U.S. patent application number 13/354029 was filed with the patent office on 2013-07-25 for multi-layered tubing.
This patent application is currently assigned to Tekni-Plex, Inc. The applicant listed for this patent is Philip BOURGEOIS, Munish Shah. Invention is credited to Philip BOURGEOIS, Munish Shah.
Application Number | 20130190714 13/354029 |
Document ID | / |
Family ID | 47258084 |
Filed Date | 2013-07-25 |
United States Patent
Application |
20130190714 |
Kind Code |
A1 |
BOURGEOIS; Philip ; et
al. |
July 25, 2013 |
MULTI-LAYERED TUBING
Abstract
Tubing comprising an inner layer, an outer layer and a middle
layer, wherein the inner layer comprises a polyethylene, the outer
layer comprises a thermoplastic polyurethane and the middle layer
comprises an ethylene ethyl acrylate copolymer or an ethylene
methyl acrylate copolymer or an anhydride grafted ethylene methyl
acrylate copolymer, a copolymer of two or more of the acrylate
copolymers or a mixture of two or more thereof.
Inventors: |
BOURGEOIS; Philip;
(Perrysburg, OH) ; Shah; Munish; (Sylvania,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BOURGEOIS; Philip
Shah; Munish |
Perrysburg
Sylvania |
OH
OH |
US
US |
|
|
Assignee: |
Tekni-Plex, Inc
King of Prussia
PA
|
Family ID: |
47258084 |
Appl. No.: |
13/354029 |
Filed: |
January 19, 2012 |
Current U.S.
Class: |
604/500 ;
138/137; 264/173.12 |
Current CPC
Class: |
B29C 48/18 20190201;
B32B 1/08 20130101; B32B 2535/00 20130101; B29C 48/09 20190201;
B29C 48/22 20190201; B32B 27/40 20130101; F16L 11/04 20130101; A61M
39/08 20130101; B32B 2597/00 20130101; B32B 27/32 20130101; B32B
27/308 20130101; F16L 11/10 20130101; F16L 11/12 20130101 |
Class at
Publication: |
604/500 ;
138/137; 264/173.12 |
International
Class: |
A61M 25/14 20060101
A61M025/14; B29C 47/06 20060101 B29C047/06; F16L 11/04 20060101
F16L011/04 |
Claims
1. A tube comprising an inner layer, an outer layer and a middle
layer, wherein the inner layer comprises a polyethylene, the outer
layer comprises a thermoplastic polyurethane and the middle layer
comprises an ethylene ethyl acrylate copolymer or an ethylene
methyl acrylate copolymer or an anhydride grafted ethylene methyl
acrylate copolymer, a copolymer of two or more of said acrylates or
a mixture of two or more of the foregoing.
2. The tube of claim 1 where the inner layer comprises more than
about 90% by weight of a polyethylene, the outer layer comprises
more than about 90% by weight of an aromatic or aliphatic polyether
based polyurethane and the middle layer comprises more than about
90% by weight of an ethylene ethyl acrylate copolymer.
3. The tube of claim 2 where the polyethylene comprises one or more
of a low density polyethylene, a linear low density polyethylene
and a high density polyethylene, the aromatic polyether based
polyurethane comprises a polytetramethyleneglycol-based
polyurethane and the ethylene ethyl acrylate copolymer comprises at
least about 19.5 percent ethyl acrylate content by weight.
4. The tube of claim 1 wherein the inner layer comprises more than
about 90% by weight of polyethylene, the outer layer comprises more
than about 90% by weight of a aromatic polyether based polyurethane
and the middle layer comprises more than about 90% by weight of an
ethylene methyl acrylate copolymer.
5. The tube of claim 4 where the polyethylene comprises one or more
of a low density polyethylene, a linear low density polyethylene
and a high density polyethylene, the aromatic polyether based
polyurethane comprises a polytetramethyleneglycol-based
polyurethane and the ethylene methyl acrylate copolymer comprises
at least about 19.5 percent by weight methyl acrylate content.
6. The tube of claim 1 where the inner layer comprises more than
about 90% by weight of low density polyethylene (LDPE), the outer
layer comprises more than about 90% by weight of a
polytetramethyleneglycol-based polyurethane and the middle layer
comprises more than about 90% an anhydride grafted ethylene methyl
acrylate copolymer.
7. The tube of claim 1 wherein the thickness of the polyurethane
outer layer is between about 0.001'' and about 0.025'', the
thickness of the inner polyethylene layer is between about 0.001''
and about 0.025'' and the thickness of the intermediate acrylate
copolymer layer is between about 0.001'' and about 0.025''.
8. The tube of claim 1 wherein the inner and outer layers do not
visually delaminate from each other at a stress up to of about 55
MPa and a strain up to about 900-950%.
9. The tube of claim 1 wherein the tube does not visually
delaminate when submersed in water at 60.degree. C. for 36
hours.
10. The tube of claim 1 wherein the tube has a central axial fluid
flow passage through which aqueous fluid is routed, the inner layer
having a radially inner wall surface that contacts the aqueous
fluid the outer and inner layers resisting delamination from each
other at a stress of up to about 55 MPa and a strain of up to about
900-950%.
11. The tube of claim 10 wherein the tube does not visually
delaminate after being submersed in water at 60.degree. C. for 36
hours.
12. A medical tube for transport of aqueous fluid comprising: an
inner layer comprising more than about 90% by weight of a
polyethylene an outer layer comprising more than about 90% by
weight of an aromatic polyether-based polyurethane and, a middle
layer disposed between the outer and inner layers comprising more
than about 90% by weight of an ethylene ethyl acrylate copolymer or
an ethylene methyl acrylate copolymer or an anhydride grafted
ethylene methyl acrylate copolymer, a copolymer of two or more of
said acrylates or a mixture of two or more of the foregoing.
13. The medical tube of claim 12 wherein the inner and outer layers
do not visually delaminate from each other at a stress of up to
about 55 MPa and a strain of up to about 900-950%.
14. The tube of claim 13 wherein the tube does not visually
delaminate after being submersed in water at 60.degree. C. for 36
hours.
15. A medical tube for transport of an aqueous fluid comprising: an
inner layer comprised of at least about 90% by weight of a
polyethylene. an outer layer comprised of at least about 90% by
weight of an aromatic polyether-based polyurethane, a middle layer
disposed between the inner and outer layers comprised of at least
about 90% by weight of an ethylene ethyl acrylate copolymer, an
ethylene methyl acrylate copolymer, an anhydride grafted ethylene
methyl acrylate copolymer, a copolymer of two or more of said
acrylates or a mixture of two or more of the foregoing, wherein
said tubing does not visually delaminate after being submersed in
water at 60.degree. C. for 36 hours.
16. A medical tube for transport of an aqueous fluid comprising: an
inner layer comprised of at least about 90% by weight of a low
density polyethylene, an outer layer comprised of at least about
90% by weight of a polytetramethyleneglycol-based polyurethane, a
middle layer comprised of at least about 90% by weight of an
ethylene ethyl acrylate copolymer, an ethylene methyl acrylate
copolymer, an anhydride grafted ethylene methyl acrylate copolymer,
a copolymer of said acrylates or a mixture of two or more of the
foregoing, wherein the tubing does not visually delaminate at a
stress of up to about 55 MPa and a strain of up to about 900-950%,
and, wherein the tubing does not visually delaminate after being
submersed in water at 60.degree. C. for 36 hours.
17. Method of forming a medical tube comprising an outer layer, an
innermost layer and an intermediate layer disposed between the
outer layer and the innermost layer, the method comprising:
selecting a first polymeric material having a selected structural
stability; selecting a second polymeric material that is inert to
aqueous fluids; selecting a third polymeric material that readily
bonds and adheres to the first and second polymeric materials on
co-extrusion and cooling of the materials; co-extruding the
selected first, second and third polymeric materials to form the
medical tubing in a configuration such that the outer layer
comprises at least about 90% by weight of the first polymeric
material, the inner layer comprises at least about 90% weight of
the second polymeric material and the intermediate layer comprises
at least about 90% by weight of the third polymeric material.
18. The method of claim 17 wherein the first polymeric material is
selected to be a polyurethane, the second polymeric material is
selected to be a polyethylene and the third polymeric material is
selected from the group consisting of an ethylene ethyl acrylate
copolymer, an ethylene methyl acrylate copolymer, an anhydride
grafted ethylene methyl acrylate copolymer, a copolymer of said
acrylates or a mixture of two or more of the foregoing.
19. Method of delivering an aqueous fluid to a subject comprising;
selecting a tube comprising an inner layer, an outer layer and a
middle layer, wherein the inner layer comprises a polyethylene, the
outer layer comprises a thermoplastic polyurethane and the middle
layer comprises an ethylene ethyl acrylate copolymer or an ethylene
methyl acrylate copolymer or an anhydride grafted ethylene methyl
acrylate copolymer, a copolymer of two or more of said acrylates or
a mixture of two or more of the foregoing; wherein the tube has a
central fluid flow passage surrounded by the layers; routing an
aqueous fluid through the central fluid flow passage of the tube,
and, delivering the aqueous fluid routed through the central fluid
flow passage into a blood vessel of the subject.
20. The method of claim 19 wherein the step of selecting comprises:
Co-extruding the outer, inner and middle layers to form the tube
such that the outer layer comprises at least about 90% by weight of
the polyurethane, the inner layer comprises at least about 90%
weight of the polyethylyene and the intermediate layer comprises at
least about 90% by weight of one or more of the arcylate
copolymers.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to polymeric tubing typically
formed by a co-extrusion process, the tubing having multiple layers
of the same or different polymeric materials each layer
successively adhered to each other.
BACKGROUND
[0002] Tubing comprised of polymeric material is used in many
industrial and commercial applications including in the medical
field. Various FDA compliant plastics are used, depending upon
properties desired and the intended applications. Where the tubing
is used to transport fluids for in vivo treatment of human
patients, selection of the polymeric materials can be a factor.
[0003] Polyvinyl chloride (PVC) is one of the most widely used
plastics. While structurally stable and easily formable into
desired shapes, PVC is typically manufactured using plasticizers
which can migrate out of the PVC matrix into bodily fluids and has
other properties not ideally suited for medical treatment
applications. Likewise, due to the inherent nature of plasticized
PVC tubing, there arises the potential absorption of medicines and
other components of aqueous fluids used in medical treatments into
the sidewall of the PVC tube. Polyurethane is potentially a
substitute for PVC. However, dual layer tubing comprised of
polyurethane and polyethylene suffers from the inability of the two
layers to remain adhered to each other under low to moderate
stress, strain or mechanical manipulation conditions. U.S. Pat. No.
4,627,844 to Schmitt ("Schmitt"), the disclosure of which is
incorporated herein by reference as if fully set forth, discloses a
tri-layer tube which is embodied in a commercial product sold under
the trademark "SUREPATH 151" by the Natvar Division of Tekni-Plex,
Inc. As disclosed in Schmitt, an outer layer of PVC and an inner
fluid-contact layer of low density polyethylene (LDPE) are
co-extruded with an intermediate tie layer of ethylene vinyl
acetate copolymer (EVA). However, while Schmitt greatly reduces the
possibility for the migration of additives from the PVC to the
fluid and absorption of components from the fluid to the PVC tubing
by providing a LDPE fluid-contact layer, elimination of the PVC is
preferred. Other tubing configurations are disclosed in U.S. Pat.
No. 7,647,949, U.S. Pat. No. 4,211,741 and U.S. Patent Publication
No. 2007/0119511, the disclosures of which are incorporated by
reference as if fully set forth herein.
SUMMARY OF THE INVENTION
[0004] In accordance with the invention there is provided a tubing,
tube or tubular device that comprises at least three concentric
layers of polymeric materials comprising an outer layer of a first
selected polymeric material (typically comprised of at least about
90% by weight of a polyurethane), an inner layer of a second
selected polymeric material (typically comprised of at least about
90% by weight of a polyethylene) and an intermediate layer of a
third polymeric material (typically comprised of at least about 90%
by weight of an acrylate containing polymer) that is disposed
between and binds the inner and outer layers together by adhesion
mechanisms, such as chemical adhesion. The layers of polymeric
materials are co-extruded together to form the tubing such that the
outer and inner layers are adhered to the intermediate or middle
layer and thus adhered to each other. The tubing is formed with a
central hollow channel, bore or passage that is radially surrounded
and defined by the polymeric layers that act as the walls of the
tubing.
[0005] The polymeric materials are preferably "contaminant free"
meaning that they do not contain more than insignificant amounts of
potentially unwanted materials (typically less than aboutout 0.5%
and preferably less than about 0.2%, by weight) and/or prevent
leaching or leaking of unwanted materials such as plasticizers,
catalysts, monomers, metals, salts, ions or other substances that
are potentially unwanted to a human being into an aqueous solution
or medium with which one or the other of the three layers may come
into contact during the normal course of use of the tubing in
delivering aqueous fluid, such as insulin, chemotherapy drugs and
other potentially unstable aqueous drug suspensions, to or from a
human subject. In addition to acting as an adhesive between and
adhering to the outer and inner layers, the intermediate layer
prevents delamination of the outer and inner layers from the
intermediate layers under conditions of relatively low to moderate
stress or strain. In addition, the intermediate layer acts as a
barrier to leaching or leaking of contaminants from the outer layer
to or through the inner layer into the hollow central bore or
passage of the tube.
[0006] Preferably the polymeric material of the outer layer is
comprised of a polyurethane thermoplastic elastomeric material
("TPU"), the inner layer is comprised of a polyethylene ("PE"),
typically a low density polyethylene ("LDPE"), linear low density
polyethylene ("LLDPE"), high density polyethylene ("HDPE") or
blends thereof, and the intermediate or middle layer is comprised
of an ethylene ethyl acrylate copolymer (EEA), ethylene methyl
acrylate copolymer (EMA), an anhydride grafted ethylene methyl
acrylate copolymer (AEMA), a copolymer of two or more of said
acrylates or a mixture of two or more of the foregoing.
[0007] With reference to FIGS. 1, 2, preferably the polyurethane
outer layer 1 is between about 0.001'' and about 0.025'' in
thickness, T3, the inner layer polyethylene layer 3 is between
about 0.001'' and about 0.025'' in thickness, T1, and the
intermediate acrylate copolymer layer 2 is between about 0.001''
and about 0.025'' in thickness, T2. The layers 1, 2, 3 collectively
form a tubular wall surrounding and defining a central fluid flow
passage 20.
[0008] Ethylene ethyl acrylate copolymers (EEA), Ethylene methyl
acrylate (EMA) copolymers and anhydride grated ethylene methyl
acrylate (AEMA) copolymers are elastomeric in nature and have
excellent visual clarity. In a typical 3M3L co-extrusion process,
TPU, EEA or EMA or AEMA and PE are melt extruded through a die head
to form a tubular shaped extrudate that is then cooled through
conventional water baths or water vacuum tanks and which are either
subsequently wound or cut into a particular length for use. The
level of elasticity and softness of the EEA, EMA AEMA or copolymer
thereof is controlled through the amount of ethyl acrylate or
methyl acrylate comonomer utilized with ethylene in the
copolymerization process. The resulting three layer tubes
manufactured by such a co-extrusion process act in a monolithic
manner in that they return to close to their original shape and
dimensions after being strained or stretched in a tensile manner
along the longitudinal axis of the tube at a stress of up to about
55 MPa and a strain of up to about 900-950% and without any visual
delaminaton between any of the layers after being submersed in
water at about 60.degree. C. for about 36 hours.
[0009] In accordance with the invention there is provided a tube
comprising an inner layer, an outer layer and a middle layer,
wherein the inner layer comprises a polyethylene, the outer layer
comprises a thermoplastic polyurethane and the middle layer
comprises an ethylene ethyl acrylate copolymer or an ethylene
methyl acrylate copolymer or an anhydride grafted ethylene methyl
acrylate copolymer, a copolymer of two or more of said acrylates or
a mixture of two or more of the foregoing.
[0010] The inner layer typically comprises more than about 90% by
weight of a polyethylene, the outer layer typically comprises more
than about 90% by weight of an aromatic or aliphatic polyether
based polyurethane and the middle layer typically comprises more
than about 90% by weight of an ethylene ethyl acrylate
copolymer.
[0011] The polyethylene typically comprises one or more of a low
density polyethylene, a linear low density polyethylene and a high
density polyethylene, the aromatic polyether based polyurethane
typically comprises a polytetramethyleneglycol-based polyurethane
and the ethylene ethyl acrylate copolymer typically comprises at
least about 19.5 percent ethyl acrylate content by weight.
[0012] The inner layer typically comprises more than about 90% by
weight of polyethylene, the outer layer typically comprises more
than about 90% by weight of a aromatic polyether based polyurethane
and the middle layer typically comprises more than about 90% by
weight of an ethylene methyl acrylate copolymer.
[0013] The inner layer can comprise more than about 90% by weight
of low density polyethylene (LDPE) while the outer layer comprises
more than about 90% by weight of a polytetramethyleneglycol-based
polyurethane and the middle layer comprises more than about 90% an
anhydride grafted ethylene methyl acrylate copolymer.
[0014] Typically, the thickness of the polyurethane outer layer is
between about 0.001'' and about 0.025'', the thickness of the inner
polyethylene layer is between about 0.001'' and about 0.025'' and
the thickness of the intermediate acrylate copolymer layer is
between about 0.001'' and about 0.025''.
[0015] Most preferably, the inner and outer layers do not visually
delaminate from each other at a stress up to of about 55 MPa and a
strain of up to about 900-950% when measured by pulling a length of
tubing about 2 inches in axial length along its axis using a Lloyd
LR5K plus mechanical tester at a pull rate of about 12
inches/minute at ambient environmental conditions of about 72
degrees F. and about 50% relative humidity, the break point of the
tubing 10 being about 57-62 MPa and about 1000-1050%.
[0016] Most preferably, the tube does not visually delaminate after
being subjected to submersion in water at 60.degree. C. for 36
hours and subsequently mechanically flattened by manual squeezing
of the tube from its normal round in cross-sectional condition to a
flattened or oval shape cross-sectional shape or condition.
[0017] Preferably the tube has a central axial fluid flow passage
through which aqueous fluid is routed, the inner layer having a
radially inner wall surface that contacts the aqueous fluid, the
outer and inner layers resisting delamination from each other at a
stress of up to about 55 MPa and a strain of up to about
900-950%.
[0018] In another aspect of the invention there is provided a
medical tube for transport of aqueous fluid comprising: [0019] an
inner layer comprising more than about 90% by weight of a
polyethylene [0020] an outer layer comprising more than about 90%
by weight of a an aromatic polyether-based polyurethane and, [0021]
a middle layer disposed between the outer and inner layers
comprising more than about 90% by weight of an ethylene ethyl
acrylate copolymer or an ethylene methyl acrylate copolymer or an
anhydride grafted ethylene methyl acrylate copolymer, a copolymer
of two or more of said acrylates or a mixture of two or more of the
foregoing.
[0022] In such an embodiment, the inner and outer layers preferably
do not visually delaminate from each other at a stress of up to
about 55 MPa and a strain of up to about 900-950%. And such a tube
preferably does not visually delaminate after being submersed in
water at 60.degree. C. for 36 hours.
[0023] In another aspect of the invention there is provided, a
medical tube for transport of an aqueous fluid comprising: [0024]
an inner layer comprised of at least about 90% by weight of a
polyethylene. [0025] an outer layer comprised of at least about 90%
by weight of an aromatic polyether-based polyurethane, [0026] a
middle layer disposed between the inner and outer layers comprised
of at least about 90% by weight of an ethylene ethyl acrylate
copolymer, an ethylene methyl acrylate copolymer, an anhydride
grafted ethylene methyl acrylate copolymer, a copolymer of two or
more of said acrylates or a mixture of two or more of the
foregoing, [0027] wherein said tubing does not visually delaminate
after being submersed in water at 60.degree. C. for 36 hours.
[0028] In another aspect of the invention there is provided a
medical tube for transport of an aqueous fluid comprising: [0029]
an inner layer comprised of at least about 90% by weight of a low
density polyethylene, [0030] an outer layer comprised of at least
about 90% by weight of a polytetramethyleneglycol-based
polyurethane, [0031] a middle layer comprised of at least about 90%
by weight of an ethylene ethyl acrylate copolymer, an ethylene
methyl acrylate copolymer, an anhydride grafted ethylene methyl
acrylate copolymer, a copolymer of said acrylates or a mixture of
two or more of the foregoing, [0032] wherein the tubing does not
visually delaminate at a stress of up to about 55 MPa and a strain
of up to about 900-950%, and, [0033] wherein the tubing does not
visually delaminate after being submersed in water at 60.degree. C.
for 36 hours.
[0034] Most preferably the middle layer serves as a barrier
against, prevents or substantially lessens migration of mobile
moieties such as monomers, short chained polymers, ions, water,
small organic molecules, metals, plasticizers, catalysts and the
like between the outer and inner layers or from the outer layer
into the inner layer or the central flow passage or from the
central flow passage or inner layer into the outer layer.
[0035] Further in accordance with the invention there is provided a
method of forming a medical tube comprising an outer layer, an
innermost layer and an intermediate layer disposed between the
outer layer and the innermost layer, the method comprising:
[0036] selecting a first polymeric material having a selected
structural stability;
[0037] selecting a second polymeric material that is inert to
aqueous fluids;
[0038] selecting a third polymeric material that readily bonds and
adheres to the first and second polymeric materials on co-extrusion
and cooling of the materials;
[0039] co-extruding the selected first, second and third polymeric
materials to form the medical tubing in a configuration such that
the outer layer comprises at least about 90% by weight of the first
polymeric material, the inner layer comprises at least about 90%
weight of the second polymeric material and the intermediate layer
comprises at least about 90% by weight of the third polymeric
material.
[0040] Preferably in such a method the first polymeric material is
selected to be a polyurethane, the second polymeric material is
selected to be a polyethylene and the third polymeric material is
selected from the group consisting of an ethylene ethyl acrylate
copolymer, an ethylene methyl acrylate copolymer, an anhydride
grafted ethylene methyl acrylate copolymer, a copolymer of said
acrylate copolymers or a mixture of two or more of the
foregoing.
[0041] Further in accordance with the invention there is provided a
method of delivering an aqueous fluid to a subject comprising;
[0042] selecting a tube comprising an inner layer, an outer layer
and a middle layer, wherein the inner layer comprises a
polyethylene, the outer layer comprises a thermoplastic
polyurethane and the middle layer comprises an ethylene ethyl
acrylate copolymer or an ethylene methyl acrylate copolymer or an
anhydride grafted ethylene methyl acrylate copolymer, a copolymer
of two or more of said acrylates or a mixture of two or more of the
foregoing;
[0043] wherein the tube has a central fluid flow passage surrounded
by the layers;
[0044] routing an aqueous fluid through the central fluid flow
passage of the tube, and,
[0045] delivering the aqueous fluid routed through the central
fluid flow passage into a blood vessel of the subject.
[0046] In such a method, the step of selecting preferably
comprises:
[0047] co-extruding the outer, inner and middle layers to form the
tube such that the outer layer comprises at least about 90% by
weight of the polyurethane, the inner layer comprises at least
about 90% weight of the polyethylyene and the intermediate layer
comprises at least about 90% by weight of one or more of the
arcylate copolymers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] The drawings depict one or more embodiments of the invention
that are shown by way of examples of the invention wherein:
[0049] FIG. 1 is a schematic perspective view of a tri-layered tube
showing the outer and middle or intermediate layers broken away in
order to better illustrate the construction and arrangement of the
tubing;
[0050] FIG. 2 is a cross-sectional view taken along lines 2-2 of
the tube 10 shown in FIG. 1.
DETAILED DESCRIPTION
[0051] There is shown in FIG. 1 an embodiment of a co-extruded
tri-layer tubing 10 according to the invention which comprises an
outer layer 1 comprised of at least about 90% by weight of a
polyurethane material, typically a polytetramethyleneglycol-based
polyurethane one example of which is Lubrizol TPU Pellethane
2363-90AE, an inner fluid-contact layer 3 comprised of at least
about 90% by weight of a polyethylene material, typically a low
density polyethylene, one example of which is Westlake LDPE EM808AA
and an intermediate bonding layer 2 comprised of at least about 90%
by weight of an ethylene ethyl acrylate copolymer, an ethylene
methyl acrylate copolymer, an anhydride grafted ethylene methyl
acrylate copolymer, a copolymer of two or more of said acrylates or
a mixture of two or more of these acrylate based compounds or
compositions. One example of a suitable ethylene ethyl acrylate
copolymer is Dow Amplify EA 103 (Ethylene Ethyl Acrylate being
about 19.5% by weight). Examples of suitable ethylene methyl
acrylate copolymers are Westlake MA SP2268 (Ethylene Methyl
Acrylate being about 24% by weight), Westlake MA SP2220 (Ethylene
Methyl Acrylate being about 20% by weight). One example of a
suitable anhydride grafted ethylene methyl acrylate copolymer is
Westlake Tymax GA 7001 (Anhydride grafted Ethylene Methyl
Acrylate)
[0052] As shown in FIG. 1 the outer layer of polyurethane 1 has a
radially inner facing surface S1 that binds and adheres to a
radially outer facing surface S2 of the intermediate acrylate
copolymer layer 2. Similarly the inner layer of polyethylene
material 3 has a radially outer facing surface S4 that binds and
adheres to the radially inner facing surface S3 of the intermediate
acrylate copolymer layer 2. The intermediate layer 2 adheres to the
outer 1 and inner 3 layers such that the layers 1 and 3 remain
adhered to layer 2 and to each other when the tube 10 is subjected
to a stress of up to about 55 MPa and a strain of up to about
900-950% as measured by pulling a length of tubing 10 of about 2
inches in axial length L along its axis A using a Lloyd LR5K Plus
mechanical tester at a pull rate of about 12 inches/minute at
ambient environmental conditions of about 72 degrees F. and about
50% relative humidity, the break point of the tubing 10 being at
about 57-62 MPa and about 1000-1050%. The layers 1, 2, 3 of such
tubing 10 does not visually delaminate after being subjected to
submersion in water at 60.degree. C. for 36 hours and subsequently
mechanically flattened by manual squeezing of the tube from its
normal round in cross-sectional condition to a flattened or oval
shape cross-sectional shape or condition.
[0053] As shown in FIGS. 1 and 2, the layers 1, 2, 3 are formed
into structurally stable walls that surround and enclose a central
hollow fluid passage 20 through which an aqueous solution is routed
and flows in an axial A direction contacting the radially inner
facing surface S5 of the inner layer 3. The intermediate layer 2
binds and holds the inner 3 and outer 1 layers together.
[0054] The inner layer 3 provides a radially inner fluid-contact
surface S5, the thickness, of the inner layer 3 typically ranging
in cross-sectional thickness T1 of between about 0.001 inches and
about 0.025 inches. The intermediate layer 2 typically ranges in
cross-sectional thickness T2 of between about 0.001 inches and
about 0.025 inches. The outer layer 1 typically ranges in
cross-sectional thickness T3 of between about 0.001 inches and
about 0.025 inches.
[0055] The polyethylene material is preferably a branched
low-density polyethylene (LDPE), such as Westlake EM808, available
from Westlake Chemical Corporation. The polyethylene material can
be a linear low density polyethylene (LLDPE) such as Dowlex 2035G,
available from the Dow Chemical Company. The polyethylene material
can also be a high-density polyethylene (HDPE), such as Chevron
9506 HDPE, Chevron 9406 HDPE, and Chevron 9503 HDPE, available from
Chevron Corporation.
[0056] The polyurethane elastomer (TPU) is typically the reaction
product of a polyol and isocyanate and usually includes a
combination of hard and soft segment domains. An aromatic
polyether-based TPU or an aliphatic polyether-based TPU can be used
such as a polytetramethyleneglycol-based polyurethane. Preferred,
TPU's include the Pellethane 2363-80 AE series available from the
Lubrizol Corporation such as Lubrizol TPU Pellethane 2363-90AE.
[0057] The respective thickness of each layer of tubing 10,20 can
be controlled by the extrusion tooling utilized, such as the "Tri
Die" extrusion apparatus manufactured by the Genca Division of
General Cable Company, Clearwater, Fla. The extrusion apparatus is
selected so as to provide a uniform thickness of the layers 1, 2, 3
along the substantial entirety of the axial length L of all three
layers 1, 2, 3.
[0058] The polymeric materials of which the layers 1, 2, 3 are
comprised are selected so as to be visually clear or transparent
and manually flexible along and around the axis A of the tubing.
The polymeric materials are also selected so as to maintain the
integrity of the tubing 10 (namely delamination does not occur) and
its transparency or clarity after being subjected to ethylene oxide
(EtO) and gamma irradiation sterilization processes.
[0059] The foregoing description is intended to illustrate and not
limit the scope of the invention, those skilled in the art will
realize that equivalents thereof are contemplated by the
description above and that changes and modifications may be made
thereto without departing from the spirit of the invention, all
such equivalents, changes and modifications falling within the
scope of the claims hereof.
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