U.S. patent application number 11/006327 was filed with the patent office on 2005-05-12 for injection blow-molded disposable tumbler and method of making same.
Invention is credited to Freek, Michael A., McCarthy, Donald C., Sandstrom, Erland R., Thomas, Michael G., Weigert, Brigitte K..
Application Number | 20050100697 11/006327 |
Document ID | / |
Family ID | 27557784 |
Filed Date | 2005-05-12 |
United States Patent
Application |
20050100697 |
Kind Code |
A1 |
Sandstrom, Erland R. ; et
al. |
May 12, 2005 |
Injection blow-molded disposable tumbler and method of making
same
Abstract
An injection blow-molded disposable tumbler is formed from a
polymeric material and includes a fortified upper rim having a
thickness greater than the adjacent sidewall. The tumbler may be
formed of a variety of resinous materials and exhibits improved
toughness and crush resistance as well as aesthetic qualities
particularly desired by consumers.
Inventors: |
Sandstrom, Erland R.;
(Menasha, WI) ; Weigert, Brigitte K.; (Appleton,
WI) ; McCarthy, Donald C.; (Appleton, WI) ;
Thomas, Michael G.; (Toronto, CA) ; Freek, Michael
A.; (Bradford, CA) |
Correspondence
Address: |
FERRELLS, PLLC
P. O. BOX 312
CLIFTON
VA
20124-1706
US
|
Family ID: |
27557784 |
Appl. No.: |
11/006327 |
Filed: |
December 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11006327 |
Dec 7, 2004 |
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09437554 |
Nov 10, 1999 |
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6866905 |
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60110239 |
Nov 30, 1998 |
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60110240 |
Nov 30, 1998 |
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60110238 |
Nov 30, 1998 |
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60146352 |
Aug 2, 1999 |
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60146354 |
Aug 2, 1999 |
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Current U.S.
Class: |
428/35.7 ;
264/509; 264/534; 264/537 |
Current CPC
Class: |
B29C 2043/046 20130101;
B65D 1/46 20130101; B29L 2031/712 20130101; Y10T 428/13 20150115;
B29K 2105/16 20130101; B65D 1/265 20130101; B29K 2069/00 20130101;
Y10T 428/1352 20150115; Y10T 428/1397 20150115; B29C 49/52
20130101; B29K 2995/006 20130101; B29K 2995/0056 20130101; B29C
49/061 20130101 |
Class at
Publication: |
428/035.7 ;
264/537; 264/509; 264/534 |
International
Class: |
B29C 049/06; F16L
001/00 |
Claims
1-50. (canceled)
51. A method of forming a durable polycarbonate permaware container
comprising: (a) injecting molten polycarbonate into a mold cavity
formed by a mold wall and a core to form a polycarbonate parison on
the core; (b) separating the parison from the mold wall by moving
the parison on the core axially in a straight path away from the
mold wall; (c) moving the parison on the core in a substantially
arcuate path into axial alignment with a blow mold which is in a
side-by-side relationship with the mold cavity; (d) moving the
parison on the core axially in a straight path into the blow mold;
and (f) expanding the parison on the core in the blow mold at a
uniform temperature to form a hollow container having a sidewall
integrally formed to a base and a fortified rim, the sidewall
having a uniform thickness of from about greater than 50 mils to
about 500 mils.
52. The method of claim 51, wherein the sidewall has a uniform
thickness of from about 75 mils to about 375 mils.
53. The method of claim 51, wherein the polycarbonate is injected
into the mold cavity at a temperature of from about 450.degree. F.
to about 700.degree. F.
54. The method of claim 53, wherein the polycarbonate is injected
into the mold cavity at a temperature of from about 500.degree. F.
to about 650.degree. F.
55. The method of claim 51, wherein the molten polycarbonate is
injected into the mold cavity at a pressure of about 1,000 to 3,000
psi.
56. The method of claim 55, wherein the molten polycarbonate is
injected into the mold cavity at an injection pressure of about
2,100 psi.
57. The method of claim 51, wherein the parison is expanded at a
uniform temperature of from about 250.degree. F. to about
500.degree. F.
58. The method of claim 57, wherein the parison is expanded at a
pressure of from about 100 to about 500 psi.
59. The method of claim 51, wherein the polycarbonate comprises
aromatic homopolycarbonate or aromatic copolycarbonate resins.
60. The method of claim 51, wherein the polycarbonate has a melt
flow rate of from about 10 to 22 g/10 min.
61. An injection blow-molded polycarbonate permaware hollow
container comprising: (a) a base forming the bottom of said
container defining an outer edge thereof; (b) a sidewall integrally
formed with said base extending upwardly from the outer edge
thereof and having a thickness of from about over 50 to about 500
mils to a fortified rim about its upper extremity.
62. The permaware polycarbonate container of claim 61, wherein the
fortified rim has a thickness of at least 2 mils greater than an
adjacent portion of the sidewall over a height of at least 2
mils.
63. The permaware polycarbonate container of claim 61, wherein both
width and height of the fortified rim are from about 1.1 to about 4
times a thickness of an adjacent sidewall.
64. The permaware polycarbonate container of claim 63, wherein both
the width and the height of the fortified rim are about 100 mils
and the adjacent sidewall is about 80 mils.
65. The permaware polycarbonate container of claim 61, wherein the
base is from about 1.1 to about 8 times the thickness of the
sidewall.
66. The permaware polycarbonate container of claim 61, wherein the
polycarbonate comprises aromatic homopolycarbonate or aromatic
copolycarbonate resins.
67. The permaware polycarbonate container of claim 66, wherein the
polycarbonate has a melt flow rate of 10 to 22 g/10 min.
68. The permaware polycarbonate container of claim 61, wherein the
bottom of said base has integrally molded thereto indicia or a
configuration different from the remaining base.
69. A method of forming a container having a wall thickness greater
than 50 mils, said container containing sidewalls and an integrally
formed base, comprising: (a) blowing a parison in a blow mold
shaped in the form of said container, (b) inserting within said
blown container a core which presses the base of said container
against a mold face having thereon indicia or other structural
configurations so as to mold said indicia or other mold
configurations onto the outside surface of said base.
70. The process of claim 69, wherein said parison is formed from a
polycarbonate plastic and said parison is blown by directing fluid
pressure initially at the top of the parison and directing the
fluid pressure from said top toward said base of said parison.
71. A method of forming a container comprising: (a) injecting
molten resin into a mold cavity formed by a mold wall and a core to
form a resinous parison on the core; (b) separating the parison
from the mold wall by moving the parison on the core axially in a
straight path away from the mold wall; (c) moving the parison on
the core in a substantially arcuate path into axial alignment with
a blow mold which is in a side-by-side relationship with the mold
cavity; (d) moving the parison on the core axially in a straight
path into the blow mold; and (e) expanding the parison on the core
in the blow mold at a uniform temperature to form a hollow
container said resin selected from the group consisting of filled
polystyrene, filled and non-filled polycarbonate, polyethylene
terephthalate, polycarbonate and ABS mixtures, acrylic resins,
clarified polypropylene and polyvinylchloride.
72. The method of claim 71, wherein the filled resins contain up to
5 wt. % of nanometer-sized particles.
73. The method of claim 72, wherein said nanometer-sized particles
comprise a clay.
74. (canceled)
75. A method of forming a container having a wall thickness greater
than 50 mils, said container containing sidewalls and an
integrally-formed base, comprising: blowing a parison in a blow
mold shaped in the form of said container to form a hollow
container, inserting within said hollow container which remains in
said blow mold a core which presses the base of said container
against a mold face having thereon indicia or other structural
configurations so as to mold said indicia or other mold
configurations onto the outside surface of said base.
76. A method of forming a container comprising: (a) injecting
molten resin into a mold cavity formed by a mold wall and a core to
form a resinous parison on the core; (b) separating the parison
from the mold wall by moving the parison on the core axially in a
straight path away from the mold wall; (c) moving the parison on
the core in a substantially arcuate path into axial alignment with
a blow mold which is in a side-by-side relationship with the mold
cavity; (d) moving the parison on the core axially in a straight
path into the blow mold; and (e) expanding the parison on the core
in the blow mold by directing fluid initially at the top of the
parison and directing the fluid pressure from said top toward the
base of said parison at a uniform temperature to form a hollow
container; said resin selected from the group consisting of
polycarbonate, polyethylene terephthalate, polycarbonate and ABS
mixtures, acrylic resins, clarified polypropylene and
polyvinylchoride.
77-85. (canceled)
Description
[0001] This non-provisional patent application is based on the
following provisional applications all filed within one year of the
filing date of this application.
1 U.S. Serial No. Title Filing Date 60/110,239 Low Taper Injection
Blow-molded Nov. 30, 1998 Tumbler 60/110,240 Injection Blow-molded
Disposable Nov. 30, 1998 Tumbler 60/110,238 Large Volume Injection
Blow-molded Nov. 30, 1998 Tumbler 60/146,352 Injection Blow-molded
Polycarbonate Aug. 2, 1999 Containers 60/146,354 Process for
Injection Blow-molded Aug. 2, 1999 Containers
[0002] The disclosures of the above applications are hereby
incorporated into this application by reference thereto and the
priority of the foregoing applications is claimed in accordance
with 37 CFR 1.78.
TECHNICAL FIELD
[0003] The present invention relates generally to disposable
tumblers and in particular to injection blow-molded tumblers of
various configurations having a fortified rim at the upper
extremity of the sidewall.
BACKGROUND
[0004] Disposable polymeric articles for packaging, bowls and cups
are well known. Such articles are formed of polystyrene,
polypropylene, polyethylene terephthalate and the like and may be
made by thermoforming, injection molding, injection blow-molding,
or other suitable technique. Injection molding has advantages in
that a short cycle time is readily achieved, but tends to be more
expensive in terms of material and articles so formed tend to have
anisotropic properties and therefore exhibit brittleness.
Thermoforming likewise tends to have advantageous cycle times,
however, the waste generated tends to be excessive. Moreover, the
draw which may be imposed on the sheet is limited. U.S. Pat. No.
5,693,278 discloses thermoformed articles produced from
polyethylene terephthalate sheet. The excessive waste problem is
addressed in the '278 patent by utilizing at least forty percent
(40%) by weight recycled material.
[0005] U.S. Pat. No. 5,433,337 of Willbrandt discloses an injection
molded drink container to fit in vehicle cup holders. The container
has an upper rim 20 with a height of from about {fraction (1/16)}
of an inch to about {fraction (1/10)} of an inch and a width of
from about 0.15 inches to about 0.25 inches. Note Col. 5 at lines
15-25. U.S. Pat. No. 5,427,269 notes at Col. 5 that this type of
container may be produced by an suitable method, but that injection
molding is preferred.
[0006] As noted hereinabove, injection molding tends to be
expensive in terms of material, requiring relatively thick-walled
parts to compensate for the anisotropy inherent in the production
technique. Disposable containers are preferably made utilizing as
little material as possible.
[0007] Many consumers are generally reluctant to use conventional
disposable drinking cups on a frequent basis due to their "look and
feel", their expense, or their performance. Survey data indicate
that consumers in many instances prefer disposable articles whose
appearance and performance more closely resemble glassware.
Conventional disposable drinking cups produced by blow-molding
typically rely upon a relatively prominent curled rim to provide
rigidity to the article and accordingly, the article does not
resemble glassware to the extent desired. Moreover, even with the
prominent top-curl, conventional blow-molded cups typically are not
rigid enough to mimic glassware. Injection blow-molding processes
and apparatus are widely known and widely used in industry. For
example, reference may be had to U.S. Pat. No. 3,183,552 to Farkas,
U.S. Pat. No. 3,819,314 to Marcus, U.S. Pat. No. 3,339,231 to
Piotrowski and Canadian Pat. No. 995,418 to Cannon et al.
[0008] It is known, in general, to use injection blow-molding of
polycarbonates to produce an assortment of containers, see
Kirk-Othmer Encyclopedia of Chemical Technology, Fourth Edition,
Vol. 19, p. 600. Further, U.S. Pat. No. 4,139,517 discloses
reusable milk bottles composed of aromatic polycarbonates and is
specifically directed to a tinted polycarbonate container to
prevent milk spoilage caused by artificial light or sunlight. The
patent discloses that the containers can be prepared by well-known
techniques, such as extrusion blow-molding, injection blow-molding,
rotational molding, thermoforming, injection molding and
lamination. No specific processing conditions for the mentioned
molding techniques are given.
[0009] U.S. Pat. Nos. 4,225,304; 4,230,298; 4,234,302 and
4,308,086, issued to Valyi, disclose a continuous process and
apparatus for blow-molding, including injection blow-molding,
containers formed of various plastics including polycarbonates.
Again, no specific process parameters for producing polycarbonate
containers are provided. It is and has been a long standing
objective of blow-molding processes to achieve a high productivity,
i.e., to develop a process with a rapid, efficient and economical
operating cycle.
[0010] State of the art processes known heretofore are subject to
one or more significant disadvantages. Frequently, they are
characterized by a relatively slow operating cycle. A shorter
operating cycle is particularly desirable since it is directly
translatable into a larger number of end products produced.
Processes are known with overlapping cycles in order to reduce
overall cycle time, for example, by providing that while one
parison is being molded another is being blown and still another is
being removed. However, even with processes using overlapping
cycles the overall cycle time still leaves much to be desired and
still necessitates improvement in cycle time. The foregoing
difficulties are further compounded by frequent lack of reliability
of prior art processes necessitating frequent interruptions of the
operation and thereby further impairing operating efficiency.
[0011] U.S. Pat. No. 4,540,543 assigned to Canada Cup, Inc., a
subsidiary of Fort James Corporation, discloses an injection
blow-molding process and apparatus for hollow plastic articles. The
method and apparatus for injection blow-molding hollow plastic
articles is characterized by a rapid and efficient operating cycle.
The injection mold includes a mold cavity and the blow mold is
located adjacent the mold cavity in a side-by-side relationship.
The parison is injection molded into the mold cavity onto a core.
The parison on the core is separated from the mold cavity by moving
the parison on the core axially in a straight path away from the
mold cavity, followed by movement in a substantially arcuate path
into axial alignment with the blow mold, followed by axial movement
in a straight path into the blow mold. The advantage of the method
and apparatus of injection blow-molding disclosed in U.S. Pat. No.
4,540,543 compared to previous injection blow-molding methods is in
its reliability, preventing interruptions of the injection
blow-molding operation and thereby improving efficiency. The method
and apparatus as disclosed in U.S. Pat. No. 4,540,543 have been
used to manufacture thin walled containers from polystyrene. In
particular, disposable containers have been successfully produced
from polystyrene. Such polystyrene containers are desirable because
they are reusable and have aesthetic clarity. However, for
producing permanent ware products which have a nominal thickness
typically over 50 mils, it has been found that polystyrene was not
acceptable because of breakage. When producing blow-molded
permaware containers, it is often useful to incorporate onto the
base indicia indicating the origin of manufacture or provide other
spatial configurations to the base to aid in subsequent processing
steps such as printing or packaging. However, for relatively thick
bases, the fluid pressure used in blow-molding is not sufficient to
adequately press the parison base against a mold and form an
adequately deep molded impression on the base. Previously, such
base molding step was accomplished by removing the containers from
the continuous blow-molding process and stamping the base of the
containers in a wholly separate apparatus. Such separate processing
adds significant energy and time costs to the overall process.
[0012] Accordingly, an object of the present invention is to
provide a reusable permanent ware polycarbonate container prepared
by injection blow-molding wherein the container mimics glass but is
not as breakable when dropped under normal usage.
[0013] Another object of the present invention is to provide a
reusable, permanent ware injection blow-molded polycarbonate
container that has good clarity but is more durable than other
plastic containers such as those formed from polystyrene.
[0014] A further object of the present invention is to provide a
process for injection blow-molding hollow polycarbonate articles
characterized by a rapid, efficient and economical operating
cycle.
[0015] A still further object of the present invention is to
provide a process as aforesaid which is convenient and easy to use
on a commercial scale and may be reliably used with high
productivity.
[0016] Still yet another object of the present invention is to
provide a process for injection blow-molding hollow articles
characterized by a rapid, efficient and economical operating cycle
such as provided by U.S. Pat. No. 4,540,543, but use resins other
than polystyrene.
[0017] A still further object of this invention is to blow mold
hollow permaware containers and mold the base of such containers in
a continuous process without having to remove the containers from
the blow-molding apparatus.
[0018] Other objects and advantages of the present invention will
become apparent form the following description and drawings.
SUMMARY OF INVENTION
[0019] In a first aspect of the invention there is provided an
injection blow-molded disposable tumbler exhibiting biaxial
toughness formed from a polymeric material comprising: a base
forming the bottom of the tumbler defining an outer edge thereof; a
sidewall integrally formed with said base extending upwardly from
the outer edge thereof defining about its upper extremity a
fortified rim.
[0020] In one preferred embodiment of the present invention there
is provided an injection blow-molded disposable tumbler exhibiting
biaxial toughness formed from a polymeric material including: a
base forming the bottom of said tumbler defining an outer edge
thereof; a sidewall integrally formed with the base extending
upwardly from the outer edge thereof having a thickness of from
about 5 to about 50 mils defining about its upper extremity a
fortified rim; the sidewall extending upwardly with a taper of from
about 1.0 to about 4.5 degrees; wherein the fortified rim has a
thickness of at least 2 mils greater than the adjacent portion of
said sidewall over a height of at least 2 mils. More typically, the
sidewall extends upwardly with a taper of from about 2.75 to about
4 degrees; and preferably the sidewall extends upwardly with a
taper of about 3 degrees. The fortified rim generally has a
thickness and a height of from about 1.5 to about 6 times the
thickness of the adjacent portion of the sidewall; with from about
3 to about 5 times the thickness of the adjacent portion of said
sidewall being more typical. The tumbler is made from a polymer
which is a thermoplastic optically clear polymer, with a haze value
of less than 10, usually selected from the group consisting of
polystyrene, clarified polypropylene, polyesters, polycarbonates,
polyacrylates and styrene acrylonitrile. The volume of said
injection blow-molded tumbler is generally from about 1.5 to about
4 times the volume of an injection molded parison from which it was
prepared; however, a volume of from about 1.75 to about 3 times the
volume of the injection molded parison from which it was prepared
is more typical, while a volume of the tumbler of about twice the
volume of the injection molded parison from which it was prepared
is sometimes preferred. The sidewall has a thickness of from about
10 to about 35 mils, with from about 15 to about 25 mils being more
common. A thickness of about 20 mils is preferred in many
instances. The sidewall may further include a pattern which alters
the cylindrical character thereof over at least a portion of the
sidewall which pattern is operative as a grip portion for a user. A
ratio of the height of the tumbler to the inside diameter of the
upper portion of the sidewall is from about 2 to about 4 in some
embodiments, for example, about 3. The tumbler may have a contained
volume of from about 12 to about 15 ounces, or inner volume of
about 14 ounces. In some embodiments, the tumbler has a height of
from about 5.75 to about 6 inches.
[0021] In another embodiment, there is provided an injection
blow-molded disposable tumbler exhibiting biaxial toughness formed
of a polymeric material including: (a) a base forming the bottom of
the tumbler defining an outer edge thereof; (b) a sidewall
integrally formed with the base extending upwardly from the outer
edge thereof having a thickness of from about 5 to about 50 mils
defining about its upper extremity a fortified rim; (c) the
sidewall extending upwardly with a taper of from about 2.5 to about
10 degrees; wherein the fortified rim has a thickness of at least 2
mils greater than the adjacent portion of the sidewall over a
height of at least 2 mils. The sidewall typically extends upwardly
with a taper of from about 4.5 to about 10 degrees and preferably
the sidewall extends upwardly with a taper of from about 4.5 to
about 7.5 degrees. The fortified rim generally has a thickness and
a height of from about 1.5 to about 6 times the thickness of the
adjacent portion of the sidewall, with from about 3 to about 5
times the thickness of the adjacent portion of said sidewall being
more typical. The tumbler is usually formed of optically clear
polymer with a haze value of less than 10 selected from the group
consisting of polystyrene, clarified polypropylene, polyesters,
polycarbonates, polyacrylates and styrene acrylonitrile. The
contained volume of the tumbler is generally from about 1.5 to
about 4 times the volume of an injection molded parison from which
it was prepared; while from about 1.75 to about 3 times the volume
of the injection molded parison from which it was prepared is more
typical. The tumbler is about twice the volume of the injection
molded parison from which it was prepared. The tumbler sidewall has
a thickness of from about 10 to about 35 mils in general, whereas,
the sidewall has a thickness of from about 15 to about 25 mils in
most embodiments. Particularly preferred articles are those wherein
the sidewall has a thickness of about 20 mils. The said sidewall
may further include a pattern which alters the cylindrical
character thereof over at least a portion of said sidewall which
pattern is operative as a grip portion for a user. The tumbler
typically exhibits a ratio of the height of the tumbler to the
inside diameter of the upper portion of the sidewall from about 1
to about 5; whereas from about 1.3 to about 1.7 is preferred. The
height of the tumbler is from about 4.6 to about 4.8 inches and it
has a typical volume of from about 12 to about 16 ounces; while
about 15 fluid ounces is preferred in this embodiment.
[0022] In another embodiment, there is provided an injection
blow-molded disposable tumbler exhibiting biaxial toughness formed
of a polymeric material including; a base forming the bottom of the
tumbler defining an outer edge thereof; a sidewall integrally
formed with the base extending upwardly from the outer edge thereof
having a thickness of from about 5 to about 50 mils defining about
its upper extremity a fortified rim; the sidewall extending
upwardly with a taper of from about 1 to about 10 degrees; wherein
the fortified rim has a thickness of at least 2 mils greater than
the adjacent portion of the sidewall over a height of at least 2
mils, said tumbler defining a volume of at least about 16 fluid
ounces. More typically, the sidewall extends upwardly with a taper
of from about 2.75 to about 9 degrees and preferably with a taper
of from about 5 to about 7 degrees. The fortified rim generally has
thickness and a height of from about 1.5 to about 6 times the
thickness of the adjacent portion of the sidewall, while a
thickness and height of from about 3 to about 5 times the thickness
of the adjacent portion of the sidewall is preferred. The tumbler
is made from a polymeric material which is an optically clear
polymer with a haze value of less than 10, selected from the group
consisting of polystyrene, clarified polypropylene, polyesters,
polycarbonates, polyacrylates and styrene acrylonitrile. The volume
of the injection molded tumbler is typically from about 1.5 to
about 4 times the volume of an injection molded parison from which
it was prepared and the tumbler defines a volume of from about
16-20 fluid ounces.
[0023] The present invention is directed in still yet another
embodiment to a reusable, permanent ware polylycarbonate container
and method of making the polycarbonate container. The polycarbonate
container mimics the clarity of glass without having the
undesirable fragile property of glass and is more durable than
other plastic containers such as polystyrene containers. Thus, the
polycarbonate containers or tumblers have the look and feel of
glass permaware and can be employed in normal usage without concern
for breakage if the container is dropped. The container or tumbler
includes a base, a sidewall and a fortified upper rim. The sidewall
is integrally formed with the base and extends upwardly from the
outer edge thereof. The sidewall is of uniform caliper or thickness
of about greater than 50 thousandths of an inch ("mils") to about
500 thousandths of an inch. The tumbler preferably has a mouth
(upper rim) which is about as wide or wider than the diameter of
the remainder of the tumbler. Such containers are not as easily
handled during the blow-molding process as blow-molded bottles and
the like in which the mouth of the bottle is substantially less
than the diameter of the shoulders and remaining portions of the
bottle. At the upper extremity of the sidewall or mouth can be
provided a fortified rim which serves to impart additional rigidity
to the container. The fortified rim area has a finite width and
height both of which exceed the thickness of the adjacent sidewall.
While the tumbler is generally cylindrical in overall shape, the
tumbler can be provided with either a uniform or non-uniform taper.
The tumbler can be embossed to impart a decorative pattern on the
sidewall. The permaware polycarbonate container of the present
invention is preferably prepared by a side-by-side injection
blow-molding method and apparatus as disclosed in U.S. Pat. No.
4,540,543. The patented method comprises: providing an injection
mold including a mold cavity formed by a mold wall and a core;
injecting molten polycarbonate into the cavity to form a parison on
the core; separating said parison from the mold wall by moving the
parison on the core axially in a straight path away from the mold
wall; providing a blow mold adjacent the mold cavity in
side-by-side relationship therewith; moving the parison on the core
in a substantially arcuate path into axial alignment with the blow
mold; moving the parison on the core axially in a straight path
into the blow mold; and expanding the parison on the core in the
blow mold at a uniform temperature to form the hollow container.
The apparatus comprises: an injection mold including a mold wall; a
core engageable with said injection mold to form a mold cavity with
the mold wall; means to inject molten polycarbonate into the mold
cavity to form a parison therein; a blow mold adjacent the mold
cavity in side-by-side relationship therewith; means to separate
the parison from the mold wall operative to move the parison
axially in a straight path away from the mold wall, followed by in
a substantially arcuate path into axial alignment with the blow
mold, followed by axially in a straight path into the blow mold;
and means to expand the parison on the core in the blow mold to
form the hollow container. The core is preferably separated from
the hollow container leaving the container in the blow mold and
returned to the injection mold for another cycle along paths
corresponding to the foregoing path, i.e., axially, substantially
arcuate and axially into the injection mold. An ejection station
may then be provided adjacent the blow mold in side-by-side
relationship. An ejection core can transfer the hollow container
from blow mold to ejection station and return along paths
corresponding to the paths of the core. In one embodiment, a second
core, second ejection station, second blow mold and second ejection
core are provided on the side opposed to the blow mold and ejection
station for operation of an overlapping cycle. The second core and
second ejection core move on paths corresponding to the paths of
the core and ejection core. That is, when the core is in the blow
mold the second core is in the injection mold. A major advantage of
the patented blow-molding process resides in the rapid operating
cycle enabled by the critical movement paths. Also, the process and
apparatus are simple, convenient to operate and reliable. The
resultant high productivity is a significant feature. In this
aspect of the invention a method of forming a durable polycarbonate
permaware container includes: (a) injecting molten polycarbonate
into a mold cavity formed by a mold wall and a core to form a
polycarbonate parison on the core; separating the parison from the
mold wall by moving the parison on the core axially in a straight
path away from the mold wall; moving the parison on the core in a
substantially arcuate path into axial alignment with a blow mold
which is in a side-by-side relationship with the mold cavity;
moving the parison on the core axially in a straight path into the
blow mold; and expanding the parison on the core in the blow mold
at a uniform temperature to form a hollow container having a
sidewall integrally formed to a base and a fortified rim, the
sidewall having a uniform thickness of from about greater than 50
mils to about 500 mils. More typically, the sidewall has a uniform
thickness of from about 75 mils to about 375 mils. In most
instances, the polycarbonate is injected into the mold cavity at a
temperature of from about 450.degree. F. to about 700.degree. F.
and more typically, at a temperature of from about 500.degree. F.
to about 650.degree. F. In general, the molten polycarbonate is
injected into the mold cavity at a pressure of about 1,000 to 3,000
psi and in a preferred embodiment at an injection pressure of about
2,100 psi. The parison is expanded at a uniform temperature of from
about 250.degree. F. to about 500.degree. F., at a pressure of from
about 100 to about 500 psi. Typically, the polycarbonate comprises
aromatic homopolycarbonate or aromatic copolycarbonate resins with
a melt flow rate of from about 10 to 22 g/10 min. The polycarbonate
tumbler is an injection blow-molded polycarbonate permaware hollow
container comprising: a base forming the bottom of the container
defining an outer edge thereof; a sidewall integrally formed with
the base extending upwardly from the outer edge thereof and having
a thickness of from about over 50 to about 500 mils to a fortified
rim about its upper extremity. The fortified rim has a thickness of
at least 2 mils greater than an adjacent portion of the sidewall
over a height of at least 2 mils. Both the width and height of the
fortified rim are from about 1.1 to about 4 times a thickness of an
adjacent sidewall. In a particularly preferred article, both the
width and the height of the fortified rim are about 100 mils and
the adjacent sidewall is about 80 mils. The base is from about 1.1
to about 8 times the thickness of the sidewall. The permaware
polycarbonate container is preferably one wherein the bottom of the
base has integrally molded thereto indicia or a configuration
different from the remaining base. A particularly preferred method
of forming a container having a wall thickness greater than 50 mils
comprises: blowing a parison in a blow mold shaped in the form of
said container; inserting within said blown container a core which
presses the base of said container against a mold face having
thereon indicia or other structural configurations so as to mold
said indicia or other mold configurations onto the outside surface
of the base. Most preferably, the parison is formed from a
polycarbonate plastic and the parison is blown by directing fluid
pressure initially at the top of the parison and directing the
fluid pressure from the top toward said base of said parison.
[0024] The present invention is directed in still yet another
aspect to improvements in forming permaware containers by a
continuous blow-molding process. The invention is also directed to
improvements in the blow-molding process as disclosed in U.S. Pat.
No. 4,540,543 so as to form containers from resins other than
polystyrene.
[0025] The present invention is characterized in these latter
aspects as a side-by-side injection blow-molding method and
apparatus and is at least in part disclosed in U.S. Pat. No.
4,540,543. The patented method comprises: providing an injection
mold including a mold cavity formed by a mold wall and a core;
injecting molten resin into the cavity to form a parison on the
core; separating said parison from the mold wall by moving the
parison on the core axially in a straight path away from the mold
wall; providing a blow mold adjacent the mold cavity in
side-by-side relationship therewith; moving the parison on the core
in a substantially arcuate path into axial alignment with the blow
mold; moving the parison on the core axially in a straight path
into the blow mold; and expanding the parison on the core in the
blow mold at a uniform temperature to form the hollow container.
The apparatus comprises: an injection mold including a mold wall; a
core engageable with said injection mold to form a mold cavity with
the mold wall; means to inject molten resin into the mold cavity to
form a parison therein; a blow mold adjacent the mold cavity in
side-by-side relationship therewith; means to separate the parison
from the mold wall operative to move the parison on the core
axially in a straight path away from the mold wall, followed by in
a substantially arcuate path into axial alignment with the blow
mold, followed by axially in a straight path into the blow mold;
and means to expand the parison on the core in the blow mold to
form the hollow container. The core is preferably separated from
the hollow container leaving the container in the blow mold and
returned to the injection mold for another cycle along paths
corresponding to the foregoing path, i.e., axially, substantially
arcuate and axially into the injection mold. An ejection station
may then be provided adjacent the blow mold in side-by-side
relationship. An ejection core can transfer the hollow container
from blow mold to ejection station and return along paths
corresponding to the paths of the core. In an additional
embodiment, a second core, second ejection station, second blow
mold and second ejection core are provided on the side opposed to
the blow mold and ejection station for operation of an overlapping
cycle. The second core and second ejection core move on paths
corresponding to the paths of the core and ejection core. That is,
when the core is in the blow mold the second core is in the
injection mold. Obviously, additional cores, ejection stations,
blow molds, and ejection cores can be provided and operated in an
overlapping cycle to increase productivity. A major advantage of
the patented blow-molding process resides in the rapid operating
cycle enabled by the critical movement paths. Also, the process and
apparatus are simple, convenient to operate and reliable. The
resultant high productivity is a significant feature.
[0026] In accordance with this invention, the above patented
process is used to form injection blow-molded containers formed of
polymers other than polystyrene. Thus, it has been found that the
above patented process can be used to form clear containers from
resins such as polycarbonate, polyethylene terephthalate,
polycarbonate/ABS mixed resin, acrylic resins, clarified
(amorphous) polypropylene and polyvinylchloride. Additionally, the
present invention is directed to a process of molding the base of a
blown container without removing the container from the blow mold.
In this invention, after the parison is blown to the container in
the blow cavity, an ejection core is inserted into the container
while the container remains in the blow cavity. The ejection core
pushes the base of the container against a mold opposed to the
outside surface of the container base. The mechanical pressure of
the ejection core against the container base is sufficient to
adequately transfer the molded configuration of the mold onto the
outside surface of the container base. Once the base is molded, the
container can be removed from the blow cavity by the ejection core
on a continuous basis. The continuous process saves considerable
time and energy over prior art processes which required a stamping
step after the container had been removed from the blow cavity.
There is thus provided a method of forming a container comprising:
injecting molten resin into a mold cavity formed by a mold wall and
a core to form a resinous parison on the core; separating the
parison from the mold wall by moving the parison on the core
axially in a straight path away from the mold wall; moving the
parison on the core in a substantially arcuate path into axial
alignment with a blow mold which is in a side-by-side relationship
with the mold cavity; moving the parison on the core axially in a
straight path into the blow mold; and expanding the parison on the
core in the blow mold at a uniform temperature to form a hollow
container; wherein the resin is selected from the group consisting
of filled polystyrene, filled and non-filled polycarbonate,
polyethylene terephthalate, polycarbonate and ABS mixtures, acrylic
resins, clarified polypropylene and polyvinylchlroide. The filled
resins contain up to 5 wt. % of nanometer-sized particles which may
comprise a clay. In one embodiment, a transparent drinking tumbler
is comprised of polystyrene filled with nanometer-sized particles
having a size within the range of visible-light wavelengths. In
another aspect, there is provided a method of forming a container
having a wall thickness greater than 50 mils, the container
containing sidewalls and an integrally formed base, the method
comprising: blowing a parison in a blow mold shaped in the form of
the container to form a hollow container, inserting within the
hollow container, which remains in the blow mold, a core which
presses the base of the container against a mold face having
thereon indicia or other structural configurations so as to mold
the indicia or other mold configurations onto the outside surface
of the base. Another method involves forming a container
comprising: (a) injecting molten resin into a mold cavity formed by
a mold wall and a core to form a resinous parison on the core; (b)
separating the parison from the mold wall by moving the parison on
the core axially in a straight path away from the mold wall; (c)
moving the parison on the core in a substantially arcuate path into
axial alignment with a blow mold which is in a side-by-side
relationship with the mold cavity; (d) moving the parison on the
core axially in a straight path into the blow mold; and (e)
expanding the parison on the core in the blow mold by directing
fluid initially at the top of the parison and directing the fluid
pressure from the top toward the base of the parison at a uniform
temperature to form a hollow container; there the resin is selected
from the group consisting of polycarbonate, polyethylene
terephthalate, polycarbonate and ABS mixtures, acrylic resins,
clarified polypropylene and polyvinylchloride.
[0027] In still further embodiments of the present invention, there
is provided an injection blow-molded tumbler with a fortified rim
having a thickness greater than the adjacent sidewall formed of a
polymeric material including a styrene/butadiene copolymer. In
general, the copolymer is from about 2 to about 40 percent by
weight butadiene residue with from about 8 to about 15 percent by
weight butadiene residue in the composition being typical. The
tumbler may consist entirely of butadiene/styrene copolymer, or the
copolymer may be blended with other polymers, for example,
polystyrene.
[0028] Alternatively, polystyrene or other polymeric composition
may be provided with an impact modifier. Typically, impact
modifiers may be core-shell polymers, olefin containing copolymers,
rubber polymers, rubber copolymers, styrene containing copolymers
and mixtures thereof. So also, the inventive tumblers may be made
from filled polymeric compositions including conventional filler
such as mica, talc and the like. Suitable filled compositions may
include from 5 to 50 weight percent filler, with from about 8 to
about 20 percent filler being more typical. From about 10 to about
15 weight percent filler is perhaps most suitable for the injection
blow-molded tumblers.
BRIEF DESCRIPTION OF DRAWINGS
[0029] The invention is described in detail below with reference to
numerous examples and drawings. In the drawings:
[0030] FIG. 1(a) is a view in elevation of a tumbler produced in
accordance with the present invention;
[0031] FIG. 1(b) is a plan view of the bottom of the tumbler of
FIG. 1(a);
[0032] FIG. 1(c) is a partial view in elevation of the tumbler of
FIG. 1(a) showing the molded-in design of the tumbler of FIG. 1(a)
and illustrating the taper of the tumbler;
[0033] FIG. 2(a) is a view in elevation of another tumbler
constructed in accordance with the present invention;
[0034] FIG. 2(b) is a plan view of the bottom of the tumbler of
FIG. 2(a);
[0035] FIG. 3(a) is a view in elevation of yet another tumbler
constructed in accordance with the present invention;
[0036] FIG. 3(b) is a plan view of the bottom of the tumbler of
FIG. 3(a);
[0037] FIG. 3(c) is a partial view in elevation of the tumbler of
FIG. 3(a) showing the molded-in design and illustrating the taper
of the tumbler;
[0038] FIG. 3(d) is a schematic view illustrating the angular
relationships of the design of FIGS. 3(a)-(c);
[0039] FIG. 4(a) is a schematic view illustrating the "lip curl" of
a conventional blow-molded plastic cup;
[0040] FIG. 4(b) is a schematic view illustrating the solid-bead
fortified rim of a tumbler produced in accordance with the present
invention; and
[0041] FIG. 5 is a schematic drawing illustrating the manufacture
of a tumbler in accordance with the present invention.
[0042] FIG. 6(a) is a view in elevation of a tumbler constructed in
accordance with the present invention;
[0043] FIG. 6(b) is a plan view of the bottom of the tumbler of
FIG. 6(a);
[0044] FIG. 6(c) is a partial view in elevation of the tumbler of
FIG. 6(a) showing the grip design in greater detail;
[0045] FIG. 7(a) is a view in elevation of an alternate embodiment
of a tumbler constructed in accordance with the present invention
with a fluted design;
[0046] FIG. 7(b) is a plan view of the bottom of the tumbler of
FIG. 7(a) showing 1 fluted surface;
[0047] FIG. 8 is a view in elevation of still yet another tumbler
constructed in accordance with the present invention;
[0048] FIG. 9 is an elevational view showing in more detail an
apparatus preferably used in the present invention to form tumblers
of the present invention, the apparatus being in the closed
position with the core in the injection mold;
[0049] FIG. 10 is a view similar to FIG. 9 with the apparatus in
the open position with the core and parison in the midst of
transfer to the blow mold;
[0050] FIG. 11 is a view similar to FIG. 9 with the apparatus in
the closed position with the core and parison in the blow mold and
with the second core in the injection mold;
[0051] FIG. 12 is a partial, expanded elevational view showing
additional details;
[0052] FIG. 13 is a detailed view of the ejection core engaged with
the hollow article in the blow mold;
[0053] FIGS. 14 and 15 are partial views showing alternate core
embodiments;
[0054] FIG. 16 is a line chart showing core movement from injection
mold to blow mold and return;
[0055] FIG. 17(a) is an elevation of a polycarbonate cup made by
injection blow-molding;
[0056] FIG. 17(b) is the bottom or base of the polycarbonate cup of
FIG. 17(a);
[0057] FIG. 17(c) is the fortified rim of the polycarbonate cup of
FIG. 17(a);
[0058] FIG. 18 is a cross sectional view of an alternative ejection
core which also provides a means to mold the base of the container;
and
[0059] FIG. 19 is a cross sectional view of an alternative blow
mold.
DETAILED DESCRIPTION
[0060] The invention is described below in connection with various
embodiments and aspects. Modifications to particular embodiments
within the spirit and scope of the present invention, which is set
forth in the appended claims, will be apparent to those of skill in
the art.
[0061] Disposable tumblers in accordance with the present invention
more closely resemble conventional glassware and mimic its
rigidity, performance and "look and feel" than do previously known
blow-molded articles. Salient features include the biaxial-induced
toughness of the blow-molded article, as well as rigidity achieved
by combing a relatively low taper with a fortified upper rim.
Conventional blow-molded cups typically include a very prominent
curled lip which is not consistent with glassware and tends to make
the article unappealing for everyday use or for use with
guests.
[0062] There is shown in FIGS. 1(a) through 1(c) a tumbler 10
constructed in accordance with the present invention. In general,
tumbler 10 has a base portion 12, a sidewall portion 14 and an
upper circular rim portion 16 which extends about the periphery 18
of an opening 20 of tumbler 10. Base portion 12 of tumbler 10 is
integrally formed with the rest of the tumbler and includes a
bottom 22 which has a meniscus portion 24 and a base sidewall 26.
Base sidewall 26 is typically thicker than sidewall 14, and has
substantially zero taper.
[0063] Tumbler 10 is optionally provided with a molded-in design 28
which is more clearly seen by reference to FIGS. 1(b) and 1(c).
Base sidewall 26 extends upwardly to define an outer edge 30 which
attaches to sidewall 14. Sidewall 14 extends upwardly to fortified
rim 16. Rim 16 is integrally formed with sidewall 14 and is a
continuous generally circular or oval, solid polymer bead extending
about periphery 18 of opening 20. Rim 16 has a width 31 which is
defined by the difference between an inner diameter 32 and an outer
diameter 34 of rim 16 and a height 35 which is the distance over
which width 31 extends. Width 31 is thicker than adjacent sidewall
portion 38 which is typically of the same caliper as the reset of
sidewall 14. In the example shown in FIGS. 1(a)-1(c), adjacent
sidewall portion 38 has a thickness of 10 mils, height 35 is
approximately 28 mils and width 31 is approximately 40 mils at its
thickest point.
[0064] Other dimensions of tumbler 10 are indicated on FIG. 1(a).
Base portion 12 has a diameter D, at edge 30 of about 2.125 inches,
an outer upper diameter 34 of 2.770 inches an inner upper diameter
32 of 2.730 inches. The overall height, H, of tumbler 10 is 5.785
inches. These dimensions define an angle of taper T as shown about
imaginary central axis 40 of about 3.degree. for sidewall 14 of
tumbler 10. As used herein "taper", "degree of taper" and like
terminology indicates the angle that the sidewall of the inventive
tumbler makes with the imaginary central longitudinal axis defined
by the sidewall which is substantially perpendicular to bottom 22,
the taper of the article may also be thought of as the angle the
sidewall makes with the bottom less 90 degrees.
[0065] FIG. 1(c) shows a molded in swirl design 28 which extends
from base portion 12 to roughly 50 percent of the height of tumbler
10. Design 28 is comprised of wall embossments at least as
prominent as 12 the caliper of sidewall 14 and typically of the
same thickness or prominence of the sidewall. Thus, design 28
substantially alters the topography of sidewall 14 and provides a
secure grip for a user, as well as a modicum of longitudinal
reinforcement.
[0066] There is shown in FIGS. 2(a) and 2(b) another tumbler 210
constructed in accordance with the present invention. In general,
tumbler 210 has a base portion 212, a sidewall portion 214 and an
upper circular fortified rim portion 216 which extends about the
periphery 218 of an opening 220 of tumbler 210. Base portion 212 of
tumbler 210 is integrally formed with the rest of the tumbler and
includes a bottom 222 which has a meniscus portion 224 and a base
sidewall 226. Base sidewall 226 is typically thicker than sidewall
214, and has slightly reversed taper as opposed to the taper of
sidewall 214.
[0067] Tumbler 210 is provided with a molded-in design 228 which is
a series of concentric rings as shown on FIGS. 2(a) and 2(b). The
dimensions of tumbler 210 are otherwise substantially identical to
the dimensions of the tumbler 10 of FIGS. 1(a)-1(c).
[0068] There is shown in FIGS. 3(a) through 3(d) a tumbler 310
constructed in accordance with the present invention. In general,
tumbler 310 has a base portion 312, a sidewall portion 314 and an
upper circular fortified rim portion 316 which extends about the
periphery 318 of an opening 320 of tumbler 310. Base portion 312 of
tumbler 310 is integrally formed with the rest of the tumbler and
includes a bottom 322 which has a meniscus portion 324 and a base
sidewall 326. Base sidewall 326 is thicker than sidewall 314 and
has a slight taper.
[0069] Tumbler 310 is optionally provided with a "cut-glass"
molded-in design 328 which is most clearly seen by reference to
FIGS. 3(b) and 3(c). The molded in design defines a series of
triangular ridges which are deeper in dimension than the wall
caliper of sidewall 314, thus providing strength by way of
corrugation. The molded in cut glass grooves 328 have a wall
thickness the same as the rest of the tumbler and a depth of up to
about {fraction (1/8)} inch as shown.
[0070] Base sidewall 326 extends upwardly to define an outer edge
330 which attaches to sidewall 314. Sidewall 314 extends upwardly
to fortified rim 316. Rim 316 is integrally formed with sidewall
314 and is a continuous generally circular or oval, solid polymer
bead extending about periphery 318 of opening 320. Rim 316 has a
width 331 which is defined by the difference between an inner
diameter 332 and an outer diameter 334 of rim 316 and a height 335
which is the longitudinal distance over which width 331 extends.
Width 331 is thicker than adjacent sidewall portion 338 which is
typically of the same caliper as the rest of sidewall 314. In the
example shown, adjacent sidewall portion 338 has a thickness of 20
mils height 335 is approximately 28 mils and width 331 is
approximately 40 mils at its thickest point. Other dimensions of
tumbler 310 are approximately identical to those of tumblers 210 of
FIGS. 2(a) and 2(b) and tumbler 10 of FIGS. 1(a)-1(c). Tumbler 310
thus has a taper of 3.degree..
[0071] Tumbler 310 is particularly rigid due to the triangular
ridge "cut glass" pattern 328 which extends upwardly from the base
over about 40% of the height of the glass, forming a grip for the
user, as can best be appreciated from FIG. 3(b). As can be seen
from FIG. 3(b), the ridges are accordion shape when viewed in
section, wherein segments have flat surfaces 344 having a width of
one quarter of an inch or so. As shown in FIGS. 3(c) and 3(d),
there is an angle, S, between connected segments of 130 degrees and
each triangular segment extends over an angle S1 of about 15
degrees of the periphery of the tumbler.
[0072] Referring to FIG. 4(a), there is schematically depicted a
lip curl characteristic of prior art disposable drinking cups. In
general, such prior art cups have a sidewall 414a of a given
thickness D.sub.4a which extends upwardly into a curl generally
indicated at 450.sub.a. The curl has a characteristic radius
R.sub.a as well as a height H.sub.a and a width W.sub.a. Such
structures are sometimes called "open top curls" and may be seen,
for example, in U.S. Pat. No. 4,540,543. See FIG. 4 thereof at
31.
[0073] FIG. 4(b) schematically depicts in section and elevation a
solid polymer bead about the upper periphery of a tumbler, that is,
an embodiment of the fortified rim of the present invention which
extends around the upper periphery of the inventive tumbler. The
tumbler has a sidewall 414b of thickness D.sub.4b. The fortified
rim, 416b is formed of solid polymer integrally formed with
sidewall 414b and has a height H.sub.b and width W.sub.b as
indicated. Inasmuch as the cross section of the embodiment shown in
circular, the width W.sub.a is approximately equal to the height
W.sub.b.
[0074] Bead 416b has advantages over the prior art top curl,
whether or not one is seeking to mimic glassware. For one, it
rounded and will not tend to snag on the mold or snag with a cup
cover as to prior art top-curls. For another advantage, a bead type
top rim can more compactly provide rigidity to a cup than does a
top curl, with less width. While polymer bead 416b is shown as
circular in cross section, other profiles may be suitable for
example, conic sections such as ellipsoid shapes of truncated conic
sections or profiles such as truncated conic section including a
semi-circle or a half ellipse.
[0075] As noted above, tumblers in accordance with the present
invention are produced by injection blow-molding. Optically opaque
materials may be used, however, optically transparent polymers are
usually preferred. Particularly preferred polymers include crystal
polystyrene available from Dow Corporation, Midland, Mich., grade
685d. this polymer may be used to produce the inventive tumblers by
the method of U.S. Pat. No. 4,540,543, the disclosure of which is
incorporated herein by reference. The subject apparatus and method
is generally shown and described in connection with FIG. 5.
[0076] There is illustrated in FIG. 5 an injection mold 555, a blow
mold 557 and an ejection station 559. Together with core 561, mold
555 defines an injection mold cavity wherein a parison 563 is
injection molded. Core 561, mold 555 are provided with passageways
565 to apply fluid pressure to aid processing of the tumbler noted
in the '543 patent. After injection molding, parison 563 is
retained on core 40 and moved to blow mold 557. Parison 563 is of
predetermined volume and has at its upper periphery a fortified rim
516 in accordance with the invention. The parison is expanded to
the desired shape in blow mold 557 to a volume of from about 1.5 to
about 4 times its former volume on core 561. This process imparts
biaxial orientation to the article, reducing the anisotropy
inherent in the injection molding process and proving biaxial
toughness to the article.
[0077] There is shown in FIGS. 6(a) through 6(c) a tumbler 610
constructed in accordance with the present invention. In general,
tumbler 610 has a base portion 612, a sidewall portion 614 and an
upper circular rim portion 16 which extends about the periphery 618
of an opening 620 of tumbler 610. Base portion 612 of tumbler 610
is integrally formed with the rest of the tumbler and includes a
bottom 622 which has a meniscus portion 624 and a base sidewall
626. Base sidewall 626 is typically thicker than sidewall 614, and
has either no taper, or a reverse taper from the taper of sidewall
614.
[0078] Tumbler 610 is optionally provided with a molded-in design
628 which is more clearly seen by reference to FIGS. 6(b) and 6(c).
Molded in designs may define ridges which are deeper in dimension
than the wall caliper of sidewall 614, thus providing strength by
way of corrugation, much like as is known in connection with
cardboard. The design shown is an alternating saw-tooth type,
slightly curved, with larger curves alternating with smaller curves
about the entire periphery of the tumbler. The design is also
operative as a grip for a user since the smooth sidewall is
substantially altered.
[0079] Base sidewall 626 extends upwardly to define an outer edge
630 which attached to sidewall 614. Sidewall 614 extends upwardly
to fortified rim 616. Rim 616 is integrally formed with sidewall
614 and is a continuous generally circular or oval, solid polymer
bead extending about periphery 618 of opening 620. Rim 616 has a
width 631 which is defined by the difference between an inner
diameter 632 and an outer diameter 634 of rim 616 and a height 635
which is the distance over which width 631 extends. Width 31 is
thicker than adjacent sidewall portion 638 which is typically of
the same caliper as the rest of sidewall 614, that is, sidewall 614
is substantially uniform in thickness on the entire tumbler. In the
example shown, adjacent sidewall portion 638 has a thickness of 20
mils, height 635 is approximately 28 mils and width 631 of rim 616
is approximately 40 mils at its thickest point.
[0080] The other dimensions of tumbler 610 are indicated on FIGS.
6(a) through 6(c). Base portion 612 has a diameter, d1, at edge 630
of about 2.125 inches, an outer upper diameter 34 of 3.32 inches
and an inner upper diameter 632 of 3.279 inches. The overall
height, H of tumbler 10 is 4.75 inches. These dimensions, as can be
seen from FIG. 6(c), define an angle of taper T as shown about
imaginary central axis 40 of about 7.degree. for sidewall 614 of
tumbler 610. As used herein, "taper", "degree of taper", or like
terminology indicates the angle that the sidewall of the inventive
tumbler makes with the imaginary central longitudinal axis defined
by the sidewall which is substantially cylindrical or conical
depending upon the embodiment. Inasmuch as the sidewall is
substantially perpendicular to bottom 622, the taper may also be
thought of as of the angle the sidewall makes with the bottom less
90 degrees.
[0081] FIG. 6(c) shows a molded in "sawtooth" swirl design 628
which extends from base portion 612 to roughly 65 percent of the
height of tumbler 610. Design 628 is comprised of wall embossments
at least as prominent as 1/2 the caliper of sidewall 614. Typically
the molded in ridges of the design are about as deep as the wall
caliper. Thus, design 628 substantially alters the topography of
sidewall 614 and provides a secure grip for a user.
[0082] There is shown in FIGS. 7(a) through 7(c) another tumbler
710 constructed in accordance with the present invention. Tumbler
710 has a base portion 712, a sidewall portion 714 and an upper
circular rim portion 716 which extends about the periphery 718 of
an opening 720 of tumbler 710. Base portion 712 of tumbler 710 is
integrally formed with the rest of the tumbler and includes a
bottom 722 which has a meniscus portion 724 and a base sidewall
726. Base sidewall 726 is typically thicker than sidewall 714, and
has a reverse taper from the taper of sidewall 714, as can be seen
from FIG. 7(a).
[0083] Tumbler 710 is optionally provided with a fluted molded-in
design 728 which is seen by reference to FIG. 7(b). Each flute 719
is substantially a flat, rectangular shape and approximately 30
degrees about the periphery 242 of the glass. Molded-in design 728
provides strength as is known in connection with injection molded
drinking vessels. Base sidewall 726 extends upwardly to define an
outer edge 730 which attaches to sidewall 714. Sidewall 714 extends
upwardly to fortified rim 716.
[0084] Rim 716 is integrally formed with sidewall 714 and is a
continuous generally circular or oval, solid polymer bead extending
about periphery 718 of opening 720. Rim 716 has a width 731 which
is defined by the difference between an inner diameter 732 and an
outer diameter 734 of rim 716 and a height 735 which is the
distance over which width 731 extends. Width 731 is thicker than
adjacent sidewall portion 738 which is typically of the same
caliper as the rest of sidewall 714. In the example shown, adjacent
sidewall portion 738 has a thickness of 20 mils, height 736 is
approximately 28 mils and width 731 is approximately 40 mils at its
thickest point.
[0085] Other dimensions of tumbler 710 are generally as indicated
in connection with tumbler 610 of FIG. 6. Sidewall 714 of tumbler
710 has a taper of approximately 6.5 degrees.
[0086] The tumblers of FIGS. 6 and 7 have the fortified rim design
of the present invention wherein the rim includes a spherical or
elliptical solid polymer bead. Typically, this bead is twice the
thickness of the adjacent sidewall or more as was discussed in
connection with FIGS. 4(a) and 4(b) above. That discussion applies
equally to the embodiments of FIGS. 6, 7, 8 and 17 as will be
appreciated from the foregoing and subsequent discussion.
[0087] Salient features of the inventive tumblers include the
biaxial-induced toughness of the blow-molded article, as well as
rigidity achieved by combining a relatively low taper with a
fortified upper rim. Conventional blow-molded cups typically
include a very prominent curled lip which is not consistent with
glassware and tends to make the article unappealing for everyday
use or for use with guests. Moreover, the rim is larger than a
comparable rim on tumblers of the invention such that there is more
rim stress upon flexing, especially in connection with larger
volume tumblers as will be appreciated from the following.
[0088] There is shown in FIG. 8 a tumbler 810 which is constructed
in accordance with the present invention. In general, tumbler 810
is cylindrical or in the shape of a truncated cone and has a base
portion 812, a sidewall portion 814 and an upper circular rim
portion 816 which extends about the periphery 818 of an opening 820
of tumbler 810. Base portion 812 of tumbler 810 is integrally
formed with the rest of the tumbler and includes a bottom 822 which
has a meniscus portion 824 and a base sidewall 826. Base sidewall
826 is typically thicker than sidewall 814, and has either no
taper, or reverse taper from the taper of sidewall 814.
[0089] Base sidewall 826 extends upwardly to define an outer edge
830 which attaches to sidewall 814. Sidewall 814 extends upwardly
to fortified rim 816. Rim 816 is integrally formed with sidewall
814 and is a continuous generally circular or oval, solid polymer
bead extending about periphery 818 of opening 820. Rim 816 has a
width 831 which is defined by the difference between an inner
diameter 832 and an outer diameter 834 of rim 816 and a height 835
which is the distance over which width 831 extends. Width 831 is
thicker than adjacent sidewall portion 838 which is typically of
the same caliper as the rest of sidewall 814, that is, sidewall 814
is substantially uniform in thickness on the entire tumbler. In the
example shown, adjacent sidewall portion 838 has a thickness of 20
mils, height 835 is approximately 28 mils and width 831 of rim 816
is approximately 28 mils and width 831 of rim 816 is approximately
40 mils at its thickest point. The tumbler is also provided with a
series of molded-in grooves 841 which extend around the tumbler.
These grooves provide a grip for a user as well as providing
rigidity to the article. Typically, the circumferential grooves 841
have a depth of from 810 to 40 mils.
[0090] Other dimensions of tumbler 810 are indicated on FIG. 8 and
Table I in connection with the tumbler of FIG. 8(b) as shown
schematically in FIG. 4(b). Base portion 812 has a diameter d1, at
edge 830 of about 2.5 inches, an outer upper diameter 834 of 3.38
inches and an inner upper diameter 832 of 3.32 inches. The overall
height, H of tumbler 810 is about 4.6 inches. These dimensions
define an angle of taper T as shown about imaginary axis 840 of
about 5.degree. for sidewall 814 of tumbler 810. As used herein,
"taper", "degree of taper" or like terminology indicates the angle
that the sidewall of the inventive tumbler makes with the
longitudinal axis defined by the sidewall which is substantially
cylindrical or conical depending upon the embodiment. Inasmuch as
the sidewall is substantially perpendicular to bottom 822, the
taper may also be though of as of the angle the sidewall makes with
the bottom less 90 degrees, because the axis of the tumbler is
substantially perpendicular to bottom 822 as shown.
[0091] Referring again to FIG. 4(a), there is schematically
depicted a lip curl characteristic of prior art disposable drinking
cups. In general, such prior art cups have a sidewall 414a with a
portion 438a adjacent the curl of a given thickness D.sub.2a which
extends upwardly into a curl generally indicated at 450a. The curl
has a characteristic radius R.sub.a as well as a height H.sub.a and
a width W.sub.a. Such structures are sometimes called "open top
curls" and may be seen, for example, in U.S. Pat. No. 4,540,543.
See FIG. 4 thereof at 31. FIG. 4(b) schematically depicts in
section and elevation a solid polymer bead 416 about the upper
periphery of a tumbler, that is, an embodiment of the fortified rim
of the present invention as is also shown in FIG. 8 hereof which
extends around the upper periphery of the inventive tumbler. The
tumbler has a sidewall 414b with a portion adjacent rim 416b of
thickness D.sub.2b. the fortified rim, 416b is formed of solid
polymer integrally formed with sidewall 414b and has a height
H.sub.b and width W.sub.b as indicated. Inasmuch as the cross
section of the embodiment shown is circular, the width W.sub.a is
approximately equal to the height H.sub.b. Bead 416b has advantages
over the prior art top curl. For one, it is rounded and will not
tend to snag on the mold or snag with a cup cover as do prior art
top-curls. For another advantage, a bead type top rim can more
compactly provide rigidity to a cup than does a top curl, with less
width as demonstrated below in Table I, even for a relatively large
volume container such as that shown in FIG. 8.
2TABLE 1 Impact of Dimensions Upon Rigidity Tumbler of FIG. 4(b)
Cup of FIG. 4(a) and FIG. 8 Container Open Rim Solid Rim Sidewall
Caliper, Inches 0.0150 0.0150 Top Curl Caliper, Inches 0.0150
0.0628 Top Curl/Sidewall Caliper 1.00 4.19 Ratio Top Curl Width,
Inches 0.084 0.063 Taper, Degrees 5.0 5.0 Inside height, Inches
4.584 4.584 Upper Inside diameter, Inches 3.3250 3.3250 Lower
Inside diameter, Inches 2.5200 2.5200 Volume, Ounces 17.1448
17.1448 Rigidity, LBS/0.25" 1.045 1.045 Deflection
[0092] Being more compact, less hoop stress about the rim is
generated upon flexing of the cup. While polymer bead 416b is shown
as circular in cross-section, other profiles may be suitable for
example, conic sections such as ellipsoid shapes or truncated conic
sections or profiles such as truncated conic section including a
semi-circle or a half ellipse. As noted above, tumblers in
accordance with the present invention are produced by injection
blow-molding optically transparent polymers. Particularly preferred
polymers include crystal polystyrene available from Dow
Corporation, Midland, Mich., with the grade designation 685D. This
polymer may be used to produce the inventive tumblers by the method
of U.S. Pat. No. 4,540,543, the disclosure of which is incorporated
herein by reference. The subject apparatus and method is shown and
described in more detail in connection with the embodiments of the
present invention which follow.
[0093] The present invention is directed in still yet further
embodiments to a reusable polycarbonate container or tumbler and
method of making the polycarbonate container. The reusable or
permaware polycarbonate container of the present invention is made
by an injection blow-molding process to provide a polycarbonate
container which mimics the aesthetic clarity of glass and
polystyrene containers but is more durable than either glass or
polystyrene containers of comparable caliper and shape. The
permaware polycarbonate containers or tumblers include a base, a
sidewall and a fortified upper rim. The sidewall is integrally
formed with the base and extends upwardly from the outer edge
thereof. The sidewall is of uniform caliper or thickness of greater
than about 50 thousandths of an inch ("mils") to about 500
thousandths of an inch. Preferably, the caliper of the sidewall
ranges from about 75 mils to about 375 mils. While the tumbler in
accordance with the invention is generally cylindrical in overall
shape, the sidewall preferably has either a uniform or non-uniform
taper from an imaginary central axis from the base to the opening.
The height of the tumbler is from about 5 to 10 inches. At the
upper extremity of the sidewall is a fortified rim which serves to
impart rigidity to the tumbler. The fortified rim area has a finite
width and height both of which exceed the thickness of the adjacent
sidewall. The rim is at least 2 mils thicker than the adjacent
sidewall over a height of at least 2 mils; preferably, both the
width and the height of the rim are from about 1.1 to about 4 times
the thickness of the adjacent sidewall. The base ranges from about
1.1 to about 8 times, preferably, from about 1.1 to about 4 times
the thickness of the sidewall. Generally speaking, the tumbler in
accordance with the invention, has a volume of at least 1.5 and up
to 4 times the volume of the injection molded parison from which it
was prepared; while volume ratios (sometimes referred to as "blow
ratio") of from about 1.75 to about 3 are typical. A blow ratio of
about 2 to about 2.5 is most preferable. Articles in accordance
with the present invention are distinguished from other containers,
such as bowls or other flat shapes where rigidity is not critical,
by virtue of the fact that the ratio of the height of the tumbler
to the diameter of the upper opening is generally in the range of
from about 1 to about 5. Ratios of 1.25 to about 4 are preferred,
while ratios of about 1.5 to about 3.5 are more preferred.
[0094] An example of a polycarbonate container in accordance with
the present invention is a "bell fountain" container illustrated in
FIGS. 17(a)-(c) and is described in detail below. The reusable
polycarbonate containers are preferably prepared by the rapidly and
economically efficient side-by-side injection blow-molding process
as disclosed in aforementioned U.S. Pat. No. 4,540,543. The process
is described below in combination with the drawings of FIGS. 9-19.
U.S. Pat. No. 4,540,543 is herein incorporated by reference in its
entirety. Referring to FIGS. 9-11, injection station 910 is secured
in fixed platen 911. Blow stations 912 and 913 are also secured to
fixed platen 911 and are situated adjacent injection station 910
and in side-by-side relationship with respect thereto, with blow
station 912 containing blow mold 916 which may be split if desired
being on one side of the injection station and blow station 913
containing blow mold 917 which may be split if desired being on the
other side. Blow molds 916 and 917 are in the shape of the hollow
articles to be made. Ejection stations 914 and 915 are also secured
to fixed platen 911 and are situated adjacent the respective blow
stations in side-by-side relationship with respect thereto, with
ejection station 914 situated adjacent blow station 913 and
ejection station 915 situated adjacent blow station 912. Core 920
is provided secured to movable platen 921 engageable with injection
station 910 as shown in FIG. 9. The injection station 910 includes
mold wall 922. Thus, when core 920 is engaged with injection
station 910 as shown in FIG. 9 the core 920 is spaced from the mold
wall 922 to form mold cavity 923 therebetween. Injection means 924
is in communication with mold cavity 923 and is connected to a
source of hot flowable plastic, i.e., polycarbonate, (not shown)
for forcing said hot formable plastic under pressure into mold
cavity 923 to form parison 925. Core 920 is movable into and out of
engagement with injection station 910 by movable platen 921
actuated by the motive means shown schematically in FIG. 9 and to
be described in more detail herein below. Naturally, the movement
of platen 921 may be accomplished by conventional means, shown only
schematically in FIG. 9, which are capable of providing a clamping
force between the two platens to keep them from separating during
the injection step and the other steps which will be described
below. It should be understood that while movement of platen 921 is
described, one may of course move platen 911 or both platens 911
and 921, if desired. The hot, newly formed parison or container 925
remains in mold cavity 923 until sufficiently cooled to be removed,
if desired using cooling means 926 adjacent mold wall 922, as for
example, by fluid circulation. If desired, such cooling means may
also be provided in core 920. After such cooling of parison 925,
the clamping force is released and platen 21 is moved away from
platen 11 carrying with it core 920 and parison 925 adhered
thereto. If a neck mold is used as to form a threaded neck portion
the neck mold is operable by conventional means and remains closed
during the formation of the parison, removal of the parison from
the injection station and blowing, which also aids in retention of
the parison on the core. In the present embodiment, a neck mold is
not employed and both the parison and final article have a
cup-shaped configuration as seen in the drawings and clearly shown
in FIG. 13 and FIG. 17. In such configuration, the top or mouth of
the container (mold) is about as wide or wider than the diameter of
the remainder of the container mold. Thus, parison 925 has a base
portion 930, a fortified rim or lip 931 and outwardly flaring side
walls 932 extending from base 930 to lip 931. Fortified rim 931 may
serve as an undercut to aid in retention of the parison on the
core. Core 920 is provided with fluid passageway 933 connected to a
source of fluid pressure for blowing the final article. If desired,
a vacuum may be drawn through passageway 933 to aid in retention of
the parison on the core. Core 920 with parison 925 thereon is then
moved to blow station 913 as shown in FIGS. 10 and 11 in a manner
which first separates the parison from the mold wall 922 by moving
parison core 920 axially in a straight path away from said mold
wall at least until the parison clears the injection station,
followed by movement in a substantially arcuate path into axial
alignment with blow station 913 and blow mold 917, followed by
moving the parison core axially in a straight path into blow mold
917. Parison 925 is then expanded on core 920 in blow mold 917 by
fluid pressure through passageway 933 to form hollow article 934.
FIG. 9 shows core 920 engaged with the injection station. FIG. 10
shows core 920 with parison 925 thereon removed from the injection
station on its arcuate path between injection station 910 and blow
station 913 with platen 921 and core 920 at the peak of their
arcuate path. FIG. 10 shows core 920 engaged with blow station 913
forming hollow article 935 therein. After the formation of hollow
article 934, core 920 is removed from blow station 913 leaving
hollow article 934 remaining therein and returned to the injection
station along paths corresponding to the path taken by core 920
from the injection station 910 to the blow mold 917, that is, the
core is moved axially in a straight path away from blow mold 917
followed by movement in a substantially arcuate path into axial
alignment with said injection station, followed by movement axially
in a straight path into said injection station for repeat of the
cycle.
[0095] Second core 940 having fluid passageway 945 similar to
passageway 933 is provided on movable platen 921 adjacent core 920
in side-by-side relationship with respect thereto. Second core 940
is engageable with injection station 910 when core 920 engages blow
mold 917 to form a second parison in an overlapping cycle with
respect to core 920. Thus, second core 940 engages injection
station 910 to form a parison 925 in a manner similar to the
formation of a parison on core 920 in the injection station 910.
The formation of a parison on core 940 takes place while core 920
is in the blow mold 917 forming the hollow article. Core 940
carrying a parison 925 is then removed from the injection station
and transferred to blow station 912 and blow mold 916 in a path
corresponding to the transfer path of core 910 to blow station 913
and blow mold 917 for formation of additional hollow article 934 in
blow mold 917. The transfer of core 940 to blow mold 917 takes
place simultaneously with the return of core 920 to injection
station 910. After removal of core 920 from blow station 913 hollow
article 934 remains in blow mold 917. Hollow article 934
corresponds in shape generally to parison 925 with an expanded
configuration caused by the blowing step. Thus, article 934 has a
base portion 941, fortified rims or lips 942 and outwardly flaring
side walls 943 extending from base 941 to lips 942. The blown
article 934 cools in contact with the walls of the blow mold which
may contain cooling means 944, as for example for cooling by fluid
circulation in a conventional manner. Article 934 may be retained
in the blow mold by any desired means as by applying a vacuum to
the inside of the blow mold or providing means on the blow mold to
engage lip 942.
[0096] Ejection core 950 and second ejection core 951 are provided
on movable platen 921 adjacent and in side-by-side relationship to
cores 940 and 920, with ejection core 951 alongside second core
940. Thus, when cores 920 and 940 leave their respective blow molds
917 and 916 with the hollow articles remaining therein for return
to the injection station, ejection cores 950 and 951 move into
engagement with said hollow articles in the blow molds along paths
corresponding to the paths of cores 920 and 940. Cores 950 and 951
then disengage from the blow molds removing hollow articles 934
with them and move from the blow stations to the ejection stations
along paths corresponding to the paths of cores 920 and 940.
Removal of hollow article 934 onto the ejection cores may be
assisted by pusher means 952 operatively associated with blow molds
916 and 917 for positively pushing article 934 away from the blow
molds, see FIGS. 12 and 13. Also, ejection cores 950 and 951 may be
provided with fluid passageways 953 connected to a source of fluid
pressure (not shown), see FIG. 13, which may be used to draw a
vacuum and aid in removal of hollow article 934 from the respective
blow molds. The final hollow article is then transferred to the
respective ejection station, which may incorporate any suitable
ejection means as the chute, suction tube or other conventional
means to convey plastic articles. Removal of article 934 from the
ejection cores 950 and 951 at ejection stations 914 and 915 may be
assisted by flow pressure from passageway 953 and also by stripper
954 including stem 955 to which a widened cap 956 is attached
(FIGS. 12 and 13) movable axially via motive means (not shown).
After removal of the hollow article 934 at the ejection stations
the cycle is repeated. The apparatus, particularly for use with
cup-shaped articles, assures holding of the articles concentrically
on the mandrels and effecting reliable transfer as shown in FIG.
13.
[0097] In operation, the parison is transferred into blow mold 917
as above described and blown into final shape therein, followed by
insertion of mandrel 950 which is shorter than the depth of the
blow mold. In order to remove the blown article 934, pusher plate
952 is advanced forcing the blown object onto mandrel 950 which is
then withdrawn. If desired, vacuum may be applied through passage
953 better to assure adherence of article 934 to the mandrel during
withdrawal from the blow mold. Clearly, pusher plate 952 and the
stripper cap 956 may also be used to shape the portion of article
934 between them. If a rim undercut is embedded in the blow mold,
it is overcome to effect release from the blow mold by the action
of pusher plate 952 which has a stroke at least sufficient for the
length of said undercut, it being understood that a given article
may exhibit more than one undercut. In this manner, sticking of the
finished article to the blow mold is avoided. Subsequently, mandrel
950 carrying article 934 is aligned with removal devices as
described above and, since all relative movement between the
mandrel and the blow mold may be precluded due to the close fit of
the mandrel and the article at the neck of the article, which may
be an interference fit or an undercut, and, if necessary due to the
vacuum, the alignment will be consistent from cycle to cycle. Upon
alignment with the ejection station, the vacuum if theretofore
applied through channel 953 is released and stripper 954 is
actuated to urge the article into engagement with the ejecting
device by positive mechanical means. The advantage of this
arrangement compared to previous practice is in its reliability,
preventing interruptions of the operation and thereby improving
efficiency. While the foregoing description shows a single
injection mold and core set, it will naturally be understood that
multiple injection mold and core sets may readily be employed, for
example, arranged side-by-side or in several rows. Thus, it can be
seen that the process and apparatus of U.S. Pat. No. 4,540,543
obtains significant advantages. The overlapping cycles enable
plural operations to be conducted simultaneously. While core 90 is
engaging injection station 910 to form a first parison, second core
940 is engaging blow mold 916 to form a final article 934, second
ejection core 951 is ejecting a hollow article at ejection station
915 and ejection core 950 is engaging a hollow article at blow
station 913 for removal thereof, with the axial, arcuate and axial
movement described hereinabove providing a considerable advantage
in reduction in cycle time which of course is a prime consideration
in this art. The so-called "dry cycle" is that part of the total
operating cycle of the apparatus described in FIGS. 9-11 which is
not attributable to process related factors but only to the
mechanism.
[0098] The total cycle divides into the dry cycle and the process
cycle. In an injection blow-molding operation the pressure molding
of the parison typically takes longer than the finishing thereof by
blowing or the removal of the blown article. These three steps
overlap so that while one parison is being molded another is being
blown and still another is being removed after having been blown.
Accordingly, the longest of these three steps determines the
overall process cycle. Considering the injection molding step by
itself it is found that the process of pressure molding and cooling
the parison sufficiently to be removable from the injection mold
takes about one (1) second for a polycarbonate cup referred to
above, while the dry cycle of the injection mold clamping apparatus
is apt to take nearly four (4) seconds in a conventional device.
The dry cycle as such, being the greatest part of the total cycle,
could not therefore be reduced because of the time consuming
movement of the core assembly away from the injection mold,
sideways into alignment with the blow mold and towards the blow
mold, including the reverse of same. This is true of prior linear
and rotary systems.
[0099] In accordance with the present invention, however, the
axial, arcuate and axial movement substantially reduces the dry
cycle time and thus reduces the overall cycle time. Referring to
FIG. 11, the movements of movable platen 921 are shown
diagrammatically, which will of necessity include the movement of
the cores thereon. Thus, when platen 921 moves from the position in
FIG. 9 to the position in FIG. 11 a given point on the platen will
follow curve A. The return movement will follow curve B. As platen
921 moves away from platen 911 the section on curve A from location
960 to 961 represents movement from the closed position of FIG. 9
to that point at which movement of core 920 with parison 925
thereon may occur laterally without mechanical interference. As
soon as location 961 is passed said point starts its lateral
movement which is subdivided into three (3) sections, namely
between locations 961 and 962 in which acceleration is taking
place, then between 962 and 963 in which the velocity of the point
is constant, followed by between 963 and 964 in which deceleration
is taking place. Finally, locations 964 and 965 show the approach
to the blow mold and the position shown in FIG. 16. Naturally, the
actual shapes of the curve segments will depend on the mass being
moved, with the segment being steeper the lighter the movement
assembly. As indicated above, curve B depicts the reverse movement.
These movements can be effected by any conventional means, e.g.
fluid actuators or by cam action. If by fluid actuators, it is
readily possible to initiate their movement and thus also that of
platen 921 by a limit switch placed to be tripped by platen 921 as
soon as said platen reaches the distance from platen 911 at which
the lateral movement of core 920 can take place unimpeded. If by
cam action, fixed cams in the shape of curves A and B of FIG. 16
may be used and platen 911 may be equipped with corresponding cam
followers, to the effect that the axial movement of platen 921 will
at the same time induce its lateral movement according to the cam
path. Other means to produce the same result may be employed so
long as the lateral movement of platen 921 is effectively
controlled by its axial movement, whereby said lateral movement
accommodates acceleration and deceleration of platen 921 according
to the mass to be moved therewith. The advantage of this improved
arrangement is evident from the gain in cycle time. Thus, in the
case referred to hereinabove the dry cycle of the injection
clamping apparatus is reduced from approximately 4 seconds to
approximately 1.2 seconds, of which the lateral shifting of platen
921 takes only 0.4 to 0.5 seconds including acceleration and
deceleration. This improvement is particularly noticeable in
connection with mechanical, e.g. toggle or crank clamping
mechanisms which are favored for rapid acting injection clamps over
fluid actuated clamps. In the former, the clamping apparatus, which
is of the "fixed stroke" type can be used to induce the movement of
platen 21 during that portion of its opening and closing stroke
respectively which is in excess of the minimum clearance between
core 920 and mold 917. Cores 920 and 940 are equipped with fluid
passageways terminating in so-called blow slots 970 as shown in
FIG. 14 in order to effect blowing of the preforms in the blow
molds, as is known in the art. If permanently open, the blow slot
970 is connected according to conventional design of a source of
pressure fluid and a source of vacuum via fluid passageway 978
whereby the change from one to the other is effected by a
conventional valve in order for the dual function of the blow slot
to be readily accomplished as needed during injection and opening
of the injection mold, and then during blowing. The blow slot may
be formed of two elements of the core, for example leading element
971 and following element 972, that are capable of relative
movement as shown in FIG. 14 by the arrow, with FIG. 11 showing
leading element being relatively moveable, with element 971 having
a leading bulb-like portion 973 connected to a movable stem 974
which in turn is connected to a motive means (not shown). It is
necessary to control the opening and closing of blow slot 970
mechanically in the following sequence: the blow slot is closed and
held in that condition while injection of the plastic into the mold
is initiated and almost immediately thereafter is opened;
alternatively, it may be kept closed until the filling of the mold
is accomplished and opened only thereafter. Vacuum is applied while
the blow slot is open and maintained as core 20 or 40 is moved away
from injection station 910 (see FIGS. 9 and 10). The blow slot
remains open and vacuum is maintained while the preform moves from
the injection station into the blow station, at which time, by
suitable valving, the vacuum is broken and fluid pressure applied
inside the preform to expand it into the shape of the finished
article. At the end of the blowing cycle, the connection between
the blow slot and the source of fluid pressure is interrupted, but
vacuum is not admitted inside the finished article. Accordingly, in
the case of an operable slot, the flow of fluid or connection to
vacuum is controlled by a valve system that operates as follows:
open to vacuum; closed to vacuum, open to pressureclosed to
pressure, open to atmosphereclosed to pressure, closed to vacuum;
blow slot closed FIG. 15 shows one embodiment of actuating the blow
slot 970. As shown, a spring 975 is provided, urging the movable
element 971 forming the blow slot to open the latter. Stem 974 is
provided with a fixed annular bar 976. Spring 975 is affixed to
stem 974 between bar 976 and internal ridge 977 on element 972.
When inserted into the injection station, the entering plastic will
tend to counteract the force of spring 975 closing the blow slot.
When the pressure of the entering plastic is relieved, spring 975
will tend to open the slot again. However, if no vacuum is applied,
then atmospheric pressure will tend to close the slot or counteract
the spring. Accordingly, the spring force chosen has to be such as
to maintain the blow slot open against the atmospheric pressure so
that vacuum may be applied.
[0100] The total force due to atmosphere pressure counteracting the
spring is of course one atmosphere times the maximum projected area
of the movable portion of the core assembly; A.sup.2.pi./4.
Accordingly, the force of the spring will be chosen well above that
figure, for example, twice or three times that much, it being noted
that the pressure of the plastic during injection is many times
higher so that even with a stronger spring the blow slot will still
be closed during the injection step. Thus, the cores may be
provided with means operative to close the blow slot under the
pressure of incoming plastic and to open the blow slot when the
pressure of the incoming plastic is relieved. If the blow slot is
to be permanently open, it must of course be held to a dimension
precluding clogging thereof by penetration of the plastic while
under pressure. That dimension is accordingly chosen according to
the viscosity of the plastic at pressure molding temperature. In
the case of very thin fluid plastics, e.g. relatively low molecular
weight polyethylene and nylon, it is not possible to produce a
narrow enough slot and to maintain it economically. In the case of
most amorphous plastics such as polystyrene, a permanently open
slot may be used. As an improvement, the faces of the corresponding
blow core components forming the slot are slightly tapered toward
the outside as shown in FIGS. 14 and 15, i.e., the side facing away
from the core, and they are preferably coated with a substance that
prevents adhesion of the entering plastic to metal surfaces, e.g.
teflon. In consequence, any slight amount of penetration into the
slot will be cured during the blowing step, at which time the
plastic that will thus have entered the blow slot will be blown
out. The above described apparatus features interact with the
process, particularly because a critical relationship exists
between the temperature of the plastic at any given stage and the
rate and magnitude of the forming operation to which it is
subjected. The process injection blow-molding is of course aimed at
providing a predetermined shape of the finished article. In
addition, in most instances, as when converting brittle plastics
into thin-walled objects the process is used to improve the
properties of the plastic, such as strength, ductility, resistance
to permeation, etc. by molecular orientation, the details of which
are well known, including the fact that the best levels of
orientation are obtained by conducting the forming process at the
lowest temperature compatible with the glass transition range of
the given plastic that the chosen procedure is capable of.
[0101] In accordance with this invention, namely the manufacture of
a bell fountain drinking cup as illustrated in FIG. 17(a) from
polycarbonate, the following process parameters can be used with
the blow-molding apparatus and process as described in U.S. Pat.
No. 4,540,543 and above. Initially, the polycarbonate in the form
of pellets is dried to remove moisture. Drying conditions of 3.5
hours at 250.degree. F. have been found useful in providing a
polycarbonate which can be injection blow-molded into the permaware
containers of this invention. The polycarbonate plastic has to be
pressure formed into the parison rapidly, hence the molten plastic
temperature is left relatively high at from about 450.degree. F. to
about 700.degree. F., preferably, from about 500.degree. F. to
about 650.degree. F.; and most preferably, a temperature of about
545.degree. F. has been found to yield the desired parison.
Injection pressures of 1,000 to 3,000 psi can be used, with an
injection pressure of about 2,100 psi being most preferred. The
parison has to be removed from the parison mold after the shortest
possible dwell therein in order to rapidly proceed to the next
molding cycle, yet without tending to adhere to the mold and become
deformed thereby. For permaware, which require a thicker parison,
the time in the parison mold must yield a stable parison. Dwell
times in the parison mold to produce the polycarbonate permaware of
this invention range from about 1 to 3 seconds, with 2.5 seconds
being most preferred. In general, the temperature of the parison
has to reach a level suitable for orientation during the short
dwell in the parison mold and the comparatively short time,
shortened by the clamp action described herein, during which the
parison is transported into the blow mold. The temperature at which
the deformation of the parison, i.e., blowing takes place, should
be uniformly maintained while the parison is expanding and until it
contacts the parison mold. Temperatures ranging from about
250.degree. F. to about 500.degree. F., and most preferably at
about 285.degree. F. can be used. In no case must the parison be
damaged, nor deformed in the course of any operation to which it is
subjected, except of course blowing. A blowing pressure of from
about 100 to about 500 psi, preferably, from about 200 to about 400
psi, and most preferably at about 250 psi, is employed. FIGS. 17(a)
through 17(c) illustrate a bell fountain tumbler 979 injection
blow-molded in accordance with the present invention. The tumbler
can be prepared using a split blow cavity employing two separate
halves which can be configured exactly the same or differently to
provide separate design elements to the tumbler. For example,
tumbler 979 can optionally be provided with an embossing design
defined by embossed flat surfaces 988 and ridges 1004 which
circumscribe the embossed areas 988. The design is operative as a
grip for a user since the smooth sidewall is substantially altered.
Such tumblers are typically characterized by a seam 1001 along the
longitudinal axis of the tumbler. The tumbler 979 has a base
portion 980, a sidewall portion 981 and an upper circular rim
portion 982 which extends about the periphery 983 of an opening 984
of tumbler 979. Base portion 980 of tumbler 979 is integrally
formed with the rest of the tumbler and includes a bottom 985, a
base sidewall 987, and an inner face 989 attached integrally to
sidewall 981. Tumbler 979 as shown is characterized as a "bell
fountain" tumbler in which sidewall 981 extends upwardly to convex
portion 990 which extends to concave portion 991 and extends to
fortified rim 982. Rim 982 is integrally formed with sidewall 981
and is a continuous generally circular or oval, solid polymer bead
extending about periphery 983 of opening 984. Rim 982 has the
advantages that it is rounded and does not snag on the mold or snag
with a cup cover as a top curl does. For another advantage, a bead
type top rim can more compactly provide rigidity and strength to a
cup than does a top curl, with less width. While polymer bead rim
982 is shown as circular in cross section, other profiles may be
suitable for example, conic sections such as ellipsoid shapes or
truncated conic sections or profiles such as truncated conic
sections including a semi-circle or a half ellipse. Rim 982 has a
width W which is defined by the difference between an inner
diameter 993 and an outer diameter 994 of rim 982 and a height H
which is the distance over which width W extends. Width W is
thicker than the rest of sidewall 981. Sidewall 981 is
substantially uniform in thickness on the entire tumbler. In a
preferred form of the bell fountain tumbler shown, sidewall 981 has
at thickness of 80 mils, height H is approximately 100 mils and
width W of rim 982 is approximately 100 mils. Also, base sidewall
987 preferably has a height or thickness of about 100 mils. While
the base sidewall 987 can have a height up to 8 times the thickness
of sidewall 81, it has been found that under harsh washing
conditions, the base tends to deteriorate if it is about 150 mils
or more in the polycarbonate tumbler shown. The overall height of
the preferred tumbler 979 is 6.625 inches, inner diameter 993 is
3.25 inches, base diameter is 2.325 inches and shoulder 990 has an
inner diameter of 3.5 inches. As noted above, tumblers in
accordance with the present invention are produced by injection
blow-molding thermoplastic optically transparent polymers.
[0102] As discussed above, crystal polystyrene available from Dow
Corporation of Midland, Mich., grade 685d have been used to produce
tumblers by the method of U.S. Pat. No. 4,540,543. However,
permaware products formed from polystyrene polymers using the
injection blow-molding process described above do not have a
consistent durability, are brittle and tend to break.
Advantageously, the polycarbonate tumblers of the present invention
provide a product having the same desirable clarity of polystyrene
tumblers but are more durable such that the polycarbonate tumblers
do not break during normal use. It is often desirable to
incorporate at the bottom of a tumbler identifying indicia,
including the location of the manufacturer, trademarks, even to
mold into the bottom certain configurations which enable the
tumbler to be printed or packaged.
[0103] Referring to FIG. 17(b), it can be seen that the bottom of
base 985 has been molded to include a concave, flat portion 986
which includes a rim 1005, both of which locations can be used to
imprint product identifying indicia (not shown). FIG. 17(b) also
shows where a lug 1006 has been molded into the bottom 985 of base
980. Molded lug 1006 can be used to align the tumbler during any
subsequent printing operation. Previous to this invention, the
incorporation of such molded indicia or components to the base of a
blow-molded article, in particular, an article in which the wall
thickness was greater than 50 ml, required a separate noncontinuous
step in which the article, such as a tumbler needed to be taken
from the blow mold at an elevated temperature, and conveyed by a
separate conveyor structure to a stamping operation. For relatively
thick walled structures including those having a wall thickness of
greater than 50 mils, the molding of the indicia could not take
place during blow-molding since the fluid pressure during the
blowing step could not press the parison to be molded sufficiently
hard against a mold surface to provide acceptable indicia or deep
structural configurations to the surface such as the printing lug
1006 shown in FIG. 17(b). In a novel aspect of the present
invention, the polycarbonate tumbler of the present invention can
be blow-molded and the base thereof reconfigured in a continuous
manner without the need to remove the tumbler from the blow mold
and convey the tumbler away from the apparatus to a separate
stamping operation. The base molding method and apparatus which are
novel to the present invention can be described by referring to
FIG. 18. Thus, after removal of the core from the blow-molding
station, as described above, an alternative ejection core can be
inserted into the blow cavity which contains the blow-molded
container. This alternative ejection core provides a slight
pressure against the inside surface of the container pressing the
bottom surface of the container against a preformed mold. More
specifically, shown in FIG. 18 is the blow cavity 1010 of a blow
mold such as a blow station 913 as shown in FIG. 11. Within the
blow cavity is the blow-molded tumbler 1012 which includes a
sidewall 1014 and a base 1016 which has a bottom surface 1018 which
is to be provided with indicia or other structural configurations
such as printing lug 1006 as shown in FIG. 17(b).
[0104] In accordance with the molding operation of the present
invention, after the blow-molding step and once the core has been
removed from the blow mold 1010 of FIG. 18, for example, an
ejection core 1020 is inserted into the blow cavity 1010 and the
tumbler 1012 which remains therein. Ejection core 1020 is wide
enough to contact the inside edge of sidewall 1014 near or at the
base 1016 of tumbler 1012. Such contact is shown at location 1022.
Bottom edge 1024 of ejection core 1020 contacts the inside surface
of base 1016 and pushes the tumbler 1012 against a mold 1026.
Ejection core 1020 can also include a circumferential lip 1021
which engages the lip 1013 of tumbler 1012 so as to aid in pushing
tumbler 1012 uniformly against the surface of mold 1026. In FIG.
18, mold 1026 is shown containing a mold configuration 1028 which
is capable of forming a printing lug on the bottom 1018 of base
1016 such as equivalent to printing lug 1006 shown in FIG. 17(b).
Mold 1026 can be secured to blow cavity 1010 via threaded connector
1027. It has been found that the mechanical pressure of ejection
core 1020 against the inside surface of base 1016 provides adequate
pressure against the mold 1026 to adequately stamp any indicia or
other configuration into the base of the tumbler. Typically, the
pressure of the ejection core 1020 against the base 1016 within the
blow cavity to mold or stamp the base takes approximately 0.5
second. Mold 1026 can include a cooling channel 1030 to provide the
cooling of the base subsequent to the molding operation. Likewise,
ejection core 1020 can also be provided with a cooling channel
1032. In each of cooling channels 1030 and 1032, cooling fluids
such as water can be circulated therein to provide the proper
temperature. Subsequent to the molding or stamping operation, the
ejection core 1020 is removed from the blow cavity. Since the
mandrel 1020 contacts the inside sidewall 1014 of tumbler 1012, the
tumbler is removed from the blow cavity as well and transferred to
any conveying station as described previously. The ejection core
1020 is an alternative to the ejection core 950 shown in FIGS. 11,
12 and 13 and can be attached to a motive means as described above
with respect to core 950 to provide a continuous process of
injection blow-molding and molding the base of the tumbler. Another
improvement in this invention for injection blow-molding permaware
polycarbonate tumblers in which a sidewall thickness of greater
than 950 mils is provided is shown in FIG. 19. FIG. 19 is an
alternative blow mold cavity configuration which is different than,
for example, the blow cores shown in FIGS. 14 and 15. Thus, in the
previous description, blowing of the parison into the molded
tumbler was achieved by directing fluid through a blow slot in the
core which directed the fluid at the base of the parison mold.
Subsequently, the fluid pressure would work its way up the mold and
be vented from the entrance of the mold. With respect to the
tumbler, the initial fluid pressure would be at the base of the
tumbler and work its way along the sidewall to the tumbler opening.
In accordance with this invention, it has been found that a uniform
blow-molded tumbler can be better achieved by directing the fluid
pressure during the blow stage from the top of the mold and working
down toward the base of the blow cavity or, with respect to the
tumbler, blowing the parison at the opening of the tumbler and
working down toward the base of the tumbler. Such configuration is
shown in FIG. 19 which includes a blow cavity 1040 into which has
already been inserted the core 1042 which contains the injected
molded parison 1044 contained along the outside surface of core
1042. The blow cavity 1040 includes a mold 1046 in the shape of the
bell fountain tumbler shown in FIG. 17(a). The core 1042 includes a
blow vent 1048 which releases a fluid into the mold 1046 of blow
cavity 1040 near the entrance thereof or with respect to the
tumbler, near the opening of the tumbler. The fluid pressure
travels down the core 1042 blowing and pressing the parison 1044
against mold 1046 from the top of the parison to the base 1050 of
the parison. Blow cavity 1040 also includes the base mold 1026 as
described in FIG. 18 which allows the molding of the base of the
blow-molded tumbler once core 1042 is removed and ejection core
1020 is inserted. Mold 1026 includes a vent 1052 connected to blow
cavity 1040 to vent excess fluid pressure. It has been found that a
more uniform sidewall can be achieved by blowing from the opening
of the parison/tumbler to the base thereof. This method of blowing
the parison has previously been done to blow polystyrene disposable
containers but is not believed to have been done with resins other
than polystyrene and not to form permaware tumblers having sidewall
thicknesses of greater than 50 mils. The reusable containers of the
present invention are formed from aromatic polycarbonates
preferably having a weight average molecular weight of from about
10,000 to 200,000, most preferably from about 20,000 to 80,000, and
most particularly a melt flow rate range of from about 10 to 22
g/10 min (ASTM D-1238) and which are prepared by methods known to
those skilled in the art and more particularly by methods disclosed
in U.S. Pat. Nos. 3,028,365, 2,999,846, 3,248,414, 3,153,008,
3,215,668, 3,187,065, 2,964,794, 2,970,131, 2,991,273 and
2,999,835, all incorporated herein by reference. The aromatic
polycarbonates useful in practice of the invention are produced by
reacting di-(monohydroxyaryl)-alkanes (bisphenols) or
dihydroxybenzenes and substituted dihydroxybenzenes with
derivatives of carbonic acid such as carbonic acid diesters,
phosgene, bis-chlorocarbonic acid esters of
di-(monohydroxyaryl)-alkanes and the bis-chlorocarbonic acid esters
of the dihydroxy-benzenes and the substituted dihydroxy-benzenes.
By aromatic polycarbonate, in the sense of the present invention,
there are understood homopolycarbonate and copolycarbonate resins
which are based, for example, on one or more of the following
bisphenols: hydroquinone, resorcinol, dihydroxydiphenyls,
bis-(hydroxyphenyl)-alkanes, bis-(hydroxyphenyl)-cycloalkanes,
bis-(hydroxyphenyl)-sulphides, bis-(hydroxyphenyl)-ethers,
bis-(hydroxyphenyl)-ketones, bis-(hydroxyphenyl)-sulphoxides,
bis-(hydroxyphenyl)-sulphones and .alpha.,
.alpha.-bis-(hydroxyphenyl)-diisopropylbenzenes, as well as heir
nuclear-alkylated and nuclear-halogenated compounds. These and
further suitable aromatic dihydroxy compounds are described, for
example, in U.S. Pat. Nos. 3,028,365, 2,999,835, 3,148,172,
3,271,368, 2,991,273, 3,271,367, 3,280,078, 3,014,891 and 2,999,846
(all incorporated herein by reference), in German
Offenlegungsschriften (German Published Specifications) Nos.
1,570,703, 2,063,050, 2,063,052, 2,211,956 and 2,211,957, in French
Patent Specification No. 1,561,518 and in the monograph "H.
Schnell, Chemistry and Physics of Polycarbonates, Interscience
Publishers, New York, 1964". Preferred bisphenols are those of the
formula I: 1
[0105] in which R is identical or different and denotes H,
C.sub.1-C.sub.4-alkyl, Cl or Br; preferably H or
C.sub.1-C.sub.4-alkyl, and in which X is a bond,
C.sub.1-C.sub.8-alkylene, C.sub.2-C.sub.8-alkylidene,
C.sub.5-C.sub.15-cycloalkyene, C.sub.5-C.sub.15--cycloalkylidene,
--S--, --SO.sub.2--, --SO--, --CO-- or 2
[0106] Examples of these bisphenols are: 4,4'-dihydroxydiphenyl,
2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A),
2,4-bis-(4-hydroxyphenyl- )-2-methylbutane,
1,1-bis-(4-hydroxyphenyl)-cyclohexane, .alpha.,
.alpha.-bis-(4-hydroxyphenyl)-p-diisopropyl-benzene,
2,2-bis-(3-methyl-4-hydroxyphenyl)-propane,
2,2-bis-(3-chloro-4-hydroxyph- enyl)-propane,
bis-(3,5-dimethyl-4-hydroxyphenyl)-methane,
2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)-propane,
bis(3,5-dimethyl-4-hydrox- yphenyl)-sulphone,
2,4-bis-(3,5-dimethyl-4-hydroxyphenyl)-methylbutane,
1,1-bis-(3,5-dimethyl-4-hydroxyphenyl)-cyclohexane,
.alpha.,.alpha.-bis-(3,5-dimethyl-4-hydroxyphenyl)-p-diisopropyl-benzene,
2-2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and
2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane and
2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane (tetrabromo bisphenol
A).
[0107] Examples of particularly preferred bisphenols are:
2,2-bis-(4-hydroxyphenyl)-propane,
2,2-bis-(3,5-dimethyl-4-hydroxyphenyl)- -propane,
2,2-bis-(3,5-dichloro-4-hydroxyphenyl)-propane,
2,2-bis-(3,5-dibromo-4-hydroxyphenyl)-propane and
1,1-bis-(4-hydroxypheny- l)-cyclohexane.
[0108] Preferred aromatic polycarbonates are those which are based
on one or more of the bisphenols mentioned as being preferred.
Particularly preferred copolycarbonates are those based on
2,2-bis-(hydroxyphenyl)-pro- pane and one of the other bisphenols
mentioned as being particularly preferred. Further particularly
preferred polycarbonates are those based solely on
2,2-bis-(4-hydroxyphenyl)-propane or 2,2-bis-(3,5-dimethyl-4-hy-
droxyphenyl)-propane.
[0109] The aromatic high-molecular weight polycarbonates can be
branched due to the incorporation of small amounts, preferably of
between about 0.05 and 2.0 mol % (relative to diphenols employed),
or trifunctional or more than trifunctional compounds, especially
compounds with three or more phenolic hydroxyl groups.
Polycarbonates of this type are described, for example, in German
Offenlegungsschriften (German Published Specifications) Nos.
1,570,533, 1,595,762, 2,116,974 and 2,113,347, British Patent
Specifications No. 3,544,514 (incorporated herein by
reference).
[0110] Some examples of compounds with three or more than three
phenolic hydroxyl groups which can be used are phloroglucinol,
4,6-dimethyl-2,4,6-tri-(4-hydroxyphenyl)-heptane-2,4,6-dimethyl-2,4,6-tri-
-(4-hydroxyphenyl)-heptane, 1,4,5-tri-(4-hydroxyphenyl)-benzene,
1,1,1-tri(4-hydroxyphenyl)ethane
tri-(4-hydroxyphenyl)-phenylmethane,
2,2-bis-[4,4-bis-(4-hydroxyphenyl)-cyclohexyl]-phenol,
2,6-bis-(4-hydroxyphenyl-isopropyl)-phenol,
2,6-bis-(2-hydroxy-5'-methylb- enzyl)-4-methylphenol,
2-(4-hydroxyphenyl)-2-(2,4-dihydroxyphenyl)-propane- ,
hexa(4-(4-hydroxyphenylisopropyl)phenyl) orthoterephthalic acid
ester, tetra-(4-hydroxyphenyl)-methane,
tetra(4-(4-hydroxyphenylisopropyl)-pheno- xy)-methane and
1,4-bis-((4',4"-dihydroxytriphenyl)-methyl)-benzene. Some of the
other trifunctional compounds are 2,4-dihydroxybenzoic acid,
trimesic acid, cyanuric chloride and
3,3-bis-(4-hydroxyphenyl)-2-oxo-2,3-- dihydroindole.
[0111] Particularly preferred polycarbonates which can be used to
injection blow mold the permaware containers of this invention are
the Calibre 200 Series polycarbonates from Dow Chemical Canada,
Inc., Sarnia, Ontario. Specifically, Calibre 200-22 has been found
particularly useful.
[0112] In high speed operation, such as the one at which this
invention is aimed, several factors have to be reconciled: the
plastic has to be pressure formed rapidly, hence its temperature is
left relatively high; the parison has to be removed from the
parison mold after the shortest possible dwell therein, in order to
proceed to the next molding cycle, all without tending to adhere to
the mold and becoming deformed thereby; the temperature of the
parison has to reach a level suitable for orientation during the
short dwell in the parison mold and the comparatively short time,
shortened by the clamp action described herein, during which the
parison is transported into the blow mold; the temperature at which
the deformation of the parison, i.e., blowing takes place should be
uniformly maintained while the parison is expanding and until it
contacts the parison mold; in no case must the parison be damaged,
nor deformed in the course of any operation to which it is
subjected, except of course blowing.
[0113] A typical use of this invention in another aspect will serve
as an example hereinbelow, namely the manufacture of a thin-walled
drinking cup of generally known configuration, from polystyrene,
e.g. Styron 685 made by the Dow Chemical Company. In order to
obtain satisfactory filling of the mold at a fast rate, it is
injected at 560'-570.degree. F. The parison tends to adhere to the
parison mold cavity wall until its temperature drops to
approximately 150.degree. F. The newly molded parison, with a wall
thickness increasing from 0.3 mm to 0.6 mm from its open end
towards its bottom dwells in the parison mold for approximately 0.8
seconds with the mold cavity wall at a temperature of 140.degree.
F. which is long enough for the parison to become removable without
sticking. The core in turn is kept at a temperature of 260.degree.
F. for the most part, with the region near the blow slot separately
controlled at 220.degree. F. or slightly lower to minimize
penetration of the plastic thereinto.
[0114] As a result, temperatures of the inner and outer surface of
the parison are so balanced under action of the core and mold
respectively that said parison remains highly deformable while
being readily separated from the parison mold cavity and
transferred to the blow mold. Once placed into the blow mold, a
blowing pressure of 100-300 psi is applied which may be accompanied
by forward movement of pusher plate 952 in order to center the
parison or the movable element of the blow core shown in FIG. 15,
to stretch it into contact with the blow mold. If such movement of
the blow core element is used, it must not precede initiation of
blowing, so as to assure that no friction or adhesion exists
between the parison and the core while the former is being moved
axially.
[0115] The injection blow-molding process and apparatus disclosed
in U.S. Pat. No. 4,540,543 have been used to form containers, cups,
tumblers and the like from thermoplastic optically transparent
polymers, in particular, from polystyrene. Such containers were
disposable having a nominal sidewall thickness substantially less
than 50 mils. Permaware products, such as those having thicknesses
of greater than 50 mils, and formed from polystyrene polymers using
the injection blow-molding process described above do not have a
consistent durability, are brittle and tend to break. Accordingly,
there has been a need to find alternative polymers which can be
injection blow-molded using the process described above and which
can provide a product having the same desirable clarity of
polystyrene tumblers but which are more durable.
[0116] In accordance with still yet another aspect of the present
invention, it has been found that the injection blow-molding
process described in U.S. Pat. No. 4,540,543 can be operated to
form hollow containers using resins other than unfilled polystyrene
which is the only polymer disclosed in the mentioned patent. Thus,
it has been found that polycarbonate, polyethylene terephthalate,
polycarbonate and ABS mixtures, acrylic resins, clarified
polypropylene and polyvinylchloride, as well as the filled polymers
described above, can be successfully injection blow-molded into
transparent containers. Additionally, the other resin or mixed
resin alternatives to unfilled polystyrene which are useful in this
invention include filled resins such as filled polystyrene,
polycarbonate, polyethylene terephthalate, mixtures of
polycarbonate and ABS resins, acrylic resins, clarified
polypropylene and polyvinyl chloride. It is most advantageous that
the filled resin systems have the flowability necessary for
injection blow-molding, can maintain at least the initial strength
of the unfilled resin and, in particular, remain transparent which
is a highly desired property when injection blow-molding containers
such as plastic drinking tumblers or "glasses". Accordingly, the
process of the present invention is particularly useful in
injection blow-molding 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 2-5% 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.
[0117] 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.
[0118] 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.
[0119] The injection blow-molding of these alternative resins can
be used to form both disposable and permaware containers having
nominal sidewall thicknesses of from 10 to 50 mils and greater than
50 mils to 500 mils, respectively. While each of the resins may
need to be processed differently from the others, typically, the
molten resin is pressure formed into the parison rapidly, at a
relatively high temperature ranging from about 300.degree. to
850.degree. F. so as to form the desired parison. Injection
pressures of 1,00 to 3,500 psi can be used. Dwell times of the
parison in the parison mold will generally range from 0.5 to 3.5
seconds depending on the setting ability of the polymer used and
the thickness of the article to be formed. The temperature at which
the deformation of the parison, i.e., blow-molding, takes place
should be uniformly maintained while the parison is expanding and
until it contacts the blow cavity mold. Temperatures ranging from
about 200.degree. to 600.degree. F. can be used. In no case must
the parison be damaged, nor deformed in the course of any operation
to which it is subjected, except of course blowing. A blowing
pressure of from about 100 to 500 psi, preferably from about 200 to
400 psi can be employed.
[0120] It is often desirable to incorporate at the bottom of a
tumbler identifying indicia, including the location of the
manufacturer, trademarks, even to mold into the bottom certain
configurations which enable the tumbler to be printed or packaged.
For example, one or more molded lugs can be molded into the base of
the container and used to align the container during any subsequent
printing operation. Previous to this invention, the incorporation
of such molded indicia or components to the base of a blow-molded
article, in particular, an article in which the wall thickness was
greater than 50 mil, required a separate noncontinuous step in
which the article, such as a tumbler needed to be taken from the
blow mold at an elevated temperature, and conveyed by a conveyor
structure to a separate stamping operation. For relatively thick
walled structures including those having a wall thickness of
greater than 50 mils, the molding of the indicia could not take
place during blow-molding since the fluid pressure during the
blowing step could not press the parison to be molded sufficiently
hard against a mold surface to mold acceptable indicia or deep
structural configurations such as a printing lug into the
surface.
[0121] In a novel aspect of the present invention, containers such
as cups, tumblers and the like can be blow-molded and the base
thereof reconfigured in a continuous manner without the need to
remove the tumbler from the blow mold and convey the tumbler away
from the apparatus to a separate stamping operation.
[0122] The base molding method and apparatus which are novel to the
present invention in one embodiment can be described by referring
to FIG. 18. Thus, after removal of the core from the blow-molding
station, as described above, an alternative ejection core can be
inserted into the blow cavity which contains the blow-molded
container. This alternative ejection core provides a slight
pressure against the inside surface of the cup pressing the bottom
surface of the cup against a preformed mold. More specifically,
shown in FIG. 18 is the blow cavity 1010 of a blow mold such as a
blow station 913 as shown in FIG. 11. Within the blow cavity is the
blow-molded tumbler 1012 in the form of a "bell fountain" tumbler
which includes a sidewall 1014 and a base 1016 which has a bottom
surface 1018 which is to be provided with indicia or other
structural configurations such as a printing. In accordance with
the molding operation of the present invention, once the core has
been removed from the blow mold 1010 subsequent to the blowing
step, an ejection core 1020 is inserted into the blow cavity 1010
and the tumbler 1012 which remains therein. Ejection core 1020 is
wide enough to contact the inside edge of sidewall 1014 near or at
the base 1016 of tumbler 1012. Such contact is shown at location
1022. Bottom edge 1024 of ejection core 1020 contacts the inside
surface of base 1016 and pushes the tumbler 1012 against a mold
1026. Ejection core 1020 can also include a circumferential lip
1021 which engages the lip 1013 of tumbler 1012 so as to aid in
pushing tumbler 1012 uniformly against the surface of mold 1026. In
FIG. 18, mold 1026 is shown containing a mold configuration 1028
which is capable of forming a printing lug on the bottom 1018 of
base 1016. Mold 1026 can contain other mold features including
indicia or trademark logos and the like. Mold 1026 can be secured
to blow cavity 1010 via threaded connector 1027. It has been found
that the mechanical pressure of ejection core 1020 against the
inside surface of base 1016 provides adequate pressure against the
mold 1026 to adequately stamp any indicia or other configuration
into the base of the tumbler. Typically, the pressure of the
ejection core 1020 against the base 1016 within the blow cavity to
mold or stamp the base takes approximately 0.5 second. Mold 1026
can include a cooling channel 1030 to provide the cooling of the
base subsequent to the molding operation. Likewise, ejection core
1020 can also be provided with a cooling channel 1032. In each of
cooling channels 1030 and 1032, cooling fluids such as water can be
circulated therein to provide the proper temperature. Subsequent to
the molding or stamping operation, the ejection core 1020 is
removed from the blow cavity. Since the mandrel 1020 contacts the
inside sidewall 1014 of tumbler 1012, the tumbler is removed from
the blow cavity as well and transferred to any conveying station as
described previously. The ejection core 1020 is an alternative to
the ejection core 950 shown in FIGS. 11, 12 and 13 and can be
attached to a motive means as described above with respect to core
950 to provide a continuous process of injection blow-molding and
molding the base of the tumbler.
[0123] Another improvement relative to U.S. Pat. No. 4,540,543 is
shown in FIG. 19. FIG. 19 is an alternative blow mold cavity
configuration which is different than, for example, the blow cores
shown in FIGS. 14 and 15. Thus, in the previous description,
blowing of the parison into the molded tumbler was achieved by
directing fluid through a blow slot in the core which directed the
fluid at the base of the parison mold. Subsequently, the fluid
pressure would work its way up the mold and be vented from the
entrance of the mold. With respect to the tumbler, the initial
fluid pressure would be at the base of the tumbler and work its way
along the sidewall to the tumbler opening. In accordance with this
invention, it has been found that a uniform blow-molded tumbler can
be better achieved by directing the fluid pressure during the blow
stage from the top of the mold and working down toward the base of
the blow cavity or, with respect to the tumbler, blowing the
parison at the opening of the tumbler and working down toward the
base of the tumbler. Such configuration is shown in FIG. 19 which
includes a blow cavity 1040 into which has already been inserted
the core 1042 which contains the injected molded parison 1044
contained along the outside surface of core 1042. The blow cavity
1040 includes a mold 1046 in the shape of the bell fountain
tumbler. The core 1042 includes a blow vent 1048 which releases a
fluid into the mold 1046 of blow cavity 1040 near the entrance
thereof or with respect to the tumbler, near the opening of the
tumbler. The fluid pressure travels down the core 1042 blowing and
pressing the parison 1044 against mold 1046 from the top of the
parison to the base 1050 of the parison. Blow cavity 1040 also
includes the base mold 1026 as described in FIG. 18 which allows
the molding of the base of the blow-molded tumbler once core 1042
is removed and ejection core 1020 is inserted. Mold 1026 includes a
vent 1052 connected to blow cavity 1040 to vent excess fluid
pressure. It has been found that a more uniform sidewall can be
achieved by blowing from the opening of the parison/tumbler to the
base thereof. This method of blowing the parison has previously
been done to blow polystyrene disposable containers but is not
believed to have been done with resins other than polystyrene and
not to form permaware tumblers having sidewall thicknesses of
greater than 50 mils.
[0124] Optical/Physical Properties
[0125] The inventive tumblers characteristically exhibit enhanced
optical properties and crack resistance over prior art disposable
cups. Unless otherwise indicated, cups described below are
fabricated from unfilled resins. There is shown in Table 2 below a
comparison of haze values of an injection blow-molded tumbler of
FIG. 8 made from PET with corresponding thermoformed cups.
3TABLE 2 Optical Properties HAZE VALUES Injection Blow-
Thermoformed Thermoformed Molded Tumbler of PET PET FIG. 8 (PET)
Cup 1 Cup 2 1 1.33 4.34 3.97 2 1.22 2.82 2.94 3 1.38 3.00 7.92 4
1.41 3.13 4.62 5 1.91 2.98 4.42 6 1.48 2.52 Avg 1.46 3.13 4.77 Std
0.239 0.628 1.875
[0126] Tumblers with a fortified, beaded rim produced in accordance
with the present invention likewise exhibit improved toughness over
cups with a "U" shaped upper rim as are known. In this regard, a
test was devised to simulate impact resistance as follows:
[0127] The tumblers (or tumbler stack in the case of a nested
column) were clamped about their bases to be in a free-standing
position and a cylindrical suspended weight was positioned to be at
rest with its cylinder wall adjacent the rim of the tumbler. The
weight was then drawn to a predetermined angle from the vertical
and released. The angle with vertical at failure was recorded and
the energy dissipated at impact was calculated based on the height
to which the cylindrical weight was raised above the rest
position.
[0128] Utilizing the above procedure, polystyrene cups having the
general characteristics of the cups of FIG. 8 ("beaded") were
compared with similar cups with a "U" shaped brim. The cups of the
invention had a wall thickness of about 15 mils and a bead
thickness of 63.7 mils about its brim. Results appear in Table 3,
wherein it can be seen the cups of the invention exhibit an energy
to failure of nearly twice that of cups with a "U" shaped brim.
4TABLE 3 Pendulum Test Energy to Failure for Beaded and "U" Shaped
Brim Polystyrene Cups (Nested Cups) Pendulum Energy Energy Pendulum
Pendulum Angle to to Weight Length At Failure Failure Failure Cup
ID lbs inches Degree lb-in Average Beaded 0.941816 25.5 20 1.45
Beaded 0.941816 25.5 25 2.25 Beaded 0.941816 25.5 25 2.25 Beaded
0.941816 25.5 25 2.25 Beaded 0.941816 25.5 25 2.25 2.09 "U"
0.941816 25.5 20 1.45 "U" 0.941816 25.5 15 0.82 "U" 0.941816 25.5
15 0.82 "U" 0.941816 25.5 15 0.82 "U" 0.941816 25.5 20 1.45
1.07
[0129] The material from which the cups are made likewise affects
the toughness of the product as does the various design elements of
the tumbler. Utilizing the above procedure (with tighter clamping
of the cups) tumblers having the general characteristics of FIGS.
3(a)-3(c) were tested for impact resistance as indicated in Table
4, as well as for crush loads and deflections (Instron).
[0130] The various tumblers of Table 4 had the characteristics
noted as well as the following:
[0131] 1. Tumbler A had a wall thickness of 0.0218 inches and a rim
bead thickness of 0.030 inches;
[0132] 2. Tumbler B had a wall thickness of 0.0227 inches and a rim
bead diameter of 0.047 inches; and
[0133] 3. Tumbler C likewise had a wall thickness of 0.0227 inches
and a rim bead diameter of 0.047 inches.
[0134] The particular grade of PET employed for Tumbler C was
MN058, available from Eastman Chemicals, Kingsport, Tenn.
5TABLE 4 "Cut Glass" IBM Tumbler Data Brim Brim Brim Cup Pendulum
Cup Crush Crush Crush Rigidity Failure Pendulum Volume Height
Weight Disp. Load Energy Dry Angle Energy Failure Tumbler Material
(oz) (in) (g) (in) (lbf) (lbf-in) (lb) (Degree) (lbf-in) Mode A PS
14 5.75 17.27 1.58 3.63 2.69 1.53 20.0 6.6 Pieces B PS 14 5.75
18.82 1.20 4.08 1.72 2.18 17.0 4.1 Cracks C PET 14 5.75 24.99 1.78
7.40 6.06 1.84 35.0 16.9 Creases
[0135] The material employed likewise has a corresponding effect on
the impact resistance of the cups of FIG. 8. Utilizing the above
procedures, cups designed in accordance with FIG. 8 having a volume
of 16 ounces, a wall thickness of 15 mils and a rim bead diameter
of 0.0637 inches were fabricated and tested as shown in Table
5.
6TABLE 5 Impact/Rigidity/Crush for PET Tumblers Pendulum Brim Brim
Brim Bottom Bottom Bottom Cup Energy Cup Crush Crush Crush Crush
Crush Crush Rigidity Failure to Volume Height Weight Disp. Load
Energy Disp. Load Energy Dry Angle Break Tumbler Material (oz) (in)
(g) (in) (lbf) (lbf-in) (in) (lbf) (lbf-in) (lb) (Degree) (lbf-in)
Failure Mode D PET 16 4.90 24.10 1.57 4.65 3.90 0.11 40.44 2.23
0.85 42.0 24.0 Minor creases E PET 16 4.90 24.60 1.58 4.70 4.01
0.12 49.64 3.19 0.86 40.0 21.9 Minor creases F PET 16 4.90 24.02
1.50 4.39 3.50 0.12 49.87 3.06 0.83 45.0 27.4 Minor creases
[0136] It can be seen from Table 5 that PET cups with dimensions
similar to the polystyrene cups of Table 3 exhibit greatly enhanced
impact resistance.
[0137] Still yet another material useful for the present invention
is K resin (Phillips Petroleum). Utilizing the procedures detailed
above, there is shown in Table 6 a comparison of a polystyrene
tumbler (Sample G) having the configuration of the tumbler of FIG.
8 hereof with a K resin/polystyrene (11.5% butadiene) tumbler
(Sample H) having the configuration of FIG. 8. The tumbler of
Sample H was made with a K resin having 24.5 wt. % butadiene
blended with polystyrene.
[0138] K resin is a copolymer of styrene and butadiene and is
available from Phillips Petroleum, Bartlesville, Okla. Particularly
preferred grades included from about 2 to about 40 wt. %
butadiene.
[0139] It can be seen from Table 6 that K resin tumblers in
accordance with the invention exhibit high impact resistance.
[0140] The polymeric composition of this invention may further
contain one or more agents to improve the impact strength, i.e., an
impact modifier other than or in addition to butadiene/styrene
copolymers.
[0141] So-called core-shell polymers built up from a rubber-like
core on which one or more shells have been grafted may be used. The
core usually consists substantially of an acrylate rubber or a
butadiene rubber. One or more shells have been grafted on the core.
Usually these shells are built up for the greater part from a
vinylaromatic compound and/or a vinylcyanide and/or an
alkyl(meth)acrylate and/or (meth)acrylic acid. The core and/or the
shell(s) often comprise multi-functional compounds which may act as
a cross-linking agent and/or as a grafting agent. These polymers
are usually prepared in several stages.
[0142] Olefin-containing copolymers such as olefin acrylates and
olefin diene terpolymers can also be used as impact modifiers in
the present compositions. An example of an olefin acrylate
copolymer impact modifier is ethylene ethylacrylate copolymer
available from Union Carbide as DPD-6169. Other higher olefin
monomers can be employed as copolymers with alkyl acrylates, for
example, propylene and n-butyl acrylate. The olefin diene
terpolymers are well known in the art and generally fall into the
EPDM (ethylene propylene diene) family of terpolymers. They are
commercially available such as, for example, EPSYN 704 from
Copolymer Rubber Company. They are more fully described in U.S.
Pat. No. 4,559,388, incorporated by reference herein.
[0143] Various rubber polymers and copolymers can also be employed
as impact modifiers. Examples of such rubbery polymers are
polybutadiene, polyisoprene, and various other polymers or
copolymers having a rubbery dienic monomer.
[0144] Styrene-containing polymers can also be used as impact
modifiers. Examples of such polymers are
acrylonitrile-butadiene-styrene, styrene-acrylonitrile,
acrylonitrile-butadiene-alpha-methylstyrene, styrene-butadiene,
styrene butadiene styrene, diethylene butadiene styrene,
methacrylate-butadiene-styrene, high rubber graft ABS, and other
high impact styrene-containing polymers such as, for example, high
impact polystyrene. Other known impact modifiers include various
elastomeric materials such as organic silicone rubbers, elastomeric
fluorohydrocarbons, elastomeric polyesters, the random block
polysiloxane-polycarbonate copolymers, and the like. The preferred
organopolysiloxane-polycarbonate block copolymers are the
dimethylsiloxane-polycarbonate block copolymers in some
embodiments.
7TABLE 6 Comparison of K Resin/Polystyrene Tumbler Cup Brim Crush
Bottom Crush Volume Height Weight Displ. Load Energy Failure Displ.
Load Energy Failure Sample (oz) (in) (g) (in) (lbf) (lbf-in) Mode
(in) (lbf) Lbf-in) Mode G 16 4.88 17.50 0.95 3.38 1.73 Cracks 0.08
26.00 1.01 Cracks H 16 4.88 17.21 2.08 3.65 4.63 Creases 0.11 34.07
1.63 Creases Cup Pendulum Rigidity Disagreeable Failure Energy Dry
Odor Angle to break Failure Sample Sample (lb) Scale 0-10 (Degree)
(lbf-in) mode size G 0.97 2 20 5.6 60% cracks 10 40% pieces H 0.57
7 33.5 15.5 60% cracks 10 40% creases
[0145] Injection blow-molded tumblers may be produced in accordance
with the present invention utilizing polymeric compositions filled
with conventional inorganic fillers such as talc, mica,
wollastonite and the like, wherein the polymer component is, for
example, a polyester, a polystyrene homopolymer or copolymer, or a
polyolefin. While any suitable polymer may be used, polypropylene
polymers which are suitable are preferably selected from the group
consisting of isotactic polypropylene, and copolymers of propylene
and ethylene wherein the ethylene moiety is less than about 10% of
the units making up the polymer, and mixtures thereof. Generally,
such polymers have a melt flow index from about 0.3 to about 4, but
most preferably the polymer is isotactic polypropylene with a
melt-flow index of about 1.5. In some preferred embodiments, the
melt-compounded composition from which the articles are made may
include polypropylene and optionally further includes a
polyethylene component and titanium dioxide. A polyethylene polymer
or component may be any suitable polyethylene such as HDPE, LDPE,
MDPE, LLDPE or mixtures thereof and may be melt-blended with
polypropylene if so desired.
[0146] The various polyethylene polymers referred to herein are
described at length in the Encyclopedia of Polymer Science &
Engineering (2d Ed.), Vol. 6; pp: 383-522, Wiley 1986; the
disclosure of which is incorporated herein by reference. HDPE
refers to high density polyethylene which is substantially linear
and has a density of generally greater that 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.
[0147] Typically, in filled plastics the primary mineral filler is
mica, talc, kaolin, bentonite, wollastonite, milled glass fiber,
glass beads (solid or hollow), silica, or silicon carbide whiskers
or mixtures thereof. We have discovered that polypropylene may be
melt-compounded with acidic-type minerals such as mica, as well as
inorganic materials and/or basic materials such as calcium
carbonate, talc, barium sulfate, calcium sulfate, magnesium
sulfate, clays, glass, dolomite, alumina, ceramics, calcium
carbide, silica, pigments such as titanium dioxide based pigments
and so on. Many of these materials are enumerated in the
Encyclopedia of Materials Science and Engineering, Vol. # 3, pp.
1745-1759, MIT Press, Cambridge, Mass. (1986), the disclosure of
which is incorporated herein by reference. Combinations of fillers
are preferred in some embodiments.
[0148] Mineral fillers are sometimes referred to by their chemical
names. Kaolins, for example, are hydrous alumino silicates, while
feldspar is an anhydrous alkalialumino silicate. Bentonite is
usually an aluminum silicate clay and talc is hydrated mangesium
silicate. Glass, or fillers based on silicon dioxide may be natural
or synthetic silicas. Wollastonite is a calcium metasilicate
whereas mica is a potassium alumino silicate. Clays may be employed
as a primary filler; the two most common of which are kaolin and
bentonite. Kaolin refers generally to minerals including kaolinite
which is a hydrated aluminum silicate
(Al.sub.2O.sub.3.2SiO.sub.2.2H.sub.2O) and is the major clay
mineral component in the rock kaolin. Kaolin is also a group name
for the minerals kaolinite, macrite, dickite and halloysite.
Bentonite refers to hydrated sodium, calcium, iron, magnesium, and
aluminum silicates known as montmorillonites which are also
sometimes referred to as smectites.
[0149] A large number of siliceous materials may also be employed
as a primary filler. These materials include diatomite, perlite,
pumice, pyrophillite, silica, and talc. These minerals typically
consist of an alkali metal oxide or alkaline earth element oxide,
and silicon dioxide together with aminor amount of water and other
elements. Talc, for example, includes from about 25% to about 35%
MgO, 35-60% SiO.sub.2 and about 5% H.sub.2O.
[0150] Diatomite or kieselguhr is a sedimentary material formed by
centuries of life cycles of aquatic diatoms, a simple plant in the
algae family with an opaline silica cell wall. Thousands of species
of diatoms have flourished and continue to do so in both marine and
lacustrine environments. Fossilized skeletal remains of diatoms in
commercial quantities are found in many parts of the world. Perlite
is believed to result from hydration of volcanic glass or obsidian.
Generally, hydration is about 2-5%; this water content is important
to the expansibility of the perlite, influencing melting point and
supplying expansion steam.
[0151] The rapid expansion of dissolved gases in silica lavas
during volcanic eruptions produces the light density pumice or
pumicite. The finer pumicite particles are transported by wind away
from the source volcano, whereas pumice accumulates closer to the
vent.
[0152] The hydrous aluminum silicate, pyrophilite, is formed by
hydrothermal metamorphism of acid tuffs or braccias.
[0153] Silica sand is frequently obtained from the weathering of
quartz-containing rock. Decomposition and disintegration of the
rock with decomposition of other minerals leaves a primary quartz
sand that has been concentrated by water movement. Induration of
sands to sandstone results in another source for silica sand.
Amorphous silica, or more properly cryptocrystalline or
microcrystalline silica, is formed by the slow leaching of
siliceous limestone or calcareous chert.
[0154] Talc is formed by the metamorphic (hydrothermal) alteration
of magnesium silicates such as serpentine, pyroxene or
dolomite.
[0155] The siliceous fillers are generally inert in most
applications as shown by pH values in the range from about
6-10.
[0156] Sulfate minerals, such as gypsum and barite may likewise be
employed as a primary filler. Gypsum is the name given to the
mineral that consists of hydrous calcium sulfate
(CaSO.sub.42H.sub.2O), and also to the sedimentary rock that
consist primarily of this mineral. In its pure state, gypsum
contains 32.6% lime (CaO), 46.5% sulfur trioxide (SO.sub.3), and
20.9% water. Single crystals and rock masses that approach this
theoretical purity are generally colorless to white, but in
practice, the presence of impurities such as clay, dolomite, silica
and iron imparts a gray brown, red or pink color to the rock.
[0157] There are three common varieties of gypsum: selenite, which
occurs as transparent or translucent crystals or plates; satin
spar, which occurs as thin veins (typically white) of fibrous
gypsum crystals; and alabaster, which is compact, fine-grained
gypsum that has a smooth, even-textured appearance. Most deposits
or rock gypsum that are suitable for industrial purposes are
aggregates of fine to coarse gypsum crystals that have intergrown
to produce a thick, massive sedimentary rock unit that is 90-98%
gypsum. Alabaster is highly prized because of its uniformly fine
particle size, but the more common deposits of rock gypsum
consisting of coarser-grained selenite can generally be crushed and
ground to produce a suitable filler and coating material.
[0158] Gypsum has a hardness of 2 on the Mohs scale, and can be
scratched with the fingernail. Large rock masses are easily crushed
and ground to a fine powder. The specific gravity of gypsum is
about 2.31 and the refractive index is about 1.53. Gypsum is
slightly soluble in water but it is an inert substance that resists
chemical change. The oil-absorption capacity of gypsum is fairly
low (0.17-0.25 cm.sup.3 g.sup.-1).
[0159] Raw or crude gypsum is one of the forms used as fillers and
coatings, but for some purposes calcined or deadburned gypsum is
desired. In calcining, the gypsum is heated to abut 120-160.degree.
C. to drive off free water and partially remove the water of
crystallization. The calcined material or stucco, has a chemical
composition of CaSO.sub.4.1/2H.sub.2O, and it readily takes up
water. Calcination at higher temperatures (500-725.degree. C.)
results in a product called deadburned gypsum, which has a
composition of CaSO.sub.4.
[0160] Anhydrite, a sulfate mineral and rock that is closely
associated with gypsum in nature and has minor uses as a filler, in
anhydrous calcium sulfate (CaSO.sub.4) containing 41.2% CsO and
58.8% SO.sub.3. It is typically fine grained (like alabaster), and
occurs in thick, massive sedimentary rock units. Anhydrite usually
is white or bluish gray when pure, but it may be discolored by
impurities. Anhydrite has a hardness of 3.5, a specific gravity of
2.98, and a refractive index of 1.57-1.61.
[0161] Thus, fillers commonly include:
[0162] Barium Salt
[0163] Barium Ferrite
[0164] Barium Sulfate
[0165] Carbon/Coke Power
[0166] Calcium Fluoride
[0167] Calcium Sulfate
[0168] Carbon Black
[0169] Calcium Carbonate
[0170] Ceramic Powder
[0171] Chopped Glass
[0172] Clay
[0173] Continuous Glass
[0174] Glass Bead
[0175] Glass Fiber
[0176] Glass Fabric
[0177] Glass Flake
[0178] Glass Mat
[0179] Graphite Powder
[0180] Glass Sphere
[0181] Glass Tape
[0182] Milled Glass
[0183] Mica
[0184] Molybdenum Disulfide
[0185] Silica
[0186] Short Glass
[0187] Talc
[0188] Whisker
[0189] Particulate fillers, besides mica, commonly include:
[0190] Glass
[0191] Calcium carbonate
[0192] Alumina
[0193] Beryllium oxide
[0194] Magnesium carbonate
[0195] Titanium dioxide
[0196] Zinc oxide
[0197] Zirconia
[0198] Hydrated alumina
[0199] Antimony oxide
[0200] Silica
[0201] Silicates
[0202] Barium ferrite
[0203] Barium sulphate
[0204] Molybdenum disulphide
[0205] Silicon carbide
[0206] Potassium titanate
[0207] Clays
[0208] Whereas fibrous fillers are commonly:
[0209] Whiskers
[0210] Glass
[0211] Mineral wool
[0212] Calcium sulphate
[0213] Potassium titanate
[0214] Boron
[0215] Alumina
[0216] Sodium aluminum
[0217] Hydroxy carbonate
[0218] Suitably the extruded polymeric compositions include
coloring agents for aesthetic appeal, preferably titanium dioxide,
carbon black, and other opacifying agents in the range of 0.5-8
weight percent based on total composition, preferably 1.5 to 6.5
weight percent. The compositions may comprise minor amounts of
other additives such as lubricants and antioxidants. These articles
of manufacture may be suitably colored with pigments or dyes.
Pigments are defined as small insoluble organic or inorganic
particles dispersed in the resin medium to promote opacity or
translucency. Usual pigments include carbon black, titanium
dioxide, zinc oxide, iron oxides, and mixed metal oxides. Dyes are
organic and soluble in the plastic, and may be used alone or in
combination with pigments to brighten up pigment based colors. All
such colorants may be used in a variety of modes which include dry
color, conventional color concentrates, liquid color and precolored
resin.
[0219] This invention may be embodied in other forms or carried out
in other ways without departing from the spirit or essential
characteristics thereof. The present embodiment is therefore to be
considered as in all respects illustrative and not restrictive, the
scope of the invention being indicated by the appended claims, and
all changes which come within the meaning and range of equivalency
are intended to be embraced therein.
* * * * *