Title of Invention

MICROPOROUS FILTER MEDIUM FILTER SYSTEM COMPRISING IT AND METHODS OF MAKING AND USING THE SAME

Abstract The invention discloses a filter medium comprising a microporous structure comprising an array of active particles, said microporous structure having a mean flow path of less than or equal to 2 microns; and a microbiological interception enhancing agent comprising a cationic material having a medium to high charge density and a molecular weight greater than or equal to 5000 Daltons, adsorbed on at least a portion of said microporous structure, and a biologically active metal in direct proximity to the cationic material and also on at least a portion of said microporous structure. The invention is also for filter system comprising such filter medium and methods of making and using the same.
Full Text MICROPOROUS FILTER MEDIUM, FILTER SYSTEM
COMPRISING IT AND METHODS OF MAKING AND USING THE SAME
The present invention is directed to filter media having
microbiological interception capability, filtration systems containing such
filter media, and methods of making and using same.
Modern consumer water filters often provide "health claims" including
reduction of particulates, heavy metals, toxic organic chemicals, and select
microbiological threats. These filtration systems have been able to intercept
microorganisms such as Cryptosporidium and Giardia using roughly 1.0
micron structures. However, in order to provide microbiological interception
of even smaller microbiological threats such as viruses, a filter medium
having a sub-micron microporous structure is required. Prior art filtration
systems often attempt to achieve broad microbiological interception using
filter media with insufficiently small pore size and with poor physical
integrity. The balance between the necessary pore structure required for
successful microbiological interception and satisfactory filter performance has
not been achieved.
Summary of the Invention
The present invention is directed to, in a first aspect, a filter medium
comprising: a microporous structure comprising an array of active particles,
the microporous structure having a mean flow path of less than about 2
microns; and a microbiological interception enhancing agent comprising a
cationic material having a medium to high charge density and a molecular
weight greater than about 5000 Daltons, adsorbed on at least a portion of the

microporous structure, and a biologically active metal in direct proximity to
the cationic material and also on at least a portion of the microporous
structure.
In another aspect, the present invention is directed to a filter system
comprising: a housing having an inlet and an outlet; a filter medium situated
within the housing in fluid communication with the inlet and outlet, the filter
medium comprising: a microporous structure having a mean flow path of less
than about 2 microns comprising active particles of activated carbon,
activated alumina, zeolites, diatomaceous earth, silicates, aluminosilicates,
titanates, bone char, calcium hydroxyapatite, manganese oxides, iron oxides,
magnesia, perlite, talc, polymeric particulates, clay, iodated resins, ion
exchange resins, ceramics, or combinations thereof; and a microbiological
interception enhancing agent comprising a cationic material having a high
charge density, a molecular weight greater than about 5000 Daltons and
having an associated counter ion therewith, the cationic material adsorbed
on at least a portion of the microporous structure, and wherein a biologically
active metal is caused to precipitate with at least a portion of the counter ion
associated with the cationic material, wherein a microbiologically
contaminated influent flowing through the housing and contacting the filter
medium has at least about 4 log reduction in microbiological contaminants in
an effluent flowing from the housing.
In yet another aspect, the present invention is directed to a process of
making a filter medium having enhanced microbiological interception
capability comprising the steps of: providing active particles having an
average particle size of about 0.1 microns to about 5,000 microns; treating
the active particles with a microbiological interception enhancing agent
comprising a cationic material having a high charge density and a molecular
weight greater than about 5000 Daltons in combination with a biologically

active metal; and forming the treated active particles into a microporous
structure having a mean flow path of less than about 2 microns.
In still yet another aspect, the present invention is directed to a
process of making a filter medium having enhanced microbiological
interception capability comprising the steps of: providing active particles
having an average particle size of about 0.1 microns to about 5,000 microns;
coalescing the active particles into a microporous structure having a mean
flow path of less than about 2 microns; and treating the microporous
structure with a microbiological interception enhancing agent comprising a
cationic material having a high charge density and a molecular weight greater
than about 5000 Daltons in combination with a biologically active metal.
In a further aspect, the present invention is directed to a method of
removing microbiological contaminants from a fluid comprising the steps of
providing a filter medium comprising a microporous structure comprising
active particles and having a mean flow path of less than about 2 microns;
and a microbiological interception enhancing agent comprising a cationic
material having a medium to high charge density and a molecular weight
greater than about 5000 Daltons in combination with a biologically active
metal, adsorbed on at least a portion of the microporous structure; contacting
a microbiologically contaminated fluid to the filter medium for a period of
time of less than or equal to about 12 seconds; and obtaining an effluent
having greater than about 4 log reduction of microbiological contaminants.
Brief Description of the Drawings
The features of the invention believed to be novel and the elements
characteristic of the invention are set forth with particularity in the appended
claims. The figures are for illustration purposes only and are not drawn to
scale. The invention itself, however, both as to organization and method of

operation, can best be understood by reference to the description of the
preferred embodiment(s) which follows, taken in conjunction with the
accompanying drawings in which:
Fig. 1 is a graph plotting the empty bed contact time versus the log
reduction values of M2 bacteriophage of the microbiological interception
enhanced activated carbon filter medium of the present invention.
Detailed Description of the Preferred Embodiment(s)
In describing the preferred embodiment of the present invention,
reference will be made herein to Fig. 1 of the drawings.
Definitions
As used herein, "absorbent" shall mean any material that is capable of
drawing a substance into its inner structure.
As used herein, "adsorbent" shall mean any material that is capable of
drawing a substance to its surface by physical means and without any
covalent bonding.
As used herein, "binder" shall mean a material used principally to
hold other materials together.
As used herein, "contaminant reduction" shall mean attenuation of an
impurity in a fluid that is intercepted, removed, and/or rendered inactive,
chemically, mechanically or biologically, in order to render the fluid safer as,
for example, for human use, or more useful as in industrial applications.
As used herein, "empty bed contact time" or "EBCT" shall mean a
measure of how much contact occurs between particles, such as, for
example, activated carbon, and a fluid as the fluid flows through the bed of
particles.

As used herein, "fiber" shall mean a solid that is characterized by a
high aspect ratio of length to diameter of, for example, several hundred to
one. Any discussion of fibers shall also be deemed to include whiskers.
As used herein, "filter medium" shall mean a material that performs
fluid filtration.
As used herein, "fluid" shall mean a liquid, gas, or combination
thereof.
As used herein, "intercept" or "interception" are taken to mean
interfering with, or stopping the passage of, so as to affect, remove, inactivate
or influence.
As used herein, "log reduction value" or "LRV" shall mean the log10 of
the number of organisms in the influent divided by the number of organisms
in the effluent after passing through a filter.
As used herein, "metal" shall mean to include the salts, colloids,
precipitates, base metal, and all other forms of a given metallic element.
As used herein, "microbiological interception enhanced filter
medium" shall mean a filter medium having a microporous structure where
at least a portion of the microporous structure is treated with a
microbiological interception enhancing agent.
As used herein, "microbiological interception enhancing agent" shall
mean a cationic material having a counter ion associated therewith in
combination with a biologically active metal.
As used herein, "microorganism" shall mean any living organism that
can be suspended in a fluid, including but not limited to, bacteria, viruses,
fungi, protozoa, and reproductive forms thereof including cysts and spores.
As used herein, "microporous structure" shall mean a structure that
has a mean flow path less than about 2.0 microns, and often less than about
1.0 micron.

As used herein, "natural organic matter" or "NOM" shall mean
organic matter often found in potable or non-potable water, a portion of
which reduces or inhibits the streaming, or zeta, potential of a positively
charged filter medium. Exemplary of NOM are polyanionic acids such as,
but not limited to, humic acid and fulvic acid.
As used herein, "nonwoven" means a web or fabric or other medium
having a structure of individual fibers that are interlaid, but not in a highly
organized manner as in a knitted or woven fabric. Nonwoven webs
generally can be prepared by methods that are well known in the art.
Examples of such processes include, but are not limited to, and by way of
illustration only, meltblowing, spunbonding, carding, and air laying.
As used herein, "particle" shall mean a solid having a size range from
colloidal to macroscopic, and with no specific limitation on shape, but
generally of a limited length to width ratio.
As used herein, "prefilter" shall mean a filter medium generally
located upstream from other filtration layers, structures or devices and
capable of reducing particulate contaminants prior to the influent contacting
subsequent filtration layers, structures or devices.
As used herein, "whisker" shall mean a filament having a limited
.aspect ratio and intermediate between the aspect ratio of a particle and a
fiber. Any discussion of fibers shall also be deemed to include whiskers.
The Microbiological Interception Enhanced Filter Medium
A filter medium of the present invention has a microporous structure
that provides microbiological interception capability using a combination of
an appropriate pore structure and a chemical treatment. The microporous
structure comprises an array of active particles that have a specific pore
structure, as well as adsorbent and/or absorbent properties. The array can be

a solid composite block, a monolith, a ceramic candle, a flat-sheet composite
of bonded or immobilized particles formed into a coherent medium using a
binder or supporting fibers, and the like. These particle arrays can be made
through processes known in the art such as, for example, extrusion, molding,
or slip casting. The chemical treatment process used to treat the surface of
the microporous structure utilizes a synergistic interaction between a cationic
material and a biologically active metal, that when combined, provide broad-
spectrum reduction of microbiological contaminants on contact. The charge
provided by the cationic material to the filter medium aids in electro-kinetic
interception of microbiological contaminants, while the tight pore structure
provides a short diffusion path and, therefore, rapid diffusion kinetics of
microbiological contaminants in a flowing fluid to a surface of the
microporous structure. The microporous structure also provides
supplemental direct mechanical interception of microbiological
contaminants. Due to the dominant role of diffusion for the interception of
extremely small particles, there is a direct correlation between the log
reduction value of viral particles and the contact time of the influent within
the filter medium, rather than a dependence upon the thickness of the filter
medium.
Characteristics of the Microbiological Interception Enhanced Filter
Medium
In order to provide full microbiological interception capability, the
microbiological interception enhanced filter medium of the present invention
has a mean flow path of less than about 2 microns, and more preferably less
than or equal to about 1 micron, if the mean flow path is greater than about
2 microns, then the diffusion efficiency of viral particles rapidly declines and
efficient biological interception fails. The volume of the microbiological
interception enhanced filter medium of the present invention compared to

the flow rate of fluid through the filter medium must be sufficient to provide a
contact time adequate for the contaminants to diffuse to a surface of the filter
medium. To provide enhanced electro-kinetic interception of
microorganisms, of which the majority are negatively charged, at least a
portion of the microporous structure is coated with a cationic material to
produce a positive charge on at least a portion of such microporous structure.
The cationic material is of sufficient molecular size to prevent fouling of the
micro-pores and mezo-pores of the active particles.
Natural organic matter (NOM), such as polyanionic acids, i.e., humic
acid or fulvic acid, that can reduce or remove the charge on the
microbiological interception enhanced filter medium, is preferably prevented
from contacting the charged microporous structure through the use of an
adsorbent prefilter that substantially removes the NOM. It is possible to
incorporate the NOM removing material directly into the microbiological
interception enhanced filter medium, thereby eliminating the need for a
separate adsorbent prefilter. Also, depending on the type of active particles
used, the upstream portion of the microbiological interception enhanced
filter medium itself can naturally reduce or remove NOM as well and prevent
a loss of performance of the downstream portions of the microbiological
interception enhanced filter medium.
When used in the context of a gravity-flow water filtration system, it is
preferable that the microbiological interception enhanced filter medium be
made with hydrophilic materials or treated with a wetting agent to provide
good, spontaneous wettability. Alternatively, in other applications, the
microbiological interception enhanced filter medium can be treated to
provide either a hydrophilic or hydrophobic characteristic as needed. It is
possible that the microbiological interception enhanced filter medium can
have both positively and negatively charged and uncharged regions, and/or

hydrophilic and hydrophobic regions. For example, the negatively charged
regions can be used to enhance the interception of less common positively
charged contaminants and uncharged hydrophobic regions can be used to
provide enhanced interception of contaminants that are attracted to
hydrophobic surfaces.
The Active Particles
The microbiological interception enhanced filter medium having
enhanced microbiological interception capabilities of the present invention
comprises an array of adsorbent and/or absorbent active particles having a
particle size distribution of 80 x 325 mesh with about 20% to about 24% pan
(particles smaller than -325 mesh). The active particles can include, but are
not limited to, activated carbon, activated alumina, zeolites, diatomaceous
earth, silicates, aluminosilicates, titanates, bone char, calcium
hydroxyapatite, manganese oxides, iron oxides, magnesia, perlite, talc,
polymeric particulates, clay, iodated resins, ion exchange resins, ceramics,
super absorbent polymers (SAPs), and combinations thereof. A
microbiological interception enhanced filter medium having requisite
properties can be obtained by combining one or more of these active
particles.
One preferred microporous structure comprises active particles of
activated carbon that naturally resist fouling by NOM and is efficient at
adsorbing the potentially interfering NOM in peripheral regions of the
microporous structure while protecting inner regions. Preferably, the
activated carbon is acid washed bituminous coal-based activated carbon.
Commercially available activated carbon suitable for use in the present
invention can be obtained from Calgon Carbon Corporation of Pittsburgh,
Pennsylvania, under the trade designation TOG-NDS or from California
Carbon Company of Wilmington, California, under the trade designation
1240ALC. Most preferably, the active particles are comprised of acid washed
bituminous coal-based activated carbon from Calgon Carbon Corporation,
having a particle size distribution as follows: about 3% to about 7%,
preferably about 5%, 80 mesh size particles; about 12% to about 18%,
preferably about 15% 100 mesh; about 44% to about 50%, preferably 47%
200 mesh; about 8% to about 14%, preferably about 11% 325 mesh; and
about 20% to about 24% pan, preferably about 22% pan.
The Microbiological Interception Enhancing Agent
The active particles of the microporous structure are chemically
treated with a microbiological interception enhancing agent capable of
creating a positive charge on the surface of the active particles. The chemical
treatment produces a strong positive charge upon the treated surfaces as
measured using streaming potential analysis and this positive charge is
retained at pH values below 10. A cationic metal complex is formed on at
least a portion of the surface of the active particles by treating the active
particles with a cationic material. The cationic material may be a small
charged molecule or a linear or branched polymer having positively charged
atoms along the length of the polymer chain.
if the cationic material is a polymer, the charge density is preferably
greater than about 1 charged atom per about every 20 Angstroms, preferably
greater than about 1 charged atom per about every 10 Angstroms, and more
preferably greater than about 1 charged atom per about every 5 Angstroms of
molecular length. The higher the charge density on the cationic material, the
higher the concentration of the counter ion associated therewith. A high
concentration of an appropriate counter ion can be used to drive the
precipitation of a metal complex. The high charge density of the cationic
polymer provides the ability to adsorb and significantly reverse the normal
negative charge of active particles such as carbon. The cationic material

should consistently provide a highly positively charged surface to the
microporous structure as determined by a streaming or zeta potential
analyzer, whether in a high or low pH environment.
The use of a polymer of sufficiently high molecular weight allows
treatment of the surfaces of the active particles without serious attendant
impact upon the adsorptive capabilities of the mezo-pores and micro-pores of
the active particles. The cationic material can have a molecular weight
greater than or equal to about 5000 Daltons, preferably greater than or equal
to 100,000 Dalton, more preferably greater than or equal to about 400,000
Daltons, and can be greater than or equal to about 5,000,000 Daltons.
The cationic material includes, but is not limited to, quaternized
amines, quaternized amides, quaternary ammonium salts, quaternized
imides, benzalkonium compounds, biguanides, cationic aminosilicon
compounds,, cationic cellulose derivatives, cationic starches, quaternized
polyglycol amine condensates, quaternized collagen polypeptides, cationic
chitin derivatives, cationic guar gum, colloids such as cationic melamine-
formaldehyde acid colloids, inorganic treated silica colloids, polyamide-
epichlorohydrin resin, cationic acrylamides, polymers and copolymers
thereof, combinations thereof, and the like. Charged molecules useful for
this application can be small molecules with a single charged unit and
capable of being attached to at least a portion of the microporous structure.
The cationic material preferably has one or more counter ions associated
therewith which, when exposed to a biologically active metal salt solution,
cause preferential precipitation of the metal in proximity to the cationic
surface to form a cationic metal precipitate complex.
Exemplary of amines may be pyrroles, epichlorohydrin derived
amines, polymers thereof, and the like. Exemplary of amides may be those
polyamides disclosed in International Patent Application No. WO 01/07090,

and the like. Exemplary of quaternary ammonium salts may be
homopolymers of diallyl dimethyl ammonium halide, epichlorohydrin
derived polyquaternary amine polymers, quaternary ammonium salts derived
from diamines and dihalides such as those disclosed in United States Patent
Nos. 2,261,002, 2,271,378, 2,388,614, and 2,454,547, all of which are
incorporated by reference, and in International Patent Application No. WO
97/23594, also incorporated by reference,
polyhexamethylenedimethylammonium bromide, and the like. The cationic
material may be chemically bonded, adsorbed, or crosslinked to itself and/or
to the active particles.
Furthermore, other materials suitable for use as the cationic material
include BIOSHIELD® available from BioShield Technologies, Inc., Norcross,
Georgia. BIOSHIELD® is an organosilane product including approximately
5% by weight octadecylaminodimethyltrimethoxysilylpropyl ammonium
chloride and less than 3% chloropropyltrimethoxysilane. Another material
that may be used is SURFACINE®, available from Surfacine Development
Company LLC, Tyngsboro, Massachusetts. SURFACINE® comprises a three-
dimensional polymeric network obtained by reacting
poly(hexamethylenebiguanide) (PHMB) with 4,4'-methlyene-bis-N,N-
dilycidylaniline (MBGDA), a crosslinking agent, to covalently bond the
PHMB to a polymeric surface. Silver, in the form of silver iodide, is
introduced into the network, and is trapped as submicron-sized particles.
The combination is an effective biocide, which may be used in the present
invention. Depending upon the active particles, the MBGDA may or may
not crosslink the PHMB to the microporous structure.
The cationic material is exposed to a biologically active metal salt
solution such that the metal complex precipitates onto at least a portion of
the surface of at least some of the active particles. For this purpose, the

metals that are biologically active are preferred. Such biologically active
metals include, but are not limited to, silver, copper, zinc, cadmium,
mercury, antimony, gold, aluminum, platinum, palladium, and combinations
thereof. The most preferred biologically active metals are silver and copper.
The biologically active metal salt solution is preferably selected such that the
metal and the counter ion of the cationic material are substantially insoluble
in an aqueous environment to drive precipitation of the metal complex.
Preferably, the metal is present in an amount of about 0.01 % to about 2.0%
by weight of the total composition.
A particularly useful microbiological interception enhancing agent is a
silver-amine-halide complex. The cationic amine is preferably a
homopolymer of diallyl dimethyl ammonium halide having a molecular
weight of about 400,000 Daltons or other quaternary ammonium salts having
a similar charge density and molecular weight. A homopolymer of diallyl
dimethyl ammonium chloride useful in the present invention is commercially
available from Nalco Chemical Company of Naperville, Illinois, under the
tradename MERQUAT® 100. The chloride counter ion may be replaced with
a bromide or iodide counter ion. When contacted with a silver nitrate
solution, the silver-amine-halide complex precipitates on at least a portion of
the active particles of the microporous structure of the microbiological
interception enhanced filter medium.
Where the active particles comprise activated carbon, the cationic
material preferably has a high charge density and a sufficiently high
molecular weight to create a strong attraction and high coordination energy
with the negatively charged surface groups of activated carbon. Also, the
enhanced interception using the charged surface of the activated carbon, in
the presence of a colloid of a biologically active metal, is supplemented by
the hydrophobic adsorption mechanism of the activated carbon. This

hydrophobic mechanism is generally resistant to the impact of fouling by
NOM, and is actually more effective under conditions of high ionic strength.
Untreated portions of the carbon surface, with their oxygen-rich chemistry,
tend to have a negative charge that can continue to adsorb positively charged
particles. The combination of positive, negative, and hydrophobic surfaces
presents a nearly insurmountable barrier for small particles to navigate. After
treating the carbon with the microbiological interception enhancing agent,
the presence of the biologically active metal and its associated counter ion on
the active particles can be detected using X-ray fluorescence.
Method Of Making The Microbiological Interception Enhanced Filter
Medium
The microbiological interception enhanced filter medium of the
present invention can be made in accordance with processes known to one
of skill in the art. Such processes include extrusion, molding, slip casting,
immobilizing the active particles on a substrate, and the like. Exemplary
processes are disclosed in United States Patent Nos. 5,019,311, and
5,792,513.
The active particles are treated with the cationic material using means
known to one of skill in the art such as, for example, spray coating.
Preferably, the active particles are coated with about 0.5% to about 3% by
weight, and more preferably about 1 % by weight of the total weight of the
microbiological interception enhanced filter medium. Once the cationic
material is coated onto at least a portion of the active particles, the particles
are exposed to the biologically active metal salt. A solution of the metal salt
is infiltrated into the particles to cause precipitation of the biologically active
metal on at least a portion of the surface of the active particles. The
precipitation process accurately deposits the majority of the metal colloid

directly adjacent to the cationic coating because the counter-ion associated
with this coating reacts with the applied metal salt to form the colloidal
particles. The metal salt can be sprayed onto the treated particles or
otherwise applied using methods known to one of skill in the art. Solutions
of the cationic material and the metal salt are preferably made with nearly
ion-free water so that the counter-ions associated with the cationic material
are drawn tightly against the cationic surface of the treated active particles
and to eliminate unwanted ions that may cause uncontrolled precipitation of
the biologically active metal into sites remote from the cationic surface.
Excess moisture is then removed from the particles, generally with
heating or under vacuum, to a desired moisture content. Preferably, the
moisture content should be less than about 10%, and more preferably less
than about 5%, if the particles are to be subsequently extruded or molded
using a thermoplastic binder.
Once the microbiological interception enhancing agent is coated on
to at least a portion of the active particles, the active particles are ground to
the desired size and potentially mixed with the binder material to form a
homogenous mixture prior to immobilizing the active particles into a desired
final form having the required microporous structure. The binder is chosen
such that the melting point of the binder material is sufficiently lower than
the melting point of the active particles so that the microbiological
interception enhanced filter medium can be heated to activate the binder
material, while the microporous structure does not melt and thereby lose
porosity. The binder particles are preferably sufficiently evenly distributed
throughout the active particles such that later, upon conversion to the
microporous structure, the binder particles will entrap or bond to
substantially all the active particles.

Binder materials useful in the present invention in coalescing the
active particles into the microporous structure can potentially include any
thermoplastic or thermoset material known in the art in either fiber, powder
or particulate form. Useful binder materials can include materials such as,
but not limited polyolefins, polyvinyl halides, polyvinyl esters, polyvinyl
ethers, polyvinyl sulfates, polyvinyl phosphates, polyvinyl amines,
polyamides, polyimides, polyoxidiazoles, polytriazols, polycarbodiimides,
polysulfones, polycarbonates, polyethers, polyarylene oxides, polyesters,
polyarylates, phenol-formaldehyde resins, melamine-formaldehyde resins,
formaldehyde-ureas, ethyl-vinyl acetate copolymers, co-polymers and block
interpolymers thereof, and combinations thereof. Variations of the above
materials and other useful polymers include the substitution of groups such
as hydroxyl, halogen, lower alkyl groups, lower alkoxy groups, monocyclic
aryl groups, and the like.
A more detailed list of binders which can be useful in the present
invention include end-capped polyacetals, such as poly(oxymethylene) or
polyformaldehyde, poly(trichloroacetaldehyde), poly(n-valeraldehyde),
poly(acetaldehyde), and poly(propionaldehyde); acrylic polymers, such as
polyacrylamide, poly(acrylic acid), poly(methacrylic acid), poly(ethyl
acrylate), and poly(methyl methacrylate); fluorocarbon polymers, such as
poly(tetrafluoroethylene), perfluorinated ethylene-propylene copolymers,
ethylene-tetrafluoroethylene copolymers, poly(chlorotrifluoroethylene),
ethylene-chlorotrifluoroethylene copolymers, polyvinylidene fluoride), and
polyvinyl fluoride); polyamides, such as poly(6-aminocaproic acid) or poly(e-
caprolactam), poly(hexamethylene adipamide), poly(hexamethylene
sebacamide), and poly(11-aminoundecanoic acid); polyaramides, such as
poly(imino-1,3-phenyleneiminoisophthaloyl) or poly(m-phenylene
isophthalamide); parylenes, such as poly-2-xylylene, and poly(chloro-1-

xylylene); polyaryl ethers, such as poly(oxy-2,6-dimethyl-1,4-phenylene) or
poly(p-phenylene oxide); polyaryl sulfones, such as poly(oxy-1,4-
phenylenesulfonyl-1,4-phenyleneoxy-1,4-phenyl-eneisopropylide ne-1,4-
phenylene), and poly(sulfonyl-1,4-phenylene-oxy-1,4-phenylenesulfonyl4,4'-
biphenylene); polycarbonates, such as poly-(bisphenol A) or
poly(carbonyldioxy-1,4-phenyleneisopropylidene-1,4-phenylene); polyesters,
such as polyethylene terephthalate), poly(tetramethylene terephthalate), and
poly(cyclohexyl-ene-1,4-dimethylene terephthalate) or poly(oxymethylene-
1,4-cyciohexylenemethyleneoxyterephthaloyl); polyaryl sulfides, such as
poly(p-phenylene sulfide) or poly(thio-1,4-phenylene); polyimides, such as
poly(pyromeHitimido-1,4-phenylene); polyolefins, such as polyethylene,
polypropylene, poly(l-butene), poly(2-butene), poly(l-pentene), poly(2-
pentene), poly(3-methyl-1-pentene), and poly(4-methyl-1-pentene); vinyl
polymers, such as polyvinyl acetate), poly(vinylidene chloride), and
polyvinyl chloride); diene polymers, such as 1,2-poIy-1,3-butadiene, 1,4-
poiy-1,3-butadiene, polyisoprene, and polychloroprene; polystyrenes; and
copolymers of the foregoing, such as acrylonitrilebutadiene-styrene (ABS)
copolymers. Polyolefins that can be useful include polyethylene, linear low
density polyethylene, polypropylene, poly(1-butene), poly(2-butene), poly(1-
pentene), poly(2-pentene), poly(3-methyl-1-pentene), poly(4-methyl-1-
pentene), and the like.
Other potentially applicable materials include polymers such as
polystyrenes and acrylonitrile-styrene copolymers, styrene-butadiene
copolymers, and other non-crystalline or amorphous polymers and structures.
Preferred binder materials include polyethylene, poly(ethylene vinyl
acetate), and nylons. Especially preferred as a binder is grade FN 510
microfine polyethylene commercially available from Equistar Chemicals, L.P.,
Tuscola, Illinois, under the trade designation MICROTHENE® F.

The binder can have an average particle size of about 0.1 micron to
about 250 microns, preferably about 1 micron to about 100 microns, and
more preferably about 5 microns to about 20 microns. It is preferable that
the binder material have a softening point that is significantly lower than a
softening point of the active particles so that the microbiological interception
enhanced filter medium can be heated to activate the binder material, while
the microporous structure does not melt and thereby lose porosity.
The amount of binder material used is dependent upon how the
microporous structure is formed whether by extrusion, molding, or other
processes. For example, when the active particles are extruded or molded
into a solid composite block, the binder material is preferably present in an
amount of about 15% to about 22% by weight, and more preferably about
17% to about 19% by weight of the microbiological interception enhanced
filter medium. When the active particles are immobilized on a substrate such
as, for example, a nonwoven material, the binder material is preferably
present in an amount of about 5% to about 20%, and preferably about 9% to
about 15% by weight of the total composition.
One or more additives either in a particulate, fiber, whisker, or
powder form may also be mixed with the active particles to aid in adsorption
or absorption of other contaminants or participate in the formation of the
microporous structure and interception of microbiological contaminants.
Useful additives may include, but are not limited to, metallic particles,
activated alumina, activated carbon, silica, polymeric powders and fibers,
glass beads or fibers, cellulose fibers, ion-exchange resins, engineered resins,
ceramics, zeolites, diatomaceous earth, activated bauxite, fuller's earth,
calcium sulfate, other adsorbent or absorbent materials, or combinations
thereof. The additives can also be chemically treated to impart
microbiological interception capabilities depending upon the particular

application. Such additives are preferably present in a sufficient amount such
that the fluid flow in the resultant microbiological interception enhanced
filter medium is not substantially impeded when used in filtration
applications. The amount of additives is dependent upon the particular use
of the filtration system.
Alternatively, the final microporous structure can be formed by slip
casting or wet-forming the particles or fibers or such mixtures and
subsequently causing binders or particles to sinter the ingredients together.
In some cases, the particles can form their own binder as in bi-component
fibers or low melting point resins. In some cases, the binder can be water
soluble or cross-linkable resins or salts that when allowed to dry, or heated,
or allowed to react, form the required bonds. Chemical binders can also be
used as well as precipitated binders such as certain phosphate salts.
Filtration Systems Utilizing The Microbiological Interception Enhanced Filter
Medium
The microbiological interception enhanced filter medium of the
present invention can be easily incorporated into prior art filtration systems
that utilize particulate filtration medium immobilized as a solid composite
blocks, flat, spiral or pleated sheets, monoliths, or candles. Preferably, a
particulate prefilter is used in conjunction with the microbiological
interception enhanced filter medium, positioned upstream from the
microbiological interception enhanced filter medium, to remove as many
particulate contaminants from the influent as possible prior to the influent
contacting the microbiological interception enhanced filter medium.

Examples
The following examples are provided to illustrate the present
invention and should not be construed as limiting the scope of the invention.
Porometry studies were performed with an Automated Capillary Flow
Porometer available from Porous Materials, Inc., Ithaca, New York.
Parameters determined, using standard procedures published by the
equipment manufacturer, include mean flow pore size and gas (air)
permeability. The flow of air was assayed at variable pressure on both the
dry and wel: microbiological interception enhanced filter medium.
Bacterial challenges of the microbiological interception enhanced
filter media were performed using suspensions of Escherichia coli of the
American Type Culture Collection (ATCC) No. 11775 to evaluate the
response to a bacterial challenge. The response to viral challenges was
evaluated using MS2 Bacteriophage ATTC No. 15597-Bi. Other
microorganisms tested include Brevundimonas diminuta ATCC No. 4335,
Bacillus subtilis, also known as BC, ATCC No. 9375. The Standard
Operating Procedures of the ATCC were used for propagation of the
bacterium and bacteriophage, and standard microbiological procedures, as
well known in the art, were used for preparing and quantifying the
microorganisms in both the influent and effluent of filters challenged with
suspensions of the microorganisms.
Individual filters were tested in duplicate with each microorganism
under a modified version of the NSF International Standard 53 cyst reduction
test protocol. This protocol is designed to assess the performance of filters
during an accelerated exposure to fine particulates to simulate accumulation
of dirt. Filters were flushed with reverse osmosis/deionized (RO/DI) water
and calibrated to an initial flow rate of 0.5 to 1.0 gallon/minute (gpm). The
mean flow path of the filter media all were about 0.9 microns to 1.1 microns.

During testing, initial samples were drawn from both the influent and
effluent sampling ports during the startup system flushing period to ensure
that there was no background interference from an improperly disinfected
test apparatus. The filter was then challenged with suspensions of the
microorganisms, with samples being taken following a minimum 2L
challenge solution, ensuring passage of the challenge water through the
entire test stand prior to sampling.
All influent and effluent samples were serially diluted, as required,
and plated in triplicate. In certain cases, carbon blocks of a given design
were tested at several flow rates to ascertain their response to changing flow
rate.
Activated carbon block filters having enhanced microbiological
interception capability were prepared as follows. Twenty (20) pounds of
12x40 mesh acid-washed bituminous-coal-based activated carbon, obtained
from Calgon Carbon Company, was gently mixed with a solution of 3%
MERQUAT® 100 in de-ionized water to thoroughly coat the carbon particles
and ensure that the MERQUAT® 100 had adsorbed onto at least a portion of
the carbon particles. Thereafter, a solution of silver nitrate, 70 g crystalline
silver nitrate in 1.0 L de-ionized water, was added to the MERQUAT® treated
carbon to allow precipitation of the silver on at least a portion of the surface
of the carbon particles in the form of silver chloride colloid. The treated
carbon particles were dried at 135°C until there was less than 5% moisture
present in the carbon particles. Drying times varied between about 3 to
about 5 hours. The dried carbon was ground in a double-roll grinder to 80 x
325 mesh size with approximately 14% by weight -325 mesh pan, and was
mixed with FN510, a low density polyethylene binder material, at
approximately 17% by weight. The mixture was extruded under suitable
heat, pressure and temperature conditions, as described in U.S. Patent No.

5,019,311. Resulting carbon block filters of various sizes were used to
construct water filter systems by applying suitable end caps using a hot melt
resin, as is well known in the art.
The filters were assayed for microbiological interception performance
under initial clean conditions and then at intervals following dirt
accumulation where the flow was reduced by 25%, 50% and 75% in
comparison to the flow rate measured on the original, clean filter.
To achieve the required reduction in flow, "nominal" test dust
challenge water was utilized. Nominal test dust is a silicate powder with
particles roughly 0 to 5.0 microns in diameter and having 96% by weight of
the particles in this range and 20% to 40% of the particles greater than 2.5
microns. When the required flow reduction has been accomplished, the
nominal test dust challenge was curtailed and the filter flushed with 4.0 L of
reverse osmosis/deionized (RO/DI) water to remove any residual test dust
from the influent and effluent lines. The filter is then challenged with the
suspensions of the microorganisms, as described above.
The efficacy of the microbiological interception enhanced filter
medium of the present invention is shown in Tables I and II below.




The microbiological interception enhanced activated carbon block
filter medium of the present invention provides greater than 8 log reduction
of larger organisms such as B. diminuta, E.coli and B. subtilis. In fact,
interception of these organisms was beyond the sensitivity of the test protocol
in all cases. The results for MS2 penetration show no apparent correlation
between wall thickness and levels of interception. This indicates that a
traditional mechanical interception mechanism is not responsible for MS2

interception. However, there is a direct relationship between the log
interception and the empty bed contact time (EBCT) of the filter. Fig. 1
shows a substantially linear relationship between the initial, clean filter log
MS2 reduction and the EBCT of the filter indicating a diffusive interception
mechanism with a requirement of approximately 6 seconds EBCT in order to
achieve effective reduction of this bacteriophage in a microbiological
interception enhanced filter medium having a mean flow path of about 0.9 to
about 1.1 microns. For this reason, larger filters operating at lower flow rates
perform more efficiently than small filters operating at elevated flow rates.
While the present invention has been particularly described, in
conjunction with a specific preferred embodiment, it is evident that many
alternatives, modifications and variations will be apparent to those skilled in
the art in light of the foregoing description. It is therefore contemplated that
the appended claims will embrace any such alternatives, modifications and
variations as falling within the true scope and spirit of the present invention.

We Claim :
1. A filter medium comprising:
a microporous structure comprising an array of active particles, said microporous
structure having a mean flow path of less than or equal to 2 microns; and
a microbiological interception enhancing agent comprising a canonic material having
a medium to high charge density and a molecular weight greater than or equal to
5000 Daltons, adsorbed on at least a portion of said microporous structure, and a
biologically active metal in direct proximity to the cationic material and also on at
least a portion of said microporous structure.
2. A filter medium as claimed in claim 1 wherein the active particles comprise of activated
carbon, activated alumina, zeolites, diatomaceous earth, silicates, aluminosilicates, titanates,
bone char, calcium hydroxyapatite, manganese oxides, iron oxides, magnesia, perlite, talc,
polymeric particulates, clay, iodated resins, ion exchange resins, ceramics, or combinations
thereof, and further including a binder.
3. A filter medium as claimed in claim 1 wherein said microporous structure has a mean
flow path of less than or equal to 1 micron.
4. A filter medium as claimed in claim 1 wherein the microbiological enhanced interception
agent is formed by treating at least a portion of said microporous structure with a cationic
material that has an associated counter ion therewith followed by precipitation of a biologically
active metal with at least a portion of the counter ion associated with the cationic material.
5. A filter medium as claimed in claim 4 wherein the cationic material comprises a
homopolymer of diallyl dimethyl ammonium chloride having a molecular weight of greater than
or equal to 400,000 Daltons.
6. A filter medium as claimed in claim 1 wherein said microporous structure comprises a
solid composite block of active particles, or a flat sheet structure of immobilized active particles.

7. A filter medium as claimed in claim 1 wherein said microporous structure is formed by
extrusion, molding, slip casting, powder coating, wet forming or dry forming of the actyile
particles.
8. A filter medium as claimed in claim 1 wherein said filter medium provides greater than
or equal to 6 log reduction of microbiological contaminants in an influent when the influent has
an empty bed contact time with said filter medium for less than or equal to 12 seconds.
9. A filter system having a filter medium as claimed in claim 1 or 2 comprising:
a housing having an inlet and an outlet;
said filter medium situated within said housing in fluid communication with the inlet
and outlet, said filter medium comprising:
a microporous structure having a mean flow path of less than or equal to 2 microns
comprising active particles of activated carbon, activated alumina, zeolites, diatomaceous
earth, silicates, aluminosilicates, titanates, bone char, calcium hydroxyapatite. manganese
oxides, iron oxides, magnesia, perlite. talc, polymeric particulates, clay, iodated resins, ion
exchange resins, ceramics, or combinations thereof; and
a microbiological interception enhancing agent comprising a cationic material
having a high charge density, a molecular weight greater than or equal to
5000 Daltons and having an associated counter ion therewith, the cationic
material adsorbed on at least a portion of the microporous structure, and
wherein a biologically active metal is caused to precipitate with at least a
portion of the counter ion associated with the cationic material.
wherein a microbiologically contaminated influent flowing through said housing and
contacting said filter medium has at least about 4 log reduction in microbiological
contaminants in an effluent flowing from said housing.
10. The filter system as claimed in claim 9 wherein the active particles of the microporous
structure are a solid composite block, or a flat sheet structure of immobilized active particles.

11. The filter system as claimed in claim 9 wherein the active particles of the microporous
structure are slip cast, wet-formed or dry-formed.
12. A process of making a filter medium as claimed in claim 1 or 2 having enhanced
microbiological interception capability comprising the steps of:
providing active particles having an average particle size of about 0.1 microns to
about 5,000 microns;
treating the active particles with a microbiological interception enhancing agent
comprising a cationic material having a high charge density and a molecular
weight greater than or equal to 5000 Daltons in combination with a biologically
active metal; and
forming the treated active particles into a microporous structure having a mean flow
path of less than or equal to 2 microns.
13. A process of making a filter medium as claimed in claim i or 2 having enhanced
microbiological interception capability comprising the steps of:
providing active particles having an average particle size of about 0.1 microns to
about 5,000 microns;
coalescing the active particles into a microporous structure having a mean flow path
of less than or equal to 2 microns; and
treating the microporous structure with a microbiological interception enhancing
agent comprising a cationic material having a high charge density and a molecular
weight greater than or equal to 5000 Daltons in combination with a biologically
active metal.
14. A process as claimed in claim 12 or 13 wherein the step of providing active particles
comprises providing active particles of activated carbon, activated alumina, zeolites.
diatomaceous earth, silicates, aluminosilicates, bone char, calcium hydroxyapatite, manganese
oxides, magnesia, perlite, talc, polymeric particulates, clay, or combinations thereof, and further
including the step of adding a binder.

15. A process as claimed in claim 12 or 13 wherein the step of treating comprises the steps
of:
coating at least a portion of the microporous structure or active particles with
cationic material having a counter ion associated therewith; and
causing precipitation of a biologically active metal with at least a portion of the
counter ion associated with the cationic material on at least a portion of the
microporous structure or active particles.
16. A process as claimed in claim 12 or 13 wherein the step of treating, the cationic material
is selected from the group consisting of amines, amides, quaternary ammonium salts.
benzalkonium compounds, biguanides, aminosilicon compounds, polymers thereof, and
combinations thereof.
17. A process as claimed in claim 12 or 13 wherein the step of treating, the biologically
active metal is selected from the group consisting of silver, copper, zinc, cadmium, mercury,
antimony, gold, aluminum, platinum, palladium, and combinations thereof.
18. A process as claimed in claim 12 or 13 wherein the step of forming or coalescing the
active particles into a microporous structure comprises extrusion, slip casting, or immobilizing
the active particles into a flat sheet structure.
19. A method of removing microbiological contaminants from a fluid using a filter medium
as claimed in claim 1 or 2, said method comprising the steps of:
providing said filter medium comprising
a microporous structure comprising active particles and having a mean flow path of
less than or equal to 2 microns; and
a microbiological interception enhancing agent comprising a cationic material having
a medium to high charge density and a molecular weight greater than or equal to
5000 Daltons in combination with a biologically active metal, adsorbed on at least
a portion of said microporous structure;

contacting a microbiologically contaminated fluid to the filter medium for a
period of time of less than or equal to 12 seconds; and
obtaining an effluent having greater than or equal to 4 log reduction of
microbiological contaminants.
20. The method as claimed in claim 19 wherein in the step of providing a filter medium, the
microporous structure comprises active particles including activated carbon.

The invention discloses a filter medium comprising a microporous structure comprising an array
of active particles, said microporous structure having a mean flow path of less than or equal to 2
microns; and a microbiological interception enhancing agent comprising a cationic material
having a medium to high charge density and a molecular weight greater than or equal to 5000
Daltons, adsorbed on at least a portion of said microporous structure, and a biologically active
metal in direct proximity to the cationic material and also on at least a portion of said
microporous structure. The invention is also for filter system comprising such filter medium and
methods of making and using the same.

Documents:

1452-KOLNP-2003-(14-03-2012)-FORM-27.pdf

1452-KOLNP-2003-CORRESPONDENCE 1.1.pdf

1452-KOLNP-2003-FORM 27.pdf

1452-KOLNP-2003-FORM-27 1.1.pdf

1452-kolnp-2003-granted-abstract.pdf

1452-kolnp-2003-granted-assignment.pdf

1452-kolnp-2003-granted-claims.pdf

1452-kolnp-2003-granted-correspondence.pdf

1452-kolnp-2003-granted-description (complete).pdf

1452-kolnp-2003-granted-drawings.pdf

1452-kolnp-2003-granted-examination report.pdf

1452-kolnp-2003-granted-form 1.pdf

1452-kolnp-2003-granted-form 18.pdf

1452-kolnp-2003-granted-form 3.pdf

1452-kolnp-2003-granted-form 5.pdf

1452-kolnp-2003-granted-form 6.pdf

1452-kolnp-2003-granted-gpa.pdf

1452-kolnp-2003-granted-reply to examination report.pdf

1452-kolnp-2003-granted-specification.pdf


Patent Number 231339
Indian Patent Application Number 1452/KOLNP/2003
PG Journal Number 10/2009
Publication Date 06-Mar-2009
Grant Date 04-Mar-2009
Date of Filing 10-Nov-2003
Name of Patentee KX TECHNOLOGIES LLC.
Applicant Address 269 SOUTH LAMBERT ROAD, ORANGE, CONNECTICUT
Inventors:
# Inventor's Name Inventor's Address
1 KOSLOW EVAN E. 14 TWELVE O'CLOCK ROAD, WESTON, CT 06883
PCT International Classification Number C02F 1/50
PCT International Application Number PCT/US2003/00065
PCT International Filing date 2003-01-02
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/345,062 2002-10-31 U.S.A.
2 10/209,803 2002-11-08 U.S.A.