U.S. patent application number 13/032327 was filed with the patent office on 2011-09-01 for compressed nanofiber composite media.
This patent application is currently assigned to CLARCOR INC.. Invention is credited to Thomas B. Green, Lei Li.
Application Number | 20110210061 13/032327 |
Document ID | / |
Family ID | 44504740 |
Filed Date | 2011-09-01 |
United States Patent
Application |
20110210061 |
Kind Code |
A1 |
Li; Lei ; et al. |
September 1, 2011 |
COMPRESSED NANOFIBER COMPOSITE MEDIA
Abstract
A coalescing media includes a compressed composite filter media
comprising substrate layers and hydrophilic fine fiber layers for
separating free water emulsified in fuels.
Inventors: |
Li; Lei; (West Chester,
OH) ; Green; Thomas B.; (Liberty Township,
OH) |
Assignee: |
CLARCOR INC.
Franklin
TN
|
Family ID: |
44504740 |
Appl. No.: |
13/032327 |
Filed: |
February 22, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61383487 |
Sep 16, 2010 |
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61383569 |
Sep 16, 2010 |
|
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61330462 |
May 3, 2010 |
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61308488 |
Feb 26, 2010 |
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Current U.S.
Class: |
210/491 |
Current CPC
Class: |
B01D 2239/0631 20130101;
B01D 2239/0695 20130101; B01D 2239/064 20130101; B01D 2239/025
20130101; B01D 39/1623 20130101; B01D 2239/0668 20130101; B82Y
30/00 20130101; B01D 2239/1233 20130101 |
Class at
Publication: |
210/491 |
International
Class: |
B01D 39/14 20060101
B01D039/14; B01D 39/18 20060101 B01D039/18 |
Claims
1. A method of forming a coalescing filter media, comprising steps
of: electrostatically spinning fine fibers having an average
diameter of less than 1 micron; applying the fine fibers to at
least one substrate comprising coarse fibers having an average
diameter greater than 1 micron; compacting the fine fibers and the
coarse fibers together; generating sufficient fine fiber coverage
and tightness through said compacting to provide coalescing of
water droplets from a fluid stream; and structuring the coarse
fibers and the fine fibers into a coalescing filter media that is
operable to remove water from a fluid stream.
2. The method of claim 1, wherein the at least one substrate
comprises a fiber entanglement that is bonded together into a
formed filter media prior to said applying, the fine fibers
deposited onto the formed filter media during said step of applying
the fine fibers.
3. The method of claim 2, wherein the at least one substrate
comprises at least one scrim formed of bi-component fibers
comprising a high melt component and a low melt component, wherein
the fine fibers are deposited on a surface of the at least one
scrim and carried by the at least one scrim.
4. The method of claim 1, further comprising generating multiple
layers of substrate with nanofibers carried on multiple individual
layers either by feeding multiple discrete substrate layers or
lapping one or more individual substrate layers, thereby spacing
fine fibers within the thickness of the coalescing filter media by
the multiple layers of substrate, wherein said compacting comprises
laminating multiple layers of the substrate carrying the fine
fibers, and compressing the multiple layers of the substrate
carrying the fine fibers to form a composite filter media.
5. The method of claim 4, further comprising permanently bonding
the multiple layers of substrate carrying the fine fibers together
to form an integrated composite filter media layer.
6. The method of claim 1, wherein each substrate individually
carries the fine fibers along one surface thereof having a fine
fiber coverage between about 0.075 g/m.sup.2 and 0.225 g/m.sup.2,
and collectively providing a total fine fiber coverage in the
composite filter media between about 0.75 g/m.sup.2 and 2.25
g/m.sup.2 in the coalescing filter media and thereby providing said
sufficient fine fiber coverage and tightness.
7. The method of claim 6, wherein the layers are compressed
together to reduce a thickness to between about 3/16'' and
1/2''.
8. The method of claim 4, further comprising laminating a drainage
filter layer on or proximate a downstream side of the coalescing
filter media, the drainage layer arranged to collect and grow water
droplets coalesced by fine fibers.
9. The method of claim 5, wherein the at least one substrate
comprises at least one scrim formed of bi-component fibers
comprising a high melt component and a low melt component, wherein
the fine fibers are deposited on a surface of the at least one
scrim and carried by the at least one scrim; further including
heating the multiple layers of the scrim carrying the fine fibers
to or near a melting temperature of the low melt component, wherein
the low melt component melts or softens to act as a bonding agent
to bond layers together.
10. The method of claim 5, the scrim carrying the fine fibers are
folded into multiple folds and compressed together, wherein the
folding creates a fine fiber to fine fiber laminated surface and a
scrim to scrim laminated surface.
11. The method of claim 1, wherein the substrate is a web of coarse
fibers comprising a loose entanglement of the coarse fibers, the
fine fibers being applied to the loose entanglement of the coarse
fibers during the said step of applying the fine fibers, and
wherein the web of coarse fibers applied with the fine fibers are
folded into multiple folds and compressed together, wherein the
fine fibers and the coarse fibers are integrated to form a single
integrated coalescing media.
12. The method of claim 1, wherein said electrostatically spinning
fine fibers comprises spinning fine fibers from a solution
including a hydrophilic polymer.
13. A method of forming a compressed filter media, comprising steps
of: electrostatically spinning a web of fine fibers having an
average diameter of less than 1 micron; applying the fine fibers to
a substrate, the substrate comprising coarse fibers that are bonded
together to form a filter media, wherein the coarse fibers have an
average fiber diameter greater than 1 micron; and lapping the
combination of the fine fiber applied substrate such that the fine
fibers overlap.
14. The method of claim 13, further comprising unwinding a roll of
filter media from an unwind station and transferring the filter
media to an electrospinning station, wherein the filter media is
kept afloat via a line tension.
15. The method of claim 13, wherein the substrate is a scrim
comprising bi-component fibers, the bi-component fibers comprising
a high melt polyester core and a low melt polyester sheath.
16. The method of claim 13, wherein the step of applying the fine
fibers provide a fine fiber coverage between about 0.075 g/m.sup.2
and 0.225 g/m.sup.2, wherein the fine fibers are carried by a
scrim.
17. The method of claim 13, wherein the step of lapping comprises
folding the substrate carrying the fine fibers into 2-20 folds,
wherein the folding provides a fine fiber to fine fiber laminated
surface and a substrate to substrate laminated surface, wherein the
folded layers are heated and compressed to form a compressed media,
wherein a thickness is adjusted by between about 50% and 300% via
heating and compressing.
18. The method of claim 17, wherein the compressed media is formed
to have a total fine fiber coverage between about 0.09 g/m.sup.2
and 5.25 g/m.sup.2.
19. The method of claim 13, wherein the step of electrostatically
spinning fine fibers comprises spinning fine fibers from a solution
including a polyamide-6.
20. A coalescing filter media, comprising: at least one substrate
comprising at least one filter media including coarse fibers having
an average fiber diameter of greater than 1 micron; fine fibers
carried by the substrate, the fine fibers comprising hydrophilic
fibers having an average fiber diameter of less than 1 micron, the
fine fibers providing a sufficient fiber surface area to coalesce
emulsified water in a hydrocarbon fuel, wherein the hydrophilic
fibers facilitate formation and growth of water droplets.
21. The coalescing filter media of claim 20, further including a
drainage layer arranged on a downstream surface of the coalescing
filter media, wherein the drainage layer is formed of a hydrophobic
porous material.
22. The coalescing filter media of claim 21, wherein the drainage
layer is formed of a cellulous material or a fiber glass
material.
23. The coalescing filter media of claim 20, wherein the fine
fibers are electrospun nanofibers formed of a hydrophilic
polymer.
24. The coalescing filter media of claim 23, wherein the fine
fibers are formed of a polyamide-6.
25. The coalescing filter media of claim 24, wherein the fine
fibers have a total fine fiber coverage between about 0.09
g/m.sup.2 and 5.25 g/m.sup.2.
26. The coalescing filter media of claim 20, wherein the substrate
is a scrim comprising bi-component fibers, the bi-component fibers
having a high melt component and a low melt component.
27. The coalescing filter media of claim 26, wherein the
bi-component fibers comprise a high melt polyester core and a low
melt polyester sheath, wherein the at least one substrate and the
fine fibers are heated and compressed together to form a coalescing
media, wherein the low melt polyester sheath melts or softens to
bond the coarse fibers and the fine fibers.
28. The coalescing filter media of claim 20, wherein the coalescing
filter media includes multiple layers of filter media, each of the
multiple filter media layers carrying a layer of fine fibers having
a fine fiber coverage between about 0.075 g/m.sup.2 and 0.225
g/m.sup.2.
29. The coalescing filter media of claim 28, wherein each of the
fine fiber layer is sandwiched between the substrate layers and/or
a media layer.
30. The coalescing filter media of claim 29, wherein the coalescing
filter media includes a fine fiber to fine fiber laminated surface
and a substrate to substrate laminated surface.
31. The coalescing filter media of claim 28, wherein the coalescing
filter media includes 10 layers of substrate, wherein each of the
substrate layer is formed of a scrim comprising bi-component
fibers, wherein each of the fine fiber layers comprises electrospun
polyamide-6 nanofibers, wherein 10 layers of fine fibers provide a
total fine fiber coverage between about 0.75 g/m.sup.2 and 2.25
g/m.sup.2.
32. The coalescing filter media of claim 31, further including a
drainage layer arranged on a downstream surface of the coalescing
filter media, the drainage layer formed of a fiber glass mat,
wherein the coalescing filter media has a total thickness between
about 3/16'' and 1/2''.
33. A compressed filter media, comprising: at least one substrate,
the at least one substrate comprising coarse fibers having an
average fiber diameter of greater than 1 micron; fine fibers
carried by the at least one substrate, the fine fibers having an
average fiber diameter of less than 1 micron, at least some of the
fine fibers being embedded at least partially within the coarse
fibers in a compressed state.
34. The compressed filter media of claim 33, wherein at least some
of the fine fibers form a dimensional matrix of fine fibers as
opposed to a planar layer.
35. The compressed filter media of claim 33, wherein at least some
of the fine fibers are generally sandwiched between layers of the
substrate.
36. The compressed filter media of claim 33, wherein the fine
fibers have a melting point higher than a melting point of at least
one component of the coarse fibers, and wherein the fine fibers are
permanently affixed and oriented
37. The compressed filter media of claim 33, wherein the at least
one substrate carrying the fine fibers are calendered together in
the compressed state.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This patent application claims the benefit of U.S.
Provisional Patent Application No. 61/330,462 filed May 3, 2010;
and U.S. Provisional Patent Application No. 61/308,488 filed Feb.
26, 2010; and U.S. Provisional Patent Application No. 61/383,487
filed Sep. 16, 2010; and U.S. Provisional Patent Application No.
61/383,569 filed Sep. 16, 2010, the entire teachings and disclosure
of which are incorporated herein by reference thereto.
FIELD OF THE INVENTION
[0002] This invention generally relates to a filter media, and in
particular to a compressed composite media comprising a substrate
and fine fibers, and method of making the same.
BACKGROUND OF THE INVENTION
[0003] Hydrocarbon fuels, such as diesel fuel, jet fuel, and
gasoline, can entrain small amount of water. The water may be
introduced in the hydrocarbon fuels, for example, by leakage,
accidental contamination, or atmospheric condensation. The
hydrocarbon fuels can dissolve about 75 to 150 parts per million
(ppm) of water at room temperature. Water solubility can increase
about 1 ppm per 1.degree. F. rise in temperature, and decrease
about 1 ppm per 1.degree. F. fall in temperature. Excess water or
undissolved water may accumulate in lower parts of a fuel handling
system as a result of temperature changes over a period of
time.
[0004] Undissolved water can be harmful to engines. Diesel engine
injectors may be damaged by steam formation, jet turbine engines
may flame-out, and gasoline engines may suffer ignition problems.
Many water separation devices and filters have been developed to
remove undissolved or free water from the fuel and prevent such
engine problems. Simple mechanical devices base on gravity or
centrifugal force separation are sufficient if free water is
present as a discrete second phase. However, free water is often
emulsified by pumps and valves, may remain as a stable emulsion,
especially in diesel or jet fuel. Two stage coalescer/separators
are designed to remove water emulsions. The coalescer breaks the
emulsion by preferential wetting of fibrous materials such as fiber
glass. The water is accumulated into large droplets and is removed
by gravity separation against a hydrophobic separator material such
as PTFE coated wire cloth or silicone impregnated paper. The
presence of wetting agents or surfactants may interfere with the
coalescence of water emulsions, especially in diesel fuel or jet
fuel. A coalescer including hydrophobic fluoropolymer fine fibers
to capture and remove water from fuel emulsions is disclosed in
Fluoropolymer Fine Fiber, U.S. Patent Application Publication No.
2009/0032475, to Ferrer et al.
[0005] Filter media including fine fibers formed using an
electrostatic spinning process is also known. Such prior art
includes Filter Material Construction and Method, U.S. Pat. No.
5,672,399; Cellulosic/Polyamide Composite, U.S. Patent Publication
No. 2007/0163217; Filtration Medias, Fine Fibers Under 100
Nanometers, And Methods, U.S. Provisional Patent Application No.
60/989,218; Integrated Nanofiber Filter Media, U.S. Provision
Patent Application No. 61/047,459; Filter Media Having Bi-Component
Nanofiber Layer, U.S. Provisional Patent No. 61,047,455, the entire
disclosures of which are incorporated herein by reference thereto.
As shown in these references nanofibers are commonly laid upon a
finished preformed filtration media substrate.
[0006] The invention provides improved coalescing medias and method
of making the coalescing media. These and other advantages of the
invention, as well as additional inventive features, will be
apparent from the description of the invention provided herein.
BRIEF SUMMARY OF THE INVENTION
[0007] A compressed nanofiber composite filter media according to
various embodiments of the present invention includes at least one
substrate and fine fibers carried thereby. Preferably, the
compressed filter media includes multiple substrate layers, each of
which carrying fine fibers. The multiple substrate and fine fiber
layers are compressed together to form the compressed composite
filter media. The compressed filter media according to various
embodiments of the present invention is particularly well suited
for a coalescing media to coalesce water in various hydrocarbon
fuels. However, the compressed filter media can also be used in
other filtration applications. For example, the compressed filter
media can make a very efficient water filter element.
[0008] Preferably, the substrate layers employed are relative open
materials with coarse fibers to provide support while at the same
time not being overly restrictive to fluid flow especially as
layers are stacked and/or compressed. This structure spaces
nano-fibers apart and affords the ability to provide for a much
heavier total coverage of nano-fibers per square unit of area while
at the same time not being overly restrictive. Further, a
relatively thin substrate may be used (and compression used), such
that the fine fibers throughout the media is spaced relatively
close and close enough to facilitate coalescing; and thickness of
the media as a whole is suitable for coalescing filtration
applications and filter element arrangement. Many embodiments also
employ hydrophilic fine fibers that attract as opposed to repelling
water. By using multiple layers of fine fibers at sufficient
coverage, water molecules or fine droplets grow within this
structure and are effectively coalesced out of a fluid stream.
[0009] The multiple substrate layers and the fine fibers may and
preferably are compressed together to form a coalescing filter
media. As such, the coalescing filter media is compacted and high
in solidity and includes a sufficient fine fiber coverage to
provide a sufficient fiber surface area to coalesce emulsified
water in a hydrocarbon fuel stream. The fine fibers are preferably
electrospun nanofibers formed of a hydrophilic material, such as
polyamide-6. The hydrophilic fine fibers further facilitate
formation and growth of water droplets.
[0010] In one embodiment and inventive aspect of the present
invention, a method of forming a coalescing filter media is
provided. The method comprises steps of electrostatically spinning
fine fibers having an average diameter of less than 1 micron,
applying the fine fibers to a substrate comprising coarse fibers
having an average diameter greater than 1 micron, and compacting
the fine fibers and the coarse fibers together. The method further
includes steps of generating sufficient fine fiber coverage and
tightness through the compacting process to coalesce water droplets
from a fluid stream, and structuring the coarse fibers and the fine
fibers into a coalescing filter media that is operable to remove
water from a fluid stream.
[0011] In some embodiments, the substrate comprise a fiber
entanglement that is bonded together, wherein the fine fibers are
deposited onto the substrate during the step of applying the fine
fibers. The substrate can be a scrim formed of bi-component fibers
comprising a high melt component and a low melt component, wherein
the fine fibers are deposited on a surface of the scrim and carried
by the scrim.
[0012] The step of compacting can involve laminating multiple
layers of the scrim carrying the fine fibers, and compressing the
multiple layers of the scrim and the fine fibers using a set of
calendering rollers. The multiple layers of the scrim and the fine
fibers can be heated to or near a melting temperature of the low
melt component, wherein the low melt component melts or softens to
act as a bonding agent to bond layers together.
[0013] In some embodiments, the multiple layers are heated before
being compressed. For example, the multiple layers can be heated in
an oven and compressed subsequently via a set of calendering
rollers. In such embodiments, a thickness of the laminated multiple
layers may increase as the scrims expand and loft during heating.
The subsequent compression of the lofted multiple layers reduces
the lofted thickness, however, the final thickness of the
compressed multiple layers may be less, equal, or greater than the
original thickness of the laminated multiple layers before heating.
In other embodiments, the multiple layers are heated and compressed
simultaneously. For example, the multiple layers can be heated and
compressed using a set of heated calendering rollers. Yet in other
embodiments, the multiple layers can be compressed first then
heated, wherein the thickness of the compressed multiple layers may
increase during heating. Further, some embodiments can including
more than one heating steps. For example, the multiple layers can
be heated before compressing, and further heated during compressing
via the set of heated calendering rollers.
[0014] In an embodiment, 10 layers of the scrim, each of which
carrying fine fibers, are laminated and compressed together. Each
scrim layer carries the fine fibers having a relatively heavy fine
fiber coverage between about 0.075 g/m.sup.2 and 0.225 g/m.sup.2.
When assembled to a stacked configuration with overlapping fine
fiber coverage, a total fine fiber coverage of the coalescing
filter media can be between about 0.75 g/m.sup.2 and 2.25
g/m.sup.2. The layers of the scrim and the fine fibers are
compressed together to form a coalescing filter media having a
thickness to between about 3/16'' and 1/2''.
[0015] In some embodiments, the scrim carrying the fine fibers is
folded into multiple folds and compressed to form a coalescing
filter media. In such embodiments, the coalescing filter media can
include a fine fiber to fine fiber laminated surface and a scrim to
scrim laminated surface.
[0016] Yet in another embodiment, the substrate is a web of coarse
fibers comprising a loose entanglement of the coarse fibers,
wherein the fine fibers are applied to the loose entanglement of
the coarse fibers during the step of applying the fine fibers. The
web of coarse fibers applied with the fine fibers can be folded
into multiple folds and compressed together, wherein the fine
fibers and the coarse fibers are integrated to form a single
integrated coalescing media.
[0017] A method of forming a coalescing filter media according to a
different embodiment includes steps of electrostatically spinning a
web of fine fibers having an average diameter of less than 1
micron, applying the fine fibers to a substrate formed of coarse
fibers having an average fiber diameter greater than 1 micron that
are bonded together, and lapping the combination of the fine fiber
applied substrate such that the fine fibers overlap. The method can
further include a step of unwinding a roll of substrate from an
unwind station and transferring the substrate to an electrospinning
station, wherein the substrate is kept afloat via a line tension.
In such embodiment, the substrate can be a scrim comprising
bi-component fibers. The bi-component fibers can include a high
melt polyester core and a low melt polyester sheath.
[0018] The step of applying the fine fibers can provide a fine
fiber coverage between about 0.03 g/m.sup.2 and 0.25 g/m.sup.2,
preferably between about 0.075 g/m.sup.2 and 0.225 g/m.sup.2,
wherein the fine fibers are carried by the scrim. Further, the step
of lapping can involve folding the scrim carrying the fine fibers
into 2-20 folds, wherein the folding provides a fine fiber to fine
fiber laminated surface and a scrim to scrim laminated surface,
wherein the folded layers are heated and compressed to form a
coalescing media. In such heating and compressing process, a
thickness of the folded layers can be adjusted from the original
thickness (thickness of each layer.times.number of layers) by about
50% to 300%, preferably about 70% to 200%, and more preferably
about 80% to 150%. (The thickness can increase after heating than
reduced during compressing. In some cases, the increase in
thickness during heating can be so great that the final thickness
may be still greater than the original thickness even after
compressing.) Two or more folded or unfolded scrims may also be
employed in a stacked combination to achieve heavy fine fiber
coverage per area.
[0019] In one embodiment, the coalescing media is formed to have a
total fine fiber coverage between about 0.09 g/m.sup.2 and 5.25
g/m.sup.2, preferably between about 0.75 g/m.sup.2 and 2.25
g/m.sup.2. Further, the step of electrostatically spinning fine
fibers preferably involves spinning fine fibers from a solution
including a polyamide-6.
[0020] In another embodiment of the present invention, a coalescing
filter media is provided. The coalescing filter media includes at
least one substrate containing coarse fibers having an average
fiber diameter of greater than 1 micron, and fine fibers carried by
the substrate. The fine fibers are hydrophilic fibers having an
average fiber diameter of less than 1 micron and provide a
sufficient fiber surface area to coalesce emulsified water in a
hydrocarbon fuel. In such embodiment, the hydrophilic fibers
facilitate formation and growth of water droplets. The coalescing
filter media can further include a drainage layer arranged on a
downstream surface of the coalescing filter media. Such drainage
layer can facilitate growth of the water droplet size. In one
embodiment, the drainage layer is formed of a cellulous material or
a fiber glass material.
[0021] The fine fibers are preferably electrospun nanofibers formed
of a hydrophilic polymer, such as polyamide-6. In one embodiment,
the coalescing filter media includes the fine fibers having a total
fine fiber coverage between about 0.09 g/m.sup.2 and 5.25
g/m.sup.2, preferably between about 0.75 g/m.sup.2 and 2.25
g/m.sup.2.
[0022] The substrate is preferably a scrim comprising bi-component
fibers, which includes a high melt component and a low melt
component. For example, the bi-component fibers can include a high
melt polyester core and a low melt polyester sheath. In such
embodiments, the substrate layers and the fine fibers are heated
and compressed together to form a coalescing media, wherein the low
melt polyester sheath melts or softens to bond the coarse fibers
and the fine fibers.
[0023] The coalescing filter media can include multiple layers of
substrate, wherein each of the multiple substrate layers carry a
layer of fine fibers having a fine fiber coverage between about
0.075 g/m.sup.2 and 0.225 g/m.sup.2. In one embodiment, each of the
fine fiber layer is sandwiched between the substrate layers and or
a media layer. In other embodiment, the coalescing filter media can
include a fine fiber to fine fiber laminated surface and a
substrate to substrate laminated surface.
[0024] In one embodiment, the coalescing filter media includes 10
layers of substrate. Each of the substrate layer is formed of a
scrim comprising bi-component fibers and carries fine fibers. The
fine fibers on each substrate layer is formed of electrospun
polyamide-6 nanofibers. The fine fibers carried by the 10 substrate
layers provide a total fine fiber coverage between about 0.75
g/m.sup.2 and 2.25 g/m.sup.2. The coalescing filter media can
further including a drainage layer arranged on a downstream surface
of the coalescing filter media formed of a fiber glass mat. In such
embodiment, the coalescing filter media can have a total thickness
between about 3/16'' and 1/2''.
[0025] In another embodiment of the present invention, a coalescing
filter media including at least one substrate containing coarser
fibers having an average fiber diameter of greater than 1 micron
and fine fibers carried by the substrate is provided. The fine
fibers have an average fiber diameter of less than 1 micron, and at
least some of the fine fibers are embedded at least partially
within the coarse fibers in a compressed state. In many of the
embodiments, at least some of the fine fibers can form a three
dimensional matrix of fine fibers extending into the substrate as
opposed to a planar layer. Further, at least some of the fine
fibers can be generally sandwiched between layers of the
substrate.
[0026] In one embodiment, the fine fibers have a melting point
higher than a melting point of at least one component of the coarse
fibers, and the fine fibers are permanently affixed and oriented.
Further, the at least one substrate and the fine fibers are
calendered together to form the compressed state.
[0027] Other aspects, objectives and advantages of the invention
will become more apparent from the following detailed description
when taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The accompanying drawings incorporated in and forming a part
of the specification illustrate several aspects of the present
invention and, together with the description, serve to explain the
principles of the invention. In the drawings:
[0029] FIG. 1 is a schematic cross-sectional view (e.g. relative
illustrated thickness not to scale) of a filter media including
tightly compacted multiple scrim layers carrying fine fibers
according to an embodiment of the present invention;
[0030] FIG. 2 is a schematic cross-sectional view of the coalescing
filter media of FIG. 1 in a pre-compressed state, which is
compressed to a compressed state;
[0031] FIG. 3 is a schematic illustration of a concentric
sheath/core type bi-component fiber of a substrate according to an
embodiment of the present invention;
[0032] FIG. 4 is a schematic illustration of an eccentric
sheath/core type bi-component fiber of a substrate according to an
embodiment of the present invention;
[0033] FIG. 5 is a schematic illustration of a side-by-side type
bi-component fiber of a substrate according to an embodiment of the
present invention;
[0034] FIG. 6 is a schematic illustration of a pie wedge type
bi-component fiber of a substrate according to an embodiment of the
present invention;
[0035] FIG. 7 is a schematic illustration of a hollow pie wedge
type bi-component fiber of a substrate according to an embodiment
of the present invention;
[0036] FIG. 8 is a schematic illustration of an islands/sea type
bi-component fiber of a substrate according to an embodiment of the
present invention;
[0037] FIG. 9 is a schematic illustration of a trilobal type
bi-component fiber of a substrate according to an embodiment of the
present invention;
[0038] FIG. 10 is a schematic illustration of tipped typed
bi-component fiber of a substrate according to an embodiment of the
present invention;
[0039] FIG. 11 is a schematic cross-sectional view of a coalescing
filter media including tightly compressed multiple scrim layers and
fine fibers and a downstream porous layer according to an
embodiment of the present invention;
[0040] FIG. 12 is a schematic illustration of a system for making a
coalescing filter media according to an embodiment of the present
invention;
[0041] FIG. 13 is a schematic illustration of a system for making a
coalescing filter media according to a different embodiment of the
present invention;
[0042] FIG. 14 is a schematic illustration of a system for making a
coalescing filter media according to yet another embodiment of the
present invention;
[0043] FIG. 15(A) is a Scanning Electron Microscopic image showing
bi-component fibers and the fine fibers of a composite media
produced using the system of FIG. 12 taken at a magnification level
.times.300;
[0044] FIG. 15(B) is a Scanning Electron Microscopic image showing
bi-component fibers and the fine fibers of a composite media
produced using the system of FIG. 12 taken at a magnification level
.times.1,000;
[0045] FIG. 15(C) is a Scanning Electron Microscopic image showing
bonding between bi-component fibers and the fine fibers of a
composite media produced using the system of FIG. 12 taken at a
magnification level .times.2,000;
[0046] FIG. 15(D) is a Scanning Electron Microscopic image showing
bonding between bi-component fibers and the fine fibers of a
composite media produced using the system of FIG. 12 at a
magnification level .times.10,000; and
[0047] FIG. 16 is a schematic cross-sectional view (e.g. relative
illustrated thickness not to scale) of a coalescing filter element
including an expanded nanofiber composite media and a compressed
nanofiber composite coalescing media according to an embodiment of
the present invention.
[0048] While the invention will be described in connection with
certain preferred embodiments, there is no intent to limit it to
those embodiments. On the contrary, the intent is to cover all
alternatives, modifications and equivalents as included within the
spirit and scope of the invention as defined by the appended
claims.
DETAILED DESCRIPTION OF THE INVENTION
[0049] Prior to turning to the details, some lexicography will be
developed to assist in understanding the present invention. As used
herein, the term "substrate" is meant to be broad in nature and
meant to include any structure upon which fine fibers are carried
or deposited. "Substrate" may include conventional formed filter
medias such as scrims and the like that may be unwound from media
rolls. Such filter medias have a fiber entanglement that typically
bonded or secured together mechanically, chemically, adhesively
and/or otherwise and thereby have strength such that they cannot be
easily torn manually (e.g. a 1 square foot sheet typically holds up
to application of tension of 5 lbs force) and have filtrations
properties. "Substrate" may also include looser fiber entanglements
that may not be bonded together or secured together (e.g. a 1
square foot sheet may fall apart upon application of tension of 5
lbs force). A "scrim" used as herein refers to woven or non-woven
fiber entanglement, wherein the fibers are bonded and compressed
into a planar formed media.
[0050] FIG. 1 is a schematic cross-sectional view of a filter media
100 according to an embodiment of the present invention. It is
schematic in the sense that in reality the fine fiber layer has
virtually no thickness, but for illustration and understanding,
thickness is illustrated in FIG. 1 and other schematic
illustrations. The filter media 100 is configured to coalesce water
in hydrocarbon fuels, such as diesel fuel, jet fuel, and gasoline.
The filter media 100 can also capture solids in a hydrocarbon fuel
stream. The filter media 100 is also referred to as a coalescer, a
coalescing media, a coalescing filter media, or other similar terms
in the present application. In preferred embodiments, the filter
media 100 includes at least two different fibers, for example,
electrospun nanofibers and a substrate of coarser fibers carrying
the nanofibers. As such, the filter media 100 is also referred to
as a composite filter media, a composite media, or other like terms
in this application. Although, the filter media 100 is particularly
well suited for coalescing applications, the filter media 100 may
be used in other filtration applications.
[0051] In the embodiment shown in FIG. 1, the filter media 100
comprises 10 layers of substrate 102, 104, 106, 108, 110, 112, 114,
116, 118, 120, each of which carrying fine fibers 124, 126, 128,
130, 132, 134, 136, 138, 140, 142, and a media 122 on top of the
fine fibers 142. The substrate, 102, 104, 106, 108, 110, 112, 114,
116, 118, 120 and the media 122 are formed of fibers having an
average fiber diameter typically larger than that of the fine
fibers. The substrate layers 102, 104, 106, 108, 110, 112, 114,
116, 118, 120, the fine fibers 124, 126, 128, 130, 132, 134, 136,
138, 140, 142, and the media 122 are laminated and tightly
compressed together to increase fiber surface area per volume to
provide a sufficient fiber surface area for water emulsified in a
hydrocarbon fuel, such as a diesel fuel, to coalesce. Further, the
fine fibers 124, 126, 128, 130, 132, 134, 136, 138, 140, 142 are
formed of a hydrophilic material, for example nylon-6, to attract
water and to enhance formation and growth of water droplets,
facilitating separation of water from a hydrocarbon fuel stream.
Although this embodiment is shown with the media layer 122, this
media layer is optional, and thus, the filter media 100 according
to other embodiments may not include this media layer 122.
[0052] The filter media of FIG. 1 may be formed using the process
shown in FIG. 2. FIG. 2 illustrates the filter media 100 in a
pre-compressed state 144 and a compressed state 146. As shown, the
filter media 100 in the pre-compressed state 144 has an initial
thickness t' (also referred herein as an original thickness.) The
filter media 100 in the pre-compressed state 144 is compressed into
the compressed state 146 using a set of calendering rollers 148 (or
progressive sets of rolls), 150, wherein the initial thickness t'
is reduced to a final thickness t.
[0053] In some embodiments, the filter media 100 in the
pre-compressed state 144 is heated before compressing. In certain
preferred embodiments, fibers of the substrate relax and reorient
to increase an average distance between the fibers during heating
(such as a scrim that has been at least partially compressed during
the scrim production process.) As such, the substrate layers expand
and loft, wherein the thickness of each of the substrate layer
increases. Further, as the fibers proximate the surface of the
substrate relax and reorient, the fine fibers which are carried by
these fibers move and reorient with the fibers. Thus, fine fibers
are extended, pushed and pulled with the larger fibers. In such
embodiments, the initial thickness t' of the pre-compressed state
144 can increase by at least 1.5 times, 2 times, 3 times or even
more via heating. In such embodiments, the final thickness t of the
filter media 100 after subsequent compression of the lofted filter
media 100 can be either less than, or equal to, or greater than the
initial thickness t', depending on the amount of expansion during
heating and the amount of reduction during compression. In other
embodiments, the filter media 100 in the pre-compressed state 144
can be heated and compressed simultaneously via a set of heated
calendering rollers. In such embodiments, there may not be any
expansion or a very slight increase in the initial thickness t'
prior to the thickness reduction to the final thickness t. In yet
different embodiments, the compressed filter media 100 having the
final thickness t can be heated post compression, wherein the
thickness t' may be increased. In some embodiments, the filter
media 100 can be heated more than once. For example, the filter
media 100 can be heated before compression, then heated again
during compression.
[0054] In one embodiment, the final thickness t can be between
about 50% and 300% of the initial thickness t', preferably between
about 70% and 200% of the initial thickness t', and more preferably
between 80% and 150% of the initial thickness t'. As the filter
media 100 in the pre-compressed state 144 is pressed down to the
final compressed state 146, the fine fibers 124, 126, 128, 130,
132, 134, 136, 138, 140, 142 become more integrated with the coarse
fibers of the adjacent substrate layers 102, 104, 106, 108, 110,
112, 114, 116, 118, 120 and form 3 dimensional fine fiber matrix
within the filter media 100. The filter media 100 in the compressed
state 146 has characteristics sufficient for a coalescing media.
Although, the filter media 100 in this embodiment includes 10
layers of substrate carrying fine fibers, other embodiments can
include more or less substrate layers carrying fine fibers.
[0055] The substrate layers 102, 104, 106, 108, 110, 112, 114, 116,
118, 120 can be formed of any suitable porous material. Each of the
substrate layer can be formed of a same type of porous material or
different types of porous material. In one embodiment, each layer
of the substrate 102, 104, 106, 108, 110, 112, 114, 116, 118, 120
comprises a formed filter media. The formed filter media comprises
fibers that are bonded together. For example, the fibers of the
formed filter media may be bonded together by solvent bonding,
thermal bonding, and/or pressure bonding. The formed filter media
can carry fine fibers and provide a structural support. The formed
filter media typically can be independently used as a filter media,
such as an air filter media, without being laminated or supported
by other media or structure. The formed filter media is also
referred to as a substrate filter media, a filter media substrate,
a substrate, a filter media, or other like terms in the present
application.
[0056] Alternatively, the substrate may comprise one or more webs
of fibers which are loosely tangled together in a highly fluffed
thick state and may not be bonded together as in the case of a
formed filter media. Thus, the web of coarse fibers can easily be
pulled apart with very little manual effort and has little
structural integrity such that it is not considered a formed filter
media in the conventional sense. The fibers of the web of fibers
typically have a larger average fiber diameter than an average
fiber diameter of the fine fibers. As such, the web of fibers is
also referred to as a web of coarse fibers or other like terms in
this application. A composite filter media including fine fibers
integrated with such web of coarse fibers is described in
Integrated Nanofiber Filter Media, US Patent Application
Publication No. 2009/0266759, which is assigned to the assignee of
the present application, the entire disclosures of which are
incorporated herein by reference thereto.
[0057] Preferably, the substrate 102, 104, 106, 108, 110, 112, 114,
116, 118, 120 is a multi-component filter media. As used herein,
the term "multi-component filter media", "multi-component media",
"multi-component fiber media" and other similar terms can be used
interchangeably to refer to filter medias including at least two
different materials. For example, a multi-component filter media
can comprise fibers formed of a first material and fibers formed of
a second material, wherein the first material and the second
material are different materials. Alternatively, a multi-component
filter media can be formed of fibers including at least two
different materials, such as fibers including a core formed of the
first material and a sheath formed of the second material, as
described in detail below. A multi-component filter media including
two different materials is refer to herein as "bi-component filter
media", "bi-component media", and like terms.
[0058] In one preferred embodiment, each of the substrate layers
102, 104, 106, 108, 110, 112, 114, 116, 118, 120 comprises a scrim
formed of bi-component fibers including two different materials
having different melting points. A composite filter media
comprising fine fibers and a substrate formed of such
multi-component fibers are described in Multi-Component Filter
Media with Nanofiber Attachment, PCT Patent Application No.
PCT/US09/50392, which is assigned to the assignee of the present
application, the entire disclosure of which are incorporated herein
by reference thereto.
[0059] In this embodiment, one component of the bi-component fibers
of the scrim has a lower melting point than the other component.
The low melt component can be any suitable polymer such as
polypropylene, polyethylene, or polyester. The other component may
be a polymer having a higher melting point than the low melt
component, or other suitable fiber materials such as glass and/or
cellulose. The bi-component fibers are bonded together and/or
compressed together to form a scrim or a substrate filter media
having a certain thickness.
[0060] The bi-component fibers of the scrim used as the substrate
102, 104, 106, 108, 110, 112, 114, 116, 118, 120 can include a high
melt polymer component and a low melt polymer component. For
example the bi-component may comprise a high-melt polyester and a
low-melt polyester, in which one has a higher melting temperature
than the other. FIG. 3 schematically illustrates a bi-component
fiber 22 according to one embodiment. As shown, the bi-component 22
is a concentric sheath/core type, wherein a core 24 is formed of a
high melt polymeric component and a sheath 26 is formed of a low
melt polymeric component.
[0061] The high melt polymer component is formed of a polymer
having a higher melting temperature than the low melt polymer
component. Suitable high melt polymers include, but are not limited
to, polyester and polyamide. Suitable low polymers include
polypropylene, polyethylene, co-polyester, or any other suitable
polymers having a lower melting temperature than the selected high
melt polymer. For example, bi-component fibers may be formed of a
polyester core and a polypropylene sheath. In this embodiment, the
bi-component fibers are formed of two different types of
polyesters, one having a higher melting point than the other.
[0062] Other types of bi-component fibers may be used to form the
substrate 102, 104, 106, 108, 110, 112, 114, 116, 118, 120 in other
embodiments. Some examples of different types of bi-component
fibers are schematically illustrated in FIGS. 4-10. An eccentric
sheath/core type bi-component fiber 28 comprising a core 30 and a
sheath 32 is shown in FIG. 4. This fiber is similar to the
concentric sheath core fiber 22, but with the core 30 shifted
off-center. The different shrinkage rates of the two polymer
components can cause the fiber to curl into a helix when heated.
This allows an otherwise flat fiber to develop crimp and bulk, and
can result in different fiber reorientation, expansion and/or
undulation of surface under heat.
[0063] FIG. 5 schematically illustrates a side-by-side type
bi-component fiber 34 including a first polymer component 36 and a
second polymer component 38. Depending on an application, the first
polymer component may be a higher or lower melt polymer than the
second polymer component. This is a further extension of the
eccentric sheath/core fiber, in which both polymers occupy a part
of the fiber surface. With proper polymer selection, this fiber can
develop higher levels of latent crimp than the eccentric
sheath/core fiber 28.
[0064] A pie wedge type bi-component fiber 40 is schematically
illustrated in FIG. 6. The pie wedge fiber 40 comprises a plurality
of adjacent wedges formed of a first polymer component 42 and a
second polymer component 44. Each of the first polymer component 42
has a second polymer component 44 on either side. The first polymer
component 42 may be a higher or lower melt polymer than the second
polymer component 44. These fibers are designed to be split into
the component wedges by mechanical agitation (typically
hydroentangling), yielding microfibers of 0.1 to 0.2 denier in the
filter media.
[0065] FIG. 7 is a schematic illustration of a hollow pie wedge
type bi-component fiber 46 comprising first polymer wedges 48 and
second polymer wedges 50. Again, depending on an application, the
first polymer wedges 48 may be formed of a higher or lower melt
polymer than the second polymer wedges 50. The hollow pie wedge
fiber 46 is similar to the pie wedge fiber 40 but with a hollow
center 52 core that prevents the inner tips of the wedges from
joining, thus making splitting easier.
[0066] FIG. 8 is a schematic illustration of a islands/sea type
bi-component fiber 54. This fiber is also known as the "pepperoni
pizza" configuration where a first polymer component 56 is the
pepperoni and a second polymer component 58 is the cheese. In some
embodiments, the first polymer component 56 is formed of a higher
melt polymer than the second polymer component 58, or the second
polymer component 58 is formed of a soluble polymer. In such
embodiments, this fiber allows the placement of many fine strands
of high melt polymer 56 within a matrix of low melt or soluble
polymer 58 that is subsequently melted or dissolved away. This
allows the production of a media made of fine microfiber because
the fibers are easier to process in the "pizza" form rather than as
individual "pepperonis." Staple fibers can be made of 37 pepperonis
on each pizza, producing fibers about 0.04 denier (about 2 microns
diameter), or even finer.
[0067] The bi-component fibers may be formed into different shapes.
For example, some bi-component fibers may not have a cylindrical
shape with a circular cross section as the bi-component fibers
described above. FIGS. 9 and 10 illustrate some examples of
bi-component fibers with irregular shapes. Although, these fibers
do not have a circular cross section, each has a diameter in
context of the present invention. The diameter of the fibers having
a non-circular cross section is measured from the outer perimeter
of the fiber. FIG. 9 is a schematic illustration of a trilobal type
bi-component fibers 60, 62. Each of the trilobal fibers 60, 62
comprises a first polymer component 64, 66 and a second polymer
component 68, 70. Each of the trilobal fibers 60, 62 are measured
by its diameter 72, 74. In some embodiments, the first polymer
component 64, 66 is formed of a higher melt or lower melt polymer
than the second polymer component 68, 70.
[0068] FIG. 10 is a schematic illustration of a tipped type
bi-component fibers 78, 80. The fiber 78 is a tipped trilobal
bi-component fiber with a first polymer center 82 and second
polymer tips 84. The fiber 80 is a tipped cross bi-component fiber
with a first polymer center 86 and second polymer tips 88.
Preferably, the first polymer center 82, 86 is formed of a higher
melt polymer than the second polymer tips 84, 88.
[0069] The fibers of the substrate 102, 104, 106, 108, 110, 112,
114, 116, 118, 120 are formed to have a larger average fiber
diameter than that of the fine fibers 124, 126, 128, 130, 132, 134,
136, 138, 140, 142. For example, the fibers of the substrate 102,
104, 106, 108, 110, 112, 114, 116, 118, 120 can have an average
fiber diameter of greater than about 1 micron, preferably greater
than about 2 micron, and more preferably, greater than 5 micron. In
one embodiment, an average diameter of the bi-component fibers of
the substrate 102, 104, 106, 108, 110, 112, 114, 116, 118, 120 are
between about 1 micron and about 40 micron.
[0070] The coarse fibers are compressed and/or heated, for example
via a set of calendering rollers and/or an oven, to form the
substrate 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, wherein
any of the substrate layers has a thickness between about 0.05 and
1.0 mm, preferably between about 0.1 and 0.5 mm. Such substrate can
provide a structural support necessary for the fine fibers.
Bi-component scrims of various thicknesses suitable for use as any
of the substrate layers 102, 104, 106, 108, 110, 112, 114, 116,
118, 120 are commercially available through various suppliers, such
as HDK Industries, Inc. of Rogersville, Tenn., or other filter
media suppliers. Thus, the substrate can be selected from such off
the shelf bi-component medias.
[0071] In one embodiment, each layer of the substrate 102, 104,
106, 108, 110, 112, 114, 116, 118, 120 and the media 122 comprise a
scrim formed of bi-component staple fibers having a high melt
polyester core and a low melt polyester sheath. The bi-component
staple fibers are compressed together to form the scrim, wherein
the bi-component staple fibers are bonded together chemically,
mechanically and/or thermally. For example, the bi-component staple
fibers are heated to or near the melting temperature of the low
melt polyester and compressed together, wherein the sheath formed
of the low melt polyester melts or softens and acts as a bonding
agent to bond fibers together.
[0072] The fine fibers 124, 126, 128, 130, 132, 134, 136, 138, 140,
142 can be deposited directly on the corresponding substrate 102,
104, 106, 108, 110, 112, 114, 116, 118, 120 as they are formed.
Alternatively, the fine fibers 124, 126, 128, 130, 132, 134, 136,
138, 140, 142 may be separately prepared as a web of fine fibers,
then laminated with the substrate 102, 104, 106, 108, 110, 112,
114, 116, 118, 120. Although, the fine fibers 124, 126, 128, 130,
132, 134, 136, 138, 140, 142 may comprise fibers having various
fiber diameters, preferably, the fine fibers 124, 126, 128, 130,
132, 134, 136, 138, 140, 142 are nanofibers having very fine fiber
diameter. Such fine fibers 124, 126, 128, 130, 132, 134, 136, 138,
140, 142 can be formed by electrospinning or other suitable
processes. In one embodiment, the fine fibers 124, 126, 128, 130,
132, 134, 136, 138, 140, 142 are electrospun nanofibers having an
average fiber diameter less than about 1 micron, preferably less
than 0.5 micron, and more preferably between 0.01 and 0.3 microns.
Such small diameter fine fibers can pack more fibers together in a
given volume to provide an increased fiber surface area in a
coalescing filter media for formation of water droplets. The fine
fibers 124, 126, 128, 130, 132, 134, 136, 138, 140, 142 may be
formed by various suitable polymeric materials. To avoid
destruction of the fine fibers during heating and/or compressing of
the filter media 100, the fine fibers 124, 126, 128, 130, 132, 134,
136, 138, 140, 142 are typically formed of a material having a
higher melt temperature than at least the low-melt component of the
bi-component fibers of the substrate. In preferred embodiments of
water coalescing applications, the fine fibers are formed of a
hydrophilic material such as polyamides. Other suitable hydrophilic
polymers include, but not limited to, poly(acrylic acid),
polyalkylene glycols, polyvinyl alcohol, polyvinyl acetate,
polyalkylene glycols, copolymers of methylvinyl ether and maleic
acid, maleic anhydride polymers, polylkylene oxides,
poly(meth)acrylamides, hydrophilic polyurethanes,
polyethyleneimines, methyl cellulose, hydroxylmethyl cellulose,
hydroxyethyl cellulose, polyvinylsulfonic acid, poly(saccharides)
such as chitosan and many other polymers or copolymers with enough
--OH, --COOH, and/or --NH2 groups.
[0073] In one embodiment, the fine fibers 124, 126, 128, 130, 132,
134, 136, 138, 140, 142 are formed of nylon-6 (polyamide-6, also
referred to as "PA-6" herein) via electrospinning, wherein the
electrospun fine fibers 124, 126, 128, 130, 132, 134, 136, 138,
140, 142 are deposited directly on the substrate 102, 104, 106,
108, 110, 112, 114, 116, 118, 120. In this embodiment, the fine
fibers 124 are generated electrostatically from a solution
containing nylon-6 and deposited on a surface of the substrate 102.
The fine fibers 126 can be similarly generated and deposited on the
substrate layer 104, and so on. The substrate layers 102, 104, 106,
108, 110, 112, 114, 116, 118, 120 coated with the electrospun
nanofibers 124, 126, 128, 130, 132, 134, 136, 138, 140, 142 are
then laminated together with the media 122, such that each layer of
the fine fibers 124, 126, 128, 130, 132, 134, 136, 138, 140, 142 is
sandwiched between the adjacent substrate 102, 104, 106, 108, 110,
112, 114, 116, 118, 120 and/or the media 122 to create the filter
media 100 in the pre-compressed state 144 as shown in FIG. 2. As
discussed above, the filter media 100 in the pre-compressed state
144 is then compressed to form the coalescing filter media 100 in
its final compressed state 146 as shown in FIGS. 1 and 2. In
preferred embodiments, the coalescing filter media 100 is heated
before, during, and/or after the compression. For example, the
filter media 100 in the pre-compressed state 144 is heated prior to
passing through the set of calendering rollers 148, 150. Further,
the set of calendering rollers 148, 150 can be heated to further
heat the filter media 100 during the compression.
[0074] The bonding between the fine fibers 124, 126, 128, 130, 132,
134, 136, 138, 140, 142 and the adjacent coarser fibers of
substrate 102, 104, 106, 108, 110, 112, 114, 116, 118, 120 and/or
media 122 may involve solvent bonding, pressure bonding, and/or
thermal bonding. For example, as the fine fibers are
electrostatically generated from a polymer solution containing a
solvent, the solvent remaining on the surface of the fine fibers
can effectuate a solvent bonding as the fiber fibers come in
contact with the coarse fibers of the substrate. Further, the low
melt component of the bi-component fibers of the substrate can be
used to enhance bonding between the fine fibers and the adjacent
coarse fibers of the substrate. In such embodiment, the filter
media 100 is heated to or near the melting point of the low melt
component and compressed, wherein the low melt component of the
bi-component coarse fibers melts or softens, which allows the
adjacent fine fibers to embed into the low melt component as they
are compressed together, thereby enhancing the bonding between the
coarse fibers and the fine fibers (via pressure bonding and thermal
bonding.)
[0075] In the embodiment shown in FIG. 11, the coalescing filter
media 500 includes 10 layers of substrate 502, 504, 506, 508, 510,
512, 514, 516, 518, 520, each of which carrying fine fibers 524,
526, 528, 530, 532, 534, 536, 538, 540, 542, and a media 522, all
of which are tightly compressed together similar to the filter
media 100. In addition, the coalescing filter media 500 includes a
porous layer 544 on the downstream surface 548. The porous layer
544 is also referred herein as a "drainage layer". Although this
embodiment is shown with the media layer 522 and the porous layer
544, these layers are optional, and thus, the filter media 500
according to other embodiments may not include the media layer 522
and the porous layer 544.
[0076] In this embodiment, the media 522 and each layer of the
substrate 502, 504, 506, 508, 510, 512, 514, 516, 518, 520 are
formed of a bi-component fiber scrim having an average fiber
diameter between about 1 and 40 microns and a base weight between
about 0.5 and 15 oz/yd.sup.2. The bi-component fibers comprise a
high-melt polyester core and a low melt polyester sheath. The fine
fibers 524, 526, 528, 530, 532, 534, 536, 538, 540, 542 are
electrospun nanofibers formed of nylon-6. The fine fibers have an
average fiber diameter between about 0.01 and 0.5 microns, wherein
each layer of the fine fibers 524, 526, 528, 530, 532, 534, 536,
538, 540, 542 has fine fiber coverage between about 0.075 g/m.sup.2
and 0.225 g/m.sup.2, providing total fine fiber coverage between
0.75 g/m.sup.2 and 2.25 g/m.sup.2.
[0077] The porous layer 544 (also referred herein as a drainage
layer) can be formed of various materials such as a cellulous
material or fiber glass. In this embodiment, the porous layer 544
is formed of a fiber glass, and has a pore size greater than or
equal the bi-component fiber scrim. The porous layer 544 allows
continual growth of water droplet that are coalesced through the
compacted substrate layers and fine fiber layers, and allows the
water droplets to pass through the porous layer 544 for subsequent
collection of water droplets. Further, the porous layer 544 can
provide additional structural support for the compacted substrate
and fine fiber layers. The media 522, the substrate layers 502,
504, 506, 508, 510, 512, 514, 516, 518, 520, the fine fibers 524,
526, 528, 530, 532, 534, 536, 538, 540, 542, and the porous layer
544 are laminated and compressed together to form the tightly
packed coalescing filter media 500 having a total thickness between
about 3/16'' to 1/2''.
[0078] In some embodiments the drainage layer 544 is formed of a
siliconized cellulous material. In such embodiments, the drainage
layer 544 is not continuously bonded to the substrate layer 502,
but may be partially secured to the substrate layer 502 to prevent
sliding movements when the coalescing filter media 500 is
subsequently pleated or formed into various filter elements. In
these embodiments, the compacted substrate and fine fiber layers
coalesce water droplets into a size sufficient to be captured by
the drainage layer 544 that is formed of the hydrophobic
siliconized cellulous material. The hydrophobic drainage layer 544
acts as a water barrier preventing the water droplets from flowing
through the pore of the hydrophobic drainage layer 544. Instead,
the water droplets flow along the hydrophobic inner surface of the
drainage layer 544 and run down between the substrate layer 502 and
the drainage layer 544. The water droplets are then collected off
line, allowing only fuel to enter the engine.
[0079] In this embodiment, a hydrocarbon fuel stream enters the
coalescing filter media 500 from the upstream surface 546, flows
through the layers of substrate and fine fibers, and exits through
the porous layer 544 on the downstream surface 548. As the
hydrocarbon fuel stream passes through the layers of substrate and
fine fibers, water emulsified in the hydrocarbon fuel stream
coalesces due to the large fiber surface area provides by the fine
fibers. Further, the hydrophilic fine fibers attract water,
enhancing formation of water droplets. The coalesced water droplets
further grow in size as they pass through large pores of the porous
layer 544 and are separated from the hydrocarbon fuel. Further,
solids and/or contaminants in the hydrocarbon fuel system can be
captured within pores of the coalescing filter media 500, thereby
providing added filtration capacity.
[0080] In other embodiments, the substrate layers 502, 504, 506,
508, 510, 512, 514, 516, 518, 520 comprise different medias. For
example, some of the substrate layers may be formed of a thicker
scrim or filter media than other layers, or may have different pore
sizes than other layers. Further, the fine fiber layers 524, 526,
528, 530, 532, 534, 536, 538, 540, 542 may have a same fine fiber
coverage or different fine fiber coverage. For example, some of the
fine fiber layers can have a fine fiber coverage of about 0.08
g/m.sup.2, while other fine fiber layers have a fine fiber coverage
of about 0.2 g/m.sup.2. Further, the fine fiber coverage of each
layer can be configured according to characteristics of a
hydrocarbon fuel stream and water content to optimize the
coalescing process.
[0081] FIG. 12 schematically illustrates a representative process
of making a coalescing filter media according to a processing
embodiment of the present invention. Although this embodiment
includes downstream process steps for making the coalescing filter
media 500 of FIG. 11, the process can produce filter medias
according to other embodiments of the present invention with minor
modifications. A system 200 shown in FIG. 12 includes an upstream
system 201 for making a composite media including a substrate and
fine fibers deposited thereon, and a downstream system 203 for
laminating and compressing multiple layers of composite media and
other additional layers to make a coalescing filter media.
[0082] The upstream system 201 includes an unwinding station 202,
an electrospinning station 204, an optional oven 206, an optional
set of calendering rollers 207 and a rewinding station 208. In this
embodiment, a roll of scrim 210, which is used here as a substrate
layer, is unwound from the unwinding station 202. The scrim 212
unwound from the roll of scrim 210 travels in a machine direction
214 toward the electrospinning station 204. In the electrospinning
station 204, fine fibers 216 are formed and deposited on one
surface of the scrim 212 to form a composite media 218 comprising
the scrim carrying the fine fibers 216. The composite media 218 may
be heated and compressed in the optional oven 206 and the optional
set of calendering rollers 207 before being wound into a roll of
composite media 230 on the rewound station 208.
[0083] The scrim may be formed in an upstream process of the system
200 (either part of a continuous line process or interrupted line
process) or may be purchased in a roll form from a supplier such as
HDK or other suitable media supplier such as H&V or Ahlstrom or
the like. The scrim can be formed of various suitable materials,
such as bi-component fibers of FIGS. 3-10 as discussed above. For
example, the scrim can be formed of high melt polyester core/low
melt polyester sheath bi-component staple fibers, which are
compressed and/or heated to form the roll of scrim 210 having a
desired thickness and solidity. Alternatively, the substrate layer
may be other single component media that may be compressed and held
in place via a solvent bond, heat bond or the like.
[0084] In the case of a bi-component, for example, the concentric
sheath/core type bi-component fibers may be coextruded using a high
melt polyester as the core and a low melt polyester as the sheath.
Such bi-component fibers can then be used to form a scrim or a
filter media. In one embodiment, the bi-component fibers are used
as staple fibers to form a multi-component filter media or a scrim
via conventional dry laying or air laying process. The staple
fibers used in this process are relatively short and discontinuous
but long enough to be handled by conventional equipment. Bales of
the bi-component fibers can be fed through a chute feed and
separated into individual fibers in a carding device, which are
then air laid into a web of fibers (which itself for purposes of
the present disclosure may be used as a substrate.) The web of
fibers is then compressed using a set of calendering rollers to
form the roll of scrim 210 (which can also be used as a substrate.)
The web of the fibers may optionally be heated before entering the
set of calendering rollers. Since the scrim 210 of this embodiment
comprises bi-component fibers, including a high melt component and
a low melt component, it is also referred to as a bi-component
filter media. In some embodiments, the web of fibers are folded
before being calendered to form a thicker bi-component filter
media.
[0085] In a different embodiment, a web comprising high melt
polymer fibers such as polyester fibers and a web comprising low
melt polymer fibers such as polypropylene fibers can be formed,
separated and laminated together to form the roll of bi-component
filter media or scrim. In such embodiment, the fine fibers 216 are
deposited on the low melt side of the scrim 212. In this
embodiment, the low melt web is substantially thinner than the high
melt web, such that the low melt component does not clog the
surface of the high melt web when heated and melted.
[0086] In another embodiment, the bi-component fiber scrim can be
formed via a melt blowing process. For example, molten polyester
and molten polypropylene can be extruded and drawn with heated,
high velocity air to form coarse fibers. The fibers can be
collected as a web on a moving screen to form a bi-component scrim
210.
[0087] The multi-component fiber filter media or scrim may also be
spun-bounded using at least two different polymeric materials. In a
typical spun-bounding process, a molten polymeric material passes
through a plurality of extrusion orifices to form a
multifilamentary spinline. The multifilamentary spinline is drawn
in order to increase its tenacity and passed through a quench zone
wherein solidification occurs which is collected on a support such
as a moving screen. The spun-bounding process is similar to the
melt blowing process, but melt blown fibers are usually finer than
spun-bounded fibers.
[0088] In yet another embodiment, the multi-component filter media
is wet-laid. In a wet laying process, high melt fibers and low melt
fibers are dispersed on a conveying belt, and the fibers are spread
in a uniform web while still wet. Wet-laid operations typically use
1/4'' to 3/4'' long fibers, but sometimes longer if the fiber is
stiff or thick. The above discussed fibers, according to various
embodiments, are compressed to form a scrim 210 or a filter media
having a desired thickness.
[0089] Referring back to FIG. 12, the scrim 212 enters the
electrospinning station 204, wherein the fine fibers 216 are formed
and deposited on one surface of the scrim 212. In the
electrospinning station 204, the fine fibers 216 are electrospun
from electrospinning cells 222 and deposited on the web of scrim
212. The electrospinning process of the system 200 can be
substantially similar to the electrospinning process disclosed in
Fine Fibers Under 100 Nanometers, And Methods, U.S. Patent
Application Publication No. U.S. 2009/0199717, assigned to the
assignee of the present application, the entire disclosure of which
has been incorporated herein by reference thereto. Alternatively,
nozzle banks or other electrospinning equipment can be utilized to
form the fine fibers. Such alternative electrospinning devices or
rerouting of chain electrodes of the cells 222 can permit the
fibers to be deposited in any orientation desired (e.g. upwardly is
shown although fibers can also be spun downwardly, horizontally or
diagonally onto a conveyor carrying coarser fibers).
[0090] The electrospinning process produces synthetic fibers of
small diameter, which are also known as nanofibers. The basic
process of electrostatic spinning involves the introduction or
electrostatic charge to a stream of polymer melt or solution in the
presence of a strong electric field, such as a high voltage
gradient. Introduction of electrostatic charge to polymeric fluid
in the electrospinning cells 222 results in formation of a jet of
charged fluid. The charged jet accelerates and thins in the
electrostatic field, attracted toward a ground collector. In such
process, viscoelastic forces of polymeric fluids stabilize the jet,
forming small diameter filaments. An average diameter of fibers may
be controlled by the design of electrospinning cells 222 and
formulation of polymeric solutions.
[0091] The polymeric solutions used to form the fine fibers can
comprise various polymeric materials and solvents. Examples of
polymeric materials include polyvinyl chloride (PVC), polyolefin,
polyacetal, polyester, cellulous ether, polyalkylene sulfide,
polyarylene oxide, polysulfone, modified polysulfone polymers and
polyvinyl alcohol, polyamide, polystyrene, polyacrylonitrile,
polyvinylidene chloride, polymethyl methacrylate, polyvinylidene
fluoride. Solvents for making polymeric solution for electrostatic
spinning may include acetic acid, formic acid, m-cresol, tri-fluoro
ethanol, hexafluoro isopropanol chlorinated solvents, alcohols,
water, ethanol, isopropanol, acetone, and N-methylpyrrolidone, and
methanol. The solvent and the polymer can be matched for
appropriated use based on sufficient solubility of the polymer in a
given solvent and/or solvent mixture (both of which may be referred
to as "solvent".) For example, formic acid may be chosen for
nylon-6. Reference can be had to the aforementioned patents for
further details on electrospinning of fine fibers.
[0092] In the electrospinning station 204, an electrostatic field
is generated between electrodes in the electrospinning cells 222
and a vacuum collector conveyor 224, provided by a high voltage
supply generating a high voltage differential. As shown in FIG. 12,
there may be multiple electrospinning cells 222, wherein fine
fibers 216 are formed. The fine fibers 216 formed at the electrodes
of the electrospinning cells 222 are drawn toward the vacuum
collector conveyor 224 by the force provided by the electrostatic
field. The vacuum collector conveyor 224 also holds and transfers
the scrim 212 in the machine direction 214. As configured, the
scrim 212 is positioned between the electrospinning cells 222 and
the vacuum collector conveyor 224, such that the fine fibers 216
are deposited on the scrim 212. In embodiments, wherein the scrim
212 is a multi-component filter media including a low melt
component on one surface and a high melt component on the other
surface, the multi-component scrim 212 is positioned between the
electrospinning cells 222 and the vacuum collector conveyor 224,
such that the low melt component surface of the multi-component
scrim faces the electrospinning cells 222.
[0093] In one preferred embodiment, the electrospinning cells 222
contain a polymeric solution comprising polyamide-6 (PA-6) and a
suitable solvent consisting of 2/3 acetic acid and 1/3 formic acid.
In such a solvent, both acetic acid and formic acid act as a
dissolving agent to dissolve PA-6, and acetic acid controls
conductivity and surface tension of the polymeric solution. The
electrospinning cells 222 generate fine fibers formed of PA-6,
which are deposited onto a surface of the scrim 212. As the fine
fibers 216 are deposited on the surface of the scrim 212, some fine
fibers 216 entangle with coarse fibers of the scrim proximate the
surface facing the electrospinning cells 222. When some fine fibers
216 entangle with some coarse fibers, solvent remaining in the fine
fibers 216 from the electrospinning process can effectuate a
solvent bonding between the fine fibers 216 and the coarse fibers
of the scrim 212.
[0094] The bonding between bi-component fibers of the scrim 212 and
the fine fibers 216 may be enhanced via thermal bonding and
pressure bonding by the optional oven 206 and the optional set of
calendering rollers 207. As the composite media 218 is heated in
the oven 206, the low melt polymer component of the bi-component
fibers softens or melts and allowing the fine fibers 216 to embed
into the low melt polymer component. Thus, during the heat
treatment, the composite filter media 218 is heated to at least
above the glass transition temperature of the low melt component,
and more preferably to or near the melting temperature of the low
melt component. For example, the composite media 218 is heated to
or near the melt point of low melt polyester, such that the outer
low melt polyester layer of the bi-component fibers melts and bonds
with the fine fibers 216 formed of PA-6. In such embodiments, PA-6
fine fibers 216 and the high melt polyester core of the
bi-component fibers do not melt, since PA-6 and the high melt
polyester have a significantly higher melting temperature than that
of the low melt polyester. The low melt polyester, which has the
lowest melting temperature, melts or softens, and adjacent PA-6
fine fibers 216 are embedded in the softened or melted low melt
polyester, thereby bonding the fine fibers 216 and the scrim 212
together. Thus, the low melt polyester acts as a bonding agent
between the bi-component fiber scrim 212 and the fine fibers 216.
The bonding between the fine fibers 216 and the scrim 212 can
further be enhanced through pressure bonding via the set of
calendering rollers 207. As the composite media passes through the
calendering rollers 207, the fine fibers 216 and the scrim 212 are
compressed together, wherein the fine fibers are further embedded
into the fibers of the scrim 212. Further, the compression reduces
voids in the composite media to form a composite media 220 with an
increased solidity.
[0095] FIGS. 15(A)-15(D) are Scanning Electron Microscopic (SEM)
images of the bi-component fibers of the scrim 212 and the fine
fibers 216 proximate the surface of the scrim 212 taken at various
magnification levels. As shown in the SEM images taken at
magnification levels .times.300 and .times.1000 of FIGS. 15(A) and
15(B), the fine fibers 216 deposited on the web of scrim 212 form a
spider web like fiber structure between the coarser bi-component
fibers that are located proximate the surface of the scrim 212. The
SEM images taken at higher magnifications (FIG. 15(C) at
.times.2,000 and FIG. 15(D) at .times.10,000) show the bonding
between the fine fibers 216 and the bi-component fibers. As shown
clearly in FIG. 15(D), the fine fibers 216 are embedded on the low
melt polyester surface of the bi-component fibers.
[0096] The roll of composite media 230 including the bi-component
scrim 212 and the fine fibers 216 is laminated with other composite
medias 232, 234, 236, 238, 240, 242, 244, 246, 248, and a media 250
in the downstream system 203. Each of the composite media rolls
230, 232, 234, 236, 238, 240, 242, 244, 246, 248, and a roll of the
media 250 are unwound from unwind stations 252, 254, 256, 258, 260,
262, 264, 266, 268, 270, 272, and laminated together by a set of
rollers 274. The set of rollers may be a calendering rollers to
apply a significant pressure to laminate and significantly reduce a
thickness of the layers of composite medias. Alternatively, the set
of rollers 274 may apply a small pressure to laminate and reduce
the thickness of the laminated layers just enough to fit through an
oven 276. In such embodiment, the laminated layers 280 is heated in
the oven 276 and compressed via a set of calendering rollers,
wherein the laminated layers 280 is compressed together into a
compressed state having a desired thickness and solidity.
[0097] In this embodiment, each roll of the composite media 232,
234, 236, 238, 240, 242, 244, 246, 248 is prepared similarly as the
roll of the composite media 230. Therefore, each of the roll of the
composite media 232, 234, 236, 238, 240, 242, 244, 246, 248
includes a substrate formed of a bi-component fiber scrim 284, 286,
288, 290, 292, 294, 296, 298, 300, and electrospun nanofibers 302,
304, 306, 308, 310, 312, 314, 316, 318, carried by the bi-component
fiber scrim 284, 286, 288, 290, 292, 294, 296, 298, 300.
[0098] In one embodiment, each of the substrates 212, 284, 286,
288, 290, 292, 294, 296, 298, 300 and the media 250 are formed of a
same bi-component fiber scrim having a thickness between about 0.05
mm and 1.0 mm. Each layer of the fine fibers 216, 302, 304, 306,
308, 310, 312, 314, 316, 318, is formed by electrospinning PA-6
polymer solution to produce a fine fiber coverage between about
0.075 g/m.sup.2 and 0.225 g/m.sup.2. In other embodiments, the
substrates may be formed of different types of filter media or
scrim, and each of the fine fibers layer may have different fine
fiber coverage.
[0099] The composite media 280 is heated in the oven 276 to or near
a melting temperature of the low melt polyester component of the
bi-component fiber scrim. During heating the substrates can relax
and expand in thicknesses. Thus, the lofted composite media 281 can
have a thickness that is at least 1.5 times, 2 times, 3 times or
even greater than the thickness of the composite media 280 before
being heated in the oven 276. The lofted composite media 281 is
then compressed via the set of calendering rollers 282 into the
compressed state 320. The composite media is compressed, such that
the thickness of the composite media 280 is reduced between about
50% and 300%, preferably between about 70% and 200%, and more
preferably between about 80% and 150% of the original thickness of
the composite media 280 prior to heating ((total thickness of 10
scrim layers carrying 10 fine fiber layers+thickness of
media-thickness of the composite media in the compressed state
320)/(total thickness of 10 scrim layers carrying 10 fine fiber
layers+thickness of media).) The thickness reduction will depend on
the amount of lofting during heating. Thus, when the lofting from
heating is large, the final thickness of the composite media after
compression may be greater than the initial thickness of the
composite media before heating. The composite media in the
compressed state 320 is then laminated with a drainage layer 322
and wound into a roll of coalescing media 324.
[0100] In this embodiment, the rolls of the composite media 230,
232, 234, 236, 238, 240, 242, 244, 246, 248. and the media 250 are
laminated together, such that each of the fine fiber layers 216,
302, 304, 306, 308, 310, 312, 314, 316, 318 is sandwiched between
adjacent substrate layer and/or media. However, in other
embodiments, the composite media layers may be laminated such that
some of the fine fiber layers face each other to form fine fiber to
fine fiber or substrate to substrate bonding within the final
composite media 320.
[0101] FIG. 13 schematically illustrates a system and a process of
making a coalescing filter media according to a different
embodiment of the present invention. A system 400 generally
includes an unwinding station 402, an electrospinning station 404,
a folding station 406, a set of rollers 408, an oven 410, and a set
of calendering rollers 412 and a rewinding station 414.
[0102] In this embodiment a roll of substrate 416 is unwound from
the unwinding station 402 and transferred to the electrospinning
station 404, wherein fine fibers are formed and deposited on a
surface of the substrate 416. The electrospinning station 404 and
the process are similar to the electrospinning station 204 and the
process described above. In this embodiment, the substrate 416 is a
scrim formed of bi-component fibers including a high melt polyester
core and a low melt polyester sheath. The fine fibers 418 are
formed of PA-6.
[0103] The composite media 420 comprising the substrate 416 and
fine fibers 418 is folded in the folding station 406. The composite
media 420 can be folded to 2-20 folds thick depending on desired
characteristics of the final coalescing media. As shown, the
folding creates fine fiber to fine fiber laminated surfaces and
substrate to substrate laminated surfaces. The folding station 406
in this embodiment is shown as folding the composite media 420 in a
line direction, such that the folds are pointing toward the set of
the rollers 408. However, in other embodiments, the composite media
402 may be folded such that the folds are pointing toward the
electrospinning station 404, or folded in cross-line directions.
The folded composite media 422 is then compressed to a thickness
appropriate to pass through an oven 410. As the composite media 424
is heated, the low melt polyester sheath melts or softens to
effectuate thermal bonding between layers. After exiting the oven
410, the composite media 424 passes through the set of calendering
rollers 412. The calendering rollers 412 are spaced apart from each
other according to a desired final thickness of the coalescing
media. The composite media 424 is pressed down into a compressed
state having a desired thickness as it passes through the set of
calendering rollers 412.
[0104] Further, a media layer 426 and a porous layer 428 are
laminated on each surface of the coalescing media 430 and wound
into a roll in the rewinding station 414. A expanded cross
sectional view of a coalescing filter media 432 including the
coalescing media 430, the media layer 426, and the porous layer 428
is shown in FIG. 13. As shown, the coalescing media 430 includes
multiple layers of substrate 416 and multiple layers of fine fibers
418 in a slanted orientation from the folding process. The media
layer 426 can be formed of any suitable media, but in this
embodiment, the media layer 426 is formed of the same bi-component
fiber scrim used for the substrate 416. The porous layer 428 can
also be formed of various porous material, but in this embodiment,
the porous layer 428 is a fiber glass material.
[0105] FIG. 14 shows yet a different embodiment of a system and a
process of making a coalescing media. A system 600 is similar to
the system 400 but the fine fibers in this embodiment are not
deposited on a substrate. Rather, the fine fibers are formed and
deposited onto a web of loosely entangled coarse fibers. The system
600 generally includes a chute 602, a carding device 603, an
electrospinning station 604, a folding station 606, a set of
rollers 608, an oven 610, and a set of calendering rollers 612 and
a rewinding station 614.
[0106] In the system 600, the web of coarse fibers 616 is formed
from staple fibers using a dry laying or air laying process. The
staple fibers of this embodiment are bi-component fibers comprising
a high melt polyester core and a low-melt polyester sheath. The
bi-component staple fibers are relatively short and discontinuous,
but long enough to be handled by conventional equipment. Bales of
staple fibers are fed through the chute feed 602. In the carding
device 603, the bi-component staple fibers are separated into
individual fibers and air laid to form the web of coarse fiber 616.
At this point, the web of coarse fiber 616 can be loosely tangled
together in a highly fluffed thick state and may not be bonded
together. The web of coarse fiber 616 can be easily pulled apart
with very little manual effort and has little structural integrity
at this point such that it is not considered a filter media or
substrate in the conventional sense.
[0107] The web of coarse fiber 616 is transferred via a conveyor
belt 617 toward the electrospinning station 604, wherein the fine
fibers 618 are formed and deposited on a surface of the web of
coarse fiber 616. As the fine fibers 618 are deposited on the web
of coarse fiber 616, the fibers 618 are integrated with the coarse
fibers of the web of coarse fiber 616 much more than in the
previous embodiment with the substrate 416, as the web of coarse
fiber 616 are much more porous and less dense to allow deeper
integration of the fine fibers 616.
[0108] The web of coarse fiber 616 integrated with the fine fibers
618 are then folded into 10-30 folds in the folding station 606 and
compressed via the set of rollers 608, which is heated in the oven
610 and compressed again via the set of calendering rollers 612 as
it was with the system 400. The coalescing media 630 is then
laminated with a media layer 626 and a porous layer 628 to from a
coalescing filter media 632. The coarse bi-component fibers and the
fine fibers of the coalescing media 630 of this embodiment are much
more integrated. Thus, a cross sectional view of the coalescing
media 630 does not show multiple layers, but rather appears more
like a single integrated media 630. The coalescing media 630 has a
sufficient fine fiber coverage and tightness to provide coalescing
of water droplets from a fluid stream, such as a hydrocarbon fuel
stream. Further, the coalescing filter media 632 is configured to
remove water from such fluid stream.
[0109] The coalescing media according to various embodiments of the
present invention can be configured into various shapes and sizes
for various applications. For example, the coalescing media can be
used in spin-on filter applications, large fuel filtration vessels,
aviation filter systems, hydraulic filter elements, and bio-fuel
systems. The coalescing media can be pleated or gathered into a
fluted filter, a pleated filter, or other such typical filter
element arrangements. Although the coalescing media works
particularly well in coalescing applications, the coalescing media
can also work effectively in other filtration applications such as
filtering particulates from water.
[0110] A typical coalescing filter element may include a pre-filter
element and a coalescing element. The pre-filter media is typically
a separate structure from the coalescing element and configured to
filter out particulates from a fuel stream before the fuel stream
enters the coalescing element to prevent particulates from blocking
coalescing media pores. In one embodiment, the coalescing filter
element is constructed to include an expanded nanofiber composite
media and a compressed coalescing filter media. Such coalescing
filter element can filter particulates and coalesce water to
eliminate the need of the pre-filter element.
[0111] FIG. 16 shows a coalescing filter element 700 that includes
an expanded nanofiber composite media 702, a compressed coalescing
media 704, and a drainage layer 706. As shown, a fuel stream 708
enters the coalescing filter media 700 via the expanded nanofiber
composite media 702 and flows though the compressed coalescing
media 704 and exits out through the drainage layer 706. Such
expanded nanofiber composite media is disclosed in U.S. Provisional
Patent Application No. 61/308,488, Expanded Composite Filter Media
Including Nanofiber Matrix and Method, assigned to the assignee of
the present application, entire disclosure of which is incorporated
herein by reference thereto.
[0112] In this embodiment, the expanded nanofiber composite media
702 includes three layers of substrate 710, 712, 714, wherein the
substrate layers 712 and 714 carry nanofibers 726, 728. The
compressed nanofiber composite media 704 includes five layers of
substrate 716, 718, 720, 722, 724, each of which carries nanofibers
730, 732, 734, 736, 738. Each of the substrate layers 710, 712,
714, 716, 718, 720, 722, 724 can be formed of a same or different
porous material. In this embodiment, each of the substrate layers
are formed of a scrim comprising bi-component fibers as described
above with regard to other embodiments of the coalescing media. The
nanofibers 726, 728, 730, 732, 734, 736, 738 are deposited on the
corresponding substrate layers via electrospinning similar to other
embodiments described above.
[0113] The expanded nanofiber composite media 702 is constructed by
laminating the nanofiber 726, 728 deposited scrim layers 712, 714
with the scrim layer 710 and heating the laminated layers in an
oven to reorient and loft fibers of scrim layers. As the scrim
layers 710, 712, 714 reorient and loft, nanofibers 726, 728 also
reorient and extend with the fibers of scrim layers. As a result, a
volumetric coverage of nanofibers can increase (more volumetric
coverage for a same basis weight application--as the expansion can
open up and expand the nanofibers into a 3D matrix); a pressure
drop can be reduced due to expansion; and/or a pressure drop
increase with dust loading can be slowed. Thus, the expanded
nanofiber composite media 702 layer can effectively filter out
particulates in the fuel stream before it enters the subsequent
compressed coalescing media layer 704.
[0114] The compressed coalescing media 704 can be constructed
similarly as the coalescing filter media 100 or 500 as described in
detail above. The nanofiber deposited scrim layers are laminated,
heated and compressed to form the compressed coalescing media to
coalesce water in the fuel stream. The drainage layer 706 can be
any porous media described above. In this embodiment, the drainage
layer 706 is a hydrophobic siliconized cellulous material. This
drainage layer 706 is not continuously attached to the substrate
layer 738, but secured to the substrate layer in several spots
along sides. The hydrophobic drainage layer 706 prevents coalesced
water droplets from passing through its pores. Rather, the
coalesced water droplets flow along the inner surface 725 of the
drainage layer 706 and are collected. As such, only the fuel stream
without the coalesced water droplets are allowed to pass through
the drainage layer to enter an engine system.
[0115] All references, including publications, patent applications,
and patents cited herein are hereby incorporated by reference to
the same extent as if each reference were individually and
specifically indicated to be incorporated by reference and were set
forth in its entirety herein.
[0116] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) is to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. The terms "comprising,"
"having," "including," and "containing" are to be construed as
open-ended terms (i.e., meaning "including, but not limited to,")
unless otherwise noted. Recitation of ranges of values herein are
merely intended to serve as a shorthand method of referring
individually to each separate value falling within the range,
unless otherwise indicated herein, and each separate value is
incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate the invention and does not
pose a limitation on the scope of the invention unless otherwise
claimed. No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of
the invention.
[0117] Preferred embodiments of this invention are described
herein, including the best mode known to the inventors for carrying
out the invention. Variations of those preferred embodiments may
become apparent to those of ordinary skill in the art upon reading
the foregoing description. The inventors expect skilled artisans to
employ such variations as appropriate, and the inventors intend for
the invention to be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all
modifications and equivalents of the subject matter recited in the
claims appended hereto as permitted by applicable law. Moreover,
any combination of the above-described elements in all possible
variations thereof is encompassed by the invention unless otherwise
indicated herein or otherwise clearly contradicted by context.
* * * * *