Note: Descriptions are shown in the official language in which they were submitted.
2~0C~4~7
--1 --
Ci~arette Filter Rod Elements and Ciqarett~s Incorporatinq
Such Filter Rod Elements
This invention relates to cigarette f ilter rod elements and
cigarettes incorporating such f ilter rod elements.
It is well known that when either a smoker or a smoking
machine smokes a conventional filter-tipped cigarette, the
amount of 'tar' in each puff increases in each successive -
puff. The 'tar' yield of the last few puffs is usually
several times higher than that from the first few puffs.
Consequently the 'tar' in the last few puffs may be
perceived by a smoker as 'too strong', and a smoker may
therefore consider a cigarette as 'smoother' if the 'tar'
delivery profile can be made more even. -
: .
There have been many attempts in the past to achieve an
'even' puff cigarette by modifying the filter. Mullor, U.S. ` -
Patent 2,763,267 and Clayton et al, U.S. Patent 3,809,097 ~-
proposed to use a plurality of discs to be placed inside a
cigarette filter rod and placed transverse to the smoke
flow. These designs, however, can only improve filtration ~;
efficiency, without any ability of evening the cigarette
'tar' profile.
- ,
Patterson, U.S. Patent 3,648,712 proposed to use a low gas
permeability disc placed transversely inside an ordinary
cellulose acetate filter rod. The disc is of a diameter
which is 5 to 25 percent less than the diameter of the
filter rod and this filter can therefore only achieve
improved filtration efficiency, with no ability to even the
'tar' delivery profile.
B.A.T. GB Patent 1,339,238 proposed placing a disc of a
blocking plug between a tobacco rod and an ordinary
cellulose acetate filter rod. This disc has an orifice for
smoke to flow through. The disadvantage of this design is
2(~(.,P('~ 7
--2--
that the pressure drop of the cigarette will lncrease to an
unacceptable level as the orifice of the plug becomes
clogged up at the later puff9.
Brackmann et al., U.S. Patent 3,882,877 proposed placing a
disc of micro-fine fibres in between two filter rod -~
segments. This filter is designed to increase filtration ~ -
efficiency. However, it could not cause the 'tar' delivery ~ -
to be more even, furthermore the pressure drop may increase
to an unacceptable level at the later puffs. ~
". ,,:
Browne et al., U.S. Patents 4,460,000 and 4,469,112 proposed ~-
using a compound filter that contains a perforated barrier --~
disc through which the whole smoke passes to a cellulose ~ -
acetate filter rod segment. As the smoking p-ocess -
proceeds, more and more 'tar' builds up on the cellulose
acetate fibres around the exit of the perforations. The
disadvantage of this design is that the build-up of 'tar'
near the perforations will greatly increase the flow ~ -
resistance of the cigarette filter to an unacceptable level.
. .
G.B. Patent 2 102 271 A, G.B. Patent 2,103,065 A and G.B. . -
Patent 2 105 566 A of Filtona (U.K.), proposed to employ two
flow paths, i.e. the low pressure drop path which has low
filtration efficiency and the high pressure drop path which ~ -;
has high filtration efficiency, for the smoke to flow in a
filter rod. During the initial few puffs of a cigarette, -~
the smoke tends to flow through the low pressure drop path.
The smoke then switches to flow through the high pressure
drop path due to the presence of a blocking mechanism on the
low pressure drop path. The disadvantage of these rilters ~-
is that they are very complicated and difficult to -~
manufacture.
,. ' ;
It is the objéctive of the present invention to provide a
cigarette with a more even puff-by-puff 'tar' delivery --~
profile and with an acceptable pressure drop by the use of a
.:
: '
2~Q(~
--3--
special cigarette filter.
The term "filter rod element" will be used herein to define
an element which may form part of a filter rod for
attachment to a cigarette, or which may itself provide the
whole filter rod.
A cigarette filter rod element can be formed comprising a
cylindrical hollow tube with a disc of fibrous material
placed inside it and which provides the whole filter rod.
If the edge of the disc is in tight contact or sealed with
the inside wall of the hollow tube, the smoke that enters
one end is confined to flowing through the disc and out
through the other end of the tube. The disc can be made of
at least one layer of micro-fine fibres of which the average
diameter is in the reqion of 0.5 to 10 microns. ~`
.,
When a filter rod element as set forth is in abuttment with
a tobacco rod, it forms a filter-tipped cigarette. When
this filter-tipped cigarette is smoked, the smoke stream
flows through the hollow tube without being filtered until
it reaches the disc. When the smoke stream passes through
the disc, it enters into the layer of micro-fine fibres,
which can be randomly oriented or oriented in any other
particular way, and a fraction of the smoke particulates - -
will be collected by the fibres by the commonly known
:~ :
mechanisms such as diffusion, impaction, interception etc.
That is to say, this disc has a certain level of filtration
efficiency to filter out the smoke particulates. As is well
known in the art of fibrous filtration, the filtration
efficiency can be increased greatly when the voidage between
the micro-fine fibres is reduced due to the accumulation of
collected smoke particulates. Consequently, the layer of
micro-fine fi-bres will be quickly clogged up and the
pressure drop acrss the disc will increase to a very high ~i
and unacceptable level. Surprisingly, it has been found -;
that if one or more suitably sized apertures are provided in
;
- 2~ 7
.
--4--
the disc, no matter whether the apertures are at the centre
or any other particular location, the disc does not clog up
and the pressure drop across the disc only increases, if at
all, to a very moderate and still acceptable level. There
will always be a fraction of the total smoke stream which
passes through the apertures without being filtered by the -
micro-fine fibres. These apertures therefore act as a -
controlled leakage venue for the smoke stream so that the
disc is not clogged up by the accumulated smoke
particulates. Due to the discoverylof a particular range of -~
packing density and thickness of these micro-fine fibres,
and together with the novel concept of providing one or more -
apertures on the said disc, the filter rod as set forth
above will increase in filtration efficiency as the smoking
proceeds without the usual enormous increase in the pressure
drop. As the filtration efficiency at the last few puffs is -
,
markedly higher than during the early puffs, less 'tar' is
being delivered to the smoker's mouth at that stage. A ---~
-smoker will therefore experience a much more even taste as
compared with the experience from a conventional filter-
tipped cigarette with a similar total 'tar' yield.
According to the present invention therefore, a cigarette-~ ~
filter rod element has a flow path therethrough which `--
includes a barrier in the form of a substantially planar
disc made from a layer of micro-fine fibres with a diameter
of between 0.5 and 10 microns and provided with one or more -
flow openings in the range 0.1 mm to 3.0 mm in diameter with
a combined total area of between 0.1 mm2 and 10 mm2.
Preferably the layer of micro-fine fibres has a packing ~
density of 0.05 to 0.3 and the thickness of said layer is- -
~-~ between 0.05 and 4 mm. -
The invention also includes a cigarette incorporating a
filter rod element as set forth above. m
:~ .-:-: - -:::
.: -
i
~ 2~004~7
5~
The invention can be performed in many ways and some
~ embodiments will now be described by way of example and with
;~ reference to the accompanying drawings in which: ~
Figure 1 i9 a perspective view, with parts broken away ,,.-
, for clarity, of a cigarette filter rod element
according to the present inventiont
~ ,
Figure 2 is a cross-sectional view of a cigarette ,
provided with the filter rod element shown in Figure
t ' ~ ,.;
Figure 3 is a cross-sectional view of another ,~ .
embodiment of a cigarette provided with the filter rod ,
` `element according to the present invention;
Figure 4 is a per~spective view of a commercially
available laminate containing micro-fine fibres; .~
Figure 5 is a perspective view of a sandwiched board ~ --
usln~ the laminate shown in Figure 4;
Figure 6 is à~p`erspect~ive view of a filter rod element
obtained from~the~sandwich shown in Flgure 5;
,Flgure 7 1 a~p-rspeGtive view~o~ another embodiment
of:an~-alternative~:form~of sandwich board;
Figure 8 is a perspective view of a double-unit filtèr: ,~
'5'~ rod.;segmen$ obtained from the 'sandwich' board shown ~:
: : ,in Figure 7;
~A ~ ' FlgUre 9 iS a~n enlarged.cross-sectional view of the
, filter rod~element shown~:in Figure 6;~
Figure 10 is a longitudinal cross_sectional view of a
multipIe length rod from which the filter rod elements
~` Z~004~7
-6-
shown in Figure 12 are cut;
Figure 11 is a cross-sectional view of the filter rod
shown ln Figure 8;
Figure 12 is a cross-sectional view of another
embodiment of a cigarette provided with a filter rod
element according to the present invention; and -
Figure 13 is a cross-sectional v,iew of another
embodiment of a filter rod element according to the
present invention;
' "'"' ~,
As shown in Figure 1, a cigarette filter rod 1 is formed
from an element which comprises a tube 4, a barrier disc 3
provided with an aperture 2 and made from a layer of micro- - --
fine fibres between 0.5 to 10 microns diameter. The tube 4
may be made of any convenient material such as paper or -~
plastics material. the edge of disc 3 is in close contact
with the inside wall of the tube 4 so that end-to-end flow
path communication through the tube has to pass through disc
3.~ The aperture 2 can be a single aperture or up to ten -- -~
apertures, between one and three apertures being preferred.
A~sing~l~e aperture maybe located conveniently at or around
t~he;centre of the disc. If multiple apertures are used, -
they~may be spread evenly on the disc or around the centre,
and each individual aperture may be different in size and -~
shape~to the others. The disc may be made of a plurality of
layers of fibres, at least one layer being of micro-fine ~ -~
fibres of 0.5-10 microns in diameter. ~ ~ ,
The aperture or apertures act as a flow opening and are 0.1
mm to 3.0 mm in diameter with a combined total opening area
of 0.1 mm2 to-10 mm2. The layer of micro-fine fibres has a
packing density of 0.05 to 0.3 and the thickness of said
layer is between 0.05 mm and 4 mm. ~ `
.~ . .. .
o~
-` Z~?~4~7
Figure 2 shows a cross-scetional view of a cigarette
provided with the filter rod 1 formed from the element shown
in Figure 1. Wrapped tobacco rod 6 1s shown abutting the
filter rod 1, the two being held ln place by a tipping paper
5.
Figure 3 shows another embodiment of the present invention
in which a filter rod 11 consists of two filter rod
elements, one of which is provided by an element 1 and the
other by a plain element 7, abutting each other and which
are held together by a plug wrap 10. The plain element 7
has a filling of known filter material 9, for example
cellulose acetate tow with the fibres extending
predominately axially along its length, or has non-woven
fibrous material such as DANAKLON ES. and is enclosed by a ~ -
wrapper 8. The filter rod 11 and the tobacco rod 6 abut
each other and are held in place by a tipping paper 5. The
use of plug wrap 10 may not be necessary if the tobacco rod -~
- 6, and the two elements are all combined together at the - ;
same time in a suitably designed cigarette making machine.
The plain element 7 is at the mouth end of the cigarette but
the filter is equally effective if the elements are
; reversed. It will be seen that in effect this arrangement
; provides a filter rod having an outer tube formed by wrapper - ~
8 and tube 4, a barrier 3 and the combined tube on one side ~ ~.
of the barrier containing a porous material.
Figure 4 is a perspective view of a commercially available
laminate fabric known as EHP (also known as EVOLUTION,
, - ; KIMGUARD) made by Kimberly-Clark, USA. Other similar
laminates which are equally suitable are SMS, BLUE DRAPE,
LX43, LX293, LX274, LX275, LX276 all made by Kimberly-Clark. ~Y-
The laminates comprise three layers. Layer 15 consists of
meltblown micro-fine polypropylene fibres with a fibre
diameter ranging from 1 micron to 8 microns,the majority
~` being 1 to 3 microns. Layers 14 and 16 consist of coarse
polypropylene fibres of around 20 microns diameter which are
::
~ -:
,~ ,
` Z~4~7
--8--
employed to protect the integrity of the micro-fine fibres.
Layers 14, 15 and 16 are point-bonded by either thermal or
ultra-sonic techniques or any other suitable technique. The
shaded area 17 represents the locations where point-bonding
takes place, and may appear as square or round dots, or any
other shapes arranged in any convenient or artistic pattern.
One grade of EHP laminate which has been tested and proved
to be effective has a total thickness of 0.5 mm, a total
fabric weight of 60 g/m2 and the three layers being
approximately the same ~hickness. Each layer has about
equal fabric weight of 20 g/m2.
As will be appreciated by those familiar with the art of
making cigarette filters with high speed machinery, it will
be very difficult to insert a thin, flexible and relatively -
fragile disc of a fabric material inside a tube with -
acceptable consistency. It is therefore advantageous to
improve the handlability of a laminate fabric that contains
~; micro-fine fibres such as EHP. One way is to sandwich the - -
laminate such as EHP between two layers of substantially
supportive porous rigid material as shown in Figure 5 in
which layer 21 represents a layer of micro-fine fibres or a ~ -
layer of laminate. Layer 21 is sandwiched by layers 20 and :
22 which can be any material that is porous and sufficiently ~- -
rigid and strong to be handled by modern filter-making - -:~
;machinery. One suitable material is a non-woven fabric, for
example, DANAKLON ES (Polypropylene/polyethylene bicomponent
fibres, 20 decitex, made by Danaklon, Denmark) which can be
used as layers 20 and 22 and EHP fabric used as layer 21.
By~selecting the right temperature, pressure and duration,
these bicomponent fibres together with EHP fabric will form
a rigid sandwich board 19 as shown in Figure 5. -~
Furthermore, the EHP fabric will be thermally bonded to
layers 20 and-22 during this process. The combined weight
of this sandwich board can be typically 2000-3000 g/m2, - ~-
having a total thickness L of 10-15 mm with acceptable
mechanical rigidity and strength. Thicker sandwich board
~: ; -. .:
2~ 4~7
g
can be made by an increase of the total fibre weight. The
layer 21 may be perforated with apertures of suitable size
at pre-determined locations before it is sandwiched. A rod
element can then be obtained from this sandwich board 19 by
punching perpendicularly through the board as shown at 23
with the necessary aperture on layer 21 situated
approximately at the centre of the punched rod element. A
rod element 25 obtained in this way is shown in Figure 6.
Alternatively, the sandwich board 19 can be made with layer
21 unperforated, the neces~ary apertures on layer 21 have to
be made by drilling through either layer 20, or layer 22, or
both layers. A laser beam, a hot needle or any other
suitable techniques may be employed for this purpose. The
rod elements, similar to rod element 25, can then be
obtained similarly by punching method described above.
Figure 9 shows a cross-sectional view of a rod element
obtained in this way. The channel 24 is made during the
process of making the aperture on layer 21 by a laser beam ;
or a hot needle and is shown to extend from layer 20, -~-
through layer 21, and penetrating into layer 22. This
channel 24 will not affect the effectiveness of the micro-
fine fibres.
After the rod element 25 shown in Figure 6, or the rod
element shown in Figure 9 has been wrapped with a suitable
plug wrap, it suitably forms a filter rod, which can be -~-
employed to replace filter rod 1 in Figure 2, or Figure 3,
to form a filter-tipped cigarette.
::
Figure 7 shows another embodiment of a sandwich board from
which filter rod segements can be obtained. In this
embodiment, layer 31 is the rigid and porous material, being
sandwiched between two layers 30 of micro-fine fibres or
laminate fabric such as EHP. Layer 31 can be any material
which is porous, rigid and strong such as the non-woven
fabric made from DANAKLON ES bicomponent fibres. The
sandwich board 34 can be obtained in a way similar to that
.
~:
~5,
~* ~
'`` 2~ 4~7
- 1 O-
of sandwich board 19 and materials in layers 30 ,and 31 may
be bonded together to form a rigid board by applying a
suitable temperature and pressure, or any other suitable
methods, such as chemical binding, application of adhesive,
mechanical stitching etc. Once a board of suitable
stability and rigidity is made, the filter rod segments can
be obtained by punching through the board perpendicularly as
indicated at 33. For example, filter rod element 35 is
obtained in this way and is shown in Figure 8.
, - ,,
;~' The filter rod element 35 consists of layers 30 of micro- '
fine fibres or the laminate fabric and layer 31. The
aperture 2 can be drilled by a conventional method such as a , ~
laser beam or a heated needle either before, during or after ~ '
~' the filter rod segments 35 are punched out of-the sandwich -~
~ board 34. -"
;~s '~ Figure 11 is a cross-sectional view of the filter rod ''-
~;; , obtained from sandwlch board 34. Channels 40 are made
'e~ ther by a laser beam or a hot needle during the process .
of making aperture 2 as-described above. The length of the ~'''~,,;,-~
channels 40 may be minimal~or may be as long as the . ,'~
thickness of layer 31~but will not affect the~effectiveness -,'
of the filter rod.
`~Figure 10 shows how a continuous multiple filter rod is
n',,'~ a,ssembled~so that a convenient multiple filter rod length~ ~
,can~be cut from it. For example, a 6-up filter rod is very ~, 3` j `,
r~ commonly used in many modèrn cigarette-making machines. -,~
,Lqngth M represents the length of a single filter rod and -'~ ~,"`,'
length N represents the common 6-up filter rod. The dual ", -,,-,-~j~,i,,-,,,
filter rod as indicated as length M may be conbined with
tobacco rod 6 as~shown in Figure 12 to form a filter-tipped ',~ 'm
cigarette. The tobacco rod 6 can be in abuttment either ;-'' ~`;'-"
with the end containing material 31 or material 9 with the ;,-'-,
; same effect.
Z~ 4Z7
Figure 13 shows another embodiment of a filter r~d element
according to the present invention. Disc 3 is made of
micro-fine fibres or a laminate fabric which contains at
least one layer of micro-fine fibres and has an uneven
surface.
Tip ventilation holes as indicated by reference numeral 45
in Figures 2, 3 and 12 may be provided to form either a
tip-ventilated filter rod, or a tip-ventilated filter-
tipped cigarette.
Example
Table l shows the comparison of puff-by-puff 'tar' yields
from a conventional filter-tipped cigarette and that from
a cigarette fitted with the present invention, the 'tar'
yield profile of the experimental cigarette is clearly
much flatter in terms of 'tar' delivery than that of the
conventional filter-tipped cigaxette.
, ~, : :
: ~:; ~ . ;,
, ~ .
0 4~7
TABLE 1
.
COMPARISON OF PUFF-BY-PUFF 'TAR' YIELDS
(1) 'TAR' PER PUFF (mg)
.
PUFF l2) CONTROL CIGARETTE (3) C~GARETTE F-ITTED WITH
NO _ EXPE R I ME NTAL FILTER
l '0.48 0.64
2 0.62 0.83
3 0.64 0.88
4 0.66 0.96
0.93 0.98
6 1.04 1.07
7 1.12 1.16
8 1.17 1.16
9 1.25 1.24
0 1.~9 1.29
Notes~
.
(1) Weight of 'tar' without water and nicotine.
(2) Conventional filter-tipped cigarette; filter rod is made with
; cellulose acetate tow, 2.7 denier per filament, 35,000 total denier.
(3) Experimental cigarette consists of the tobacco rod as that of the
control, but fitted with a filter rod as shown in Figure 12. -
Material 9 is cellulose acetate tow, 8 denier per filament, 30,000
total denier. The layer 30 is the EHP fabric ~60 g/m2), the size
of aperture 2 is 0.8 mm diameter. Layer 31 is made of DANAKLON ES
fibres.
.
.. . . . . . , . . . , , .. . . ...... , . . , . . . . ~ .... ... .. . . .
