U.S. patent application number 10/967803 was filed with the patent office on 2005-06-02 for pet copolymer composition with enhanced mechanical properties and stretch ratio, articles made therewith, and methods.
This patent application is currently assigned to The Coca-Cola Company. Invention is credited to Anthony, Linda K., Kjorlaug, Christopher C., Milton, Thomas H., Rule, Mark, Shi, Yu.
Application Number | 20050118371 10/967803 |
Document ID | / |
Family ID | 32312623 |
Filed Date | 2005-06-02 |
United States Patent
Application |
20050118371 |
Kind Code |
A1 |
Shi, Yu ; et al. |
June 2, 2005 |
PET copolymer composition with enhanced mechanical properties and
stretch ratio, articles made therewith, and methods
Abstract
A container is made from a preform comprising a PET Copolymer
comprising a diol component having repeat units from ethylene
glycol and a non-ethylene glycol diol component and a diacid
component having repeat units from terephthalic acid and a
non-terephthalic acid diacid component. The total amount of
non-ethylene glycol diol component and non-terephthalic acid diacid
component is present in the poly(ethylene terephthalate) copolymer
in an amount from about 0.2 mole percent to less than 2.2 mole
percent. The container is useful in packaging beverages and
corresponding methods are disclosed.
Inventors: |
Shi, Yu; (Alpharetta,
GA) ; Rule, Mark; (Atlanta, GA) ; Kjorlaug,
Christopher C.; (Alpharetta, GA) ; Anthony, Linda
K.; (Alpharetta, GA) ; Milton, Thomas H.;
(Greensboro, NC) |
Correspondence
Address: |
SUTHERLAND ASBILL & BRENNAN LLP
999 PEACHTREE STREET, N.E.
ATLANTA
GA
30309
US
|
Assignee: |
The Coca-Cola Company
|
Family ID: |
32312623 |
Appl. No.: |
10/967803 |
Filed: |
October 18, 2004 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10967803 |
Oct 18, 2004 |
|
|
|
10696858 |
Oct 30, 2003 |
|
|
|
60423221 |
Nov 1, 2002 |
|
|
|
Current U.S.
Class: |
428/35.7 |
Current CPC
Class: |
B29B 2911/14653
20130101; B29B 2911/14133 20130101; B29K 2067/00 20130101; B29B
2911/1498 20130101; B29B 2911/14026 20130101; B29B 2911/1402
20130101; B65D 1/0207 20130101; B29K 2995/0077 20130101; B29L
2031/565 20130101; Y10T 428/1352 20150115; B29B 2911/1404 20130101;
B29C 49/0005 20130101; B29K 2995/0067 20130101; B29K 2995/0017
20130101; B29B 2911/14906 20130101; B29L 2031/7158 20130101; B29B
2911/14033 20130101; B29B 2911/14593 20130101; B29B 2911/14986
20130101; B29B 2911/14713 20130101; C08G 63/672 20130101; B29K
2667/00 20130101; B29K 2995/004 20130101; B29C 49/06 20130101; B29B
2911/14106 20130101; B29K 2995/0041 20130101; C08G 63/183 20130101;
B29K 2105/253 20130101 |
Class at
Publication: |
428/035.7 |
International
Class: |
B65D 001/00 |
Claims
We claim:
1. A container made from an injection molded preform, the preform
having an open ended mouth forming portion, an intermediate body
forming portion, and a closed base forming portion and comprising a
poly(ethylene terephthalate) copolymer (PET Copolymer) comprising a
diol component having repeat units from ethylene glycol and a
non-ethylene glycol diol component and a diacid component having
repeat units from terephthalic acid and a non-terephthalic acid
diacid component, wherein the total amount of non-ethylene glycol
diol component and non-terephthalic acid diacid component present
in the PET Copolymer is in an amount from about 0.2 mole percent to
less than about 2.2 mole percent and the PET Copolymer is based on
100 mole percent of the diol component and 100 mole percent of the
diacid component.
2. A container as in claim 1 wherein the total amount of
non-ethylene glycol diol component and non-terephthalic acid diacid
component is present in the PET Copolymer in an amount from about
1.1 mole percent to about 2.1 mole percent.
3. A container as in claim 1 wherein the total amount of
non-ethylene glycol diol component and non-terephthalic acid diacid
component is present in the. PET Copolymer in an amount from about
1.2 mole percent to about 1.6 mole percent.
4. A container as in claim 1 wherein the repeat units from the
non-terephthalic acid diacid component are present in the PET
Copolymer in an amount from about 0.1 to about 1.0 mole
percent.
5. A container as in claim 1 wherein the repeat units from the
non-terephthalic acid diacid component are present in the PET
Copolymer in an amount from about 0.2 to about 0.75 mole
percent.
6. A container as in claim 1 wherein the repeat units from the
non-terephthalic acid diacid component are present in the PET
Copolymer in an amount from about 0.25 to about 0.6 mole
percent.
7. A container as in claim 1 wherein the repeat units from the
non-terephthalic acid diacid component are present in the PET
Copolymer in an amount from about 0.25 to less than about 0.5 mole
percent.
8. A container as in claim 1 wherein the repeat units from the
non-ethylene glycol diol component are present in the PET Copolymer
in an amount from about 0.1 to about 2.0 mole percent.
9. A container as in claim 1 wherein the repeat units from the
non-ethylene glycol diol component are present in the PET Copolymer
in an amount from about 0.5 to about 1.6 mole percent.
10. A container as in claim 1 wherein the repeat units from the
non-ethylene glycol diol component are present in the PET Copolymer
in an amount from about 0.8 to about 1.3 mole percent.
11. A container as in claim 1 wherein the repeat units from the
non-terephthalic acid diacid component are present in the PET
Copolymer in an amount from about 0.1 to about 1.0 mole percent and
the repeat units from the non-ethylene glycol diol component are
present in the PET Copolymer in an amount from 0.1 to about 2.0
mole percent.
12. A container as in claim 1 wherein the non-terephthalic acid
diacid component comprises repeat units from diacids selected from
the group consisting of adipic acid, succinic acid, isophthalic
acid, phthalic acid, 4,4'-biphenyl dicarboxylic acid, and
naphthalenedicarboxylic acid.
13. A container as in claim 1 wherein the non-terephthalic acid
diacid component comprises repeat units from
2,6-naphthalenedicarboxylic acid.
14. A container as in claim 1 wherein the non-ethylene glycol diol
component comprises repeat units from a diol selected from the
group consisting of cyclohexanedimethanol, propanediol, butanediol,
and diethylene glycol.
15. A container as in claim 1 wherein the non-ethylene glycol diol
component comprises repeat units from diethylene glycol.
16. A container as in claim 1 wherein the repeat units from the
non-terephthalic acid diacid component are
2,6-naphthalenedicarboxylic acid and present in the PET Copolymer
in an amount from about 0.1 to about 1.0 mole percent and wherein
the repeat units from the non-ethylene glycol diol component are
diethylene glycol and present in the PET Copolymer in an amount
from about 0.1 to about 2.0 mole percent.
17. A container as in claim 1 wherein the preform has a stretch
ratio in the range from about 8 to about 12.
18. A container as in claim 1 wherein the preform has a stretch
ratio in the range from about 8 to about 10.
19. A container as in claim 1 wherein the PET Copolymer is a
reaction grade copolymer.
20. A container as in claim 1 wherein the intermediate body forming
portion of the preform has a wall thickness from about 1.5 to about
8 mm and an inside diameter from about 10 to about 30 mm, and the
preform has a finish, a closed end opposite the finish, and a
height from the closed end to the finish of from about 50 to about
150 mm.
21. A container as in claim 1 wherein the container has a volume
within the range from about 0.25 to about 3 liters.
22. A container as in claim 1 wherein the container is a bottle,
drum, carafe, or cooler.
23. A preform having an open ended mouth forming portion, an
intermediate body forming portion, and a closed base forming
portion, and comprising a PET Copolymer comprising a diol component
having repeat units from ethylene glycol and a non-ethylene glycol
diol component and a diacid component having repeat units from
terephthalic acid and a non-terephthalic acid diacid component,
wherein the total amount of non-ethylene glycol diol component and
non-terephthalic acid diacid component present in the PET Copolymer
is in an amount from about 0.2 mole percent to less than about 2.2
mole percent and the PET Copolymer is based on 100 mole percent of
the diol component and 100 mole percent of the diacid
component.
24. A preform as in claim 23 wherein the non-terephthalic acid
diacid component comprises repeat units from
2,6-naphthalenedicarboxylic acid and the non-ethylene glycol diol
component comprises repeat units from diethylene glycol.
25. A preform as in claim 24 wherein the repeat units from
2,6-naphthalenedicarboxylic acid are present in the PET Copolymer
in an amount from about 0.1 to about 1.0 mole percent and wherein
the repeat units from the diethylene glycol are present in the PET
Copolymer in an amount from about 0.1 to about 2.0 mole
percent.
26. The preform as in claim 24 wherein 2,6-naphthalenedicarboxylic
acid is present from about 0.2 to about 0.75 mole percent and the
diethylene glycol is present in an amount of about 0.5 to about 1.6
mole percent.
27. A preform as in claim 23 wherein the preform has a stretch
ratio in the range from about 8 to about 12.
28. A preform as in claim 23 wherein the preform has a stretch
ratio in the range from about 8 to about 10.
29. A preform as in claim 23 wherein the PET Copolymer is a
reaction grade copolymer.
30. A preform for use in making a container comprising a PET
Copolymer comprising a diol component having repeat units from
ethylene glycol and a non-ethylene glycol diol component and a
diacid component having repeat units from terephthalic acid and a
non-terephthalic acid diacid component; wherein the total amount of
non-ethylene glycol diol component and non-terephthalic acid diacid
component present in the PET Copolymer is in an amount from about
0.2 mole percent to less than about 3.0 mole percent based on 100
mole percent of the diol component and 100 mole percent of the
diacid component, and wherein the non-ethylene glycol diol
component is present in an amount of from about 0.1 to about 2.0
mole percent and the non-terephthalic acid diacid component is
present in an about of about 0.1 to about 1.0 mole percent.
31. A preform as in claim 30 wherein the total amount of
non-ethylene glycol diol component and non-terephthalic acid diacid
component present in the PET Copolymer is in an amount from about
0.2 mole percent to less than about 2.6 mole percent.
32. A preform as in claim 30 wherein the non-ethylene glycol diol
component is derived from diethylene glycol.
33. A preform as in claim 30 wherein the non-terephthalic acid
diacid component is derived from 2,6-naphthalenedicarboxylic acid
or its diester.
34. A preform as in claim 30 wherein the preform has a stretch
ratio in the range from about 8 to about 12.
35. A preform as in claim 30 wherein the preform has a stretch
ratio in the range from about 8 to about 10.
36. A packaged beverage comprising a container made from an
injection molded preform and a beverage disposed in the container,
wherein the preform: (a) has an open ended mouth forming portion,
an intermediate body forming portion, and a closed base forming
portion, and (b) comprises a PET Copolymer comprising a diol
component having repeat units from ethylene glycol and a
non-ethylene glycol diol component and a diacid component having
repeat units from terephthalic acid and a non-terephthalic acid
diacid component, wherein the total amount of non-ethylene glycol
diol component and non-terephthalic acid diacid component present
in the PET Copolymer is in an amount from about 0.2 mole percent to
less than about 2.2 mole percent and the PET Copolymer is based on
100 mole percent of the diol component and 100 mole percent of the
diacid component.
37. A packaged beverage as in claim 36 wherein the repeat units
from the non-terephthalic acid diacid component are
2,6-naphthalenedicarboxylic acid and present in the PET Copolymer
in an amount from about 0.1 to about 1.0 mole percent and wherein
the repeat units from the non-ethylene glycol diol component are
diethylene glycol and present in the PET Copolymer in an amount
from about 0.1 to about 2.0 mole percent.
38. A packaged beverage as in claim 36 wherein the preform has a
stretch ratio in the range from about 8 to about 12.
39. A packaged beverage as in claim 36 wherein the preform has a
stretch ratio in the range from about 8 to about 10.
40. A method for reducing the cycle time for making a container
comprising the steps of: (1) providing a PET Copolymer melt
comprising a diol component having repeat units from ethylene
glycol and a non-ethylene glycol diol component and a diacid
component having repeat units from terephthalic acid and a
non-terephthalic acid diacid component, wherein the total amount of
non-ethylene glycol diol component and non-terephthalic acid diacid
component is present in the PET Copolymer in an amount from about
0.2 mole percent to less than about 2.2 mole percent, (2) then
injecting the PET Copolymer into a mold, (3) then cooling the mold
and the contained polymer, (4) then releasing from the mold a
preform, (5) then reheating the preform, and (6) then blow molding
the preform into a container; wherein the cycle time for making the
container is reduced as compared to a second cycle time for making
a second container comprising a poly(ethylene terephthalate) resin
having comonomer modification greater than about 2.2 mole percent
of a combination of a non-ethylene glycol diol component and a
non-terephthalic acid diacid component.
41. A method as in claim 40 wherein the repeat units from the
non-terephthalic acid diacid component are
2,6-naphthalenedicarboxylic acid and present in the PET Copolymer
in an amount from about 0.1 to about 1.0 mole percent and wherein
the repeat units from the non-ethylene glycol diol component are
diethylene glycol and present in the PET Copolymer in an amount
from about 0.1 to about 2.0 mole percent.
42. A method as in claim 40 wherein the preform has a stretch ratio
in the range from about 8 to about 12.
43. A method as in claim 40 wherein the preform has a stretch ratio
in the range from about 8 to about 10.
44. A method for making a container comprising blow molding an
injection molded preform (a) having an open ended mouth forming
portion, an intermediate body forming portion, and a closed base
forming portion, and (b) comprising a PET Copolymer comprising a
diol component having repeat units from ethylene glycol and a
non-ethylene glycol diol component and a diacid component having
repeat units from terephthalic acid and a non-terephthalic acid
diacid component, wherein the total amount of non-ethylene glycol
diol component and non-terephthalic acid diacid component present
in the PET Copolymer is in an amount from about 0.2 mole percent to
less than about 2.2 mole percent and the PET Copolymer is based on
100 mole percent of the diol component and 100 mole percent of the
diacid component.
45. A method as in claim 44 wherein the repeat units from the
non-terephthalic acid diacid component are
2,6-naphthalenedicarboxylic acid and present in the PET Copolymer
in an amount from about 0.1 to about 1.0 mole percent and wherein
the repeat units from the non-ethylene glycol diol component are
diethylene glycol and present in the PET Copolymer in an amount
from about 0.1 to about 2.0 mole percent.
46. A method as in claim 44 wherein the preform has a stretch ratio
in the range from about 8 to about 12.
47. A method as in claim 44 wherein the preform has a stretch ratio
in the range from about 8 to about 10.
48. A method for making a preform for use in making containers
comprising injection molding a PET Copolymer comprising a diol
component having repeat units from ethylene glycol and a
non-ethylene glycol diol component and a diacid component having
repeat units from terephthalic acid and a non-terephthalic acid
diacid component, wherein the total amount of non-ethylene glycol
diol component and non-terephthalic acid diacid component present
in the PET Copolymer is in an amount from about 0.2 mole percent to
less than about 2.2 mole percent, and the PET Copolymer is based on
100 mole percent of the diol component and 100 mole percent of the
diacid component.
49. A method as in claim 48 wherein the repeat units from the
non-terephthalic acid diacid component are
2,6-naphthalenedicarboxylic acid and present in the PET Copolymer
in an amount from about 0.1 to about 1.0 mole percent and wherein
the repeat units from the non-ethylene glycol diol component are
diethylene glycol and present in the PET Copolymer in an amount
from about 0.1 to about 2.0 mole percent.
50. A method as in claim 48 wherein the preform has a stretch ratio
in the range from about 8 to about 12.
51. A method as in claim 49 wherein the preform has a stretch ratio
in the range from about 8 to about 10.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority Under 35 U.S.C. .sctn.119
to U.S. provisional patent application Ser. No. 60/423,221 filed on
Nov. 1, 2002.
FIELD OF THE INVENTION
[0002] This invention relates to preforms and their containers made
with poly(ethylene terephthalate)-based resin compositions that
possess low levels diol and acid modification, such as
naphthalenedicarboxylic acid and diethylene glycol. More
particularly, this invention relates to low stretch ratio preforms
and their containers, which exhibit enhanced mechanical properties
relative to containers made using conventional poly(ethylene
terephthalate)-based resin compositions.
BACKGROUND OF THE INVENTION
[0003] Poly(ethylene terephthalate)-based resins, which are
commonly referred to in the industry simply as "PET" even though
they may and often do contain minor amounts of additional
components, have widely been used to make containers for carbonated
soft drink, juice, water and the like due to their excellent
combination of mechanical and gas barrier properties. As the use of
plastics such as PET for packaging increases, concerns regarding
the environmental impact of plastic waste are becoming more and
more significant. Source reduction is a preferred strategy for
reducing the environmental impact of plastic containers. Source
reduction saves resources and energy; however, with PET additional
source reduction is difficult to achieve, because of the physical
performance requirements necessary for the major applications for
this polymer.
[0004] One source reduction opportunity that does exist is related
to the degree of material utilization achieved in blow-molding of
PET preforms into PET containers. The degree of material
utilization is defined as the amount of unoriented polymer present
in the sidewall of the container. For large sized containers, the
amount of material utilization is already high, and further
increases offer limited opportunity for source reduction. However,
for small sized containers, the amount of material utilization is
significantly lower, with degrees of material utilization typically
ranging from 80 to 85 percent. Improving material utilization using
conventional PET can be achieved by increasing the stretch ratio of
the preform. Increasing the stretch ratio of the preform provides
an added benefit by increasing the mechanical properties of the
container, because the stiffness of PET is directly affected by the
degree of orientation imposed by stretching the polymer. However,
there is a significant cost associated with increasing the preform
stretch ratio. Increasing the preform stretch ratio necessarily
means increasing the wall thickness of the preform, which adversely
impacts injection molding and blow molding cycle times. This
consequently consumes more energy and increases the capital and
operating cost for making PET containers.
[0005] Previous methods of source reduction have focused simply on
reducing the weight of the container, with a concomitant reduction
in the sidewall thickness of the resulting container. This approach
inherently sacrifices the mechanical integrity of the container,
since sidewall rigidity relates to the second power of the
thickness. Although in principle the sidewall rigidity of a
container could be maintained by increasing the modulus of the
polymer, in practice this is difficult to achieve. In addition,
sidewall rigidity varies only to the first power of modulus;
therefore, a much higher increase in the modulus would be required
to counter-balance any thickness reduction. While an increase in
the molecular weight of the PET or crystallinity level of the
containers can increase the modulus of PET, these approaches have
inherent limits. An even minor increase in molecular weight also
increases the melt viscosity of the PET, which can lead to
significantly greater polymer degradation during the melt
processing that produces the preforms. To increase the
crystallinity level of the container substantially, additional
steps in the container manufacturing process, such as heat-setting
at high temperature, are required. Other means to achieve much
higher crystallinity of containers, such as through nucleation
agents or hyper-stretching, have not been successful.
[0006] U.S. Pat. Nos. 5,631,054 and 5,162,091 described methods to
increase the mechanical properties of PET through use of specific
low molecular weight additives. Those additives provided modest
improvements to the tensile modulus of PET. However, the amount of
additives required is high (1-5% by weight), and the additives
claimed are relatively expensive compared to the cost of PET. In
addition, because these additives were not part of the polymer
chains, they are potentially extractable, which is detrimental to
their use in food contact applications.
[0007] Thus, there exists a need in the art for a container that
has a high degree of material utilization, is lighter weight, has
sufficient mechanical properties, and consumes less energy in its
production. Accordingly, it is to the provision of such that the
present invention is directed.
SUMMARY OF THE INVENTION
[0008] This invention addresses the above-described need for
lighter weight containers by providing an injection molded preform
having an open ended mouth forming portion, an intermediate body
forming portion, and a closed base-forming portion. In one
embodiment, the preform comprises a poly(ethylene terephthalate)
copolymer (hereinafter "PET Copolymer") comprising a diol component
having repeat units from ethylene glycol and a non-ethylene glycol
diol component and a diacid component having repeat units from
terephthalic acid and a non-terephthalic acid diacid component. The
total amount of non-ethylene glycol diol component and
non-terephthalic acid diacid component is present in the PET
Copolymer in an amount from about 0.2 mole percent to less than
about 2.2 mole percent. The mole percentages are based on 100 mole
percent diacid component and 100 mole percent diol component. This
definition is applicable to mole percentages throughout this
specification. The preform, the container and corresponding methods
of making each are additional embodiments of this invention.
[0009] In another embodiment, a preform for use in making a
container comprises a PET Copolymer comprising a diol component
having repeat units from ethylene glycol and a non-ethylene glycol
diol component and a diacid component having repeat units from
terephthalic acid and a non-terephthalic acid diacid component. The
total amount of non-ethylene glycol diol component and
non-terephthalic acid diacid component is present in the PET
Copolymer in an amount from about 0.2 mole percent to less than
about 3.0 mole percent based on 100 mole percent of the diol
component and 100 mole percent of the diacid component.
Furthermore, the non-ethylene glycol diol component is present in
an amount of from about 0.1 to about 2.0 and the non-terephthalic
acid diacid component is present in an about of about 0.1 to about
1.0.
[0010] In preferred embodiments, the preforms are designed to have
a stretch ratio in the range from about 8 to about 12, enabling the
preforms to have a reduced wall thickness. Thus the cycle time for
manufacture of the preforms is reduced. Because the material
utilization is higher, less material needs to be used and the cost
of goods is lowered, while the containers produced exhibit improved
thermal stability and sidewall rigidity characteristics.
[0011] In still another embodiment of the present invention, a
method for reducing the cycle time for making a container comprises
the steps of:
[0012] (1) providing a PET Copolymer melt comprising a diol
component having repeat units from ethylene glycol and a
non-ethylene glycol diol component and a diacid component having
repeat units from terephthalic acid and a non-terephthalic acid
diacid component, wherein the total amount of non-ethylene glycol
diol component and non-terephthalic acid diacid component is
present in the PET Copolymer in an amount from about 0.2 mole
percent to less than about 2.2 mole percent,
[0013] (2) then injecting the PET Copolymer into a mold,
[0014] (3) then cooling the mold and the contained polymer,
[0015] (4) then releasing from the mold a preform,
[0016] (5) then reheating the preform, and
[0017] (6) then blow molding the preform into a container.
[0018] The cycle time for making the container is reduced as
compared to a second cycle time for making a second container
comprising a poly(ethylene terephthalate) resin having comonomer
modification greater than about 2.2 mole percent of a combination
of a non-ethylene glycol diol component and a non-terephthalic acid
diacid component.
[0019] Thus, embodiments of this invention provide two sets of
improvements. In one set, the PET Copolymer is used with a
conventional preform design to produce a container with enhanced
mechanical properties, higher crystallinity and improved shelf
life. In the other set, the PET Copolymer is used with a redesigned
preform that has a stretch ratio of from about 8 to about 12, a
reduced preform wall thickness, and reduced cycle time to produce a
container of similar or improved quality compared to a container
produced using conventional PET resin and a conventional preform
design.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1 is a sectional elevation view of an injection molded
preform having a conventional configuration, made with the PET
Copolymer in accordance with a preferred embodiment of this
invention.
[0021] FIG. 2 is a sectional elevation view of an injection molded
preform having an unconventional configuration in accordance with a
preferred embodiment of this invention.
[0022] FIG. 3 is a sectional elevation view of a blow molded
container made from the preform of FIG. 1 in accordance with a
preferred embodiment of this invention.
DETAILED DESCRIPTION OF THE INVENTION
[0023] In the present invention, a PET Copolymer is made into an
injection molded preform which is then blow molded into a
container. The preform comprises an open ended mouth forming
portion, an intermediate body forming portion, and a closed base
forming portion. The preform comprises a PET Copolymer comprising a
diol component having repeat units from ethylene glycol and a
non-ethylene glycol diol component and a diacid component having
repeat units from terephthalic acid and a non-terephthalic acid
diacid component, wherein the total amount of non-ethylene glycol
diol component and non-terephthalic acid diacid component is
present in the PET Copolymer in an amount from about 0.2 mole
percent to less than about 2.2 mole percent. The mole percentages
of diol components and diacid components include all residual
comonomers in the PET Copolymer composition such as those formed
during or passing through the manufacturing process of the PET
Copolymer. In all instances throughout the specification, the PET
Copolymer is based on a total of 200 mole percent including 100
mole percent of the diol component and 100 mole percent of the
diacid component.
[0024] The amount of each of the non-ethylene glycol diol component
and non-terephthalic acid diacid component in the PET Copolymer can
vary to some extent within the total amount of both, which is from
about 0.2 mole percent to less than about 2.2 mole percent.
Preferably, the total amount of non-ethylene glycol diol component
and non-terephthalic acid diacid component is present in the PET
Copolymer in an amount from about 1.1 mole percent to about 2.1
mole percent, and even more preferably in an amount from about 1.2
mole percent to about 1.6 mole percent. Repeat units from the
non-terephthalic acid diacid component are preferably present in
the PET Copolymer in an amount from about 0.1 to about 1.0 mole
percent, more preferably in an amount from about 0.2 to about 0.75
mole percent, still more preferably in an amount from about 0.25 to
about 0.6 mole percent, and yet more preferably in an amount from
about 0.25 to less than about 0.5 mole percent. The repeat units
from the non-ethylene glycol diol component are preferably present
in the PET Copolymer in an amount from about 0.1 to about 2.0 mole
percent, more preferably in an amount from about 0.5 to about 1.6
mole percent, and even more preferably in an amount from about 0.8
to about 1.3 mole percent. The PET Copolymer preferably has an
intrinsic viscosity (IV), measured according to ASTM D4603-96, from
about 0.6 to about 1.1 dL/g, more preferably from about 0.7 to
about 0.9, and even more preferably from about 0.8 to about 0.84.
Desirably, the PET resin of this invention is a reaction grade
resin, meaning that the PET resin is a direct product of a chemical
reaction between comonomers and not a polymer blend.
[0025] In another embodiment of the invention, a preform for use in
making a container comprises a PET Copolymer comprising a diol
component having repeat units from ethylene glycol and a
non-ethylene glycol diol component and a diacid component having
repeat units from terephthalic acid and a non-terephthalic acid
diacid component. The total amount of non-ethylene glycol diol
component and non-terephthalic acid diacid component present in the
PET Copolymer is in an amount from about 0.2 mole percent to less
than about 3.0 mole percent based on 100 mole percent of the diol
component and 100 mole percent of the diacid component. The
non-ethylene glycol diol component is present in an amount of from
about 0.1 to about 2.0 and the non-terephthalic acid diacid
component is present in an about of about 0.1 to about 1.0.
Preferably, the total amount of non-ethylene glycol diol component
and non-terephthalic acid diacid component is present in an amount
from about 0.2 mole percent to less than about 2.6 mole
percent.
[0026] The non-terephthalic acid diacid component can be any of a
number of diacids, including adipic acid, succinic acid,
isophthalic acid (IPA), phthalic acid, 4,4'-biphenyl dicarboxylic
acid, naphthalenedicarboxylic acid, and the like. The preferred
non-terephthalate acid diacid component is
2,6-naphthalenedicarboxylic acid (NDC). The non-ethylene glycol
diols contemplated in this invention include cyclohexanedimethanol,
propanediol, butanediol, and diethylene glycol. Of these,
diethylene glycol (DEG) is preferred since it is already naturally
present in the PET Copolymer. The non-terephthalic acid diacid
component and the non-ethylene glycol diol component may also be
mixtures of diacids and diols, respectively.
[0027] The levels of DEG in PET Copolymers of the present invention
range from about 0.1 to about 2.0 mole percent, which is below the
typical residual levels of DEG present in the manufacture of
conventional PET (hereinafter "Conventional PET"). Conventional PET
typically contains from about 2.4 to about 2.9 mole percent DEG,
which is equivalent to more commonly referenced weight percent
values of about 1.3 to about 1.6. Those skilled in the art of PET
manufacture generally regard DEG as a harmless by-product of the
polymer manufacture; consequently, little effort has been directed
toward reduction of DEG levels in PET intended for use in
containers. Thus, modifications to the PET production process for
containers must occur to achieve the lower DEG levels in the PET
Copolymer of the present invention. Any method suitable for
reducing DEG content of polyester can be employed. Suitable methods
include reducing the mole ratio of diacid or diester relative to
ethylene glycol in the esterification or transesterification
reaction; reducing the temperature of the esterification or
transesterification reaction, addition of DEG-suppressing
additives, including tetra-alkyl ammonium salts and the like; and
reduction of the DEG content of the ethylene glycol that is
recycled back to the esterification or transesterification
reaction.
[0028] In desirable embodiments, the preforms have a stretch ratio
in the range from about 8 to about 12 when used to make containers,
and more desirably from about 8 to about 10. The stretch ratio as
used herein refers to the nomenclature that is well known in the
art and is defined as following:
Stretch ratio=(maximum container diameter/internal preform
diameter).times.[(height of container below finish)/(height of
preform below finish)]
[0029] The natural stretch ratio is an inherent property of a
polymer. The measurement of the free blow volume of a polymer
relative to a preform, which is used in the Examples herein,
provides a method to measure the natural stretch ratio of a
polymer. The natural stretch ratio of a polymer influences the
preform design by determining the stretch ratio limitations of a
preform used in the blow molding process for making a container. A
polymer with a lower natural stretch ratio allows a preform to be
designed with a lower stretch ratio. Whenever the stretch ratio of
a preform is lower, the sidewall thickness of the preform required
to make a bottle of a target sidewall thickness can be reduced. An
important factor in blow molding lightweight containers is also
uniform wall thickness distribution, especially in the label panel
area. Using polymers with lower natural stretch ratios inherently
causes more material to be uniformly oriented and distributed
during the blow molding process. With an understanding of the
natural stretch ratio of a polymer, preform dimensions such as
height, inside diameter, and wall thickness can be selected so that
the preform can be blow molded into a container having certain
selected physical properties such as weight, height, maximum
diameter, thermal stability, and sidewall rigidity.
[0030] In another embodiment of the present invention, a method for
reducing the cycle time for making a container comprises the steps
of:
[0031] (1) providing a PET Copolymer melt comprising a diol
component having repeat units from ethylene glycol and a
non-ethylene glycol diol component and a diacid component having
repeat units from terephthalic acid and a non-terephthalic acid
diacid component, wherein the total amount of non-ethylene glycol
diol component and non-terephthalic acid diacid component is
present in the PET Copolymer in an amount from about 0.2 mole
percent to less than about 2.2 mole percent,
[0032] (2) then injecting the PET Copolymer into a mold,
[0033] (3) then cooling the mold and the contained polymer,
[0034] (4) then releasing from the mold a preform,
[0035] (5) then reheating the preform, and
[0036] (6) then blow molding the preform into a container.
[0037] The cycle time for making the container according to the
steps above is reduced as compared to a second cycle time for
making a second container comprising a poly(ethylene terephthalate)
resin having comonomer modification greater than about 2.2 mole
percent of a combination of a non-ethylene glycol diol component
and a non-terephthalic acid diacid component.
[0038] In another method embodiment, a method for making a
container comprises blow molding an injection molded preform that
has an open ended mouth forming portion, an intermediate body
forming portion, and a closed base forming portion, The preform
comprises a PET Copolymer comprising a diol component having repeat
units from ethylene glycol and a non-ethylene glycol diol component
and a diacid component having repeat units from terephthalic acid
and a non-terephthalic acid diacid component. The total amount of
non-ethylene glycol diol component and non-terephthalic acid diacid
component present in the PET Copolymer is in an amount from about
0.2 mole percent to less than about 2.2 mole percent.
[0039] In still another method embodiment, a method for making a
preform for use in making containers comprises injection molding a
PET Copolymer, which comprises a diol component having repeat units
from ethylene glycol and a non-ethylene glycol diol component and a
diacid component having repeat units from terephthalic acid and a
non-terephthalic acid diacid component. The total amount of
non-ethylene glycol diol component and non-terephthalic acid diacid
component present in the PET Copolymer: is in an amount from about
0.2 mole percent to less than about 2.2 mole percent.
[0040] In the method embodiments, the PET Copolymer preferably
comprises 2,6-naphthalenedicarboxylic acid as the non-terephthalic
acid diacid component present in an amount from about 0.1 to about
1.0 mole percent and diethylene glycol as the non-ethylene glycol
diol component present in the PET Copolymer in an amount from about
0.1 to about 2.0 mole percent. Preferably, the preform has a
stretch ratio in the range from about 8 to about 12 and more
preferably in the range from about 8 to about 10.
[0041] To understand the significance of the present invention, an
understanding of the conventional process of making containers is
needed. Firstly, PET pellets that are obtained from a conventional
polyester esterification/polycondensation process are melted and
subsequently formed into preforms through an injection molding
process. Secondly, the preforms are heated in an oven to a
temperature above the polymer's glass transition temperature, and
then formed into containers via a blow molding process. The desired
end result is clear containers with sufficient mechanical and
barrier properties to provide appropriate protection for the
contained beverage or food product.
[0042] An important consideration in producing clear or transparent
containers is to first produce clear or transparent preforms.
During the injection molding step thermally induced crystallization
can occur in the conversion of the polymer to a preform. Thermally
induced crystallization tends to form large crystallites in the
polymer, with a concomitant formation of haze. In order to minimize
the formation of crystallites and thus have clear preforms, the
rate of thermal crystallization needs to be slow enough so that
preforms with little or no crystallinity can be produced. However,
if the rate of thermal crystallization is too low, the production
rates of PET resin can be adversely affected, since PET must be
thermally crystallized prior to solid-state polymerization, a
process used to increase the molecular weight of PET and
simultaneously remove unwanted acetaldehyde. Solid state
polymerization increases the molecular weight of the polymer so
that a container made from the polymer will have the requisite
strength. Prior art techniques for reducing thermal crystallization
rate include the use of PET containing a certain amount of
co-monomers. The most commonly used comonomer modifiers are
isophthalic acid or. 1,4-cyclohexanedimethanol, which are added at
levels ranging from 1.5 to 3.0 mole %.
[0043] Counterbalancing the need to reduce the rate of thermal
crystallization during injection molding is the need to increase
the rate of strain-induced crystallinity that occurs during blow
molding. Strain-induced crystallinity results from the rapid
mechanical deformation of PET, and generates extremely small,
transparent crystallites. The amount of crystallinity present in
the container sidewall correlates with the strength and barrier
performance of the container. Previously, it has been demonstrated
that increasing the DEG content of PET from 2.9 to 4.0 mole percent
causes an increase in crystallization rates of PET compared to
Conventional PET containing between 2.4 to 2.9 mole percent DEG.
The rationale for this phenomenon is that the increased polymer
chain flexibility resulting from the higher DEG content allows for
more rapid ordering and packing of the polymer chains into polymer
crystals.
[0044] In the PET Copolymer of the present invention both a reduced
rate of thermal crystallization and an increased rate of
strain-induced crystallization is unexpectedly found to occur by
the comonomer modification of non-terephthalic acid diacid
component at about 0.1 to about 1.0 mole percent and of
non-ethylene glycol diol component at about 0.1 to about 2.0 mole
percent, respectively. The non-terephthalic acid diacid such as NDC
is believed to reduce the thermal crystallization rate due to the
rigidity of the NDC moiety hindering polymer chain flexibility, and
thus makes formation of crystallites more difficult. The addition
of NDC has also been discovered to enhance the stiffness of the PET
chains and results in an unexpected increase in the sidewall
rigidity of the containers made from PET Copolymer. Furthermore and
contrary to expectations, reducing the DEG content to less than
about 2.0 mole percent in the PET Copolymer results in an increase
in the rate of strain-induced crystallization relative to
Conventional PET containing between 2.4 and 2.9 mole percent
DEG.
[0045] A consequence of this unique combination of low amounts of
DEG and NDC, at least in preferred embodiments, is a reduction in
the natural stretch ratio of PET Copolymer as compared to that of
Conventional PET. The physical dimensions of the preform can
therefore be altered so as to make a thinner walled preform that
produces a lighter weight container that has an acceptable level of
strength and similar container sidewall thickness compared to
containers made from Conventional PET using conventional preform
designs, or to make similar weight containers having a higher level
of strength and greater container sidewall thickness. The physical
properties of the preform can also be selected to reduce the
preform injection molding cycle time and the container blow molding
cycle time without compromising the container strength or shelf
life of the container contents.
[0046] By using the PET Copolymer of the present invention,
containers that have enhanced mechanical properties, higher
crystallinity, thicker sidewalls, and improved shelf-life can be
made utilizing preforms that have conventional stretch ratios of
about 14. Alternatively and in preferred embodiments,
unconventional preforms; can be designed to have a longer length
and thinner walls and that have a stretch ratio of from about 8 to
about 12. Containers made using the PET Copolymer of the present
invention and such unconventional preforms exhibit improved
material utilization, stiffness, and higher levels of strain
induced crystallinity during the blow molding process as compared
to conventional preforms made from Conventional PET even when the
preforms have reduced sidewall thickness and lower stretch ratios
than that of conventional preforms made with Conventional PET.
[0047] The present invention can be more fully appreciated when
comparing container properties relative to the preform stretch
ratio. A preform designed to have a stretch ratio of about 14 and a
sidewall thickness of about 3.2 mm using Conventional PET having
DEG content above 2.0 mole percent will result in a blow molded
container having a sidewall thickness of about 0.23 mm. When using
the same preform design with the PET Copolymer of the present
invention, the blow molded container will have a sidewall thickness
of about 0.35 mm. To obtain the same resulting container sidewall
thickness using the PET Copolymer, the preform needs to be
redesigned to be longer and have a sidewall thickness of 2.3 mm.
This thinner sidewall preform exhibits improved cycle times and
reduced energy usage as well as a reduced total weight as compared
with preforms made of Conventional PET resins, while at the same
time producing an equivalent or improved container. To further
illustrate, a preform made with Conventional PET using the
redesigned preform having a sidewall thickness of 2.28 mm would
result in a useless container because the sidewall thickness of the
container would be only 0.16 mm, which would not provide enough
structural integrity to the container, and would also exhibit
reduced shelf-life for carbonated beverages.
[0048] Thus, an important benefit of the reduced natural stretch
ratio of the PET Copolymer of the present invention is the redesign
of preforms so that a longer-length, thinner-walled preform can be
designed to achieve the same or better final PET container
properties as obtained from Conventional PET and conventional
preform designs. As well known to those skilled in the art, the
sidewall thickness of the preform correlates with the injection
molding cooling time. The cooling time is proportional to the
square of the wall thickness. Since injection molding cycle time is
to a large degree determined by cooling time, the preform design of
the present invention will substantially reduce the injection
molding cycle time. A thinner-walled preform is also easier to
reheat since it will take less time for heat to transfer throughout
the preform sidewall. This potentially can reduce the blow molding
reheat and beat saturation time, resulting in an improvement in
productivity and a reduction in energy usage in the blow molding
process.
[0049] The light weighting potential for a container can be
illustrated with two tests: thermal expansion and sidewall
deflection as described in the following sections. Both tests
demonstrate the mechanical properties of the bottles of thermal
stability and sidewall rigidity, respectively. For the same resin
composition, a lighter weight bottle has lower mechanical strength,
poorer thermal stability (and concomitantly greater thermal
expansion), and less sidewall rigidity (or greater sidewall
deflection). The low DEG, low NDC PET Copolymer of the present
invention displays enhanced performance in both thermal stability
and sidewall rigidity tests. Such performance is possibly caused by
the increased crystallinity of the PET Copolymer and the decreased
moisture sorption therein. Both of these factors can substantially
decrease creep, which is the dimensional change under stress of a
container measured by the change in diameter and height. This is an
important factor, because most containers undergo some stress
during and after the filling process. Therefore, thermal expansion
and sidewall deflection tests are used herein to compare the
performance of containers, and especially the performance of
pressurized containers.
[0050] In preferred embodiments, containers of this invention
include bottles, drums, carafes, and coolers, and the like. As is
well known to those skilled in the art, such containers can be made
by blow molding an injection molded preform. Examples of suitable
preform and container structures and methods for making the same
are disclosed in U.S. Pat. No. 5,888,598, the disclosure of which
is expressly incorporated herein by reference in its entirety.
Other preform and container structures, not disclosed in U.S. Pat.
No. 5,888,598, are described herein as well.
[0051] Turning to the FIGS. 1-3, a polyester preform 10 having a
conventional configuration is illustrated in FIG. 1 and a polyester
preform 11 having a configuration in accordance with an embodiment
of this invention is illustrated in FIG. 2. These preforms 10 and
11 in FIGS. 1 and 2 each have the same components, and therefore,
like reference numerals indicate like components throughout the
Figs., but the dimensions of the preforms are different. The
dimensions in FIGS. 1 and 2 are not drawn to scale.
[0052] The preforms 10 and 11 are made by injection molding the PET
Copolymer of this invention and comprise a threaded neck finish 12
which terminates at its lower end in a capping flange 14. Below the
capping flange 14, there is a generally cylindrical section 16
which terminates in a section 18 of gradually decreasing external
diameter so as to provide for an increasing wall thickness. Below
the section 18 there is an elongated body section 20. The height of
the preform is measured from the capping flange 14 to a closed end
21 of the elongated body section 20.
[0053] The preforms 10 and 11 illustrated in FIGS. 1 and 2 can each
be blow molded to form a container 22 illustrated in FIG. 3. The
container 22 comprises a shell 24 comprising a threaded neck finish
26 defining a mouth 28, a capping flange 30 below the threaded neck
finish, a tapered section 32 extending from the capping flange, a
body section 34 extending below the tapered section, and a base 36
at the bottom of the container. The height of the container is
measured from the capping flange 30 to a closed end at the base 36.
The container 22 is suitably used to make a packaged beverage 38,
as illustrated in FIG. 3. The packaged beverage 38 includes a
beverage such as a carbonated soda beverage disposed in the
container 22 and a closure 40 sealing the mouth 28 of the
container.
[0054] According to preferred embodiments of this invention, the
intermediate body forming portion of the preform has a wall
thickness from 1.5 to 8 mm. Furthermore, according to preferred
embodiments, the intermediate body forming portion of the preform
has an inside diameter from 10 to 30 mm, and the height of the
preform, which extends from the closed end of the preform opposite
the finish to the finish, is from 50 to 150 mm. Preferably,
containers made in accordance with preferred embodiments of this
invention have a volume within the range from 0.25 to 3 liters and
a wall thickness of 0.25 to 0.65 mm.
[0055] In this specification, reference is made to dimensions of
the preforms 10 and 11 and the resulting containers 22. The height
H of the preforms is the distance from the closed end 21 of the
preform opposite the finish 12 to the capping flange 14 of the
finish. The inside diameter ID of the preforms 10 and 11 is the
distance between the interior walls of the elongated body section
20 of the preforms. The wall thickness T of the preforms 10 and 11
is measured at the elongated body section 20 of the preforms also.
The height H' of the containers 22 is the distance from the closed
end of the base 36 of the container opposite the finish 26 to the
capping flange 30 of the finish. The maximum container diameter MD
is the diameter of the container at its widest point along the
height of the container 22. The hoop stretch ratio of the preforms
equals the maximum container diameter divided by the internal
preform diameter and the axial stretch ratio equals the height of
container below the finish divided by the height of preform below
the finish. The stretch ratio of the preforms equals the product of
the hoop stretch ration and the axial stretch ratio.
[0056] The preforms 10 and 11, container 22, and packaged beverage
38 are but exemplary embodiments of the present invention. It
should be understood that the PET Copolymers of the present
invention can be used to make a variety of preforms and containers
having a variety of configurations.
[0057] The present invention is described above and further
illustrated below by way of 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 suggest
themselves to those skilled in the art without departing from the
spirit of the present invention and/or scope of the appended
claims.
EXAMPLE 1
[0058] Different PET resins were injection molded with a lab-scale
Arburg 75 unit cavity injection machine into conventional preform
molds with a stretch ratio about 12.3 but with different gram
weights. Resins were pre-dried to moisture levels below 30 parts
per million (ppm). The preforms were then stretch blow molded with
a SBO-1 stretch blow-molding machine into 500 ml Coca-Cola Contour
bottles. A description of the weights and compositions of the
samples is listed in Table 1. The #3 Samples are representative of
embodiments of the present invention and the #1 and #2 Samples are
comparative.
1 TABLE 1 Gram DEG NDC IPA Sample weight mole % mole % mole % #1-27
27 2.89 0 3 #2-27 27 1.45 0 2.5 #3-27 27 1.45 0.5 0 #1-26 26 2.89 0
3 #2-26 26 1.45 0 2.5 #3-26 26 1.45 0.5 0 #1-24 24 2.89 0 3 #2-24
24 1.45 0 2.5 #3-24 24 1.45 0.5 0
EXAMPLE 2
[0059] The containers produced in Example 1 were subjected to a
standard thermal stability test, which involves filling the
containers with carbonated water, holding them at 22 deg C. for 24
hours, subjecting them to a temperature of 38 deg C. for an
additional 24 hours, and then measuring the dimensional changes
that occurred relative to the unfilled containers. The data in
Table 2 shows that low DEG, low NDC PET Copolymers of the #3
Samples from Example 1 have increased thermal stability property
for pressurized containers over that of the comparable Samples #1
and #2, as evidenced by lower thermal expansion results. The 24
gram Sample #3 exhibits enhanced thermal stability compared to the
27 gram Sample #1 control.
2 TABLE 2 Label Diameter Pinch Diameter Sample Expansion (%)
Expansion (%) #1-27 3.1 5.4 #2-27 2.6 5.6 #3-27 2.3 4.8 #1-26 3.2
5.4 #2-26 3.9 7.5 #3-26 2.7 5.4 #1-24 3.6 5.8 #2-24 2.4 4.9 #3-24
2.6 4.7
EXAMPLE 3
[0060] In Example 3, containers made in Example 1 were tested for
sidewall rigidity using a sidewall deflection test. The sidewall
deflection test is designed to measure the amount of force required
to deflect the label panel of PET bottles 12 mm (0.47") with an 8
mm (0.32") round tip probe at a cross-head speed of 508 mm/min.
This measurement gives information about the rigidity of the
container. The greater the force required to achieve a specific
sidewall deflection, the greater the rigidity of the bottle
sidewall.
[0061] The data in Table 3 shows that the low DEG, low NDC PET
Copolymers of the #3 Samples from Example 1 have increased sidewall
rigidity over that of the comparable Samples #1 and #2. The
sidewall rigidity of the 24 gram sample #3 is equivalent to 27 gram
sample #1 control.
3 TABLE 3 Sidewall Deflection Sample (Kgf.) #1-27 4.87 #3-27 5.36
#2-27 5.35 #1-26 4.25 #3-26 4.67 #2-26 4.53 #1-24 4.14 #3-24 4.80
#2-24 4.50
EXAMPLE 4
[0062] The data in Table 4 shows that the crystallinity of
containers prepared from low DEG, low NDC PET Copolymer samples
using a conventional preform design are higher than that of
containers prepared from Conventional PET using the same preform
design. The PET containers having the compositions shown in Table 4
above were made in the same manner as the containers in Example
1.
[0063] The PET Copolymer made from 1.09 mole percent DEG and 0.5
mole percent of NDC has a significantly higher crystallinity than
that of the other formulas. The containers made from the PET
Copolymers, however, are clear and haze-free, which indicates that
in spite of the increased crystallinity of these resins, the rate
of thermal crystallization is still sufficiently slow that minimal
crystallization occurs under the injection molding conditions
employed. The higher container sidewall crystallinity is believed
to contribute to the improved thermal stability and the improved
sidewall rigidity.
4 TABLE 4 Strain Composition Induced mole % mole % mole %
Crystallinity IPA DEG NDC (%) 3.0 2.72 0 25.8 3.0 1.09 0 22.4 3.0
2.00 0 22.3 0 1.09 0.5 28.8 0 1.09 0.5 29.9 0 1.09 1 26.4
EXAMPLE 5
[0064] The free blow volumes of PET preforms from Example 1 and PET
preforms made in accordance with the procedure in Example 1 were
determined by heating the preforms to 105 deg C., and then blowing
balloons from the heated preforms with 125 psig air pressure. The
volume of the resulting balloons was measured by filling the
balloons with water, and determining the volume of water contained
in the balloons by weighing. The results of these measurements are
shown in Tables 5 and 6. The free blow volume is directly
correlates to the natural stretch ratio of the polymers. Under the
same free blow conditions, the higher the free blow volume, the
higher the natural stretch ratio of the polymer. These results show
that the 1.45 mole percent DEG and the 0.5 mole percent NDC
containing PET Copolymer exhibits a 25 to 47 percent reduction in
the free blow volume relative to the control. This is equivalent to
an 18 to 30 percent reduction in the natural stretch ratio of the
resin.
5 TABLE 5 Example 1 Free Blow Samples Volume(ml) #1-27 2099.76
#2-27 1756.88 #1-24 1480.18 #2-24 1480.52 #3-24 1114.49
[0065]
6 TABLE 6 Additional PET Copolymer Samples for 23 g preform IPA DEG
NDC Free Blow (mole %) (mole %) (mole %) Volume (ml) 3.0 2.72 0
2079 3.0 1.09 0 2092 3.0 2.00 0 2205 0 1.09 0.5 1523
EXAMPLE 6
[0066] In order to further demonstrate the benefit of the PET
Copolymer of the present invention, light-weighted preforms and
bottles were produced. Instead of the normal 27 g preform for 500
ml bottles, 23 g preforms were produced and were blown into the
same 500 ml bottle mold used in Example 1. The injection molding
was performed with a lab-scale Arburg 75 unit cavity injection
machine into a conventional preform mold as illustrated in FIG. 1.
The preforms were then stretch blow molded with a SBO-1 stretch
blow molding machine into 500 ml Coca-Cola Contour bottle as in
FIG. 3. The preform IV was measured according to ASTM D 4603-96 and
the sidewall deflection and thermal expansion were measured as
described above.
[0067] The data in Table 7 shows that the combination of low DEG,
low NDC PET Copolymer has higher crystallinity, higher sidewall
rigidity and increased thermal stability as compared to
conventional resin compositions.
7TABLE 7 Bottle Resin Composition Sidewall Sidewall Thermal mole %
mole % mole % IV Thickness Deflection Expansion IPA DEG NDC (dL/g)
(mm) (Kgf) (%) 3.00 2.72 0 0.794 0.23 6.49 3.60 3.00 1.09 0 0.782
0.25 7.25 2.80 3.00 2.00 0 0.773 0.25 6.69 2.50 0 1.09 0.5 0.779
0.25 7.30 2.20 0 1.09 1 0.788 0.24 6.86 3.00
EXAMPLE 7
[0068] In order to demonstrate the effect of reduced natural
stretch ratio on injection molding cycle time, two PET resins were
made, a Conventional PET resin having a conventional formula and a
PET Copolymer made in accordance with an embodiment of this
invention. The compositions are shown in Table 8. The free blow
volumes of the Conventional PET resin and the PET Copolymer were
determined in accordance with the procedure described above and
four sets of preforms, 7A, 7B, 7C, and 7D, were made. Preforms 7A
and 7C were both made with the Conventional PET resin using with a
conventional preform design (Conv) as illustrated in FIG. 1.
Preforms 7B and 7D were both made with the PET Copolymer using an
unconventional preform design (Uncon) as illustrated in FIG. 2. The
physical dimensions and molding cycle times of the preforms are set
forth in Table 9.
8 TABLE 8 IPA (mole %) DEG (mole %) NDC (mole %) Conventional 3
2.72 0 PET PET Copolymer 0 1.09 0.5
[0069]
9TABLE 9 Preform 7A 7B 7C 7D Resin Conventional PET Conventional
PET PET Copolymer PET Copolymer Design Conv Uncon Conv Uncon
Preform weight 24 24 27 27 (grams) Hoop stretch 4.86 4.93 5.24 4.35
ratio Axial stretch 2.52 1.95 2.34 1.95 ratio Preform stretch 12.25
9.61 12.26 8.48 ratio Height (mm) 80.74 103.99 86.95 103.99 Inside
diameter 13.69 13.50 12.69 15.30 (mm) Wall 3.43 2.65 3.86 2.80
thickness (mm) Cycle Time 23.6 17.9 28.5 21.0 (sec)
[0070] The data in Table 9 demonstrates that the injection molding
cycle time can be reduced and the injection molding productivity
can be increased by 24 to 26% at the same preform weight by using
the PET Copolymer made in accordance with an embodiment of this
invention when used in conjunction with a preform designed to take
advantage of the lower natural stretch ratio of the PET Copolymer
resin.
EXAMPLES 8-15
[0071] The following preforms whose physical properties are set
forth in Table 10 illustrate additional embodiments of this
invention. Each of Examples 8-15 are made with the PET Copolymer
Resin identified in Table 8 and have configurations generally like
that of preform 11 illustrated in FIG. 2.
10 TABLE 10 Example 8 9 10 11 12 13 14 15 Preform 24 24 24 27 27 27
27 23 weight (grams) Hoop stretch 4.86 5.0 4.35 4.93 4.35 4.86 5.0
4.67 ratio Axial stretch 2.2 2.06 2.2 1.95 2.2 2.2 2.06 2.52 ratio
Preform 10.69 10.3 9.57 9.61 9.57 10.69 10.3 11.76 stretch ratio
Height 92.48 98.49 92.48 103.99 92.48 92.48 98.49 80.73 (mm) Inside
13.68 13.3 15.29 13.5 15.29 13.68 13.30 14.24 diameter (mm) Wall
2.95 2.8 2.64 3.06 3.15 3.4 3.33 3.15 thickness (mm)
EXAMPLE 16
[0072] The data in Table 11 below shows the comparison of the free
blow volume and crystallinity of various PET resins. In this
Example, the free-blow pressure used was 95 psig. In this Example,
the PET Copolymers of the present invention having low DEG and low
NDC content exhibit a reduction in free blow volume of 21 to 27
percent relative to Conventional PET resin.
11TABLE 11 Resin Composition mole % mole % mole % Free blow Strain
Induced IPA DEG NDC volume (ml) Crystallinity (%) 3 2.80 0 713 27.1
0 1.60 0 532 28.1 0 1.60 0.25 542 27.8 0 1.60 0.50 520 27.0 0 1.60
1.00 560 28.1 0.50 1.60 0 529 27.2
EXAMPLE 17
[0073] In this Example, the sidewall deflection test was performed
on the free blow bubbles of Example 16 according to the method
described above. Because the bubble volumes were different for each
resin due to their different inherent natural stretch ratio, the
rigidity values were normalized by the bubble diameter and bubble
thickness. The normalized values are shown in Table 12.
12TABLE 12 Resin Composition mole % IPA mole % DEG mole % NDC
Rigidity (Kgf/cm) 3 2.80 0 16.6 0 1.60 0 25.0 0 1.60 0.25 27.9 0
1.60 0.50 29.3 0 1.60 1.00 25.2
[0074] These results show that a maximum sidewall rigidity is
obtained when about 0.5 mole % NDC is present as a comonomer.
EXAMPLE 18
[0075] Two resins, a PET Copolymer made in accordance with an
embodiment of this invention and a Conventional PET resin were
injection molded into preforms on a 48 cavity Husky XL 300 machine.
The control was molded into a 52-gram 2-L preform with sidewall
thickness of 3.93 mm, while the PET Copolymer was molded into a
50-gram 2-L preform with a sidewall thickness of 3.71 mm. Both
preforms were of conventional design. The preforms were then blown
into bottles using a Sidel SBO 16 machine. The bottles were tested
for thermal stability, sidewall deflection, and shelf life.
[0076] The thermal stability of the bottles made from the two
resins were tested as in the previous Examples. The results set
forth in Table 13 show that with the PET Copolymer, a 50-gram
bottle performed similarly or better than the 52-gram control, in
spite of the 2-g light weighting in the bottles.
13TABLE 13 % Height % Diameter Max. Fill Point Resin Change
Increase Drop (in) PET Copolymer 2.0 1.72 1.541 50 gram preform
Conventional PET 1.9 2.30 1.562 52 gram preform
[0077] The sidewall deflection tests were performed on the above
described bottles as per the test method described hereinbefore.
The results set forth in Table 14 show that the bottles made from
the PET Copolymer performed better than bottles made from the
control, even though the bottles made from the PET Copolymer weigh
2 grams less than the bottles made from the Conventional PET.
[0078] The bottles from both the PET Copolymer and Conventional PET
resins were filled with 385.84 Kpa of carbon dioxide and tested for
shelf life. The shelf life of the bottles were defined as the time
for the bottle to lose 17.5% of the carbon dioxide in the bottle,
or until the carbon dioxide pressure inside the bottles decreased
to 318.3 Kpa. Normally, a heavier bottle having a thicker sidewall
thickness has a longer the shelf life. The shelf life values are
shown in the following Table 14. It can be seen that 2-L bottles
made from 50 gram preforms of the PET Copolymer resin have
essentially the same shelf life as 2-L bottles made from 52 gram
preform made using the Conventional PET resin.
14TABLE 14 Sidewall Resin deflection (Kgf) FTIR shelf life Std.
Dev. PET Copolymer 50 1.63 13.9 week -0.3/+0.4 gram preform
Conventional PET 52 1.40 13.7 week -0.4/+0.6 gram preform
[0079] It should be understood that the foregoing relates to
particular embodiment 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.
* * * * *