Note: Descriptions are shown in the official language in which they were submitted.
2Q~172'~
CONCENTRIC SMOKING FILTER HAVING
DISCRETE TOW AND WEB FILTER MEDIA
Backcxround of the Invention
This invention relates to smoking filters,
and particularly to concentric smoking filters. More
particularly, this invention relates to concentric
smoking filters having tow and web filter media
portions arranged concentrically.
Most smoking filters, particularly cigarette
filters, sold commercially as part of cigarettes
consist of a cylindrical rod or "plug" of a "tow" of
plasticized cellulose ~acetate fibers. Some filters are
variants of the standard filter, having recessed mouth
ends, or being made of two plugs placed end-to-end with
a space in between, the space being either empty or
filled with another material such as charcoal. It is
also known to provide such filters having multiple
plugs abutting one another, the different plugs
differing in density or other characteristics.
Similarly, it is known to provide filtering
media other than cellulose acetate. One such medium is
an appropriate sheet or web material. The web
material, which is gathered into a cylindrical plug,
can be paper or any other web material,~including
cellulose acetate in sheet form. When such web
materials are used as filters, they are frequently
corrugated before being gathered. Paper webs may also
be creped to improve tensile strength.
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Some of these different materials and
different constructions have been combined. For
example, it is known to provide filters having two or
more abutting plugs, at least one of which is cellulose
5 acetate tow, and at least one of which is a web
material.
Finally, it is known to provide "concentric
filters" in which two different forms of cellulose
acetate tow -- differing, e.g., in density -- are
10 formed in to a filter. One cellulose acetate tow forms
a cylindrical "core", while the other tow forms an
annular peripheral layer.
Smoking filters are characterized by various
parameters, including pressure drop, which is referred
15 to as resistance-to-draw ("RTD") and usually measured
as the height of a column of water, and efficiency,
which is measured as the percentage of the total
particulate matter ("TPM") in the unfiltered
smokestream that is trapped by the filter. The RTD of
20 a filter affects how smokers perceive the filter in
terms of how hard they must draw on it to receive a
desired amount of smoke, while the filter efficiency
controls the amount of TPM delivered in the smoke.
It has been found that while web filters, and
25 particularly paper filters, are more efficient than tow
filters, the web material, especially paper, adds an
off taste to the smoke which decreases smoker
satisfaction. In addition, the appearance of the
visible deposited smoke components on the end of a
30 paper filter is much less regular, and more spotty,
than on a cellulose acetate tow filter,~again affecting
the aesthetic impact on the smoker. This difference in
appearance is believed to result from the channelling
of deposited material in the channels formed by the
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corrugation and gathering of the web during plug
making.
As consumer preferences tend toward lower
delivery cigarettes, the need for,higher efficiency
5 filters, which allow lower delivery without increased
filter RTD, increases. However, the higher efficiency
of paper filters could not previously be taken
advantage of because of the negative consumer impacts
of paper filters.
l0 It would be desirable to be able to provide a
high efficiency filter which produced low delivery
while also delivering acceptable taste, RTD and other
aesthetic impacts.
Summary of the Invention
15 - It is an object of this invention to provide
a high efficiency filter which produces low delivery
while also delivering acceptable taste, RTD and other
aesthetic impacts.
In accordance with this invention, there is
20 provided a smoking filter comprising a first filter
plug having a central core of a first filter material
and a peripheral layer of a second filter material
surrounding the central core. One of the first and
second filter materials is cellulose acetate tow and
25 the other of the first and second filter materials is a
gathered corrugated web material. When the filter is
attached to a smoking article and delivers, when the
smoking article is smoked, a particular level of total
particulate matter; the taste of the smoking article is
30 a taste associated with a level of total particulate
matter higher than that particular level.
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Brief Description of the Drawings
The above and other objects and advantages of
the invention will be apparent upon consideration of
the following detailed description, taken in
5 conjunction with the accompanying drawings, in which
like reference characters refer to like parts
throughout, and in which:
FIG. 1 is a mouth end perspective view of a
cigarette having a first embodiment of a filter
10 according to the present invention;
FIG. 2 is a radial cross-sectional view of
the filter of FIG. 1;
FIG. 3 is a mouth end perspective view of a
cigarette having a second embodiment of a filter
15 according to the present invention;
FIG. 4 is a radial cross-sectional view of
the filter of FIG. 3;
FIG. 5 is a mouth end perspective view of a
cigarette having.a third embodiment of a filter
20 according to the present invention; and
FIG. 6 is a mouth end perspective view of a
cigarette having a fourth embodiment of a filter
according to the present invention.
Detailed Description of the Invention
25 In accordance with the present invention, it
has unexpectedly been found that when a concentric
filter is made with paper or other web material in the
core, and cellulose acetate tow in the periphery, or
vice-versa, not only is high filtration efficiency
30 achieved without the introduction of an~~off taste from
the paper, but a cigarette with low TPM delivery can be
produced which has the taste of a cigarette with a
higher TPM delivery.
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As shown in FIGS. 1 and 2, cigarette 10
includes a tobacco rod 11 and a first preferred
embodiment of a filter 12 according to this invention.
Tobacco rod il is wrapped in conventional wrapper 13,
while filter 12 is wrapped by conventional tipping 14.
Filter 12 includes cellulose acetate tow peripheral
layer 20 and central paper core 21. Cellulose acetate
peripheral layer 20 is a conventional cellulose acetate
tow, preferably wrapped by porous plug wrap 22,
although self-supporting filter rod technology, such as
steam bonding or spray coating of the outer surface of
peripheral layer 20, can be used to make a filter that
need not be wrapped, if desired. Paper core 21 is a
paper web that has been corrugated and gathered into
cylindrical form and wrapped with plug wrap paper 23.
Plug wrap 23 improves the processibility of
core 21 as well as its aesthetic appearance, and also
helps to assure substantially perfect concentricity.
Flavorants or other additives, such as soluble tobacco
components, could be applied to plug wrap 23 to enhance
the subjective impact of the filtered smoke. A similar
result might be achieved by forming plug wrap 23 from a
tobacco-containing material, such as reconstituted
tobacco sheet. Plug wrap 23 is preferably porous, to
allow smoke and air to freely move radially between
peripheral layer 20 and core 21. At the same time, the
presence of plug wrap 23 helps prevent channelling of
smoke along the interface between peripheral layer 20
and core 21.
fihe most preferred embodiment of filter 12
has a circumference of about 24.45 mm and an average
weight of about 258 mg. The cross-sectional area of
core 21 preferably makes up about 60% of the total
cross-sectional area of filter 12. Filter 12
preferably has an RTD of between about 130 mm W.G. and
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about 160 mm W.G., with the RTD of central core 21
being between about 350 mm W.G. and about 450 mm W.G..
More preferably, filter 12 has an RTD of about
146 mm W.G., with the RTD of central core 21 being
about 400 mm W.G. _.
In the particularly preferred embodiment, the
cellulose acetate tow of peripheral layer 20 is
preferably an 8.0/30000 cellulose acetate tow having a
denier per fiber of 8, a total denier of 30,000, and a
"Y" cross-sectional shape. The web of core 21 is
preferably a 100% cellulose semi-creped softwood pulp
paper with 10% crosswise creping for added tensile
strength. Such a paper is available from Tela
Papierfabrik AG, of Balsthal, Switzerland.
Cigarette 10 is preferably ventilated to
between about 65% and about 75% ventilation, and more
preferably about 67% ventilation, with appropriate
ventilation holes 15 provided in tipping 14. If the
surface of filter 12 is not air permeable, appropriate
holes would also be provided in filter 12.
FIGS. 3 and 4 show a cigarette 30 having a
second preferred embodiment of filter 31 similar in
construction to filter 12, except that core 40 is a tow
material and peripheral layer 41-is a web material.
Similarly, in this embodiment plug wrap 42 is necessary
to contain the web material of peripheral layer 41,
while plug wrap or other permeable wrap 43 around tow
core 40 is optional, as tow core 40 could be made using
self-supporting filter rod technology, as above.
The most preferred embodiment of filter 31
has a circumference of about 24.45 mm and an average
weight of about 240 mg. The cross-sectional area of
core 40 preferably makes up about 60% of the total
cross-sectional area of filter 31. Filter 31
preferably has an RTD of between about 165 mm W.G. and
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about 195 mm W.G., with the RTD of central core 40
being between about 285 mm W.G. and about 385 mm W.G:
More preferably, filter 31. has an RTD of about
182 mm W.G., with the RTD of central core 40 being
about 334 mm W.G. _.
In this embodiment, the cellulose acetate tow
of core 40 is preferably a 1.6/35000 cellulose acetate
tow having a denier per fiber of 1.6, a total denier of
35,000, and a "Y" cross-sectional shape. The web of
l0 peripheral layer 41 is preferably the same 100%
cellulose semi-creped softwood pulp paper, with 10%
crosswise creping for added tensile strength, that is
used in core 21 of filter 12.
Cigarette 30 is preferably ventilated to
between about 65% and about 75% ventilation, and more
preferably about 67% ventilation, with appropriate
ventilation holes 15 provided in tipping 14, as in
cigarette 10.
FIG. 5 shows a cigarette 50 having a third
preferred embodiment of a,filter 51 according to the
invention. Filter 51 is a so-called "dual" filter,
made up of two abutting filter segments 52, 53. Filter
segment 52, which is adjacent tobacco rod il, is a
concentric filter as discussed above, is which one of
core 54 and peripheral layer 55 is of a web material
and the other of core 54 and peripheral layer 55 is of
a tow material. Filter segment 53, which is at the
mouth end, is a conventional tow filter, such as a
cellulose acetate filter, and is provided primarily for
cosmetic purposes. Nevertheless, segment 53 has
filtration and RTD characteristics, and~segment 52 mush
be adjusted so that the overall filter 51 has the
desired characteristics.
In a preferred form of this embodiment,
segment 52 is constructed like filter 12, but has a
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length of only 18-20 mm, while segment 53 is a 7-9 mm
long plug of 2.6/42000 cellulose acetate for tow having
a denier per fiber of 2.6, a total denier of 42,000,
and a "Y" cross-sectional shape. Total filter RTD is
between about 125 mm W.G. and about 175 mm W.G.,
preferably about 141 mm W.G. The RTD of segment 53 is
between about 15 mm W.G. and about 45 mm W.G.,
preferably about 36 mm W.G. The RTD of segment 52 is
between about 85 mm W.G. and about 175 mm W.G.,
preferably about 93 mm W.G. The RTD of the paper core
54 of segment 52 is between about 250 mm W.G. and about
450 mm W.G., preferably about 267 mm. W.G. Cigarette
50 made with this embodiment of filter 51 is ventilated
to between about 65% and about 75% ventilation,
preferably about 71% ventilation, with appropriate
ventilation holes 15 in tipping 14.
FIG. 6 shows a cigarette 60 having a fourth
embodiment of a filter 6~1 according to the invention.
Filter 61 is a recessed filter, made up of filter
segment 62 recessed into tipping 14 at 63. Filter
segment 62, which is adjacent tobacco rod 11, is a
concentric filter as discussed above, in which one of
core 64 and peripheral layer 65 is of a web material
and the other of core 64 and peripheral layer 65 is of
a tow material.
The filter parameters discussed herein are
given for 85 mm cigarettes. It is to be understood
that filters according to the present invention can
also be used with longer cigarettes. If a longer
cigarette is provided, the filter parameters would have
to be adjusted, in accordance with the knowledge of
those skilled in the art.
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EXAMPLE I
A filter according to the most preferred
embodiment discussed above in connection with FIGS. 1
and 2, except that the tow in the peripheral layer was
an 8:0/25000 cellulose acetate tow having a denier per
fiber of 8.0 and a total denier of 25000, was prepared
and mated to an "ultra-light" tobacco rod having the
following characteristics:
Tobacco 487 mg
1 O Total RTO 107 mm
W.G.
Filter RTD 146 mn
V.G.
Ventilation 6TX
Tipping length 32.0 am
The cigarette was smoked in a smoking machine under FTC
conditions with the following results:
TPN 1.8 og
Nicotine 0.16 mg
lfater 0.21 mg
"Tar" 1.5 mg
2 0 Puff Count 6.2
The cigarette, which generates 1.5 mg of
"tar", was also smoked by expert smokers, who reported
that the cigarette had the taste of a cigarette that
generates 4-5 mg of "tar". At 67% ventilation, the
filter has an efficiency of about 76%. If there had
been no ventilation, the efficiency would have been
about 61%.
The cigarette also exhibited a pattern of
visible deposition of filtrate on the end of the filter
much more like a tow filter as opposed to a web filter,
even though most of the filtrate was deposited on the
web core. This is believed to be the result of the
smoke being forced into core 21 as the ventilation air
is introduced at holes 15, and then trying to spread
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back into peripheral tow layer 20 through permeable
wrapper 23.
EXAMPLE II
A filter according to the preferred form of
the embodiment of FIG. 5 was prepared and mated to an
"ultra-light" tobacco rvd having the following
characteristics:
Tobacco 429 mg
Total RTO 93 mn W.G.
1 0 Filter RTO 141 mm W.G.
Ventilation 71X
Tipping length 32 rtm
The cigarette was smoked in a smoking machine under FTC
conditions with the following results:
TPN 1.6 mg
Nicotine 0.13 ng
Water 0.10 ag
"TarN 1.4 rtg
Puff Count 5.3
As in the case of Example I, this cigarette
was smoked by expert smokers who reported that the
cigarette had the taste of a cigarette that generates
- 4-5 mg of "tar".
The filter of this invention will improve the
taste of low delivery cigarettes. It is also possible
that the filter of this invention may offer similar
performance at higher deliveries. For example, a
medium delivery cigarette may be perceived as a full-
flavor cigarette. ..
30_ Thus it is seen that a high efficiency filter
which produces low delivery while also delivering
acceptable taste and other aesthetic impacts is
provided. One skilled in the art will appreciate that
the present invention can be practiced by other than
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the described embodiments, which are presented for
purposes of illustration and not of limitation, and the
present invention is limited only by the claims which
follow.
