U.S. patent application number 11/481888 was filed with the patent office on 2006-11-16 for stretch blow-molded stackable tumbler.
This patent application is currently assigned to Fort James Corporation. Invention is credited to Samuel L. Belcher, Donald C. McCarthy.
Application Number | 20060255049 11/481888 |
Document ID | / |
Family ID | 37418148 |
Filed Date | 2006-11-16 |
United States Patent
Application |
20060255049 |
Kind Code |
A1 |
McCarthy; Donald C. ; et
al. |
November 16, 2006 |
Stretch blow-molded stackable tumbler
Abstract
The inventive drinking vessels are prepared by stretch
blow-molding a preform and exhibit increased Rigidity as well as
elevated, preferably relatively uniform crystallinity. A preferred
method of making blow-molded stackable drinking vessels includes
expanding a preform both axially and radially to make an
intermediate article with a neck, a transition portion and a
tumbler portion. The transition portion and neck are severed from
the tumbler which is then fortified around its upper aperture which
is larger than its base.
Inventors: |
McCarthy; Donald C.;
(Appleton, WI) ; Belcher; Samuel L.; (Moscow,
OH) |
Correspondence
Address: |
PATENT GROUP GA030-43;GEORGIA-PACIFIC CORPORATION
133 PEACHTREE STREET, N.E.
ATLANTA
GA
30303-1847
US
|
Assignee: |
Fort James Corporation
Atlanta
GA
|
Family ID: |
37418148 |
Appl. No.: |
11/481888 |
Filed: |
July 6, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10635722 |
Aug 6, 2003 |
|
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11481888 |
Jul 6, 2006 |
|
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60402314 |
Aug 9, 2002 |
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Current U.S.
Class: |
220/703 |
Current CPC
Class: |
B29B 2911/1446 20130101;
B29K 2023/086 20130101; B29B 2911/1408 20130101; B29K 2995/0067
20130101; B29B 2911/14053 20130101; B29B 2911/14066 20130101; B29K
2067/00 20130101; B29B 2911/14336 20150501; B29B 2911/14906
20130101; B29B 2911/1404 20130101; B29B 2911/14335 20150501; B29B
2911/1498 20130101; B29B 2911/1444 20130101; B29K 2105/162
20130101; B29K 2025/00 20130101; B29K 2069/00 20130101; B29B
2911/14593 20130101; B29K 2105/0094 20130101; B29B 2911/14331
20150501; B29B 2911/14337 20150501; B29K 2023/12 20130101; B29B
2911/14033 20130101; B29C 49/22 20130101; B29B 2911/14093 20130101;
B29B 2911/14146 20130101; B29B 2911/14326 20130101; B29B 2911/14366
20130101; B29C 49/0073 20130101; B29K 2067/046 20130101; B29C 49/06
20130101; B29B 2911/1433 20150501; B29B 2911/14026 20130101; B29B
2911/14466 20130101; B29K 2027/06 20130101; A47G 19/2205 20130101;
B29K 2023/0641 20130101; B29K 2077/00 20130101; B29B 2911/1412
20130101; B29B 2911/14333 20130101; B29K 2105/0032 20130101; B29B
2911/1402 20130101; B29B 2911/14713 20130101; B29B 2911/1436
20130101 |
Class at
Publication: |
220/703 |
International
Class: |
A47G 19/22 20060101
A47G019/22 |
Claims
1) A method of making a blow-molded tumbler comprising: (a)
injection-molding a preform provided with a neck portion, a body
portion and a bottom portion; (b) stretch blow-molding the preform
to form a first intermediate article therefrom wherein the preform
is expanded radially as well as axially, the first intermediate
article being characterized by having a neck portion corresponding
to the neck portion of the preform, a transition portion adjacent
the neck portion of the first intermediate article and a tumbler
portion adjacent the transition portion thereof, the tumbler
portion of the first intermediate article being further
characterized by having a base formed from the bottom portion of
the preform and a sidewall formed from the body portion of the
preform; (c) severing the tumbler portion of the first intermediate
article from its transition portion to form a second intermediate
article having a base corresponding to the base of the first
intermediate article and a sidewall extending upwardly therefrom to
define an upper aperture, the aperture being generally larger in
area than the base of the second intermediate article such that the
tumbler portions are stackable; and (d) fortifying the sidewall of
the second intermediate article around the upper aperture to form
the tumbler.
2. The method according to claim 1, further comprising the step of
heating the preform after it is injection-molded and prior to
blow-molding thereof.
3. The method according to claim 1, wherein said first intermediate
article has a blow-up ratio of at least about 3 with respect to
said preform.
4. The method according to claim 3, wherein said first intermediate
article has a blow-up ratio of from about 7.5 to about 14 with
respect to said preform.
5. The method according to claim 1, wherein said preform consists
essentially of polyethylene terephthalate.
6. The method according to claim 5, wherein said polyethylene
terephthalate has an intrinsic viscosity of from about 0.55 to
about 1.05.
7. The method according to claim 1, wherein said preform has a
weight of from about 10 grams to about 200 grams.
8. The method according to claim 1, wherein said tumbler has a
contained volume of from about 7 to about 64 fluid oz.
9. The method according to claim 1, wherein said tumbler has an
outward taper from its base to its upper aperture of from about 2
to about 12.degree..
10. The method according to claim 1, wherein the tumbler has a
generally smooth sidewall adjacent to its fortified rim, free from
thread features.
11. The method according to claim 1, wherein the fortified rim of
the tumbler has a lateral thickness of from about 1.5 to about 10
times the thickness of the adjacent sidewall.
12. The method according to claim 1, wherein the tumbler sidewall
has a wall caliper of generally from about 0.005 inches to about
0.1 inches.
13. The method according to claim 1, wherein the transition portion
of the first intermediate article is provided with a
circumferential groove adapted to receive a drive member for
rotating the article during the step of severing the tumbler
portion therefrom.
14. The method according to claim 1, wherein the tumbler comprises
a polyethylene terephthalate polymer and lip curl is provided with
a curling tool maintained at a temperature of from about
275.degree. F. to about 350.degree. F. around the upper aperture of
the second intermediate article.
15. The method according to claim 1, wherein the step of fortifying
the sidewall of the second intermediate article around the upper
aperture comprises applying a rim-forming member to the sidewall
around the upper aperture.
16. The method according to claim 15, wherein said rim-forming
member comprises the same material as the tumbler.
17. The method according to claim 15, wherein said rim-forming
member has U-shaped profile.
18. The method according to claim 33, wherein the preform is an
unthreaded preform.
19. A tumbler prepared by the method of claim 1.
20. The tumbler of claim 1, wherein the tumbler is stackable.
Description
CLAIM FOR PRIORITY
[0001] This application claims the benefit of the filing date of
U.S. Provisional Patent Application Ser. No. 60/402,314, filed Aug.
9, 2002. This application also claims priority to U.S. patent
application Ser. No. 10/635,722, filed Aug. 6, 2003. The
disclosures of each of these applications are incorporated herein
in their entireties by this reference.
TECHNICAL FIELD
[0002] The present invention relates generally to drinking vessels
and in preferred embodiments to a stretch blow-molded tumbler
formed from an injection molded preform which is expanded radially
and axially to form the tumbler. The tumblers exhibit high
Rigidity, orientation and relatively high crystallinity.
BACKGROUND
[0003] In quick service restaurants, one of the highest margin
items offered is the fountain beverage. In many cases, it is
possible for the quick service restaurant owners to boost their
sales of beverages by providing promotional cups either with
printing tied to some media phenomenon, such as a popular
children's movie or by offering cups in an unusual configuration.
However, the ability to offer cups in unusual configurations or
shapes is greatly limited by the technology currently used to
produce such cups. In particular, injection-molding is relatively
inefficient in use of materials when cups are formed from polymeric
resins, while injection blow-molding is best applied to only a
limited range of polymers and vacuum thermoforming produces a
relatively weak cup. The cups produced by these methods are usually
limited to traditional straight taper designs and are usually not
transparent, particularly in large sizes as are typically employed
in connection with promotional cups.
[0004] We have found that we can produce high strength cups with
improved attributes from relatively small amounts of resin using a
stretch blow-molding technique followed by a rim fortifying
process. In particular, these cups have high Rigidity as the
stretch blow-molding process orients the polymer axially as well as
radially during the forming process and thereby increases the
Rigidity of the cup considerably as compared to cups prepared by
technologies that do not orient the polymers in both directions. A
stretch blow-molding process makes it possible to use much higher
molecular weight polymers and can induce increased crystallinity.
Therefore the cups produced are stronger for this reason as well.
Unique product benefits include: unmatched strength, clarity,
printability, and the versatility to make reverse taper shapes or
blow-molded embossed sidewall designs or logos. As will be
appreciated from the comparisons described hereinafter, the cups or
tumblers of the invention exhibit improved properties, especially
Rigidity as compared with conventional cups. For example, there is
reported in U.S. Pat. No. 6,554,154 to Chauhan et al. Rigidity data
for thermoformed cups which are five times (5.times.) lower at 1
inch deflection than Relative Cup Rigidity values realized with the
invention at 1 inch deflection.
[0005] The following patents are generally illustrative extrusion
and injection blow-molding art, the disclosures of which are
incorporated herein by reference.
[0006] Blow-molded containers are well known in the form of
bottles, cans, jars and the like. There is disclosed in U.S. Pat.
No. 6,237,791 to Beck et al. a method of making wide mouth
containers by way of stretch blow-molding, which containers include
threads or flanges so they may be used as jars or "hot-fill" food
containers. The containers are prepared by stretch blow-molding a
bottle, heat-setting the bottle and removing the upper neck
portion. In some embodiments a curled rim is provided about the
upper opening of the container by way of heating the upper sidewall
of the bottle to or above its glass transition temperature, Tg, and
curling the sidewall to form a curled rim. The containers may have
a base with an annular peripheral chime surrounding an inward
sloping base portion if so desired. See U.S. Pat. No. 4,889,752 to
Beck.
[0007] U.S. Pat. No. 4,665,682 to Kerins et al. discloses a method
of making polyester containers including blow-molding a bottle and
severing the upper portion to make a jar or can.
[0008] U.S. Pat. No. 4,559,197 to Dick et al. discloses a method
and apparatus for flanging a tubular polyester article in order to
make a polyester can. The flange is used for sealing the can with a
curled end unit as is well known in the art.
[0009] Stretch blow-molding is perhaps one of the most widely
employed methods for making blow-molded bottles; however, the
method is not believed to have been employed to make stackable
drinking vessels. Rather, plastic blow-molded cups have been
produced by the method of U.S. Pat. No. 4,540,543 to Canada Cup,
Inc. where a stretch-rod is not used and the preform has a large
opening. This process is more intricate to coordinate than stretch
blow-molding processes and does not utilize generally available
molding equipment since the injection-molding and blow-molding
operations are practiced concurrently. Moreover, the process of the
'543 patent does not extend the length of the injection molded
parison and thus generally requires a relatively thin-walled
parison which, in turn, restricts the selection of polymer material
utilized in the process. So also, the process of the '543 patent
does not include heating the parison sufficiently to relieve
molded-in stress.
SUMMARY OF INVENTION
[0010] The tumblers of the invention are typically relatively rigid
including a base, a sidewall and an upper aperture preferably
prepared by stretch blow-molding an injection-molded preform at
blow-up ratios of 3 or more. The tumblers exhibit a Rigidity Index
of more than 1.25 lb.sub.f fluid oz./gram at 2/3 cup height and 1/4
inch sidewall deflection. Rigidity Indices of about 1.35, 1.4 and
higher are still more preferred; Rigidity Indices from about 1.4 to
about 2 are typical. The Relative Cup Rigidity is equal to the
Rigidity Index for PET tumblers made of the reference resin; but
may differ somewhat for resins of different composition. As used
herein, PET per se refers to polymer resins consisting essentially
of ethylene terephthalate repeat units, that is, over about 90 mole
%; while other PET polymers may have more comonomer(s) as
hereinafter discussed.
[0011] The tumblers typically exhibit a Rigidity of at least 4 or 5
lb.sub.f at 2/3 cup height and 1 inch sidewall deflection as is
seen in Table 6 hereinafter. A weight to volume ratio of less than
about 1.2 gram/oz. is preferred; the volume being the contained
volume of the tumbler. Weight to volume ratios of about 1 g/oz. or
less are still more preferred. The inventive process provides
relatively high crystallinity in the sidewall as will be seen from
the calorimetry data which follows. Crystallinities of 20%, 25% and
higher may readily be achieved with PET. The high Rigidity makes
the process especially suitable for large tumblers of low weight.
Tumblers of 20 fluid oz. volumes, 30 fluid oz. volumes and more are
advantageously fabricated in accordance with the invention.
[0012] The Rigidity Index (hereinafter defined) of the cups of the
invention tend to be significantly higher than those of other
disposable cups. This is perhaps better appreciated by reference to
FIG. 1, where it is seen the cups of the invention exhibit Rigidity
Index Values of 1.4 and higher while values of 1.2 and lower were
observed for other products.
[0013] One preferred method of making a blow-molded tumbler
includes: (a) injection-molding a preform provided with a neck
portion, a body portion and a bottom portion; (b) blow-molding the
preform to form a first intermediate article therefrom wherein the
preform is expanded radially as well as axially, the intermediate
article being characterized by having a neck portion corresponding
to the neck portion of the preform, a transition portion adjacent
the neck portion of the first intermediate article and a tumbler
portion adjacent the transition portion thereof, the tumbler
portion of the first intermediate article being further
characterized by having a base formed from the bottom portion of
the preform and a sidewall formed from the body portion of the
preform; (c) severing the tumbler portion of the first intermediate
article from its transition portion to form a second intermediate
article having a base corresponding to the base of the first
intermediate article and a sidewall extending upwardly therefrom to
define an upper aperture, the aperture being generally larger in
area than the base of the second intermediate article such that the
tumbler portions are stackable; and (d) fortifying the sidewall of
the second intermediate article around the upper aperture to form
the tumbler. Typically the step of blow-molding the preform
includes, reheating the preform after it is injection molded,
stretching the preform with a solid or hollow stretch rod prior to
blow-molding, and then blow-molding the bottle, usually first with
a low pressure and then with high pressure. Alternatively, uniform
pressure may be used, but this is not preferred for the present
invention. Generally, the first intermediate article has an axial
stretch ratio of 1.5 to 7 and a hoop stretch ratio of 1.5 to 10. In
some cases, the first intermediate article has an axial stretch
ratio of 2.0 to 3.5 times and a hoop stretch ratio of 1.5 to 4. A
blow-up ratio (hereinafter defined) of at least 3 is desirable,
typically a blow-up ratio of at least 5 is used. Blow-up ratios of
from about 7.5 to about 14 with respect to the preform are
preferred in some cases; for instance, the first intermediate
article may have a blow-up ratio of from about 9 to about 12. The
tumblers or cups of the invention are stackable because their bases
have a perimeter that is smaller than the inner perimeter of their
upper apertures and of suitable shape, such that one tumbler may be
stacked with a like tumbler. Preferably, the tumbler's perimeter
from its base up to about 60% of its height is likewise smaller
than the interior of its upper aperture so that the lower 60% at
least fits within a lower adjacent tumbler in a stack. In many
cases, it is desirable that the tumbler's perimeter at its base and
its perimeter up to at least 90 or 95% of its height is smaller
than the interior of its upper aperture such that the tumblers are
compactly stackable.
[0014] While any suitable resin composition may be used, resins
without mineral filler are preferred in many embodiments.
[0015] Typically, the tumbler has a generally circular
cross-section and comprises in some embodiments a polyethylene
terephthalate ("PET") polymer. The tumbler may consist essentially
of polyethylene terephthalate having an intrinsic viscosity of from
about 0.55 to about 1.05. An intrinsic viscosity of about 0.72 or
greater is sometimes desirable. Typically, the preform has a weight
of from about 10 grams to about 200 grams, whereas the tumbler has
a contained volume of at least about 7 fluid oz. Sometimes the
preforms weigh between about 25 grams and 100 grams. A tumbler
volume of from about 12 oz. to 64 oz. is typical as is an outward
taper from its base to its upper aperture of from about 2.degree.
to about 12.degree.. A tumbler volume of from about 20 to about 35
fluid oz. is typical in many embodiments, especially for
promotional cups. In some cases a taper from the tumbler base to
its upper aperture of from about 3.degree. to about 8.degree. is
preferred and the tumbler has a reverse (or inward) taper over a
portion of its sidewall. Preferably, the tumbler has a generally
smooth sidewall adjacent its fortified rim, free from thread
features. Generally, the tumbler rim has a lateral thickness of
from about 1.5 to about 10 times the thickness of the sidewall
adjacent its fortified rim. The tumbler sidewall usually has a wall
caliper of generally from about 0.005 inches to about 0.100 inches,
covering the range of lightweight, disposable tumblers to heavy
weight, reusable products. Reusable products may have a wall
caliper of from about 0.025 inches to about 0.09 inches; typically
in the range of from about 0.040 to about 0.080 inches;
significantly thicker than blow-molded bottles, for example.
[0016] The tumblers may be made in a variety of shapes including
oval cross-sections, rounded square cross-sections, rounded
triangular cross-sections and so forth. A tumbler may have a
cross-sectional shape selected from the group consisting of
non-circular ovals, rounded polygons and combinations of curved and
linear segments forming a closed perimeter. Likewise, there may be
included features such as grips, handle portions or other surface
features. For example, one could include tooling with insertable
logos in the blow-molds for producing products for different
promotional campaigns.
[0017] In a particularly preferred embodiment, the first
intermediate article is provided with a circumferential cutting
notch or knife guide joining the transition portion with the
tumbler portion, as well as provided with a circumferential groove
in the transition portion of the first intermediate article adapted
to receive a drive member for rotating the article during the step
of severing the tumbler portion therefrom.
[0018] The step of fortifying the sidewall of the second
intermediate article around the upper aperture may involve shaping
the dome portion of the bottle such that the angle of the severed
end remaining on the intermediate article will facilitate the
formation of a fortified rim. The action required to form the
fortified rim may range from pinching two sidewalls together to
reshaping the severed end such that the end of the fortifying
portion follows a curvilinear path, which may be varied up to
360.degree. or more. In a typical case, the tumbler is made from a
polyethylene terephthalate polymer and the fortified lip is
provided with a die or other curling tool, such as a curling screw,
maintained at a temperature of from about 275.degree. F. to about
350.degree. F. A die maintained at a temperature of from about
285.degree. F. to about 330.degree. F. is suitable for PET, which
may also be cold curled. The curling tool may be a worm gear-type
screw, a paper cup brim forming die, a can double seamer, or a
curling die which may be operated from about typical room ambient
temperatures to about 325.degree. F. for PET. In typical cases, the
curling tool is operated from ambient temperatures up to the glass
transition temperature of the polymer.
[0019] The step of fortifying the sidewall of the second
intermediate article around the upper aperture may alternatively
include applying a rim-forming member to the sidewall around the
upper aperture, preferably wherein the rim-forming member is the
same material as the tumbler. The rim-forming member may be an end
unit including a lid portion, wherein at least a part of the lid
portion is removable and includes a removable pull-tab. The
rim-forming member may have a U-shaped profile. Likewise, the
sidewall of the tumbler around the upper aperture may be configured
to have a downwardly projecting U-shaped terminal portion
interlocked with an upwardly projecting U-shaped terminal portion
of the rim-forming member.
[0020] The tumbler portion of the first intermediate article may be
provided with a flange projecting inwardly or outwardly from its
sidewall joining the tumbler portion of the first intermediate
article to the transition portion thereof. The flange may project
downwardly as well and is generally configured to be incorporated
into the fortified rim of the tumbler and facilitate formation of
the tumbler rim.
[0021] The preform from which the tumbler is made need not be
threaded. Inasmuch as the neck portion of the first intermediate
article is severed in any event, it is only necessary to have some
means for securing the preform during blow-molding; in this
respect, either a flange projecting outwardly from the preform at
its upper portion or a recess formed therein is sufficient.
[0022] In another aspect of the invention, there is provided a
stackable tumbler produced by blow-molding a preform wherein the
preform is expanded radially and axially to form the tumbler which
is characterized by a sidewall, an upper aperture and a base
wherein the upper aperture is of generally larger area than the
base and the sidewall is provided with a fortified rim around the
upper aperture. Here again, the tumbler generally has an axial
stretch ratio of 1.5 to 7 times and a hoop stretch ratio of 1.5 to
10 times. Usually the tumbler has an axial stretch ratio of 2.0 to
3.5 times and a hoop stretch ratio of 1.5 to 4 times with respect
to the preform. The tumbler may have a weight of from about 10 to
about 200 grams and typically has a contained volume of at least 7
fluid oz. as noted above; sometimes a contained volume of at least
about 12 oz. up to typically 64 oz., but sometimes as high as 96
oz., which is beyond the normal consumption needs of an individual
but which may be fitted with a handle or carrying device and a lid
with a pour spout.
[0023] Optionally, the method of the invention includes a
heat-setting step in connection with the blow-molding of the first
intermediate article. The first intermediate article is heat-set in
the blow-mold by controlling the temperature of the blow-mold and
the "residence time" of the first intermediate article in the mold.
This procedure is particularly advantageous for reusable cups which
are relatively thick-walled. The residence time is (for practical
purposes) the time in seconds from commencing either stretching or
blowing of the preform to the mold being opened for removal of the
blow-molded container. The residence time and mold temperature may
be controlled to achieve the desired crystallinity, which may be
from about 25 to about 45% (on a weight basis) and in some
embodiments from about 35% to about 42%. A preferred method of
determining crystallinity is to use differential scanning
calorimetry. Alternatively, ASTM Method 1505 provides a density
gradient method. The temperature of the blow-mold on its portion
corresponding to the sidewall of the tumbler is generally
maintained at a temperature of from about 200.degree. F. to about
to about 350.degree. with from about 250.degree. F. to about
280.degree. F. being typical for heat setting. The temperature of
the blow-mold at its portion corresponding to the base of the
tumbler is generally maintained at a temperature of at least about
150.degree. F. during heat-setting and typically at a temperature
of at least about 165.degree. F., which is less than the
temperature of the mold at its portion corresponding to the
sidewall of the tumbler. Residence times for heat-setting cycles
may be from 0.5 to 5 seconds with from about 1 to about 3 seconds
being typical.
[0024] The tumblers may be made from a multilayer or laminated
preform which contains, for example, a barrier layer of ethylene
vinylalcohol, polyamide such as nylon or vinylidene chloride
polymer. Other functional layers might include a thermally
conductive layer, for example, a layer containing heat conducting
materials such as carbon black, carbon nanotubes (buckytubes),
metallic fibers or particles, or inherently conductive polymers. In
some cases, if delamination is sought, adjacent layers may be
formed from polymers which form a low adhesion interface such as
PET and polypropylene or reactive agents may be used to generate a
gas to foam the layers and/or separate them. Suitable reactive
agents may be foaming agents such as sodium bicarbonate on one
layer and citric acid on an adjacent layer. Heat-setting the
article in the mold can be especially advantageous in connection
with multilayer preforms wherein one layer has not been heated
above its orientation temperature during the blow-molding process.
For example, at PET/PP multilayer preform could be blow-molded at
200.degree. F. or so which may be sufficient to orient the PET
which typically has an orientation temperature of from about
190.degree. F. to 240.degree. F., but not sufficient to orient the
polypropylene, which has an orientation temperature of from about
250.degree. F. to about 280.degree. F. If the article is heat set
at 275.degree. F. or so, the orientation temperature of the
polypropylene may be exceeded and the polymer will orient in the
desired configuration.
[0025] The multilayer preform may contain two contiguous layers of
polymer with different compositions, but including a common
monomeric repeat unit to improve compatibility and adhesion of the
various layers while providing for a spectrum of properties. For
example, there could be provided an interior layer of polypropylene
copolymer which is relatively stiff and an outer layer of
polypropylene copolymer which is relatively soft to improve "hand
feel" of the tumblers.
[0026] The tumblers of the invention may be made of any suitable
material in addition to PET. Suitable materials may include:
polystyrene; polycarbonate; styrene; acrylonitrile; polyvinyl
chloride; polyolefin polymers including polypropylene, cyclic
polyolefin copolymers, polyethylene, polybutylene polymers and the
like; polyamide polymers; polysulfones; polyacetals; polyarylates;
polyacrylonitrile -stryrene copolymers; polyolefin ionomers;
styrene-acrylonitrile copolymers; environmentally degradable
polymers and mixtures thereof, as is described hereinafter. The
inventive method provides remarkable improvements in many cases.
For example, a styrene tumbler made by the inventive method resists
splitting upon flexing to a remarkable degree as compared with
polystyrene cups made by other methods.
[0027] In some embodiments, the tumblers of the invention can be
made relatively thick-walled, e.g., a wall thickness of greater
than 25 thousandths of an inch such that it is not necessary to
fortify the rim; rather the tumbler portion may simply be severed
from the upper portion of the intermediate article and the rim
optionally smoothed with a flame treatment, abrasive, or other
honing technique. Of course, curling the rim or flanging it with a
hot tool will likewise provide the needed smoothness after cutting
the tumbler from the transition section.
[0028] Still yet another technique for making the inventive cups is
by molding them directly in a stretch blow-molding process of the
type described in U.S. Pat. No. 4,731,011 to Nakamura et al., the
disclosure of which is incorporated herein by reference. In this
process the rim of the preform is not expanded and corresponds to
the rim of the tumbler so that severing a portion of an
intermediate article is not required. Generally, the rim of the
tumbler is from about 1.2 to 5 times the thickness of the adjacent
sidewall of the tumbler when employing this process as noted
hereinafter.
[0029] These and other features and advantages of the present
invention will be better understood by considering the following
description and appended drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0030] The invention is described in detail below with reference to
the drawings wherein like numerals designate similar parts and
wherein:
[0031] FIG. 1 is a comparison of observed Rigidity Index values,
comprising disposable cups of the invention with various other
cups.
[0032] FIG. 2A is a schematic view in elevation of a preform used
for making a tumbler of the invention;
[0033] FIG. 2B is a schematic view in elevation of an alternate
design of a preform used for making a tumbler of the invention;
[0034] FIG. 3 is a schematic view in elevation of a blow-mold with
a stretch rod and an intermediate article of the invention;
[0035] FIG. 4A is a schematic view in elevation of a first
intermediate article of the invention;
[0036] FIG. 4B is a partial schematic view in elevation of another
configuration of a first intermediate article of the invention;
[0037] FIG. 4C is yet another partial schematic view in elevation
of still another configuration of a first intermediate article of
the invention;
[0038] FIG. 5 is a schematic view in elevation of a second
intermediate article of the invention wherein the transition
portion has been severed;
[0039] FIGS. 6-10 are schematic diagrams illustrating providing a
lip curl to the second intermediate article of FIG. 4;
[0040] FIG. 11 is a perspective view of a tumbler of the
invention;
[0041] FIGS. 12 and 13 are schematic diagrams illustrating a
fortified rim of a tumbler of the present invention provided by way
of using a U-shaped rim forming member;
[0042] FIGS. 14-17 are schematic diagrams illustrating a lidded
tumbler of the invention wherein the lid is formed with a double
sealing end unit; and
[0043] FIG. 18 is a schematic view in elevation of another
blow-mold for fabricating biaxially-oriented tumblers of the
invention.
DETAILED DESCRIPTION
[0044] The invention is described in detail below with reference to
numerous embodiments, which description is provided for purposes of
illustration only. Modifications to those embodiments, within the
spirit and scope of the present invention, set forth in the
appended claims, will be readily apparent.
[0045] Unless otherwise defined or the context clearly indicates a
more specific meaning, terminology as used herein is given its
ordinary meaning. "Tumbler", for example, refers to a stemless
drinking vessel. "Taper" refers to the angle with a vertical
defined by a line from the base of a tumbler to its rim. A
"polyethylene terephthalate" or "PET" polymer is a polymer having
more than 50 mole % polyethylene terephthalate repeat units,
whereas a polymer or material "consisting essentially of"
polyethylene terephthalate has at least about 90% on a molar basis
polyethylene terephthalate repeat units. Such materials are
sometimes referred to in the art as "bottle resin" and may include,
for example, isophthalic residues if so desired. "Caliper" refers
to the thickness of an article or the thickness at a particular
point in the article as the context indicates.
[0046] "Axial" and "hoop stretch" ratios as used herein are
characteristics of a blow-molded article with respect to its
preform and express the amount of expansion a preform undergoes to
make the blow-molded article. "The Blow-Up Ratio" (BUR) is a
combined ratio in which the axial stretch ratio is multiplied by
the hoop stretch ratio to give an overall or blow-up ratio. The
equations for calculating the axial, hoop, and blow-up ratios are
as follows: Axial .times. .times. Stretch .times. .times. .times.
Ratio .times. = La Lp Hoop .times. .times. .times. Stretch .times.
.times. Ratio = Da Dp Blow .times. - .times. Up .times. .times.
Ratio .times. .times. ( BUR ) = ( Axial .times. .times. .times.
Stretch .times. .times. Ratio ) .times. ( Hoop .times. .times.
Stretch .times. .times. Ratio ) ##EQU1## wherein: [0047] Da=the
maximum inside diameter of the article at the midpoint height
[0048] Dp=the minimum inside diameter of the preform at the
midpoint height [0049] La=the length of the article below the neck
(typically measured from the capping ring minus 0.100 inch to the
top of the push-up on the inside of the article) [0050] Lp=the
length of the preform below the neck (typically measured from the
capping ring minus 0.100 inch to the bottom of the inside surface
of the preform) For articles or preforms with a non-circular
cross-section, the diameters employed for purposes of calculating
the draw ratio may be based on the corresponding cross-sectional
area, for instance, the diameter may be taken as the square root of
4/.pi. times the corresponding area.
[0051] When a polymeric material has a higher molecular weight or
the polymer is oriented, many of the attributes desired in the
products are enhanced; because increased molecular weight,
increased orientation, and increased crystallinity work
predominantly toward enhancing the desirable physical properties of
the products, it is desirable to devise fabrication procedures
which allow for realizing the potential of the material. Table 1
below lists the physical properties and other attributes of
polymeric articles and whether that property increases or decreases
with increasing molecular weight, increased orientation, or
increasing crystallization. TABLE-US-00001 TABLE 1 Property
Relationships With Molecular Weight, Orientation and
Crystallization Increasing Molecular Increased Increasing Property
Weight Orientation Crystallization Tensile Strength + + + Modulus +
+ + Yield Strength + + + Elongation + - - Impact (Toughness) + +
+/- Hardness + + + Abrasion Resistance + + + Chemical Resistance +
+ + Environmental Stress + + +/- Cracking Resistance Barrier
Properties + + + Adhesion - - - Solubility - - - + Property
increases - Property decreases
[0052] Another benefit of the stretch blow-molding process is the
annealing that takes place to relieve the stress in the
injection-molded preform. The result is primarily a stress-free
product that is highly biaxially orientated. This property is of
particular interest in heavier weight tumblers that will be washed
and reused in a casual dining setting where environmental stress
cracking results from dishwasher detergents. Plastic cups that have
problems with detergent stress cracking have limited life cycles
and, thus, provide a lower value to the purchaser. The two most
critical parameters that will reduce or eliminate environmental
stress cracking (ESCR) are increased molecular weight (decrease in
melt flow) and stress free products. Polycarbonate (PC), for
example, has an ESCR problem with strongly alkaline detergents.
Heavy weight polycarbonate tumblers (used in casual dining
restaurants) made by the injection blow-molding process using 22
melt flow PC begin to stress crack (1/4 inch cracks) after 6 dish
washer cycles. When the molecular weight is increased to 10 melt
flow PC, the equivalent level of stress cracking does not appear
until after the 34.sup.th wash cycle. However, the limit on the
ability to increase molecular weight is defined by the wall
thickness of the product and the height of the tumbler. The flow
properties of the polymer need to allow timely filling of a
multi-cavity injection mold. As the size of the cup increases in
volume or height, increasing the molecular weight is difficult with
prior art processes such as that of the '543 patent noted above
("IBM" process) because the preform is the length of the cup and
when it is blown it is only stretched in the hoop direction. The
preform stresses are not annealed out in the IBM process and can
only be controlled by rigorous temperature control in the mold.
Once made, the solidified, but still hot, preform is shuttled to a
blow cavity and blow-molded. ESCR related problems in polycarbonate
made by the IBM process are as follows: blow-up ratios for the IBM
process are low and uniaxial; stress-free parts are not produced;
and the polycarbonate is not "blown" in the ideal temperature range
for orientation.
[0053] Heavy weight polycarbonate cups made by the two-step stretch
blow-molding process eliminate these disadvantages. The stretch
blow-molding process uses a higher molecular weight polycarbonate
resin; the reheating process anneals the stress out of the preform;
and the preform temperature can be precisely controlled so that
blow-molding takes place in the ideal temperature range for
orientation. When these conditions are met the tumbler or cup will
have greatly reduced molded-in stress and greatly improved ESCR
performance.
[0054] The various features of the invention will be better
understood by reference to the drawings.
[0055] There is shown in FIGS. 2A and 2B alternative designs of an
injection molded preform 10 having generally a preform length 12
below its neck 14. Neck 14 is provided with a flange 16 as well as
optional threads indicated at 18 in FIG. 2A. The threads and/or
flange 16 may be used to hold the preform in place during
processing. A preform designed specifically for blow-molding a
tumbler as shown in FIG. 2B has a cost advantage in that no threads
are needed in the neck area and only a small flange is needed to
hold the preform in the mold. Cost savings would result from (1)
reducing the weight of the preform and (2) lowering the mold costs
by eliminating thread splits. Typically, soda bottle preforms weigh
about 26 grams for a 20-oz. bottle and 48.5 grams for a 2-liter
bottle. Tumblers of this invention may vary considerably in weight
depending on the intended final use. If the intended use were to
provide a foodservice customer with a take-out tumbler for soda,
then a lightweight tumbler would be appropriate. If the customer is
a dine-in customer who uses a tumbler that the casual dining
restaurant washes and reuses multiple times, then the tumbler needs
to be made using a heavy weight construction for durability.
Therefore, the weight range from lightweight use to a heavy weight
use can be considerable. For example, a 22-oz. tumbler for take-out
could weigh as little as 16-18 grams and a reusable tumbler of the
same size could weigh 50 to 95 grams. Preform 10 may be relatively
thick, having a wall thickness 20 of generally from 0.060 inches to
0.180 inches, which need not be a constant thickness over its body
portion 22 and bottom portion 24; the thickness can be optimized to
provide enhanced Rigidity about 2/3 of the way up from the base by
thickening at this level.
[0056] FIG. 2B depicts a multilayer preform 10 provided with an
outer layer 17, an inner layer 19 and an intermediate layer 21
which may be a barrier layer if so desired. So also, contiguous
layers may be provided with reactive chemicals and so forth as
noted above, or may be materials such as polypropylene and PET
which do not readily adhere to one another. If so desired, one or
more of the layers may be further provided with functional
attributes such as high or low thermal conductivity if so desired.
So also, adhesives may be employed when delamination is to be
avoided.
[0057] Preferably, the preform comprises a PET polymer and in
preferred embodiments is made of bottle resin having an intrinsic
viscosity or IV (a measure of molecular weight) of from about 0.55
to about 1.05 as measured according to ASTM D4603, Standardized
Test Method for Determining Inherent Viscosity of PET. This test
standard also establishes a method for calculating Intrinsic
Viscosity. The primary equipment used is a capillary viscometer,
such as the Cannon Ubbelohde Type 1 B Viscometer referred to in
ASTM D4603.
[0058] The IV or intrinsic viscosity of a PET sample is a relative
number and represents a measure of its average molecular weight. An
IV is determined by dissolving between 1/4% and 1/2% PET in a
solvent and measuring the time required for 100 ml of the solution
to flow through a capillary. Concentration and time are then used
to mathematically compute the IV. The term "inherent viscosity"
refers to any IV determined at a specific concentration of the PET
solution. A series of IV's are determined at varying concentrations
and the data plotted on a curve of IV vs. concentration. The curve
is extrapolated back to zero concentration, and this point is
defined as the "intrinsic viscosity."
[0059] Preform 10 is typically preheated to a temperature of from
about 1 90.degree. F. to 240.degree. F. or so when made from PET so
that it may be blow-molded as shown schematically in FIG. 3.
[0060] The blow-up ratio (BUR) for PET tumblers of this invention
generally range from about 3 to about 14.
[0061] FIG. 3 illustrates schematically a blow-mold 30 having mold
halves 32 and 34 as well as a stretch rod 36 used to stretch
preform 10 in a stretch blow-molding step. Preform 10 is positioned
in mold 30 and stretched with rod 36 and a blow-head provides
pressurized air into the interior of the preform. The preform is
thus expanded axially as well as radially in mold 30 to form a
first intermediate article 40 (FIGS. 3, 4A, 4B, 4C) having a length
42 and a maximum outside diameter 44.
[0062] When using a preform having a length 12 of four inches or
so, intermediate article 40 may have a length 42 of 8 inches or so.
Diameter 44 may be about 3.5 inches when using a preform having an
inside diameter 46 of an inch or so. The axial and hoop stretch
ratios with respect to preform 10 are thus: Axial .times. .times.
Stretch .times. .times. Ratio = 8 4 = 2 ##EQU2## Hoop .times.
.times. Stretch .times. .times. Ratio = 3.5 1 = 3.5 ##EQU2.2## Thus
, .times. .times. the .times. .times. Blow .times. - .times. Up
.times. .times. Ratio .times. .times. ( BUR ) .times. .times. is
.times. .times. ( Axial .times. .times. .times. Stretch .times.
.times. Ratio ) .times. ( Hoop .times. .times. .times. Stretch
.times. .times. Ratio ) .times. .times. or .times. .times. ( 2
.times. 3.5 ) = 7 ##EQU2.3##
[0063] Stackable tumblers of the invention may be blow-molded from
clear materials such as: PS (polystyrene), PC (polycarbonate), SAN
(styrene acrylonitrile), PVC (polyvinyl chloride), PP
(polypropylene), nylon, COC (cyclic polyolefin copolymers), and
other polyolefins, and may be combined in multi-layer constructions
with barrier materials such as ethylene vinyl alcohol (EVOH), Nylon
MXD6 from Mitsubishi Gas Chemical Company, Inc., or with oxygen
scavenging materials and with adhesive layers as appropriate. Other
suitable polymers may include polysulfones, polyacetals,
polarylates (wholly aromatic polyesters), ionomeric polyolefins
sold under the tradename Surlyn.RTM. and environmentally degradable
polymers. Environmentally degradable plastics generally include
those which undergo significant changes in their chemical structure
under specific environmental conditions, such polymers include
oxidatively degradable polymers, photodegradable polymers, and
biodegradable polymers. A biodegradable plastic polymer is a
material in which the degradation results from the action of
naturally occurring microorganisms such as bacteria, fungi and
algae. Suitable polymers are described in Volume 19 of the
Kirk-Othmer Encyclopedia of Chemical Technology, 4.sup.th Ed., pp.
983-996 (Wiley) the disclosure of which is incorporated herein by
reference. Carboxylated polymers are generally a preferred class,
including poly(lactic acid), polyanhydrides, functionalized natural
polymers and so forth. Insofar as the tumblers of the invention are
concerned, the polymer selected must have sufficient moisture
resistance for the products' intended end uses. Preferred
biodegradable polymers including polylactic acid,
polyhydroxybutyrate and polycaprolactones which may optionally be
melt-blended with PET.
[0064] Suitable polymer compositions include melt blends of
cycloolefin copolymers of norbomene and ethylene with various
polyethylene polymers. Cycloolefin copolymers are described in U.S.
Pat. No. 5,698,645 to Weller et al., the disclosure of which is
incorporated herein by reference. The various polyethylene polymers
referred to herein are described at length in the Encyclopedia of
Polymer Science & Engineering (2 Ed), Vol. 6, pp. 383-522,
Wiley 1986, the disclosure of which is also incorporated herein by
reference. HDPE refers to high density polyethylene which is
generally linear and has a density of generally greater than 0.94
up to about 0.97 g/cc. LDPE refers to low density polyethylene
which is characterized by relatively long chain branching and a
density of about 0.912 to about 0.925 g/cc. LLDPE or linear low
density polyethylene is characterized by short chain branching and
a density of from about 0.92 to about 0.94 g/cc. Finally,
intermediate density polyethylene (MDPE) is characterized by
relatively low branching and a density of from about 0.925 to about
0.94 g/cc. Unless otherwise indicated, these terms have the above
meaning throughout the description and claims.
[0065] The materials may be tinted; colored with opaque organic or
inorganic pigments; contain fillers such as calcium carbonate,
talc, mica, nano-size particulates, flame retardants, nucleating
agents, clarifiers, antistats, foaming agents; and/or combined with
blends of any of the listed polymers with or without
compatibilizing agents or in combination with biodegradable
polymers.
[0066] Monolayer performs may contain multiple colors of dispersed
regions of colorants so that the stretch blow-molded article has
the visual effect of swirl or marbleized patterns of
distinguishable colors. Multilayer performs may contain different
colors in layers of different thickness so that, when blow-molded,
the colors of the thicker layers predominate as the background
color and the thinner layer produces color differentiated patterns.
Dispersed flakes or particles that add a sparkle effect to the
blow-molded article may be added in combination with colorants in
monolayer or multilayer constructions.
[0067] Nano-size particulates may be clays, conductive carbons,
silicas, titanium dioxide, aluminum trihydrate, or similar sized
materials chosen to enhance a specific property such as modulus,
tensile strength, fire retardancy, insulation, conductivity, visual
appearance, or tactile feel. The process of the present invention
is particularly useful in connection with transparent drinking
containers from filled resins which have been characterized as
"nano-composites". Nano-composites are reinforced resins which
comprise the resins enumerated above and nanometer-sized filler
particles. It has been found that resins containing small amounts
of approximately 2-6% of the nanometer-sized particles can provide
improvements in mechanical and thermal properties, improvements in
gas barrier and flame resistance and do not reduce the light
transmission of the resins inasmuch as the nanometer-sized
particles are in the same size range as visible light wave lengths.
A discussion of nano-composites is provided in Plastics Technology,
June, 1999. Accordingly, nano-composites can advantageously be used
to injection blow-mold drinking containers such as tumblers and the
like. Thus, not only would the transparent nature of the resins be
maintained, but the strength of the resin could be improved. For
polystyrene, the use of a nanometer-sized filler could improve the
strength of the resin and provide more uses of this resin than for
just disposable tumblers. Nylon composites are likewise of
interest. At present, nanometer-sized clay has been used to form
nano-composites. For example, montmorillonite, which is a layered
alumino-silicate having individual platelets that measure on the
order of 1 micron diameter and have an aspect ratio of 1,000:1 have
been added to nylon. Suppliers of the nanometer montmorillonite are
Nanocor, Inc. and Southern Clay Products. For some of the above
listed resins, it may be useful to chemically modify the surface of
the montmorillonite inasmuch as this hydrophilic clay may not be
compatible with the more hydrophobic resins. Surface treatments can
include exchanging the inorganic cations on the surface of the clay
with materials which can induce hydrogen bonding with the resin
including hydrogen cations, ammonium cations, silane cations and
the like. Other fillers can be formed chemically or ground to the
appropriate size and used as fillers for the injection
blow-moldable resins of this invention. For example, inorganic or
organic pigments such as zinc oxide, or titanium oxide can be used.
Even plastic fillers can be provided in nanometer sizes and added
to the blow-moldable resins. The nanocomposites can be formed by
forming the resin itself in the presence of the nano-filler
particles or by simply melt-compounding the formed resin with the
nano-filler particles. During the melt-compounding method of
forming nano-clay composites, it has been found necessary to
delaminate the clay particles sufficiently so that the ultimate
level of reinforcement and transparency can be achieved.
[0068] Preforms may be made of a single component such as PET, may
be monolayer blends of different materials, or may consist of
multi-layers designed to enhance specific properties or to provide
a unique feature(s) in the final product. Examples of such unique
features are as follows: the addition of a barrier layer for
reducing oxygen, carbon dioxide, or water vapor transmission; the
addition of a layer with increased thermal conductivity to speed
the heating or cooling of the contents of the tumbler.
[0069] The addition of adjacent layers each containing a component
of a reactive mixture that may be used to promote a property change
at the interface of the two layers. An example of such a reactive
mixture would be to have incompatible polymers such as PET and
polypropylene injection molded into a two-layer preform with one
layer containing sodium bicarbonate and the other layer containing
citric acid. The desired effect at the interface would be to
facilitate the separation of the two distinct layers that are
formed in the tumbler made by the blow-molding process. The purpose
of the layer separation is to allow the formation of an air gap
between the layers. Such an air gap would provide insulation for
the tumbler for keeping hot beverages hotter longer and would also
increase the hold time for the customer. Similarly, cold beverages
would stay cold longer and the outside of the tumbler would not
sweat from moisture condensation. The rim fortification process
would fix the two layers at the top of the tumbler and there may be
an optional point of attachment at the original gate of the preform
at the bottom of the tumbler.
[0070] In FIG. 4A, article 40 is formed from preform 10 and thus
has at its upper portion neck 14 of preform 10, a transition
portion 48 as well as a tumbler portion 50. Portions 48 and 50
correspond to the body portion 22 of preform 10 (radially and
axially expanded) whereas a base portion 52 corresponds to bottom
portion 22 of preform 10.
[0071] Base portion 52 is generally circular in most embodiments
and has a diameter, D.sub.b, that is smaller than the diameter,
D.sub.r, of the intermediate article at the portion of the
intermediate article where the rim of the tumbler is formed.
[0072] An angle 54 is defined between a line 53 joining the outer
edge of base 52 and the circumference of the upper portion of the
tumbler with a vertical line 55 and is generally referred to as the
taper or taper angle of the tumbler. The articles of the invention
generally have an outward taper with increasing height as shown,
since their upper apertures are larger than their bases. For
purposes of brevity, this geometry is simply referred to as an
"outward" taper, or simply taper.
[0073] Note that the tapered portion of the tumbler also has
reverse (or inward) taper regions 58, 60, which would not be
practical with forming techniques such as thermoforming or
injection-molding.
[0074] Intermediate article 40 of FIG. 4A has formed in transition
portion 48 a circumferential drive groove 62 suitable for receiving
a drive belt 64 which may be used for rotating the article during
severing of portion 48 from portion 50. To facilitate separation
there is provided a circumferential notch 66 which is operable as a
knife guide for guiding a knife 68 used for severing portion 50
from portion 48.
[0075] That is to say, article 40 shown schematically in FIGS. 3
and 4A is rotated by way of belt 64 while knife 68 is inserted in
notch 66 in order to sever the tumbler portion 50 from transition
portion 48 to produce a second intermediate article 70 as shown in
FIG. 5.
[0076] Article 70 has a base portion 52 corresponding to base
portion 52 of article 40 as well as the other features of tumbler
portion 50 noted in connection with FIGS. 3 and 4A. There are
optionally provided a plurality of flutes 72, 74, 76 in a sidewall
78 of article 70. Sidewall 78 extends upwardly from base 52 to
define an upper aperture 80 which is generally circular and has
diameter D.sub.r. D.sub.r is larger than D.sub.b such that article
70 is stackable with like articles. To finish the tumbler, sidewall
78 is fortified around aperture 80 by one of a variety of
techniques, including curling a lip portion 82 of article 70 to
form a fortified rim as described in connection with FIGS. 6 and
following. Note that articles 40 and 70 are optionally provided
with an interior raised portion 84 which defines a chime 86 if so
desired.
[0077] There is shown in FIGS. 4B and 4C alternate configurations
of the first intermediate article provided with flanges as part of
the tumbler portion to aid in the formation of a fortified rim. In
these embodiments, article 40 has a neck portion 14, a transition
portion 48, a tumbler portion 50 and optionally a knife guide notch
68. Sidewall 78 of tumbler portion 50 has at its upper portion a
flange configured to be incorporated into the fortified rim of the
tumbler. In FIG. 4B flange 79 projects outwardly and downwardly
from the sidewall; downwardly that is, with respect to a horizontal
line 81 from the sidewall. After transition portion 48 is severed,
the flange may be utilized to form a rim either by curling it to
the sidewall or by cooperation with a rim forming member.
[0078] In FIG. 4C a flange 83 projects inwardly and optionally
downwardly with respect to sidewall 78; that is, downwardly with
respect to a horizontal line 81 from the sidewall. Here again,
after severing portion 48 the flange may be further curled and
incorporated into the rim. It is not necessary to utilize a flange
in order to provide a fortified rim as will be appreciated from
FIGS. 6, 7, 8, 9, 10 and 11. Indeed, while horizontal flanges may
be readily prepared, flanges with inclination with respect to the
sidewall will require more complex mold design and operation,
perhaps including severing the transition portion from the tumbler
portion while the first intermediate article is still in the
mold.
[0079] Referring to FIG. 6, lip portion 82 of article 70 is curled
by upper and lower tools, 90, 99. The curling portion of upper tool
90 is indicated at 92. Die 92 and lower tool 99 may be heated to or
maintained at a temperature of between 275.degree. F. to about
350.degree. F. during a curling operation as the tools are axially
advanced towards each other as shown schematically in FIGS. 7, 8
and 9. It is desirable to rotate die 92 with respect to article 70
during the curling operation. If so desired, one may pre-heat the
sidewall prior to curling as noted in U.S. Pat. No. 6,237,791 to
Beck et al. or provide auxiliary radiant heating as indicated in
FIG. 10 at 94 or insulate die portion 92 from the rest of tool 90
as indicated at 96 in FIG. 10; depending upon the temperatures and
materials employed.
[0080] Lip 82 may be curled at 360.degree. or more as seen at 98 in
FIG. 9.
[0081] Another preferred tooling for providing a rim curl is to use
a curling screw apparatus as disclosed in U.S. Pat. No. 6,164,949
to Lamson. This apparatus includes an oven and four co-rotating
helical curling screws; alternatively, a like apparatus with a
single curling screw is seen in U.S. Pat. No. 3,337,919 to Brown.
The disclosures of the above patents are incorporated herein by
reference.
[0082] A finished stackable tumbler 100 is shown in perspective in
FIG. 11. Tumbler 100 has a curled fortified rim 102, sidewall 78
and base 52 corresponding to like parts of articles 40 and 70
described above. Upper aperture 80 is circular in shape and larger
in diameter than base 52 so that tumbler 100 is stackable with like
articles. The tumbler retains the molded-in features such as flutes
72, 74 and 76 as well as raised portion 84 and chime 86. Likewise,
reverse taper regions are provided in sidewall 78; that regions
where the diameter of the tumbler decreases with increasing height
such as at 58 and 60.
[0083] Tumbler 100 is readily differentiated from jars or other
containers in that it has a positive taper angle 54 as noted above
and is free from threads adjacent its upper aperture 80. The
fortified rim is distinguished from closure flanges and the like
since it projects laterally a distance 104 which is relatively
small with respect to the aperture diameter, typically from 11/2 to
10 times the adjacent wall caliper.
[0084] Other modes of fortifying the tumbler rim may be employed.
For example, there is shown schematically in FIGS. 12 and 13 a
rim-forming member 110 with a U-shaped profile 112 folded over
sidewall 78 of the tumbler. Member 110 is preferably of the same
material as the tumbler and may be heat-bonded therewith to form a
fortified rim structure 114 shown in FIG. 13.
[0085] There are numerous other options for fortifying the rim of a
second intermediate article of the invention. Another method, for
example, is to design the blow-molded first intermediate article so
that its transition portion can be further severed so that a
portion or band fashioned therefrom can be utilized as a
rim-forming member such as member 110. Alternatively, the
transition portion is designed so that it can function as a lid
which also provides rigidity to a combined structure after removal
from the first intermediate structure and recombination with the
second intermediate structure. That is to say, the process of
fortifying second intermediate article 70 may include providing a
band or lid made from transition portion 48 of first intermediate
article 40. This process may be more expedient than forming a lid
or reinforcing member separately and more efficient in terms of
material usage. Thus, the process of fortifying the second
intermediate article of the invention around its upper aperture
comprises fashioning a reinforcing member from the transition
portion of the first intermediate article preferably selected from
the group consisting of a band or lid and applying the reinforcing
member so-produced to the second intermediate article around its
upper aperture.
[0086] As a still further alternative, there may be provided an end
unit such as end unit 116 shown in FIGS. 14, 15, 16 and 17 of the
double seal type used on polyethylene terephthalate cans as are
known in the art. To this end, there is provided a flanged
container 118 having a flange 120 about its upper aperture 122, a
sidewall 124 and a bottom 126. End unit 116 has a curled periphery
128 which is crimped about flange 120 to make a double seal as
shown sequentially in FIGS. 14, 15. FIG. 16 is an enlarged
schematic view showing the double seal joint wherein the tumbler is
lidded with end unit 116. A preferred technique for applying the
lid is to use a curling tool as disclosed in U.S. Pat. No.
4,559,197 to Dick et al., the disclosure of which is incorporated
herein by reference. This results in a double seal with an upwardly
U-shaped portion 130 defined by the lid and a downwardly U-shaped
portion 132 defined by flange 120 after it is crimped.
[0087] The end unit may include a pull-tab 134 coupled to a
localized removable portion indicated at 136, or, the lid may be
weakened around its entire periphery as indicated at 138 in FIG. 17
which is a schematic top view of a lidded tumbler produced in
accordance with the present invention. End unit 116 may be metal or
plastic, but most preferably is thermoformed from the same material
as the rest of the tumbler.
[0088] Still yet another method of making the tumblers of the
present invention is a coordinated injection-molding, stretch
blow-molding process as disclosed in U.S. Pat. Nos. 4,731,011 and
5,753,279 (Nissei). The process involves injection-molding preforms
on a core and transferring the preforms to a blow-mold in some
respects like the process of the '543 patent noted above; however,
the preform is expanded both axially and radially to provide for
greater orientation. The rim of the preform corresponds to the rim
of the tumbler as is shown schematically in FIG. 18.
[0089] In FIG. 18 there is shown a mold 30 having mold halves 32,
34 as well as a stretch rod 36 used to stretch the preform. The
preform is expanded to a height 42; however, the diameter 44 of the
tumbler rim corresponds to the diameter of the upper portion of the
preform from which it was made. Tumbler 40 is thus formed without
the need for severing a portion of an intermediate article. Tumbler
40 is preferably provided with an injection-molded rim 41 which has
a thickness greater than the thickness of the adjacent sidewall.
The thickness of the rim is indicated schematically at 43, while
the thickness of the sidewall is indicated schematically at 45.
Complex shapes including inward taper region 58, 60 and raised
portion 84 of base 52 are readily achieved by way of this process;
indeed other stretch molding processes are likewise possible within
the spirit and scope of the present invention. In addition, the rim
may be locally thickened or a flange provided so that a lid may be
more readily attached to a surface with some radial extent.
Rigidity
[0090] Commercially available plastic cups are typically made by
injection-molding and/or thermoforming, neither of which techniques
induce biaxial orientation. In order to characterize Rigidity, the
force required to deflect the cup sidewall at 2/3 of the cup height
is measured. This measurement is convenient because it is the
location on the cup that the majority of people will grip. To
assess Rigidity, an empty (dry) cup is restrained by V-blocks at
its base, preferably having a weight placed in the bottom of the
cup for stability. A movable probe and a stationary probe are
positioned on the surface of the cup in opposed positions across
the cup sidewall at 2/3 of the cup's height. The cup is then
compressed between the probes and the force required for an inward
deflection of specified distance of the sidewall is recorded in
lb.sub.f. This value is referred to herein as the "Rigidity" of the
cup. Preferably, the Rigidity is measured at 75.degree. F. and 50%
relative humidity, the features of the test including securing the
base of the cup, the height of the cup at which the deflection is
measured, the deflection displacement and the force required to
cause the deflection. Unless otherwise indicated below, the force
required for a 1/4 inch deflection at 2/3 cup height is reported as
the Rigidity. For comparative purposes and to further characterize
the cups of the invention, Rigidity at 1 inch sidewall deflection
is sometimes used; in such instances, it is made clear that
Rigidity at a 1 inch sidewall inward deflection is referred to. In
the event peak force occurs before the specified deflection, peak
force is used.
[0091] The Rigidity is preferably determined using a JS-1 Rigidity
tester modified with a Chantillon Gauge. The Chantillon Gauge is
available from: [0092] Chatillon [0093] Force Measurements Division
[0094] P.O. Box 35668 [0095] Greensboro, N.C. 27425-5668
[0096] 919-668-0841 FAX 919-668-2746.
The test method was developed by:
[0097] Georgia-Pacific Corporation [0098] Neenah Technical Center
[0099] 1915 Marathon Avenue [0100] Neenah, Wis. 54956 [0101]
920-729-8415, Test Method TM-4671-OM
[0102] As noted above, available cups are usually produced by
thermoforming or by injection-molding-neither of which techniques
induce biaxial orientation into the product. The Table 2 below
shows Rigidity data for two commercially thermoformed 20-oz. PET
cups and for a 22-oz. stretch blow-molded cup. Note that the
Rigidity is much higher for the stretch blow-molded cup. Normally
the stretch blow-molding process that is used for bottle making
uses an optimized preform design in order to maximize the physical
properties of the bottle produced. The preform used in this case
was an off-the-shelf 2-liter bottle preform that was not
specifically designed to produce the 22-oz. cup characterized in
the table. TABLE-US-00002 TABLE 2 Cup Rigidity Dry Rigidity Average
(lb.sub.f/1/4 in. Manufacturing Weight Volume Deflection at Sample
Method (g) (oz.) 2/3 height) PET Cup A Thermoformed 19.886 20 oz.
0.744 PET Cup B Thermoformed 19.03 20 oz. 0.827 Blow-Molded PET
Stretch Blow- 22.53 22 oz. 1.430 Prototype* Molded *Not optimized
for weight distribution or preform design, made by invention
method
Relative Cup Rigidity
[0103] An equation to describe the Rigidity as a function of its
strength to weight ratio is as follows: Relative .times. .times.
Cup .times. .times. .times. Rigidity = ( Rigidity ) .times. ( Cup
.times. .times. .times. Volume ) ( Cup .times. .times. .times.
Weight ) ##EQU3##
[0104] where,
[0105] Rigidity is the force in pounds required to deflect the
sidewall of the cup 1/4 inch (usually) at 2/3 height,
[0106] Volume is in fluid-oz., and
[0107] Cup weight is in grams.
[0108] Below in Table 3 are the Relative Cup Rigidities for the
cups of Table 2. TABLE-US-00003 TABLE 3 Relative Cup Rigidity of
20-Oz. Cups Sample Manufacturing Method Average Weight (g) Volume
(oz.) ( Rigidity ) .times. ( Cup .times. .times. Volume ) ( Cup
.times. .times. Weight ) .times. .times. ( lb f .times. .times.
fluid .times. - .times. oz . / .times. gram ) ##EQU4## PET Cup A
Thermoformed 19.886 20-oz. 0.782 PET Cup B Thermoformed 19.03
20-oz. 0.832 Blow-Molded Stretch Blow- 22.53 22-oz. 1.396 Prototype
of Molded Invention
[0109] Relative Cup Rigidity parameter is a universal way of
comparing and organizing data on the Rigidity of PET cups
manufactured by different methods such as thermoforming,
injection-molding, or IBM to those made by stretch blow-molding
without regard to structural features or composition. Broadly
speaking for all cups made of PET, whether injection molded,
thermoformed, injection blow-molded, or injection stretch
blow-molded, our data indicates that: (i) Relative Cup Rigidities
of less than 0.6 are characteristic of cups with unoriented
sidewall material: (ii) Cups with sidewall material with low
orientation have Relative Cup Rigidities between 0.61 and 0.95:
(iii) Somewhat oriented, design fortified or injection molded cups
have Relative Cup Rigidities between 0.96 and 1.25; and (iv)
Biaxially oriented PET cups, such as those made by a two-step
injection stretch blow-molding process have relative Rigidities of
at least 1.26 or often greater than 1.35. TABLE-US-00004 Less than
0.60 Unoriented 0.61 to 0.95 Low Orientation 0.96 to 1.25 Somewhat
Oriented or Fortified Greater than 1.26 Biaxially Oriented
[0110] The Relative Cup Rigidity parameter, while seemingly simple,
factors in orientation gains in Rigidity from tensile strength,
flexural modulus, and crystallinity that are achieved at low
product weights and high surface areas, as measured by the weight
of the cup in grams and the liquid volume held by the cup in fluid
oz. The parameter provides an easy way to rank the efficiency of a
material, process, and/or design to yield stiffness per unit weight
and surface area. The volume factors in how the weight of the cup
is distributed--accounting for wall thickness and added structural
features. The Relative Cup Rigidity parameter is intended to
provide a method for comparing lightweight cups of different
shapes, sizes, and structural features. The method is dependent on
the ability to deflect the sidewall 1/4 inch at 2/3 of the cup
height.
[0111] A series of commercially available and experimental cups
were evaluated for Relative Cup Rigidity. Results appear below.
TABLE-US-00005 TABLE 4 Selected Relative Cup Rigidities Relative
Weight/ Cup Cup Cup Volume Rigidity Volume Weight Ratio Rigidity
(lb.sub.f-fluid Sample Material Method (oz.) (grams) (g/oz.)
(lb.sub.f) oz./gram) C -Red PS/HIPS Thermoformed 16 11.82 0.74
0.688 0.931 Multilayer D - PS/HIPS Thermoformed 16 13.51 0.84 0.840
0.995 Red Multilayer E PS IBM* 13.6 18.82 1.38 2.18 1.575 F PS IBM*
9.0 13.16 1.46 1.88 1.286 G PET IBM* 13.6 24.93 1.83 2.03 1.107 H
White Injection 32 36.4 1.14 1.16 1.019 HDPE Molded I White
Injection 44 49.4 1.12 1.23 1.095 HDPE Molded J PET Stretch Blow-
14.2 18.62 1.31 1.19 0.908 Molded (one Step)** K Thermoformed 32
28.01 0.875 0.917 1.048 L PET Thermoformed 16 17.58 1.10 0.672
0.612 M PET Thermoformed 16 15.5 0.97 0.552 0.570 N PS/K IBM* 20
17.91 0.86 0.687 0.767 resin O White Injection- 32 36.6 1.14 1.00
0.874 HDPE molding *Experimental tumbler; injection blow-molded
without axial expansion **Experimental Cup; not optimized
[0112] Relative Cup Rigidity of the inventive tumblers as compared
with other cups is even more striking at 1 inch deflection as is
seen, for example, by way of comparison with U.S. Pat. No.
6,554,154, to Chauhan et al. The test procedure of the '154 patent
is detailed in Col. 5 thereof and is essentially the test procedure
detailed above for measuring Rigidity described above except that
the cups are placed on their sides and the force for a 1 inch
deflection at 2/3 of the cup height is measured. For purposes of
comparison, the above procedure for measuring Rigidity was followed
for the cups of the invention (and others enumerated below) except
the force required for 1 inch deflection at 2/3 cup height is
recorded.
[0113] Table 5 below compares the data of Table 1 of the '154
patent for 16 oz. cups with Rigidity data (1 inch deflection)
obtained with a nominal 22 oz. (26.4 oz.) cup of the present
invention. TABLE-US-00006 TABLE 5 Comparison of Relative Cup
Rigidity at 1 Inch Deflection Mean Cup Relative Mean Force at 1
Rigidity Cup Cup inch (lb.sub.f) at 1 Vol- Rigidity Weight
deflection inch ume Weight at 1 inch Design (oz.) (oz.) Deflection
(oz.) (grams) Deflection U.S. 0.35960 10.210 0.638 16 10.195 1.001
Pat. No. 6,554,154 "Old" U.S. 0.33433 9.994 0.625 16 9.478 1.055
Pat. No. 6,554,154 "New" Stretch -- -- 5.227 (at 26.4 24.969 5.527
Blow- 1 inch) Molded Cup of Invention (PET)
[0114] Thus, it is seen that the cups of the invention are over
five hundred % (500%) more rigid than cups of the '154 patent at 1
inch deflection on a Relative Cup Rigidity basis. Similar
differences are seen with respect to other commercially available
cups. Rigidity data (lb.sub.f) appears in Table 6. TABLE-US-00007
TABLE 6 Rigidity Values* Load Load Load Load at .25 at .5 at .75 at
1.0 inch inch inch inch dflc dflc dflc dflc Sample (lb.sub.f)
(lb.sub.f) (lb.sub.f) (lb.sub.f) Nominal 22 oz. 1.690 3.114 4.036
5.227 Stretch Blow-Molded PET tumbler 16 oz. 0.789 1.593 2.260
2.722 Thermoformed PET 16 oz. 0.669 1.373 2.038 2.999 Thermoformed
PET 32 oz. 0.730 1.472 2.284 3.153 Injection- Molded (PP) *Rigidity
Value at 1 inch sidewall deflection
[0115] It is seen in Table 6 that a tumbler of the invention
typically exhibits Relative Cup Rigidity values at 1 inch
deflection at least about 65% greater than the other cups
tested.
Rigidity Index
[0116] The Relative Cup Rigidity parameter may also be modified so
as to index the Rigidity of cups of different polymer compositions
to biaxially oriented PET cups by normalizing the data to PET. This
is accomplished by multiplying the Relative Cup Rigidity by the
ratio of the densities of the polymer to that of PET. Thus, a
polystyrene cup may be indexed against a PET cup by multiplying the
Relative Cup Rigidity by 1.05/1.33. Table 7 lists typical
blow-moldable polymers and their densities. The Rigidity Index thus
calculated allows one to compare various cups whether thermoformed,
injection-molded, 1-step stretch blow-molded, and IBM (injection
blow-molded as described in the '543 patent noted above) cups
regardless of their design or material of construction, see Table
9. Furthermore, when cup Rigidity is measurable by sidewall
deflection, the normalized parameter also extends to filled or
reinforced materials such as calcium carbonate-filled polypropylene
and to PP nanocomposites. See Table 10. Rigidity .times. .times.
.times. Index .ident. ( Rigidity ) .times. ( Cup .times. .times.
Volume ) ( Cup .times. .times. Weight ) .times. ( Density .times.
.times. of .times. .times. Resin ) ( Density .times. .times.
.times. of .times. .times. PET ) ##EQU5## ( units : lb f .times.
.times. fluid .times. - .times. oz . / gram ) ##EQU5.2##
[0117] where,
[0118] Rigidity is the force in pounds required to deflect the
sidewall of the cup 1/4 inch at 2/3 height,
[0119] Cup Volume is in fluid oz.,
[0120] Cup Weight is in grams,
[0121] Density of Resin is the specific gravity of the base resin
disregarding the effects of fillers or additives, and
[0122] Density of PET is the specific gravity of PET, which is
taken as 1.33. TABLE-US-00008 TABLE 7 Densities of Blow-Moldable
Resins Factor to Polymer Grade Density Index Data to PET PET Kosa
2201 1.39 1.0451 PET Eastapak 9921 1.33 1.0000 PS Styron 685D 1.04
0.7820 PP Exxon PP 9574 E6 0.91 0.6842 HDPE Exxon HYA-301 0.954
0.7173 PC Dow Calibre 200-3 1.20 0.9022 SAN Tyril 880B 1.08 0.8120
K-Resin Chevron-Phillips KR03 1.01 0.7594 HIPS Atofina 825 1.05
0.7895
[0123] The stretch blow-molded cups of this invention highlight the
differentiating aspects of these cups compared to the various types
of cups on the market today. The 22-oz. reverse taper glass shape
was used to demonstrate that reverse taper designs with sidewall
embossed logos are possible with crystal clear, rigid, lightweight,
indestructible characteristics. Design options make it more
possible than ever to link Brand identification with cup shape at
competitive prices.
[0124] Relative Cup Rigidity and Rigidity Index data on fortified
brims, made by the top curl method and the can seamer method, are
shown in Table 8. Note that without the advantage of process
optimization of preform design and weight to volume ratios, the
Rigidities of stretch blow-molded cups made from typical 2-liter
bottle preforms are dramatically higher than cups made by other
methods--up to 60% higher than the best thermoformed cups and
90-140% higher than typical cups. An experiment was performed by
cutting stretch blow-molded PET bottles in two places--31/2 inches
from the base and 61/2 inches from the base. The Relative
Rigidities measured on the bottle samples were 0.87 for the 31/2
inch sample and 0.79 for the 61/2 inch sample. The Relative
Rigidities of these samples are low for biaxially oriented PET
materials because they did not have brims. Typically a brim can
contribute up to 80% of the Rigidity of a thin-walled cup as
compared to a similar cup without a brim.
[0125] There appears in Tables 9 and 10 comparisons of Rigidity
Indices for cups of the invention and various other products.
TABLE-US-00009 TABLE 8 Rigidities of PET Cups Cup Cup Cup Relative
Rig- Mate- Weight Volume Rigidity Cup idity Description rial
(grams) (oz.) (pounds) Rigidity Index 22-oz. Reverse PET 24.969
26.4 1.360 1.438 1.438 Taper Stretch Blow-Molded Brim Curled by Can
Seamer 22-oz. Reverse PET 26.561 27.1 1.781 1.817 1.817 Taper
Stretch Blow-Molded Brim Curled by Top Curl Tooling Structural
Ledge Thermoformed 12-14 oz. PET 14.923 14 1.209 1.13 1.13 16 oz.
16.311 16 0.844 0.83 0.83 20 oz. 18.420 20 1.045 1.13 1.13 24 oz.
21.575 24 0.950 1.06 1.06 Thermoformed 12-14 oz. PET 12.920 14.2
0.620 0.68 0.68 16 oz. 15.933 16 0.681 0.68 0.68 20 oz. 20.357 20
0.776 0.76 0.76 24 oz. 19.000 24 0.646 0.82 0.82 32 oz. 28.103 32
0.789 0.90 0.90 Thermoformed 16 oz. PET 15.764 18.3 0.516 0.60 0.60
Thermoformed 16 oz. PET 16.249 18.3 0.662 0.74 0.74 IBM (Injection
Blow-Molded) 14 oz. Cut PET 25.105 14 1.960 1.093 1.093 Crystal
Design 14 oz. Cut 24.952 14 2.034 1.141 1.141 Crystal Design IBM
(Injection Blow-Molded) 16 oz. PET 24.097 16 0.850 0.564 0.56 One
Step Stretch Blow-Molded 14 oz. Cut PET 20.638 13.9 0.916 0.62 0.62
Crystal
[0126] TABLE-US-00010 TABLE 9 Rigidities of Cups Made of Different
Materials by Various Processes Cup Cup Relative Cup Weight Volume
Rigidity Cup Rigidity Description Material (grams) (oz.) (pounds)
Rigidity Index 22-oz. Reverse PET 24.969 26.4 1.360 1.438 1.438
Taper Stretch Blow-Molded Brim Curled by Can Seamer 22-oz. Reverse
PET 26.561 27.1 1.781 1.817 1.817 Taper Stretch Blow-Molded Brim
Curled by Top Curl Tooling Structural Ledge 16 oz. Thermoformed
12.983 17.6 0.598 0.811 0.63 Clear PS 16 oz Thermoformed 14.931
18.3 0.617 0.756 0.59 Clear/Colored PS 14 oz. - Swirl IBM 17.272
13.9 1.545 1.243 0.97 Shape Clear PS 14 oz. - Low 14.807 14.1 0.853
0.812 0.64 Faceted Shape 14 oz. - Cut 17.244 13.7 1.513 1.202 0.94
Crystal Design Red Multilayer Thermoformed 10.324 16.1 0.672 1.048
0.82 16 oz. PS/HIPS Blue Multilayer Thermoformed 13.881 18.3 0.764
1.049 0.82 16 oz. PS/HIPS Red Multilayer Thermoformed 11.332 18.6
0.544 0.892 0.70 16 oz. PS/HIPS Multilayer Thermoformed 14.143 17.8
0.977 1.230 0.97 16 oz. PS/HIPS 16 oz. Thermoformed 9.282 15.9
0.488 0.836 0.65 Opaque PS 16 oz. Thermoformed 9.843 16.2 0.585
0.963 0.76 Opaque PS 16 oz. Thermoformed 9.903 16.1 0.400 0.650
0.51 Opaque PS 16 oz. Thermoformed 11.191 17.6 0.495 0.778 0.61
White PS 32 oz. Thermoformed 26.126 32.7 1.273 1.593 1.25 HIPS/PS
32 oz. Thermoformed 28.830 31.9 1.266 1.401 1.10 White HIPS/PS 32
oz. Thermoformed 29.290 32.6 0.971 1.081 0.85 White HIPS/PS 32 oz.
Injection 36.533 31.8 1.059 0.922 0.62 Molded White PP 32 oz.
Injection 35.483 32.6 0.748 0.687 0.47 Molded Georgia- Green PP 22
oz. Injection 32.881 25.2 1.350 1.035 0.70 Molded Colored PP White
HDPE Injection 36.567 32 1.001 0.876 0.62 32 oz. Molded White
HDPE
[0127] TABLE-US-00011 TABLE 10 Rigidities of Mineral-Filled
Injection Molded Cups are Compared to Stretch Blow-Molded Cups Cup
Cup Relative Cup Weight Volume Rigidity Cup Rigidity Description
Material (grams) (oz.) (pounds) Rigidity Index 22-oz. Reverse PET
24.969 26.4 1.360 1.438 1.438 Taper Stretch Blow-Molded Brim Curled
by Can Seamer 22-oz. Reverse PET 26.561 27.1 1.781 1.817 1.817
Taper Stretch Blow-Molded Brim Curled by Top Curl Tooling
Structural Ledge 44-oz. Car Cup 100% Solvay Injection 47.422 44
1.401 1.300 0.880 1801 PP 90% PP/10% Molded 50.497 1.621 1.412
0.956 CaCO.sub.3 80% PP/20% PP 54.290 1.798 1.457 0.986 CaCO.sub.3
70% PP/30% 59.364 2.070 1.534 1.038 CaCO.sub.3 44-oz. Car Cup 100%
PP Injection 47.310 44 1.704 1.584 1.078 97% PP/3% Molded 48.392
1.810 1.646 1.114 Nanoclay 94% PP/6% PP 49.217 2.029 1.814 1.227
Nanoclay 44-oz. Car Cup - Injection 48.751 44 0.809 0.730 0.519
HDPE Molded HDPE
[0128] From the foregoing data, it is seen the cups of the
invention exhibit significantly higher Rigidity Index values than
one seen with other disposable cups. The observed values may be
summarized as set forth in Table 11. TABLE-US-00012 TABLE 11
Rigidity Index Summary Observed Rigidity Index Range, Cup Type
lb.sub.f fluid oz./gram Stretch Blow-Molded Cups of 1.4-1.8
Invention Thermoformed PET Cups 0.6-1.1 IBM PET 0.55-1.15
Thermoformed PS 0.5-1.1 IBM PS 0.6-1 Injection-Molded PP/HDPE
0.5-0.7 (unfilled) Injection Molded PP/HDPE (filled) 0.5-1.2
[0129] The differences in observed Rigidity Index Values are
perhaps better appreciated by reference to FIG. 1, wherein the
observed ranges for the various cups are presented.
Crystallinity
[0130] Samples from the sidewall of Thermoformed Cup A,
Thermoformed Cup B, and the Blow-Molded prototype of the invention
were taken at the top of the sidewall (1 inch down), the middle of
the sidewall and the bottom of the sidewall (1 inch up) and in some
cases from the bottom of the cups using the following
procedure.
[0131] Exemplars were cut from either #1 or #2 cork borers and
placed in pre-weighed DSC pans that had known amounts of
Dow-Corning 340 silicone heat sink compound (zinc oxide and
polydimethylsiloxane). The heat sink compound improves thermal
conductivity so that good quality first-heating DSC thermal data
can be obtained. Known amounts of heat sink compound were also
placed on top of the PET exemplars prior to the lids being clamped
onto the pans.
[0132] For DSC experiments, samples were taken through
heat/cool/heat regimens at heating and cooling rates of 10.degree.
C. per minute. The DSC instrument was calibrated with an indium
metal standard.
[0133] Any suitable commercially available machine may be used such
as a Perkin Elmer.RTM. Pyris.RTM. 6 DSC. The instrument is operated
in the heating mode method. Data and results appear in Table 12
below wherein % crystallinity is calculated as follows: % .times.
.times. Crystallinity = .DELTA. .times. .times. H melt - .DELTA.
.times. .times. H cc .DELTA. .times. .times. H.degree. .times. 100
.times. % ##EQU6##
[0134] where .DELTA.H.degree.=140.1 J/g for PET [0135]
.DELTA.H.sub.melt=measured heat of melting [0136] .DELTA.H.sub.cc
measured heat of cold crystallization
[0137] Reference: DSC as Problem Solving Tool: Measurement of
percent Crystallinity of Thermoplastics, W. J. Sichina,
International Marketing Manager, Perkin Elmer.RTM. Instruments.
TABLE-US-00013 TABLE 12 Thermal Properties of Poly(ethylene
terephthalate) Samples Determined by DSC Heating Mode Method Heat
Sink Cold Sample Cmpd Weight Glass Transition Crystallization
Melting Weight Bottom Top T.sub.onset T.sub.mid T.sub.end .DELTA.Cp
T.sub.peak .DELTA.H.sub.cc T.sub.onset T.sub.peak .DELTA.H.sub.melt
Crystallinity Sample (mg) (mg) (mg) (.degree. C.) (.degree. C.)
(.degree. C.) (J/g.degree. C.) (.degree. C.) (J/g) (.degree. C.)
(.degree. C.) (J/g) (%) (1) PET Thermoformed Cup B (20-oz.)
Sidewall Top (One inch down) 3.82 1.76 3.42 First Heating 44 61 --
0.12 142 -3.96 235 241 43.84 28 Second Heating -- 77 80 0.24 150
-5.43 241 246 32.55 19 Sidewall Middle 4.61 3.88 7.66 First Heating
65 68 70 0.12 102 -4.49 232 246 40.84 26 Second Heating -- 78 86
0.18 152 -5.21 238 248 38.86 24 Sidewall Bottom (One-inch up) 5.69
1.66 3.45 First Heating 73 74 -- 0.31 118 -22.74 231 246 36.81 10
Second Heating -- 78 -- 0.17 147 -5.82 237 249 41.80 26 Bottom of
Cup 8.23 1.92 3.31 First Heating 65 67 69 0.35 127 -26.09 231 246
36.74 8 Second Heating 75 80 85 0.14 159 -6.43 235 247 35.83 21 (2)
PET Thermoformed Cup A (20-oz.) Sidewall Top (One inch down) 5.74
5.95 3.17 First Heating -- 67 74 0.45 127 -27.09 233 246 38.56 8
Second Heating 78 80 82 0.17 148 -5.21 238 249 41.58 26 Sidewall
Middle 6.79 1.86 2.08 First Heating 70 72 -- 0.23 128 -28.19 235
247 39.18 8 Second Heating 74 78 81 0.11 152 -4.30 237 249 44.67 29
Sidewall Bottom (One-inch up) 5.34 2.46 4.64 First Heating 69 71 74
0.40 128 -28.53 233 247 38.56 7 Second Heating 68 78 90 0.20 145
-5.76 238 249 41.36 25 Bottom of Cup 9.43 1.46 2.84 First Heating
-- 67 75 0.38 129 -30.95 232 247 40.06 7 Second Heating 73 79 --
0.15 146 -3.66 238 249 42.23 28 (3 Prototype Sidewall Top (One inch
down) 5.99 3.52 1.10 First Heating 46 61 -- 0.10 92 -2.70 239 247
39.64 26 Second Heating 76 81 85 0.18 147 -4.85 232 246 31.94 19
Sidewall Middle 10.89 2.00 4.59 First Heating 57 59 66 0.07 97
-4.41 236 248 41.12 26 Second Heating 72 80 89 0.14 156 -5.16 238
251 42.84 27 Sidewall Bottom (One-inch up) 11.17 2.05 4.01 First
Heating 61 63 67 0.05 106 -2.90 238 248 43.83 29 Second Heating 77
82 88 0.16 137 -1.14 234 248 35.34 24
[0138] The thicknesses of the thermoformed cups was also measured
and samples of the blow-molded prototype tumbler were cold
stretched in room temperature Instron.RTM. Tests and then evaluated
further for crystallinity changes. Results appear in Table 13 for
cold-stretched samples vs. unstretched samples. TABLE-US-00014
TABLE 13 Effect of Cold-Stretch on Crystallinity - Blow-molded
Prototype Heat Sink Cold Sample Cmpd Weight Glass Transition
Crystallization Melting Weight Bottom Top T.sub.onset T.sub.mid
T.sub.end .DELTA.Cp T.sub.peak .DELTA.H.sub.cc T.sub.onset
T.sub.peak .DELTA.H.sub.melt Crystallinity Sample (mg) (mg) (mg)
(.degree. C.) (.degree. C.) (.degree. C.) (J/g.degree. C.)
(.degree. C.) (J/g) (.degree. C.) (.degree. C.) (J/g) (%) Dog-Bone
CD Non-Stretch Area 9.36 2.99 3.31 First Heating -- 66 69 0.07 98
-3.01 226 247 41.12 27 Second Heating -- 81 -- 0.17 155 -6.91 237
250 39.01 23 Dog-Bone CD Stretch Area 8.02 3.09 7.92 First Heating
-- -- -- -- 100 -3.01 241 239 48.31 32 Second Heating -- 81 87 0.18
137 -1.59 233 237 32.78 22 Dog-Bone MD Non-Stretch Area 10.02 2.99
3.31 First Heating -- 68 -- 0.06 107 -5.20 219 247 39.64 25 Second
Heating -- 80 84 0.12 142 -2.09 239 250 40.97 28 Dog-Bone MD
Stretch Area 9.49 1.53 12.49 First Heating -- 65 76 0.13 88 -7.45
244 250 59.67 37 Second Heating 78 82 85 0.16 146 -5.41 233 248
32.58 19 % Crystallinity = (.DELTA.H.sub.melt -
.DELTA.H.sub.cc/.DELTA.H.degree.) .times. (100%)
[0139] Results of the foregoing tests are further summarized in
Tables 14, 15 and 16. TABLE-US-00015 TABLE 14 Thicknesses of Cups
at Four Positions PET Thickness (mils) Thermoformed Thermoformed
Position Measured Cup B Cup A Sidewall Top (One-inch down) 8.5 15.5
Sidewall Middle 10.3 16.6 Sidewall Bottom (One-inch up) 15.0 12.3
Bottom of Cup 42.5 33.0 Weights of a typical cup are: Thermoformed
Cup B 19.00 g and Thermoformed Cup A 19.65 g
[0140] TABLE-US-00016 TABLE 15 % Crystallinities of "As Received"
PET Samples (First Heating DSC Data) Crystallinities (%) Stretch
Thermoformed Thermoformed Blow- Cup B Cup A Molded Position Assayed
20-oz. Cup 20-oz. Cup Prototype Sidewall Top 28 8 26 (One-inch
down) Sidewall Middle 26 8 26 Sidewall Bottom 10 7 29 (One-inch up)
Bottom of Cup 8 7 --
[0141] TABLE-US-00017 TABLE 16 MD and CD Films From
Stretch-Blow-Molded Prototype Cups Showing the Effect That
Stretching (at Room temperature) Has on % Crystallinities
Crystallinities (%) "Dog-Bone" Sample Non-Stretched Stretched MD of
Stretch Blow-Molded Prototype Cup 25 37 CD of Stretch Blow-Molded
Prototype Cup 27 32
[0142] It will be appreciated from the foregoing that the stretch
blow-molded cups of the invention exhibited high levels of
relatively uniform crystallinity at all levels of the sidewall
whereas the thermoformed cups did not. Moreover, room temperature
stretching experiments indicate that further crystallinity gains
can be realized by optimizing preform design. Thermoformed cup B
had relatively elevated levels of crystallinity in its upper
portion while thermoformed cup A was more uniform in terms of
thickness and crystallinity; albeit at relatively low levels of
crystallinity.
[0143] While the invention has been described in connection with
its numerous features and improvements, modifications to specific
examples given within the spirit and scope of the present invention
will be readily apparent to those of skill in the art.
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