U.S. patent application number 10/838876 was filed with the patent office on 2005-01-06 for method and composition for mentholation of charcoal filtered cigarettes.
Invention is credited to Shi, Xuling.
Application Number | 20050000531 10/838876 |
Document ID | / |
Family ID | 23323673 |
Filed Date | 2005-01-06 |
United States Patent
Application |
20050000531 |
Kind Code |
A1 |
Shi, Xuling |
January 6, 2005 |
Method and composition for mentholation of charcoal filtered
cigarettes
Abstract
The present invention relates to smoking articles such as
cigarettes, and in particular to a method and composition for
mentholation of smoking articles, including microencapsulation of
menthol or other flavorants in a material melting below the
pyrolysis zone of the smoking article.
Inventors: |
Shi, Xuling; (Raleigh,
NC) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
23323673 |
Appl. No.: |
10/838876 |
Filed: |
May 3, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10838876 |
May 3, 2004 |
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PCT/US02/35741 |
Nov 7, 2002 |
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60338168 |
Nov 9, 2001 |
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Current U.S.
Class: |
131/347 ;
131/360 |
Current CPC
Class: |
A24B 15/283 20130101;
A24B 15/287 20130101; A24B 15/28 20130101; A24D 3/061 20130101;
A24D 3/163 20130101 |
Class at
Publication: |
131/347 ;
131/360 |
International
Class: |
A24F 047/00 |
Claims
What is claimed is:
1. A smoking composition comprising a smokable material, a
plurality of microcapsules, and a filter, the smoking composition
comprising a cigarette, wherein the smokable material comprises a
tobacco, the filter comprises an activated charcoal or an activated
carbon, and the microcapsules comprise a shell material and a
filler material, wherein the filler material comprises menthol, and
wherein the shell material comprises a waxy thermomeltable material
having a melting point of from about 35.degree. C. to about
200.degree. C.
2. A smoking composition comprising a smokable material and a
plurality of microcapsules, the microcapsules comprising a shell
material and a filler material, wherein the shell material melts
upon exposure to a temperature above an ambient temperature and
below a pyrolysis temperature of the smokable material, whereby the
filler material is released into a mainstream smoke, a sidestream
smoke, or both the mainstream smoke and the sidestream smoke.
3. The composition of claim 2, wherein the smokable material
comprises tobacco.
4. The composition of claim 3, wherein the tobacco has a reduced
nicotine content or a negligible nicotine content.
5. The composition of claim 3, wherein the tobacco has a reduced
content of a nitrosamine or a negligible content of a
nitrosamine.
6. The composition of claim 2, wherein the filler material
comprises a flavorant.
7. The composition of claim 6, wherein the flavorant comprises
menthol.
8. The composition of claim 2, wherein the smoking composition
further comprises a filter.
9. The composition of claim 8, wherein the filter further comprises
an activated charcoal or an activated carbon.
10. The composition of claim 9, wherein the filter is a cavity
filter.
11. The composition of claim 10, wherein the cavity filter is at
least about 95 vol. % filled.
12. The composition of claim 10, wherein the cavity filter is about
100 vol. % filled.
13. The composition of claim 2, wherein the shell material
comprises a waxy thermomeltable material having a melting point of
from about 35.degree. C. to about 200.degree. C.
14. The composition of claim 13, wherein the waxy thermomeltable
material is selected from the group consisting of carnauba wax,
montan wax, ouricury wax, candelilla wax, coconut wax, paraffin
wax, beeswax, spermaceti wax, microcrystalline wax, rice wax, low
molecular weight polyethylene wax, stearic acid, palmitic acid,
myristic acid, stearylamide, stearone, and mixtures thereof.
15. The composition of claim 2, wherein the shell material
comprises a water insoluble polymer.
16. The composition of claim 15, wherein the water insoluble
polymer is selected from the group consisting of cellulose ethers,
cellulose esters, ureaformaldehyde resins, polyvinyl chloride,
polyvinylidene chloride, polyethylene, polypropylene,
polyacrylates, polymethacrylates, polymethyl-methacrylates, nylon,
and mixtures thereof.
17. The composition of claim 2, wherein the shell material
comprises a water soluble polymer.
18. The composition of claim 17, wherein the water soluble polymer
is selected from the group consisting of polyvinyl pyrrolidone,
water soluble celluloses, polyvinyl alcohol, ethylene maleic
anhydride copolymer, methyl vinyl ether maleic anhydride copolymer,
polyethylene oxides, water soluble polyamide, water soluble
polyesters, polymers of acrylic acid, polystyrene acrylic acid
copolymers, and mixtures thereof.
19. The composition of claim 2, wherein the shell material is
selected from the group consisting of starch, gums, gelatin,
dextrins, hydrolyzed gums, hydrolyzed gelatin, gum arabic, larch,
pectin, tragacanth, locust bean, guar, alginates, carrageenans,
carboxy methyl cellulose, karaya, maltodextrins, and mixtures
thereof.
20. A method for providing a smokable material comprising a
volatile flavorant, the method comprising: providing a plurality of
microcapsules comprising a shell material and a filler material,
the filler material comprising a volatile flavorant, wherein the
shell material melts upon exposure to a temperature above an
ambient temperature and below a pyrolysis temperature of the
smokable material; and depositing the microcapsules on the smokable
material, whereby a smokable material comprising a volatile
flavorant is obtained.
21. The method of claim 20, wherein the smokable material comprises
tobacco.
22. The method of claim 20, wherein the volatile flavorant
comprises menthol.
23. The method of claim 20, wherein the shell material comprises a
waxy thermomeltable material having a melting point of from about
35.degree. C. to about 200.degree. C.
Description
RELATED APPLICATIONS
[0001] This application is a continuation, under 35 U.S.C. .sctn.
120, of International Patent Application No. PCTUS02/35741, filed
on Nov. 7, 2002 under the Patent Cooperation Treaty (PCT), which
was published by the International Bureau in English on May 22,
2003, which designates the United States and which claims the
benefit of U.S. Provisional Patent Application No. 60/338,168,
filed Nov. 9, 2001.
FIELD OF THE INVENTION
[0002] The present invention relates to smoking articles such as
cigarettes, and in particular to a method and composition for
mentholation of smoking articles, including microencapsulation of
menthol or other flavorants in a material melting below the
pyrolysis zone of the smoking article.
BACKGROUND OF THE INVENTION
[0003] Menthol, or 2-isopropyl-5-methyl-cyclohexanol, is a cyclic
monoterpene. It is a major constituent of peppermint oil which has
a minty taste and odor and which produces a cooling sensation when
inhaled or consumed. Menthol is used as a flavorant in a variety of
products, including toothpaste, mouthwashes, oral sprays, drugs,
cough drops, cough lozenges, analgesic balms, inhalers, chewing
gums, hard candies, chocolates, beverages, liquors, lotions,
after-shave lotions, shampoo, moist towelettes, perfumes,
deodorants, and the like.
[0004] Menthol is also a popular flavorant for use in cigarettes,
pipe tobacco, chewing tobacco, and other smoking materials. It is
used extensively because of the refreshing cooling effect it
imparts to tobacco smoke. Menthol, however, has a high degree of
volatility at room temperature. This volatility makes it difficult
to control the concentration of menthol in cigarettes and can
result in problems in packaging and handling. Smoking products
containing menthol may also have a short shelf life due to loss of
menthol from the product during storage. This problem is especially
acute for menthol flavored cigarettes that also incorporate a
charcoal filter. Menthol is irreversibly bound to charcoal and
other adsorbants commonly used in filter cigarettes, and over time
a substantial and unacceptable decrease in the available menthol
results. Adsorption of menthol may also adversely affect the
performance of the filter in removing undesirable components from
the smoke generated during combustion of the tobacco product.
[0005] Accordingly, considerable time and expense has been spent on
development of a satisfactory method for producing a menthol
flavored charcoal filtered cigarette. Methods for mentholating
unfiltered cigarettes or filtered cigarettes not incorporating an
adsorbent are generally unsatisfactory for use on charcoal filtered
cigarettes. For example, the classic method of using mentholated
strips sealed in a cigarette pack is unsatisfactory because the
charcoal will simply absorb the menthol during storage, resulting
in what is essentially a non-mentholated cigarette.
[0006] Other methods for producing mentholated smoking products
that have been investigated have included providing menthol on a
support, for example, diatomaceous earth, from which the menthol is
later released. Such methods suffer from low menthol yields, and
may result in unacceptable taste or appearance of the smoking
product.
[0007] Other methods have focused on the preparation of menthol
derivatives or similar compounds which release menthol or
menthol-like flavorants upon pyrolysis or hydrolysis. Such
derivatives include ester and carbonate derivatives of menthol,
such as, for example, the derivatives disclosed in U.S. Pat. Nos.
3,312,226, 3,332,428, 3,419,543, 4,119,106, 4,092,988, 4,171,702,
4,177,339, and 4,212,310, 4,532,944, and 4,578,486. However, such
derivatives may suffer from one or more drawbacks. For example,
they may have a degree of volatility that makes them unsuited for
use with adsorbents, they may not yield a sufficient quantity of
free menthol upon decomposition, they may be unstable or difficult
to process, or the pyrolysis or hydrolysis products may be toxic,
carcinogenic, or may result in an unacceptable taste.
SUMMARY OF THE INVENTION
[0008] While various methods have been provided for mentholating
unfiltered cigarettes, no satisfactory method has been proposed for
mentholating a cigarette or other smoking article incorporating a
menthol adsorbing material, such as activated charcoal or zeolite.
There is, therefore, a need for smoking materials containing an
effective menthol delivery system that is compatible with the use
of adsorbing filter materials.
[0009] In a first embodiment, a smoking composition is provided,
the smoking composition including a smokable material, a plurality
of microcapsules, and a filter, the smoking composition including a
cigarette, wherein the smokable material includes a tobacco, the
filter includes an activated charcoal or an activated carbon, and
the microcapsules include a shell material and a filler material,
wherein the filler material includes menthol, and wherein the shell
material includes a waxy thermomeltable material having a melting
point of from about 35.degree. C. to about 200.degree. C.
[0010] In a second embodiment, a smoking composition is provided
including a smokable material and a plurality of microcapsules, the
microcapsules including a shell material and a filler material,
wherein the shell material melts upon exposure to a temperature
above an ambient temperature and below a pyrolysis temperature of
the smokable material, whereby the filler material is released into
a mainstream smoke, a sidestream smoke, or both the mainstream
smoke and the sidestream smoke.
[0011] In an aspect of the second embodiment, the smokable material
includes tobacco. The tobacco may have a reduced or a negligible
nicotine content, or a reduced or a negligible content of a
tobacco-specific nitrosamine.
[0012] In an aspect of the second embodiment, the filler material
includes a flavorant, such as menthol.
[0013] In an aspect of the second embodiment, the smoking
composition further includes a filter. The filter may further
include an activated charcoal or an activated carbon. The filter
may include a cavity filter. The cavity filter may be at least 95
vol. % filled, or about 100 vol. % filled.
[0014] In an aspect of the second embodiment, the shell material
includes a waxy thermomeltable material having a melting point of
from about 35.degree. C. to about 200.degree. C. The waxy
thermomeltable material may include carnauba wax, montan wax,
ouricury wax, candelilla wax, coconut wax, paraffin wax, beeswax,
spermaceti wax, microcrystalline wax, rice wax, low molecular
weight polyethylene wax, stearic acid, palmitic acid, myristic
acid, stearylamide, stearone, or mixtures thereof.
[0015] In an aspect of the second embodiment, the shell material
includes a water insoluble polymer. The water insoluble polymer may
include cellulose ethers, cellulose esters, ureaformaldehyde
resins, polyvinyl chloride, polyvinylidene chloride, polyethylene,
polypropylene, polyacrylates, polymethacrylates,
polymethyl-methacrylates, nylon, or mixtures thereof.
[0016] In an aspect of the second embodiment, the shell material
includes a water soluble polymer. The water soluble polymer may
include polyvinyl pyrrolidone, water soluble celluloses, polyvinyl
alcohol, ethylene maleic anhydride copolymer, and methyl vinyl
ether maleic anhydride copolymer, polyethylene oxides, water
soluble polyamide, water soluble polyesters, polymers of acrylic
acid, polystyrene acrylic acid copolymers, or mixtures thereof.
[0017] In an aspect of the second embodiment, the shell material
includes starch, gums, gelatin, dextrins, hydrolyzed gums,
hydrolyzed gelatin, gum arabic, larch, pectin, tragacanth, locust
bean, guar, alginates, carrageenans, carboxy methyl cellulose,
karaya, maltodextrins, or mixtures thereof.
[0018] In a third embodiment, a method for providing a smokable
material including a volatile flavorant is provided, the method
including providing a plurality of microcapsules including a shell
material and a filler material, the filler material including a
volatile flavorant, wherein the shell material melts upon exposure
to a temperature above an ambient temperature and below a pyrolysis
temperature of the smokable material, and depositing the
microcapsules on the smokable material, whereby a smokable material
including a volatile flavorant is obtained.
[0019] In an aspect of the third embodiment, the smokable material
includes tobacco.
[0020] In an aspect of the third embodiment, the volatile flavorant
includes menthol.
[0021] In an aspect of the third embodiment, the shell material
includes a waxy thermomeltable material having a melting point of
from about 35.degree. C. to about 200.degree. C.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Introduction
[0023] The following description and examples further illustrate
the preferred embodiments of the present invention. Those of skill
in the art will recognize that there are numerous variations and
modifications of this invention that are encompassed by its scope.
Accordingly, the description of preferred embodiments should not be
deemed to limit the scope of the present invention.
[0024] In preferred embodiments, methods and compositions for
delivering menthol or other flavorants into the smoke stream of a
smoking article, such as a cigarette, are provided. The method
involves microencapsulation of the flavorant and incorporation of
the microcapsules into the smoking article. The microcapsules
isolate the flavorant from adsorbents, such as activated charcoal,
and provide for the controlled release of the flavorant during
smoking, as well as provide for a longer shelf life for the
smokable article than is possible when unencapsulated flavorants
are present. The shell wall of the microcapsule is preferably
sufficiently compatible with the flavorant contained therein to
retain the flavorant until such time as the heat generated during
smoking causes-the shell to open. Encapsulating materials that melt
rather than volatize are generally preferred so as to prevent
introduction of the shell material into the smoke stream.
[0025] The preferred embodiments relate to smoking articles such as
cigarettes, cigars, or pipe tobacco, and in particular to
cigarettes having reduced content of various polyaromatic
hydrocarbons (PAHs), tobacco specific nitrosamines (TSNAs),
phenolic compounds, and certain other undesired components in
cigarette smoke, including both mainstream and sidestream smoke, or
having reduced content of nicotine or other undesired components in
the uncombusted smoking product. The tobacco products of preferred
smoking articles may also include a catalytic system including
metallic or carbonaceous particles and a source of nitrate or
nitrite, as described in copending U.S. application Ser. No.
10/007,724 filed on Nov. 9, 2001, the disclosure of which is
incorporated herein by reference in its entirety. The preferred
smoking articles for use with the microcapsules of preferred
embodiments typically incorporate an activated charcoal filter.
However the microcapsules are also suitable for use with unfiltered
smoking articles.
[0026] While the compositions and methods of preferred embodiments
generally refer to tobacco, particularly in the form of cigarettes,
it is to be understood that such compositions and methods encompass
any smokable material or smokable composition, as will be apparent
to one skilled in the art. Likewise, while the compositions and
methods of preferred embodiments generally refer to menthol, it is
to be understood that such compositions and methods encompass any
flavorant, volatile material adsorbable by activated charcoal, or
any other additive wherein it may be desirable to encapsulate the
additive for release upon exposure to heat generated by combustion
or pyrolysis of the smokable material.
[0027] Flavorants
[0028] Any suitable flavorant, odorant, additive, or other volatile
component that is capable of being adsorbed by activated charcoal
or any other adsorbent which may be present in a smoking article
may be added to a smoking material in the form of microcapsules.
Preferred flavorants include, but are not limited to, menthol,
menthol derivatives, menthol precursors, and other compounds
capable of imparting menthol-like flavoring.
[0029] Suitable flavorants include natural fragrances, synthetic
fragrances, synthetic essential oils, and natural essential oils.
Examples of synthetic fragrances include, but are not limited to,
terpenic hydrocarbons, esters, ethers, alcohols, aldehydes,
phenols, ketones, acetals, oximes, and mixtures thereof. Examples
of terpenic hydrocarbons include, but are not limited to, lime
terpene, lemon terpene and limonene dimer. Examples of essential
oils include, but are not limited to, natural oils obtained from
Angelica archangelica, Pimpinella anisum, Myroxylon pereirae,
Ocimum basilicum, Pimenta racemosa, Laurus Nobilis, Apis mellifera,
Styrax tonkinensis, Citrus bergamia, Mentha citrata, Aniba
roseodora, Boronia megastigma, Melaleuca leucadendron, Elettaria
cardamomum, Daucus carota, Cedrus atlantica, Juniperus virginiana,
Matricaria chamomilla, Anthemis nobilis, Cinnamomum zeylanicum,
Cymbopogon nardus, Salvia sclarea, Eugenia caryophyllata,
Coriandrum sativum, Cupressus sempervirens, Anethum graveolens,
Canarium luzonicum, Eucalyptus globulus, Eucalyptus citriodora,
Eucalyptus radiata, Foeniculum vulgare, Abies alba, Boswellia
carterii, Ferula galbaniflua, Pelargonium graveolens, Pelargonium
roseum, Zingiber officinale, Citrus paradisi, Helichrysum
angustifolia, Hyssopus officinalis, Helichrysum angustifolia,
Jasminum officinalis, Juniperus communis, Leptospermum ericoides,
Lavendula officinalis, Lavandula hybrida, Citrus limon, Cymbopogon
citratus, Citrus aurantifolia, Tilia vulgaris, Citrus reticulata,
Leptospermum scoparium, Origanum majorana, Litsea cubeba,
Commiphora myrrha, Myrtus communis, Backhousia citriodora, Citrus
aurantium, Melaleuca quinquenervia, Myristica fragrans, Evernia
prunastri, Boswellia carterii, Citrus aurantium, Citrus sinensis,
Oreganum vulgare, Cymbopogon martini, Petroselinum sativum,
Pogostemon cablin, Piper nigrum, Mentha piperita, Citrus aurantium,
Pinus sylvestris, Ravensara aromatica, Rosa damascena, Rosmarinus
officinalis, Aniba roseodora, Santalum album, Mentha spicata,
Nardostachys jatamansi, Picea mariana, Tagetes minuta, Citrus
reticulata, Melaleuca alternifolia, Leptospermum petersonii,
Leptospermum scoparium, Thymus vulgaris, Nicotania tabacum,
Polianthes tuberosa, Vanilla planifolia, Vetiveria zizanoides,
Viola odorata, Achillea millefolium, Cananga odorata, Trachyspermum
copticum, Prunus dulcis var. amara, Arnica Montana, Betula lenta,
Peumus boldus, Spartium junceum, Acorus calamus var. angustatus,
Cinnamomum camphora, Carphephorus odoratissimus, Allium sativum,
Armoracia rusticana, Pilocarpus jaborandi, Melilotus officinalis,
Artemisia vulgaris, Brassica nigra, Allium cepa, Mentha pulegium,
Ruta graveolens, Sassafras albidum, Thuja occidentalis, Gaultheria
procumbens, Chenopodium ambrosioides var. anthelminticum, and
Artemisia absinthium, and the synthetic versions thereof.
[0030] Other suitable flavors include include various aromatic
aldehydes, ketones, and alcohols. Examples of aldehyde flavors
include acetaldehyde (apple), benzaldehyde (cherry, almond), anisic
aldehyde (licorice, anise), cinnamic aldehyde (cinnamon), citral or
alpha citral (lemon, lime), neral or beta citral (lemon, lime),
decanal (orange, lemon), ethyl vanillin (vanilla, cream),
heliotropine or piperonal (vanilla, cream), vanillin (vanilla,
cream), alpha-amyl cinnamaldehyde (spicy fruity flavors),
butyraldehyde (butter, cheese), valeraldehyde (butter, cheese),
citronellal, decenal (citrus fruits), aldehyde C-8 (citrus fruits),
aldehyde C-9 (citrus fruits), aldehyde C-12 (citrus fruits),
2-ethyl butyraldehyde (berry fruits), hexenal (berry fruits), tolyl
aldehyde (cherry, almond), veratraldehyde (vanilla),
2-6-dimethyl-5-heptenal (melon), 2,6-dimethyloctanal (green fruit),
and 2-dodecenal (citrus, mandarin). Examples of ketone flavors
include d-carvone (caraway), 1-carvone (spearmint), diacetyl
(butter, cheese, cream), benzophenone (fruity and spicy flavors,
vanilla), methyl ethyl ketone (berry fruits), maltol (berry
fruits), menthone (mints), methyl amyl ketone, ethyl butyl ketone,
dipropyl ketone, methyl hexyl ketone, ethyl amyl ketone (berry
fruits, stone fruits), pyruvic acid (smokey, nutty flavors),
acetanisole (hawthorn heliotrope), dihydrocarvone (spearmint),
2,4-dimethylacetophenone (peppermint), 1,3-diphenyl-2-propanone
(almond), acetocumene (orris and basil, spicy), isojasmone
jasmine), d-isomethylionone (orris-like, violet), isobutyl
acetoacetate (brandy-like), zingerone (ginger), pulegone
(peppermint-camphor), d-piperitone (minty), and 2-nonanone (rose
and tea-like). Examples of alcohol flavors include anisic alcohol
or p-methoxybenzyl alcohol (fruity, peach), benzyl alcohol
(fruity), carvacrol or 2-p-cymenol (pungent warm odor), carveol,
cinnamyl alcohol (floral odor), citronellol (rose odor), decanol,
dihydrocarveol (spicy, peppery), tetrahydrogeraniol or
3,7-dimethyl-1-octanol (rose odor), eugenol (clove), and perillyl
alcohol (floral-pine).
[0031] Other suitable flavorants include aromatic esters including,
but not limited to, .gamma.-undecalactone, ethyl methyl phenyl
glycidate, allyl caproate, amyl salicylate, amyl benzoate, amyl
acetate, benzyl acetate, benzyl benzoate, benzyl salicylate, benzyl
propionate, butyl acetate, benzyl butyrate, benzyl phenylacetate,
cedryl acetate, citronellyl acetate, citronellyl formate, p-cresyl
acetate, 2-t-pentyl-cyclohexyl acetate, cyclohexyl acetate,
cis-3-hexenyl acetate, cis-3-hexenyl salicylate, dimethylbenzyl
acetate, diethyl phthalate, .delta.-decalactone dibutyl phthalate,
ethyl butyrate, ethyl acetate, ethyl benzoate, fenchyl acetate,
geranyl acetate, .gamma.-dodecalatone, methyl dihydrojasmonate,
isobornyl acetate, .beta.-isopropoxyethyl salicylate, linalyl
acetate, methyl benzoate, o-t-butylcylohexyl acetate, methyl
salicylate, ethylene brassylate, ethylene dodecanoate, methyl
phenyl acetate, phenylethyl isobutyrate, phenylethylphenyl acetate,
phenylethyl acetate, methyl phenyl carbinyl acetate,
3,5,5-trimethylhexyl acetate, terpinyl acetate, triethyl citrate,
p-t-butylcyclohexyl acetate and vetiver acetate.
[0032] Also suitable are aromatic ethers including, but not limited
to, p-cresyl methyl ether, diphenyl ether,
1,3,4,6,7,8-hexahydro-4,6,7,8,8-he- xamethyl
cyclopenta-.beta.-2-benzopyran and phenyl isoamyl ether.
[0033] Other substances that may be incorporated into the
microcapsules of preferred embodiments include various excipients
and other substances well known in the art of smoking article
formulations or microcapsule formulations. Such substances are
preferably nontoxic and do not yield undesirable decomposition
products or impart an unpleasant taste when the smoking material is
combusted. These other substances may include ionic and nonionic
surfactants (e.g., PLURONIC.TM., TRITON.TM.), detergents (e.g.,
polyoxyl stearate, sodium lauryl sulfate), emulsifiers,
demulsifiers, stabilizers, aqueous and oleaginous carriers (e.g.,
white petrolatum, isopropyl myristate, lanolin, lanolin alcohols,
mineral oil, sorbitan monooleate, propylene glycol, cetylstearyl
alcohol), solvents, preservatives (e.g., methylparaben,
propylparaben, benzyl alcohol, ethylene diamine tetraacetate
salts), thickeners (e.g., pullulin, xanthan, polyvinylpyrrolidone,
carboxymethylcellulose), plasticizers (e.g., glycerol, polyethylene
glycol), antioxidants (e.g., vitamin E), buffering agents, and the
like.
[0034] Microencapsulated Flavorants
[0035] Certain flavorants may have a high degree of volatility.
This volatility may result in loss of the flavorant through
adsorption by filter materials or escape through packaging during
storage. Microencapsulation is an effective technique to avoid
undesired loss of flavorant prior to use of the smoking
article.
[0036] In a preferred embodiment, menthol is entrapped into
hydrophilic gelatin microcapsules and mixed with cut tobacco. Other
preferred shell materials include water soluble alcohols and
polyethylene oxides. The microcapsule's shell blocks loss of the
flavorant by volatilization. Microencapsulation permits volatile
flavorants to be used with adsorbing filter materials in smoking
products. The microencapsulated flavorants provide controlled
release of the flavorant from the microcapsule at a preselected
temperature, typically from slightly below the pyrolysis
temperature of the smoking material down to slightly above room
temperature. However, higher temperatures may be preferred for
certain applications.
[0037] Microencapsulation techniques involve the coating of small
solid particles, liquid droplets, or gas bubbles with a thin film
of a material, the material providing a protective shell for the
contents of the microcapsule. Microcapsules suitable for use in the
preferred embodiments may be of any suitable size, typically from
about 1 .mu.m or less to about 1000 .mu.m or more, preferably from
about 2 ,.mu.m to about 50, 60, 70, 80, 90, 100, 200, 300, 400,
500, 600, 700, 800, or 900 ,.mu.m, and more preferably from about
3, 4, 5, 6, 7, 8, or 9 .mu.m to about 10, 15, 20, 25, 30, 35, 40 or
45 .mu.m. In certain embodiments, it may be preferred to use
nanometer-sized microcapsules. Such microcapsules may range from
about 10 nm or less up to less than about 1000 nm (1 .mu.m),
preferably from about 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70,
80, or 90 nm up to about 100, 200, 300, 400, 500, 600, 700, 800, or
900 nm.
[0038] While in many embodiments a solid phase flavorant or other
substance, such as menthol, is encapsulated, in certain embodiments
it may be preferred to encapsulate a liquid or gaseous substance.
Liquid or gas containing microcapsules may be prepared using
conventional methods well known in the art of microcapsule
formation, and such microcapsules may be incorporated into the
smoking articles of the preferred embodiments.
[0039] Microcapsule Components
[0040] The microcapsules of preferred embodiments contain a filling
material. The filling material is typically one or more flavorants,
optionally in combination with substances other than flavorants. In
certain embodiments, it may be preferred that the microcapsules
contain one or more substances not including flavorants. The
filling material is encapsulated within the microcapsule by a shell
material.
[0041] Typical shell materials may include, but are not limited to,
gum arabic, gelatin, ethylcellulose, polyurea, polyamide,
aminoplasts, maltodextrins, and hydrogenated vegetable oil. While
any suitable shell material may be used in the preferred
embodiments, it is generally preferred to use an edible or nontoxic
shell material approved for use in food or pharmaceutical
applications. It is also preferred to use a shell material that
melts at a temperature below the pyrolysis temperature of the
smokable material. Temperatures in the combustion zone of tobacco
are typically from about 600.degree. C. to about 900.degree. C.,
and those in the pyrolysis/distillation zone are typically between
about 200.degree. C. and 600.degree. C. The most preferred shell
materials are those that melt at a temperature below about
200.degree. C., but above the highest ambient temperature that the
cigarette may be exposed to prior to use. Such shell materials may
include waxes, polymers, fats, hydrogenated vegetable oils, and
other substances with suitable melting points.
[0042] In certain preferred embodiments, the encapsulating material
is a waxy thermomeltable material having a melting point of from
about 35.degree. C. or lower to about 200.degree. C. or higher,
more preferably from about 36.degree. C., 37.degree. C., 38.degree.
C., 39.degree. C., or 40.degree. C. to about 150.degree. C.,
160.degree. C., 170.degree. C., 180,.degree. C., or 190.degree. C.,
and most preferably from about 41.degree. C., 42.degree. C.,
43.degree. C., 44.degree. C., 45.degree. C., 50.degree. C.,
60.degree. C., 70.degree. C., 80.degree. C., 90.degree. C. or
100.degree. C. to about 110.degree. C., 120.degree. C., 130.degree.
C., or 140.degree. C. Examples of suitable materials include, but
are not limited to, carnauba wax, montan wax, ouricury wax,
candelilla wax, coconut wax, paraffin wax, microcrystalline wax,
Hoechst wax (such as OP and O), Bareco wax (such as WB wax), NPS
wax, rice wax, low molecular weight polyethylene wax, stearic acid,
palmitic acid, myristic acid, fatty acid amide (such as
stearylamide) and ketone wax (such as stearone). Any suitable waxy
material having a suitable melting point may be used. The term
"waxy material" is used herein in its broadest sense, and includes,
but is not limited to, to a material which melts into liquid form
having low viscosity upon heating and sets again to a crystalline
solid state upon cooling. Such waxy materials include, without
limitation, paraffinic waxes, microcrystalline waxes, animal waxes,
vegetable waxes, substantially water-insoluble polymers, saturated
fatty acids and fatty alcohols having from 12 to 40 carbon atoms in
their alkyl chain, fatty esters such as fatty acid triglycerides,
and fatty acid esters of sorbitan and fatty acid esters of fatty
alcohols. Specific suitable waxy materials may be derived from
compounds including lauric, myristic, palmitic, stearic, arachidic
and behenic acids, stearyl and behenyl alcohol, microcrystalline
wax, beeswax, spermaceti wax, candelilla wax, sorbitan tristearate,
sorbitan tetralaurate, tripalmitin, trimyristin and octacosane, and
stearyl alcohol.
[0043] In other preferred embodiments, the encapsulant is a water
insoluble polymer. Examples of suitable water-insoluble polymeric
materials include, but are not limited to, cellulose ethers such as
ethyl, propyl or butyl cellulose; cellulose esters such as
cellulose acetate, propionate, butyrate or acetate-butyrate;
ureaformaldehyde resins, polyvinyl chloride, polyvinylidene
chloride, polyethylene, polypropylene, polyacrylates,
polymethacrylates, polymethyl-methacrylates and nylon. Such
materials and their equivalents are described in greater detail in
any handbook of synthetic organic plastics, for example, in Modern
Plastics Encyclopaedia, Vol. 62, No. 10A (for 1985-1986) at pages
768-787, published by McGraw-Hill, New York, N.Y. (October 1985),
incorporated herein by reference in its entirety. A preferred
polymeric material is ethyl cellulose. The polymeric coating
materials can be plasticized with known plasticizing agents such as
phthalate esters, adipate esters, sebacate esters, polyols (e.g.,
ethylene glycol), tricresyl phosphate, castor oil, and camphor. A
preferred polymeric material is ethyl cellulose.
[0044] In other preferred embodiments, the encapsulant is a water
soluble polymer. Examples of suitable synthetic water soluble
polymers include, but are not limited to, polyvinyl pyrrolidone,
water soluble celluloses, polyvinyl alcohol, ethylene maleic
anhydride copolymer, methyl vinyl ether maleic anhydride copolymer,
polyethylene oxides, water soluble polyamide or polyester,
copolymers or homopolymers of acrylic acid such as polyacrylic
acid, polystyrene acrylic acid copolymers, and mixtures thereof.
Other suitable water soluble polymers include water-soluble
hydroxyalkyl celluloses and carboxyalkyl celluloses, such as
hydroxyethyl cellulose, carboxymethyl cellulose, hydroxyethyl
cellulose, carboxyethyl cellulose, hydroxymethyl cellulose,
carboxymethyl cellulose, hydroxypropyl carboxymethyl cellulose,
hydroxypropyl methyl carboxyethyl cellulose, hydroxypropyl
carboxypropyl cellulose, hydroxybutyl carboxymethyl cellulose,
alkali metal salts of these carboxyalkyl celluloses, such as sodium
and potassium salts, and the like. Examples of water soluble
natural and modified natural polymers include starch, gums, and
gelatin. Modified starch in its various forms, including dextrins,
may be also be suitable, as well as hydrolyzed gums and hydrolyzed
gelatin. Hydrolyzed gums suitable for use as encapsulants include
gum arabic, larch, pectin, tragacanth, locust bean, guar,
alginates, carrageenans, cellulose gums such as carboxy methyl
cellulose and karaya. Suitable modified starches typically have a
dextrose equivalent of 0.25 up to about 20, preferably 5 to 15.
Starch hydrolysates having dextrose equivalents of up to 95 are
also useful, e.g., maltodextrins and dextrins and other starches
are derived from corn, waxy maise, tapioca, and the like.
[0045] Microcapsules may be prepared using the M-CAP Process of
Insulation Technologies Corporation of Darby, Pa. The M-CAP shell
walls are microcapsules as small as three microns with melt
temperatures of from about 20.degree. C. to 350.degree. C.
Microcapsules with varied melt temperatures can be included in a
single cigarette to ensure a constant release of menthol as the
coal burns down the tobacco rod. Where the rate control is designed
to vary, the shell material, thickness or microcapsule size can be
accordingly varied. The M-CAP construction provides for uniform
microcapsule size and for microcapsules smaller than fifty
microns.
[0046] Microcapsules may be prepared using ethylene/vinyl acetate
copolymers or a similar cellulite material having the desired
characteristics of a programmable shell wall release temperature of
between 20.degree. C. to 350.degree. C. ELVAX.TM. is an ethylene
vinyl acetate resin available from E. I. DuPont de Nemours &
Co. of Wilmington, Del. Other suitable shell materials include
EUDRAGIT E.TM. manufactured by Rohm America of Piscataway, N.J.,
which is a cationic copolymer synthesized from dimethylaminoethyl
methacrylate and neutral methacrylic acid ester, and can form a
rapidly disintegrating film coating; BERMOCOLL.TM., which is an
ethylhydroxy ethylcellulose manufactured by Berol Kemi AB of
Stenungsund, Sweden; K & K Gelatin, which is a gelatin
manufactured by Kind & Knox, which is a division of Knox
Gelatine, Inc., of Saddle Brook, N.J.; N-LOK.TM., which is an
emulsion stabilizing material produced by National Starch and
Chemical Corporation, Food Products Division, of Bridgewater, N.J.;
and CAPSUL.TM., a modified starch also manufactured by National
Starch. CAPSUL is made from waxy maize, and is especially suited
for encapsulation and has an excellent shelf-life stability.
[0047] In preferred embodiment, the shell wall may make up from
less than about 20% to more than about 50% of the microcapsule's
volume for stability and durability. The microcapsules are
preferably less than 10 .mu.m in diameter so as not to be visible
on the cut tobacco. However larger diameters may be preferred in
certain embodiments. The microcapsules can be further hardened with
a plasticizer to control their melt temperatures. The microcapsules
can be dyed with suitable food dyes to match the color of the
cigarette tobacco. In certain embodiments, double encapsulation or
more may be desirable, depending upon the flavorant to be
encapsulated.
[0048] In certain applications it may be preferred to use a shell
material that decomposes or dissolves, for example, in the presence
of water vapor in tobacco smoke, thereby releasing the encapsulated
flavorant. In certain applications it may also be preferred to use
a shell material that releases the enclosed encapsulant upon
pyrolysis of the smoking material.
[0049] Suitable shell materials include, but are not limited to,
gum arabic, gelatin, diethylcellulose, maltodextrins, and
hydrogenated vegetable oils. Gelatin is particularly preferred
because of its low cost and the ease with which gelatin shell
microcapsules may be prepared. In certain embodiments, however,
other shell materials may be preferred. The optimum shell material
may depend upon the particle size and particle size distribution of
the filling material, the shape of the filling material particles,
compatibility with the filling material, stability of the filling
material, and the timing of the release of the filling material
from the microcapsule.
[0050] Microencapsulation Processes
[0051] A variety of encapsulation methods may be used to prepare
the microcapsules of preferred embodiments. These methods include
gas phase or vacuum processes wherein a coating is sprayed or
otherwise deposited on the filler material particles so as to form
a shell, or wherein a liquid is sprayed into a gas phase and is
subsequently solidified to produce microcapsules. Suitable methods
also include emulsion and dispersion methods wherein the
microcapsules are formed in the liquid phase in a reactor.
[0052] Spray Drying
[0053] Encapsulation by spray drying involves spraying a
concentrated solution of shell material containing filler material
particles or a dispersion of immiscible liquid filler material into
a heated chamber where rapid desolvation occurs. Any suitable
solvent system may be used. However, the method is most preferred
for use with aqueous systems. Spray drying is commonly used to
prepare microcapsules including shell materials such as, for
example, gelatin, hydrolyzed gelatin, gum arabic, modified starch,
maltodextrins, sucrose, or sorbitol. When an aqueous solution of
shell material is used, the filler material typically includes a
hydrophobic liquid or water-immiscible oil. Dispersants and/or
emulsifiers may be added to the concentrated solution of shell
material. Relatively small microcapsules may be prepared by spray
drying methods, e.g., from less than about 1 .mu.m to greater than
about 50 .mu.m. The resulting particles may include individual
particles as well as aggregates of individual particles. The amount
of filler material that may be encapsulated using spray drying
techniques is typically from less than about 20 wt. % of the
microcapsule to more than 60 wt. % of the microcapsule. The process
is preferred because of its low cost compared to other methods, and
has wide utility in preparing food grade microcapsules. The method
may not be preferred for preparing heat sensitive materials,
however.
[0054] In another variety of spray drying, chilled air rather than
desolvation is used to solidify a molten mixture of shell material
containing filler material in the form of particles or an
immiscible liquid. Various fats, waxes, fatty alcohols, and fatty
acids are typically used as shell materials in such an
encapsulation method. The method is generally preferred for
preparing microcapsules having water-insoluble shells.
[0055] Fluidized-Bed Microencapsulation
[0056] Encapsulation using fluidized bed technology involves
spraying a liquid shell material, generally in solution or melted
form, onto solid particles suspended in a stream of gas, typically
heated air, and the particles thus encapsulated are subsequently
cooled. Shell materials commonly used include, but are not limited
to, colloids, solvent-soluble polymers, and sugars. The shell
material may be applied to the particles from the top of the
reactor, or may be applied as a spray from the bottom of the
reactor, e.g., as in the Wurster process. The particles are
maintained in the reactor until a desired shell thickness is
achieved. Fluidized bed microencapsulation is commonly used for
preparing encapsulated water-soluble food ingredients and
pharmaceutical compositions. The method is particularly suitable
for coating irregularly shaped particles. Fluidized bed
encapsulation is typically used to prepare microcapsules larger
than about 100 .mu.m, however smaller microcapsules may also be
prepared.
[0057] Complex Coacervation
[0058] A pair of oppositely charged polyelectrolytes capable of
forming a liquid complex coacervate (namely, a mass of colloidal
particles that are bound together by electrostatic attraction) can
be used to form microcapsules by complex coacervation. A preferred
polyanion is gelatin, which is capable of forming complexes with a
variety of polyanions. Typical polyanions include gum arabic,
polyphosphate, polyacrylic acid, and alginate. Complex coacervation
is used primarily to encapsulate water-immiscible liquids or
water-insoluble solids. The method is generally not suitable for
use with water soluble substances, or substances sensitive to
acidic conditions.
[0059] In the complex coacervation of gelatin with gum arabic, a
water insoluble filler material is dispersed in a warm aqueous
gelatin emulsion, then gum arabic and water are added to this
emulsion. The pH of the aqueous phase is adjusted to slightly
acidic, thereby forming the complex coacervate which adsorbs on the
surface of the filler material. The system is cooled, and a
cross-linking agent, such as glutaraldehyde, is added. The
microcapsules may optionally be treated with urea and formaldehyde
at low pH so as to reduce the hydrophilicity of the shell, thereby
facilitating drying without excessive aggregate formation. The
resulting microcapsules may then be dried to form a powder.
[0060] Polymer-Polymer Incompatibility
[0061] Microcapsules may be prepared using a solution containing
two liquid polymers that are incompatible, but soluble in a common
solvent. One of the polymers is preferentially absorbed by the
filler material. When the filler material is dispersed in the
solution, it is spontaneously coated by a thin film of the polymer
that is preferentially absorbed. The microcapsules are obtained by
either crosslinking the absorbed polymer or by adding a nonsolvent
for the polymer to the solution. The liquids are then removed to
obtain the microcapsules in the form of a dry powder.
[0062] Polymer-polymer incompatibility encapsulation can be carried
out in aqueous or nonaqueous media. It is typically used for
preparing microcapsules containing polar solids with limited water
solubility. Suitable shell materials include ethylcellulose,
polylactide, and lactide-glycolide copolymers. Polymer-polymer
incompatibility encapsulation is often preferred for encapsulating
oral and parenteral pharmaceutical compositions, especially those
containing proteins or polypeptides, because biodegradable
microcapsules may be easily prepared. Microcapsules prepared by
polymer-polymer incompatibility encapsulation tend to be smaller
than microcapsules prepared by other methods, and typically have
diameters of 100 .mu.m or less.
[0063] Interfacial Polymerization
[0064] Microcapsules may be prepared by conducting polymerization
reactions at interfaces in a liquid. In one such type of
microencapsulation method, a dispersion of two immiscible liquids
is prepared. The dispersed phase forms the filler material. Each
phase contains a separate reactant, the reactants capable of
undergoing a polymerization reaction to form a shell. The reactant
in the dispersed phase and the reactant in a continuous phase react
at the interface between the dispersed phase and the continuous
phase to form a shell. The reactant in the continuous phase is
typically conducted to the interface by a diffusion process. Once
reaction is initiated, the shell eventually becomes a barrier to
diffusion and thereby limits the rate of the interfacial
polymerization reaction. This may affect the morphology and
uniformity of thickness of the shell. Dispersants may be added to
the continuous phase. The dispersed phase can include an aqueous or
a nonaqueous solvent. The continuous phase is selected to be
immiscible in the dispersed phase.
[0065] Typical polymerization reactants may include acid chlorides
or isocyanates, which are capable of undergoing a polymerization
reaction with amines or alcohols. The amine or alcohol is
solubilized in the aqueous phase in a nonaqueous phase capable
solubilizing the amine or alcohol. The acid chloride or isocyanate
is then dissolved in the water-immiscible or nonaqueous
solvent-immiscible phase. Similarly, solid particles containing
reactants or having reactants coated on the surface may be
dispersed in a liquid in which the solid particles are not
substantially soluble. The reactants in or on the solid particles
then react with reactants in the continuous phase to form a
shell.
[0066] In another type of microencapsulation by interfacial
polymerization, commonly referred to as in situ encapsulation, a
filler material in the form of substantially insoluble particles or
in the form of a water immiscible liquid is dispersed in an aqueous
phase. The aqueous phase contains urea, melamine, water-soluble
urea-formaldehyde condensate, or water-soluble urea-melamine
condensate. To form a shell encapsulating the filler material,
formaldehyde is added to the aqueous phase, which is heated and
acidified. A condensation product then deposits on the surface of
the dispersed core material as the polymerization reaction
progresses. Unlike the interfacial polymerization reaction
described above, the method may be suitable for use with sensitive
filler materials since reactive agents do not have to be dissolved
in the filler material. In a related in situ polymerization method,
a water-immiscible liquid or solid containing a water-immiscible
vinyl monomer and vinyl monomer initiator is dispersed in an
aqueous phase. Polymerization is initiated by heating and a vinyl
shell is produced at the interface with the aqueous phase.
[0067] Gas Phase Polymerization
[0068] Microcapsules may be prepared by exposing filler material
particles to a gas capable of undergoing polymerization on the
surface of the particles. In one such method, the gas comprises
p-xylene dimers that polymerize on the surface of the particle to
form a poly(p-xylene) shell. Specialized coating equipment may be
necessary for conducting such coating methods, making the method
more expensive than certain liquid phase encapsulation methods.
Also, the filler material to be encapsulated is preferably not
sensitive to the reactants and reaction conditions.
[0069] Solvent Evaporation
[0070] Microcapsules may be prepared by removing a volatile solvent
from an emulsion of two immiscible liquids, e.g., an oil-in-water,
oil-in-oil, or water-in-oil-in-water emulsion. The material that
forms the shell is soluble in the volatile solvent. The filler
material is dissolved, dispersed, or emulsified in the solution.
Suitable solvents include methylene chloride and ethyl acetate.
Solvent evaporation is a preferred method for encapsulating water
soluble filler materials, for example, polypeptides. When such
water soluble components are to be encapsulated, a thickening agent
is typically added to the aqueous phase, then the solution is
cooled to gel the aqueous phase before the solvent is removed.
Dispersing agents may also be added to the emulsion prior to
solvent removal. Solvent is typically removed by evaporation at
atmospheric or reduced pressure. Microcapsules less than 1 .mu.m or
over 1000 .mu.m in diameter may be prepared using solvent
evaporation methods.
[0071] Centrifugal Force Encapsulation
[0072] Microencapsulation by centrifugal force typically utilizes a
perforated cup containing an emulsion of shell and filler material.
The cup is immersed in an oil bath and spun at a fixed rate,
whereby droplets including the shell and filler material form in
the oil outside the spinning cup. The droplets are gelled by
cooling to yield oil-loaded particles that may be subsequently
dried. The microcapsules thus produced are generally relatively
large. In another variation of centrifugal force encapsulation
referred to as rotational suspension separation, a mixture of
filler material particles and either molten shell or a solution of
shell material is fed onto a rotating disk. Coated particles are
flung off the edge of the disk, where they are gelled or desolvated
and collected.
[0073] Submerged Nozzle Encapsulation
[0074] Microencapsulation by submerged nozzle generally involves
spraying a liquid mixture of shell and filler/material through a
nozzle into a stream of carrier fluid. The resulting droplets are
gelled and cooled. The microcapsules thus produced are generally,
relatively large.
[0075] Desolvation
[0076] In desolvation or extractive drying, a dispersion filler
material in a concentrated shell material solution or dispersion is
atomized into a desolvation solvent, typically a water-miscible
alcohol when an aqueous dispersion is used. Water-soluble shell
materials are typically used, including maltodextrins, sugars, and
gums. Preferred desolvation solvents include water-miscible
alcohols such as 2-propanol or polyglycols. The resulting
microcapsules do not have a distinct filler material phase.
Microcapsules thus produced typically contain less than about 15
wt. % filler material, but in certain embodiments may contain more
filler material.
[0077] Liposomes
[0078] Liposomes are microparticles typically ranging in size from
less than about 30 nm to greater than 1 mm. They consist of a
bilayer of phospholipid encapsulating an aqueous space. The lipid
molecules arrange themselves by exposing their polar head groups
toward the aqueous phase, and the hydrophobic hydrocarbon groups
adhere together in the bilayer forming close concentric lipid
leaflets separating aqueous regions. Flavorants can either be
encapsulated in the aqueous space or entrapped between the lipid
bilayers. Where the flavorant is encapsulated depends upon its
chemical characteristics and the composition of the lipid.
[0079] Miscellaneous Microencapsulation Processes
[0080] While the microencapsulation methods described above are
generally preferred for preparing the microcapsules of preferred
embodiments, other suitable microencapsulation methods may also be
used, as are known to those of skill in the art. Moreover, in
certain embodiments, in addition to the encapsulated material, it
may be desired to incorporate an unencapsulated flavorant or other
substance directly on the smoking material, the filter materials,
wrapping paper, or other components of the smoking article. The
microcapsules added to the smoking material may all be of the same
type and contain the same flavorants or other substances, or may
include a variety of types and/or encapsulated flavorants or other
substances.
[0081] Smokable Articles Containing Microencapsulated
Flavorants
[0082] Microcapsules containing one or more flavorants or other
substances are prepared as described above. To ensure that
premature release of the flavorant does not occur upon addition of
the microcapsules, it is desirable to ensure that the microcapsules
are thoroughly dried and do not contact any substance that may
negatively impact the integrity of the microcapsule shell.
[0083] The microcapsules may incorporated into the smoking article
in any convenient manner and at any convenient time in the
fabrication process. In preferred embodiments, the microcapsules
containing the flavorant are deposited onto the smokable material,
for example, cut tobacco. The microcapsules may be added to the
smokable material as part of the casing solution if the
microcapsules will not degrade or melt in the presence of the
solution. Alternatively, the microcapsules may be added to the
smokable material in a separate step from the addition of other
components. The microcapsules are preferably added to the smokable
material at a point in the fabrication process of the smoking
article such that no subsequent processing steps are conducted that
may result in the exposure of the microcapsules to conditions
resulting in premature release of the flavorant.
[0084] The microcapsules may be added to the smokable material in
pure form, for example, as a powder. Alternatively, the
microcapsules may be applied as a suspension in a suitable liquid.
The microcapsules or suspension of microcapsules may also contain a
material to facilititate adhesion of the microcapsules to the
smokable material. Suitable materials include gelatin or other
viscous materials as are known in the art. In order to form a
homogenous mixture of microcapsules and liquid carrier or other
components, any suitable mixing method may be used, for example,
mechanical stirring, shaking, or sonication. It is preferred that
the mixing method not result in substantial damage of the
microcapsules and the resulting premature release of flavorant or
other substances contained therein. Preferably, the components are
mixed and stored under an inert atmosphere or sealed in an airtight
container prior to application.
[0085] The microcapsules are typically added to the smokable
material to provide a concentration of flavorant of from less than
about 0.001, 0.005, or 0.01 wt. % flavorant to more than about 3,
4, or 5 wt. % flavorant on a tobacco weight basis, preferably from
about 0.05, 0.1, or 0.2 wt. % to about 1, 1.5, 2, or 2.5 wt. %, and
more preferably from about 0.3, 0.4, or 0.5 wt. % to about 0.6,
0.7, 0.8 or 0.9 wt. %. The optimal concentration may depend upon
the concentration of flavorant material in the microcapsules, the
type of flavorant or flavorants used, the desired release rate and
level of the flavorant, the encapsulating material, and the method
of encapsulation used to prepare the flavorant microcapsules.
[0086] In certain embodiments, it may be preferred to incorporate
the microcapsules into a portion of the smoking article other than
the cut tobacco or other smokable material, for example, in one or
more of the filter materials, in a cartridge contained within the
filter or tobacco rod, or any other location, as will be
appreciated by one skilled in the art.
[0087] Catalyst System for Reducing Carcinogens in Smoke
[0088] In preferred embodiments, smoking articles incorporating the
microencapsulated flavorant also incorporates a catalyst system
including catalytic metallic and/or carbonaceous particles and a
nitrate or nitrite source. The catalyst system is incorporated into
the smokable material so as to reduce the concentration of certain
undesirable components in the resulting smoke. In embodiments
wherein the particles are metallic, the particles are preferably
prepared by heating an aqueous solution of a metal ion source and a
reducing agent, preferably a reducing sugar or a metal ion source
with hydroxide. Preferably, after the metallic particles are formed
in solution, the nitrate or nitrite source is added to the
solution, and the solution is applied to the smokable material.
However, embodiments in which the particles and the nitrate or
nitrite source are added separately to the smokable material are
also contemplated. The catalyst system and smoking articles
incorporating the same are described in detail in copending U.S.
application Ser. No. 10/007,724 filed Nov. 9, 2001 and entitled
"METHOD AND PRODUCT FOR REMOVING CARCINOGENS FROM TOBACCO SMOKE,"
the contents of which is incorporated herein by reference in its
entirety.
[0089] Metallic Particles
[0090] In preferred embodiments, particles of a catalytic metallic
substance are applied to the smokable materials. The term
"metallic," as used herein, is a broad term and is used in its
ordinary sense, including without limitations, pure metals,
mixtures of two or more metals, mixtures of metals and non-metals,
metal oxides, metal alloys, mixtures or combinations of any of the
aforementioned materials, and other substances containing at least
one metal. Suitable catalytic metals include the transition metals,
metals in the main group, and their oxides. Many metals are
effective in this process, but preferred metals include, for
example, Pd, Pt, Rh, Ag, Au, Ni, Co, and Cu.
[0091] Many transition and main group metal oxides are effective,
but preferred metal oxides include, for example, AgO, ZnO, and
Fe.sub.2O.sub.3. Zinc oxide and iron oxide are particularly
preferred based on physical characteristics, cost, and carcinogenic
behavior of the oxide. A single metal or metal oxide may be
preferred, or a combination of two or more metals or metal oxides
may be preferred. The combination may include a mixture of
particles each having different metal or metal oxide compositions.
Alternatively, the particles themselves may contain more than one
metal or metal oxide. Suitable particles may include alloys of two
or more different kinds of metals, or mixtures or alloys of metals
and nonmetals. Suitable particles may also include particles having
a metal core with a layer of the corresponding metal oxide making
up the surface of the particle. The metallic particles may also
include metal or metal oxide particles on a suitable support
material, for example, a silica or alumina support. Alternatively,
the metallic particles may include particles including a core of
support material substantially encompassed by a layer of
catalytically active metal or metal oxide. In addition to the
above-mentioned configurations, the metallic particles may in any
other suitable form, provided that the metallic particles have the
preferred average particle size.
[0092] The particles may be prepared by any suitable method as is
known in the art. When preparing metallic particles, suitable
methods include, but are not limited to, wire electrical explosion,
high energy ball milling, plasma methods, evaporation and
condensation methods, and the like. However, in preferred
embodiments, the particles are prepared via reduction of metal ions
in aqueous solution, as described below.
[0093] While any suitable metal, metal oxide, or carbonaceous
particle (as described below) is preferred, it is particularly
preferred to use a metal, metal oxide, or carbonaceous particle
that has a relatively low level of transfer to cigarette or other
smoke condensate produced upon combustion of the smokable material.
For example, palladium has a lower level of transfer than silver.
Also, metal oxides tend to have relatively low levels of transfer.
However, in certain embodiments it may be preferred to use a metal,
metal oxide, or carbonaceous particle having a relatively high
level of transfer to smoke condensate. In providing a compound that
effectively catalyzes the decomposition of nitrate salts, it is
also generally preferred that the metal, metal oxide, or
carbonaceous particle have a relatively low specific heat.
[0094] Carbonaceous Particles
[0095] In certain embodiments, particles of a catalytic
carbonaceous substance are applied to the smokable materials. The
term "carbonaceous", as used herein, is a broad term and is used in
its ordinary sense, including without limitations, graphitic
carbon, fullerenes, doped fullerenes, carbon nanotubes, doped
carbon nanotubes, other suitable carbon-containing substances, and
mixtures or combinations of any of the aforementioned
substances.
[0096] The carbonaceous particles may be prepared by any suitable
method as is known in the art. When preparing graphitic particles
suitable methods may include, but are not limited to, milling
techniques, and the like.
[0097] Fullerenes include, but are not limited to, buckminster
fullerene (C.sub.60), as well as C.sub.70 and higher fullerenes.
The structure of fullerenes and carbon nanotubes may permit them to
be doped with other atoms, for example, metals such as the alkali
metals, including potassium, rubidium and cesium. These other atoms
may be included within the carbon cage or carbon nanotube, as is
observed for certain atoms when enclosed within endohedral
fullerene. Atoms may also be incorporated into a crystal structure,
e.g., the bct structure of A4C60 (wherein A=K,Rb,Cs, and
C=buckminster fullerene) or the bcc structure of A6C60 (wherein
A=K,Rb,Cs, and C=buckminster fullerene). Fullerenes may also be
dimerized or polymerized. Certain fullerenes, such as C.sub.70
fullerenes, are known radical traps and as such may be suitable for
use in a catalyst system without the presence of nitrate or other
radical trap generators.
[0098] Fullerenes are preferably prepared by condensing gaseous
carbon in an inert gas. The gaseous carbon is obtained, for
example, by directing an intense pulse of laser at a graphite
surface. The released carbon atoms are mixed with a stream of
helium gas, where they combine to form clusters of carbon atoms.
The gas containing clusters is then led into a vacuum chamber where
it expands and is cooled to a few degrees above absolute zero. The
clusters are then extracted. Other suitable methods for preparing
fullerenes as are known in the art may also be used.
[0099] Carbon nanotubes may be prepared by electric arc discharge
between two graphite electrodes. In the electric arc discharge
method, material evaporates from one electrode and deposits on the
other in the form of nanoparticles and nanotubes. Purification is
achieved by competitive oxidation in either the gas or liquid
phase. Carbon nanotubes may also be catalytically grown. In
catalytic methods, filaments containing carbon nanotubes are grown
on metal surfaces exposed to hydrocarbon gas at temperatures
typically between 500-1100.degree. C. Other techniques for forming
carbon nanotubes include laser evaporation techniques, similar to
those used to form fullerenes. However, any suitable method for
forming carbon nanotubes may be used.
[0100] Particle Size
[0101] The particles of preferred embodiments preferably have an
average particle size of greater than about 0.5 micron (0.5 .mu.m),
more preferably greater than about 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2,
1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 .mu.m. The preferred size
may depend on the metallic or carbonaceous substance. Particle
sizes can be as large as 150 .mu.m or more, more preferably 150,
140, 130, 120, 110, 100, 90, 80, 70, 60, 50, 40, 30, 20, 19, 18,
17, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3 .mu.m or less in
diameter. In other embodiments, preferred particle size may be less
than about 0.5 .mu.m (500 nm), or 400, 300, 200, 100, 90, 80, 70,
60, 50, 40, 30, 20, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 nm or less. In
preferred embodiments, the particles are of a substantially uniform
size distribution, that is, a majority of the metallic particles
present have a diameter generally within about .+-.50% or less of
the average diameter, preferably within about .+-.45%, 40%, 35%,
30% or less of the average diameter, more preferably within .+-.25%
or less of the average diameter, and most preferably within .+-.20%
or less of the average diameter. The term "average" includes both
the mean and the mode.
[0102] While a uniform size distribution may be generally
preferred, individual particles having diameters above or below the
preferred range may be present, and may even constitute the
majority of the particles present, provided that a substantial
amount of particles having diameters in the preferred range are
present. In other embodiments, it may be desirable that the
particles constitute a mixture of two or more particle size
distributions, for example, a portion of the mixture may include a
distribution on nanometer-sized particles and a portion of the
mixture may include a distribution of micron-sized particles. The
particles of preferred embodiments may have different forms. For
example, a particle may constitute a single, integrated particle
not adhered to or physically or chemically attached to another
particle. Alternatively, a particle may constitute two or more
agglomerated or clustered smaller particles that are held together
by physical or chemical attractions or bonds to form a single
larger particle. The particles may have different atomic level
structures, including but not limited to, for example, crystalline,
amorphous, and combinations thereof. In various embodiments, it may
be desirable to include different combinations of particles having
various properties, including, but not limited to, particle size,
shape or structure, chemical composition, crystallinity, and the
like.
[0103] Nitrate or Nitrite Source
[0104] Any suitable source of nitrate or nitrite may be preferred.
Preferred nitrate or nitrite sources include the nitrate or nitrite
salts of metals selected from Groups Ia, Ib, IIa, IIb, IIIa, IIIb,
IVa, IVb, Va, Vb, and the transition metals of the Periodic Table
of Elements.
[0105] In preferred embodiments, the nitrate or nitrite source
includes a nitrate of lithium, sodium, potassium, rubidium, cesium,
magnesium, calcium, strontium, yttrium, lanthanum, cerium,
neodymium, samarium, europium, gadolinium, terbium, dysprosium,
erbium, scandium, manganese, iron, rhodium, palladium, copper,
zinc, aluminum, gallium, tin, bismuth, hydrates thereof and
mixtures thereof. Preferably, the nitrate salt may be an alkali or
alkaline earth metal nitrate. More preferably, the nitrate or
nitrite source may be selected from the group of calcium,
magnesium, and zinc with magnesium nitrate being the most preferred
salt. In a particularly preferred embodiment,
Mg(NO.sub.3).sub.2-6H.sub.2O may be preferred as a nitrate source.
While nitrate and nitrite salts are generally preferred, any
suitable metal salt or organometallic compound, or other compound
capable of releasing nitric oxide may be preferred.
[0106] While not wishing to be limited to any particular mechanism,
it is believed that the nitrate or nitrite source forms nitric
oxide radicals and that this reaction process is catalyzed by the
metallic or carbonaceous particles in the combustion zone of
tobacco. The nitric oxide radicals are believed to act as a trap
for other organic radicals that are responsible for formation of
PAHs and other carcinogenic compounds.
[0107] The temperature at which a particular nitrate or nitrite
source decomposes to form nitric oxide may vary. Since a
temperature gradient exists across the combustion zone of a tobacco
rod, the choice and concentration of the nitrate or nitrite source
may be selected so as to provide optimum production of nitric oxide
during combustion. Certain nitrates and nitrites alone, especially
those of the Group Ia metals, function as effective combustion
promoters, accelerating the burn rate of the smokable material and
decreasing the total smoke yield, but not necessarily decreasing
the quantity of PAHs within the smoke. The nitric oxide yield of
such nitrates may also be relatively low.
[0108] In certain embodiments, it may be preferred that the metal
ion source and the nitrate or nitrite source constitute the same
compound, for example, palladium(II) nitrate.
[0109] Catalyst Preparation
[0110] In preferred embodiments, metallic particles may be prepared
from an aqueous solution. For example, metal particles may be
prepared from an ion source containing one or more metal ion
sources and one or more reducing sugars. Suitable metal ion sources
include any ionic or organometallic compound that is soluble in
aqueous solution and is capable of yielding metal ions that may be
reduced to particles of a catalytic metal or utilized to form a
metal oxide. In a particularly preferred embodiment, the catalytic
source includes a metal such as palladium, and the palladium ion
source includes water-soluble palladium salts. Illustrative
non-limiting examples of suitable palladium salts include simple
salts such as palladium nitrate, palladium halides such as
palladium di or tetrachloride diammine complexes such as
dichlorodiamminepalladium(II) (Pd(NH.sub.3).sub.2Cl.sub.2), and
palladate salts, especially ammonium salts such as ammonium
tetrachloropalladate(II- ) and ammonium
hexachloropalladate(IV).
[0111] One form of palladium that may be especially preferred is
ammonium tetrachloropalladate(II), (NH.sub.4).sub.2PdCl.sub.4.
Ammonium tetrachloropalladate is generally preferred over ammonium
hexachloropalladate because under typical conditions for preparing
the metallic particles, a higher metal ion to metal conversion may
be observed for ammonium tetrachloropalladate(II).
[0112] In a preferred embodiment, an aqueous solution of reducing
agent is prepared, to which the metal ion source is added. In
preferred embodiments, the reducing agent may be a reducing sugar,
however other suitable reducing agents may be preferred. Although
any compound capable of reducing the metal ion can be employed, as
a practical matter the reducing agent is preferably non-toxic and
preferably does not form toxic byproducts when pyrolyzed during
smoking. In addition, the reducing agent is preferably
water-soluble.
[0113] Preferred reducing agents are the reducing sugars, including
organic aldehydes, including hydroxyl-containing aldehydes such as
the sugars, for example glucose, mannose, galactose, xylose,
ribose, and arabinose. Other sugars containing hemiacetal or keto
groupings may be employed, for example, maltose, sucrose, lactose,
fructose, and sorbose. Pure sugars may be employed, but crude
sugars and syrups such as honey, corn syrup, invert syrup or sugar,
and the like may also be employed. Other reducing agents include
alcohols, preferably polyhydric alcohols, such as glycerol,
sorbitol, glycols, especially ethylene glycol and propylene glycol,
and polyglycols such as polyethylene and polypropylene glycols. In
alternative embodiments, other reducing agents may be preferred
such as carbon monoxide, hydrogen, or ethylene.
[0114] The solution is preferably heated before the metal ion
source is added to the solution, and maintained at an elevated
temperature afterwards so as to reduce the time for conversion of
the metal ions to metallic particles. In a preferred embodiment, a
reducing sugar such as low invert sugar may be preferred as the
reducing agent. In certain embodiments, it may be desirable to have
an excess or deficiency of reducing agent present in solution.
Generally, it is preferred to prepare an aqueous solution
containing from about 5 wt. % to about 20 wt. % of the reducing
sugar, preferably about 6 wt. % to about 16 or 17 wt. %, more
preferably from about 7, 8, 9, 10, or 11 wt. % to about 12, 13, 14,
or 15 wt. %. When the reducing agent is invert sugar, it is
preferred to prepare a 11 wt. % to about 12 wt. % solution. The
amount of reducing agent preferred may vary depending on the type
of reducing agent preferred and the amount of metal ion source to
be added to the solution.
[0115] It may be preferred to prepare the solution in a glass-lined
vessel equipped with a heating jacket. In certain embodiments,
however, it may be preferred to prepare the solution in another
kind of vessel constructed of or lined with another type of
material, for example, plastic, stainless steel, ceramic, and the
like. It is generally preferred to conduct the reaction in a closed
vessel. In certain embodiments, it may be desirable to conduct the
reaction under reduced pressure or elevated pressure, or under an
inert atmosphere, such as nitrogen or argon.
[0116] In preparing the aqueous solution of the reducing sugar, it
is preferred to use deionized ultrafiltered water. While in
preferred embodiments the metallic particles are prepared from
aqueous solution, in other embodiments it may be desirable to use
another suitable solvent system, for example, a polar solvent such
as ethanol, or a mixture of ethanol and water. Additional
components may be present in the solution as well, provided that
they do not substantially adversely impact the catalytic activity
of the metallic particles.
[0117] After adding the reducing sugar to the deionized
ultrafiltered water, the solution is preferably heated with
constant mixing so as to avoid hot spots in the solution. Although
in certain embodiments it may be desirable to prepare the particles
from a room temperature solution, or even a solution cooled below
room temperature, it is generally preferred to heat the solution so
as to speed the reaction between the reducing sugar and the metal
ion source once it is added to the solution. The solution may be
heated to any suitable temperature, but boiling of the solution and
decomposition of the reducing sugar is preferably avoided. In a
preferred embodiment wherein low invert sugar is the reducing
sugar, the solution is typically heated up to about 95.degree. C.
or more, preferably from above room temperature to about 90.degree.
C., more preferably from about 50.degree. C., 55.degree. C.,
60.degree. C., or 65.degree. C. to about 85.degree. C., and most
preferably from about 70.degree. C. or 75.degree. C. to about
80.degree. C.
[0118] The metal ion source is added to the heated aqueous solution
of reducing agent, which is stirred while the metal ions react with
the reducing sugar to produce metallic particles. It is generally
preferred to add sufficient metal ion source so as to produce a
solution containing from less than about 3000 ppm to more than
about 5000 ppm metal. Preferably, sufficient metal ion source is
added to produce a solution containing from about 3250, 3500, or
3750 ppm to about 4250, 4500, 4750 ppm metal, more preferably from
about 3800, 3850, 3900, or 3950 ppm to about 4050, 4100, 4150, or
4200 ppm metal, and most preferably about 4000 ppm metal.
[0119] The reaction time for conversion of metal ion to metal
particles may vary depending upon the reducing agent and metal ion
source preferred, but generally ranges from about 30 minutes or
less to about 24 hours or more, and typically ranges from about 1
or 2 hours up to about 3, 4, or 5 hours. In a preferred embodiment,
wherein ammonium tetrachloropalladate is the metal ion source, a
substantial conversion of palladium ion to palladium metal may be
achieved after 3 hours for a solution heated to a temperature of
about 75.degree. C. Although in certain embodiments a lower
conversion may be acceptable, it is generally desirable to achieve
a conversion of metal ion to metal of at least 50%, preferably at
least 60%, more preferably at least 70%, and most preferably at
least 75, 80, 85% or more.
[0120] The metallic particles produced in this manner generally
have diameters of about 1 .mu.m or less. In certain other
embodiments metallic particles having individual diameters and
average diameters below about 20 nm or above about 1 .mu.m may be
produced. The size of the metallic particles may be conveniently
determined using conventional methods of X-ray diffraction or other
particle size determination methods, for example, laser
scattering.
[0121] After a sufficient conversion of metal ion to metal or metal
oxide is achieved, and the metallic particles are formed, the
nitrate or nitrite source is added to the suspension. Any suitable
compound that yields nitrate or nitrite ion in aqueous solution may
be preferred. Preferably, the nitrate or nitrite source is an
alkali metal or alkaline earth metal nitrate or nitrite. In a
particularly preferred embodiment, the nitrate or nitrite source is
magnesium nitrate, Mg(NO.sub.3).sub.2-6H.sub.2O. It is generally
preferred to add a sufficient amount of nitrate or nitrite source
so as to produce a solution containing from less than about 70 ppm
to more than about 100 ppm nitrogen (in the form of nitrate or
nitrite). Preferably, sufficient nitrate or nitrite source is added
to produce a solution containing from about 75, 80, or 85 ppm to
about 90 or 95 ppm nitrogen, more preferably from about 80 ppm
nitrogen.
[0122] Generally, it is preferred that the suspension of metallic
particles not be excessively concentrated or dilute, so as to
facilitate efficient application of the suspension to the smokable
material.
[0123] While it is generally preferred to prepare a suspension of
particles as described above by reduction of metal ion in solution,
followed by addition of the nitrate or nitrite source, in other
embodiments it may be preferred to use a different method to
prepare the particles. If the metallic or carbonaceous particles
are not prepared in solution, the particles may be mixed with an
appropriate liquid to form a suspension. Because of their high
surface area, it may be difficult to sufficiently wet the surface
of the particles so as to form a uniform suspension. In such cases,
any suitable method may be preferred to facilitate forming the
suspension, including, but not limited to, mechanical methods such
as sonication or heating, or chemical methods such as the use of
small quantities of surfactants, provided the surfactants do not
interfere with the catalytic activity of the particles. Once the
suspension is formed, addition of the nitrate or nitrite source may
proceed as described above.
[0124] While it is generally preferred to apply the metallic or
carbonaceous particles and nitrate or nitrite source to the
smokable material in the form of a suspension, other methods of
applying the particles and nitrate or nitrite source are also
contemplated. For example, if the particles are in dry form, they
may be added to the smokable material as a powder. It may be
advantageous to moisten the smokable material with a suitable
substance, for example, water, prior to application of the powder
in order to provide better adhesion of the particles to the
smokable material.
[0125] When the carbonaceous or metallic particles are added to the
smokable material in powder form, the nitrate or nitrate source in
solid form may also be applied to the smokable material in powder
form, either in a separate step before or after the addition of the
particles, or simultaneously with the particles, for example, in
admixture with the particles. Suitable methods as are well known in
the art may be used to prepare a suitable solid form of nitrate or
nitrate source. In particularly preferred methods, the solid form
of nitrate or nitrite source is prepared by freeze drying or spray
drying methods, both of which may yield extremely small particle
sizes. It is generally preferred that the nitrate or nitrite source
be in the form of particles having an average diameter on the order
of the preferred average diameters for the particles. The nitrate
or nitrite source may also be provided as a solution applied to the
smokable material as a separate step from adding the particle
powder, preferably before adding the particle in dry form to the
smokable material.
[0126] Optimization of the Catalyst System
[0127] There are many aspects to consider when attempting to
optimize the catalyst system, the first of which is the conversion
of the palladium salt to palladium metal in the aqueous reducing
solution. This conversion requires a chemical reduction reaction in
an aqueous solution. Earlier work was directed to the conversion of
the palladium salt to palladium metal in a casing solution. It was
suggested from the patent literature that the reducing agent for
this reaction in the casing solution was fructose--a known reducing
sugar. One origin of fructose in the casing solution is from low
invert sugar. In order to try to repeat this earlier research with
casing solutions and produce a more consistent/controllable
reaction, all of the components in the casing solution were
eliminated that were considered non-essential to the reduction
reaction (e.g. propylene glycol, licorice, cocoa, and the like),
while the components thought to be essential (e.g. water, palladium
salt and low invert sugar) were retained in the same ratios as
found in the casing solution, namely 93 g water to 1 g palladium
salt to 8 g low invert sugar per pound of tobacco, respectively.
Another component that was in the original casing solution but is
considered non-essential to the reduction reaction was
Mg(NO.sub.3)2-6H.sub.2O. This component was present in early
formulations, however nitrate analysis of the tobacco verified that
Mg(NO.sub.3)2-6H.sub.2O decomposes to a certain degree when mixed
in aqueous solutions containing palladium metal. It was also found
through early testing that carcinogen reduction in cigarettes was
not reproducible when the Mg(NO.sub.3)2-6H.sub.2O was allowed to be
in contact with palladium metal for extended periods of time. Upon
removal of the Mg(NO.sub.3)2-6H.sub.2O from the reacting solution,
and instead the addition of it prior to catalyst application on the
tobacco, consistent and reproducible carcinogen reductions in
experimental cigarettes were obtainable.
[0128] One feature of the preferred reduction reaction is the
percent conversion of palladium salt to palladium metal in the
aqueous solution containing low invert sugar as a reducing agent.
At a temperature of approximately 70-75.degree. C., the percent
conversion typically increases steadily with time and after the
first three hours of the reaction more than 60-70% of the salt has
typically been converted to the metal. Most of the palladium salt
is typically converted to metal within the first hour
(approximately 50%). Longer reaction times (for example, above
three hours) generally only increase the percent conversion
modestly. Given the task of balancing maximum conversion with an
acceptable production schedule, three hours is generally preferred
as the minimum time for this reaction to occur before application
of the catalyst solution to the tobacco.
[0129] To increase production rates and lower production costs, it
is desirable to increase the percent conversion of palladium salt
to palladium metal. An immediate benefit of increasing the percent
conversion is the capacity to use less total palladium salt in the
reaction as an increase in percent conversion with less salt could
in fact produce equivalent amounts of palladium metal in the
reaction. This results in lower consumption of the most expensive
reagent in the reaction.
[0130] Several possibilities exist to increase the percent
conversion of this reaction. The reduction reaction is based on an
aldehyde being oxidized and releasing electrons to the Pd II
nucleus, thereby producing metallic palladium. 1
[0131] In a particularly preferred catalyst system as described
above, it is believed that the aldehyde source is the reducing
sugar fructose. In theory, any compound containing an aldehyde
functional group can reduce the palladium salt to palladium metal,
however to apply the resulting mixture to tobacco it is preferred
that the reducing agent is non-toxic. As discussed previously in
regard to the particularly preferred catalystsystem, low invert
sugar is used as the "reducing agent" for this reaction and it is
believed that the fructose component of low invert sugar is the
active reducing agent. Interestingly, pure fructose when supplied
as a reducing agent for the palladium reduction has been shown not
to be very effective, even when the fructose is in 10 molar excess.
This observation suggests that there is an additional "co-reducing
agent" or possibly a catalyst for the reducing agent contained
within the low invert sugar solution. Due to the complex mixture
associated with low invert sugar it will continue to be a challenge
to discover exactly what the reducing agent or agents are when
utilizing low invert sugar as a reactant. Nevertheless, the
particularly preferred system performs remarkably well given the
fact that the mechanism for palladium reduction is not well
understood in this system.
[0132] Application of Catalyst to Smokable Material
[0133] After the nitrate or nitrite source has been added to the
suspension containing metallic or carbonaceous particles, it is
applied to the smokable material. If the smokable material is
tobacco, it is preferred to apply the suspension to cut filler
prior to addition of the top flavor. If a top flavor is not
applied, then it is preferred to apply the suspension to the cut
filler as a final step, for example, before it is formed into a
tobacco rod. The catalytic particles may be applied before, during
or after application of a casing solution, however in a preferred
embodiment the catalytic particles are applied after application of
the casing solution. Casing solutions are pre-cutting solutions or
sauces added to tobacco and are generally made up of a variety of
ingredients, such as sugars and aromatic substances. Such casing
solutions are generally added to tobacco in relatively large
amounts, for example, one part casing solution to five parts
tobacco.
[0134] The particles and nitrate or nitrite source are preferably
well dispersed throughout the tobacco so as to provide uniform
effectiveness throughout the entire mass of smokable material and
throughout the entire period during which the material is smoked.
In the case of cigarette tobacco wherein a blend of various
tobaccos is preferred, the suspension may be applied to one or more
of the blend constituents, or all of the blend constituents, as
desired. Preferably, the suspension is applied to all of the blend
constituents so as to ensure substantially uniform coverage of the
particles and nitrate or nitrite source.
[0135] For certain types of suspensions of particles, a degradation
in performance may be observed if an excessive period of time is
allowed to elapse before the suspension is applied to the smokable
product. This degradation in performance may be due to various
factors, including loss of particles from the suspension due to
their accumulation on the interior surfaces of the reaction vessel,
or an undesirable increase in particle size over time. When the
suspension includes palladium particles, the suspension is
generally applied to the cut filler within about ten hours after
the desired degree of metal ion conversion is reached and the
nitrate or nitrite source is added to the suspension. The
suspension is preferably applied within about 9, 8, 7, or fewer
hours, more preferably within about 6, 5, or 4 hours, and most
preferably within 3, 2, or 1 hours or less. However, in certain
embodiments, including those utilizing palladium particles, it may
be possible to apply the suspension after a delay of longer than
ten hours while maintaining acceptable catalytic performance.
[0136] It is preferred to apply the suspension to the smokable
material in the form of a fine mist, such as is produced using an
atomizer. In a particularly preferred embodiment, the suspension is
applied to tobacco, preferably cut filler, in a rotating tumbler
equipped with multiple spray heads. Such a method of application
ensures an even coating of the metallic particles on the tobacco
product. The tobacco may be heated during or after application of
the solution so as to facilitate evaporation of excess solvent.
[0137] It is preferred to add a sufficient quantity of the metallic
or carbonaceous particle suspension to the smokable material such
that the smokable material contains from about 500 ppm or less to
about 1500 or more ppm of the metal or carbon in the form of
catalytic particles. Preferably, the smokable material contains
from about 500 ppm to about 1000, 1100, 1200, 1300, or 1400 ppm of
the metal or carbon in the form of catalytic particles, more
preferably 500, 600 or 700 to about 800, 900, or 1000 ppm, and most
preferably about 800 ppm. It is generally preferred that the
smokable material contains from about 0.4 to about 1.5 wt. %
nitrogen (from nitrate or nitrite). Preferably, the smokable
material contains from about 0.5 or 0.6 wt. % to about 1.0, 1.1,
1.2, 1.3, or 1.4 wt. % nitrogen, more preferably from about 0.6,
0.7, or 0.8 wt. % to about 0.9 wt. %, and most preferably about 0.9
wt. % nitrogen. In a preferred embodiment, one kilogram of tobacco
constitutes 800 milligrams of metal or carbon in the form of
catalytic particles, and 9 grams of nitrogen in the form of the
nitrate or nitrite source.
[0138] Once the metallic or carbonaceous particles and nitrate or
nitrite source have been applied, the smokable material may be
further processed and formed into any desired shape or used
loosely, for example, in cigars, cigarettes, or pipe tobacco, in
any suitable manner as is well-known to those skilled in the
art.
[0139] The Filter
[0140] In preferred embodiments wherein the smokable material to
which the microencapsulated flavorant has been applied is fashioned
into a smokable article, a filter for the smokable article is
provided. The filter can be provided in combination with cigarettes
or cigars or other smokable devices containing divided tobacco or
other smokable material. Preferably, the filter is secured to one
end of the smokable article, positioned such that smoke produced
from the smokable material passes into the filter before entering
the smoker. Alternatively, the filter can be provided by itself, in
a form suitable for attachment to a cigarette, cigar, pipe, or
other smokable device utilizing the smokable material to which
microencapsulated flavorant has been applied according to preferred
embodiments.
[0141] The filter according to preferred embodiments advantageously
removes at least one undesired component from tobacco smoke or the
smoke of any other smokable material. Undesired components in
tobacco smoke may include permanent gases, organic volatiles,
semivolatiles, and nonvolatiles. Permanent gases (such as carbon
dioxide) make up 80 percent of smoke, and are generally unaffected
by filtration or adsorption materials. The levels of organic
volatiles, semivolatiles, and nonvolatiles may be reduced by
filters of various designs. The filters according to preferred
embodiments may advantageously remove undesired components
including, but not limited to, tar, nicotine, carbon monoxide,
nitrogen oxides, HCN, acrolein, nitrosamines, particulates, oils,
various carcinogenic substances, and the like.
[0142] The filter preferably permits satisfactory or improved smoke
flavor, nicotine content, and draw characteristics. The filter is
preferably designed to be acceptable to the user, being neither
cumbersome nor unattractive. Further, filters according to
preferred embodiments may be made of inexpensive, safe and
effective components, and may preferably be manufactured with
standard cigarette manufacturing machinery.
[0143] The filter may incorporate one or more materials capable of
absorbing, adsorbing, or reacting with at least one undesirable
component of tobacco smoke. Such absorbing, adsorbing, or reacting
materials may be incorporated into the filter using any suitable
method or device. In a preferred embodiment, the absorbing,
adsorbing, or reacting material may be contained within a
smoke-permeable cartridge to be placed within the filter, or
contained within a cavity within the filter. In another embodiment,
the absorbing, adsorbing, or reacting material is deposited on
and/or in the filter material.
[0144] Application methods may include forming a paste of the
absorbing, adsorbing, or reacting material in a suitable liquid,
applying the paste to the filter material, and allowing the liquid
to evaporate. Alternatively, the absorbing, adsorbing, or reacting
material may be mixed with an adhesive substance and applied to the
filter material. All of the filter material may include the
absorbing, adsorbing, or reacting material, or only a portion of
the filter material may include the adsorbing or reacting material.
The portion of the filter material containing the absorbing,
adsorbing, or reacting material is generally referred to as a "a
smoke-altering filter segment."
[0145] The cigarette filters of the preferred embodiments
preferably include activated carbon (commonly referred to as
charcoal) as an adsorbing material. The process by which activated
carbon removes compounds is adsorption, which is a different
process than absorption. Absorption is the process whereby
absorbates are dispersed throughout a porous absorbent, while
adsorption is a surface attraction effect. Both adsorption and
absorption can be physical or chemical effects. The adsorptive
effect associated with activated carbon is mainly a physical
effect. In activated carbon filters, smoke compounds in the organic
volatile and semivolatile phases diffuse through the carbon
particles, move over the surface and then move into the activated
carbon pores compelled by a phenomenon known as Van der Waal's
forces. Although these forces are generally considered weak, at
very short range (one or two molecular diameters), they are strong
enough to attract and effectively hold smoke components.
[0146] Activated carbon may be obtained from a variety of sources,
including, but not limited to, wood, coconut shells, coal, and
peat. Wood generally produces soft and macroporous activated carbon
(pores from 50 to 1,000 nm in diameter). Peat and coal materials
generally produce activated carbon that is predominantly mesoporous
(pores 2 to 50 nanometers in diameter). Activated carbon derived
from coconut shells is generally microporous (pores of less than 2
nm in diameter), has a large surface area, and has a low ash and
base metal content when compared to certain other types of
activated carbon.
[0147] Preferred activated carbons are microporous and have a high
density, which imparts improved structural strength to the
activated carbon so that it can resist excessive particle abrasion
during handling and packaging.
[0148] The filters of preferred embodiments may also contain
various other adsorptive, absorptive, or porous materials in
addition to activated carbon as described above. Examples of such
materials, include, but are not limited to, cellulosic fiber, for
example, cellulose acetate, cotton, wood pulp, and paper; polymeric
materials, for example, polyesters and polyolefins; ion exchange
materials; natural and synthetic minerals such as activated
alumina, silica gel, and magnesium silicate; natural and synthetic
zeolites and molecular sieves (see, for example U.S. Pat. No.
3,703,901 to Norman et al., incorporated herein by reference in its
entirety); natural clays such as meerschaum; diatomaceous earth;
activated charcoal and other materials as will be understood by
those with skill in the art. The adsorptive, absorptive, or porous
material may be any nontoxic material suitable for use in filters
for smokable devices that are compatible with other substances in
the smoking device or smoke to be filtered.
[0149] Typically, the filter element may include as the major
component a porous material, for example, cellulose acetate tow or
cellulosic paper, referred to below as a "filter material." The
adsorptive or absorptive component, often a granular or particulate
substance such as activated carbon, is generally dispersed within
the porous filter material of the filter segment or positioned
within a cartridge or cavity (for example, within a cavity of a
triple filter, as discussed below).
[0150] The filter material may have the form of a non-woven web of
fibers or a tow. Alternatively, the filter material may have a
sheet-like form, particularly when the material is formed from a
mixture of polymeric or natural fibers, such as cotton or wood
pulp. Filter material in web or sheet-like form can be gathered,
folded, crimped, or otherwise formed into a suitable (for example,
cylindrical) configuration using techniques which will be apparent
to one skilled in the art. See, for example, U.S. Pat. No.
4,807,809 to Pryor et al., which is incorporated herein by
reference in its entirety.
[0151] In preferred embodiments, the filter material constitutes
cellulose acetate tow or cellulose paper. Cellulose acetate tow is
the most widely preferred filter material in cigarettes worldwide.
Cellulose paper filter materials generally provide better tar and
nicotine retention than do acetate filters with a comparable
pressure drop, and have the added advantage of superior
biodegradability. Cellulose and cellulose acetate reduce the amount
of chemicals in the semivolatile phase and the nonvolatile phase,
which is composed of solid particulates (commonly referred to as
"tar"). These compounds are reduced in direct proportion to the
amount of cellulose or cellulose acetate in the filter. Increasing
density of the cellulose or cellulose acetate generally means
increasing the pressure drop, which increases the filter retention
and therefore decreases tar delivery. Filters retain generally less
than 10 percent of vapor phase components.
[0152] In certain embodiments, it may be preferred to use a
polymeric material such as cellulose acetate as the filter material
rather than a material such as cellulose paper. Polymeric materials
may be preferred in embodiments wherein superior chemical inertness
or structural integrity during use are desired attributes of the
filter, for example, when certain smoke altering components
reactive to cellulose paper are present in the filter, or when
components reactive to cellulose paper are generated within the
filter. Cellulose acetate tow (such as that available from Celanese
Acetate of Charlotte, N.C.) is the most commonly preferred
polymeric material, however suitable polymeric materials may
include other synthetic addition or condensation polymers, such as
polyamides, polyesters, polypropylene, or polyethylene.
[0153] The polymeric material may be any nontoxic polymer suitable
for use in filters for smokable devices that are compatible with
other substances in the smoking device or smoke to be filtered, and
which possess the desired degree of inertness. The polymeric
material is preferably in fibrous tow form, but may optionally be
in other physical forms, for example, crimped sheet. The polymeric
material may constitute a single polymer or a mixture of different
polymers, for example, two or more of components such as
homopolymers, copolymers, terpolymers, functionalized polymers,
polymers having different molecular weights, polymers constituting
different monomers, polymers constituting two or more of the same
monomers in different proportions, oligomers, and nonpolymeric
components. The polymer may also be subjected to suitable
pre-treatment or post-treatment steps, for example,
functionalization of the polymer, coating with suitable materials,
and the like.
[0154] When polymeric fibers are the filter material, they can make
up all or a portion of the composition of the filter material of
the filter. Alternatively, the filter material can be a mixture or
blend of polymer fibers, or a mixture or blend of polymer fibers
and nonpolymeric fibers, for example, cellulose fibers obtained
from wood pulp, purified cellulose, cotton fibers, or the like. A
mixture of filter materials may be preferred in certain embodiments
where it is desired to reduce materials costs, as polymeric
materials may be more expensive than natural fibers. Any suitable
proportion of polymeric material may be present, from 100% by
weight polymeric material down to 80, 60, 50, 40, 30, 25, 20, 15,
or 10% by weight or less polymeric material.
[0155] As discussed above, in certain embodiments it may be
desirable to coat the filter material with one or more substances
that may react chemically with an undesirable component of the
smoke. Such substances may include natural or synthetic polymers,
or chemicals known in the art to provide for a treated filter
material capable of altering the chemistry of tobacco smoke. One
method for coating the filter material is to prepare a solution or
dispersion of the substance with a suitable solvent. Suitable
solvents may include, for example, water, ethanol, acetone, methyl
ethyl ketone, toluene, or the like.
[0156] The solution or dispersion can be applied to the surface of
the filter material using gravure techniques, spraying techniques,
printing techniques, immersion techniques, injection techniques, or
the like. Most preferably, the filter material is essentially
insoluble in the preferred solvent, and as such does not
substantially affect the general structure of the filter material.
After the solution or dispersion is applied to the surface of the
filter material, the solvent is removed, typically by air-drying at
room temperature or heating, for example, in a convection or
forced-air oven. The amount of solution or dispersion which is
applied to the filter material is typically sufficient to cover the
outer surface of the filter material, but not sufficient to fill
the void spaces between the fibers of filter material.
[0157] Typically, the amount of solution or dispersion applied to
the filter material is sufficient to deposit at least about 5
percent, preferably at least about 8 percent, more preferably at
least about 10 percent, and most preferably at least about 15
percent of the substance, based on the weight of the filter
material prior to treatment.
[0158] When the substance is a polymer, the polymer can be
synthetic polymer or a natural polymer. Synthetic polymers are
derived from the polymerization of monomeric materials (for
example, addition or condensation polymers) or are isolated after
chemically altering the substituent groups of a polymeric material.
Natural polymers are isolated from organisms (for example, plants
such as seaweed), usually by extraction.
[0159] Exemplary synthetic polymers that may be applied to filter
materials include, but are not limited to, carboxymethylcellulose,
hydroxypropylcellulose, cellulose esters such as cellulose acetate,
cellulose butyrate and cellulose acetate propionate (for example,
from Eastman Chemical Corp. of Kingsport, Tenn.), polyethylene
glycols, water dispersible amorphous polyesters with aromatic
dicarboxylic acid functionalities (for example, Eastman AQs from
Eastman Chemical Corp. of Kingsport, Tenn.), ethylene vinyl alcohol
copolymers (for example, from Mica Corp. of Shelton, Conn.),
partially or fully hydrolyzed polyvinyl alcohols (for example, the
Airvols from Air Products and Chemicals of Allentown, Penn.),
ethylene acrylic acid copolymers (for example, Envelons from Rohm
and Haas of Philadelphia, Penn. and Primacors from The Dow Chemical
Co. of Wilmington, Del.), polysaccharides (for example, Keltrol
from CP Kelco of San Diego, Calif.), alginates (for example, from
International Specialty Products of Wayne, N.J.), carrageenans (for
example, Viscarin GP109 and Nutricol GP120F konjac flour from FMC)
and starches (for example, Nadex 772, K-4484 and N-Oil from
National Starch & Chemical Co.).
[0160] Typically, natural or synthetic polymers tend to coat the
surface of the filter material very efficiently, and have a high
viscosity, making high coating levels unnecessary and sometimes
difficult. Typically, certain natural or synthetic polymers can be
applied to the filter material at levels of at least about 0.001
percent, preferably at least about 0.01 percent, more preferably at
least about 0.1 percent, and most preferably at least about 1
percent, based on the weight of the filter material prior to
treatment. Typically, the amount of certain natural or synthetic
polymers applied to the filter material does not exceed about 10
percent, and normally does not exceed about 5 percent, based on the
weight of the filter material prior to treatment.
[0161] The natural or synthetic polymeric material which is applied
to the filter material can vary, depending upon factors such as the
chemical functionality, hydrophilicity or hydrophobicity desired.
If desired, more than one type of natural or synthetic polymer can
be applied to the filter material in a single dispersion or
solution. If desired, the filter material can have at least one
type of natural or synthetic polymer dissolved or dispersed in a
suitable solvent applied thereto and the solvent removed, after
which the resulting coated filter material has at least one other
natural or synthetic polymer applied in similar fashion. If
multiple applications are conducted in this way, it is desirable
that the solvent or solvents do not substantially dissolve any
natural or synthetic polymer already coated onto the filter
material.
[0162] Filters of preferred embodiments may include more than one
segment. One configuration of such filters is the dual filter,
wherein the filter constitutes two different segments, with one
segment adjacent to the mouth and the other segment of the filter
adjacent to the tobacco rod. A common type of dual filter is one
wherein a cellulose acetate segment is situated on the mouth side
of the filter, and a cellulose paper segment is situated on the
side of the filter adjacent to the tobacco rod. Activated charcoal
may be incorporated into the cellulose paper segment of the filter
to assist in removal of undesired components from tobacco
smoke.
[0163] Another filter configuration, referred to as a triple
filter, has three segments, including a segment adjacent to the
mouth, a segment adjacent to the tobacco rod, and a segment
situated between the two other segments. The different segments may
be prepared from different materials, or may be materials having
the same composition but different physical form, for example,
crimped sheet or tow, or may be materials having the same
composition and physical form, but wherein one segment contains an
additional component not present in another segment. A common
triple filter configuration includes two segments selected from one
or both of cellulose acetate and cellulose, one adjacent to the
mouth and one adjacent to the filter, with a segment in between
containing a smoke altering component. Examples of smoke altering
components include activated carbon or other absorbents, or
components imparting flavor to the smoke.
[0164] One variety of triple filter is the cavity filter. The
cavity filter is composed of two segments separated by a cavity
containing one or more smoke altering components. The cavity may
contain an adsorbent material as described above, optionally in
combination with other suitable components such as activated
charcoal.
[0165] Dual and triple filters may be symmetrical (all filter
segments are the same length) or asymmetrical (two or more segments
are of different lengths). Filters may be recessed, with an open
cavity on the mouth side, reinforced by an extra stiff plug wrap
paper.
[0166] When the filter element contains a solid material in a form
other than tow or sheet, it may be incorporated into the filter
element using any suitable method or device, such as those
described above for incorporating an absorbing, adsorbing, or
reacting material into the filter element. Liquids may be
incorporated into the porous filter material by immersing the
filter material in the liquid, spraying the liquid onto the filter
material, or combining the liquid with another component, for
example, a component capable for forming a gel or a solid, then
applying the liquid-containing substance to the porous filter
material using methods well known to those skilled in the art.
[0167] The form of the filter material and the configuration of the
filter material, as well as the filtration efficiency for
particulate matter and vapor phase components of each segment of
the filter element may be varied so as to yield the desired balance
of performance characteristics for the filter element, as will be
recognized by those skilled in the art. Filter materials in tow
form can be processed and manufactured into filter rods using known
techniques. Filter materials in sheet-like or web form can be
formed into filter rods using techniques described in U.S. Pat. No.
4,807,809 to Pryor et al., and U.S. Pat. No. 5,074,320 to Jones,
Jr. et al. Filter materials also can be formed into rods using a
rod-making unit (for example, from Molins Tobacco Machinery, Ltd.
of Bucks, United Kingdom).
[0168] The porous filter material may contain various additional
minor components. These components may include pigments, dyes,
preservatives, antioxidants, defoamers, solvents, lubricants,
waxes, oils, resins, adhesives, and other materials, as are known
in the art.
[0169] In a preferred embodiment, the smoking article is provided
with a cavity filter composed of two cellulose acetate segments
separated by a cavity containing activated charcoal, wherein the
filter segments are wrapped in a paper plug wrap. The plug wrap may
be provided with perforations in the cellulose acetate segment
adjacent to the tobacco rod if air dilution is desired, for
example, for low or ultra-low tar cigarettes. The cellulose acetate
segment adjacent to the tobacco rod is preferably about 9 mm in
length, the mouth end segment is preferably 11 mm in length, and
the cavity is preferably 5 mm in length. The cavity is preferably
substantially filled. Substantially filled generally refers to a
cavity segment wherein more than about 95 vol. % is filled with
packed particles, preferably more than about 96, 97, 98, or 99 vol.
% is filled with packed particles, and most preferably about 100
vol. % is filled with packed particles. However, in certain
embodiments it may be desirable for the cavity to be less than
substantially filled, for example, less than about 95, 94, 93, 92,
91, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15,
10, or 5 vol. % or less. In a preferred embodiment, the cavity is
substantially filled with one type of activated charcoal. However,
in certain other embodiments the activated charcoal may constitute
a mixture of activated charcoals (for example, charcoals of varying
particle size or source), or the activated charcoal may be mixed or
combined with one or more inert ingredients, such as magnesium
silicate (available as CAVIFLEX.TM. and SEL-X-4.TM. from
Baumgartner, Inc. of Melbane, N.C.), inert carbon, or semolina.
Most preferably, the cavity segment contains 0.1 g of a single type
of activated charcoal as the sole component in a 5 mm long cavity
segment of filter. In various embodiments various types of
activated charcoal or carbon prepared from different starting
materials, having different surface area and particle size, or
having different properties may be preferred. Suitable activated
carbons, including specialty activated carbons, may be obtained
from Calgon Carbon Corporation of Pittsburgh, Pa.
[0170] Additives
[0171] Additional components, as are known in the art, may also be
added to the smokable material, or may be contained within the
filter, the tobacco rod, or other components of the smoking
articles of preferred embodiments. Nonlimiting examples of such
components include tobacco extracts, lubricants, flavorings, and
the like. These additional components preferably do not react with
the microcapsules on the smoking material in such a way as to
prematurely release their contents.
[0172] The filter element optionally can include a tobacco or
flavor extract in intimate contact with the filter material. If
desired, the tobacco or flavor extract can be spray dried and/or
subjected to heat treatment. The filter element prior to smoking
may include less than about 10% tobacco or flavor extract to more
than 50% percent tobacco or flavor extract, based on the total dry
weight of the filter element and extract. In some embodiments, the
tobacco Filter elements typically include a lubricating substance
in intimate contact with the filter material. Normally, prior to
smoking the cigarette, the filter element includes at least about
0.1 percent lubricating substance, based on the weight of the
filter material of that segment. The lubricating substance can be a
low molecular weight liquid (for example, glycerine) or a high
molecular weight material (for example, an emulsifier).
[0173] Flavorants can be incorporated into the cigarette using
conventional techniques familiar to the skilled artisan in addition
to the microencapsulation technique described herein. If desired,
flavor additives such as organic acids can be incorporated into the
cigarette as additives to cut filler. See, for example, U.S. Pat.
No. 4,830,028 to Lawson et al. If metallic or carbonaceous
particles and nitrate or nitrite source are applied to the cut
filler, it is preferred that they are added prior to addition of
flavorants or flavor extract is between 15%, 20%, 25% or 30% and
35%, 40%, or 45%, of the total dry weight of the filter element and
the extract.
[0174] The Smokable Material
[0175] The microcapsules may be applied to any suitable smokable
material. Examples of preferred smokable materials are the tobaccos
that include but are not limited to Oriental, Virginia, Maryland,
and Burley tobaccos, as well as the rare and specialty tobaccos.
The tobacco plant may be a variety produced through conventional
plant breeding methods, or may be a genetically engineered variety.
Low nicotine and/or low TSNA tobacco varieties, including
genetically engineered varieties, are especially preferred. The
tobacco may be cured using any acceptable method, including, but
not limited to, flue-curing, air-curing, sun-curing, and the like,
including curing methods resulting in low nitrosamine levels, such
as the curing methods disclosed in U.S. Pat. No. 6,202,649 and U.S.
Pat. No. 6,135,121 to Williams.
[0176] Generally, the tobacco material is aged. The cured or
uncured tobacco may be subjected to any suitable processing step,
including, but not limited to, microwave or other radiation
treatment, treatment with ultraviolet light, or extraction with an
aqueous or nonaqueous solvent.
[0177] The tobacco can be in the form of tobacco laminae, processed
tobacco stems, reconstituted tobacco material, volume expanded
tobacco filler, or blends thereof. The type of reconstituted
tobacco material can vary. Certain suitable reconstituted tobacco
materials are described in U.S. Pat. No. 5,159,942 to Brinkley et
al. Certain volume expanded tobacco materials are described in U.S.
Pat. No. 5,095,922 to Johnson et al. Blends of the aforementioned
materials and tobacco types can be employed. Exemplary blends are
described in U.S. Pat. No. 5,074,320 to Jones, Jr. et al. Other
smokable materials, such as those smokable materials described in
U.S. Pat. No. 5,074,321 to Gentry et al., and U.S. Pat. No.
5,056,537 to Brown et al., also can be employed.
[0178] The smokable materials generally are employed in the form of
cut filler as is common in conventional cigarette manufacture. For
example, the smokable filler material can be employed in the form
of pieces, shreds or strands cut into widths ranging from about 1/5
inch (5 mm) to about {fraction (1/60)} inch (0.04 mm), preferably
from about {fraction (1/20)} inch (1.3 mm) to about {fraction
(1/40)} inch (0.6 mm). Generally, such pieces have lengths between
about 0.25 inch (6 mm) and about 3 inches (76 mm). In certain
embodiments, however, it may be preferred to use cut filler having
widths more than about 1/5 inch (5 mm) or less than about {fraction
(1/60)} inch (0.04 mm), and lengths less than about 0.25 inch (6
mm) or more than about 3 inches (76 mm).
[0179] The smokable material can have a form (for example, a blend
of smokable materials, such as a blend of various types of tobacco
in cut filler form) having a relatively high nicotine content. Such
a smokable material typically has a dry weight nicotine content
above about 2.0%, 2.25%, 2.5%, 2.75%, or 3.0% or more. Such
smokable materials are described in U.S. Pat. No. 5,065,775 to
Fagg.
[0180] Alternatively, the smokable material can have a form having
a relatively low or negligible nicotine content. Such a smokable
material typically has a dry weight nicotine content below about
1.5%, 1.25%, 1.0%, 0.75%, 0.5%, 0.1%, 0.05% or less. Tobacco having
a relatively low nicotine content is described in U.S. Pat. No.
5,025,812 to Fagg et al.
[0181] As used herein, the term "dry weight nicotine content" in
referring to the smokable material is meant the mass alkaloid
nicotine as analyzed and quantitated by spectroscopic techniques
divided by the dry weight of the smokable material analyzed. See,
for example, Harvey et al., Tob. Sci., Vol. 25, p. 131 (1981).
[0182] In a preferred embodiment, the smokable material constitutes
a tobacco product obtained from tobacco plants that are
substantially free of nicotine and/or tobacco-specific nitrosamines
(TSNAs). Tobaccos that may be substantially free of nicotine or
TSNAs may be produced by interrupting the ability of the plant to
synthesize nicotine using genetic engineering. Copending
provisional application Ser. No. 60/297,154 filed Jun. 08, 2001,
filed Jun. 8, 2001 and WO9856923 to Conkling et al. (both
incorporated herein by reference in their entirety) describe
tobacco that is substantially free of nicotine and TSNAs that is
made by exposing at least one tobacco cell of a selected variety to
an exogenous DNA construct having, in the 5' to 3' direction, a
promoter operable in a plant cell and DNA containing a portion of a
DNA sequence that encodes an enzyme in the nicotine synthesis
pathway. The DNA is operably associated with the promoter, and the
tobacco cell is transformed with the DNA construct, the transformed
cells are selected, and at least one transgenic tobacco plant is
regenerated from the transformed cells. The transgenic tobacco
plants contain a reduced amount of nicotine and/or TSNAs as
compared to a control tobacco plant of the same variety. In
preferred embodiments, DNA constructs having a portion of a DNA
sequence that encodes an enzyme in the nicotine synthesis pathway
may have the entire coding sequence of the enzyme, or any portion
thereof.
[0183] In a preferred embodiment, the smokable material constitutes
a tobacco product obtained from tobacco plants that have reduced
nicotine content and/or TSNAs such as those described in copending
provisional application Ser. No. 60/229,198, filed Aug. 30, 2000
(incorporated herein by reference in its entirety).
[0184] Tobacco products having specific amounts of nicotine and/or
TSNAs may be created through blending of low nicotine/TSNA tobaccos
such as those described above with conventional tobaccos. Some
blending approaches begin with tobacco prepared from varieties that
have extremely low amounts of nicotine and/or TSNAs. By blending
prepared tobacco from a low nicotine/TSNA variety (for example,
undetectable levels of nicotine and/or TSNAs) with a conventional
tobacco (for example, Burley, which has 30,000 parts per million
(ppm) nicotine and 8,000 parts per billion (ppb) TSNA; Flue-Cured,
which has 20,000 ppm nicotine and 300 ppb TSNA; and Oriental, which
has 10,000 ppm nicotine and 100 ppb TSNA), tobacco products having
virtually any desired amount of nicotine and/or TSNAs can be
manufactured. Tobacco products having various amounts of nicotine
and/or TSNAs can be incorporated into tobacco use cessation kits
and programs to help tobacco users reduce or eliminate their
dependence on nicotine and reduce the carcinogenic potential.
[0185] For example, a step 1 tobacco product can constitute
approximately 25% low nicotine/TSNA tobacco and 75% conventional
tobacco; a step 2 tobacco product can constitute approximately 50%
low nicotine/TSNA tobacco and 50% conventional tobacco; a step 3
tobacco product can constitute approximately 75% low nicotine/TSNA
tobacco and 25% conventional tobacco; and a step 4 tobacco product
can constitute approximately 100% low nicotine/TSNA tobacco and 0%
conventional tobacco. A tobacco use cessation kit can include an
amount of tobacco product from each of the aforementioned blends to
satisfy a consumer for a single month program. That is, if the
consumer is a one pack a day smoker, for, example, a single month
kit provides 7 packs from each step, a total of 28 packs of
cigarettes. Each tobacco use cessation kit may include a set of
instructions that specifically guide the consumer through the
step-by-step process. Of course, tobacco products having specific
amounts of nicotine and/or TSNAs may be made available in
conveniently sized amounts (for example, boxes of cigars, packs of
cigarettes, tins of snuff, and pouches or twists of chew) so that
consumers could select the amount of nicotine and/or TSNA they
individually desire. There are many ways to obtain various low
nicotine/low TSNA tobacco blends using the teachings described
herein and the following is intended merely to guide one of skill
in the art to one possible approach.
[0186] To obtain a step 1 tobacco product, which is a 25% low
nicotine/TSNA blend, prepared tobacco from an approximately 0 ppm
nicotine/TSNA tobacco can be mixed with conventional Burley,
flue-cured, or Oriental in a 25%/75% ratio respectively to obtain a
Burley tobacco, product having 22,500 ppm nicotine and 6,000 ppb
TSNA, a flue-cured product having 15,000 ppm nicotine and 225 ppb
TSNA, and an Oriental product having 7,500 ppm nicotine and 75 ppb
TSNA. Similarly, to obtain a step 2 product, which is 50% low
nicotine/TSNA blend, prepared tobacco from an approximately 0 ppm
nicotine/TSNA tobacco can be mixed with conventional Burley,
flue-cured, or Oriental in a 50%/50% ratio respectively to obtain a
Burley tobacco product having 15,000 ppm nicotine and 4,000 ppb
TSNA, a flue-cured product having 10,000 ppm nicotine and 150 ppb
TSNA, and an Oriental product having 5000 ppm nicotine and 50 ppb
TSNA. Further, a step 3 product, which is a 75%/25% low
nicotine/TSNA blend, prepared tobacco from an approximately 0 ppm
nicotine/TSNA tobacco can be mixed with conventional Burley,
flue-cured, or Oriental in a 75%/25% ratio respectively to obtain a
Burley tobacco product having 7,500 ppm nicotine and 2,000 ppb
TSNA, a flue-cured product having 5,000 ppm nicotine and 75 ppb
TSNA, and an Oriental product having 2,500 ppm nicotine and 25 ppb
TSNA.
[0187] It is appreciated that tobacco products are often a blend of
many different types of tobaccos, which were grown in many
different parts of the world under various growing conditions. As a
result, the amount of nicotine and TSNAs may differ from crop to
crop. Nevertheless, by using conventional techniques one can easily
determine an average amount of nicotine and TSNA per crop used to
create a desired blend. By adjusting the amount of each type of
tobacco that makes up the blend one of skill can balance the amount
of nicotine and/or TSNA with other considerations such as
appearance, flavor, and smokability. In this manner, a variety of
types of tobacco products having varying level of nicotine and/or
nitrosamine, as well as, appearance, flavor and smokability can be
created.
[0188] While in the preferred embodiments the microcapsules are
applied to a smokable material including tobacco, any other
smokable materials may preferred in other embodiments. For example,
the microcapsules may be applied to smokable plant materials as are
commonly preferred in various herbal smoking materials. Mullein and
Mugwort are commonly preferred base materials in blends of herbal
smoking materials. Some other commonly preferred plant materials
that are also smokable materials include Willow bark, Dogwood bark,
Pipsissewa, Pyrola, Kinnikinnik, Manzanita, Madrone Leaf,
Blackberry, Raspberry, Loganberry, Thimbleberry, and
Salmonberry.
[0189] The microencapsulated flavorant of preferred embodiments may
be applied to any smokable material in order to provide
improved-taste to the smokable material. However, the preferred
flavorant or flavorants, as well as the amount of such flavorants
may vary depending upon the type of smokable material used.
[0190] The Wrapping Material
[0191] The wrapping material which circumscribes the charge of
smokable material can vary. Examples of suitable wrapping materials
are cigarette paper wrappers available from Schweitzer-Mauduit
International in Alpharetta, Ga. Cigarette paper wraps the column
of tobacco in a cigarette and can be made from flax, wood, or a
combination of fibers. Certain properties such as basis weight,
porosity, opacity, tensile strength, texture, ash appearance,
taste, brightness, good gluing, and lack of dust are selected to
provide optimal performance in the finished product, as well as to
meet runnability standards of the high-speed production processes
preferred by cigarette manufacturers.
[0192] A more porous paper is one that allows air to easily pass
into a cigarette. Porosity is measured in Coresta units and can be
controlled to determine the rate and direction of airflow through
the cigarette. The higher the number of Coresta units, the more
porous the paper. Tar and nicotine yields are commonly controlled
without altering the flavor of the cigarette through the choice of
paper. The use of highly porous papers can help create lower tar
levels in the cigarette. Higher paper porosity increases the
combustibility of a cigarette by adding more air to the process,
which increases the heat and the burning rate. A higher burn rate
may lower the number of puffs that a smoker takes per cigarette.
Papers having porosities up to 200 Coresta units or higher are
generally preferred, however different kinds of cigarettes may use
papers of preferred porosities. For example, American-blend
cigarettes typically use 40 to 50 Coresta unit papers. Flue-cured
tobacco cigarettes, which burn slower, generally use higher
porosities, ranging from 60 to 80 Coresta unit papers. Higher
porosities may be obtained by electronically perforating (EP) the
paper.
[0193] Cigarette papers are available that are prepared from
various base fibers. Flax and wood are commonly preferred base
fibers. In addition to 100% flax and 100% wood papers, papers are
also available with flax and wood fibers mixed in various ratios.
Wood based papers are widely preferred because of their low cost,
however certain consumers prefer the taste of flax based
papers.
[0194] Suitable cigarette papers may be obtained from RFS (US)
Inc., a subsidiary of privately-held PURICO (IOM) Limited of the
United Kingdom, which is the current owner of P. H. Glatfelter
Company's Ecusta mill which manufactures tobacco papers. In
preferred embodiments, a paper having a porosity of about 26
Coresta EP to 90 Coresta EP is preferred. Suitable papers include
Number 409 papers having a porosity of 26 Coresta and 0.85% citrate
content, and Number 00917 papers having a porosity of 26 Coresta
EP. However, in certain embodiments, it may be preferred to use a
paper having a lower air permeability, for example, a paper that
has not been subjected to electronic perforation and which has a
low inherent porosity, for example, less than 26 Coresta.
[0195] In preferred embodiments, the cigarette paper is suitable
for use in "self-extinguishing" cigarettes. Examples of cigarette
papers suitable for use in self-extinguishing cigarettes include,
for example, papers saturated with a citrate or phosphate fire
retardant or incorporating one or more fire retardant bands along
the length of the paper. Such papers may also be thicker papers of
reduced flammability.
[0196] Wrapping materials described in U.S. Pat. No. 5,220,930 to
Gentry may be preferred in certain embodiments. More than one layer
of circumscribing wrapping material can be employed, if desired.
See, for example, U.S. Pat. No. 5,261,425 to Raker et al. Other
wrapping material includes plug wrap paper and tipping paper. Plug
wrap paper wraps the outer layer of the cigarette filter plug and
holds the filter material in cylindrical form. Highly porous plug
wrap papers are preferred in the production of filter-ventilated
cigarettes.
[0197] Tipping paper joins the filter element with the tobacco rod.
Tipping papers are typically made in white or a buff color, or in a
cork pattern, and are both printable and glueable at high speeds.
Such tipping papers are used to produce cigarettes that are
distinctive in appearance, as well as to camouflage the use of
activated carbon in the filter element. Pre-perforated tipping
papers are commonly preferred in filter-ventilated cigarettes.
[0198] In the case of cigars, reconstituted tobacco wrapper is
often wrapped around the outside of machine-made cigars to provide
a uniform, finished appearance. The wrapper material can
incorporate printed veins to give the look of natural tobacco leaf.
Such wrapper material is manufactured utilizing tobacco leaf
by-products. Reconstituted tobacco binder holds the "bunch" or
leaves of tobacco in a cylindrical shape during the production of
machine-made cigars. It is also manufactured utilizing tobacco leaf
by-products.
[0199] An extremely small amount of a sideseam adhesive is
preferred to secure the ends of the cigarette paper wrapper around
the tobacco rod (and filter element, if present). Any suitable
adhesive may be used. In a preferred embodiment, the sideseam
adhesive is an emulsion of ethylene vinyl acetate copolymer in
water.
[0200] The cigarette wrapper may include extremely small amounts of
inks containing oils, varnishes, pigments, dyes, and processing
aids, such as solvents and antioxidants. Ink components may include
such materials as linseed varnish, linseed oil polymers, white
mineral oils, clays, silicas, natural and synthetic pigments, and
the like, as are known in the art.
[0201] Smoking Articles
[0202] The smoking articles of the preferred embodiments may have
various forms. Preferred smoking articles may be typically
rod-shaped, including, for example, cigarettes and cigars. In
addition, the smoking article may be tobacco for a pipe. For
example, the smoking article can have the form of a cigarette
having a smokable material (for example, tobacco cut filler)
wrapped in a circumscribing paper wrapping material. Exemplary
cigarettes are described in U.S. Pat. No. 4,561,454 to Guess. In a
preferred embodiment, the smoking article is a cigarette having a
smokable filter material or tobacco rod.
[0203] In another preferred embodiment, a cigarette is provided
which yields relatively low levels of "tar" per puff on average
when smoked under FTC smoking conditions (for example, an "ultra
low tar" cigarette).
[0204] In another preferred embodiment, a cigarette is provided
having a smokable filler material or tobacco rod having a
relatively low or negligible nicotine content, and a filter
element.
[0205] In another preferred embodiment, a cigarette is provided
having a smokable filler material or tobacco rod having a
relatively low TSNA content, and a filter element.
[0206] The amount of smokable material within the tobacco rod can
vary, and can be selected as desired. Packing densities for tobacco
rods of cigarettes are typically between about 150 and about 300
mg/cm.sup.3, and are preferably between about 200 and about 280
mg/cm.sup.3, however, higher or lower amounts may be preferred for
certain embodiments.
[0207] Typically, a tipping material circumscribes the filter
element and an adjacent region of the smokable rod such that the
tipping material extends about 3 mm to about 6 mm along the length
of the smokable rod. Typically, the tipping material is a
conventional paper tipping material. The tipping material can have
a porosity which can vary. For example, the tipping material can be
essentially air impermeable, air permeable, or can be treated (for
example, by mechanical or other perforation techniques) so as to
have a region of perforations, openings or vents, thereby providing
a means for providing air dilution to the cigarette. The total
surface area of the perforations and the positioning of the
perforations along the periphery of the cigarette can be varied in
order to control the performance characteristics of the
cigarette.
[0208] The mainstream cigarette smoke may be diluted with air from
the atmosphere via the natural porosity of the cigarette wrapper
and/or tipping material, or via perforations, openings, or vents in
the cigarette wrapper and/or tipping material. Air dilution means
may be positioned along the length of the cigarette, typically at a
point along the filter element which is at a maximum distance from
the extreme mouth-end thereof. The maximum distance is dictated by
factors such as manufacturing constraints associated with the type
of tipping employed and the cigarette manufacturing apparatus and
process. For example, for a filter element having a 27 mm length,
the maximum distance may be between about 23 mm and about 26 mm
from the extreme mouth-end of the filter element. In a preferred
aspect, the air dilution means is positioned toward the extreme
mouth-end of the cigarette relative to the smoke-altering filter
segment. For example, for a filter element having a 27 mm length
including a smoke-altering filter segment of 12 mm length and a
mouth-end segment of 15 mm, a ring of air dilution perforations can
be positioned either 13 mm or 15 mm from the extreme mouth-end of
the filter element.
[0209] As used herein, the term "air dilution" is the ratio
(generally expressed as a percentage) of the volume of air drawn
through the air dilution means to the total volume of air and smoke
drawn through the cigarette and exiting the extreme mouth-end
portion of the cigarette. For air diluted or ventilated cigarettes,
the amount of air dilution can vary. Generally, the amount of air
dilution for an air-diluted cigarette is greater than about 10
percent, typically greater than about 20 percent, and often greater
than about 30 percent. Typically, for cigarettes of relatively
small circumference (namely, about 21 mm or less) the air dilution
can be somewhat less than that of cigarettes of larger
circumference. The upper limit of air dilution for a cigarette
typically is less than about 85 percent, more frequently less than
about 75 percent. Certain relatively high air diluted cigarettes
have air dilution amounts of about 50 to about 75 percent, often
about 55 to about 70 percent.
[0210] Cigarettes of certain embodiments may yield less than about
0.9, often less than about 0.5, and usually between about 0.05 and
about 0.3 FTC "tar" per puff on average when smoked under FTC
smoking conditions (FTC smoking conditions include 35 ml puffs of 2
second duration separated by 58 seconds of smolder). Such
cigarettes are "ultra low tar" cigarettes which yield less than
about 7 mg FTC "tar" per cigarette. Typically, such cigarettes
yield less than about 9 puffs, and often about 6 to about 8 puffs,
when smoked under FTC smoking conditions. While "ultra low tar"
cigarettes are generally preferred, in certain embodiments,
however, cigarettes providing less than about 0.05 or more than
about 0.9 FTC "tar" per puff are contemplated.
[0211] In certain embodiments, cigarettes yielding a low or
negligible amount of nicotine are provided. Such cigarettes
generally yield less than about 0.1, often less than about 0.05,
frequently less than about 0.01, and even less than about 0.005 FTC
nicotine per puff on average when smoked under FTC smoking
conditions. In other embodiments, a cigarette delivering higher
levels of nicotine may be desired. Such cigarettes may deliver
about 0.1, 0.2, 0.3, or more FTC nicotine per puff on average when
smoked under FTC smoking conditions.
[0212] Cigarettes yielding a low or negligible amount of nicotine
may yield between about 1 mg and about 20 mg, often about 2 mg to
about 15 mg FTC "tar" per cigarette; and may have relatively high
FTC "tar" to FTC nicotine ratios of between about 20 and about
150.
[0213] Cigarettes of the preferred embodiments may exhibit a
desirably high resistance to draw, for example, a pressure drop of
between about 50 and about 200 mm water pressure at 17.5 cc/sec of
air flow. Typically, pressure drop values of cigarettes are
measured using instrumentation available from Cerulean (formerly
Filtrona Instruments and Automation) of Milton Keynes, United
Kingdom. Cigarettes of preferred embodiments preferably exhibit
resistance to draw values of about 70 to about 180, more preferably
about 80 to about 150 mm water pressure drop at 17.5 cc/sec of
airflow.
[0214] Cigarettes of preferred embodiments may include a
smoke-altering filter segment. The smoke-altering filter segment
may reduce one or more undesirable components in the smoke, and/or
may provide an enhanced tobacco smoke flavor, a richer smoking
character, enhanced-mouthfeel and increased smoking satisfaction,
as well as improvement of the perceived draw characteristics of the
cigarette.
[0215] The above description provides several methods and materials
of the present invention. This invention is susceptible to
modifications in the methods and materials, such as the choice of
flavorant, encapsulant, and the like, as well as alterations in the
fabrication methods and equipment. Such modifications will become
apparent to those skilled in the art from a consideration of this
disclosure or practice of the invention disclosed herein.
Consequently, it is not intended that this invention be limited to
the specific embodiments disclosed herein, but that it cover all
modifications and alternatives coming within the true scope and
spirit of the invention as embodied in the attached claims.
[0216] Every patent and other reference mentioned herein is hereby
incorporated by reference in its entirety.
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