Note: Descriptions are shown in the official language in which they were submitted.
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FILTER MATERIAL FOR PREPARING A BEVERAGE
The present invention relates to a filter
material which is capable of removing chlorine from
water such that the water is more acceptable for use in
preparing human-consumable beverages, especially in that
the taste of the water and, hence, the taste of the
beverage is improved.
BACKGROUND OF THE INVENTION
It has long been known that typical city water
supplies have a variety of contaminants which contribute
to an unpleasant taste of a beverage made from that city
water. Among these contaminants are lead, hydrocarbons,
calcium, iron, sulfides, and especially chlorine used in
purifying the city water. While all of these
contaminants contribute to the unpleasant taste of
beverages prepared from such city water, chlorine is
probably the most usual and troublesome contaminant,
since it is normally present in all city water, due to
the purification process, and since it can be detected
in beverages in very small amounts. While the
unpleasant taste of the beverage prepared from such city
water is detectable in almost every beverage so
prepared, including reconstituted orange juice, soft
drinks, iced drinking water, and the like, it is
= 25 particularly troublesome in connection with beverages
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which are heated during preparation, e.g. tea and
coffee.
The art has long sought effective means of
removing such contaminants, especially chlorine, from
such city water, and a number of approaches in the art
have been taken. For example, one approach is that of
a porous plastic film filter with pores sufficiently
small to filter contaminants, such as chlorine, from the
water, but such filters have a very low gravity flow
rate, and to use such filters requires considerable time
for filtration of the water in beverage preparation.
Another approach is that of providing a matrix
of fibers and activated charcoal where the activated
charcoal will remove contaminants, especially chlorine,
but to make such filters satisfactory, the fibers must
be made of materials which will not support bacterial
growth, since, otherwise, continued use of such filters
would cause a health problem. To substantially avoid
bacterial growth, such filters, with activated carbon
therein, are made with hydrophobic synthetic polymer
fibers, which are generally non-porous, and hence will
not support bacterial growth resulting from absorbed
nutrients from the water. However, filters made from
such hydrophobic fibers have a very low gravity flow
rate, and to be useful in a practical sense, filters of
that nature must be operated under substantial pressure,
e.g. city water pressure. Thus, filters of that nature
have been limited, generally, to "in-line" filters, i.e.
filters disposed in the city water pressure lines of a
house, manufacturing facility, or the like or at the
taps thereof. These filters, therefore, operate
generally with city water pressure, e.g. about 40 psi or
more. While this arrangement is satisfactory for
in-line filters, such an arrangement is not satisfactory
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for gravity flow filters. In addition, filters of this
nature must be contained in a canister and protected by
media around the filter for preventing particles of
= activated carbon from passing through the filter, during
use, and into the consumable water. This further
decreases the pressure drop across those filters and,
consequently, requires the higher city water pressures
for effective use thereof.
Efforts have been made in the art to improve
flow rates with less pressure for effective use thereof,
and U. S. Patents 4,395,332; 4,505,823; and 4,569,756
are representative thereof. These patents describe
filters for removing contaminants from water, where the
filters contain cellulose fibers and an additional
1ri ~~'rcnrrf-}icrirrr fil.er n~ n rrlcscc~cr fiYcr aQ cjcll
~+~ r7 b.i Glly 1..11GlJiliy l iJ.J'GL , r1. YViI C1r7 U t.IV 12' GV \.GL L
iJ.JGl , C1J W G11
as a contaminant adsorbent, which, among others, can be
activated carbon or charcoal. In addition, these
filters contain micro-bits of polymers, which polymers
can be, for example, polystyrene polymers, polyolefin
polymers and the like. These micro-bits retain porosity
in the filters and, therefore, provide greater flow rate
with less pressure drop through the filters. Thus, the
filters are said to be useful for filtering tap water
for drinking and cooking use in a gravity flow filter
device and, particularly, a conical filter for filtering
tap water from a tap with such conical filter device is
disclosed. However, the filters of these patents, while
said to be useful in filtering tap water by gravity flow
filtration for drinking and cooking purposes, are
composed, in a specific example, of cellulose fibers,
polyester fibers, activated charcoal, a binder for
binding the fibers together to improve the strength
thereof, and the micro-bits, which combination still has
a very low gravity flow filtration rate. While that low
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filtration rate is suitable for some purposes, it is not
suitable for a variety of other purposes.
In this latter regard, as noted above,
beverages which are heated in preparing the beverage are =
particularly susceptible to the taste of tap water
contaminants, especially chlorine, and very typical of
such beverages are coffee and tea. Both coffee and tea
may be brewed in a conventional coffee making machine,
where cold water is heated by an electrical heating
element and, after being heated, is fed through a basket
containing the coffee or tea by which the brewed coffee
or brewed tea is made and discharged from that basket by
gravity into a pot. As the art has well appreciated, in
order to make a filter suitable for such machines, the
filter must have a flow rate consistent with the brewing
rate of the machine. Otherwise, the time for brewing,
for example, a pot of coffee, would be greatly
increased, and the heating element of the machine could
be starved for water and burn out or the hot water
supplied to the basket containing the tea or coffee
could be seriously reduced, and ineffective brewing and
long brewing time would result. Thus, gravity filters
with such reduced flow rates are not satisfactory for
those purposes. Moreover, those patents do not describe
any practical means of retaining the activated charcoal
in the filter, and any substantial amount of activated
charcoal that passes through the filter into the brewed
coffee or tea, of course, would be quite unacceptable.
A somewhat similar but yet slightly different
approach in the art is described in U. S. Patent
4,160,059, where a filter is proposed that is made of
wood pulp and/or synthetic fiber, a heat-fusible fiber,
and an adsorptive material, such as activated charcoal.
The heat-fusible fiber is heated to fuse the charcoal to
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the fibers of the filter, which, therefore, presumably
locks the activated charcoal particles in place and
prevents that activated charcoal from passing through
the filter and into a beverage. This fusing of the
charcoal particles to the fibers is considered a better
approach than that of the prior art where latex binders
have been used for binding the charcoal to fibers.
In this latter regard, U. S. Patent 3,158,532
teaches a filter material made of various fibers,
including polyester fibers and paper fibers, and a
bonding agent or binder for binding particulate material
to deposited layers of fibers, and the particulate
material, in addition to a number of others, can be
activated carbon. Among the binders suggested are
polyacrylic resins.
It has also long been recognized that
hydrophilic fibers forming a filter material will
substantially increase the flow rate of water and
similar water-containing fluids through the filter, and
commercial milk filters are commonly made of cellulose
fibers for this purpose, e.g. cotton, rayon and mixtures
thereof. Such filters have also been made with a
combination of rayon fibers and synthetic fibers, such
as polyester fibers, polyolefin fibers, polyacrylate
fibers, and polyamide fibers, in order to provide better
physical properties to those filters, and U. S. Patent
3,307,706, is representative thereof.
Various forms of filters using activated
carbon have also been described in the art, such as
pleated forms and tape-like porous material, and U. S.
Patents 4,130,487 and 4,645,597 are representative
thereof.
From the foregoing, it can be seen that the
art has approached filters of the present nature from
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various directions, but the art has not been successful
in providing a filter which will give high flow rates of
gravity-f iltered water, which will remove substantial
amounts of contaminants, especially chlorine, which will
ensure that a chlorine absorbent or adsorbent will not
be displaced from the filter and into the water for
producing the beverage, which will not support bacterial
growth with considerable reusage of the filter, and
which can be so inexpensively produced as to be
practical, especially, for home use, and more especially
in conventional coffee making machines. It would,
therefore, be of considerable advantage to the art to
provide a filter which meets all of the foregoing
requirements, and which, in addition, can remove very
substantial amounts of contaminants, especially
chlorine.
BRIEF DESCRIPTION OF THE INVENTION
The present invention, therefore, provides a
filter material for removing chlorine (as well as other
contaminants) from cold water used in preparing a
human-consumable beverage and which can be reused a
number of times with safety and which will provide a
high flow rate with gravity filtration. The invention
is based on several primary and several subsidiary
discoveries.
First of all, it was discovered that the
dilemma of the art of hydrophilic fibers versus
hydrophobic fibers briefly mentioned above can be
solved. Thus, while hydrophilic fibers, such as
cellulose fibers, provide much higher gravity flow rates, those fibers, being
pervious to water, can
support bacterial growth on absorbed nutrients from the
water and are therefore not acceptable for serial, time
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spaced-apart uses of the filter. On the other hand,
synthetic hydrophobic fibers, such as polyester fibers,
are not pervious to water and, hence, will not support
bacterial growth, due to the lack of absorbed nutrients
from the water for bacterial growth, but those fibers,
being hydrophobic, seriously decrease the gravity flow
rate of a filter made therefrom. This dilemma of the
art has been solved by the present invention in that
either or both of cellulosic fibers or synthetic fibers
may be used to provide an effective filter with high
gravity flow rates when those fibers have deposited
thereon a food-grade hydrophilic latex binder. With
such binder substantially coating the fibers of the
filter, the filter will have high gravity flow rates
because of the hydrophilic nature of the binder,
irrespective of whether the fibers are hydrophobic, e.g.
polyester fibers, or hydrophilic, e.g. cellulosic
fibers. In addition, since the binder is a food-grade
binder, it will not, by definition, support bacterial
growth, even when used for a number of serially, time
spaced-apart filtrations.
As a subsidiary discovery in this regard, it
was found that acrylic latex binders are particularly
useful in this regard, since those binders provide more
of a sticky property for adhering activated charcoal to
the binder, as described below.
As a further primary discovery, it was found
that the amount of the binder deposited onto the fibers
within a mat of fi:bers must be sufficient to so bind the
fibers together within the mat that, during filtration
of cold water through the mat, no substantial amount of
fibers are displaced from the mat but, at the same time,
in an amount insufficient to substantially reduce a
gravity flow rate of cold water through the mat to less
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that 0.3 liters per minute per 100 square centimeters of
the mat.
Thus, by providing, substantially a covering
of the hydrophilic food-grade latex binder on the
fibers, bacterial growth will be inhibited, even with
serial, time spaced-apart uses of the filter, while, at
the same time, the gravity flow rate through the filter
will be maintained at a rate sufficient for use in
conventional devices, such as coffee making machines.
A third primary discovery again solves a
dilemma in the art. While the art, as noted above, had
used binders in connection with such filters, activated
charcoal, in the form of a powder, was substantially
"blinded" by the binders, i.e. the binders substantially
covered the particles of activated charcoal and
"blinded" those particles from removing contaminants,
especially chlorine. On the other hand, if such binders
were not used, or used in such small amounts so as to
avoid that blinding of the activated charcoal, the
activated charcoal was liable to pass through the filter
and into the water used for making beverages, which is
quite undesirable. This dilemma in the art was solved
by an arrangement such that the powder used for
adsorbing or absorbing contaminants, e.g. chlorine, such
as activated charcoal, is disposed on the binder, as
opposed to largely within the binder, and disposed on
the binder such that no more than 65% of the total
outside surface area of the powder is substantially
contacted by the binder, and preferably a much smaller
percentage thereof. This still provides considerable
outside surface area of the powder for removing contaminants. At the same
time, that powder is so
attached to the binder that it will not be displaced
during use of the filter and into the water intended for
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beverage making.
As a subsidiary discovery, it was found that
the stickiness of the binder may be such as to provide
good adhesion of fibers to fibers such that the mat
forming the filter material has high strengths and can
be manipulated and used a number of times without being
substantially disrupted or the fibers displaced from the
filter into the water or so displaced that channeling or
the like of the water through the filter occurs, which
is, of course, not desired.
As another primary discovery, it was found
that the powder could be deposited onto the binder, in
the above-described manner, by a step in a process for
making the filter material. In this regard, an
emulsion-breaking agent is added during processing of
the fibers and binder such that the latex binder, in
emulsion form, precipitates onto the fibers, and,
thereafter, the powder is added to that combination such
that a large portion of the surface area of the powder
remains out of contact with the binder, while at the
same time the powder is firmly attached to the binder
and will not be displaced.
Thus, briefly stated, the present invention
provides a filter material for removing chlorine from
cold water used in preparing a human-consumable
beverage. The filter material comprises at least one
layer of a mat of laid fibers selected from the group
consisting of cellulosic fibers and synthetic textile
fibers and mixtures thereof. A synthetic hydrophilic
food-grade latex binder is deposited onto the fibers
within the mat in an amount sufficient to so bind the
fibers together within the mat that, during a filtration
of cold water through the mat, no substantial amount of
fibers are displaced therefrom and in an amount
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insufficient to substantially reduce a gravity flow rate
of cold water through the mat to less than 0.3'liters
per minute per 100 square centimeters of the mat. A
water-insoluble chlorine adsorbent or absorbent solid
powder is disposed on the binder such that no more than
65% of the total surface area of the powder is
substantially contacted by the binder.
In the method of the invention, the fibers are
mixed in water to form a dispersion of the fibers in the
water. The latex binder in the form of an emulsion is
added and mixed with the dispersion to form a dispersed
mixture of the fibers and emulsion. An
emulsion-breaking agent is added and mixed therewith to
precipitate the binder onto the fiber combination, where
the precipitated binder is deposited onto the fibers
within the mat. The powder is then added to that
combination, with mixing, to dispose the powder on the
binder and form a matting material. Thereafter, a mat
is formed of that matting material, which constitutes
the filter material of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagrammatic illustration of a
layer of the filter material of the invention;
Figure 2 is a highly idealized diagrammatic
illustration of the binder on fibers of the filter
material of Figure 1 and adhering activated carbon
powder thereto;
Figure 3 is a diagrammatic illustration of a
plurality of layers of Figure 1 combined into a single
filter media;
Figure 4 also shows a plurality of layers of
filter material forming a filter media, but with an
enclosing top cover and bottom cover for cosmetic
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purposes;
Figure 5 shows, in diagrammatic form, a closed
end of a suitable filter media.
Figures 6, 7 and 8 show embodiments of
configurations of the filter material;
Figure 9 shows the filter material in place on
a pot for filtering tap water for producing a beverage;
Figure 10 shows a conventional coffee making
machine; and
Figures 11, 12 and 13 show embodiments of
disposition of the present filter material in a
conventional coffee making machine.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
While, as noted above, the invention is
adaptable to a variety of applications for gravity
filtering of water for beverage use, and, as further
noted above, the filter material of the invention will
remove a number of contaminants from tap water, and the
specification and claims should be so construed, for
conciseness in this specification, the invention will be
illustrated in terms of filters, primarily, useful in
conventional coffee making machines and will reference,
by example, chlorine removal from the filtered tap
water.
As can be seen from Figure 1, the filter
material comprises at least one layer of a mat,
generally 1, of laid fibers 2. In this regard, the term
"laid" is used in its common meaning, i.e. that the
fibers have been laid (air laid or wet laid) onto a
forming device, e.g. a screen, on which the fibers
entangle into mat form. While in such conventional
laying process, the fibers extend in all of the X, Y and
Z directions of the mat, the fibers more generally are
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parallel to the forming surface, e.g. parallel to a
screen on which the fibers are laid. Laid fibrous mats
of this nature are conventionally made on conventional
paper-making machines and are consolidated during the
laying and forming steps, generally with further
consolidation through pressure rolls, all of which is
well known in the art and need not be recited herein in
detail for purposes of conciseness. However, it is
noted that within the meaning of the term "laid" is the
condition that the mat is not a woven mat or a needled
mat or a felted mat, but only a"laid11 mat. It is
important for purposes of the present invention that the
mat be of laid fibers, since such laid fibers provide
orientations of the fibers that are most useful in
applying the binder, as described below, and in
providing uniform filtration for removal of chlorine.
The fibers are selected from the group
consisting of cellulosic fibers and synthetic textile
fibers and mixtures thereof. Again, these terms are
used in their ordinary sense, in that a textile fiber
is, generally speaking, from about 1 to 20 deniers,
capable of being formed into a textile, and may be of
either continuous or staple form. Synthetic textile
fibers are made from a variety of synthetic hydrophobic
polymers. Thus, the textile fibers may be polyester
fibers, nylon fibers, vinyl fibers, acrylic fibers, and
the like, and the particular synthetic textile fiber is
not critical to the invention. Inherent in this
definition is that the fibers are non-porous and
hydrophobic.
While cellulosic fibers may be in the form of
textile fibers, that term also includes fibers which are
not useful in forming textiles, but are more useful in
forming paper and the like. Thus, the term "cellulosic
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fibers" includes not only fibers in a form suitable for
textile formation, but'suitable for paper making. The
fibers may be cellulose fibers, modified cellulose
fibers, and the like. The particular cellulosic fiber
is not critical so long as the cellulose of the fibers
has not been so modified that the fiber is no longer
hydrophilic. Thus, within the definition of the term
"cellulosic fibers" is included the requirement that the
fibers are porous and hydrophilic.
As can be seen from Figure 2, deposited on the
fibers 2 is a synthetic hydrophilic food-grade latex
binder 3. That binder, preferably, substantially covers
the entire surface area of the fibers in layer 1, as
shown in Figure 2, and is in an amount sufficient to so
bind the fibers together within the mat, e.g. at
crossover points 4, that during a filtration of cold
water through the layer(s) 1 of the mat no substantial
amount of fibers 2 are detached therefrom. In addition,
the amount of binder must be insufficient to reduce a
gravity flow rate of cold water through the mat to less
than about 0.3 liters per minute per 100 square
centimeters of the mat, since, otherwise, the gravity
flow rate of cold water through the mat would not be
sufficient to supply an ordinary and conventional coffee
maker with sufficient water for making coffee at the
usual rate of that coffee maker.
As also shown in Figure 2, a water insoluble
chlorine adsorbent or absorbent solid powder 5 (in
particle form) is disposed on the binder 3 such that no
more than 65% of the total outside surface area of the
powder is substantially contacted by the binder, as
shown in Figure 2. Also as shown in Figure 2, portions
of the particles do contact and are submerged or
embedded into the sticky binder 3, but portions of the
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particles 5 protrude out of the binder 3 and are free
from and do not substantially contact the binder. Those
protruding portions are, therefore, available for
contacting water passing through the filter and
adsorbing and/or absorbing contaminants, especially
chlorine, therefrom. In addition, since activated
carbon has a multitude of inner-connected passageways
inside the particles 5, by providing this unimpeded
outer surface of the powder, sufficient total surface
area (outside and inside surface area) is provided to
remove contaminants from the water and to move those
contaminants deep into the passageways of the particles
of powder, even thought deeper passageways of the
particles are submerged within the binder.
As shown in Figure 3, a plurality of layers 1
may make a filter media, generally 10, and five such
layers 1 are shown in Figure 3. Generally speaking,
however, if multiple layers are used, as opposed to only
one layer, there will be at least 2 and up to 20 layers
in a filter media 10, but more preferably there are
about 3 to 7 layers of the mat in a filter media.
Figure 4 shows an optional embodiment where
three layers 1 of the mat are contained within a top
cover 11 and a bottom cover 12. The coverings 11, 12
are not required, but since, as explained below, the
layers 1 will contain substantial amounts of activated
carbon, which is black in color, and which color will
show through the layers 1, the covers 11 and 12 may be
used simply for cosmetic or appearance purposes to hide
the black color of the layers. This is because some
users would object to a black filter for filtering water
for beverage purposes.
The fibers of the mat of layers 1 may be all
cellulosic fibers or all synthetic textile fibers or a
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mixture of cellulosic fibers and synthetic textile
fibers. Alternately, one layer 1 of the mat may be all
cellulosic fibers and another layer 1 of the mat be all
synthetic textile fibers, with yet a further layer of
the mat being a mixture of synthetic textile fibers and
cellulosic fibers. In other words, alternating layers,
as shown in Figure 3, may have various compositions of
the synthetic textile fibers, the cellulosic fibers or
mixtures thereof. When there is a mixture of the
cellulosic fibers and the synthetic textile fibers, the
ratio thereof can be as desired, but, generally
speaking, it is preferable that the mixture have a
preponderance of cellulosic fibers, e.g. where the
weight percent of the synthetic fibers is from about 1
to 20%, especially about 5 to 15%, since these ranges
give better results, especially where the synthetic
fibers are the preferred fibers, i.e. an acrylic fiber
or a polyester fiber.
While, as noted above, it is preferable that
the binder substantially cover all of the surface area
of the fibers, in certain applications it may be
desirable to have less than such coverage, especially
where the filter material is intended for complicated
configurations and bendings. In such case, for example,
only 60% or 70% or, perhaps, 80% of the surface area of
the fibers is covered by a binder, and when a synthetic
fiber is in the composition, that uncovered portion of
the synthetic fiber will present a hydrophobic surface.
This will decrease the flow rate, and, in that case, it
is preferred that a solid food-grade surfactant is
disposed within the mat, and more preferably disposed
within the binder itself. This will provide less
surface tension to the water being filtered and still
maintain the appropriate flow rate. When such a solid
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food-grade surfactant is used, preferably, about 0.1 to
2% thereof is used, based on the weight of the mat. A
suitable surfactant is Dow-Corning Q2-5247, which is a
silicone food-grade surfactant.
A wide variety of synthetic fibers may be
used, including acrylic fibers, polyester fibers, nylon
fibers, olefin fibers, and vinyl fibers, and the
particular synthetic fiber is not critical, especially
when essentially covered with a binder or when a
surfactant is used. However, as noted above, acrylic
fibers and polyester fibers are preferred.
Likewise, the cellulosic fiber is not critical
and may be cellulose fibers, methylcellulose fibers,
rayon and cotton fibers, although cellulose fibers are
preferred.
While the latex binder, again, can be chosen
from a wide variety of binders, including an acrylic
latex, a vinyl latex, an acrylonitrile latex, and an
acrylate latex, the preferred latex is an acrylic latex,
and especially a modified polyacrylic polymer latex.
Such latex is commercially available under the trademark
HYCAR sold by B. F. Goodrich. HYCAR 26083 is a
particularly good latex in this regard and is a
self-crosslinking carboxylated latex with excellent
abrasion resistance. It forms a film with substantial
clarity. However, other acceptable latexes are vinyl
latexes, nitrile latexes, styrene-butylene latexes, also
sold by B. F. Goodrich under the trademarks GEON, HYCAR
and GOOD-RITE. Nevertheless, for the reasons noted
above, the acrylic latex is preferred.
While the amount of binder should be as
described above, for most of the latexes immediately
described above, the amount of the binder in the mat is
from about 5% to 40% based on the weight of the mat, and
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more preferably about 10% to 30%.
The water-insoluble chlorine adsorbent or
absorbent solid powder, as noted above, also absorbs
other contaminants, but for sake of conciseness in this
specification, the contaminants are illustrated as
chlorine. That powder, therefore, may be a variety of
powders, such as diatomaceous earth, fuller's earth and
the like, but for substantial and desired reductions in
chlorine content of the filtered water, the powder is
activated carbon. The activated carbon may be activated
carbon er se, or impregnated with silver or nickel so
as to increase the bacterial static property of the
activated carbon. In this regard, since the binder is
a food-grade binder, it is, by definition, a binder
which will not support bacterial growth and is referred
to as bacterially static, i.e. the amount of bacterial
growth that will occur on the binder is not significant
from a human health point of view. Thus, in order to
complement the bacterial static property of the binder,
the powder should also be bacterially static. While
activated carbon is essentially bacterially static, at
least for reasonable times of use, for certain waters,
e.g those high in bacterial nutrients or bacterial
content, it may be advisable to use nickel- or
silver-impregnated activated carbon, since these
increase the bacterial resistance of the activated
carbon and ensures that bacterial static property.
The amount of the powder contained in a mat
will depend upon the amount of contaminants to be
removed from the filtered water, the number of times a
mat is envisioned for repeated and time spaced-apart
use, and the ability of the binder to hold amounts of
the powder firmly and substantially non-detachably
thereto. In this latter regard, certain binders can so
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retain different amounts of the powder. Therefore, with
some of the binders, the amount of the powder should not
be more than about 20%, based on the weight of the mat,
while with other of the binders, up to about 70% of the
powder may be used in the mat, again based on the weight
of the mat. With the preferred acrylic binder, as
briefly noted above, that binder presents a very sticky
surface and is capable of retaining large amounts of
powder, e.g. activated charcoal, up to 70%, based on the
weight of the mat. However, more usually, that
percentage will be between about 40% and 60%, and more
ideally about 50%. However, for high removal of
chlorine, the amount of the powder should be more than
40%.
The amount of chlorine that can be removed
from the powder, of course, will depend upon the average
particle size of the powder. For purposes of the
present specification, a powder is defined as a solid
adsorbent or absorbent having an average particle size
of less than 2,000 microns, but more preferably the
average particle size will be less than 1,000 microns,
and more preferably less than 100 microns, so as to
maximize chlorine removal, in view of the larger outer
and internal surface areas provided per weight amount of
the powder with decreasing particle size.
By use of such sticky binder to retain both
the fibers and the powder so that they do not pass from
the filter material, and by use of the present
bacterially static components, a mat of filter material
may be used for up to 50 time spaced-apart filtrations,
i.e. time spaced apart sufficiently that substantial
bacterial growth could take place between uses, as in
daily use of a coffee maker. This must be, also,
without significant displacement of either fibers or
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activated carbon from the filter and into the water for
beverage purposes. That number of filtrations, of
course, will depend upon the number of layers, the
amount of activated carbon, and the particular binder,
but even with a small number of layers and with other
than the most preferred binder, i.e. the acrylic binder,
at least up to 50 such filtrations may so take place.
Even with only one layer, and especially with the
preferred binder, the mat will remain substantially
bacterially static for up to 10 time spaced-apart
filtrations, and this is particularly true where the
binder substantially covers the surfaces of the fibers
in the mat, and more especially where the binder is
substantially continuous over the fibers of mat.
Turning again to the drawings, Figure 5 shows
a single layer 1 with covers 11, 12 and sealed edges 13,
e.g. by heat welding, gluing, etc. Figure 6 shows the
filter material in the form of a cone 60, which could be
used, for example, to filter water into a pitcher for
removing chlorine in preparation of frozen orange juice,
or that configuration could be used for preparing coffee
in a coffee maker which consists essentially of a filter
holder and a pot, where the coffee is placed in the
filter holder and hot water is poured therethrough.
Alternatively, a filter media may be made in the form of
a disk 70, as shown in Figure 7, with a number of layers
1 of filter material forming that disk 70. In this
case, the edges 71 of the disk 70 will normally be
gathered together and sealed, as in Figure 5, so as to
make the composite of the layers a somewhat unitary
structure. This sealing, again, can be by gluing, heat
sealing, ultrasonic welding, and the like, and the
particular means of sealing is not critical to the
invention.
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As a further embodiment, the filter material
may be a pleated filter 80, as shown in Figure 8, having
a plurality of pleats 81 held in a holder 82 to retain
those pleats.
As yet a further alternative, as shown in
Figure 9, the filter material 90 may be in something of
a conical disk shape 91 for fitting over the top of the
conventional pot 92 for filtering water therethrough.
Figure 10 shows a conventional coffee making
machine with a housing 100 having a cold water reservoir
101, a coffee-containing basket compartment 102, a
coffee pot 103 and a heated hot plate 104.
Figure 11 shows that same coffee making
machine 100 having the pleated filter 80 of Figure 8
disposed in the bottom of the cold water reservoir 101.
That pleated configuration can be so disposed by way of
a water-tight drawer (not shown) removable from the
reservoir or can be simply placed at the bottom of the
reservoir by manual insertion.
Figure 12 shows the same coffee making machine
100 with the cone filter 60 of Figure 6 fitted into the
upper portion of the cold water reservoir 101.
Preferably, in this case, the cone will have a
peripheral bead (not shown) of an elastomer, such as
rubber, to make the filter material 60 more secure
therein.
Figure 13 shows that same coffee machine 100
having a disk 70, as shown in Figure 7, placed at the
bottom of the cold water reservoir, and again, either by
a water-tight drawer (not shown) or by manual insertion.
The filter material is made by the following
method. The fibers, as described above, are mixed with
water to form a dispersion of the fibers in the water.
The latex binder, in the form of an emulsion (5% to 70%
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solids), is then added with mixing to the dispersion to
form a dispersed mixture of fibers and emulsion. After
sufficient mixing, an emulsion-breaking agent is added,
with mixing, to the mixture to form a precipitated
binder on the fiber combination, where the precipitated
binder is deposited onto the fiber within the mat, as
shown in Figure 2. Thereafter, to that combination is
added the powder, with mixing, to dispose the powder
onto the binder, again as shown in Figure 2, and form a
matting material. That matting material isthen formed
into a mat by conventional paper-making processes, as
briefly described above.
By first depositing the binder on the fibers,
by such precipitation, and only thereafter depositing
the powder on the binder, the powder is stuck to the
binder, during mixing, as briefly described above, in
such a manner that it is firmly attached to the binder
within the mat, but, at the same time, a substantial
amount of the outer surface area of a particle of the
binder upstands from and is not contacted with the
binder, again as shown in Figure 2. When the binder is
a very sticky material, such as the preferred acrylic
binder, substantial amounts of the powder can be
disposed on the fibers (on the binder) to maximize
chlorine removal from the water being filtered.
The emulsion-breaking agent is not critical
and will depend, in part, on the particular emulsion in
which the binder is dispersed. The combination of the
latex and fibers, naturally, exhibit overall negative
charges. Therefore, unless this natural condition is
altered, the latex particles of the emulsion will not
precipitate. This natural charge, and hence stability
of the latex emulsion, can be broken by adjusting the pH
of the latex emulsion and/or neutralizing the natural
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negative charge. Alum, for example, can both lower the
pH and neutralize the natural negative charge and,
hence, is a preferred emulsion-breaking agent. Alum, as
well as other compounds, provides accessible positive
charges for breaking the latex emulsion. Alternatively,
modified starches are cationic and, thus, will provide
positive charges for emulsion breaking. Starches will
also enhance the dry strength of the formed mat and,
thus, are a preferred agent.
It is also useful to provide a viscosity
control agent in the mix the enhance the mat forming
process. Gums, such as Karaya gum, are useful in this
regard.
Conventional retention aids, such as
Cartaretin AEM (an acrylamide), can be used to assure
that all of the fibers and powder remain in the mat
during the forming step.
Since emulsions are normally pH sensitive, as
noted above, the binder emulsion can be broken by the
adding thereto of a base to lower the pH. Any of the
usual bases are useful, and the particular base is not
critical.
The amount of the emulsion-breaking agent
will, of course, depend upon the particular emulsion and
the particular binder therein, but, generally speaking,
the amount need be only that amount which will lower the
pH or neutralize the negative charge to that
emulsion-breaking point. For most emulsions, however,
a pH of below about 4 will be sufficient for breaking
that emulsion.
As noted above, the viscosity control agents
are useful in the mixing processes and in depositing the
mixture onto a formacious surface, such as a screen, for
producing the laid mat. The viscosity control agent may
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be added in amounts up to about 2% or 3% and any of the
conventional viscosity control agents may be used, e.g.
gums, and the preferred gum is Karaya gum.
With the preferred embodiments, i.e. the
acrylic binder, activated carbon, and the mode of
placing that activated carbon on the binder, as
explained above, gravity flow rates of at least 0.5
liter per minute per 100 square centimeters of the mat
can easily be obtained, and flow rates even up to 5
liters per minute per 100 square centimeters of mat are
obtainable. This is a very significant and high gravity
flow rate, which makes the present filter material an
ideal material for producing filter media for coffee
pots and the like, as described above. Gravity flow is
defined as the flow rate of water through the filter
with no more than one foot of static head pressure on
the water.
The invention will now be illustrated by the
following examples, but it is to be understood that the
examples are not limiting thereof but merely illustrate
the same. In the examples, as in the specification and
claims, all percentages and parts are by weight, unless
otherwise specified.
EXAMPLE 1
This example illustrates a method of producing
the filter material. The apparatus used in this example
is a conventional paper-making machine, the details of
which need not be described herein, for sake of
conciseness, since those details are well known to those
skilled in the art.
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Preparation of Starch and Alum
Using a 1000 ml beaker on top of a Corning hot
plate and a G.K. Heller heavy duty laboratory stirrer
with a series "H" motor controller @ a speed of 500 rpm,
add 32g Cato 2A starch to 500 mls of cold water, heat to
200 F for 30 min., turn heat off, add 32g alum and 300
mis of cold water. Total amount of solution 800 mis.
Preparation of Gum
Using a 1000 ml beaker on top of a Corning hot
plate and a G.K. Heller heavy duty laboratory stirrer
with a series "H" motor controller @ a speed of 500 rpm,
heat water (615 mls) to 180 F, then add 3.67g
triethanolamine and 1.76g ammonia (gum dispersing
agents), then slowly add 8g Karaya gum; add 185g cold
water, agitate for 5 min. @ a speed of 250 rpm. Total
amount of solution 800 mls.
Preparation of Flocculant
Using a 500 ml beaker and a G.K. Heller heavy
duty laboratory stirrer with a series "H" motor
controller @ a speed of 250 rpm, add 6.3g Cartaretin AEM
liquid to 393.7 ml of water. Total amount of solution
400 mis.
Preparation of the Matting Material
Using a small Osterizer 12-speed blender with
700 mls of water, pulp 9g (dried) bleached Kraft
softwood pulp (cellulose fibers -"HP11" - Trademark of
Buckeye Cellulose) on "high" (liquify selection button)
for 30 seconds, stop blender; add 2.8g acrylic fiber and
pulp an additional 30 seconds. Transfer slurry to 1800
ml beaker. Using a G.K. Heller heavy duty laboratory
stirrer with a series "H" motor controller @ a speed of
200 rpm, add 5.7g of B.F. Goodrich 26083 latex with 5.7g water; add 15g of
Starch and Alum solution, wait 2 min.,
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add 27.4g gum solution; in the above blender using 400
ml of water, add 11.8g activated carbon; run on low
speed for 5 seconds and transfer to slurry rinse with 50
ml of water, agitate for 2 min., then add 4.2 g. of
Flocculant solution and transfer to handsheet mold which
has a water level of 12.5 liters; while stirring slurry
pull vacuum switch to form sheet, with 24 inch vacuum.
Open cover of handsheet mold, take out formed sheet and
use a vacuum machine (Dayton wet & dry) for additional
removal of moisture; transfer sheet to an Emerson speed
dryer - temp setting 270 F - wait until dry (10 mi.n.).
EXAMPLE 2
Using a small Osterizer 12 speed blender with
700 mis of water, pulp 11.8g staple polyester fiber on
"high" (liquify selection button) for 60 seconds.
Transfer slurry to 1800 ml beaker. Using a G.K. Heller
heavy duty laboratory stirrer with a series "H" motor
controller @ a speed of.200 rpm, add 5.7g of B.F.
Goodrich 26083 latex with 5.7g water; add 15g of Starch
and Alum solution, wait 2 min., add 27.4g gum solution;
in the above blender using 400 ml of water, add 11.8g
activated carbon run on low speed for 5 seconds and
transfer to slurry rinse with 50 ml of water, agitate
for 2 min., then add 4.2g of Flocculant solution and
transfer to handsheet mold which has a water level of
12.5 liters; while stirring slurry pull vacuum switch to
form sheet, with 24 inch vacuum. Open cover of
handsheet mold and take out formed sheet and use a
vacuum machine (Dayton) for additional removal of
moisture; transfer sheet to an Emerson speed dryer -
temp. setting 270 F - wait until dry (10 min.).
EXAMPLE 3
This example demonstrates the dechlorination
abilities of the filter material produced by Example 1.
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In this test 20 cc. per minute of distilled water
containing 10 to 11 ppm chlorine were continuously
injected through a sample holder containing 10 layers of
1 inch diameter filter material produced according to
Example 1. The 10 layers of mat were placed in a sample
cell and the cell closed and tightened. At a flow rate
of 20 cc. per minute, the residual chlorine was tested
at 10 minute intervals using a HACH testing method
DR2000 Program #80 for a period of 1 hour. The residual
chlorine in parts per million was as follows:
Time-Minutes Chlorine Residual
10 .01
.01
.01
15 40 .01
50 .03
60 .04
As can be seen from the above results, the present
filter material has considerable capabilities for
20 removing chlorine and reduces the chlorine content from
10 to 11 ppm to 0.01 ppm for up to 40 minutes and with
no more than 0.04 ppm for up to 60 minutes, which would
translate into the equivalent of about 80 pots of brewed
coffee with more than 80% chlorine removal efficiency.
25 EXAMPLE 4
This example shows the flow rate produced by
the filter media of Example 1. One layer of the filter
media was placed in a 4-3/8 inch diameter by 2-1/2 inch
high disk sample holder. 500 ml of distilled water was
30 passed through the above sample holder by pouring to
measure the flow rate. The flow rate obtained was 500
ml in 65 seconds.
As a comparison a filter material identical to
that of Example 1, with the exception that the filter
material had a conventional non-hydrophilic acrylate
binder and not the present hydrophilic binder, was
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likewise tested. Without the present hydrophilic
binder, the fibers remained,hydrophobic. The flow rate
in that sample was 3 ml in 150 minutes.
As can be seen, this second flow rate test
shows that conventional fibers or filter materials with
conventional hydrophobic properties have a very low flow
rate and are not acceptable for uses such as in coffee
making machines, but with the present invention, flow
rates quite acceptable for such conventional coffee
making machines are obtainable.
