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United States Patent |
5,693,387
|
Rosenbaum
,   et al.
|
December 2, 1997
|
Multilayer, halide free, retortable barrier film
Abstract
A multiple layer structure comprising a skin layer, a barrier layer, a
radio frequency susceptible layer having a first polyolefin in an amount
within a range of 30-60% by weight, a second polyolefin in an amount
within the range of 25-50% by weight, a radio frequency susceptible
polymer in an amount within the range of 3-40% by weight, a styrene and
hydrocarbon block copolymer in an amount within the range of 5-40% by
weight of the sealant layer.
Inventors:
|
Rosenbaum; Larry (Gurnee, IL);
Giovanetto; Steven (Vernon Hills, IL);
Smith; Sidney T. (Lake Forest, IL);
Bacehowski; David V. (Wildwood, IL);
Nebgen; Gregg (Burlington, WI);
Kalyankar; Varsha (Round Lake Beach, IL)
|
Assignee:
|
Baxter International Inc. (Deerfield, IL)
|
Appl. No.:
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484767 |
Filed:
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June 7, 1995 |
Intern'l Class: |
B29D 022/00; 345; 332 |
Field of Search: |
428/35.2,35.4,35.7,36.6,36.7,36.8,36.9,475.5,475.8,476.1,476.3,476.9,515,523
|
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Other References
Polymer Handbook, 3rd. Ed., J. Brandrup and E. H. Immergut, John Wiley &
Sons.
Encyclopedia of Polymer Science and Engineering, vol. 16, Styrene, Polymers
to Toys, John Wiley & Sons.
Toughened Plastics, C.B. Bucknall, Applied Science Publishers, Ltd.
Polymer Blends, vol. 1, Seymour Newman, Academic Press.
Thermoplastics for Health-Care Products: Clear Choices Are Not So Clear,
K.Z. Hong, Ph.D., Baxter Healthcare Corporation.
Plastics Engineering, Oct., 1995, Official Publication of The Society of
Plastics Engineers.
|
Primary Examiner: Buffalow; E. Rollins
Attorney, Agent or Firm: Buonaiuto; Mark J., Fuchs; Joseph A.
Claims
We claim:
1. A multiple layer structure comprising:
a skin layer;
a barrier layer;
a radio frequency susceptible layer having a first polyolefin in an amount
within a range of 30-60% by weight of the susceptible layer, a second
polyolefin in an amount within the range of 25-50% by weight, a radio
frequency susceptible polymer in an amount within the range of 3-40% by
weight of the susceptible layer a styrene and hydrocarbon block copolymer
in an amount within the range of 5-40% by weight of the susceptible layer;
and
wherein the structure has a mechanical modulus of less than 40,000 psi when
measured in accordance with ASTM D-882.
2. The structure of claim 1 wherein the barrier layer is selected from the
group consisting of ethylene vinyl alcohol, and polyamides.
3. The structure of claim 2 wherein the skin layer comprises: a
polypropylene copolymer with styrene ethylene-butene-styrene block
copolymer within a range of 0-20% by weight of the polypropylene.
4. The structure of claim 3 wherein the first polyolefin is a
polypropylene, and the second polyolefin is selected from the group of
ethylene copolymers including ultra low density polyethylene,
polybutene-1, butene ethylene copolymers, ethylene vinyl acetate
copolymers with vinyl acetate contents between approximately 18-50%,
ethylene methyl acrylate copolymers with methyl acrylate contents being
between approximately 20-40%, ethylene n-butyl acrylate copolymers with
n-butyl acrylate content of between 20-40%, and ethylene acrylic acid
copolymers with the acrylic acid content of greater than approximately
15%.
5. The structure of claim 3 wherein the radio frequency susceptible polymer
is selected from the group of polyamides, ethylene vinyl acetate with
vinyl acetate in an amount of 18-50% by weight, ethylene methyl acrylate
copolymers with methyl acrylate in an amount between 20%-40% by weight,
and ethylene vinyl alcohol with vinyl alcohol in an amount of 15%-70%.
6. The structure of claim 5 wherein the styrene and hydrocarbon block
copolymer is a styrene-ethylene-butene-styrene block copolymer.
7. The structure of claim 6 further including two tie layers, one tie layer
being disposed between the skin layer and the barrier layer, and the other
tie layer being disposed between the barrier layer and the radio frequency
susceptible layer.
8. The structure of claim 7 wherein the tie layers are selected from the
group of maleic anhydride modified polyolefins, and maleic anhydride
modified propylene and ethylene copolymers.
9. The structure of claim 7 wherein the radio frequency polymer is a dimer
fatty acid polyamide.
10. The structure of claim 7 wherein the skin layer has a thickness within
a range of 0.5 mil-4.0 mil, the barrier layer has a thickness within the
range of 0.3 mil-5.0 mil, the radio frequency susceptible layer has a
thickness within the range of 2.0 mil-8.0 mil, and the tie layers each
have a thickness within the range 0.3 mil-1.0.
11. A multiple layer structure comprising:
a skin layer;
a barrier layer;
a first and a second radio frequency susceptible layer having a first
polyolefin in an amount within a range of 30-60% by weight of the
susceptible layer, a second polyolefin in an amount within the range of
25-50% by weight of the susceptible layer, a radio frequency susceptible
polymer in an amount within the range of 3-40% by weight of the
susceptible layer, a styrene and hydrocarbon block copolymer in an amount
within the range of 5-40% by weight of the susceptible layer;
a first polypropylene layer disposed between the first and the second radio
frequency susceptible layers, each of the first and second radio frequency
susceptible layers having a thickness; and
wherein the structure has a mechanical modulus of less than 40,000 psi when
measured in accordance with ASTM D-882.
12. The structure of claim 11 wherein the first and second radio frequency
susceptible layer are of the same thickness.
13. The structure of claim 11 wherein the first and second radio frequency
susceptible layer are of different thicknesses.
14. The structure of claim 11 wherein the layers are stacked in consecutive
order.
15. The structure of claim 14 further comprising:
a first tie layer disposed between the skin layer and the barrier layer;
and
a second tie layer disposed between the barrier layer and the first radio
frequency susceptible layer.
16. The structure of claim 11 wherein the barrier layer is selected from
the group consisting of ethylene vinyl alcohol, and polyamides.
17. The structure of claim 16 wherein the first polyolefin is a second
polypropylene, and the second polyolefin is selected from the group of
ethylene copolymers including ultra low density polyethylene,
polybutene-1, butene ethylene copolymers, ethylene vinyl acetate
copolymers with vinyl acetate contents between approximately 18-50%,
ethylene methyl acrylate copolymers with methyl acrylate contents being
between approximately 20-40%, ethylene n-butyl acrylate copolymers with
n-butyl acrylate content of between 20-40%, and ethylene acrylic acid
copolymers with the acrylic acid content of greater than approximately
15%.
18. The structure of claim 17 wherein the skin layer comprises: a
polypropylene copolymer with styrene ethylene-butene-styrene block
copolymer within a range of 0-20% by weight of the polypropylene.
19. A multiple layer structure comprising:
a skin layer;
a barrier sandwich layer having from 2 to 10 units of a barrier layer and a
tie layer; and
a radio frequency susceptible layer having a first polyolefin in an amount
within a range of 30-60% by weight, a second polyolefin in an amount
within the range of 25-50% by weight, a radio frequency susceptible
polymer in an amount within the range of 3-40% by weight, a styrene and
hydrocarbon block copolymer in an amount within the range of 5-40% by
weight.
20. The structure of claim 19 further comprising a tie layer between the
skin layer and the barrier sandwich.
21. The structure of claim 20 wherein the first polyolefin is a
polypropylene, and the second polyolefin is selected from the group of
ethylene copolymers including ultra low density polyethylene,
polybutene-1, butene ethylene copolymers, ethylene vinyl acetate
copolymers with vinyl acetate contents between approximately 18-50%,
ethylene methyl acrylate copolymers with methyl acrylate contents being
between approximately 20-40%, ethylene n-butyl acrylate copolymers with
n-butyl acrylate content of between 20-40%, and ethylene acrylic acid
copolymers with the acrylic acid content of greater than approximately
15%.
22. The structure of claim 21 wherein the barrier layer is selected from
the group consisting of ethylene vinyl alcohol, and polyamides.
23. The structure of claim 22 wherein the tie layer is selected from the
group of maleic anhydride modified polyolefins, and maleic anhydride
modified propylene and ethylene copolymers.
Description
TECHNICAL FIELD
The present invention relates generally to materials for making medical
grade products and more specifically to a film product which may be used
to manufacture articles such as plastic containers and medical tubing.
BACKGROUND ART
In the medical field, where beneficial agents are collected, processed and
stored in containers, transported, and ultimately delivered through tubes
by infusion to patients to achieve therapeutic effects, materials which
are used to fabricate the containers must have a unique combination of
properties. For example, in order to visually inspect solutions for
particulate contaminants, the container must be optically transparent. To
infuse a solution from a container by collapsing the container walls,
without introducing air into the container, the material which forms the
walls must be sufficiently flexible. The material must be functional over
a wide range of temperatures. The material must function at low
temperatures by maintaining its flexibility and toughness because some
solutions, for example, certain premixed drug solutions are stored and
transported in containers at temperatures such as -25.degree. to
-30.degree. C. to minimize the drug degradation. The material must also be
functional at high temperatures to withstand the heat of sterilization; a
process which most medical packages and nutritional products are subjected
to prior to shipment. The sterilization process usually includes exposing
the container to steam at temperatures typically 121.degree. C. and at
elevated pressures. Thus, the material needs to withstand the temperature
and pressures without significant distortions ("heat distortion
resistance").
For ease of manufacture into useful articles, it is desirable that the
material be sealable using radio frequency ("RF") generally at about 27.12
MHz. Therefore, the material should possess sufficient dielectric loss
properties to convert the RF energy to thermal energy.
A further requirement is to minimize the environmental impact upon the
disposal of the article fabricated from the material after its intended
use. For those articles that are disposed of in landfills, it is desirable
to use as little material as possible and avoid the incorporation of low
molecular weight leachable components to construct the article. Thus, the
material should be light weight and have good mechanical strength. Further
benefits are realized by using a material which may be recycled by
thermoplastically reprocessing the post-consumer article into other useful
articles.
For those containers which are disposed of through incineration, it is
necessary to use a material which helps to eliminate the dangers of
biological hazards, and to minimize or eliminate entirely the formation of
inorganic acids which are environmentally harmful, irritating, and
corrosive, or other products which are harmful, irritating, or otherwise
objectionable upon incineration. It is also desirable that the material be
free from or have a low content of low molecular weight additives such as
plasticizers, stabilizers and the like which could be released into the
medications or biological fluids or tissues thereby causing danger to
patients using such devices or are contaminating such substances being
stored or processed in such devices. For containers which hold solutions
for transfusion, such contamination could make its way into the
transfusion pathway and into the patient causing injury or death to the
patient.
Traditional flexible polyvinyl chloride materials meets a number of, and in
some cases, most of the above-mentioned requirements. Polyvinyl chloride
("PVC") also offers the distinct advantage of being one of the most cost
effective materials for constructing devices which meet the above
requirements. However, PVC may generate objectionable amounts of hydrogen
chloride (or hydrochloric acid when contacted with water) upon
incineration, causing corrosion of the incinerator. PVC sometimes contains
plasticizers which may leach into drugs or biological fluids or tissues
that come in contact with PVC formulations. Thus, many materials have been
devised to replace PVC. However, most alternate materials are too
expensive to implement and still do not meet all of the above
requirements.
There have been many attempts to develop a film material to replace PVC,
but most attempts have been unsuccessful for one reason or another. For
example, in U.S. Pat. No. 4,966,795 which discloses multilayer film
compositions capable of withstanding the steam sterilization, cannot be
welded by radio frequency dielectric heating thus cannot be assembled by
this rapid, low costs, reliable and practical process. European
Application No. EP 0 310 143 A1 discloses multilayer films that meet most
of the requirements, and can be RF welded. However, components of the
disclosed film are cross-linked by radiation and, therefore, cannot be
recycled by the standard thermoplastic processing methods. In addition,
due to the irradiation step, appreciable amounts of acetic acid is
liberated and trapped in the material. Upon steam sterilization, the
acetic acid migrates into the packaging contents as a contaminant and by
altering the pH of the contents acts as a potential chemical reactant to
the contents or as a catalyst to the degradation of the contents.
The main objective of the present invention is the creation of
thermoplastic materials which are, overall, superior to those materials,
of which we are aware, which have been heretofore known to the art or have
been commercially used or marketed. The properties of such materials
includes flexibility, extensibility, and strain recoverability, not just
at room temperatures, but through a wide range of ambient and refrigerated
temperatures. The material should be sufficiently optically transparent
for visual inspection, and steam sterilizable at temperatures up to
121.degree. C. The material should be capable of being subjected to
significant strains without exhibiting strain whitening, which can
indicate a physical and a cosmetic defect. A further objective is that the
material be capable of assembly by the RF methods. Another objective is
that the material be substantially free of low molecular weight leachable
additives, and be capable of safe disposal by incineration without the
generation of significant amounts of corrosive inorganic acids. Another
objective is that the material be recyclable by standard thermoplastic
processing methods after use. It is also desirable that the material
incorporate reground scrap material recovered during the manufacturing
process to save material costs and reduce manufacturing waste. Finally,
the material should serve as a cost effective alternative to various PVC
formulations currently being used for medical devices.
When more than one polymer is blended to form an alloying composition, it
is difficult to achieve all of the above objectives simultaneously. For
example, in most instances alloy composition may scatter light; thus, they
fail to meet the optical clarity objective. The light scattering intensity
(measured by haze) depends on the domain size of components in the
micrometer (.mu.) range, and the proximity of the refractive indices of
the components. As a general rule, the selection of components that can be
satisfactorily processed into very small domain sizes, and yet with a
minimum of refractive index mismatches, is a difficult task.
In addition to the desirable properties above, in many medical and food
storage applications, it is desirable to provide a film that has barrier
properties to oxygen, carbon dioxide, and water permeability. For medical
solutions that are packaged having a desired concentration of a drug or
solute, the barrier to water helps maintain this concentration by
preventing water from escaping from the container. In solutions that have
a buffer to prevent pH changes, such as a commonly used sodium bicarbonate
buffer, the barrier to carbon dioxide helps maintain the buffer by
preventing carbon dioxide from escaping from the container. For medical
solutions containing proteins or amino acids, the oxygen barrier helps
prevent the ingress of oxygen which can oxidize the protein or amino acid
rendering the solution ineffective for its intended purpose. For food
containers, these barriers help keep the flavor in the food and out of the
surrounding food items.
Such a film may be used to construct containers, and other medical devices,
for containing, processing and handling oxygen sensitive enteral and
parenteral solutions. Many of these solutions are stored and shipped in a
container which must be terminally sterilized after filling the container.
Current containers for storing oxygen sensitive materials such as
vitamins, are constructed from a film that is laminated and incorporates
foil and/or polyvinylidene dichloride (PVDC) barrier layers. Such
laminated films are quite costly on a unit basis as compared to the
coextruded film products of the present invention. Further, the laminate
foil and PVDC films are not susceptible to radio frequency energy and thus
cannot be sealed using RF welding techniques. The foil containers, even
when toughened using nylon, remain a fragile structure prone to flex
cracking, pinholes, and have low impact resistance. Additionally, the
films containing PVDC have high quantities of extractables which are known
to originate from the adhesives used to laminate the film. PVDC also
contains chlorine which may have a deleterious environmental impact upon
disposal.
Ethylene vinyl alcohol is another effective barrier material. However,
ethylene vinyl alcohol has presented difficulties in use where the
material must be subjected to an autoclaving sterilization process which
at normal autoclave temperatures exceed the melt point of the ethylene
vinyl alcohol.
The present invention is provided to solve these and other problems.
DISCLOSURE OF INVENTION
In accordance with the present invention certain multiple layer polymer
based structures are disclosed. The structures may be fabricated into
medical articles such as containers for storing medical solutions or blood
products, blood bags, and related items, or other products constructed
from multi-layered structures.
It is an object of the present invention to prepare a multi-layered film
having the following physical properties: (1) a mechanical modulus less
than 40,000 psi and more preferably less than 25,000 psi when measured in
accordance with ASTM D-882, (2) a greater than or equal to 70%, and more
preferably greater than or equal to 75%, recovery in length after an
initial deformation of 20%, (3) and optical haze of less than 30%, and
more preferably less than 15%, when measured for a composition 9 mils
thick and in accordance to ASTM D-1003, (4) the loss tangent measured at 1
Hz at processing temperatures is greater than 1.0, and more preferably
greater than 2.0, (5) the content of elemental halogens is less than 0.1%,
and more preferably less than 0.01%, (6) the low molecular weight water
soluble fraction is less than 0.1%, and more preferably less than 0.005%,
(7) the maximum dielectric loss between 1 and 60 MHz and between the
temperature range of 25.degree.-250.degree. C. is greater than or equal to
0.05 and more preferably greater than or equal to 0.1, (8) autoclave
resistance measured by sample creep at 121.degree. C. under 27 psi loading
is less than or equal to 60% and more preferably less than or equal to
20%, and (9) there is no strain whitening after being strained at moderate
speeds of about 20 inches (50 cm) per minute at about 100% elongation and
the presence of strain whitening is noted or the lack thereof.
The multiple layer structure of the present invention comprises a skin
layer preferably composed of a polypropylene copolymers with styrene and
hydrocarbon block copolymers. More preferably a propylene copolymer with
ethylene-butene styrene ("SEBS") within a range of 0-20% by weight of the
skin layer. The structure further includes a radio frequency ("RF")
susceptible layer adhered to the skin layer. The RF layer is composed of a
first component of a polypropylene polymer, a second component of a
non-propylene polyolefin (one that does not contain propylene repeating
units), a third component of a radio frequency susceptible polymer, and a
fourth component of a polymeric compatibilizing agent. In alternate
embodiments, additional layers such as core, scrap, and barrier layers are
added to the skin and RF layers to confer additional or enhanced
functionality of the resultant film structure.
The RF layer is the subject of the concurrently filed U.S. patent
application docket no. 1417 P030 now Ser. No. 08/487,361 which is
incorporated herein by reference. The multi-layered film structure of the
present invention offers additional features that the compositions of the
RF layer alone do not provide. The additional features of the multi-layer
film include an exterior surface gloss and reduced tackiness to the
outside surface of the film structure. Additionally, the multilayered film
structure has improved vapor barrier properties, greater strength and
optical clarity, and is cleaner or has reduced tendency to migrate into
the contents of the container.
The core layer, which is interposed between the skin layer and the RF layer
consists of three components. Preferably, the first component is
polypropylene which constitutes about 40% of the core layer, the second
component is an ultra low density polyethylene ("ULDPE") which constitutes
about 50% by weight of the core layer, and the third component is
styrene-hydrocarbon block copolymer and more preferably an SEBS block
copolymer which constitutes about 10% by weight of the core layer. The
entire core layer should be 4.0 mils thick.
It is also desirable, for economic reasons among others, to incorporate
reground scrap material recovered during the processing of the film
material back into the composition of a film structure. This can lead to
using significant amount of scrap material as a weight percent of the
entire layer structure, thereby substantially decreasing the costs of the
film product. The reground scrap may be incorporated into the
above-described structure either as an additional discrete layer located
somewhere between the skin layer and the RF layer or may be blended into
the core layer as an additional component. In either case, significant
resources are saved by reprocessing the scrap material.
To increase gas barrier properties of the structure, it is desirable to
incorporate a barrier layer between the skin layer and the RF layer. The
barrier layer may be attached to surrounding layers using adhesive tie
layers. The barrier layer may be selected from ethylene vinyl alcohols
such as that sold under the name Evalca (Evalca Co.), highly glass or
crystalline polyamide such as Sclar PA.RTM. (Dupont Chemical Co.), high
nitrile content acrylonitrile copolymers such as those sold under the
tradename Barex.RTM. sold by British Petroleum. In particular the barrier
structure will have a skin layer of polypropylene having a thickness
within the range of 0.5 mil-4.0 mil, more preferably 1.0 mil-3.0 mil, and
most preferably 1.0 mil, a barrier layer of ethylene vinyl alcohol having
a thickness within the range of 0.3 mil-5.0 mil, more preferably 1.5
mil-4.0 mil, and most preferably 2.0 mil, and an RF susceptible layer
within the range of 2.0-8.0 mil, more preferably 3.0-6.0, and most
preferably 4.0 mil. It has been found that such a structure may be
subjected to autoclave sterilization temperatures without loss of
integrity of the ethylene vinyl alcohol layer.
Increased resistance to oxygen, water, and carbon dioxide permeability has
been realized by dividing the barrier layer into a multi-ply stack of thin
barrier layers separated by tie layers. A single barrier layer 3.0 mil
thick may be divided into anywhere from two to ten barrier layers. In the
ten barrier layer embodiment each barrier layer would be 0.3 mil thick,
and each layer separated by a tie layer. A film structure with such a
multi-ply barrier sandwich would resemble the barrier film structures
discussed immediately above having a skin layer of polypropylene, a tie
layer, and a multi-ply barrier sandwich having from say 1 to 10
consecutive barrier and tie layer units, followed by the RF active layer
or a sealant layer of a polyolefin such as a polyethylene or
polypropylene.
Films having the aforesaid structure and compositions have been found to be
flexible, optically clear, non-strain whitening, and steam and radiation
sterilizable. Additionally, the films are compatible with medical
applications because the components which constitute the film have a
minimal extractability to the fluids and contents that the composition
come in contact with. Further, the films are environmentally sound in that
they do not generate harmful degradants upon incineration. Finally, the
films provide a cost effective alternative to PVC.
Additional features and advantages of the present invention are described
in, and will be apparent from, the drawing and the detailed description of
the presently preferred embodiments.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows a cross-sectional view of a two layered film structure of the
present invention;
FIG. 2 shows a cross-sectional view of a three layered film structure of
the present invention including a core layer added to the film of FIG. 1;
FIG. 3 shows a cross-sectional view of the film of FIG. 1 with a solution
contact layer;
FIG. 4 shows a cross-sectional view of a four layered structure of the
present invention having a discrete layer of scrap material between the
skin and the core layers;
FIG. 5 shows a cross-sectional view of a film structure using reground
scrap as a discrete layer between the core and the RF layers;
FIG. 6 shows a cross-sectional view of a film structure using reground
scrap as a discrete layer which splits the core layer into two core
layers;
FIG. 7 shows a cross-sectional view of a film structure of the present
invention having seven layers including a barrier layer between the core
and the RF layers and two tie layers;
FIG. 8 shows the same structure of FIG. 6 except the barrier layer is
disposed between the core layer and the skin layers; FIG. 9 shows a
cross-sectional view of a film structure having a barrier layer dividing
the core layers; FIG. 10 shows a container constructed from one of the
film structures of the present invention; FIG. 11 shows a cross-sectional
view of a structure having a skin layer, a barrier layer and an RF layer;
FIG. 12 shows the structure of FIG. 11 further including tie layers between
the principal layers;
FIG. 13 shows a multiple layered film having a layer of polypropylene
dividing the RF layer; and
FIG. 14 shows a multiple layered film having a barrier layer divided into
2-10 layers.
BEST MODE FOR CARRYING OUT THE INVENTION
While this invention is susceptible of embodiments in many different forms,
and will herein be described in detail, preferred embodiments of the
invention are disclosed with the understanding that the present disclosure
is to be considered as exemplifications of the principles of the invention
and are not intended to limit the broad aspects of the invention to the
embodiments illustrated.
According to the present invention, multiple layered film structures are
provided which meet the requirements set forth above.
FIG. 1 shows a two layered film structure 10 having a skin layer 12 and a
radio frequency ("RF") susceptible layer 14. The skin layer 12 confers
heat distortion resistance and abrasion resistance and is preferably a
polypropylene and more preferably a polypropylene copolymer blended with
styrene and hydrocarbon block copolymers. More preferably, the skin layer
12 is a polypropylene copolymer blended with SEBS block copolymer within a
range of 0-20% by weight. The skin layer 12 should have a thickness within
the range of 0.2-3.0 mils thick.
The RF susceptible layer 14 of the present invention should have a
dielectric loss of greater than 0.05 at frequencies within the range of
1-60 MHz within a temperature range of ambient to 250.degree. C. The RF
layer 14 preferably has four components. The RF layer 14 confers RF
sealability, flexibility, heat distortion resistance, and compatibility to
the film structure 10. The first component of the RF layer 14 is chosen
from polypropylene copolymers and preferably the propylene alpha-olefin
random copolymers ("PPE"). The PPE's possess the required rigidity and the
resistance to yielding at the autoclave temperatures of about 121.degree.
C. However, by themselves, the PPE's are too rigid to meet the flexibility
requirements. When combined by alloying with certain low modulus polymers,
good flexibility can be achieved.
These low modulus copolymers can include ethylene based copolymers such as
ethylene-co-vinyl acetate ("EVA"), ethylene co-alpha olefins, or the
so-called ultra low density (typically less than 0.90 Kg/L) polyethylenes
("ULDPE"). These ULDPE include those commercially available products sold
under the trademarks TAFMER.RTM. (Mitsui Petrochemical Co.) under the
product designation A485, Exact.RTM. (Exxon Chemical Company) under the
product designations 4023-4024, and Insite.RTM. technology polymers (Dow
Chemical Co.). In addition, poly butene-1 ("PB"), such as those sold by
Shell Chemical Company under product designations PB-8010, PB-8310;
thermoplastic elastomers based on SEBS block copolymers, (Shell Chemical
Company), poly isobutene ("PIB") under the product designations Vistanex
L-80, L-100, L-120, L-140 (Exxon Chemical Company), ethylene alkyl
acrylate, the methyl acrylate copolymers ("EMA") such as those under the
product designation EMAC 2707, and DS-1130 (Chevron), and n-butyl
acrylates ("ENBA") (Quantum Chemical) were found to be acceptable
copolymers. Ethylene copolymers such as the acrylic and methacrylic acid
copolymers and their partially neutralized salts and ionomers, such as
PRIMACOR.RTM. (Dow Chemical Company) and SURYLN.RTM. (E.I. DuPont de
Nemours & Company) were also acceptable. Typically, ethylene based
copolymers have melting point temperatures of less than about 110.degree.
C. are not suited for autoclaving at 121.degree. C. applications.
Furthermore, only a limited range of proportions of each component allows
the simultaneous fulfillment of the flexibility and autoclavability
requirements.
Preferably the first component is chosen from the group of polypropylene
homo and random copolymers with alpha olefins which constitutes
approximately 30-60%, more preferably 35-45%, and most preferably 45%, by
weight of the susceptible layer. For example, random copolymers of
propylene and ethylene where the ethylene content is in an amount within
the range of 0-6%, and more preferably within the range of 2-6%, of the
weight of the propylene is preferred as the first component.
The second component of the RF layer 14 confers flexibility and low
temperature ductility to the RF layer 14 and is chosen from the group
consisting of polyolefins that do not have propylene repeating units ("non
propylene based polyolefins") including ethylene copolymers including
ULDPE, polybutene, butene ethylene copolymers, ethylene vinyl acetate,
copolymers with vinyl acetate contents between approximately 18-50%,
ethylene methyl acrylate copolymers with methyl acrylate contents being
between approximately 20-40%, ethylene n-butyl acrylate copolymers with
n-butyl acrylate content of between 20-40%, ethylene acrylic acid
copolymers with the acrylic acid content of greater than approximately
15%. An example of these products are sold under such product designations
as Tafmer A-4085 (Mitsui), EMAC DS-1130 (Chevron), Exact 4023, 4024 and
4028 (Exxon). Preferably, the second component is either ULDPE sold by
Mitsui Petrochemical Company under the designation TAFMER A-4085, or
polybutene-1, PB8010 and PB8310 (Shell Chemical Co.), and should
constitute approximately 25-50%, more preferably 35-45%, and most
preferably 45%, by weight of the susceptible layer.
The first and second components of the RF layer 14 may be replaced by a
single component selected from a high melting temperature and flexible
olefins such as those polypropylenes sold by the Rexene Company under the
product designation FPO. The melting point temperature of this component
should be greater than 130.degree. C. and the modulus less than 20,000
psi. This component should constitute between 30-60% by weight of the RF
layer.
To impart RF dielectric loss to the RF layer 14, certain known high
dielectric loss ingredients are included as the third component of the
film structure 10. For example, EVA and EMA of sufficiently high
co-monomer contents exhibit significant loss properties at 27 MHz to allow
the compositions to be sealed by the dielectric process. Polyamides as a
class of material, and ethylene vinyl alcohol ("EVOH") copolymers
(typically produced by hydrolysing EVA copolymers), both possess high
dielectric loss properties at suitable temperatures. Other active
materials include PVC, vinylidine chlorides, and fluorides, copolymer of
bis-phenol-A and epichlorohydrines known as PHENOXYS.RTM. (Union Carbide).
However, significant contents of these chlorine and fluorine containing
polymers would make them environmentally unsound as incineration of such a
material would generate inorganic acids. Therefore, the third component of
the RF layer 14 is preferably chosen from the class of polyamides.
Preferably, the polyamides of the present invention will be chosen from
aliphatic polyamides resulting from the condensation reaction of di-amines
having a carbon number within a range of 2-13, aliphatic polyamides
resulting from a condensation reaction of di-acids having a carbon number
within a range of 2-13, polyamides resulting from the condensation
reaction of dimer fatty acids, and amide containing copolymers (random,
block or graft).
Polyamides such as nylons are widely used in film material because they
offer abrasion resistance to the film. However, rarely are the nylons
found in the layer which contacts medical solutions as they typically
contaminate the solution by leaching out into the solution. However, it
has been found by the applicants of the present invention that various
dimer fatty acid polyamides sold by, for example, Henkel Corporation under
the product designations MACROMELT and VERSAMID do not lead to such
contamination and thus are the most preferred third component of the RF
layer 14. The third component should constitute approximately 3-40%, more
preferably between 7-13%, and most preferably 10%, by weight of the RF
layer 14.
The fourth component of the RF layer 14 confers compatibility between the
polar and nonpolar components of the RF layer 14. The fourth component was
chosen from styrene-hydrocarbon block copolymers and preferably SEBS block
copolymers that are modified by maleic anhydride, epoxy, or carboxylate
functionalities. Most preferably the fourth component is an SEBS block
copolymer that is maleic anhydride functionalized. Such a product is sold
by Shell Chemical Company under product designation KRATON RP-6509. The
fourth component should constitute approximately 5-40%, more preferably
7-13%, and most preferably 10% by weight of the RF layer 14.
It may also be desirable to include a fifth component to the RF layer 14 of
an SEBS block copolymer, not modified by the above functional groups, such
as the one sold by the Shell Chemical Company under the product
designation KRATON G-1652. This component should constitute between 5-40%
by weight of the RF Layer, more preferably between 7-13%, and most
preferably 10%.
Preferably the RF susceptible layer will have a thickness within the range
of 1-9 mils are more preferably 5.0 mils-8.0 mils, and most preferably 5.0
mils. The skin layer will have a thickness within the range of 0.2-3.0
mils and most preferably 0.5 mils.
FIG. 2 shows another embodiment of the present invention having a core
layer 16 interposed between the skin layer 12 and the RF layer 14. The
core layer 16 confers heat distortion resistance, and flexibility to the
film structure 10 and compatibility among the components of the film
structure 10. Preferably, the core layer will have a thickness within the
range of 0.5-10 mils and more preferably 1-4 mils. The core layer 16
includes three components. The first component is a polyolefin and
preferably a polypropylene in an amount that constitutes in a range of
20-60% by weight of the core layer 16, more preferably 35-50%, and most
preferably 45% of the core layer 16.
The second component of the core layer 16 is chosen from a group consisting
of compounds that confer flexibility to the core layer 16 including ULDPE,
polybutene copolymers. Preferably, the second component of the core layer
is ULDPE or polybutene-1 in an amount by weight of 40%-60%, more
preferably 40-50%, and most preferably 40%.
The third component of the core layer 16 is chosen from a group of
compounds that confer compatibility among the components of the core layer
16 and includes styrene-hydrocarbon block copolymers and most preferably
SEBS block copolymers. The third component is in an amount preferably
within a range of 5-40% by weight of the core layer 16, more preferably
7-15%, and most preferably 15%.
It is also possible to add as a fourth component of the core layer 16,
reground trim scrap material recovered during the manufacturing of
containers. The scrap material is dispersed throughout the core layer 16.
Scrap may be added in an amount preferably between approximately 0-50% by
weight of the core layer 16, and more preferably within the range of
10-30% and most preferably within the range of 3-12%.
FIG. 3 shows the film or sheet structure of FIG. 1 including a solution
contact layer 17 adhered to a side of the RF layer opposite the skin layer
12. The solution contact layer 17 includes three components that may be
chosen from the same first three components and the same weight percentage
ranges of the core layer 16 set forth above. Preferably, the solution
contact layer 17 has a thickness within the range of 0.2-1.0 mils and most
preferably 1.0 mils.
FIG. 4 shows another embodiment of the multiple layer film structure having
the skin layer 12, core layer 16, and RF layer 14 as described above with
an additional discrete layer of scrap 20 between the skin layer 12 and the
core layer 16. FIG. 5 shows the discrete scrap layer 20 between the core
layer 16 and the RF layer 20. FIG. 6 shows the scrap layer 20 dividing the
core layer 16 into first and second core layers 14a and 14b. Preferably,
the layer of regrind should have a thickness within the range of 0.5-5.0
mils and most preferably 1.0 mils.
FIG. 7 shows another embodiment of the present invention having seven
layers including the skin 12, core 16, and RF layers 14 discussed above,
with a barrier layer 26 interposed between the core 16 and RF layers 14
and adhered thereto with tie layers 28 attached to opposite sides of the
barrier layer 26. FIG. 8 shows the barrier layer 26 between the core layer
16 and the skin layer 12. FIG. 9 shows the barrier layer 26 dividing the
core layer 14 into two core layers 14a and 14b. The barrier layer 26
increases the gas barrier properties of the film structure 10. The barrier
layer 26 is selected from the group consisting ethylene vinyl alcohols
such as that sold under the name Evalca (Evalca Co.), highly glassy or
crystalline polyamide such as Sclar PA.RTM. (Dupont Chemical Co.), high
nitrile content acrylonitrile copolymers such as Barex.RTM. sold by
British Petroleum. Preferably, the barrier layer 26 is ethylene vinyl
alcohol, and has a thickness within the range of 0.3-1.5 mils and most
preferably 1.0 mils.
The tie layers 28 may be selected from modified polyolefins, and modified
ethylene and propylene copolymers such as those sold under the product
designations Admer (Mitsui) which is a maleic anhyrdide modified
polypropylene, Prexar (Quantum Chemical Co.) and Bynel (Dupont) and should
have a thickness within the range of 0.2-1.0 mils and most preferably 0.5
mil.
FIG. 11 shows a barrier structure having a skin layer 12 a barrier layer 26
and an RF layer 26. The skin layer may be a polyolefin, including
polypropylene (modified and unmodified), polyethylene, and polyolefins
blended with styrene and hydrocarbon block copolymers such as
styrene-ethylene-butene-styrene block copolymer. FIG. 12 shows the
structure of FIG. 11 having optional tie layers 28 interposed between the
principal layers. Preferably, the skin layer 12 has a thickness within the
range of 0.5 mil-4.0 mil, more preferably within the range of 1.0 mil-3.0
mil, and most preferably 2.0 mil; the barrier layer 26 has a thickness
within the range of 0.3 mil-5.0 mil, more preferably 1.5 mil-4.0 mil, and
most preferably 2.0 mil; the RF layer 14 has a thickness within the range
of 2.0 mil-8.0 mil, more preferably 3.0 mil-6.0 mil, and most preferably
4.0 mil, and the tie layer (when used) preferably has a thickness within
the range 0.3 mil-1.0 mil, and more preferably 0.3 mil-0.5 mil.
Preferably, the barrier structures shown in FIGS. 11 and 12 are
coextruded.
FIG. 13 shows another barrier structure having a layer of polypropylene 32
dividing the RF layer 14 either symmetrically or asymmetrically. The
structure shown in FIG. 13 has a 1.0 mil polypropylene skin layer 12, 0.5
mil tie layer, 2.0 mil EVOH barrier layer 26, 0.5 mil tie layer, 2.0 mil
RF layer 14, 1.0 mil polypropylene, 2.0 mil RF layer 14. An example of an
asymmetrical structure would have a 1.0 mil RF layer 14 and a 2.0 mil RF
layer.
FIG. 14 shows another barrier structure having a skin layer 12, a tie layer
28, a barrier sandwich layer 34 having anywhere from 2-10 sublayer units
comprising a barrier layer 26 and a tie layer 28. The structure further
includes an RF layer 14 attached to the barrier sandwich 34. The barrier
sandwich 34 should have a thickness within the ranges set forth above for
the individual barrier layer 26.
The above layers may be processed by coextrusion, coextrusion coating, or
other acceptable process. These materials may be used to manufacture I.V.
therapy bags such as the one shown in FIG. 10 and generally designated as
30. The structures used to form the container 30 may be sealed by any
conventional means such as using heated die and platen which may be
followed by a chill die and platen as is well known in the industry. It is
also possible to seal the structures using conductive and inductive heat
sealing techniques including using RF sealing techniques.
Films having various combinations of the above components and weight
percentages as set forth in the examples below were tested using the
following methods.
(1) AUTOCLAVABILITY:
Autoclave resistance is measured by sample creep, or the increase in the
sample length, at 121.degree. C. under 27 psi loading for one hour. The
autoclave resistance must be less than or equal to 60%.
(2) LOW AND AMBIENT TEMPERATURE DUCTILITY:
(A) Low Temperature Ductility
In an instrumented impact tester fitted with a low temperature
environmental chamber cooled with liquid nitrogen, film samples about 7 by
7 inches (18 cm by 18 cm) are mounted onto circular sample holders about 6
inches (15 cm) in diameter. A semi-spherical impact head with stress
sensors is driven at high velocities (typically about 3 m/sec) into the
preconditioned film loading it at the center. The stress-displacement
curves are plotted, and the energy of impact is calculated by integration.
The temperature at which the impact energy rises dramatically, and when
the fractured specimen changes from brittle to ductile, high strain
morphology is taken as a measure of the low temperature performance of the
film ("L.Temp").
(B) Mechanical Modulus and Recovery: The autoclaved film sample with a
known geometry is mounted on a servohydraulically driven mechanical tester
having cross heads to elongate the sample. At 10 inches (25 cm) per minute
crosshead speed, the sample is elongated to about 20% elongation. At this
point, the cross-heads travel and then reverse to travel in a direction
opposite that originally used to stretch the sample. The stress strain
behavior is recorded on a digital recorder. The elastic modulus
("E(Kpsi)") is taken from the initial slope on the stress-strain curve,
and the recovery taken from the excess sample dimension as a percentage of
sample elongation.
(3) RF PROCESSIBILITY:
Connected to a Callahan 27.12 MHz, 2 KW Radio Frequency generator, is a
rectangular brass die of about 0.25 (6.3 mm) by 4 inches (10 cm) opposing
to a flat brass electrode, also connected to the generator. Upon closing
the die with two sheets of the candidate material in between with solution
sides facing each other, RF power of different amplitudes and durations
are applied. When the RF cycle is over, the die is opened and the
resultant seal examined by manually pulling apart the two sheets. The
strength of the seal (versus the film strength) and the mode of failure
(peel, tear, or cohesive failures) are used to rate the RF responsiveness
of the material.
Alternatively, the candidate film is first sputter coated with gold or
palladium to a thickness of 100 angstroms to render the surface
conductive, cut into a circular geometry and mounted between the parallel
electrodes in a dielectric capacitance measuring cell. Using a Hewlett
Packard 4092 automatic RF bridge, the dielectric constant and the
dielectric losses are measured at different frequencies up to 10 MHz and
temperatures up to 150.degree. C. The dielectric loss allows the
calculation of heat generation under an RF field. From calculations or
correlations with RF seal experiments the minimum dielectric loss for
performance is obtained.
If the RF seal performance is obtained from the Callahan sealer, the
following ranking scale is adopted:
##STR1##
(4) OPTICAL CLARITY:
Post autoclaved film samples are first cut into about 2 by 2 inches (5 by 5
cms) squares, mounted on a Hunter Colorimeter and their internal haze
measured according to ASTM D-1003. Typically, internal haze level of less
than 30% is required, preferably less than 20% for these thicknesses
("Haze %").
(5) STRAIN WHITENING:
The autoclaved film is strained at moderate speeds of about 20 inches (50
cm) per minute to about 100% elongation (twice the original length) and
the presence of strain whitening (indicated by 1) or lack thereof
(indicated by 0) is noted ("S.Whitening").
(6) ENVIRONMENTAL COMPATIBILITY:
The environmental compatibility comprises three important properties: (a)
the material is free of low molecular weight plasticizers which could
leach into landfills upon disposal, (2) the material can be
thermoplastically recycled into useful items upon fulfilling the primary
purpose of medical delivery, and (3) when disposed of by energy reclaim by
incineration, no significant inorganic acids are released to harm the
environment. ("Envir."). The composition will also contain less than 0.1%
halogens by weight. In order to facilitate recycling by melt processing,
the resultant composition should have a loss tangent greater than 1.0 at 1
Hz measured at processing temperatures.
(7) SOLUTION COMPATIBILITY
By solution compatibility we mean that a solution contained within the film
is not contaminated by components which constitute the composition.
("S.Comp.") The low molecular weight water soluble fraction of the
composition will be less than 0.1%.
(8) BARRIER PROPERTIES
The barrier film structure shown in FIG. 11 was tested by an independent
laboratory for water vapor transmission rate (WVTR) expressed in units of
gm/100in.sup.2 /24 hours, oxygen transmission rate at a 50% relative
humidity (RH) and an 80% relative humidity, and carbon dioxide
transmission rate and the oxygen and carbon dioxide transmission rates are
expressed in units of cc/100in.sup.2 /24 hours.
The following combinations were tested using the above test for the films
set forth below.
__________________________________________________________________________
Refer- Strain Low
ence
Layer Modulus
Recover
% Environ- Dielectric
Temp-
S.
Number
Type
Layer Composition (psi)
y E(kpsi)
Haze
mental
Autoclav.
Loss erature
Comp.
__________________________________________________________________________
FIG. 1
Skin
0.5 mil
100% Amoco PP Copolymer 8410
25 75 10 Yes Yes 3 -35.degree.
Yes
RF 8.0 mils
40% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
10% Shell Kraton .TM. RP-6509
10% Henkel Macromelt .TM. 6301
FIG. 2
Skin
0.5 mil
100% Amoco PP Copolymer
25 75 12 Yes Yes 4 -40.degree.
Yes
8410
Core
4.0 mils
45% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. G1657
RF 5.0 mils
40% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
10% Shell Kraton .TM. RP-6509
10% Henkel Macromelt .TM. 6301
FIG. 3
Skin
0.5 mil
100% Amoco PP Copolymer 8410
25 70 15 Yes Yes 2 -35.degree.
Yes
RF 8.0 mils
40% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
10% Shell Kraton .TM. EP-6509
10% Henkel Macromelt .TM. 6301
Solution
1.0 mils
45% Solvay Fortiline .TM. PP
Contact Copolymer 4208
Skin 40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. G1657
FIG. 4
Skin
0.5 mil
100% Amoco PP Copolymer 8410
25 75 16 Yes Yes 4 -35.degree.
Yes
Regrind
1.0 mil
100% Regrind
Core
3.0 mils
45% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. G1657
RF 5.0 mils
40% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
10% Shell Kraton .TM. RP6509
10% Henkel Macromelt .TM.
6301
FIG. 5
Skin
0.5 mil
100% Amoco PP Copolymer
25 75 16 Yes Yes 4 35.degree.
Yes
8410
Core
3.0 mils
45% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. G1657
Regrind
1.0 mil
100% Regrind
RF 5.0 mils
40% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
10% Shell Kraton .TM. RP6509
FIG. 6
Skin
0.5 mil
100% Amoco PP Copolymer
25 75 16 Yes Yes 4 -35.degree.
Yes
8410
Core
1.5 mils
45% Solvay Fortiline .TM. PP
Copoymer 4208
40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. G 1657
Regrind
1.0 mil
100% Regrind
Core
1.5 mils
45% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. 1657
RF 5.0 mils
45% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. RP6509
10% Henkel Macromelt .TM. 6301
FIG. 7
Skin
0.5 mil
100% Amoco PP Copolymer
30 20 20 Yes Yes 4 -20.degree.
Yes
8410
Core
2.0 mils
45% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. G 1657
Tie 0.5 mil
100% Bynel
Barrier
1.0 mil
100% EVOH
Tie 0.5 mil
100% Bynel
RF 5.0 mils
40% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPF
10% Shell Kraton .TM. RP6509
10% Henkel Macromelt .TM. 6301
FIG. 8
Skin
0.5 mil
100% Amoco PP Copolymer
30 70 20 Yes Yes 3 -20.degree.
Yes
8410
Tie 0.5 mil
100% Bynel
Barrier
1.0 mil
100% EVOH
Tie 0.5 mil
100% Bynel
Core
2.0 mils
45% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. G 1657
RF 5.0 mils
40% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
10% Shell Kraton .TM. RP6509
10% Henkel Macromelt .TM. 6301
FIG. 9
Skin
0.5 mil
100% Amoco PP Copoymer
30 70 20 Yes Yes 3 -20.degree.
Yes
8410
Core
1.0 mils
45% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. G 1657
Tie 0.5 mil
100% Bynel
Barrier
1.0 mil
100% EVOH
Tie 0.5 mil
100% Bynel
Core
1.0 mils
45% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
15% Shell Kraton .TM. G 1657
RF 5.0 mils
40% Solvay Fortiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
10% Shell Kraton .TM. RP6509
10% Henkel Macromel .TM. 6301
FIG. 11
Skin
0.5 mils
0.5 mil - 100% Amco PP
O.sub.2 Tran
O.sub.2 Tran
WVTR
Co2
Copolymer 8410 Rate RH-
Rate 0.0409
Trans
50% RH-80% Rate
0.0171
0.0708 Less
Than
0.0645
Tie 0.5 mils
0.5 mil ADMER RQF551A
Barrier
3.0 mil
100% EVOH
Tie 0.5 mil
ADMER RQF5518
RF 0.5 mil
40% Solvay Fotiline .TM. PP
Copolymer 4208
40% Mitsui Tafmer .TM. ULDPE
10% Shell Kraton .TM. RP6509
0% Henkel Macromelt .TM.
6301
__________________________________________________________________________
It will be understood that the invention may be embodied in other specific
forms without departing from the spirit or central characteristics
thereof. The present examples and embodiment, therefore, are to be
considered in all respects as illustrative and not restrictive, and the
invention is not to be limited to the details given herein.
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