Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CIG~RETTE FILTER CON~TNTNG NI~O~PSULE8
BACKGROUnnD
It is widely known that tobacco smoke contains toxic
and ~utagenic compounds which cause substantial morbidity and
mortality to smokers. Attempts to reduce the amount of toxic
and mutagenic compounds that reach the smoker include tobacco
smoke filters positioned between the burning tobacco and the
smoker.
Conventional filters are made of cellulose acetate,
with or without activated charcoal. These conventional
filters, however, are only partially effective in reducing the
amount of toxic and mutagenic compounds reaching the smoker.
Further, conventional filters disadvantageously remove flavor
compounds, thereby decreasing acceptance by the smoker.
There is, therefore, a need for an improved filter
for a smokable device that more completely removes toxic and
mutagenic compounds from tobacco smoke. Further, there is a
need for an improved filter which allows the passage of flavor
compounds while substantially removing toxic and mutagenic
compounds for tobacco smoke. Such an improved filter would
preferably be simple and inexpensive to manufacture, and
convenient to use.
8UMMARY
The present invention is directed to a tobacco smoke
filter that meets these needs. In one embodiment, the filter
comprises a porous substrate having a humectant, such as
sodium pyroglutamate, dispersed therein. The humectant
absorbs moisture from the tobacco smoke and thus serves to
wet-filter the tobacco smoke during use.
In another aspect, the present invention is directed
to a tobacco smoke filter comprising a porous substrate having
microcapsules dispersed therein. The microcapsules comprise a
core and a shell. The shell comprises a humectant, preferably
sodium pyroglutamate. The shell further preferably comprises
methylcellulose. The core preferably comprises chlorophyllin.
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The core further preferably comprises at least one vegetable
oil.
The filters of the present invention can
additionally comprise at least one surfactant or at least one
substance which aids in the removal of toxic and mutagenic
compounds from tobacco smoke.
The filters of the present invention can be provided
by themselves or in combination with a smokable device having
a body of tobacco, such as a cigarette, cigar or pipe.
These and other features of the present invention
will become better understood from the following description
and appended claims.
DESCRIPTION
According to one aspect of the present invention,
there is provided a filter for tobacco smoke. In a preferred
embodiment, the filter is affixed to a smokable device having
a body of tobacco such as a cigarette, cigar or pipe.
The filter comprises a porous substrate and at least
one humectant. The porous substrate can be any non-toxic
material suitable for use in filters for smokable devices that
are also suitable for incorporation with a humectant. Such
materials include cellulosic fiber such as cellulose acetate,
cotton, wood pulp, and paper; and polyesters, polyolefins, ion
exchange materials and other materials as will be understood
by those with skill in the art with reference to the
disclosure herein.
The humectant is capable of absorbing moisture from
tobacco smoke and releasing it into the porous substrate such
that tobacco smoke passing through the filter is wet-filtered
thereby. In a preferred embodiment, the humectant is present
in an amount of from about 5 to about 60% by dry weight of the
filter.
The humectant can be any suitable humectant. For
example, the humectant can be selected from the group
consisting o~ glycerol, sorbitol, propylene glycol, sodium
_ _
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lactate, calcium chloride, potassium phosphate, sodium
pyrophosphate or sodium polyphosphate, calcium citrate,
calcium gluconate, potassium citrate, potassium gluconate,
sodium tartrate, sodium potassium tartrate, and sodium
glutamate.
In a preferred embodiment, the humectant
incorporated into the filter i5 sodium pyroglutamate (al80
known as sodium 2-pyrrolidone-5-carboxylate or NaPCA).
Advantageously, sodium pyroglutamate is non-toxic, effective
at removing charged particles from tobacco smoke and functions
as a humectant in the temperature range of tobacco smoke.
Further, it is non-hazardous, stable, simple to manufacture
and convenient to use. Sodium pyroglutamate has the following
structure:
H O
O~/N~ C -O N a+
~
Filters according to the present invention are
simple and inexpensive to manufacture. In one method of
manufacture, a solution containing the humectant, such as
sodium pyroglutamate, is prepared. Then, the porous substrate
is wetted with the solution. The wetted substrate is then
dried, leaving a residue of the humectant dispersed on or in
the porous substrate.
These and other advantages of the present invention
are demonstrated by the following comparative example.
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Ea~MPLE8 I
rison of Efi~Qctivene~s Between Conventional Tobacco ~;mok~
Filter~ Wet-Filtration Tobacco 8moke Filter conta;ni~g 80dium
Pyroglutamate ~nd Co~mercially ~vailable Wet-Filtration
s ~obacco 8moke F~lter
Three types of filters were tested for relative
effectiveness in removing tar from cigarette smoke:
1) Conventional cellulose acetate filter ("Cell-
Ac");
2) Wet-filtration tobacco smoke filter containing
cellulose acetate with sodium pyroglutamate ("SoPyro")
according to the present invention; and
3) Commercially available wet-filtration tobacco
smoke filter ("Aquafilter").
Cellulose acetate filters containing sodium
pyroglutamate were prepared by, first, removing cellulosic
filters from commercial cigarettes. The fibers weighed
approximately 0.21 g. Next, approximately 0.5 ml of a 10% by
weight solution of sodium pyroglutamate was applied to each
filter, and the filter was dried overnight at 60~C.
The conventional cellulose acetate filter and the
cellulose acetate filters containing sodium pyroglutamate were
weighed and inserted into a 3.75 cm (1.5 inch) segment of
polycarbonate tubing having an inside diameter identical to
the outside diameter of a standard cigarette. A filterless
cigarette having 0.85 g of tobacco was inserted into one end
of the polycarbonate tubing in proximity to one end of the
filter. The other end of the polycarbonate tubing was
attached to tubing connected to a suction pump. Duplicates of
each filter type were tested. Aquafilters used in this test
were also attached to a filterless cigarette having 0.85 g of
tobacco and then attached to tubing connected to a suction
pump.
The filtered cigarettes were lit and intermittent
suction, simulating inhalation of cigarette smoke, was applied
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until the cigarette had burned to within 0.5 inch of the unlit
end. The filters were removed from either the polycarbonate
tube or from the Aquafilter, weighed, and placed in 10 ml of
methanol to elute tar and other substances from the smoke that
were retained in the filter. Light absorbance (at a
wavelength of 350 nm) of the ethanolic filter eluates was used
as an index of the amount of smoke components retained on the
filters. The weight gained by the filters during smoke
passage was also recorded. The results of the test are
presented in Table 1.
TABLE 1
TEST FILTER ABSORBANCE at 350 nm Weight Gain
1 Cell-Ac 0.470 A.U. 35 mg
2 Cell-Ac 0.381 A.U. 30 mg
3 SoPyro 0.731 A.U. 71 mg
4 SoPyro 0.625 A.U. 60 mg
5Aquafilter 0.540 A.U. *
6Aquafilter 0.560 A.U. *
*The weight gain due to absorbance of smoke components on the
Aquafilter could not be determined, since the Aquafilter
actually lost weight during passage of smoke, presumably due
to evaporation of water.
Based on the absorbance data, the filters according
to one aspect of the present invention (Tests 3 and 4) are
significantly more effective than conventional cellulose
acetate filters without the humectant (Tests 1 and 2), and
also more effective than the Aquafilter (Tests 5 and 6).
According to another aspect of the present
invention, there is provided a filter for tobacco smoke
comprising a porous substrate having microcapsules dispersed
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therein. The microcapsules preferentially include an inner
core with an outer shell.
The core of the microcapsules comprise at least one
vegetable oil. Suitable vegetable oils include at least one
oil selected from the group consisting of castor oil, cotton
seed oil, corn oil, sunflower oil, sesame oil, soybean oil,
and rape oil. In a preferred embodiment, the vegetable oil is
safflower oil. Other oils are also suitable, as will be
understood by those with skill in the art with reference to
the disclosure herein. In a preferred embodiment, the
vegetable oil is present in an amount of from about 20 to
about 80% by dry weight of the microcapsules, and more
preferably from about 30 to about 70~ by dry weight of the
microcapsules.
In a preferred embodiment, the microcapsule cores
also contain chlorophyllin. When present, the chlorophyllin
is preferably in an amount of from about 1 to about 10% by dry
weight of the microcapsules, and more preferably from about 2
to about 5% by dry weight of the microcapsules.
The microcapsule shells comprise a humectant. In a
preferred embodiment, the humectant is sodium pyroglutamate,
though other humectants can be used as will be understood by
those with skill in the art with reference to the disclosure
herein. In a preferred embodiment, the humectant, such as
sodium pyroglutamate, is present in an amount of from about 10
to about 90% by dry weight of the microcapsules, and more
preferably from about 20 to about 70% by dry weight of the
microcapsules.
In another preferred em~odiment, the microcapsule
shells also comprise methylcellulose. In a preferred
embodiment, the methylcellulose is present in an amount of
from about 5 to about 30% by dry weight of the microcapsules,
and more preferab~y from about 10 to about 25% by dry weight
of the microcapsules.
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In another preferred embodiment, the microcapsule
shells also comprise a polymeric agent such as
polyvinylalcohol or polyvinyl pyrrolidone, or can comprise
both polyvinylalcohol or polyvinyl pyrrolidone, in addition to~ 5 methylcellulose or in place of methylcellulose. In a
preferred embodiment, the polymeric agent is present in an
amount of from about 2 to about 30~ by dry weight of the
microcapsules, and more preferably from about 5 to about 20%
by dry weight of the microcapsules.
Compounds used in formulation of microcapsules
according to the present invention are available from a
variety of sources known to those with skill in the art, such
as Sigma Chemical Co., St. Louis, M0 USA.
Microcapsules suitable for use in the present
~5 invention can be made according to a variety of methods known
to those with skill in the art. For example, microcapsules
according to the present invention can be produced by
combining 200 g of vegetable oil with 500 g of an aqueous
suspension comprising 25 g of low-viscosity methylcellulose, 5
g of chlorophyllin, 50 g of sodium pyroglutamate and 150 g of
corn starch in water. The mixture is emulsified and spray-
dried to form microcapsules.
Microcapsules according to the present invention can
be formed by spray drying methods at the site of cigarette
manufacturing machinery by spraying onto sheets of cellulose
acetate filter tow before the tow is formed into cylindrical
filters. Alternatively, suitable microcapsules can be
premanufactured and added to sheets of cellulose acetate
filter tow by dropping the microcapsule onto the tow with a
vibrating pan or by other t~chn;ques as will be understood by
those with skill in the art with reference to the disclosure
herein.
As will be appreciated by those with skill in the
art, the manufacture of filters containing microcapsules
according to the present invention will require only minor
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modification of conventional filter-cigarette manufacturing
e~uipment. Further, the manufacture of filters containing
microcapsules according to the present invention is only t
marginally more expensive than conventional filters.
In use, the humectant portion of the microcapsules
traps moisture from tobacco smo~e passing through the filter.
Sodium pyroglutamate is particularly preferred because it can
be incorporated into the filter in a dry form.
When present, the oil portion of the microcapsules
traps certain harmful volatile compounds like pyridine without
impeding the flow of flavor and aroma producing compounds.
When present, chlorophyllin is a potent inactivator of
carcinogenic components of tobacco smoke.
The methylcellulose portion of the microcapsules
imparts structural stability to the microcapsules but
disperses upon warming and when exposed to moisture. Unlike
most commonly used viscosity-imparting substances,
methylcellulose precipitates from warm solutions. Further, it
is soluble at lower temperatures than most commonly used
viscosity-imparting substances.
When tobacco smoke filters containing microcapsules
comprising a shell of sodium pyroglutamate and methylcellulose
and a core of vegetable oil and chlorophyllin, according to
the present invention, filter tobacco smoke, the microcapsules
capture heat and moisture from the tobacco smoke. The
methylcellulose precipitates into a fibrous material which
increases the effective surface area available for wet-
filtration of the tobacco smoke. This allows the moisture
retained by the sodium pyroglutamate to rapidly disperse into
the filter material. The chlorophyllin partitions
approximately evenly between the aqueous and oil environments r
allowing increased inactivation of both particulate and vapor-
phase toxic and mutagenic compounds of tobacco smoke than if
the chlorophyllin was available in only one phase.
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According to another aspect of the present
invention, there is provided a cigarette filter comprising
copper phthalocyanine trisulfonate. This compound can be
added directly to tobacco smoke filters. Alternatively, the
copper phthalocyanine trisulfonate can be incorporated into a
tobacco smoke filter as a covalently bound ligand to cotton,
such as "blue cotton", or to rayon or other suitable material.
Also alternatively, copper phthalocyanine trisulfonate can be
added to other tobacco smoke filter embodiments of the present
invention. In a preferred embodiment, the copper
phthalocyanine trisulfonate is present in an amount of from
about 0.1 to about 5% by dry weight of the filter whether free
or covalently bound. In a particularly preferred embodiment,
the copper phthalocyanine trisulfonate is present in an amount
of from about 1 to about 3% by dry weight of the filter. In
use, this compound functions to remove toxic and mutagenic
compounds present in tobacco smoke such as carcinogenic
polycyclic aromatic hydrocarbons.
In another preferred embodiment, the filters of the
present invention additionally comprise at least one
surfactant to improve the effectiveness of wet-filtering the
tobacco smoke. In a particularly preferred embodiment, the
surfactant is present in an amount of from about 0.1 to about
10%, and more preferably from about 0.1 to about 2% by weight
of the filter.
The surfactant is preferably nontoxic and can
include one or more of the following classes of compounds: (1)
a polyoxyalkylene derivative of a sorbitan fatty acid ester
(i.e., polyoxyalkylene sorbitan esters), (2) a fatty acid
monoester of a polyhydroxy-alcohol, or (3) a fatty acid
diester of a polyhydroxy alcohol, though other suitable
surfactants will be understood by those with skill in the art
with reference to the disclosure herein. Examples of suitable
surfactants include ethoxylates, carboxylic acid esters,
glycerol esters, polyoxyethylene esters, anhydrosorbitol
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esters, ethoxylated anhydrosorbitol esters, ethoxylated
natural fats, oils and waxes, glycol esters of fatty acids,
polyoxyethylene fatty acid amides, polyalkylene oxide block
copolymers, and poly(oxyethylene-co-oxypropylene). Other
suitable surfactants can also be used as will be understood by
those with skill in the art with reference to the disclosure
herein.
The filter can additionally include other substances
which filter or inactivate toxic or mutagenic components of
tobacco smoke. Examples of such substances include anti-
oxidants and radical scavengers such as glutathione, cysteine,
N-acetylcysteine, mesna, ascorbate, and N,N'-diphenyl-p-
phenyldiamine; aldehyde inactivators such as ene-diol
compounds, amines, and aminothiols; nitrosamine traps and
carcinogen inactivators such as ion-exchange resins,
chlorophyll, chlorophyllin, copper phthalocyanine
trisulfonate; and nicotine traps such as tannic acid and other
organic acids. Other suitable substances can also be used as
will be understood by those with skill in the art with
reference to the disclosure herein. In a particularly
preferred embodiment, the other substances are present in an
amount of from about 0.1 to about 10%, and more preferably
from about 0.1 to about 2~ by weight of the filter.
Further, the filters of the present invention are
preferably provided with an exterior, circumferential,
moisture-impervious barrier or casing to prevent wetting of
the smoker's hands. Such a barrier can be made from a
polymeric material such as ethylvinyl acetate copolymer,
polypropylene, or nylon, as is understood by those with skill
in the art.
~ he filters of the present invention can be provided
in combination with cigarettes or cigars or other smokable
devices containing divided tobacco, being secured to one end
of the smokable device. The filter can also be provided by
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itself, in a form ~uitable for attachment to a cigarette,
cigar, pipe, or other smokable device.
Although the present invention has been discussed in
considerable detail with reference to certain preferred
embodiments thereof, other embodiments are possible.
Therefore, the spirit and scope of the appended claims should
not be limited to the description of the preferred embodiments
contained herein.
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