Note: Descriptions are shown in the official language in which they were submitted.
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SMOKING ARTICLE HAVING AN INNER WRAPPER COMPRISING
RECONSTITUTED TOBACCO MATERIAL
Field
The invention relates to a low ignition propensity smoking article comprising
a wrapped rod
of smokeable material.
Background
As used herein, the term "smoking article" includes smokeable products such as
cigarettes,
cigars and cigarillos whether based on tobacco, tobacco derivatives, expanded
tobacco,
reconstituted tobacco or tobacco substitutes and also heat-not- burn products.
Low ignition propensity (LIP) cigarettes have previously been manufactured by
providing
circumferential bands of burn suppressant in specifically developed cigarette
papers. The
bands of burn suppressant are designed to inhibit the burn rate of the tobacco
rod and to
cause the cigarette to self-extinguish unless a smoker regularly draws on the
filter.
ASTM E2187-04 specifies a standardized test against which the ignition
propensity
properties of smoking articles can be assessed. National regulation often
requires that low
ignition propensity smoking articles comply with specific requirements when
tested in
accordance with ASTM E2187-04. For example, when tested in accordance with
ASTM
E2187-04, national regulation may require that at least 75% of a test sample
of forty LIP
smoking articles self-extinguish before burning to the end of the tobacco rod.
The development of specific LIP cigarette papers with bands of burn
suppressant has
allowed the tobacco industry to produce cigarettes which comply with
regulatory
requirements for LIP smoking articles in accordance with ASTM E2187- 04.
The manufacture of cigarette papers incorporating bands of burn suppressant
has involved
applying the bands of burn suppressant to a pre-formed base paper to create
the LIP cigarette
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paper. The burn suppressant application process generally takes place
separately from
cigarette assembly and requires specialised equipment for applying the burn
suppressant to
the base paper. The use of a burn suppressant also adds expense to the overall
cigarette
production process.
Summary
In accordance with the invention, there is provided a low ignition propensity
smoking article
comprising: a rod of smokeable material; an inner wrapper comprising
reconstituted tobacco
material wrapped around the smokeable material, the inner wrapper having a
permeability of
between 17 and 38 CORESTA; and an outer wrapper wrapped around the smokeable
material and the inner wrapper, the outer wrapper having a permeability of
between 25 and
100 CORESTA.
The inner and outer wrappers may not comprise bands of burn suppressant
material.
The circumference of the smoking article may be between 15mm and 22mm.
The circumference of the smoking article may be between 15mm and 19mm.
The circumference of the smoking article may be between 15mm and 17mm.
The circumference of the smoking article may be between 16.9mm and 17.0mm.
The circumference of the smoking article may be between 20.5mm and 21.5mm.
The length of the smoking article may be between 80mm and 120mm.
The length of the smoking article may be between 82mm and 84mm.
The permeability of the inner wrapper may be 10 CU or less.
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The permeability of the outer wrapper may be between 25 and 100 CU.
The permeability of the outer wrapper may be between 70 and 100 CU.
The inner wrapper may be reconstituted tobacco material, such as reconstituted
tobacco
sheet.
The outer wrapper may be a low sidestream cigarette paper.
The smoking article may be a cigarette comprising a filter, a smokeable
material rod and a
tipping paper overlapping the filter and the rod to axially join the rod and
the filter together.
In an LIP test according to ASTM E2187-04 carried out on a plurality, for
example forty, of
the cigarettes, at least 75% of the cigarettes self extinguish before the
burning end of the rod
reaches the tipping paper.
In accordance with the invention, there is also provided a method of forming a
low ignition
propensity smoking article comprising: wrapping an inner wrapper comprising
reconstituted
tobacco material around a rod of smokeable material, the inner wrapper having
a
permeability of between 17 and 38 CORESTA; and wrapping an outer wrapper
around the
rod of smokeable material and the inner wrapper, the outer wrapper having a
permeability of
between 25 and 100 CORESTA.
For the purposes of example only, embodiments of the invention are described
below with
reference to the accompanying drawings, in which:
Brief Description of the Drawings
Figure 1 is a perspective illustration of a low ignition propensity smoking
article comprising
a rod of smokeable material wrapped in first and second wrappers;
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figure 2 is a perspective illustration of a part-assembled rod of smokeable
material
for a low ignition propensity smoking article. The rod comprises a tobacco
core
wrapped in an inner wrapper and partially wrapped in an outer wrapper; and
figure 3 is an illustration of an end face of a rod of smokeable material
having a
core of smokeable material, an inner wrapper wrapped around the core of
smokeable material and an outer wrapper wrapped around the inner wrapper.
Detailed Description
An example of a low ignition propensity (LIP) smoking article 1 is shown in
Figure
1.
The smoking article 1 shown in Figure 1 comprises an LIP cigarette 1 having a
filter
2 and a rod 3 of smokeable material such as tobacco. The smoking article 1 may
however comprise another type of smoking article such as one of those referred
to
above.
The filter 2 and the rod 3 are coaxially joined together by a sheet of
overlapping
tipping paper 4, which is secured around the external surfaces of the rod 3
and the
filter 2 in a conventional manner in order to secure the two together. The
dotted
line in Figure 1 indicates the location of the abutting end faces of the
filter 2 and
the rod 3, overlapped by the tipping paper 4.
If a plurality of the smoking articles 1, for example forty, are tested in
accordance
with ASTM E2187-04, 75% or more of the plurality of smoking articles 1 self-
extinguish before the burning end of the smokeable material rod 3 reaches the
tipping paper 4. Therefore, 25% or less of the plurality of smoking articles
burn the
full length of the smokeable material rod.
The filter 2 may be substantially cylindrical in shape with a conventional
construction. For example, a substantially cylindrical plug of filter material
comprising cellulose acetate tow may be wrapped in a sheet of plug wrap around
its
circumferential surface. Any type of filter 2 could be used, including for
example
more complex filters 2 comprising carbon and/or one or more flavourant
materials
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for flavouring a gaseous flow inside the filter 2. The filter 2 may be vented
by vent
channels formed using laser or electrostatic perforation techniques. The vent
channels may provide an overall vent percentage of between 20% and 80%,
preferably between 50% and 70%.
The rod 3 may also be substantially cylindrical in shape, with an external
diameter
substantially equal to the external diameter of the filter 2. Referring to
Figure 2, the
rod 3 comprises a substantially cylindrical core of packed tobacco material 7
wrapped in a first wrapper 8 and a second wrapper 9. The tobacco material 7
may
comprise a blend of shredded tobacco, and may also include reconstituted
tobacco
material. In the examples discussed below, the first wrapper 8 is positioned
inwardly of the second wrapper 9 and as such is closer to the core of tobacco
material 7. The first wrapper 8 will therefore be referred to herein as the
inner
wrapper 8. The second wrapper 9 is positioned outwardly of the first wrapper 8
and
will be referred to herein as the outer wrapper 9. The outer wrapper 9 may
form
the external surface of the rod 3, with the inner wrapper 8 positioned between
the
outer surface of the core of tobacco material 7 and the inner surface of the
outer
wrapper 9.
The inner wrapper 8 is a sheet wrapping material comprising reconstituted
tobacco
material, and may be configured to impart desirable and varied flavour and
sensing
characteristics to the smoking article. For example, the inner wrapper 8 may
comprise or consist of reconstituted tobacco sheet, which may in turn comprise
or
consist of one or more types of reconstituted tobacco material. The
reconstituted
sheet can comprise a range of different tobacco types selected to improve the
transmission of tobacco tastes and flavours to a smoker of the cigarette. For
example, the reconstituted material can comprise one or more of sun-cured
tobacco,
dark air-cured tobacco, fire-cured tobacco or any other suitable tobacco type.
The
permeability of the inner wrapper 8 may be in a range between 5 Corcsta (CU)
and
50 Coresta, preferably between 17 Coresta and 38 Coresta. The one-ply
thickness
of the inner wrapper 8 may be any value in a range of between approximately 85
microns and approximately 121 microns. The dry basis weight of the inner
wrapper
8 may be any value between approximately 35 g/m2 and approximately 43 erri2.
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The diffusivity of the inner wrapper 8 may be any value between approximately
0.8
cm/s and approximately 2.8 cm/s.
Examples of three specific inner wrappers 8 that can be used are given in
Table 1
below. All of the inner wrappers 8 shown in Table 1 are sheets of
reconstituted
tobacco material.
Table 1
Inner Wrapper 1 2 3
Value S.D. Value S.D. Value S.D.
Diffusivity (cm/s) 0.973 0.1407 1.139 0.1735 2.657 0.5575
Grammage (gsm) 43.8 0.51 43.3 0.10 42.5 0.12
Width (mm) 18.587 0.0540 18.594 0.0471 16.180 0.0354
Strain 0.89 1.11 0.83
Tensile Strength
9.7 9.1 7.6
(N/15mm)
Permeability (CU) 37.5 12.12 17.9 4.93 26.7 6.18
Thickness (um) 102 13.4 106 14.4 109 11.2
As is shown in Figure 2, the inner wrapper 8 may extend around the
circumferential
surface of the core of tobacco material 7. For example, referring to Figures 2
and 3,
the inner wrapper 8 may extend fully around the circumference of the core 7
and
fully along the axial length of the rod 3. The inner wrapper 8 may thereby
cover
substantially the whole of the circumferential surface of the core 7.
Alternatively,
the inner wrapper 8 may extend partially around the circumference of the core
7
and/or partially along the length of the rod 3. The inner wrapper 8 may
therefore
comprise a patch underneath a full length outer wrapper 9. The end faces of
the
core 7 are left open to allow a gaseous flow to enter and exit the rod 3 at
its distal
and filter ends respectively.
The outer wrapper 9 is also a sheet wrapping material, for example comprising
or
consisting of a cigarette paper or low sidestream (LSS) cigarette paper.
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Alternatively, the outer wrapper 9 may comprise or consist of a plurality of
types of
cigarette paper and/or LSS cigarette paper.
The dry basis weight of the outer wrapper 9 may be any value between
approximately 28 g/m2 and approximately 40 g/m2, with between approximately
16.0 g/m2 and approximately 32.0 g/m2 of fibre, between approximately 0.3 g/m2
and approximately 2.0 g/m2 of 1(3 citrate, between 0 g/m2 and approximately 2
g/m2 of MgO and between approximately 4 g/m2 and approximately 11 g/m2 of
CaCO3. Other ranges can be used. The amount of total filler in the outer
wrapper
9 may be any value between approximately 6 g/m2 and 10 g/m2, which is a total
filler percentage by weight of between approximately 15% and 40%. Other ranges
can be used.
The permeability of the outer wrapper 9 may be any value between approximately
25 Coresta and approximately 100 Coresta. Within this range, the permeability
of a
cigarette paper may be approximately 25 Coresta, whilst the permeability of a
LSS
cigarette paper may be between approximately 70 Coresta and approximately 100
Coresta. The diffusivity of the outer wrapper 9 may be any value between
approximately 0.30 cm/s and approximately 0.50 cm/s.
Examples of three specific outer wrappers 9 are given in Table 2 below.
Example 1
is a cigarette paper, whilst examples LSS 1 and LSS 2 arc low sidcstream
cigarette
papers. LSS 1 is ventilated by electroperforation (EP) and has a permeability
of 70
Coresta units. LSS 2 is also ventilated by electroperforation and has a
permeability
of 100 Coresta units.
Table 2
Outer LSS 1 LSS 2
1
Wrapper EP70 EP100
Basis Weight
28 40 40
Total Dry
(100%) (100%) (100%)
(g/rn2)
Fibre (g/m2) 16.8 31.5 31.5
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(60%) (78.75%) (78.75%)
K, Citrate
0.3 (1%) 2 (5%) 2 (5%)
(g/m2)
MgO (g/m2) 2 (5%) 2 (5%)
CaCO3 10.9 4.5 4.5
(g/m2)
(39%) (11.25%) (11.25%)
Total Filler 10.9 6.5 6.5
(g/m2)
(39%) (16.25%) (16.25%)
Diffusivity
0.392 0.447 0.447
(cm/s)
The outer wrapper 9 may extend around the outer circumferential surface of the
inner wrapper 8. For example, as shown in Figures '1 to 3, the outer wrapper 9
may
extend fully around the outer circumference of the inner wrapper 8 and fully
along
the axial length of the rod 3, thereby covering substantially the whole of the
outer
circumferential surface of the inner wrapper 8. In this manner, the outer
wrapper 9
encloses both the inner wrapper 8 and the core of tobacco material 7. The end
faces of the rod 3 are left open to allow a gaseous flow to pass axially
through the
rod 3. In the examples shown in Figures 1 to 3, the outer surface of the outer
wrapper 9 forms the outer surface of the rod 3 to which the tipping paper 4 is
adhered at the filter end.
In terms of dimensions, the cigarette 1 can have an external circumference of
approximately 16.96mm and an overall length (pre-smoking) of approximately
83rnm. The length of the rod 3 (pre-smoking) can be approximately 56mm and the
length of the filter 2 can he approximately 27mm. It will he appreciated that
these
dimensions can be varied. For example, the external circumference of the
cigarette
1 may be any value between 15mm and 22mm, whilst the overall length of the
cigarette 1 may be any value between 80mm and 120mm. The external
circumference may, for example be approximately 21mm. The overall length of
the
cigarette 1 can be varied by increasing/decreasing the length of either or
both of the
rod 3 and the Filter 2.
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The cigarette 'I does not comprise a specifically developed HP cigarette paper
having bands of burn suppressant designed to limit the burn rate of the rod 3.
Manufacture of the cigarette 1 therefore does not require the pre-production
of a
specifically developed banded LIP cigarette paper, and accordingly does not
require
the specialised equipment necessary for applying burn suppressant to cigarette
paper.
Ignition propensity tests carried out on samples of forty cigarettes 1 show
that
significantly less than 25% of the cigarettes 1 burn down to the tipping paper
4
when tested in accordance with ASTM E2187-04. For example, Table 3 below
illustrates the ignition propensity of six different sample cigarettes 1 in
accordance
with the invention (Samples 1-6). For each sample cigarette (1-6), forty
cigarettes
were tested in accordance with ASTM 2187-04. The rightmost column of Table 3
indicates the percentage of cigarettes which did not self-extinguish before
the
burning end of the smokeable material rod 3 reached the tipping paper 4.
Table 3
% of cigarettes
exhibiting full
Cigarette Inner Wrapper Outer Wrapper
length burn of
tobacco rod
Sample 1 1 1 2.5
Sample 2 1 LSS 1 5
Sample 3 1 LSS 2 12.5
Sample 4 3 1 0
Sample 5 3 LSS 1 7.5
Sample 6 3 LSS 2 2.5
The cigarette 1 therefore has LIP properties that are comparable to cigarettes
incorporating specifically developed LIP papers, but can be produced without
the
requirement to manufacture the LIP papers.
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The cigarette 1 has a relatively high puff number compared to single wrapped
cigarettes. For example, when smoked under ISO standard conditions, the
cigarette
1 may have an average puff number of approximately 7.5 compared to an average
puff number of approximately 6.5 for a control, single wrapped cigarette
wrapped in
outer wrapper #1 (see Table 2 above).
The diffusivity of the combination of the inner wrapper 8 and the outer
wrapper 9
of the cigarette 1 is comparable to the diffusivity of specifically developed
LIP
cigarette papers with bands of burn suppressant. The diffusivity value for the
combination of inner and outer wrappers 8, 9 may be any value in a range of
between 0.080 cm/s and 0.095 cm/s.
The cigarette 1 exhibits low sidestream smoke compared to control cigarettes
manufactured with commercially available materials.
For example, Table 4 below illustrates sidestream smoke chemistry results for
the
six example cigarettes 1 listed in Table 3 (Samples 1-6). Also illustrated in
Table 4
are sidestream smoke chemistry results for two control, single-wrapped
cigarettes.
The tobacco density of all of the cigarettes in Table 4 is 263 g/cm3 at 13.5%
moisture. The tobacco blend used in the tobacco rod 3 is the same for all of
the
cigarettes other than Control #1, in which a different blend was used.
Table 4
Inner Outer NFDPAI Nicotine CO CO, Total
Cigarette
wrapper wrapper (mg/cig) (mg/cig) (mg/cig) (mg/cig) (mg/cig)
Control
1 14.0 2.49 28.3 235.7 280.5
1
Control
1 12.9 2.56 28.3 228.6 272.5
2
Sample
1 1 8.9 1.29 28.5 237.6 276.3
1
Sample
1 LSS 1 5.7 0.87 27.2 265.8 299.5
2
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Sample
1 LSS 2 6.7 1.15 28.9 265.4 302.1
3
Sample
3 1 9.4 1.43 27.7 241.2 279.7
4
Sample
3 LSS 1 6.2 0.89 29.7 276.3 313.2
Sample
3 LSS 2 6.5 1.07 29.5 269.0 306.1
6
As can be seen from Table 4, the sidestream Nicotine Free Dry Particulate
Matter
(NFDP \I) and sidestream Nicotine is significantly reduced compared to the
control
cigarettes.
5
The visible sidestream produced by cigarettes 1 in accordance with the
invention is
also reduced as compared to control cigarettes manufactured with commercially
available materials. For example, the cigarettes 1 may emit approximately 40%
to
60% less visible sidestream smoke than a control cigarette which is single-
wrapped
in outer wrapper #1 (see Table 2 above). The amount of visible side stream
smoke
is least when the outer wrapper 9 comprises an LSS cigarette paper. Either of
the
LSS papers described above can be used.
The reduction in visible sidestream smoke can be calculated by comparing a
photograph of a burning control cigarette with a corresponding photograph of a
burning cigarette 1 in accordance with the invention, and counting the
difference
between the number of pixels in the two photographs representing sidestream
smoke. .
Table 5 illustrates the visible sidestream smoke from three examples of the
cigarette
1 (Samples 4-6), together with the visible sidestream smoke from a control,
single-
wrapped cigarette (Control 2). The sidestream smoke reductions are calculated
using the photographic method explained above, with each measurement being
taken at an equivalent burn length percentage of the rod 3. The filter,
tobacco
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density and tobacco blend used in the rod 3 is the same for all cigarettes
listed in
Table 5. The tobacco density is 263 g/cm3 at 13.5% moisture.
Table 5
Pixels
Reduction (%)
Inner Outer representing
Cigarette in pixels
Wrapper Wrapper visible
versus Control
sidestream
Control 2 1 985,741
Sample 4 3 1 505,735 49
Sample 5 3 LSS 1 434,001 56
Sample 6 3 LSS 2 475,311 52
An example method of manufacturing the cigarette 1 will now be briefly
described.
Beginning with the filter 2, as is known in the field, a plug of filter
material can be
formed by feeding a substantially continuous flow of cellulose acetate tow
into a
funnel to provide a generally cylindrical body of cellulose acetate material.
The
cellulose acetate material can be passed through a garniture that attaches the
plugwrap to the filter material from a plugwrap reel. 'rhe resulting wrapped
filter
material can subsequently be cut into individual segments for use in making
the
filter 2. The cut length may be suitable for producing two cigarettes 1 in
tandem or
individual cigarettes 1, as required. Also, the cutting may be carried out as
a multi-
stage process in which lengths of filter material for use with multiple
cigarettes 2 are
cut initially, and are then later cut into lengths suitable for use in
manufacturing
cigarettes 1 in tandem or individually.
Assembly of the cigarette 1 can be carried out using a suitable rod maker
fitted with
a tipping unit. The inner wrapper 8 and outer wrapper 9 can be provided as
bobbins with lengths of approximately 2500m and widths of 16.2mm. Alternative
widths can be 15.8mm, 18.5mm, 20.0min or 23mm, depending on the desired
cigarette circumference. The wrappers 8, 9 are pulled from bobbin carriers
located
next to the rod maker and guided simultaneously to a garniture by a series of
rollers
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and a paper guide for assembly of the cigarette. Inner wrapper 8 from the
inner
wrapper bobbin is wrapped around a column of smokeable material, and
concurrently wrapped with outer wrapper 9 from the outer wrapper bobbin. The
relative positions of the inner 8 and outer 9 wrappers can be adjusted in the
rod
maker in order to adjust the size of an overlap seam for each wrapper 8, 9.
As an alternative, assembly of the cigarette 1 can comprise cutting patches of
the
inner wrapper 8 and applying the patches 8 to an internal surface of the outer
wrapper 9 in a gluing process. The combination of the outer wrapper 9 and
patches
8 can then be fed to a garniture for wrapping around a smokeable material
column.
The alternatives described above can be used singly or in combination to
achieve
the effects of the invention. It will be appreciated that the cigarette 1
could
alternatively comprise another type of smoking article such as a cigar or a
cigarillo.
