U.S. patent application number 17/382660 was filed with the patent office on 2021-11-11 for air filters comprising metal-containing polymeric sorbents.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Austin D. Groth, Michael W. Kobe, Derek M. Maanum, Michael S. Wendland.
Application Number | 20210346832 17/382660 |
Document ID | / |
Family ID | 1000005728231 |
Filed Date | 2021-11-11 |
United States Patent
Application |
20210346832 |
Kind Code |
A1 |
Wendland; Michael S. ; et
al. |
November 11, 2021 |
AIR FILTERS COMPRISING METAL-CONTAINING POLYMERIC SORBENTS
Abstract
An air filter including a filter support that supports porous,
polymeric sorbent particles that comprise a divalent metal
impregnated therein.
Inventors: |
Wendland; Michael S.; (North
St. Paul, MN) ; Maanum; Derek M.; (St. Paul, MN)
; Kobe; Michael W.; (Lake Elmo, MN) ; Groth;
Austin D.; (Minneapolis, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
1000005728231 |
Appl. No.: |
17/382660 |
Filed: |
July 22, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16349673 |
May 14, 2019 |
11103822 |
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PCT/US2017/061258 |
Nov 13, 2017 |
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17382660 |
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62421438 |
Nov 14, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01D 2257/406 20130101;
B01J 20/3236 20130101; B01D 2239/0618 20130101; B01D 46/2418
20130101; B01D 39/083 20130101; B01D 2253/202 20130101; B01D
2239/0622 20130101; B01D 2239/0654 20130101; B01D 2257/40 20130101;
A41D 13/1146 20130101; A62B 19/00 20130101; B01D 46/0036 20130101;
B01J 20/3208 20130101; B01D 2259/4541 20130101; B01D 46/0032
20130101; B01D 2239/0407 20130101; B01D 2258/06 20130101; B01D
53/04 20130101; A62B 18/025 20130101; A62B 23/02 20130101; B01J
20/264 20130101; B01D 2259/4508 20130101; A62B 23/025 20130101;
B01D 46/2411 20130101; B01D 39/1607 20130101; B01D 2239/0435
20130101; B01D 46/521 20130101; A41D 13/1115 20130101; B01D
2259/4566 20130101 |
International
Class: |
B01D 46/00 20060101
B01D046/00; A41D 13/11 20060101 A41D013/11; A62B 18/02 20060101
A62B018/02; A62B 19/00 20060101 A62B019/00; A62B 23/02 20060101
A62B023/02; B01D 39/16 20060101 B01D039/16; B01D 46/24 20060101
B01D046/24; B01D 46/52 20060101 B01D046/52; B01D 53/04 20060101
B01D053/04; B01J 20/26 20060101 B01J020/26; B01J 20/32 20060101
B01J020/32; B01D 39/08 20060101 B01D039/08 |
Claims
1. An air filter comprising a filter support that supports sorbent
particles, wherein at least some of the sorbent particles are
porous and comprise a polymeric material comprising: a) a polymer
comprising i) 15 to 65 weight percent of a first monomeric unit
that is of Formula (I), Formula (II), or a mixture thereof;
##STR00015## ii) 30 to 85 weight percent of a second monomeric unit
that is of Formula (III); and ##STR00016## iii) 0 to 40 weight
percent (or 5 to 40 weight percent) of a third monomeric unit that
is of Formula (IV) ##STR00017## wherein R.sup.1 is hydrogen or
alkyl; and b) a divalent metal incorporated into the polymeric
material in an amount equal to at least 1.5 mmoles per gram of the
polymeric material.
2. The air filter of claim 1 wherein the filter support comprises a
substrate with at least one major surface with at least some of the
porous polymeric sorbent particles disposed thereon.
3. The air filter of claim 2 wherein the porous polymeric sorbent
particles are present substantially as a monolayer on the major
surface of the substrate.
4. The air filter of claim 1 wherein the filter support comprises a
porous, air-permeable material with porous polymeric sorbent
particles disposed on a major surface thereof and/or with porous
polymeric sorbent particles disposed within the interior of the
material at least in a location proximate the major surface of the
material.
5. The air filter of claim 4 wherein porous polymeric sorbent
particles are disposed throughout the interior of the porous,
air-permeable material.
6. The air filter of claim 1 wherein the air filter consists
essentially of the filter support with the porous polymeric sorbent
particles supported thereon.
7. The air filter of claim 1 wherein the filter support exhibits a
major plane and exhibits a thickness of less than about 3 mm and is
configured to allow airflow through the filter support at least in
a direction at least generally perpendicular to the major plane of
the filter support.
8. The air filter of claim 1 wherein the filter support comprises a
netting with a major surface with at least some porous polymeric
sorbent particles adhesively attached thereto.
9. The air filter of claim 1 wherein the filter support comprises a
fibrous web that exhibits an interior and wherein the porous
polymeric sorbent particles are disposed within at least portions
of the interior of the web.
10. The air filter of claim 9 wherein the porous polymeric sorbent
particles are disposed throughout an interior of the fibrous
web.
11. The air filter of claim 9 wherein the web is a nonwoven fibrous
web.
12. The air filter of claim 11 wherein the nonwoven fibrous web is
a meltblown web.
13. The air filter of claim 9 wherein at least some fibers of the
fibrous web are each bonded to at least one porous polymeric
sorbent particle.
14. The air filter of claim 1 wherein the filter support is one
layer of a multilayer, air-permeable assembly.
15. The air filter of claim 14 wherein the multilayer air-permeable
assembly includes at least one layer that is not the same layer as
the filter support and that comprises electret moities.
16. The air filter of claim 1 wherein the filter support is
pleated.
17. An assembly comprising an air-handling apparatus with the air
filter of claim 1 installed in an air filter receptacle thereof,
wherein the air-handling apparatus is chosen from the group
consisting of a forced air heating unit, a forced air cooling unit,
a forced-air heating/cooling unit, a room air purifier, and a cabin
air filtration unit for a motor vehicle.
18. The air filter of claim 1 wherein the filter support comprises
a honeycomb with through-apertures within which sorbent particles
are disposed.
19. The air filter of claim 1 wherein the filter support provides a
layer of a filtering face-piece respirator.
20. The air filter of claim 19 wherein the filtering face-piece
respirator is chosen from the group consisting of flat-fold
respirators and molded respirators.
21. The air filter of claim 1 wherein the filter support comprises
a container with an interior within which porous polymeric sorbent
particles are disposed, and with at least one air inlet and at
least one air outlet.
22. The air filter of claim 21 wherein the filter support comprises
a filter cartridge.
23. An assembly comprising a personal protection device with the
filter cartridge of claim 22 installed therein, wherein the
personal protection device is chosen from the group consisting of
half-face negative-pressure respirators, full-face
negative-pressure respirators, escape hoods, and powered
air-purifying respirators.
Description
BACKGROUND
[0001] It is often desired to remove substances such as, e.g.,
ammonia, from air.
SUMMARY
[0002] In broad summary, herein are disclosed air filters
comprising filter supports that comprise porous, polymeric sorbent
particles that comprise a divalent metal. These and other aspects
will be apparent from the detailed description below. In no event,
however, should this broad summary be construed to limit the
claimable subject matter, whether such subject matter is presented
in claims in the application as initially filed or in claims that
are amended or otherwise presented in prosecution.
BRIEF DESCRIPTION OF DRAWINGS
[0003] FIG. 1 depicts a portion of an exemplary air filter
comprising a filter support comprising sorbent particles as
disclosed herein.
[0004] FIG. 2 depicts a portion of another exemplary air
filter.
[0005] FIG. 3 depicts a portion of another exemplary air
filter.
[0006] FIG. 4 depicts a portion of another exemplary air
filter.
[0007] FIG. 5 depicts a portion of another exemplary air
filter.
[0008] FIG. 6 depicts an exemplary respirator comprising a filter
support comprising sorbent particles as disclosed herein.
[0009] FIG. 7 discloses another exemplary respirator.
[0010] FIG. 8 discloses a framed, pleated air filter comprising a
filter support comprising sorbent particles as disclosed
herein.
DETAILED DESCRIPTION
Glossary
[0011] The term "air filter" denotes any apparatus or device in
which herein-described polymeric sorbent particles, supported by a
filter support, are presented to air, e.g. a stream of moving air,
so that an airborne substance can be removed from the air. The term
"filter support" denotes any structure that can retain sorbent
particles and present them to, e.g., a stream of moving air, but
that does not necessarily perform any filtration of microscopic
particles from moving air. The term "filter media" denotes a filter
support that is itself capable of filtering microscopic particles.
A "microscopic" particle is a particle with an average diameter (or
equivalent diameter, in the case of non-spherical particles) of
less than 100 microns. A "fine" particle is a particle with an
average diameter or equivalent diameter of less than 10
microns.
[0012] The terms "polymeric sorbent" and "porous polymeric sorbent"
are used interchangeably to refer to a polymeric material that is
porous and that can sorb airborne materials (e.g., gaseous or
vaporous substances; in particular, basic, nitrogen-containing
compounds as exemplified by ammonia). By a porous material is meant
a material that, whether hydrolyzed or not, exhibits a BET specific
surface area (measured in the absence of a divalent metal, e.g.
before impregnation of a divalent metal as disclosed herein) of at
least about 50 m.sup.2/g. Such materials are often characterized
based on e.g. the size of their pores. The term "micropores" refers
to pores having a diameter less than 2 nanometers. The term
"mesopores" refers to pores having a diameter in a range of 2 to 50
nanometers. The term "macropores" refers to pores having a diameter
greater than 50 nanometers.
[0013] The term "upstream" is applicable to a circumstance in which
a filter is exposed to moving air, and refers to the direction from
which moving air encounters a filter; "downstream" refers to the
direction in which filtered air exits a filter.
[0014] The term "netting" refers to a filter support that is
comprised of relatively few layers (five or less, often one) of
solid material, e.g. filaments.
[0015] The term "fibrous web" refers to a filter support that is
comprised of numerous layers (e.g., more than five) of fibers.
[0016] The term "meltblown" refers to fibers (and the resulting
fibrous webs) that are formed by extruding molten polymer streams
into converging high velocity air streams introduced by way of
air-blowing orifices located in close proximity to the extrusion
orifices. The skilled person will appreciate that meltblown fibers
and webs will characteristically exhibit features and signatures
(e.g., differences in the orientation of the molecules of the
material making up the fibers, as revealed e.g. by optical
properties such as birefringence, melting behavior, and so on) by
which such fibers and webs can be identified and distinguished from
other types of web.
[0017] Disclosed herein is an air filter 1 as shown in generic
representation in FIG. 1. Air filter 1 can be any apparatus or
device that exposes herein-disclosed porous polymeric sorbent
particles 100 to air, e.g. to a stream of moving air (with the
general direction of airflow indicated in exemplary embodiment by
the block arrow in FIG. 1 and in other Figures) so that airborne
(e.g. gaseous or vaporous) basic, nitrogen-containing materials can
be at least partially removed from the air. Air filter 1 is thus
distinguished from devices that process liquids, for example
ion-exchange membranes and devices.
[0018] Air filter 1 comprises at least one filter support 10. A
filter support 10 can be any structure that supports sorbent
particles 100 in such manner that exposes them to air, while
retaining the sorbent particles so that, if the air is moving, the
sorbent particles are not dislodged by the moving air. If the air
is moving, it may encounter individual sorbent particles while in
laminar flow or while in turbulent flow, or may transition between
flow regimes in, for example, passing through a collection of
sorbent particles. In embodiments of one general type, filter
support 10 may take the form of a substrate on which sorbent
particles 100 are provided (e.g., are attached to a major surface
thereof) and across which e.g. a moving stream of air may traverse,
as shown in generic representation in FIG. 1. In some embodiments
of this type, filter support 10 may retain sorbent particles 100
e.g. by way of the sorbent particles being attached (e.g.,
adhesively bonded) to the filter support. In embodiments of another
general type, a filter support 10 may retain sorbent particles 100
e.g. by mechanically retaining the sorbent particles within the
filter support, as shown in generic representation in FIG. 2. (In
other words, in such embodiments the sorbent particles may not
necessarily be attached to the filter support, but the filter
support can physically block the sorbent particles from being
dislodged and removed from the filter support.) In some
embodiments, a combination of mechanical retention, and attachment
(e.g. bonding), of sorbent particles to the filter support may be
employed.
[0019] In some embodiments, an air filter 1 may be (e.g., may
consist essentially of) a filter support 10 comprising sorbent
particles 100 (for example, a freestanding piece of such a filter
support could be installed into e.g. a room air purifier). In other
embodiments, an air filter 1 may comprise (in addition to the at
least one filter support 10) other layers as desired for any
purpose, and/or may additionally comprise any other ancillary
components such as e.g. a perimeter frame, one or more reinforcing
or stabilizing members, one or more housing pieces, and so on.
Various specific exemplary embodiments and arrangements are
discussed in detail later herein.
[0020] As noted with reference to FIG. 1, in some embodiments a
filter support may take the form of a substrate (which substrate
may be air impermeable, or air permeable) on a major surface of
which sorbent particles 100 are disposed, e.g. attached. Air
filters of this type may comprise, for example, a planar substrate
bearing sorbent particles attached to a major surface thereof; a
hollow tube with sorbent particles attached to an interior surface
thereof; or, an array of flow-through channels provided by stacked
or nested microstructured substrates (e.g., of the general type
described in U.S. Pat. No. 7,955,570 to Insley) with sorbent
particles attached to interior surfaces of the flow-through
channels; and so on. In some embodiments sorbent particles 100 may
be provided at least substantially as a monolayer on a surface of
the substrate (e.g. as shown in FIG. 1), except for such occasional
stacking as may occur statistically e.g. in any industrial-scale
deposition process.
[0021] With reference to FIG. 2, the term filter support broadly
encompasses any container that is designed to retain sorbent
particles 100 therein and that includes at least one air inlet 11
for admitting air to the interior 13 of the container and at least
one air outlet 12 to allow treated air to leave the container. Such
supports of this general type may include well known filter
cartridges in which sorbent particles 100 are retained within a
cartridge housing made of e.g. one or more injection molded housing
parts. In such filter cartridges, a single air inlet and/or outlet
may be provided; or, a number of through-apertures may be provided
in the filter cartridge housing to collectively provide an air
inlet or outlet. Such through-apertures may be of appropriate size
to prevent sorbent particles from passing therethrough; and/or, in
some embodiments, an air-permeable protective layer (e.g., a screen
or mesh) may be provided to ensure that the sorbent particles are
retained within the cartridge housing. In some embodiments a filter
support may be impermeable to air (e.g., may contain no
through-apertures) in the locations of the support that are
proximate to (e.g., that support and retain) sorbent particles, as
in the design of FIG. 1. In other embodiments, a filter support may
be permeable to air (e.g., may include one or more
through-apertures) in locations of the support that are proximate
sorbent particles, as in the design of FIG. 2. In some embodiments,
a filter support in the form of a container (e.g., a filter
cartridge) may be comprised of e.g. one or more injection molded
housing parts that are assembled together and that may be
air-impermeable except for the air inlet(s) and outlet(s). Such
housing parts may be conveniently made of e.g. thermoplastic or
thermoset polymers or copolymers chosen from e.g. polyamides,
polystyrenes, ABS polymers, polyolefins, and so on. Such containers
may also include ancillary components such as e.g. one or more
resilient gaskets, latches, splash guards, connectors (e.g. as
needed for connecting the cartridge to e.g. a personal respiratory
protection device) and so on.
[0022] It is emphasized that a filter support 10 that is in the
form of a container (as in e.g. FIG. 2) does not necessarily have
to take the form of a rigid cartridge made e.g. of injection molded
parts. Rather, in some embodiments such a container might take the
form of e.g. two air-transmissive "walls" at least one of which is
made of a relatively flexible material (e.g., a porous substrate
such as a fibrous web, a perforated or microperforated flexible
polymer film, and so on) with sorbent particles sandwiched between
the two walls. Such a container (which may still be referred to in
general as a filter "cartridge") might take the form of e.g. a
pouch or sachet.
[0023] Still further, the term filter support also broadly
encompasses any porous, air-permeable material on which or within
which sorbent particles 100 are disposed. (By a porous,
air-permeable material is meant a material comprising internal
porosity that is interconnected so as to allow airflow through the
material, as distinguished from e.g. a closed cell foam.) Such
materials might be e.g. open-celled foam materials of any suitable
type; or, such a material might be a porous membrane; for example,
a phase-inversion membrane, a track-etch membrane (e.g., of the
type exemplified by various products available from Whatman under
the trade designation NUCLEPORE); or, a stretch-expanded membrane
(e.g., of the type exemplified by various products available from
W.L Gore and Associates under the trade designation GORE-TEX and
available from Celgard corporation under the trade designation
CELGARD.) It will be appreciated that filter supports 10 of this
general type are not limited to being used e.g. in pairs so as to
define a space therebetween as described above. Regardless of the
specific mode of use, such a filter support 10 may, in some
embodiments, take the form of a sheet-like material that exhibits a
major plane and that exhibits a thickness of less than about 8, 5,
3, or 1 mm and that is configured to allow airflow therethrough at
least in a direction at least generally perpendicular to the major
plane of the sheet-like material.
[0024] From the above discussions it will be appreciated that a
filter support as disclosed herein widely embraces any material or
arrangement, in any form or geometric shape (and whether consisting
e.g. of a single entity such as a nonporous substrate, an
air-permeable netting, or a porous foam, or made of an assembled
combination of parts that collectively form a filter cartridge),
that can present sorbent particles to air, e.g. to a stream of
moving air. In some embodiments a filter support can be configured
so that moving air may flow e.g. at least generally parallel to a
major surface of the support that bears sorbent particles (e.g., as
in the arrangement of FIG. 1). In some embodiments the moving air
may flow at least generally perpendicular to a major surface of the
support (e.g., as in the arrangement of FIG. 2). In some
embodiments, moving air may flow in directions intermediate between
these two extremes. In some embodiments, airflow in both directions
and/or in directions intermediate between these two extremes, may
occur e.g. in different portions of the air filter.
[0025] In embodiments of the general type illustrated in exemplary
manner in FIG. 3, an air filter 1 may comprise a filter support 10
that is in the form of a "honeycomb" 15. The skilled person will
recognize a honeycomb as being a flow-through support structure
that comprises numerous macroscopic through-apertures that allow
airflow therethrough, the apertures being separated from each other
by partitions (walls) of the honeycomb structure. (While the term
honeycomb is used here for convenience, the skilled person will
appreciate that the structure may be of any geometry (e.g., with
apertures that are square, triangular, round, etc.) and may exhibit
a somewhat irregular appearance rather than being limited strictly
to the regular hexagonal geometry shown in the exemplary design of
FIG. 3.) Often, such honeycombs may comprise through-apertures with
rather large diameter or equivalent diameter (e.g. from 10-15 mm),
in contrast to the above-described stacked microstructured
substrates, which may often comprise flow-through channels with a
diameter or equivalent diameter of only e.g. a few mm or smaller.
The walls of the honeycomb may be made of any suitable material,
e.g. molded or extruded plastic, paperboard or cardboard, metal,
and so on.
[0026] In some embodiments, sorbent particles may be attached to
interior walls that define the apertures of the honeycomb. However,
in some embodiments, it may be convenient to partially, or at least
substantially, fill the apertures of the honeycomb with sorbent
particles (to the extent permitted by packing behavior, depending
e.g. on the average size, size distribution, and shape of the
sorbent particles) as in FIG. 3. In such a case the honeycomb may
be provided with upstream and downstream air-permeable substrates
(e.g., suitable meshes or screens) that allow airflow to enter and
exit the through-apertures of the honeycomb and yet retain the
sorbent particles within the through-apertures of the honeycomb.
(The direction of airflow in the exemplary honeycomb of FIG. 3 is
out-of-plane as indicated by the circle/dot arrow.) In some
embodiments, the sorbent particles may be packed loosely within the
apertures e.g. so that the particles are able to move or shift
slightly. In other embodiments, the sorbent particles may be bonded
to each other (e.g., by use of an adhesive, a heat-activated
binder, etc., in amounts sufficient to bond particles to each other
at contact points but not in amounts that would unacceptably
occlude the particles so as to impact their ability to capture
airborne substances) e.g. so as to minimize shifting or settling of
the particles within the apertures. In other words, in some
embodiments (not necessarily limited to use in honeycombs) sorbent
particles 100 may be provided in the form of a monolithic,
air-permeable block (of any desired size and shape) collectively
provided by an aggregation of particles that are bonded together,
rather than being provided as individual particles. Exemplary
methods of making such monolithic structures (which again, may have
any suitable size and shape for incorporation into any desired air
filter, for example, for fitting into a container such as e.g. a
cartridge or canister, or for forming a layer of e.g. a respirator)
are discussed e.g. in U.S. Pat. No. 5,033,465 to Braun. Methods of
bonding sorbent particles together to make, in particular, a
structure that is at least semi-flexible (and thus may be
particularly suited for use in e.g. a flexible respirator mask),
are discussed e.g. in U.S. Pat. No. 6,391,429 to Senkus.
[0027] The skilled person will appreciate that there may not
necessarily be a firm dividing line between some of the
above-mentioned embodiments (for example, between sorbent particles
being provided within hollow tubes, versus being provided within
channels defined by a stacked microstructured substrate, versus
being provided within apertures of a honeycomb). All such designs
and arrangements, and combinations thereof, are encompassed within
the general concept of an air filter that comprises one or more
filter supports as disclosed herein. It is noted in particular that
in some embodiments, an air filter 1 as disclosed herein can
comprise sorbent particles that are partially filled, or at least
substantially filled, into the interior of any suitable container
(of any geometric form and made of any material, whether e.g. rigid
or at least semi-flexible) so as to form e.g. a packed bed. In some
embodiments, such a container might take the form of a hollow tube,
e.g. a tube resembling the gas-detection tubes often referred to as
Drager tubes.
[0028] In some embodiments, a filter support 10 may comprise a
thin, sheet-like material with numerous through-apertures 22 that
allow airflow therethrough, as shown in exemplary, generic
representation in FIG. 4. In various embodiments, filter support 10
may take the form of any suitable netting, mesh, screen, scrim,
woven or knitted material, meltspun material, microperforated film,
and so on. The term netting will be used herein for convenience in
describing any such material, that is comprised of relatively few
layers (five or less; often, a single layer as in FIG. 4) of
filaments (or, in general, layers of solid material in between
through-openings). Often, such filaments (or solid portions of a
sheet-like filter support material, e.g. a microperforated film)
are relatively large (for example, 0.1, 0.2, or 0.5 mm or more) in
diameter or the equivalent thereof. Such a netting may be comprised
of any suitable material, e.g. an organic polymer, an inorganic
material (e.g., glass or ceramic), or a metal or metal alloy.
[0029] In such embodiments airflow may occur primarily through the
through-apertures 22 between the solid portions 21 (e.g. filaments)
of the netting so that the airflow is oriented at least generally
perpendicular to the support; however, if desired the airflow could
occur at least generally parallel to the netting. In the case of
generally perpendicular airflow that passes through the netting, it
may be convenient that the sorbent particles are positioned on the
upstream side 23 of the netting (as in FIG. 4). However, if desired
the sorbent particles may be positioned on the downstream side 24
of the netting. In particular embodiments, sorbent particles may be
positioned on both sides of the netting. In some embodiments, a
netting (or, in general, any sufficiently air-permeable substrate)
comprising sorbent particles may be used "open-face" as in the
illustrative embodiments of FIGS. 1 and 4. In other embodiments, a
secondary retaining layer that is sufficiently air-permeable (e.g.,
a second layer of netting, or a layer of a fibrous web, a
microporous membrane, or the like) may be positioned atop the
sorbent particles to assist in retaining the sorbent particles in
position. (In other words, the sorbent particles may be sandwiched
between the netting and a secondary retaining layer.)
[0030] In many embodiments, sorbent particles 100 may be bonded,
e.g. adhesively bonded, to the solid material (e.g., filaments) of
the netting, e.g. by way of an adhesive, e.g. a pressure-sensitive
adhesive, a hot-melt adhesive, an epoxy adhesive, and the like 28
that is provided on at least one major surface of one side of the
netting. Sorbent particles may each be bonded e.g. to a single
filament, or may be bonded to multiple filaments. The average
diameter of the filaments, and the average size of the
through-apertures between the filaments, can be chosen in view of
the average size of the sorbent particles if desired. In various
embodiments, such nettings may exhibit an average filament diameter
in the range of e.g. 0.2 mm to about 2.0 mm. In various
embodiments, the openings of the netting may range from e.g. about
0.5 mm in shortest dimension to about 5 mm in longest dimension,
and may be chosen in view of the particle size of the sorbent. By
way of specific example, a netting with openings in a range of
about 1-2 mm may be well suited for use with a sorbent that
exhibits a particle size in the range of 8.times.20 mesh. Exemplary
nettings that might be suitable for use as disclosed herein include
various products available (e.g. under the trade designations
DELNET) from Delstar Technologies; for example, the products
available under the trade designations KX215P, R0412-10PR,
RB0404-10P, N02014-90PP, RB0404-28P, N03011-90PP, and
TK16-SBSH.
[0031] In particular embodiments, a suitable pressure sensitive
adhesive 28 may be provided on a major surface of the netting (in
other words, the pressure-sensitive adhesive may be provided on
surfaces of the filaments that collectively provide that major
surface of the netting). This may be done e.g. by coating a
pressure-sensitive adhesive precursor onto the netting and then
transforming the precursor into a pressure-sensitive adhesive. The
precursor may be e.g. a solution in an organic solvent(s), an
emulsion, a hot-melt composition, and so on. Such a precursor may
be transformed e.g. by drying to remove solvent and/or water, by
cooling to solidify a hot-melt composition, and so on. The
deposition and transformation should be done in such manner as to
avoid unacceptably filling or clogging the through-apertures of the
netting (unless the airflow is not to pass through the netting in
ordinary use of the filter).
[0032] It will be appreciated that in some embodiments particles
that are disposed on a netting may be attached to the netting
primarily due to e.g. adhesive bonding (rather than through e.g.
mechanical entanglement). In some embodiments, the sorbent
particles may be present on a filter support at least substantially
in the form of a monolayer. In other embodiments sorbent particles
may be present in multiple layers (made e.g. by adhesively bonding
a first layer of sorbent particles to a major surface of a netting,
applying additional adhesive atop the first layer of sorbent
particles, depositing more sorbent particles, and repeating the
process to build up a collection of sorbent particles of any
desired depth).
[0033] In some embodiments a filter support 10 may comprise a
sheet-like material comprised of numerous fibers, often entangled
with each other and often present in numerous "layers" (e.g., more
than five layers) as shown in exemplary embodiment in FIG. 5. The
term fibrous web will be used herein for convenience in describing
any such material. It will be appreciated of course that due to the
random nature of many such fibrous webs, the fibers may not
necessarily be, and often will not be, present in discrete layers
(e.g., layers that can be peeled apart from each other); however,
it will be readily apparent if e.g. five or more separate fibers or
sections of fibers are encountered in traversing the thickness
(depth) of such a web from a first major surface 43 thereof to a
second major surface 44 thereof (as in FIG. 5). Any material
exhibiting such a fiber arrangement falls under the definition of a
fibrous web as used herein.
[0034] Often, such fibers may be relatively small (for example,
less than 100, 80, 60, 40, 20, 10, 5, or 2 .mu.m) in diameter or
the equivalent thereof. Mixtures of fibers of various diameters may
of course be used. Such a fibrous web may be any suitable type of
web, e.g. a nonwoven web in which the fibers are relatively
randomly arranged (e.g. except for such partial amounts of fiber
alignment as may occur with e.g. carded webs and with certain types
of fiber-deposition methods). Alternatively, such a fibrous web may
be comprised of a knitted or woven web in which the fibers are
provided in a sufficient number of layers. Typically, air will flow
through the web by passing through interstitial spaces between the
numerous fibers of the web; often, such airflow is oriented at
least generally perpendicular to a major plane of the fibrous web
as in FIG. 5. However, if desired the airflow could occur at least
generally parallel to a major plane of the fibrous web. The fibers
of such a fibrous web can be bonded to each other (so that the web
has sufficient mechanical integrity to be processed and handled) in
any suitable manner. Such bonding methods might be chosen from e.g.
hydroentangling, needle-punching, calendering, and the like. In
some embodiments, the fibers may be autogenously bonded to each
other, meaning that the fibers are bonded at an elevated
temperature as obtained in an oven or with a so-called through-air
bonder without application of solid contact pressure such as in
point-bonding or calendering. In particular embodiments, the fibers
may be bonded using autogenous bonding methods of the general type
described in U.S. Pat. No. 7,947,142 to Fox (in which a stream of
heated air is passed through the collection of fibers followed by
forceful quenching). Or, one or more binders (whether in the form
of fibers, solid particles, a water-born emulsion, and so on) may
be added and then activated (e.g. by heating) to bond the fibers
together to form the final web. Any such bonding operation (whether
achieved primarily mechanically by entanglement of fibers, or by
use of a melt-bonding of fibers and/or by use of an added binder)
may additionally serve to bind sorbent particles into or onto the
web, as noted below.
[0035] In some embodiments sorbent particles 100 may be deposited
primarily, or exclusively, on a major surface (e.g., a major
upstream surface) of the fibrous web, in somewhat similar manner to
the arrangement of particles on the netting of FIG. 4. In some
embodiments at least some of the sorbent particles may penetrate at
least partly into the interior of the fibrous web. (This is in
contrast to the situation with a netting provided by e.g. a
monolayer of filaments as in FIG. 4, in which case the support
exhibits little or no "interior" into which sorbent particles could
penetrate.) In some such embodiments the sorbent particles may be
found primarily in the region of the fibrous web proximate the
major surface onto or into which the sorbent particles were
deposited. In many embodiments, however, it may be desirable to
provide that sorbent particles 100 are distributed widely
throughout the thickness of the fibrous web (as shown in exemplary
embodiment in FIG. 5), as opposed to the particles being e.g.
deposited onto one surface so that they either remain on the
surface or only penetrate a short distance into the interior of the
fibrous web. Suitable methods of forming fibrous webs with sorbent
particles distributed widely (e.g., randomly) throughout the
interior of the web are discussed later herein.
[0036] In particular embodiments, a fibrous web filter support may
be a nonwoven web. By definition, nonwoven fibrous webs do not
encompass e.g. woven or knitted webs or microperforated films. Such
a web can be made by any suitable method and can be of any suitable
type. For example, such a nonwoven web might be: a carded web; a
wet-laid web (made e.g. by papermaking processes); a dry-laid web
made e.g. by a conventional airlaying process such as the
well-known Rando-Webber process, or made by a specialized process
such as the gravity-laying process described in U.S. Pat. No.
8,834,759 to Lalouch; or, a meltspun web (e.g. a spunbonded web, a
spunlaced web, and so on). (It will be appreciated that certain
e.g. spunbonded or spunlaced webs may qualify as nettings rather
than as fibrous webs, depending e.g. on the depth of fibers that
are laid down.) In particular embodiments, the nonwoven web may be
a meltblown web, which process and resulting web will be well known
to the skilled person. Any combination of layers of these various
materials (including combination with layers that are not nonwoven
webs) can be used. The fibers may be made of any suitable material,
e.g. thermoplastic organic fibers (such as e.g. polyolefin fibers,
cellulosic fibers, polyester fibers, nylon fibers, etc.), inorganic
fibers (such as e.g. fiberglass or ceramic fibers), metal fibers,
and so on.
[0037] Sorbent particles 100 may be provided on and/or within a
porous material, e.g. a fibrous web such as a nonwoven web to form
a herein-disclosed filter support of an air filter, by any suitable
method. In some embodiments, the sorbent particles may be deposited
on or into a pre-existing fibrous web. For example, in some
embodiments a nonwoven web may comprise one or more binding
components such as bondable fibers and/or a non-fibrous binder (a
non-fibrous binder may take the form of e.g. particles, an emulsion
or latex, and so on). The web may be heated to a temperature to
soften and activate such a binding component(s), and the sorbent
particles may then be deposited onto a major surface of the
nonwoven web to be bonded thereto. It will be appreciated that many
such processes may preferentially result in sorbent particles being
present on or proximate a major surface of the nonwoven web onto
which the sorbent particles were deposited. If desired, such a
process may be repeated multiple times with the successive layers
being bonded together to form a multilayer product comprising
sorbent particles therein.
[0038] In other embodiments, the sorbent particles may be
introduced into a nonwoven web during the process of making the
web. For example, if a nonwoven web is made by meltblowing, it may
be convenient to introduce the sorbent particles into the flowing
stream of incipient fibers (the term incipient fibers refers to
molten streams that may or may not have begun to solidify into
fibers, or finished solidifying into fibers). General methods of
performing such operations are disclosed in US Patent Application
Publication No. 20120272829 to Fox, which is incorporated by
reference herein. The incipient fibers may be deposited (e.g., onto
a temporary collection surface or onto a secondary web that remains
as part of the filter support) in a condition in which the
incipient fibers are at least slightly sticky (bondable). Such
arrangements can provide that at least some of the fibers of the
meltblown nonwoven web are bonded (e.g., melt-bonded) to the
sorbent particles. In this manner a meltblown web can be made
comprising sorbent particles therein, in a single operation.
[0039] Of course, it is also possible to use other methods to
introduce sorbent particles into a mixture of fibers prior to the
fibers being collected as a web. For example, sorbent particles may
be mixed with fibers that are input to a web-formation process
(e.g., the above-mentioned gravity-laying web-formation process),
to form a collected mass of fibers comprising sorbent particles
therein. Such an approach can include adding binder (whether in the
form of fibers, or as non-fibrous binders such as particles, an
emulsion, etc.) to the input materials so that the collected mass
of fibers can be heated to bind the fibers together to form a web
and/or to bond the sorbent particles into the web. Whatever
approaches is/are used, the primary mechanism by which sorbent
particles are bound into or onto the fibrous web can be the same or
different from the binding mechanism that is used to bind the
fibers together to form the web.
[0040] With particular regard to a meltblown fibrous web, a variety
of fiber-forming polymeric materials may be used to form such
fibers. At least some fibers may be made of a material that
exhibits sufficient bonding (adhesive) properties under the
conditions (e.g., melt-blowing conditions) used in making the
nonwoven web. Examples include thermoplastics such as polyurethane
elastomeric materials, polybutylene elastomeric materials,
polyester elastomeric materials, polyether block copolyamide
elastomeric materials, polyolefin-based elastomeric materials
(e.g., those available under the trade designation VERSIFY from
Dow), and elastomeric styrenic block copolymers (e.g., those
available under the trade designations KRATON from Kraton Polymers,
Houston, Tex.). Multicomponent fibers (e.g., core-sheath fibers,
splittable or side-by-side bicomponent fibers and so-called
"islands in the sea" fibers) in which at least one exposed surface
of the fibers (e.g., the sheath portion of a core-sheath fiber)
exhibits sufficient adhesive properties, may also be used.
[0041] In some embodiments, fibers that are able to bond to sorbent
particles 100 may be the only fibers present in the meltblown web.
In other embodiments, other fibers (e.g. that do not participate to
any significant extent in bonding the sorbent particles) may be
present e.g. as long as sufficient bondable fibers are present. In
various embodiments, bondable fibers may comprise at least about 2
weight percent, at least about 4 weight percent, and at least about
6 weight percent of the meltblown nonwoven web. In further
embodiments, bondable fibers may comprise no greater than about 20
weight percent, no greater than about 17 weight percent, and no
greater than about 15 weight percent of the meltblown nonwoven web.
Any nonbondable fibers that are present in the web may be of any
suitable type and composition; for example, any of the well known
polyolefinic fibers (e.g. polypropylene, polyethylene, and the
like) may be used, as may any of the well known polyester fibers.
In at least some embodiments, the nonwoven web is essentially free
of any added binder of any kind. That is, in such cases essentially
all binding of the sorbent particles (to retain them in the
meltblown nonwoven web) is performed by the bondable fibers. Such
embodiments thus exclude the presence of binder in such forms as
particles or powders, liquids such as latexes, emulsions,
suspensions, or solutions, and so on.
[0042] It will be appreciated that the above discussions have
concerned methods in which bonding of fibers to the sorbent
particles is at least partially used to retain the particles within
the nonwoven web. Physical entanglement of the sorbent particles
within the fibers can also assist in retaining the sorbent
particles within the nonwoven web. In some embodiments, a secondary
air-permeable layer (e.g. a scrim or facing) can be applied to
(e.g., bonded to) one or more major surfaces of the nonwoven web to
minimize the chances of any of the sorbent particles becoming
dislodged therefrom. In fact, in some embodiments it may be
convenient to deposit the incipient fibers that will form a
meltblown nonwoven web (along with the sorbent particles that are
merged into the stream of incipient fibers), onto a major surface
of a secondary web (e.g., scrim or facing) so that the meltblown
web is bonded to the secondary web in the act of making the
meltblown web.
[0043] In some embodiments, air filter 1 may comprise at least one
filter media 40. A filter media is a filter support 10 that can
retain sorbent particles 100 and expose them to air; beyond this, a
filter media is a particular type of filter support that is capable
of filtering significant amounts of microscopic particles (i.e.,
particles of average diameter of 100 microns or less) from moving
air. A filter media 40 may comprise any material that can provide
an air-permeable network structure into or onto which sorbent
particles can be incorporated so as to present the sorbent
particles to an airstream that is moving through the air-permeable
network structure, and that furthermore is itself capable of
filtering microscopic particles. Such a filter media might be e.g.
a nonwoven web that is a meltblown and/or charged web.
[0044] As noted, a filter media is able to capture a significant
amount of microscopic particles (with diameter 100 .mu.m or less).
In specific embodiments, a filter media may be able to capture a
significant amount of fine particles in the range of e.g. 10 .mu.m
or less, or even in the range of 2.5 .mu.m or less. In particular
embodiments, the filter media may be capable of performing HEPA
filtration. It will be appreciated that use of electret (charged)
materials as described below, may substantially enhance the ability
to perform e.g. fine-particle filtration or HEPA-filtration. In
various embodiments, a filter media 40 may exhibit a Percent
Penetration (specified herein as using Dioctyl Phthalate as a
challenge material, and tested using methods described in U.S. Pat.
No. 7,947,142 to Fox) of less than about 80, 70, 60, 50, 40, 30,
20, 10, or 5. All processes (e.g., fiber-bonding, charging,
pleating, and the like), parameters and characterizations that are
described herein with respect to filter supports in general, may be
applied in particular to filter media.
[0045] In some embodiments, a nonwoven web (e.g., a meltblown
nonwoven web) for use as a filter support (or, in particular, as a
filter media) may include electrostatically charged fibers.
Charging of such fibers may be done by any suitable method, for
example, by imparting electric charge to the nonwoven web using
water as taught in U.S. Pat. No. 5,496,507 to Angadjivand, or as
taught in U.S. Patent Publication No. 2009/0293279 to Sebastian.
Nonwoven electret webs may also be produced by corona charging as
described in U.S. Pat. No. 4,588,537 to Klaase, or using mechanical
approaches to impart an electric charge to fibers as described in
U.S. Pat. No. 4,798,850 to Brown. Any combination of such
approaches may be used. Fibers may be charged before being formed
into the nonwoven web, or after the nonwoven web is formed. (In any
case, any such charging may be conveniently performed before the
air filter media is pleated, if it is to be pleated.) In the case
that an air filter is to include a particle-filtration layer that
is a different layer from filter support 10 (as described below),
such a particle-filtration layer may be charged if desired, e.g. by
any of the above approaches.
[0046] If the filter support (whether free-standing, or part of a
multilayer assembly) is to be pleated, pleat formation and pleat
spacing may be performed using any suitable technique including
those disclosed in U.S. Pat. No. 4,798,575 to Siversson, U.S. Pat.
No. 4,976,677 to Siversson, and U.S. Pat. No. 5,389,175 to Wenz.
Pleating procedures that may be useful are also described e.g. in
U.S. Pat. No. 7,235,115 to Duffy. (It will be appreciated, however,
that in at least some embodiments the use of score-pleating may be
avoided since the scoring process may serve to crush at least some
of the sorbent particles.) In various embodiments, the pleated air
filter support may include about 0.5 to about 5 pleats per 2.5
centimeters. More specifically, the pleat spacing may be e.g. from
about 6, 8, 10, or 12 mm, to about 50, 40, 30, 20, or 15 mm. In
various embodiments, the pleat height may be e.g. from about 15,
20, 25, or 30 mm, to about 100, 80, 60 or 40 mm.
[0047] An air filter 1 may comprise a filter support 10 (which by
definition supports at least some polymeric sorbent particles 100)
that consists of a single layer; or, multiple layers of filter
support 10 (e.g., each layer including at least some polymeric
sorbent particles 100) may be present in an air filter 1.
Particularly if the filter support(s) 10 is not itself an air
filter media as defined herein, the air filter 1 may include (in
addition to the at least one filter support layer 10) one or more
particle-filtration layers (e.g., capable of filtration of
microscopic particles, fine particles, and/or HEPA filtration) that
do not include polymeric sorbent particles 100. Such a particle
filtration layer may be electrostatically charged if desired, and
in various embodiments may exhibit a Percent Penetration of less
than about 80, 70, 60, 50, 40, 30, 20, 10, or 5. (The term particle
broadly encompasses e.g. aerosols, dust, mist, fumes, smoke, mold,
bacteria, spores, pollen, and so on.) In particular embodiments,
such a particle-filtration layer may be a high-loft spunbonded
nonwoven web e.g. of the type described in U.S. Pat. No. 8,240,484
to Fox, and comprising a solidity of from less than 8%, to about
4%, and that is comprised of meltspun fibers that are substantially
free of crimped fibers, gap-formed fibers and bicomponent
fibers.
[0048] Regardless of whether or not any particle-filtration layers
are present, an air filter 1 may comprise (in addition to at least
one filter support layer 10 and any optional particle-filtration
layers) one or more secondary layers (e.g., scrims, nettings,
covers, and so on), e.g. to serve as a cover layer, a coarse
prefilter, a carrier layer, a skin-contacting layer, to provide
mechanical support or stiffness, and so on. That is, in general,
and without regard to the particular type, configuration or
construction of a filter support layer 10, such a filter support
layer may be provided as one layer of a multilayer air-permeable
assembly (stack) that can collectively provide an air filter 1. Any
such multilayer stack may of course be pleated, framed, and so on,
as described herein.
[0049] The herein-disclosed sorbent particles (whether e.g.
dispersed within a nonwoven fibrous web, disposed on a surface of a
substrate, filled into a receptacle(s) e.g. to form a packed bed,
etc.), may be used in combination with any secondary sorbent
particles, configured to capture any desired component present in
air (e.g. a noxious gas/vapor). In some embodiments, such secondary
sorbent particles may be present in a separate layer that is e.g.
upstream or downstream of polymeric sorbent particles 100. In other
embodiments, sorbent particles 100 and any desired secondary
sorbent particle(s) may be mixed together. Secondary sorbent
particles (whether used in a separate layer or as a commingled
mixture with polymeric sorbent particles 100) may be chosen from,
for example, activated carbon, alumina and other metal oxides,
clay, hopcalite, ion exchange resins, molecular sieves and
zeolites, silica, sodium bicarbonate, metal-organic frameworks
(MOFs), and so on including combinations of any of these materials.
In some embodiments, secondary sorbent particles (e.g. activated
carbon) may be impregnated sorbent particles that are suitably
impregnated with e.g. any desired metal salt or compound. Various
particles that may be suitable for use as secondary sorbent
particles are described in detail in U. S. Patent Application
Publication No. 2015/0306536 to Billingsley; and, in U.S.
Provisional Application No. 62/269,613, filed 18 Dec. 2015 and
entitled POLYMERIC SORBENTS FOR ALDEHYDES; both of which are
incorporated by reference in their entirety herein. Any combination
of any of such particles may be used. Porous polymeric sorbent
particles 100 and one or more sets of secondary sorbent particles
may be used in any weight ratio. In particular, the term
"secondary" is used for convenience of description and does not
require that any secondary sorbent particles must be present, for
example, in a lower amount than the porous polymeric sorbent
particles 100. Furthermore, the disclosed sorbent particles 100 may
be mixed e.g. with particles, granules or the like, that are not
porous and/or do not perform any sorbing function (such particles
may e.g. perform a spacing or separating function).
[0050] In some embodiments, an air filter 1 comprising sorbent
particles 100 as disclosed herein, may be used in combination with
a secondary air filter that is provided separately from air filter
1. In some embodiments, an air filter 1 and a secondary air filter
may be separately installed into different areas of an air-handling
apparatus. (For example, an air filter 1 and a secondary air filter
may each be a framed air filter and may each be separately inserted
e.g. into a room air purifier.) Alternatively, an air filter 1 and
a secondary air filter may be assembled together (and e.g. attached
to each other) before being installed into e.g. an air-handling
apparatus. Air filter 1 can be placed e.g. upstream or downstream
of the secondary air filter (if air filter 1 is upstream, it may
serve e.g. as a prefilter for the secondary filter). In some
exemplary embodiments, a secondary air filter may be configured
e.g. to capture fine particles, and may exhibit a Percent
Penetration of e.g. less than about 80, 70, 60, 50, 40, 30, 20, 10,
or 5.
[0051] A filter support 10 comprising sorbent particles 100 as
disclosed herein may be used in any kind of air filter 1,
configured for any suitable end use. By way of specific examples,
filter support 10 may find use in e.g. an air filter that is, or is
part of, a personal respiratory protection device. It has already
been noted that filter support 10 may take the form of a filter
cartridge that can be fluidly coupled to a mask body to provide a
personal respiratory protection device (e.g., the filter cartridge
being disposable and the mask body being a piece that is shaped to
fit a user's face and that is retained and a replacement filter
cartridge attached thereto at an appropriate time). In other
embodiments, filter support 10 may be incorporated into a
"filtering face-piece" respirator mask 60. In products of this
general type, the mask body itself provides the filtering function.
That is, unlike respirators that use mask bodies in conjunction
with attachable filter cartridges or the like, filtering face-piece
respirators are designed to have the filtration layer(s) present
over much or essentially all of the entire mask body so that there
is no need for installing or replacing a filter cartridge. (That
is, in a filtering face-piece respirator the mask body itself
performs the filtering function rather than relying on one or more
cartridges attached thereto.) Filtering face-piece respirators 60
often come in one of two configurations: molded (e.g. shaped, into
a generally cup-shape so as to fit on a user's face) as shown in
exemplary representation in FIG. 6, and flat-fold, that can be
supplied in a flat or nearly-flat condition and can then be
unfolded and expanded to fit on a user's face, as shown in
exemplary representation in FIG. 7.
[0052] Such a respirator mask (whether e.g. a flat-fold or molded
respirator) 60 may comprise any desired ancillary layers (e.g., one
or more cover layers, stiffening layers, pre-filter layers, and the
like) and components (e.g. one or more exhaust valves, attachment
bands or strings, nose-pieces, and so on). If used in a flat-fold
respirator mask, filter support 10 may often take the form of a
relatively flexible layer (e.g. with one or more preferential
folding lines 63 provided to make the material more easily
foldable). If filter support 10 is to be used in a molded
respirator mask (that is not designed to be foldable), filter
support 10 may be e.g. a semi-rigid material (noting however that
since in many molded, cup-shaped respirator masks much of the
stiffness may be provided by a stiffening layer that is separate
from the filtering layer(s), it may not be strictly necessary that
filter support 10 be rigid, or even semi-rigid, for use in such a
product).
[0053] It will be appreciated that the above-described uses fall
primarily into the category of so-called "negative-pressure"
respirators; that is, products in which the motive power for moving
air is the breathing of a user rather than a separately provided
motorized fan. Such negative-pressure respirators are often
configured as e.g. full-face respirators, half-face respirators,
and hoods (e.g., escape hoods, smoke hoods, and the like). All such
products are encompassed by the term negative-pressure respirator
as used herein, and filter support 10 may be used with any such
product.
[0054] In other embodiments, filter support 10 may be used in a
respirator in which the motive power for moving air is a motorized
fan or blower. Such products may include e.g. a PAPR (powered air
purifying respirator). In such products, filter support 10 (and, in
general, air filter 1) may be located proximate the user's face or
head; or, it may be located remotely (e.g., positioned in a
receptacle of a belt-worn housing).
[0055] In some embodiments as shown in exemplary embodiment in FIG.
8, a filter support 10 (e.g., whether pleated or not, and whether
or not including any other layers such as particle-filtration
layers, etc.) may be incorporated into an air filter 1 that
includes a perimeter frame 70 (e.g. a rigidifying or supporting
frame), which may be e.g. arranged around a perimeter edge region
of the filter support. Suitable materials for the frame include
chip board, or paperboard, synthetic plastic materials and metal.
Suitable frame constructions might be chosen from e.g. the "pinch"
frame construction illustrated in FIGS. 1-4 of U.S. Pat. No.
6,126,707 to Pitzen, the "box" frame construction illustrated in
FIGS. 5 and 6 of the '707 Patent, the hybrid frame construction
illustrated in FIGS. 7-11 of the '707 Patent, any of the frame
constructions disclosed in U.S. Pat. No. 7,503,953 to Sundet, and
any of the frame constructions disclosed in U.S. Pat. No. 7,235,115
to Duffy. Any such frame may be attached to the filter support by
any suitable method, e.g. hot-melt bonding, room-temperature glue,
and so on.
[0056] An air filter 1 (whether framed or not) comprising filter
support 10 may be advantageously used to filter moving air in any
suitable powered air-handling system, e.g. in HVAC systems (e.g.,
in forced-air heating, cooling, and/or heating/cooling systems
often used in residences, office buildings, retail establishments,
and so on). Such filters may also find use in room air purifiers,
motor vehicles (such as in e.g. cabin air filtration of
automobiles), clean rooms, operating rooms, and the like. In some
embodiments, air filter 1 (e.g., as part of a filter cartridge) may
be inserted into an air pathway of a powered air-purifying
respirator, as noted above. While in any or all such uses it may
not be necessary that air filter 1 be a framed air filter, in many
such uses it may be advantageous for air filter 1 to be a framed
air filter.
[0057] The above discussions all relate to methods of providing
porous polymeric sorbent particles 100 on a suitable filter support
10 to provide an air filter 1 and positioning the air filter so
that the supported sorbent particles are exposed to air (the term
air is used broadly and encompasses any gas or gaseous mixture,
e.g. nitrogen, dehumidified nitrogen or air, oxygen-enriched air,
air including an anesthetic gas or gas mixture, and so on). In many
embodiments, the air to which the sorbent particles are exposed is
in the form of a moving airstream. In some cases (which may be
referred to as "active" filtration) such moving air may be
motivated by a motorized blower, fan, and so on. In other cases
(which may be referred to as "passive" filtration) such moving air
may be motivated e.g. by the breathing of a person rather than by
any motorized mechanism. The term "passive" filtration also
encompasses situations in which an air filter 1 is exposed to
currents, eddies, and the like, e.g. in an ambient atmosphere. Such
currents and eddies might take the form of e.g. wind (such as might
be impinged against an exterior surface of a filter support 10 that
is provided in the form of e.g. a window screen). Or, in indoor
environments, such currents and eddies might take the form of
convection currents, random air currents, and the like, which
regularly occur e.g. in rooms of buildings (due e.g. to doors
opening and closing, persons moving, and so on). It will thus be
appreciated that an air filter 1 as disclosed herein encompasses
such devices as e.g. a cartridge, bag, pouch, canister, or, in
general, any kind of container that holds sorbent particles 100
therein and that has at least one air-permeable wall so as to allow
air to enter the container and contact the sorbent particles and to
then exit the container, regardless of whether such a device is or
is not used with any kind of mechanical blower or is used in any
kind of respirator.
[0058] In broad summary, air filters 1 as described herein can find
use in any suitable application in which it is desired to remove at
least some basic, nitrogen-containing airborne substances from air.
Such uses may involve personal devices (e.g. personal respiratory
protection devices) designed for use by a single user, or
collective devices (e.g. room air purifiers, HVAC systems, and so
on) designed for e.g. buildings, vehicles, and other places where
persons reside, work, or gather. As noted, such uses may involve
"active" or "passive" filtration, and may use an air filter 1 that
is configured in any of a wide variety of geometric formats and
that is comprised of any of a wide variety of materials. Also as
noted, one or more secondary sorbents may be used in addition to
the herein-described polymeric sorbent particles 100, whether mixed
with particles 100 and/or provided in a separate layer. As further
noted, an air filter 1 may include at least one layer (in addition
to the at least one support layer 10 that supports polymeric
sorbent particles 100) that provides fine-particle filtration
and/or that captures some gas/vapor other than basic,
nitrogen-containing materials such as ammonia. Instead of this, or
as an adjunct to this, a secondary air filter may be provided in
addition to air filter 1, e.g. to perform filtration of fine
particles and/or to capture some other gas/vapor. Moreover,
combinations of any of the above-described embodiments of filter
supports may be used. For example, polymeric sorbent particles 100
might be disposed within a fibrous web, or onto a surface of a
netting, which web or netting might e.g. be placed within a housing
to provide a filter cartridge.
[0059] Sorbent particles 100 are porous polymeric materials that
comprise one or more divalent metals. The polymeric materials are
divinyl-benzene/maleic anhydride polymers, partially hydrolyzed
divinylbenzene/maleic anhydride polymers, or fully hydrolyzed
divinylbenzene/maleic anhydride polymers. (The terms "polymer" and
"polymeric material" are used interchangeably and refer to
materials formed by reacting one or more monomers. The terms
include homopolymers, copolymers, terpolymers, or the like.
Likewise, the terms "polymerize" and "polymerizing" refer to the
process of making a polymeric material that can be a homopolymer,
copolymer, terpolymer, or the like.) It will be understood that
such polymeric materials will be crosslinked materials (rather than
e.g. linear polymers) due to the relatively high concentration of
divinylbenzene among the monomer units. The divalent metal is
selected from Group 2 or Group 6 to Group 12 of the IUPAC Periodic
Table. The metal-containing polymeric materials can be used to
capture basic, nitrogen-containing airborne materials having a
molecular weight no greater than 150 grams/mole. This capture
results in the formation of a metal complex-containing polymeric
materials. The metal-containing polymeric materials often change
color upon exposure to basic, nitrogen-containing compounds.
[0060] The term "divalent metal" refers to a metal having an
oxidation state of +2. The divalent metal typically is from Group 2
or Groups 6 to 12 of the IUPAC Periodic Table of Elements. To avoid
confusion, Group 2 has beryllium as its lightest member, Group 6
has chromium as its lightest member, Group 7 has manganese as its
lightest member, Group 8 has iron as its lightest member, Group 9
has cobalt as its lightest member, Group 10 has nickel as its
lightest member, Group 11 has copper as its lightest member, and
Group 12 has zinc as its lightest member. The divalent metal can be
in the form of a metal salt, a metal complex, a metal oxide, or the
like.
[0061] The polymeric material is the reaction product of a
polymerizable composition that includes a monomer mixture. The term
"monomer mixture" refers to that portion of a polymerizable
composition that includes the monomers. More specifically, the
monomer mixture includes at least divinylbenzene and maleic
anhydride. The term "polymerizable composition" includes all
materials included in the reaction mixture used to form the
polymeric material. The polymerizable composition includes, for
example, the monomer mixture, the organic solvent, the initiator,
and other optional components. Some of the components in the
polymerizable composition such as the organic solvent may not
undergo a chemical reaction but can influence the chemical reaction
and the resulting polymeric material that is formed.
[0062] The term "divinylbenzene/maleic anhydride polymeric
material" refers to a polymeric material derived from
divinylbenzene, maleic anhydride, and optionally a styrene-type
monomer. The term "styrene-type monomer" refers to styrene, an
alkyl substituted styrene (e.g., ethyl styrene), or mixtures
thereof (Such monomers are often present in divinylbenzene as
impurities.) Typically, the divinylbenzene/maleic anhydride
polymeric material contain 15 to 65 weight percent monomeric units
derived from maleic anhydride and 35 to 85 weight percent monomeric
units derived from divinylbenzene or a mixture of divinylbenzene
and styrene-type monomers. The monomeric units derived from maleic
anhydride can be monomeric units of Formula (I), Formula (II), or a
mixture thereof. That is, these monomeric units can have an
anhydride group as in Formula (I) or two carboxyl groups as in
Formula (II) depending on the extent that the polymeric material
has been hydrolyzed.
##STR00001##
The monomeric units derived from divinylbenzene are of Formula
(III) and those derived from styrene-type monomers are of Formula
(IV):
##STR00002##
[0063] wherein R.sub.1 is hydrogen or alkyl. Each asterisk (*) in
Formulas (I) to (IV) indicates the attachment site to another
monomeric unit or to a terminal group in the polymeric
material.
[0064] The polymeric material can be considered to be
non-hydrolyzed, partially hydrolyzed, or fully hydrolyzed depending
on the form of the monomeric unit derived from maleic anhydride.
The polymeric material can be referred to as being "non-hydrolyzed"
if 90 to 100 weight percent of the monomeric units derived from
maleic acid are of Formula (I) and 0 to less than 10 weight percent
of the monomeric units derived from maleic anhydride are of Formula
(II). The polymeric material can be referred to as being "partially
hydrolyzed divinylbenzene/maleic anhydride polymeric material" if
10 to 90 weight percent of the monomeric units derived from maleic
anhydride are of Formula (I) and 10 to 90 weight percent of the
monomeric units derived from maleic anhydride are of Formula (II).
The polymeric material can be referred to as being "fully
hydrolyzed divinylbenzene/maleic anhydride polymeric material" if 0
to less than 10 weight percent of the monomeric units derived from
maleic anhydride are of Formula (I) and greater than 90 to 100
percent of the monomeric units derived from maleic anhydride are of
Formula (II). Frequently, however, a polymeric material that is
non-hydrolyzed or partially hydrolyzed prior to incorporation of
divalent metal undergoes some hydrolysis during incorporation of
the divalent metal. That is, incorporation of the divalent metal,
which is usually done in an aqueous solution, can result in some
hydrolysis of the polymeric material having monomer units of
Formula (I). Incorporation of the divalent metal can change a
non-hydrolyzed divinylbenzene/maleic anhydride polymeric material
to a partially hydrolyzed divinylbenzene/maleic anhydride polymeric
material or can further hydrolyze a partially hydrolyzed
divinylbenzene/maleic anhydride polymeric material.
[0065] The polymeric material is prepared from a polymerizable
composition that includes a monomer mixture that includes at least
divinylbenzene, maleic anhydride, and an optional styrene-type
monomer. (The term "styrene-type monomer" refers to styrene, an
alkyl substituted styrene (e.g., ethyl styrene), or mixtures
thereof, which monomers are often present in divinylbenzene as
impurities.) The resulting non-hydrolyzed divinylbenzene/maleic
anhydride polymeric material can then be treated with divalent
metal. Alternatively, all or any portion of the anhydride groups in
the non-hydrolyzed divinylbenzene/maleic anhydride polymeric
material can be treated with a hydrolyzing agent to prepare a
partially hydrolyzed divinylbenzene/maleic anhydride polymeric
material or fully hydrolyzed divinylbenzene/maleic anhydride
polymeric material that is then treated with the divalent
metal.
[0066] The polymeric material that is subsequently incorporated
with divalent metal is typically porous. More specifically, the
amount of divinylbenzene crosslinker, the amount of maleic
anhydride, the amount of optional styrene-type monomer, and the
organic solvent used to prepare the non-hydrolyzed polymeric
material are carefully selected to prepare polymeric materials that
are porous. Porous materials can be characterized based on the size
of their pores. The term "micropores" refers to pores having a
diameter of less than 2 nanometers. The term "mesopores" refers to
pores having a diameter in a range of 2 to 50 nanometers. The term
"macropores" refers to pores having a diameter greater than 50
nanometers. In particular, the polymeric materials, at least prior
to incorporation of the divalent metal, usually have pores in the
size range of micropores and/or mesopores.
[0067] The porosity of the polymeric material can be characterized
from an adsorption isotherm of an inert gas such as nitrogen or
argon by the porous material under cryogenic conditions. The
adsorption isotherm is typically obtained by measuring adsorption
of the inert gas by the porous material at multiple relative
pressures in a range of about 10.sup.-6 to about 0.98. The
isotherms are then analyzed using various methods to calculate
specific surface areas (such as BET specific surface area) and
total pore volume. The conditions used to synthesize the
non-hydrolyzed divinylbenzene/maleic anhydride polymeric material
are selected to produce a porous polymeric material that can, even
after having a divalent metal impregnated therein, exhibit a BET
specific surface area of at least 15 m.sup.2/gram, at least 20
m.sup.2/gram, at least 25 m.sup.2/gram, or at least 50
m.sup.2/gram.
[0068] The term "surface area" refers to the total area of a
surface of a material including the internal surfaces of accessible
pores. The surface area is typically calculated from adsorption
isotherms obtained by measuring the amount of an inert gas such as
nitrogen or argon that adsorbs on the surface of a material under
cryogenic conditions (i.e., 77.degree. K) over a range of relative
pressures. The term "BET specific surface area" is the surface area
per gram of a material that is typically calculated from adsorption
isotherm data of the inert gas over a relative pressure range of
0.05 to 0.3 using the BET method (Brunauer-Emmett-Teller
Method).
[0069] The non-hydrolyzed divinylbenzene/maleic anhydride polymeric
material is synthesized from a monomer mixture that includes at
least maleic anhydride and divinylbenzene, and may include
styrene-type monomer. Typically, the divinylbenzene/maleic
anhydride polymeric material contain 15 to 65 weight percent
monomeric units derived from maleic anhydride and 35 to 85 weight
percent monomeric units derived from divinylbenzene or a mixture of
divinylbenzene and styrene-type monomers. More particularly, the
monomer mixture used to form the non-hydrolyzed
divinylbenzene/maleic anhydride typically includes 1) 15 to 65
weight percent maleic anhydride, 2) 30 to 85 weight percent
divinylbenzene, and 3) 0 to 40 weight percent (or 5 to 40 weight
percent) of a styrene-type monomer, wherein the styrene-type
monomer is styrene, an alkyl substituted styrene, or a combination
thereof. The amount of each monomer is based on the total weight of
monomers in the monomer mixture.
[0070] The amount of maleic anhydride used in the monomer mixture
to prepare the non-hydrolyzed polymeric material effects the amount
of divalent metal that can be incorporated into the polymeric
material. If the amount of maleic anhydride is too low (e.g., below
15 weight percent of the monomers in the monomer mixture), the
amount of divalent metal in the metal-containing polymeric material
may be too low to effectively and efficiently capture basic,
nitrogen-containing compounds of formula Q. On the other hand, if
the amount of maleic anhydride is greater than 65 weight percent or
60 weight percent based on the total weight of monomers in the
monomer mixture, the polymeric material may not have a sufficiently
high BET specific surface area. If the BET specific surface area is
too low, the polymeric material may not have sufficient porosity to
incorporate a suitable amount of divalent metal.
[0071] In some embodiments, the amount of maleic anhydride in the
monomer mixture is at least 15 weight percent, at least 20 weight
percent, at least 25 weight percent, at least 30 weight percent, at
least 35 weight percent, or at least 40 weight percent. The amount
of maleic anhydride can be up to 65 weight percent, up to 62 weight
percent, up to 61 weight percent, up to 60 weight percent, up to 55
weight percent, up 50 weight percent, up to 45 weight percent, or
up to 40 weight percent. For example, the amount can be in a range
of 15 to 65 weight percent, 15 to 60 weight percent, 20 to 60
weight percent, 25 to 60 weight percent, 30 to 60 weight percent,
35 to 60 weight percent, 40 to 60 weight percent, 15 to 55 weight
percent, 15 to 50 weight percent, 15 to 45 weight percent, 20 to 50
weight percent, 20 to 45 weight percent, 25 to 50 weight percent,
or 25 to 45 weight percent. The amounts are based on the total
weight of monomers in the monomer mixture.
[0072] Stated differently, the polymeric material contains 15 to 65
weight percent monomeric units derived from maleic anhydride. The
monomeric units derived from maleic anhydride are of Formula (I),
Formula (II), or both. The relative amounts of Formula (I) and
Formula (II) can vary depending on the degree of hydrolysis that
has occurred. The amount of the monomeric units derived from maleic
anhydride can be, for example, in a range of 15 to 60 weight
percent, 20 to 60 weight percent, 25 to 60 weight percent, 30 to 60
weight percent, 35 to 60 weight percent, 40 to 60 weight percent,
15 to 55 weight percent, 15 to 50 weight percent, 15 to 45 weight
percent, 20 to 50 weight percent, 20 to 45 weight percent, 25 to 50
weight percent, or 25 to 45 weight percent based on a total weight
of the polymeric material.
[0073] The amount of divinylbenzene crosslinker can strongly
influence the BET specific surface area of the
divinylbenzene/maleic anhydride polymeric material whether it is
non-hydrolyzed, partially hydrolyzed, or fully hydrolyzed. The
divinylbenzene contributes to the high crosslink density and to the
formation of a crosslinked, rigid polymeric material having
micropores and/or mesopores. The BET specific surface area tends to
increase with an increase in the amount of divinylbenzene in the
monomer mixture. If the amount of divinylbenzene in the monomer
mixture is less than 30 weight percent, the polymeric material may
not have a sufficiently high BET specific surface area,
particularly if the polymeric material is fully hydrolyzed. On the
other hand, if the amount of divinylbenzene is greater than 85
weight percent, the anhydride and/or carboxylic acid content may be
insufficient to incorporate the desired amount of the divalent
metal.
[0074] In some embodiments, the amount of divinylbenzene is at
least 30 weight percent, at least 35 weight percent, at least 40
weight percent, at least 45 weight percent, at least 50 weight
percent, at least 55 weight percent, or at least 60 weight percent.
The amount of divinylbenzene can be up to 85 weight percent, up to
80 weight percent, up to 75 weight percent, up to 70 weight
percent, or up to 65 weight percent. For example, the
divinylbenzene can be in a range of 30 to 85 weight percent, 30 to
80 weight percent, 30 to 75 weight percent, 30 to 70 weight
percent, 30 to 60 weight percent, 30 to 55 weight percent, 30 to 50
weight percent, 40 to 80 weight percent, 50 to 80 weight percent,
40 to 75 weight percent, 50 to 75 weight percent, or 55 to 75
weight percent. The amounts are based on the total weight of
monomers in the monomer mixture.
[0075] Stated differently, the polymeric material contains 30 to 85
weight percent of monomeric units derived from divinylbenzene. The
amount of the monomeric unit derived from divinylbenzene can be,
for example, in a range of 30 to 80 weight percent, 30 to 75 weight
percent, 30 to 70 weight percent, 30 to 60 weight percent, 30 to 55
weight percent, 30 to 50 weight percent, 40 to 80 weight percent,
50 to 80 weight percent, 40 to 75 weight percent, 50 to 75 weight
percent, or 55 to 75 weight percent. The amounts are based on the
total weight of the polymeric material.
[0076] Divinylbenzene can be difficult to obtain in a pure form.
For example, divinylbenzene is often commercially available with
purity as low as 55 weight percent. Obtaining divinylbenzene with
purity greater than about 80 weight percent can be expensive. The
impurities accompanying divinylbenzene are typically styrene-type
monomers such as styrene, alkyl substituted styrene (e.g., ethyl
styrene), or mixtures thereof. Thus, styrene-type monomers are
often present in the monomer mixture along with divinylbenzene and
maleic anhydride. The monomer mixture typically contains 0 to 40
weight percent (or 5 to 40 weight percent) styrene-type monomers
based on a total weight of monomers in the monomer mixture. If the
content of the styrene-type monomer is greater than 40 weight
percent, the crosslink density may be too low and/or the distance
between crosslinks may be too large to provide a polymeric material
with the desired BET specific surface area. This is particularly
the situation if the polymeric material is fully hydrolyzed. As the
crosslink density decreases, the resulting polymeric material tends
to be less rigid and less porous.
[0077] In some embodiments, the amount of styrene-type monomers is
at least 1 weight percent, at least 2 weight percent, at least 5
weight percent, or at least 10 weight percent. The amount of
styrene-type monomer can be up to 40 weight percent, up to 35
weight percent, up to 30 weight percent, or up to 25 weight
percent. For example, the amount of styrene-type monomer in the
monomer mixture can be in a range of 0 to 40 weight percent, 1 to
40 weight percent, 5 to 40 weight percent, 1 to 30 weight percent,
5 to 30 weight percent, 1 to 20 weight percent, 5 to 20 weight
percent, 5 to 15 weight percent, 10 to 40 weight percent, or 10 to
30 weight percent. The amounts are based on the total weight of
monomers in the monomer mixture.
[0078] Stated differently, the polymeric material can contain 0 to
40 weight percent of monomeric units derived from styrene-type
monomers. For example, the amount can be in a range of 1 to 40
weight percent, 5 to 40 weight percent, 1 to 30 weight percent, 5
to 30 weight percent, 1 to 20 weight percent, 5 to 20 weight
percent, 5 to 15 weight percent, 10 to 40 weight percent, or 10 to
30 weight percent. The amounts are based on the total weight of the
polymeric material.
[0079] Overall, the monomer mixture includes 15 to 65 weight
percent maleic anhydride based on a total weight of monomers in the
monomer mixture, 30 to 85 weight percent divinylbenzene based on
the total weight of monomers in the monomer mixture, and 0 to 40
weight percent (or 5 to 40 weight percent) styrene-type monomer
based on the total weight of monomers in the monomer mixture. In
other embodiments, the monomer mixture contains 25 to 60 weight
percent maleic anhydride, 30 to 75 weight percent divinylbenzene,
and 1 to 30 weight percent styrene-type monomer. In other
embodiments, the monomer mixture contains 30 to 60 weight percent
maleic anhydride, 30 to 60 weight percent divinylbenzene, and 5 to
20 weight percent styrene-type monomer. In still other embodiments,
the monomer mixture contains 40 to 60 weight percent maleic
anhydride, 30 to 50 weight percent divinylbenzene, and 5 to 15
weight percent styrene-type monomer.
[0080] The monomer mixture typically contains at least 95 weight
percent monomers selected from maleic anhydride, divinylbenzene,
and styrene-type monomer. For example, at least 97 weight percent,
at least 98 weight percent, at least 99 weight percent, at least
99.5 weight percent, or at least 99.9 weight percent of the
monomers in the monomer mixture are selected from maleic anhydride,
divinylbenzene, and styrene-type monomer. In many embodiments, the
only monomers purposefully added to the monomer mixture are maleic
anhydride and divinylbenzene with any other monomers being present
(including the styrene-type monomers) as impurities in the maleic
anhydride and the divinylbenzene.
[0081] That is, the polymeric material typically contains 15 to 65
weight percent monomeric units derived from maleic anhydride, 30 to
85 weight percent monomeric units derived from divinylbenzene, and
0 to 40 weight percent (or 5 to 40 weight percent) monomeric units
derived from styrene-type monomers. In other embodiments, the
polymeric material contains 25 to 60 weight percent monomeric units
derived from maleic anhydride, 30 to 75 weight percent monomeric
units derived from divinylbenzene, and 1 to 30 weight percent (or
10 to 30 weight percent) monomeric units derived from styrene-type
monomers. In other embodiments, the polymeric material contains 30
to 60 weight percent monomeric units derived from maleic anhydride,
30 to 65 weight percent monomeric units derived from
divinylbenzene, and 5 to 20 weight percent (or 10 to 20 weight
percent) monomeric units derived from styrene-type monomer. In
still other embodiments, the polymeric material contains 40 to 60
weight percent monomeric units derived from maleic anhydride, 30 to
55 weight percent monomeric units derived from divinylbenzene, and
5 to 20 weight percent (or 10 to 20 weight percent) monomeric units
derived from styrene-type monomers.
[0082] In addition to the monomer mixture, the polymerizable
composition used to form the non-hydrolyzed divinylbenzene/maleic
anhydride polymeric material includes an organic solvent. The
polymerizable composition is a single phase prior to
polymerization. Stated differently, prior to polymerization, the
polymerizable composition is not a suspension. The organic solvent
is selected to dissolve the monomers included in the monomer
mixture and to solubilize the polymeric material as it begins to
form.
[0083] The organic solvent can function as a porogen as the
divinylbenzene/maleic anhydride polymeric material is formed. The
organic solvent choice can strongly influence the BET specific
surface area and the size of the pores formed in the non-hydrolyzed
polymeric material. Using organic solvents that are miscible with
both the monomers and the forming polymer tend to result in the
formation of polymeric material having micropores and mesopores.
Good solvents for the monomers and the forming polymer tend to
result in a larger fraction of the porosity of the final polymeric
material being in the form of micropores and mesopores.
[0084] Organic solvents that can dissolve both the monomers and the
forming polymeric material include, but are not limited to,
ketones, esters, acetonitrile, and mixtures thereof. Other organic
solvents can be added along with one or more of these organic
solvents to provide that the resulting polymeric material (before
any hydrolysis) exhibits a BET specific surface area of e.g. at
least 100 m.sup.2/gram. Examples of suitable ketones include, but
are not limited to, alkyl ketones such as methyl ethyl ketone and
methyl isobutyl ketone. Examples of suitable esters include, but
are not limited to, acetate esters such as ethyl acetate, propyl
acetate, butyl acetate, amyl acetate, and tert-butyl acetate.
[0085] The organic solvent can be used in any desired amount. The
polymerizable compositions often have percent solids in a range of
1 to 70 weight percent. If the percent solids are too low, the
polymerization time may become undesirably long. The percent solids
are often at least 1 weight percent, at least 2 weight percent, at
least 5 weight percent, at least 10 weight percent, or at least 15
weight percent. If the percent solids are too great, however, the
monomers do not form a single phase with the organic solvent.
Further, increasing the percent solids tends to result in the
formation of larger diameter pores and as a result the polymeric
material tends to have a lower BET specific surface area. The
percent solids can be up to 70 weight percent, up to 65 weight
percent, up to 60 weight percent, up to 50 weight percent, up to 40
weight percent, up to 30 weight percent, or up to 25 weight
percent. For example, the percent solids can be in a range of 5 to
70 weight percent, 5 to 60 weight percent, 10 to 60 weight percent,
20 to 60 weight percent, or 25 to 50 weight percent.
[0086] In addition to the monomer mixture and organic solvent, the
polymerizable compositions typically include an initiator for free
radical polymerization reactions. Any suitable free radical
initiator can be used. Suitable free radical initiators are
typically selected to be miscible with the monomers included in the
polymerizable composition. In some embodiments, the free radical
initiator is a thermal initiator that can be activated at a
temperature above room temperature (defined herein as 20-25.degree.
C.). In other embodiments, the free radical initiator is a redox
initiator. Because the polymerization reaction is a free radical
reaction, it is desirable to minimize the amount of oxygen in the
polymerizable composition.
[0087] Both the type and amount of initiator can affect the
polymerization rate. In general, increasing the amount of the
initiator tends to lower the BET specific surface area; however, if
the amount of initiator is too low, it may be difficult to obtain
high conversions of the monomers to polymeric material. The free
radical initiator is typically present in an amount in a range of
0.05 to 10 weight percent, 0.05 to 8 weight percent, 0.05 to 5
weight percent, 0.1 to 10 weight percent, 0.1 to 8 weight percent,
0.1 to 5 weight percent, 0.5 to 10 weight percent, 0.5 to 8 weight
percent, 0.5 to 5 weight percent, 1 to 10 weight percent, 1 to 8
weight percent, or 1 to 5 weight percent. The weight percent is
based on a total weight of monomers in the polymerizable
composition. Suitable thermal initiators include organic peroxides,
azo compounds, and redox initiators. Potentially useful thermal
initiators are listed and discussed in detail in International
(PCT) Application No. PCT/US2016/030974 and in U.S. Provisional
Patent Application No. 62/298,089, both of which are incorporated
by reference herein.
[0088] The polymerizable composition is typically free or
substantially free of surfactants. As used herein, the term
"substantially free" in reference to the surfactant means that no
surfactant is purposefully added to the polymerizable composition
and any surfactant that may be present is the result of being an
impurity in one of the components of the polymerizable composition
(e.g., an impurity in the organic solvent or in one of the
monomers). The polymerizable composition typically contains less
than 0.5 weight percent, less than 0.3 weight percent, less than
0.2 weight percent, less than 0.1 weight percent, less than 0.05
weight percent, or less than 0.01 weight percent surfactant based
on the total weight of the polymerizable composition. The absence
of a surfactant is advantageous because these materials tend to
restrict access to and, in some cases, fill micropores and
mesopores in a porous material. The presence of a surfactant could
reduce the capacity of the metal-containing polymeric material to
adsorb low molecular weight basic molecules.
[0089] When the polymerizable composition is heated in the presence
of a free radical initiator, polymerization of the monomers in the
monomer mixture occurs. By balancing the amounts of each monomer in
the monomer mixture and by selection of an organic solvent that can
solubilize all of the monomers and the growing polymeric material
during its early formation stage, a non-hydrolyzed polymeric
material can be prepared that exhibits a BET specific surface area
equal to at least 100 m.sup.2/gram. In various embodiments, the BET
specific surface area of the non-hydrolyzed polymer can be at least
150 m.sup.2/gram, at least 200 m.sup.2/gram, at least 250
m.sup.2/gram, or at least 300 m.sup.2/gram. The BET specific
surface area can be, for example, up to 1000 m.sup.2/gram or
higher, up to 900 m.sup.2/gram, up to 800 m.sup.2/gram, up to 750
m.sup.2/gram, or up to 700 m.sup.2/gram.
[0090] The high BET specific surface area is at least partially
attributable to the presence of micropores and/or mesopores in the
non-hydrolyzed divinylbenzene/maleic anhydride polymeric material.
The argon adsorption isotherms of the non-hydrolyzed
divinylbenzene/maleic anhydride polymeric materials indicate that
there is considerable adsorption at relative pressures below 0.1,
which suggests that micropores are present. There is an increase in
adsorption at higher relative pressures up to about 0.95. This
increase is indicative of a wide distribution of mesopores. In some
embodiments, at least 20 percent of the BET specific surface area
is attributable to the presence of micropores and/or mesopores. The
percentage of the BET specific surface area attributable to the
presence of micropores and/or mesopores can be at least 25 percent,
at least 30 percent, at least 40 percent, at least 50 percent, or
at least 60 percent. In some embodiments, the percentage of the BET
specific surface area attributable to the presence of micropores
and/or mesopores can be up to 90 percent or higher, up to 80
percent or higher, or up to 75 percent or higher.
[0091] The non-hydrolyzed divinylbenzene/maleic anhydride polymeric
material may be particular (e.g. granular) as formed and if desired
can be used directly as the polymeric material used to incorporate
a divalent metal forming the metal-containing polymeric material.
Alternatively, the non-hydrolyzed polymeric material can be treated
with a hydrolyzing agent to provide a partially or fully hydrolyzed
divinylbenzene/maleic anhydride polymeric material. The hydrolyzing
agent reacts with the maleic anhydride units resulting in the
formation of two carboxylic acid groups (--COOH groups). Any
suitable hydrolyzing agent can be used that can react with the
anhydride group (--(CO)--O--(CO)--) of the maleic anhydride units.
In many embodiments, the hydrolyzing agent is a base such as a
basic material dissolved in water. One exemplary basic material is
an alkali metal hydroxide such as sodium hydroxide (e.g., an
aqueous solution of sodium hydroxide). Alternatively, the
hydrolyzing agent could be water alone at elevated temperatures
(e.g., above room temperature to boiling) or a dilute acid at
slightly elevated temperatures (e.g., above room temperature to
about 80.degree. C.). In many embodiments, the preferred
hydrolyzing agent is a base such as an alkali metal hydroxide. The
non-hydrolyzed divinylbenzene/maleic anhydride polymeric material
is mixed with a solution of alkali metal hydroxide dissolved in
water or an alcohol such as methanol. The mixture is heated at a
temperature near 80.degree. C. for several hours (e.g., 4 to 12
hours). The hydrolyzed polymeric material can then be treated with
hydrochloric acid to convert any carboxylate salts to carboxylic
acid groups.
[0092] Stated in terms of the monomeric units present in the
non-hydrolyzed, partially hydrolyzed, or fully hydrolyzed anhydride
polymeric material, the polymeric material contains i) 15 to 65
weight percent of a first monomeric unit that is of Formula
(I),
##STR00003##
Formula (II),
##STR00004##
[0093] or a mixture thereof; ii) 30 to 85 weight percent of a
second monomeric unit that is of Formula (III); and
##STR00005##
iii) 0 to 40 weight percent (or 5 to 40 weight percent) of a third
monomeric unit that is of Formula (IV)
##STR00006##
wherein R.sup.1 is hydrogen or alkyl. Formula (I) corresponds to a
non-hydrolyzed monomeric unit derived from maleic anhydride. This
non-hydrolyzed monomeric unit contains an anhydride group
(--(CO)--O--(CO)--). Formula (II) corresponds to a hydrolyzed
monomeric unit derived from maleic anhydride. The hydrolyzed
monomeric unit has two carboxylic acid groups (--(CO)OH) rather
than an anhydride group. Formula (III) corresponds to a monomeric
unit derived from divinylbenzene. The two alkylene groups attached
to the aromatic ring can be in a meta- or para-position to each
other. Formula (IV) is for a styrene-type monomeric unit. The group
R.sup.1 is hydrogen or an alkyl (e.g., an alkyl with 1 to 4 carbon
atoms or 2 carbon atoms). In many embodiments R.sup.1 is ethyl and
the monomeric unit of Formula (IV) is derived from ethyl styrene,
an impurity often present in divinylbenzene. The R.sup.1 group is
often in a meta- or para-position relative to the alkylene group
attached to the aromatic ring. Each asterisk (*) in Formulas (I) to
(IV) indicates the attachment site to another monomeric unit or to
a terminal group in the polymeric material. The amounts of each of
the first, second, and third monomeric units are the same as
described above for the amounts of each monomer used to form the
non-hydrolyzed divinylbenzene/maleic anhydride polymeric
material.
[0094] If either partially or fully hydrolyzed, the polymeric
material contains carboxylic acid groups. If the pH is sufficiently
high, the polymeric material can be negatively charged. Typically,
the polymeric material itself does not have any positively charged
groups.
[0095] The hydrolyzed (e.g., fully hydrolyzed)
divinylbenzene/maleic anhydride polymeric material has a BET
specific surface area less than that of the non-hydrolyzed
divinylbenzene/maleic anhydride polymeric material. The opening of
the anhydride group may sufficiently increase the conformational
freedom in the backbone resulting in decreased porosity. In
addition, hydrogen bonding between carboxylic acids in the
hydrolyzed material may possibly restrict or block access to pores.
The BET specific surface area of the hydrolyzed polymeric material
is often about 30 to 80 percent, 30 to 60 percent, 40 to 80
percent, or 40 to 60 percent of the BET specific surface area of
the non-hydrolyzed polymeric material. Because of this decrease, it
is often desirable to prepare a non-hydrolyzed
divinylbenzene/maleic anhydride polymeric material having the
highest possible BET specific surface area yet having sufficient
maleic anhydride units to allow adequate incorporation of the
divalent metal.
[0096] The hydrolyzed (e.g., fully hydrolyzed)
divinylbenzene/maleic anhydride polymeric material typically
exhibits a BET specific surface area equal to at least 50
m.sup.2/gram, or at least 100 m.sup.2/gram. In some embodiments,
the BET specific surface area is at least 150 m.sup.2/gram, at
least 175 m.sup.2/gram, at least 200 m.sup.2/gram, at least 225
m.sup.2/gram, at least 250 m.sup.2/gram, or at least 300
m.sup.2/gram. The BET specific surface area can be up to 600
m.sup.2/gram or higher, up to 500 m.sup.2/gram, or up to 400
m.sup.2/gram. In some embodiments, the BET specific surface area is
in a range of 50 to 600 m.sup.2/gram, in a range of 75 to 600
m.sup.2/gram, in a range of 100 to 600 m.sup.2/gram, or in a range
of 200 to 600 m.sup.2/gram.
[0097] The argon adsorption isotherms of the hydrolyzed (e.g.,
fully hydrolyzed) divinylbenzene/maleic anhydride polymeric
materials indicate that there is some adsorption at relative
pressures below 0.1, which suggests that micropores are present.
There is an increase in adsorption at higher relative pressures up
to about 0.95. This increase is indicative of a wide distribution
of mesopores. In some embodiments, at least 20 percent of the BET
specific surface area is attributable to the presence of micropores
and/or mesopores. The percentage of the BET specific surface area
attributable to the presence of micropores and/or mesopores can be
at least 25 percent, at least 30 percent, at least 40 percent, at
least 50 percent, or at least 60 percent. In some embodiments, the
percentage of the BET specific surface area attributable to the
presence of micropores and/or mesopores can be up to 90 percent or
higher, up to 80 percent, or higher, or up to 75 percent or higher.
In many embodiments, the BET specific surface area is attributable
mainly to the presence of mesopores.
[0098] After formation of the polymeric material (i.e.,
non-hydrolyzed, partially hydrolyzed, or fully hydrolyzed
divinylbenzene/maleic anhydride polymeric material), a divalent
metal is incorporated into the polymeric material. The divalent
metal is typically incorporated by treating the polymeric material
with a solution of a metal salt dissolved in water. The metal salt
contains a cation that is the divalent metal (i.e., a metal with a
+2 oxidation state) and an anion. Suitable metal ions (divalent
metals) are typically from Group 2 or Groups 6 to 12 of the
periodic table. Example divalent metals include, but are not
limited to, chromium, nickel, cobalt, copper, zinc, manganese,
cadmium, iron, magnesium, calcium, barium, or a mixture thereof. In
many embodiments, the divalent metal is a Group 6 to 12 metal such
as, for example, chromium, nickel, cobalt, copper, zinc, iron, or a
mixture thereof. In some particular embodiments, the divalent metal
is copper, cobalt, zinc, or nickel. In some even more particular
embodiments, the divalent metal is zinc or copper. It will be
understood that by a divalent metal is meant at least one divalent
metal; mixtures of any of the above divalent metals can thus be
used.
[0099] The metal salts are typically selected from those that are
soluble in water. The anion of the metal salt is often a halide
(e.g., chloride), nitrate, sulfate, carboxylate (e.g., acetate,
formate, and propanoate), or halogen-substituted carboxylates
(e.g., chloroacetate, dichloroacetate, and chloro-substituted
propanoate). In many embodiments, the anion is chloride, acetate,
or nitrate.
[0100] Examples of specific metal salts include, but are not
limited to, zinc acetate, copper acetate, nickel acetate, cobalt
acetate, iron acetate, manganese acetate, chromium acetate, cadmium
acetate, zinc formate, copper formate, nickel formate, cobalt
formate, iron formate, manganese formate, cadmium formate, zinc
propanoate, copper propanoate, nickel propanoate, cobalt
propanoate, iron propanoate, manganese propanoate, cadmium
propanoate, zinc chloroacetate, copper chloroacetate, nickel
chloroacetate, cobalt chloroacetate, iron chloroacetate, manganese
chloroacetate, cadmium chloroacetate, zinc dichloroacetate, copper
dichloroacetate, nickel dichloroacetate, cobalt dichloroacetate,
iron dichloroacetate, manganese dichloroacetate, cadmium
dichloroacetate, zinc chloride, copper chloride, nickel chloride,
cobalt chloride, iron chloride, manganese chloride, cadmium
chloride, chromium chloride, magnesium chloride, zinc sulfate,
copper sulfate, nickel sulfate, cobalt sulfate, iron sulfate,
manganese sulfate, cadmium sulfate, zinc nitrate, copper nitrate,
nickel nitrate, cobalt nitrate, iron nitrate, and the like.
Mixtures of any of these may be used if desired.
[0101] The divalent metal is typically incorporated by treating the
polymeric material with a solution of the metal salt dissolved in
water. The concentrations of the metal salt solutions are often in
a range of 0.1 to 10 moles/liter. In some embodiments, the
concentration is in a range of 0.5 to 10 moles/liter, in a range of
1 to 10 moles/liter, in a range of 1 to 8 moles/liter, in a range
of 2 to 8 moles/liter, or in a range of 3 to 6 moles/liter. The
resulting solution is mixed with the polymeric material. The amount
of metal salt is typically added such that the moles of divalent
metal are in excess compared to the moles of anhydride, carboxyl
groups (--COOH groups), or both in the polymeric material.
[0102] The mixing time of the metal salt solution with the
polymeric material is often up to 1 hour, up to 2 hours, up to 4
hours, up to 8 hours, up to 16 hours, up to 24 hours, or up to 48
hours. The mixing temperature can be at room temperature or above.
The metal-containing polymeric material is then separated from the
water and dried. Any suitable method of drying can be used. In some
embodiments, the metal-containing polymeric material is dried under
vacuum in an oven set at 80.degree. C. to 120.degree. C. The
process of incorporation of the divalent metal into non-hydrolyzed
polymeric material or partially hydrolyzed polymeric materials may
result in some hydrolysis or further hydrolysis of at least a
portion of the anhydride groups.
[0103] In some embodiments, the resulting metal-containing
polymeric material contains at least 10 weight percent of the
divalent metal based on a total weight of the polymeric material.
The amount of the divalent metal can be at least 15 weight percent,
at least 20 weight percent, at least 25 weight percent, at least 30
weight percent, at least 40 weight percent, or at least 50 weight
percent based on a total weight of the polymeric material. The
metal-containing polymeric material can include up to 100 weight
percent or more of the divalent metal (i.e., the weight of the
divalent metal can be equal to or exceed the weight of the
polymeric material). For example, the amount can be up to 90 weight
percent, up to 80 weight percent, up to 75 weight percent, up to 70
weight percent, up to 60 weight percent, or up to 50 weight percent
based on the total weight of the polymeric material. For example,
the amount is often in a range of 10 to 100 weight percent, 10 to
80 weight percent, 10 to 60 weight percent, 10 to 50 weight
percent, 10 to 40 weight percent, 10 to 30 weight percent, 15 to 60
weight percent, 15 to 50 weight percent, 15 to 40 weigh percent, 15
to 30 weight percent, 20 to 60 weight percent, 20 to 50 weight
percent, 20 to 40 weight percent or 20 to 30 weight percent.
[0104] In other embodiments or stated differently, the resulting
metal-containing polymeric material contains at least 1.5 mmoles
(millimoles) of the divalent metal per gram of the polymeric
material. The amount of the divalent metal can be at least 2.0
mmoles, at least 2.25 mmoles, at least 3.0 mmoles, at least 3.75
mmoles, at least 4.0 mmoles, at least 4.5 mmoles, at least 5
mmoles, at least 6.0 mmoles, at least 7 mmoles, or at least 7.5
mmoles per gram of the polymeric material. The metal-containing
polymeric material can include up to 15 mmoles or more of the
divalent metal per gram. For example, the amount can be up to 14
mmoles, up to 13.5 mmoles, up to 13 mmoles, up to 12 mmoles, up to
11.25 mmoles, up to 11 mmoles, up to 10.5 mmoles, up to 10 mmoles,
up to 9 mmoles, up to 8 mmoles, or up to 7.5 mmoles per gram of the
polymeric material. For example, the amount is often in a range of
1.5 to 15 mmoles, 1.5 to 12 mmoles, 1.5 to 9 mmoles, 1.5 to 7.5
mmoles, 1.5 to 6 mmoles, 1.5 to 4.5 mmoles, 2.25 to 9 mmoles, 2.25
to 7.5 mmoles, 2.25 to 6 mmoles, 2.25 to 5 mmoles, 2.25 to 4.5
mmoles, 3.0 to 9 mmoles, 3.0 to 7.5 mmoles, 3.0 to 6 mmoles, or 3.0
to 4.5 mmoles per gram of the polymeric material.
[0105] In summary, the metal-containing polymeric material includes
a) a polymeric material and b) a divalent metal incorporated into
(i.e., sorbed on) the polymeric material in an amount equal to at
least 10 weight percent based on the weight of the polymeric
material (or at least 1.5 mmoles per gram of the polymeric
material). The polymeric material contains i) 15 to 65 weight
percent of a first monomeric unit that is of Formula (I),
##STR00007##
Formula (II),
##STR00008##
[0106] or a mixture thereof; ii) 30 to 85 weight percent of a
second monomeric unit that is of Formula (III); and
##STR00009##
iii) 0 to 40 weight percent (or 5 to 40 weight percent) of a third
monomeric unit that is of Formula (IV)
##STR00010##
wherein R.sup.1 is hydrogen or alkyl.
[0107] In some embodiments, the metal-containing polymeric material
further includes an acid-base indicator. The acid-base colorimetric
indicator (i.e., a dye (typically an organic dye) that changes
color when it undergoes a transition from being in an acidic form
to being in a basic form) is often added at the same time as the
divalent metal. The acid-base colorimetric indicator is typically
selected such that the basicity of the nitrogen-containing compound
being sorbed is sufficient to shift the acid-base colorimetric
indicator from its acidic form to its basic form.
[0108] A further consideration in the selection of the appropriate
acid-base colorimetric indicator involves choosing an acid-base
indicator that has a sufficiently lower affinity for the
nitrogen-containing compound than the divalent metal such that the
acid-base indicator does not change color until all or nearly all
of the nitrogen-containing compound sorptive capacity of the
divalent metal is exhausted. That is, the acid-base colorimetric
indicator is selected to change from a first color to a second
color when all or a significant portion of the available divalent
metal atoms have had their sorptive capacity for
nitrogen-containing compounds exhausted. The change in color then
signals that the capacity of the polymeric sorbent for sorption of
nitrogen-containing compounds has been reached or is close to being
reached. As used herein, the term "close to being reached" means
that at least 60 percent or more of the capacity has been reached
(i.e., a least 60 percent or more of the available sorption sites
have been used for sorption of a nitrogen-containing compound). For
example, at least 70 percent, at least 80 percent, at least 90
percent, or at least 95 percent of the sorption sites have been
used for sorption of a nitrogen-containing compound.
[0109] A final consideration in selecting an acid-base colorimetric
indicator involves taking into account the color inherent to the
metal-containing polymeric material. Some divalent metals when
incorporated into the porous polymeric material impart the
resulting metal-containing polymeric material with a color (i.e.,
ZnCl.sub.2 metal-containing polymeric material is pink, CuCl.sub.2
metal-containing polymeric material is dark gray/green and the
NiCl.sub.2 metal-containing polymeric material is tan). Selection
of an acid-base colorimetric indicator whose color change from its
acidic form to its basic form is obvious in light of the color
change that may be inherent from the metal-containing polymeric
material itself can be important. It can be advantageous to add an
acid-base indicator even to metal-containing polymeric materials
which inherently undergo a color change upon sorption of
nitrogen-containing compounds in order to access a wider range of
colors for the colorimetric indication, and in some cases, to
mitigate the moisture sensitivity of the color shift of some
metal-containing polymeric materials.
[0110] Example acid-base colorimetric indicators include, but are
not limited to, methyl red, bromoxylenol blue, pararosaniline,
chrysoidine, thymol blue, methyl yellow, bromophenyl blue, Congo
red, methyl orange, bromocresol green, azolitmin, bromocresol
purple, bromothymol blue, phenol red, neutral red,
naphtholphthalein, cresol red, phenolphthalein, and
thymolphthalein. The acid-base colorimetric indicators can be added
to the polymeric sorbent using any suitable method. In some
embodiments, the polymeric sorbent is soaked in a solution of the
acid-base colorimetric indicator for at least 10 minutes, at least
20 minutes, at least 30 minutes, at least 1 hour, at least 2 hours,
at least 4 hours, or at least 8 hours. The solution of the
acid-base colorimetric indicator is often in a concentration range
of 1 to 10 milligrams per milliliter. Often, about 0.5 grams of the
polymeric sorbent is soaked in about 10 milliliters of the
solution.
[0111] Although the polymeric material can be non-hydrolyzed,
partially hydrolyzed, or fully hydrolyzed, in some applications it
may be preferable to use fully hydrolyzed polymeric material. The
hydrolyzed polymeric material may perform more consistently than
either the non-hydrolyzed or partially hydrolyzed polymeric
materials because such materials may change with time (i.e., they
have a tendency to undergo hydrolysis or further hydrolysis that
may alter their performance characteristics).
[0112] In some embodiments such as with zinc-containing,
cobalt-containing, nickel-containing, and magnesium-containing
polymeric materials, the divalent metal may be present as an ionic
species. For divalent metal that is ionic, a crystalline phase that
includes the metal species usually cannot be detected when the
metal-containing polymeric materials are analyzed using x-ray
diffraction. In other embodiments such as with copper-containing
polymeric materials, the divalent metal may be present as an oxide.
For metal oxides, a crystalline phase may be detected when the
metal-containing polymeric materials are analyzed using x-ray
diffraction.
[0113] When analyzed using infrared spectroscopy, a shift in the
carbonyl peak can be observed for the polymeric material after
incorporation of the divalent metal. While not wanting to be bound
by theory, it is believed that the divalent metal may be associated
with (i.e., the metal may interact with or may coordinate with) the
carboxyl groups or anhydride groups in the polymeric material.
[0114] Some of the metal-containing polymeric materials can be
colored. Some colored examples include, but are not limited to,
those containing zinc (II), copper (II), and nickel (II). Zinc
containing-polymeric materials are often pink, copper-containing
polymeric materials are often a dark grayish-green, and
nickel-containing polymeric materials are often tan.
[0115] The metal-containing polymeric materials typically have a
lower BET specific surface area than the corresponding polymeric
material. The divalent metal resides in the pores of the polymeric
material resulting in a decrease in the BET specific surface area.
In many embodiments, the BET surface area of the porous polymeric
material after divalent metal impregnation, may be at least 15
m.sup.2/gram, at least 20 m.sup.2/gram, at least 25 m.sup.2/gram,
at least 30 m.sup.2/gram, at least 40 m.sup.2/gram, or at least 50
m.sup.2/gram.
[0116] After formation and drying and being deposited on any
desired filter support by any suitable method, the
metal-containing, porous polymeric material, provided in the form
of sorbent particles supported by a filter support, can be used to
capture airborne basic, nitrogen-containing compounds. Thus, a
method of capturing basic, nitrogen-containing compounds from air
is provided. The method includes providing the metal-containing
polymeric material as described herein and then exposing the
metal-containing polymeric material to air that potentially
includes a basic, nitrogen-containing compound of formula Q e.g. in
gaseous or vaporous form. A metal complex is formed. The metal
complex includes the reaction product of the divalent metal as
defined above and at least one compound of formula Q.
[0117] The basic nitrogen-containing compounds of formula Q that
react with the divalent metal to form a metal complex can be
classified as Lewis bases, Bronsted-Lowry bases, or both. Suitable
basic nitrogen-containing compounds often have a low molecular
weight (e.g., no greater than 150 grams/mole). That is, the basic,
nitrogen-containing compounds can be volatile at or near room
temperature or can be volatile under conditions of use. Examples of
basic, nitrogen-containing compounds include, but are not limited
to, ammonia, hydrazine compounds, amine compounds (e.g., alkyl
amines, dialkylamines, triaalkylamines, alkanolamines, alkylene
diamines, arylamines), and nitrogen-containing heterocyclic
(saturated and unsaturated) compounds. Specific basic
nitrogen-containing compounds include, for example, ammonia,
hydrazine, methylhydrazine, methylamine, dimethylamine,
trimethylamine, ethylamine, diethylamine, triethylamine,
propylamine, dipropylamine, tripropylamine, isopropylamine,
diisopropylamine, triisopropylamine, ethanolamine, cyclohexylamine,
morpholine, pyridine, benzylamine, phenylhydrazine, ethylene
diamine, and 1,3-propane diamine.
[0118] After exposure to gases or vapors of the basic,
nitrogen-containing compound, the metal-containing polymeric
material is converted to a metal complex-containing polymeric
material. The metal complex-containing polymeric material includes
a) a polymeric material and b) a metal complex incorporated into
(i.e., sorbed on) the polymeric material. The polymeric material
contains i) 15 to 65 weight percent of a first monomeric unit that
is of Formula (I),
##STR00011##
Formula (II),
##STR00012##
[0119] or a mixture thereof; ii) 30 to 85 weight percent of a
second monomeric unit that is of Formula (III); and
##STR00013##
iii) 0 to 40 weight percent (or 5 to 40 weight percent) of a third
monomeric unit that is of Formula (IV)
##STR00014##
wherein R.sup.1 is hydrogen or alkyl. The metal complex includes a
reaction product of a divalent metal and at least one basic,
nitrogen-containing compound.
[0120] In many embodiments of the metal complex-containing
polymeric material, divalent metal incorporated into the polymeric
material remains that has not been converted to a metal complex.
That is, the metal complex-containing polymeric material includes a
mixture of divalent metal that is not complexed with the basic,
nitrogen-containing compound and divalent metal that is complexed
with at least one basic, nitrogen-containing compound.
[0121] The total amount of divalent metal (whether it is complexed
or not with the basic, nitrogen-containing compound) is at least 10
weight percent based on a total weight of the polymeric material.
The total amount of the divalent metal can be at least 20 weight
percent, at least 25 weight percent, at least 30 weight percent, at
least 40 weight percent, or at least 50 weight percent based on a
total weight of the polymeric material. The amount can be up to 100
weight percent or more. For example, the amount can be up to 90
weight percent, up to 80 weight percent, up to 75 weight percent,
up to 70 weight percent, up to 60 weight percent, or up to 50
weight percent based on the total weight of the polymeric material.
For example, the amount is often in a range of 10 to 100 weight
percent, 10 to 80 weight percent, 10 to 60 weight percent, 10 to 50
weight percent, 10 to 40 weight percent, 10 to 30 weight percent,
15 to 60 weight percent, 15 to 50 weight percent, 15 to 40 weigh
percent, 15 to 30 weight percent, 20 to 60 weight percent, 20 to 50
weight percent, 20 to 40 weight percent or 20 to 30 weight
percent.
[0122] Stated differently, the total amount of divalent metal
(whether it is complexed or not with the basic, nitrogen-containing
compound) is at least at least 1.5 mmoles (millimoles) per gram of
the polymeric material. The total amount of the divalent metal can
be at least 2.0 mmoles, at least 2.25 mmoles, at least 3.0 mmoles,
at least 3.75 mmoles, at least 4.0 mmoles, at least 4.5 mmoles, at
least 5 mmoles, at least 6.0 mmoles, at least 7 mmoles, or at least
7.5 mmoles per gram of the polymeric material. The metal-containing
polymeric material can include up to 15 mmoles or more of the
divalent metal per gram. For example, the amount can be up to 14
mmoles, up to 13.5 mmoles, up to 13 mmoles, up to 12 mmoles, up to
11.25 mmoles, up to 11 mmoles, up to 10.5 mmoles, up to 10 mmoles,
up to 9 mmoles, up to 8 mmoles, or up to 7.5 mmoles per gram of the
polymeric material. For example, the amount is often in a range of
1.5 to 15 mmoles, 1.5 to 12 mmoles, 1.5 to 9 mmoles, 1.5 to 7.5
mmoles, 1.5 to 6 mmoles, 1.5 to 4.5 mmoles, 2.25 to 9 mmoles, 2.25
to 7.5 mmoles, 2.25 to 6 mmoles, 2.25 to 5 mmoles, 2.25 to 4.5
mmoles, 3.0 to 9 mmoles, 3.0 to 7.5 mmoles, 3.0 to 6 mmoles, or 3.0
to 4.5 mmoles per gram of the polymeric material.
[0123] The maximum amount of basic, nitrogen-containing compounds
sorbed (e.g., complexed) by the metal-containing polymeric material
is related to the amount of divalent metal incorporated into the
polymeric material. The maximum amount of basic,
nitrogen-containing compound sorbed is often at least 0.5
milliequivalents per gram of metal-containing polymeric material
(i.e., 0.5 milliequivalents of the sorbed basic,
nitrogen-containing compound per gram of metal-containing polymeric
material) and can be up to 10 milliequivalents per gram or even
higher. In many embodiments, the maximum amount sorbed is at least
1 milliequivalents per gram, at least 2 milliequivalents per gram,
or at least 3 milliequivalents per gram. The amount sorbed can be,
for example, up to 9 milliequivalents per gram, up to 8
milliequivalents per gram, up to 7 milliequivalents per gram, up to
6 milliequivalents per gram, or up to 5 milliequivalents per
gram.
[0124] Although the amount of divalent metal in the
metal-containing polymeric material is an important factor for
maximizing the capacity for sorption of basic, nitrogen-containing
compounds, an upper amount of divalent metal is reached beyond
which the capacity does not continue to increase. That is, beyond a
certain point, incorporating more divalent metal into the
metal-containing polymeric materials does not result in increased
capacity for basic, nitrogen-containing compounds. If the amount of
divalent metal incorporated is too large, the surface of the
polymeric material may become saturated with the divalent metal and
clustering and/or layering of the divalent metal may result. The
clustering and/or layering may lead to a decreased amount of the
divalent metal being available for coordination with (i.e.,
complexing with) the basic, nitrogen-containing compounds. Thus,
the amount of divalent metal incorporated into the polymeric
material can be optimized to obtain maximum sorption capacity for
the basic, nitrogen-containing compounds.
[0125] The porosity of the polymeric material also affects the
capacity of the metal-containing material for sorption of basic,
nitrogen-containing compounds. Typically, polymeric materials with
higher porosity have greater accessibility to functional group
sites. Higher porosity polymeric materials, probably due to the
presence of mesopores and/or micropores in the polymeric material,
typically lead to higher incorporation of divalent metal. Higher
incorporation of divalent metal (at least up the point where
clustering and/or layering occurs) results in more coordination
sites available for sorption of the basic, nitrogen-containing
compounds. The porosity and BET specific surface area of the
polymeric material can be altered by the amount of crosslinking
(i.e., the amount of divinylbenzene) used to prepare the polymeric
materials as well as the identity and amount of organic solvent
present during formation of the polymeric materials.
[0126] In some embodiments, only a portion of the divalent metal in
the metal-containing polymeric materials is complexed with the
basic, nitrogen-containing compound of formula Q. That is, the
maximum amount of Q is not sorbed. In this situation, the polymeric
materials contain both a metal complex and divalent metal that is
not complexed to the basic, nitrogen-containing compound.
[0127] Any method of capturing (i.e., sorbing) the basic,
nitrogen-containing compound of formula Q on the metal-containing
polymeric material can be used. In some embodiments, particularly
if the divalent metal in the metal-containing polymeric material is
selected from zinc, nickel, or copper, a color change occurs upon
exposure to a basic, nitrogen-containing compound. For example,
zinc-containing polymeric materials change from pink to tan,
copper-containing polymeric materials change from dark grayish
green to turquoise, and nickel-containing polymeric materials
change from tan to olive green upon exposure to basic,
nitrogen-containing compounds. This color change can be used to
indicate exposure to the basic, nitrogen-containing compounds. The
intensity of the color after exposure to the basic,
nitrogen-containing compound may be related to the amount of
exposure. It will be appreciated that even if such a color change
might occur with a divalent metal provided on an activated carbon
support upon being exposed to a basic compound, such a color change
may not have been previously appreciated since the dark color of
activated carbon will typically obscure any such subtle color
change of a divalent metal incorporated therein.
[0128] Metal-containing porous materials, methods of making such
materials, and methods of using such materials to capture basic,
nitrogen-containing compounds are described in detail in
International Application No. PCT/US2016/030974 and in U.S.
Provisional Patent Application No. 62/298,089, both entitled
Metal-Containing Polymeric Materials and both of which are
incorporated by reference herein in their entirety. In some
embodiments, sorbent particles that are supported on a filter
support as disclosed herein may comprise a binder. Such approaches
and arrangements are described in detail in U.S. Provisional Patent
Application No. 62/421,584, Attorney Docket Number 78842US002,
filed evendate herewith and entitled Composite Granules Including
Metal-Containing Polymeric Materials, which is incorporated by
reference herein in its entirety.
[0129] This application is a continuation of U.S. patent
application Ser. No. 16/349,673 (published as U.S. Patent
Application Publication No. 2019/0275454, and now allowed), which
was a national stage filing under 35 U.S.C. 371 of PCT Application
No. PCT/US2017/061258 (published as International Publication No.
WO2018/089877), which claimed priority to U.S. Provisional
Application No. 62/421,438, the disclosures of all of which are
incorporated by reference in their entirety herein.
List of Exemplary Embodiments
[0130] Embodiment 1 is an air filter comprising a filter support
that supports sorbent particles, wherein at least some of the
sorbent particles are porous and comprise a polymeric material
comprising: a) a polymer comprising i) 15 to 65 weight percent of a
first monomeric unit that is of Formula (I), Formula (II), or a
mixture thereof; ii) 30 to 85 weight percent of a second monomeric
unit that is of Formula (III); and iii) 0 to 40 weight percent (or
5 to 40 weight percent) of a third monomeric unit that is of
Formula (IV); wherein R.sup.1 is hydrogen or alkyl; and b) a
divalent metal incorporated into the polymeric material in an
amount equal to at least 1.5 mmoles per gram of the polymeric
material. Embodiment 2 is the air filter of embodiment 1 wherein
the filter support comprises a substrate with at least one major
surface with at least some of the porous polymeric sorbent
particles disposed thereon.
[0131] Embodiment 3 is the air filter of embodiment 2 wherein the
porous polymeric sorbent particles are present substantially as a
monolayer on the major surface of the substrate.
[0132] Embodiment 4 is the air filter of embodiment 1 wherein the
filter support comprises a porous, air-permeable material with
porous polymeric sorbent particles disposed on a major surface
thereof and/or with porous polymeric sorbent particles disposed
within the interior of the material at least in a location
proximate the major surface of the material.
[0133] Embodiment 5 is the air filter of embodiment 4 wherein
porous polymeric sorbent particles are disposed throughout the
interior of the porous, air-permeable material.
[0134] Embodiment 6 is the air filter of any of embodiments 1-5
wherein the air filter consists essentially of the filter
support.
[0135] Embodiment 7 is the air filter of any of embodiments 1-6
wherein the filter support comprises a sheet-like material that
exhibits a major plane and that exhibits a thickness of less than
about 3 mm and that is configured to allow airflow through the
filter support at least in a direction at least generally
perpendicular to the major plane of the sheet-like material.
[0136] Embodiment 8 is the air filter of any of embodiments 1-3 and
6-7 wherein the filter support comprises a netting with a major
surface with at least some porous polymeric sorbent particles
adhesively attached thereto.
[0137] Embodiment 9 is the air filter of any of embodiments 1-7
wherein the filter support comprises a fibrous web that exhibits an
interior and wherein the porous polymeric sorbent particles are
disposed within at least portions of the interior of the web.
[0138] Embodiment 10 is the air filter of embodiment 9 wherein the
porous polymeric sorbent particles are disposed throughout an
interior of the fibrous web.
[0139] Embodiment 11 is the air filter of any of embodiments 9-10
wherein the web is a nonwoven fibrous web.
[0140] Embodiment 12 is the air filter of embodiment 11 wherein the
nonwoven fibrous web is a meltblown web.
[0141] Embodiment 13 is the air filter of any of embodiments 9-12
wherein at least some fibers of the fibrous web are each bonded to
at least one porous polymeric sorbent particle.
[0142] Embodiment 14 is the air filter of any of embodiments 1-5
and 7-13 wherein the filter support is one layer of a multilayer,
air-permeable assembly.
[0143] Embodiment 15 is the air filter of embodiment 14 wherein the
multilayer air-permeable assembly includes at least one layer that
is not the same layer as the filter support and that is a
particle-filtration layer exhibiting a Percent Penetration of less
than 50.
[0144] Embodiment 16 is the air filter of embodiment 15 wherein the
particle-filtration layer comprises electret moities.
[0145] Embodiment 17 is the air filter of any of embodiments 1-14
wherein the filter support is a filter media that exhibits a
Percent Penetration of less than 50.
[0146] Embodiment 18 is the air filter of any of embodiments 1-17
wherein the filter support is pleated. Embodiment 19 is the air
filter of any of embodiments 1-18 wherein the air filter is a
framed air filter that is configured to be inserted into an air
filter receptacle of an air-handling apparatus chosen from the
group consisting of a forced air heating unit, a forced air cooling
unit, a forced-air heating/cooling unit, a room air purifier, and a
cabin air filtration unit for a motor vehicle.
[0147] Embodiment 20 is the air filter of any of embodiments 1, 6,
and 14-16 wherein the filter support comprises a honeycomb with
through-apertures within which sorbent particles are disposed.
[0148] Embodiment 21 is the air filter of any of embodiments 1-5
and 7-17 wherein the filter support provides a layer of a filtering
face-piece respirator.
[0149] Embodiment 22 is the air filter of embodiment 21 wherein the
filtering face-piece respirator is chosen from the group consisting
of flat-fold respirators and molded respirators.
[0150] Embodiment 23 is the air filter of embodiment 1 wherein the
filter support comprises a container with an interior within which
porous polymeric sorbent particles are disposed, and with at least
one air inlet and at least one air outlet.
[0151] Embodiment 24 is the air filter of embodiment 23 wherein the
filter support comprises a filter cartridge.
[0152] Embodiment 25 is the air filter of embodiment 24 wherein the
filter cartridge is configured to be used with a personal
protection device chosen from the group consisting of half-face
negative-pressure respirators, full-face negative-pressure
respirators, escape hoods, and powered air-purifying
respirators.
[0153] Embodiment 26 is the air filter of any of embodiments 1-25
wherein the porous sorbent particles are comprised of
non-hydrolyzed polymeric material and exhibit a BET specific
surface area of >100 m.sup.2/g, when measured in the absence of
divalent metal.
[0154] Embodiment 27 is the air filter of any of embodiments 1-26
wherein the porous sorbent particles are comprised of hydrolyzed
polymeric material and exhibit a BET specific surface area of
>50 m.sup.2/g, when measured in the absence of divalent
metal.
[0155] Embodiment 28 is the air filter of any of embodiments 1-27
wherein at least some of the porous sorbent particles are bound to
neighboring porous sorbent particles by a binder.
[0156] Embodiment 29 is a method of capturing at least some of a
basic, nitrogen-containing compounds having a molecular weight no
greater than 150 grams/mole from air, the method comprising:
positioning the air filter of any of embodiments 1-28 so that the
porous polymeric sorbent particles are exposed to the air; and,
sorbing at least some of the basic, nitrogen-containing compound
onto the porous polymeric sorbent particles.
[0157] Embodiment 30 is the method of embodiment 29, wherein the
filter support exhibits a major surface and wherein the air is
present in the form of an airstream moving in a direction that is
at least generally aligned with a plane of the major surface of the
filter support.
[0158] Embodiment 31 is the method of embodiment 29, wherein the
filter support allows airflow therethrough and wherein the air is
present in the form of an airstream that passes through at least a
portion the filter support in a direction at least generally
perpendicular to a major surface of the filter support.
[0159] Embodiment 32 is a method of making an air filter comprising
a filter support that comprises porous polymeric sorbent particles,
the method comprising: providing porous polymeric sorbent particles
that comprise a polymeric material comprising: a) a polymer
comprising i) 15 to 65 weight percent of a first monomeric unit
that is of Formula (I), Formula (II), or a mixture thereof; ii) 30
to 85 weight percent of a second monomeric unit that is of Formula
(III); and iii) 0 to 40 weight percent (or 5 to 40 weight percent)
of a third monomeric unit that is of Formula (IV); wherein R.sup.1
is hydrogen or alkyl; and b) a divalent metal incorporated into the
polymeric material in an amount equal to at least 1.5 mmoles per
gram of the polymeric material; and, supporting the porous
polymeric sorbent particles on a filter support.
[0160] Embodiment 33 is the air filter of any of embodiments 1-28,
wherein the air filter further comprises at least one secondary
sorbent.
[0161] Embodiment 34 is the air filter of embodiment 33, wherein
the at least one secondary sorbent comprised activated carbon.
[0162] Embodiment 35 is the air filter of any of embodiments 1-28
and 33-34, the polymeric sorbent further comprising an acid-base
dye.
[0163] In the above-listed Exemplary Embodiments, Formulas (I),
(II), (III) and (IV) are stipulated to be the materials with
structure as presented in the "Sorbent" portion of the Detailed
Description.
EXAMPLES
TABLE-US-00001 [0164] List of Materials Chemical Name Chemical
Supplier Aqueous boric acid solution (4 weight %) Sigma-Aldrich,
Milwaukee, WI Bromocresol green Sigma-Aldrich, Milwaukee, WI
Aqueous hydrogen chloride solution Sigma-Aldrich, Milwaukee, WI
(0.1M) Divinylbenzene (DVB) (80% technical Sigma-Aldrich,
Milwaukee, WI grade)* Maleic anhydride (MA) Alfa Aesar, Ward Hill,
MA Benzoyl peroxide (BPO) Sigma-Aldrich, Milwaukee, WI Ethyl
acetate (EtOAc) EMD Millipore Chemicals, Billerica, MA Sodium
hydroxide (NaOH) EMD Millipore Chemicals, Billerica, MA
Concentrated hydrogen chloride (HCl) EMD Millipore Chemicals,
Billerica, MA Zinc (II) chloride (ZnCl.sub.2), anhydrous, Alfa
Aesar, Ward Hill, MA 99.99% *Reported to contained 80 weight
percent DVB and 20 weight percent styrene-type monomers. The
calculation of moles of DVB used to prepare the polymeric material
does take into account the purity.
Procedures
Analysis and Characterization Procedures
[0165] Porosity and gas sorption experiments, and calculation of
parameters such as BET specific surface areas and pore volumes,
were performed in similar manner as described in the "Gas Sorption
Analysis" section of International Application No.
PCT/US2016/030974 and U.S. Provisional Patent Application No.
62/298,089, both entitled METAL-CONTAINING POLYMERIC MATERIALS and
both of which are incorporated by reference herein in their
entirety. (These applications are referred to below as the PCT'974
application and the US'089 application, respectively.) All pore
volumes reported in the Examples are measured at a relative
pressure (p/p.degree.) of approximately 0.98 unless otherwise
specified.
Ammonia Lifetime Cartridge Test
[0166] A simple flow-through custom-built delivery system was used
to deliver known concentrations of ammonia to the sample for
measurement. Stainless steel and poly(vinyl chloride) (PVC) tubing
was used throughout the delivery system. Ammonia was delivered to
the system from an anhydrous ammonia pressurized gas cylinder
(Oxygen Service Company, St. Paul, Minn., USA). The ammonia stream
was diluted with compressed air to deliver a 1000 ppm stream of
ammonia at a flow of 25.2 or 32 L/minute (LPM) to the test chamber.
The air flow rate was set using a 0-300 LPM TSI flowmeter (TSI,
Shoreview, Minn.). The ammonia concentration was determined by a
series of titrations. A 1 LPM flow of the challenge gas was pulled
into a 15 mL impinger and bubbled through a 4% by weight aqueous
boric acid solution. After about 15 minutes, the contents were
poured into a beaker and a few drops of bromocresol green were
added. 0.10 M hydrochloric acid was metered into the mixture until
the mixture turned from blue to yellow. The relative humidity (RH)
of the ammonia test was maintained at a constant set point using a
proportional integral derivative (PID) controller which detects the
% RH of the system and heats a water bath to raise the humidity if
it falls outside 0.2% of the desired % RH. The PID sensor was
calibrated with a Vaisala HMM1014A1AE humidity probe (Vaisala,
Vanta, Finland).
[0167] A cartridge was placed in a test chamber in line with the
system allowing the 1000 ppm ammonia gas stream to flow through the
cartridge. To the downstream side of the test chamber, tubing was
connected that led to a photoacoustic gas detector Innova 1412
(California Analytical, Orange, Calif.). At the time the ammonia
gas stream began to pass through the cartridge, the test was
considered started, and a timer was started. The Innova
photoacoustic gas detector sampled approximately every 50 seconds,
and the system was flushed between samples.
[0168] Prior to testing, a certified 57 ppm ammonia in nitrogen
pressurized gas cylinder (Oxygen Services Company, St. Paul, Minn.,
USA) was used to calibrate the photoacoustic gas detector. The
signal generated by this effluent was used to set the software to
50 ppm ammonia. The end point of the ammonia vapor test was defined
as the point corresponding to the time at which the ammonia
effluent passing through the bed of test material produced a signal
on the photoacoustic gas detector that exceeded the signal
corresponding to 50 ppm. The performance of each cartridge was
reported as the number of minutes until 50 ppm breakthrough was
observed performing the test as described above.
Ammonia Lifetime Disposable Respirator Test
[0169] A simple flow-through custom-built delivery system was used
to deliver known concentrations of ammonia to the disposable
respirator for measurement. Stainless steel and PVC tubing was used
throughout the delivery system. Ammonia was delivered to the system
from an anhydrous ammonia pressurized gas cylinder (Oxygen Service
Company, St. Paul, Minn., USA). The ammonia stream was diluted with
compressed air to deliver a 56 ppm stream of ammonia at a flow of
30 LPM to the test chamber. The air flow rate was set using a 0-300
LPM TSI flowmeter (TSI, Shoreview, Minn.). The RH of the test was
maintained at a constant 50% RH using a PID controller. The PID
sensor was calibrated with a Vaisala HMM1014A1AE humidity probe
(Vaisala, Vanta, Finland). The ammonia concentration was determined
using a photoacoustic gas detector Innova 1412 (California
Analytical, Orange, Calif.).
[0170] A respirator was placed in a test chamber in line with the
system, allowing the 56 ppm ammonia gas stream to flow through the
test material. To the downstream side of the test chamber, tubing
was connected that led to the photoacoustic gas detector. At the
time the ammonia gas stream began to pass through the disposable
respirator, the test was considered started, and a timer was
started. The Innova photoacoustic gas detector sampled
approximately every 50 seconds, and the system was flushed between
samples.
[0171] Prior to testing, a certified 57 ppm ammonia in nitrogen
pressurized gas cylinder (Oxygen Services Company, St. Paul, Minn.,
USA) was used to calibrate the photoacoustic gas detector. The
signal generated by this effluent was used to set the software to
50 ppm ammonia. The end point of the ammonia vapor test was defined
as the point corresponding to the time at which the ammonia
effluent passing through the bed of test material produced a signal
on the photoacoustic gas detector that exceeded a signal
corresponding to 5 ppm. The performance of each disposable
respirator was reported as the number of minutes until 5 ppm
breakthrough was observed performing the test as described
above.
REPRESENTATIVE EXAMPLE
[0172] A batch of precursor polymeric material was made in
generally similar manner as described in Example PE-15-1 of the
above-referenced PCT'974 and US '089 applications. The precursor
polymeric material had a SA.sub.BET in the range of approximately
240 m.sup.2/gram and a total pore volume in the range of
approximately 0.275 cm.sup.3/gram (measured at a p/p.degree. equal
to 0.96). The precursor polymeric material was sieved to
12.times.40 mesh particles. The precursor polymeric material was
reacted with a 4.0 M aqueous zinc (II) chloride (ZnCl.sub.2)
solution in generally similar manner as described in Example 15 of
the PCT'974 application and the US'089 application. The
ZnCl.sub.2-containing porous polymeric sorbent had a SA.sub.BET in
the range of approx. 35 m.sup.2/gram and a total pore volume in the
range of approximately 0.050 cm.sup.3/gram.
[0173] Filter cartridges were obtained from 3M Company, St. Paul,
Minn., of a type usable with the 3M HALF FACEPIECE REUSABLE
RESPIRATOR 6000 SERIES. The cartridges were empty as obtained and
comprised an empty interior volume of approximately 105 mL. The
ZnCl.sub.2-containing porous polymeric sorbent particles described
above were manually deposited into the interior of the cartridge
housing as a packed bed that occupied the 105 mL interior volume of
the cartridge to the packing density allowed by the manual loading
of the particles. The lid of the cartridge was then put in place
with ultrasonic welding. By mass, this cartridge contained 59.3
grams of ZnCl.sub.2-containing porous polymeric sorbent particles.
This cartridge was used to perform an ammonia lifetime cartridge
test as described above, at 15% RH and 32 LPM. The ammonia lifetime
of the Representative Example cartridge was determined to be
approximately 133 minutes.
Comparative Example (1)
[0174] An activated carbon was obtained and impregnated with
ZnCl.sub.2 in generally similar manner as described in Comparative
Example 3 of the PCT'974 and US'089 applications, excepting that
the activated carbon was of mesh size 12.times.40. An empty filter
cartridge housing was obtained as described in the Representative
Example and the 105 mL interior volume of the cartridge housing was
filled with the ZnCl.sub.2-impregnated activated carbon to form a
packed bed. The lid of the cartridge was then put in place with
ultrasonic welding. By mass, this cartridge contained 61.9 grams of
ZnCl.sub.2-containing activated carbon. This cartridge was used to
perform an ammonia lifetime cartridge test as described above, at
15% RH and 32 LPM. The ammonia lifetime of the Comparative Example
(1) cartridge was determined to be approximately 78 minutes.
VARIATION EXAMPLES
Variation Example (1)
[0175] A batch of ZnCl.sub.2-containing porous polymeric sorbent
particles was made and loaded into the interior volume of a filter
cartridge housing in similar manner as in the Representative
Example. The ammonia lifetime of the Variation Example (1)
cartridge was tested in similar manner as for the Representative
Example, except that the RH was approximately 0% rather than 15%.
Under these conditions, the ammonia lifetime of the Variation
Example (1) cartridge was determined to be approximately 178
minutes.
Variation Example (2)
[0176] An activated carbon of the type described in U.S. Pat. No.
6,767,860 to Hem as "URC" carbon was obtained and was not
impregnated with ZnCl.sub.2. The activated carbon was 12.times.30
mesh. Approximately 75 mL of this activated carbon was loaded into
the (105 mL) interior volume of a filter cartridge housing of the
type described above. A batch of ZnCl.sub.2-containing porous
polymeric sorbent particles was made in similar manner as in the
Representative Example, excepting that the precursor polymer
material was sieved to 40.times.80 mesh and the impregnation was
done with a 6.0 M aqueous ZnCl.sub.2 solution. The precursor
material was not hydrolyzed, and exhibited a SA.sub.BET in the
range of approximately 240 m.sup.2/gram and a total pore volume in
the range of approximately 0.275 cm.sup.3/gram (measured at a
p/p.degree. equal to 0.96). Approximately 30 mL of the
ZnCl.sub.2-containing porous polymeric sorbent particles was loaded
into the filter cartridge housing, as a layer atop the 75 mL layer
of activated carbon. The lid of the cartridge was then put in place
with ultrasonic welding. By mass, this cartridge contained 47.3
grams of activated carbon (as a layer occupying approximately 75
mL) and 18.2 grams of the ZnCl.sub.2-containing polymeric sorbent
(as a layer occupying approximately 25 mL). This cartridge was used
to perform an ammonia lifetime cartridge test as described above,
at 15% RH and 32 LPM. The ammonia lifetime of the Variation Example
(2) cartridge was determined to be approximately 39 minutes.
Variation Example (3)
[0177] An activated carbon of the general type described above in
Variation Example (2) was obtained and was not impregnated with
ZnCl.sub.2. The activated carbon was 12.times.30 mesh.
Approximately 75 mL of the activated carbon was loaded into the
(105 mL) interior volume of a filter cartridge housing of the type
described above. A batch of porous polymeric sorbent particles was
made in similar manner as in Variation Example (2). This precursor
material exhibited a SA.sub.BET in the range of approximately 240
m.sup.2/gram and a total pore volume in the range of approximately
0.275 cm.sup.3/gram (measured at a p/p.degree. equal to 0.96). This
precursor material was hydrolyzed in generally similar manner as
described in Example PE-10-2 of the PCT'974 and US'089
applications. The hydrolyzed, porous polymeric material exhibited a
SA.sub.BET in the range of approximately 110 m.sup.2/gram and a
total pore volume in the range of approximately 0.135
cm.sup.3/gram. The hydrolyzed, porous polymeric material was then
impregnated with ZnCl.sub.2 in generally similar manner as in
Variation Example (2). The ZnCl.sub.2-containing, hydrolyzed,
porous polymeric sorbent had a SA.sub.BET in the range of
approximately 35 m.sup.2/gram and a total pore volume in the range
of approximately 0.050 cm.sup.3/gram.
[0178] Approximately 30 mL of the ZnCl.sub.2-containing,
hydrolyzed, porous polymeric sorbent particles was loaded into a
filter cartridge housing, as a layer atop a 75 mL layer of
activated carbon as in Variation Example (2). The lid of the
cartridge was then put in place with ultrasonic welding. By mass,
this cartridge contained 47.3 grams of activated carbon and 17.6
grams of the ZnCl.sub.2-containing hydrolyzed polymeric sorbent.
This cartridge was used to perform an ammonia lifetime cartridge
test as described above, at 15% RH and 32 LPM. The ammonia lifetime
of the Variation Example (3) cartridge was determined to be 34
minutes.
Variation Example (4)
[0179] A batch of precursor polymeric material was made in
generally similar manner as described in Example PE-7-1 of the
above-referenced PCT'974 and US'089 applications. The precursor
polymeric material had a SA.sub.BET in the range of approximately
290 m.sup.2/gram and a total pore volume in the range of
approximately 0.240 cm.sup.3/gram. The precursor polymeric material
was sieved to 40.times.80 mesh particles.
[0180] This precursor material was hydrolyzed in generally similar
manner as described in Example PE-7-2 of the PCT'974 and US'089
applications. The hydrolyzed, porous polymeric material exhibited a
SA.sub.BET in the range of approximately 110 m.sup.2/gram and a
total pore volume in the range of approximately 0.135
cm.sup.3/gram. The hydrolyzed, porous polymeric material was then
impregnated with ZnCl.sub.2 in generally similar manner as in
Example 7 of the PCT'974 and US'089 applications. The
ZnCl.sub.2-containing, hydrolyzed, porous polymeric sorbent had a
SA.sub.BET in the range of approximately 35 m.sup.2/gram and a
total pore volume in the range of approximately 0.050
cm.sup.3/gram.
[0181] A netting was obtained from Delstar Technologies (Middleton,
DE) under the trade designation DELNET. The netting comprised two
sets of filaments oriented substantially perpendicular to each
other to form an array of generally rectangular through-apertures
(openings) each with an approximate dimension of 0.2.times.1.1 mm.
A pressure-sensitive adhesive (PSA) precursor (coating solution)
comprised primarily of an acrylic latex (Novacryl PSP-180; Omnova
Solutions, Beachwood, Ohio) and a tackifier (Aquatac 6085; Arizona
Chemicals, Jacksonville, Fla.) was applied to both sides of the
netting, and the liquid was removed via evaporation to leave a PSA
on each side of the netting. Particles of the ZnCl.sub.2-containing
polymeric sorbent described above were manually sprinkled onto both
sides of the netting so that sorbent particles were adhesively
attached to the PSA on the major surfaces of the netting.
[0182] Pieces of this sorbent-loaded netting were cut to the same
size as the inner dimensions of a filter cartridge housing that was
similar to the above-described filter cartridge housing excepting
with an interior volume of 75 mL rather than 105 mL. Two pieces of
the sorbent-loaded netting were loaded into the interior of the
cartridge. The remaining portion of the interior volume of the
cartridge was filled with a 12.times.30 mesh activated carbon of
the general type described in Variation Example 2 (and that had not
been impregnated with ZnCl.sub.2). The lid of the cartridge was
then put in place with ultrasonic welding. The mass of the
ZnCl.sub.2-containing polymeric sorbent within the cartridge was
calculated (based on the loading on the netting and the area of
netting used) to be approximately 2.71 grams. This cartridge was
used to perform an ammonia lifetime cartridge test as described
above at 5% RH and 25.2 LPM. The ammonia lifetime of the cartridge
was determined to be 31 minutes.
Comparative Example (4)
[0183] An activated carbon was obtained and impregnated with
ZnCl.sub.2 in generally similar manner as described above for
Comparative Example (1), excepting that the activated carbon was of
mesh size 20.times.40. The ZnCl.sub.2-loaded activated carbon was
manually deposited onto a netting and adhered thereto with a PSA,
in similar manner as described in Variation Example (4). Two layers
of the netting were loaded into a filter cartridge housing, and the
remaining volume of the filter cartridge housing was filled with
activated carbon (that had not been loaded with ZnCl.sub.2) in
similar manner as in Variation Example (4). The lid of the
cartridge was then put in place with ultrasonic welding. The mass
of the ZnCl.sub.2-containing activated carbon within the cartridge
was calculated (based on the loading on the netting and the area of
netting used) to be approximately 3.35 grams. This cartridge was
used to perform an ammonia lifetime cartridge test as described
above at 5% RH and 25.2 LPM. The ammonia lifetime of the cartridge
was determined to be 22 minutes.
Variation Example (5)
[0184] A batch of precursor polymeric material was made in
generally similar manner as described above in the Representative
Example. The precursor polymeric material had a SA.sub.BET in the
range of approximately 240 m.sup.2/gram and a total pore volume in
the range of approximately 0.275 cm.sup.3/gram (measured at a
p/p.degree. equal to 0.96). The precursor polymeric material was
sieved to 20.times.40 mesh particles. The precursor polymer
material was impregnated with ZnCl.sub.2 in similar manner as in
Example 15 of the PCT'974 and US'089 applications. The
ZnCl.sub.2-containing porous polymeric sorbent had a SA.sub.BET in
the range of approx. 35 m.sup.2/gram and a total pore volume in the
range of approx. 0.050 cm.sup.3/gram. A meltblown polypropylene
nonwoven web was obtained with a basis weight of approximately 70
g/m.sup.2. An acrylic based pressure-sensitive adhesive (Acronal A
220; BASF, Ludwigshafen, Germany) was screen printed onto one major
surface of the meltblown polypropylene nonwoven web. Particles of
the ZnCl.sub.2-containing polymeric sorbent were manually sprinkled
onto the adhesive-bearing major surface of the nonwoven web so that
sorbent particles were adhesively attached to the major surface of
the web by way of the PSA. This sorbent-loaded nonwoven web was
then incorporated (via ultrasonic welding) into a prototype
flat-fold disposable respirator mask. By mass, the disposable
respirator mask contained approximately 4.69 grams of
ZnCl.sub.2-containing porous polymeric sorbent. The respirator (in
an unfolded configuration) was used to perform an ammonia lifetime
disposable respirator test as described above. The ammonia lifetime
of the disposable respirator was determined to be approximately 211
minutes.
Comparative Example (5)
[0185] An activated carbon was obtained and impregnated with
ZnCl.sub.2 in generally similar manner as described above for
Comparative Example (1). The ZnCl.sub.2-loaded activated carbon
particles were manually deposited onto a major surface of a
meltblown nonwoven web and adhered thereto with a PSA, in similar
manner as described for the porous polymeric sorbent particles in
Variation Example (5). The nonwoven web was incorporated into a
prototype flat-fold disposable respirator mask in similar manner as
in Variation Example (5). The respirator was then used to perform
an ammonia lifetime disposable respirator test as described above
at 5% RH and 25.2 LPM. The ammonia lifetime of the disposable
respirator was determined to be approximately 112 minutes.
[0186] This application incorporates by reference International
Application No. PCT/US2016/030974 and U.S. Provisional Patent
Application No. 62/298,089. Those applications contain working
examples in which porous polymeric sorbents were made and
impregnated with a variety of divalent metals (e.g. zinc, copper,
nickel, and magnesium), using a variety of counterions (e.g.
chloride, acetate and nitrate). Although those examples are not
reproduced in the present application for reasons of brevity, the
performance of those examples as described in the PCT'974 and
US'089 applications would lead an ordinary artisan to expect that
the properties (in particular the enhanced ability to sorb basic,
nitrogen-containing compounds such as ammonia) displayed by those
Working Example sorbents would be similarly exhibited were these
sorbents to be disposed on a suitable filter support in the manner
disclosed in the present application.
[0187] Many of the Working Examples have included results presented
in terms of the "ammonia lifetime" achieved by various formulations
and configurations. It will be appreciated that the use of a
parameter such as an "ammonia lifetime" is purely for convenience
in characterizing an enhanced ability to sorb basic,
nitrogen-containing compounds; a relatively low value of such a
parameter does not necessarily imply that a particular formulation
or configuration cannot exhibit satisfactory filtration performance
(e.g. in terms of passing any applicable government standards). It
will also be appreciated that the achievement of a relatively long
ammonia lifetime may indicate that with a particular formulation or
configuration, a reduced amount of sorbent and/or a reduced amount
of metal impregnated thereinto may be able to be used while still
meeting all applicable performance standards.
[0188] The foregoing Examples have been provided for clarity of
understanding only, and no unnecessary limitations are to be
understood therefrom. The tests and test results described in the
Examples are intended to be illustrative rather than predictive,
and variations in the testing procedure can be expected to yield
different results. All quantitative values in the Examples are
understood to be approximate in view of the commonly known
tolerances involved in the procedures used.
[0189] It will be apparent to those skilled in the art that the
specific exemplary elements, structures, features, details,
configurations, etc., that are disclosed herein can be modified
and/or combined in numerous embodiments. All such variations and
combinations are contemplated by the inventor as being within the
bounds of the conceived invention, not merely those representative
designs that were chosen to serve as exemplary illustrations. Thus,
the scope of the present invention should not be limited to the
specific illustrative structures described herein, but rather
extends at least to the structures described by the language of the
claims, and the equivalents of those structures. Any of the
elements that are positively recited in this specification as
alternatives may be explicitly included in the claims or excluded
from the claims, in any combination as desired. Any of the elements
or combinations of elements that are recited in this specification
in open-ended language (e.g., comprise and derivatives thereof),
are considered to additionally be recited in closed-ended language
(e.g., consist and derivatives thereof) and in partially
closed-ended language (e.g., consist essentially, and derivatives
thereof). Although various theories and possible mechanisms may
have been discussed herein, in no event should such discussions
serve to limit the claimable subject matter. To the extent that
there is any conflict or discrepancy between this specification as
written and the disclosure in any document that is incorporated by
reference herein, this specification as written will control.
* * * * *