U.S. patent application number 10/923103 was filed with the patent office on 2005-09-29 for complex shaped fiber for particle and molecular filtration.
Invention is credited to Bause, Dan E., Hendricks, Neil H., Le Claire, Randy, McGeever, William, Miller, Jeff, Rohrbach, Ron, Tannous, Adel, Unger, Peter.
Application Number | 20050214188 10/923103 |
Document ID | / |
Family ID | 37589767 |
Filed Date | 2005-09-29 |
United States Patent
Application |
20050214188 |
Kind Code |
A1 |
Rohrbach, Ron ; et
al. |
September 29, 2005 |
Complex shaped fiber for particle and molecular filtration
Abstract
An ultra-efficient multilobal cross-sectioned fiber filter for
chemical contaminant filtering applications is described. An
absorptive chemically reactive reagent, preferably an acid or base
and in liquid or an adsorptive chemically reactive reagent (an acid
or base) in solid form, is disposed within longitudinal slots in
each length of fiber. The reagent may be used alone or in
conjunction with solid adsorptive particles which may also be
utilized with the reagents in the longitudinal slots within the
fibers. Reagents within the fibers remain exposed to a
base-contaminated airstream passing through the filter. Base
contaminants in the airstream, chemicals such as ammonium and
amines (as well as particles), react with the acid reagent within
the longitudinal slots of the fibers. As the contaminant and
reagent react, the ammonium or amine becomes irreversibly absorbed
(or adsorbed if reagent is a solid acid) to the liquid acid reagent
and multilobal fiber.
Inventors: |
Rohrbach, Ron; (Flemington,
NJ) ; Bause, Dan E.; (Flanders, NJ) ; Unger,
Peter; (Morristown, NJ) ; Miller, Jeff; (Los
Gatos, CA) ; Hendricks, Neil H.; (Sonora, CA)
; Tannous, Adel; (Santa Clara, CA) ; Le Claire,
Randy; (Santa Clara, CA) ; McGeever, William;
(Morgan Hill, CA) |
Correspondence
Address: |
BINGHAM McCUTCHEN LLP
Three Embarcadero Center
San Francisco
CA
94111-4067
US
|
Family ID: |
37589767 |
Appl. No.: |
10/923103 |
Filed: |
August 19, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10923103 |
Aug 19, 2004 |
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10652230 |
Aug 28, 2003 |
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10652230 |
Aug 28, 2003 |
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09834581 |
Apr 12, 2001 |
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6623715 |
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Current U.S.
Class: |
423/237 ;
210/506; 55/524 |
Current CPC
Class: |
B01D 2251/50 20130101;
B01D 39/2058 20130101; B01D 39/1623 20130101; B01J 20/28038
20130101; B01D 2239/065 20130101; B01J 20/28014 20130101; B01D
2239/0407 20130101; B01J 20/28033 20130101; B01D 53/58 20130101;
D01D 5/253 20130101; B01D 39/1607 20130101; B01D 2239/0464
20130101; B01D 2239/0492 20130101; B01D 2251/70 20130101; B01D
53/54 20130101; B01D 53/34 20130101; B01J 20/28028 20130101 |
Class at
Publication: |
423/237 ;
055/524; 210/506 |
International
Class: |
C01C 003/00 |
Claims
We claim:
1-85. (canceled)
86. A fiber mat comprising: a plurality of elongated fibers, each
fiber comprising an internal cavity; a plurality of powdered
particulate matter; and a chemically-reactive reagent disposed
within the internal cavities of the fibers, wherein the reagent
comprises at least one acid, at least one base, at least one
coordinating agent, at least one complexing agent, at least one
deliquescent agent or a combination thereof.
87. The mat of claim 86, wherein the at least one complexing agent
comprises urea, a cyclodextrin or a crown ether.
88. The mat of claim 86, wherein the at least one deliquescing
agent comprises lithium, a potassium halide, fructose, propylene or
ethylene glycol.
89. The mat of claim 86, wherein the at least one acid comprises a
liquid acid.
90. The mat of claim 86, wherein the at least one acid comprises a
powdered acid.
91. The mat of claim 86, wherein the at least one base comprises a
liquid base.
92. The mat of claim 86, wherein the at least one base comprises a
powdered base.
93. The mat of claim 92, wherein the powdered base comprises sodium
bicarbonate, sodium carbonate, sodium hydroxide, trisodium
phosphate, potassium carbonate, potassium hydroxide or sodium
tetraborate.
94. The mat of claim 86, wherein the coordinating agent comprises
at least one transition metal.
95. The mat of claim 94, wherein the at least one transition metal
comprises copper.
96. The mat of claim 95, wherein the plurality of fibers comprise
at least one thermoplastic polymer.
97. The mat of claim 86, wherein the powdered particulate matter
comprises carbon powder.
98. The mat of claim 86, wherein the powdered particulate matter
comprises zeolite, aluminum oxide or silica.
99. The mat of claim 86, wherein at least some of the plurality of
fibers are trilobal.
100. The mat of claim 86, wherein at least some of the plurality of
fibers are quadrilobal.
101. The mat of claim 86, wherein at least some of the plurality of
fibers contains a plurality of T shaped lobes.
102. The mat of claim 86, wherein the mat is pleated.
103. The mat of claim 86, further comprising a frame coupled to the
mat.
104. A gas filter comprising the mat of claim 86.
105. A filtering chamber comprising the mat of claim 86.
106. A housing comprising the mat of claim 103.
Description
[0001] This application is a divisional of application Ser. No.
10/652,230, filed Aug. 28, 2003, which claims priority to
application Ser. No. 09/834,581, filed Apr. 12, 2001 (U.S. Pat. No.
6,623,715), both of which are incorporated herein by reference in
their entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] This invention relates to a filter system and specifically
to a system utilizing solid and liquid reagents.
[0004] 2. Description of Related Art
[0005] It is conventionally known to use activated charcoal and
other materials as adsorptive elements to remove impurities from an
airstream. With the advent of effective fiber cross sections, it is
possible to produce fibers which are partially hollow. A
particularly effective cross section is one having three T-shaped
lobes extending from a central core, as described in U.S. Pat. No.
5,057,368, which is incorporated herein by reference. Conventional
filters have used filtering media coated with solid or liquid
materials in a variety of applications; however, many of these
applications have relied on absorption, rather than adsorption.
Adsorption occurs where particles to be removed attach to the
surface of the filter material elements; whereas, absorption occurs
where molecular motion mobility is harnessed to move unwanted
particles from one zone to another in a non-mechanical manner. The
multilobal fiber has been particularly effective as a wicking fiber
where certain contaminant-removing liquids or solids are filled in
cavities formed within the fiber.
[0006] The multilobal fiber filled with solid filtering particles
have been used in adsorptive air filtration and odor-removing
applications. Such filtering particles have included the use of
carbon particles, zeolites, baking soda, cyclodextrins, and solids
which could adsorb certain contaminants (see U.S. Pat. No.
5,759,394, which is incorporated herein by reference). Other
applications utilizing multilobal-type fibers as wicking fibers
also have involved absorptive properties of certain liquids which
are filled within the cavities of the fibers. These liquids were
typically chosen to lightly absorb odor and gas molecules in a
reversible manner from a contaminated airstream to aid in the
eventual dispersion of these molecules into a second airstream (see
U.S. Pat. Nos. 5,891,221 and 5,704,966, which are incorporated
herein by reference).
[0007] Maintaining environments free of contaminants is
particularly critical in the manufacturing of integrated circuits
because wafers are very susceptible to small particles and low
levels of certain chemicals. This can be done by manufacturing
wafers inside cleanroom's with filtered air. The filters are used
to reduce particle and chemical levels to extremely low levels
(less than 1 part-per-billion). Semiconductor tools are also
sometimes equipped with environmental controls that provide local
ultra clean airflow during processing. However, conventional
chemical filters have a very short life span, require frequent
replacement, and are ineffective at efficiently filtering out
certain chemicals.
SUMMARY
[0008] In accordance with the invention, an ultra-high efficient
multilobal fiber filter is described with long life use for
chemical contaminant filtering applications. The unexpected ultra
efficiency of the fiber filter reduces contaminants to low levels
in the parts-per-billion. A reactive reagent, preferably an acid or
base and in either liquid or solid form, is disposed within
longitudinal slots in each length of fiber. The reagent may be
reactive with base contaminants by any known mechanism, such as an
acid-base reaction to form ionic bonds, an oxidation-reduction
reaction, and various other organic and inorganic reaction
mechanisms as known in the art to form covalent bonds, hydrogen
bonds, coordination compounds, or complex compounds. The reagent
may be used alone or in conjunction with solid adsorptive particles
which may also be utilized with the reagents in the longitudinal
slots within the fibers. The fibers are formed into a single
layered, in one embodiment, or a multi-layered fiber mat, in
another embodiment, but the reagents remain exposed to the flow of
a contaminated airstream passing through the filter. The
contaminants in a fluid stream react within the longitudinal slots
of the fibers. As the base contaminant and reagent react, the
contaminant is retained within the longitudinal slots of the
fiber.
[0009] In a preferred embodiment, the contaminants are ammonium
and/or amines and the reagent is an acid. The acid-impregnated
multilobal fiber is significantly more efficient than several
commercially available filters. The filter can be used in a variety
of applications including clean rooms and in filtering chambers for
installation in the field.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows a detailed cross-sectional view of an
individual multilobal fiber.
[0011] FIG. 2 shows a close-up view of a fiber mat made of
multilobal fibers with a reagent disposed within each multilobal
fiber.
[0012] FIG. 3 shows a wider view of the fiber mat of FIG. 2.
[0013] FIG. 4 shows a plot comparing the percentage of contaminant
breakthrough over time for the acid-impregnated multilobal fiber
versus two other commercially available filters.
[0014] FIG. 5 shows a chamber in one embodiment for use in
filtering an airstream with the acid-impregnated multilobal fiber
filter.
[0015] FIG. 6 shows the chamber of FIG. 5 with a multi-layered
multilobal fiber filter.
[0016] Use of the same reference symbols in different figures
indicates similar or identical items.
DETAILED DESCRIPTION
[0017] FIG. 1 shows a detailed view of a cross section of an
individual multilobal fiber 2. Fiber 2 is a type of fiber made of
thermoplastic polymers and formed by conventional fiber forming
techniques, such as spinning a fiber composition through a
conventional spinnerate, as described in the above-referenced U.S.
Pat. No. 5,057,368. Fiber 2 includes a core 4, from which three
lobes 6 extend outwardly. Each of lobes 6 terminates with a cap 8
which is perpendicularly attached to the end of lobe 6. The cavity
formed between lobe 6 and adjacent caps 8 runs along the entire
length of multilobal fiber 2 forming longitudinal slot 10.
Multilobal fiber 2 has the ability to retain powdered particulate
matter, such as powdered carbon. The carbon powder can be
mechanically held within slot 10 entrapped by caps 8 without the
use of any liquids. Entrapping the powder within slot 10 can be
accomplished by dusting the powder into the fibers and then shaking
off the excess powder or blowing the excess powder off with a
fan.
[0018] Preferably, fiber 2 can hold, through capillary forces,
liquids within slot 10. FIG. 2 shows a close-up view of fiber mat
100 where liquid reagent 12 is filled within slots 10 of meshed
fibers 2. Liquid reagent 12 can be utilized to fill slots 10 by
having liquid droplets penetrate fiber mat 100 and wicking into
slots 10 after impacting with the surfaces of fibers 2. After the
liquid droplets impact with fibers 2, they quickly coalesce into
slots 10 while leaving open voids between fibers 2 and allowing for
unencumbered airflow through fiber mat 100. Fibers 2 can
alternatively wick reagent 12 up within slots 10 by capillary force
by dipping fibers 2 into reagent 12 and removing excess reagent
12.
[0019] Reagent 12 can be formed into liquid droplets by different
methods such as forcing reagent 12 through a mechanical atomizer or
preferably by using a conventional liquid dropper. Reagent 12 can
range from a variety of liquids such as acids, oxidants,
reductants, complexing agents, coordinating agents, and
deliquescent agents; however, it is preferable to use acids. Acids
for use as reagent 12 include, but are not limited to, inorganic
acids such as boric acid and preferably phosphoric or sulfuric
acid. Organic acids may also be used rather than inorganic acids.
Organic acids include, but are not limited to, moncarboxylic,
dicarboxylic, and tricarboxylic acids; these types of organic acids
include citric, lactic, maleic, fumaric, caproic, lauric, oxalic,
malonic, tartaric, succinic, salicyclic, and malic acids. In
another embodiment, powdered acids may also be used in place of the
liquid acid and impregnated within slots 11 in a method similar to
that described above for carbon powder. In an alternative
embodiment, powdered bases may also be used to filter non-basic
contaminants. Such powdered bases may include, e.g., sodium
bicarbonate (baking soda), sodium carbonate, sodium hydroxide,
trisodium phosphate, potassium carbonate, potassium hydroxide, and
sodium tetraborate. Also, reagent 12 may include coordinating
agents which comprise transition metals, e.g., copper, and
complexing agents which comprise entrapping agents, e.g.,
cyclodextrines.
[0020] FIG. 3 shows a wider view of fiber mat 100. Fibers 2 can be
pleated or formed in layers to form fiber mat 100 in a variety of
configurations. Generally, the volume within slot 10 makes up about
half the volume of multilobal fiber 2 and depending upon the
density of the contaminant, fibers 2 can gain around 100% in weight
of liquid contaminants and anywhere from 25% to 125% in weight for
solid powders within slots 10. Utilizing the multilobal fiber 2
property to capture both liquid or solid contaminants, reagent 12
is used for adsorptive and absorptive filtration applications.
Reagents 12 are intentionally impregnated within slots 10 and can
be a reactive liquid or a solid reagent, preferably both acid, and
fiber mat 100 is used as a supportive network to hold reagents 12
in a highly dispersed configuration for adsorptive and absorptive
molecular contaminant removal. Multilobal fiber 2 can retain not
only a liquid or solid (acid) reagent 12, but is effective in also
retaining a combination of a liquid reagent and solid particulates.
Solid adsorbants such as zeolites, aluminum oxides, activated
carbons (both impregnated and virgin), and chemically modified
silicas can be combined with acid reagent 12, in either liquid or
solid form, and impregnated within slots 10 of multilobal fibers 2.
Solid adsorbants may also be used in combination with base reagent
12 and impregnated within slots 10.
[0021] Fiber mat 100 is particularly effective in filtering base
contaminants from a passing fluid stream. Bases are considered any
chemicals or compounds conventionally regarded as a base in the
chemical arts. These chemicals and compounds include Lewis bases,
shift bases, aqueous bases, and preferably any compounds that are
alkaline in an aqueous environment. Ammonium and amines are
preferable bases.
[0022] A fiber mat 100 impregnated with liquid acid reagents 12 is
particularly effective in specifically absorbing base contaminants,
such as ammonium, NH.sub.3, and amines (for example,
n-methyl-2-pyrrolidone (NMP)) from a passing fluid stream. An
airstream with contaminants, for example, ammonium ions, passes
through fiber mat 100. As it passes over multilobal fibers 2
impregnated with acid reagent 12, the ammonium ion chemically
reacts (in a reaction well known in the art) with and is adsorbed
by acid reagent 12 to form a salt. Acid reagent 12 exchanges
hydrogen atoms with the ammonium ions, forming water as a byproduct
and leaving the ammonium ion to react with and attach to acid
reagent 12. Reagent 12 irreversibly retains the ammonium ions
within the slots 10 of multilobal fiber 2.
[0023] The combination of multilobal fibers 2 impregnated with a
liquid acid reagent 12 gives unexpected, ultra-high efficient
results in filtering out base contaminants. The effectiveness of
fiber mat 100 utilizing multilobal fibers 2 impregnated with acid
reagent 12 can be seen in FIG. 4 when compared to two
conventionally available acid-impregnated commercial filters. All
three filters were subjected to a continuous 90 parts-per-million
(ppm) exposure of a gas contaminated with ammonium diluted in air.
The air was conditioned to 50% relative humidity and 23.degree. C.;
the air was blown through the filters at a velocity of 150 ft/min
giving an equivalent pressure drop for all three filters. The basic
gas concentration was measured continuously downstream of each
filter and the breakthrough percentage of the contaminants were
plotted over time. The breakthrough percentage is the amount of
contaminants remaining in the air downstream of the filter relative
to the amount of contaminants initially in the air upstream of the
filter.
[0024] As seen in FIG. 4, curve A represents multilobal fiber 2
impregnated with acid reagent 12. Curves B and C represent the
results of other commercially available filters. The results of
curve A show significant retention of contaminants from the
acid-impregnated multilobal filter 2 over either curve B or C
showing the effectiveness and longer life of the acid-reagent 12
used in conjunction with multilobal fiber 2: The retention time of
fiber mat 100 is nearly three times as long as the retention time
shown in curve B (120 minutes at about 0% breakthrough versus 40
minutes at about 4% breakthrough for curve B).
[0025] Fiber mat 100 utilizing acid reagent 12 in multilobal fiber
2 can be used in a variety of applications, e.g., pleating or
layering multilobal fiber 2 to form fiber mat 100. Fiber mat 100
can be used, in one embodiment, as a filtering element in a
filtering chamber 102 as shown in FIG. 5. Chamber 102 consists of a
housing 18, which can be designed from a conventional metal, e.g.,
aluminum, to accommodate handling and field installation. The
pleated or layered fiber mat 100 is attached to housing 18,
preferably by an adhesive or a low outgassing glue. It is also
possible, in an alternative embodiment, to have fiber mat 100
attached to a frame (frame is not shown); this frame with fiber mat
100 can then be installed or removed interchangeably within housing
18. Housing 18 also has an inlet 14 and an outlet 16 to allow an
airstream 20 to pass through filtering chamber 102 while being
filtered through fiber mat 100. Chamber 102 can be used to provide
particle and chemical filtration for ammoniums, amines, and
particles for chemical clean room environments.
[0026] FIG. 6 shows an alternative embodiment of fiber mat 100.
FIG. 6 is similar to chamber 102 in FIG. 5 in most respects except
for the substitution of multi-layered fiber mat 100' for fiber mat
100. Multi-layered fiber mat 100' is a filter composed of a number
of individual adjacent layers. Each individual layer is impregnated
with any of the reagents discussed above; and several individual
layers, each layer with a different reagent, are combined into a
single multi-layered fiber mat. The number of layers can range from
one to N and fiber mat 100' can contain any combination of layers
and reagents depending upon the desired functionality.
[0027] Although the invention has been described with reference to
particular embodiments, the description is only an example of the
invention's application and should not be taken as a limitation. In
particular, even though much of preceding discussion was aimed at
liquid acid-impregnated multilobal fibers 2, alternative
embodiments of this invention include multilobal fibers 2
impregnated with solid acid reagents 12 and multilobal fibers 2
impregnated with a base, both in liquid and solid form to filter
non-basic contaminants. Various other adaptations and combinations
of features of the embodiments disclosed are within the scope of
the invention as defined by the following claims.
* * * * *