CA 02284230 1999-09-30
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SMOKING ARTICLES
This application is divided from Canadian Patent
Application Serial Number 2,196,907, filed September 6,
1995.
The present invention relates to smoking articles, and
in particular to smoking articles which have an other than
conventional structure and combustion regime, yet which
have the outward appearance similar to a conventional
smoking article.
Many attempts have been made to produce a smoking
article which provides the smoker with an aerosol which is
similar to tobacco smoke. Some ideas have centred on
generating an aerosol vapour from an aerosol generating
means by heating the aerosol generating means with a
surrounding fuel source, such as cut tobacco. Smoke from
the fuel source is prevented by a smoke barrier from
reaching the smoker's mouth, whilst the aerosol vapour can
pass to the smoker. These can be seen in US Patent Nos.
3,258015 (Ellis) and 3,356,094 (Ellis). The first of these
proposed a smoking article having an outer cylinder of fuel
with good smouldering characteristics, preferably cut
tobacco or reconstituted tobacco, surrounding a metal tube
containing tobacco, reconstituted tobacco or other source
of nicotine and water vapour. A substantial disadvantage
of this article was the ultimate protrusion of the metal
tube as the tobacco fuel was consumed. Other disadvantages
include the formation of substantial tobacco pyrolysis
products and substantial tobacco sidestream smoke. This
design was later modified in the second patent mentioned
above by employing a tube made out of a material such as
inorganic salts or an epoxy bonded ceramic, which became
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frangible on heating and was discharged as an ash by the
smoker. In this invention also there are substantial
tobacco pyrolysis products and, because of the combustion of
tobacco, visible sidestream smoke.
Aerosol inhalation devices such as European Patent
Applications, Publication N.os. 0 174 645 and 0 339 690
describe means of using heat transfer from a fuel element to
physically separate aerosol generating means. The main
feature of these inventions is that the aerosol generating
means is always physically separate from the fuel element
and is always heated by heat transfer from a heat conducting
member, never burned. To this end the fuel element is
always short, located to one end of the smoking article and
kept out of direct contact with the aerosol generating
means.
Other and mainly more recent devices have included GB 1
185 887 (Synectics), US 5,060,667 (Strubel) and EPA 0 405
190 (R. J. Reynolds). In all of these devices the patentee
has arranged the fuel element as an annulus around aerosol
generating means.
GB 1 185 857 provided a substantially inorganic smoke
of readily absorbable salts to the smoker and produced an
ash which could be removed in normal fashion by the smoker.
However, the smoking article is presumed to have given off
an amount of visible sidestream smoke because of the
cellulosic components within individual items of the smoking
article.
US 5,060,667 provided a co-axially arranged tobacco-
containing fuel element encircled by a metallic heat
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transfer tube with a flange portion at the end to be lit in
order to prevent smoke from the burning tobacco from passing
through the flavour source material circumscribing the heat
transfer tube. Only aerosol from the flavour source
material passes to the smoker. The device does not burn
down and tobacco material is combusted, as well as providing
the flavour source material, thereby producing visible
sidestream smoke and utilising a high percentage of a costly
item such as tobacco.
EPA 0 405 190 seeks to provide a smoking article which
provides the user with the pleasures of smoking by heating
without burning tobacco. Most of the articles comprise an
annular carbonaceous fuel segment, a physically separate
aerosol generating means disposed concentrically within the
fuel segment, a barrier member between the fuel segment and
the aerosol generating means, which substantially precludes
fluid flow radially therethrough and which is disposable as
the smoking article is smoked, and a mouthend segment. As
the fuel source is disposed annularly around the aerosol
generating means it is advantageous to surround the fuel
source longitudinally with an insulating sleeve which may
then be wrapped with a conventional wrapper. One
alternative embodiment is postulated which comprises a co-
axial carbonaceous fuel source of slow burning rate
encircled along its longitudinal length by an insulation
member, which in turn is encircled along its length by
tobacco wrapped in a paper wrapper. The tobacco is only
heated and not burnt, as in the other embodiments, but
unlike the other embodiments of EPA 0 405 190 the device
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cannot burn down as t:obacco would then be burnt. No actual
practical embodiment is described and thus this embodiment
appears to be an armchair, or paper, proposal. The
patentees appear to have had some difficulty in reducing to
practice this particular concept. This concept also
utilises considerab7_e amounts of expensive tobacco, to
provide the aerosol source material, which the smoker never
truly experiences.
The present invention provides a smoking article which
does not produce substantial tobacco pyrolysis products.
The present invention also provides a smoking article
which exhibits very little visible sidestream smoke, and
considerably less visible sidestream smoke than prior
proposed conventional smoking article comprising tobacco
rods of cut tobacco wrapped in a paper wrapper containing
a visible sidestream reducing r_ompound or being a visible
sidestream reducing paper.
The invention function in the manner described above
whilst maintaining a substantially conventional outward
appearance of a smoking article as we know the same today.
The invention preserves the physical elements of the
smoking process, including the ashing of a cigarette to
produce an ash which. can be removed by the smoker in the
normal way.
The present invention provides a smoking article fuel
source of substantially the whole length of a smoking
article, the fuel source comprising 25-70% carbon or
carbonaceous material and 10-65% inorganic non-combustible
binder and 0-10% burn promoter, all by weight of the fuel
source, said inorganic non-combustible binder comprising
one or more of potassium silicate, magnesium oxide in
combination with potassium silicate, or cement.
As used herein the terms 'smoking material rod' or
'smoking material' a.re merely intended to mean that part of
the smoking article which is contained within the
substantially non-combustible wrapper and should not have
imported therein any association as to the combustibility
CA 02284230 2001-07-13
or otherwise of individual components of the rod of the
smoking material.
The present invention further provides a smoking
article fuel source of substantially the whole length of a
5 smoking article, the=_ fuel source comprising 15-70% carbon,
84-5% non-combustible inorganic filler material, 1-20%
organic binder and 0-20% inorganic binder, and a
plasticiser being one or more of low melting point fats or
low melting point oils.
The present invention provides a smoking article
aerosol generating means comprising a non-combustible
inorganic filler material, aerosol forming means, and an
organic or inorgan_Lc binder, said aerosol forming means
being 12% or more by weight of said aerosol generating
means.
Preferably tr~.e non-combustible inorganic filler
material is a particulate mater_:ial and even more preferably
is a non-metallic material.
This invention also provides a smoking article aerosol
generating means comprising 95-30% inorganic, non
combustible binder, 45-90% non-combustible inorganic filler
material and 5-30% aerosol forming means, said aerosol
generating means containing no tobacco, charcoal oz' other
carbon material.
The present inj,rention also provides a smoking article
aerosol generating means comprising 1-25% organic binder,
50-94% non-combustible inorganic filler material, and 5-30%
aerosol forming means, said aerosol generating means
containing no tobacco, charcoal or other_ carbon material.
The present invention also provides a smoking article
aerosol generating means comprising 1-25% organic binder,
50-94% non-combustible inorganic filler material, and 5-30%
aerosol forming means, said aerosol generating means
containing no tobacco, charcoal or other carbon material.
The present invention also provides a smoking article
aerosol generating means comprising an organic filler
material, aerosol forming means, an organic binder and 0-
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93% inorganic' filler material, said aerosol forming means
being 10-2% or more' by weight of said aerosol generating
means.
The present invention provides a smoking article
aerosol generating means comprising 1-25% organic binder,
1-94% organic filler material. other than tobacco, 0-93%
inorganic filler mat=erial and 5-30% aerosol forming means,
said aerosol generating means containing no tobacco,
charcoal or other c<~rbon material.
The present invention further provides a smoking
article aerosol generating fuel source comprising a non
combustible inorganic filler material, aerosol forming
means, an organic or inorganic binder and carbon, said
aerosol forming means being present in the range of 10.2
30% by weight of said aerosol generating fuel source.
The present invention alsc provides a smoking article
aerosol generating fuel. source comprising 0-35% inorganic
filler material, 10.2-30% aerosol forming means, 30-60%
inorganic binder, 30-65% carbon and 0-10% burn promoter.
The present invention alsc provides a smoking article
aerosol generating fuel source comprising 86-0% inorganic
filler material, 10.2-30°. aerosol forming means, 1-25%
organic binder and 8-60% carbon.
The present invention also provides a smoking article
aerosol generating fuel source comprising organic filler
material being one cr more of inorganic salts of organic
acids or polysaccharide material, aerosol forming means,
organic binder and carbon.
Preferably the substantially non-combustible wrapper
is comprised of predominantly non-combustible inarganic
filler material. The term 'predominantly' as used herein
means at least about 65 % and usually 70 % . The inorganic
filler material advantageously yields very little or
substantially no vi:~ible sidestream smoke when the smoking
article is lit. Preferably the non-combustible wrapper
comprises at least 80%, and more preferably at least 90%
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inorganic filler material by weight of the wrapper.
Advantageously the non-combustible inorganic filler
material is one or more of perlite, vermiculite,
diatomaceous earth, colloidal silica, chalk, magnesium
oxide, magnesium sulphate, magnesium
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carbonate or other low density, non-combustible inorganic
filler materials known to those skilled in the art.
The non-combustible wrapper may comprise a small amount
of cellulosic fibre material. Preferably the fibre material
comprises less than 10%, more preferably less than 5%, and
even more preferably less than 2% by weight of the non-
combustible wrapper. Most advantageously the fibre material
is not present in the wrapper.
Preferably the wrapper comprises a binder and/or a
plasticiser. These components may be present at up to 30%
by weight of the wrapper. Advantageously the binder is not
present at more than 25% by weight of the wrapper. The
exact proportions will depend on the taste characteristics,
acceptable visible sidestream smoke emission and strength of
the desired product, and the processing techniques used.
The binder may be present at about 8-10% by weight of the
wrapper, although it may be present at about 5% or less by
weight of the wrapper. The binder may be organic binders,
for example, cellulose derivatives, such as sodium
carboxymethylcellulose, methyl cellulose,
hydroxypropylcellulose, hydroxyethyl cellulose or cellulose
ethers, alginic binders including soluble alginates such as
ammonium alginate, sodium alginate, sodium calcium alginate,
calcium ammonium alginate, potassium alginate, magnesium
alginate, triethanol-amine alginate and propylene glycol
alginate or insoluble alginates which can be rendered
soluble by the addition of solubilising agents, such as
ammonium hydroxide. Examples of these include aluminium,
copper, zinc and silver alginates. Alginates which are
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initially soluble but which, during processing, undergo
treatment to render them insoluble in the final product may
also be used, e.g. sodium alginate going to calcium alginate
(see below). Other organic binders include gums such as gum
arabic, gum ghatti, gum tragacanth, Karaya, locust bean,
acacia, guar, quince seed or xanthan gum, or gels such as
agar, agarose, carrageenans, fucoidan and furcellaran.
Pectins and pectinaceous materials can also be used as
binders. Starches can also be used as organic binders.
Other suitable gums can be selected by reference to
handbooks, such as Industrial Gums, Ed. Whistler (Academic
Press). Combinations of the above may also be used.
Inorganic non-combustible binders, such as potassium
silicate, magnesium oxide in combination with potassium
silicate, or some cements, for example, and mixtures
thereof, may be used.
The wrapper, although not giving much, if any, visible
sidestream smoke, does produce ash of an acceptable colour
and quality. The smoking article also has a visible burn
line which advances along the article and enables the smoker
to determine whether the article is alight and to monitor
the smoking process. The visible burn line may be formed as
a result of burning the organic binder. Alternatively,
colour changing compounds can be included in the wrapper
composition. Colourants which give the wrapper an other
than white colour may also be included. These colourants
may also change colour as heating occurs, providing a
visible burn line, e.g. CuS04.5H20.
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The nature of the binder selected will also determine
the permeability of the outer wrapper. Binders, such as
sodium carboxymethylcellulose and propylene glycol alginate,
have been found to be particularly effective at producing an
outer wrapper sufficiently permeable to sustain combustion
of the fuel source within the wrapper. The latter binder
gave the more permeable outer for the same outer wrapper
composition. Hydration time of some binders can play a part
in determining the efficacy of the binders. Conventionally
understood strong binders such as hydroxypropylcellulose can
be used at lower levels to increase the wrapper permeability
but this has to be balanced against the strength of the
wrapper.
The plasticiser may be present in the wrapper at up to
20% by weight thereof. The plasticiser is preferably
present at about 10% or less, preferably 5% or less, by
weight of the wrapper. The plasticiser may be glycerol,
propylene glycol, or low melting point fats or oils for
example. Depending on the method of production selected for
the wrappers, the plastisicer may be absent from the wrapper
composition. The plasticiser helps in the drying stages of
the wrapper to prevent shape distortion, particularly if
direct heat, e.g. hot air, is the drying medium. The amount
of plasticiser, binder or other organic filler material will
affect the appearance of the burn line, i.e. the burn line
width, and the amount of visible sidestream of the article.
Preferably the width of the burn line is not greater than
lOmm, is preferably not more than 5mm and more preferably is
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between 2-3mm in width. The width of the burn line depends
on the composition of the burnable material in the article.
The wrapper may comprise materials which provide an
odour to any sidestream smoke which may come from the
article. Suitable deodorisers include citronellal, vanillin
and geraniol, for example.
The wrapper may be formed by producing a thick slurry
of the wrapper components, coating the slurry about a
rotating mandrel, and removing excess moisture by physical
or chemical means. Alternatively, the slurry may be cast as
a sheet on a drum or band caster, or extruded as a hollow
tube, through a 'torpedo' die-head, for example, which has a
solid central section, or extruded as a sheet material.
The slurry could be sprayed, coated or pumped onto a
suitably shaped fuel/aerosol assembly.
The extrusion process is suitably carried out at a
pressure which does not detrimentally affect the wrapper
permeability and is suitably not greater than 3-4 bar (300-
400kPa) at the extruder die of a ram extruder, for example,
and not more than 9 bar (900kPa) for an APV Baker Perkins
screw extruder. The extrusion process may require foaming
to occur at the die exit to produce a cellular structure, in
which case greater pressure can be exerted, at the die,
whilst retaining permeability.
After extrusion or coating the hollow extrudate or
coated mandrel is suitably subj ected to heat at or exit the
die to drive off excess moisture. The wrapper slurry may
comprise a heat activated binder, such as potassium
silicate, magnesium oxide, or hydroxypropylcellulose at
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temperatures above 40-50°C, for example. Subjecting the
coated mandrel or hollow extrudate to heat would activate
the binder causing the wrapper to set. Infra-red or
microwave heating is advantageous as direct heating, e.g.
the use of hot air blowers, can affect the shape of the
extrudate, especially at temperatures of greater than 100°C.
Extrusion may be carried out using a single or double
screw extruder, a ram extruder or slurry pump.
The wrapper suitably has a thickness within the range
of 0.1-1.0 mm, although 2-3 mm may be desirable. The
thickness required depends on the weight and permeability of
the wrapper. Thus, a dense thin wrapper or a thick low
density wrapper could be provided, depending on the
composition of the wrapper materials.
Alternative setting methods for the wrapper include the
use of water scavenging substances. These substances remove
water from the wrapper slurry thereby, in effect, drying the
wrapper. For example, light magnesium oxide can be in the
wrapper slurry mixture at up to 45~ by weight of the dry
slurry constituents, depending on the residence time in the
extruder and the temperature in the extruder. The addition
of magnesium oxide can also have advantageous visible
sidestream reducing effects. Alternatively, the wrapper
material can be extruded into an ethanol bath, or other
strongly hydrophilic substance, the ethanol scavenging the
water from the extrudate. A further alternative is the
precipitation of an insoluble alginate from a soluble
alginate in the extruded wrapper. This can be achieved by,
for example, extruding a hollow tube of, for example, sodium
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alginate-containing wrapper material into a bath of simple
electrolyte(s), for example, 1. OM calcium chloride solution.
The calcium ions substitute for the sodium ions and cause
the extrudate to set extremely quickly. In the latter two
methods, spraying of the water scavenger onto the extrudate
or wrapper sheet may be carried out instead of passing the
extrudate into a bath.
Some precipitation can be achieved by adding a sub-
critical level of a precipitating agent into the extruder
barrel, then completely precipitating the structure by
raising the level of the precipitating agent post extrusion.
Other precipitation methods include precipitation of the
extrudate into a highly ionic electrolyte bath or into a
water miscible non-solvent for the alginate.
A further method includes, as briefly mentioned above
with respect to the binders, use of a conventionally
insoluble alginate as the binding material by rendering it
soluble with a solubilising agent and then setting of the
wrapper structure by removal of the solubilising agent or
addition of a sequestering agent.
These methods may be used sequentially, e.g. the
wrapper may be set by precipitating a soluble alginate
containing wrapper material in a bath containing calcium
ions. The extrudate may be subsequently passed into a bath
of water scavenging agent, such as ethanol, and then heated
to drive off liquid residues. Alternatively, after setting
the wrapper may be dried using the methods described above.
These methods are particularly effective for achieving
a good shape to the extrudate because of the speed of the
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reaction and the lack of volume reduction in the processes,
particularly the drying stages.
The wrapper may have a rigid structure, although we
have found that flexible wrappers can be produced using
sodium alginate as the binder, which is then precipitated to
form calcium alginate and then slowly dried. Flexibility is
advantageous in terms of the increased robustness of the
product during machine and manual handling.
The wrapper suitably has a air permeability within the
range of 1-300 Coresta Units (cc/min/lcm2/lOcm WG).
Permeability can be controlled by a number of methods, such
as coating an extrudate with a film forming or other
permeability reducing agent. Alternatively, sacrificial
molecules can be introduced into the wrapper mixture, which
molecules can be removed after the formation of the
structure by moderate temperature or chemical reaction to
increase the permeability of the wrapper structure.
Alternatively, the wrapper may be a cellulose-based
wrapper, such as conventional cigarette paper, which has
been treated to prevent the wrapper from burning and thereby
producing visible sidestream smoke. Preferably the treated
wrapper will char and therefore provide a visible burn line.
The paper should also produce an ash which can be knocked
off by the smoker.
The ashing characteristics of the wrapper should be
such that, unburnt, the wrapper is strong enough or flexible
enough to resist digital pressure prior to, and during
smoking, but upon thermal degradation of the wrapper the
structure is considerably weakened, leaving an ash which can
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be readily disintegrated by pressure or a flicking movement.
Some wrappers may require ash charring agents which char to
leave some black residue to simulate conventional cigarette
ash.
Fuel source
Preferably the fuel source extends continuously from
the mouth end of the smoking article to the lighting end
thereof, excluding any filter or mouthpiece element. In the
alternative, the fuel source may comprise a number of
sections closely located so that burning of the fuel source
does not cease.
Advantageously, the end of the article to be lit has
the appearance of a conventional article. Suitably the end
of the smoking article at the end to be lit is of a tobacco-
like or dark colour, e.g. brown.
The fuel source may be provided by three distinct
systems, but overlap may occur between them. In these
systems the fuel source is physically discrete from the
aerosol generating means.
When physically discrete from the aerosol generating
means and in the form of a rod, in a first system the fuel
source is suitably prepared from carbonaceous material by
pyrolysing wood, such as rods of balsa wood, cotton, rayon,
tobacco or other cellulosic containing material, which are
prepared to a shape which is particularly useful in the
present invention. In this system, the fuel source
comprises at least 85% by weight pyrolysed carbonaceous
material. Preferably the fuel source comprises at least 90%
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carbonaceous material. A burn promoter such as, for example,
potassium nitrate, potassium citrate or potassium chlorate,
is also advantageously present at 10% or less by weight of
the fuel source. Other suitable burn promoters would be
known to those skilled in the art. Alternatives for an
almost wholly carbon-containing system include the use of
carbon fibres or carbon aerogels.
The term 'carbon' as used herein can be taken to cover
a material which is substantially solely carbon and any
carbon precursors, such as carbonaceous material. As used
herein the term carbonaceous includes material which has
been pyrolysed, which material preferably contains carbon,
although some incomplete combustion products may still be
present. Ready pyrolysed coconut fibre may, for example, be
the carbonaceous material from which carbon is derived.
In a second system, the fuel source may be a
substantially inorganic system and comprise an inorganic,
non-combustible binder, selected from the list outlined
above with respect to the wrapper, for example, Portland
cement, or potassium silicate. The binder may be present
within the range of 10-65% by weight of the fuel source. The
binder is advantageously present in an amount of less than
40% by weight of the fuel source. The fuel source may also
comprise 5-20% of a burn promoter, preferably less than 10%,
by weight of the fuel source. The fuel source may comprise
25-70% carbon, advantageously at least 55% carbon, and more
suitably at least 60% carbon by weight of the fuel source.
However, we have found that acceptable combustion
characteristics can still be maintained with about 30%
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carbon, 60% inorganic, non-combustible binder and less than
about 10% burn promoter when the fuel source is provided as
a rod. A proportion of inorganic, non-combustible filler in
the range of 0-60% may also be incorporated in this
alternative to reduce the density of the fuel source or to
improve the strength of the fuel source.
The fuel source in this instance may, for example, be a
shaped rod of carbon having a porous structure to sustain
continuous combustion throughout the length of the fuel
source. Shaping techniques which do not disadvantageously
lose water during shaping of the rod are preferred. Shaping
of a thick slurry comprising carbon and a binder within a
hollow tube and removing the shaped rod from the tube after
a curing or setting stage is one method of fuel source
production. Alternatively, an extrusion process may be used.
In the third system, the fuel source is a partially
organic system and comprises 15-70% carbon, 84-5% non-
combustible inorganic filler material such as, for example,
one or more of the inorganic filler materials listed above
with respect to the wrapper, 0-5% plasticiser, such as
glycerol or other materials listed above with respect to the
outer wrapper, and 1-20% organic binder, such as cellulosic,
alginic or pectinaceous binders, for example, and/or the
other organic binders described above with respect to the
wrapper. A mixture of inorganic or organic binders may be
used, the inorganic binder being present within the range of
0-20% by weight of the fuel source. The plasticiser is
included to improve the mechanical strength and flexibility
of the fuel source and the amount present together with the
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amount of organic binder, should not provide a significant
quantity of mainstream smoke. A high level of organic
binder might be utilisable if the binder produces a low
level of mainstream smoke, i.e. particulate matter. The
amount of carbon is subject to the type and amount of binder
and/or filler utilised, thus the range above should not be
considered too limiting. The amount of carbon required will
also depend on the composition of the outer wrapper.
Furthermore, at low levels of carbon usage the outer wrapper
will need to be more permeable than at higher carbon levels.
Most suitably the carbon is present in the range of 25-35%.
Extrusion may be a low pressure extrusion through a
nozzle using a driving force not substantially greater than
atmospheric pressure, or a high pressure extrusion process.
Foaming of the extrudate to achieve a cellular structure may
be required, particularly in the second and third systems,
depending on final product design. In the second system,
foaming could be achieved by the introduction of air
entraining agents instead of a proportion of the inorganic,
non-combustible binder and/or the inorganic filler, if
present. The air-entraining agents can be powdered or
liquid additives or porous particulate materials. In the
third system when foaming is required it may be achieved by
the presence of, for example, a polysaccharide expansion
medium such as starch, and the expanding effect of water
under high temperature and pressure. The expansion medium
would replace the binder or the plasticiser or inorganic
filler, if present. Alternative expansion mediums, such as
pullulan or other polysaccharides, including cellulose
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derivatives, may be used. Other agents capable of causing
foaming may be solid foaming agents, such as sodium
bicarbonate, inorganic salts and organic acids providing in
situ gaseous agents; propane or isobutane as organic gaseous
agents; nitrogen, carbon dioxide or air as inorganic gaseous
agents; and volatile liquid foaming agents, such as ethanol
and acetone, for example. Polysaccharide expansion mediums
are preferred because of their ease of usage and safety
aspects.
Extrusion may produce thin elongate strands, which may
be longitudinally arranged, or more solid thicker rods,
preferably co-axially located within the smoking material
rod. In the first two alternatives, i.e. the pyrolysed
structure and the inorganic system, a central rod could be
replaced by several thinner strands. Extruded sheet may
also be produced, then shredded to produce cut filler
similar to cut tobacco filler. These processes are all
suitable for the production of the fuel source, the aerosol
generating means and the combined aerosol generating fuel
source to be described later. Band casting, heated drum
casting and other sheet making techniques can also be used.
In all of the above fuel source alternatives, except in
the pyrolysed rod embodiment, 0-2% fibre is optional. This
also applies to those methods of preparation of aerosol
generating means which involve casting or paper making
techniques.
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Aerosol generating means
The aerosol generating means may be provided by three
distinct systems, but overlap may occur between them.
The first system may be a substantially inorganic
system comprising 95-30% inorganic, non-combustible binder,
such as those binders described above with respect to the
fuel source, 0-65% non-combustible inorganic filler
material, such as those materials described above with
respect to the fuel source, and 5-30% aerosol forming means,
as described below.
The second system may be a partially inorganic system
comprising 1-25% organic binder, 45-94% non-combustible
inorganic filler material and 5-30% aerosol forming means.
The third system may be a partially organic system
comprising 1-25% organic binder, 1-94% organic filler
material, 0-93% inorganic filler material and 5-30% aerosol
forming means. Preferably the aerosol forming means
comprises 5-25% by weight of the mixture. These systems are
intended to be substantially non-combustible. The inorganic
filler material is therefore selected, in combination with
the proportions of the other materials, to provide
substantially non-combustible aerosol generating means.
Some inorganic fillers, such as perlite, magnesium hydroxide
and magnesium oxide, readily serve to render the aerosol
generating means non-combustible. Other fillers, such as
chalk, at some incorporation levels, do not detract from the
combustibility of the aerosol generating means and as such
are unsuitable at those levels.
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The organic filler material is preferably a material
other than tobacco and may include inorganic salts of
organic acids, or polysaccharide material, and should
provide smoke with an acceptable taste characteristic.
These two systems represent two ends of a spectrum in
which inorganic and organic components of the binder and
filler material can be gradually substituted for one
another. The third system may also incorporate an amount of
expansion medium, such as described above, as part of the
organic filler material. An example of foamed aerosol
generating means comprises 20% organic binder, 20% aerosol
forming means, 15% starch as an expansion medium and 45%
inorganic filler material. The aerosol generating means may
also comprise flavouring means.
A small amount of fibre material may also be required
in the above systems to assist in the formation of a sheet,
depending on the manner of manufacture.
The aerosol generating means preferably comprises
aerosol forming means, such as polyhydric alcohols,
glycerol, propylene glycol and triethylene glycol, for
example, or esters such as triethyl citrate or triacetin, or
high boiling point hydrocarbons.
Flavouring agents in the smoking material rod are
designed to contribute towards an aerosol which has a unique
but very acceptable taste and flavour characteristic to the
aerosol smoke. The taste and flavour may not necessarily be
designed to imitate tobacco smoke taste and flavour.
Flavouring agents may include tobacco extract flavours,
menthol, vanillin, toffee, chocolate or cocoa flavours, for
CA 02284230 1999-09-30
22
example. Colouring means, such as food grade dyes, for
example, or colourants such as liquorice, caramel or malt,
or extracts thereof, may be used to darken the colour of the
filler material. The presence of vermiculite or other
inorganic material, such as iron oxide, may also give a
darker colour to the filler material of the smoking article.
Flavouring agents may also be incorporated on or into a
substrate, which may be the aerosol generating means and/or
the fuel source, at a location close to or at the mouth end
of the smoking material rod of the smoking article, or along
the length of the smoking material rod provided that they
are not affected by combustion temperatures. The
percentages given above are given without the addition of
any flavouring agent. These percentages will be
consequently reduced by the addition of flavouring agents.
Where inorganic or organic filler material is present in the
aerosol generating means or fuel source, the percentages of
these elements would be decreased as flavourants increased.
Where filler material is not present, either the carbon or
aerosol forming means would be consequently reduced as the
flavourants increased.
As mentioned above, the aerosol generating means may be
formed by conventional paper-making techniques or by
extrusion techniques. The sheet material may be cut or
rolled. The inorganic filler materials of these systems can
be used in the system mixtures without pre-treatment stages
before providing a complete aerosol generating mixture.
CA 02284230 1999-09-30
23
Aerosol generating fuel source
As described above both of the fuel source and the
aerosol generating means are kept substantially separate
from oneanother, each forming a distinct area of either fuel
source or aerosol generating means. In some instances
though it may be advantageous to combine the two elements.
This can be done by mixing physically discrete fuel source
and aerosol generating material or by producing a totally
combined aerosol generating fuel source. In the first case,
a preferred embodiment is mixing the fuel source as cut
filler material with aerosol generating means as cut filler
material. Thus, an aerosol generating fuel source
comprising a mixture of physically discrete individual cut
filler material is provided, which filler material extends
the full length of the smoking material rod. This embodiment
is particularly advantageous in that it can be made in a
manner very similar to conventional cigarette making
procedures by providing a mixture of cut filler material to
a cigarette making machine. In the second case, carbon is
added to the aerosol generating means composition.
The aerosol generating fuel source may be provided by
three distinct systems, but overlap may occur between them.
The first system is a predominantly inorganic system
comprising 0-35% inorganic filler material, 5-30% aerosol
forming means, 30-60% inorganic binder, 30-65% carbon and 0-
10% burn promoter. The aerosol forming means is selected
from the group outlined above with respect to the aerosol
generating means. The other components are also to be
selected from the respective groups outlined above with
CA 02284230 1999-09-30
24
respect to the other elements of the invention. This also
applies to the systems described below.
The second system is a partially inorganic system
comprising 86-0% inorganic filler material, 5-30% aerosol
forming means, 1-25% organic binder and 8-60% carbon.
The third system is a more organic system comprising
93-0% organic filler material, 0-93% inorganic filler
material, 5-30% aerosol forming means, 1-25% organic binder
and 1-60% carbon. The more organic system may be foamed by
the presence of an expansion medium and/or expansion agent,
at the levels described above.
Preferably the aerosol forming means comprises 5-25% by
weight of the mixture.
The binders and aerosol forming means for the above
aerosol generating fuel sources may be any one or more of
the binders or aerosol forming means exemplified above.
With the increase in organic components and the
respective increase in sidestream, the permeability of the
outer wrapper must be controlled to reduce the visible
sidestream given off by this fuel source composition or, as
described below, sidestream reducing agents can be added to
the wrapper to reduce the amount of particulate matter
forming the sidestream smoke. The thickness of the outer
wrapper can also be varied to reduce visible sidestream
smoke.
Structure of Article
The smoking article may be provided in a number of
physical structures. In all three fuel source systems the
CA 02284230 1999-09-30
fuel source may be provided as a longitudinally extending
rod, strands or filaments, advantageously located co-axially
of the smoking article. The rods, strands or filaments can
be of various shapes, e.g. round, square, star or polygonal,
all of which may be hollow or solid, and may be co-axially
clustered. In the second and third system the fuel source
may also be a sheet material which can be cut to produce
shreds. Material of the third system may also be rolled to
the desired shape.
When the fuel source is provided as a central rod of
either carbonised wood or an extruded rod of the second or
third fuel systems, i.e. a cement/carbon fuel source or the
partially organic fuel system, the aerosol generating means
may be an annulus of cut aerosol generating material or a
roll of such material, rolled to provide a sufficient
annular density to support the fuel rod, while still
allowing air to be drawn through the article by the smoker.
A preferred option is to provide the rod filler
material as a cut filler material. In one case, there may
be provided a central core of cut fuel material surrounded
by an annulus of cut aerosol generating material. This
arrangement can also be provided with the aerosol generating
means as the core material and the fuel source as the
annulus material. Known techniques for producing co-axial
structures for cut filler material can be used, e.g.
providing a small dimension first wrapped rod which is fed
to a further garniture and cut filler material is arranged
around the first rod.
CA 02284230 1999-09-30
26
In the alternative, if an aerosol generating fuel
source is provided, discrete cut aerosol generating means
may be intimately mixed with discrete cut fuel source
material.
The overall percentages of mixed cut fuel source
material and cut aerosol generating material preferably
falls within the range of 30-35% carbon, 5-10% binder, 0-2%
fibre, 5-10% plasticiser and 40-60% inorganic material.
This range may be comprised of the individual sheets of
material having the following compositions:
Fuel source: 60-70% carbon, 7% propylene glycol
alginate binder, 1% fibre and 32-22% perlite inorganic
material.
Aerosol generating means: 7% propylene glycol alginate
binder, 1% fibre, 15% glycerol plasticiser and 77% perlite
inorganic material.
These materials would typically be mixed in the ratio
of 1:l. Other ratios of mixing could be used to give the
desired overall range of components described above.
If the aerosol generating means and fuel source are
actually combined together chemically, the sheet material
may be cut and provided within the outer wrapper as cut
filler material. It may be desirable to increase the
proportion of fuel material in a further combined sheet
material, and to provide this material as a central region
of higher carbon density surrounded by a less carbon-
containing combined cut sheet material.
When the fuel and aerosol components are produced by
extrusion methods, they may be provided as rods, strands or
CA 02284230 1999-09-30
27
filaments. A coaxial core of several strands (or rods or
filaments) may be provided of fuel material surrounded by an
annulus of gathered strands of aerosol generating means.
The vice versa arrangement is also possible as above. A
further arrangement is the intimate inter-mixing of strands
of discrete fuel source and aerosol generating means within
the outer wrapper. The rods, strands or filaments may also
be comprised of the chemically combined aerosol generating
fuel source material. These extruded rods, strands or
filaments may all be somewhat foamed, if desired.
Where foaming to provide a cellular structure is
desired, a core of foamed fuel source may be surrounded by
an annulus of foamed aerosol generating means. This may be
produced by co-extrusion techniques using cross-head dies,
for example. The vice versa arrangement is also possible.
It is also possible in all of the above structural
embodiments that only one of the core or annulus material is
foamed.
Smoking article
Advantageously the smoking article incorporates a
filter element which may be conventional fibrous cellulose
acetate, polypropylene or polyethylene material or gathered
paper material. Multiple filter elements may also be
utilised. Filter elements having particular pressure drop
characteristics, such as the filter sold by Filtrona and
known as The Ratio Filter, may also be utilised. Disposed
upon or within the material of the filter element may be
further flavouring materials, as described above, which are
CA 02284230 1999-09-30
28
released or eluted from the filter element by the aerosol
generated by the heated or burnt aerosol generation means.
Disposed about the fuel source at the mouthend thereof
and/or between the fuel source and the filter element may be
a firebreak. The firebreak may suitably comprise a more
densely packed region of the material comprising the aerosol
generating means. Preferably the firebreak also comprises
aerosol forming means to enhance the delivery of aerosol to
the smoker, as well as protecting the smoker from
potentially over-hot smoke as the length of the smoking
article decreases. Alternatively, the firebreak may
comprise a band of burn retarding material on the exterior
of the wrapper, for example. The firebreak may be
substantially combustible or substantially non-combustible
material.
The proportions of the non-inorganic materials are
selected to give a smoking article which exhibits extremely
low visible sidestream smoke. A conventional smoking
article comprises cut tobacco wrapped in a paper wrapper. A
smoking article which exhibits low visible sidestream smoke
is required to give a reduction of at least 30% in rate of
sidestream particulate matter, known as NFDPM (nicotine
free, dry particulate matter) emission, in order for there
to be a reduction in visible sidestream which is visible to
the naked eye. European Patent Application, Publication No.
0 404 580 describes a smoking article having a paper wrapper
which is extremely effective in reducing visible sidestream
smoke. Reductions in visible sidestream particulate matter
of up to 60% against control cigarettes without the
CA 02284230 1999-09-30
29
inventive papers are achievable with smoking articles
incorporating the paper according to that application. When
smoking articles according to the present invention and
cigarettes according to EPA 0 404 580 are smoked head to
head, smoking articles according to the present invention
have even less visible sidestream than the cigarettes of EPA
0 404 580. Smoking articles of the present invention are
thus effective to provide visible sidestream reductions far
greater than any other smoking article available at the
present time.
Smoking articles according to the present invention
preferably comprise at least 50% by weight of the article as
inorganic material.
In order that the present invention may be easily
understood and readily carried into effect, reference will
now be made, by way of example to the following diagrammatic
drawings, in which:
Figure 1 shows, in longitudinal cross-section, a
smoking article according to the present invention,
Figure la shows, in axial cross-section, another
embodiment of a smoking article according to Figure 1,
Figure 2 shows, in longitudinal cross-section, a
further smoking article according to the present invention,
Figure 3 shows, in longitudinal cross-section a yet
further embodiment according to the present invention, and
Figure 4 shows another embodiment of the present
invention in longitudinal cross-section.
One embodiment of a smoking article of the present
invention is depicted in Figure 1 of the drawings hereof.
CA 02284230 1999-09-30
Figure 1 shows a cigarette 1 comprising a smoking material
rod 2 and a filter element 3. The filter element 3 is
composed of conventional fibrous cellulose acetate tow but
may be of any other type of fibrous material with
conventional pressure drop and filtration efficiency, or a
high pressure drop, low filtration efficiency, non-fibrous
material, if appropriate. The filter element 3 is attached
to the smoking material rod 2 by a tipping wrapper 4. The
filter element 3 may be ventilated, either using ventilation
perforations produced by laser for example, or by means of
the natural permeability of the tipping wrapper 4 and any
underlying plugwrap. The smoking material rod 2 comprises
an exterior wrapper 5, a co-axially located combustible fuel
source 6 and cut smoking material 7 disposed between the
fuel source 6 and the wrapper 5.
The exterior wrapper 5 comprises 1% fibre, 4% propylene
glycol alginate as a combustible binder, 5% glycerol as a
plastisicer and 90% perlite as an inorganic non-combustible
filler material. The exterior wrapper 5 has a white colour,
is about lmm in thickness, and looks very similar to the
paper wrapper of a conventional smoking article, or
cigarette.
The co-axial fuel source 6 was produced in accordance
with the first fuel system above by pyrolysing a circular
rod of balsa wood having a diameter of about 4mm. The shape
of the balsa wood rod is ideal for the purpose of providing
an elongate, circular fuel source. The pyrolysed rod has an
acceptable strength and is quite robust when surrounded by
the cut smoking material 7. The density of the initial rod,
CA 02284230 1999-09-30
31
and also in its final form, is important. We have found
that if the fuel source is too dense after pyrolysation
insufficient oxygen reaches the interior thereof and
therefore the fuel source will not continue to burn. On the
other hand, if the density of the pyrolysed fuel source is
too low then the fuel source combusts too actively and thus
too rapidly. Balsa and ash have been found to be the more
suitable woods for use in this invention, though other wood
species may be found to be appropriate.
The smoking material 7 is an aerosol generating means
consisting of a high proportion of non-combustible,
inorganic material, namely 80% perlite, 12% glycerol aerosol
forming means, 7% propylene glycol alginate binder and 1%
fibre, i.e. the partially inorganic system. The smoking
material is produced by forming a slurry of the components
and making a reconstituted sheet in accordance with standard
sheet making techniques. The sheet of reconstituted
inorganic material is then cut to provide cut filler
material 7 and is disposed about the pyrolysed balsa wood
fuel source 6.
At the mouth end of the smoking article there is
located a region 9 of aerosol generating means onto which
has been deposited flavouring agents, such as vanilla and
toffee, for example. More of these flavouring agents were
disposed within the filter element 3.
In operation, the cigarette 1 is lit and the cigarette
burns along the fuel source length producing very little
visible sidestream smoke. The visible sidestream smoke
produced is derived from the organic components in the
CA 02284230 1999-09-30
32
smoking article and is most visible at the end of a puff.
The substantially non-combustible wrapper chars to produce a
frangible, white ash, similar to conventional cigarette ash
and which can be tapped off by the smoker, as required. The
non-combustible exterior wrapper 5 upon charring also
produces a dark burn line which advances along the smoking
article as burning progresses. The smoking article burns
back along the fuel source 6. As burning occurs an aerosol
is produced from the aerosol-generating cut smoking material
7, which aerosol is drawn into the smoker's mouth. The
aerosol, in this instance, is predominantly glycerol and
water but also comprises vanilla and toffee flavours. Other
flavours such as tobacco extracts, nicotine compounds, or
other tobacco-like flavours, give the aerosol an acceptable
taste and quality but without burning any tobacco material.
Additional flavour material is also carried on the filter
element, which material is designed to be released upon the
approach of 'smoke' or aerosol from the burning aerosol-
generating smoking material rod 2, Filter flavourant is not
always required if sufficient flavour material is held in
the aerosol generating means.
Figure la shows a very similar embodiment to Figure 1
except that in this cigarette, instead of the smoking
material rod 2 incorporating cut smoking material 7, the
smoking material 7' is present as a rolled sheet 8 of
smoking material which is rolled about the longitudinal
length of the fuel source 6. The rolled sheet 8 of the
smoking material 7' is attached by a line or band of
adhesive, such as propylene glycerol alginate, extending
CA 02284230 1999-09-30
33
along the length of the fuel source 6. The rolled sheet 8
of smoking material must be rolled to allow air to pass to
the burning coal of the cigarette 1.
The smoking article 10 depicted in Figure 2 has a
similar structural arrangement to that of Figure 1.
Identical elements of the cigarette 11 have been given the
reference numerals of Figure 1 increased by ten.
In this embodiment the wrapper 15 comprised 1% fibre,
4.5% propylene glycol alginate and 94.5% perlite inorganic,
non-combustible filler material. No plasticiser was present
in the wrapper.
The fuel source 16 of this embodiment is comprised of
combustible material held together with a non-combustible
binder. The fuel source 16 comprises carbon in the form of
pyrolysed coconut fibre, Portland cement and a small amount
of potassium nitrate burn promoter in the ratio of 8:4:1
respectively. The fuel source 16 was produced by hydrating
the cement with a 1.3M solution of potassium nitrate
sufficient to form a slurry, adding the powdered carbon to
the slurry with a small amount of detergent to 'wet' the
carbonaceous material, and additional water to provide a
slurry of mud-like consistency. A rod of fuel material was
formed by shaping the slurry mixture within a hollow tube,
the shaped rod being expelled from within the tube once the
rod had sufficient mechanical strength after a period of
drying, curing or setting. Any excess moisture is driven
off by heating after removal from the hollow tube. The fuel
source 16 had a diameter of about 4mm. Surrounded by filler
material 17 the fuel source 16 is quite robust and is well
CA 02284230 1999-09-30
34
able to withstand normal handling in the packing process and
by the consumer.
In this embodiment, cocoa flavour was provided at a
downstream location of the aerosol generation means 17 and
within the filter element 13.
The smoking article 20 depicted in Figure 3 is a
further refinement of the embodiment of Figure 2. Reference
numerals referring to identical elements have again been
increased by ten. In this cigarette 21 the smoking material
rod 22 comprises cut smoking material 27 disposed about a
carbon fuel source 26. The exterior wrapper 25 is composed
of two layers. An inner layer 40 is composed of the wrapper
material described in Figures 1 and 2. An outer layer 41 is
comprised of a coating of a visible sidestream reducing
filler, such as magnesium oxide bound by a small amount of
propylene glycol alginate. The proportions of the wrapper
in total were 79.5% perlite, 1% fibre, 4.5% propylene glycol
alginate and 15% magnesium oxide. The magnesium oxide
coating is capable of further reducing the visible
sidestream smoke emanating from the smoking article 10 of
Figure 2, for example. Indeed, the visible sidestream smoke
from smoking article 20 is virtually non-existent. However,
the exterior wrapper 25 still produces a dark burn line, the
advance of which enables the smoker to determine whether the
cigarette 21 is, in fact, alight and to thereby monitor the
progress of combustion.
In the alternative to a coating of visible sidestream
reducing filler, the visible sidestream reducing filler may
be included in the wrapper furnish to form a single wrapper.
CA 02284230 1999-09-30
A typical composition of the treated wrapper 25 consists of
87.5% perlite inorganic material, 4% propylene glycol
alginate binder, 7.5% magnesium oxide visible sidestream
reducing filler and 1% fibre. Levels of 15% magnesium oxide
have been used effectively with 80% perlite.
In this embodiment, tobacco extract flavours were
disposed within the filter element 23.
The drawing of Figure 4 shows a further embodiment of
the invention in which reference numerals which refer to the
same features as in Figure 3 have been increased by ten.
The smoking material rod 32 of cigarette 31 comprised a
wrapper 35 enclosing cut smoking material which is also
combined with fuel means to provide an aerosol generating
fuel source 37. The aerosol generating fuel source 37
together comprises a lengthwise extending fuel source and
lengthwise aerosol extending generation means. The aerosol
generating fuel source 37 comprises 55% carbon (pyrolysed
coconut fibre), 12% glycerol aerosol forming means, 7%
propylene glycol alginate binder, 1% fibre and 25% perlite
inorganic material, i.e. the partially inorganic system.
This material is produced using the reconstituted sheet
method described above and casting either on a drum or band
caster. At one end of the aerosol generating fuel source 37
there was applied chocolate and mint flavours. Flavour
material was also present in the filter element 33.
Examples of another aerosol generating fuel source from
the second aerosol generating fuel source system were also
produced which comprised as little as 10% carbon and 70%
CA 02284230 1999-09-30
36
perlite inorganic material. The other proportions remained
the same as above.
The wrapper 35 in this embodiment had the composition
of 4.5% propylene glycol alginate binder and 94.5% perlite
inorganic non-combustible filler material in one instance.
In another instance, the wrapper had the composition of 4%
propylene glycol alginate, 5% glycerol plasticiser and 90%
perlite.
All of the aerosol generating compositions described
above may be modified in colour by replacing up to 10% of
the inorganic filler material with a colourant, such as
caramel or liquorice or extracts thereof.
The percentages given in this specification are on a
dry weight basis. The amount of water required to make a
suitable slurry of solid components amounting to 5008
(including glycerol) is usually about 1200m1.
The following tables give further details of
embodiments prepared to illustrate the invention.
Table 1 gives details regarding the influence of
material formulation on the physical properties of the
outer.
A slurry was prepared from hydrated binder and
inorganic material to the recipe given in Table 1. Outer
wrappers were made from the slurry to a length of 70mm and
0.5mm wall thickness by use of a ram extruder. The outer
wrappers were dried at exit from the extruder die by use of
two infra-red heaters placed 5-lOcm from the extrudate. The
physical properties of the outer wrappers are detailed in
Table 1.
CA 02284230 1999-09-30
37
Table 2 gives details regarding the influence of
process conditions on the efficiency of setting outer
wrappers using calcium chloride solution.
A slurry was prepared from lOg sodium alginate, 45g
chalk and 45g perlite in 200m1 of water. A ram extruder was
filled with the slurry and the outer wrappers were prepared
by extrusion of the slurry through an 8mm outer diameter,
7mm inner diameter torpedo die into calcium chloride
solution. Firmness of the outer was judged subjectively by
a panel of three individuals, on a ten point scale running
from 1 (indicating that the extrudate was completely
unchanged by immersion in the bath) to 10 (indicating that
the extrudate was completely set and rigid).
The Table illustrates that as the number of uses of the
bath is increased, the firmness of the outer wrapper
decreases. The firmness of the outer wrapper increases as
the concentration of the electrolyte solution increases and
as immersion time increases.
Table 3 gives details of the combustion limits of
carbon and glycerol based aerosol generating fuel sources
using a single strand of extruded material of l.OOmm
diameter.
Table 4 shows the effect of binder type on the
combustion characteristics of a variety of carbon and
glycerol based aerosol generating fuel sources using single
strands of extruded material of l.OOmm diameter. Some
binders are more combustible then others and therefore
influence the proportions of material used in the aerosol
generating fuel source.
CA 02284230 1999-09-30
38
Table 5 shows the effect of filler type on the
combustion characteristics of a variety of carbon and
glycerol based aerosol generating fuel sources using single
strands of extruded material of l.OOmm diameter. Some
inorganic filler materials facilitate combustion of a range
of aerosol generating fuel source mixtures. Chalk is the
preferred filler over the ranges illustrated. This table
should not necessarily be taken to indicate that the fillers
used in mixtures outside these illustrated ranges would not
burn.
The tests performed for Tables 3, 4 and 5 were
performed on single strands smouldering in free air rather
than on a number of strands within an outer wrapper in order
to exclude any influence on the combustion of the strands
due to the properties of the outer wrapper.
Table 6 gives smoke yields from filter-tipped
cigarettes which had the following construction:
A 5mm filter was obtained from a State Express
International cigarette, the filter comprising fibrous
cellulose acetate of 2.8 filament denier of Y cross-section,
34,000 total denier and having a pressure drop of l3mm WG.
The substantially non-combustible outer wrapper was
extruded using a ram extruder through an 8mm outer diameter,
7mm inner diameter torpedo die and the aerosol generating
fuel source was extruded as l.OOmm diameter strands from a
ram extruder, the strands being gathered together and
inserted into dried extruded outer wrappers. The cigarette
rod length, i.e. excluding the filter element, was 67mm.
One cigarette of each was smoked under standard machine
CA 02284230 1999-09-30
39
smoking conditions in which a 35cm3 puff of two seconds
duration is taken every minute.
The first five examples of Table 4 illustrate that
carbon fuel strands will burn without producing significant
levels of total particulate matter (TPM) even with organic
material (PGA) in the fuel strands.
The cigarettes according to the invention have very low
visible sidestream smoke levels. However, the nature of the
sidestream smoke from the inventive articles does not render
the conventional fishtail sidestream measuring apparatus
described in Analyst, October 1988, Volume 113, pp 1509-1513
a suitable measuring apparatus. We are thus unable to
provide yield details in this respect.
CA 02284230 1999-09-30
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