U.S. patent number 3,828,801 [Application Number 05/357,361] was granted by the patent office on 1974-08-13 for filter for removing polynuclear aromatic hydrocarbons from tobacco smoke.
Invention is credited to Edward W. Merrill.
United States Patent |
3,828,801 |
Merrill |
August 13, 1974 |
FILTER FOR REMOVING POLYNUCLEAR AROMATIC HYDROCARBONS FROM TOBACCO
SMOKE
Abstract
Polynuclear Aromatic Hydrocarbons (PAH) can be absorbed and
thereby removed from tobacco gas-smoke by polysiloxane
compositions. The polysiloxanes employed have a molecular weight
greater than 100,000 and can be located in the filter section of a
tobacco smoking device in admixture with an endothermically
dissociable hydrate or carbonate filler. The latter functions to
limit the temperature rise of the polysiloxane and thus prevents
the desorption of hydrocarbons adsorbed thereon.
Inventors: |
Merrill; Edward W. (Cambridge,
MA) |
Assignee: |
|
Family
ID: |
26999610 |
Appl.
No.: |
05/357,361 |
Filed: |
May 4, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
888505 |
Dec 29, 1969 |
3679625 |
Jul 25, 1972 |
|
|
233935 |
Mar 13, 1972 |
3774623 |
|
|
|
Current U.S.
Class: |
131/332; 131/342;
131/335 |
Current CPC
Class: |
A24B
15/246 (20130101); A24B 15/30 (20130101); A24D
3/08 (20130101); C08L 83/04 (20130101); C08G
77/14 (20130101); C08G 77/16 (20130101); C08G
77/70 (20130101); C08G 77/20 (20130101) |
Current International
Class: |
A24D
3/00 (20060101); A24D 3/08 (20060101); A24B
15/00 (20060101); A24B 15/30 (20060101); C08L
83/00 (20060101); C08L 83/04 (20060101); A24b
015/02 () |
Field of
Search: |
;131/261,262,264,265,266,267,268,269,10-10.9,17 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Rein; Melvin D.
Attorney, Agent or Firm: Kenway & Jenney
Parent Case Text
This application is a divisional application of Ser. No. 888,505
filed Dec. 29, 1969, now U.S. Pat. No. 3,679,625, issued July 25,
1972 and a divisional application of Ser. No. 233,935, filed Mar.
13, 1972, now U.S. Pat. No. 3,774,623.
Claims
I claim:
1. A smoking device having a filter section and a
tobacco-containing section wherein tobacco is arranged to be smoked
with the passage of tobacco gas-smoke through the
tobacco-containing section and the filter section, said filter
section containing a lipophilic absorbent comprising an organic
polysiloxane, said polysiloxane having a molecular weight greater
than 100,000 and being capable of absorbing hydrocarbon
constituents without evolving toxic materials when heated and
containing admixed therewith from about 50 to about 300 parts of
filler per 100 parts polysiloxane, said filler being selected from
the group consisting of hydrates and carbonates endothermically
dissociable to release water or carbon dioxide at a temperature
less than about 350.degree.C to limit the temperature rise of the
absorbent during smoking to prevent substantial desorption of
hydrocarbons absorbed by said polysiloxane.
2. The device of claim 1 wherein said tobacco section contains a
lipophilic absorbent comprising a polysiloxane having a molecular
weight greater than 100,000 and being capable of absorbing
hydrocarbon constituents without evolving toxic materials when
heated and containing admixed therewith from about 50 to about 300
parts of filler per 100 parts of polysiloxane, said filler being
selected from the group consisting of hydrates and carbonates
endothermically dissociable to release water or carbon dioxide at a
temperature less than about 350.degree.C to limit the temperature
rise of the polysiloxane admixed with tobacco during smoking to
prevent substantial desorption of hydrocarbons absorbed by said
polysiloxane.
3. The device of claim 1 wherein the filler endothermically
liberates water vapor when the tobacco is burned.
4. The device of claim 2 wherein the filler endothermically
liberates water vapor when the tobacco is burned.
5. The device of claim 1 wherein the filler endothermically
liberates carbon dioxide when the tobacco is burned.
6. The device of claim 2 wherein the filler endothermically
liberates carbon dioxide when the tobacco is burned.
7. The device of claim 1 wherein the filler endothermically
liberates water vapor and carbon dioxide when the tobacco is
burned.
8. The device of claim 2 wherein the filler endothermically
liberates water and carbon dioxide when the tobacco is burned.
Description
This invention relates to a composition for removing polynuclear
aromatic hydrocarbons (PAH) from tobacco gas-smoke.
It is generally thought that the carcinogens in the gas-smoke
produced from burning tobacco are found primarily among the
polynuclear aromatic hydrocarbons (PAH) of which benz (a) pyrene
and benz (a) anthracene are particularly recognized examples. PAH
are generated by the destructive distillation of more complicated
chemical compounds in the burning tobacco. The quantity of PAH
formed increases with the combusion temperature of tobacco.
Presently available cigarette filters are aimed at reducing the
hazard of carcinogenic matter from cigarettes. However, because of
the material used in these filters, their placement relative to the
tobacco and other factors, they serve primarily to condense
moisture and some of the water soluble materials in the gas-smoke
and to precipitate, by impaction, a small fraction of the colloidal
particles generated as the gasses moving from the combustion zone
of the burning tobacco are cooled by passage through the downstream
bed of tobacco.
The PAH are generated as a molecular dispersion but because of
their low vapor pressures they tend to adsorb and condense on any
surfaces with which they contact including unburned tobacco leaves,
cigarette wrapping paper or colloidal particles being generated in
the gas-smoke. The PAH that have recondensed on unburned tobacco or
paper later will be revolatilized as they are heated and burned,
whereas the PAH that are captured by adsorption and condensation on
colloidal smoke particles will travel with them through the
cigarette and follow them to their ultimate destination, whether it
be captured by impaction on a cigarette filter or the deepest
reaches of the smoker's lung. Presently employed filter techniques
are relatively ineffectual for removing PAH either in vaporous form
or when captured by colloidal particles not impacting the
filter.
Carbon black and granulated charcoal in their various forms have
been used in the filter portions of cigarettes, but these materials
suffer the disadvantage that they are far more active toward polar
materials such as nicotine than they are toward PAH and thus even
if PAH are adsorped on these surfaces they later may be re-evolved
into the gas phase by preferential adsorption of nicotine.
Furthermore the efficacy of any surface in the filter end of a
conventional cigarette is fundamentally limited by the well-known
principles of impaction of colloidal particles.
It would be highly desirable to provide a means for removing or
substantially reducing the amount of PAH in tobacco gas-smoke
especially by means that could be incorporated easily in
cigarettes, cigar or pipe tobacco. In addition it would be
desirable that the means for removing PAH be selective so that the
physiologically satisfying material is retained in the tobacco
gas-smoke. In contradistinction to the prior art, this invention
provides for the capture of PAH upon liberation from burning
tobacco in predominantly molecular forms by absorption onto
materials having high solubility for the PAH and negligible or low
solubility for the polar components such as nicotine and other
alkaloids.
This invention provides a novel composition for removing or
substantially reducing the PAH in tobacco gas-smoke. A particulate
polysiloxane absorbent composition capable of absorbing PAH is
mixed with tobacco and/or employed in a filtering means adjacent
burning tobacco. The temperature on the absorbent surface is
maintained at a substantially lower temperature than adjacent
burning tobacco during absorption of PAH to prevent desorption of
PAH by effecting an endothermic chemical reaction or desorption of
a filler material in the particles to liberate a physiologically
harmless by-product such as carbon-dioxide or water. The
polysiloxane itself does not decompose at the temperature generated
by the burning tobacco. The PAH, such as benz (a) pyrene are
absorbed and having been absorbed are so highly diluted by
solvation of the polymer that subsequent reheating as the
combustion zone passes the material does not cause significant
desorption of them.
When the polysiloxane composition is incorporated in the tobacco,
it is conveniently removed with the ash of the burning tobacco so
that the carcinogenic compounds, instead of progressively
accumulating in even higher concentrations by condensation on yet
unburned tobacco, are instead mostly removed as the ash is flicked
off leaving a smoke-gas mixture that is physiologically satisfying
because of its nicotine content but having a significantly lowered
concentration of PAH.
Because of the factors noted above, it will be understood that as
the gas-smoke mixture passes through a conventional cigarette
filter a certain amount of PAH may yet be in a molecular form and
therefore susceptible of capture by absorption, in
contradistinction to colloidal particles susceptible of capture
primarily by impaction or electrostatic mechanisms rather than
diffusion. Therefore, to render the cigarette, cigar or other
product of this form even safer it is preferred to replace the
conventional filter with or add to the conventional filter an
extension containing PAH absorbing polymer in finely divided form
with high surface area such as shredded polysiloxane rubber. There
need not be present in the polysiloxane composition in the filter a
material capable of undergoing an endothermic reaction since the
low surface temperature sufficient to substantially reduce
desorption is maintained by virtue of its remoteness from the
combustion zone. However, it is preferred that the primary site for
capture of PAH and similar carcinogens be the adsorbent materials
admixed with the tobacco flake.
A more detailed understanding of this invention can be obtained by
reference to the attached figures and the discussion below:
FIG. 1 is a cross-sectional view of a cigarette, the tobacco
portion of which contains the polysiloxane composition of the
invention.
FIG. 2 is a cross-sectional view of the cigarette of FIG. 1 having
in addition, a filter containing a polysiloxane.
FIG. 3 is an axial cross section view of a cigar and FIG. 3a is a
transverse cross section at 3a--3a of FIG. 3.
FIG. 4 is a plan view showing a perforated polysiloxane film and a
tobacco leaf to be layered together.
FIG. 5 is a longitudinal and FIG. 5a is a transverse cross section
of the filter portion of a cigarette.
Referring to FIG. 1, 1 represents the solid residue, or ash, from
the combustion of the tobacco 4, in mixture 2, 3 is the filter, or
end of the cigarette in the mouth of the smoker, 4 is tobacco flake
shredded leaf or other conventional form of tobacco and 5 is the
absorbent in flake, fiber or other particulate form. As the
combustion zone midplane moves from position mm to position nn in
FIG. 1, the evolved PAH are absorbed by immediately adjacent
absorbent particles 5, while carbon dioxide, water, and the more
polar material such as nicotine pass through the cigarette. The ash
1 is tapped off of the cigar or cigarette from time to time
carrying with it the polysiloxane having the absorbed PAH.
Referring to FIG. 2, the tobacco-absorbent mixture 2, is followed
by a conventional filter 3, that removes the major part of the
aqueous condensate and an extension 7, comprising finely divided
silicone polymer 8, as for example, in a fibrous configuration, not
necessarily containing any filler component, which serves to absorb
the now very small content of PAH and other lipophilic molecules
that may have escaped prior adsorbtion in the adsorbent tobacco
mixture 2. Referring to FIG. 3, a cigar is formed by wrapping
spirally alternating layers of tobacco leaf 9 and of sheeted
polysiloxane material 10. The sheeted polysiloxane material is
prepared in thicknesses comparable to the thickness of tobacco leaf
and is scored or perforated so as to form narrow ribbons 11
(approximately one-fourth inch wide) which are held together by a
limited number of junction points 12.
When the cigar of FIG. 3 is formed, the polysiloxane material with
absorbed PAH 10 becomes part of the incombustible ash and is
detached by tapping the cigar.
Referring to FIG. 4, the major axis of the cigar is shown relative
to the tobacco leaf and to the perforated or scored polysiloxane
sheeted material, prior to spiral wrapping. It will be understood
that, depending on the grade of leaf, thickness of leaf, thickness
of polysiloxane material and so on, the alteration of one leaf with
one polysiloxane sheet shown in FIGS. 3 and 4 is only one
embodiment, and that two or more leaves of tobacco may be rolled
with one sheet of polysiloxane material.
Referring to FIG. 5, which shows the cross section of a cigarette
cut along the major axis, silicone absorbent in the form of
parallel lengths of round tubing, 13, of small diameters are
assembled as a bundle containing 20 or more individual tubes, of
which the end section is shown corresponding to section 5a--5a from
the side section. Conventional shredded cigarette-grade tobacco 14
is packed beyond the filter section 15 and is enclosed with the
filter section by a common cigarette paper wrapping.
The polysiloxanes employed in this invention have sufficient
thermal stability to undergo negligible or no degradation at
temperatures encountered in the combustion of tobacco when
appropriate amounts of fillers, to be specified below, are used.
While linear siloxanes of high molecular weight may be used without
cross-linking, for example gum stock, it is more satisfactory in
general to cross-link the polymer to render it rubbery and more
stable against thermal degradation, as well as non-flowing with
respect to admixed tobacco flake. Cross-linking in effect forms a
polymeric network of infinite molecular weight and zero vapor
pressure which can be destroyed only by scission of the
silicone-oxygen backbone and oxidation of the side groups. The
conventional silicone oils of low molecular weight are not useful
in this invention, because they are too readily volatilized under
the combustion conditions of tobacco and furthermore they are not
as convenient to admix with the fillers used in this invention as
are the silicone polymers set forth below that may be subsequently
cross-linked.
Among the polymers that may be used in the adsorbent material to be
co-mixed with tobacco are poly (dimethyl) siloxane, poly
(co-phenylmethyl dimethyl) siloxane, poly
(co-vinylmethyl-phenylmethyl-dimethyl) siloxane and the classes of
these polymers conventionally terminated with silanol groups or
polymers of the RTV class that are prepared with acetoxy
termination for the purpose of cross-linking by hydrolysis of the
acetate groups and subsequent cross-linking of the silanol groups
generated by hydrolysis: provided that in their final state, the
polymer be of high molecular weight, exceeding 100,000, or
preferably that it have been cross-linked.
The surface temperature of the polysiloxane is regulated during
combustion by incorporating an endothermically reactive filler in
the polysiloxane. The filler is dispensed throughout the polymer
but the permeability of the polymer to CO.sub.2 and water vapor is
so that the reaction products are easily diffused through the
absorbent to its surface. The filler absorbs heat from the surface
by virtue of the endothermic reaction or endothermic evolution of
vaporous material. Furthermore, as the vapors evolved from the
filler pass through the particle surface, they absorb heat from the
surface. In this manner, the surface temperature of the absorbent
particles is maintained sufficiently low to prevent substantial
desorption of PAH. Among the fillers that may be used are those
capable of releasing water vapor carbon dioxide or both
endothermically regardless of whether the vapor evolved is
generated by chemical reaction or physical desorption.
The preferred fillers are those which, per gram, absorb the most
heat from the surrounding combustion zone while liberating the
harmless gaseous product at a temperature low enough to prevent
destruction of the polysiloxane absorbent. At the same time, the
filler must not spontaneously decompose under conditions of storage
with the tobacco product prior to use.
Preferred fillers are listed in Table I, which also tabulates the
nature of the vapor evolved, the endothermic heat in cal./gram of
filler and the approximate temperature at which the endothermic
heat absorption occurs.
TABLE I ______________________________________ Heat cal/g. Temp.
Vapor ______________________________________ Milk of magnesia
(magnesium hydroxide) 350 350.degree.C Water Epsom salt (mag.
sulfate heptahydrate) 356 150.degree.-200.degree.C Water Sodium
metasilicate nonahydrate 412 45.degree.-300.degree.C Water
Artinite, natural (basic mag. carbonate trihydrate) 400
100.degree.-350.degree.C Water 350.degree.C Carbon dioxide
Nesguehonite, nat. (mag. carbonate trihydrate) 400 165.degree.C
Water 350.degree.C Carbon dioxide Sodium bicarbonate 188
270.degree.C Carbon dioxide Gypsum (calcium sulfate dihydrate) 158
128.degree. Water 163.degree.C Water
______________________________________
Any of the fillers mentioned above may be milled into poly dimethyl
siloxane silicone gum stock on a cool mill without significant loss
of water of other gaseous product and the silicone rubber may then
be cross-linked at essentially room temperature by ionizing
radiation. The cured material has only the endothermic filler and
no toxic components such as found in products cured by free radical
initiators. Alternatively, one can easily admix Gypsum or Glauber's
salt or porous water-containing material with RTV silicone and
allow room temperature vulcanization to occur by hydrolysis of
terminal acetoxy groups, or by other means with the use of trival
amounts of water according to the type of RTV silicone used. When
sodium bicarbonate is to be used for evolution of carbon dioxide
and water it is impractical to use the acidic RTV rubbers
containing acetoxy terminal groups because of partial conversion of
the sodium bicarbonate to sodium acetate. On the other hand it is
completely practical and indeed desirable to admix the bicarbonate
with pure silicone gum stock, especially pure polydimethyl siloxane
and then to effect cross-linking by ionizing radiation, such as by
a Van der Graaf generator. It will be understood that mechanical
strength is irrelevant to the properties of the silicone adsorbent
material admixed with the tobacco. Thus, it is not necessary to use
silica filler of the fume type or other inert fillers customarily
used for reinforcement, but these inert fillers if present in the
silicone gum stock will not interfere with the action of the
decomposing fillers recited above.
The filler is used to maintain the temperature of the silicone
polymer absorbent below its decomposition point and at the same
time allow more effective absorption of the PAH molecules liberated
from the tobaccos since the PAH are the more soluble in the
polymer, the lower is the temperature.
The temperature of tobacco in the combustion zone of a cigarette
can exceed about 800.degree.C. depending on moisture content
tightness of packing, rate of smoking by the user and so on. Thus,
the amount and type of filler in each polymer particle and the
concentration of polymer particles in the tobacco are controlled to
obtain the desired results set forth above in relation to the
moisture content of the tobacco and to the tightness of packing. At
least 50 phr (parts of filler per 100 parts of rubber) are to be
used while 100 phr to 150 phr are preferred. The maximum amount of
filler that may be incorporated depends on a variety of factors
such as filler density, assymetery of the particles, particle size
distribution, particle porosity and other factors, and the
practical upper limit may be as high as 300 phr. This can be easily
ascertained taking care to account for these factors for each
filler material. Small amounts of a filler can be directly exposed
on the particle surface but it should not be sufficient to
adversely effect the absorbent property of the particles nor permit
excessively high temperatures on the surface. At the same time the
filler particles must be sufficiently near the surface, (within
less than about 10 microns) so that by their decomposition they
will maintain the surface at the desired temperature and because of
their distribution throughout the mass at the same time they will
maintain the mass essentially isothermal.
The physical shape and form of the silicone absorbent to be admixed
with the tobacco is not critical provided that the maximum surface
to volume ratio consistent with practical admixture with the
tobacco is realized. In general, the thickness of the absorbent
should be comparable to that of the tobacco flake or leaf. The
absorbent may take the form of discontinuous flake as in FIGS. 1, 2
or as continuous ribbon as in FIG. 5, or in any other form,
provided that after combustion of the intervening tobacco, the ash
and spent absorbent can be easily tapped off together, and provided
that the absorbent material can be so disposed relative to the
tobacco that local "hot" spots are avoided.
When the silicone polymer is cross-linked by thermal decomposition
of a free-radical initiator such as dichlorbenzoyl peroxide, it is
necessary to remove the potentially harmful by-products resulting
from the cross-linking step that might escape by subsequent heating
of the silicone rubber, such as phenyl benzoate. This can be
effected, for instance, by extraction with acetone and
acetone-ether mixtures. For this reason the RTV acetoxy terminated
siloxanes and dimethyl silicone gum stocks cured by ionizing
radiation (x-ray, Van der Graaf, cobalt 60 etc.) are preferred
because no molecular fragments remain after cross-linking that can
escape subsequently during heating in the combustion zone of a
burning cigarette, cigar or pipe tobacco.
In admixing the silicone absorbent with the tobacco no restriction
is placed on the weight ratio of absorbent to tobacco except that
the upper limit cannot exceed approximately 6 because otherwise it
would be difficult to prpoagate the combustion front and thus
maintain the tobacco lit. Up to this ratio, increased absorption is
obtained with increased concentration of absorbent. Therefore, for
maximum protection it is preferred to use at least 60 parts of
absorbent to 40 parts of tobacco. The weight of the tobacco is
measured after equilibration under one atmosphere pressure at 60
plus or minus 2 percent relative humidity, at 22 plus or minus
2.degree.C. This can be obtained by placing a mixture containing 74
volumes of glycerin and 26 volumes of water or other dessicant on a
suitable covered dessicator.
It is obvious from the foregoing statement that the admixture of
silicone rubber absorbent will result in a significantly lower mean
combustion zone temperature than would occur if the same quality of
tobacco at the same relative humidity were used without admixture
with the adsorbent. The presence of the adsorbent reduces the total
effective area of combustion in the combustion zone relative to the
amount of air being drawn through the cigarette, thus leading to a
much higher ratio of oxygen to fuel than is stociometrically
required. By itself, this has the well known effect of reducing the
temperature of the combustion zone in a calcuable way, and in
addition decreasing the small but finite content of carbon monoxide
found in the smoke-gas mixture from burning tobacco. It is well
known carbon monoxide represents a special health hazard. In
addition, the liberation of water or carbon dioxide or other
harmless gaseous element from the filler contained within the
silicone absorbent demands latent heat of dessication or of
evaporation or of desorption and thereby further reduces the
temperature of the combustion zone. Consequently the production of
PAH is significantly reduced and with the extensive absorptive area
immediately adjacent to the zone of production the total PAH
passing out of the tobacco mixture into the filter of the cigarette
is very substantially reduced compared to a cigarette without
admixed absorbent.
As an alternative embodiment in the filter section 3 of FIG. 1 or
FIG. 2, the clean-up absorbent in section 8 may be of any inert
lipophilic polymer including butyl rubber, butadiene rubber,
ethylene-propylene co-polymers etc. Among the various polymers that
may be used, the silicone polymers broadly are preferred because of
their very high capacity for the PAH. However, since the cigarette
filter will never operate a temperature in excess of 50.degree.C.,
the exceptional thermal resistance of the silicones is not
specifically required in the filter section 8.
From the foregoing disclosure, it will be understood that there is
no practical limit on the length of the lipophilic filter of
section 8. Indeed, it could be greater than half the length of the
entire cigarette. It will also be understood that a cigarette
consisting of a filter composed of silicone polymers extending over
80 per cent of the cigarette would be of significant value in
removing substantially all of the PAH from the small amount of
tobacco in such a cigarette, constituting 20 per cent of the total
length. In this case the length of the tobacco that may be burned
is so short and the distance from the combustion zone to the
nearest silicone surface is so short that most of the effects
obtainable with the admixture of silicone absorbent would be
obtained in a cigarette with an 80 to 20 ratio of filter to tobacco
section. It will be understood that in such a cigarette, because
the combustion zone could approach and come in contact with the
filter medium, it would be manditory to have silicone polymers with
high heat resistance of the classes specified above, and containing
some gas releasing filler to prevent over-heating of the end
nearest the tobacco.
It will be understood therefore, that this invention includes the
use of silicone polymers either in admixture with gas releasing,
temperature moderating fillers, as absorbent matter to cigarette,
and preferably for maximum elimination of PAH from the gas-smoke
mixture inhaled by the smoker the cigarette consists of an
admixture of tobacco with a silicone absorbent in the combustion
section and additionally a filter section containing a lipophilic
polymer, preferably silicone, to absorb final traces of PAH.
The following examples illustrate the present invention and are not
intended to limit the same.
EXAMPLE I
The following mixture is prepared in a laboratory Brabender mixer
or on a laboratory rubber mill (cool rolls) until uniformity of
color is achieved:
Dow Corning Medical Grade Silastic.sup.TM (devoid at catalyst, but
containing 25phr silica) 100.0g Magnesium hydroxide, CP powder
100.0g Red iron oxide 4.0g Ground activated charcoal 0.5g
This raw stock is extruded through a laboratory extruder containing
a die with 100 holes of 20 mils diameter, there being a continuous
light dusting of sodium bicarbonate powder on the 100 emerging
filaments to prevent blocking. The filaments are lightly twisted
into a cord and the cord is coiled loosely in piles about 4 inches
high. The coils are then transformed to a Van der Graaf or
equivalent generator of ionizing radiation and are exposed to a
dose of about 10 megarads, whereby the silicone polymer is
effectively cross-linked.
Final preparation consists of drawing the cured cord through a
water bath to remove superficial bicarbonate, drying in high
velocity warm air (120.degree.F mix), and then passing continuously
through a flying-knife chopper that produces bundles not over 200
mils long. The bundles are passed between closely adjusted knurled
rolls the upper running 10 percent faster than the lower at about
100 rpm set to a clearance of about 50 mils as determined by feeler
gauge. This effects the separation of the individual filaments in
the bundles and randomizes them. The randomized chopped filament is
comixed with shredded cigarette tobacco (previously conditioned at
60 percent RH at 22.degree.C.) over 74 percent glycerol 26 percent
water in a weight ratio of 2 parts filament to 1 part tobacco and
is packed into cigarette paper to form cigarettes.
EXAMPLE II
100 grams of Dow Corning Silastic RTV-732, a semiliquid is mixed
with 140 grams finely ground Epsom salt in a laboratory Brabender
mixer and 1 gram red iron oxide (to provide color indication of
thoroughness of mixing).
The paste after mixing is extruded through the laboratory extruder
described in example 1, and the issuing filaments are sprayed with
fine water fog to hasten superficial hydrolysis and gel formation.
The filament thus moistened is stored in chambers held at 95
percent RH at 25.degree.C. for 48 hours, and is then air dried at
90.degree.F. for 2 hours.
This filamentory material is then chopped as in example I and is
mixed with cigarette tobacco, previously conditioned at
22.degree.C. over 74 percent glycerol, in a weight ratio of 3 to
1.
EXAMPLE III
Union Carbide silicone gum stock W 96, predominantly polydimethyl
siloxane devoid of any peroxide catalysts, is diluted with diethyl
either to form a solution containing 15 percent polymer. To this is
added with effective mixing finely powdered sodium metasilicate
nonahydrate (1.4 grams/gram dry rubber), ground activated charcoal
(0.02 grams/gram dry rubber) and red iron oxide (0.04 grams/gram
dry rubber). When uniform red-brown color is achieved the paste is
knife spread onto a polished stainless steel belt which passes
through a solvent recovery chamber wherein the ether is evolved by
infra red heating to a surface temperature of 120.degree.F. The
knife is adjusted to produce a sheet which, after ether evolution,
is 15 mils thick.
This sheet is, because of its high filler content, relatively
non-blocking. It is loosely folded in layers up to 50 deep. The
layered material is transferred to a Van der Graaf generator and
irradiated with 10 megarods, whereby it is cured. The folded
sheeted stock is then unfolded and passed under a rotary perforator
whereby it is slit into nearly detached ribbons three-sixteenths
inch wide connected at one-half inch intervals by an uncut length
about 25 mils long.
This sheet stock, thus slit, is co-wrapped with whole leaves of
tobacco in a 1/1 ratio, so as to form cigars, in which the nearly
separated ribbons of absorbent are at right angles to the axis of
the cigar.
EXAMPLE IV
100 grams of Dow Corning Medical Grade Silastic and 110 grams of
finely ground artinite are blended together as a master batch on a
cool laboratory mill. This is then supplied to a miniature tubing
extruder wherein it is extruded as tubing with an outside diameter
of 50 mils and an inside diameter of 30 mils. Depending on the die
design of the extruder, it may be necessary to add up to 10 parts
per hundred rubber of a volatile plasticizer such as dimethoxy
flurane, to prevent excessive heat build up. Partial cure is
effected by continuous passes through a Van der Graaf generator
wherein it receives a dose of 1.5 megarads. The partially cured
tubing is then rolled in coils, which are subjected to a final
radiation dose of 10 megarods.
The tubing assembled in round bundles of 36 secured by bands of
cigarette paper is cut into lengths of 1 cm. Seven of these bundles
are placed serially, but out of alignment one with another, so as
to form an absorbent section 7cm in length, in the place of the
conventional filter. Following the absorbent section is a tobacco
section 1.5cm in length. The tobacco and the silicone absorbent are
enclosed in a common cigarette paper wrapper.
From the foregoing description it will be seen that the
absorptivity of polysiloxanes to PAH may be utilized to remove PAH
from tobacco gas-smoke. The polysiloxane may be placed in the
tobacco mixture or in the gas-smoke-stream, but should be presented
to maintain a relatively low maximum temperature to minimize the
regeneration of PAH vapors. Siloxane polymers situated close to
burning tobacco in the combustion zone may include endothermic
fillers that generate physiologically harmless vapors such as
water, carbon dioxide or they may be present in relatively high
proportions, to keep down the temperature in the combustion zone
and minimize regeneration of previously absorbed PAH.
The foregoing description sets forth several preferred and
representative examples of the embodiments of this invention. It
is, however, contemplated that the principles herein set forth will
lead others to employ various modifications from the present
disclosure, which will still be within the skill of the art and not
beyond the spirit of this invention.
In particular the formulations of tobacco and silicone are aimed at
presenting the silicone in form and arrangement to be adsorptive of
PAH from the gas-smoke and to prevent subsequent desorption of PAH.
The maintenance of low temperatures in the silicone polymers is
important, and is provided for by incorporating endothermic fillers
or by the presence of relatively large proportions of silicone in
the combustion zone. In either case the objective is to present the
siloxane in absorptive relationship to the tobacco gas-smoke, and
to prevent subsequent over-heating sufficient to regenerate
previously absorbed PAH. When the silicone polymer is mixed with
the tobacco, low temperatures may be maintained through the
presence of relatively large amounts of silicone, or by
incorporating large amounts of physiologically harmless absorptive
fillers in the siloxane polymer. When the "filler" is situated
downstream of the filler, in the gas-smoke stream, but not consumed
lipophilic solids other than silicone also are effective to remove
PAH.
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