Note: Descriptions are shown in the official language in which they were submitted.
CA 02829718 2015-02-03
1
Smoking Article with a Filter
Field
The invention relates to smoking articles and, in particular, to modifying
smoke in
smoking articles.
3 Background
Smoking articles comprising smoke modifying agents are known in the art.
Examples
include absorbents or adsorbents located in the filter section or tobacco rod
of the
smoking article. Particulate filters absorb smoke constituents residing in the
particulate
phase of a smoke stream. Adsorbents are often included and are known to adsorb
smoke
constituents travelling in the vapour phase of the smoke stream.
While such absorbents and adsorbents have removed smoke constituents from the
smoke
stream as it passes through the smoking article, the arrangement of the
smoking article
has not allowed the temperature profile of the smoke to be controlled. As
such, smoke
constituents are not removed when it is desirable that they be removed.
13 Summary
An embodiment of the present invention provides a smoking article with a
filter
comprising: a first region of filtration material for removing particulate
matter from a
smoke stream, wherein the smoking article is arranged to enhance heat transfer
towards
the first region of filtration material, a second region of filtration
material downstream of
the first region and of lower filtration efficiency than the filtration
efficiency of the first
region of filtration material, and a configuration to cool the smoke stream
downstream of
the first region of filtration material prior to entry into the second region.
In one embodiment a rod of smokable material is provided wrapped by a wrapper
and
arranged to form a coal at one end thereof when lit, wherein the wrapper has
heat
conducting strips attached thereto to enhance heat transfer from the coal
towards the
first region of filtration material.
CA 02829718 2015-02-03
2
The rod of smokable material may have at least one channel extending
therethrough to
enhance heat transfer from the coal towards the first region of filtration
material.
The at least one channel may comprise a plurality of channels disposed
radially about the
circumference of the rod of smokable material.
In one embodiment the configuration to cool the smoke comprises a cooling
chamber. A
region of adsorbent material may be provided in or downstream of the cooling
chamber.
Perforations for cooling the smoke may be included in a wrapper circumscribing
the filter
section.
The configuration to cool the smoke may include at least one gap in the
wrapper
circumscribing the filter section.
A diluent may be provided, for example adjacently downstream of the first
region of
filtration material.
The rod of smokable material may comprise a pelletised composite of tobacco
and may
further comprise carbon.
The filter may be configured to alter the composition of the smoke stream as
the smoking
article is smoked.
The first region of filtration material may form an annulus around a bore
which becomes
obstructed as the smoking article is smoked.
The filter may be arranged to channel the smoke stream onto the first region
of filtration
material.
The first region of filtration material may be wrapped by an insulating
material.
The first region of filtration material may have a retention value greater
than 30 percent
or even greater than 70 percent.
CA 02829718 2015-02-03
2a
The smoking article may be configured such that the first region of filtration
material only
removes matter with boiling points of or greater than a predetermined level.
The predetermined
level may be one of about 250 C, 300 C, 350 C, 400 C, 450 C and 500 C.
Brief description of the drawings
So that the present invention may be more fully understood several embodiments
thereof
will now be described, by way of example only, with reference to the
accompanying
drawings, in which:
CA 02829718 2013-09-10
WO 2012/126721 PCT/EP2012/053802
3
Figure 1 is a side cross sectional view of a smoking article according to one
embodiment of the present invention;
Figure 2 is a side cross sectional view of a smoking article according to an
alternative embodiment of the present invention;
Figure 3 is a side cross sectional view of a smoking article according to an
alternative embodiment of the present invention;
Figure 4 is a side cross sectional view of a smoking article according to an
alternative embodiment of the present invention;
Figure 5 is a side cross sectional view of a smoking article according to
another
embodiment of the present invention; and
Figure 6 is a side cross sectional view of a smoking article according to
another
embodiment of the present invention;
Figure 7 is an end view of a smoking article according to one embodiment of
the
present invention;
Figure 8 is a plan view of a tobacco rod wrapper according to an embodiment of
the
present invention; and
Figure 9 is an end view of a smoking article in accordance with another
embodiment
of the present invention.
Detailed description
Figure 1 shows a cylindrical cigarette 10 in accordance with one embodiment of
the
present invention. The cigarette 10 comprises a tobacco rod 15 and a filter
section
20. The tobacco rod 15 and filter section 20 shown in Figure 1 are attached to
each
other by tipping paper 25 although other means for attaching tobacco rods to
filter
CA 02829718 2013-09-10
WO 2012/126721 PCT/EP2012/053802
4
sections that are known in the art may be employed in the alternative. The
filter
section 20 is wrapped in a length of tipping paper 25 which is longer than the
filter
section 20 and connects the tobacco rod 15 to the filter section 20 in a
manner well
known in the art.
The tobacco rod 15 shown in Figure 1 may be shorter than conventional tobacco
rods that are well known in the art. The tobacco rod 15 may be formed from
reconstituted or pelletised tobacco circumscribed by a wrapper 26. The wrapper
26
may be formed from any paper suitable for wrapping tobacco rods that is known
in
the art. The wrapper 26 may have a natural permeability between 0 and 25
Coresta
units (hereinafter denoted as CU) although preferably between 2 and 10 CU. A
higher permeability may be achieved using electrostatic perforation.
The tobacco rod may be 10 to 50 millimetres (hereinafter denoted as mm) in
length,
although 30 to 40 mm is a preferred length. The tobacco rod 15 may be between
14
and 28 mm in circumference although 17 to 25 mm is a preferred circumference.
A binder may be added to the tobacco during manufacture of the tobacco rod 15
to
make the tobacco easier to manipulate and form into rods. Carbon, in granular
form e.g. activated carbon or any other carbon additive known in the art, may
also
be added to the tobacco which, as well as making the tobacco rod 15 easier to
manipulate, facilitating combustion and increasing combustion heat, is also
known
to act as an adsorbent of certain smoke constituents.
The wrapper 26 which circumscribes the tobacco rod 15 is made from low
permeability paper although wrapping materials other than paper that are known
in
the art may be used. The permeability or porosity of an object is known to
affect its
burn rate. As such, the low permeability of the wrapper 26 ensures that the
tobacco
rod 15 burns more slowly than a tobacco rod wrapped in a higher permeability
wrapper would burn. Where the tobacco rod 15 is shorter than conventional
tobacco rods that are known in the art the decreased burn rate increases the
number
of draws or puffs that a user may take from the cigarette 10 during use.
CA 02829718 2013-09-10
WO 2012/126721 PCT/EP2012/053802
The filter section 20 of the cigarette 10 may be wrapped in a plugwrap 27 in
addition to the tipping paper 25. The plugwrap 27 may have a permeability
between
0 and 2000 Coresta units.
5 The filter section 20 comprises a region of high filtration efficiency
(hereinafter FE)
material 30. The region of high FE material 30 is located at the upstream end
of the
filter section 20 and is adjacent to the tobacco rod 15. The high FE material
30 may
be heat resistant as it will be exposed to high temperatures and may be a
Cambridge
filter pad formed from fibre glass. The high FE material 30 may also contain
materials, such as zeolites, which can selectively remove individual smoke
constituents. The region of high FE material may be between 1 and 15 mm in
length. The filtration efficiency and/or retention value of the high FE
material
should be selected to achieve a high level of particulate filtration. The
retention
value according to embodiments of the invention is greater than 30% and
preferably
greater than 70% of particulate matter, although the invention is also
effective with
retention values greater than 40%, 50%, 60%, 80% and/or 90%.
Since the region of high FE material 30 is likely to become hot during use an
insulating layer 31 may be provided between the high FE material 30 and the
tipping
paper 25 to reduce the risk of a user burning himself upon contact with the
filter
section 20.
A diluent holding material 35 or aerosol forming agent may be located within
the
region of high FE material 30. The diluent holding material 35 may contain
glycerol
although other diluents known in the art may equally be used. The diluent
holding
material 35 provides another means for modifying the contents of the smoke by
introducing other constituents into and thereby diluting the smoke aerosol.
The diluent holding material 35 may alternatively be located inside a cooling
chamber 40 downstream of the region of high FE material 30. Additional regions
of diluent may be located further downstream the filter section 20. The
cooling
chamber 40 shown in Figure 1 provides a space for smoke to circulate and cool
as it
CA 02829718 2013-09-10
WO 2012/126721 PCT/EP2012/053802
6
travels downstream. The cooling chamber 40 may be between 10 and 30 mm in
length.
Further downstream from the cooling chamber 40 is a region of low FE material
45.
The low FE material 45 may be formed from cellulose acetate threads although
other filtration materials of low FE that are known in the art may be used.
The low
FE material 45 may be formed into a plug which absorbs smoke constituents
passing through. The region of low FE material 45 may be between 10 and 30 mm
in length.
Located within the region of low FE material 45 there may be adsorbent
material 50
which adsorbs smoke constituents. Examples of suitable adsorbent materials
include activated carbon granules, carbon husks or any other material which is
known in the art to adsorb smoke constituents.
A mouth end filter section 55 is located at the mouth end 60 of the smoking
article
10. The mouth end filter section may be between 5 and 15 mm in length. The
mouth end filter section 55 may be formed from a plug of low FE filtration
material
without adsorbent material located therein. The mouth end filter section 55
prevents the adsorbent material 50 from coming into contact with the users
mouth.
Although not shown in Figure 1, flavourants may be included in the mouth end
filter section 55. This can have the effect of counteracting any change to the
taste
that may be caused by the adsorbent material 50.
The tipping paper 25 is provided with a gap 65 along its length which allows
air to
permeate into the filter section 20 and some smoke constituents to permeate
out of
the filter section 20.
An alternative embodiment of the cigarette 10 is shown in Figure 2. The filter
section 20 is substantially the same as the filter section 20 shown in Figure
1. A
bore 70 extends along the longitudinal axis of the tobacco rod 15. The bore 70
provides a passage for smoke to travel downstream from a burning coal 75
towards
the region of high FE filtration material 30. The bore 70 may have a diameter
of
CA 02829718 2013-09-10
WO 2012/126721 PCT/EP2012/053802
7
between 1 and 3 mm. Multiple bores, substantially parallel to each other, may
also
be applied. The bore 70 assists in heat transfer towards the filter section
20.
Forming the tobacco rod 15 from an extruded or compressed composite of tobacco
and carbon, as described above with reference to Figure 1, may also make
forming
the bore 70 easier since the composite material will aid in the retention of
the bore
shape and form. Addition of a binding agent such as guar gum or adhesive
material
to cut tobacco can also be used as an aid in retaining bore shape.
A cigarette 10 similar to that shown in Figure 2 but with a modified filter
section 20
is shown in Figure 3. No gaps, such as the gaps 65 shown in Figure 2, are
provided
in the tipping paper 25. Air permeates through the tipping paper 25 and
plugwrap
27 which are naturally porous. Similarly, some constituents of the smoke are
able to
permeate out of the filter section 20.
A cigarette 10 similar to that shown in Figure 1 comprising an alternative
arrangement of the filter section 20 is shown in Figure 4. In this embodiment,
the
adsorbent material 50 has been included in the cooling chamber 40, for
instance in
granule form filling or substantially filling the cooling chamber cavity.
As the cigarette 10 shown in Figure 1 is lit by a user a coal 75 is formed
where the
tobacco rod 15 and the wrapper 26 circumscribing the tobacco rod 15 are
combusted. A smoke stream is formed which moves towards the filter section 20
as
a pressure differential is formed as a user draws through the mouth end filter
section 55.
The smoke stream is formed from various constituents, each of which exist in a
vapour phase and/or a particulate phase. The amount of each smoke constituent
that exists in each phase depends on the temperature of the smoke. The
proportion
of a particular smoke constituent that exists in the vapour phase rises with
rising
temperature.
CA 02829718 2013-09-10
WO 2012/126721 PCT/EP2012/053802
8
As the smoke moves downstream through the tobacco rod 15 towards the filter
section 20 the temperature of the smoke falls as it moves further from the
coal 75.
The fall in temperature of the smoke is reduced by factors such as changes in
the
downstream flow of the smoke. The flow is affected by using short, slim
tobacco
rods or via channels or bores of low flow resistance in the tobacco and the
use of
low permeability wrappers around the tobacco rod. Additional factors such as
use
of thermal conducting materials and reducing the thermal mass of the tobacco
rod
are also important factors.
As the smoke reaches the region of high FE material 30 a large proportion of
those
constituents travelling in the particulate phase will be removed from the
smoke
stream. The constituents in the particulate phase have higher boiling points
than
those constituents travelling in the vapour phase. A relatively small amount
of the
vapour phase constituents will inevitably be removed from the smoke stream by
the
high FE material 30. However, a proportion of these constituents may be eluted
from the high FE filtration material 30 as more smoke is subsequently drawn
through the filter section 20.
The smoke stream passes through the diluent holding material 35 which dilutes
the
smoke by adding further constituents to the smoke aerosol. As stated above,
the
diluent holding material 35 may be located either within the region of high FE
material 30 or inside the cooling chamber 40.
Inside the cooling chamber 40 the smoke cools to a lower temperature. As the
smoke cools various constituents that were previously in the vapour phase
condense
into the particulate phase.
The rate at which the smoke cools will be affected by factors such as the
positioning
of any perforations such as gap 65 in the tipping paper 26 and the level of
natural
permeability of the tipping paper 25 and plugwrap 27 as the smoke is
ventilated
with ambient air. The gaps 65 may be between 1 and 30 mm in length.
CA 02829718 2013-09-10
WO 2012/126721
PCT/EP2012/053802
9
It will be apparent to those skilled in the art that the choice of tipping
paper 25 and
plugwrap 27 is therefore important since it allows the cooling of the smoke,
and the
proportions of constituents residing in the vapour and particulate phases to
be
better controlled.
As smoke enters the region of low FE material 45 particulate phase
constituents are
removed. The amount of particulate material removed from the smoke stream at
the region of low FE material 45 is lower than that removed at the region of
high
FE material 30 due to the lower filtration efficiency of the region 45
relative to the
region 30.
Adsorbent material 50, such as activated carbon or any other adsorbent of
smoke
constituents that is known in the art, may be located within the region of low
FE
material 45. The adsorbent material 50 removes smoke constituents mainly in
the
vapour phase.
Finally, the smoke stream is drawn through the mouth end filter section 55.
The
mouth end filter section 55 comprises a plug of low FE material. The mouth end
filter section 55 may be impregnated with flavourants of a type known in the
art,
particularly where carbon or other such adsorbents have been employed
upstream.
Figure 5 shows an alternative filter arrangement. The filter section 20
comprises an
annular region of high FE material 80 located where the tobacco rod 15 abuts
the
filter section 20. Downstream of the annular filter section 80 there is
provided a
region of medium FE material 85. The region of high FE material 80 and the
region of medium FE material 85 may be wrapped in thermal conduction material
90, which in turn may be wrapped in insulating material 95.
Downstream of this medium FE material 85 there is provided a filter
arrangement
substantially similar to the arrangement described above with reference to
Figure 1.
The FE of the region 85 is higher than the FE of the region 45 and lower than
the
FE of the region 80.
CA 02829718 2013-09-10
WO 2012/126721 PCT/EP2012/053802
Before use, the centre of the annular region 80 forms a longitudinal bore 86
extending along the length of the annular region 80 which may be approximately
0.1
to 2 mm in width. During use, certain smoke constituents build up in the
central
bore 86, eventually at least partially blocking the bore 86 to smoke
constituents.
5
Therefore, the pressure drop across the filter region 80 during the first few
draws,
for instance while the filter region 80 has yet to become hot and while the
tobacco
rod 15 is at its longest, will differ from that after later draws when the
filter region
80 has become hot and when the tobacco rod 15 has been at least partially
10 combusted and is therefore shorter. Smoke that passes through the filter
region 80
following the first few draws will therefore contain different proportions of
certain
smoke constituents than will smoke passing through the region 80 from later
draws.
This is because some smoke that is drawn through the region 80 from the
earliest
draws will travel through the central bore 86 and will be substantially
unfiltered by
the region 80. However, smoke from later draws will be forced through the
filtration material located in the outer annulus of the annular region 80.
Alternative
configurations of filter region 80, differing in shape or composition, that
will be
apparent to those skilled in the art may be employed.
In the cigarette 10 shown in Figure 5 the region of low FE filtration material
45 may
be wrapped in a plugwrap 96 of high porosity between the region 45 and the
plugwrap 27 which may also be of similar porosity. The mouth end filter
section 55
may be wrapped in a plugwrap 97 with a porosity lower than that of the
plugwrap
96 which wraps the region of low FE filtration material 45.
Additional modifications can be made to the various components within the
filter
section 20 either in combination or separately. For example, the plugwrap 27
surrounding the cooling chamber 40 may be impregnated with an aerosol forming
material such as glycerol or an additional lining layer of a material that can
hold an
aerosol forming material can be added.
Figure 6 shows a cigarette 10 according to yet another embodiment. The
cigarette
10 is similar to that shown in Figure 1 however an annular washer 100 is
located
CA 02829718 2013-09-10
WO 2012/126721 PCT/EP2012/053802
11
upstream of the region of high FE material 30. The washer 100 focuses or
channels
the smoke stream to impinge on the region of high FE material 30 and maintains
the velocity of the smoke stream so as to help minimise heat loss. The region
of
high FE material 30 and washer 100 may be wrapped in thermal conduction
material
90 which, in turn, may be wrapped in an insulating material 95.
The washer 100 may be formed from a conducting material thereby further
enhancing the transfer of heat to the filter section 20. The cooling chamber
40 may
be shaped so to provide a pressure gradient to assist in aerosol formation.
Alternatively, the cooling chamber 40 may be at least partially filled with an
adsorbent material such as carbon.
The wrapper 26, shown in Figures 1-6 may have additional heat conducting means
extending along its length. Figures 7 and 8 show heat conducting strips 110.
The
heat conducting strips can conduct heat from the coal 75 to the region of high
FE
material 30, 80, shown in Figures 1-6, thus increasing the temperature of
smoke at
the point where it leaves the tobacco rod 15 and enters the filter section 20.
The
heat conducting strips 110 may be metallic or comprise any other suitable
conductive material.
As an alternative or in addition to the strips 110 shown in Figures 7 and 8, a
liner
inside the wrapper 26 or a laminate with the wrapper 26 may be included, both
of
which may be in the form of aluminised paper.
The heat conducting strips 110 shown in Figures 7 and 8 may alternatively
allow
heat conducting channels 115 to be formed along the length of the tobacco rod
15.
Smoke may be transferred from the coal 75 to the filter section 20 with
reduced loss
of heat along these channels 115. The strips may be formed from paper,
reconstituted tobacco or any other suitable material that would be apparent to
those
skilled in the art. The strips may be applied to the wrapper 26 before or
after the
wrapper 26 is wrapped around the tobacco rod 15. Figure 8 shows a wrapper 26
with strips 110 applied thereto prior to being wrapped around a tobacco rod
15.
The strips 110 may extend along part of the length of the tobacco rod 15 or
along
CA 02829718 2013-09-10
WO 2012/126721
PCT/EP2012/053802
12
the entire length of the tobacco rod 15. Channels 115 may alternatively be
formed
by placing a corrugated inner wrapping material 120 between the wrapper 26 and
the tobacco rod 15 as shown in Figure 9.
While Figures 7 and 9 show end views of cigarettes 10 without bores 70
present,
such bores 70 may be present according to various embodiments of the present
invention.
Modifications made to alter the temperature profile of smoke passing through
the
length of the cigarette 10 and the order of components within the cigarette 10
can
be made without departing from the scope of the invention which is defined by
the
appended claims.
It should also be understood that while the foregoing description refers to
cigarettes, the scope of the present invention may apply equally to other
smoking
articles known in the art.
Experimental Data
The smoke profile of a cigarette similar to the cigarette 10 shown in Figure 1
was
analysed. The cigarette differed from the cigarette 10 shown in Figure 1 in
that the
filter section did not contain diluents, adsorbents or ventilation gaps. Smoke
constituents measured included particulate nicotine, particulate water, tar
(NFDPM), benzo(a)pyrene (B(a)P) and catechol. Also shown in the table are the
ratios of B(a)P to NFDPM and catechol to NFDPM as well as the number of puffs
or draws from each cigarette. The cigarette according to the invention was
compared with two control cigarettes and the results are set out in the
following
table. The cigarettes were investigated by analysing draws of 55 cubic
centimetres
(cc) of 2 seconds' duration and with a 30 second interval between draws.
CA 02829718 2013-09-10
WO 2012/126721 PCT/EP2012/053802
13
Table 1
Invention Control 1 Control 2
example
Tip ventilation NO YES NO
Total particulate mg/cigarette 19 20 45.8
matter (TPM)
Nicotine mg/cigarette 0.7 1.5 2.11
Water mg/cigarette 8.7 3.8 19.2
Nicotine-Free Dry mg/cigarette 9.7 14.7 24.5
Particulate Matter
(NFDPM)
Puff Number 7.1 9.1 7
Benz o(a)pyrene ng/cigarette 5.2 14.8 17.7
(B(a)P)
B(a)P/NFDPM x10-6 0.54 1.01 0.72
Catechol Ilg/cigarette 21.2 59.5 74.2
Catechol/NFDPM x10-3 2.19 4.05 3.03
Exemplary cigarettes according to the invention, together with Control 1 and
Control 2 contained the same blend of tobacco, tobacco rod and filter length.
The
cigarette labelled Control 1 had a conventional cellulose acetate filter with
ventilation gaps so that the total particulate matter (TPM) matched that of
the
cigarette of the invention. The cigarette referred to as Control 2 was similar
to the
invention cigarette however the region of high FE filtration material 30 was
replaced with a low efficiency cellulose acetate filter. In the invention
cigarette the
high FE material was made from glass fibre.
The results, as displayed in the above table, show that the ratios of B(a)P
and
catechol to NFDPM are lower in the example of a cigarette in accordance with
the
invention than in either of the control cigarettes. B(a)P and catechol have
relatively
high boiling points and are therefore removed, in their particular phases, by
the high
FE filter portion.
CA 02829718 2015-02-03
14
Embodiments of the invention can therefore be arranged to control the levels
of smoke
constituents based on their relative boiling points. For instance, the high FE
filter region
of embodiments of the invention can be used to selectively remove only smoke
constituents having relatively high boiling points, for instance boiling
points above a
particular temperature, for instance above temperatures in the region of 250
C, 300 C,
350 C, 400 C, 450 C or 500 C. Such constituents would be in the particulate
phase when
passing through the high FE filter region 30, 80, 85.
By cooling the smoke in the cooling chamber 40, the low FE filter material 45
having the
adsorbent material 50, according to certain embodiments of the invention, can
selectively
remove smoke constituents having relatively low boiling points for instance
constituents
having boiling points below about 300 C, 250 C, 200 C, 150 C or 100 C.
