredients were added and mixed into the compound. Sheets of compound were removed
from the mill, cooled, and cut into pieces small enough to fit into a gas measurement
cell. Results are as follows:
The data shows that a standard PVC lining compound will react to
a small extent with oxygen. The addition of only sodium ascorbate (i.e.,
without a source of transition metal catalyst) very slightly increases the reactivity.
Ferrous EDTA has a significant effect on the amount of oxygen scavenged. The combination
of ferrous EDTA and sodium ascorbate, however, causes a disproportionate increase
in oxygen scavenged. Both ferrous EDTA by itself and in conjunction with sodium
ascorbate demonstrate significant oxygen removal.
Other compounds may advantageously be used in practicing this invention.
For example, salicylic acid is a strong chelator for Fe+++ (and less
so for Fe++): the iron of the "chelated Fe++" form will rapidly
oxidize in the presence of oxygen, analogously to the behavior of Fe++
EDTA used in experiments previously described herein. Consequently, an iron complex
of salicylic acid (or a salt thereof) is also useful in practicing the present
invention. The Fe+++ (salicylic acid)3 complex is less soluble
in aqueous solution than is the comparable Fe++ EDTA complex; consequently such
salicylic acid complexes should yield lower rates of leach from container or gasket
materials (wherein they are incorporated) into the contained products. Use of
these oxygen-scavenging materials would be preferred when the consideration is
to minimize the leaching of package components.
Furthermore, it is preferable to utilize the Fe+++
acid)3 complex in combination with an ascorbate as detailed above, so
that the transition metal ions from the complex can serve to catalyze the aerobic
oxidation of the ascorbate, and/or the ascorbate can reduce the oxidation state
of the ferric ion.
The following experiment illustrates the utility of this combination.
120 micromole/gram finished plastic of Fe+++
acid)3 and 200 micromole/gram finished plastic of sodium ascorbate were
blended together into PVC crown lining materials in accordance with techniques
known in the art and as described above.
The resulting plastic material was used to form completed, lined
crowns using standard crown making machinery. To test for oxygen uptake capacity,
completed liners were then removed from drown shells, wetted with 8% ethanol beer
simulant, and placed in glass test chambers filled with air. Oxygen absorption
was measured versus time as change in percent oxygen in the air in test chambers
for replicate liners. The samples were analyzed using a gas chromatograph with
a mass selective as is well known in the art. The results are as follows:
Sample micromoles O2 Absorbed (normalized to "per gram of liner") at Hour 3 6 micromoles O2 Absorbed (normalized to "per gram of liner") at Hour
27 R14.028.6 S10.526.7 T10.526.1
To attain the desired combination of characteristics (e.g.,
low leach rate plus high oxygen absorption potential), certain modifications to
simple salicylate salts/complexes suggest themselves. For instance, leach rates
might be appreciably lowered by chemically modifying the salicylic complex to be
more hydrophobic, hence, less soluble in aqueous media. Certain of these modifications
are included in the formulae for suitable salicylic acid derivatives described
A concentrated low-density polyethylene (LDPE) oxygen scavenging
polymer ("master blend") containing 41 weight percent sodium ascorbate and 0.6
weight percent copper sulfate (anhydrous) was prepared as follows. LDPE base resin
(Quantum Chemical Corporation, Cincinnati, Ohio) was mixed with the oxygen scavenging
ingredients in a Banbury style mixer. The resulting mixture was converted into
sheets on a two-roll mill which were then chopped into pellets and extruded into
To measure oxygen uptake, the thin films were punched into 15/16"
diameter disks and accurately weighed. The disks, one each, were placed in glass
bottles containing 370 mL of air saturated water and no headspace gas and closed
with a crown closure. Twice each day, the bottles were agitated to mix the water
in the bottle, eliminating oxygen concentration gradients in the bottle. Dissolved
oxygen concentration was measured using a polarographic oxygen sensor and the
oxygen uptake was calculated by calculating the difference in oxygen concentration
between bottles containing the disks and bottles containing no polymer. In general,
five containers were measured at each time point.
The oxygen uptake from 2000 µmole/g ascorbate scavenger and 40 µmole/g
catalyst (normalized using a 0.3 g disk) was 310±70 µmoles O2/g polymer
after 24 hours. At that time, all the available oxygen had been consumed from
the container (91 µmoles of O2 available in the bottle).
Oxygen uptake from 1000 µmole/g ascorbate scavenger and 20 µmoles/g
catalyst was observed as follows:
The total oxygen capacity of the oxygen scavenging polymer was also
determined. In this case, samples of the above polymers (at 1000 and 2000 µmole/g
ascorbate loading) were frozen in liquid nitrogen and ground in a small grinding
mill until all the particles were smaller than 15 mesh. The sample was then dried
in a beaker for 1 hour at 50°C. A sample theoretically capable of scavenging 900
µmoles of oxygen (1/2 the oxygen in the container) was added to a 215 mL container
containing 6 mL of water. The container was closed with a crown closure and stored
at 50°C and measured 10, 14 and 21 days after bottling.
The total oxygen capacity from 2000 µmole/g ascorbate scavenger and
40 µmole/g catalyst was 2540 µmoles/gram polymer, 127% of the theoretical capacity.
The oxygen uptake from 1000 µmole/g ascorbate scavenger and 20 µmoles/g
catalyst was 1350 µmoles/gram polymer, 135% of the theoretical capacity.
The master blend from Example 4 was used to make thin films 0.001
to 0.050 inches in compositions containing ratios of concentrate to base resin
of 1:0, 1:1, 1:3, and 1:7. The dilution was accomplished by shaking the desired
ratio of master batch and base resin in a clear plastic bag and then dumping the
contents into the desired processing equipment. In all the processes, the resin
mixture containing mater batch was heated to a molten state and mixed before extruding,
blowing film or injection molding. The resulting films were used in ketchup closures,
cosmetic closures and fragrance closures. In each case, the appropriate loading
of oxygen scavenging material, in the form of tape, was glued to the inside of
the gasket of a closure. In the case of ketchup, the headspace oxygen content
monitored during the first 6 weeks was as follows. The container was a PET bottle
with an oxygen transmission rate of 0.04-0.05 cc/package/day.
Headspace oxygen content was measured using an Ingold Instruments
polarographic oxygen sensor model IL 307 with a soft package sampling device. To
measure the bottle, a septum was applied to the outside of the inner seal of the
closure and the inner seal was pierced by the sampling device. The gas inside
the bottle was then analyzed for oxygen content by the Ingold analyzer.
Color evaluations were taken after 4 months using a Hunter Color
Analyzer. After four months, projected ketchup shelf life in the oxygen scavenger
closure package was judged to be 20 months, and the control was judged to be 14
The concentrate was also diluted in ratios of 1:13, 1:19, and 1:39
with base resin to form injection molded fitments. The fitments were made with
Dowlex 2553 (Dow Chemical Co., Midland, MI) as the base resin. These fitments
were tested on ketchup in a barrier bag. The barrier bag was a multi-layer polymer
bag with an oxygen transmission rate of 0.05 cc/1002in/day. The fitments
were heat sealed into the inside of the bag before the bag was made. One set of
samples was held at 90 degrees Fahrenheit and the another set was held at 100 degrees
Fahrenheit. After 75 days, color evaluations were made using the Hunter Color
Analyzer. No control was run but the bag with the best color retention was the
bag containing the 1:13 letdown of the oxygen scavenging concentrate. The difference
in effectiveness between the fitments was most pronounced near the top of the
bag. In the body of the bag, away from the fitments, the effect was much less pronounced.
The method described in Example 4 was used to prepare a concentrate
of ethylene vinyl acetate (ELVAX 450, DuPont Company, Wilmington, DE) having a
19.8 weight percent sodium ascorbate loading and a 0.3 weight percent copper sulfate
The film was made by extruding the EVA compound from a Brabender
extruder with a 1 inch wide ribbon die. The tape samples were evaluated for oxygen
capacity using the method outlined in Example 5. The oxygen uptake from 1000 µmole/g
ascorbate scavenger and 20 µmoles/g catalyst was as follows:
The total oxygen uptake from 1000 µmole/g ascorbate scavenger and
20 µmoles/g catalyst was 1380 µmoles/gram polymer, 138% of the theoretical capacity.
The master batch LDPE concentrate of Example 4 was combined with
LDPE resin in a ratio of 1:1 and 1:7 and made into the following multilayer films:
(A) a 3-layer film containing LDPE: Master Batch/LDPE (1:1): LDPE; and (B) a five
layer film containing LDPE: Master Batch Tie-layer Resin (7:1): EVOH: Master Batch/Tie-Layer
Resin (7:1): LDPE. The multilayer films were prepared using three one inch Killion
Extruders with a coat hanger design Killion combining adapter. The extruder was
configured in an ABCBA design, capable of extruding 3 different polymers in 5
layers. In each case, the die gaps were adjusted so that each layer was of equal
thickness. Film thickness for the 3 layer films ranged from 0.005" to 0.010" and
for the 5-layer films they ranged from 0.003" to 0.005".
Oxygen transmission rates of the films were measured using a Mocon
Oxtran 100 with a Macon DL200 Oxygen Rate Data Logger. To measure oxygen transmission
rates, moist nitrogen was passed on both sides of a sample film until no oxygen
was detected. Then moist air was blown across one side of the film and the quantity
of oxygen migrating through the film was measured. The oxygen transmission rate
of the 3-layer LDPE films decreased between 2 to 13 times less than the controls,
depending upon pretreatment processes. The Mocon results are shown in the following
Oxygen transmission rates of the 5-layer films showed that the oxygen
transmission rate of the film did not change when exposed to extreme heat and humidity.
In contrast, the oxygen transmission rate through a typical 5-layer EVOH laminate
increases 10 to 100 times during exposure to extreme head and humidity as experienced
during typical retort cycles (40 minutes @ 250°F and 100% RH).
Sauerstoff-Fänger-Konzentrat, umfassend einen polymeren Träger, der sowohl für
Sauerstoff als auch Wasser oder Wasserdampf durchlässig ist; eine organische Verbindung,
die in einer Menge im Bereich von 10 bis 50 Gew.-% des Konzentrats relativ gleichmäßig
im polymeren Träger dispergiert ist, wobei die organische Verbindung erst nach
Aktivierung mit Wasser oder Wasserdampf, das/der den polymeren Träger durchdringt,
mit dem Sauerstoff reaktiv ist; und einen Katalysator in einer Menge, welche die
Reaktionsgeschwindigkeit der organischen Verbindung mit Sauerstoff, der im polymeren
Träger vorhanden ist oder diesen durchdringt bzw. in diesen eindringt, wirksam
Konzentrat nach Anspruch 1, worin die organische Verbindung eine oxidierbare
organische Säure oder ein Derivat davon ist.
Konzentrat nach Anspruch 1, worin die organische Verbindung D- oder L-Ascorbinsäure
oder ein Salz oder ein Fettsäurederivat davon ist.
Konzentrat nach Anspruch 1, worin die organische Verbindung ein Natrium-, Kalium-
oder Kalziumsalz von D- oder L-Ascorbinsäure oder ein Fettsäurederivat davon ist.
Konzentrat nach Anspruch 1, worin der Katalysator Eisen, Kupfer, Nickel oder
Konzentrat nach Anspruch 1, worin der Katalysator ein(e) Übergangsmetallverbindung,
-komplex oder -chelat ist.
Konzentrat nach Anspruch 6, worin die Übergangsmetallverbindung als Sulfat-
oder Chloridsalz bereitgestellt ist.
Konzentrat nach Anspruch 7, worin die Übergangsmetallverbindung Eisensulfat,
Eisenchlorid oder Kupfersulfat ist und in einer Menge von 0,3 bis 8 Gew.-% des
Konzentrats eingesetzt wird.
Konzentrat nach Anspruch 1, worin die organische Verbindung Natriumascorbat
ist und der Katalysator Kupfersulfat ist.
Konzentrat nach Anspruch 1, worin der Träger ein Polymer ist, das aus der aus
Polyethylen, Ethylen-Vinylacetat-Polymer, Polyvinylchlorid, Ethylen-Vinylalkohol-,
Ethylen/α-Olefin-Copolymeren und Ethylocten-Copolymeren bestehenden Gruppe
ein erstes Konzentrat, das einen ersten polymeren Träger umfaßt, der im wesentlichen
frei von Katalysatoren ist, und
ein Sauerstoff-Fänger-Material, das in einer Konzentration von zwischen 10 und
50 Gew.-% im ersten polymeren Träger dispergiert ist und nur in Gegenwart von Wasser
oder Wasserdampf mit Sauerstoff reaktiv ist; und
ein zweites Konzentrat, das einen zweiten polymeren Träger umfaßt, der im wesentlichen
frei von Sauerstoff-Fänger-Material ist; sowie
einen Katalysator, der in einer Konzentration zwischen 0,3 und 8 Gew.-% im
zweiten polymeren Träger dispergiert ist, wobei der Katalysator, wenn er in einer
vorbestimmten Menge mit dem Sauerstoff-Fänger-Material kombiniert wird, die Reaktionsgeschwindigkeit
des Sauerstoff-Fänger-Materials mit Sauerstoff erhöht.
System nach Anspruch 11, worin der erste und der zweite polymere Träger gleich
System nach Anspruch 11, worin das Sauerstoff-Fänger-Material eine Ascorbatverbindung
System nach Anspruch 13, worin das Sauerstoff-Finger-Material Natriumascorbat
System nach Anspruch 11, worin der Katalysator Kupfersulfat ist.
System nach Anspruch 11, worin der erste und der zweite Träger aus der aus
Polyethylen, Ethylen-Vinylacetat, Polyvinylchlorid, Ethylen-Vinylalkohol-, Ethylen/α-Olefin-Copolymeren
und Ethylocten-Copolymeren bestehenden Gruppe ausgewählt sind.
Verfahren zur Herstellung einer Sauerstoff-Fänger-Zusammensetzung, wobei das
Verfahren das Vermischen eines ersten Konzentrats mit einem zweiten Konzentrat
umfaßt, worin das erste Konzentrat ein Sauerstoff-Finger-Material, das in einer
Konzentration zwischen 10 und 50 Gew.-% im ersten Konzentrat dispergiert ist und
nur in Gegenwart von Wasser oder Wasserdampf mit Sauerstoff reaktiv ist, und einen
ersten polymeren Träger umfaßt, der im wesentlichen frei von Katalysatoren ist,
und worin das zweite Konzentrat einen Katalysator, der in einer Konzentration zwischen
0,3 und 8 Gew.-% im zweiten Konzentrat dispergiert ist, und einen zweiten polymeren
Träger umfaßt, der im wesentlichen frei vom Sauerstoff-Fänger-Material ist.
Verfahren nach Anspruch 17, worin der erste und der zweite polymere Träger
Verfahren nach Anspruch 18, worin die Träger aus der aus Polyethylen, Ethylen-Vinylacetat,
Polyvinylchlorid, Ethylen-Vinylalkohol-, Ethylen/α-Olefin-Copolymeren und
Ethylocten-Copolymeren bestehenden Gruppe ausgewählt sind.
Verfahren nach Anspruch 17, worin der erste und der zweite Träger Polyethylen
sind, das Sauerstoff-Fänger-Material Natriumascorbat ist und der Katalysator Kupfersulfat
An oxygen scavenging concentrate comprising a polymeric carrier which is permeable
to both oxygen and water or water vapor; an organic compound which is dispersed
relatively uniformly throughout the polymeric carrier in an amount ranging from
10 to 50% by weight of the concentrate, the organic compound only being reactive
with oxygen after activation with water or water vapor which permeates the polymeric
carrier; and a catalyzing agent in an amount effective to increase the rate of
reaction of the organic compound with oxygen which is present in or permeates through
or into the polymeric carrier.
The concentrate of claim 1 wherein the organic compound is an oxidizable organic
acid or derivative thereof.
The concentrate of claim 1 wherein the organic compound is D- or L- ascorbic
acid or a salt or fatty acid derivative thereof.
The concentrate of claim 1 wherein the organic compound is a sodium, potassium
or calcium salt of D- or L-ascorbic acid or a fatty acid derivative thereof.
The concentrate of claim 1 wherein catalyzing agent includes iron, copper,
nickel or cobalt.
The composition of claim 1 wherein the catalyzing agent is a transition metal
compound, complex or chelate.
The concentrate of claim 6 wherein the transition metal compound is supplied
as a sulfate or chloride salt.
The concentrate of claim 7 wherein the transition metal compound is iron sulfate,
iron chloride or copper sulfate, and is used in an amount of from 0.3 to 8% by
weight of the concentrate.
The concentrate of claim 1 wherein the organic compound is sodium ascorbate
and the catalyzing agent is copper sulfate.
The concentrate of claim 1 wherein the carrier is a polymer selected from the
group consisting of polyethylene, ethylene vinyl acetate polymer, polyvinyl chloride,
ethylene vinyl alcohol, ethylene/alpha-olefin copolymers, and ethyl-octene copolymers.
A two-part oxygen scavenging system comprising:
a first concentrate including a first polymeric carrier which is substantially
free of catalyzing agents, and
an oxygen scavenging material dispersed throughout the first polymeric carrier
in a concentration of between 10 and 50% by weight and only being reactive with
oxygen in the presence of water or water vapor; and
a second concentrate including a second polymeric carrier which is substantially
free of the oxygen scavenging material; and
a catalyzing agent dispersed throughout the second polymeric carrier in a concentration
of between 0.3 and 8% by weight, the catalyzing agent when combined with the oxygen
scavenging material in a predetermined amount increases the rate of reaction of
the oxygen scavenging material with oxygen.
The system of claim 11 wherein the first and second polymeric carriers are
The system of claim 11 wherein the oxygen scavenging material is an ascorbate
The system of claim 13 wherein the oxygen scavenging material is sodium ascorbate.
The system of claim 11 wherein the catalyzing agent is copper sulfate.
The system of claim 11 wherein the first and second carriers are selected from
the group consisting of polyethylene, ethylene vinyl acetate, polyvinyl chloride,
ethylene vinyl alcohol, ethylene/alpha-olefin copolymers, and ethyl-octene copolymers.
A method for forming an oxygen scavenging composition, the method comprising
mixing a first concentrate with a second concentrate, wherein the first concentrate
includes an oxygen scavenging material dispersed throughout the first concentrate
in a concentration of between 10 and 50% by weight and only being reactive with
oxygen in the presence of water or water vapour, and a first polymeric carrier
which is substantially free of catalyzing agents, and wherein the second concentrate
includes a catalyzing agent dispersed throughout the second concentrate in a concentration
of between 0.3 and 8% by weight, and a second polymeric carrier which is substantially
free of the oxygen scavenging material.
The method of claim 17 wherein the first and second polymeric carriers are
The method of claim 18 wherein the carriers are selected from the group consisting
of polyethylene, ethylene vinyl acetate, polyvinyl chloride, ethylene vinyl alcohol,
ethylene/alpha-olefin copolymers and ethyl-octene copolymers.
The method of claim 17 wherein the first and second carriers are polyethylene,
the oxygen scavenging material is sodium ascorbate and the catalyzing agent is
Concentrat de fixation d'oxygène comprenant un support polymère qui est perméable
à la fois à l'oxygène et à l'eau ou à la vapeur d'eau; un composé organique qui
est dispersé de manière relativement uniforme à travers le support polymère en
une quantité se situant dans le domaine de 10 à 50% en poids du concentrat, le
composé organique ne manifestant sa réactivité avec l'oxygène qu'après activation
avec de l'eau ou avec de la vapeur d'eau qui traverse le support polymère; et
un catalyseur en une quantité efficace pour augmenter la vitesse de réaction du
composé organique avec l'oxygène, qui est présent dans le support polymère ou
bien qui traverse le support polymère ou qui pénètre dans ce dernier.
Concentrat selon la revendication 1, dans lequel le composé organique est un
acide organique oxydable ou un de ses dérivés.
Concentrat selon la revendication 1, dans lequel le composé organique est l'acide
D- ou L-ascorbique ou un de ses sels ou encore un de ses dérivés d'acides gras.
Concentrat selon la revendication 1, dans lequel le composé organique est un
sel de sodium, un sel de potassium ou un sel de calcium de l'acide D- ou L-ascorbique
ou un de ses dérivés d'acides gras.
Concentrat selon la revendication 1, dans lequel le catalyseur englobe du fer,
du cuivre, du nickel ou du cobalt.
Composition selon la revendication 1, dans laquelle le catalyseur est un composé,
un complexe ou un chélate de métal de transition.
Concentrat selon la revendication 6, dans lequel le composé de métal de transition
est fourni sous la forme d'un sel de sulfate ou d'un sel de chlorure.
Concentrat selon la revendication 7, dans lequel le composé de métal de transition
est le sulfate de fer, le chlorure de fer ou le sulfate de cuivre et on l'utilise
en une quantité de 0,3 à 8% en poids du concentrat.
Concentrat selon la revendication 1, dans lequel le composé organique est l'ascorbate
de sodium et le catalyseur est le sulfate de cuivre.
Concentrat selon la revendication 1, dans lequel le support est un polymère
choisi parmi le groupe constitué par le polyéthylène, un polymère d'éthylène-acétate
de vinyle, le chlorure de polyvinyle, des copolymères d'éthylène-alcool vinylique,
des copolymères d'éthylène-alpha-oléfine et des copolymères d'éthyl-octène.
Système de fixation d'oxygène en deux parties comprenant:
un premier concentrat englobant
un premier support polymère qui est essentiellement exempt de catalyseurs,
et une matière de fixation d'oxygène dispersée à travers le premier support polymère
en une concentration entre 10 et 50% en poids, et qui ne manifeste sa réactivité
avec l'oxygène qu'en présence d'eau ou de vapeur d'eau; et
un second concentrat englobant
un second polymère qui est essentiellement exempt de la matière de fixation
d'oxygène; et un catalyseur dispersé à travers le second support polymère en une
concentration entre 0,3 et 8% en poids,
le catalyseur, à l'état combiné avec la matière de fixation d'oxygène en une quantité
prédéterminée, augmentant la vitesse de réaction de la matière de fixation d'oxygène
Système selon la revendication 11, dans lequel les premier et second supports
polymères sont identiques.
Système selon la revendication 11, dans lequel la matière de fixation d'oxygène
est un composé d'ascorbate.
Système selon la revendication 13, dans lequel la matière de fixation d'oxygène
est l'ascorbate de sodium.
Système selon la revendication 11, dans lequel le catalyseur est le sulfate
Système selon la revendication 11, dans lequel les premier et second supports
sont choisis parmi le groupe constitué par le polyéthylène, un polymère d'éthylène-acétate
de vinyle, le chlorure de polyvinyle, des copolymères d'éthylène-alcool vinylique,
des copolymères d'éthylène-alpha-oléfine et des copolymères d'éthyl-octène.
Procédé pour former une composition de fixation d'oxygène, le procédé comprenant
le fait de mélanger un premier concentrat avec un second concentrat, dans lequel
le premier concentrat englobe une matière de fixation d'oxygène dispersée à travers
le premier concentrat en une concentration entre 10 et 50% en poids et ne manifestant
sa réactivité avec l'oxygène qu'en présence d'eau ou de vapeur d'eau, ainsi qu'un
premier support polymère qui est essentiellement exempt de catalyseurs, et dans
lequel le second concentrat englobe un catalyseur dispersé à travers le second
concentrat en une concentration entre 0,3 et 8% en poids, et un second support
polymère qui est essentiellement exempt de la matière de fixation d'oxygène.
Procédé selon la revendication 17, dans lequel les premier et second supports
polymères sont identiques.
Procédé selon la revendication 18, dans lequel les supports sont choisis parmi
le groupe constitué par le polyéthylène, un polymère d'éthylène-acétate de vinyle,
le chlorure de polyvinyle, des copolymères d'éthylène-alcool vinylique, des copolymères
d'éthylène-alpha-oléfine et des copolymères d'éthyloctène.
Procédé selon la revendication 17, dans lequel les premier et second supports
sont du polyéthylène, la matière de fixation d'oxygène est l'ascorbate de sodium
et le catalyseur est du sulfate de cuivre.