U.S. patent application number 11/894342 was filed with the patent office on 2008-06-26 for cigarette filter incorporating nanofibers.
Invention is credited to Michael J. Gardiner, Stephen B. Squires.
Application Number | 20080149120 11/894342 |
Document ID | / |
Family ID | 34102638 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080149120 |
Kind Code |
A1 |
Squires; Stephen B. ; et
al. |
June 26, 2008 |
Cigarette filter incorporating nanofibers
Abstract
A cigarette is equipped with a filter incorporating nanofibers.
The nanofibers can be used either alone or in conjunction with
other filtering media such as larger fibers, paper, activated
charcoal, etc. With a nanofiber filter, the filter need not be as
dense as the molecules of the smoke become attracted to the
nanofiber due to quantum mechanics instead of being sieved out. The
efficacy of the filter is better than filters with larger diameter
fibers.
Inventors: |
Squires; Stephen B.;
(Colleyville, TX) ; Gardiner; Michael J.; (Alodo,
TX) |
Correspondence
Address: |
THE HECKER LAW GROUP
1925 CENTURY PARK EAST, SUITE 2300
LOS ANGELES
CA
90067
US
|
Family ID: |
34102638 |
Appl. No.: |
11/894342 |
Filed: |
August 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10896762 |
Jul 21, 2004 |
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11894342 |
|
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60481111 |
Jul 21, 2003 |
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Current U.S.
Class: |
131/345 ;
131/331 |
Current CPC
Class: |
A24D 3/163 20130101;
A24D 3/04 20130101; A24D 3/10 20130101; A24B 15/286 20130101 |
Class at
Publication: |
131/345 ;
131/331 |
International
Class: |
A24F 1/20 20060101
A24F001/20 |
Claims
1. A cigarette, comprising: a) a tobacco rod; b) a filter coupled
to the tobacco rod and comprising a tow made of nanofibers.
2. The cigarette of claim 1, wherein the pressure drop across the
filter is between 50-150 mm wg.
3. The cigarette of claim 1, wherein the weight of the filter is
between 50-400 g/1000 rods.
4. The cigarette of claim 1, wherein the filter tow is comprised of
cellulose acetate.
5. The cigarette of claim 1, wherein the filter comprises activated
charcoal.
Description
SPECIFICATION
[0001] This application is a continuation of U.S. application Ser.
No. 10/896,762 filed Jul. 21, 2004, which claims the benefit of
U.S. provisional patent application Ser. No. 60,481,111, filed Jul.
21, 2003.
FIELD OF THE INVENTION
[0002] The present invention relates to filters, and in particular
to cigarette filters.
BACKGROUND OF THE INVENTION
[0003] Cigarettes are frequently provided with filters to remove
some of the contaminants, or hazardous components, of cigarette
smoke before the smoke is inhaled. Such hazardous components
include tar, carbon monoxide and various carcinogens. Various
cigarette filters are known in the prior art which decrease the
toxic effect of tobacco smoke. These consist of a base made of
acetate, cellulose or acetate-cellulose fibers with substances
applied to the base which have adsorption properties or are
impregnated with these substances. Activated charcoal, inorganic
and organic slats of various acids are used as the adsorbing
agents.
[0004] In one known form of construction, the filter body consists
of a tow of continuous filaments, commonly cellulose acetate
(acetate) filaments, arranged parallel to the longitudinal axis of
the cigarette. In another known form of construction, the filter
body consists of pleated or fluted paper compressed into a
cylinder. The paper is subjected to a grooving process to allow it
to be so pleated or fluted. Such forms of construction contain a
single filter element and may be called "mono" filters. Another
known form of construction is the so-called "dual" filter which
contains two filter elements, namely a paper filter towards the
interior and a tow filter towards the exterior of the cigarette. A
further known form of construction is the so-called "triple"
filter, which contains three elements, namely a paper filter and a
tow filter, as in the "dual" construction, separated by an air gap
or by an activated carbon filter. Paper filters are known to be
generally more efficient at removing tar from tobacco smoke than
are tow filters. High tar removable efficiency is particularly
desirable in view of the trend towards low-tar cigarettes.
[0005] A drawback of these filters is that the range of substances
absorbed by them is restricted. The filters themselves can degrade
on heating, which is accompanied by the formation of toxic
compounds.
[0006] Also, in the prior art, there exists filtered cigarettes
that fall into the category of Less Harmful Cigarettes (LHCs) or
Reduced Risk Cigarettes (RRCs). But these are chemical based and
require extensive testing to prove efficacy. In fact, there
continues to be debate about the efficacy of LHCs and RRCs.
[0007] It would be desirable to provide a cigarette filter element
which is capable of removing certain gas phase components of
mainstream cigarette smoke, while not adversely affecting the
flavor.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to provide a
cigarette filter that removes contaminants or hazardous byproducts
of cigarette smoke, such as tar and carbon monoxide, from cigarette
smoke.
[0009] It is another object of the present invention to provide a
cigarette filter that filters out hazardous components of cigarette
smoke by mechanical means.
[0010] The present invention provides a cigarette that comprises a
tobacco rod and a filter coupled to the tobacco rod. The filter
comprises a tow made of nanofibers.
[0011] In accordance with one aspect of the present invention, the
pressure drop across the filter is between 50-150 millimeters
wg.
[0012] In accordance with another aspect of the present invention,
the weight of the filter is between 50-400 g/1000 rods.
[0013] In accordance with another aspect of the present invention,
the filter tow is comprised of cellulose acetate.
[0014] In accordance with another aspect of the present invention,
the filter comprises activated charcoal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a longitudinal cross-sectional view of a portion
of cigarette of the present invention, in accordance with a
preferred embodiment.
[0016] FIG. 2 is a schematic view of a prior art filter fiber
illustrating gas flow around the fiber.
[0017] FIG. 3 is a schematic view of a nanofiber used in the filter
of the present invention, with an illustration of gas flow around
the nanofiber.
[0018] FIG. 4 is a longitudinal cross-sectional view of a portion
of a cigarette in accordance with another embodiment.
[0019] FIG. 5 is longitudinal cross-sectional view of a portion of
a cigarette in accordance with another embodiment.
[0020] FIG. 6 is a longitudinal cross-sectional view of a portion
of a cigarette in accordance with another embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] The present invention provides a filter so as to make a
filtered cigarette 11. The cigarette 11, shown in FIG. 1, has
smoking material 13 and a filter 15 located at one end. The filter
15 utilizes nanofibers 17 to remove harmful components of the smoke
produced when the smoking material is burned. The filter does not
adversely affect the taste of the smoke and produces less drag, or
resistance, to the flow of smoke. The nanofiber filter can be
substituted for any type of filter that uses fibrous filter
elements, such as cellulose acetate filament filters (known as
"tow").
[0022] The smoking material 13 is typically tobacco or a blend of
tobaccos. The smoking material is in the form of a charge or roll
and is contained in single or multiple layers to form a so-called
"tobacco rod". The tobacco rod is encompassed by a wrapping
material 21 that is generally a paper-based product. The wrapping
material can be one or more layers.
[0023] The filter 15 contains fiber material 17 that is formed into
a tow. During manufacturing, the tow is cut to length and is
typically circumscribed with a wrapping material 21 that is
generally a paper-based product. The filter is joined to the
tobacco rod by wrapping material.
[0024] The filter comprises nanofibers. "Nanofibers" are fibers
with diameters of 1000 nanometers (nm) or less. In the preferred
embodiments, the nanofibers are 500 nanometers or less, in order to
provide slip-flow (which will be described below). The nanofibers
can be 100-250 nm.
[0025] The nanofibers can be made of a variety of materials. In the
preferred embodiment, the nanofibers are made of cellulose acetate.
The advantage of using cellulose acetate is that it is already used
in conventional cigarette filters and thus does not change the
taste of cigarette smoke when used in the nanofiber filter. Other
materials suitable for use as nanofibers are organic polymers (such
as PLA). Another material that can be used is PBI (poly
benzimidazole). However, PBI may alter the taste. Also, carbon
nanofibers can be used. After the carbon nanofibers are spun into a
filament, the carbon can be activated, in accordance with
conventional techniques.
[0026] The nanofibers are made in accordance with conventional
processes such as spunbonding, melt blown and electrospinning.
Spunbonding is a non-woven manufacturing process involving direct
conversion of a polymer into continuous filaments and the filaments
are laid randomly into a non-woven fabric by thermal bonding. In
melt blown, fibrous webs are produced directly from the polymers or
resins using high velocity air to attenuate the filaments. In
electrospinning, one step combines the charging of the polymer and
the spinning of nano-scale fibers. Repulsive electrostatic forces
are used to spin the fibers from a polymer solution or melt.
[0027] In addition, carbon nanotubes can be used either alone, or
in combination with nanofibers.
[0028] The nanofibers are spun into filaments, in accordance with
conventional techniques. The filaments are then made into the tow,
also in accordance with conventional techniques. The tow has a
denier of 1.0 or less per filament. The filament cross-section can
be "Y" shaped. The tow weight is between 50-400 g/1000 rods and has
a pressure drop of 50-150 mm wg. This is compared to a conventional
tow, with larger diameter fibers, having a tow weight of between
540-700 g/1000 rods and a pressure drop of 250-435 mm wg.
[0029] The nanofiber tow can be entirely cellulose acetate
nanofibers or a combination of cellulose acetate nanofibers and
activated charcoal nanofibers.
[0030] FIGS. 2 and 3 show respectively a conventional filter fiber
and the nanofilter fiber of the present invention, and associated
gas flow velocities across the fibers. The conventional filter
fiber 31 of FIG. 2 is relatively large, about 2-3 microns in
diameter. Filters containing conventional, large fibers work by
sieving, wherein particles are blocked by the filter filaments and
the fibers therein. As the gas passes around a fiber 31, the
velocity of the gas adjacent to the fiber drops to zero. Gas
flowing a distance away from the fiber has a non-zero velocity; the
further away from the fiber, the higher the velocity, until the
velocity becomes constant. Classical filtration mechanics dictate
that one assumes continuous flow around the individual fiber,
exhibiting a no-slip behavior. This classical theory has proven its
acceptability with large fibers on a relatively larger sized, macro
scale, where the flow path was generally considered axially and the
fiber size was larger than the molecules being filtered.
[0031] The nanofiber 17 of FIG. 3 exhibits slip-flow behavior. On a
submicron scale, such as with nanofibers, one must consider that
most particles are larger than the filter fiber media through which
it is passing. As a result of the density of the filter media, the
flow path becomes less and less linear (axial) as the molecules are
forced to circumnavigate the fibers because of their relatively
larger size. The generally accepted threshold for when slip-flow
becomes relevant is when the fiber diameter is approximately 500
nanometers or less. In true slip-flow, the velocity of the gas is
assumed to be non-zero. As can be seen in FIG. 3, the velocity of
the gas that is adjacent to the nanofiber is non-zero. The velocity
increases the further away the gas flow is from the nanofiber. As
such, the drag force created by the molecules is less than in the
case of non-slip-flow and results in a lower pressure drop across
the filter. Consequently, this action results in more molecules
being subject to the filter media and yielding higher rates of
diffusion, retention and overall efficiency for a greater number of
molecule types and sizes. Nanofibers offer the advantages which
capitalize on the ability to create a more apparently dense filter
media without the often corresponding pressure drop across the
filter normally associated with a dense filter. In most cases,
nanofiber air filtration devices exhibit longer life and a greater
ability to entrap a larger number of contaminants. Quantum
mechanics comes in to play when the molecules are coupled to the
nanofibers. In particular, London van der Waals forces come into
play between the molecules in the gas flow and the nanofibers.
[0032] The contaminants typically found within the byproducts of
tobacco smoke have a nominal size of approximately 0.2 microns or
larger. The filter of the present invention effectively reduces the
contaminants that exit the filter and are subsequently inhaled by
the smoker by as little as 38% and as much as 72%.
[0033] The pressure drop caused by the filter 17 is lower than
conventional filters. This means that a smoker does not have to
draw in as hard and consequently need not draw the smoke in as
deeply into the lungs.
[0034] FIGS. 4-6 show some other exemplary embodiments of the
invention. The nanofiber filter 15 can be used in conjunction with
other types of filters. For example in FIG. 4, there is a section
15 of the filter that is nanofibers and another section 41 of the
filter that is microfibers, that is fibers that are 1 micron or
larger in size. The different filter sections 15, 41 can be placed
end to end as shown in FIG. 4 or they can be concentrically
arranged.
[0035] FIG. 5 shows a nanofiber filter 15 with a rigid plug 43 at
the mouthpiece end of the filter. The plug prevents the end of the
filter from collapsing when placed in the mouth of a smoker. The
plug can be used with a nanofilter fiber either by itself or a
nanofilter fiber in conjunction with some other kind of filter.
[0036] FIG. 6 shows a nanofiber filter 15 used with a cartridge 45
that encompasses the circumference of the filter. The cartridge can
contain nanofibers, microfibers, activated charcoal, paper,
etc.
[0037] In addition, nanofibers can be used to make other types of
filtration media. For example, nanofibers spun into filament can
make air filters for use in heating, ventilation and air
conditioning (HVAC) systems. The filter has a frame or cartridge
that holds the nanofibers and the support structure for the
nanofibers. A nanofiber has a lower pressure drop, thus increasing
the overall efficiency of the HVAC system.
[0038] The foregoing disclosure and showings made in the drawings
are merely illustrative of the principles of this invention and are
not to be interpreted in a limiting sense.
* * * * *