U.S. patent application number 11/653856 was filed with the patent office on 2007-10-25 for cigarette components having encapsulated catalyst particles and methods of making and use thereof.
This patent application is currently assigned to Philip Morris USA Inc.. Invention is credited to Shalva Gedevanishvili, Kathryne E. Paine, Yezdi Pithawalla, Budda Reddy.
Application Number | 20070246054 11/653856 |
Document ID | / |
Family ID | 38255036 |
Filed Date | 2007-10-25 |
United States Patent
Application |
20070246054 |
Kind Code |
A1 |
Gedevanishvili; Shalva ; et
al. |
October 25, 2007 |
Cigarette components having encapsulated catalyst particles and
methods of making and use thereof
Abstract
Encapsulated catalyst particles can be incorporated in tobacco
cut filler and/or cigarette paper used to form a cigarette. The
encapsulated catalyst particles, which can decrease carbon monoxide
and/or nitric oxide in mainstream tobacco smoke, comprise catalyst
particles that are encapsulated with a volatile coating. During the
smoking of a cigarette comprising the encapsulated catalyst
particles, the volatile coating is volatilized to expose an active
surface of the catalyst particles.
Inventors: |
Gedevanishvili; Shalva;
(Richmond, VA) ; Reddy; Budda; (Glen Allen,
VA) ; Pithawalla; Yezdi; (Midlothian, VA) ;
Paine; Kathryne E.; (Midlothian, VA) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Philip Morris USA Inc.
Richmond
VA
|
Family ID: |
38255036 |
Appl. No.: |
11/653856 |
Filed: |
January 17, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60759036 |
Jan 17, 2006 |
|
|
|
Current U.S.
Class: |
131/284 ;
131/297 |
Current CPC
Class: |
A24B 15/286 20130101;
A24B 15/283 20130101; A24B 15/18 20130101; A24B 15/282 20130101;
A24B 15/28 20130101; A24B 15/287 20130101; A24D 1/02 20130101; A24D
3/16 20130101; A24B 15/288 20130101 |
Class at
Publication: |
131/284 ;
131/297 |
International
Class: |
A24B 15/24 20060101
A24B015/24 |
Claims
1. A component of a cigarette comprising encapsulated catalyst
particles capable of decreasing carbon monoxide and/or nitric oxide
in mainstream tobacco smoke, wherein the catalyst particles are at
least partially coated with a volatile encapsulant, and wherein the
component is selected from the group consisting of tobacco cut
filler, cigarette paper and cigarette filter.
2. The component of claim 1, wherein: (a) the catalyst particles
are fully coated with the volatile encapsulant; (b) the catalyst
particles comprise an elemental metal, alloy, oxide and/or
oxyhydroxide of at least one element selected from the group
consisting of Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Y,
Zr, Nb, Mo, Ru, Ag, Sn, Ce, Pr, La, Hf, Ta, W, Re, Os, Ir and Au;
(c) the catalyst particles comprise an oxide and/or oxyhydroxide of
manganese, iron, copper or cerium; (d) the catalyst particles
comprise nanoscale particles; and/or (e) the catalyst particles
have an average particle size of less than about 100 nm or less
than about 50 nm.
3. The component of claim 1, wherein the volatile encapsulant
comprises: (a) a wax, a water-soluble polymer or a water insoluble
polymer; (b) a wax selected from the group consisting of beeswax,
coconut wax, candelilla wax, carnauba wax, montan wax, ouricury
wax, paraffin wax, rice wax and mixtures thereof; (c) a
water-soluble polymer selected from the group consisting of
polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxides,
water-soluble polyamides, water soluble polyesters, water soluble
celluloses, acrylic acid polymers, starches, dextrins, gums,
gelatins, pectin, alginates, gum arabic and mixtures thereof;
and/or (d) a water insoluble polymer selected from the group
consisting of polyethylene, polypropylene, polyacrylates,
polymethacrylates, polymethyl-methacrylates, polyvinyl chloride,
polyvinylidene chloride, polysaccharides and mixtures thereof.
4. The component of claim 1, wherein: (a) the volatile encapsulant
has a volatilization temperature of between about 40.degree. C. and
350.degree. C.; (b) the volatile encapsulant is adapted to
volatilize in an atmosphere having a relative humidity of greater
than about 5%; (c) the volatile encapsulant comprises a first layer
in contact with the catalyst particles and a second layer formed
over the first layer; and/or (d) the volatile encapsulant comprises
a first layer comprising a flavor-bearing compound and a second
layer formed over the first layer.
5. The component of claim 1, wherein the volatile encapsulant
comprises a flavor-bearing compound.
6. The component of claim 5, wherein the flavor-bearing compound
comprises menthol, a menthol derivative, a menthol precursor, or a
mixture thereof.
7. The component of claim 5, wherein the flavor-bearing compound
comprises a synthetic fragrance, a natural fragrance, an essential
oil, an aldehyde, an alcohol, an ester, a ketone, a phenol or
mixture thereof.
8. The component of claim 1, wherein the catalyst particles are
capable of acting as a catalyst for the conversion of carbon
monoxide to carbon dioxide and/or nitric oxide to nitrogen, an
oxidant for the conversion of carbon monoxide to carbon dioxide and
as a reducing agent for the conversion of nitric oxide to
nitrogen.
9. A cigarette comprising a tobacco rod, cigarette paper and an
optional filter, wherein at least one of the tobacco rod, cigarette
paper and filter comprise encapsulated catalyst particles capable
of decreasing carbon monoxide and/or nitric oxide in mainstream
tobacco smoke, wherein the catalyst particles are at least
partially coated with a volatile encapsulant.
10. The cigarette of claim 9, wherein: (a) the volatile encapsulant
is adapted to volatilize during the smoking of a cigarette to
expose an active surface of the catalyst particles; and/or (b) the
volatile encapsulant is adapted to thermally or chemically degrade
during the smoking of the cigarette to expose a surface of the
catalyst particles.
11. The cigarette of claim 9, wherein the catalyst particles are
fully coated with the volatile encapsulant.
12. The cigarette of claim 9, wherein: (a) the encapsulated
catalyst particles are incorporated in an amount effective to
convert at least 5% of the carbon monoxide in mainstream tobacco
smoke to carbon dioxide and/or convert at least 5% of the nitric
oxide in mainstream tobacco smoke to nitrogen; (b) the total amount
of the encapsulated catalyst particles in the cigarette is up to
about 200 mg per cigarette; and/or (c) the encapsulated catalyst
particles are homogeneously or non-homogeneously distributed along
the length of a tobacco rod.
13. The cigarette of claim 9, wherein: (a) the cigarette paper
comprises a wrapper having a first layer and a second layer formed
around the first layer, and wherein the encapsulated catalyst
particles are incorporated in the first layer; and/or (b) the
cigarette paper comprises a wrapper and the encapsulated catalyst
particles are coated and/or printed on at least one surface of the
wrapper.
14. The cigarette of claim 9, wherein the cigarette comprises a
mixture of different encapsulated catalyst particles.
15. A method of making a cigarette comprising: (i) incorporating
encapsulated catalyst particles in and/or on at least one of
tobacco cut filler, cigarette filter and a cigarette wrapper; (ii)
providing the tobacco cut filler to a cigarette making machine to
form a tobacco column; and (iii) placing the cigarette wrapper
around the tobacco column to form a tobacco rod of a cigarette; and
(iv) optionally attaching the cigarette filter to the tobacco
column using tipping paper.
16. The method of claim 15, wherein the incorporating comprises
spraying, dusting or immersion.
17. The method of claim 15, wherein the encapsulated catalyst
particles are incorporated in the cigarette paper by spraying or
coating the encapsulated catalyst particles onto a wet base web,
intermediate web or finished web.
18. The method of claim 15, wherein the step of incorporating
comprises combining the encapsulated catalyst particles and at
least one of the tobacco cut filler and cigarette wrapper in the
absence of a liquid.
19. A method of treating tobacco smoke produced by the cigarette of
claim 9, comprising lighting the cigarette to form tobacco smoke
and drawing the smoke through the cigarette, wherein the volatile
encapsulant at least partially volatilizes to expose a surface of
the catalyst particles.
20. The method of claim 19, wherein (a) the volatile encapsulant is
volatilized at a distance of from about 0.1 mm to 10 mm in advance
of the charline; (b) the catalyst particles decrease carbon
monoxide and/or nitric oxide in the tobacco smoke drawn through the
cigarette; and/or (c) the volatile encapsulant contributes one or
more flavors to the tobacco smoke.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority under 35 U.S.C. 119
to U.S. Provisional Patent Application No. 60/759,036 filed on Jan.
17, 2006, the entire content of which is hereby incorporated by
reference.
BACKGROUND
[0002] In the description that follows reference is made to certain
structures and methods, however, such references should not
necessarily be construed as an admission that these structures and
methods qualify as prior art under the applicable statutory
provisions. Applicants reserve the right to demonstrate that any of
the referenced subject matter does not constitute prior art.
[0003] Cigarettes produce both mainstream smoke during a puff and
sidestream smoke during static burning. Constituents of both
mainstream smoke and sidestream smoke are carbon monoxide (CO) and
nitric oxide (NO). The reduction of carbon monoxide and/or nitric
oxide in smoke is desirable.
SUMMARY
[0004] Disclosed are cigarettes and components of cigarettes (e.g.,
tobacco cut filler and cigarette paper) comprising encapsulated
catalyst particles capable of decreasing carbon monoxide and/or
nitric oxide in mainstream tobacco smoke, wherein the encapsulated
catalyst particles comprise catalyst particles that are at least
partially coated with a volatile encapsulant. Preferably, the
catalyst particles are fully coated with the volatile
encapsulant.
[0005] The catalyst particles, which can comprise nanoscale
particles, preferably comprise an elemental metal, alloy, oxide
and/or oxyhydroxide of at least one element selected from the group
consisting of Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Y,
Zr, Nb, Mo, Ru, Ag, Sn, Ce, Pr, La, Hf, Ta, W, Re, Os, Ir and
Au.
[0006] Preferred catalyst particles can decrease tobacco smoke
constituents, e.g., catalyze the conversion of carbon monoxide to
carbon dioxide and/or nitric oxide to nitrogen, oxidize carbon
monoxide to carbon dioxide and reduce nitric oxide to nitrogen.
[0007] The volatile encapsulant is preferably a wax, a
water-soluble polymer or a water insoluble polymer. The volatile
encapsulant can comprise a flavor-bearing compound such as menthol,
a menthol derivative or a menthol precursor. Preferred volatile
encapsulants have a volatilization temperature of between about
40.degree. C. and 350.degree. C. or volatilize upon exposure to an
atmosphere having a relative humidity of greater than about 5%.
[0008] In an embodiment, the volatile encapsulant comprises a first
layer (e.g., a flavor-bearing layer) in contact with the catalyst
particles and a second layer formed over the first layer.
[0009] In a cigarette comprising the encapsulated catalyst
particles, the volatile encapsulant is adapted to volatilize (e.g.,
thermally or chemically degrade) during the smoking of a cigarette
to expose an active surface of the catalyst particles.
[0010] In one embodiment, the encapsulated catalyst particles can
be incorporated homogeneously or non-homogeneously along the
tobacco rod of a cigarette. In a further embodiment, the
encapsulated catalyst particles can be incorporated into the paper
wrapper or filter of a cigarette. For example, the encapsulated
catalyst particles can be incorporated into the first (i.e., inner)
layer of a multi-layer wrapper. The encapsulated catalyst particles
can be distributed throughout the paper wrapper or printed on a
surface of the paper wrapper. A cigarette can comprise a mixture of
different encapsulated catalyst particles.
[0011] A method of making a cigarette comprising (i) incorporating
encapsulated catalyst particles in and/or on at least one of
tobacco cut filler and a cigarette wrapper; (ii) providing the
tobacco cut filler to a cigarette making machine to form a tobacco
column; and (iii) placing the cigarette wrapper around the tobacco
column to form a tobacco rod of a cigarette; and (iv) optionally
attaching the cigarette filter to the tobacco column using tipping
paper. The encapsulated catalyst particles can be incorporated by
spraying, dusting or immersion. For example, encapsulated catalyst
particles can be incorporated in cigarette paper by spraying or
coating the encapsulated catalyst particles onto a wet base web,
intermediate web or finished web.
[0012] A method of smoking a cigarette comprising encapsulated
catalyst particles comprises lighting the cigarette to form smoke
and drawing the smoke through the cigarette, wherein during the
smoking of the cigarette, the volatile encapsulant at least
partially volatilizes to expose a surface of the catalyst
particles. In a preferred method, the volatile encapsulant is
volatilized at a distance of from about 0.1 mm to 10 mm in advance
of the charline of a lit cigarette.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1(a) shows an optical microscope image of as-received
NANOCAT iron oxide catalyst particles. FIGS. 1(b)-1(c) show optical
microscope images of alginate encapsulated NANOCAT iron oxide in
the form of particles and fibers, respectively.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0014] Disclosed are cigarette components, cigarettes, and methods
for smoking cigarettes having incorporated therein encapsulated
catalyst particles. The encapsulated catalyst particles comprise a
core of one or more catalyst particles and a volatile encapsulating
layer (i.e., coating) formed around the core. A volatile
encapsulating layer can be a protective layer for the catalyst
particles at near-ambient temperatures (e.g., during cigarette
storage and downstream of the combustion/pyrolysis zone in a lit
cigarette), but upon exposure to an elevated temperature, humidity
or gas-phase constituents of cigarette smoke the volatile material
can volatilize (e.g., thermally or chemically degrade) to expose
the underlying catalyst particles.
[0015] Encapsulated catalyst particles can be incorporated into one
or more components of a cigarette such as tobacco cut filler,
cigarette paper and cigarette filter of the cigarette. In
cigarettes comprising the encapsulated catalyst particles, the
amount of carbon monoxide and/or nitric oxide in mainstream smoke
can be reduced. Methods for providing cigarettes comprising
encapsulated catalyst particles include encapsulation of the
catalyst particles and incorporation of the encapsulated catalyst
particles into one or more components used to form a cigarette.
[0016] The incorporation of catalyst particles into one or more
components of a cigarette has been disclosed in commonly-owned U.S.
Patent Publication Nos. 2004/0131859; 2004/0040566 and
2004/0110633, the contents of which are hereby incorporated by
reference. Catalyst particles can be incorporated into a cigarette
in order to reduce the concentration in mainstream smoke and/or in
sidestream smoke of one or more gas-phase constituents (e.g., CO or
NO). However, during smoking of a cigarette comprising catalyst
particles, semi-volatile or non-volatile combustion products such
as tar can form on the catalyst particles. Early deposition of
semi-volatile and non-volatile deposits can effectively deactivate
the catalyst particles (e.g., by forming a barrier between the
catalyst particles and gas-phase constituents and/or by chemically
interacting with the catalyst particles). For example, a layer of
semi-volatile or non-volatile material can be effectively
impervious to gas phase constituents found in mainstream smoke.
Furthermore, at elevated temperatures, semi-volatile or
non-volatile materials can react with the catalyst particles and
diminish their catalytic activity.
[0017] Disclosed are encapsulated catalyst particles comprising a
volatile coating that is formed directly on an exposed surface
(e.g., a catalytic surface) of the catalyst particles. By volatile
is meant that the encapsulating layer preferably has a
volatilization temperature that is less than the volatilization
temperature of tar or other solid-phase byproducts of tobacco
combustion/pyrolysis. Prior to smoking a cigarette comprising the
encapsulated catalyst particles, the volatile coating preferably at
least partially encapsulates, more preferably fully encapsulates,
the catalyst particles. Preferred volatile coatings are volatilized
during smoking of a cigarette.
[0018] In a cigarette comprising the encapsulated catalyst
particles, when the encapsulated catalyst particles are exposed to
a temperature that is less than the volatilization temperature of
the coating, the volatile coating forms a protective layer upon
which semi-volatile and non-volatile materials (e.g., tar) can
deposit. Semi-volatile or non-volatile materials can form and
deposit on the volatile coating and not on the catalyst particles.
When the temperature reaches or exceeds the volatilization
temperature of the encapsulant, the volatile coating--as well as
any materials formed thereon--can be removed to expose an active
surface of the catalyst particles. Thus, an active surface of the
catalyst particles can be exposed under smoking conditions (i.e.,
in advance of the combustion zone) to catalyze and/or oxidize
gaseous constituents of mainstream and/or sidestream smoke.
Applicants have unexpectedly found that encapsulated catalyst
particles that are incorporated into a cigarette have a higher
catalytic efficiency during smoking of the cigarette than catalyst
particles that are not encapsulated.
[0019] In an embodiment, a cigarette comprises encapsulated
catalyst particles wherein during smoking of the cigarette the
volatile encapsulant is volatilized at a distance of from about 0.1
mm to 10 mm, preferably from about 0.5 mm to 2 mm in advance of the
charline. As used herein, the "charline" is the line created in a
cigarette paper wrapper at the edge of the combustion zone of the
cigarette, produced during smoking of the cigarette.
[0020] The encapsulating layer is formed from a volatile material
that can thermally or chemically degrade. In a first embodiment,
the encapsulant material can thermally degrade (e.g., melt, sublime
or pyrolyze) upon exposure to a temperature above an ambient
temperature, but below about 350.degree. C., preferably below about
200.degree. C. to expose a surface of the catalyst particles to
mainstream smoke, sidestream smoke or both. Preferred encapsulant
materials thermally degrade at a temperature between about
40.degree. C. and 200.degree. C. In a further embodiment, the
encapsulant material can chemically degrade (e.g., dissolve) upon
exposure to components of cigarette smoke that are generated during
smoking. For example, moisture in mainstream smoke can interact
with the encapsulating layer to volatilize the encapsulant material
and expose the catalyst particles. Preferred encapsulating layers
chemically degrade upon exposure to mainstream smoke or sidestream
smoke having a relative humidity of greater than about 5%, more
preferably greater than about 20%.
[0021] By providing a volatile encapsulating layer, an active
catalytic surface of particles that are incorporated into a
cigarette (e.g., into tobacco cut filler) can be exposed in advance
of the combustion region of a cigarette. The volatile encapsulating
layer can minimize physical interaction and chemical reaction
between the catalyst particles and non-volatile or semi-volatile
combustion and/or pyrolysis products (e.g., tar). For example, high
temperature cracking of tar molecules via reaction with the
catalyst particles can be minimized.
[0022] The catalyst particles, which comprise the core of the
encapsulated catalyst particles, can comprise an elemental metal,
alloy, oxide and/or an oxyhydroxide of at least one element
selected from the group consisting of Mg, Al, Si, Ti, V, Cr, Mn,
Fe, Co, Ni, Cu, Zn, Ge, Y, Zr, Nb, Mo, Ru, Ag, Sn, Ce, Pr, La, Hf,
Ta, W, Re, Os, Ir and Au.
[0023] The catalyst particles preferably comprise nanoscale
particles. By "nanoscale" is meant that the catalyst particles have
an average particle diameter of less than a micron. Preferably, the
nanoscale particles have an average particle size of less than
about 100 nm, more preferably less than about 50 nm, and most
preferably less than about 10 nm.
[0024] Preferred catalyst particles comprise oxides and/or
oxyhydroxides of iron. For instance, MACH I, Inc., King of Prussia,
Pa. markets Fe.sub.2O.sub.3 nanoscale particles under the trade
names NANOCAT.RTM. Superfine Iron Oxide (SFIO) and NANOCAT.RTM.
Magnetic Iron Oxide. The NANOCAT.RTM. Superfine Iron Oxide (SFIO)
is amorphous ferric oxide in the form of a free flowing powder,
with a particle size of about 3 nm, a specific surface area of
about 250 m.sup.2/g, and a bulk density of about 0.05 g/mL. The
NANOCAT.RTM. Superfine Iron Oxide (SFIO) is synthesized by a
vapor-phase process, which renders it substantially free of
impurities that may be present in conventional catalysts, and is
suitable for use in food, drugs, and cosmetics. The NANOCAT.RTM.
Magnetic Iron Oxide is a free flowing powder with a particle size
of about 25 nm and a surface area of about 40 m.sup.2/g. Further
preferred catalyst particles comprise oxides and/or oxyhydroxides
of manganese, copper or cerium.
[0025] The encapsulant, which forms a coating that encapsulates the
catalyst particles, can comprise a wax, a water-soluble polymer, a
water insoluble polymer or other material capable of volatilizing
during the smoking of a cigarette to expose the underlying catalyst
particles. Preferred encapsulating materials are non-toxic, easily
coated onto catalyst particles, and stable (e.g., thermally and
chemically stable) under typical cigarette storage conditions. A
preferred encapsulant comprises one or more flavor-bearing
compounds.
[0026] The encapsulant can comprise a wax. Preferable waxes include
thermomeltable materials having a melting temperature of from about
40.degree. C. to about 350.degree. C. Exemplary waxes include
beeswax, coconut wax, candelilla wax, carnauba wax, montan wax,
ouricury wax, paraffin wax, rice wax, or mixtures thereof.
[0027] The encapsulant can comprise a water-soluble polymer.
Exemplary water-soluble polymers include polyvinyl alcohol,
polyvinyl pyrrolidone, polyethylene oxides, water-soluble
polyamides, water soluble polyesters, water soluble celluloses,
acrylic acid polymers, or mixtures thereof. Natural and modified
water-soluble polymers include starches, dextrins, gums, gelatins,
pectin, alginates, gum arabic, or mixtures thereof.
[0028] Preferred encapsulants are alginates. Alginates are salts of
the long-chain, carbohydrate biopolymer alginic acid, and include
sodium alginate, calcium alginate, potassium alginate, and
propylene glycol alginate. Though alginic acid is insoluble in
water, the salts are hydrocolloids (i.e., they bind or absorb
water) and can be formed into a coating.
[0029] Alginates are generally acid stable and heat resistant.
Adjusting the concentration of calcium ions, which cause
cross-linking, controls gel strength. Combining alginate with other
gums, such as pectin, can increase the viscosity.
[0030] Alginates can be dispersed in ambient temperature water,
though the solubility is typically less as the water temperature
decreases. Alginate concentrations above 2 wt. % can be dispersed
using high shear mixing to eliminate clumps. High-speed mixers
combine high flow with high shear to increase mixing efficiency. A
preferred method of forming encapsulated catalyst particles
comprising a calcium alginate coating is discussed below.
[0031] The encapsulant can comprise a water-insoluble polymer.
Exemplary water-insoluble polymers include polyethylene,
polypropylene, polyacrylates, polymethacrylates,
polymethyl-methacrylates, polyvinyl chloride, polyvinylidene
chloride, polysaccharides, or mixtures thereof.
[0032] The encapsulant can comprise a flavor-bearing compound.
Preferred flavor compounds include menthol, menthol derivatives,
and menthol precursors. Other suitable flavor compounds include
synthetic and natural fragrances, essential oils, alcohols,
aldehydes, esters, ethers, ketones, phenols, and mixtures thereof.
The flavor compound can be an aromatic compound or a non-aromatic
compound.
[0033] Catalyst particles can be coated with one or more layers of
the same or different volatile encapsulants. For example, multiple
coating steps can be used to achieve the desired thickness and/or
coverage of a desired encapsulant. In a further example, catalyst
particles can be coated with a first volatile coating, and then
with a second volatile coating. In a preferred embodiment, the
first volatile coating comprises a flavor-bearing compound.
[0034] A variety of methods can be used to form the encapsulated
catalyst particles. Suitable methods include providing the catalyst
particles and forming at least one volatile encapsulating layer
over the catalyst particles. The methods include gas phase
techniques and liquid phase techniques.
[0035] In an exemplary gas phase technique, catalyst particles can
be mixed with a liquid phase encapsulant (e.g., solution or neat
liquid of a volatile compound) to form a mixture. During the
mixing, the temperature and the amount of agitation can be
controlled. For example, catalyst particles and a solution of an
encapsulant can be mixed at room temperature and ultrasonicated to
form a homogeneous mixture.
[0036] A catalyst particle-encapsulant mixture can be dried to form
the encapsulated catalyst particles. According to a preferred
method, the mixture can be aspirated to form an aerosol comprising
catalyst particles coated with the encapsulant. The aerosolization
temperature and dispensation rate can be controlled to form solid
phase encapsulated catalyst particles (i.e., wherein the
encapsulant layer dries to form a solid coating on the catalyst
particles).
[0037] By way of example, encapsulated catalyst particles
comprising 50 wt. % NANOCAT.RTM. iron oxide particles coated with
gum arabic can be prepared by first mixing iron oxide particles
(.about.1 g) with gum arabic (.about.1 g) in about 30 ml of
de-ionized water under constant agitation to form a uniform
suspension of the iron oxide particles. The suspension is
aerosolized using a 0.5 mm nozzle at about 170.degree. C. whereby
the water present in the mixture is evaporated and gum
arabic-coated iron oxide particles are formed. Depending on the
processing conditions, the encapsulated catalyst particles can be
in the form of a powder, granulate or agglomerate. The encapsulated
catalyst particles can be in the shape of spheres, spheroids,
threads, fibrils, and the like.
[0038] In an exemplary liquid phase technique, catalyst particles
can be immersed in a liquid phase encapsulant or encapsulant
precursor (e.g., solution or neat liquid of a volatile compound) to
form a mixture wherein a coating is formed on the catalyst
particles. The temperature during the immersion can be controlled
and the mixture can optionally be agitated (e.g., stirred).
Catalyst particles and an encapsulant can be mixed at room
temperature to form the coating. After immersing, the coated
catalyst particles can be dried and optionally processed further to
form encapsulated catalyst particles. Further processing can
comprise cross-linking the encapsulating polymer, such as via an
ion exchange reaction.
[0039] A method of forming alginate-encapsulated catalyst particles
comprises immersing catalyst particles in a solution of an alginate
salt to form coated catalyst particles, and then treating the
coated catalyst particles to form a cross-linked polymeric alginate
coating.
[0040] By way of example, encapsulated catalyst particles
comprising 50 wt. % NANOCAT.RTM. iron oxide particles coated with
calcium and/or sodium alginate can be prepared by first mixing iron
oxide particles (.about.1 g) with a solution of sodium alginate (1
g of sodium alginate in 100 ml of de-ionized water) under constant
agitation to form sodium alginate coated iron oxide particles. The
mixture is preferably homogenized (e.g., 30-130 seconds), allowed
to sit in air (e.g., 10-60 min.), and then re-homogenized (e.g.,
30-130 seconds).
[0041] The sodium alginate coating can be at least partially and
preferably fully converted (e.g., polymerized) to a calcium
alginate coating via an ion exchange reaction. A known volume of
the sodium alginate coated iron oxide particles is preferably
contacted with a solution comprising a multivalent cation. The
solution can comprise an aqueous or a non-aqueous (e.g., alcoholic)
solution. In a preferred method, the solution comprises calcium
chloride (e.g., 0.1 M aqueous solution of calcium chloride) whereby
Ca.sup.2+ is exchanged for Na.sup.1+ via an ion exchange reaction
that forms a cross-linked volatile calcium alginate shell around
the iron oxide particles. Other multivalent cation solutions
suitable for forming a cross-linked encapsulating layer can
comprise aluminum, manganese, iron, copper, zinc, strontium, silver
and barium. The hardness of a cross-linked polymer encapsulant can
be controlled by varying the degree of cross-linking. The amount of
cross-linking is proportional to the reaction time (i.e., cure
time) between the encapsulant and the multivalent cation solution.
Other polymers that can be cross-linked via ion exchange include
polysaccharides.
[0042] In a preferred method, a known volume of the sodium alginate
coated iron oxide particles is dispersed drop-wise (e.g., through a
syringe such as a 26.5 gauge needle) into a calcium chloride
solution. The height and rate of dispensation can be controlled to
control the size of the encapsulated particles. Excess calcium
chloride solution can be removed (e.g., filtered or decanted) after
a pre-set cure time (e.g., up to about 2 hours) and the calcium
alginate-coated particles can be washed and dried. Encapsulated
catalyst particles comprising at least about 10, 20, 30, 40, 50,
60, 70, 80 or 90.+-.5 wt. % catalyst particles (e.g., iron oxide
particles) can be prepared.
[0043] Optical micrographs of iron oxide/calcium alginate samples
are shown in FIG. 1. FIG. 1 (a) shows an optical micrograph of
as-received NANOCAT.RTM. iron oxide particles. FIG. 1 (b) shows an
optical micrograph of calcium alginate encapsulated iron oxide
particles in the form of irregular and spherical particles. FIG. 1
(c) shows an optical micrograph of calcium alginate encapsulated
iron oxide particles in the form of fibrils.
[0044] Additional methods for forming encapsulated catalyst
particles include polymer-polymer incompatibility (wherein catalyst
particles are coated via preferential adsorption of one polymer
from a solution of incompatible polymers that are dissolved in a
common solvent); fluidized-bed encapsulation and gas phase
polymerization.
[0045] Encapsulated micron sized catalyst particles can have an
average particle size of from about 1 micron or less to about 1000
microns or more. The encapsulated catalyst particles can have an
average particle size of 10, 20, 30, 40, 50, 60, 70, 80 or 90
microns.+-.5 microns up to about 100, 200, 300, 400, 500, 600, 700,
800, 900 nm.+-.50 microns. The encapsulated catalyst particles can
comprise individual particles or an agglomerate of coated catalyst
particles. Preferred encapsulated catalyst particles have an
average particle size of less than 1 micron. Submicron and
nanoscale catalyst particles can be encapsulated to form
encapsulated catalyst particles having an average particle size of
10, 20, 30, 40, 50, 60, 70, 80 or 90 nm.+-.5 nm up to about 100,
200, 300, 400, 500, 600, 700, 800, 900 nm.+-.50 nm, depending on
the average thickness of the encapsulant.
[0046] According to a preferred method, the encapsulated catalyst
particles are incorporated in at least one of tobacco cut filler,
cigarette paper and cigarette filter that are used to form a
cigarette. By incorporating the catalyst particles into one or more
components of a cigarette, the amount of carbon monoxide and/or
nitric oxide in mainstream smoke during smoking can be reduced.
[0047] Preferably, the encapsulated catalyst particles are
incorporated in tobacco cut filler, cigarette paper and/or
cigarette filter in an amount effective to reduce the concentration
in mainstream smoke of carbon monoxide and/or nitric oxide by at
least 5% (e.g., by at least 10, 15%, 20%, 25%, 30%, 35%, 40%, 45%,
50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%). A preferred
amount of the catalyst particles per cigarette is up to about 200
mg (e.g., 1 to 200 mg, 1 to 50 mg, or 50 to 100 mg). The
encapsulated catalyst particles can be incorporated into a
cigarette in an amount effective to convert at least 5%, more
preferably at least 25%, of the carbon monoxide in mainstream
tobacco smoke to carbon dioxide at a temperature of less than about
200.degree. C. and/or convert at least 5%, more preferably at least
25%, of the nitric oxide in mainstream tobacco smoke to nitric
oxide at a temperature of less than about 200.degree. C.
[0048] Disclosed is a method of making a cigarette comprising the
steps of (i) incorporating encapsulated catalyst particles in
and/or on at least one of tobacco cut filler, cigarette paper and
cigarette filter; (ii) providing the tobacco cut filler to a
cigarette making machine to form a tobacco column; (iii) placing
the cigarette wrapper around the tobacco column to form a tobacco
rod of a cigarette; and (iv) optionally attaching the cigarette
filter to the tobacco column using tipping paper.
[0049] While not wishing to be bound by theory, it is believed that
during smoking of a cigarette having encapsulated catalyst
particles incorporated therein, CO and/or NO can be catalyzed in
the presence of oxygen to reduce the level of CO and/or NO in
mainstream and/or sidestream smoke. It is also believed that
subsequent to the catalytic reaction, the catalyst particles may
oxidize CO in the presence or absence of oxygen and/or reduce NO to
decrease the level of CO and/or NO in the mainstream and/or
sidestream smoke. Preferably, the encapsulated catalyst particles
can catalyze both the conversion of CO to CO.sub.2 and NO to
N.sub.2.
[0050] As used herein, a catalyst is capable of affecting the rate
of a chemical reaction, e.g., a catalyst can increase the rate of
oxidation of carbon monoxide to carbon dioxide without
participating as a reactant or product of the reaction. An oxidant
is capable of oxidizing a reactant, e.g., by donating oxygen to the
reactant, such that the oxidant itself is reduced. A reducing agent
is capable of reducing a reactant, e.g., by receiving oxygen from
the reactant, such that the reducing agent itself is oxidized.
[0051] "Smoking" of a cigarette means the heating or combustion of
the cigarette to form smoke, which can be drawn through the
cigarette. Generally, smoking of a cigarette involves lighting one
end of the cigarette and, while the tobacco contained therein
undergoes a combustion reaction, drawing smoke from the combustion
through the mouth end of the cigarette. The cigarette may also be
smoked by other means. For example, the cigarette may be smoked by
heating the cigarette and/or heating using electrical heater means
as described in commonly-assigned U.S. Pat. Nos. 6,053,176;
5,934,289; 5,591,368 or 5,322,075.
[0052] The term "mainstream" smoke refers to the mixture of gases
passing down the tobacco rod and issuing through the filter end,
i.e., the smoke issuing or drawn from the mouth end of a cigarette
during smoking of the cigarette. The mainstream smoke contains
smoke that is drawn in through both the lighted region, as well as
through the cigarette wrapper. The term "sidestream" smoke refers
to smoke produced during static burning.
[0053] Several factors contribute to the formation of carbon
monoxide and nitric oxide in a cigarette. In addition to the
constituents in the tobacco, the temperature and the oxygen
concentration in a cigarette during combustion can affect their
formation. For example, the total amount of carbon monoxide formed
during smoking comes from a combination of three main sources:
thermal decomposition (about 30%), combustion (about 36%) and
reduction of carbon dioxide with carbonized tobacco (at least 23%).
Formation of carbon monoxide from thermal decomposition, which is
largely controlled by chemical kinetics, starts at a temperature of
about 180.degree. C. and finishes at about 1050.degree. C.
Formation of carbon monoxide and carbon dioxide during combustion
is controlled largely by the diffusion of oxygen to the surface
(k.sub.a) and via a surface reaction (k.sub.b). At 250.degree. C.,
k.sub.a and k.sub.b, are about the same. At 400.degree. C., the
reaction becomes diffusion controlled. Finally, the reduction of
carbon dioxide with carbonized tobacco or charcoal occurs at
temperatures around 390.degree. C. and above.
[0054] During combustion, nitric oxide is produced in mainstream
smoke at a concentration of about 0.5 mg/cigarette. However, nitric
oxide can be reduced by carbon monoxide according to the following
reactions: 2NO+CO.fwdarw.N.sub.2O+CO.sub.2
N.sub.2O+CO.fwdarw.N.sub.2+CO.sub.2
[0055] During smoking there are three distinct regions in a
cigarette: the combustion zone, the pyrolysis/distillation zone,
and the condensation/ filtration zone. The combustion zone is the
burning zone of the cigarette produced during smoking of the
cigarette, usually at the lighted end of the cigarette. The
temperature in the combustion zone ranges from about 700.degree. C.
to about 950.degree. C., and the heating rate can be as high as
500.degree. C./second. Oxygen is consumed in the combustion of
tobacco to produce carbon monoxide, carbon dioxide, nitric oxide,
water vapor and other organic compounds (e.g., tar). The combustion
zone is highly exothermic and the heat generated is carried to the
pyrolysis/distillation zone.
[0056] The pyrolysis zone is the region behind the combustion zone,
where the temperature ranges from about 200.degree. C. to about
600.degree. C. The pyrolysis zone is where most of the carbon
monoxide is produced. The major reaction is the pyrolysis (i.e.,
the thermal degradation) of the tobacco that produces carbon
monoxide, carbon dioxide, nitric oxide, charcoal and other smoke
components (e.g., tar) using the heat generated in the combustion
zone.
[0057] In the condensation/filtration zone the temperature ranges
from ambient to about 150.degree. C. The major process in this zone
is the condensation/filtration of the smoke components. Some amount
of carbon monoxide, carbon dioxide, nitric oxide and nitrogen
diffuse out of the cigarette and some oxygen (e.g., air) diffuses
into the cigarette.
[0058] During the smoking of a cigarette, the mainstream smoke
flows toward the filter end of the cigarette. As carbon monoxide
and nitric oxide travel within the cigarette, oxygen diffuses into
and carbon monoxide and nitric oxide diffuse out of the cigarette
through the wrapper. After a typical 2-second puff of a cigarette,
CO and NO are concentrated in the periphery of the cigarette, i.e.,
near the cigarette wrapper, in front of the combustion zone. Due to
diffusion of O.sub.2 into the cigarette, the oxygen concentration
is also high in the peripheral region. Air flow into the tobacco
rod is largest near the combustion zone at the periphery of the
cigarette and is approximately commensurate with the gradient of
temperature, i.e., higher airflow is associated with larger
temperature gradients. In a typical cigarette, the highest
temperature gradient is from the combustion zone
(>850-900.degree. C.) axially toward the filter end of the
cigarette. Within a few millimeters behind the combustion zone the
temperature drops to near ambient. Further information on air flow
patterns, the formation of constituents in cigarettes during
smoking and smoke formation and delivery can be found in Richard R.
Baker, "Mechanism of Smoke Formation and Delivery", Recent Advances
in Tobacco Science, vol. 6, pp. 184-224, (1980) and Richard R.
Baker, "Variation of the Gas Formation Regions within a Cigarette
Combustion Coal during the Smoking Cycle", Beitrage zur
Tabakforschung International, vol. 11, no. 1, pp. 1-17, (1981), the
contents of both are incorporated herein by reference.
[0059] Non-volatile compounds such as tar produced from the
combustion and/or pyrolysis of tobacco can coat un-encapsulated
catalyst particles and decrease their catalytic efficiency.
Non-volatile compounds that form on the surface of encapsulated
catalyst particles, however, can be removed by removing the
volatile encapsulating layer from the catalyst particles, thereby
exposing the catalyst particles to cigarette smoke.
[0060] Encapsulated catalyst particles may be provided in the form
of a dry powder, paste or dispersion in a liquid. For example,
encapsulated catalyst particles can be dusted on, sprayed on, or
combined with the cut filler tobacco or cigarette paper. In a
further example, tobacco cut filler or cigarette paper material may
be rinsed or dip-coated with a liquid containing the encapsulated
catalyst particles.
[0061] Techniques for cigarette manufacture are known in the art.
Any conventional or modified cigarette making technique may be used
to incorporate the encapsulated catalyst particles. In production
of a cigarette, typically the cut filler composition is optionally
combined with other cigarette additives, and provided to a
cigarette-making machine to produce a tobacco column, which is then
wrapped in cigarette paper to form a tobacco rod that is cut into
sections, and optionally tipped with filters. The resulting
cigarettes can be manufactured to desired specifications using
standard or modified cigarette making techniques and equipment.
Cigarettes may range from about 50 mm to about 120 mm in length.
The circumference is from about 15 mm to about 30 mm in
circumference, and preferably around 25 mm. The tobacco packing
density is typically between the range of about 100 mg/cm.sup.3 to
about 300 mg/cm.sup.3, and preferably 150 mg/cm.sup.3 to about 275
mg/cm.sup.3.
[0062] One embodiment provides a method for forming the
encapsulated catalyst particles and then depositing the catalyst
particles on and/or incorporating them in tobacco cut filler, which
is then used to form a cigarette. Tobacco cut filler is normally in
the form of shreds or strands cut into widths ranging from about
1/10 inch to about 1/20 inch or even 1/40 inch. The lengths of the
strands range from between about 0.25 inches to about 3 inches. The
cigarettes may further comprise one or more flavorants or other
additives (e.g., burn additives, combustion modifying agents,
coloring agents, binders, etc.).
[0063] Any suitable tobacco mixture may be used for the cut filler.
Examples of suitable types of tobacco materials include flue-cured,
Burley, Bright, Maryland or Oriental tobaccos, the rare or
specialty tobaccos, and blends thereof. The tobacco material can be
provided in the form of tobacco lamina, processed tobacco materials
such as volume expanded or puffed tobacco, processed tobacco stems
such as cut-rolled or cut-puffed stems, reconstituted tobacco
materials, or blends thereof. The tobacco can also include tobacco
substitutes.
[0064] The encapsulated catalyst particles may be added to cut
filler tobacco stock (e.g., loose cut filler) supplied to a
cigarette-making machine or incorporated directly on a tobacco rod
prior to wrapping a cigarette wrapper around the cigarette rod to
form a tobacco column. Preferably the encapsulated catalyst
particles are provided continuously along the length of a tobacco
rod, though the encapsulated catalyst particles can be provided at
discrete locations along the length of a tobacco rod. Thus, the
encapsulated catalyst particles may be homogeneously or
non-homogeneously distributed along the length of a tobacco rod.
For example, a tobacco rod can comprise a first loading of
encapsulated catalyst particles at one location along the tobacco
rod and a second loading of encapsulated particles at a second
location along the tobacco rod. A preferred tobacco rod comprising
encapsulated catalyst particles has a first loading of encapsulated
catalyst particles at the filter end of the tobacco rod and a
second loading of encapsulated catalyst particles at the distal end
of the tobacco rod, wherein the first loading is greater than the
second loading.
[0065] The encapsulated catalyst particles and tobacco cut filler
can be provided in any desired ratio, e.g., 1 to 90 wt. %
encapsulated catalyst particles and 99 to 10 wt. % tobacco cut
filler, more preferably from about 1 to 50 wt. % encapsulated
catalyst particles, most preferably from about 1 to 20 wt. %
encapsulated catalyst particles.
[0066] In addition to or in lieu of incorporating the encapsulated
catalysts in the tobacco rod, the encapsulated catalyst particles
may be incorporated in cigarette paper before or after the
cigarette paper is incorporated into a cigarette. The encapsulated
catalyst particles can be incorporated into the cellulosic web of
the paper by depositing the particles directly on the cellulosic
web or on web-filler material that is incorporated in the paper.
Encapsulated catalyst particles can be incorporated into cigarette
paper and/or into the raw materials used to make cigarette paper
(e.g., incorporated into the paper stock of a cigarette paper
making machine).
[0067] The encapsulated catalyst particles can be incorporated in
cigarette paper by spraying or coating the particles onto a wet
base (e.g., cellulosic) web, an intermediate web or a finished web.
According to one method, encapsulated catalyst particles in the
form of a dry powder are physically admixed with the cigarette
paper material during the paper manufacturing process. In another
method, slurry (e.g., aqueous slurry) of the encapsulated catalyst
particles can be incorporated into the head box of a paper-making
machine and the encapsulated catalyst particles can be incorporated
into cigarette paper during the paper-making process.
[0068] The encapsulated catalyst particles and cigarette paper can
be provided in any desired ratio, e.g., 1 to 90 wt. % catalyst and
99 to 10 wt. % cigarette paper. In a preferred embodiment, the
amount of encapsulated catalyst particles comprise from about 1 to
50 wt. %, more preferably from about 1 to 20 wt. % of the cigarette
paper.
[0069] The quantity, location and distribution in a cigarette of
the encapsulated catalyst particles can be selected as a function
of the temperature and air flow characteristics exhibited during
smoking in order to adjust, e.g., increase or maximize the
conversion rate of CO to CO.sub.2 and/or NO to N.sub.2. The amount
of the encapsulated catalyst particles incorporated into a
cigarette can be selected such that the amount of carbon monoxide
and the amount of nitric oxide in mainstream smoke is reduced
during smoking of a cigarette.
[0070] The encapsulated catalyst particles can be coated and/or
printed on at least one surface of a paper wrapper (e.g., an
interior and/or exterior surface) to form text or images on the
cigarette wrapper. The amount of printing and/or the amount of
catalyst can be varied to adjust the amount of CO and/or NO
reduction.
[0071] The volatile encapsulating layer can be dyed (e.g., with a
food dye) to control the appearance of the encapsulated catalyst
particles. For example, the color of the encapsulated catalyst
particles can be provided to match or contrast with the color of
the cigarette paper (or the tobacco cut filler).
[0072] A cigarette can comprise a mixture of different encapsulated
catalyst particles. The composition of the encapsulated catalyst
particles (i.e., the composition and/or size of the catalyst
particles and/or the composition and/or thickness of the
encapsulant) can be selected to operate in a given temperature
range, and a catalytically effective amount of the catalyst
particles can be incorporated into a component of a cigarette
(e.g., tobacco cut filler, cigarette filter and/or cigarette paper)
to control the conversion efficiency and/or selectivity of the
catalyst. For example, first encapsulated catalyst particles can be
incorporated in the tobacco cut filler of a cigarette and second
encapsulated catalyst particles can be incorporated in the
cigarette paper. Cigarette paper having encapsulated catalyst
particles incorporated therein can be used as paper wrapper, paper
filter and/or paper filler within a cigarette.
[0073] A cigarette wrapper can be any wrapping suitable for
surrounding the cut filler, including wrappers containing flax,
hemp, kenaf, esparto grass, rice straw, cellulose and so forth.
Optional filler materials, flavor additives, and burning additives
can be included in the cigarette wrapper. The wrapper can have more
than one layer in cross-section, such as in a bi-layer wrapper as
disclosed in commonly-owned U.S. Pat. No. 5,143,098, the entire
content of which is herein incorporated by reference.
[0074] The encapsulated catalyst particles can be incorporated into
a cigarette wrapper. The paper wrapper, which comprises a web of
fibrous cellulosic material, can further comprise particles of
web-filler material, such as calcium carbonate (CaCO.sub.3). In
practice, the web-filler material serves as an agent for
controlling the permeability of the wrapper. The permeability of
the wrapper is typically measured in units of Coresta, which is
defined as the volume of air, measured in cubic centimeters, that
passes through one square centimeter of material in one minute at a
pressure drop of 1.0 kilopascals.
[0075] The paper wrapper can comprise one or more layers. A
preferred cigarette comprises a first wrapper, a second wrapper
formed around the first wrapper, and encapsulated catalyst
particles incorporated in the first wrapper.
[0076] Encapsulated catalyst particles will preferably be
distributed throughout the tobacco rod and/or the cigarette wrapper
portions of a cigarette. By providing the encapsulated catalyst
throughout one or more components of a cigarette it is possible to
reduce the amount of carbon monoxide drawn through the cigarette,
particularly at the combustion, pyrolysis, condensation and/or
filter regions.
[0077] A further embodiment provides a method of treating tobacco
smoke comprising lighting a cigarette to form tobacco smoke and
drawing the smoke through the cigarette, wherein the volatile
encapsulant at least partially volatilizes to expose a surface of
the catalyst particles. In a preferred embodiment, the volatile
encapsulant is volatilized at a distance of from about 0.1 mm to 10
mm in advance of the charline.
[0078] While various embodiments have been described, it is to be
understood that variations and modifications may be resorted to as
will be apparent to those skilled in the art. Such variations and
modifications are to be considered within the purview and scope of
the claims appended hereto.
[0079] All of the above-mentioned references are herein
incorporated by reference in their entirety to the same extent as
if each individual reference was specifically and individually
indicated to be incorporated herein by reference in its
entirety.
* * * * *