U.S. patent application number 14/238436 was filed with the patent office on 2014-11-06 for liquid filtration media containing melt-blown fibers.
This patent application is currently assigned to DONALDSON COMPANY, INC.. The applicant listed for this patent is Brian Babcock, Mike J. Madsen. Invention is credited to Brian Babcock, Mike J. Madsen.
Application Number | 20140326661 14/238436 |
Document ID | / |
Family ID | 46724646 |
Filed Date | 2014-11-06 |
United States Patent
Application |
20140326661 |
Kind Code |
A1 |
Madsen; Mike J. ; et
al. |
November 6, 2014 |
LIQUID FILTRATION MEDIA CONTAINING MELT-BLOWN FIBERS
Abstract
A filter and filter media configured and arranged for placement
in a fuel stream is disclosed. The filter and filter media allow
for filtering of liquid fuels, such as diesel fuel. In certain
embodiments the filter media includes a media fiber, such as melt
blown polyester; and a scaffold fiber, also such as such as melt
blown polyester, having a larger diameter than the media fiber. The
media and scaffold fibers combine to create a media structure
having low solidity and relatively low compressibility, and which
contain a pore structure that avoids premature fouling of the
filter by fuel degradation products.
Inventors: |
Madsen; Mike J.; (Chaska,
MN) ; Babcock; Brian; (Bloomington, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Madsen; Mike J.
Babcock; Brian |
Chaska
Bloomington |
MN
MN |
US
US |
|
|
Assignee: |
DONALDSON COMPANY, INC.
Minneapolis
MN
|
Family ID: |
46724646 |
Appl. No.: |
14/238436 |
Filed: |
August 9, 2012 |
PCT Filed: |
August 9, 2012 |
PCT NO: |
PCT/US12/50176 |
371 Date: |
July 28, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61523068 |
Aug 12, 2011 |
|
|
|
Current U.S.
Class: |
210/505 |
Current CPC
Class: |
B01D 39/16 20130101;
B01D 39/18 20130101; B01D 39/1607 20130101; B01D 39/1623
20130101 |
Class at
Publication: |
210/505 |
International
Class: |
B01D 39/16 20060101
B01D039/16 |
Claims
1. A filter for filtering liquid fuels, the filter comprising:
filter media configured and arranged for placement in a liquid fuel
stream, the filter media comprising: a) media fiber; and b)
scaffold fiber having an average diameter greater than the media
fiber.
2. The filter for filtering liquid fuels of claim 1, wherein at
least one of the media fiber and scaffold fiber comprise a melt
blown fiber.
3. The filter for filtering liquid fuels of claim 1, wherein both
of the media fiber and scaffold fiber comprise a melt blown
fiber.
4. The filter for filtering liquid fuels of claim 1, wherein the
scaffold fiber comprises bicomponent fiber.
5. The filter for filtering liquid fuels of claim 1, wherein the
media fiber has an average diameter of less than 5 microns.
6. (canceled)
7. The filter for filtering liquids claim 1, wherein the filter
media has a Compressibility Solidity Factor of less than 600.
8-9. (canceled)
10. The filter for filtering liquids of claim 1, wherein the filter
media has a solidity of less than 12 percent.
11. The filter for filtering liquid fuels of claim 1, wherein the
filter media has a compressibility of less than 40 percent at a
pressure of 1.24 kg/cm2.
12-13. (canceled)
14. The filter for filtering liquid fuels of claim 1, wherein the
filter media has a max flow pore size at least 200 percent greater
than the mean flow pore size.
15. (canceled)
16. The filter for filtering liquid fuels of claim 1, wherein the
filter media has a mode flow pore of at least 20 microns.
17. The filter for filtering liquid fuels of claim 1, wherein the
filter media has an upstream portion and a downstream portion, and
wherein the upstream portion has a pore size mode greater than the
pore size mode of the downstream portion.
18. The filter for filtering liquid fuels of claim 1, further
comprising a second filter media, the second filter media
comprising cellulose fibers, and the second filter media positioned
downstream from the filter media comprising a media fiber and a
scaffold fiber.
19. A filter for filtering liquid fuels, the filter comprising:
filter media configured and arranged for placement in a liquid fuel
stream, the filter media comprising: a) first fiber; and b) a
second fiber having an average diameter greater than the first
fiber; wherein the filter media has a solidity of less than 12
percent, and a compressibility of less than 40 percent at a
pressure of 1.24 kg/cm.sup.2.
20. The filter for filtering liquid fuels of claim 19, wherein the
first fiber comprises a melt blown fiber.
21-25. (canceled)
26. A filter for filtering liquid fuels, the filter comprising: A
first filter media configured and arranged for placement in a
liquid fuel stream, the first filter media comprising: a) a first
fiber, and b) a second fiber having an average diameter greater
than the first fiber; and a second filter media, the second filter
media comprising cellulose; wherein the first filter media is
arranged upstream of the second filter media in the flow of liquid
fuels during filtration.
27. The filter for filtering liquid fuels of claim 26, wherein the
first fiber in the first filter media comprises glass fiber, melt
blown fiber, or combinations thereof.
28-32. (canceled)
33. A filter for filtering liquid fuels comprising: filter media
configured and arranged for placement in a liquid stream, the
filter media comprising an upstream media portion and a downstream
media portion, wherein: a) a first portion containing fiber having
an average diameter of less than 15 microns; and b) a second
portion containing fiber having an average diameter different than
the average diameter of the media fiber in the first portion;
wherein the mode pore size of the first portion is at least 20
percent greater than the mode pore size of the second portion; and
wherein the mean flow pore size of the media in the first portion
is less than 90 percent of the mean pore flow size of the media in
the second portion.
34. The filter for filtering liquid fuels of any claim 33, wherein
the fiber of the first portion comprises melt blown fiber and the
fiber of the second portion comprises cellulose.
35-39. (canceled)
40. A filter for filtering liquid fuels, the filter comprising: A
first filter media configured and arranged for placement in a
liquid fuel stream, the first filter media comprising: a) media
fiber, and b) scaffold fiber; wherein the first filter media has a
pore size distribution geometric standard deviation of greater than
2.5.
41-43. (canceled)
44. The filter for filtering liquids of claim 40, further
comprising s second filter media, wherein the second filter
comprises cellulose.
45-48. (canceled)
Description
[0001] This application is being filed as a PCT International
Patent application on Aug. 9, 2012, in the name of Donaldson
Company, Inc., a U.S. national corporation, applicant for the
designation of all countries except the U.S., and Mike J. Madsen, a
U.S. Citizen, and Brian Babcock, a U.S. Citizen, applicants for the
designation of the U.S. only, and claims priority to U.S.
Provisional Patent Application Ser. No. 61/523,068, filed Aug. 12,
2011; the contents of which are herein incorporated by
reference.
FIELD OF THE INVENTION
[0002] The present invention is directed to filtration media,
filter elements, and methods of filtering liquid fuels. In
particular, the invention is directed to filtration media for the
removal of fuel degradation products (FDPs) and other contaminants
from liquid fuels.
BACKGROUND
[0003] Liquid fuels, such as diesel fuel, are used in internal
combustion engines of various configurations and sizes. Such fuels
must generally be filtered so as to remove particulate
contaminants, which can otherwise create significant problems in
engine performance and can result in damage to the engine. Filter
media for removal of these particulate contaminants has generally
been required to remove very high percentages of particles,
necessitating use of filter media with tight pore structures.
Without such tight pore structures, unacceptable levels of
particles can pass through the filter media and detrimentally
affect engine performance.
[0004] One media currently used for removal of particulate
contaminants from fuel streams is melt-blown media. Although
melt-blown media can perform adequately in removing particulate
contaminants from liquid fuels, the melt-blown media can readily
foul from buildup of contaminants other than traditional
particulate contaminants. This premature fouling appears to be
particularly pronounced in situations where fuel undergoes repeated
heating and cooling cycles, such as in common rail systems used on
many diesel engines. In such systems diesel fuel is pumped from a
fuel tank at high pressure along a common conduit (or rail) that is
connected to multiple fuel injectors. Some of the diesel fuel
passes through the fuel injectors and is combusted, but the
remainder is delivered back to the fuel tank at an increased
temperature as a result of travelling down the common rail through
portions of the hot diesel engine. Once back in the tank the fuel
rapidly cools. Repeated cycles of heating and cooling of the fuel
are believed to contribute in the production of fuel degradation
products that accelerate fouling of traditional fuel filter
media.
[0005] In addition to filter-clogging materials generated as a
result of heating and cooling cycles, additional sources of
contaminants that can reduce fuel filter performance include
ingredients found in various biodiesel mixtures. Although often
distinct in origin from the fuel degradation products formed during
heating and cooling cycles, these contaminants can also contribute
to significant reductions in fuel filter life by accumulating on
the filter media. Finally, even normal aging of fuel, especially
when it occurs at heightened temperatures, can result in production
of fuel contaminants that further limit fuel filter life due to
fouling and clogging of filter media earlier than would otherwise
be expected if only hard particle contaminants were present.
[0006] Therefore, a substantial need exists for filtration media,
filter elements, and filtration methods that can be used for
removing contaminant materials from liquid fuel streams.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to filter media configured
and arranged for placement in a fluid fuel stream, to filter
elements manufactured using the filter media, and to methods of
filtering fuel streams. The filter media and elements are
configured for applications where fuel can contain various other
contaminants besides conventional hard particles. These additional
contaminants can include (for example) waxes, asphaltenes, sterol
glucosides, steryl glucosides, sterol glycosides, and various fuel
degradation products (FDPs). Collectively, these additional
contaminants can be referred to as fuel contamination products
(FCPs). For diesel fuel filtration, in particular, the filter media
is especially configured to remove fuel degradation products
(FDPs), as well as similar fuel contamination products (FCPs).
[0008] In a first example embodiment, the filter media comprises an
upstream layer of filter media and a downstream layer of filter
media. The upstream layer of filter media contains melt blown
polymeric fibers, such as polyester fibers. The downstream layer of
filter media comprises cellulose fibers. In this example
embodiment, the upstream layer of media containing melt blown
fibers can be laminated to the downstream cellulose media. The
upstream layer of media removes fuel degradation products in a
manner such that filter life is preserved, or even extended,
relative to prior art filter media.
[0009] The downstream cellulose layer serves a dual role as a
support layer for the upstream filter layer, while also functioning
to remove hard particles from the fuel stream. The upstream removal
of the fuel degradation products avoids fouling of the downstream
cellulose layer with the fuel degradation products, thereby
allowing the downstream cellulose layer to capture hard particles
without premature fouling, despite a tight pore structure. In
addition, in certain embodiments the downstream cellulose layer can
be constructed with a tighter pore structure than would otherwise
be possible without the upstream layer (or layers) of media
containing melt blown fibers, because the upstream layer (or
layers) remove fuel degradation products (or fuel contaminant
products) that would otherwise prematurely foul the tighter pore
structures.
[0010] More generally, the invention is directed to various filter
constructions that allow for removal of contaminants such as fuel
degradation products and other fuel contamination products. Such
filter constructions can comprise, for example, one or more areas
of filter media containing a mixture of at least two types of
fibers: (1) a media fiber and (2) a scaffold fiber. Media fiber is
generally that fiber that provides primary filtration properties to
the media, such as controllable pore size, permeability and
efficiency. The media fiber used in accordance with the invention
may be, for example, melt blown fiber, glass fiber or carbon fiber.
The scaffold fiber may be, for example, a melt blown or bicomponent
fiber. Suitable melt blown fibers include, in particular, polyester
fibers.
[0011] The scaffold fiber provides support for the media fiber, and
adds improved handling, adds greater strength, and results in lower
compressibility to the media. The use of the scaffold fiber reduces
compressibility, and allows for lower solidity, increases tensile
strength and improves bonding of media fiber such as melt blown
fiber or glass fiber and other sub-micron fiber materials that are
added to the media layer or filter element.
[0012] In general the media fiber has a much smaller diameter than
the scaffold fiber. In example embodiments the media fiber has an
average diameter less than 5 microns, while the scaffold fiber has
an average diameter greater than 5 microns. More typically, the
media fiber will have an average diameter from 0.1 to 20 microns,
and optionally from 0.1 to 15 microns. In some implementations the
media fiber will have an average diameter from 0.4 to 12 microns,
and in some implementations from 0.4 to 6.5 microns. Media fibers
with an average diameter of less than 10 microns, less than 7.5
microns, less than 6.5 microns, and less than 5 microns are often
desirable.
[0013] The scaffold fiber will typically have a diameter from 5 to
40 microns, more typically from 7 to 20 microns, and often from 10
to 14 microns. In certain implementations the scaffold fiber will
have an average diameter of greater than 5 microns, greater than 7
microns, greater than 10 microns, greater than 20 microns, or
greater than 30 microns. It will be noted that the diameter of both
the media fibers and the scaffold fibers can be variable. In some
cases the fiber diameters will vary along their lengths, while more
commonly multiple different fibers of various diameters will be
incorporated. It will be understood that, as used herein, fiber
diameters are based upon average fiber diameters for the fibers
present in the media.
[0014] A further characteristic of filter media made in accordance
with the present invention, and in particular that portion of the
media associated with sequestering FDPs (and related contaminants),
is that the media typically has a relatively low solidity level. As
used herein, solidity is the solid fiber volume divided by the
total volume of the filter medium at issue, usually expressed as a
percentage. In a typical implementation, solidity of the filter
media associated with sequestering FDPs is less than 15 percent,
more typically less than 12 percent, and more frequently less than
10 percent. In certain embodiments the solidity is less than 9
percent, less than 8 percent, or less than 7 percent.
[0015] An additional characteristic of the filter media made in
accordance with the present invention is that it is relatively
incompressible, especially relative to the solidity of the media.
In a first example embodiment, the filter media has a
compressibility of less than 40 percent at a pressure of 1.24
kg/cm.sup.2. In other implementations the filter media has a
compressibility of less than 30 percent at a pressure of 1.24
kg/cm.sup.2, less than 20 percent at a pressure of 1.24
kg/cm.sup.2, and less than 10 percent at a pressure of 1.24
kg/cm.sup.2. It will thus be understood that the fitter media of
the present invention, at least that portion of the media most
suitable for FDP removal, will typically have a relatively low
solidity as well as a relatively low compressibility (or high
stiffness).
[0016] The pore structures of the media provide further metrics by
which the properties of the media associated with sequestering FDPs
can be measured. In general, it is possible to characterize the
properties of a porous media in terms of such parameters as mean
flow pore, mode flow pore, and max flow pore. In accordance with
the teachings of the present invention, it is desirable in general
to have at least a portion of the media with small mean flow pores,
while also having a large max flow pore.
[0017] The ratio of max pore size to mean flow pore is often at
least 2.5, optionally at least 5.0, and in some implementations
greater than 7.5. In certain embodiments, where the mean flow pore
is very small and the max flow pore is relatively high, this ratio
may be greater than 10.0, and optionally greater than 12.5 or 15.
High ratios of the max flow pore to the mean flow pore reflect a
wider pore size distribution, which can provide for reduced fouling
from FDPs (and related) contaminants.
[0018] The media can also be selected to have a favorable pore size
distribution, as measured by the ratio of pore sizes at the
15.9.sup.th percentile to that at the 50th percentile, which is
geometric standard deviation for a lognormal distribution (a
distribution which is normal for the logarithm transformed value).
While the media pore size distribution is not necessarily
lognormal, the ratio is employed here to approximate the geometric
standard deviation of the pore size distribution. Unless otherwise
stated, the geometric standard deviation mentioned below will refer
to the ratio defined above. The geometric standard deviation is
analogous to the slope of the curve of pore diameter plotted
against cumulative pore volume. A geometric standard deviation of
1.0 gives a single pore size, while a larger geometric standard
deviation reflects a broadening of the pore distribution. Thus, a
geometric standard deviation of 1.2 reflects a narrow distribution,
and a geometric standard deviation of 2.0 indicates a meaningfully
broader distribution. A geometric standard deviation of 2.5 is a
relatively broad distribution. A geometric standard deviation of
3.0 is a very broad distribution. Generally, the upstream filter
material of the present invention containing media fiber and
scaffold fiber will have a geometric standard deviation of greater
than 2.0, more typically greater than 3.0, and in some
implementations greater than 4.0.
[0019] As noted above, filter media made in accordance with the
present invention is often comprised of two or more layers: an
upstream filter material (containing media fiber and scaffold
fiber, such as: melt blown fibers; glass fiber and bicomponent
fibers, glass and melt blown fibers; or melt blown fibers and
bicomponent fibers) is desirably combined with a downstream filter
material. This downstream filter material is generally selected for
favorable removal of particulate contaminants. The downstream
material may comprise, for example, cellulose fiber.
[0020] In some embodiments, the mode pore size of the upstream
portion is greater than the mode pore size of the downstream
portion. For example, the mode pore size of the upstream portion
(bicomponent/glass) may be at least 20 percent or at least 40
percent greater than the mode pore size of the downstream portion
(cellulose media). In another embodiment, the mode pore size of the
upstream portion is at least 20 percent greater than the mode pore
size of the downstream portion; and the mean flow pore size of the
upstream portion is less than 90 percent of the mean pore flow size
of the downstream portion. In some embodiments, the mode pore size
of the upstream portion is greater than the mode pore size of the
downstream portion. For example, the mode pore size of the upstream
portion may be at least 40 percent greater or at least 60 percent
greater than the mode pore size of the downstream portion. In some
embodiments, the mean flow pore size of the upstream portion is
less than the mean pore flow size of the downstream portion. For
example, the mean flow pore size of the upstream portion may be
less than 70 percent or less than 50 percent of the mean pore flow
size of the downstream portion.
[0021] It will be appreciated that the downstream portion may
contain fiber having an average diameter or cross-section greater
than the average diameter of the media fiber the upstream
portion.
[0022] Throughout this specification descriptions are provided as
to the properties of the various portions of the filter media. In
particular, properties are described for filter media having
specific attributes, such as fiber diameter, solidity,
compressibility, mean flow pore, mode pore flow, and max pore. It
will be understood that media made in accordance with the present
invention will often show unintentional variability in these
properties, such as variability along a media web, as well as
unintentional variability along the thickness or depth of a sheet
of media. In addition, there can be intentional variation of the
properties of the filter media, such as by providing multiple
layers of media with intentionally different properties, or by
providing a media with a gradient construction such that media
properties gradually change along the depth of the media. It will
be understood that such unintentional variability, as well as
intentional variation, are intended to be within the scope of the
present invention.
[0023] The above summary of the present invention is not intended
to describe each discussed embodiment of the present invention.
This is the purpose of the figures and the detailed description
that follows.
FIGURES
[0024] The invention may be more completely understood in
connection with the following drawings, in which:
[0025] FIG. 1 is a schematic diagram of a fuel system for a diesel
engine.
[0026] FIG. 2 is a graph of pore density versus diameter to show
mode pore size for a media.
[0027] FIG. 3 is a graph of cumulative pore size distribution to
show mean flow pore size for a media.
[0028] FIG. 4A is a cross sectional schematic view of a media
construction made in accordance with an implementation of the
invention.
[0029] FIG. 4B is a cross sectional schematic view of a second
media construction made in accordance with an implementation of the
invention.
[0030] FIG. 4C is a cross sectional schematic view of a third media
construction made in accordance with an implementation of the
invention.
[0031] FIG. 4D is a cross sectional schematic view of a fourth
media construction made in accordance with an implementation of the
invention.
[0032] FIG. 5 is a schematic representation of a cross section of a
portion of a filter structure according to one embodiment of the
invention, showing relative pore sizes.
[0033] FIG. 6 is a multi-stage fuel filter according to one
embodiment of the present invention.
[0034] While the invention is susceptible to various modifications
and alternative forms, specifics thereof have been shown by way of
example and drawings, and will be described in detail. It should be
understood, however, that the invention is not limited to the
particular embodiments described. On the contrary, the intention is
to cover modifications, equivalents, and alternatives falling
within the spirit and scope of the invention.
DETAILED DESCRIPTION
[0035] The present invention is directed in part to filter media
and filter elements for the removal of contaminant material from a
liquid fuel stream. The filter elements and media are configured
for removal of additional contaminants besides hard particles,
these additional contaminants including (for example) waxes,
asphaltenes, sterol glucosides, steryl glucosides, sterol
glycosides, and fuel degradation products--collectively referred to
as fuel contamination products. The filter elements and media allow
for improved filter performance and longevity.
[0036] Although existing fuel filtration media can perform
adequately in removing particulate contaminants from liquid fuels,
the existing media can prematurely foul by buildup of contaminants
other than traditional particulates. This premature fouling appears
to be particularly pronounced in situations where fuel undergoes
repeated heating and cooling cycles, such as in common rail systems
used on many diesel engines.
[0037] FIG. 1 is a schematic diagram of a common rail fuel system
for a diesel engine. In FIG. 1, a fuel tank 100 is in fluid
communication with a fuel pump 102 and fuel filter 104. Fuel is
pumped from the fuel tank 100 through the filter 104, and then into
a common rail 106 that serves as a manifold from which the diesel
fuel is distributed to a plurality of injectors 108. Some of the
fuel passes through the injectors 108 into combustion chambers, but
excess fuel is allowed to flow back by way of return line 110 to
the fuel tank 100. The fuel that is delivered back to the fuel tank
is typically returned at an increased temperature as a result of
travelling down the common rail through portions of the hot diesel
engine. The fuel cools upon return to the fuel tank. In this manner
portions of the fuel in the tank are continuously being heated and
cooled whenever the engine is running.
[0038] Repeated cycles of heating and cooling of the fuel are
believed to result in the production of fuel degradation products
(FDPs). The FDPs can quickly accumulate on traditional fuel
filtration media, resulting in premature fouling of the media. Such
fouling can occur, for example, on melt blown polyester filter
media, as well as on cellulose fitter media. The fouling occurs as
the FDPs, and potentially other fuel contaminant products (such as
various waxes, asphaltenes, sterol glucosides, steryl glucosides,
sterol glycosides) build up upon the filter media, causing plugging
of the pores and premature failure.
[0039] The present invention overcomes the shortcoming of the prior
art by providing a media construction that removes fuel
contaminants in a manner such that their impact on filter
performance and filter life can be limited. In particular, the
present invention provides one or more layers or areas of media
that effectively sequester contaminants such as FDPs, while being
constructed to avoid becoming prematurely plugged. By effectively
sequestering the FDPs, other components within the filter eluding
in some cases other layers within a multi-layered media) avoid
premature plugging. The result is a longer life, better performing
filter media and filter element.
[0040] In an example embodiment of the invention, the filter media
comprises various sized melt blown fibers laminated on the upstream
side of cellulose media, with the cellulose also serving a dual
role as a hard particle filter and a support for the thermally
bonded glass. The melt blown media functions to remove the FDPs in
a fashion such that the FDPs are removed while premature plugging
of the cellulose layer is avoided. This improved performance is
achieved, in part, by selecting the a fiber mixture so that the
media has a relatively low solidity, while retaining a relatively
low compressibility. Typically some of the fibers are relatively
thin and in high concentrations while other fibers are relatively
thick and in lower concentrations, result in a media having small
mean flow pore sizes, but also typically relatively high maximum
pore sizes.
[0041] The use of a media that has relatively low solidity and low
compressibility, while also having a small mean flow pore size but
a high maximum flow pore size, results in a media construction that
effectively removes FDP compounds without premature plugging.
Preferred materials for the media fiber are those that have
relatively high tensile strength and can be meltspun into small
diameter fibers. Preferred materials for scaffold fiber have
relatively higher values for modulus of elasticity than materials
used for media fibers.
[0042] The performance of the media can be measured by a
compressibility-solidity factor ("CS Factor") which is determined
as the multiple of the compression percent times the solidity
percent. In both cases, lower numbers are generally preferred. A
compression percent of 40 percent, multiplied by a solidity of 15
percent, gives a CS Factor of 600. A compression percent of 10
percent, along with a solidity percent of 10 percent, will provide
a CS Factor of 100. Generally, a CS Factor of below 600 is desired.
CS Factors of less than 500, less than 450, less than 400, and less
than 350 are all suitable for certain implementations of the
invention. CS Factors of less than 300 can be particularly
desirable, as are CS Factors of less than 250, less than 200, and
even less than 150. CS Factors of less than 150 are also desirable,
in particular less than 125, less than 100, and less than 75.
[0043] Suitable materials and configurations of filter media and
elements will now be described in greater detail, including a
discussion of the media for removing fuel contaminant products
(especially FDPs), followed by a discussion of various media
configurations having additional media layers or areas for removing
of both FDP contaminants and traditional contaminants, a discussion
of filter element configurations, and a discussion of experimental
results.
Media for Removal of Fuel Contamination Products (Including Fuel
Degradation Products)
[0044] The present invention is directed, in part to various filter
constructions that allow for removal of contaminants such as fuel
degradation products, and in some implementations contaminants such
as waxes, asphaltenes, sterol glucosides, steryl glucosides, and
sterol glycosides. Such filter constructions can contain one or
more layers or areas of filter media containing a mixture of two
(or more) types of fibers: (1) a media fiber and (2) a scaffold
fiber. These fibers are typically selected to include at least some
melt blown fibers, optionally with the use of non-meltblown
fibers.
[0045] Meltblown fibers are generally formed by extruding a molten
thermoplastic material through a plurality of die capillaries as
molten threads or filaments into converging high velocity, usually
hot, gas (e.g. air) streams which attenuate the filaments of molten
thermoplastic material to reduce their diameter. Thereafter, the
meltblown fibers can be carried by the high velocity gas stream and
are deposited on a collecting surface to form a web of randomly
dispersed meltblown fibers. Meltblown processes are disclosed, for
example, in U.S. Pat. No. 3,849,241 to Butin et al.; U.S. Pat. No.
4,100,324 to Anderson et al., U.S. Pat. No. 3,959,421 to Weber et
al.; U.S. Pat. No. 5,652,048 to Haynes et al.; and U.S. Pat. No.
5,271,883 to Timmons et al.
[0046] Suitable thermoplastic polymers for forming the meltblown
fibers include, but are not limited to, polyolefins,
polycondensates (e.g., polyamides, polyesters, polycarbonates, and
polyarylates), vinyl polymers, polyols, polydienes, polyurethanes,
polyethers, polyacrylates, polycarbonates, polystyrenes, and so
forth. Examples of suitable polyolefins include, by way of example
only, polyethylene, polybutene and copolymers and/or blends
thereof. As examples, the fibers can comprise ethylene polymers and
copolymers thereof and more particularly can comprise copolymers of
ethylene with alpha-olefins.
[0047] Additional examples of polymers suitable for making media
fibers also include poly(1-pentene), poly(2-pentene),
poly(3-methyl-1-pentene), poly(4-methyl-1-pentene), nylon,
polybutylene, polyethylene terephthalate, polybutylene
terephthalate, and so forth.
[0048] Additionally, thermoplastic elastomers are also suitable for
use with the present invention such as, for example,
ethylene-propylene rubbers, styrenic block copolymers, copolyester
elastomers, polyamide elastomers and so forth. In a particular
embodiment, the first layer of the nonwoven web comprises fibers of
crystalline polymers having a crystallinity greater than 20% and
still more desirably a crystallinity of about 30% or more and even
still more desirably a crystallinity of about 50% or more. In an
exemplary embodiment, the media fiber web can comprise a polyester
polymer.
[0049] Polyester, and more particularly poly(butylene
terephthalate) resin (PBT) can be used in accordance with the
teachings of the present invention. PBT resins generally have good
characteristics for meltblown processes. The polyester resins used
to form the meltblown webs of the invention include an aromatic
dicarboxylic acid (or derivative thereof), a linear diol, and at
least one additional aliphatic branched or cyclic diol. The
polyester resins may include polybutylene terephthalate) based
polymers (PBT) or polybutylene napthalate) based polymers (PBN),
where the resins are modified with one or more additional aliphatic
dials.
[0050] The polyester copolymers produced according to the present
invention should have properties suitable for meltblown processes
and nonwoven applications. If the polyester used to make the
meltblown webs is a terephthalate resin, it may have a melting
point in the range of from 200-220.degree. C. If the polyester used
is a naphthalate resin, it may have a melting point in the range of
from 220-240.degree. C. The polyester resins may have an intrinsic
viscosity (I.V.) in the range of from 0.5 to 0.8 dl/g. If the
intrinsic viscosity of the polyester constituting the meltblown
webs of this invention is lower than 0.5, the polymer produces
molten fibers with melt strengths that are too low for
attenuation--the fibers tend to break under the high velocity gas
streams. Additionally, if the intrinsic viscosity is in excess of
0.8, the polymer is too viscous to be extruded through the die
orifices.
[0051] Larger fibers can be achieved on conventional meltblowing
assets by reducing the primary air temperature and pressure as well
as lowering the formation height. The thickness or basis weight of
the second layer can be increased as desired by increasing the
number of consecutive meltblown banks altered to provide such
fibers. It is noted that alteration of other parameters alone or in
combination with the aforesaid parameters may also be used to
achieve large fibers and/or thicker webs. Methods of making larger
meltblown fibers are described in more detail in U.S. Pat. No.
5,639,541 to Adam and U.S. Pat. No. 4,659,609 to Lamers et al.; the
entire contents of each of the aforesaid references are
incorporated herein by reference. In a further aspect, it is
possible to deposit more than one large fiber layer on the first
media fiber layer.
[0052] The scaffold fiber layer comprises larger fibers of
sufficient number and size so to create an open structure having
improved strength relative to the first media fiber layer.
Desirably the scaffold fiber layer has a significant number of
fibers in excess of about 15 micrometers and still more desirably
has a substantial number of fibers in excess of about 25
micrometers. In this regard, it is noted that the coarse fibers can
comprise a plurality of smaller fibers having diameters between
about 10 and about 35 micrometers and still more desirably an
average fiber diameter of between about 12 micrometers and about 25
micrometers wherein the individual fibers "rope" or otherwise
become length-wise bonded so as to collectively form large, unitary
fibers or filaments. In calculating average fiber size, the
length-wise bonded fibers are treated as a single fiber. The
meltblown fiber can be used either as a media fiber or as a binder
fiber, or both, depending upon the desired properties of the
material.
Media Fiber
[0053] Media fiber is that fiber that provides primary filtration
properties to the media, such as controllable pore size,
permeability and efficiency. The media fiber used in accordance
with the invention may be, for example, melt blown fiber, glass
fiber, carbon fiber, ceramic fibers, polyester or cellulose.
[0054] Generally suitable media fibers should have an average
diameter of less than 15 microns, more desirably less than 10
microns, and preferably less than 5 microns.
[0055] In embodiments, the filter media useful in the filter media
packs of the invention
contain media fibers in an amount corresponding to about 10% to 90%
by weight of the total solids in the filter medium, or about 20 to
80% by weight of the total solids in the filter medium, or about
25% to 75% by weight of the total solids in the filter medium, or
about 50% by weight of the total solids in the filter medium. In
certain implementations the media fibers correspond to greater than
10% by weight of the total solids in the filter media, while in
other implementations, the media fibers correspond to greater than
20% by weight of the total solids in the filter media, and in yet
other implementations the media fibers correspond to greater than
50% by weight of the total solids in the filter media. In certain
implementations the media fibers correspond to less than 75% by
weight of the total solids in the filter media, while in other
implementations, the media fibers correspond to less than 50% by
weight of the total solids in the filter media, and in yet other
implementations the media fibers correspond to greater than 25% by
weight of the total solids in the filter media.
[0056] In some embodiments, a blend of more than one source of
media fiber is employed, wherein the blend of more than one source
of glass fiber is employed to form the total weight percent of
media fiber in the filter medium. In some such embodiments, the
blend of glass fiber sources is selected to control the
permeability of the filter media. For example, in some embodiments,
combining glass fibers from more than one source of media fiber
having an average fiber diameter of about 0.3 to 0.5 micrometer,
media fiber having an average fiber diameter of about 1 to 2
micrometers, glass fiber having an average fiber diameter about 3
to 6 micrometers, glass fiber with a fiber diameter of about 6 to
10 micrometers, and media fiber with fiber diameter of about 10 to
100 micrometers in varying proportions, including blends of two or
more thereof, increases the permeability of the filter media pack.
In some such embodiments, the glass fiber blends are selected to
impart a controlled pore size, resulting in a defined permeability,
to a filter medium.
[0057] In addition (or as an alternative to) to melt blown fibers,
the media fiber can include glass fiber. Suitable media fiber
comprises a glass fiber used in media of the present invention
include glass types known by the designations: A, C, D, E, Zero
Boron E, ECR, AR, R, S, S-2, N, and the like, and generally, any
glass that can be made into fibers either by drawing processes used
for making reinforcement fibers or spinning processes used for
making thermal insulation fibers. Such fiber is typically used as a
diameter about 0.1 to 10 micrometers and an aspect ratio (length
divided by diameter) of about 10 to 10,000. These commercially
available fibers are characteristically sized with a sizing
coating. Commercial sources for suitable glass materials include
the following: Lauscha International, Evanite, Johns Manville, Owen
Corning, and others. In addition to glass fibers, an alternative
fiber suitable in some implementations for the media fiber
comprises carbon fibers.
[0058] Generally suitable carbon fibers should have an average
diameter of less than 25 microns, more desirably less than 15
microns, and preferably less than 10 microns. Commercial sources
for suitable carbon materials include the following: Unitika,
Kynol, and others.
Scaffold Fiber
[0059] The scaffold fiber provides support for the media fiber, and
adds improved handling, strength, and resistance to compression to
the media fiber. In certain implementations the scaffold fiber also
provides improved processability during furnish formulation, sheet
or layer formation and downstream processing (including thickness
adjustment, drying, cutting and filter element formation).
[0060] The scaffold fiber may be, for example, a melt blown
fiber.
[0061] Conventional meltblowing or meltspinning equipment can be
used to produce such larger, coarse fibers by properly balancing
the polymer throughput, diameter of the die tip orifice, formation
height (i.e. the distance from the die tip to the forming surface),
melt temperature and/or draw air temperature. As a specific
example, the last bank in a series of meltblown fiber banks can be
adjusted whereby the last meltblown bank makes and deposits a layer
of scaffold fibers over the newly formed media fiber nonwoven web.
With regard to making larger thermoplastic polyester fibers, by
reducing the primary air temperature and/or lowering the formation
height, production of larger, coarse fibers is achieved. The
thickness or basis weight of the scaffold fiber layer can be
increased as desired by increasing the number of consecutive
meltblown banks altered to provide larger, coarse fibers. It is
noted that alteration of other parameters alone or in combination
with the aforesaid parameters may also be used to achieve scaffold
fiber layers and/or webs. Methods of making such larger, coarse
fibers are described in more detail in U.S. Pat. No. 4,659,609 to
Lamers et al. and U.S. Pat. No. 5,639,541 to Adam, the entire
contents of the aforesaid references are incorporated herein by
reference.
[0062] The scaffold fiber layer can be deposited co-extensively
with the media fiber layer. In this regard, it will be appreciated
that the scaffold fibers are not significantly drawn and/or
oriented. Nevertheless, since the scaffold fibers are deposited
upon the media fibers in a semi-molten state they form good
inter-fiber bonds with the media fiber fibers as well as other
coarse fibers and thereby provide a composite structure which has
improved strength and resistance to pilling during handling,
converting and/or use. Moreover, despite the formation of a layer
having increased irregularity, polymeric globules and/or shot, the
scaffold fiber layer forms an open structure that does not
significantly decrease the filtration efficiency and/or create
tinting or other particulates detrimental to use of the same in
filtration applications.
[0063] The scaffold fiber may also be a bicomponent fiber. As used
herein, "bicomponent fiber" means a fiber formed from a
thermoplastic material having at least one fiber portion with a
melting point and a second thermoplastic portion with a lower
melting point. The physical configuration of these fiber portions
is typically in a side-by-side or sheath-core structure. In
side-by-side structure, the two resins are typically extruded in a
connected form in a side-by-side structure. Other useful
morphologies include lobed bicomponent fibers, wherein the tips of
the fibers have lobes that are formed from a lower melting point
polymer than the rest of the fiber.
[0064] The use of the bicomponent fiber enables the formation of a
media layer or filter element that can be formed with no separate
resin binder or with minimal amounts of a resin binder that
substantially reduces or prevents film formation from the binder
resin and also prevents lack of uniformity in the media or element
due to migration of the resin to a particular location of the media
layer. The use of the bicomponent fiber can permit reduced
compression, improved solidity, and increased tensile strength in
the filter media and improves utilization of media fiber such as
glass fiber and other sub-micron fiber materials that are added to
the media layer or filter element.
[0065] The media fibers and scaffold fibers combine in various
proportions to forma high strength material having substantial
filtration capacity, permeability and filtration lifetime. Such a
media can be made with optional secondary fibers and other additive
materials. These components combine to form a high strength
material having substantial flow capacity, permeability and high
strength.
[0066] Bicomponent fibers may also be used as the scaffold fiber.
Various combinations of polymers for the bicomponent fiber may be
useful in the present invention, in an embodiment the first polymer
component melts at a temperature lower than the melting temperature
of the second polymer component and typically below 205.degree. C.
Further, the bicomponent fibers are typically integrally mixed and
evenly dispersed with the media fibers. Melting of the first
polymer component of the bicomponent fiber is necessary to allow
the bicomponent fibers to form a tacky skeletal structure, which
upon cooling, captures and binds many of the media fibers, as well
as binds to other bicomponent fibers. In the sheath-core structure,
the low melting point (e.g., about 80 to 205.degree. C.)
thermoplastic is typically extruded around a fiber of the higher
melting (e.g., about 120 to 260.degree. C.) point material.
[0067] In use, the bicomponent fibers typically have a fiber
diameter of about 5 to 50 micrometers, often about 10 to 20
micrometers, and typically in a fiber form generally have a length
of 0.1 to 20 millimeters or often have a length of about 0.2 to
about 15 millimeters. Such fibers can be made from a variety of
thermoplastic materials including polyolefins (such as
polyethylenes), polyesters (such as polyethylene terephthalate,
polybutylene terephthalate, polycyclohexylenedimethylene
terephthalate), nylons including nylon 6, nylon 6,6, nylon 6,12,
etc.
[0068] Bicomponent fibers are useful in forming mechanically
stable, but strong, permeable filtration media. The bicomponent
fibers useful in the filter assemblies of the invention are of a
core/shell (or sheathed) morphology, side-by-side morphology,
islands-in-the-sea morphology, or lobed morphology. The bicomponent
fibers are made up of at least two thermoplastic materials having
different melting points. In some embodiments, thermoplastic
polymers useful in forming either the core or the sheath of the
bicomponent fibers useful in filter media of the present invention
include polyolefins such as polyethylene, polybutylene,
poly-.alpha.-octene, and copolymers thereof including linear low
density, low density, high density, ultra-high density, and other
morphological and compositional designations;
polytetrahaloethylenes such as polytetrafluoroethylene and
polychlorotrifluoroethylene; polyesters such as polyethylene
terephthalate, polybutylene terephthalate, or polyethylene naphtha
late; polyvinyl acetate, polyvinyl alcohol, and copolymers thereof;
polyvinyl halides such as polyvinyl chloride, polyvinylidene
halides such as polyvinylidene chloride, polyvinylidene fluoride,
and the like and copolymers thereof; polyacetals such as polyvinyl
butyral, acrylic resins (polyacrylates) such as polymethylacrylate
esters and polymethylmethacrylate esters and copolymers thereof
including copolymers of acrylic acid and salts thereof; polyamides
such as nylon 6, nylon 66, nylon 6,10, nylon 46, and the like and
copolymers thereof; polystyrene and copolymers thereof;
polyurethanes; polyureas; cellulosic resins, namely cellulose
nitrate, cellulose acetate, cellulose acetate butyrate, ethyl
cellulose, and the like; copolymers of any of the above materials,
such as ethylene-vinyl acetate copolymers, ethylene-acrylic acid
copolymers, styrene-butadiene block copolymers, KRATON.RTM.
rubbers, and the like. In embodiments, a polyolefin/polyester
sheath/core bicomponent fiber is employed whereby the polyolefin
sheath melts at a lower temperature than the polyester core. In an
embodiment, the bicomponent fiber comprises a polyester sheath and
a polyester core. In other embodiments, two polyolefins, or two
polyesters, two polyvinyl halide, two polyvinylidene halide, two
polyamide polymers, or any other two polymers that are similar or
identical chemically are employed as core and sheath, wherein
compositional (e.g. the particular monomer composition mix used to
synthesize the polymer, or the blockiness of the monomer
concentration in a copolymer), molecular weight, or morphological
differences such as degree of branching or degree of side chain
crystallization and the like provide lower and higher melting or
softening polymer materials.
[0069] In some embodiments, the lower melting point component of
the bicomponent fibers is employed as the sheath in a core/sheath
morphology (or shell in a core/shell morphology), as the lobes in a
lobed morphology, as the "islands" in an islands-in-the-sea
morphology, or as one side of a side-by-side morphology. The lower
melting component provides a melt fusing capability to the formed
filter media pack, wherein the nonwoven wet laid or air laid webs
are heated to a temperature above the melting point or glass
transition temperature of the lower melting component and below the
melting point or glass transition temperature of the higher melting
component. In embodiments, melt fusing is accomplished when the
molten or softened fiber components contact other bicomponent
fibers, as well as any other fibers and additives within the formed
wet laid or air laid filter media pack. In such embodiments, when
the temperature is subsequently reduced to at or below the intended
end use temperature, the bicomponent fibers have become at least
partially melt fused by virtue of the sheath (or lobe or side),
while substantially retaining the nonwoven characteristics of loft,
permeability, porosity, basis weight, thickness, and the like
imparted by the air laid or wet laid process employed to form the
media. These nonwoven characteristics are retained by virtue of the
higher melting core or side of the bicomponent fiber that retains
its fibrous morphology during melt fusing. Further, the melt fused
bicomponent fiber imparts desirable properties, including reduced
compression and increased tensile strength; the melt fused
bicomponent fiber further improves utilization and retention of
media fiber and other secondary fibers and/or additive materials in
the filter media or filter assemblies of the invention.
[0070] In some embodiments, core/sheath bicomponent fibers known as
Advansa 271P available from E. I. Dupont Nemours, Wilmington Del.
is useful in forming both the high loft and low loft filter media
useful in the filter assemblies of the invention. Other useful
bicomponent fibers include the T-200 series of concentric
core/sheath fibers available from Fiber Innovation Technology, Inc.
of Johnson City, Tenn.; Kuraray N720, available from Engineered
Fibers Technology, LLC of Shelton, Conn.; Nichimen 4080, available
from Nichimen America Inc. of New York, N.Y.; and similar
materials. All of these fibers demonstrate the characteristics of
melt fusing as described above.
[0071] Spunbond fibers can also be used as the scaffold fibers.
Spunbond fibers are often about 10 microns or greater in diameter.
Spunbond webs (having an average fiber diameter less than about 10
microns) may be achieved by various methods including, but not
limited to, those described in U.S. Pat. No. 6,200,669 to Marmon et
al. and U.S. Pat. No. 5,759,926 to Pike et al. As used herein, the
term "polymer" generally includes, but is not limited to,
homopolymers, copolymers, such as for example, block, graft, random
and alternating copolymers, terpolymers, etc. and blends and
modifications thereof. Furthermore, unless otherwise specifically
limited, the term "polymer" shall include all possible geometrical
configurations of the molecule. These configurations include, but
are not limited to isotactic, syndiotactic and random
symmetries.
Media Properties
[0072] The performance properties of the filter media are
significantly impacted by controlling attributes relating to the
fiber size, pore structure, solidity, and compressibility of the
filter media. Generally, the use of a media that has relatively low
solidity and low compressibility, while also having a small mean
flow pore size but a large maximum flow pore size, results in an
example media construction that can remove FDP compounds without
premature plugging.
[0073] In general the media fiber has a much smaller diameter than
the scaffold fiber. In example embodiments, the media fiber has an
average diameter of less than 5 microns, while the scaffold fiber
has an average diameter of greater than 5 microns. More typically,
the media fiber will have an average diameter from 0.1 to 20
microns, and optionally from 0.1 to 15 microns. In some
implementations the media fiber will have an average diameter from
0.4 to 12 microns, and in some implementations from 0.4 to 6.5
microns. Media fibers with an average diameter of less than 10
microns, less than 7.5 microns, less than 6.5 microns, and less
than 5 microns are often desirable. The scaffold fiber will
typically have a diameter from 5 to 40 microns, more typically from
7 to 20 microns, and often from 10 to 14 microns. In some
implementations the scaffold fibers can have significantly larger
diameters, including up to 100, 150, 250, 300, 350, 400 or 500
microns in various implementations. Note that the diameter of both
the media fibers and the scaffold fibers can be variable. In some
cases the fiber diameters will vary along their lengths, white more
commonly fibers of different diameters will be incorporated.
[0074] A further characteristic of filter media made in accordance
with the present invention, and in particular that portion of the
media associated with sequestering FDPs (and related filet
contaminant products), is that it typically has a relatively low
solidity level. As used herein, solidity is the solid fiber volume
divided by the total volume of the filter medium at issue, usually
expressed as a percentage. In a typical implementation, solidity of
the filter media associated with sequestering FDPs is less than 15
percent, more typically less than 12 percent, and more frequently
less than 10 percent. In certain embodiments the solidity is less
than 9 percent, less than 8 percent, or less than 7 percent.
[0075] An additional characteristic of the filter media made in
accordance with the present invention is that it is relatively
incompressible, especially relative to the solidity of the media.
Compressibility is the resistance (i.e.) to compression or
deformation in the direction of fluid flow through the media. A
suitable test for media compression is a compression force vs.
distance test, wherein a stack of media is compressed under a load
to determine compression percent. An example of such a test is as
follows: A 2.54 centimeter diameter probe and a 5 kg load cell are
used to compress a stack of media having a total thickness of 25
mm. The test is performed at a speed of 1 mm/sec, with a 30 mm
start distance from the bottom, and a data trigger of 0.5 g. The
end force target is 4,800 g. The media sample size can be 2.22
centimeter diameter circle, oriented with media samples to form a
stack directly underneath the test probe. The pressure on the media
in such implementations is approximately 1.24 kg/cm.sup.2. The
number of stacked samples used should be sufficient to have a total
thickness of 25 mm, thus the total number of samples will vary
depending upon individual thickness of the tested media material.
The data is analyzed in terms of the following equation:
compression percent=t.sub.2/t.sub.1
[0076] wherein t.sub.1=thickness from the bottom of stacked samples
when force=0.5 grams, and t.sub.2=thickness from bottom of stacked
samples when force=4,800 g, with x equal to the distance the probe
traveled during the test, which is the distance t.sub.1-t.sub.2.
Suitable instruments for performing this test include, for example,
a TA.XT2i Texture Analyzer from Stable Micro Systems utilizing
Texture Expert Exceed software version 2.64.
[0077] The compressive resistance must be sufficient to maintain a
material's thickness and thereby maintain its pore structure and
filtration flow and particulate removal performance.
Compressibility typical of the materials made by the invention are
as follows: In a first example embodiment, the filter media
containing the scaffold fiber and media fiber has a compressibility
of less than 40 percent at a pressure of 1.24 kg/cm.sup.2. In other
implementations the filter media has a compressibility of less than
30 percent at a pressure of 1.24 kg/cm.sup.2, less than 20 percent
at a pressure of 1.24 kg/cm.sup.2, and less than 10 percent at a
pressure of 1.24 kg/cm.sup.2. As noted above, in a typical
implementation, solidity of the filter media associated with
sequestering FDPs is less than 15 percent, more typically less than
12 percent, and more frequently less than 10 percent. In certain
embodiments the solidity is less than 9 percent, less than 8
percent, or less than 7 percent.
[0078] In an example embodiment of the invention, the filter media
comprises various sized melt blown fibers laminated on the upstream
side of cellulose media, with the cellulose also serving a dual
role as a hard particle filter and a support for the thermally
bonded glass. The melt blown media functions to remove the FDPs in
a fashion such that the FDPs are removed white premature plugging
of the cellulose layer is avoided. This improved performance is
achieved, in part, by selecting the fiber mixture so that the media
has a relatively low solidity, while retaining a relatively low
compressibility.
[0079] Typically some of the fibers are relatively thin and in high
concentrations while other fibers are relatively thick and in lower
concentrations, result in a media having small mean flow pore
sizes, but also typically relatively high maximum pore sizes. The
use of a media that has relatively low solidity and low
compressibility, while also having a small mean flow pore size but
a high maximum flow pore size, results in a media construction that
effectively removes FDP compounds without premature plugging.
Preferred materials for the media fiber are those that have
relatively high tensile strength and can be meltspun into small
diameter fibers. Preferred materials for scaffold fiber have
relatively higher values for modulus of elasticity than materials
used for media fibers. Identification of suitable materials based
on relative tensile strength and modulus of elasticity can be
enhanced by comparison of the materials disclosed in "The Science
And Engineering of Materials" by Donald R. Askeland, including in
"Table 15-6: The Mers and Properties of Selected Thermoplastics
Produced by Addition Polymerization".
[0080] The performance of the media can be measured by a
compressibility-solidity factor ("CS Factor") which is determined
as the multiple of the compression percent times the solidity
percent. In both cases, lower numbers are generally preferred. A
compression percent of 40 percent, multiplied by a solidity of 15
percent, gives a CS Factor of 600. A compression percent of 10
percent, along with a solidity of 10 percent, will provide a CS
Factor of 100. Generally, a CS Factor of below 600 is desired. CS
Factors of less than 500, less than 450, less than 400, and less
than 350 are all suitable for certain implementations of the
invention. CS Factors of less than 300 can be particularly
desirable, as are CS Factors of less than 250, less than 200, and
even less than 150. CS Factors of less than 150 are also desirable,
in particular less than 125, less than 100, and less than 75.
[0081] Further metrics by which the properties of the media
associated with sequestering FDPs (and optionally other similar
fuel contaminant products) are described relates to the pore
structures of the media. In general, it is possible to characterize
the properties of a porous media in terms of such parameters as
mean flow pore, mode flow pore, and max flow pore. The "mode pore
size" is the most frequently occurring pore size in a material.
FIG. 2 shows Flow Pore Size Density Distribution of an example
media material. The "mode pore size" is shown as the highest peak
of the curve at approximately 30 microns. "Mean pore size" is the
average size of the pores in the material, and "cumulative flow
pore size" is a measure of the total percentage of flow that passes
through the media as a function of pore diameter, determined using
a capillary flow porometer instrument. "Mean flow pore size" is
defined as the pore size where 50% of cumulative flow passes
through the media. "Porosity" is defined as the amount of void
space in a material. FIG. 3 shows Flow Pore Size Cumulative
Distribution. The "mean flow pore size" (indicated by the arrow) is
the point at which the curve intersects 50% on the y-axis.
[0082] With regard to pore size, the portion of the filter media
primarily responsible for removal of FDPs and related contaminants
will typically have a mean flow pore size of 5 to 20 microns, or 5
to 10 microns. Suitable mean flow pore sizes include less than 20
microns less than 15 microns, and less than 10 microns. The portion
of the filter media primarily responsible for removal of FDPs and
related contaminants will typically have a mode flow pore size of
from 10 to 50 microns, from 20 to 40 microns, or from 25 to 35
microns. Suitable mode flow pore sizes include, for example,
greater than 10, greater than 15, greater than 20 and greater than
25 microns. With regard to max flow pore size, the portion of the
filter media primarily responsible for removal of FDPs and related
contaminants will often have a max flow pore size greater than that
of cellulose or melt blown media. Suitable max flow pore sizes
include greater than 10 microns, preferably, greater than 20
microns, and in some implementations greater than 30 microns. In
example implementations the max flow pore size is from 20 to 50
microns, or from 2.5 to 45 microns.
[0083] Typically, the mode pore size is larger in the upstream
portion than in the downstream portion of the filter media, and the
mean (or average) pore size is smaller in the upstream portion than
in the downstream portion. In accordance with the teachings of the
present invention, it is desirable in general to have at least a
portion of the media with small mean flow pores, while also having
a large max flow pore. The ratio of max pore size to mean flow pore
is often at least 2.5, optionally at least 5.0, and in some
implementations greater than 7.5. In certain embodiments, where the
mean flow pore is very small and the max flow pore relatively high,
this ratio may be greater than 10, and optionally greater than 12.5
or 15. High numbers reflect a wider particle size distribution,
which can provide for improved removal of FDP (and related)
contaminants.
Additional Fibers
[0084] The media layer for removal of FDPs and similar fuel
contaminant products can contain secondary fibers made from a
number of both hydrophilic, hydrophobic, oleophilic, and oleophobic
fibers. These fibers cooperate with the glass fiber and the
bicomponent fiber to form a mechanically stable, but strong,
permeable filtration media that can withstand the mechanical stress
of the passage of fluid materials and can maintain the loading of
particulate during use. Secondary fibers are typically
monocomponent fibers with a diameter that can range from about 0.1
to about 50 micrometers and can be made from a variety of
materials. One type of secondary fiber is a scaffold fiber that
cooperates with other components to bind the materials into a
sheet. Another type of secondary fiber is a structural fiber that
cooperates with other components to increase the tensile and burst
strength of the materials in dry and wet conditions. Additionally,
the scaffold fiber can include fibers made from such polymers as
polyvinyl chloride and polyvinyl alcohol. Secondary fibers can also
include inorganic fibers such as carbon/graphite fiber, metal
fiber, ceramic fiber and combinations thereof.
[0085] Secondary thermoplastic fibers include, but are not limited
to, polyester fibers, polyamide fibers, copolyetherester fibers,
polyethylene terephthalate fibers, polybutylene terephthalate
fibers, polyetherketoneketone (PEKK) fibers, polyetheretherketone
(PEEK) fibers, liquid crystalline polymer (LCP) fibers, and
mixtures thereof. Polypropylene fibers are generally not desirable,
because they have lower resistance to fuels and because the have a
relatively low modulus. Polyamide fibers include, but are not
limited to, nylon 6, 66, 11, 12, 612, and high temperature "nylons"
(such as nylon 46) including cellulosic fibers, polyvinyl acetate,
polyvinyl alcohol fibers (including various hydrolysis of polyvinyl
alcohol such as 88% hydrolyzed, 95% hydrolyzed, 98% hydrolyzed and
99.5% hydrolyzed polymers), cotton, viscose rayon, thermoplastic
such as polyester, polyethylene, etc., polyvinyl acetate,
polylactic acid, and other common fiber types. The thermoplastic
fibers are generally fine (about 0.5-20 denier diameter), short
(about 0.1-5 cm long), staple fibers, possibly containing
precompounded conventional additives, such as antioxidant,
stabilizers, lubricants, tougheners, etc. The preferred
thermoplastic fibers are polyamide and polyethylene terephthalate
fibers, with the most preferred being polyethylene terephthalate
fibers.
[0086] Staple fibers are typically added to a nonwoven web in
solidified form (such as by the exemplary process described later)
as opposed to being meltblown into the web. Often, they are made by
processes such that the fiber diameter more closely resembles the
size of the orifice through which the fiber is extruded (compared
to e.g. meltblown fibers).
[0087] The staple fibers are typically synthetic polymeric
materials. Their composition may be chosen so that they can be
melt-bonded to each other and/or to the meltblown fibers during a
typical molding process (such as used to form a shaped respirator
body). Regardless of their process of manufacture or composition,
staple fibers are typically machine cut to a specific predetermined
or identifiable length. The staple fibers will typically have a
length of about 0.1 to 8 cm, more preferably about 0.1-2.0 cm. The
average geometric fiber diameter for the staple fibers is generally
greater than about 5 .mu.m on average, and in various embodiments
can be greater than 10, 20, 30, 40, 50, 100, 150, 250, 300, 350,
400 or 500 .mu.m depending upon whether its use, and whether it is
providing media fiber functionality or scaffold fiber
functionality, or both.
[0088] Suitable staple fibers may be prepared from polyethylene
terephthalate, polyester, polyethylene, polypropylene, copolyester,
polyamide, or combinations of one of the foregoing. If bondable,
the staple fibers typically retain much of their fiber structure
after bonding. The staple fibers may be crimped fibers like the
fibers described in U.S. Pat. No. 4,118,531 to Hauser. Crimped
fibers may have a continuous wavy, curly, or jagged profile along
their length. The staple fibers may comprise crimped fibers that
comprise about 10 to 30 crimps per cm. The staple fibers may be
single component fibers or multi-component fibers.
[0089] The different components may be different types of polymers
(e.g. polyester), or may be the same type of polymer but with
different melting points. The multi-component fibers may be
bicomponent fibers that have a coextensive side-by-side
configuration, a coextensive concentric sheath-core configuration,
or a coextensive elliptical sheath-core configuration.
Configurations Containing Multiple Layers or Multiple Functional
Areas
[0090] As noted above, the upstream filter material selected for
sequestering FDPs (containing media fiber and scaffold fiber, such
as glass fiber and bicomponent fiber) is often combined with a
downstream filter material. This downstream filter material is
generally selected for favorable removal of particulate
contaminants. The downstream portion may comprise, for example,
cellulose. The difference between the ability of the upstream
portion and downstream portion to attract various contaminants,
combined with the pore size distribution of the upstream and
downstream portions, allow the filter media of the present
invention to effectively remove a range of contaminants without
premature plugging the filter.
[0091] The upstream (for example, bicomponent fiber and polyester
meltblown fiber) portion of the media typically has a smaller mean
flow pore size than the downstream (for example, cellulose)
portion, but this smaller average pore size is often combined with
a larger mode pore size on the upstream portion, which can be
useful for improving filter loading with certain contaminants, in
particular fuel degradation products. Typically, the mode (or most
common) pore size is larger in the upstream portion than in the
downstream portion, and the mean (or average) pore size is smaller
in the upstream portion than in the downstream portion.
[0092] The upstream portion may also have its own pore size
variance, characterized at least by different pore sizes at
different depths of the upstream portion. On the "top" of the
upstream portion, the mode pore size is optionally increased. For
some media, the downstream mode pore size of the upstream portion
is significantly greater than the mode pore size of the downstream
portion, which is typically cellulose. In some embodiments, the
mode pore size of the upstream portion is greater than the mode
pore size of the downstream portion. For example, the mode pore
size of the upstream portion may be at least 20 percent greater
than the mode pore size of the downstream portion in some
implementations, and at last 40 percent greater than the mode pore
size of the downstream portion in other implementations.
[0093] In an example embodiment, the mode pore size of the upstream
portion is at least 20 percent greater than the mode pore size of
the downstream portion; and the mean flow pore size of the upstream
portion is less than 90 percent of the mean pore flow size of the
downstream portion. It will be appreciated that the downstream
portion may contain fiber having an average diameter or
cross-section greater than the average diameter of the media fiber
in the upstream portion. In some embodiments, the mode pore size of
the upstream portion is greater than the mode pore size of the
downstream portion. For example, the mode pore size of the upstream
portion may be at least 40 percent greater or at least 60 percent
greater than the mode pore size of the downstream portion. In some
embodiments, the mean flow pore size of the upstream portion is
less than the mean pore flow size of the downstream portion. For
example, the mean flow pore size of the upstream portion may be
less than 70 percent or less than 50 percent of the mean pore flow
size of the downstream portion.
[0094] Media fiber diameter may also be selected to improve
performance between the upstream and downstream portions. In one
embodiment, the upstream portion contains media fiber having an
average diameter of less than 10 microns based upon total fiber
count; and the downstream portion contains media fiber having an
average diameter different than the diameter of the media fiber in
the upstream portion. In one embodiment, the media fiber of the
upstream portion has an average diameter of less than 5 microns.
Generally, the downstream portion contains fiber having an average
diameter or cross-section greater than the average diameter of the
media fiber in the upstream portion. The upstream portion may
comprise, for example, glass fiber, scaffold fiber, or bicomponent
fiber. In some embodiments, the downstream portion comprises
cellulose, polymeric fibers such as polyester, or a combination
thereof.
[0095] In one embodiment, the upstream portion contains media fiber
having an average diameter of less than 10 microns based upon total
fiber count; and the downstream portion contains media fiber having
an average diameter different than the average diameter of the
media fiber in the upstream portion; wherein the mode pore size of
the upstream portion is at least 20 percent greater than the mode
pore size of the downstream portion; and wherein the mean flow pore
size of the media in the upstream portion is less than 90 percent
of the mean pore flow size of the media in the downstream
portion.
[0096] In some embodiments, the filter for filtering liquids
comprises an upstream portion comprising media having a porosity of
at least 50 percent, the media comprising a media fiber and a
scaffold fiber having an average diameter greater than the media
fiber; and a downstream portion comprising cellulose. The upstream
portion may comprise carbon or glass fiber. In one embodiment, the
media fiber of the upstream portion has an average diameter of less
than 5 microns. In another embodiment, the media fiber of the
upstream portion has an average diameter of less than 15 microns.
In some embodiments, the mode pore size of the upstream portion is
greater than the mode pore size of the downstream portion. For
example, the mode pore size of the upstream portion may be at least
20 percent or at least 40 percent greater than the mode pore size
of the downstream portion.
[0097] In another embodiment, the invention is directed to a filter
media comprising an upstream portion containing fibers selected
from carbon and meltblown fibers; and a downstream portion
comprising cellulose; wherein the mode pore size of the upstream
portion is at least 20 percent greater than the mode pore size of
the downstream portion; and wherein the mean flow pore size of the
upstream portion is less than 90 percent of the mean pore flow size
of the downstream portion. It will be appreciated that the
downstream portion may contain fiber having an average diameter
greater than the average diameter of the media fiber in the
upstream portion. In some embodiments, the mode pore size of the
upstream portion is greater than the mode pore size of the
downstream portion. For example, the mode pore size of the upstream
portion may be at least 40 percent greater or at least 60 percent
greater than the mode pore size of the downstream portion. In some
embodiments the mean flow pore size of the upstream portion is less
than the mean pore flow size of the downstream portion. For
example, the mean flow pore size of the upstream portion may be
less than 70 percent or 50 percent of the mean pore flow size of
the downstream portion.
[0098] In some embodiments, the upstream fitter portion loads fuel
degradation products at a level of capture of at 50 percent greater
than the downstream filter portion. In some embodiments, the first
filter portion loads fuel degradation products at a level of
capture of at least 100 percent greater than the second filter
portion. In some embodiments, the first filter portion loads fuel
degradation products at a level of capture of at least 200 percent
greater than the second filter portion. The percentage may be
normalized for media volume or for media surface area.
[0099] In some embodiments, low temperature crystalline polymer
powder is used to laminate the synthetic and cellulose media
together so as to make the composite media easily manufacturable
into a number of different fitter element configurations. Other
methods of laminating the media layers together such as adhesive
lamination or thermal bonding means are possible as well.
[0100] In reference now to FIG. 4A to 4D, example configurations
for filter media constructions are shown, in these cross sectional
schematic diagrams, only the basic positioning of the media
components are described, and it will be understood that these
figures are not drawn to scale. It will also be understood that the
figures are simplifications of the media constructions, and that
they are alternative embodiments, but non-limiting as to the types
of constructions possible under the present invention. FIG. 4A is a
cross sectional schematic view of a media construction made in
accordance with an implementation of the invention, showing a two
layer construction. In this example embodiment, the media
construction 120 includes a first portion containing upstream media
122 and a second portion containing downstream media 124. The
upstream media can be, for example a combination of glass media
fiber and bicomponent scaffold fiber. The downstream portion can
be, for example, cellulose media.
[0101] FIG. 4B is a cross sectional schematic view of another media
construction made in accordance with an implementation of the
invention, showing a three layer construction. In this example
embodiment, the media construction 130 includes first and second
portions containing upstream media 132 and 133, plus a third
portion containing downstream media 134. The upstream media
portions can be, for example a combination of glass media fiber and
bicomponent scaffold fiber. In some embodiments these upstream
media portions 132, 133 can have different properties from one
another, such as different pore sizes and distributions. It is not
necessary that both layers (Or portions if not in discrete layers)
remove FDPs or similar contaminants, as long as at least one layer
or portion do so. The downstream portion can be, for example,
cellulose media. Further embodiments can have, for example,
additional upstream and downstream layers.
[0102] FIG. 4C is a cross sectional schematic view of a media
construction made in accordance with an implementation of the
invention showing a two layer construction with a spacer between
media layers. In this example embodiment, the media construction
140 includes a first portion containing upstream media 142, a
second portion containing downstream media 144, and a spacer 146
between the upstream and downstream portions 142, 144. The upstream
media can be, for example, a combination of glass media fiber and
bicomponent scaffold fiber. The downstream portion can be, for
example, cellulose media. The spacer 146 can be, for example, a
non-filtering scrim material.
[0103] FIG. 4D is across sectional schematic view of a media
construction made in accordance with an implementation of the
invention wherein the upstream portion 152 and downstream portion
154 are further separated from one another by a gap. The upstream
media can be, for example a combination of meltblown media fiber
and bicomponent scaffold fiber. The downstream portion can be, for
example, cellulose media. The gap can be relatively small, or
relatively large. In this embodiment, the functional orientation of
the two media is important: that one portion media be positioned
upstream of the other portion. It will be understood support
materials can be placed intermediate these two portions 152,
154.
[0104] FIG. 5 illustrates the pore relationship of the media in an
example embodiment of the invention, wherein the upstream portion
comprises synthetic bicomponent-glass media and the downstream
portion comprises cellulose. In particular, a layered structure of
the present invention is shown in this example implementation,
wherein the pore size can vary from wide open in the upstream
portion to much smaller in the downstream portion where fine
particulate filtration occurs. The upstream portion may comprise
two or more layers with different pore sizes as is shown here.
However, the mode pore size of the cellulose is smaller than the
mode pore sizes of both portions of the depicted upstream
portion.
[0105] A filter with a structure where the media pores are smaller
on the downstream side than on the upstream side is often helpful.
In other words, the porous structure is denser going from upstream
to downstream side. As a result, the particles or contaminants to
be filtered are able to penetrate to varying depths dependent on
particle size. This causes the particles or contaminants to be
distributed throughout the depth of the fitter material, reducing
the increase in pressure drop, and extending the life of the
filter. In one embodiment, the pore sizes change by steps, as in
FIG. 7. In another embodiment, the size of the pores gradually
increases from smaller on the downstream side to larger on the
upstream side.
[0106] FIG. 6 shows an example of one embodiment of a multi-stage
fuel filter 180, having concentric layers of media 182, 184, 186.
The concentric layers can comprise layers of media and scaffold
fibers with varying pore dimensions from the exterior to the
interior. Generally the mean flow pore size will get smaller from
the outer layers 182 to the inner layers 186. FDPs and other
similar products have the tendency to adsorb to the outer media
surface and create a layer or film across the media. The
agglomeration of the degradation products starts to fill the pores.
The higher number of large pores in the upstream media allows the
outer media to capture and store the degradation products without
plugging as quickly. The tighter downstream layer is designed to
have high efficiency for particles.
[0107] This application incorporates by reference in its entirety
U.S. patent application Ser. No. 13/027,119, filed Feb. 14, 2011,
and entitled "Liquid Filtration Media, Filter Elements, and
Methods".
[0108] It will be appreciated that, although the implementation of
the invention described above is directed to the removal of FDPs
from fuel streams, such as the fuel tanks of diesel engines or bulk
storage tanks, the present device may be used in other filter
applications and is not limited to the removal of FDPs. Embodiments
of this invention would also be suitable for removing numerous
contaminants of a hydrocarbon fluid chemistry that include such
contaminants as waxes, asphaltenes, sterol glucosides, steryl
glucosides, sterol glycosides and fuel degradation products. The
contaminants can comprise, for example, deformable particles,
non-deformable particles, and mixtures of deformable and
non-deformable particles. Hydrocarbons such as tube and hydraulic
oil may also be filtered using the present invention.
[0109] While the present invention has been described with
reference to several particular implementations, those skilled in
the art will recognize that many changes may be made hereto without
departing from the spirit and scope of the present invention.
* * * * *