U.S. patent application number 14/331375 was filed with the patent office on 2015-01-08 for multilayered composite.
The applicant listed for this patent is Zeus Industrial Products, Inc.. Invention is credited to Bruce L. Anneaux, Robert L. Ballard, David P. Garner.
Application Number | 20150012108 14/331375 |
Document ID | / |
Family ID | 43533906 |
Filed Date | 2015-01-08 |
United States Patent
Application |
20150012108 |
Kind Code |
A1 |
Anneaux; Bruce L. ; et
al. |
January 8, 2015 |
MULTILAYERED COMPOSITE
Abstract
In accordance with certain embodiments of the present
disclosure, a process for forming a multilayered electrospun
composite is provided. The process includes forming a dispersion of
polymeric nanofibers, a fiberizing polymer, and a solvent, the
dispersion having a viscosity of at least about 50,000 cPs.
Nanofibers from the dispersion are electrospun onto a first ePTFE
layer. A second ePTFE layer is applied onto the nanofibers to form
a composite structure. The composite structure is heated.
Inventors: |
Anneaux; Bruce L.;
(Lexington, SC) ; Ballard; Robert L.; (Orangeburg,
SC) ; Garner; David P.; (Lexington, SC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zeus Industrial Products, Inc. |
Orangeburg |
SC |
US |
|
|
Family ID: |
43533906 |
Appl. No.: |
14/331375 |
Filed: |
July 15, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13564925 |
Aug 2, 2012 |
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14331375 |
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12852989 |
Aug 9, 2010 |
8257640 |
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13564925 |
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61232252 |
Aug 7, 2009 |
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Current U.S.
Class: |
623/23.7 ;
138/177; 428/422; 442/397 |
Current CPC
Class: |
B32B 27/322 20130101;
B32B 2250/242 20130101; A61F 2210/0076 20130101; A61F 2250/0067
20130101; B32B 7/04 20130101; A61L 31/041 20130101; B32B 5/18
20130101; B82Y 5/00 20130101; D01D 5/06 20130101; A61L 31/129
20130101; B32B 2262/0253 20130101; D10B 2321/042 20130101; A61L
2400/18 20130101; B32B 5/26 20130101; A61L 31/048 20130101; B32B
2266/025 20130101; Y10T 442/677 20150401; A61F 2/92 20130101; A61L
31/06 20130101; Y10T 442/66 20150401; A61F 2/07 20130101; B32B
2250/20 20130101; D01D 5/003 20130101; A61L 27/26 20130101; A61L
27/507 20130101; A61L 27/26 20130101; B01D 2239/0631 20130101; D01D
5/0084 20130101; B32B 5/022 20130101; D01D 5/0038 20130101; D01F
6/12 20130101; A61F 2/06 20130101; C08L 27/18 20130101; D04H 1/492
20130101; D04H 1/728 20130101; F16L 11/12 20130101; A61L 31/146
20130101; B32B 2250/03 20130101; A61F 2240/001 20130101; B32B
2535/00 20130101; B01D 39/1623 20130101; Y10T 428/31544 20150401;
A61F 2/04 20130101; A61L 31/06 20130101; B01D 2239/025 20130101;
D10B 2509/06 20130101; A61L 27/26 20130101; D01D 5/0076 20130101;
A61F 2002/072 20130101; C08L 71/02 20130101; B32B 1/08 20130101;
B32B 27/08 20130101; C08L 71/02 20130101; D04H 1/54 20130101; A61L
2400/12 20130101 |
Class at
Publication: |
623/23.7 ;
428/422; 442/397; 138/177 |
International
Class: |
A61L 31/04 20060101
A61L031/04; A61F 2/04 20060101 A61F002/04; F16L 11/12 20060101
F16L011/12; D04H 1/492 20060101 D04H001/492 |
Claims
1. A composite structure comprising a plurality of nanofibers on a
first surface of a first polymeric layer.
2. The composite structure of claim 1, wherein the nanofibers
comprise one of polytetrafluoroethylene (PTFE), nylon,
polyurethane, polyester, fluorinated ethylene propylene, or
combinations thereof.
3. The composite structure of claim 1, wherein the plurality of
nanofibers is a plurality of spun nanofibers.
4. The composite structure of claim 3, wherein the plurality of
spun nanofibers is a plurality of electrospun nanofibers.
5. The composite structure of claim 1, wherein the first polymeric
layer is a first layer of expanded polytetrafluoroethylene (ePTFE)
and wherein the composite structure further comprises a second
ePTFE layer.
6. The composite structure of claim 5, wherein the plurality of
nanofibers are sandwiched between and bind together the first ePTFE
layer and the second ePTFE layer.
7. A stent, comprising: a first layer of polytetrafluoroethylene
(PTFE) fibers disposed such that it defines an outside surface of
the stent; and a second layer of PTFE fibers disposed such that it
defines an inside surface of the stent.
8. The stent of claim 7, wherein the surface properties of at least
one of the layers is modulated to manipulate cellular ingrowth and
response.
9. A composite structure comprising a tubular polymeric inner
surface and a tubular polymeric outer surface, wherein at least one
of the tubular polymeric inner surface and tubular polymeric outer
surface comprises a plurality of polytetrafluoroethylene (PTFE)
nanofibers.
10. The composite structure of claim 9, wherein both the tubular
polymeric inner surface and tubular polymeric outer surface
comprise a plurality of PTFE nanofibers.
11. The composite structure of claim 10, wherein the
polytetrafluoroethylene (PTFE) nanofibers comprise spun
polytetrafluoroethylene (PTFE) nanofibers.
12. The composite structure of claim 11, wherein the spun
polytetrafluoroethylene (PTFE) nanofibers comprise electrospun
polytetrafluoroethylene (PTFE) nanofibers.
13. The composite structure of claim 9, further comprising a
substrate and one or more additional layers of polymeric material,
wherein the one or more additional layers of polymeric material
comprises a second plurality of polytetrafluoroethylene (PTFE)
nanofibers.
14. The composite structure of claim 13, wherein the one or more
additional layers of polymeric material comprises a second
plurality of electrospun polytetrafluoroethylene (PTFE)
nanofibers.
15. The composite structure of claim 9, wherein the PTFE nanofibers
have a density such that there is a range of distances of about
0.1.mu. to about 50.mu. between points of contact of the
nanofibers.
16. The composite structure of claim 9, wherein the tubular
polymeric inner surface and a tubular polymeric outer surface have
different pore sizes.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation application of
U.S. application Ser. No. 13/564,925, filed Aug. 2, 2012; which
application is a continuation application of U.S. application Ser.
No. 12/852,989, filed Aug. 9, 2010, now U.S. Pat. No. 8,257,640,
issued Sep. 4, 2012; which application claims priority to U.S.
Provisional Application Ser. No. 61/232,252, filed Aug. 7, 2009;
all of which are incorporated by reference.
BACKGROUND
[0002] Electrostatic spinning of polytetrafluoroethylene (PTFE)
into continuous fiber allows for the formation of non-woven sheets,
tubes, and coatings with potential for multiple other applications
and forms. The process of electrostatic spinning is well known in
the literature and the patenture as represented by U.S. Pat. Nos.
2,158,416; 4,432,916; 4,287,139; 4,143,196; 4,043,331; 4,689,186
and 6,641,773 each of which is incorporated herein by reference
thereto. While most of these patents pertain to soluble polymers or
thermoplastics, none pertain directly to the formation of fibers or
mat from virtually insoluble polymers or those that do not flow
readily on heating to elevated temperatures. A review of the
literature and patenture revealed limited reference to the process
whereby a polymer that meets the properties of limited solubility
and inability to readily flow upon heating such as PTFE can be
formed into a fiber suitable for electrostatic spinning into
various structures. U.S. Pat. Nos. 4,323,525 and 4,044,404, both of
which are incorporated herein by reference, provide information
related to processing and electrostatic spinning of PTFE from an
aqueous or other dispersion.
[0003] However, such conventional processes have several
shortcomings. Such processes describe the use of low viscosity PTFE
dispersions (15,000 cPs) which do not result in uniform or
consistent fiber formation. Furthermore, such processes describe
the use of a grounded spinning head and a charged target.
Observation shows various levels of degradation in samples produced
by reverse polarity. Conventional processes also fail to
accommodate for shrinkage of a mat during sintering.
[0004] Thus, a need exists for processes that address the
deficiencies described above. Materials made from such processes
would also be particularly beneficial.
SUMMARY
[0005] In accordance with certain embodiments of the present
disclosure, a process for forming a multilayered electrospun
composite is provided. The process includes forming a dispersion of
polymeric nanofibers, a fiberizing polymer, and a solvent, the
dispersion having a viscosity of at least about 50,000 cPs.
Nanofibers from the dispersion are electrospun onto a first ePTFE
layer. A second ePTFE layer is applied onto the nanofibers to form
a composite structure. The composite structure is heated.
[0006] In other embodiments of the present disclosure, a process
for forming a multilayered electrospun composite structure is
disclosed. The process includes electrospinning a dispersion having
a viscosity of at least about 50,000 cPs and comprising polymeric
nanofibers, a fiberizing polymer, and a solvent, onto a first side
of an ePTFE layer. The process further includes electrospinning a
dispersion having a viscosity of at least about 50,000 cPs and
comprising polymeric nanofibers, a fiberizing polymer, and a
solvent, onto a second side of the ePTFE layer to form a composite
structure. The composite structure is heated.
[0007] In still other embodiments of the present disclosure, a
process for forming a multilayered electrospun composite structure
is described. The process includes forming a dispersion of
polymeric nanofibers, a fiberizing polymer, and a solvent, the
dispersion having a viscosity of at least about 50,000 cPs.
Nanofibers from the dispersion are electrospun onto a first ePTFE
layer. A substrate is applied onto the nanofibers to form a
composite structure. The composite structure is heated.
[0008] Through diligent research the inventors have determined that
electrospun materials, such as PTFE, when applied to ePTFE
membranes constitutes an additional application, form, and use of
electrospun materials. Furthermore, the inventors have determined
that a wide range of electrospun materials when combined in layers
with ePTFE membranes and/or other substrates can create composite
membrane structures with new and unique properties.
[0009] Other features and aspects of the present disclosure are
discussed in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] A full and enabling disclosure, including the best mode
thereof, directed to one of ordinary skill in the art, is set forth
more particularly in the remainder of the specification, which
makes reference to the appended figures in which:
[0011] FIG. 1 illustrates an SEM image of a multilayered composite
construction in accordance with the present disclosure; and
[0012] FIGS. 2-5 illustrate cross-sectional views of different
multilayered composites in accordance with the present
disclosure.
DETAILED DESCRIPTION
[0013] Reference now will be made in detail to various embodiments
of the disclosure, one or more examples of which are set forth
below. Each example is provided by way of explanation of the
disclosure, not limitation of the disclosure. In fact, it will be
apparent to those skilled in the art that various modifications and
variations can be made in the present disclosure without departing
from the scope or spirit of the disclosure. For instance, features
illustrated or described as part of one embodiment, can be used on
another embodiment to yield a still further embodiment. Thus, it is
intended that the present disclosure covers such modifications and
variations as come within the scope of the appended claims and
their equivalents.
[0014] The present invention is related to multilayered composites
comprising one or more electrospun (also referred to herein as
"espin" and/or "espun" and/or "espinning") membranes attached to
one or more expanded polytetrafluoroethylene (also referred to
herein as "ePTFE") membranes. In certain embodiments, the espin
membranes can include polytetrafluoroethylene (also referred to
herein as "espin PTFE"), however, many other suitable materials can
be espun and used in addition to or in combination with such espin
PTFE. For example, other suitable materials that can be espun in
accordance with the present disclosure include nylons,
polyurethanes (PU), polyesters, fluorinated ethylene propylene
(FEP), or the like. Polymers that can be placed in a solution have
the potential to be espun. Polymer particles that can be made into
dispersions (such as, PTFE, FEP, and the like) also have the
potential to be espun. The dispersions (espun PTFE) must be
sintered to develop the desired properties, but many polymers espun
from solution develop their properties during spinning and drying.
The attachment of the espin layer(s) can occur during
sintering.
[0015] For example, in certain embodiments the high molecular
weight of the polytetrafluoroethylene that is present in the espin
PTFE layer and the ePTFE layer melts at the sintering temperatures,
but does not flow. Thus, PTFE present in each of the layers has an
opportunity to form physical bonding between adjacent layers.
Compression of the layers to force more intimate contact is
advantageous. The multi-layered composite is particularly useful in
medical, industrial, filtration, military and consumer
applications.
[0016] A particularly preferred ePTFE is an air permeable expanded
membrane. A membrane which is exemplary for demonstrating the
invention is described in U.S. Pat. No. 4,902,423 which is
incorporated herein by reference. Another exemplary membrane is
described in U.S. Pat. No. 3,962,152 which is incorporated herein
by reference.
[0017] Numerous configurations are contemplated in accordance with
the present disclosure. For instance, the construction can be a two
layer or multiple layer composite of the materials described
herein.
[0018] Referring to FIG. 2, a cross-section of a multilayer
composite in accordance with the present disclosure is illustrated.
The composite includes an ePTFE layer 1 and an espin layer 2. FIG.
1 illustrates an SEM image of such a multilayered composite in
which the espin layer is espin PTFE. Advantages of such a
configuration include an asymmetrical flow structure because pore
size can be controlled. In addition, the presence of the espin
material can result in improved adhesion of the composite to
subsequent layers. Importantly, the espin material can also result
in modification of the ePTFE surface properties.
[0019] Turning to FIG. 3, another cross-section of a multilayer
composite in accordance with the present disclosure is illustrated.
The composite includes an ePTFE layer 1, an espin layer 2, and an
ePTFE layer 1. The espin layer 2 is sandwiched between the ePTFE
layers 1. Such a configuration allows the mechanical properties of
the composite to be modified, as desired. For example, material
recovery can be improved after compression. The espin material
selection can be adjusted to improve bonding properties between
layers. In this regard, any espun material that has adhesive
potential can act to bond layers together. Espun PTFE can act to
bond the ePTFE layers together. Espun PU can also bond ePTFE layers
together. In certain embodiments, espun PTFE must be heated to
385.degree. C. to develop bonding characteristics while materials
such as PU can create a bonding situation at much lower
temperatures.
[0020] In yet another embodiment of the present disclosure, a
cross-sectional view of an espin layer 2, an ePTFE layer 1, and an
espin layer 2 are illustrated as FIG. 4. The ePTFE layer 1 is
sandwiched between the espin layers 2. Advantages of such a
construction include modulation of surface properties through the
espin layer including a) better adhesion to the composite
construction if desired, b) changing the surface functionality of
the composite, c) manipulation of cellular in-growth and response,
and d) increased porosity for improved ingress of other
materials.
[0021] FIG. 5 illustrates yet another embodiment of a cross-section
of a multilayer composite construction in accordance with the
present disclosure. The composite includes a substrate layer 3, an
espin layer 2, and an ePTFE layer 1. The substrate layer can
include woven and nonwoven fabrics of natural or man-made fibers,
plastic or ceramic membranes, metal, ceramic, and plastic meshes,
or the like. For instance, metal stents are a type of metal mesh.
Such a construction allows for a structure which has increased
robustness and durability, while maintaining porosity, air
permeability and other desired properties of porous materials. The
composite can be thermally or adhesively bonded to other woven or
nonwoven porous substrates. Such a composite also results in
improved pore size distribution and improved durability, which can
be very beneficial in filtration applications where debris and
particulate are contacting the media surface at high velocities. In
addition, the overall filtration efficiency can be improved as a
result of the microstructure of the espin fiber entanglement.
[0022] The electrospun layer is preferably applied directly to the
membrane through electrospinning methods understood by those
skilled in the art; however, it could also be applied using
mechanical nips or lamination as well. These latter techniques
include pressing an electrospun layer onto a second material layer
and heating to a complimentary temperature. The pressing technique
may use a flat press or mechanical nip roller.
[0023] The properties and characteristics are a compilation of both
a non-woven and a membrane. The composite can be prepared with
controlled fiber, node and fibril sizes and manipulated mechanical
values such as bond strength, elongation properties and tensile
strengths.
[0024] The properties and characteristics of the composite can be a
compilation of the individual properties of the substrate layer,
espin layer, and the ePTFE layers. The composite can be prepared
with controlled fiber, node and fibril sizes and manipulated
mechanically, such as to improve bond strength, elongation
properties and tensile strengths, in the final composite.
[0025] Typical construction of multiple layers may produce
thickness ranging from about 0.0001 inches to about 0.25 inches
overall thicknesses at widths of about 0.032 inches to about 80
inches. The individual layers can have a thickness that varies from
about 0.0001 inches to about 0.25 inches. Final material size
varies greatly as the composites can be produced as sheets or tubes
at continuous roll lengths. The composite internodal distance (IND)
can be about 0.1 to about 200 .mu.m with porosity ranging from
about 20 to 90%. Pore structure as defined by ASTM F316,
incorporated by reference herein, can range from about 0.05 to
about 50 .mu.m. Due to the construction of the composites, the IND,
pore size and porosity can vary from layer to layer, within the
cross section of the composite, depending on the construction. An
example would be an asymmetrical construction where pores change in
size from large to small based on layer evaluations from surface to
surface throughout the media.
[0026] In certain embodiments of the present disclosure, the
process can require a dispersion or suspension of PTFE solids
between about 10 to 85% by weight to aid in the processing of the
collected fibrous mat into a form that has sufficient green
strength. However, as described above, other suitable polymers can
be utilized for the espin dispersion. If the solid content in the
dispersion is too low, there will be no, or poor, mechanical
integrity to the resulting material. Second, the selection of the
polymer used to increase the viscosity of the solution, suspension
or dispersion to be spun must be selected carefully.
[0027] Additionally, when sintering or bonding espin layers it is
necessary to insure that temperatures are selected to properly
sinter the material, such that the resulting product has good
mechanical integrity.
[0028] To produce a non-woven espin PTFE material, a narrow
particle size distribution PTFE powder is provided in an aqueous
dispersion. The particle size would preferably be about 0.05 to
0.8.mu.. About 1 to 10 wt % by weight of a fiberizing polymer is
added to the volume of PTFE aqueous dispersion. The fiberizing
polymer should have a high solubility in water with a solubility of
greater than about 0.5 wt % being preferred. It is preferable that
the fiberizing polymer has an ash content of less than about 5 wt
%, when sintered at about 400.degree. C., with even lower being
more preferred. Without limit thereto, particularly preferred
fiberizing polymers can include dextran, alginates, chitosan, guar
gum compounds, starch, polyvinylpyridine compounds, cellulosic
compounds, cellulose ether, hydrolyzed polyacrylamides,
polyacrylates, polycarboxylates, polyvinyl alcohol, polyethylene
oxide, polyethylene glycol, polyethylene imine,
polyvinylpyrrolidone, polylactic acid, polymethacrylic acid
polyitaconic acid, poly 2-hydoxyelthyl acrylate, poly
2-dimethylaminoethyl methacrylate-co-acrylamide, poly
n-isopropylacrylamide, poly 2-acrylamido-2-methyl-1-propanesulfonic
acid, poly(methoxyethylene), poly(vinyl alcohol), poly(vinyl
alcohol) 12% acetyl, poly(2,4-dimethyl-6-triazinylethylene),
poly(3-morpholinylethylene), poly(N-1,2,4-triazolyethylene),
poly(vinyl sulfoxide), poly(vinyl amine), poly(N-vinyl
pyrrolidone-co-vinyl acetate), poly(g-glutamic acid),
poly(N-propanoyliminoethylene), poly(4-amino-sulfo-aniline),
poly[N-(p-sulphophenyl)amino-3-hydroxymethyl-1,4-phenyleneimino-1,4-pheny-
lene)], isopropyl cellulose, hydroxyethyl, hydroxylpropyl
cellulose, cellulose acetate, cellulose nitrate, alginic ammonium
salts, i-carrageenan,
N-[(3'-hydroxy-2',3'-dicarboxy)ethyl]chitosan, konjac glocomannan,
pullulan, xanthan gum, poly(allyammonium chloride),
poly(allyammonium phosphate), poly(diallydimethylammonium
chloride), poly(benzyltrimethylammonium chloride),
poly(dimethyldodecyl(2-acrylamidoethyly) ammonium bromide),
poly(4-N-butylpyridiniumethylene iodine),
poly(2-N-methylpridiniummethylene iodine), poly(N
methylpryidinium-2,5-diylethenylene), polyethylene glycol polymers
and copolymers, cellulose ethyl ether, cellulose ethyl hydroxyethyl
ether, cellulose methyl hydroxyethyl ether, poly(1-glycerol
methacrylate), poly(-ethyl-2-oxazoline), poly(2-hydroxyethyl
methacrylate/methacrylic acid) 90:10, poly(2-hydroxypropyl
methacrylate), poly(2-methacryloxyethyltrimethylammonium bromide),
poly(-vinyl-1-methylpyridinium bromide), poly(2-vinylpyridine
N-oxide), poly(2-vinylpyridine),
poly(-chloro-2-hydroxypropyl-2-methacryloxyethyldimethylammonium
chloride), poly(4-vinylpyridine N-oxide), poly(4-vinylpyridine),
poly(acrylamide/2-methacryloxyethyltrimethylammonium bromide)
80:20, poly(acrylamide/acrylic acid), poly(allylamine
hydrochloride), poly(butadiene/maleic acid),
poly(diallyldimethylammonium chloride), poly(ethyl acrylate/acrylic
acid), poly(ethylene glycol) bis (2-aminoethyl), poly(ethylene
glycol) monomethyl ether, poly(ethylene glycol)-bisphenol A
diglycidyl ether adduct, poly(ethylene oxide-b-propylene oxide),
poly(ethylene/acrylic acid) 92:8, poly(1-lysine hydrobromide),
poly(l-lysine hydrobromide), poly(maleic acid), poly(n-butyl
acrylate/2-methacryloxyethyltrimethylammonium bromide),
poly(N-iso-propylacrylamide),
poly(N-vinylpyrrolidone/2-dimethylaminoethyl methacrylate),
dimethyl sulfatequaternary, poly(N-vinylpyrrolidone/vinyl acetate),
poly(oxyethylene) sorbitan monolaurate (Tween 20.RTM.),
poly(styrenesulfonic acid), poly(vinyl alcohol),
N-methyl-4(4'-formylstyryl)pyridinium, methosulfate acetal,
poly(vinyl methyl ether), poly(vinylamine) hydrochloride,
poly(vinylphosphonic acid), poly(vinylsulfonic acid) sodium salt,
polyaniline, and combinations thereof. Again, however, such
fiberizing polymers are also contemplated for use with other
polymer espin dispersions.
[0029] A particularly preferred fiberizing polymer is polyethylene
oxide with a molecular weight between about 50,000 to 4,000,000 amu
polyethyleneoxide. After mixing, the PTFE and fiberizing polymer
dispersion is preferably allowed to homogenize. In a particularly
preferred method the polymer solution is allowed to form slowly,
without agitation, followed by transfer to a jar roller that will
turn it at a constant rate for several more days. The present
disclosure contemplates the use of dispersions of greater than
50,000 cPs to provide for more uniform and consistent fiber
formation as well as faster builds. It is preferred to create a
uniform solution that has little to no air trapped in the resulting
highly viscous mixture. Once the dispersion is of uniform
consistency it is preferably filtered to remove any clumps or gels.
The filtered dispersion with the desired viscosity is then loaded,
in a controlled pumping device with a fixed conductive element
which acts as the charge source.
[0030] A particularly preferred conductive element is one with one
or several orifices. The orifice size is preferably, but not
limited to, about 0.01 to 3.0 mm in diameter. The ejection volume
from the pumping device is set to a predetermined rate that is
dependent on the form being made and the desired fiber diameters.
The charge source is preferably connected to the positive side of a
precision DC power supply. The negative side of the power supply is
preferably connected to the collection surface or target. The
polarity can be reversed but this is not preferred.
[0031] The surface can be a drum, device or sheet. The surface can
be a metal, ceramic or polymeric material with particularly
preferred materials selected from stainless steel, cobalt chrome,
nickel titanium (nitinol) and magnesium alloys. The voltage on the
power supply is increased to the desired voltage to uniformly draw
out the polymer/PTFE solution.
[0032] The applied voltage is typically from about 2,000 to 80,000
volts. The charge induced by the connection of the power supply
repels the charged polymer away from the charge source and attracts
them to the collection surface.
[0033] The collection target is preferably placed perpendicular to
the pump and orifice system and is moved in at least one direction
such that the entire surface is uniformly covered, with the fibers
drawn towards the target. Once the collection surface has been
adequately covered the material is preferably cured, sintered, and
dried (which can occur simultaneously or in a series of steps),
either in place, by placing the entire collection surface in an
oven, or by removing the sheet tube or other form from the
collection surface and sintering it in an oven.
[0034] It is well known to those skilled in the art that espin
fabrics undergo shrinkage upon sintering. While not limited to any
theory the shrinkage is believe to occur in two steps. Initially,
the fibers and fabrics as spun contain both water and a fiberizing
polymer as previously described. Upon completion of spinning the
samples dry and undergo a small degree of fiber rearrangement. At a
later time the samples are heated by exposing the fibers and
fabrics to temperatures of about 35.degree. C. to about 485.degree.
C. for a period of time.
[0035] To accommodate for shrinkage, the fiber and fabrics can be
spun onto an expanded structure. The structure can then be removed
or contracted. During sintering of the espin layer, the fabric
shrinks to a smaller size without cracking. Another method involves
spinning the fibers and fabrics onto a structure which can then be
expanded and/or contracted prior to or during sintering. The range
of contraction or expansion and contraction is on the order of
about 3 to 100% and depends upon the thickness and size of the
electrodeposited fabric. Alternatively the espin layer can be
placed upon a surface which also contracts during sintering.
[0036] For a sheet of fabric, if the direction of the deposition is
given as the perpendicular to the plane of the fabric then
contraction or expansion/contraction must occur in at least one or
more of the directions in the plane of the fabric. For a fabric
deposited upon a cylindrical surface the fabric must be contracted
or contracted/expanded radially and/or longitudinally. For a
spherical surface the fabric must be contracted or
contracted/expanded radially. These basic concepts of contraction
and/or expansion/contraction can be applied to any electrospun
fabric independent to the shape of the surface upon which it was
spun. Thus, very complex fabric shapes based upon espin fabric
become possible.
[0037] The espin layer is preferably fibrous. Particularly
preferred espin fibers have a diameter of at least 0.1.mu.. In a
particularly preferred embodiment the product, after sintering, has
fibers deposited in a density such there is a range of distances of
0.1 to 50.mu. between points of contact.
[0038] The present disclosure can be better understood with
reference to the following examples.
EXAMPLES
[0039] The following general guidelines are used for the processing
examples described herein of various ePTFE and espin composite
constructions.
[0040] 1. In espin PTFE embodiments, the viscosity of the
dispersion may be changed by the addition or removal of water from
the dispersion without changing the PEO to PTFE ratio.
[0041] 2. A radially expanded ePTFE tube or biaxial oriented sheet
is placed over a round or flat base plate to form a desired
geometric shape.
[0042] 3. The espin polymer layer is applied at a desired
thickness, typically about 0.5 to 1000 .mu.m, onto the ePTFE or
onto a surface which is then mated to the ePTFE membrane, resulting
in a composite structure.
[0043] 4. If the espin coating is applied wet to the ePTFE, it is
allowed to dry before moving to the next process. However, if it is
processed as a single espin sheet and has dried, it will be mated
to the oriented porous ePTFE layer. The mating process between the
materials can be repeated multiple times until a desired
multilayered composite structure is created.
[0044] 5. The ePTFE/espin composite is then covered with a
non-sticking release foil.
[0045] 6. Once the composite is positioned against a base tool,
pressure is applied to the surface of the foil, thereby aiding the
bonding process.
[0046] 7. The composite construction is placed in an oven at
temperatures of about 35.degree. C. to about 485.degree. C. to
allow all materials to bond together. The bonding temperature
selection is based on material selection.
[0047] 8. Once the part is removed from the oven and cooled at a
rate of about 15 to 25 degrees per minute, it is uncovered and
tested for specified properties.
Example 1
Type I Construction: ePTFE/Espin PTFE
[0048] An 80.mu. thick stainless steel (SS) sheet 46 cm.times.36 cm
was wrapped around a rotating drum. The drum assembly was placed
into a rotating chuck such that it was positioned to allow
espinning along the entire length of the turning drum assembly.
[0049] An approximately 80,500 cPs espinning dispersion based on a
mixture of 4.2% (PEO/PTFE), 300,000 amu polyethylene oxide and
Daikin D210 60% PTFE dispersion which had been allowed to
homogenize and then turned and filtered to achieve a smooth
consistency was placed into a 10 ml plastic syringe fitted with a
21 gauge needle. The syringe was placed into a KD Scientific Model
780200L syringe pump and set to a 0.5 ml/hour pumping rate. The
needle tip was positioned at approximately 13 cm from the rotating
drum assembly. The rotation of the drum assembly was approximately
30 rpm. A traverse was used to move the espinning needle along the
length of the drum with a rate of travel of 3.0 mm/sec. The return
points for the traverse were set at the ends of the SS sheet. A
voltage of 10.0 kV was employed. PTFE was electrospun onto the drum
for 60 minutes under these conditions to yield an approximately
40.mu. (as deposited post sintering) thick covering of PTFE fibers.
The sheet containing the PTFE membrane was removed from the drum
and dried overnight.
[0050] A biaxially (Biax) expanded approximately 35 cm.times.40 cm
ePTFE sheet with an intermodal distance (IND) of 10-30.mu.,
thickness of 34.mu., and bubble point <3.mu. was placed over and
centered onto a 46 cm.times.36 cm stainless steel sheet.
[0051] The SS sheet holding the dried espin PTFE membrane was then
directly positioned over the SS sheet holding the ePTFE membrane
and the two sheets brought together such that the ePTFE and espin
PTFE membranes were in intimate contact. The SS foil/ePTFE/espin
PTFE/SS foil structure was then wrapped onto a 3'' ID stainless
steel tube to create the assembly. The entire assembly was then
wrapped in unsintered 40.mu. thick ePTFE membrane with 5 wraps
tightly applied around the entire assembly. This was then placed in
an oven at 385.degree. C. for 15.5 minutes. Sintering temperature
and time may vary depending on the composite's thickness and basis
weight. After sintering, the assembly was removed from the oven and
placed in a cooling air box to cool for 30-60 minutes. After
cooling, the ePTFE membrane was unwrapped and a 22 cm.times.28 cm
portion was removed from the center of the espin/ePTFE
composite.
Examples 2-6
Type I Construction: ePTFE/Espin PTFE
[0052] Examples 2-6 were made similarly with the modifications from
Example 1 and are shown in Table I. In general, the major predictor
of the Mean Pore Size Diameter is the ePTFE membrane IND. However,
the pore size is also affected by the pressure applied on the
composite during sintering as shown by comparison of the composite
thicknesses of Examples 1 and 4 with greater pressure yielding a
smaller pore size. The thickness of the espin PTFE layer also has
an effect as shown by Examples 1, 2, and 3 with greater thickness
yielding a smaller pore size.
Example 7
Type I Construction: ePTFE/Espin Polyurethane (PU)
[0053] A biaxially (Biax) expanded approximately 35 cm.times.40 cm
ePTFE sheet with an intermodal distance (IND) of 10-30.mu.,
thickness of 34.mu., and bubble point <3.mu. was placed over and
centered onto a 46 cm.times.36 cm stainless steel sheet.
[0054] An approximately 500 cPs espinning solution based on a
mixture of Chronoflex AR (AdvanSource Biomaterials) (PU) 11% in a
mixture of 37.5% acetone and 62.5% Dimethylacetamide was placed
into a 10 ml plastic syringe fitted with a 21 gauge needle. The
syringe was placed into a KD Scientific Model 780200L syringe pump
and set to a 0.35 ml/hour pumping rate. The needle tip was
positioned at approximately 13 cm from the rotating drum assembly.
The rotation of the drum assembly was approximately 30 rpm. A
traverse was used to move the espinning needle along the length of
the drum with a rate of travel of 3.0 mm/sec. The return points for
the traverse were set at the ends of the SS sheet. A voltage of 9.2
kV was employed. PTFE was electrospun onto the drum for 240 minutes
under these conditions to yield an approximately 2.mu. thick
covering of PU fibers. The sheet containing the PTFE/PU composite
membrane was removed from the drum and dried overnight.
Example 8
Type I Construction: ePTFE/Espin Polyurethane (PU)
[0055] Example 8 was made similarly with the modifications from
Example 7 shown in Table II. Again a thicker layer of the espin PU
resulted in decreased pore size.
Example 9
Type II Construction: ePTFE/Espin PTFE/ePTFE
[0056] A biaxially (Biax) expanded approximately 10 cm long ePTFE
tube with an intermodal distance (IND) of 30.mu., internal diameter
(ID) of 4 mm, wall thickness (WT) of 0.4 mm, and porosity of 80.33%
was stretched over and centered along a 10 mm exterior diameter
(OD) aluminum rod of 35 cm length. The tube assembly was placed
into a rotating chuck such that it was positioned to allow
espinning along the entire length of the turning tube assembly.
[0057] An approximately 94,000 cPs espinning dispersion based on a
mixture of 4.2% (PEO/PTFE), 300,000 amu polyethylene oxide and
Daikin D210 60% PTFE dispersion which had been allowed to
homogenize and then turned and filtered to achieve a smooth
consistency was placed into a 10 ml plastic syringe fitted with a
16 gauge needle. The syringe was placed into a Harvard Model 702100
syringe pump and set to a 0.5 ml/hour pumping rate. The needle tip
was positioned at approximately 13 cm from the rotating tube
assembly. The rotation of the tube assembly was approximately 60
rpm. A traverse was used to move the espinning needle along the
length of the tube with a rate of travel of 2.5 mm/sec. The return
points for the traverse were set at the ends of the Biax tube. A
voltage of 9.3 kV was employed. PTFE was electrospun onto the tube
for 30 minutes under these conditions to yield an approximately
20.mu. (as deposited post sintering) thick covering of PTFE
fibers.
[0058] After allowing the tube assembly to dry overnight an ePTFE
membrane of basis weight 8.426 g/m2 and thickness of 30.mu. was
wrapped 6 times around the tube assembly. The tube assembly was
then wrapped in 80.mu. thick stainless steel foil followed by being
further wrapped 5 times with unsintered 40.mu. thick ePTFE membrane
applied tightly around the entire assembly. The tube assembly was
then placed into an oven preheated to 385.degree. C. for 4.0
minutes. After removal from oven, cooling, and unwrapping the
composite tube was determined to have a thickness of 0.149 mm.
Examples 10-15
Type II Construction: ePTFE/Espin PTFE/ePTFE
[0059] Examples 10-15 were made similarly with the particulars of
each Example shown in Table III.
Example 16
Type III Construction: Espin PTFE/ePTFE/Espin PTFE
[0060] A 40.mu. thick aluminum foil sheet 46 cm.times.6.2 cm was
wrapped around a rotating drum. The drum assembly was placed into a
rotating chuck such that it was positioned to allow espinning along
the entire length of the turning drum assembly.
[0061] An espinning dispersion based on a mixture of 5.2%
(PEO/PTFE) 300,000 amu polyethylene oxide and Daikin D210, 60% PTFE
dispersion which had been allowed to homogenize and then turned and
filtered to achieve a smooth consistency was placed into a 10 ml
plastic syringe fitted with a 16 gauge needle. The syringe was
placed into a KD Scientific Model 780200L syringe pump and set to a
0.09 ml/hour pumping rate. The needle tip was positioned at
approximately 20 cm from the rotating drum assembly. The rotation
of the drum assembly was approximately 30 rpm. A traverse was used
to move the espinning needle along the length of the drum with a
rate of travel of 3.0 mm/sec. The return points for the traverse
were set at the ends of the aluminum foil. A voltage of 18.0 kV was
employed. PTFE was electrospun onto the drum for 30 minutes under
these conditions to yield an approximately 80.mu. (as deposited
post sintering) thick covering of PTFE fibers. The aluminum foil
containing the PTFE membrane was removed from the drum and
dried.
[0062] After drying the green strength of the composite allowed the
removal of the PTFE membrane from the foil and placement,
centering, and loose wrapping of a 10 cm.times.6.5 cm portion of
the PTFE membrane around a 1.0 cm exterior diameter (OD) aluminum
tube twice. An ePTFE membrane: thickness--130.mu., IND--12.45.mu.,
and porosity of--51% was then wrapped 3 times around the espin PTFE
to create a tube/espin PTFE/ePTFE assembly. The tube assembly was
placed into a rotating chuck such that it was positioned to allow
espinning along the entire length of the turning tube assembly.
[0063] An espinning dispersion based on a mixture of 5.2%
(PEO/PTFE) 300,000 amu polyethylene oxide and Daikin D210, 60% PTFE
dispersion which had been allowed to homogenize and then turned and
filtered to achieve a smooth consistency was placed into a 10 ml
plastic syringe fitted with a 16 gauge needle. The syringe was
placed into a KD Scientific Model 780200L syringe pump and set to a
0.05 ml/hour pumping rate. The needle tip was positioned at
approximately 11.5 cm from the rotating tube assembly. The rotation
of the tube assembly was approximately 30 rpm. A traverse was used
to move the espinning needle along the length of the tube with a
rate of travel of 3.0 mm/sec. The return points for the traverse
were set at the ends of the espin PTFE/ePTFE assembly. A voltage of
16.0 kV was employed. PTFE was electrospun onto the assembly for 15
minutes under these conditions to yield an approximately 60.mu. (as
deposited post sintering) thick covering of PTFE fibers. The
assembly was removed from the drum, dried, and placed onto a
fixture. The assembly was then placed upright into an oven
preheated to 385.degree. C. for 4.0 minutes.
Example 17
Type IV Construction: Substrate/Espin PTFE/ePTFE
[0064] A 40.mu. thick non stick aluminum foil sheet 43 cm.times.38
cm was wrapped around a rotating drum. An approximately 35
cm.times.30 cm ePTFE sheet with a basis weight of 4.997 gsm,
thickness of 7.mu., and porosity of 72% was placed over, centered,
and affixed onto the aluminum foil. The drum assembly was placed
into a rotating chuck such that it was positioned to allow
espinning along the entire length of the turning drum assembly.
[0065] An approximately 163,000 cPs espinning dispersion based on a
mixture of 4.2% (PEO/PTFE), 300,000 amu polyethylene oxide and
Daikin D210 60% PTFE dispersion which had been allowed to
homogenize and then turned and filtered to achieve a smooth
consistency was placed into two 10 ml plastic syringes fitted with
16 gauge needles. The syringes were placed into a KD Scientific
Model 780200L syringe pump and set to a 0.75 ml/hour pumping rate.
The needle tips were positioned at approximately 20.3 cm from the
rotating drum assembly. The rotation of the drum assembly was
approximately 30 rpm. A traverse was used to move the espinning
needle along the length of the drum with a rate of travel of 3.0
mm/sec. The return points for the traverse were set at the ends of
the ePTFE membrane sheet. A voltage of 17.5 kV was employed. PTFE
was electrospun onto the drum for 30 minutes under these conditions
to yield an approximately 50.mu. (as deposited post sintering)
thick covering of PTFE fibers. The aluminum foil sheet containing
the ePTFE/espin PTFE composite membrane was then removed from the
drum and dried overnight. After drying the green strength was
sufficient to allow the removal of the ePTFE/espin PTFE composite
membrane from the foil.
[0066] A 5 cm wide section of the composite membrane was wound 3
times around a 5 cm long, 0.5 cm OD porous metal tube with the
espin layer in contact with the tube. The entire assembly was then
placed on a fixture, wrapped in aluminum foil and then wrapped with
unsintered 40.mu. thick ePTFE membrane tightly applied around the
entire assembly. The assembly was then placed in an oven at
385.degree. C. for 4 mins. After cooling the composite membrane had
good appearance and adherence to the metal tube.
TABLES
TABLE-US-00001 [0067] TABLE I Type I: ePTFE/espin PTFE Examples
PTFE Espin ePTFE ePTFE Dispersion Espin PTFE/ePTFE Mean Membrane
Membrane Viscosity PTFE Composite Pore Size Example Thickness IND
cPs Thickness Thickness Diameter Membrane 1.3029.mu. 1 34.mu.
10-30.mu. 80,500 40.mu. 31.mu. 0.5564.mu. 2 34.mu. 10-30.mu. 80,500
50.mu. 31.mu. 0.4690.mu. 3 34.mu. 10-30.mu. 80,500 80.mu. 32.mu.
0.4401.mu. 4 34.mu. 10-30.mu. 87,000 40.mu. 30.mu. 0.5406.mu.
Membrane 0.2968.mu. 5 23.mu. 2-5.mu. 101,000 20.mu. 18.mu.
0.2915.mu. 6 23.mu. 2-5.mu. 105,000 30.mu. 22.mu. 0.2921.mu.
TABLE-US-00002 TABLE II Type I: ePTFE/espin PU Examples Espin ePTFE
ePTFE PU Espin PTFE/ePTFE Mean Membrane Membrane Viscosity PU
Composite Pore Size Example Thickness IND cPs thickness Thickness
Diameter Membrane 0.2968.mu. 7 23.mu. 2-5.mu. 500 2.mu. 25.mu.
0.2809.mu. 8 23.mu. 2-5.mu. 500 1.mu. 24.mu. 0.2930.mu.
TABLE-US-00003 TABLE III Type II: ePTFE/espin PTFE/ePTFE Examples
Example 9 10 11 12 13 14 15 Rod 10 mm 12 mm 20 mm 20 mm 20 mm 20 mm
26 mm Diameter Tube IND 30.mu. 40.mu. 40.mu. 40.mu. 40.mu. 40.mu.
40.mu. Tube ID 4 mm 4.1 mm 4.1 mm 4.1 mm 4.1 mm 4.1 mm 4.1 mm Tube
WT 0.4 mm 0.5 mm 0.5 mm 0.65 mm 0.65 mm 0.65 mm 0.65 mm Tube 80.33%
78.97% 78.97% 78.97% 78.97% 78.97% 78.97% Porosity Membrane 8.426
gsm 8.426 gsm 8.426 gsm 15.500 gsm 15.500 gsm 15.500 gsm 15.500 gsm
Basis Weight Membrane 40.mu. 40.mu. 40.mu. 75.mu. 75.mu. 75.mu.
75.mu. Thickness Membrane 6 4 6 4 5 5 4 Layers Sintering 4 min 4
min 5 min 6 min 6.5 min 6.33 min 8.33 min Time Composite 0.149 mm
0.143 mm 0.137 mm 0.185 mm 0.232 mm 0.244 mm 0.220 mm Thickness
[0068] In the interests of brevity and conciseness, any ranges of
values set forth in this specification are to be construed as
written description support for claims reciting any sub-ranges
having endpoints which are whole number values within the specified
range in question. By way of a hypothetical illustrative example, a
disclosure in this specification of a range of 1-5 shall be
considered to support claims to any of the following sub-ranges:
1-4; 1-3; 1-2; 2-5; 2-4; 2-3; 3-5; 3-4; and 4-5.
[0069] These and other modifications and variations to the present
disclosure can be practiced by those of ordinary skill in the art,
without departing from the spirit and scope of the present
disclosure, which is more particularly set forth in the appended
claims. In addition, it should be understood that aspects of the
various embodiments can be interchanged both in whole or in part.
Furthermore, those of ordinary skill in the art will appreciate
that the foregoing description is by way of example only, and is
not intended to limit the disclosure.
* * * * *