Note: Descriptions are shown in the official language in which they were submitted.
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Field of Invention
This invention relates to odor-removing
filters and relates to the subject matter of U.S.
Patent 4,227,904, and U.S. Patent 4,699,681.
Background of Invention
In U.S. Patent 3,019,127 a glass fibrous mat
made of fibers measuring from approximately 20-25
microns is sprayed with an adhesive, carbon particles
of 12 to 50 mesh are sprinkled on the pad, the pad
vibrated to distribute the particles and the adhesive
cured to adhere the particles in the mat. The method
results in a relatively low carbon particle loading,
i.e., on the order of 4 percent of particulate material
per unit volume of pad. In U.S. Patent 4,227,904,
carbon particles measuring 12/28 to 4/6 ~Tyler Screen
Series) are glued to the face of a perforated substrate
to provide a layer of particles on the substrate. This
results in a medium loaded product. A highly loaded,
thin-bed filter has been made by D-Mark, Inc. of Mt.
Clemens, Michigan and others wherein the space between
two perforated sheets is filled with loose carbon
particles. This results in a high capacity filter, but
the particles tend to settle resulting in channeling
and shedding of carbon dust. As used herein, the term
thin-bed filter refers to a filter having a bed or
substrate measuring in thickness anywhere up to two
inches.
It has been a long-sought objective to
provide an odor-removing thin-bed filter with
reasonably high carbon loading, low carbon shedding
sd/rn
DMI 0104 P CA -2- 13375~0
\
and no induced channeling at a low unit cost. In some
instances, as for the commercial/industrial filter
market, a highly efficient, high-capacity filter is
desired, while for the range hood and appliance
markets a somewhat less efficient and lower capacity
filter may suffice. In providing filters for these
two markets, allowable pressure drops must be adhered
to. For example, in the range hood market, this
pressure drop should preferably not exceed 0.15 inches
of water column, while in the commercial/industrial
market, 0.3 inches is typically allowable.
In the manufacture of the filter according
to U.S. Patent 4,227,904, relatively large, odor-
removing, pelletized particles are employed such as
6/8 mesh (Tyler Screen Series). This size pelletized
material has become difficult to acquire and
substitute materials have been difficult to reliably
adhere to the filter substrates. As the filter made
under U.S. Patent 4,227,904 was particularly adapted
for manufacture with the 6/8 pellet, the need has
arisen to find other approaches to the manufacture of
thin-bed type filters.
In addition, there has been a need to
provide a combination odor and grease removing filter
that will visually indicate when it has become grease
laden and should be replaced.
In seeking to provide suitable filters for
both the range hood/appliance and the commercial/
industrial markets at the lowest cost, it has become
desirable to provide a method of manufacture that
utilizes readily available granular carbon and is
sufficiently flexible so filters especially designed
for these different markets may be produced without
requiring separate dedicated production lines. This
~ DMI 0104 P CA -3- 1 337550
has lead to the desirability of a filter wherein the
odor-removing media is so suspended in the air stream
that greater or lesser quantities of the media may be
provided (in accordance with the different market
requirements) by simple changes in the method of
filter manufacture.
Summary of Invention
We have discovered how to provide a filter
having carbon particles suspended in the air stream in
a quantity approaching that of a conventional filled
filter but without the disadvantages associated
therewith such as shedding or channeling or the high
pressure drop associated with some filled-filter
lS designs. This is accomplished by suspending the
carbon particles in a substrate which is formed of a
porous fibrous air- permeable mat having a denier of
from 3 to 400, spraying the mat with an adhesive
sufficient to penetrate as far through the mat as the
carbon particles are to be suspended, then depositing
carbon on the mat and driving them thereinto and
thereafter curing the adhesive to lock the particles
in the substrate. If desired, the odor- removing
particles may extend completely through the thickness
of the substrate.
We have found that the particles may be more
effectively locked in the substrate, in some cases, by
applying a second coating of adhesive thereto. In
addition the thickness of the final substrate may be
controlled by passing it through sizing rollers.
We have also discovered that a substantial improvement
in the state of the art may be provided by matching
the particle size to the void size in the substrate.
For example, a larger denier, more open mat may be
~ ~MI 0104 P CA -4- l 337550
filled with larger particles whose size tend to fill
the voids between the fibers of the mat. We have
further found that the effectiveness of the adhesive
bond may be improved by working the particles against
the adhesive-coated fibers. Techniques for effecting
such working are disclosed.
Methods of making thin-bed type filters
which are capable of producing a more heavily loaded
filter than that shown in U.S. Patent 3,019,127 or a
more uniform and more securely attached carbon layer
than that in U.S. Patent 4,227,904, are herein
disclosed. In addition, a basic design concept for
the filter enables manufacture of filters for both the
range hood/appliance market and the commercial/
industrial markets utilizing the same production line
with simple changes to accommodate the particular end
result desired. According to the method, a porous
substrate is coated on one or both sides by an
adhesive spray, odor-removing particles are deposited
on one or both sides and then driven into the
substrate, the adhesive is cured and the carbon loaded
substrate is assembled into a filter. Following the
teaching herein, utilizing 6/12 carbon particles in a
250 denier unwoven polyester mat (substrate) carbon
loadings approaching one pound per square foot in a
1/2 inch thick finished substrate have been achieved.
This is believed to be substantially greater than any
loading heretofore achieved in the prior art. The
odor-removing particles are driven into the substrate
either by application of an air stream impinging on
the particles and driving them into the substrate, or
they may be pressed into the substrate through the
application of a roller pressing against them or by a
combination of an air stream and a roller. Pressing
~ DMI 0104 P CA -5- 1 337550
of the odor-removing particles into the substrate by
the roller has been found to improve the adhesive
retention of the particles in the substrate. Excess
particles are removed from the substrate by
application of an air stream directed against them.
Where it is desired to further improve
retention of the odor-removing particles in the
substrate, the substrate may be sprayed with a second
adhesive coat (overcoat) before the substrate is
passed through the curing stage to cure the adhesive
thereon. This second coat of adhesive spray serves to
lock the odor-removing particles in the substrate.
The second coat follows driving of the particles into
the substrate and/or removal of excess particles from
the surface of the substrate.
The adhesive is cured as by passing the
substrate through an oven. Adjacent the outlet of the
oven, the thickness of the substrate may be sized by
passing the substrate between sizing rollers.
Where both sides of a substrate are to be
filled with the odor-removing particles, the process
is preferably carried out by first coating one side of
the substrate, depositing the odor-removing particles
thereon and driving them thereinto, removing excess
particles and then curing the adhesive. Thereafter
the process is repeated on the opposite side of the
substrate.
A so-called ~clean" filter may be produced
according to the method herein disclosed. A white
fibrous mat may have one side sprayed with adhesive
and the odor- removing particles deposited thereon and
partially driven thereinto, excess particles removed,
and the adhesive cured. This will result in a filter
pad having one side which is white or "clean" while
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~ DMI 0104 P CA -6- 1 3 37 5 50
the opposite face is covered by the odor-removing
particles. By placing such a substrate in a filter
assembly so that the white side is exposed to view, a
particle-removing filter having an odor-removing
capability is provided.
Another type of so-called "clean" filter
which is also an "indicator" filter may be provided by
coating one side of a light colored or white fibrous
substrate with an ink pattern according to the
teaching of German Patent 27 08 435. The printed
surface of this substrate is then coated with an
adhesive spray insoluble with respect to the aforesaid
ink, and odor-removing particles are then deposited on
the adhesive-coated surface, and may then be driven
into the substrate and the adhesive cured. This will
provide a particle and odor-removing indicator filter.
A further filter embodiment made according
to the method herein disclosed comprises an expanded
metallic layer which has a coating of carbon adhered
to the face thereof. The carbon is attached to this
substrate following the teachings of the method herein
disclosed.
Brief Description of the Drawings
Fig. 1 is a schematic view of a processing
line embodying the method described herein;
Fig. 2 is a cross-sectional view through a
substrate being processed in the spraying station of
Fig. 1;
Fig. 3 is a cross-sectional view through a
substrate being processed in the particulate filling
station of Fig. 1;
Fig. 4 is a cross-sectional view through a
mat having odor-removing particles driven thereinto
~ DMI 0104 P CA -7- 1 337 5 50
and excess particles removed therefrom by an air
driver;
Fig. 5 is a cross-sectional view through a
substrate having the odor-removing particles extending
substantially half-way therethrough and manufactured
according to the method shown in Fig. l;
Fig. 6 is a cross-sectional view through a
substrate manufactured according to the teaching of
Fig. 1 and showing the odor-removing particles
extending substantially uniformly through the
thickness of the substrate;
Fig. 7 is a cross-sectional view of a
substrate as shown in Fig. 6 with the same being
enclosed within an air-permeable envelope or scrim;
Fig. 8 is a cross-sectional view through what we have
termed as a nclean" odor-removing filter;
Fig. 9 is a cross-sectional view through a
perforated, self-supporting sheet coated with odor-
removing particles according to the method disclosed
herein;
Fig. 10 is a cross-sectional view through a
substrate being processed through a modified form of
the particulate filling station of Fig. 1;
Fig. 11 is a cross-sectional view through a
substrate being processed according to a still further
modification of the method shown in the particulate
filling station of Fig. 1;
Fig. 12 is a cross-sectional view through a
non-woven polyester pad having odor-removing particles
adhered to but one face thereof;
Fig. 13 is a modified form of "cleanN
filter; which also is an "indicator" filter
manufactured according to the methods herein
disclosed;
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DMI 0104 P CA -8- 1 337550
Fig. 14 is a cross-sectional view through an
expanded metal substrate through which odor-removing
particles have been adhered according to the methods
herein taught; and
Fig. 15 is a cross-sectional view through a
modified form of the filter shown in Fig. 7.
Brief Des~ription of the Preferred Embodiment
In Fig. 6 a porous, air-permeable,
10 non-woven, fibrous substrate S has been filled with
odor-removing particulate media 22, adhesively secured
in the substrate. The media has been shown as being
substantially uniformly distributed over both of the
opposed faces 24 and 26 of the substrate and
15 throughout the thickness T of the substrate. The
filter of Fig. 6 may find particular utility in
industrial or commercial applications where a greater
pressure drop can be tolerated and a greater capacity
is desired. The process herein disclosed allows for
20 varying the amount of particulate media filling the
substrate not only as between a distribution partially
or completely through the thickness T, but also as to
the density of the loading. For example, in the
embodiment of Fig. 6, the filling may be on the order
25 of from 50 grams to 355 grams of particulate per
square foot of substrate where the finished substrate
is approximately 1/2 inch thick. The amount of
loading depends on variations in the method employed
in the manufacture as well as the particulate size and
30 the character of the substrate. As much as 1 pound
(454 grams) of particulate per square foot of
substrate (nominally 1/2" substrate thickness) has
been achieved and up to about 500 grams appears
feasible. Comparing particulate loading of the filter
1 337 ~5~
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~ DMI 0104 P CA -9-
.
of Fig. 6 with the loading of a filled filter of
comparable thickness, between 75 percent to 80 percent
by weight has been achieved in pre-production
testing. A very light weight filter may be made
utilizing a light denier fibrous, non- woven mat of,
for examples from 3 to 100 denier and a density of
from 1 to 6 ounces per square yard. Filling may
utilize odor removing media or the order of 20/50
carbon (U.S. Mesh) to -400. The percent of loading
may lie in the range of from 8.8% by volume to 88%.
In preparing a filter such as shown in Figs.
5 and 6, a non-woven fibrous mat substrate having a
fiber denier of from 3 to 400 may be utilized. For
example, a 250 denier fiber with a nominal thickness
of 1/2 inch and a weight of 10 to 28 grams per square
foot is placed on the upstream end 32 of a conveyor
line shown in Fig. 1 with one of the opposed faces
disposed upwardly. Mats move along the line in the
direction of arrow D passing through a series of
stations where various steps in the method of
manufacturing the filter are performed. The first
station is the spraying station 34. It comprises a
water trough 36 containing an adhesive entraining
water bath disposed below adhesive spray nozzles 38,
which may be model No. 61 manufactured by Binks
Manufacturing Co. of Franklin Park, Illinois and which
are mounted to reciprocate back and forth across the
substrate as it passes through the station. The bath
will catch overspray of adhesive. Station 34 also
includes a conveyor 40 having an upper run 40'adapted
to support the substrate to move it through the
station and a return run 40" which dips down into the
water bath. The spray nozzles may be housed in a
spray booth with a suitable exhaust system (not shown)
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1 337550
DMI 0104 P CA -10-
for removing adhesive aerosols. Adhesive is delivered
to the nozzles to emit a spray that will penetrate a
substrate to be filled with the odor-removing
particulate. For example, at 30-55 PSIG adhesive
pressure and 20-65 PSIG air pressure at the nozzles,
a conveyor speed of 5-35 feet per minute and the
nozzles being disposed approximately 11-12 inches from
the mat, the substrate fibers may be wetted with the
adhesive to somewhat greater than one-half the
thickness of the mat. Depth of penetration of the
adhesive into the mat will be dictated by the nature
of the filter to be made, i.e., if the odor-removing
particulate media is to extend substantially half way
through the mat, then the spray should extend at least
that far. Where a filter of the nature shown in Fig.
6 is to be manufactured, the spray should extend
substantially half way through the thickness of the
substrate so that upon inverting the substrate and
passing it again through the spray station 34, the
opposite face and remaining depth of the substrate may
be wetted.
In Fig. 2 the upwardly disposed face 24a, of
the substrate S is shown being sprayed with the
adhesive A from the spray nozzles 38 which reciprocate
back and forth across the substrate. The adhesive is
shown at A' on the substrate fibers and as having
penetrated substantially one-half the way through the
substrate.
Following application of the spray, the
substrate S is moved to the particulate filling
station 44. Such station comprises a hopper 46
containing the particulate odor-removing media to be
loaded into the substrate. A hopper of conventional
construction provided with a media discharge slot in
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~MI 0104 P CA ~ 337550
its lower end is disposed above substrates passing
through the station on the conveyor. The filling
station includes its own conveyor 48 which is adapted
to receive on its upper run 48' substrates S delivered
by the conveyor 40 and moves the substrates through
the filling station. Beneath the conveyor 48 is a
media catch trough 50 for catching media which is not
deposited on or does not remain on the substrates for
recycling through the hopper. As the substrates pass
beneath the nozzle 52 of the hopper the particulate
media is dropped onto the upwardly disposed face of
the substrate to uniformly coat the same as the
substrate passes beneath. Fig. 3 shows the upwardly
disposed face 24a having been loaded with the
particulate media from the nozzle 52 of the hopper.
Particulate media 22 builds up on top of the substrate
as it issues from the nozzle 52 and some of the
particulate will sift down into the substrate as shown
in Fig. 3 to the right of the nozzle 52. However, for
the most part, the particulate will remain essentially
on the surface of the substrate. The conveyor 48 has
an open substrate supporting surface enabling excess
odor-removing particulate to fall through the conveyor
to the trough 50.
Downstream from the nozzle 52 is the
particulate driving means generally indicated in Fig.
1 at 54. The particulate driving means is shown in
three embodiments in this disclosure, the first being
illustrated in Fig. 4 while the second and third are
shown in Figs. 10 and 11 respectively. In each case
the function of the particulate driver is to press the
particulate media 22 down into the substrate and/or
remove excess media from the substrate.
1 337550
DMI 0104 P CA -12-
Turning to Fig. 4 the particulate driver
comprises an air pipe 56 which extends transversely of
the conveyor 48 in the filling station 44 spaced just
above the substrates on the conveyor upper run 48'.
The upper run 48' is of a sufficiently open character
as to allow air and excess media to pass downwardly
therethrough. The air pipe is provided with a series
of nozzles 58 which are simply 5/32n openings through
the wall thereof disposed at substantially 1/2-inch
intervals. The pipe may be pressurized with a source
of compressed air to approximately 60 PSI. This air
is delivered from the nozzles and is directed against
the substrates passing beneath the air pipe. As the
air jets 59 impinge on the particulate media 22, the
jets drive the media down into the substrate and also
serve to blow off from the top of the substrate excess
media. By controlling the force of the jets and the
distance of the pipe from the upwardly facing surface
of the media coated substrate, the amount of
penetration of the particulate into the substrate can
be regulated as can the amount of media blown off the
substrate. By varying the rotated position of the
pipe 56, the amount of odor-removing media blown off
the surface of the substrate or driven down into the
substrate may be varied. Desirably, the effect of the
air driver is regulated so that a substantially
uniform layer of particulate media lies on and in the
substrate just to the downstream side of the air pipe
and excess media which is not in contact with adhesive
coated fibers is blown off of the substrate. In Fig.
4 the particulate media 22' is shown at the downstream
side of the pipe 56 as generally uniformly covering
the upwardly disposed face of the substrate and as
having penetrated substantially half the thickness of
DMI 0104 P CA -13- 1 337 550
the substrate. To the upstream side of the air
driver, the particulate 22" essentially lies on the
upwardly disposed face of the substrate in preparation
for being driven thereinto.
In Fig. 4, the air-driver pipe 56 is shown
with the jet openings 58 being disposed substantially
perpendicular to the substrate passing therebeneath.
The rotated position of the pipe may be varied.
In Fig. 10 the second form of driver 54 is
shown. Essentially it comprises the driver of Fig. 4
designated by reference numeral 56a supplemented at
its downstream side by a pair of rollers 58 and 58a.
The rollers are mounted in suitable trunions at
opposite sides of the conveyor and are driven by a
suitable drive mechanism (not shown). The substrates
are fed between the rollers. The distance between the
rollers is adjustable, but in a preferred embodiment
the rollers are adjusted relative to the substrate so
as to press substantially halfway down through the
substrate. The effect of rollers 58 and 58a, which
may be rotated at the same surface speed as that of
the conveyor 48 is to press the particulate media down
into the substrate. In addition, as the rollers press
the media down into the substrate, they work the media
against the adhesive coating the fibers and effect a
more secure lock of the substrate fibers and the media
than simply the air driver alone in Fig. 4. Doctor
blades (63 and 65) wipe the surface of the rollers to
keep them clear of accumulating adhesive.
In Fig. 11, the third form of particulate
driver comprises a pair of driver rollers 61 and 61a
of substantially the same character as that shown in
Fig. 10 disposed immediately upstream from an air
driver 56b. The rollers are arranged to press the
~ DMI 0104 P CA -14- 1 33~5 5 0
particulate 22, which has been deposited by the spout
52 upon the upwardly disposed surface of the
substrate S, downwardly into the substrate and embed
the same therein. The action of the roller 61 in
pressing the particulate media into the substrate also
serves to work the media against the adhesive on the
substrate fibers to effect a good bond between the
fibers and the particulate media. As the substrate
passes beneath the air driver 56b downstream of the
roller, excess media is blown therefrom. The driver
shown in Fig. 11 will serve to embed the greatest
amount of particulate media in the substrate as
compared with the drivers of either Figs. 4 or 10.
Downstream of the driver means 54 is a
second spraying station 62 for applying a second or
"overcoat~ on the upwardly disposed face of the
substrate. As with the spraying station 34, the
second spraying station 62 is provided with a
reciprocating sprayhead 64 disposed within a sprayhood
66 and adapted to reciprocate across the substrates as
they pass through the station. A conveyor 68 of a
construction similar to conveyor 40, and dipping on
its return run into a water through 36', serves to
transport the substrates through station 62. The
purpose of station 62 is to spray the media filled
surface of the substrate with a second coating of
adhesive to more effectively lock the odor removing
media in or on the substrate by providing a coating of
adhesive to bridge between the individual media
particles and the substrate fibers to bond the same
together. This second spraying station is utilized in
those instances where it is desired to obtain the most
effective locking of the odor removing media on or in
the substrate. When the second coat or over coat
DMI 0104 P CA -15- 1 337 5 50
provided by Station 62 is utilized in combination with
the air driver alone, as in Fig. 4, a more secure
locking of the media in the substrate is obtained than
if the second coat was not applied. This does result
in some lessening of the efficiency of the odor
removing media, but does not appear to reduce
significantly its capacity. If the second coat is
omitted, but either the driver of Fig. 10 or the
driver of Fig. 11 is utilized, the working of the
particulate media effected by the rollers improves the
bonding action of the media with the substrate. The
bond may not be quite as effective as with the second
coating afforded by station 62, but the efficiency of
the media is not affected as much. The most secure
locking of the media to the substrate is effected by
utilizing the second coating provided by station 62
with the driver of either Figs. 10 or 11.
A substantial advantage of the second coat
is in connection with the adhering of smaller size
particles to the the substrate. We have found that by
utilizing the second spray, it may be possible to
eliminate altogether the necessity of enclosing the
particulate filled substrate in an envelope or scrim
to prevent shedding or contamination during handling
or use of the filter. We have also found that the
second coating is most effective in smaller size
particles such as 20/50 (U.S. Screen). As the
particle size increases the amount of adhesive that
must be applied in the second coat to effect a more
secure bond reaches the point where it adversely
affects the efficiency of the odor removing
particulate.
Downstream from station 62 the substrates
pass through a drying/curing station comprising an
DMI 0104 P CA -16- 1 3 3 7 5 5 0
oven 70 having a conveyor span 71 whose upper run
receives the substrates S from station 62 and conveys
them through the oven. In the oven the adhesive is
cured sufficiently so that upon emerging from the oven
the substrates may be handled without the odor
removing media dislodging therefrom.
Downstream of station 74 is a tolerance
determining or thickness sizing station 76. This
station comprises a pair of driven rollers 78 and 78a
extending transversely of the conveyor 72 and adapted
to receive therebetween the substrates emerging from
the curing station and compress the substrates a
predetermined amount. The space between the rollers
may be adjusted to effectively squeeze the substrates
a predetermined amount. As the substrates are hot as
they emerge from the oven, the roller will serve to
"set" the thickness of the substrates.
Downstream of the tolerance station as at
the end 80 of the conveyor, the substrates are
successively removed from the processing line for
further handling. If it is intended to fill both
sides of the substrates, the substrates will be
returned to the upstream end 32 and replaced on the
conveyor with the unfilled side or face disposed
upwardly for passage through the processing line. The
steps previously described would then be repeated to
provide a substrate which is filled from both sides
with the odor removing particles. Utilizing the
method heretofore described and passing the substrate
through the processing line twice to fill opposite
faces 24 and 26 thereof, and using the particulate
driver of Fig. 11, it has been possible to provide a
loading in a 1/2 inch nominal final thickness
substrate of substantially one pound of activated
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DMI 0104 P CA -17- 1 337550
carbon per square foot of substrate.
In Fig. 7, the substrate S of Fig. 6, has
been enclosed within a scrim envelope 64 comprising
upper and lower layers 64A and 64B which have been
stitched together or otherwise secured around the
periphery of the substrate as at 67. The scrim is an
open mesh material through which air will readily
pass. The function of the scrim is to contain within
the envelope carbon which may become dislodged from
the substrate. The scrim envelope is particularly
useful where the substrate has not been subjected to
the overcoat spray of station 62, nor the action of
rollers 58 and 58a or 60 and 60a.
If desired, a layer to filter airborne
particles may be disposed inside the envelope to
overlie one or both of the faces of the substrate.
One such layer is shown in Fig. 15 wherein the filled
substrate S' is enclosed within a scrim 64' with a
particle filter 68 disposed within the envelope. The
intended direction of air flow through this filter is
as shown by arrow A. The particle filter pad 68 may
be a fuzzy pad that is intended to remove airborne
particles before they reach the odor-removing
substrate. A suitable pad is sold under the brand
name FILTRETE and manufactured by 3M Company of St.
Paul, Minnesota.
In Fig. 8, there is shown what may be termed
a "clean" filter. In this embodiment a white (or
light- colored) pad or substrate S'' of approximately
1/4 inch thickness of a non-woven, fibrous character
having fibers of from 3 to 40 denier and a density of
from 2.0 to 6.0 ounces per square yard, is sprayed on
one surface with adhesive as in spraying station 34.
Odor-removing media, such as activated carbon granules
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~ DMI 0104 P CA -18- 1 337550
of 20/50 (U.S.) mesh , are deposited on the
adhesively-coated face of the substrate. The air
driver of Fig. 4 then removes the excess carbon
particles to provide a generally uniform layer of
carbon particles on the pad approximately one particle
thick. The pressure of the air supply to pipe 56 and
the direction of the air jets is so controlled that
the carbon particles are not driven too deeply into
the relatively thin substrate to essentially provide
simply a thin coating of the carbon granules on the
surface as shown at 22A. The substrate with carbon
thereon is then sprayed with a second coating of
adhesive in station 62 and then passed through the
curing oven to set the adhesive. The substrate would
not normally be passed between the tolerance rollers
78and 78a, but rather would be directly packaged in a
supporting frame. Air flow through this substrate
would be in the direction of Arrow A in Fig. 8. This
filter is intended to be used primarily in range
hoods and to give the householder an indication when
the filter is contaminated and should be replaced
because the clean appearance of surface 26A will
become discolored by the entrainment of grease
particles in the pad.
In Fig. 9, a substrate Sa comprises a
perforated self-supporting sheet similar to those of
U. S. Patent 4,227,904. It is provided with
perforations 70. The substrate is sprayed with
adhesive as in spraying station 34 and odor-removing
particles 22b are deposited thereon as in station 44
and excess particles are blown off the surface as by
the air driver of Fig. 4 to provide a generally
uniform layer of carbon particles approximately one
particle thick. An overcoating of adhesive is then
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~MI 0104 P CA -19- 1 3 37 5 5 0
applied as by station 62 and the substrate then passed
through the drying/curing station 74. Such substrate
need not be subjected to the tolerance station 76 but
may be removed from the end 80 for subsequent use.
The second or overcoat provided by station
62 enables such a substrate to retain the
odor-removing media thereon and in this respect, the
method herein disclosed represents an improvement on
the method of making a filter disclosed in U.S. Patent
10 4,227,904, wherein the substrate is coated by a roller
coating technique. The second or overcoat disclosed
herein makes it possible to lock the odor-removing
particles on the substrate without resort to roller
coating with the resulting product having a more
15 uniform particulate loading without shedding.
Fig. 12 is a filter corresponding to that of
Fig. 8 except that following deposit of the carbon
particles and removal of the excess carbon, a second
adhesive coating is sprayed over the carbon coated
20 face of the substrate as in Station 62 to lock the
carbon particles on the substrate. The filter is, of
course, passed through the curing station. If
desired, the substrate may be sized in thickness as by
the roller 78. This substrate may be more dense than
25 that of Fig. 8 where an increased pressure drop can be
tolerated and greater particle filtering action is
desired.
In Fig. 13 another type of "clean" filter is
disclosed which is also an nindicatorn filter, i.e.,
30 will indicate to the user when the filter has become
loaded with grease and should be replaced. A light
colored or white fibrous non-woven substrate Sc is
printed on one side 72 with an ink pattern such as
disclosed in German Patent 27 08 435. This ink
1 337550
DMI 0104 P CA -20-
pattern may be printed on a face of the substrate in
any suitable fashion. The ink itself should be of a
color that contrasts with that of the substrate. It
may be made up, for example, of 5 parts of grease
soluble (water insoluble) organic dye stirred with
5-10 parts of a suitable emulsifier having the
property of dispersing grease soluble but not water
soluble dyes in water. Thereafter, 30 parts of a
water soluble binder are stirred in until the mixture
is homogeneous. The mixture is then treated with 55
parts water and printed on the substrate face 72. The
non-woven substrate Sc will function as a particle
filter.
The substrate is then passed through the
processing line shown in Fig. 1 with face 72 disposed
upward and the face coated with a spray of the
adhesive in station 34, then coated with odor-removing
particles in Station 44 and then passed beneath the
air driver shown in Fig. 4 to drive the odor removing
media down into the substrate and also remove excess
particles. A second or overcoating of adhesive is
then applied in station 62 to the side 82 of the
substrate to lock the odor-removing particles on the
substrate. Following this the substrate is passed
through the curing or drying oven in station 74. The
substrate may then be optionally passed through the
tolerance station 76 to size the thickness of the pad.
The substrate is then mounted in a suitable frame
with the media covered face 72 disposed downstream so
that the normal air flow is in the direction of Arrow
A and the exposed face 75 will be the one observed by
the user. This type of filter is particularly
desirable for use in range hoods. As the substrate
Sc becomes grease-laden, the ink 73 will migrate toward
l 337550
DMI 0104 P CA -21-
the surface 74 and when visible to the user will
indicate that the substrate has become grease-loaded
and the filter is ready to be replaced. Of course,
the odor-removing particulate 77 will remove the odors
from the air stream as it passes through the
substrate.
Fig. 14 shows an expanded metal substrate St
on the face 79 of which has been adhesively secured a
layer of odor-removing particulate 81. The substrate
Sd may be prepared by placing the substrate at the
entry end of the processing line shown in Fig. 1 with
the face 78 uppermost, and then sprayed with adhesive
in the spraying station 34, the substrate then passed
to station 44 where odor-removing particles are
applied and then passed beneath the air driver of Fig.
4. The air pressure is adjusted to remove only enough
particulate so that a uniform dense layer
approximately one particle thick remains on the
substrate surface as shown in Fig. 14. The substrate
is then passed to station 62 where a second or over
coat of adhesive is applied to lock the particles on
the substrate. The substrate is then passed through
station 74 to dry or cure the adhesive. In the case
of this type of substrate, the rollers 78 and 78a are
not utilized for sizing. The resultant substrate may
be processed through the line once more to coat the
opposite surface of the substrate in like fashion if
desired. The substrate, thus prepared, may be mounted
in a suitable frame for use as a filter.
The substrates of Figs. 2-8 may be formed
of polyester, nylon, polypropylene or glass fibers.
Other fibers, either natural or man-made to meet the
particular requirements of the intended use of the
filters may be utilized. In addition, open cell
-
DMI 0104 P CA -22- 1 337550
polyurethane, or the like, reticulated foam may be
utilized.
The adhesive to be used may be styrene
acrylic latex, vinyl acetate, ethylene vinyl acetate,
polyvinyl acetate, p.v.c. and acrylic latex, or other
adhesives meeting the requirements for the use of the
filter.
The odor-removing particles useful herein
may be either activated carbon, activated aluminum
impregnated with potassium permanganate, silica gel
and the like. As used herein the term "odor-removing
particles~ is also intended to cover oxidizing
materials such as manganese dioxide.
The scrim material shown in Fig. 7 may be
spun bonded nylon or polypropylene, knitted polyester,
or woven fiber of a variety of materials.
Examples of filters made utilizing the
method disclosed herein are as follows:
EXANP~E 1
(a) A 1/4 inch nominal
thickness polyester pad measuring
12 by 12 made of a 32 denier
non-woven fiber with a density of
252 to 3 ounces per square yard was
placed at the entry end of the
processing line shown in Fig. 1
and passed through various steps
as hereinafter detailed.
30(b) In spraying station 34,
the upwardly disposed face of the
substrate was sprayed with an
acrylic latex adhesive identified
as UCAR 153~ manufactured by Union
r~ k
-
-
DMI 0104 P CA -23- 1 337 550
Carbide Corporation having a
viscosity of less than 500 cps. at
20'C. This adhesive was sprayed
through a two-component spray head
with the air at 40 to 60 psig and
the adhesive at 30 to 55 psig at
a distance of approximately 11
inches with the spray head, or
heads, reciprocating across the
pad. Between 20 and 30 grams of
adhesive per square foot was thus
applied.
(c) Following the spraying
of the upwardly disposed face, the
substrate was passed to station 44
where 20/50 U.S. mesh activated
carbon particles in 30 to 60
activity was applied to the
upwardly disposed adhesive sprayed
face of the mat at the rate of
between 30 to 55 grams per square
foot. A suitable carbon granule
for this purpose is made by
Sorbtech, Inc. of Woodlands,
Texas. Following application of
the activated carbon, the
substrate was passed beneath an
air driver as in Fig. 4 where air
jets are directed downwardly at
the substrate of sufficient force
to drive the activated carbon
particles down into the substrate
and at the same time blow off the
excess particles. For this
-
~ DMI 0104 P CA -24- 1 337 55 0
purpose the air pipe 56 may be of
a 1 inch inside diameter with air
holes of 5/32 inch diameter spaced
1/2 inch apart and with an air
pressure of 60 psig. The pipe is
spaced 1-1/2 inches above the
substrate.
(d) Following the air
driver, the substrate was passed
to the station 62 where a second
or overcoat spray was applied at
the rate of 2 to 10 grams per
square foot of the same adhesive
as was applied in station 34. The
adhesive was sprayed using a spray
head and at pressures similar to
those described in sub-paragraph
(b) at a distance of approximately
11/12 inches. The second coat
bridged the particles and also
bridged between particles and
fibers so that upon curing the
adhesive the particles are quite
securely locked in the mat.
(e) The substrate was then
passed through the curing station
74 where it was raised to a
temperature of 200' to 350' F. for
a period of approximately 2
minutes. During this interval the
water content of the adhesive was
evaporated out. Following the
oven, the filled substrate was
passed through a sizing station
~ DMI 0104 P CA -25- 1337 550
similar to station 76 to size the
thickness of the mat. Thereafter
the filled substrate was mounted
in a suitable frame for use as a
filter.
EXAMPLE 2
(a) A filter was made
according to the process described
in Example 1, except after passing
out of the curing oven in station
74, the substrate was re-entered
in the processing line with its
opposite or uncoated face disposed
upper-most and each of the steps
thereafter repeated on the
upwardly disposed face of the
substrate. The pressure of the
air driver on both passages
through the processing line was
selected so that the carbon
particles were driven
substantially half way through the
substrate with the result that the
final product had the activated
carbon distributed substantially
uniformly through the entire
thickness of the substrate.
EXAMPLE 3
(a) A one-half inch nominal
thickness, non-woven polyester pad
measuring approximately 12 x 18
and made of 200 denier fiber with
-
-
DMI 0104 P CA -26- l 337550
a density of between 4 and 9
ounces per square yard was entered
at the upstream end of the
processing line of Fig. 1.
(b) In station 34, the
adhesive corresponding to that
mentioned in Example 1 was applied
to give a wet loading of
approximately 25 grams per square
foot.
(c) At station 44 activated
carbon measuring 6/12 U.S. mesh of
50 to 65 activity was deposited at
the rate of 160 grams per square
foot. The substrate was then
subjected to the action of the air
driver as in subparagraph (c) of
Example 1, to drive the carbon
particles substantially half way
through the thickness of the
substrate.
(d) The substrate was then
subjected to a second coat as in
station 62 of 2 to 10 grams of
adhesive per square foot of
substrate.
(e) The substrate was then
passed through the curing station
74 and following such was
subjected to the sizing in the
tolerance station 76 and its
thickness (which has grown during
processing) is reduced to 1-2.
-
-
DMI 0104 P CA -27- l 3 3 7 5 S O
EXAMPLE 4
(a) A substrate was made
according to the process of
Example 3 except no overcoat as in
Station 62 was applied to the
substrate. The finished product
emerging from the curing station
74 was enclosed in a non-woven
highly porous scrim envelope to
prevent shedding. The scrim
material found suitable for this
purpose is manufactured by James
River Corporation, and has a
denier of 3.5 and a density of 0.4
ounces per square yard.
EXAMP~E 5
(a) A substrate was
processed according to Example 3
but in lieu of the air driver of
Fig. 4, a driver of the character
shown in Fig. 10 was utilized.
It was found that the resulting
substrate, following cure and
sizing in tolerance station 76
exhibited enhanced activated
carbon granule retention upon
shaking the substrate in an effort
to dislodge the particles
therefrom.
1 337550
DMI 0104 P CA -28-
EXAMPLE 6
(a) A substrate was
manufactured in accordance with
Example 3, but in lieu of the air
driver of Fig. 4, a particle
driver of the character shown in
Fig. 11 was utilized. In this
instance carbon loading on the
order of from 304 to 323 grams
per square foot was achieved.
Retention of the activated carbon
particles in the substrate was
very good as measured by shaking
the substrate following curing and
thickness sizing. For example, in
checking several samples, between
.85 and 1.74 grams of carbon were
lost by the shaking.
Several further samples were made using the
processing line illustrated in Fig. 1 to determine the
amount of particulate that could be effectively filled
and retained in a substrate and the data is tabulated
below. In the table, the substrates measured (before
filling) nominally 13n by 13" and were of original and
final thicknesses as indicated. Original thickness
refers to the nominal pad thickness prior to filling
while the final thickness is that which it measured
following squeezing in the tolerance station 76. The
substrates being filled were non-woven of 200 denier
polyester fiber and had a density of 4.4 ounces per
square yard. All substrates were filled from both
sides using activated carbon particles measuring 6/12
U.S. screen series. The series D samples were
DMI 0104 P CA -29- 1 337550
subjected to an overcoat on both sides in station 62 .
Each sample was cured twice once for each side after
coating. For comparison purposes, it was calculated
that a filled filter one inch thick would contain
about 1135 grams per square foot and would have an
average pressure drop thereacross of 1.0 inches water
column at 2 00 fpm. The pressure drop measurement for
the samples was taken by placing two of the sample
layers together and passing air therethrough at 200
fpm.
The term "percent of volume loadingn refers
to the percentage by volume of carbon in the substrate
after the loading. It is determined in accordance
with the following formula:
15(Specific Volume of Carbon -:
Specific Volume of Substrate) x 100
The basis would be one square foot of substrate
one-half inch thick. For example:
Carbon weighs = 301bs/ft3 or
1/301b/ft3 = .0333 ft3/lb specific volume
1/2" mat = 1/24 ft3 or . 0417 ft3.
25If .0333 ft3 carbon is in . 0417 ft3 of mat =
.0333/. 0417 = . 799 or 79 . 9% by volume
~ DMI 0104 P CA -30- 1 337~50
Sample: A(1) B(1) C(1)D(1)
Original
Thickness
Nom, in. 1/2 1/2 1/2 1/2
Pad, Dry
Wgt. gms. 14.10 14.05 3.4414.45
Adhesive
Wgt. gms. 42.84 51.24 55.5565.78
Activated
Carbon,net gms*
6/12 U.S. Mesh
(granular) 270.62 300.67 313.18 314.96
Shake loss gms. 2.18 0.54 1.60 0.14
Finished thick-
ness before
compression in. 5/8 5/8 5/8 5/8
% Vol.loading
before compres-
sion,% (4) 38.4 42.6 44.544.7
Finished thick-
ness after com-
pression
in. (2) 7/16 7/16 7/167/16
% Vol. loading
after compres-
sion,% (5,2) 54.4 60.5 63.163.4
Pressure drop
@ 200fpm,in
H20 (6) .13 .15 .16.15
Pressure drop
@200fmp, in
H20 (7,2) .16 .17 .22.20
Pressure drop
of 1" thick
(nom) filled
filter at 200
fpm 1.0 1.0 1.01.0
*After deducting carbon lost from shaking.
~ DMI 0104 P CA ~ 33~55~
NOTES
1. A, B, C, and D are averages of 4
samples each.
2. Averages of A (3&4), B (3&4),C (3&4),
and D (3&4) only, and sized.
3. A. Samples made with air driver only.
B. Samples rolled after air driver.
C. Samples rolled before air driver.
D. Samples rolled after air driver,
and overcoated.
4. Based on 5/8" thickness before
compression.
5. Based on 7/16" thickness after
compression.
6. 2 layers in ln frame before
compression.
7. 2 layers in 1" frame after compression.
From the foregoing chart, it may be
determined that with the driver of the type shown in
Fig. 4, it was possible to suspend the equivalent of
about 48 percent of the activated carbon in the
substrate as compared with the carbon weight of a
filled filter of the same thickness. Where the
substrate was filled using the driver of Fig. 10,
approximately 53 percent of the carbon, by weight,
could be suspended in the substrate as compared with
the carbon in a comparable size filled filter.
Finally, in a substrate which was filled using the
driver of Fig. 11, approximately 55 percent of the
carbon weight of a filled filter could be suspended in
the substrate. At the same time, the table shows that
the pressure drop across the samples was between 13
percent and 22 percent of the pressure drop of a
comparable filled filter.
Utilizing the substrate filling techniques
above-described, a substrate was made up using a pad
of non-woven polyester with a denier of 30 and a
density of 3.6 ounces per square yard and filled with
20/50 (U.S. Mesh) activated carbon particles. Only
DMI 0104 P CA l 33755~
one side of the substrate was filled with carbon and
an overcoat was provided to insure locking of the
carbon on the substrate. This resulted in a filter
substrate which would be satisfactory for domestic
range hood use. The amount of carbon can be controlled
quite accurately by regulating the blow-off provided
by the filling step. The filling may be accomplished
by utilizing the driver of Fig. 4. This product will
provide quite an efficient filter because of the small
size carbon grains being used.
A relationship exists between the
effectiveness of the overcoat in station 62 in locking
the particles in place and the density and denier of
the substrate itself. As the particle size of the
media increases, the overcoat provided in station 62
becomes less effective to hold the particles in place.
If sufficient adhesive is applied to retain the
larger particles the adhesive tends to coat the
surface of the activated carbon particles so that the
carbon is less effective to absorb odors. The
capacity of the carbon may not be reduced but the
efficiency is diminished by the overcoat.
In those instances where a substrate is
filled at both sides to provide the maximum loading of
the substrate with the odor-removing media, the filter
is normally intended for a commercial/industrial use
and in this instance, high-efficiency is generally
required. Therefore, in those instances, an overcoat
may not be desired because the efficiency of the
filter is to be maintained at the highest level. In
such cases the filter substrate may be enclosed in the
scrim envelope shown in Fig. 7.
Thus, it has been determined that with large
activated carbon particles such as 4/6 U.S. Mesh on a
DMI 0104 P CA -33- 1 337550
high denier mat such as 250 to 300 denier, or more,
and where high efficiency is desired, an overcoat as
provided by station 62 may not be desired. However,
with high carbon loading (100 grams to 500 grams per
square foot) the overcoat provided by station 62 may
enable the manufacture of the filter without the use
of the scrim envelope as shown in Fig. 7.
The second or overcoat provided by station
62 is desirable when it is intended to effect better
particle- to-particle or particle to substrate bonding
and to minimize shedding or defoliation of the carbon
particles. The overcoat may be particularly
beneficial a) where there is a small denier mat with
small mesh carbon, i.e., 20/50 (U.S. Mesh); b) where
there is an essentially impervious substrate with
larger carbon particles such as 6/12 (U.S. Mesh); or
c) where a high carbon loading is intended (such as
100 grams to 500 grams per square foot), and it is
desired to avoid the use of the scrim cover as in Fig.
7.
It has also been found that the overcoat
provided by station 62 in Fig. 1 is particularly
useful where the carbon or odor removing media are no
longer regularly shaped, but are irregular in
configuration. In such instance the irregular
configuration appears to lend itself well to the
particle to particle or particle to fiber bonding or
particle to substrate surface bonding provided by the
overcoat of station 62.
As indicated above, it has also been found
that improved adhesive bonding between the
odor-removing particles and the substrate is effected
without the overcoat where the driving techniques of
either Fig. 10 or Fig. 11 is utilized, i.e., where the
DMI 0104 P CA -34- 1 337550
carbon or odor- removing particles are worked in the
substrate by the rollers.
