U.S. patent application number 11/095053 was filed with the patent office on 2005-10-06 for polyester composition with enhanced gas barrier, articles made therewith, and methods.
This patent application is currently assigned to The Coca-Cola Company. Invention is credited to Shi, Yu.
Application Number | 20050221036 11/095053 |
Document ID | / |
Family ID | 35054666 |
Filed Date | 2005-10-06 |
United States Patent
Application |
20050221036 |
Kind Code |
A1 |
Shi, Yu |
October 6, 2005 |
Polyester composition with enhanced gas barrier, articles made
therewith, and methods
Abstract
A polyester composition with enhanced gas barrier properties
comprises a polyester and an organic gas barrier enhancing additive
having the chemical formula OH-AR--OH, wherein AR is substituted or
unsubstituted naphthalene. Articles with enhanced gas barrier and
methods for making gas barrier enhanced polyesters and articles are
disclosed.
Inventors: |
Shi, Yu; (Alpharetta,
GA) |
Correspondence
Address: |
SUTHERLAND ASBILL & BRENNAN LLP
999 PEACHTREE STREET, N.E.
ATLANTA
GA
30309
US
|
Assignee: |
The Coca-Cola Company
|
Family ID: |
35054666 |
Appl. No.: |
11/095053 |
Filed: |
March 31, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60558494 |
Apr 1, 2004 |
|
|
|
Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
C08K 5/053 20130101;
C08K 2201/008 20130101; C08L 67/02 20130101; Y10T 428/1352
20150115; C08K 5/053 20130101 |
Class at
Publication: |
428/035.7 |
International
Class: |
B65D 001/00 |
Claims
I claim:
1. A polyester composition comprising: a polyester; and an organic
gas barrier enhancing additive having the chemical formula
OH-AR--OH, wherein AR is substituted or unsubstituted
naphthalene.
2. A polyester composition as in claim 1 wherein the polyester is
present in the polyester composition in an amount from about 99.9%
to about 90% by weight of the polyester composition and the
additive is present in the polyester composition in an amount from
about 0.1% to about 10% by weight of the polyester composition.
3. A polyester composition as in claim 1 wherein the additive is
selected from the group comprising 1,2-dihydroxy naphthalene,
1,3-dihydroxy naphthalene, 1,5-dihydroxy naphthalene, 1,6-dihydroxy
naphthalene, and 2,6-dihydroxy naphthalene.
4. A polyester composition as in claim 1 wherein the additive is
1,3-dihydroxy naphthalene.
5. A polyester composition as in claim 1 wherein the polyester
comprises a poly(ethylene terephthalate) based copolymer (PET
copolymer) having less than 20% diacid component modification
and/or less than 10% diol component modification, based on 100 mole
% diacid component and 100 mole % diol component.
6. A polyester composition as in claim 5 wherein the PET copolymer
is present in the polyester composition in an amount from about
99.9% to about 90% by weight of the polyester composition and the
additive is present in the polyester composition in an amount from
about 0.1% to about 10% by weight of the polyester composition.
7. A polyester composition as in claim 5 wherein the PET copolymer
is present in the polyester composition in an amount from about
99.9% to about 95% by weight of the polyester composition and the
additive is present in the polyester composition in an amount from
about 0.1% to about 5% by weight of the polyester composition.
8. A polyester composition as in claim 5 wherein the PET copolymer
is present in the polyester composition in an amount from about
99.9% to about 97% by weight of the polyester composition and the
additive is present in the polyester composition in an amount from
about 0.1% to about 3% by weight of the polyester composition.
9. A polyester composition as in claim 5 wherein the additive is
selected from the group comprising 1,2-dihydroxy naphthalene,
1,3-dihydroxy naphthalene, 1,5-dihydroxy naphthalene, 1,6-dihydroxy
naphthalene, and 2,6-dihydroxy naphthalene.
10. A polyester composition as in claim 1 wherein the polyester has
a free volume and at least a portion of the additive is unreacted
with the polyester and disposed in the free volume of the
polyester.
11. A polyester composition as in claim 1 wherein the polyester
comprises a poly(ethylene terephthalate) based copolymer (PET
copolymer) and, based on 100 mole % diacid component and 100 mole %
diol component, the PET copolymer has less than 20% diacid
component modification and less than 10% diol component
modification, and at least a portion of the additive is reacted
with the PET copolymer such that the diol component comprises 0.1
to about 5 mole % of the additive.
12. Method for enhancing gas barrier or gas scavenging capability
of a polyester composition comprising blending a polyester and an
organic gas barrier enhancing additive having the chemical formula
OH-AR--OH, wherein AR is substituted or unsubstituted
naphthalene.
13. Method as in claim 12 wherein the polyester is present in the
polyester composition in an amount from about 99.9% to about 90% by
weight of the polyester composition and the additive is present in
the polyester composition in an amount from about 0.1% to about 10%
by weight of the polyester composition.
14. Method as in claim 12 wherein the additive is selected from the
group comprising 1,2-dihydroxy naphthalene, 1,3-dihydroxy
naphthalene, 1,5-dihydroxy naphthalene, 1,6-dihydroxy naphthalene,
and 2,6-dihydroxy naphthalene.
15. Method as in claim 12 wherein the additive is 1,3-dihydroxy
naphthalene.
16. Method as in claim 12 wherein the polyester comprises a
poly(ethylene terephthalate) based copolymer (PET copolymer) having
less than 20% diacid component modification and/or less than 10%
diol component modification, based on 100 mole % diacid component
and 100 mole % diol component.
17. Method as in claim 16 wherein the PET copolymer is present in
the polyester composition in an amount from about 99.9% to about
90% by weight of the polyester composition and the additive is
present in the polyester composition in an amount from about 0.1%
to about 10% by weight of the polyester composition.
18. Method as in claim 16 wherein the PET copolymer is present in
the polyester composition in an amount from about 99.9% to about
95% by weight of the polyester composition and the additive is
present in the polyester composition in an amount from about 0.1%
to about 5% by weight of the polyester composition.
19. Method as in claim 16 wherein the PET copolymer is present in
the polyester composition in an amount from about 99.9% to about
97% by weight of the polyester composition and the additive is
present in the polyester composition in an amount from about 0.1%
to about 3% by weight of the polyester composition.
20. Method as in claim 16 wherein the additive is selected from the
group comprising 1,2-dihydroxy naphthalene, 1,3-dihydroxy
naphthalene, 1,5-dihydroxy naphthalene, 1,6-dihydroxy naphthalene,
and 2,6-dihydroxy naphthalene.
21. Method as in claim 12 wherein the polyester has a free volume
and at least a portion of the additive is unreacted with the
polyester and disposed in the free volume of the polyester.
22. Method as in claim 12 wherein the polyester comprises a
poly(ethylene terephthalate) based copolymer (PET copolymer) and,
based on 100 mole % diacid component and 100 mole % diol component,
the PET copolymer has less than 20% diacid component modification
and less than 10% diol component modification, and at least a
portion of the additive is reacted with the PET copolymer such that
the diol component comprises 0.1 to about 5 mole % of the
additive.
23. A container comprising a polyester composition comprising: a
polyester; and an organic gas barrier enhancing additive having the
chemical formula OH-AR--OH, wherein AR is substituted or
unsubstituted naphthalene.
24. A container as in claim 23 wherein the container is a stretch
blow molded container comprising a base, an open ended mouth, and a
body extending from the base to the open ended mouth.
25. A container as in claim 23 wherein the polyester is present in
the polyester composition in an amount from about 99.9% to about
90% by weight of the polyester composition and the additive is
present in the polyester composition in an amount from about 0.1%
to about 10% by weight of the polyester composition.
26. A container as in claim 23 wherein the additive is selected
from the group comprising 1,2-dihydroxy naphthalene, 1,3-dihydroxy
naphthalene, 1,5-dihydroxy naphthalene, 1,6-dihydroxy naphthalene,
and 2,6-dihydroxy naphthalene.
27. A container as in claim 23 wherein the polyester comprises a
poly(ethylene terephthalate) based copolymer (PET copolymer) having
less than 20% diacid component modification and/or less than 10%
diol component modification, based on 100 mole % diacid component
and 100 mole % diol component.
28. A container as in claim 27 wherein the PET copolymer is present
in the polyester composition in an amount from about 99.9% to about
90% by weight of the polyester composition and the additive is
present in the polyester composition in an amount from about 0.1%
to about 10% by weight of the polyester composition.
29. A container as in claim 27 wherein the PET copolymer is present
in the polyester composition in an amount from about 99.9% to about
95% by weight of the polyester composition and the additive is
present in the polyester composition in an amount from about 0.1%
to about 5% by weight of the polyester composition.
30. A container as in claim 27 wherein the PET copolymer is present
in the polyester composition in an amount from about 99.9% to about
97% by weight of the polyester composition and the additive is
present in the polyester composition in an amount from about 0.1%
to about 3% by weight of the polyester composition.
31. A container as in claim 27 wherein the additive is selected
from the group comprising 1,2-dihydroxy naphthalene, 1,3-dihydroxy
naphthalene, 1,5-dihydroxy naphthalene, 1,6-dihydroxy naphthalene,
and 2,6-dihydroxy naphthalene.
32. A container as in claim 23 wherein the polyester has a free
volume and at least a portion of the additive is unreacted with the
polyester and disposed in the free volume of the polyester.
33. A container as in claim 23 wherein the polyester comprises a
poly(ethylene terephthalate) based copolymer (PET copolymer) and,
based on 100 mole % diacid component and 100 mole % diol component,
the PET copolymer has less than 20% diacid component modification
and less than 10% diol component modification, and at least a
portion of the additive is reacted with the PET copolymer such that
the diol component comprises 0.1 to about 5 mole % of the additive.
Description
CROSS-REFERENCE
[0001] This application claims priority under 35 U.S.C. .sctn.
119(e) to U.S. Provisional Application 60/558,494 filed on Apr. 1,
2004, the disclosure of which is expressly incorporated herein by
reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates to polyester and polyester articles.
In particular, this invention relates to polyesters for use in
applications such as packaged beverages wherein enhanced gas
barrier or oxygen scavenging is desirable.
BACKGROUND OF THE INVENTION
[0003] Polyethylene terephthalate and its copolyesters (hereinafter
referred to collectively as "PET") are widely used to make
containers for carbonated soft drinks, juice, water, and the like
due to their excellent combination of clarity, mechanical, and gas
barrier properties. In spite of these desirable characteristics,
insufficient gas barrier of PET to oxygen and carbon dioxide limits
application of PET for smaller sized packages, as well as for
packaging oxygen sensitive products, such as food, beer, juice, and
tea products. A widely expressed need exists in the packaging
industry to further improve the gas barrier properties of PET.
[0004] The relatively high permeability of PET to carbon dioxide
limits the use of smaller PET containers for packaging carbonated
soft drinks. The permeation rate of carbon dioxide through PET
containers is in the range of 3 to 14 cc's per day or 1.5 to 2% per
week loss rate at room temperature depending on the size of the
container. A smaller container has a larger surface to volume ratio
resulting in a higher relative loss rate. For this reason, PET
containers are currently used only as larger containers for
packaging carbonated soft drinks, while metal cans and glass
containers are the choice for smaller carbonated soft drink
containers.
[0005] Numerous technologies have been developed or are being
developed to enhance the barrier of PET to small gas molecules. For
example, external or internal coatings for enhancing the gas
barrier of PET containers have been developed. The coating layer is
normally a very high barrier layer, either inorganic or organic,
and slows down the diffusion of gases. Implementation of this
technology, however, requires coating equipment not normally
utilized in the manufacture of packaged beverages and therefore
requires substantial capital investment, increased energy usage,
and increased floor space. In many beverage packaging plants that
are already crowded, the additional space is not an option.
[0006] Multi-layered containers have also been developed with a
high barrier layer sandwiched between two or more PET layers.
Implementation of this technology also requires substantial capital
investment and delamination of the container layers impacts
appearance, barrier, and mechanical performance of the
containers.
[0007] A barrier additive for the PET or a polymer with inherent
barrier properties would be preferred solutions. Neither such
solution requires additional capital investment, and therefore,
does not have the limitations inherent with other technologies. A
barrier additive can also be added during the injection molding
process which gives more flexibility for downstream operations.
[0008] L. M. Robeson and J. A. Faucher disclose in J. Polymer
Science, Part B 7, 35-40 (1969) that certain additives could be
incorporated into polymers to increase their modulus and gas
barrier properties through an antiplasticization mechanism. This
article discloses utilizing additives with polycarbonate, polyvinyl
chloride, polyphenylene oxide, and polythyelene oxide.
[0009] In WO 01/12521, Plotzker et al. proposed the use of
additives selected from 4-hydroxybenzoates and related molecules to
increase the gas barrier properties of PET. This published patent
application discloses barrier additives of the following
structure:
HO--Ar--COOR, HO--Ar--COOR1COO-AR--OH, HO-AR--CONHR,
HO-AR--CO--NHR3-COO-AR--OH, HO-AR--CONHR2NHCO-AR--OH
[0010] In the foregoing structure, AR is selected from the group
consisting of substituted or unsubstituted phenylene or
naphthalene. And R1, R2, and R3 are selected from the group
consisting from C1 to C6 alkyl groups, a phenyl group, and a
naphthyl group.
[0011] The foregoing additives described in the art provide only
moderate improvement in PET barrier, less than 2.1 times (.times.)
for oxygen barrier for the best examples with a 5 weight percent
loading level. At this loading level, however, PET experiences
substantial degradation and a significant drop in intrinsic
viscosity (IV). Although lowering the level of additive reduces the
degradation of PET, it also reduces the barrier improvement factor,
so much so that no real benefit exists in using these additives in
packaging carbonated soft drinks or oxygen sensitive food.
Furthermore, PET with a significantly lower IV cannot be used in
blow molding containers, such as beverage containers. Furthermore,
lower IV PET makes containers with poor mechanical performance,
such as creep, drop impact, and the like. Still further, PET
containers made from lower IV PET have poor stress cracking
resistance, which is undesirable in container applications.
[0012] PET has been modified or blended with other components to
enhance the gas barrier of the PET. Examples include polyethylene
naphthalate (PEN)/PET copolymers or blends, isophthalate (IPA)
modified PET, PET blended with polyethylene isophthalate (PEI) or a
polyamide, such as nylon, and PET modified with resorcinol based
diols. For a PET copolymer to achieve moderate barrier enhancement
of 2.times. or higher, the modification is normally more than 10 to
20 weight or mole % of the total co-monomers. When PET is modified
to such a high level, the stretching characteristics of the PET are
changed dramatically such that the normal PET container preform
design could not be used in the manufacture of containers. Using
these PET copolymers to mold conventional PET container preforms
results in preforms that can not be fully stretched and the
ultimate containers are very difficult, if not impossible, to make.
Even if such a container can be made, it does not show improved
barrier performance and shows deteriorated physical performance
such that it can not be used to package carbonated soft drinks.
U.S. Pat. Nos. 5,888,598 and 6,150,450 disclose redesigned PET
container preforms with thicker side walls to compensate for the
increased stretch ratio. This thicker preform, however, requires
new molds which require additional capital investment and is also
made at a lower rate of productivity because it takes longer to
cool and heat the thicker wall preform. Furthermore, PET blends
with polyamide such as nylon developed yellowness and haze and are
not clear like conventional PET.
[0013] Products sensitive to oxygen, such as foods, beverages and
medicines, deteriorate and spoil in the presence of oxygen. To
prevent oxygen ingress to the products, different oxygen scavenger
technologies have been developed. These oxygen scavengers are
called active barrier technologies. They are different from the
passive barrier technologies that work to improve barrier to small
gas molecules only. U.S. Pat. No. 5,021,515 discloses a
multi-layered, nylon based oxygen scavenger. U.S. Pat. No.
5,744,056 discloses an oxygen scavenger composition that can be
incorporated into bottle sidewall in a monolayer fashion.
Similarly, U.S. Pat. No. 5,700,554 discloses an oxygen scavenger
composition. The monolayer oxygen scavengers provide additional
benefits over the multi-layered oxygen scavenger in that the
monolayer oxygen scavenger can react with the headspace oxygen in
the container, in addition to blocking the oxygen ingress to the
container. Therefore, the monolayer oxygen scavenger can prevent
the product oxidation from the headspace oxygen. The oxygen
scavenger compositions disclosed in these and other similar
patents, however, all contain transition metals as catalysts. The
transition metals can cause degradation in PET and cause
discoloration in PET. In addition, in certain countries, certain
transition metals also raise environmental and regulatory
concerns.
[0014] Thus, there is a need in the art to enhance the barrier
performance of PET for use in applications that will require
enhanced barrier, such as in the packaging of carbonated beverages
and oxygen sensitive beverages and foods, in a manner that does not
cause substantial degradation of the PET, does not substantially
impact the stretch ratio of the PET, does not include transition
metals, and allows the use of existing PET perform toolings.
SUMMARY OF THE INVENTION
[0015] This invention addresses the above described need for
enhanced gas barrier PET by providing a polyester composition
comprising a polyester and an organic gas barrier enhancing
additive having the chemical formula OH-AR--OH, wherein AR is
substituted or unsubstituted naphthalene.
[0016] In accordance to a particular embodiment, the polyester in
the polyester composition comprises a poly(ethylene terethphalate)
based copolymer (PET copolymer). In a desired embodiment, the
polyester comprises a PET copolymer having less than 20% diacid
component modification and/or less than 10% diol component
modification, based on 100 mole % diacid component and 100 mole %
diol component. With the organic gas barrier enhancing additive,
this embodiment provides acceptable gas barrier despite having a
low level of diacid or diol modification, if any modification.
Without wishing to be bound by theory, it is believed that some
embodiments of this invention possess gas barrier capability, while
another possesses more oxygen scavenging capability or both gas
barrier and oxygen scavenging capability.
[0017] According to another embodiment, this invention encompasses
a method for enhancing gas barrier of a polyester composition
comprising blending a polyester and an organic gas barrier
enhancing additive having the chemical formula OH-AR--OH, wherein
AR is substituted or unsubstituted naphthalene. According to a
preferred embodiment, the polyester is a PET copolymer.
[0018] According to still another embodiment, this invention
encompasses an article comprising a polyester and an organic gas
barrier enhancing additive having the chemical formula OH-AR--OH,
wherein AR is substituted or unsubstituted naphthalene. According
to a particular embodiment, the article is a container and in other
preferred embodiments is a stretch blow molded container. In a
preferred embodiment, the polyester is a PET copolymer.
[0019] According to yet another embodiment, this invention
encompasses a method for making an article with enhancing gas
barrier comprising the steps of blending a polyester and an organic
gas barrier enhancing additive having the chemical formula
OH-AR--OH, wherein AR is substituted or unsubstituted naphthalene.
In a particular embodiment, the polyester is a PET copolymer.
Furthermore, in another embodiment, the article is a stretch blow
molded container.
[0020] Particular embodiments of this invention provide polyesters,
such as PET copolymers, with enhanced gas barrier, and in
particular, enhanced barrier to carbon dioxide and oxygen. This
makes certain embodiments of this invention particularly suited for
packaging carbonated soft drinks and oxygen sensitive beverages and
foods. Particular embodiments achieve this enhanced gas barrier
while maintaining acceptable physical properties.
[0021] Other objects, features, and advantages of this invention
will become apparent from the following detailed description,
drawings, and claims.
BRIEF DESCRIPTION OF DRAWINGS
[0022] FIG. 1 is a schematic illustration of a system for making a
PET container with enhanced gas barrier in accordance with an
embodiment of this invention.
[0023] FIG. 2 is a sectional elevation view of a molded container
preform made in accordance with an embodiment of this
invention.
[0024] FIG. 3 is a sectional elevation view of a blow molded
container made from the preform of FIG. 2 in accordance with an
embodiment of this invention.
[0025] FIG. 4 is a perspective view of a packaged beverage made in
accordance with an embodiment of this invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0026] This invention encompasses a polyester composition with
enhanced gas barrier or oxygen scavenging capability or both, a
method for enhancing gas barrier or oxygen scavenging capability of
a polyester composition, articles comprising such a polyester
composition, and a method for making such articles. As explained in
more detail below, embodiments of this invention provide a
polyester composition and articles made therewith which exhibit
enhanced barrier to gases or oxygen scavenging capability while
maintaining physical properties.
[0027] This invention is applicable to any polyester and is
suitable for uses in which a high gas barrier is desirable.
Suitable polyesters include those that are suitable for packaging
carbonated or non-carbonated beverages and oxygen sensitive
beverages or food products. Suitable polyesters for use in
embodiments of this invention include PET copolymers, polyethylene
naphthalate (PEN), polyethylene isophthalate, and the like. PET
copolymers are particularly useful because they are used for many
barrier applications such as films and containers. Suitable
containers include but are not limited to bottles, drums, carafes,
coolers, and the like.
[0028] PET copolymers suitable for use in embodiments of this
invention comprise a diol component having repeat units from
ethylene glycol and a diacid component having repeat units from
terephthalic acid. Desirably, in some embodiments, the PET
copolymer has less than 20% diacid component modification and/or
less than 10% diol component modification, based on 100 mole %
diacid component and 100 mole % diol component. Such PET copolymers
are well known.
[0029] In accordance with embodiments of this invention, suitable
organic gas barrier enhancing additives are those having the
chemical formula OH-AR--OH, wherein AR is substituted or
unsubstituted naphthalene. Suitable additives include, but are not
limited to, 1,2-dihydroxy naphthalene, 1,3-dihydroxy naphthalene,
1,5-dihydroxy naphthalene, 1,6-dihydroxy naphthalene, and
2,6-dihydroxy naphthalene. 1,5-dihydroxy naphthalene degrades at
polyester melt processing temperatures, and therefore is not a
preferred additive, but is useful at lower melt processing
temperatures. 2,7-dihydroxy naphthalene is not listed because it
has an even lower degradation temperature and is not suitable for
use as an additive for PET.
[0030] The organic gas barrier enhancing additive compound is added
to the polyester in an amount sufficient to enhance the gas barrier
properties of the polyester. In accordance with an embodiment of
this invention, the polyester is present in the polyester
composition in amount from 99.9% to 90% by weight of the polyester
composition and the organic gas barrier enhancing additive is
present in the polyester composition in an amount of 0.1% to about
10% by weight of the polyester composition. In accordance to
another embodiment of this invention, the PET copolymer is present
in the polyester composition in an amount from 99.9% to about 95%
by weight of the polyester composition and the additive is present
in the polyester composition in an amount from about 0.1% to about
5% by weight of the polyester composition. In accordance with still
another embodiment of this invention, the PET copolymer is present
in the polyester composition in an amount from about 99.9% to about
97% by weight of the polyester composition and the additive is
present in the polyester composition in an amount from about 0.1%
to about 3% by weight of the polyester composition.
[0031] Polyesters, including PET copolymers, have free volume
between polymer chains. As is known to those skilled in the art,
the amount of free volume in polyesters such as PET copolymers
determines their barrier to gas molecules. The lower the free
volume, the lower the gas diffusion, and the higher the barrier to
gas molecules. In some embodiments, it is believed that the
additive is at least partially disposed in the free volume of the
polyester between the polyester chains and solidifies in the free
volume when the blend is cooled down to room temperature after melt
processing. Due to the presence of the two hydroxyl groups, it is
possible that the additive reacts with the polyester chain and
causes the intrinsic viscosity (IV) to drop although the reactivity
of the hydroxy group in the current additive is very low.
Therefore, when melt blending the additive with polyester, it is
possible that the additive partially reacts with the polyester and
forms a mixture of polyester/dihydroxy naphthalene copolymer,
polyester, and the additive. For example, when the additive is
1,3-dihydroxy naphthalene, it is believed that the additive at
least partially reacts with the polyester and becomes part of the
polyester backbone chain. According to a particular embodiment, the
polyester comprises a poly(ethylene terephthalate) based copolymer
(PET copolymer) and, based on 100 mole % diacid component and 100
mole % diol component, the PET copolymer has less than 20% diacid
component modification and less than 10% diol component
modification, and at least a portion of the additive is reacted
with the PET copolymer such that the diol component comprises 0.1
to about 5 mole % of the additive.
[0032] The additive may be incorporated into the polyester in
different ways. For example, at lower loading levels, i.e., 3
weight % or below, the additive can be incorporated directly into
polyester during the injection molding process, can be preblended
in the polyester resin making process, or can be incorporated into
melt polyester prior to the discharge of the polyester in the melt
polymerization process. At higher loading levels, 3 weight % or
higher, the additives can be preblended with the polyester, melt
extruded and solid state polymerized to the desired IV. The solid
stated mixture can then be injection molded into container performs
as described in more detail below.
[0033] In some embodiments, it is desirable to reduce the latent
effect of any residual polycondensation catalyst in the polyester.
These catalysts include commonly used catalyst such as compounds
containing antimony, titanium, tin, and the like, and are
deactivated by phosphorus containing compounds. The phosphorus
containing compounds include both organic and inorganic compounds.
Examples include but are not limited to phosphoric acid,
polyphosphoric acid, and tris(2,4-di-t-butylphenyl) phosphite, tris
monononylphenyl phosphite. These additives are typically added in
amounts less than 2000 ppm.
[0034] As described above, the polyester composition of this
invention is useful for making articles in which enhanced gas
barrier is desirable. In short, such articles are made by forming
the above described polyester compositions into the desired article
by conventional methods such as melt forming. Suitable melt forming
processes include, but are not limited to, injection molding,
extrusion, thermal forming and compression molding.
[0035] In particular, embodiments of this invention are suitable
for making containers for packaging applications in the carbonated
and non-carbonated soft drink industry and the food industry. A
common manufacturing method for forming these containers includes
injection molding container preforms, and then, making the
containers from the preforms in single stage, two stage, and double
blow molding manufacturing systems. Such methods are well known to
those skilled in the art and examples of suitable preform and
container structures and are disclosed in U.S. Pat. No. 5,888,598,
the disclosure of which is expressly incorporated herein by
reference in its entirety.
[0036] More particularly, a container preform is formed by
injection molding the polyester into a blowable geometric form. The
preform or blowable form is then contained within a mold cavity
having the volumetric configuration of the desired container and
the preform is expanded by blowing it with compressed air within
the confines of the mold cavity.
[0037] Commercially available equipment, as is used in the
manufacture of thin walled single use PET beverage containers, may
be used to make the containers in accordance with embodiments of
the present invention. In addition, commercial equipment like that
used in manufacturing conventional thick wall refillable PET
containers may also be used.
[0038] Suitable containers in accordance with embodiments of this
invention may be blow-molded from a cylindrical injection-molded
preform having an open top end and neck finish. The preform may
have a tapered shoulder-forming portion, substantially uniform
thickness along the sides of the cylinder, and a base-forming
portion preferably in a champagne design, but including a
hemispherical base with a base cup or a footed design such as a
petaloid design. In preferred embodiments, the preform is amorphous
and substantially transparent and is injection molded.
[0039] In accordance with preferred embodiments of this invention,
container preforms are subsequently placed in a blow molding
apparatus having an upper mold section which engages the neck
finish, a middle mold section having an interior cavity forming the
shape of the container side wall, and a lower mold section having
an upper surface forming the outwardly concave dome portion of the
container base. In accordance with a standard reheat stretch blow
mold process, the injection-molded preform is first reheated to a
temperature suitable for stretching and orientation of about 70 to
130.degree. C., placed in the blow mold, and an axial stretch rod
is then inserted into the open upper end and moved downwardly to
axially stretch the preform. Subsequently or simultaneously, an
expansion gas is introduced into the interior of the preform to
radially expand the shoulder, sidewall and base forming portions
outwardly into contact with the interior surfaces of mold sections.
The resulting blown container has the same neck finish with outer
threads and lowermost neck flange as the preform. The remainder of
the bottle undergoes expansion, although to varying degrees. A
removable cap is attached to the open upper end of the container.
The cap includes a base portion having internal threads which
engage the outer threads on the neck finish.
[0040] FIG. 1 illustrates a system 10 in accordance with an
embodiment of this invention for making a rigid container preform
12 (illustrated in FIG. 2) and a rigid container 14 (illustrated in
FIG. 3) from the preform. As is shown in FIG. 1, solid PET
copolymer pellets 20 and an organic gas barrier enhancing additive
such as dimethyl terephthalate 22 are added to a feeder or hopper
24 that delivers the components to a hot melt extruder 26 in which
the components are melted and blended. The hot melt extruder 26
then extrudes the molten mixture of PET copolymer and organic gas
barrier enhancing additive into an injection molding device 28 to
form the preform 12. The preform is cooled and removed from the
injection molding device 28 and delivered to a blow molding device
30 which blow molds the preform 12 into a finished rigid container
14.
[0041] As explained above, the melt residence time of the preform
production is preferably less than three minutes and more
preferably from about 100 to about 120 seconds. The melt
temperatures desirably from 270 to about 300.degree. C. and more
desirably from about 270 to about 290.degree. C. The melt residence
time begins when the PET copolymer and organic barrier enhancing
additive enter the melt extruder 26 and start melting, and ends
after injection of the molten blend into the injection mold to form
the preform 12.
[0042] Turning to FIG. 2, a polyester container preform 12 is
illustrated. This preform 12 is made by injection molding PET based
resin and comprises a threaded neck finish 112 which terminates at
its lower end in a capping flange 114. Below the capping flange
114, there is a generally cylindrical section 116 which terminates
in a section 118 of gradually increasing external diameter so as to
provide for an increasing wall thickness. Below the section 118
there is an elongated body section 120.
[0043] The preform 12 illustrated in FIG. 2 can be blow molded to
form a container 14 illustrated in FIGS. 3 and 4. The container 14
comprises a shell 124 comprising a threaded neck finish 126
defining a mouth 128, a capping flange 130 below the threaded neck
finish, a tapered section 132 extending from the capping flange, a
body section 134 extending below the tapered section, and a base
136 at the bottom of the container. The container 14, for the most
part, is highly biaxially oriented, but the neck finish 126 is
non-oriented. The container 14 is suitably used to make a packaged
beverage 138, as illustrated in FIG. 4. The packaged beverage 138
includes a beverage such as a carbonated soda beverage disposed in
the container 14 and a closure 140 sealing the mouth 128 of the
container.
[0044] The preform 12, container 14, and packaged beverage 138 are
but examples of applications using the preforms of the present
invention. It should be understood that the process and apparatus
of the present invention can be used to make preforms and
containers having a variety of configurations.
[0045] The present invention is described above and further
illustrated below by way examples which are not to be construed in
any way as imposing limitations upon the scope of the invention. On
the contrary, it is to be clearly understood that resort may be had
to various other embodiments, modifications, and equivalents
thereof which, after reading the description herein, may suggestion
themselves to those skilled in the art that without departing from
the scope of the invention and the appended claims.
EXAMPLE 1
[0046] A commercially available polyester container grade resin was
used as a control. The polyester composition (PET) had a diacid
component of 97.2 mole % terephthalic acid and 2.8 mole %
isophthalic acid and a glycol component of 97.2 to 97.3 mole %
ethylene glycol and 2.7 to 2.8 mole % diethylene glycol. The PET
was dried in a vacuum oven at 140.degree. C. overnight to a
moisture level below 50 ppm. The additives listed in Table 1 were
dried in a vacuum oven at 70.degree. C. overnight to remove
absorbed moisture. The PET and 5 weight % of different additives
were mixed prior to injection molding. A lab scale Arburg unit
cavity injection molding machine was used for injection molding. A
24.5-g preform was used to make a 500 ml container. The preforms
were blow molded with a Sidel SBO 2/3 blow molding machine to make
acceptable 500 ml contour containers. The oxygen transmission rate
of the containers was then measured using a Macon 2/60 model
instrument at 22.2.degree. C. and 50% relative humidity (RH) with
the 99% N.sub.2/1% H.sub.2 purging rate of 10 ml/min on one side
and air on the other side. The results are shown in Table 1. The
barrier improvement factor (BIF) was defined as the ratio of the
oxygen transmission rate of the control and the additive package.
BIF is a measurement of the barrier enhancement as comparison to
control.
[0047] Table 1 Oxygen transmission rate of the control and additive
containers at 5 weight % additive loading
1TABLE 1 O.sub.2 transmission rate Barrier Improvement Additive
(cc/pkg/day) Factor (BIF) PET Control 0.046 1.00 1,5 dihydroxy
naphthalene 0.0097 4.74 1,6 dihydroxy naphthalene 0.005 9.20 2,6
dihydroxy naphthalene 0.0064 7.19
EXAMPLE 2
[0048] The resins and additives listed in Table 2 were dried, mixed
and injection molded as in Example 1. Instead of 5 weight % of
additive loading, a 3 weight % of additive loading was used. A
24.5-g preform was used to make a 500 ml container. The preforms
were blow molded with a Sidel SBO 2/3 blow molding machine to make
acceptable 500 ml contour containers. The oxygen transmission rate
of the containers was then measured using a Macon 2/60 model
instrument at 22.2.degree. C. and 50% RH with the 99% N.sub.2/1%
H.sub.2 purging rate of 10 ml/min on one side and air on the other
side. The results are shown in Table 2.
2TABLE 2 Oxygen transmission rate of the control and additive
containers at 3 weight % additive loading O.sub.2 transmission rate
Barrier Improvement Additive (cc/pkg/day) Factor (BIF) PET control
0.046 1.0 1,6 dihydroxy naphthalene 0.008 5.75 2,6 dihydroxy
naphthalene 0.008 5.75
EXAMPLE 3
[0049] A commercially available carbonated soft drink grade PET
resin and 3 weight % 1,3-dihydroxy naphthalene were dried, mixed
and injection molded as in Example 1. A 24.5 g preform was used to
make a 500 ml container. The preforms were blow molded with a Sidel
SBO 2/3 blow molding machine to make acceptable 500 ml contour
containers. The bottle sidewalls were then cut into a 2 in by 2 in
square and mounted into a Mocon Permeatran to measure the CO.sub.2
transmission rate. A PET control film was also used for the
CO.sub.2 transmission rate. The results are shown in table 3.
3TABLE 3 CO.sub.2 transmission rate of the control and additive
films CO.sub.2 transmission rate Barrier Improvement Additive
(cc/mil/100 in.sup.2/day) Factor (BIF) PET control 29.1 1.0 3
weight % 1,3 13.7 2.12 dihydroxy naphthalene
EXAMPLE 4
[0050] A commercially available carbonated soft drink grade PET
resin and 5 weight % of 1,3 dihydroxy naphthalene additive were
dried, mixed and injection molded as in Example 1. A 24.5-g preform
was used to make a 500 ml container. The preforms were blow molded
with a Sidel SBO 2/3 blow molding machine to make acceptable 500 ml
contour containers. The oxygen transmission rate of the containers
were then measured using a Macon 2/60 model instrument at
22.2.degree. C. and 50% RH with the 99% N.sub.2/1% H.sub.2 purging
rate of 10 ml/min on one side and air on the other side. The
results are shown in Table 4.
4TABLE 4 Oxygen transmission rate of the control and additive
containers O.sub.2 transmission Barrier Improvement Additive rate
(cc/pkg/day) Factor (BIF) PET control 0.046 1.00 5 weight % 1,3
dihydroxy 0.0000 NA naphthalene
[0051] Surprisingly, the 5 weight % 1,3 dihydroxy naphthalene gave
unexpected low oxygen transmission rate. The O.sub.2 transmission
rate was too low to be detected from the measurement equipment.
This clearly showed an oxygen scavenger effect. This oxygen
scavenger composition has the added benefit over the prior art
oxygen scavenger composition in that it does not contain any
transition metals.
EXAMPLE 5 (COMPARISON EXAMPLES)
[0052] The resins and additives were dried, mixed and injection
molded as in Example 1. Two comparison additives were used. One was
selected from the best performing additive list from WO 01/12521,
methyl-4-hydroxy-benzonate. Another was selected from a high
barrier comonomer from U.S. Pat. No. 6,320,014, 1,3-dihydroxy
benzene. The additives were added at 3 weight % first, then at 5
weight %. When added at 5 weight %, excessive degradation occurred
for the 1,3-dihydroxy benzene. The excessive degradation caused
substantial IV drop so much so that acceptable containers could not
be made. A 24.5-g preform was used to make a 500 ml container. The
preforms were blow molded with a Sidel SBO 2/3 blow molding machine
to make acceptable 500 ml contour containers. The oxygen
transmission rate of the containers were then measured using a
Macon 2/60 model instrument at 22.2.degree. C. and 50% RH with the
99% N.sub.2/1% H.sub.2 purging rate of 10 ml/min on one side and
air on the other side. The results are shown in Table 5.
5TABLE 5 Comparison oxygen transmission rate for the control and
additive containers Barrier O.sub.2 transmission Improvement
Additive Loading rate (cc/pkg/day) Factor (BIF) PET control 0.046
1.00 1,3 dihydroxy 3 wt % 0.034 1.35 benzene Methyl-4-hydroxy 5 wt
% 0.023 2.00 benzoate Methyl-4-hydroxy 3 wt % 0.03 1.53
benzoate
[0053] As can be seen from the data in table 5, embodiments of this
invention have much higher gas barrier than containers made with
conventional barrier additives.
[0054] It should be understood that the foregoing relates to
particular embodiments of the present invention, and that numerous
changes may be made therein without departing from the scope of the
invention as defined by the following claims.
* * * * *