U.S. patent application number 17/413315 was filed with the patent office on 2022-01-20 for aerosol-generating article with ventilated hollow segment.
This patent application is currently assigned to Philip Morris Products S.A.. The applicant listed for this patent is Philip Morris Products S.A.. Invention is credited to Jerome UTHURRY.
Application Number | 20220015414 17/413315 |
Document ID | / |
Family ID | |
Filed Date | 2022-01-20 |
United States Patent
Application |
20220015414 |
Kind Code |
A1 |
UTHURRY; Jerome |
January 20, 2022 |
AEROSOL-GENERATING ARTICLE WITH VENTILATED HOLLOW SEGMENT
Abstract
An aerosol-generating article for producing an inhalable aerosol
upon heating is provided, the article including: a rod of
aerosol-generating substrate; a mouthpiece segment including a plug
of filtration material and being disposed downstream of and in
longitudinal alignment with the rod; a hollow tubular segment
between and in longitudinal alignment with the rod and the
mouthpiece segment, the hollow tubular segment defining a cavity
extending to an upstream end of the mouthpiece segment; and a
ventilation zone at a location along the hollow tubular segment,
the rod of aerosol-generating substrate including at least an
aerosol former, the rod having an aerosol former content of at
least 10 percent on a dry weight basis.
Inventors: |
UTHURRY; Jerome; (Neuchatel,
CH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Philip Morris Products S.A. |
Neuchatel |
|
CH |
|
|
Assignee: |
Philip Morris Products S.A.
Neuchatel
CH
|
Appl. No.: |
17/413315 |
Filed: |
December 20, 2019 |
PCT Filed: |
December 20, 2019 |
PCT NO: |
PCT/EP2019/086801 |
371 Date: |
June 11, 2021 |
International
Class: |
A24D 1/20 20060101
A24D001/20; A24D 1/02 20060101 A24D001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 20, 2018 |
EP |
18214929.4 |
Claims
1.-15. (canceled)
16. An aerosol-generating article for producing an inhalable
aerosol upon heating, the aerosol-generating article comprising: a
rod of aerosol-generating substrate; a mouthpiece segment
comprising a plug of filtration material, the mouthpiece segment
being disposed downstream of the rod and in longitudinal alignment
with the rod; a hollow tubular segment at a location between the
rod and the mouthpiece segment, the hollow tubular segment being in
longitudinal alignment with the rod and the mouthpiece segment,
wherein the hollow tubular segment defines a cavity extending to an
upstream end of the mouthpiece segment; and a ventilation zone at a
location along the hollow tubular segment, wherein the rod of
aerosol-generating substrate has a length of less than 35
millimetres; wherein an equivalent internal diameter of the hollow
tubular segment at the location of the ventilation zone is at least
5.5 millimetres, wherein the rod of aerosol-generating substrate
comprises at least an aerosol former, the rod of aerosol-generating
substrate having an aerosol former content of at least 10 percent
on a dry weight basis, and wherein the aerosol-generating article
has an overall RTD of less than 70 millimetres H.sub.2O (700
Pa).
17. The aerosol-generating article according to claim 16, wherein
the hollow tubular segment comprises a wrapper circumscribing the
rod and the mouthpiece segment.
18. The aerosol-generating article according to claim 16, wherein
the hollow tubular segment comprises a tube formed from a
cellulosic material.
19. The aerosol-generating article according to claim 18, further
comprising a wrapper circumscribing the rod, the tube, and the
mouthpiece segment.
20. The aerosol-generating article according to claim 16, wherein
an equivalent internal diameter of the hollow tubular segment is
substantially constant along a length of the hollow tubular
segment.
21. The aerosol-generating article according to claim 16, wherein
the ventilation zone is at a location along the hollow tubular
segment at least 2 millimetres from the upstream end of the
mouthpiece segment.
22. The aerosol-generating article according to claim 16, wherein
the aerosol-generating article has a ventilation level of at least
10 percent.
23. The aerosol-generating article according to claim 16, wherein
the aerosol-generating article has a ventilation level of less than
60 percent.
24. The aerosol-generating article according to claim 16, wherein
the hollow tubular segment has a length of between 10 millimetres
and 30 millimetres.
25. The aerosol-generating article according to claim 16, wherein a
thickness of a peripheral wall of the hollow tubular segment at the
location of the ventilation zone is less than 1.5 millimetres.
26. The aerosol-generating article according to claim 16, wherein a
thickness of the hollow tubular segment is at least 100
micrometres.
27. The aerosol-generating article according to claim 16, wherein
an RTD of the aerosol-generating article is at least 30 millimetres
H.sub.2O (300 Pa).
Description
[0001] The present invention relates to an aerosol generating
article comprising an aerosol-generating substrate and adapted to
produce an inhalable aerosol upon heating.
[0002] Aerosol-generating articles in which an aerosol-generating
substrate, such as a tobacco-containing substrate, is heated rather
than combusted, are known in the art. Typically in such heated
smoking articles, an aerosol is generated by the transfer of heat
from a heat source to a physically separate aerosol-generating
substrate or material, which may be located in contact with,
within, around, or downstream of the heat source. During use of the
aerosol-generating article, volatile compounds are released from
the aerosol-generating substrate by heat transfer from the heat
source and are entrained in air drawn through the
aerosol-generating article. As the released compounds cool, they
condense to form an aerosol.
[0003] A number of prior art documents disclose aerosol-generating
devices for consuming aerosol-generating articles. Such devices
include, for example, electrically heated aerosol-generating
devices in which an aerosol is generated by the transfer of heat
from one or more electrical heater elements of the
aerosol-generating device to the aerosol-generating substrate of a
heated aerosol-generating article.
[0004] Substrates for heated aerosol-generating articles have, in
the past, typically been produced using randomly oriented shreds,
strands, or strips of tobacco material. As an alternative, rods for
heated aerosol-generating articles have been proposed, for example
in international patent application WO-A-2012/164009, that are
formed from gathered sheets of tobacco material. The rods disclosed
in WO-A-2012/164009 have a longitudinal porosity that allows air to
be drawn through the rods. Effectively, folds in the gathered
sheets of tobacco material define longitudinal channels through the
rod.
[0005] Alternative rods for heated aerosol-generating articles are
known from international patent application WO-A-2011/101164. These
rods are formed from strands of homogenised tobacco material, which
may be formed by casting, rolling, calendering or extruding a
mixture comprising particulate tobacco and at least one aerosol
former to form a sheet of homogenised tobacco material. In an
alternative embodiments, the rods of WO-A-2011/101164 may also be
formed from strands of homogenised tobacco material obtained by
extruding a mixture comprising particulate tobacco and at least one
aerosol former to form continuous lengths of homogenised tobacco
material.
[0006] Substrates for heated aerosol-generating articles typically
further comprise an aerosol former, that is, a compound or mixture
of compounds that, in use, facilitates formation of the aerosol and
that preferably is substantially resistant to thermal degradation
at the operating temperature of the aerosol-generating article.
Examples of suitable aerosol-formers include: polyhydric alcohols,
such as propylene glycol, triethylene glycol, 1,3-butanediol and
glycerin; esters of polyhydric alcohols, such as glycerol mono-,
di- or triacetate; and aliphatic esters of mono-, di- or
polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl
tetradecanedioate.
[0007] It is also common to include in an aerosol-generating
article for producing an inhalable aerosol upon heating one or more
additional elements that are assembled with the substrate in a same
wrapper. Examples of such additional elements include a mouthpiece
filtration segment, a support element adapted to impart structural
strength to the aerosol-generating article, a cooling element
adapted to favour cooling of the aerosol prior to reaching the
mouthpiece, and so forth. However, although the inclusion of such
additional elements has been proposed in view of their advantageous
effects, it generally complicates the overall structure of the
aerosol-generating article and makes it manufactures more complex
and costly. In fact, manufacturing such multi-element
aerosol-generating articles typically requires rather complex
making machinery and combining machinery.
[0008] In view of this, aerosol-generating articles have also been
proposed that have a simpler structure. However, in the absence of
certain additional components, such as, for example,
an-aerosol-cooling element, it may become more difficult to
manufacture aerosol-generating articles that consistently provide
the consumer with a satisfactory aerosol delivery and RTD.
[0009] Thus, it would be desirable to provide an aerosol generating
article that enables the provision of a consistently satisfactory
aerosol delivery to the consumer during use. Further, it would be
desirable to provide one such improved aerosol-generating article
that has a satisfactory RTD value. It would be equally desirable to
provide one such aerosol-generating article that can be
manufactured efficiently and at high speed, preferably with a low
RTD variability from one article to another. The present invention
aims at providing a technical solution adapted to achieve at least
one of the desirable results described above.
[0010] According to an aspect of the present invention, there is
provided an aerosol-generating article for producing an inhalable
aerosol when heated, the aerosol-generating article comprising: a
rod of aerosol-generating substrate; a mouthpiece segment
comprising a plug of filtration material, the mouthpiece segment
being arranged downstream of the rod and in longitudinal alignment
with the first segment; and a hollow tubular segment at a location
between the rod and the mouthpiece segment. The hollow tube segment
is in longitudinal alignment with the rod and the mouthpiece
segment. Further, the hollow tubular segment defines a cavity
extending all the way to an upstream end of the mouthpiece segment.
The aerosol-generating article further comprises a ventilation zone
at a location along the hollow tubular segment. An equivalent
internal diameter of the hollow tubular segment at the location of
the ventilation zone is at least about 5 millimetres. The rod of
aerosol-generating substrate comprises at least an aerosol former,
the rod of aerosol-generating substrate having an aerosol former
content of at least about 10 percent on a dry weight basis.
[0011] The term "aerosol generating article" is used herein to
denote an article wherein an aerosol generating substrate is heated
to produce an deliver inhalable aerosol to a consumer. As used
herein, the term "aerosol generating substrate" denotes a substrate
capable of releasing volatile compounds upon heating to generate an
aerosol.
[0012] A conventional cigarette is lit when a user applies a flame
to one end of the cigarette and draws air through the other end.
The localised heat provided by the flame and the oxygen in the air
drawn through the cigarette causes the end of the cigarette to
ignite, and the resulting combustion generates an inhalable smoke.
By contrast, in heated aerosol generating articles, an aerosol is
generated by heating a flavour generating substrate, such as
tobacco. Known heated aerosol generating articles include, for
example, electrically heated aerosol generating articles and
aerosol generating articles in which an aerosol is generated by the
transfer of heat from a combustible fuel element or heat source to
a physically separate aerosol forming material. For example,
aerosol generating articles according to the invention find
particular application in aerosol generating systems comprising an
electrically heated aerosol generating device having an internal
heater blade which is adapted to be inserted into the rod of
aerosol generating substrate. Aerosol generating articles of this
type are described in the prior art, for example, in EP
0822670.
[0013] As used herein, the term "aerosol generating device" refers
to a device comprising a heater element that interacts with the
aerosol generating substrate of the aerosol generating article to
generate an aerosol.
[0014] In the present specification, the term "tubular segment" is
used to denote an elongate element defining a lumen or airflow
passage along a longitudinal axis thereof. In particular, the term
"tubular" will be used in the following with reference to a tubular
element having a substantially cylindrical cross-section and
defining at least one airflow conduit establishing an uninterrupted
fluid communication between an upstream end of the tubular element
and a downstream end of the tubular element. However, it will be
understood that alternative geometries of the cross-section of the
tubular element may be possible.
[0015] As used herein, the term "longitudinal" refers to the
direction corresponding to the main longitudinal axis of the
aerosol-generating article, which extends between the upstream and
downstream ends of the aerosol-generating article. As used herein,
the terms "upstream" and "downstream" describe the relative
positions of elements, or portions of elements, of the
aerosol-generating article in relation to the direction in which
the aerosol is transported through the aerosol-generating article
during use.
[0016] During use, air is drawn through the aerosol-generating
article in the longitudinal direction. The term "transverse" refers
to the direction that is perpendicular to the longitudinal axis.
Any reference to the "cross-section" of the aerosol-generating
article or a component of the aerosol-generating article refers to
the transverse cross-section unless stated otherwise.
[0017] The term "length" denotes the dimension of a component of
the aerosol-generating article in the longitudinal direction. For
example, it may be used to denote the dimension of the rod or of
the elongate tubular elements in the longitudinal direction.
[0018] The term "thickness of a peripheral wall of the tubular
element" is used in the present specification to denote the minimum
distance measured between the outer surface and the inner surface
of the wall delimiting peripherally the tubular element. In
practice, the distance at a given location is measured along a
direction locally substantially perpendicular to the outer surface
and the inner surface of the tubular element. For a tubular element
having a substantially circular cross-section, the distance is
measured along a substantially radial direction of the tubular
element.
[0019] In some embodiments, the thickness of the peripheral wall of
the tubular element is constant. In alternative embodiments, the
thickness of the peripheral wall of the tubular element varies
along the length of the tubular element. This may be because the
tubular element is formed from a material having an irregular
surface finish (for example, the tubular element is provided in the
form of a cellulose acetate tube). Alternatively, this may be
because the tubular element is designed to include a tapered
section or the like. In embodiments wherein the thickness of the
peripheral wall of the tubular element varies along the length of
the tubular element, the "thickness of a peripheral wall of the
tubular element" is taken as the average value calculated on the
basis of several values measured as the minimum distance between
the outer surface and the inner surface of the wall at different
locations along the length of the tubular element.
[0020] In any embodiment, a particularly significant parameter is
the thickness of the peripheral wall of the tubular element at the
location of the ventilation zone.
[0021] The expression "air-impervious material" is used throughout
this specification to mean a material not allowing the passage of
fluids, particularly air and smoke, through interstices or pores in
the material. If the hollow tubular segment is formed of a material
impervious to air and aerosol particles, air and aerosol particles
drawn through the hollow tubular segment are forced to flow through
the airflow conduit internally defined by the hollow tubular
segment, but cannot flow across the peripheral wall of the hollow
tubular segment.
[0022] As used in the present specification, the term "homogenised
tobacco material" encompasses any tobacco material formed by the
agglomeration of particles of tobacco material.
[0023] Sheets or webs of homogenised tobacco material are formed by
agglomerating particulate tobacco obtained by grinding or otherwise
powdering of one or both of tobacco leaf lamina and tobacco leaf
stems. In addition, homogenised tobacco material may comprise a
minor quantity of one or more of tobacco dust, tobacco fines, and
other particulate tobacco by-products formed during the treating,
handling and shipping of tobacco. The sheets of homogenised tobacco
material may be produced by casting, extrusion, paper making
processes or other any other suitable processes known in the
art.
[0024] The term "porous" is used herein to refer to a material that
provides a plurality of pores or openings that allow the passage of
air through the material.
[0025] The term "ventilation level" is used throughout the present
specification to denote a volume ratio between of the airflow
admitted into the aerosol-generating article via the ventilation
zone (ventilation airflow) and the sum of the aerosol airflow and
the ventilation airflow. The greater the ventilation level, the
higher the dilution of the aerosol flow delivered to the
consumer.
[0026] As briefly described above, the aerosol-generating article
of the present invention comprises a rod of aerosol-generating
substrate; a mouthpiece segment comprising a plug of filtration
material, and a hollow tubular segment at a location between the
rod and the mouthpiece segment. All three elements are
longitudinally aligned. The rod of aerosol-generating substrate
comprises at least an aerosol former.
[0027] In contrast to known aerosol-generating articles, the rod of
aerosol-generating substrate has an aerosol former content of at
least about 10 percent on a dry weight basis. Further, the hollow
tubular segment defines a cavity that extends all the way to an
upstream end of the mouthpiece segment, and a ventilation zone is
provided at a location along the hollow tubular segment. In
addition, an equivalent internal diameter of the hollow tube
segment is at least about 5 millimetres.
[0028] By providing an aerosol-generating article wherein a hollow
tubular element is arranged between the rod of aerosol-generating
substrate and the mouthpiece, wherein the hollow tubular element
defines a cavity extending all the way to an upstream end of the
mouthpiece segment, the overall structural complexity of the
article may be significantly reduced compared with existing
aerosol-generating articles. This advantageously simplifies the
manufacturing process and reduces the complexity of the making and
combining apparatus required for implementing the manufacturing
process.
[0029] One such aerosol-generating article does not necessarily
comprise an aerosol-cooling element adapted to lower the
temperature of a stream of aerosol drawn through the
aerosol-generating article--as is the case, for example, with the
aerosol-generating articles described in international patent
application WO 2013/120565.
[0030] The inventors have found that a satisfactory cooling of the
stream of aerosol generated upon heating the article and drawn
through the hollow tubular element is achieved by providing a
ventilation zone at a location along the hollow tubular segment.
Further, the inventors have surprisingly found that, by utilising a
hollow tubular segment having an equivalent internal diameter of at
least about 5 millimetres, it may be possible to counter the
effects of the increased aerosol dilution caused by the admission
of ventilation air into the article.
[0031] Without wishing to be bound by theory, it is hypothesised
that, because the temperature of the aerosol stream is rapidly
lowered by the introduction of ventilation air as the aerosol is
travelling towards the mouthpiece segment, the ventilation air
being admitted into the aerosol stream at a location relatively
close to the upstream end of the hollow tubular segment (that is,
sufficiently close to the heat source and to the rod of
aerosol-generating substrate), a dramatic cooling of the aerosol
stream is achieved, which has a favourable impact on the
condensation and nucleation of the aerosol particles. Accordingly,
the overall proportion of the aerosol particulate phase to the
aerosol gas phase may be enhanced compared with existing,
non-ventilated aerosol-generating articles.
[0032] At the same time, utilising a hollow tubular element with an
equivalent internal diameter of 5 millimetres or more ensures that
the overall internal volume of the hollow tubular element--which is
made available for the aerosol to begin the nucleation process as
soon as the aerosol components leave the rod of aerosol-generating
substrate--and the cross-sectional surface area of the hollow
tubular segment are effectively maximised, whilst at the same time
ensuring that the hollow tubular segment has the necessary
structural strength to prevent a collapse of the aerosol-generating
article as well as to provide some support to the rod of
aerosol-generating substrate, and that the RTD of the hollow
tubular segment is minimised. Greater values of cross-sectional
surface area of the cavity of the hollow tubular segment are
associated with a reduced speed of the aerosol stream travelling
along the aerosol-generating article, which is understood to favour
aerosol nucleation. In practice, without wishing to be bound by
theory, by providing a cavity having one such large volume as is
the case with articles in accordance with the invention, a cooling
chamber is effectively provided within which the condensation of
aerosol particles upstream of a mouth end of the article may be
favoured, as nucleation phenomena are enhanced by slowing down the
flow of the aerosol stream.
[0033] The provision of a sufficiently wide tubular cavity
downstream of the rod of aerosol-generating substrate is understood
to favour the formation of a satisfactory amount of aerosol during
use. In turn, a greater fraction of the generated aerosol particles
to begin to condense prior to reaching the mouth end of the
article.
[0034] In fact, the inventors have surprisingly found how the
favourable effect of enhanced nucleation may significantly counter
the less desirable effects of dilution, such that satisfactory
values of aerosol delivery are consistently achieved with
aerosol-generating articles in accordance with the invention. This
is particularly advantageous with "short" aerosol-generating
articles, such as ones wherein a length of the rod of
aerosol-generating substrate is less than about 40 millimetres,
preferably less than 25 millimetres, even more preferably less than
20 millimetres, or wherein an overall length of the
aerosol-generating article is less than about 70 millimetres,
preferably less than about 60 millimetres, even more preferably
less than 50 millimetres. As will be appreciated, in such
aerosol-generating articles, there is little time and space for the
aerosol to form and for the particulate phase of the aerosol to
become available for delivery to the consumer.
[0035] Further, because the hollow tubular element substantially
does not contribute to the RTD of the aerosol-generating article,
in aerosol-generating articles in accordance with the invention the
overall RTD of the article can advantageously be fine-tuned by
adjusting the length and density of the rod of aerosol-generating
substrate or the length and density of the segment of filtration
material of the mouthpiece. This enables the manufacture of
aerosol-generating substrates having a predetermined RTD
consistently and with great precision, such that satisfactory
levels of RTD can be provided for the consumer even in the presence
of ventilation.
[0036] Aerosol-generating articles in accordance with the invention
can be made in a continuous process which can be efficiently
carried out at high speed, and can be conveniently manufactured on
existing production lines for the manufactured of heated aerosol
generating articles without requiring extensive modifications of
the manufacturing equipment.
[0037] The rod of aerosol generating substrate preferably has an
external diameter that is approximately equal to the external
diameter of the aerosol generating article.
[0038] Preferably, the rod of aerosol generating substrate has an
external diameter of at least 5 millimetres. The rod of aerosol
generating substrate may have an external diameter of between about
5 millimetres and about 12 millimetres, for example of between
about 5 millimetres and about 10 millimetres or of between about 6
millimetres and about 8 millimetres. In a preferred embodiment, the
rod of aerosol generating substrate has an external diameter of 7.2
millimetres, to within 10 percent.
[0039] The rod of aerosol generating substrate may have a length of
between about 5 millimetres and about 100 mm. Preferably, the rod
of aerosol generating substrate has a length of at least about 5
millimetres, more preferably at least about 7 millimetres. In
addition, or as an alternative, the rod of aerosol generating
substrate preferably has a length of less than about 80
millimetres, more preferably less than about 65 millimetres, even
more preferably less than about 50 millimetres. In particularly
preferred embodiments, the rod of aerosol generating substrate has
a length of less than about 35 millimetres, more preferably less
than 25 millimetres, even more preferably less than about 20
millimetres. In one embodiment, the rod of aerosol generating
substrate may have a length of about 10 millimetres. In a preferred
embodiment, the rod of aerosol generating substrate has a length of
about 12 millimetres.
[0040] Preferably, the rod of aerosol generating substrate has a
substantially uniform cross-section along the length of the rod.
Particularly preferably, the rod of aerosol generating substrate
has a substantially circular cross-section.
[0041] In preferred embodiments, the aerosol-generating substrate
comprises one or more gathered sheets of homogenised tobacco
material. Preferably the one or more sheets of homogenised tobacco
material are textured. As used herein, the term `textured sheet`
denotes a sheet that has been crimped, embossed, debossed,
perforated or otherwise deformed. Textured sheets of homogenised
tobacco material for use in the invention may comprise a plurality
of spaced-apart indentations, protrusions, perforations or a
combination thereof. According to a particularly preferred
embodiment of the invention, the rod of aerosol-generating
substrate comprises a gathered crimped sheet of homogenised tobacco
material circumscribed by a wrapper.
[0042] As used herein, the term `crimped sheet` is intended to be
substantially synonymous with the term `creped sheet` and denotes a
sheet having a plurality of substantially parallel ridges or
corrugations. Preferably, the crimped sheet of homogenised tobacco
material has a plurality of ridges or corrugations substantially
parallel to the cylindrical axis of the rod according to the
invention. This advantageously facilitates gathering of the crimped
sheet of homogenised tobacco material to form the rod. However, it
will be appreciated that crimped sheets of homogenised tobacco
material for use in the invention may alternatively or in addition
have a plurality of substantially parallel ridges or corrugations
disposed at an acute or obtuse angle to the cylindrical axis of the
rod. In certain embodiments, sheets of homogenised tobacco material
for use in the rod of the article of the invention may be
substantially evenly textured over substantially their entire
surface. For example, crimped sheets of homogenised tobacco
material for use in the manufacture of a rod for use in an
aerosol-generating article in accordance with the invention may
comprise a plurality of substantially parallel ridges or
corrugations that are substantially evenly spaced-apart across the
width of the sheet.
[0043] Sheets or webs of homogenised tobacco material for use in
the invention may have a tobacco content of at least about 40
percent by weight on a dry weight basis, more preferably of at
least about 60 percent by weight on a dry weight basis, more
preferably or at least about 70 percent by weight on a dry basis
and most preferably at least about 90 percent by weight on a dry
weight basis.
[0044] Sheets or webs of homogenised tobacco material for use in
the aerosol-generating substrate may comprise one or more intrinsic
binders, that is tobacco endogenous binders, one or more extrinsic
binders, that is tobacco exogenous binders, or a combination
thereof to help agglomerate the particulate tobacco. Alternatively,
or in addition, sheets of homogenised tobacco material for use in
the aerosol-generating substrate may comprise other additives
including, but not limited to, tobacco and non-tobacco fibres,
aerosol-formers, humectants, plasticisers, flavourants, fillers,
aqueous and non-aqueous solvents and combinations thereof.
[0045] Suitable extrinsic binders for inclusion in sheets or webs
of homogenised tobacco material for use in the aerosol-generating
substrate are known in the art and include, but are not limited to:
gums such as, for example, guar gum, xanthan gum, arabic gum and
locust bean gum; cellulosic binders such as, for example,
hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl
cellulose, methyl cellulose and ethyl cellulose; polysaccharides
such as, for example, starches, organic acids, such as alginic
acid, conjugate base salts of organic acids, such as
sodium-alginate, agar and pectins; and combinations thereof.
[0046] Suitable non-tobacco fibres for inclusion in sheets or webs
of homogenised tobacco material for use in the aerosol-generating
substrate are known in the art and include, but are not limited to:
cellulose fibres; soft-wood fibres; hard-wood fibres; jute fibres
and combinations thereof. Prior to inclusion in sheets of
homogenised tobacco material for use in the aerosol-generating
substrate, non-tobacco fibres may be treated by suitable processes
known in the art including, but not limited to: mechanical pulping;
refining; chemical pulping; bleaching; sulphate pulping; and
combinations thereof.
[0047] Preferably, the sheets or webs of homogenised tobacco
material comprise an aerosol former. As used herein, the term
"aerosol former" describes any suitable known compound or mixture
of compounds that, in use, facilitates formation of an aerosol and
that is substantially resistant to thermal degradation at the
operating temperature of the aerosol-generating article.
[0048] Suitable aerosol-formers are known in the art and include,
but are not limited to: polyhydric alcohols, such as propylene
glycol, triethylene glycol, 1,3-butanediol and glycerine; esters of
polyhydric alcohols, such as glycerol mono-, di- or triacetate; and
aliphatic esters of mono-, di- or polycarboxylic acids, such as
dimethyl dodecanedioate and dimethyl tetradecanedioate.
[0049] Preferred aerosol formers are polyhydric alcohols or
mixtures thereof, such as propylene glycol, triethylene glycol,
1,3-butanediol and, most preferred, glycerine.
[0050] The sheets or webs of homogenised tobacco material may
comprise a single aerosol former. Alternatively, the sheets or webs
of homogenised tobacco material may comprise a combination of two
or more aerosol formers.
[0051] The sheets or webs of homogenised tobacco material have an
aerosol former content of greater than 10 percent on a dry weight
basis. Preferably, the sheets or webs of homogenised tobacco
material have an aerosol former content of greater than 12 percent
on a dry weight basis. More preferably, the sheets or webs of
homogenised tobacco material have an aerosol former content of
greater than 14 percent on a dry weight basis. Even more preferably
the sheets or webs of homogenised tobacco material have an aerosol
former content of greater than 16 percent on a dry weight
basis.
[0052] The sheets of homogenised tobacco material may have an
aerosol former content of between approximately 10 percent and
approximately 30 percent on a dry weight basis. Preferably, the
sheets or webs of homogenised tobacco material have an aerosol
former content of less than 25 percent on a dry weight basis.
[0053] In a preferred embodiment, the sheets of homogenised tobacco
material have an aerosol former content of approximately 20 percent
on a dry weight basis.
[0054] Sheets or webs of homogenised tobacco for use in the
aerosol-generating article of the present invention may be made by
methods known in the art, for example the methods disclosed in
International patent application WO-A-2012/164009 A2. In a
preferred embodiment, sheets of homogenised tobacco material for
use in the aerosol-generating article are formed from a slurry
comprising particulate tobacco, guar gum, cellulose fibres and
glycerine by a casting process.
[0055] Alternative arrangements of homogenised tobacco material in
a rod for use in an aerosol-generating article will be known to the
skilled person and may include a plurality of stacked sheets of
homogenised tobacco material, a plurality of elongate tubular
elements formed by winding strips of homogenised tobacco material
about their longitudinal axes, etc.
[0056] As a further alternative, the rod of aerosol-generating
substrate may comprise a non-tobacco-based, nicotine-bearing
material, such as a sheet of sorbent non-tobacco material loaded
with nicotine (for example, in the form of a nicotine salt) and an
aerosol-former. Examples of such rods are described in the
international application WO-A-2015/052652. In addition, or as an
alternative, the rod of aerosol-generating substrate may comprise a
non-tobacco plant material, such as an aromatic non-tobacco plant
material.
[0057] In the rod of aerosol-generating substrate of articles in
accordance with the invention, the aerosol-generating substrate is
preferably circumscribed by a wrapper. The wrapper may be formed of
a porous or non-porous sheet material. The wrapper may be formed of
any suitable material or combination of materials. Preferably, the
wrapper is a paper wrapper.
[0058] The mouthpiece segment comprises a plug of filtration
material capable of removing particulate components, gaseous
components or a combination. Suitable filtration materials are
known in the art and include, but are not limited to: fibrous
filtration materials such as, for example, cellulose acetate tow,
viscose fibres, polyhydroxyalkanoates (PHA) fibres, polylactic acid
(PLA) fibres and paper; adsorbents such as, for example, activated
alumina, zeolites, molecular sieves and silica gel; and
combinations thereof. In addition, the plug of filtration material
may further comprise one or more aerosol-modifying agent. Suitable
aerosol-modifying agents are known in the art and include, but are
not limited to, flavourants such as, for example, menthol. In some
embodiments, the mouthpiece may further comprise a mouth end recess
downstream of the plug of filtration material. By way of example,
the mouthpiece may comprise a hollow tube arranged in longitudinal
alignment with, and immediately downstream of the plug of
filtration material, the hollow tube forming a cavity at the mouth
end that is open to the outer environment at the downstream end of
the mouthpiece and of the aerosol-generating article.
[0059] A length of the mouthpiece is preferably at least about 4
millimetres, more preferably at least about 6 millimetres, even
more preferably at least about 8 millimetres. In addition, or as an
alternative, a length of the mouthpiece is preferably less than 25
millimetres, more preferably less than 20 millimetres, even more
preferably less than 15 millimetres. In some preferred embodiments,
a length of the mouthpiece is from about 4 millimetres to about 25
millimetres, more preferably from about 6 millimetres to about 20
millimetres. In an exemplary embodiment, a length of the mouthpiece
is about 7 millimetres. In another exemplary embodiment, a length
of the mouthpiece is about 12 millimetres.
[0060] The hollow tubular segment is preferably an annular tube
delimiting and defining an air gap within the aerosol-generating
article. In practice, the hollow tubular segment provides a chamber
for the volatilised aerosol components released upon heating the
aerosol-generating substrate to accumulate and flow in. As
described briefly above, this chamber extends longitudinally all
the way to an upstream end of the mouthpiece. This means that no
intermediate element is provided between the hollow tubular segment
and the mouthpiece, and that when the aerosol flowing through the
aerosol-generating article reaches the downstream end of the hollow
tubular segment, the aerosol flowing through the aerosol-generating
article effectively also reaches the upstream end of the
mouthpiece. In more detail, the aerosol flowing through the
aerosol-generating article generally reaches the upstream end of
the segment of filtration material of the mouthpiece.
[0061] Thus, in aerosol-generating articles in accordance with the
invention, the hollow tubular segment maintains the rod of
aerosol-generating substrate at a predetermined distance from the
mouthpiece and provides an elongate airflow conduit for the aerosol
to form and flow towards the mouthpiece. During use, a thermal
gradient is established along this airflow conduit. In practice, a
temperature differential is provided, such that a temperature of
the volatilised aerosol components entering the hollow tubular
segment at the upstream end is greater than a temperature of the
volatilised aerosol components exiting the hollow tubular segment
at the downstream end (that is, the upstream end of the
mouthpiece).
[0062] On the one hand, the hollow tubular segment is required to
withstand any axial compressive load or bending moment that may be
applied on the hollow tubular segment during manufacture of the
aerosol-generating article. Further, the hollow tubular segment is
required to impart structural strength to the aerosol-generating
article, such that it can easily be handled by the consumer and
inserted into an aerosol-generating device for use. On the other
hand, it is desirable that the overall volume of the chamber
internally defined by the hollow tubular element is as large as
possible, so as to favour the formation of aerosol and enhance the
delivery of aerosol to the consumer.
[0063] To satisfy these requirements, as described briefly above,
an equivalent internal diameter of the hollow tubular segment is at
least about 5 millimetres. The term "equivalent internal diameter"
is used herein to denote the diameter of a circle having the same
surface area of a cross-section of the airflow conduit internally
defined by the hollow tubular segment. A cross-section of the
airflow conduit may have any suitable shape. However, as described
briefly above, a circular cross-section is preferred--that is, the
hollow tubular segment is effectively a cylindrical tube. In that
case, the equivalent internal diameter of the hollow tubular
segment effectively coincides with the internal diameter of the
cylindrical tube.
[0064] More preferably, an equivalent internal diameter of the
hollow tubular segment is at least about 5.25 millimetres, even
more preferably at least about 5.5 millimetres. In some
embodiments, an equivalent internal diameter of the hollow tubular
segment is at least about 6 millimetres or at least about 6.5
millimetres or at least about 7 millimetres.
[0065] In addition, an equivalent internal diameter of the hollow
tubular segment is preferably less than about 10 millimetres. More
preferably, an equivalent internal diameter of the hollow tubular
segment is less than about 9.5 millimetres, even more preferably
less than 9 millimetres.
[0066] The equivalent internal diameter of the hollow tubular
segment is measured at the location of the ventilation zone.
[0067] In preferred embodiments, the equivalent internal diameter
of the hollow tubular segment is substantially constant along the
length of the hollow tubular segment. In other embodiments, the
equivalent internal diameter of the hollow tubular segment may vary
along the length of the hollow tubular segment.
[0068] The inventors have surprisingly found that
aerosol-generating articles in accordance with the invention that
comprise a hollow tubular segment having an equivalent internal
diameter within the ranges described above could provide
particularly satisfactory values of aerosol delivery. Without
wishing to be bound by theory, it is hypothesized that the aerosol
stream flowing along a hollow tubular segment having an equivalent
internal diameter falling within the ranges described above is
caused to flow at a relatively low speed when the incoming flow of
cooler ventilation air is received into and mixed with the aerosol
stream. Because the aerosol stream advances relatively slowly along
the hollow tubular segment, the favourable impact of cooling on
aerosol nucleation is expected to be maximised under such
conditions.
[0069] Preferably, an equivalent internal diameter of the hollow
tubular segment is substantially constant along the length of the
hollow tubular segment. However, in some embodiments, the
cross-sectional surface area of the hollow tubular segment may vary
along the length of the hollow tubular segment. In such
embodiments, the equivalent internal diameter is measured at the
location of the ventilation zone.
[0070] In preferred embodiments a thickness of a peripheral wall of
the hollow tubular segment is less than 1.5 millimetre. More
preferably, the thickness of the peripheral wall of the hollow
tubular segment is less than 1250 micrometres, even more preferably
less than 1000 micrometres, most preferably less than 900
micrometres. In particularly preferred embodiments, the thickness
of the peripheral wall of the hollow tubular segment is less than
800 micrometres.
[0071] In addition, or as an alternative, the thickness of the
peripheral wall of the hollow tubular segment is at least about 100
micrometres. Preferably, the thickness of the peripheral wall of
the hollow tubular segment is at least about 200 micrometres.
[0072] Without wishing to be bound by theory, it would appear that
by utilising a hollow tubular segment having a peripheral wall with
a thickness falling within the ranges described above, it is
advantageously possible to limit or even substantially prevent
diffusion of the ventilation air prior to its contacting and mixing
with the stream of aerosol. This is understood to further favour
nucleation phenomena. In practice, by providing a more controllably
localised cooling of the stream of volatilised species being drawn
through the hollow tubular segment, it is possible to enhance the
effect of cooling on the formation of new aerosol particles.
[0073] As described briefly above, aerosol-generating articles in
accordance with the present invention comprise a ventilation zone
at a location along the hollow tubular segment. Preferably, the
ventilation zone is provided at a location less than about 18
millimetres from an upstream end of the hollow tubular segment.
Preferably, a distance between the ventilation zone and an upstream
end of the hollow tubular segment is less than about 15
millimetres. Even more preferably, a distance between the
ventilation zone and upstream end of the hollow tubular segment is
less than about 10 millimetres.
[0074] In addition, or as an alternative, a distance between the
ventilation zone and an upstream end of the hollow tubular segment
is preferably at least 2 millimetres. More preferably, a distance
between the ventilation zone and an upstream end of the hollow
tubular segment is at least about 4 millimetres. Even more
preferably, a distance between the ventilation zone and an upstream
end of the hollow tubular segment is at least about 6
millimetres.
[0075] Preferably, the ventilation zone is provided at a location
along the hollow tubular segment at least 2 millimetres from the
upstream end of the mouthpiece. Preferably, the ventilation zone is
provided at a location along the hollow tubular segment at least 4
millimetres from the upstream end of the mouthpiece. Even more
preferably, the ventilation zone is provided at a location along
the hollow tubular segment at least 6 millimetres from the upstream
end of the mouthpiece.
[0076] As the mixture of air and aerosol particles flowing through
the aerosol-generating article reaches the ventilation zone,
external air drawn into the hollow tubular segment via the
ventilation zone is mixed with the aerosol. This rapidly reduces
the temperature of the aerosol mixture whilst partially diluting
the mixture of air and aerosol particles. As will be discussed in
greater detail below, however, by providing the ventilation zone at
a distance from the upstream end of the mouthpiece segment falling
within the ranges described above, a cooling chamber is effectively
provided immediately upstream of the mouthpiece, wherein nucleation
and growth of aerosol particles is advantageously favoured. As
such, the diluting effect of the ventilation air admitted into the
hollow tubular segment is at least partly countered, which
advantageously enables the provision of aerosol delivery levels
that are satisfactory for the consumer.
[0077] In some embodiments, a ratio between the distance between
the ventilation zone and an upstream end of the hollow tubular
segment and an equivalent internal diameter of the hollow tubular
segment at the location of the ventilation zone is less than 4.
Preferably, a ratio between the distance between the ventilation
zone and an upstream end of the hollow tubular segment and an
equivalent internal diameter of the hollow tubular segment at the
location of the ventilation zone is less than 3.5. More preferably,
a ratio between the distance between the ventilation zone and an
upstream end of the hollow tubular segment and an equivalent
internal diameter of the hollow tubular segment at the location of
the ventilation zone is less than 3. Even more preferably, a ratio
between the distance between the ventilation zone and an upstream
end of the hollow tubular segment and an equivalent internal
diameter of the hollow tubular segment at the location of the
ventilation zone is less than 2.5.
[0078] In particularly preferred embodiments, a ratio between the
distance between the ventilation zone and an upstream end of the
hollow tubular segment and an equivalent internal diameter of the
hollow tubular segment at the location of the ventilation zone is
less than 2, more preferably less than 1.5, even more preferably
less than 1.2.
[0079] Preferably, the ventilation zone is provided at a location
along the hollow tubular segment at least 10 millimetres from a
downstream end of the mouthpiece segment. More preferably, the
ventilation zone is provided at a location along the hollow tubular
segment at least 12 millimetres from a downstream end of the
mouthpiece segment. Even more preferably, the ventilation zone is
provided at a location along the hollow tubular segment at least 15
millimetres from a downstream end of the mouthpiece segment. This
is advantageous in that is ensures that, during use, the
ventilation zone is not occluded by the consumer's lips.
[0080] In addition, or as an alternative, the ventilation zone is
preferably at a location along the hollow tubular segment less than
25 millimetres from a downstream end of the mouthpiece segment.
More preferably, the ventilation zone is at a location along the
hollow tubular segment less than 20 millimetres from a downstream
end of the mouthpiece segment. This advantageously ensures that
during use, when the aerosol-generating article is received within
a heating chamber of an electrically heated aerosol-generating
device, the ventilation zone is effectively at a location along the
hollow tubular segment that projects outside of the heating
chamber, such that external cooling air can easily be drawn into
the hollow tubular segment.
[0081] In some preferred embodiments, the ventilation zone is
provided at a location along the hollow tubular segment from about
10 millimetres to about 25 millimetres from a downstream end of the
mouthpiece segment, more preferably from about 12 millimetres to
about 20 millimetres from a downstream end of the mouthpiece
segment. In an exemplary embodiment, the ventilation zone is
provided at a location along the hollow tubular segment 18
millimetres from the downstream end of the mouthpiece segment. In
another exemplary embodiment, the ventilation zone is provided at a
location along the hollow tubular segment 13 millimetres from the
downstream end of the mouthpiece segment.
[0082] The aerosol-generating article may typically have a
ventilation level of at least about 10 percent, preferably at least
about 20 percent.
[0083] In preferred embodiments, the aerosol-generating article has
a ventilation level of at least about 30 percent. More preferably,
the aerosol-generating article has a ventilation level of at least
about 35 percent. In addition, or as an alternative, the
aerosol-generating article preferably has a ventilation level of
less than about 60 percent. More preferably, the aerosol-generating
article has a ventilation level of less than about 50 percent. In
particularly preferred embodiments, the aerosol-generating article
has a ventilation level from about 30 percent to about 60 percent.
More preferably, the aerosol-generating article has a ventilation
level from about 35 percent to about 50 percent. In some
particularly preferred embodiments, the aerosol-generating article
has a ventilation level of about 40 percent.
[0084] Without wishing to be bound by theory, the inventors have
found that the temperature drop caused by the admission of cooler,
external air into the hollow tubular segment via the ventilation
zone may have an advantageous effect on the nucleation and growth
of aerosol particles.
[0085] Formation of an aerosol from a gaseous mixture containing
various chemical species depends on a delicate interplay between
nucleation, evaporation, and condensation, as well as coalescence,
all the while accounting for variations in vapour concentration,
temperature, and velocity fields. The so-called classical
nucleation theory is based on the assumption that a fraction of the
molecules in the gas phase are large enough to stay coherent for
long times with sufficient probability (for example, a probability
of one half). These molecules represent some kind of a critical,
threshold molecule clusters among transient molecular aggregates,
meaning that, on average, smaller molecule clusters are likely to
disintegrate rather quickly into the gas phase, while larger
clusters are, on average, likely to grow. Such critical cluster is
identified as the key nucleation core from which droplets are
expected to grow due to condensation of molecules from the vapour.
It is assumed that virgin droplets that just nucleated emerge with
a certain original diameter, and then may grow by several orders of
magnitude. This is facilitated and may be enhanced by rapid cooling
of the surrounding vapour, which induces condensation. In this
connection, it helps to bear in mind that evaporation and
condensation are two sides of one same mechanism, namely gas-liquid
mass transfer. While evaporation relates to net mass transfer from
the liquid droplets to the gas phase, condensation is net mass
transfer from the gas phase to the droplet phase. Evaporation (or
condensation) will make the droplets shrink (or grow), but it will
not change the number of droplets.
[0086] In this scenario, which may be further complicated by
coalescence phenomena, the temperature and rate of cooling can play
a critical role in determining how the system responds. In general,
different cooling rates may lead to significantly different
temporal behaviours as concerns the formation of the liquid phase
(droplets), because the nucleation process is typically nonlinear.
Without wishing to be bound by theory, it is hypothesised that
cooling can cause a rapid increase in the number concentration of
droplets, which is followed by a strong, short-lived increase in
this growth (nucleation burst). This nucleation burst would appear
to be more significant at lower temperatures. Further, it would
appear that higher cooling rates may favour an earlier onset of
nucleation. By contrast, a reduction of the cooling rate would
appear to have a favourable effect on the final size that the
aerosol droplets ultimately reach.
[0087] Therefore, the rapid cooling induced by the admission of
external air into the hollow tubular segment via the ventilation
zone can be favourably used to favour nucleation and growth of
aerosol droplets. However, at the same time, the admission of
external air into the hollow tubular segment has the immediate
drawback of diluting the aerosol stream delivered to the consumer.
The inventors have surprisingly found that the diluting effect on
the aerosol--which can be assessed by measuring, in particular, the
effect on the delivery of glycerin included in the
aerosol-generating substrate as the aerosol former--is
advantageously minimised when the ventilation level is between 30
percent and 50 percent. In particular, ventilation levels between
35 percent and 42 percent have been found to lead to particularly
satisfactory values of glycerin delivery.
[0088] In addition, the inventors have found that in
aerosol-generating articles in accordance with the invention the
cooling and diluting effect caused by the admission of ventilation
air at the location along the conduit defined by the hollow tubular
segment described above has a surprising reducing effect on the
generation and delivery of phenol-containing species.
[0089] The ventilation zone may comprise one or more rows of
perforations formed through the peripheral wall of the hollow
tubular segment. Preferably the ventilation zone comprises only one
rows of perforations. This is understood to be advantageous in
that, by concentrating the cooling effect brought about by
ventilation over a short portion of the cavity defined by the
hollow tube segment, it may be possible to further enhance aerosol
nucleation. This is because a faster and more drastic cooling of
the stream of volatilised species is expected to particularly
favour the formation of new nuclei of aerosol particles.
[0090] Preferably, the one or more rows of perforations are
arranged circumferentially around the wall of the hollow tube.
Where the ventilation zone comprises two or more rows of
perforations formed through the peripheral wall of the hollow
tubular segment, the rows are longitudinally spaced apart from one
another along the hollow tubular segment. By way of example,
adjacent rows of perforations may be longitudinally spaced from one
another by a distance of between about 0.25 millimetres and 0.75
millimetres.
[0091] An equivalent diameter of at least one of the ventilation
perforations is preferably at least about 100 micrometres.
Preferably, an equivalent diameter of at least one of the
ventilation perforations is at least about 150 micrometres. Even
more preferably, an equivalent diameter of at least one of the
ventilation perforations is at least about 200 micrometres. In
addition, or as an alternative, an equivalent diameter of at least
one of the ventilation perforations is preferably less than about
500 micrometres. More preferably, an equivalent diameter of at
least one of the ventilation perforations is less than about 450
micrometres. Even more preferably, an equivalent diameter of at
least one of the ventilation perforations is less than about 400
micrometres. The term "equivalent diameter" is used herein to
denote the diameter of a circle having the same surface area of a
cross-section of the ventilation perforation. A cross-section of
the ventilation perforations may have any suitable shape. However,
circular ventilation perforations are preferred.
[0092] The ventilation perforations may be of uniform size. As an
alternative, the ventilation perforations may vary in size. By
varying the number and size of the ventilation perforations, it is
possible to adjust the amount of external air admitted into the
hollow tubular segment when the consumer draws on the mouthpiece of
the aerosol-generating article during use. As such, it is
advantageously possible to adjust the ventilation level of the
aerosol-generating article.
[0093] The ventilation perforations can be formed using any
suitable technique, for example by laser technology, mechanical
perforation of the hollow tubular segment as part of the
aerosol-generating article or pre-perforation of the hollow tubular
segment before it is combined with the other elements to form the
aerosol-generating article. Preferably, the ventilation
perforations are formed by online laser perforation.
[0094] A length of the hollow tubular segment is preferably at
least about 10 millimetres. More preferably, a length of the hollow
tubular segment is at least about 15 millimetres. In addition, or
as an alternative, a length of the hollow tubular segment is
preferably less than about 30 millimetres. More preferably, a
length of the hollow tubular segment is less than about 25
millimetres. Even more preferably, a length of the hollow tubular
segment is less than about 20 millimetres. In some preferred
embodiments, a length of the hollow tubular segment is from about
10 millimetres to about 30 millimetres, more preferably from about
12 millimetres to about 25 millimetres, even more preferably from
about 15 millimetres to about 20 millimetres. By way of example, in
a particularly preferred embodiment the length of the hollow
tubular segment is about 18 millimetres. In another particularly
preferred embodiment the length of the hollow tubular segment is
about 13 millimetres.
[0095] An overall length of an aerosol-generating article in
accordance with the invention is preferably at least about 40
millimetres. In addition, or as an alternative, an overall length
of the aerosol-generating article in accordance with the invention
is preferably less than about 70 millimetres, more preferably less
than 60 millimetres, even more preferably less than 50 millimetres.
In preferred embodiments, an overall length of the
aerosol-generating article is from about 40 millimetres to about 70
millimetres. In an exemplary embodiment, an overall length of the
aerosol-generating article is about 45 millimetres.
[0096] The hollow tubular segment is preferably formed from a
substantially air-impervious material. Accordingly, air and aerosol
particles drawn through the hollow tubular segment are forced to
flow through the hollow tubular segment from its upstream end to
its downstream end, but cannot flow across the peripheral wall of
the hollow tubular element.
[0097] In some embodiments, the hollow tubular segment comprises a
wrapper, the wrapper also circumscribing the rod and the mouthpiece
segment. In practice, a wrapper having a thickness falling within
the ranges described above is used for circumscribing and
connecting the rod of aerosol-generating substrate and the
mouthpiece segment, the wrapper effectively forming the peripheral
wall of the hollow tubular element.
[0098] By way of example, one such combining wrapper connecting the
rod and the mouthpiece segment may have a basis weight of less at
least about 70 grams/square metre (gsm). Preferably, one such
combining wrapper connecting the rod and the mouthpiece segment has
a basis weight of at least about 80 grams/square metre, more
preferably at least about 90 grams/square metre. In particularly
preferred embodiments, the combining wrapper connecting the rod and
the mouthpiece segment has a basis weight of at least about 110
grams/square metre, more preferably at least about 130 grams/square
metre.
[0099] In other embodiments, the hollow tubular segment comprises a
tube formed from a polymeric material or a cellulosic material, the
heated aerosol-generating article further comprising a wrapper
circumscribing the rod, the tube and the mouthpiece segment. By way
of example, the cellulosic material may comprise paper or cardboard
or a mixture thereof.
[0100] By way of example, the hollow tubular segment can comprise a
tube formed from an extruded plastic tube. As an alternative, the
hollow tubular segment may comprise a tube formed from a plurality
of overlapping paper layers, such as a plurality of parallel wound
paper layers or a plurality of spirally wound paper layers. Forming
tube from a plurality of overlapping paper layers can help to
further improve resistance to collapse or deformation. Preferably
the tube comprises two or more paper layers. Alternatively, or
additionally, the tube preferably comprises fewer than eleven paper
layers.
[0101] One such tube may be made air-impervious by using a
substantially air-impermeable paper. The term "substantially
air-impermeable paper" is used herein to denote a paper having an
air permeability of less than about 20 CORESTA units, more
preferably less than about 10 CORESTA units, most preferably less
than about 5 CORESTA units as measured in accordance with ISO
2965:2009. As an alternative, adjacent paper layers in the tube may
be held together with an adhesive imparting sealing properties to
the tube.
[0102] Suitable materials for forming the tube are known in the art
and comprise, but are not limited to, cellulose acetate, stiff
paper (that is, paper having a basis weight of at least 90
grams/square metre), polymeric films, such as cellulosic films, and
cardboard.
[0103] In some embodiments, a ratio between a weight of the hollow
tubular segment and a volume of the internal cavity defined by the
hollow tubular segment is preferably less than 1 milligram/cubic
millimetre. More preferably, a ratio between a weight of the hollow
tubular segment and a volume of the internal cavity defined by the
hollow tubular segment is less than 0.5 milligrams/cubic
millimetres.
[0104] In particularly preferred embodiments, a ratio between a
weight of the hollow tubular segment and a volume of the internal
cavity defined by the hollow tubular segment is less than 0.25
milligrams/cubic millimetres. More preferably, a ratio between a
weight of the hollow tubular segment and a volume of the internal
cavity defined by the hollow tubular segment is less than 0.2
milligrams/cubic millimetres. Even more preferably, a ratio between
a weight of the hollow tubular segment and a volume of the internal
cavity defined by the hollow tubular segment is less than 0.1
milligrams/cubic millimetres.
[0105] In hollow tubular segments having a ratio between a weight
of the hollow tubular segment and a volume of the internal cavity
defined by the hollow tubular segment falling within the ranges
described above, the volume of the cavity is advantageously
maximised, whilst ensuring that the hollow tubular segment
contributes to the overall structural strength of the
aerosol-generating article and effectively maintains the rod of
aerosol-generating substrate spaced from the mouthpiece.
[0106] In an exemplary embodiment, the hollow tubular segment has
an internal equivalent diameter of 7 millimetres and is formed from
a wrapper having a basis weight of 110 gsm, with a weight of 2.5
milligram/millimetre. For one such hollow tubular segment, the
ratio between a weight of the hollow tubular segment and a volume
of the internal cavity defined by the hollow tubular segment is
about 0.065 milligrams/cubic millimetres.
[0107] In another exemplary embodiment, a hollow tubular segment
has an internal equivalent diameter of 5.3 millimetres may be
provided as a cellulose acetate tube with a weight of 9.5
milligram/millimetre. For one such hollow tubular segment, the
ratio between a weight of the hollow tubular segment and a volume
of the internal cavity defined by the hollow tubular segment is
about 0.43 milligrams/cubic millimetres.
[0108] In aerosol-generating articles in accordance with the
present invention the overall RTD of the article depends
essentially on the RTD of the rod and on the RTD of the mouthpiece,
as the hollow tubular segment is substantially empty and, as such,
substantially only marginally contribute to the overall RTD. In
practice, the hollow tubular segment may be adapted to generate a
RTD in the range of approximately 0 millimetre H.sub.2O (about 00
Pa) to approximately 20 m millimetres H.sub.2O (about 200 Pa).
Preferably, the hollow tubular segment is adapted to generate a RTD
between approximately 0 millimetres H.sub.2O (about 00 Pa) to
approximately 10 millimetres H.sub.2O (about 100 Pa).
[0109] The aerosol-generating article preferably has an overall RTD
of less than about 90 millimetres H.sub.2O (about 900 Pa). More
preferably, the aerosol-generating article has an overall RTD of
less than about 80 millimetres H.sub.2O (about 800 Pa). Even more
preferably, the aerosol-generating article has an overall RTD of
less than about 70 millimetres H.sub.2O (about 700 Pa).
[0110] In addition, or as an alternative, the aerosol-generating
article preferably has an overall RTD of at least about 30
millimetres H.sub.2O (about 300 Pa). More preferably the
aerosol-generating article has an overall RTD of at least about 40
millimetres H.sub.2O (about 400 Pa). Even more preferably, the
aerosol-generating article has an overall RTD of at least about 50
millimetres H.sub.2O (about 500 Pa).
[0111] The RTD of the aerosol-generating article may be assessed as
the negative pressure that has to be applied, under test conditions
as defined in ISO 3402, to downstream end of the mouthpiece in
order to sustain a steady volumetric flow of air of 17.5 ml/s
through the mouthpiece. The values of RTD listed above are intended
to be measured on the aerosol-generating article on its own (that
is, prior to inserting the article into an aerosol-generating
device) without blocking the perforations of the ventilation
zone.
[0112] If desired or required, for example to achieve a
sufficiently high RTD of the aerosol-generating article, the length
and density (denier per filament count) of the filtration material
of the mouthpiece may be adjusted. In addition, or as an
alternative, an additional filter section may be included in the
aerosol-generating article. By way of example, such additional
filter section may be included between the rod of
aerosol-generating substrate and the hollow tubular segment.
Preferably, such additional filter section comprises a filtration
material such as, for example, cellulose acetate. Preferably, the
length of the additional filter section is between about 4
millimetres and about 8 millimetres, preferably, between about 5
millimetres and about 7 millimetres.
[0113] In some embodiments, the aerosol-generating article in
accordance with the invention may comprise an additional support
element arranged between, and in longitudinal alignment with, the
rod of aerosol-generating substrate and the hollow tubular segment.
In more detail, the support element is preferably provided
immediately downstream of the rod and immediately upstream of the
hollow tubular element.
[0114] The support element is provided as a tubular element. The
support element may be formed from any suitable material or
combination of materials. For example, the support element may be
formed from one or more materials selected from the group
consisting of: cellulose acetate; cardboard; crimped paper, such as
crimped heat resistant paper or crimped parchment paper; and
polymeric materials, such as low density polyethylene (LDPE). In
preferred embodiment, the support element is provided as a hollow
cellulose acetate tube.
[0115] The support element preferably has an external diameter that
is about equal to the external diameter of the aerosol-generating
article. The support element may have an external diameter of
between about 5 millimetres and about 12 millimetres, for example
of between about 5 millimetres and about 10 millimetres or of
between about 6 millimetres and about 8 millimetres. In a preferred
embodiment, the support element has an external diameter of about
7.2 millimetres.
[0116] A peripheral wall of the support element may have a
thickness of at least 1 millimetre, preferably at least about 1.5
millimetres, more preferably at least about 2 millimetres.
[0117] The support element may have a length of between about 5
millimetres and about 15 millimetres. In an preferred embodiment,
the support element has a length of about 8 millimetres.
[0118] During insertion of a heating element of an
aerosol-generating device into an aerosol-forming substrate of an
aerosol-generating article, a user may be required to apply some
force in order to overcome the resistance of the aerosol-forming
substrate of the aerosol-generating article to insertion of the
heating element of the aerosol-generating device. This may damage
one or both of the aerosol-generating article and the heating
element of the aerosol-generating device. In addition, the
application of force during insertion of the heating element of the
aerosol-generating device into the aerosol-forming substrate of the
aerosol-generating article may displace the aerosol-forming
substrate within the aerosol-generating article. This may result in
the heating element of the aerosol-generating device not being
fully inserted into the aerosol-forming substrate, which may lead
to uneven and inefficient heating of the aerosol-forming substrate
of the aerosol-generating article. The support element is
advantageously configured to resist downstream movement of the
aerosol-forming substrate during insertion of the heating element
of the aerosol-generating device into the aerosol-forming substrate
of aerosol-generating article.
[0119] Preferably, a distance between the ventilation zone and an
upstream end of the aerosol-generating article is less than about
50 millimetres. More preferably, a distance between the ventilation
zone and an upstream end of the aerosol-generating article is less
than about 45 millimetres. Even more preferably, a distance between
the ventilation zone and an upstream end of the aerosol-generating
article is less than about 40 millimetres.
[0120] In addition, or as an alternative, a distance between the
ventilation zone and an upstream end of the aerosol-generating
article is preferably at least about 12 millimetres. More
preferably, a distance between the ventilation zone and an upstream
end of the aerosol-generating article is preferably at least about
15 millimetres. Even more preferably, a distance between the
ventilation zone and an upstream end of the aerosol-generating
article is preferably at least about 20 millimetres. In
particularly preferred embodiments, a distance between the
ventilation zone and an upstream end of the aerosol-generating
article is preferably at least about 25 millimetres.
[0121] Preferably, a distance between the ventilation zone and a
downstream end of the rod of aerosol-generating substrate is at
least about 2 millimetres. More preferably, a distance between the
ventilation zone and a downstream end of the rod of
aerosol-generating substrate is at least about 5 millimetres. Even
more preferably, a distance between the ventilation zone and a
downstream end of the rod of aerosol-generating substrate is at
least about 10 millimetres. In some, particularly preferred
embodiments, a distance between the ventilation zone and a
downstream end of the rod of aerosol-generating substrate may be at
least about 15 millimetres.
[0122] In addition, or as an alternative, a distance between the
ventilation zone and a downstream end of the rod of
aerosol-generating substrate is preferably less than about 35
millimetres. More preferably, a distance between the ventilation
zone and a downstream end of the rod of aerosol-generating
substrate is less than about 30 millimetres. Even more preferably,
a distance between the ventilation zone and a downstream end of the
rod of aerosol-generating substrate is less than about 25
millimetres.
[0123] In practice, the ventilation zone divides the cavity
internally defined by the hollow tubular segment into an upstream
sub-cavity, which extends longitudinally from an upstream end of
the hollow tubular segment to the location of the ventilation zone,
and a downstream sub-cavity, which extends longitudinally from the
location of the ventilation zone to the downstream end of the
hollow tubular segment. Without wishing to be bound by theory, it
is understood that in the upstream sub-cavity the volatilised
species of the aerosol stream advance along the hollow tubular
segment slowly cool down by yielding some of the heat to the
peripheral wall of the hollow tubular segment and thus aerosol
particles begin to nucleate. On the other hand, in the downstream
sub-cavity, the aerosol stream and the ventilation air rapidly mix
up, which causes a quick cooling of the volatilised species of the
aerosol stream and so favours the nucleation of new aerosol
particles and the growth of already existing aerosol particles as
the aerosol advances towards the mouthpiece.
[0124] Preferably, a ratio between a length of the upstream cavity
and a length of the downstream cavity is less than 1.5. More
preferably, a ratio between a length of the upstream cavity and a
length of the downstream cavity is less than 1. Even more
preferably, a ratio between a length of the upstream cavity and a
length of the downstream cavity is less than 0.67.
[0125] In addition, or as an alternative, a ratio between a length
of the upstream cavity and a length of the downstream cavity is
preferably at least about 0.15. More preferably, a ratio between a
length of the upstream cavity and a length of the downstream cavity
is preferably at least about 0.2. Even more preferably, a ratio
between a length of the upstream cavity and a length of the
downstream cavity is preferably at least about 0.35.
[0126] Similarly, the ventilation zone divides the
aerosol-generating article in two sections, upstream and downstream
of the location of the ventilation zone, respectively.
[0127] Preferably, a ratio between a length of the upstream section
of the aerosol-generating article and a length of the downstream
section of the aerosol-generating article is less than 2.5. More
preferably, a ratio between a length of the upstream section of the
aerosol-generating article and a length of the downstream section
of the aerosol-generating article is less than 2. Even more
preferably, a ratio between a length of the upstream section of the
aerosol-generating article and a length of the downstream section
of the aerosol-generating article is less than 1.5. In particularly
preferred embodiments, a ratio between a length of the upstream
section of the aerosol-generating article and a length of the
downstream section of the aerosol-generating article is less than
1.
[0128] In addition, or as an alternative, a ratio between a length
of the upstream section of the aerosol-generating article and a
length of the downstream section of the aerosol-generating article
is preferably at least about 0.25. More preferably, a ratio between
a length of the upstream section of the aerosol-generating article
and a length of the downstream section of the aerosol-generating
article is at least about 0.33. Even more preferably, a ratio
between a length of the upstream section of the aerosol-generating
article and a length of the downstream section of the
aerosol-generating article is at least about 0.5.
[0129] In aerosol-generating articles in accordance with the
invention it is advantageously easy to adjust and control the
overall RTD of the article. This is because the overall RTD of the
article depends on the RTD of a finite, small number of components
and the provision of the ventilation zone also contributes to
lowering the overall RTD of the article. Therefore, it is
advantageously possibly to reduce an RTD variability between
aerosol-generating articles.
[0130] Accordingly, the invention may also provide a pack
comprising ten or more aerosol-generating articles as described
above, wherein a difference between an RTD of the
aerosol-generating article having the highest RTD among the at
least ten aerosol-generating articles and an RTD of the
aerosol-generating article having the lowest RTD among the at least
ten aerosol-generating articles is less than 10 mm H.sub.2O (about
100 Pascal). Preferably, in one such pack, the difference between
an RTD of the aerosol-generating article having the highest RTD
among the at least ten aerosol-generating articles and an RTD of
the aerosol-generating article having the lowest RTD among the at
least ten aerosol-generating articles is less than 9 mm H.sub.2O
(about 90 Pascal, more preferably less than 8 mm H.sub.2O (about 80
Pascal), even more preferably less than 7 mm H.sub.2O (about 70
Pascal).
[0131] In the following, the invention will be further described
with reference to the drawings of the accompanying figures, in
which:
[0132] FIG. 1 shows a schematic side sectional view of an
aerosol-generating article in accordance with the invention;
[0133] FIG. 2 shows a schematic side sectional view of another
example of an aerosol-generating article in accordance with the
invention; and
[0134] FIG. 3 shows a schematic side sectional view of a further
example an aerosol-generating article in accordance with the
invention.
[0135] The aerosol-generating article 10 shown in FIG. 1 comprises
a rod of aerosol-generating substrate 12, a hollow cellulose
acetate tube 14, a hollow tubular segment 16 and a mouthpiece
segment 18. These four elements are arranged in end-to-end,
longitudinal alignment and are circumscribed by a wrapper 20 to
form the aerosol-generating article 10. The aerosol-generating
article 10 has a mouth end 22 and an upstream, distal end 24
located at the opposite end of the article to the mouth end 22. The
aerosol-generating article 10 shown in FIG. 1 is particularly
suitable for use with an electrically operated aerosol-generating
device comprising a heater for heating the rod of
aerosol-generating substrate.
[0136] The rod of aerosol-generating substrate 12 has a length of
about 12 millimetres and a diameter of about 7 millimetres. The rod
12 is cylindrical in shape and has a substantially circular
cross-section. The rod 12 comprises a gathered sheet of homogenised
tobacco material. The sheet of homogenised tobacco material
comprises 10 percent by weight on a dry basis of glycerine. The
hollow cellulose acetate tube 14 has a length of about 8
millimetres and a thickness of 1 millimetre.
[0137] The mouthpiece segment 18 comprises a plug of cellulose
acetate tow of 8 denier per filament and has a length of about 7
millimetres.
[0138] The hollow tubular segment 16 is provided as a cylindrical
tube having a length of about 18 millimetres and a thickness of the
tube wall is about 100 micrometres.
[0139] In more detail, the hollow tubular segment 16 may for
example be formed from a paper having a basis weight of 110 gsm and
has a weight of 45 milligrams (that is, 2.5 milligrams/millimetre
of length). An equivalent internal diameter of the hollow tubular
segment 16 is about 7 millimetres. Thus, a volume of the cavity
internally defined by the hollow tubular segment 16 is about 693
cubic millimetres. As such, a ratio between the weight of the
hollow tubular segment and the volume of the internal cavity
defined by the hollow tubular segment 16 is about 0.065. The
aerosol-generating article 10 comprises a ventilation zone 26
provided at about 5 millimetres from an upstream end of the
mouthpiece segment 18. Thus, the ventilation zone 26 is at about 12
millimetres from the downstream end of the aerosol-generating
article, and about 13 millimetres from the upstream end of the
hollow tubular segment.
[0140] Thus, the ventilation zone 26 is at about 21 millimetres
from a downstream end of the rod 12. FIG. 2 illustrates another
example of an aerosol-generating article in accordance with the
invention. The aerosol-generating article 30 of FIG. 2 has the same
structure of the aerosol-generating article 10 of FIG. 1 and
differs from the aerosol-generating article 10 substantially only
in the length of certain components, and will be described below
only insofar as it differs from the aerosol-generating article 10.
In the following the same reference numerals will be used, wherever
possible, for corresponding components having the same structural
or functional function.
[0141] In the aerosol-generating article 30 of FIG. 2, the rod 12
and the hollow cellulose acetate tube 14 have the same length as in
the aerosol-generating article 10 of FIG. 1. However, the
mouthpiece segment comprises a plug of cellulose acetate tow of 11
denier per filament and having a length of about 12 millimetres,
and a hollow tubular segment 14 having a length of about 13
millimetres. The ventilation zone 26 is provided at about 6
millimetres from the upstream end of the mouthpiece segment 18, and
at about 7 millimetres from the upstream end of the hollow tubular
segment. Thus, the ventilation zone 26 is at about 15 millimetres
from a downstream end of the rod 12.
[0142] In the embodiment of FIG. 2, the hollow tubular segment 16
may for example be provided as a cylindrical tube of cellulose
acetate having a length of about 18 millimetres and a peripheral
wall thickness of about 1 millimetre, with a weight of 171
milligrams (that is, 9.5 milligrams/millimetre of length).
[0143] An equivalent internal diameter of the hollow tubular
segment 16 may be about 5.3 millimetres. Thus, a volume of the
cavity internally defined by the hollow tubular segment 16 is about
397 cubic millimetres. As such, a ratio between the weight of the
hollow tubular segment and the volume of the internal cavity
defined by the hollow tubular segment 16 is about 0.43. FIG. 3
illustrates yet another example of an aerosol-generating article in
accordance with the invention. The aerosol-generating article 40 of
FIG. 3 differs structurally from the aerosol-generating articles 10
of FIGS. 1 and 30 of FIG. 2 in that it does not include a hollow
cellulose acetate tube as a support element. Accordingly, the
lengths of the three main components are also different. In the
following the same reference numerals will be used, wherever
possible, for corresponding components having the same structural
or functional function.
[0144] In the aerosol-generating article 40 of FIG. 3, the rod 12
has a length of about 12 millimetres, the hollow tubular segment 14
has a length of about 26 millimetres, and the mouthpiece segment 18
comprises a plug of cellulose acetate tow has a length of about 12
millimetres and 11 denier per filament. The ventilation zone 26 is
provided at about 5 millimetres from the upstream end of the
mouthpiece segment 18, and at about 21 millimetres from the
upstream end of the hollow tubular segment, which in this
embodiment coincides with the downstream end of the rod 12.
[0145] The following example records experimental results obtained
during tests carried out on a specific embodiment of an
aerosol-generating article in accordance with the present
invention. Conditions for smoking and smoking machine
specifications are set out in ISO Standard 3308 (ISO 3308:2000).
The atmosphere for conditioning and testing is set out in ISO
Standard 3402.
EXAMPLE 1
[0146] This experiment is performed to assess the effect of
incorporation of a hollow tubular segment wherein a ventilation
zone is provided at a location along the hollow tubular segment in
accordance with the present invention. The experiment investigates
the effect of the ventilation level on the delivery of nicotine and
aerosol former (glycerin). A comparative measurement with a
reference aerosol-generating article without ventilation is also
provided.
[0147] Materials and Methods
[0148] Article A is an aerosol-generating article formed of: a rod
of aerosol-generating substrate comprising a gathered sheet of
homogenised tobacco material and about 18 percent on a dry weight
basis of glycerin, the rod having a length of 12 millimetres; a
support element in the form of a hollow cellulose acetate tube in
alignment with and immediately downstream of the rod, the support
element having a length of 8 millimetres; a hollow tubular segment
in the form of a cardboard tube in alignment with and immediately
downstream of the rod, the hollow tubular segment having a length
of 13 millimetres; a mouthpiece segment of filtration material in
alignment with and immediately downstream of the hollow tubular
segment, the mouthpiece segment having a length of 12 millimetres.
A ventilation zone is provided at a location along the hollow
tubular segment at 18 millimetres from a downstream end of the
mouthpiece segment. A level of ventilation of aerosol-generating
article A is 30 percent.
[0149] Article B is a reference aerosol-generating article having
the same structure of article A, but without the ventilation zone.
Thus, a level of ventilation of aerosol-generating article B is 0
percent.
[0150] Nicotine and glycerin deliveries are measured by gas
chromatography/time-of-flight mass spectrometry (GC/MS-TOF) on the
nicotine and glycerin collected on a Cambridge filter pad. Runs
were performed as described in example 1
[0151] Results.
[0152] The average nicotine and glycerin deliveries from Article A
and Article B are shown in the following Table 1.
TABLE-US-00001 TABLE 1 Effect of ventilation level on nicotine and
glycerin deliveries. Nicotine Ventilation delivery Glycerin [%]
[mg] [mg] Article A 30 1.41 5.6 Article B 0 1.17 3.5
* * * * *