U.S. patent application number 12/814103 was filed with the patent office on 2010-10-21 for foamed-wall container with foamed and unfoamed regions.
Invention is credited to Eugene M. Sadzewicz, Frank E. Semersky, William D. Voyles.
Application Number | 20100264052 12/814103 |
Document ID | / |
Family ID | 45098374 |
Filed Date | 2010-10-21 |
United States Patent
Application |
20100264052 |
Kind Code |
A1 |
Semersky; Frank E. ; et
al. |
October 21, 2010 |
FOAMED-WALL CONTAINER WITH FOAMED AND UNFOAMED REGIONS
Abstract
A container comprises a micro cellular foamed polymer having
foamed and unfoamed regions, wherein the container has one of a
silvery appearance and a white appearance without the use of a
colorant.
Inventors: |
Semersky; Frank E.;
(Holland, OH) ; Voyles; William D.; (Toledo,
OH) ; Sadzewicz; Eugene M.; (Toledo, OH) |
Correspondence
Address: |
FRASER CLEMENS MARTIN & MILLER LLC
28366 KENSINGTON LANE
PERRYSBURG
OH
43551
US
|
Family ID: |
45098374 |
Appl. No.: |
12/814103 |
Filed: |
June 11, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11384979 |
Mar 20, 2006 |
7790255 |
|
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12814103 |
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12276687 |
Nov 24, 2008 |
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11384979 |
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Current U.S.
Class: |
206/524.6 |
Current CPC
Class: |
B29B 2911/14026
20130101; B29K 2105/046 20130101; C08J 9/122 20130101; B29B
2911/14033 20130101; B29B 2911/1408 20130101; B29K 2023/12
20130101; B29B 2911/14066 20130101; B29B 2911/14166 20130101; C08J
2205/044 20130101; B29B 11/14 20130101; B29K 2077/00 20130101; B29B
2911/14106 20130101; B29C 49/06 20130101; C08J 2203/06 20130101;
B29B 2911/1402 20130101; B29K 2067/00 20130101; B29B 2911/14053
20130101; B29B 2911/14113 20130101; B29B 2911/1404 20130101; B29C
49/0005 20130101; B29B 2911/1414 20130101; B29B 2911/14133
20130101; B29B 2911/14093 20130101; B29B 11/08 20130101; B29B
2911/1416 20130101; B29K 2027/06 20130101 |
Class at
Publication: |
206/524.6 |
International
Class: |
B65D 85/00 20060101
B65D085/00 |
Claims
1. A blow molded plastic container comprising a hollow body formed
from a micro cellular foamed polymer formed without a chemical
blowing agent, cells of the micro cellular foamed polymer
containing a non-reactive gas therein, wherein said hollow body
includes foamed and unfoamed regions.
2. The plastic container of claim 1, wherein the hollow body has a
silvery appearance without the use of a colorant.
3. The blow molded plastic container according to claim 2, wherein
the silver color of the container is Pantone Color Formula Guide
number 420, 421, 422, 423, 424, 425, 877, 8001, 8400, or 8420.
4. The blow molded plastic container according to claim 3, wherein
the silver color of the container is Pantone Color Formula Guide
number 420, 421, 422, 423, 424, or 425.
5. The plastic container of claim 1, wherein the hollow body has a
white appearance without the use of a colorant.
6. The blow molded plastic container according to claim 1, wherein
the polymer comprises one or more of a polyester, polypropylene,
acrylonitrile acid ester, vinyl chloride, polyolefin, polyamide, or
a derivative or copolymer thereof.
7. The blow molded plastic container according to claim 1, wherein
the polymer comprises polyethylene terephthalate.
8. The blow molded plastic container according to claim 1, wherein
the non-reactive gas comprises one or more of carbon dioxide,
nitrogen, or argon.
9. The blow molded plastic container according to claim 1, wherein
the non-reactive gas comprises nitrogen.
10. The blow molded plastic container according to claim 1, wherein
the foamed and unfoamed regions include an unfoamed region disposed
between a pair of foamed regions.
11. The blow molded plastic container according to claim 1, wherein
the foamed and unfoamed regions include a foamed region disposed
between a pair of unfoamed regions.
12. A preform suitable for blow molding a plastic container
comprising a hollow body formed from a micro cellular foamed
polymer formed without a chemical blowing agent, cells of the micro
cellular foamed polymer containing a non-reactive gas therein,
wherein said hollow body includes foamed and unfoamed regions.
13. The preform of claim 11, wherein the plastic container formed
from the preform has a silvery appearance without the use of a
colorant.
14. The preform of claim 11, wherein the plastic container formed
from the preform has a white appearance without the use of a
colorant.
15. The preform of claim 11, wherein the preform has a silvery
appearance without the use of a colorant.
16. The preform of claim 11, wherein the preform has a white
appearance without the use of a colorant.
17. The preform of claim 11, wherein the foamed and unfoamed
regions include an unfoamed region disposed between foamed
regions.
18. The preform of claim 11, wherein the foamed and unfoamed
regions include a foamed region disposed between a pair of unfoamed
regions.
19. An overmolded plastic container comprising a hollow body formed
from an unfoamed polymer abutting a micro cellular foamed polymer
formed without a chemical blowing agent, cells of the micro
cellular foamed polymer containing a non-reactive gas therein,
wherein said hollow body includes foamed and unfoamed regions.
20. The container of claim 19, wherein the unfoamed polymer is
colored.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of and claims the
benefit of priority of U.S. patent application Ser. No. 12/276,687
filed on Nov. 24, 2008 which is a continuation-in-part of and
claims the benefit of priority of U.S. patent application Ser. No.
11/384,979 filed on Mar. 20, 2006.
FIELD OF THE INVENTION
[0002] The present invention relates generally to a foamed-wall
polymer container having a unique appearance. More particularly,
the invention is directed to a container having foamed and unfoamed
regions, the foamed regions comprising micro cellular foam
containing a non-reactive gas, and the container has one of a
silvery appearance and a white appearance. Also contemplated as a
part of the present invention is a method of manufacturing the
foamed-wall container.
BACKGROUND OF THE INVENTION
[0003] Biaxially oriented single and multi-layered bottles may be
manufactured from polymer materials such as, for example,
polyethylene terephthalate (PET) using a hot preform process,
wherein a single or multi-layered preform is heated to its desired
orientation temperature and drawn and blown into conformity with a
surrounding mold cavity. The preform may be prepared by any
conventional process such as, for example, by extruding a preform
comprising single or multiple layers of polymer, or by injecting
subsequent layers of polymer over a previously injection molded
preform. Generally, multiple layers are used for beverage
containers, to add diffusion barrier properties not generally found
in single layer containers.
[0004] The various layers of polymers in the prior art
multi-layered containers are generally in intimate contact with one
another, thereby facilitating the conduct of thermal energy through
the walls of the containers. This allows the chilled contents of
the container to quickly warm to the ambient temperature.
Accordingly, such containers are often sheathed in, for example, a
foamed polystyrene shell to impart thermal insulating properties to
the container.
[0005] It would be desirable to prepare an improved plastic
container which is opaque with unique visual properties without the
addition of a coloring agent. Further, it is deemed desirable to
impart thermal insulating properties to the improved plastic
container. Also, it would be desirable to prepare an improved
plastic container having a silvery appearance without requiring the
addition of a coloring agent which would adversely effect the
recycling characteristics of the container.
SUMMARY OF THE INVENTION
[0006] Accordant with the present invention, a foamed-wall
container having a unique appearance has surprisingly been
discovered. The container comprises a micro cellular foamed
polymer, and a non-reactive gas contained within the micro cellular
foam cells, wherein the container has a silvery appearance without
the addition of a coloring agent.
[0007] Also contemplated as an embodiment of the invention is a
process for preparing a foamed-wall container having a unique
appearance. The process comprises the steps of injection molding a
polymer preform having a non-reactive gas entrapped within the
walls thereof, cooling the preform to a temperature below the
polymer softening temperature, reheating the preform to a
temperature above the polymer softening temperature, and blow
molding the preform, to prepare a container comprising a micro
cellular foamed polymer having a non-reactive gas contained within
the micro cellular foam cells, wherein the container has a silvery
appearance.
[0008] The container according to the present invention is
particularly useful for packaging carbonated beverages, such
carbonated beverages typically packaged in a container having a
hollow body and a threaded finish adapted to receive a
corresponding threaded closure providing communication with an
interior of the hollow body.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0009] The present invention is directed to a container having
foamed and unfoamed regions, the foamed regions comprising micro
cellular foam containing a non-reactive gas, and the container has
one of a silvery appearance and a white appearance.
[0010] Another embodiment of the present invention is directed to a
process for making a foamed-wall container having a unique
appearance, comprising injection molding a polymer preform having a
non-reactive gas entrapped within the walls thereof, cooling the
preform to a temperature below the polymer softening temperature,
reheating the preform to a temperature above the polymer softening
temperature, and blow molding the preform, to prepare a container
comprising a micro cellular foamed polymer having a non-reactive
gas contained within the micro cellular foam cells, wherein the
container has a silvery appearance.
[0011] Suitable polymers from which the container may be prepared
include, but are not necessarily limited to, polyethylene
terephthalate (PET) and other polyesters, polypropylene,
acrylonitrile acid esters, vinyl chlorides, polyolefins,
polyamides, and the like, as well as derivatives, blends, and
copolymers thereof. A suitable polymer for commercial purposes is
PET.
[0012] Polymer flakes are melted in a conventional plasticizing
screw extruder, to prepare a homogeneous stream of hot polymer melt
at the extruder discharge. Typically, the temperature of the
polymer melt stream discharged from the extruder ranges from about
225 degrees Centigrade to about 325 degrees Centigrade. One
ordinarily skilled in the art will appreciate that the temperature
of the polymer melt stream will be determined by several factors,
including the kind of polymer flakes used, the energy supplied to
the extruder screw, etc. As an example, PET is conventionally
extruded at a temperature from about 260 degrees Centigrade to
about 290 degrees Centigrade. A non-reactive gas is injected under
pressure into the extruder mixing zone, to ultimately cause the
entrapment of the gas as micro cellular voids within the polymer
material. By the term "non-reactive gas" as it is used herein is
meant a gas that is substantially inert vis-a-vis the polymer.
Preferred non-reactive gases comprise carbon dioxide, nitrogen, and
argon, as well as mixtures of these gases with each other or with
other gasses.
[0013] According to the present invention, the extrudate is
injection molded to form a polymer preform having the non-reactive
gas entrapped within the walls thereof. Methods and apparatus for
injection molding a polymer preform are well-known in the art.
[0014] It is well-known that the density of amorphous PET is 1.335
grams per cubic centimeter. It is also known that the density of
PET in the melt phase is about 1.200 grams per cubic centimeter.
Thus, if the preform injection cavity is filled completely with
molten PET and allowed to cool, the resulting preform would not
exhibit the proper weight and would have many serious deficiencies,
such as sink marks. The prior art injection molding literature
teaches that, in order to offset the difference in the densities of
amorphous and molten PET, a small amount of polymer material must
be added to the part after the cavity has been filled and as the
material is cooling. This is called the packing pressure. Thus,
about ten per cent more material must be added during the packing
pressure phase of the injection molding cycle in order to insure
that a preform made by injection molding is filled adequately and
fully formed. The packing pressure phase of the injection molding
operation is likewise used for polymer materials other than
PET.
[0015] According to the present invention however, the polymer
preform is injection molded and simultaneously foamed using a
non-reactive gas. The gas is entrained in the material during the
injection phase. The foaming of the polymer is discussed
hereinbelow in more detail. The foaming occurs without the use of a
chemical blowing agent. Chemical blowing agents are frequently used
by plastic container manufactures to foam a polymer melt. Blowing
agents are chemicals added to plastics that generate gases and
water on heating, causing the resin to assume a cellular structure.
Use of chemical blowing agents typically results in an organic
residue mixed with the foamed polymer. Use of a blowing agent to
foam a PET polymer melt will result in the generation of water (an
organic residue) in the polymer matrix of an object formed from the
polymer melt. Due to the presence of water in the PET matrix, the
chains of the PET polymer used to form the object will break down
upon heating during processing, such as in an extruder or blow
molding machine, thereby resulting in an undesired decrease in the
resilience of the object. Therefore, a blow molded foamed object
formed from a polymer melt foamed without a chemical blowing agent
is structurally different from, and would have increased resilience
as compared to, a foamed object formed from a polymer melt foamed
with a chemical blowing agent.
[0016] Contrary to the prior art injection molding process, wherein
additional polymer material is injected during the packing phase,
the present invention utilizes minimal packing pressure. As the
polymer material is still in a molten state, the partial pressure
of the non-reactive gas is sufficient to permit the release of the
dissolved gas from the polymer into the gas phase where it forms
the micro cellular foam structure. Thus, the preform made by the
inventive process weighs less than, but has the same form and
geometry as, the polymer preforms produced by the conventional
injection molding operations that employ the packing process.
[0017] The micro cells may contain one or more of a variety of
gases typically used in processes for making micro cellular foam
structures. In one commercially acceptable embodiment, the
non-reactive gas comprises carbon dioxide in a concentration of at
least ten percent by weight of the total weight of the non-reactive
gas. This level of carbon dioxide concentration provides adequate
partial pressure to retard the diffusion of carbon dioxide from a
carbonated beverage within the inventive container to the exterior
atmosphere. The micro cellular foam tends to act as an effective
thermal insulator, to retard the conduct of heat energy from the
atmosphere to the chilled carbonated beverage within the
container
[0018] Upon completion of the injection molding step, the preform
is cooled to a temperature below the polymer softening temperature.
For example, the softening temperature for PET is approximately 70
degrees Centigrade. Thus, the entrapped non-reactive gas is
retained within the walls of the polymer preform. This cooling step
conditions the polymer and preserves its desirable properties for
the successful preparation of a blow molded container. This cooling
step is also useful when employing polymers such as polyesters,
which cannot be blow molded directly from an extruded parison. This
cooling step may be effected by any conventional process used in
the polymer forming art such as, for example, by passing a stream
of a cooling gas over the surfaces of the preform, or cooling the
preform while in-mold by cooling the forming mold.
[0019] The preform is thereafter reheated to a predetermined
temperature above the polymer softening temperature. This heating
step may be effected by well-known means such as, for example, by
exposure of the preform to a hot gas stream, by flame impingement,
by exposure to infra-red energy, by passing the preform through a
conventional oven or an oven having infrared heaters, or the like.
It is understood that the heating step of the preform may also
occur in a heated mold or with a heated fluid in a mold. By heating
the preform to a desired and predetermined temperature, the
translucence, and therefore appearance, of the container blow
molded from the preform may be selectively varied. The translucence
of the container may be selectively varied across a range until the
container is opaque. In one instance, at temperatures of about 106
degrees Centigrade, the container has a silvery appearance and is
translucent. At temperatures of about 112 degrees Centigrade, the
container has a silvery appearance and less translucent than the
container formed from the preform heated to 106 degrees Centigrade.
At temperatures of about 116 degrees Centigrade, the container has
a silvery appearance and is less translucent still and may be
opaque. Thus, as the desired temperature for reheating the preform
increases, the translucence of the container formed therefrom
decreases. The desired temperature may be increased to temperatures
above 116 degrees Centigrade, thereby resulting in an opaque
container having a silvery appearance or an opaque container having
a white appearance. Other preforms may exhibit this phenomenon but
at different temperatures depending on many factors including the
amount of gas bubbles entrained in cells of the micro cellular foam
in the sidewall of the preform.
[0020] If PET is reheated too far above its glass transition
temperature, or held at a temperature above its softening
temperature for an excessive period of time, the PET undesirably
will begin to crystallize. Likewise, if the preform is heated to a
temperature above which the mechanical properties of the material
are exceeded by the increasing pressure of the non-reactive gas in
the micro cells, the micro cells undesirably will begin to expand
thus distorting the preform.
[0021] Finally, the preform is blow molded, to prepare a container,
consisting essentially of a micro cellular foamed polymer having a
non-reactive gas contained within the micro cellular foam cells.
Methods and apparatus for blow molding a container from a polymer
preform are well-known.
[0022] If the blow molded foamed-wall polymer container so produced
has a silvery appearance; as though the container were made of
metal. The blow molded container is silvery in color, and may
exhibit Pantone Color Formula Guide numbers in the range of about
420 through 425, 877, 8001, 8400, and 8420. While not wishing to be
bound by any particular theory regarding the reason that the
ultimately produced container has a unique silvery appearance, it
is believed that, as the preform cavity is being filled with
polymer, bubbles of gas are formed at the flow front of the polymer
due to the pressure drop between the dissolved gas and the
relatively lower pressure in the preform cavity. During the filling
process which can take several seconds, non-nucleated polymeric
material is introduced into each injection molding cavity. The
non-nucleated, molten material that contacts the chilled sidewalls
of the preform cavity and the core rod therein solidifies. As the
pressure of the injected material in the system is still greater
than a nucleation pressure, the solidified material remains
unfoamed. When the preform cavity is from about 1% to about 5%
filled or greater, a pin gate for each of the preform cavities is
closed and the preform cavity is no longer in fluid communication
with the pressurized non-nucleated fluid. The pressure in the
cavity is less than the critical pressure required for the gas in
the polymer to nucleate and the sections of the preform that remain
molten are caused to foam, which results in "packing out" the
preform, i.e. filling the remaining portion of the preform cavity.
The melted polymer flows along the central axis of the preform as
the preform mold is filled with polymer solution. Thus, it is the
center-most portion of the preform that remains molten at the time
of closing of the pin gate. It is the center-most portion of the
preform in which the foaming occurs.
[0023] In addition to the nucleation which occurs in the central
portion of the preform, as described above, and while not wishing
to be bound by any particular theory regarding the reason that the
ultimately produced container has a unique silvery appearance, it
is noted that, as the preform cavity is being filled with molten
polymer, bubbles of gas are formed at the flow front of the polymer
due to the pressure drop between the dissolved gas and the
relatively lower localized pressure in the preform cavity. The
bubbles formed at the flow front of the polymer material as it is
introduced into the preform cavity are subsequently deposited on
the outside and inside surfaces of the preform. Thus,
macroscopically, the cross-section of the preform shows a
non-uniform structure having a foamed region disposed between two
unfoamed regions, the unfoamed regions being the plastic material
which hardened at the interface of the polymeric material and the
cold mold surfaces of the cavity and the core rod, respectively,
prior to the release of pressure in the cavity. To the inside and
outside of this structure are microscopically thin regions of
open-cell foam as a result of the bubbles erupting at the flow
front. The preform having this foamed core section is then blow
molded in a conventional fashion to produce a container having a
multi-regioned structure in concordance with the multi-regioned
structure of the preform.
[0024] According to another embodiment of the invention, the
preform and a container blow molded from the preform may include an
unfoamed region disposed between two foamed regions.
[0025] According to another embodiment of the invention, the
preform is an overmolded preform suitable for blow molding an
overmolded container. Either or both of the preform being
overmolded or the polymer used to overmold the preform may include
a foamed layer having a foamed region disposed between two unfoamed
regions. Alternatively, either or both of the preform being
overmolded or the polymer used to overmold the preform may include
a foamed layer having an unfoamed region disposed between two
foamed regions. A process for forming an overmolded preform and
container having at least one foamed layer is disclosed in
commonly-owned U.S. patent application Ser. No. 12/144,885 hereby
incorporated herein by reference in its entirety, and in
commonly-owned U.S. patent application Ser. No. 12/778,291. It is
understood that the foamed layer may have a silvery appearance or a
white appearance as described hereinabove. It is also understood
that the foamed layer may be overmolded over or be overmolded by
one of a clear polymer or a polymer having a color. If the polymer
has a color, the silvery and/or white foamed layer may accentuate,
enhance, and make vibrant the colored polymer, and/or the silvery
or white foamed layer may give the colored polymer a metallic
appearance.
[0026] From the forgoing description, one ordinarily skilled in the
art can easily ascertain the essential characteristics of the
invention, and without departing from its spirit and scope, can
make various changes and modifications to adapt the invention to
various uses and conditions.
* * * * *