U.S. patent application number 10/450540 was filed with the patent office on 2004-07-22 for modified container.
Invention is credited to Chiu, Boris, Goodrich, Nina, Li, Steven, Mulholland, Lindsay, Senior, David.
Application Number | 20040142129 10/450540 |
Document ID | / |
Family ID | 22974320 |
Filed Date | 2004-07-22 |
United States Patent
Application |
20040142129 |
Kind Code |
A1 |
Mulholland, Lindsay ; et
al. |
July 22, 2004 |
Modified container
Abstract
The gas permeance of polyester bottles or other packaging
article is improved by the combination of an oxygen scavenging
material provided in the wall of the article and an external
barrier to gas flow.
Inventors: |
Mulholland, Lindsay;
(Cambridge, CA) ; Goodrich, Nina; (Cambridge,
CA) ; Senior, David; (Burlington, CA) ; Chiu,
Boris; (Hamilton, CA) ; Li, Steven;
(Mississauga, CA) |
Correspondence
Address: |
SIM & MCBURNEY
330 UNIVERSITY AVENUE
6TH FLOOR
TORONTO
ON
M5G 1R7
CA
|
Family ID: |
22974320 |
Appl. No.: |
10/450540 |
Filed: |
December 1, 2003 |
PCT Filed: |
December 21, 2001 |
PCT NO: |
PCT/CA01/01840 |
Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
C08L 53/00 20130101;
B65D 1/0207 20130101; C08L 67/02 20130101; Y10T 428/1352 20150115;
B65D 81/266 20130101; C08L 67/02 20130101 |
Class at
Publication: |
428/035.7 |
International
Class: |
B65D 001/00 |
Claims
What we claim is:
1. A packaging article having at least a wall constructed of a
polyester having an oxygen scavenging material therein and having
an external barrier to gas flow thereon.
2. The article of claim 1 wherein said oxygen scavenging material
is uniformly distributed through the thickness of the wall.
3. The article of claim 2 wherein said oxygen scavenging material
is polyester copolymer comprising predominantly polyester segments
and an oxygen scavenging amount of polyolefin oligomer
segments.
4. The article of claim 3 wherein said copolymer is capable of
absorbing at least 0.4 cc of oxygen per gram of copolymer at
temperature in the range of about 4.degree. to about 60.degree.
C.
5. The article of claim 3 wherein said polyolefin oligomer is
selected from the group consisting of polypropylene,
poly(4-methyl)1-pentene unhydrogenated polybutadiene, and mixtures
thereof.
6. The article of claim 5 wherein the polyolefin segments comprise
from about 0.5% to about 12 wt % of the polyester copolymer.
7. The article of claim 1 wherein the external barrier comprises a
thin coating of an epoxy-amine resin.
8. The article of claim 8 wherein the epoxy-amine resin has an
amine hydrogen to epoxy equivalent cure ratio lower than 1.5 to
1.
9. The article of claim 1 wherein the external barrier coating is a
thin coating of silica.
10. The article of claim 1 wherein the external barrier is applied
to the whole external surface of the article.
11. The article of claim 1 wherein said polyester is
polyethylene-terephthalate.
12. The article of claim 11 wherein said article is a bottle.
Description
FIELD OF INVENTION
[0001] This invention relates to a packaging article, specifically
a normally air-permeable container, which has been modified to
reduce its gas permeability.
BACKGROUND TO THE INVENTION
[0002] Polyethylene-terephalate (PEI) is widely used as the
construction material for packaging articles for a variety of
beverages, for example, juices, which may be carbonated, such as
soft drinks and beer. PET is known to be permeable to gases, such
as oxygen and carbon dioxide, which leads to a finite shelf-life to
oxygen-sensitive products, such as juices and beer, packaged
therein.
[0003] Attempts have been made to decrease the permeability of PET
bottle walls by manipulation of the structure of the wall, to
provide a shelf-life at least 2 to 3 times that of the unmodified
bottle. One manner of manipulation of the structure of the wall is
to incorporate substances capable of intercepting or scavenging
oxygen as it attempts to pass through the walls of the
container.
[0004] One method for use of such active absorbent is a sandwich
arrangement in which the gas scavenging material is provided as an
inner layer while the outer layers are formed of PET or other
polyester packaging material. Alternatively, the gas scavenging
material may be uniformly distributed in the wall structure.
[0005] A variety of materials has been suggested for use as the gas
scavenging material, including poly(1,2-butadiene), as described,
for example, in U.S. Pat. No. 5,310,497, polyamide, as described,
for example, in U.S. Pat. No. 5,639,815, and condensation polymers
comprising predominantly polyester segments and an oxygen
scavenging amount of polyolefin oligomer segments, such as
unhydrogenated polybutadiene, as described, for example, in U.S.
Pat. No. 6,083,585.
[0006] Such scavenging materials tend to be expensive. The gas
scavenging material eventually becomes exhausted of the ability to
absorb oxygen, which leads to concerns with respect to empty bottle
life.
SUMMARY OF INVENTION
[0007] It has now surprisingly been found that the oxygen
transmission rate and capacity of the gas scavenging material may
be greatly improved by applying an external passive barrier to gas
flow both from exterior of the bottle and from interior of the
bottle to at least the walls of the container.
[0008] Accordingly, in one aspect of the present invention, there
is provided a packaging article having at least a wall constructed
of a polyester and having an oxygen scavenging material therein and
having an external barrier to gas flow therein. Since the oxygen
barrier performance of the wall is improved, the quantity of active
oxygen scavenger material can be significantly reduced while, at
the same time, achieving an improved shelf-life.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIGS. 1 to 5 are graphical representative of data generated
with respect to oxygen permeability, as described in detail in the
Examples below.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0010] The packaging article provided herein preferably is in the
form of a bottle, which may have any convenient volume and
generally is formed by blow moulding. At least a wall and
preferably the entire article, is constructed of a linear
polyester, preferably PET, prepared by condensation of an aromatic
dicarboxylic acid component and a diol component. For the provision
of PET, terephthaltic acid and diethylene glycol are condensed.
[0011] The polyester contains at least one oxygen scavenging
material, which may be provided as a discrete layer or preferably
is uniformly distributed throughout the container wall. The oxygen
scavenging material may be any of the materials known to be useful
in the art for such purposes, but preferably is a polyester
copolymer comprising predominantly polyester segments and an oxygen
scavenging amount of polyolefin oligomer segments. Such polyester
copolymers are described in detail in U.S. Pat. No. 6,083,585, the
disclosure of which is incorporated herein by reference. Such
materials are available commercially under the trademark
AMOSORB.
[0012] The polyester segment of the polyester copolymer usually is
the same polyester used to construct the container, preferably PET.
The polyolefin oligomer segments are distributed throughout the
predominant polyester segments of the copolymer and are present in
sufficient quantity in the copolymer to provide the needed oxygen
scavenging capacity. The hydrocarbon segments are the only moieties
present which have oxygen scavenging propensity and capacity. The
polyester copolymer preferably has an oxygen scavenging capacity of
at least about 0.4 cc of oxygen per gram of copolymer at a
temperature in the range of about 4.degree. to about 60.degree. C.,
preferably at least 10 cc of oxygen per gram of copolymer and more
preferably at least 20 cc per gram.
[0013] The polyolefin segments may be provided by polypropylene,
poly(4-methyl) 1-pentene, unhydrogenated polybutadiene or mixtures
thereof, preferably dihydroxy-terminated unhydrogenated
polybutadiene, which may have a molecular weight in the range of
about 100 to about 10,000, preferably in the range of about 1000 to
about 3000. The polyolefin segments may comprise about 0.5 to about
12 wt % of the polyester copolymer.
[0014] To provide an adequate oxygen absorbing capacity to the
container, such polyester copolymer often is employed in amounts of
about 4 to 5 wt % of the container wall. By employing the external
barrier coating in accordance with the invention, this amount of
oxygen scavenging material may be significantly reduced to about 1
wt % and still provide improved performance.
[0015] The external coating of barrier material is applied as a
very thin continuous layer, often less than a micron in thickness,
at least to the walls of the container and preferably also to the
neck and base of a bottle. Depending on the size of the bottle and
the nature of the coating, a coating applied to the walls only may
be sufficient. The external coating may be applied in any
convenient manner, depending on the material used to provide the
coating, preferably by spraying. Generally, sufficient material
only is used to provide a continuous coating of barrier layer on
the desired portion of the bottle so as to minimize the material
costs and to provide transparency to the coating. Each coating may
have a thickness of about 0.3 to about 0.5 mil (about 5 to 15
microns).
[0016] The material used to provide the external barrier coating
should be a material generally impervious to gaseous flow
therethrough, particularly oxygen, and, where the container is to
be used for carbonated beverages, also by carbon dioxide. The
material utilized to provide the barrier coating may be an epoxy
resin, plasma-deposited silica or carbons, vapor-deposited silica
or an ester-based UV-curable polymeric material. Any other suitable
material which provides a passive barrier to the passage of air
and/or carbon dioxide may be employed.
[0017] Preferably, the barrier coating is provided by an
epoxy-amine resin. Such barrier materials are described in U.S.
Pat. Nos. 5,300,541, 5,637,365 and 4,309,367 among others, the
disclosures of which are incorporated herein by reference. Such
film-forming epoxy-amine resins are generally formed by reacting a
polyamine and a polyepoxide.
[0018] Preferably, the barrier material is provided by an
epoxy-amine copolymer constructed as described in the
aforementioned U.S. Pat. No. 5,637,365. Such materials employ an
amine hydrogen to epoxy equivalent cure ratio lower than 1.5 to 1.
The amino contents of the cured coating may be less than seven
percent with good results being obtainable as low as four percent
or lower. The relatively lower amino content of the coating
generally has the advantage of less yellowing of the coating over
time. Such material are sold by PPG Industries under the trademark
BAIROCADE.
[0019] As mentioned above, when the barrier coating is employed in
conjunction with a PET constructed of a monolayer of material
having an active oxygen scavenger material distributed throughout
the walls, then the amount of oxygen scavenger material which is
used can be reduced and an improved bottle performance can be
achieved. This ability to employ less oxygen scavenger material is
advantageous, in terms of cost of materials and has the effect of
improving bottle clarity.
[0020] By employing the barrier coating herein in conjunction with
the oxygen scavenger material, the overall performance of the
container in terms of gas permeability is improved. Both the empty
bottle and full bottle shelf-lives are improved. In the case of
carbonated beverages, the barrier coating prevents carbon dioxide
from exiting the container through the walls, thereby improving the
shelf-life for such materials.
[0021] In particular, as may be seen from the data presented in the
Examples, the presence of an epoxy-amine polymer coating on bottles
constructed of PET having an oxygen scavenger uniformly distributed
in the walls generally improves both the barrier to oxygen
transmission and oxygen absorbing capacity, as compared to the
absence of such coating. While permitting bottles to stand prior to
filling reduces the combined effectiveness of the epoxy-amine
polymer coating on an oxygen-scavenger containing wall, the total
oxygen transmittance can be significantly reduced and the package
with the combination is much more effective for bottling all types
of beer and other oxygen-sensitive foods and beverages.
EXAMPLES
[0022] The oxygen permeance measurements made in the Example are
obtained by a liquid oxygen sensitive indicator method, which
represents oxygen ingress into the liquid. The method correlates
were with oxidative degradation of a model ascorbic acid solution
and with results by trained taste pnaelists.
Example 1
[0023] This Example illustrates the invention.
[0024] A 34 g PET beer bottle having 1% of an oxygen scavenger
dispersed in the walls was provided with an epoxy-amine coating. An
improvement in oxygen barrier rate when compared to the absence of
the epoxy-amine coating was determined to be 3.8 times.
Example 2
[0025] This Example illustrates the significant effect of an oxygen
scavenger in conjunction with an external barrier layer.
[0026] Polyethylene-terephthalate (PET) bottles were blown from a
blend of commercial PET and 1 wt % Amosorb (OFC grade) with 473 ml
capacity. Amosorb is a proprietary oxygen scavenging copolymer
material supplied by BP chemicals. The copolymer is a copolymer of
PET having polybutadiene oligomer segments and is produced as
described in the aforementioned U.S. Pat. No. 6,083,585. The
bottles were spray coated on the outside of the bottles with a
contiguous outer film of an epoxy-amine resin supplied by PPG
Industries under the trademark "BAIROCADE" and produced as
described in the aforementioned U.S. Pat. No. 5,637,365. The
thickness of the layer was about 0.4 mil.
[0027] Control bottles were also prepared in which there was only
no modification to the bottle walls, in which only 1% Amosorb was
present and in which only the epoxy-amine resin coating was
present.
[0028] The bottles were filled with oxygen-sensitive liquid and the
total oxygen absorbance by the liquid was determined for a period
of time. The results obtained were plotted graphically and appear
in FIG. 1. As may be seen from the Figure, while both 1% Amosorb
and epoxy-amine oxygen resin alone led to a longer period of time
over which oxygen was absorbed, the combination of the 1% Amosorb
and epoxy-amine resin led to a significant increase in scavenging
time with the absorbtion increasing only slowly once steady state
conditions had been enhanced.
[0029] The oxygen transmission rate (OTR) was also determined and
these results are plotted graphically in FIG. 2. While both 1%
Amosorb and epoxy-oxygen resin alone reduced the oxygen
transmission rate of the bottle when compared to the absence of
such materials, the combination leads to a further order of
magnitude reduction in the oxygen transmission rate.
Example 3
[0030] This Example illustrates the synergistic effect of an oxygen
scavenger material in conjunction with an external barrier
layer.
[0031] The procedure of Example 2 was repeated except that a
comparison was made between bottles which were filled immediately
after the bottles were made and these which were filled after 5
weeks standing empty ("aged").
[0032] The results obtained for oxygen absorbance of the aged
bottles were plotted graphically and appear in FIG. 3. These
results show the same kind of results as FIG. 1 for the unaged
bottles. The oxygen transmission rate (OTR) for the aged and unaged
("Time 0") bottles were plotted graphically and appear in FIG. 4.
These results show that, while the 1% Amosorb containing bottles
exhibited a greater OTR in the aged bottles, showing some loss of
effectiveness of the Amosorb material, the external epoxy-amine
coating significantly reduced the OTR by an order of magnitude.
Example 4
[0033] This Example describes a study of the effect of Amosorb and
PPG on total oxygen absorbance over a four month period.
[0034] Beer in plastic bottles has a finite shelf-life due to
oxygen permeation. A four-month period of time usually is
considered acceptable. For light-flavoured beer, less oxygen
absorbance is tolerable than for stronger-flavoured beer.
[0035] The procedure of Example 2 was repeated except that 0.473 L
(16 oz) bottles were prepared, and filled immediately following
manufacture or after 5 weeks ("aged"). Bottles were prepared with
no alteration to the bottle, 1 wt % Amosorb, 4 wt % Amosorb,
epoxy-amine coating and 1% Amosorb plus epoxy-amine coating. The
total ppm oxygen absorbed by oxygen-sensitive liquid during a 4
month period was determined and the results are shown graphically
in FIG. 5.
[0036] As may be seen from the data presented in FIG. 5, the total
oxygen permeance was reduced below 1 ppm by either using 4% Amosorb
or by using 1% Amosorb with epoxy-amine external coating, i.e.
below the acceptable levels for any beer.
Example 5
[0037] The Example illustrates the use of a different barrier layer
material.
[0038] PCT bottles were blown from a blend of commercial PET and 2
wt % Amosorb with 700 ml capacity. The bottles are coated with
silica by high vacuum deposition on the outside of the bottles with
a spray-applied polymeric top coat. The coating materials are sold
under the tradename BestPET by Krones.
[0039] The bottles were filled with oxygen-sensitive liquid and the
total absorbance by the liquid was determined for a period of time
and the oxygen transmission rate (OTR) for bottles which has been
aged (see Example 3) for 3, 7 and 14 weeks prior to filing. The
results obtained are set forth in the following Table I:
1 TABLE I O.sub.2 ingress OTR Bottles (ppm) (cc/pkg/day) Aged 3
weeks 0.81 0.0021 Aged 7 weeks 2.07 0.0056 Aged 14 weeks 4.39
0.0153 Control 8.49 0.413
[0040] As may be seen from Table I, significantly decreased oxygen
permeance is obtained by the combination of Amosorb and BestPET as
compared to the control, although the effect is eroded by bottle
aging as the oxygen scavenging capacity of the Amosorb is decreased
by the bottles standing empty.
SUMMARY OF DISCLOSURE
[0041] In summary of this disclosure, the present invention
provides containers having walls constructed of polyester with an
oxygen scavenging material therein and a barrier coating applied
thereto to provide an improved performance with respect to gas
permeation. Modifications are possible within the scope of the
invention.
* * * * *