U.S. patent application number 09/789247 was filed with the patent office on 2001-09-20 for oxygen scavenging packaging.
This patent application is currently assigned to Chevron Phillips Chemical Company LP. Invention is credited to Ching, Ta Yen, Goodrich, Joseph L., Jerdee, Gary D., Leonard, James P., Rodgers, Brad D., Schmidt, Richard P..
Application Number | 20010023025 09/789247 |
Document ID | / |
Family ID | 22494487 |
Filed Date | 2001-09-20 |
United States Patent
Application |
20010023025 |
Kind Code |
A1 |
Jerdee, Gary D. ; et
al. |
September 20, 2001 |
Oxygen scavenging packaging
Abstract
Oxygen scavenging materials incorporated into or attached to a
package such as a gable-top or rectangular carton, used to package
foods, beverages or other oxygen sensitive materials, and thereby
increase shelf-life by decreasing oxygen in the headspace of the
package, and decreasing oxidation of the packaged product.
Inventors: |
Jerdee, Gary D.; (Orange,
TX) ; Leonard, James P.; (San Rafael, CA) ;
Ching, Ta Yen; (Novato, CA) ; Goodrich, Joseph
L.; (Lafayette, CA) ; Rodgers, Brad D.;
(Orange, TX) ; Schmidt, Richard P.; (Plainfield,
IL) |
Correspondence
Address: |
Raymund F. Eich
WILLIAMS, MORGAN & AMERSON, P.C.
Suite 250
7676 Hillmont
Houston
TX
77040
US
|
Assignee: |
Chevron Phillips Chemical Company
LP
|
Family ID: |
22494487 |
Appl. No.: |
09/789247 |
Filed: |
February 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09789247 |
Feb 20, 2001 |
|
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|
09141168 |
Aug 27, 1998 |
|
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Current U.S.
Class: |
428/478.8 ;
428/481; 428/511 |
Current CPC
Class: |
Y10T 428/3188 20150401;
Y10T 428/1359 20150115; Y10T 428/31757 20150401; Y10T 428/31772
20150401; Y10T 428/31746 20150401; Y10T 428/3175 20150401; Y10T
428/31725 20150401; Y10T 428/1372 20150115; Y10T 428/31775
20150401; Y10T 428/31899 20150401; Y10T 428/31855 20150401; Y10T
428/1362 20150115; Y10T 428/1303 20150115; Y10T 428/3192 20150401;
Y10T 428/1352 20150115; C09K 15/04 20130101; Y10T 428/31783
20150401; Y10T 428/1383 20150115; A23L 3/3436 20130101; Y10T 428/28
20150115; Y10T 428/31895 20150401; Y10T 428/31902 20150401; Y10T
428/3179 20150401 |
Class at
Publication: |
428/478.8 ;
428/481; 428/511 |
International
Class: |
B32B 009/02; B32B
027/10 |
Claims
What is claimed is:
1. A method of using oxygen scavenging material to decrease
oxidation and maintain product properties in packaged beverages,
foods, oxygen sensitive materials or oxygen sensitive components
comprising the steps of: a) incorporating an oxygen scavenging
material into the structure of a container used to package
beverages, foods, oxygen sensitive materials or oxygen sensitive
components; b) placing beverages, foods, oxygen sensitive materials
or oxygen sensitive components in the container; c) sealing the
container; and d) storing the container at a temperature between
20.degree. F. and 120.degree. F.
2. The method of claim 1 wherein the method is performed under
aseptic packaging conditions.
3. The method of claim 1 wherein the method is performed under
cold-filled packaging conditions.
4. The method of claim 1 wherein the oxygen scavenging material is
selected from the group consisting of oxidizable polymers,
ethylenically unsaturated polymers, benzylic polymers, allylic
polymers, polybutadiene, poly[ethylene-methyl acrylate-cyclohexene
acrylate]terpolymers, poly[ethylene-vinylcyclohexene]copolymers,
polylimonene resins, poly .beta.-pinene and poly
.alpha.-pinene.
5. The method of claim 1 wherein the oxygen scavenging material
comprises a polymeric backbone, cyclic olefinic pendent groups and
linking groups linking the olefinic pendent groups to the polymeric
backbone.
6. The method of claim 5, wherein the polymeric backbone is
ethylenic and the linking groups are selected from the group
consisting of: --O--(CHR).sub.n--; --(C.dbd.O)--O--(CHR).sub.n--;
--NH--(CHR).sub.n--; --O--(C.dbd.O)--(CHR).sub.n--;
--(C.dbd.O)--NH--(--CHR).sub.n--; and
--(C.dbd.O)--O--CHOH--CH.sub.2--O--; wherein R is hydrogen or an
alkyl group selected from the group consisting of methyl, ethyl,
propyl and butyl groups and where n is an integer in the range from
1 to 12.
7. The method of claim 5 wherein the cyclic olefinic pendent groups
have the structure (I): 3where q.sub.1, q.sub.2, q.sub.3, q.sub.4,
and r are selected from the group consisting of --H, --CH.sub.3,
and --C.sub.2H.sub.5; and where m is --(CH.sub.2).sub.n-- with n
being an integer in the range from 0 to 4; and wherein, when r is
--H, at least one of q.sub.1, q.sub.2, q.sub.3 and q.sub.4 is
--H.
8. The method of claim 5 wherein the polymeric backbone comprises
monomers selected from the group consisting of ethylene and
styrene.
9. The method of claim 1 wherein the oxygen scavenging material is
incorporated into the container as a film.
10. The method of claim 9 wherein the film is a strip attached to
the container's interior surface.
11. The method of claim 9 wherein the film is a layer of the
container's interior surface.
12. The method of claim 11 wherein the container is manufactured
from a paperboard comprising a laminated or coated oxygen barrier
layer.
13. The method of claim 1 wherein the container is a gable-top
carton or a rectangular carton.
14. The method of claim 1 wherein the container comprises an oxygen
barrier.
15. The method of claim 14 wherein the oxygen barrier comprises an
oxygen scavenging composition.
16. The method of claim 14 wherein the oxygen barriers are selected
from the group consisting of polyamides, ethylene vinyl alcohol
(EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC),
polyethylene terephthalate (PET), polyethylene naphthalate (PEN),
polyacrylonitrile (PAN), and oxygen barrier films.
17. The method of claim 16 wherein the oxygen barrier films are
selected from the group consisting of polyamide films, ethylene
vinyl alcohol films, silica coated films,-foil, metallized films,
nylon/EVOH/nylon, oriented polypropylene, polyester films, oriented
polyethylene, and PVDC coated substrates.
18. The method of claim 17 wherein the substrates of the PVDC
coated substrates are selected from the group consisting of
polypropylene, polyester, cellophane and paper.
19. The method of claim 17 wherein the substrates of the PVDC
coated substrates are monolayer films or multi-layer films.
20. The method of claim 14 wherein the oxygen barriers are
polymers, films or papers coated with silica oxide or metal
oxide.
21. The method of claim 1 wherein the container comprises sealing
layers.
22. The method of claim 1 wherein the material is an oxygen
scavenging composition further comprising a transition metal
catalyst.
23. The method of claim 22 wherein the oxygen scavenging
composition is initiated by moisture or actinic radiation.
24. The method of claim 22 wherein the transition metal catalyst is
a metal salt.
25. The method of claim 24 wherein the metal in the metal salt is
cobalt.
26. The method of claim 24 wherein the metal salt is selected from
the group consisting of cobalt neodecanoate, cobalt
2-ethylhexanoate, cobalt oleate and cobalt stearate.
27. The method of claim 22 wherein the oxygen scavenging
composition further comprises at least one triggering material to
enhance initiation of oxygen scavenging.
28. The method of claim 27 wherein the triggering material is a
photoinitiator.
29. The method of claim 1 wherein the oxygen scavenging material is
initiated by moisture or actinic radiation.
30. A method of storing beverages, foods, oxygen-sensitive
materials or oxygen-sensitive components for an extended period
while maintaining product properties comprising the steps of: a)
incorporating an oxygen scavenging material into the structure of a
container used to package beverages, foods, oxygen-sensitive
materials or oxygen-sensitive components; b) placing beverages,
foods, oxygen sensitive materials or oxygen sensitive components in
the container; c) sealing the container; and d) storing the
container at a temperature between 20.degree. F. and 120.degree.
F.
31. The method of claim 30 wherein the method is performed under
aseptic packaging conditions.
32. The method of claim 30 wherein the method is performed under
cold-filled packaging conditions.
33. The method of claim 30 wherein the oxygen scavenging material
is selected from the group consisting of oxidizable polymers,
ethylenically unsaturated polymers, benzylic polymers, allylic
polymers, polybutadiene, poly[ethylene-methyl acrylate-cyclohexene
acrylate]terpolymers, poly[ethylene-vinylcyclohexene]copolymers,
polylimonene resins, poly .beta.-pinene and poly
.alpha.-pinene.
34. The method of claim 33 wherein the oxygen scavenging material
comprises a polymeric backbone, cyclic olefinic pendent groups and
linking groups linking the olefinic pendent groups to the polymeric
backbone.
35. The method of claim 34 wherein the polymeric backbone is
ethylenic and the linking groups are selected from the group
consisting of: --O--(CHR).sub.n--; --(C.dbd.O)--O--(CHR).sub.n--;
--NH--(CHR).sub.n--; --O--(C.dbd.O)--(CHR).sub.n--;
--(C.dbd.O)--NH--(--CHR).sub.n--; and
--(C.dbd.O)--O--CHOH--CH.sub.2--O--; wherein R is hydrogen or an
alkyl group selected from the group consisting of methyl, ethyl,
propyl and butyl groups and where n is an integer in the range from
1 to 12.
36. The method of claim 34 wherein the cyclic olefinic pendent
groups have the structure (I): 4where q.sub.1, q.sub.2, q.sub.3,
q.sub.4, and r are selected from the group consisting of --H,
--CH.sub.3, and --C.sub.2H.sub.5; and where m is
--(CH.sub.2).sub.n-- with n being an integer in the range from 0 to
4; and wherein, when r is --H, at least one of q.sub.1, q.sub.2,
q.sub.3 16 and q.sub.4 is --H.
37. The method of claim 34 wherein the polymeric backbone comprises
monomers selected from the group consisting of ethylene and
styrene.
38. The method of claim 30 wherein the oxygen scavenging material
is incorporated into the container as a film.
39. The method of claim 38 wherein the film is a strip attached to
the containers interior surface.
40. The method of claim 38 wherein the film is a layer of the
container's interior surface.
41. The method of claim 40 wherein the container is manufactured
from a paperboard comprising a laminated or coated oxygen barrier
layer.
42. The method of claim 30 wherein the container is a gable-top
carton or a rectangular carton.
43. The method of claim 30 wherein the container comprises an
oxygen barrier.
44. The method of claim 43 wherein the oxygen barrier comprises an
oxygen scavenging composition.
45. The method of claim 43 wherein the oxygen barriers are selected
from the group consisting of polyamides, ethylene vinyl alcohol
(EVOH), polyvinylidene chloride (PVDC), polyvinyl chloride (PVC),
polyethylene terephthalate (PET), polyethylene naphthalate (PEN),
polyacrylonitrile (PAN), and oxygen barrier films.
46. The method of claim 45 wherein the oxygen barrier films are
selected from the group consisting of polyamide films, ethylene
vinyl alcohol films, silica coated films, foil, metallized films,
nylon/EVOH/nylon, oriented polypropylene, polyester films, oriented
polyethylene, and PVDC coated substrates.
47. The method of claim 46 wherein the substrates of the PVDC
coated substrates are selected from the group consisting of
polypropylene, polyester, cellophane and paper.
48. The method of claim 46 wherein the substrates of the PVDC
coated substrates are monolayer films or multi-layer films.
49. The method of claim 45 wherein the oxygen barriers are
polymers, films or papers coated with silica oxide or metal
oxide.
50. The method of claim 30 wherein the container comprises sealing
layers.
51. The method of claim 30 wherein the material is an oxygen
scavenging composition further comprising a transition metal
catalyst.
52. The method of claim 51 wherein the oxygen scavenging
composition is initiated by moisture or actinic radiation.
53. The method of claim 51 wherein the transition metal catalyst is
a metal salt.
54. The method of claim 53 wherein the metal in the metal salt is
cobalt.
55. The method of claim 53 wherein the metal salt is selected from
the group consisting of cobalt neodecanoate, cobalt
2-ethylhexanoate, cobalt oleate and cobalt stearate.
56. The method of claim 51 wherein the oxygen scavenging
composition further comprises at least one triggering material to
enhance initiation of oxygen scavenging.
57. The method of claim 56 wherein the triggering material is a
photoinitiator.
58. The method of claim 30 wherein the oxygen scavenging material
is initiated by moisture or actinic radiation.
59. A rigid paperboard container, the container being constructed
from extrusion coated or laminated paperboard comprising: (a) a
paperboard substrate having opposed inner and outer surfaces; (b) a
first polymer layer coated or laminated onto the outer surface of
said paperboard substrate; and (c) an inner, product contact
sandwich layer comprising an oxygen barrier layer and an oxygen
scavenging layer.
60. A rigid paperboard container according to claim 59 wherein the
inner, product contact sandwich layer further comprises a tie layer
adjacent to the barrier layer.
61. A rigid paperboard container according to claim 59 wherein the
inner product contact sandwich layer further comprises a seal layer
coating or laminating the innermost surface of the inner, product
contact sandwich layer.
62. A rigid paperboard container according to claim 59 wherein a
second polymer layer is coated or laminated onto the inner surface
of said paperboard substrate.
63. A rigid paperboard container according to claim 62 wherein a
tie layer is juxtaposed between the barrier layer and the second
polymer layer coated or laminated onto the inner surface of the
paperboard substrate.
64. A rigid paperboard container according to claim 59 wherein a
third polymer layer is coated or laminated onto the inner surface
of the oxygen scavenging layer of the inner, product contact,
sandwich layer.
65. A rigid paperboard container according to claim 64 wherein the
inner, product contact, sandwich layer further comprises a fourth
polymer layer and a second oxygen scavenging layer, the second
oxygen scavenging layer being on the inner surface of the third
polymer layer and the fourth polymer layer coating or laminating
the inner surface of the second oxygen scavenging layer.
66. A rigid paperboard container according to claim 64 wherein a
tie layer is coated or laminated onto the inner surface of the
oxygen scavenging layer and an ethylene vinyl alcohol layer is
coated or laminated onto the inner surface of the tie layer coating
or laminating the inner surface of the oxygen scavenging layer.
67. A rigid paperboard container according to claim 64 wherein the
inner, product contact, sandwich layer further comprises a second
barrier layer and a second tie layer, the second barrier layer
being on the inner surface of the first tie layer and the second
tie layer being juxtaposed between the inner surface of the second
barrier layer and the outer surface of the oxygen scavenging
layer.
68. A rigid paperboard container according to claims 59, 60, 61,
62, 63, 64, 65, 66 or 67 wherein the oxygen scavenging material is
selected from the group consisting of oxidizable polymers,
ethylenically unsaturated polymers, benzylic polymers, allylic
polymers, polybutadiene, poly[ethylene-methyl acrylate-cyclohexene
acrylate]terpolymers, poly[ethylene-vinylcyclohexene]copolymers,
polylimonene resins, poly P-pinene and poly .alpha.-pinene.
69. A rigid paperboard container according to claims 59, 60, 61,
62, 63, 64, 65, 66 or 67 wherein the oxygen scavenging material
comprises a polymeric backbone, cyclic olefinic pendent groups and
linking groups linking the olefinic pendent groups to the polymeric
backbone.
70. A rigid paperboard container according to claim 69 wherein the
polymeric backbone is ethylenic and the linking groups are selected
from the group consisting of: --O--(CHR).sub.n--;
--(C.dbd.O)--O--(CHR).sub.n-- -; --NH--(CHR).sub.n--;
--O--(C.dbd.O)--(CHR).sub.n--; --(C.dbd.O)--NH--(--CHR).sub.n--;
and --(C.dbd.O)--O--CHOH--CH.sub.2--O--- ; wherein R is hydrogen or
an alkyl group selected from the group consisting of methyl, ethyl,
propyl and butyl groups and where n is an integer in the range from
1 to 12.
71. A rigid paperboard container according to claim 69 wherein the
cyclic olefinic pendent groups have the structure (I): 5where
q.sub.1, q.sub.2, q.sub.3, q.sub.4, and r are selected from the
group consisting of --H, --CH.sub.3, and --C.sub.2H.sub.5; and
where m is --(CH.sub.2).sub.n-- with n being an integer in the
range from 0 to 4; and wherein, when r is --H, at least one of
q.sub.1, q.sub.2, q.sub.3 and q.sub.4 is --H.
72. A rigid paperboard container according to claim 69 wherein the
polymeric backbone comprises monomers selected from the group
consisting of ethylene and styrene.
73. A rigid paperboard container according to claim 59, 60, 61, 62,
63, 64, 65, 66 or 67 wherein the polymer layer or the seal layer is
selected from the group consisting of low density polyethylene
polymer, linear low density polyethylene polymer, a blend of low
density polyethylene polymer and linear low density polyethylene
polymer, and a coextrusion of low density polyethylene polymer and
linear low density polyethylene polymer.
74. A rigid paperboard container according to claim 59, 60, 61, 62,
63, 64, 65, 66 or 67 wherein the tie layer of the inner, product
contact, sandwich layer comprises ethylene acrylic acid.
75. A rigid paperboard container according to claim 59, 60, 61, 62,
63, 64, 65, 66 or 67 wherein the tie layer of the inner, product
contact, sandwich layer comprises ethylene methacrylic acid.
76. A rigid paperboard container according to claim 59, 60, 61, 62,
63, 64, 65, 66 or 67 wherein the tie layer of the inner, product
contact, sandwich layer comprises maleated tie layer polymers.
77. A rigid paperboard container according to claim 59, 60, 61, 62,
63, 64, 65, 66 or 67 wherein the tie layer of the inner, product
contact, sandwich layer comprises ionomer.
78. A rigid paperboard container according to claim 77 wherein the
tie layer of the inner, product contact, sandwich layer comprises
zinc ionomer.
79. A rigid paperboard container according to claim 77 wherein the
tie layer of the inner, product contact, sandwich layer comprises
sodium ionomer.
80. A rigid paperboard container according to claim 59, 60, 61, 62,
63, 64, 65, 66 or 67 wherein the barrier layer of the inner,
product contact, sandwich layer comprises foil.
81. A rigid paperboard container according to claim 59, 60, 61, 62,
63, 64, 65, 66 or 67 wherein the barrier layer of the inner,
product contact, sandwich layer comprises metallized film.
82. A rigid paperboard container according to claim 59, 60, 61, 62,
63, 64, 65, 66 or 67 wherein the barrier layer of the inner,
product contact, sandwich layer comprises ethylene vinyl alcohol
(EVOH).
83. A rigid paperboard container according to claim 59, 60, 61, 62,
63, 64, 65, 66 or 67 wherein the barrier layer of the inner,
product contact, sandwich layer comprises polyamides.
84. A rigid paperboard container according to claim 83 wherein an
ethylene vinyl alcohol (EVOH) layer is coated onto at least one of
the inner and outer surfaces of the polyamides barrier layer.
85. A rigid paperboard container according to claim 59, 60, 61, 62,
63, 64, 65, 66 or 67 wherein an ethylene vinyl alcohol (EVOH) layer
is coated onto at least one of the inner and outer surfaces of the
barrier layer.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to oxygen scavenging for use
in packaging, such as in gable-top or rectangular cartons used to
package food products, beverages, oxygen-sensitive materials and
components.
BACKGROUND OF THE INVENTION
[0002] It is well known that regulating the exposure of
oxygen-sensitive products to oxygen maintains and enhances the
quality and "shelf-life" of the product. For instance, by limiting
the exposure of oxygen sensitive food products to oxygen in a
packaging system, the quality or freshness of food is maintained,
spoilage reduced, and the food shelf life extended. In the food
packaging industry, several means for regulating oxygen exposure
have already been developed. These means include modified
atmosphere packaging (MAP) and oxygen barrier film packaging.
[0003] For packaging material used in gable top or rectangular
cartons, a coated paper or cardboard stock is often used. The
coating for the paper or cardboard stock is usually a polymer-based
resin, such as polyethylene, which can be applied to the paper or
paperboard stock by extrusion coating or laminating. Such a coating
serves not only to make the packaging material waterproof, but can
also serve as an oxygen barrier.
[0004] In one known example of such an extrusion coated paper
packaging material, the extrusion coating composition is comprised
of greater than 20 and less than 98 weight percent of a high
pressure low density polyethylene homopolymer and/or copolymer and
greater than 2 and less than 80 weight percent of at least one
linear low density ethylene hydrocarbon copolymer.
[0005] In an example of such a resin coated packaging material
specifically designed to have enhanced oxygen barrier qualities, an
additional layer of polyamide is added to the low density
polyethylene laminated paperboard. In a similar example, an
additional layer of heat-sealable ethylene vinyl alcohol copolymer
is added to the low density polyethylene laminated paperboard.
[0006] One method currently being used for regulating oxygen
exposure is "active packaging", whereby the package containing the
food product has been modified in some manner to regulate the
food's exposure to oxygen. One form of active packaging uses
oxygen-scavenging sachets which contain a composition which
scavenges the oxygen through oxidation reactions. One type of
sachet contains iron-based compositions which oxidize to their
ferric states. Another type of sachet contains unsaturated fatty
acid salts on a particulate adsorbent. Yet another sachet contains
metal/polyamide complex. However, one disadvantage of sachets is
the need for additional packaging operations to add the sachet to
each package. A further disadvantage arising from the iron-based
sachets is that certain atmospheric conditions (e.g., high
humidity, low CO.sub.2 level) in the package are sometimes required
in order for scavenging to occur at an adequate rate. Further, the
sachets can present a problem to consumers if accidentally
ingested.
[0007] Another means for regulating exposure of a packaged product
to oxygen involves incorporating an oxygen scavenger into the
packaging structure itself. A more uniform scavenging effect
through the package is achieved by incorporating the scavenging
material in the package instead of adding a separate scavenger
structure (e.g., a sachet) to the package. This may be especially
important where there is restricted airflow inside the package. In
addition, incorporating the oxygen scavenger into the package
structure provides a means of intercepting and scavenging oxygen as
it permeates the walls of the package (herein referred to as an
"active oxygen barrier"), thereby maintaining the lowest possible
oxygen level in the package. Limited success has been achieved in
incorporating oxygen scavenging material into the walls of packages
for various types of food.
[0008] One attempt to prepare an oxygen-scavenging wall involves
the incorporation of inorganic powders and/or salts. However,
incorporation of these powders and/or salts causes reduction of the
wall's optical transparency, discoloration after oxidation, and
reduced mechanical properties such as tear strength. In addition,
these compounds can lead to processing difficulties, especially
when fabricating thin films. The oxidation products, which can be
absorbed by food in the container, typically would not have FDA
approval for human consumption.
[0009] Some oxygen scavenging systems produce an oxygen-scavenging
wall. This is done by incorporating a metal catalyst-polyamide
oxygen scavenging system into the package wall. Through catalyzed
oxidation of the polyamide, the package wall regulates the amount
of oxygen which reaches the interior volume of the package (active
oxygen barrier) and has been reported to have oxygen scavenging
rate capabilities up to about 5 cubic centimeters (cc) oxygen per
square meter per day at ambient conditions. However, this system
suffers from significant disadvantages.
[0010] One particularly limiting disadvantage of polyamide/catalyst
materials can be a low oxygen scavenging rate. Adding these
materials to a high-barrier package containing air can produce a
package which is not generally suitable for creating the desired
internal oxygen level.
[0011] There are also disadvantages to having the oxygen-scavenging
groups in the backbone or network structure in this type of
polyamide polymer. The basic polymer structure can be degraded and
weakened upon reaction with oxygen. This can adversely affect
physical properties such as tensile or impact strength of the
polymer. The degradation of the backbone or network of the polymer
can further increase the permeability of the polymer to those
materials sought to be excluded, such as oxygen.
[0012] Moreover, polyamides previously used in oxygen scavenging
materials, such as MXD6, are typically incompatible with
thermoplastic polymers used in most plastic packaging walls, such
as ethylene-vinyl acetate copolymers and low density polyethylene.
Even further, when such polyamides are used by themselves to make a
package wall, they may result in inappropriately stiff structures.
They also incur processing difficulties and higher costs when
compared with the costs of thermoplastic polymers typically used to
make flexible packaging. Even further, they are difficult to heat
seal. Thus, all of these are factors to consider when selecting
materials for packages, especially multi-layer flexible packages
and when selecting systems for reducing oxygen exposure of packaged
products.
[0013] Another approach to scavenging oxygen is an
oxygen-scavenging composition comprising an ethylenically
unsaturated hydrocarbon and a transition metal catalyst.
Ethylenically unsaturated compounds such as squalene, dehydrated
castor oil, and 1,2-polybutadiene are useful oxygen scavenging
compositions, and ethylenically saturated compounds such as
polyethylene and ethylene copolymers are useful as diluents.
Compositions utilizing squalene, castor oil, or other such
unsaturated hydrocarbon typically have an oily texture as the
compound migrates toward the surface of the material. Further,
polymer chains which are ethylenically unsaturated in the backbone
would be expected to degrade upon scavenging oxygen, weakening the
polymer due to polymer backbone breakage, and generating a variety
of off-odor, off-taste by-products.
[0014] Oxygen scavenging layers extruded or laminated onto the
surface of paperboard stock have been tried with limited success.
In one of these examples, the oxygen scavenging layer is an
ethylenically unsaturated hydrocarbon and a transition metal
catalyst. Other known examples of an oxygen scavenging layer that
can be coated onto the surface of paper board stock and which
furthermore retain oxygen scavenging capabilities at low
temperatures are atactic-1,2-polybutadiene, EPDM rubbers,
polyoctenamer, and 1,4-polybutadiene.
[0015] An oxygen-scavenging composition comprising a blend of a
first polymeric component comprising a polyolefin is known, the
first polymeric component having been grafted with an unsaturated
carboxylic anhydride or an unsaturated carboxylic acid, or
combinations thereof, or with an epoxide; a second polymeric
component having --OH, --SH, or --NHR.sup.2 groups where R.sup.2 is
H, C.sub.1-C.sub.3 alkyl, substituted C.sub.1-C.sub.3 alkyl; and a
catalytic amount of metal salt capable of catalyzing the reaction
between oxygen and the second polymeric component, the polyolefin
being present in an amount sufficient so that the blend is non
phase-separated. A blend of polymers is utilized to obtain oxygen
scavenging, and the second polymeric component is preferably a
polyamide or a copolyamide such as the copolymer of
m-xylylene-diamine and adipic acid (MXD6).
[0016] Other oxidizable polymers recognized in the art include
"highly active" oxidizable polymers such as poly(ethylene-methyl
acrylate-benzyl acrylate), EBZA, and poly(ethylene-methyl
acrylate-tetrahydrofuryl acrylate), EMTF, as well as
poly(ethylene-methyl acrylate-nopol acrylate), EMNP. Blends of
suitable polymers are also acceptable, such as a blend of EMTF and
poly-d-limonene. Although effective as oxygen scavengers, these
polymers have the drawback of giving off a strong odor before
oxygen scavenging and large amounts of volatile byproducts before
and after oxygen scavenging.
[0017] Also known are oxygen-scavenging compositions which comprise
a transition-metal salt and a compound having an ethylenic or
polyethylenic backbone and having allylic pendent or terminal
moieties which contain a carbon atom that can form a free radical
that is resonance-stabilized by an adjacent group. Such a polymer
needs to contain a sufficient amount and type of transition metal
salt to promote oxygen scavenging by the polymer when the polymer
is exposed to an oxygen-containing fluid such as air. Although
effective as oxygen scavengers, upon oxidation, it has been found
that allylic pendent groups on an ethylenic or polyethylenic
backbone tend to generate considerable amounts of organic
fragments. It is believed that this is a result of oxidative
cleavage. These fragments can interfere with the use of allylic
pendent groups as oxygen scavengers in food packaging by generating
compounds that can affect taste and odor of the packaged
products.
[0018] The present invention solves many of the problems of the
prior art encountered when oxygen scavenging material has been
incorporated into packaging materials. In various specific
embodiments, the present invention solves many of the particular
problems encountered with incorporating oxygen scavenging material
into the structure of food packaging material such as paperboard
stock for gable-top or rectangular cartons.
SUMMARY OF THE INVENTION
[0019] In one embodiment, the present invention relates to a method
of using oxygen scavenging material to decrease oxidation and
maintain product properties in packaged foods, beverages,
oxygen-sensitive materials or oxygen-sensitive components
comprising the steps of:
[0020] (a) incorporating an oxygen scavenging material into the
structure of a container used to package foods, beverages,
oxygen-sensitive materials or oxygen-sensitive components;
[0021] (b) placing beverages, foods, oxygen sensitive materials or
oxygen sensitive components in the container;
[0022] (c) sealing the container; and
[0023] (d) storing the container at a temperature between
20.degree. F. and 120.degree. F.
[0024] In another embodiment, the present invention relates to a
method of storing foods, beverages, oxygen-sensitive materials or
oxygen-sensitive components for an extended period while
maintaining product properties comprising the steps of:
[0025] (a) incorporating an oxygen scavenging material into the
structure of a container used to package foods, beverages,
oxygen-sensitive materials or oxygen-sensitive components;
[0026] (b) placing beverages, foods, oxygen sensitive materials or
oxygen sensitive components in the container;
[0027] (c) sealing the container; and
[0028] (d) storing the container at a temperature between
20.degree. F. and 120.degree. F.
[0029] In a preferred embodiment of the above-described invention,
the method is performed under aseptic packaging conditions.
[0030] In another preferred embodiment of the above-described
invention, the method is performed under cold-filled packaging
conditions.
[0031] In yet another preferred embodiment of the above-described
invention, the oxygen scavenging material is selected from the
group consisting of oxidizable polymers, ethylenically unsaturated
polymers, benzylic polymers, allylic polymers, polybutadiene,
poly[ethylene-methyl acrylate-cyclohexene acrylate]terpolymers,
poly[ethylene-vinylcyclohexene- ]copolymers, polylimonene resins,
poly .beta.-pinene and poly .alpha.-pinene.
[0032] In another preferred embodiment of the above-described
invention, the oxygen scavenging material of either of the above
methods comprises a polymeric backbone, cyclic olefinic pendent
groups and linking groups linking the olefinic pendent groups to
the polymeric backbone.
[0033] In a more preferred embodiment of the above-described
invention, the polymeric backbone is ethylenic and the linking
groups are selected from the group consisting of:
--O--(CHR).sub.n--; --(C.dbd.O)--O--(CHR).sub.n--;
--NH--(CHR).sub.n--; --O--(C=O)--(CHR).sub.n--;
--(C=O)--NH--(--CHR).sub.n--; and
--(C=O)--O--CHOH--CH.sub.2--O--;
[0034] wherein R is hydrogen or an alkyl group selected from the
group consisting of methyl, ethyl, propyl and butyl groups and
where n is an integer in the range from 1 to 12.
[0035] In another more preferred embodiment of the above-described
invention, the cyclic olefinic pendent groups have the structure
(I): 1
[0036] where q.sub.1, q.sub.2, q.sub.3, q.sub.4, and r are selected
from the group consisting of --H, --CH.sub.3, and --C.sub.2H.sub.5;
and where m is --(CH.sub.2).sub.n-- with n being an integer in the
range from 0 to 4; and wherein, when r is --H, at least one of
q.sub.1, q.sub.2, q.sub.3 and q.sub.4 is --H.
[0037] In yet another preferred embodiment of the above-described
invention, the polymeric backbone comprises monomers selected from
the group consisting of ethylene and styrene.
[0038] In a more preferred embodiment of the above-described
invention, the oxygen scavenging material is incorporated into the
container as a film.
[0039] In a yet more preferred embodiment of the above-described
invention, the film is a strip attached to the container's interior
surface.
[0040] In a still more preferred embodiment of the above-described
invention, the film is a layer of the container's interior
surface.
[0041] In a yet more preferred embodiment of the above-described
invention, the container is manufactured from a paperboard
comprising a laminated oxygen barrier layer.
[0042] In another preferred embodiment of the above-described
invention, the container in the above method is a gable-top carton
or a rectangular carton.
[0043] In yet another preferred embodiment of the above-described
invention, the container in the above method comprises an oxygen
barrier.
[0044] In a more preferred embodiment of the above-described
invention, the oxygen barrier comprises an oxygen scavenging
composition.
[0045] In a still more preferred embodiment of the above-described
invention, the oxygen barriers in the container are selected from
the group consisting of polyamides, ethylene vinyl alcohol (EVOH),
polyvinylidene chloride (PVDC), polyethylene terephthalate (PET),
polyethylene naphthalate (PEN), polyacrylonitrile (PAN), and oxygen
barrier films.
[0046] In a yet more preferred embodiment of the above-described
invention, the oxygen barrier films in the above method are
selected from the group consisting of polyamide films, ethylene
vinyl alcohol films, silica films, foil, metallized films,
nylon/EVOH/nylon, oriented polypropylene, polyester films, oriented
polyethylene, and PVDC coated substrates.
[0047] In a still more preferred embodiment of the above-described
invention, the substrates of the PVDC coated substrates are
selected from the group consisting of polypropylene, polyester,
cellophane and paper.
[0048] In a yet more preferred embodiment of the above-described
invention, the substrates of the PVDC coated substrates are
monolayer films or multi-layer films.
[0049] In a still more preferred embodiment of the above-described
invention, the oxygen barriers are polymers, films or papers coated
with silica oxide or metal oxide.
[0050] In another preferred embodiment of the above-described
invention, the container comprises sealing layers.
[0051] In yet another preferred embodiment of the above-described
invention, the oxygen scavenging material further comprises a
transition metal catalyst.
[0052] In still another preferred embodiment of the above-described
invention, the oxygen scavenging composition is initiated by
moisture or actinic radiation.
[0053] In a more preferred embodiment of the above-described
invention, the transition metal catalyst is a metal salt.
[0054] In another more preferred embodiment of the above-described
invention, the metal in the metal salt is cobalt.
[0055] In yet another more preferred embodiment of the
above-described invention, the metal salt is selected from the
group consisting of cobalt neodecanoate, cobalt 2-ethylhexanoate,
cobalt oleate and cobalt stearate.
[0056] In still another more preferred embodiment of the
above-described invention, the oxygen scavenging composition
further comprises at least one triggering material to enhance
initiation of oxygen scavenging.
[0057] In yet another more preferred embodiment of the
above-described invention, the triggering material is a
photoinitiator.
[0058] In another preferred embodiment of the above-described
invention, the oxygen scavenging material in the above method is
initiated by moisture or actinic radiation.
[0059] In another embodiment, the present invention relates to a
rigid paperboard container, the container being constructed from
extrusion coated or laminated paperboard comprising:
[0060] (a) a paperboard substrate having opposed inner and outer
surfaces;
[0061] (b) a first polymer layer coated or laminated onto the outer
surface of said paperboard substrate; and
[0062] (c) an inner, product contact, sandwich layer comprising a
barrier layer and an oxygen scavenging layer.
[0063] In a preferred embodiment of the above-described embodiment
of the invention, the inner, product contact sandwich layer further
comprises a tie layer adjacent to the barrier layer.
[0064] In another preferred embodiment of the above-described
embodiment of the invention, the inner product contact sandwich
layer further comprises a seal layer coating or laminating the
innermost surface of the inner, product contact sandwich layer.
[0065] In another preferred embodiment of the above-described
embodiment of the invention, a second polymer layer is coated or
laminated onto the inner surface of the paperboard substrate.
[0066] In another preferred embodiment of the above-described
embodiment of the invention, a tie layer is juxtaposed between the
barrier layer and the second polymer layer coated or laminated onto
the inner surface of the paperboard substrate.
[0067] In yet another preferred embodiment of the above-described
embodiment of the invention, a third polymer layer is coated or
laminated onto the inner surface of the oxygen scavenging layer of
the inner, product contact, sandwich layer.
[0068] In still another preferred embodiment of the above-described
embodiment of the invention, the inner, product contact, sandwich
layer further comprises a fourth polymer layer and a second oxygen
scavenging layer, the second oxygen scavenging layer being on the
inner surface of the third polymer layer and the fourth polymer
layer coating or laminating the inner surface of the second oxygen
scavenging layer.
[0069] In yet another preferred embodiment of the above-described
embodiment of the invention, a tie layer is coated or laminated
onto the inner surface of the oxygen scavenging layer and an
ethylene vinyl alcohol layer is coated or laminated onto the inner
surface of the tie layer coating or laminating the inner surface of
the oxygen scavenging layer.
[0070] In still another preferred embodiment of the above-described
embodiment of the invention, the inner, product contact, sandwich
layer further comprises a second barrier layer and a second tie
layer, the second barrier layer being on the inner surface of the
first tie layer and the second tie layer being juxtaposed between
the inner surface of the second barrier layer and the outer surface
of the oxygen scavenging layer.
[0071] In a more preferred embodiment of the above-described
embodiments of the invention, the oxygen scavenging material is
selected from the group consisting of oxidizable polymers,
ethylenically unsaturated polymers, benzylic polymers, allylic
polymers, polybutadiene, poly[ethylene-methyl acrylate-cyclohexene
acrylate]terpolymers, poly[ethylene-vinylcyclohexene]copolymers,
polylimonene resins, poly .beta.-pinene and poly
.alpha.-pinene.
[0072] In a more preferred embodiment of the above-described
embodiments of the invention, the oxygen scavenging material of
either of the above methods comprises a polymeric backbone, cyclic
olefinic pendent groups and linking groups linking the olefinic
pendent groups to the polymeric backbone.
[0073] In a more preferred embodiment of the above-described
embodiments of the invention, the polymeric backbone is ethylenic
and the linking groups are selected from the group consisting
of:
--O--(CHR).sub.n--; --(C.dbd.O)--O--(CHR).sub.n--;
--NH--(CHR).sub.n--; --O--(C.dbd.O)--(CHR).sub.n--;
--(C.dbd.O)--NH--(--CHR).sub.n--; and
--(C.dbd.O)--O--CHOH--CH.sub.2--O--;
[0074] wherein R is hydrogen or an alkyl group selected from the
group consisting of methyl, ethyl, propyl and butyl groups and
where n is an integer in the range from 1 to 12.
[0075] In a more preferred embodiment of the above-described
embodiments of the invention, the cyclic olefinic pendent groups
have the structure (I): 2
[0076] where q.sub.1, q.sub.2, q.sub.3, q.sub.4, and r are selected
from the group consisting of --H, --CH.sub.3, and --C.sub.2H.sub.5;
and where m is --(CH.sub.2).sub.n-- with n being an integer in the
range from 0 to 4; and wherein, when r is --H, at least one of
q.sub.1, q.sub.2, q.sub.3 and q.sub.4 is --H.
[0077] In a more preferred embodiment of the above-described
embodiments of the invention, the polymeric backbone comprises
monomers selected from the group consisting of ethylene and
styrene.
[0078] In a more preferred embodiment of the above-described
embodiments of the invention, the polymer layer or the seal layer
is selected from the group consisting of low density polyethylene
polymer, linear low density polyethylene polymer, a blend of low
density polyethylene polymer and linear low density polyethylene
polymer, and a coextrusion of low density polyethylene polymer and
linear low density polyethylene polymer.
[0079] In another more preferred embodiment of the above-described
embodiments of the invention, the tie layer of the inner, product
contact, sandwich layer comprises ethylene acrylic acid.
[0080] In another more preferred embodiment of the above-described
embodiments of the invention, the tie layer of the inner, product
contact, sandwich layer comprises ethylene methacrylic acid.
[0081] In another more preferred embodiment of the above-described
embodiments of the invention, the tie layer of the inner, product
contact, sandwich layer comprises maleated tie layer polymers.
[0082] In another more preferred embodiment of the above-described
embodiments of the invention, the tie layer of the inner, product
contact, sandwich layer comprises ionomer. In a yet more preferred
embodiment of the above-described embodiment, the tie layer of the
inner, product contact, sandwich layer comprises zinc ionomer or
sodium ionomer.
[0083] In another more preferred embodiment of the above-described
embodiments of the invention, the barrier layer of the inner,
product contact, sandwich layer comprises foil.
[0084] In another more preferred embodiment of the above-described
embodiments of the invention, the barrier layer of the inner,
product contact, sandwich layer comprises metallized film.
[0085] In another more preferred embodiment of the above-described
embodiments of the invention, the barrier layer of the inner,
product contact, sandwich layer comprises ethylene vinyl alcohol
(EVOH).
[0086] In another more preferred embodiment of the above-described
embodiments of the invention, the barrier layer of the inner,
product contact, sandwich layer comprises polyamides. In a yet more
preferred embodiment of the above-described embodiment, an ethylene
vinyl alcohol (EVOH) layer is coated onto at least one of the inner
and outer surfaces of the barrier layer.
DESCRIPTION OF THE DRAWINGS
[0087] FIG. 1 is a graph showing the measured vitamin C retention
in orange juice packaged in glass container, PBL and OS cartons as
described in Example 1. The graph is plotted as mg/liter vitamin C
vs. time.
[0088] FIG. 2 is a graph showing the measured dissolved oxygen in
orange juice packaged in glass container, PBL and OS cartons as
described in Example 1. The graph is plotted as mg/liter oxygen vs.
time.
[0089] FIG. 3 is a graph showing the measured vitamin C retention
in orange juice packaged in OS and PBL cartons with OS films as
described in Example 1. The graph is plotted as mg/liter vitamin C
vs. time.
[0090] FIG. 4 is a graph showing the measured dissolved oxygen in
OS and PBL cartons with OS films as described in Example 1. The
graph is plotted as mg/liter oxygen vs. time.
DETAILED DESCRIPTION OF THE INVENTION
[0091] The oxygen scavenging system of the present invention has a
number of benefits including, but not limited to: extending shelf
life; preserving product color; improving taste and odor; reducing
mold growth; and retaining vitamin and other nutritional value.
[0092] Because these scavengers are actually part of the package,
they eliminate the additional handling steps and safety concerns
associated with oxygen scavenging sachets. In fact, the oxygen
scavenging system of the present invention could be incorporated
into an existing packaging structure without any consumer awareness
of change in the package appearance.
[0093] The oxygen scavenging polymers can be incorporated into a
layer of a film or rigid package using standard extrusion
equipment. Because the scavenger material permeates an entire layer
incorporated into the package wall, the capacity per cost of
scavenger compares very favorably to systems where the scavenger is
added into the package wall in some fashion.
[0094] This invention relates to the use of oxygen scavengers in
packaging materials, for example, extrusion-coated, rigid
containers. In a more specific embodiment, the containers are in
the form of gable top and rectangular cartons, for beverages,
foods, and other oxygen sensitive materials and components. A
non-limiting list of possible products include fruit juices,
prepared foods, snack foods, as well as other oxygen-sensitive
materials such as chemicals and oxygen-sensitive components, such
as computer parts.
[0095] The containers in the present invention can be filled under
either aseptic packaging conditions or under cold-filled packaging
conditions, without the specific procedures used for aseptic
packaging conditions (which is how the samples discussed in the
Examples are prepared).
[0096] A non-limiting description of a typical procedure used for
aseptic packaging conditions for carton containers is as follows.
The packaging materials are formed into cartons and sterilized in
the filler machine with hot hydrogen peroxide vapor. Once the vapor
is evaporated with hot, sterile air or ultraviolet light, the
sterilized package is filled at ambient temperature with the
sterilized product and then sealed within a sterile zone.
[0097] By incorporating an oxygen scavenging layer as an inner
layer in the walls of the packaging material or as a strip attached
somewhere on the inner surface of the packaging material, oxidation
of product properties, such as the nutritional value in beverages
or foods, is reduced significantly.
[0098] In a preferred embodiment, the oxygen scavengers are
combined with a transition-metal salt to catalyze the oxygen
scavenging properties of the materials. A transition-metal salt, as
the term is used here, comprises an element chosen from the first,
second and third transition series of the periodic table of the
elements, particularly one that is capable of promoting oxygen
scavenging. This transition-metal salt is in a form, which
facilitates or imparts scavenging of oxygen by the composition of
this invention. A plausible mechanism, not intended to place
limitations on this invention, is that the transition element can
readily inter-convert between at least two oxidation states and
facilitates formation of free radicals. Suitable transition-metal
elements include, but are not limited to, manganese II or III, iron
II or III, cobalt II or III, nickel II or III, copper I or II,
rhodium II, III or IV, and ruthenium.
[0099] The oxidation state of the transition-metal element when
introduced into the composition is not necessarily that of the
active form. It is only necessary to have the transition-metal
element in its active form at or shortly before the time that the
composition is required to scavenge oxygen. The transition-metal
element is preferably iron, nickel or copper, more preferably
manganese, and most preferably cobalt.
[0100] Suitable counter-ions for the transition metal element are
organic or inorganic anions. These include, but are not limited to,
chloride, acetate, stearate, oleate, palmitate, 2-ethylhexanoate,
citrate, glycolate, benzoate, neodecanoate or naphthenate. Organic
anions are preferred. Particularly preferable salts include cobalt
2-ethylhexanoate, cobalt benzoate, cobalt stearate, cobalt oleate
and cobalt neodecanoate. The transition-metal element may also be
introduced as an ionomer, in which case a polymeric counter-ion is
employed.
[0101] The composition of the present invention when used in
forming an oxygen scavenging packaging article can be composed
solely of the above-described polymer and transition metal
catalyst. However, components, such as photoinitiators, can be
added to further facilitate and control the initiation of oxygen
scavenging properties. For instance, it is often preferable to add
a photoinitiator, or a blend of different photoinitiators, to the
oxygen scavenger compositions, especially when antioxidants are
included to prevent premature oxidation of that composition during
processing.
[0102] Suitable photoinitiators are well known in the art. Such
photoinitiators are discussed in U.S. patent application Ser. No.
08/857,325 in which some of the present inventors were contributing
inventors and which is incorporated herein by reference. Specific
examples include, but are not limited to, benzophenone,
o-methoxy-benzophenone, acetophenone, o-methoxy-acetophenone,
acenaphthenequinone, methyl ethyl ketone, valerophenone,
hexanophenone, .alpha.-phenyl-butyrophenone,
p-morpholinopropiophenone, dibenzosuberone,
4-morpholinobenzophenone, benzoin, benzoin methyl ether,
4-o-morpholinodeoxybenzoin, p-diacetylbenzene, 4-aminobenzophenone,
4'-methoxyacetophenone, substituted and unsubstituted
anthraquinones, .alpha.-tetralone, 9-acetylphenanthrene,
2-acetyl-phenanthrene, 10-thioxanthenone, 3-acetyl-phenanthrene,
3-acetylindole, 9-fluorenone, 1-indanone, 1,3,5-triacetylbenzene,
thioxanthen-9-one, xanthene-9-one, 7-H-benz[de]anthracen-7-one,
benzoin tetrahydropyranyl ether,
4,4'-bis(dimethylamino)-benzophenone, 1 '-acetonaphthone,
2'-acetonaphthone, acetonaphthone and 2,3-butanedione,
benz[a]anthracene-7,12-dione, 2,2-dimethoxy-2-phenylacetophenone,
.alpha.,.alpha.-diethoxy-acetophenone,
.alpha.,.alpha.-dibutoxyacetopheno- ne, etc. Singlet oxygen
generating photosensitizers such as Rose Bengal, methylene blue,
and tetraphenyl porphine may also be employed as photoinitiators.
Polymeric initiators include polyethylene carbon monoxide and
oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanon- e].
Use of a photoinitiator is preferable because it generally provides
faster and more efficient initiation. When actinic radiation is
used, the initiators may also provide initiation at longer
wavelengths which are less costly to generate and less harmful.
[0103] When a photoinitiator is used, its primary function is to
enhance and facilitate the initiation of oxygen scavenging upon
exposure to radiation. The amount of photoinitiator can vary. In
many instances, the amount will depend on the amount and type of
monomers present in the present invention, the wavelength and
intensity of radiation used, the nature and amount of antioxidants
used, as well as the type of photoinitiator used. The amount of
photoinitiator also depends on how the scavenging composition is
used. For instance, if the photoinitiator-coating composition is
placed underneath a layer, which is somewhat opaque to the
radiation used, more initiator may be needed. For most purposes,
however, the amount of photoinitiator, when used, will be in the
range of 0.01 to 10% by weight of the total composition. The
initiating of oxygen scavenging can be accomplished by exposing the
packaging article to actinic or electron beam radiation, as
described below.
[0104] Antioxidants may be incorporated into the scavenging
compositions used in this invention to control degradation of the
components during compounding and shaping. An antioxidant, as
defined herein, is any material, which inhibits oxidative
degradation or cross-linking of polymers. Typically, such
antioxidants are added to facilitate the processing of polymeric
materials and/or prolong their useful lifetime.
[0105] Antioxidants such as Vitamin E, Irganox.RTM. 1010,
2,6-di(t-butyl)4-methyl-phenol(BHT),
2,2'-methylene-bis(6-t-butyl-p-creso- l), triphenylphosphite,
tris-(nonylphenyl)phosphite and dilaurylthiodipropionate would be
suitable for use with this invention.
[0106] When an antioxidant is included as part of the packaging, it
should be used in amounts which will prevent oxidation of the
scavenger composition's components as well as other materials
present in a resultant blend during formation and processing but
the amount should be less than that which would interfere with the
scavenging activity of the resultant layer, film or article after
initiation has occurred. The particular amount needed will depend
on the particular components of the composition, the particular
antioxidant used, the degree and amount of thermal processing used
to form the shaped article, and the dosage and wavelength of
radiation applied to initiate oxygen scavenging and can be
determined by conventional means. Typically, they are present in
about 0.01 to 1% by weight.
[0107] Other additives which may also be included in oxygen
scavenger layers include, but are not necessarily limited to,
fillers, pigments, dyestuffs, stabilizers, processing aids,
plasticizers, fire retardants, anti-fog agents, etc.
[0108] The amounts of the components which are used in the oxygen
scavenging compositions, or layers have an effect on the use,
effectiveness and results of this method. Thus, the amounts of
polymer, transition metal catalyst and any photoinitiator,
antioxidant, polymeric diluents and additives, can vary depending
on the article and its end use.
[0109] For instance, one of the primary functions of the polymer
described above is to react irreversibly with oxygen during the
scavenging process, while the primary function of the transition
metal catalyst is to facilitate this process. Thus, to a large
extent, the amount of polymer present will affect the oxygen
scavenging capacity of the composition, i.e., affect the amount of
oxygen that the composition can consume. The amount of transition
metal catalyst will affect the rate at which oxygen is consumed.
Because it primarily affects the scavenging rate, the amount of
transition metal catalyst may also affect the induction period.
[0110] Any further additives employed normally will not comprise
more than 10% of the scavenging composition, with preferable
amounts being less than 5% by weight of the scavenging
composition.
[0111] Optionally, the methods of this invention can include
exposure of the polymer containing the oxygen scavenging-promoting
transition metal catalyst to actinic radiation to reduce the
induction period, if any, before oxygen scavenging commences. A
method is known for initiating oxygen scavenging by exposing a film
comprising an oxidizable organic compound and a transition metal
catalyst to actinic radiation. Such methods are discussed in U.S.
Pat. No. 5,211,875, the disclosure of which patent is incorporated
herein by reference. A composition of the present invention which
has a long induction period in the absence of actinic radiation but
a short or non-existent induction period after exposure to actinic
radiation is particularly preferred. Compositions which are
activated by actinic radiation can be stored without special
preparation or storage requirements, such as being packaged or kept
in a nitrogen environment. They maintain a high capability for
scavenging oxygen upon activation with actinic radiation. Thus,
oxygen scavenging can be activated when desired.
[0112] The radiation used in this method could be light, e.g.,
ultraviolet or visible light having a wavelength of about 200 to
750 nanometers (nm), and preferably having a wavelength of about
200 to 600 nm, and most preferably from about 200 to 400 nm. When
employing this method, it is preferable to expose the oxygen
scavenger to at least 1 Joule per gram of scavenging composition. A
typical amount of exposure is in the range of 10 to 2000 Joules per
gram. The radiation can also be an electron beam radiation at a
dosage of about 2 to 200 kiloGray, preferably about 10 to 100
kiloGray. Other sources of radiation include ionizing radiation
such as gamma, X-rays and corona discharge. The duration of
exposure depends on several factors including, but not limited to,
the amount and type of photoinitiator present, thickness of the
layers to be exposed, thickness and opacity of intervening layers,
amount of any antioxidant present, and the wavelength and intensity
of the radiation source. The radiation provided by heating of
polyolefin and the like polymers (e.g., 100-250.degree. C.) during
processing does not enable triggering to take effect.
[0113] In various specific embodiments, the use of
oxygen-scavenging compositions in the present invention can be
accomplished by coating oxygen scavenging composition onto
materials such as metallic foil, polymer film, metallized film,
paper or cardboard to provide oxygen scavenging properties. The
compositions are also useful in making articles such as single or
multi-layer rigid thick-walled plastic containers or bottles
(typically, between 8 and 100 mils in thickness) or in making
single or multi-layer flexible films, especially thin films (less
than 3 mil, or even as thin as about 0.25 mil). Some of the
compositions of the present invention are easily formed into films
using well-known means. These films can be used alone or in
combination with other films or materials.
[0114] The compositions used in the present invention may be
further combined with one or more polymers, such as thermoplastic
polymers which are typically used to form film layers in plastic
packaging articles. In the manufacture of certain packaging
articles, well-known thermosets can also be used as a polymeric
diluent.
[0115] Selecting combinations of a diluent and the composition used
in the present invention depends on the properties desired.
Polymers which can be used as the diluent include, but are not
limited to, polyethylene, low or very low density polyethylene,
polypropylene, polyvinyl chloride, and ethylene copolymers such as
ethylene-vinyl acetate, ethylene-alkyl acrylates or methacrylates,
ethylene-acrylic acid or methacrylic acid, and ethylene-arylic or
methacrylic acid ionomers. In rigid packaging applications,
polystyrene is used; and in rigid articles such as beverage
containers, polyethylene terephthalate (PET) is often used. Blends
of different diluents may also be used. However, as indicated
above, the selection of the polymeric diluent largely depends on
the article to be manufactured and the end use. Such selection
factors are well known in the art.
[0116] If a diluent polymer such as a thermoplastic is employed, it
should further be selected according to its compatibility with the
composition of the present invention. In some instances, the
clarity, cleanliness, effectiveness as an oxygen-scavenger, barrier
properties, mechanical properties and/or texture of the article can
be adversely affected by a blend containing a polymer which is
incompatible with the composition of the present invention.
[0117] A blend of a composition used in the present invention with
a compatible polymer can be made by dry blending or by
melt-blending the polymers together at a temperature in the
approximate range of 50.degree. C. to 250.degree. C. Alternative
methods of blending include the use of a solvent followed by
evaporation. When making film layers or articles from
oxygen-scavenging compositions, extrusion or coextrusion, solvent
casting, injection molding, stretch blow molding, orientation,
thermoforming, extrusion coating, coating and curing, lamination or
combinations thereof would typically follow the blending.
[0118] Layers in the package wall of the present invention may be
in several forms. They may be in the form of stock films, including
"oriented" or "heat shrinkable" films, which may ultimately be
processed as bags, etc., or in the form of stretch-wrap films. The
layers may also be in the form of sheet inserts to be placed in a
packaging cavity. In a preferred embodiment of a rigid paperboard
beverage container, the layer may be within the container's walls.
Even further, the layer may also be in the form of a liner placed
with or in the container's lid or cap. The layer may even be coated
or laminated onto any one of the articles mentioned above.
[0119] In multi-layered articles, the scavenging layer used in the
present invention may be included with layers such as, but not
necessarily limited to, "oxygen barriers", i.e., layers of material
having an oxygen transmission rate equal to or less than 100 cubic
centimeters per square meter (cc/m.sup.2) per day per atmosphere
pressure at room temperature, i.e., about 25.degree. C. Typical
oxygen barriers comprise poly(ethylene vinyl alcohol),
polyacrylonitrile, polyvinyl chloride, poly(vinylidene dichloride),
polyethylene terephthalate, silica coated materials and polyamides.
Metal foil layers can also be employed.
[0120] To determine the oxygen scavenging capabilities of a
composition, the rate of oxygen scavenging can be calculated by
measuring the time that elapsed before the article depletes a
certain amount of oxygen from a sealed container. For instance, a
film comprising the scavenging component can be placed in an
air-tight, sealed container of a certain oxygen containing
atmosphere, e.g., air which typically contains 20.9% oxygen by
volume. Then, over a period of time, samples of the atmosphere
inside the container are removed to determine the percentage of
oxygen remaining. The scavenging rates of the compositions and
layers used in the present invention will change with changing
temperature and atmospheric conditions.
[0121] When an active oxygen barrier is prepared, the scavenging
rate can be as low as 0.1 cc oxygen per gram of composition of the
present invention per day in air at 25.degree. C. and 1 atmosphere
pressure. However, preferable compositions of this invention have
rates equal to or greater than 1 cc oxygen per gram per day, thus
making them suitable for scavenging oxygen from within a package,
as well as suitable for active oxygen barrier applications. Many
compositions are even capable of more preferable rates equal to or
greater than 5.0 cc O.sub.2 per gram per day.
[0122] Generally, film layers suitable for use as an active oxygen
barrier can have an oxygen transmission rate as high as 10 cc
oxygen per square meter per mil per day when measured in air at
25.degree. C. and 1 atmosphere pressure. Preferably, a layer of
this invention has an oxygen transmission rate less than about 1 cc
oxygen per square meter per mil per day, and more preferably has an
oxygen transmission rate less than about 0.2 cc oxygen per square
meter per mil per day under the same conditions, thus making it
suitable for active oxygen barrier applications as well as for
scavenging oxygen from within a package.
[0123] In an active oxygen barrier application, it is preferable
that the combination of oxygen barriers and any oxygen scavenging
activity create an overall oxygen transmission rate of less than
about 1.0 cubic centimeter-mil per square meter per day per
atmosphere pressure at 25.degree. C. Another definition of
acceptable oxygen scavenging is derived from testing actual
packages. In actual use, the scavenging rate requirement will
largely depend on the internal atmosphere of the package, the
contents of the package and the temperature at which it is
stored.
[0124] In a packaging article made according to this invention, the
scavenging rate will depend primarily on the amount and nature of
the composition of the present invention in the article, and
secondarily on the amount and nature of other additives (e.g.,
diluent polymer, antioxidant, etc.) which are present in the
scavenging component, as well as the overall manner in which the
package is fabricated, e.g., surface area/volume ratio.
[0125] The oxygen scavenging capacity of an article comprising the
invention can be measured by determining the amount of oxygen
consumed until the article becomes ineffective as a scavenger. The
scavenging capacity of the package will depend primarily on the
amount and nature of the scavenging moieties present in the
article, as discussed above.
[0126] In actual use, the oxygen scavenging rapacity requirement of
the article will largely depend on three parameters of each
application:
[0127] (1) the quantity of oxygen initially present in the
package;
[0128] (2) the rate of oxygen entry into the package in the absence
of the scavenging property; and
[0129] (3) the intended shelf life for the package.
[0130] The scavenging capacity of the composition can be as low as
1 cc oxygen per gram, but is preferably at least 10 cc oxygen per
gram, and more preferably at least 50 cc oxygen per gram. When such
compositions are in a layer, the layer will preferably have an
oxygen capacity of at least 250 cc oxygen per square meter per mil
thickness and more preferably at least 500 cc oxygen per square
meter per mil thickness.
[0131] Other factors may also affect oxygen scavenging and should
be considered when selecting compositions. These factors include
but are not limited to temperature, relative humidity, and the
atmospheric environment in the package.
EXAMPLES
[0132] Experiments were performed with several kinds of orange
juice containers to measure both the amount of oxygen in the
headspace of the containers as well as the amount of oxygen
dissolved in the juice and the amount of ascorbic acid contained in
the juice over a period of six weeks.
Example 1
[0133] A six-week shelf life study was conducted with orange juice
packaged in commercial paperboard barrier laminate (PBL) cartons
and in experimental carton samples using laminated board stock
containing oxygen scavenging polymer in the inner layers of the
cartons. PBL cartons consist of a laminated paperboard with a low
density polyethylene coated on the outer surface of the paperboard
and an oxygen barrier layer on the inside surface of the
paperboard. The experimental oxygen scavenging (OS) cartons
consisted of the PBL carton with a three-layer oxygen scavenging
film (ABA Structure: Polyethylene/oxygen scavenging
polymer/Polyethylene) further laminated on the inside surface of
the oxygen barrier layer. PBL cartons containing loose strips of
the three-layer oxygen scavenging film were also used. The oxygen
scavenging films were one of three sizes: 4".times.31/2",
4".times.7", and 4".times.14".
[0134] The juice cartons were stored at 40.degree. F. and the
orange juice was tested for ascorbic acid (vitamin C) and dissolved
oxygen on a weekly basis. After six weeks, the orange juice
packaged in the oxygen scavenger cartons retained a significantly
greater amount of vitamin C as compared to the commercial PBL
cartons.
[0135] Cartons were filled with orange juice and the amount of
dissolved oxygen in the orange juice was measured using a YSI
Dissolved Oxygen meter. The amount of vitamin C was measured by a
visual titration method used extensively by the citrus industry,
(AOAC Method, 1965, Official methods of Analysis, p. 764).
[0136] Orange juice in glass bottles was used as the control. PBL
cartons were used as a standard. The oxygen scavenger laminate
portion of the PBL carton with oxygen scavenger laminate was
extrusion coated and later converted into trial cartons.
[0137] The six packaging constructions filled with orange juice
were:
[0138] (1) Glass--Control.
[0139] (2) PBL carton--Standard.
[0140] (3) PBL carton with oxygen scavenger laminate (OS).
[0141] (4) PBL carton with 4".times.31/2" oxygen scavenger film
strip (Film 3).
[0142] (5) PBL carton with 4".times.7" oxygen scavenger film strip
(Film 4).
[0143] (6) PBL carton with 4".times.14" oxygen scavenger film strip
(Film 5).
[0144] The oxygen scavenging cartons and films were exposed to
ultra-violet light to activate the oxygen scavenger. The rapid
decrease of dissolved oxygen in these cartons is noted in the data.
The oxygen scavenger at day one, (week 0), had already begun to
remove oxygen from the juice. By week one, the dissolved oxygen had
dropped significantly and remained low throughout the study. This
correlated with the retention of vitamin C in these cartons.
[0145] Agitation of the juice during filling increases the oxygen
present in solution. The oxygen scavenger filmstrips, which were
dropped into PBL cartons, were aggressive in removing oxygen from
the orange juice but were not as effective as the extruded OS
cartons. This may be due to the limited exposure and surface area
of the strips in relation to the volume of the orange juice.
[0146] Graphs have been separated into four groups for ease of
interpretation:
[0147] FIG. 1) Vitamin C retention in glass container, PBL and OS
cartons.
[0148] FIG. 2) Amount of dissolved oxygen in glass, PBL and OS
cartons.
[0149] FIG. 3) Vitamin C retention in OS carton and PBL cartons
with OS film strips.
[0150] FIG. 4) Dissolved oxygen in OS carton and PBL cartons with
OS film strips.
1 VITAMIN C DATA, MG/LITER WEEK GLASS PBL OS FILM 3 FILM 4 FILM 5 0
34.34 34.27 34.54 34.54 33.85 34.73 1 33.67 33.06 34.86 33.37 33.42
34.86 2 32.37 30.75 34.33 33.35 33.35 34.08 3 31.24 29.58 32.21
31.34 31.04 30.95 4 32.86 30.15 33.72 31.25 32.76 32.76 5 33.42
26.77 32.32 28.68 29.8 30.42 6 32.96 24.76 31.36 27.28 27.67
28.16
[0151]
2 TOTAL VITAMIN C LOSS AFTER SIX WEEKS GLASS PBL OS FILM 3 FILM 4
FILM 5 % 3.8 27.2 9.1 20.9 18.3 18.7
[0152]
3 DISSOLVED OXYGEN, MG/LITER WEEK GLASS PBL OS FILM 3 FILM 4 FILM 5
0.0 4.3 3.8 2.5 2.7 2.9 1.8 1.0 4.3 2.9 0.3 0.7 0.9 0.9 2.0 0.3 1.4
0.2 0.8 1.3 1.5 3.0 0.1 1.0 0.3 1.1 1.1 0.9 4.0 0.2 1.0 0.8 0.8 1.1
1.1 5.0 0.2 1.6 1.0 0.4 1.5 1.3 6.0 0.2 3.4 0.3 1.7 2.3 4.0
[0153] Nutritional labeling of the orange juice requires that the
stated percent of vitamin C be maintained through the out date
posted on the carton. Oxygen will cause vitamin C to oxidize
resulting in a loss of vitamin C. The purpose of the oxygen
scavenger is to remove oxygen from the juice, from the package
headspace, and any fugitive oxygen that permeates through the
package wall. This action is accomplished by a catalyzed metal
reaction of the scavenger polymer with oxygen. The oxygen
scavenging polymer used in this test was a
styrene/butadiene/styrene-base- d oxygen scavenger containing 1000
ppm of cobalt ion (as cobalt neodecanoate) and 1000 ppm of
benzoylbiphenyl (BBP) photoinitiator.
[0154] Barrier films, such as polyamides used in PBL, slow the
permeation rate of oxygen through the board structure, but do not
remove the oxygen from the package headspace or contents. The
oxygen scavenger works to remove residual and/or fugitive oxygen
present in the package contents.
[0155] These preliminary results indicate that this oxygen
scavenging package provides superior results for the extension of
orange juice shelf life.
Example 2
Organoleptic Tests
[0156] The organoleptics (negative effects on taste and odor) of
the present invention were tested by comparing the taste of water
and a fatty food packaged in an extrusion coated package having a
layer of oxygen scavenging material incorporated as an internal
layer of the package material with water and a fatty food packaged
in a control package of identical structure but without the oxygen
scavenging layer. Triangle tests with forced preferences were run
using 28 trained panelists. In all cases, the sensory panel results
showed a statistically significant (P<0.0001) preference for the
packages containing the oxygen scavenging system over the
control.
[0157] Although a few embodiments of the invention have been
described in detail above, it will be appreciated by those skilled
in the art that various modifications and alterations can be made
to the particular embodiments shown without materially departing
from the novel teachings and advantages of the invention.
Accordingly, it is to be understood that all such modifications and
alterations are included within the spirit and scope of the
invention as defined by the following claims.
* * * * *