MULTI-LAYER CONTAINER AND METHOD OF MAKING SAME

CONTENANT STRATIFIE, ET METHODE DE FABRICATION CONNEXE

English Abstract

8026
MULTI-LAYER CONTAINER
AND METHOD OF MAKING SAME
ABSTRACT
A rigid container is made by injection molding a
parison having plural layers of polymers. The parison is
blow molded to the final shape of the container. Control
during injection is exercised over each of the plural po-
lymers so as to produce uninterrupted layers extending
throughout the walls of the parison and to insure that the
interior layers are completely encapsulated within the outer
layers.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of making a multi-layer rigid article
comprising the steps of: A) injection molding a parison in
an injection mold cavity by: 1) commencing the flow of a first
polymer stream to become the inside surface layer of the pari-
son and the flow of a second polymer stream to become the
outside surface layer of the parison, 2) subsequent to the
commencement of the flow of the first and second polymer streams,
commencing the flow of a third polymer stream between the first
and second polymer streams, 3) continuing the flow of the
first, second and third polymer streams concurrently, when the
cavity is nearly filled, 4) terminating the flow of the first
polymer stream, 5) subsequently terminating the flow of the
third polymer stream, and then 6) subsequently terminating the
flow of the second polymer stream, B) transferring the injec-
tion molded parison to a blow molding cavity having the config-
uration of the article, C) inflating the parison in the blow
molding cavity to form the article.



2. The method of claim 1 wherein a fourth polymer
stream is introduced between the third and first polymer
streams and a fifth polymer stream is introduced between the
third and second polymer streams, the flow of the fourth and
fifth polymer streams terminating before termination of the
flow of the second polymer stream.



3. A method of making a multi-layer rigid container
comprising the steps of:
A) infection molding a parison having an open end
and a closed end in an injection mold cavity having a core
pin and an entrance for polymer at the closed end of the
parison by:
1) establishing in the entrance a flow of po-
lymer comprising a central stream of a first polymer sur-
rounded by an annular stream of a second polymer,
2) subsequently commencing an annular stream
of a third polymer between the first and second polymer
streams,
3) maintaining the flow of the three polymer
streams until the cavity is nearly filled,
4) terminating the flow of the first polymer
stream,
5) terminating the flow of the third polymer
stream,
6) terminating the flow of the second polymer
stream,

21

B) transferring the parison to a blow mold cavity, C) inflat-
ing the parison in the blow mold cavity to flow mold the pari-
son into the finished container.
4. The method of claim 3 wherein following the ter-
mination of flow of the third polymer, flow of the first poly-
mer is recommenced and flow of the first polymer is terminated
approximately simultaneously with the flow of the second polymer.
5. The method of making a multi-layer injection
molded article comprising the steps of: 1) commencing the
flow of a first polymer stream to become the inside surface
layer of the article and the flow of a second polymer stream to
become the outside surface layer of the article, 2) subsequent
to the commencement of the flow of the first and second polymer
streams, commencing the flow of a third polymer stream between
the first and second polymer streams, 3) continuing the flow
of the first, second and third polymer streams concurrently,
4) terminating the flow of the first polymer stream, 5) sub-
sequently terminating the flow of the third polymer stream,
and then 6) subsequently terminating the flow of the second
polymer stream.
6. The method of claim 5 wherein a fourth polymer
stream is introduced between the third and first polymer streams
and a fifth polymer stream is introduced between the third and
second polymer streams, the flow of the fourth and fifth poly-
mer streams terminating before termination of the flow of the
second polymer stream.
7. A method of forming a multi-layer plastic parison
for an injection blow molded article comprising the steps of:
1) initially commencing the injection of a first inside sur-
face layer; 2) commencing the injection of a second outside
surface layer while continuing to inject the first layer;
3) then commencing the injection of a third core layer between

22

the first and second layers while continuing to inject the
first and second layers; 4) then terminating the injection of
the first layer while continuing to inject the second and third
layers; 5) then terminating the injection of the third layer;
6) then terminating the injection of the second layer.

23




8. An injection blow molded multi-layer rigid plastic
container having a continuous core layer completely encap-
sulated within outer layers.



9. An injection molded multi-layer plastic parison for
a blow molded container, said parison having a continuous
core layer completely encapsulated within outer layers.



10. The container of claim 8 wherein the inside surface
layer is a polyolefin, the core layer is ethylene vinyl al-
cohol copolymer having a layer of an adherent polymeric
material on each face of the ethylene vinyl alcohol
copolymer, and the outside surface layer is a polyolefin.



11. The container of claim 10 wherein the polyolefin
layers are a blend of polyethylene and polypropylene and the
layers of adherent polymeric material are a blend of
ethylene vinyl acetate copolymer and a graft copolymer of
polyethylene and an unsaturated fused ring carboxylic acid
anhydride.



12. The container of claim 8 wherein the inside surface

layer is a polyolefin, the core layer is ethylene vinyl al-
cohol copolymer having a layer of maleic anhydride grafted
polyolefin on each face of the ethylene vinyl alcohol copo-
lymer, and the outside surface layer is a polyolefin.

24




13. The container of claim 12 wherein the polyolefin
layers are a copolymer of propylene and ethylene.



14. The product of the process of claim 5.



15. The product of the process of claim 6.



16. The product of the process of claim 7.



17. The container of claim 10 wherein the polyolefin is
polyethylene.



18. The container of claim 10 wherein the polyolefin is
polypropylene.



19. The container of claim 10 wherein one surface layer
is polypropylene and the other surface layer is polyethy-
lene.




20. The container of claim 12 wherein the polyolefin is
polypropylene.



21. The container of claim 10 wherein at least one of
the surface layers is a blend of polyethylene and polypropylene.

22. The container of claim 10 wherein at least one of
the surface layers is a copolymer of propylene and
ethylene.



23. A method of making a multi-layer rigid article
comprising the steps of A) injection molding a parison in an in-
jection mold cavity by: 11 commencing the flow of a first poly-
mer stream of moisture-protective material to become the inside
surface layer of the parison and the flow of a second polymer
stream of moisture-protective material to become the outside
surface layer of the parison, 2) subsequent to the commence-
ment of the flow of the first and second polymer streams, com-
mencing the flow between the first and second polymer streams
of a third polymer stream of moisture-sensitive, barrier layer
material, 3) continuing the flow of the first, second and third
polymer streams concurrently, when the cavity is nearly filled,
4) terminating the flow of the first polymer stream, 5) subse-
quently terminating the flow of the third polymer stream, and
then 6) subsequently terminating the flow of the second polymer
stream, thereby to provide a parison having a continuous inner
barrier layer completely encapsulated between the inside and
outside surface layers, B) transferring the injection molded
parison to a blow molding cavity having the configuration of
the article, and C) inflating the parison in the blow molding
cavity to form the article.
24. The method of claim 23 wherein a fourth polymer
stream of adhesion-promoting material is introduced between the
third and first polymer streams and a fifth polymer stream of
adhesion-promoting material is introduced between the third
and second polymer streams, the flow of the fourth and fifth
polymer streams terminating before termination of the flow of
the second polymer stream.
25. A method of making a multi-layer rigid container
comprising the steps of: A) injection molding a parison having
an open end and a closed end in an injection mold cavity having
a core pin and an entrance for polymer at the closed end of the

26

parison by: 1) establishing in the entrance a flow of polymer
comprising a central stream of a first polymer of moisture-
protective material surrounded by an annular stream of a second
polymer of moisture-protective material, 2) subsequently com-
mencing between the first and second polymer streams an annular
stream of a third polymer of moisture-sensitive, barrier layer
material, 3) maintaining the flow of the three polymer streams
until the cavity is nearly filled, 4) terminating the flow of the
first polymer stream, 5) terminating the flow of the third poly-
mer stream, 6) terminating the flow of the second polymer stream,
thereby to provide a parison having a continuous inner barrier
layer completely encapsulated between the inside and outside sur-
face layers, B) transferring the parison to a blow mold cavity,
C) inflating the parison in the blow mold cavity to blow mold
the parison into the finished container.
26. The method of claim 25 wherein following the
termination of flow of the third polymer, flow of the first
polymer is recommenced and flow of the first polymer is ter-
minated approximately simultaneously with the flow of the second
polymer.
27. The method of making a multi-layer injection
molded article comprising the steps of: 1) commencing the flow
of a first polymer stream of moisture-proof material to become
the inside surface layer of the article and the flow of a second
polymer stream of moisture-proof material to become the outside
surface layer of the article, 2) subsequent to the commencement
of the flow of the first and second polymer streams, commenc-
ing between the first and second polymer streams the flow of
a third polymer stream of moisture-sensitive, barrier layer mater-
ial, 3) continuing the flow of the first, second and third polymer
streams concurrently, 4) terminating the flow of the first poly-
mer stream, 5) subsequently terminating the flow of the third

27

polymer stream, and then 6) subsequently terminating the flow
of the second polymer stream, thereby to provide an article hav-
ing a continuous inner barrier layer completely encapsulated be-
tween the inside and outside surface layer.
28. The method of claim 27 wherein a fourth polymer
stream of adhesion-promoting material is introduced between the
third and first polymer streams and a fifth polymer stream of
adhesion-promoting material is introduced between the third and
second polymer streams, the flow of the fourth and fifth polymer
streams terminating before termination of the flow of the second
polymer stream.
29. An injection blow molded multi-layer rigid plas-
tic container, comprising a continuous, barrier layer completely
encapsulated within protective outer layers.
30. The container of claim 29, wherein said barrier
layer is moisture-sensitive and said outer layers are moisture-
protective outer layers of moisture-protective material.
31. An injection molded multi-layer plastic parison
for a blow molded container, said parison having a continuous
barrier layer completely encapsulated within protective outer
layers.
32. The container of claim 31, wherein said barrier
layer is moisture-sensitive and said outer layers are moisture-
protective.
33. A method of making a multi-layer rigid article
comprising the steps of: A) injection molding, from a nozzle
having an exit, a parison in an injection mold cavity by: 1)
establishing in the nozzle prior to the exit the flow of a
first polymer stream to become the inside surface layer of the
parison and the flow of a second polymer stream to become the
outside surface layer of the parison, 2) subsequently establish-
ing in the nozzle prior to the exit of the flow of a third poly-

28

mer stream between the first and second polymer streams, 3
continuing the flow of the first, second and third polymer
streams concurrently, when the cavity is nearly filled, 4)
terminating the flow of the first polymer stream, 5) subsequent-
ly terminating the flow of the third polymer stream, and then 6)
subsequently terminating the flow of the second polymer stream,
B) transferring the injection molded parison to a blow molding
cavity having the configuration of the article, and C) inflat-
ing the parison in the blow molding cavity to form the article.
34. A method of making a multi-layer rigid article
comprising the steps of: A) injection molding, from a nozzle
having an exit, a parison in an injection mold cavity by: 1)
establishing in the exit the flow of a first polymer stream to
become the inside surface layer of the parison and the flow of
a second polymer stream to become the outside layer of the pari-
-son, and the flow of a third polymer stream between the first
and second polymer streams, when the cavity is nearly filled,
2) terminating the flow of the first polymer stream, 3) subse-
quently terminating the flow of the third polymer stream, and
then 4) subsequently terminating the flow of the second polymer
stream, B) transferring the injection molded parison to a
blow molding cavity having the configuration of the article,
and C) inflating the parison in the blow molding cavity to form
the article.
35. In a method of making a multi-layer injection
molded rigid article using a nozzle having an exit, the steps
comprising: 1) establishing in the exit the flow of a first
polymer stream to become the inside surface layer of the article,
the flow of a second polymer stream to become the outside sur-
face layer of the article, and the flow of a third polymer stream
between the first and second polymer streams, 2) terminating
the flow of the first polymer stream, 3) subsequently terminat-

29



ing the flow of the third polymer stream, and 4) subsequently
terminating the flow of the second polymer stream.
36. In a method of making a multi-layer injection
molded rigid article using a nozzle having an exit, the steps
comprising: 1) establishing in the exit the flow of a central
first polymer stream, the flow of an annular second polymer
stream substantially surrounding the first stream, and the flow
of an annular third polymer stream between the first and second
polymer streams, 2) terminating the flow of the first polymer
stream, 3) terminating the flow of the third polymer stream, and
4) terminating the flow of the second polymer stream.
37. The method of claim 1, 3 or 5, wherein the flows
of the first and second polymer streams are established substan-
tially simultaneously.
38. The method of claim 23 or 24, wherein the flows
of the first and second polymer streams are established substan-
tially simultaneously.
39. The method of claim 35 or 36, wherein the flows
of the first and second streams are established before the flow
of the third stream is established.
40. The method of claim 35 or 36, wherein the flows
of the first and second streams are established before the flow
of the third stream is established, and wherein the flows of the
first and second streams are established substantially simul-
taneously.
41. The method of claim 35 or 36, wherein the flows
of the first and second streams are established before the
flow of the third stream is established, and wherein the flow of
one of said first and second streams is established before the
flow of the other of said first and second streams is established.
42. The method of claim 1 or 2 wherein, there is
included the step of controlling the relative thicknesses of the


layers of the multi-layer article by independently controlling
the relative flow rates of the polymer streams.
43. The method of claim 3 or 4 wherein there is in-
cluded the steps of controlling the relative thicknesses of the
layers of the multi-layer rigid container by independently con-
trolling the relative flow rates of the polymer streams.
44. The method of claim 5 or 6 wherein there is in-
cluded the step of controlling the relative thicknesses of the
layers of the multi-layer injection molded article by indepen-
dently controlling the relative flow rates of the polymer streams.
45. The method of claim 7 wherein there is included
the step of controlling the relative thicknesses of the layers
of the multi-layer plastic parison by independently controlling
the relative flow rates of the layers.
46. The method of claim 33 wherein there is included
the step of controlling the relative thicknesses of the layers
of the article formed from the first, second and third polymer
streams by independently controlling the relative flow rates of
the streams.
47. The method of claim 34 wherein there is included
the step of controlling the relative thicknesses of the layers
of the article formed from the first, second and third polymer
streams by independently controlling the relative flow rates of
the streams.
48. The method of claim 35 or 37 wherein there is
included the step of controlling the relative thicknesses of
the layers of the article formed from the first, second and
third polymer streams by independently controlling the relative
flow rates of the streams.
49. The method of claim 1, 3 or 5, wherein the layer
formed from the third polymer stream is thinner than the layer
formed from the first polymer stream and is thinner

31


than the layer formed from the second polymer stream.
50. The method of claim 1, 3 or 5, wherein the layer
formed from the third polymer stream is the thinnest layer of
the article.
51. The container of claim 8, wherein the
layer is thinner than the encapsulating outer layers.
52. The parison of claim 9 wherein the core layer is
thinner than the encapsulating outer layers.
53. The container of claim 29, wherein the barrier
layer is thinner than the encapsulating outer layers.
54. The parison of claim 31, wherein the harrier
layer is thinner than the encapsulating outer layers.
55. The container of claim 10 or 11 wherein the core
layer is thinner than the combined thicknesses of the inside
surface layer and of the layer of adherent material which is
proximate to said surface layer.
56. A method of making a multi-layer injection molded
article in an injection mold cavity having an entrance sprue
comprising the steps of (1) providing at least three concentric
streams of polymeric materials concurrently flowing through the
sprue into the injection cavity, said flowing streams comprising
a first stream to become the inside surface layer of the inject-
ed article, a second stream to become the outside surface layer
of the injected article, and at least one stream flowing be-
tween said first and second streams to become a core layer in the
injected article, and (2) independently and continuously control-
ing the rate of flow of each of the flowing streams into the
injection cavity to control the location and thickness of the
flowing core layer stream relative to said flowing first and se-
cond streams.
57. A method of making a multi-layer injection molded
article in an injection mold cavity having an entrance sprue

32

comprising the steps of (1) providing at least three concentric
streams of polymeric materials concurrently flowing through the
sprue into the injection cavity, said flowing streams comprising
a first stream to become the inside surface layer of the in-
jected article, a second stream to become the outside surface
layer of the injected article, and at least one stream flowing
between said first and second streams to become a core layer in
the injected article, and (2) controlling the relative thick-
nesses of the streams by independently and continuously control-
ling the relative flow rates of the streams.
58. A method of making a multi-layer injection mold-
ed article by use of a coinjection nozzle having an exit com-
prising the steps of (1) flowing at least three concentric
streams of polymeric material concurrently through the nozzle
exit, said flowing streams comprising a first stream to become
the inside surface layer of the injected article, a second stream
to become the outside surface layer of the injected article, and
at least one stream flowing between said first and second streams
to become a core layer in the injected article, and (2) inde-
pendently and continuously controlling the rate of flow of each
of the streams through the nozzle exit to control the thickness
of each of said layers of the article.
59. The method of claim 56, 57, or 58, wherein there
are included the steps of terminating the flow of the first poly-
mer stream, subsequently terminating the flow of the third poly-
mer stream, and subsequently terminating the flow of the second
polymer stream.
60. The method of claim 42, 43 or 44, wherein said
core layer is thinner than said inside surface layer and is
thinner than said outside surface layer.
61. The method of claim 42, 43, or 44, wherein said
core layer is the thinnest layer of the article.

33


62. The method of claim 1, 3 or 5, wherein the first
and second streams are of substantially the same polymeric
material.

34

Description

~5~S~L




BACI~GROU~D OF THE INVENTION

Food p~oduct ri~id containers generally must be
impermeable to oxygen. Most comr,on structural polymers for
rigid ~ood containers are permeable to oxygen which invades
the food product causing degradation or spoilage. Those po-
lymers which are sufficiently impermeable to oxygen general-
ly are not suitable alone for rigid containers for foods be-
cause they do not possess adequate structural properties,
; are moisture sensitive, or are not approved for or are of
questionable safety when used in contact with foods. Ethy-
lene vinyl alcohol copolymer (EVOH) is a transparent extru-
sible material possessing high impermeability to oxygen when
dry, many times less permeable than acrylonitrile
copolymers, but is very moisture sensitive. The oxygen
barrier properties of EVOH are markedly diminished in the
~- presence of significant quantities of water. To be useful
- for food packaging, particularly where extended shelf lifeis required, EVOH must be kept dr-y as by total encapsulation
within polymers which have good moisture barrier properties.
Many foods are processed in the container in a
~; pressure cooker or retort~ Retort conditions commonly are
250F. at 30 psia steam pressure. ~ rigid container must
survive retort conditions. It must not permanently distort
during cooking or during cooling, and must not suEEer an
alteration of the desirable properties of its components.
PolyoleEins, particularly blends or copolymers of poly-
''


~ 2 ~

365~
propylene and polyethylene, are well suited to manufacture of
rigid containers and have adequate physical properties to sur-
vive retorting. Polyolefins are relatively poor oxygen bar-
riers, but are relatively good moisture barriers. The use of
polyolefins with a central core of an oxygen barrier polymer
is a desired goal of the food packaging industry.
Nohara et al. U.S. Patent No. 3,882,259, issued May
1975, discloses a three ply plastic bottle having a core of
EVOH blended with Surlyn A brand ionomer resin and outer plies
of polyethylene blended with Surlyn A (Trade Mark). The Surlyn
A (Trade Mark) ionomer is added to both the EVOH and the poly-
ethylene resin materials to improve adhesion between layers.
The bottle is to be made by extrusion blow molding whereby the
three layers are simultaneously extruded to produce a three
ply tube. While still hot from extrusion, the tube is pinched
together at the bottom to form a seal and inflated in a blow
mold having the shape of the desired bottle.
Extrusion blow molding has four serious drawbacks
when used to form multi-layer containers having a core ply of
a moisture sensitive barrier material such as EVOH.
First, the pinch seal at the bottom leaves the core
ply of EVOH exposed on the bottle exterior. Since EVOH and
certain other barrier materials are adversely affected by mois-
ture, exposure of the core ply at the container bottom renders
the container susceptible to loss of barrier quality by intru-
sion of moisture. The risk that the container exterior will
encounter damp conditions in storage or transport is high and
the resulting loss of barrier quality will




-- 3 --

65~l



degrade or spoil the food. Further, retort conditions are
such that moisture from the steam will intrude into the
barrieI layer through the exposed barrier at the bottom.
Second, extrusion blow molding necessarily produces
scrap as a result of the pinch sealing procedure. Since the
, scrap contains materials from each of the three layers, re-
extrusion of the scrap i-s difficult and expensive.
Third, the pinch seal produces a bottom of non-uni-
- form thickness and strength. The sealing takes place along
a line between the abutting faces of the inner layer ma-
terial. The seal line is bordered by regions of relatively
i thick material. When stretched during blow molding, the
bottom varies in thickness in the vicinity of the pinch
seal. Because of the thickness variation due to the pinch
seal, the stiffness of the bottom is not uniform along all
diameters. Consequently, the bottom does not evenly respond
. to expansion and contraction as the product changes in tem-
perature. This lack of even response causes unpredictable
performance of the container when retorted.
Fourth, the pinch seal may create an interruption
in the barrier layer. If the inside surface layer is inter-
posed between the barrieI layer at the seal, a line lacking
barrier material will result. The area of the interruption
.
- may be great enough to allow sufficient oxygen to enter to
be a problem.
Because of these disadvantages, extrusion blow
molding cannot produce an entirely satisfactory three layer
rigid container having a core barrieI layer of a moisture



.. , , , - - -

~5~65~



sensitive polymer such as EVOH, particularly where the con-
tainer is intended Eor retorting.

SUMM~RY OF THE PRESENT INVENTION

- ;~ The present invention is concerned with ~
making a plastic container by injection molding or by an
injection blow molding technique which produces a container
whose walls are multiple plies of different polymers. In
particular, the container walls comprise inner and outer
layers of structural polymers such as polyolefins or a blend
of polyolefins on either side of a core layer of a polymer
having oxygen b~rrie~ properties such 3s EVOH.
Injection blow molding is a process whereby a pre-
form or parison is formed by injection molding in a cavity.
The parison is transferred to a blow mold cavity and blown
to the shape of the desired container. The parison can be
; retained on the core pin of the injection mold and trans-
ferred on the core pin to the blow molding cavity. The
parison can be temperature conditioned before blow molding
to achieve an optimum temperature or profile of tempera-
tures. The core pin can be temperature controlled and the
exterior of the parison can be temperature conditioned by
contact with air or other fluid such that blow molding
occurs at optimal conditions. Orientation can be achieved
as the parison is stretched during blow molding. Injection
blow molding produces no scrap and requires no pinch;seal. ~
:


According to the present invention there is provided
a method of making a multi-layer rigid article comprising the
steps of: A) injection molding a parison in an injection mold
cavity by: 1~ commencing the flow of a first polymer stream to
become the inside surface layer of the parison and the flow of
a second polymer stream to become the outside surface layer of
the parison, 2) subsequent to the commencement of the flow of
the first and second polymer streams, commencing the flow of a
third polymer stream between the first and second polymer streams,
3) continuing the flow of the first, second and third polymer
streams concurrently, when the cavity is nearly filled, 4)
terminating the flow of the first polymer stream, 5) subsequent-
ly terminating the flow of the third polymer stream, and then
6) subsequently terminating the flow of the second polymer
stream, B) transferring the injection molded parison to a blow
molding cavity having the configuration of the article, C) in-
flating the parison in the blow molding cavity to form the
article.




- Sa -

Polymer melts for the inside and outside surface
layers and the core layer of the container walls are substan-
tially simultaneously injected into a parison mold cavity
through an injection nozzle having separate passages for each
polymer melt arranged to lead to coaxial annular nozzle orifices
surrounding the central orifice. Additional layers or layers
interposed between the surface and core layers can also be in-
jected simultaneously to produce a container wall having four
or more layers.
The initiation, rate, and termination of flow for
each layer can be independently and continuously controlled to
provide control over the thickness of each layer and to insure
that the core layer or layers are totally encapsulated between
the surface layers. The injection molded parison is trans-
ferred on the core pin to a blow mold cavity having the shape
of the container and is then blow molded into the finished
container. Temperature conditioning of the parison just prior
to blowing can result in biaxial orientation of the various
polymers to achieve desirable improvements in physical proper-
ties such as impermeability, clarity, tensile strength, impact
strength, and resistance to creep. The resulting product has
a barrier layer or layers which extend without interruption
throughout the container, yet are completely encapsulated
within the material of the inside and outside surface layers.
Since the barrier layer is protected from moisture by the
moisture barrier properties of the surface layers, the oxygen
barrier quality is preserved.





5.~
DESCRIPTION OF A PREFERRED E~lBODIMENT
The invention will now be described in more detail,
by way of example only, with reference to the accompanying
drawings, in which:-

Figure 1 is a schematic view in cross section of in-
jection blow molding apparatus;
Figure 2 is a schematic view of the apparatus of the
present invention;
Figure 3 is a simplified view of the injection appara-

tus of the present invention;
Figure 4 is a schematic view illustrating the controlsystem for one of the injection rams;
Figure 5 is a plot of the position of one of the
injection rams as a function of time;
Figure 6 is a flow chart for the control system for
the apparatus;
Figure 7 is a plot of ram position as a function of
time for three rams; :
Figures 8-15 are views in cross-section taken through
the nozzle and cavity showing the confluence of flow of the
various layers at various times during the injection cycle;
Figure 16 is a view in cross-section of the injection
nozzle;
Figure 17 is a view in cross-section of the parison;





65~l



i Figure 18 is a view in cross-secti~n of the
finished container,
Figure 19 is an enlarged view of a portion of a
container wall having three layers,
; 5 Figure 20 is a plot of the oxygen permeability of a
barrier material as a function of moisture content.
Figure 21 is an enlarged view of a portion of a
container wall having five layers, and

`:- The machine of the present invention injection
;. 10 molds a multi-layer parison from a plurality of polymers,
-~ 1 each separately plasticated and fed to separate injection
rams. The rams each force a shot of polymer to appropriate
nozzle passages which lead to the entrance to the injection
mold cavity. Conditions are contlolled to advance the
` 15 several polymer melts substantially simultaneously in the
J die cavity unde~ non-turbulent flow conditions to preserve
. the polymers as discrete layers in the parison. The fol-
lowing detailed description explains how the foregoing is
accomplished.
Figure 1 shows a portion of the injection blow
molding machine (IBM) of the present invention. Two core
,.~
~i pins lOA, lOB are mounted on a transversely moveable plate
- 40 on the axially moveable platen 42 of the machine. ~Core
pin lOA is positioned in an injection mold 20 while core pin
lOB is positioned in a blow mold 30B. When plate 40 is tra-
versed to the left, core pin 10~ will be in blow mold 30A





~L~S~6~



and core pin lOB will be in the injection mol~ 20. A paIi-
son is removed fLom tne mold by axial retreat of the move-
able platen 42 and the plate 40 with core pins 10 is tra-
versed either left or right to the available blow mold.
Figure 1 shows blow mold 30A ready to receive the parison
and shows blow mold 30B containing a parison 60B. Parison
603 is inflated with air to assume the shape of blow molding
cavity 30B while parison 60A is being injected in cavity 20.
The blow molds open as the platen retreats to eject the fi-
nished container. The plate 40 shuttles back and forth each
cycle so that a container is blown simultaneously each time
"~.i a parison is injected.
- Figure 2 shows the general layout of the injection
blow molding machine and indicates the control means. Plas-
ticators 82A, 82B, 82C feed three rams 70A, 70B, 70C for
three polymer melts which are fed to a manifold block 75
which contains separate passages leading to a multi-passage
` nozzle 50 for the injection mold 20. The platen 42 is moved
axially of the mold by a hydraulic press 44. Control cir-
cuitry means for the press and blowing cycles are indica.ed
at press control block 110. A microprocessor 100 is pro-
grammed to control the servo hydraulics 120 which control
the individual in~ection rams and to command the press con-
,
trol block 110.
Figure 3 shows one of the plural plasticators 82B
for melting and supplying molten polymer B to an injection

-

~15~651



ram 70B. The plasticator 82s is a conventional reciprocat-
ing screw device which forces molten polymer into the cylin-
der 71 of the ram when manifold valve 84B is closed and ma-
nifold valve 85s is openecl and the ram is retreated to the
5 left by hydraulic actuator 72. When the ram cylinder 71 is
- s charged with molten resin, valve 85B is closed. Upon a con-
~: trol signal from the microprocessor lOO, valve 84B is opened
and the servo control 120 for the ram causes the ram to ad-
vance to the right, according to a displacement-time sche-
dule stored in the microprocessor program. A displacement
transducer 76 provides an analog signal proportional to ram
: :! displacement to complete a feed-back loop for the servo 120.
Polymer B forced according to the program flows past valve
- 84B through the manifold passages to the injection nozzle,
through the nozzle passages and into the injection mold ca-
vity where polymer B becomes the outside layer of a parison
60.
Figure 4 shows schematically the servo loop where
the control signal from the microprocessor 100 (shown as
voltage as a function of time) and a position signal from
the displacement tranducer 76 are algebraically combined in
an amplifier 78 and the resulting signal is used to control
::~
the hydraulic servo 120 for the hydraulic actuator 72. A
typical ram position control signal is shown in Figure 5.
Since displacement is measured by transducer 76, the plot is
in voltage as a function of time.




. . ~ : ,
':

6~;1



Figure 6 is a flow chart of the system used to con-
trol the machine. The injection blow molding machine is in-
dicated as IBM on the chart. Upon initiati~n of the cycle,
the program checks positions of valves, rams, etc. and iE
; 5 all are proper, recharges the ram cylinders 71 from the
plasticators 82. The IBM control circuit 110 provides an
"inject" signal to the microprocessor 100. Injection is
caLried out according to the ram displacement-time schedule
of the microprocessor and is terminated at the end of the
schedule. 7~n "injection complete" signal is sent to the
~ I~M. The control 110 then causes the IsM to traverse to
.5 place the parison in the blow mold and to procede with the
blow molding phase. The machine continues to cycle through
this sequence. Keyboard 115 may be used to change the dis-
placement-time schedule or to s-hut down the machine.
Figure 7 is a plot of ram displacement as a func-
tion of time for three rams. The positions of the rams are
measured as the voltage analog output of the transducers 76
for each ram. The polymer for the inside surface layer is
"~"; that for the core layer "C"; and that for the outside
surface layer is "s". In this figure an upward slope indi-
cates a forward motion of the ram to deliver polymer, a
horizontal slope indicates a stopped ram, and a downward
slope indicates a retreat of the ram. The significance oE
Figure 7 is perhaps better understood by reference to Fi-
gures 8-15, which show the flow of the polymers at the exit
of the nozzle 50 and the entrance 52 of the injection mold
cavity 2n at the rounded bottom of the parison. Figures





8-15 ale taken at different times in the cycle and those
times are keyed to Figure 7.
Figure 8 IepLesents the conditions at the start o~
a cycle at time 0. The cavity 20 is empty. The entrance 52
- 5 of the cavity 20 initially contains only the polymers A and
. .
for the inside and cutside surface layers. The rams for
polymers A and B begin to advance to force those polymers
into the cavity. At about 100 milliseconds into the cycle
the ram for the core layer, polymer C, begins to advance.
Figure 9 shows that polymer C has joined the flow stream in
the entrance and polymer C is about to enter the cavity.
Figure 10, taken at about 520 milliseconds, shows the flow
.. .i
of the three polymers as the cavity continues to be filled.
All three polymer layers must extend throughout the entire
length of the parison. Since the flow in the mold cavity is
laminar, the velocity in the middle of the stream is higher
than the velocities at the cavity walls. Therefore, initia
. tion oE flow of polymer C is retarded enough (i.g., about
100 milliseconds) so that polymer C will reach the far end
of the cavity just as the slower moving surface layers ~A
and B) reach the end. In this way, the far end of the parl-
son, that which becomes the mouth end of the container, will
~ . .
-~' have all layers present in their proper positions.
.~
~`` At about 1000 milliseconds into the injection
cycle, the ram for polymer A (the inside surface layer) is
stopped and the ram for polymer C (the core layer) can be
accelerated slightly to achieve the desired thickness of ma-
terial in the bottom of the container. Polymer A is necked
`''


~ 12


~5~6~



down in the entrance 52 as is shown in Figure 11 until it
e~fectively is se~ered as shown in Figure 12. At 110 milli-
seconds the ram for polymer C is stopped and the ram for po-
lymer A is restarted. ~igules 13 and 14 show polymer A ad-
vancing to pinch off polymer C in the entrance, thereby
. pushing the last of polymer C into the cavity 20 with poly- -
mer A to bury or encapsulate to isolate polymer C from expo-
sure at the surface of the parison. Figure 15 shows polymer
A knit to polymer B at the entrance to complete the encapsu-
- 10 lation of polymer C and to return to the conditions a-t the
start as shown in Figure 8. At the time of Figure 15 (1300
; ¦ milliseconds) all three rams are retreated to depressurize
the cavity to prevent expansion of the parison when the ca-
vity is opened and to depressurize the polymers remaining in
the nozzle and entrance to prevent ex~dation from the nozzle
while the cavity is open. This exudation leads to premature
, flow of polymers into the cavity during the next cycle which
. can lead to smearing of polymer C on the surfaces of the
container.
2Q 1500 milliseconds marks the end of the injection
phase of the machine cycle for this example. Subsequent to
the end of the injection phase of the cycle, manifold valves
. .~
~j - 84, 85 are actuated and the ram cylinders 71 are recharged
with their polymers by the plasticators 82. The injection
- 25 mold is opened by eetreating the hydraulic press 44 to with-
draw the core pin 10 from the cavity 20. The parison just
- formed is transferred to one of the blow mold cavities 30A,
30B and the container which was blow molded simultaneously



- 13


65i~



with the injection cycle is ejected from the blow mold in
which it was finished.
Figure 16 shows a nozzle 50 appropriate for injec-
tion of a parison having a three layer wall. Polymer R,
which forms the outside surface layer, is delivered by the
ram 70B to an annular distribution channel 5~ which dis-
tributes the polymer circumferentially of the nozzle struc-
ture. Polymer B advances along a conical passage 56B to an
annular orifice 58B at the exit of the nozzle which leads to
the injection cavity. Similarly, polymer C, which forms the
core layer, is delivered by ram 70C to annular distribution
~ channel 54C and thence along conical passage 56C to annular
:~ orifice 58C. Polymer ~, which forms the inside surface
layer, is delivered by the ram 70A to a passage 56A which
exits at the center of the concentric flows issuing from
orifices 58B and 58C. A nozzle shut off valve 59 can be
moved axially to arrest flow of polymer A.
Figures 17 and 18 compare the parison 60 as injec-
tion molded with the finished container. The neck portion
62 remains virtually unchanged during blow molding. The
parison is held by the chill~ed neck portion while the hot
and soft parison is blown. Thus, the neck 62 including the
- flange 64 is essentially formed in the in~ection mold. The
..!
remainder of the parison walls are thinned as the parison is
stretched during blow molding.
Figure 18 shows that the core layer C extends
throughout the flange 64, but does not penetrate the flange
edge. This is accomplished in large part by selection of


.


14

~S~651



~` the delay time in starting the ram for the core polymer.
The flange 54 will be employed in a double seam seal when a
metal end is crimped, by well known techniques, onto the
container mouth to close the filled container. Since the
~ 5 flange represents a significant area, it is important that
- ~ the cole layer extend well into the flange. The programmed
flows of the various polymers also ensure that the core
layer is not exoosed at the sprue mark at the central ex-
terior of the container.
Figure 19 is an enlargement of the container wall
~ within the circle of Figure 18. Layer A is the inside sur-
-~1 face layer formed from polymer A in the foregoing descrip-
i~ tion. Layer B is the outside surface layer, forme~ from
polymer B. Layer C is the core or barrier layer formed Erom
polymer C. The thinnest layer is the relatively expensive
barrieL polymer C. The relative thickness of the three
layers is controlled by controlling the relative flow rates
~-` of the three polymers by microprocessor control of the dis-
: ....................................................................... .
S l placement rates of the rams. A preferred wall structure is
a layer of a blend of high density polyethylene and polypro-
pylene on each face of a core barrier layer of ethylene
vinyl alcohol copolymer (EVOH).
F'igure 20 shows how the oxygen barrier quality of
EVOH decreases abruptly at high levels of moisture. Where
the EVOH layer is thin, only a small quantity of water will
cause a large increase in oxygen permeability. For this
reason, the EVOH layer must adequately be protected against
the intrusion of moisture.
,





Polyolefins do not adhere well to EVOH. Adhesion can
be improved by adding adhesion promotors to the polyolefin,
the EVOH or both. Another approach is to provide an intermedi-
ate layer of an adherent polymeric material which adheres to
the polyolefin and the EVOH. Such materials include modified
polyolefins sold under the name Plexar tTrade Mark) by the
Chemplex Company of Rolling Meadows, Illinois. These comprise
a blend of a polyolefin and a graft copolymer of high density
polyethylene and an unsaturated fused ring carboxylic acid an-

hydride. The polyolefin component of the blend can be poly-
ethylene or preferably is an olefin copolymer such as ethylene
vinyl acetate. Schroeder U.S. Patent No. 4,254,169, issued
March 3, 1981, teaches the use of these materials to bond to
EVOH. The materials themselves are disclosed in U.S. Patent
Nos. 4,087,587 and 4,087,588. We have found these modified
polyolefins to be suitable as interlayers to improve adhesion
between the polyolefin surface layers and the EVOH core layer.
Another suitable material for use as an interlayer
to improve adhesion between the EVOH polyolefins are maleic
anhydride grafted polyolefins sold under the name Admer (Trade
Mark) by Mitsui Petrochemical Industries of Tokyo, Japan.
The use of interlayers on each side of the EVOH
oxygen barrier layer results in a five layer container. To -
produce such a container, the three passage nozzle of Figure 16
is replaced with a five passage nozzle of similar construction.
Where the inside and outside surface layers are of the same
polymer one ram can be used for both those




- 16 -

.~ :
' ~

~5~



layers. The flow from that ram is divided and proportioned
with part supplying the central axial passageway to form the
inside surface layer and the balance supplying the outermost
nozzle annular orifice. The two additional nozzle orifices
are located just inside and just outside the nozzle orifice
for the EVOH barrier layer. The two additional annular noz-
~le orifices can be supplied with the interlayer polymer
from a single ram, the flow being divided and proportioned.
Thus, a three ram-machine can produce a five layer parison.
Greater control can be exercised over the polymer flows by
using a machine with an independently control1able ram for
each layer. R nozzle shut off valve can be employed to
selectively control the polymer flows. The three layers of
interlayer polymer and the barrier polymer can be treated as
a single core layer. A five layer wall is shown in Figure
21B wherein layers R and B are the inside and outside sur-
-~ face layers of polyolefin, layer C is the barrier layer ofEVOH, and two layers D are the interlayer material.

: EXAMPLE I
".
t 20 Five layer containers having a capacity of about
5 1/2 ounces, of 202 x 307 size, weighing about llg were
made using a five orifice nozzle on a three ram machine.
The inside and outside surface layers were polypr~p ~ e~
; polyethylene block copolymer (Hercules Profax 7~1). The
j,
:
adhesive interlayers were ethylene vinyl acetate copolymer
blended with a graft copolymer of high density

5~
polyethylene and a fused ring carboxylic acid anhydride (Plexar
1615-2 (Trade Mark)). The oxygen barrier was EVOH (Kuraray
EVAL EP-F, tTrade Mark), available from Kuraray Co. Ltd.,
Osaka, ~apan). The layers were well aahered. The barrier ex-
tended to the flange lip and was completely encapsulated.
EXAMPLE II
Five layer containers similar to those of Example 1
were made wherein the inside and outside surface layers were
polypropylene (EXXON E612 (Trade Mark)); the interlayer material
was Plexar III (Trade Mark), a blend of ethylene vinyl acetate
copolymer and a graft copolymer; and the barrier was EVAL EP-F
(Trade Mark). The layers were well adhered. The barrier layer
extended to the lip of the flange and was completely encapsulat-
ed.
EXAMPLE III
Five layer containers similar to those of Example I
were made wherein the inside and outside surface layers were
a 50-50 blend of polypropylene (EXXON E612 (Trade Mark)) and
high density polyethylene (Chemplex 5701 (Trade Mark)); the
interlayer material was Plexar III (Trade Mark); and the barrier
layer was EVAL EP-F (Trade Mark). The layers were well ad-
hered. The barrier layer extended to the lip of the flange
and was completely encapsulated.




- 18 -

~ ~ `J

. . .

s~




EX~MPLE IV
~;'
Five layer containers similar to those of Example I
were made wherein the inside and outside surface layers were
a copolymer of propylene and ethylene (Hercules Profax
7631); the interlayer material was maleic anhydride grafted
polyolefin (Mitsui Admer QB 530); and the barrier layer was
EVAL EP-F. The layers were well adhered. The barrier layer
extended to the lip of the flange and was completely
, encapsulated.
¦ 10 In the making of the containers of Examples I-IV
. _ ~
the injection schedule began feeding the inside and outside
surface layer polymer then the polymel for the adhesive
interlayer was started and substantially simultaneously the
barrier layer polymer was started. The flows of the adhe-
sive interlayer polymer and the barrier layer polymer were
~, terminated before the outside surface layer polyme~ flow was
terminated.


~`; ,1
.~
:~ ~



~,

''' :


19
a~