Note: Descriptions are shown in the official language in which they were submitted.
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METHOD. APPARATUS. AND SYSTEM FOR TRIGGERING OXYGEN SCAVENGING
FILMS
Background Of The Invention
The invention relates generally to a method, apparatus, and system for
packaging
oxygen sensitive materials, and particularly to a method, apparatus, and
system for triggering
an oxygen scavenging film.
It is well known that limiting the exposure of oxygen sensitive articles to
oxygen
maintains and enhances the quality and shelf life of the article. For
instance, by limiting the
oxygen exposure of oxygen sensitive food articles in the packaging system, the
quality of the
food article is maintained and spoilage is reduced. In addition, such
packaging also keeps the
article in inventory longer, thereby reducing restocking costs, and costs
incurred from waste.
Commonly used packaging systems include modified atmosphere packaging (MAP)
and vacuum packaging in conjunction with oxygen barrier films. In these
instances, reduced
oxygen environments are employed at the time of packaging, while the oxygen
barrier film
reduces the amount of oxygen that physically enters the package during
storage.
U.S. Patent No. 5,211,875 to Speer et al. discloses methods and compositions
for
scavenging oxygen. The "oxygen scavenger" materials disclosed by Speer et al.
are
compositions which consume, deplete or reduce the amount of oxygen from a
given
2 0 environment.
Oxygen scavenging materials are useful in MAP and barrier packaging
environments.
However, oxygen scavenging materials typically require triggering or
activation to bring on
the oxygen scavenging properties, and delays referred to as an induction
period are sometimes
experienced before the onset of useful oxygen scavenging properties.
Compositions exhibiting
2 5 lengthy induction times must be held by an end user in inventory for a
sufficient period of time
before use. On the other hand, oxygen scavenging compositions having a shorter
induction
period must be used within a relatively short period of time so that the
oxygen scavenging
properties of the material are not prematurely exhausted.
The need remains for an effective method of triggering an oxygen scavenger
film so as
3 0 to trigger oxygen scavenging properties when desired; preferably a method
having a short
induction period so that the film can be triggered at or immediately prior to
use during
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packaging of an oxygen sensitive article; and
preferably one which :i~: simpl.e and readily incorporated into
existing packaging procedures.
The need also remains for an apparatus for
triggering an oxygen :scavenging film so as to provide the
film with a short or negligible induction period; preferably
enhanced oxygen scaver~g.ing rate and longevity; preferably an
apparatus which is read:i7.y incorporated in-line into
existing packaging systems for triggering oxygen scavenging
film at or irr~mediately prior to packaging.
Summa:rv Of 'The Invention
In a first aspect the invention provides a method
comprising: a) prcaviding an unwind roll, said roll adapted
to hold a rol.1 of oxygen scavenging film, the film
comprising an oxidizabl.e c>rganic compound and a transition
metal catalyst.; b) providing an apparatus for triggering
said film, thE: apparatus c:omprising~ a series of bulbs
adapted to emit UV-C light having a wavelength of between
200 and 280 nanometers, i~ne bulbs arranged in banks so as to
expose the oxygen scaveng=ing film to a dose of said UV-C
light of at least 100 mJ~<:mz as the film passes the bulbs; c)
advancing the film from t:he unwind roll to the apparatus for
triggering the film by rne~ans of a series of rollers that
define a film path extending from the unwind roll to the
apparatus for triggering the film; d) passing the film past
the series of iJV bulbs arranged in hanks; e) exposing the
film to UV-C Eight having a wavelenc;th of between 200 and
280 nanometers,. so as to provide a triggered film; f)
advancing the triggered film from the apparatus for
triggering to an apparatus for packaging articles; and g)
applying said triggered f:ilm, in the apparatus far packaging
articles, to m«ke packages for <ront:aining said articles;
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whereby said triggered f~.:~lm is continuously triggered and
incorporated into said packages so as to provide oxygen
scavenging packages.
In a second aspect the invention provides an
apparatus for tri_gger.,ng an oxygen scavenging film
comprising: rneans for e~ni.tting LJV-C light having a
wavelength of. between 20(i nm and 280 nm; means for defining
a film path associatecl with said nneans for emitting UV-C
light; and means for feeding a f=ilm having an oxidizable
1C organic compc>und to said film path whereby said film is
exposed to a dose of said W-C light of at least 100 mJ/cm2
so as to provide a triggered 'il.m.
In a third aspe~~t the invention provides a
packaging system ~compr:ising: means for emitting W-C light
having a wavelength of ber_ween 200 and 280 nm; means for
defining a film path associates with said means for emitting
W-C light; means for feeding a fi:Lm having an oxidizable
organic compound to said film path whereby said film is
exposed to a dose of said UV-C' light of at least 100 mJ/cm2
so as to provide a tric~ge.red film; means for feeding said
triggered film to a means for packaging articles; and means
for applying said triggered film to the articles to make
packages; whereby said tr:i.ggered film is continuously
triggered and incorporated into said packages so as to
provide oxygen scavenging packages.
Brief Descri..~tion Of The Drawings
A detailed description of preferred embodiments of
the invention follows, w_t.h reference to the attached
drawings, wherein:
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Figure 1 schematically illustrates a stand alone
apparatus and method i:or triggering an oxygen scavenging
film;
Figure 2 schematically illustrates an apparatus
E~ and method incorporated i.n-line into a packaging system;
Figures 3 and 4 illustrate the amount of oxygen
scavenged by various cxygen scavenging lidstock films
triggered at 254 and 365 .nm respectively;
Figures 5 and 6 illustrate the oxygen scavenged by
various oxygen scavenging laminates made into barrier
packages which were triggered at 254 and :365 nm
respectively;
Figure 7 illl.zstrates a comparison of oxygen
scavenging fo:r films triggered a single exposure of 40
seconds to a film triggered in 4 sequential 10 second
periods;
Figure 8 illL~s~rates a relationship between lamp
intensity and vertical displacement from the bulb for
sleeved and unsleeved bulbs;
Figure 9 illustrates the relationship between
average oxygen scavenginc;.rate and dose applied to the film
at 254 nm;
Figure 10 comparativE:ly illustrates the oxygen
concentration in a bologna package having a triggered oxygen
scavenging film and a ncar~-c.~xygen scavenging film;
Figure 11 illustrates the average 02 residuals of
packages being placed ir~.tc lighted display;
Figure 12 illustrates the cai.ib:ration curve of
dose vs . Hunter- a-value ; anal
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Figure 13 i:~lustrates the relative improvement in
color (highe:r Hunter a-value) of bologna slices packaged in
the oxygen scavenging film of Example 4, as opposed to
bologna pack<~ged in TE>23~.
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Description of the Preferred Embodiments
The invention relates to an improved method,
apparatus, and system for triggering an oxygen scavenging
film, preferably for use in packaging articles. The
invention can be used in the packaging of a wide variety of
oxygen sensitive articles including fresh red meat such as
beef, pork, lamb, and veal, smoked and processed meats such
as sliced turkey, pepperoni, ham and bologna, vegetable
articles such as tomato based products, other food products,
including baby food, beverages such as beer, and products
such as electronic components, pharmaceuticals and the like.
The invention is readily adaptable to various vertical form-
fill-and-seal (VFFS) and horizontal form-fill-and-seal
(HFFS) packaging lines.
A method, apparatus, and system for triggering
oxygen scavenging film are provided wherein an induction
period of the film after triggering can be reduced to
periods of substantially less than one day, whereby
triggering can be incorporated as an in-line step,
preferably by an end user of the oxygen scavenging film, so
as to avoid inventory problems with respect to triggered
films.
Oxygen scavenging compositians generally are
described in U.S. Patent No. 5,211,875, U.S. Patent
No. 5,350,622 and U.S. Patent No. 5,399,289 to Speer et al.
As used herein, oxygen scavenging film refers to film having
a composition which consumes, depletes or reduces the amount
of oxygen from a given environment to which the composition
is exposed. The method and apparatus for triggering the
oxygen scavenging film serves to trigger or activate the
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oxygen scavenging capability of the film.
Other oxygen scavengers which can be used in
connection with this invention are disclosed in PCT patent
publication WO 94/12590 (Commonwealth Scientific and
Industrial Research Organisation). These oxygen scavengers
include at least one reducible organic compound which is
reduced under predetermined conditions, the reduced form of
the compound being oxidizable by molecular oxygen, wherein
the reduction and/or subsequent oxidation of the organic
compound occurs independent of the presence of a transition
metal catalyst. The reducible organic compound is
preferably a quinone, a photoreducible dye, or a carbonyl
compound which has absorbence in the UV spectrum.
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Films for use with the invention preferably include an oxidizable organic
compound
and a transition metal catalyst. Optionally, the oxygen scavenging film may
also include
photoinitiator compositions, antioxidants and other additives, for example as
disclosed in U.S.
Patent 5,211,875. Preferred films contain oxidizable organic compound of
substituted or
5 unsubstituted ethylenically unsaturated hydrocarbon polymers, preferably
having a molecular
weight of at least 1000. More preferably, the oxidizable organic compound is
selected from
the group consisting of styrene/butadiene copolymers, styrene/isoprene
copolymers,
polybutadiene, polyisoprene, or mixtures thereof.
The transition metal catalyst of the oxygen scavenging composition is
preferably a
transition metal salt of cobalt, manganese, or mixtures thereof Other suitable
transition metal
catalysts are disclosed in U.S. Patent 5,211,875.
The ethylenically unsaturated hydrocarbon and transition metal catalyst may be
further
combined with one or more polymeric diluents, 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 the polymeric
diluent. Polymers
which can be used as the diluent include, but are not limited to, polyethylene
terephthalate
(PET), polyethylene, low or very low density polyethylene, ultra-low density
polyethylene,
linear low density polyethylene, polypropylene, polyvinyl chloride,
polystyrene, and ethylene
copolymers such as ethylene-vinyl acetate, ethylene-alkyl (meth)acrylates,
ethylene-
2 0 (meth)acryiic acid and ethylene-(meth)acrylic acid ionomers. Blends of
different diluents may
also be used. The selection of the polymeric diluent depends in part on the
article to be
manufactured and the end use.
It has been discovered that exposing oxygen scavenging film to UV light at
certain
wavelength, intensity, residence time and distance from the film results in a
triggering of the
2 5 oxygen scavenging properties of the film in a relatively short period of
time, i. e. the induction
period. UV-C light such as UV light of germicidal wavelengths has been found
particularly
effective at triggering oxygen scavenging films. Preferred wavelengths are
between 200 nrn
and 280 nm, such as 254 nm.
Oxygen scavenging films to be triggered are exposed to UV-C light at the
desired
3 0 wavelength, at an intensity and residence time sufficient to provide the
film with a dose of UV-
C light of at least 100 mJ/cm2, preferably at least 200 mJ/cm2, more
preferably between 350
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and 1600 mJ/cm2. It has been found that, within this range, different doses of
UV-C light
affect the scavenging rate of the film after triggering. When the triggered
film is to be used in
packages having a head space, such as modified atmosphere packages (MAP), a
faster oxygen
scavenging rate, preferably with a very short induction period, is preferred.
With such
packages, the preferred doses of UV-C light are between 350 and 1600 mJ/cmz,
such as
between 500 and 800 mJ/cm2.
When the oxygen scavenging film is to be used in oxygen barrier packaging, the
scavenging film provides a function of assisting in preventing the influx of
oxygen through the
package layers. In this application, lower oxygen scavenging rates are
acceptable and
preferred so that the oxygen scavenging film enhances the oxygen barrier
nature of the
package for longer periods of time. For use with barrier packages, especially
high barrier long
hold packages, the preferred dose of triggering UV-C light is between 100 and
600 mJ/cm2.
The intensity and residence time of UV-C light may be utilized to provide the
desired
dose for a particular film. It is preferred to expose film to be triggered to
UV-C light with a
wavelength between about 240 and 265 nm at an intensity of at least 0.8
mW/cmz, more
preferably at least 2.0 mW/cm2. In order to provide film paths which are not
very long, film
to be triggered is exposed more preferably to UV-C light at an intensity of
between 3.0 and
10 mW/cm2, such as between 3.0 and 7.5 mW/cm2. This intensity is provided at a
distance
from the source of UV-C light to the film of preferably between 1 cm and 3 cm.
2 0 The desired dose of UV-C light is provided to a particular film by
traversing the film
over a path having a particular length over which the film is exposed to the
UV-C light. At
intensities as set forth above, oxygen scavenging film is usefully triggered
over film paths
preferably having a length between 1 m and 12 m, preferably 2 to 4 m and at
average traveling
speed of the film along the path of between 1 m/min and 30 m/min, typically
1.2 to 4 m/min.
2 5 This procedure results in exposure times of the film to UV-C light of
typically between 15 and
90 seconds. The above described wavelength, intensity and residence time of UV-
C light have
been found to trigger oxygen scavenging film to excellent oxygen scavenging
rates, and with
very small or negligible induction periods, thereby allowing the method of the
present
invention to be incorporated in-line to existing packaging methods so that
oxygen scavenging
3 0 film can be triggered at or shortly prior to packaging, and ameliorating
problems related to
storage and inventory of triggered oxygen scavenging films.
r ___ -_ ._. . ___._..__.~__. _.. ._.
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Oxygen scavenging films thus triggered exhibit oxygen scavenging rates,
depending
upon the formulation and type of package to which the film is applied, of
between 1 cc/m2/day
and 100 cc/m2/day at temperatures of 4°C when measured 4 days after
triggering. For
modified atmosphere packages (MAP) having a modified atmosphere headspace,
(MAP, 1-2%
OZ), triggered oxygen scavenging film exhibits an oxygen scavenging rate of
between 20 and
66 cc/m2/day at 4°C when measured 4 days after triggering, thereby
removing oxygen from
the head space of such a package so as to reduce or eliminate adverse affects
upon the article
packaged therein.
Oxygen scavenging films, triggered as set forth above for use in high barrier
long hold
packages, exhibit oxygen scavenging rates of preferably between 1 and 10
cc/m2/day when
measured at room temperature, and 30 days after triggering, thereby providing
a further
oxygen barrier in the oxygen barrier layers of the package to which the oxygen
scavenging film
is applied, which oxygen scavenging exists over a longer period of time.
Triggered oxygen scavenging films can be used to rapidly reduce the residual
oxygen
content of a refrigerated MAP package to less than or equal to 0.5%,
preferably less than or
equal to 0.1 % within less than or equal to 7 days, preferably less than or
equal to 4 days and
ideally as quickly as possible after article packaging. This allows packages
that include the
triggered oxygen scavenging film to be packaged with an initial residual
oxygen content of 1
to 2% or higher. The oxygen scavenging film rapidly reduces the residual
oxygen content to
2 0 acceptable levels, and packaging at a higher initial residual oxygen
content allows for faster
machine cycles, thereby enhancing article output.
Referring now to the drawings, the method and apparatus for triggering oxygen
scavenging film according to the invention will be further described. Figure 1
illustrates a free
standing triggering unit 10 having an unwind roll 12 for feeding film to unit
10, a series of
2 5 rollers 14 defining a film path 16 through triggering unit 10, and a
windup roll 18 for receiving
triggered film for subsequent use. Triggering unit 10 includes a series of low
pressure
germicidal wavelength UV bulbs 20 arranged in banks 22, with film path 16
being arranged to
pass a film relative to banks 22 so as to expose the film to the desired dose
of UV-C light.
The oxygen scavenging film may include a number of layers, with the oxidizable
3 0 organic compound and transition metal catalyst layer preferably being
arranged toward one
side thereof. Multilayer oxygen scavenging films are described in U.S. Patent
No. 5,350,622.
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It is preferable to expose only the oxidizable organic compound and the
transition metal
catalyst side of the multilayer film to UV-C light. Further, it is preferred
that any layers of the
multilayer film that are between the source of UV-C light and the oxygen
scavenging film be
effectively transparent between 240 and 265 nm. Thus, as illustrated in Figure
1, film path 16
can be arranged so as to expose only one side of film to banks 22 of bulbs 20,
although
optionally both sides of the film can be exposed to bulbs 20.
It is preferred to provide film path 16 at a distance from banks 22 of bulbs
20 of
between 1 cm and 3 cm, such as 2 cm. At distances greater than 3 cm, the
intensity of UV-C
light loses affect at triggering films. At distances of less than 1 cm, the
film can be adversely
affected by bulb heat and static electricity.
Figure 2 illustrates an embodiment of triggering unit 10 wherein triggering
unit 10 is
incorporated in-line into a packaging apparatus. Triggering unit 10 is
positioned so as to
receive film from unwind roll 12, pass film along film path 16 for exposure to
UV-C light, and
feed triggered film directly to a packaging unit, for example, sealing/gas
flush dies 24.
Triggered film is immediately incorporated as a layer into packages along with
formed web 26
supplied from other elements of the packaging assembly. Sealing/gas flush dies
24 serve to
apply triggered film 28 to formed web 26 so as to provide packages 30
including triggered
film.
Optionally, triggering unit 10 can be provided with a sensor unit 32 for
monitoring the
2 0 dose of UV-C light emitted by bulbs 20. This allows detection of
deteriorating or
malfunctioning bulbs 20 so that the use of un-triggered film in packaging can
be substantially
avoided. Sensor unit 32 can be, for example, an Online UV Intensity Display
Module (EIT,
Inc., Sterling, VA) having 250-260 nm Standard UVI Sensors. Of course,
numerous other
apparatus are available for use in measuring the level of UV-C light output of
banks 22.
2 5 Sensor unit 32 can be interlocked or operatively associated with a
controller for the packaging
line so that packaging can be automatically interrupted if UV-C light output
is insufftcient.
Bulbs 20 are preferably shielded so as to insure that the UV exposure to
workers
during an 8 hour shift is within a permissible level. This corresponds to an
effective intensity
or irradiance E (as defined in Radiation Curing, May 1985, pages 10 to 13) of
less than or
30 equal to 0.1 ~W/cm2 in the range of 200 to 315 nm.
T __ ___.. __ __..._ .._ ~..._
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Bulbs 20 are preferably provided with a sleeve member for protecting the film
in the
film path 16 against contact with broken elements such as glass, etc., of a
bulb 20, should bulb
20 break or otherwise fail. This avoids contamination of the film due to such
a failure. The
sleeve can be a shrinkable member or coating to be applied to bulbs 20,
preferably having a
minimal affect upon intensity of UV-C light emitted from bulbs 20. The
preferred sleeve is a
heat-shrunk FEP-Teflon~ sleeve, which does not adversely affect the intensity
of germicidal
254 nm bulbs used to provide UV-C light.
Bulbs 20 can be fluorescent tube-type bulbs, which preferably have a width
sufficient
to extend beyond either side of the width of a film to be treated, thereby
insuring a complete
dose of UV-C light to be applied to oxygen scavenging film to be triggered.
Bulbs have a
width of preferably between 20 and 48 inches, which may be suitable for
treating films having
a width of between 13 and 40 inches. Suitable bulbs are sold by Voltarc under
part
designation UV-LUX GRFX5194
The step of exposing oxygen scavenging film to UV-C light can optionally be
carried
out in a stepwise procedure wherein the film is exposed in a plurality of
discrete periods of
time. For example, if the intended exposure time or residence time is to be 40
seconds, the
exposing step can be carried out in a series of four exposing steps, each 10
seconds long,
preferably with a two second interval therebetween. Such stepwise exposure
provides
enhanced oxygen scavenging characteristics of the film triggered thereby. This
embodiment is
2 0 readily adaptable to packaging machines which operate with intermittent
motion such as
MULTIVAC 87000 distributed by KOCH of Kansas City, Missouri.
The following examples are provided in order to further illustrate the
advantageous
features of the present invention.
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In
EXAMPLE 1
A three-layer oxygen scavenging film was prepared by a flat coextrusion
process. The
outer layers of the film consisted of LLDPE (Dowlex~ 3010, Dow Chemical,), and
the inner
oxygen scavenging layer (OSL) consisted of 68% 1,2-polybutadiene {RB830, JSR
(Japan
Synthetic Rubber)), 12% EPDM rubber (Vistalon~ 3708, Exxon), and 20% of an EVA-
9
(ethylene/vinyl acetate copolymer , Exxon) based cobalt neodecanoate and
benzophenone
masterbatch, which had been prepared previously in a twin screw extruder. The
final
concentration of cobalt in the scavenging layer of the film was 540 ppm as
cobalt metal, and
the final concentration of benzophenone was 0.5%. The total thickness of the
film was 3
mils, with each layer being 1 mil thick. Portions of film (200 cm2) were
irradiated as
described below in Table 1 with a UVP Inc. model XX-1 SS germicidal lamp. The
output of
the lamp was measured at a distance of 2 cm with an International Light model
1400A
radiometer equipped with a SEL 240 detector, a 254 nm narrow band pass filter
(NS254), W
diffuser, and a neutral density filter (QNDS2). After a 5 minute warm up
period, the output
ranged from 4.2-5.7 mW/cm2 at 254 nm. Irradiated films were then sealed in
barrier bags
(BDF 2001, Cryovac~ Division of W. R. Grace & Co.), and inflated with 300 cc
of air.
Portions of the headspace were periodically withdrawn and analyzed for oxygen
with a Mocon
LC 700F oxygen analyzer. The resulting scavenging data is summarized below in
Table 1.
The average rate is calculated by considering only the end points, with the
following formula:
2 0 Average Rate = cc OZ scavenged/(mz~day)
and in this example was calculated after 30 days. The peak instantaneous rate
is the highest
scavenging rate observed during any sampling period, and is given by: 0 cc OZ
scavenged/(m2~Dday), where D is the incremental change. The number in
parenthesis is the
number of days after triggering required to reach the peak rate.
2 5 TABLE I
Low Intensity Germicidal UV (254 nm) Triggering
LLDPE/OSL/L,LDPE films at room temperature
Dose Irradiation Induction PeriodAverage Peak Ins.
(J/cmz) Time (days) Rate Rate
(seconds) (cc02/m2/day)(cc OZ/m2/day)
0.26-0.36 63 >1<2 50 134 (3)
0.63-0.86 150 <I 40 134 (3)
1.3-1.8 310 I <1 I 40 ~ 206 (2)
I
T...._~. ____. ....._..._~.."...~._..__... _..__ _ _.
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2.7-3.6 I 630 ~ <1 I 44 i 190 (2)
The data in Table 1 shows that low intensity short wavelength UV is quite
effective in
triggering oxygen scavenging. In addition, higher doses have little effect on
the average
scavenging rate, but do seem to increase the peak instantaneous rate.
EXAMPLE 2
This example illustrates the advantage of UV-C light at 254 nm over other
wavelengths for use in triggering oxygen scavenging film. Samples of film were
evaluated for
a lidstock film, and a laminate for vertical/form/fill/seal pouches ("ONPACK"
in Table 3). The
lidstock film was a three layered film having the structure LLDPE/OSL/LLDPE (
1 / 1 / 1 mil).
The LLDPE layers were layers of Dowlex 3010 film from Dow Chemical. The OSL
(oxygen
scavenging layer) consisted of 50% styrene- isoprene- styrene tribiock
copolymer (VectorTM
4114-D from Dexco), 40% LDPE 1017 (Chevron), 10% SF (side feed) containing
Quantum
MU763-EVA, 5% benzophenone and 3% cobalt neodecanoate (Ten-Cem~ from OMG,
Inc.),
and 1 % calcium oxide. The laminate was also a three layer structure
LLDPE/OSL/LLDPE
(1/1/1 mil), having an OSL layer of RB-830TM from Japan Synthetic Rubber, and
Vistalon
3708 (Exxon) (a final concentration of 540 ppm cobalt and 0.5% Benzophenone).
Triggering of the films was evaluated at two wavelengths and various dosages
using four
different types of lamps as the light source. It should be noted in these
examples that dose is
measured at or about the wavelength specified. Tables 2 to 4 set forth the
parameters of each
test.
2 0 TABLE 2
Parameters Used in the Triggering of Iidstock and laminate Structures
LAMP WAVELENGTH INTENSITY DOSAGE USED
(nm) (mW/cmz) (J/cm2)
AMERGRAPH~ 365 3 0.5, 0.75, 1.0
rom American
Graphics
ANDERSON- 365 25 0.5, 0.75, 1.0
VREELAND
CYREL 365 32 0.5, 0.75, 1.0
VP~BIak-ray-XX-254 5.7 0.36, 0.71,
3.6
15s ~ ~ ~
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ZG
ANDERSON- 254 9.2 0.39, 0.76,
3.8
VREELAND
TABLE 3
Triggering Experiments at 365 nm
NO. Film Type Dose Intensity Exposure Time
(Joules/cmz)(mW/cmz) (dependent variabie)
(seconds)
1 ONPACK 0. _5 25 20
2 LIDSTOCK 0.75 3 250
3 ONPACK 0.75 32 24
4 LIDSTOCK 0.5 3 166
LAMINATE 1.00 3 333
6 LAMINATE 0.75 25 30
7 LAMINATE 0.75 32 24
8 LIDSTOCK 0.50 32 16
9 LAMINATE 1.0 32 32
IO LIDSTOCK 1.0 3 333
11 LIDSTOCK 1.0 32 32
12 LAMINATE 1.0 25 40
I3 LIDSTOCK 1.0 25 40
14 LAMINATE 0.50 3 166
LAMINATE 0.75 3 250
16 LIDSTOCK 0.50 25 20
17 LAMINATE 0.50 32 16
18 LIDSTOCK 0.75 25 30
r . _._ ~_.. ._
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TABLE 4
Triggering Experiments at 254 nm
NO. Film Type Dose Intensity Exposure Time
(Joules/cm2)(mW/cm2) (dependent variable)
(seconds)
1 LAMINATE 0.05 9.2 42
2 LIDSTOCK 0.50 5.7 625
3 LIDSTOCK 0.05 5.7 62.5
4 LAMINATE 0.50 9.2 420
LIDSTOCK 0.05 9.2 42
6 LAMINATE 0.10 9.2 84
7 LIDSTOCK 0.10 5.7 125
8 LIDSTOCK 0.50 9.2 420
9 LAMINATE 0.10 5.7 125
LIDSTOCK 0.10 9.2 84
11 LAMINATE 0.05 5.7 62.5
12 LAMINATE 0.50 5.7 625
Each film was provided as a 200 cm' piece, which was triggered at the
specified dose and
tested in a barrier bag having 300 cc headspace of air at room temperature.
The oxygen
5 scavenging rates for each sample were determined and are set forth in Figs.
3-6. As shown,
the exposure times ranged from as short as 16 seconds to as long as 625
seconds. As shown
in Fig. 3, the lidstock film was successfully triggered using low intensity
light at 254 nm.
Lidstock films triggered with dosages of 0.4 J/cmz had scavenging rates
similar to films
triggered at 3.6-3.8 J/cmz. Triggering with 365 nm resulted in longer
induction periods and
10 lower oxygen scavenging rates (see Figure 4) thereby clearly indicating the
superiority of low
intensity light at 254 nm for triggering. For the laminate film, 254 nm light
also provided
better results as shown by Figs. 5 and 6.
EXAMPLE 3
In this example, lidstock film as in Example 2 was exposed to light at 254 nm
(1) for
40 seconds and (2) for four periods of 10 seconds, each separated by 2 second
breaks. Figure
7 illustrates the oxygen scavenging rates exhibited by the films,
demonstrating that the
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stepwise triggering resulted in at least equivalent or better oxygen
scavenging than the single
triggering step.
EXAMPLE 4
This example further illustrates the effective triggering of oxygen scavenging
films
according to the present invention. Samples of a lidstock film were triggered
using the
apparatus in Fig. 1 employing 254 nm light at several dose rates and web
speeds, and the
triggered samples were tested for oxygen scavenging rates and induction
period. Film samples
with the following structure: Saran coated PET//EVA/OSL/LLDPE
(0.48//1.2/0.5/0.3 mil)
were provided. The EVA layer was an ethyiene/vinyl acetate copolymer layer
(Rexene
PE1375). The OSL layer was 50% SBS (Vector~8508 from Dexco), 40% LDPE (Chevron
PE1017), 8.54% EVA (Quantum), 0.90% cobalt neodecanoate (Ten-Cem~ from OMG,
Inc.), 0.5% benzophenone, 0.05% Ca0 and 0.01% stabilizer (Irganox~ 1076 from
Ciba-
Geigy). The LLDPE layer was Dowlex 2244A. The film was refrigerated to
4°C and
triggered, and then exposed to a 300 cc headspace containing 99% Nz and 1 % Oz
and further
stored at 4°C. The scavenging rates for each sample are set forth below
in Table 5.
TABLE S
SCAVENGING PERFORMANCE OF LAMINATED FILM TRIGGERED ON
APPARATUS OF FIG. 1 f 200 CMz FILM SAMPLEI
DOSE WEB AVERAGE PEAK
SPEED RATE(a) INST. RATE
(mJ/cm2) (FPM) (CC/(MZDAY)) INDUCTIO(CC/(MzDAY))(b)
can St.
Dev. MEAN
PERIOD
661 8 28.7 0.8 < 1 87.1 1
559 12(c) 41.0 6.2 <t 58.1 1
483 16 26.6 0.8 <1 68.6 1
(a) average rate calculated after 4 days.
2 0 (b) days to reach peak rate.
(c) packages run on Multivac~ 87000.
As shown, each sample had an induction period of less than one day, and
exhibited
excellent average and peak instantaneous oxygen scavenging rates.
r_____~~~..~___. . _ _.__.__~.__ _~.___~.__.._ _._
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EXAMPLE 5
This example demonstrates the effectiveness of bulbs having a sleeve member in
triggering oxygen scavenging film. The UV intensity of sleeved and unsleeved
bulbs were
determined using a radiometer described in Example 1. The intensity between
two bulbs, at a
5 distance of 2.54 cm from the plane of the bulbs and vertical displacement
along the path from
one bulb to the other was determined and is illustrated in Fig. 8. As shown,
the intensity of
sleeved bulbs is not significantly impacted.
A film having the same composition as described in Example 4 was triggered
using the
sleeved and unsleeved bulbs as set forth above. Dose rate calibration was
accomplished using
10 radiochromic Control Cure~ labels (UV Process Supply/Chicago, IL). These
labels were
exposed at varying dose rates using the Blak Ray XX-15S. Dose Rate was
measured with the
IL1400A/SEL240. The dose received is proportional to the degree of color
change of the label
(green to red). The Hunter a-value of the labels was measured with the Minolta
CR-001 (D-
65 illuminant). A calibration curve is illustrated in Figure 12. In Figure 12,
the horizontal axis
15 (abscissa) represents dose, measured in mJ/cm2, and the vertical axis
(ordinate) represents the
Hunter a-value. The average dose received by each sample was determined and is
set forth
below in Table 6.
TABLE 6
DOSIMETERY OF SLEEVED AND UNSLEEVED UV BULBS.
2 0 LINE SPEED 12 FPM.
AVERAGE HUNTER AVERAGE DOSE
TREATMENT A-VALUE (mJ/cm2)
UNSLEEVED 12 FPM 7.37 475.5
SLEEVED 12 FPM 6.68 447.4
DOSE REDUCTION 5.91%
As shown, the dose was reduced by only 6% with the sleeved bulbs.
Standard refrigerated MAP headspace scavenging tests were performed on the
film
triggered as described above. Triggered specimens were affixed to the inside
of a P640B
pouch (available from Cryovac~ Division of W. R. Grace & Co.), vacuum sealed,
and inflated
2 5 with 300 cc modified atmosphere ( I % O2, 99% NZ) and stored at
4°C. Samples were
withdrawn and tested for oxygen content as described above in Example 1. The
results are set
forth below in Table 7.
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TABLE 7
SCAVENGING PERFORMANCE OF LAMINATED FILM TRIGGERED WITH FEP-
TEFLON SLEEVED BULBS. 100 CMZ FILM SAMP1.F
AVERAGE PEAK
RATE(a) INST. RATE
(CC/MZ/DAY) INDUCTION (CC/Mz/DAY
TREATMENT MEAN ST.DEV. PERIOD MEAN {b)
SLEEVED 34.8 0.1 <1 73.3 1
UNSLEEVED 34.1 2.7 <1 64.8 1
(a) average rate calculated after 6 days.
(b) days to reach peak rate.
As shown, film triggered with sleeved bulbs exhibited substantially unchanged
oxygen
scavenging capability as compared to the film triggered with unsleeved bulbs.
EXAMPLE 6
This example illustrates the advantages obtained using a triggered oxygen
scavenging
film as compared to packages prepared without a triggered oxygen scavenging
film.
As shown in Fig. 9, doses of UV-C light at 254 nm of greater than 200-250
mJ/cmz
provided excellent average oxygen scavenging rates.
As shown in Fig. 10, the lidstock Film of Example 4 including a triggered
oxygen
scavenging film provides consistently lower residual oxygen levels as compared
to T6235B
packaging (a standard barrier lidstock of Cryovac) without the triggered
oxygen scavenging
film, over an extended period of time.
EXAMPLE 7
This example demonstrates the scavenging rate of film triggered in accordance
with the
present invention. The film of Example 4 was selected for this example. The
article tested
2 0 was sliced bologna obtained from Greenwood Packing/Greenwood SC. Bologna
was selected
because its color is extremely sensitive to Oz and light exposure. Also, the
color of this article
tends to be very uniform, which helps reduce variability in color
measurements. The film was
triggered on the module in FIG. 1 at 12 FPM(559 mJ/cm2), and slit to 405 mm
width.
Packages were produced on the Multivac 87000 (pocket size: 1 I Omm X 1 l Omm X
40mm).
2 5 Packages were gas flushed with Nz to approximately 0.1 % residual O2. In
order to simulate a
worst-case gas-flush scenario, the residue OZ was then raised to 0.7% to 1.0%
by injecting 2
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cc of 90% OZ:10% NZ into the package. Packages were then stored in the dark at
4.4°C
(40°F) for various lengths of time, from 0 to 19 days. Samples of each
treatment were run in
duplicate. Packages were placed under the display lights at 4.4°C
(40°F) for 5 days prior to
sampling. Oxygen concentration was measured on each package at three times:
1. After packaging,
2. When package was placed into lighted display,
3. After 5 days lighted display.
Color was measured using the Minolta CR-100 (C illuminant) on the Hunterlab
L*a*b scale.
Color measurements were taken through 1 layer of 75 ga. BDF-2001 at 4 points
around the
perimeter, and once in the center of the bologna slice. Figure 13 illustrates
the relative
improvement in color (higher Hunter a-value) of bologna slices packaged in the
oxygen
scavenging film of Example 4, as opposed to bologna packaged in T6235. In
Figure 13, the
horizontal axis {abscissa) represents days after packaging. The lower line
represents days in
dark storage, and the upper line represents days in lighted display. Thus, for
example, for the
last pair of bars appearing in the extreme right part of the graph, each
sample was exposed to
19 days in dark storage, followed by 5 days in lighted display. The vertical
axis (ordinate) of
Figure 13 represents the Hunter a-value. Figure 11 illustrates the average OZ
residuals of
packages being placed into lighted display. It can be seen that the film
scavenged well,
reducing the OZ residua! from 1 % to less than 0.2% within 5 days.
2 0 The invention is not limited to the illustrations described herein, which
are deemed to
be merely illustrative, and susceptible of modification of form, size,
arrangement of parts and
details of operation.
