C
FILTRONA NOVEL FILTERS
On 3rd Ma7ch, 1983, Filtrona (UK) Ltd.' presented
details of a number of
their nov---T filters to representatives from the
BAT Group. Smal 1
samples were accepted for visual examination. In
addition, further
informatim on these filters has been obtained from
various Filtrona
patents. It is intended to purchase larger samples
of these filters
for more extensive laboratory tests.
Details o-' the construction of the filters,
together with comments on
the filtr-=--ion characteristics claimed by
Filtrona, are included in
this docunent. This note replaces the brief note
dated 11th March,
circulatec: under a covering letter of 24th March,
1983, which should
be destroyed.
CO
BATCo document for Province of BritiSh Columbia 10
November 1999


THE FILTRONA CPF FILTER
Patent No. UK 1308661, filed 21/Feb/1970
This filter (which used to be known as RDF)
consists of a cellulose
acetate plug wrapped in two layers of porous plug
wrap. The inner
layer has 22 small longitudinal grooves extending
part way along the
length with some 5mm of the filter left ungrooved.
The ungrooved end
of the filter is intended to be the mouth end and
the whole construction
is wrapped in an outer porous plug wrap (Figure
1).
The principle of operation for this filter is that
sinoke will preferen-
tially travel along the grooves until it reaches
the non-grooved section
towards the mouth end. At this point, the smoke
must flow across and
through the porous plugwrap, giving a flow across
or at an angle to the
filaments rather than parallel to them. This
cross-flow effect will
occur whether ventilation is present or absent. It
is claimed that
this produces a worthwhile increase in the
effectiveness of the filter
compared to the performance of a conventional
cellulose acetate filter.
It is also claimed that filters of this type are
more resiliant to hot
collapse. Since ventilating air and smoke mix in
the body of the
filter, this filter does not impinge on Actron
technology.
In our opinion, the principle is sound, but the
magnitude of the
increased filtration efficiency is fairly small
(6% increase for an
85 mm PD filter). A comparable performance could
be obtained by simply
increasing the pressure drop of the cellulose
acetate filter. In modern
ventilated cigarettes, filters with a high
pressure (frop can be used as
the overall cigarette pressure drop can be kept to
the required level
by ventilation.
It is only possible to speculate on the method of
manufacture as nothing
was disclosed by Filtrona. One method would be to
use pre-grooved plug-
wrap, but this could present registration problems
as it is necessary
to cut the filter rods through the mid point of
the grooved or non-
grooved part of the filter. Since the two layers
of plugwrap appear to
be glued along the same line, it is likely that
the pre-grooved paper
and outer plug wrap are put on at the same time
and are used as a single
paper.
This filter has been available for some time.
Filtrona say that this
filter has not been used on any cigarette brand.
Such filters are
likely to be more expensive than conventional
filters.
CD
co
__-j
NJ
C:D
-14
C"
BATCo document for Province of British Columbia 10
November 1999


FIGURE 1
THE FILTRONA CPF FILTER
I porous plugwraps
cellulose acetate
Tobacco End Air Gap Mouth End
Mouth End
View from Tobacco End
obacco End
cc
BATCo document for Province of British Columbia 10
November 1999


THE FILTRONA LRV FILTER
This filter is designed to provide a low CO/Tar
ratio by the use of
ventilation whilst maintaining a relatively high
pressure drop.
The filter consists of a central non-wrapped
acetate core with a very
high pressure drop (100 mm WG/mm filter). The
outer core is made of
a low pressure drop, low efficiency cellulose
acetate, wrapped in a
porous plugwrap, to provide a preferred smoke path
(Figure 2). The
principle is to provide a high pressure drop, low
efficiency filter so
that smoke flows down the outer annulus of low
efficiency CA and mixes
with the ventilating air. The filter can be made
available as part of
a dual filter, e.g. LRV combined with a
conventional cellulose acetate
filter used with the LRV section at either the
mouth or tobacco end.
Filtrona provided very little data on the
performance of these filters,
but one example showed that the filtration
efficiency of an LRV for
nicotine was 36% compared with 56% for a
conventional cellulose acetate
filter of similar pressure drop. The LRV filter
can be supplied with
different cross-sections of the central core (e.g.
triangular, square)
or different colours.
The basic concept of high pressure drop/low
efficiency is not new to
BAT. It is doubtful whether this filter would meet
the requirements
set for the current work in GR&DC where a pressure
drop of 100 mm with
a filtration efficiency of less than 20% was
required. However, the
Filtrona LRV filter could be useful for less
stringent requirements,
e.g. LOCO cigarettes. Although a small number of
samples was obtained
at the meeting, a larger number of samples, with
various PD central
cores, has been ordered for a more detailed
evaluation.
AS far as is known at present, the filter has not
appeared on any
commercial cigarette brand.
cz:>
co
___4
N-)
CZ)
_`j
co
BATCo document for Province of British Columbia 10
November 1999


FIGURE 2
THE FILTRONA LRV FILTER
/--Low PO Cellulose Acetate
High PO Cellulose Acetate
(Non-Wrapped)
0 Porous Plugwrap
/Tipr
Tipping Paper
CO
-11
N-)
CD
BATCo document for Province of BritiSh Columbia 10
November 1999


5
THE FILTRONA TCT FILTER
This filter is designed to provide a low CO/Tar
ratio whilst maintaining
a reasonable level of pressure drop as perceived
by the smoker.
Deliveries are controlled by varying the degree of
ventilation and the
retention capability of the central core.
The filter consists of a central core
(circumference = 16 mm) of low
pressure drop, low retention cellulose acetate
wrapped in an impervious
cellulose film wrap. The outer core is also made
of low retention non-
wrapped cellulose acetate (Figure 3). This filter
achieves a low
retention because air and smoke are separated by
the film wrap on the
core. Air enters through the ventilation holes in
the tipping paper
into the outer annulus and can flow both towards
the tobacco and towards
the mouth. Smoke flows mainly down the low
pressure drop, low retention
central core.
Filtrona stated that, when measured
conventionally, the filter has a
low pressure drop, but when measured under
conditions simulating human
smoking, where the mouth end of the annulus or
grooves is sealed or
partly sealed, a higher PD was obtained. When this
occurs, the ventila-
ting air has to flow towards the tobacco or emerge
from a small cross-
section of the annulus at the mouth end, via a
higher PD path. The PD
of the TCT filter is, therefore, perceived to be
higher by the human
smoker than that measured by conventional means.
Although a higher
perceived PD is obtained, it is claimed by
Filtrona that ventilation
levels and yields are not affected to any great
degree.
Two forms of the TCT filter were presented, one of
which had a conven-
tional non-wrapped outer core while the other had
four longitudinal
grooves in the non-wrapped outer core. The TCT
filters are available
with different retention central cores ranging
from 25% to 50%.
This filter is probably outside the ACTRON filter
technology because
the grooves extend throughout the length of the
filter and the diluting
air and the smoke passing through the grooves will
mix.
CX:)
CD
CO
BATCo document for Province of British Columbia 10
November 1999


- 6 -
FIGURE 3
THE FILTRONA TCT FILTER
Ungrooved
,---Cellulose Film Wrapper
Low Density Cellulose
Acetate Core
Low Density Cellulose
Acetate Annulus
Grooved
4 Groove..
4 Groove
Grooved
C.
CO
NJ
00
BATCo document for Province of British Columbia 10
November 1999


THE FILTRONA ASTRA FILTER
Filtrona believe that mixing smoke and air in the
mouth is beneficial
to the smoker and, in order to achieve this, they
have developed the
ASTRA filter.
There are three variants of the ASTRA filter, two
of which were presented
at the meeting (Figure 4). The simplest version
consists of a cellulose
acetate core wrapped in a heavy longitudinally
corrugated, air imper-
meable plugwrap. There are 22 or 23 longitudinal
grooves around the
periphery of the filter. Although not mentioned by
Filtrona at the
meeting, the plugwrap could be a
paper/polyethylene/paper laminate as
mentioned in UK Patent Application No. G8
2104372A.
It was stated by Filtrona that, when this filter
is used on a ventilated
cigarette, the diluting air will flow down through
the grooves and not
enter the cellulose acetate core due to the
impermeable plugwrap.
However, some smoke is likely to flow down through
the grooves, but
most will flow through the filter core. The
proportion of smoke passing
through the grooves and filter core will depend
upon the pressure drop
through the core and grooves. Hence, the filter
probably provides a
means of substantially, but not completely,
separating the diluting air
and smoke. The filter differs from the ACTRON
filter in that the
grooves traverse the whole length of the filter.
The second version of the ASTRA filter consists of
the filter mentioned
above but circumferential grooves have been
inserted in the plugwrap
at the tobacco end of the filter. This filter is
described in UK Patent
Application No. 2102271A. The effect of this is to
provide a resistance
to the passage of smoke through the grooves. In
the patent application,
it is stated that "there can be little or no
previous.mixing of air and
smoke". In this respect, the concept is quite
close to that of the
ACTRON filter. However, in practice, where the two
sets of grooves
intersect there are still small passages through
which some smoke will
be able to pass and, in this respect, the ASTRA
filter differs slightly
from the ACTRON filter.
The third version of the ASTRA filter consists of
a dual core within
the corrugated wrapper in which the cross-grooves
can be present or
absent. The dual core can be in the form of a
paper/acetate or acetate/
acetate and presumably it could be possible to use
acetate containing
activated carbon as one of the sections in
combination with an acetate
filter second section.
The acetate/acetate dual version (without
cross-grooves) of this filter
has been used on the St. Moritz cigarette launched
recently by Rothmans
in Holland. So far, we have not been able to
understand the advantages C:D
of this particular dual construction over the use
of the single acetate
core version. It is intended to purchase samples
of these three versions cc
for evaluation. -4
N.;
CD
According to the patent (2102271A), there are
other variants of the cc
cross-grooved ASTRA filter. The cross-grooving can
be moved towards r-1;
the mouth end, but no such samples were exhibited
by Filtrona.
BATCo document for Province of British Columbia 10
November 1999


- 8 -
FIGURE 4
ASTRA MK.I
THE FILTRONA ASOA' FILTER
Impermeah
Plugwrap
Cellulose Acetate
(From Patent) Cellulose
t)
-7 Acetate
Paper Paper
Pblyethylene/
Thermoplastic
Wrapper
ASTRA MK.11 (From Patent)
Tipping Paper
impermeable Plug Wraps
Cellulose Acetate
ASTRA MK.II (As Received)
Impermeable Plug Wrap
CO
Cellulose Acetate
CD
cn
BATCo document for Province of British Columbia 10
November 1999


THE FILTRONA SCS FILTER
This filter is well known and has been used
commercially for many years.
It consists of a thick Walled tube of cellulose
acetate filaments closed
at one end with the' other end open. It can be
attached to the cigarette
with the open end towards the mouth or tobacco.
The concept of this filter is that smoke is caused
to flow across the
filaments instead of along the length as in a
conventional filter.
Filtration efficiencies are higher in the SCS
filter than in a conven-
tional cellulose acetate filter of similar
pressure drop due to the
cross-flow effect. The main disadvantage of this
filter is the high
cost due to the relatively high weight of
cellulose acetate, the high
packing density of the tube and slow production
speeds. Advantages of
the filter are the high tar retention and novelty
since the inner wall
of the tube can be made in various shapes -
circular, triangular,
X-shaped, Y-shaped, corrugated, etc.
There are three variants of this filter (Figure
5). The SCS III has
peripheral grooves for use with ventilation. The
SCS I has been used
by R.J. Reynolds on the Vantage cigarette for many
years. The SCS III
is used on the Ducados brand in Spain.
CxD
CXD
-.P-
BATCo document for Province of British Columbia 10
November 1999


- 10 -
FIGURE 5
THE FILTRONA SCS FILTER
Cellulose Acetate Tube
Tobacco End
Cellulose Acetate Tut-2
Tobacco End
~,7
Grooves
CeTlulose Acetate
Tobacco End
CD
CO
BATCO document for Province of British Columbia 10
November 1999


THE FILTRONA PBF FILTER
Patent No. 3B.2098051A
This filter consists of a cellulose acetate filter
wrapped in an air
impervious 3lug wrap. Along the length of the
filter are longitudinal
grooves which are formed in the impervious plug
wrap. There are two
depths and vidths of grooves formed as shown in
the diagram. Ventilating
air is allowed to enter the grooves via the
ventilated tipping paper
and may flcw towards the tobacco or mouth end of
the filter depending
upon the gr-zove orientation (Figure 6).
Although Fitrona claim that this filter will give
a low CO/tar ratio
and is des-'.--ned to be used with ventilation,
its concept is very similar
to the ACT,-~ON filter. This filter has not been
used for commercial
brands and 7iltrona added that no further
developments were envisaged
unless some interest is shown by a customer. Any
further information
concerning -.his filter must be obtained from
Filtrona, USA. Although
a list of --uestions was submitted to Filtrona
prior to the meeting,
Filtrona. UK said it had not been possible to
obtain answers from
Filtrona USA. We felt they did not want to discuss
this further.
CD
%10
CO
-~j
NJ
00
ON
BATCo document for Province of British Columbia 10
November 1999


- 12 -
FIGURE 6
THE FILTRONA PSF FILTER
Deep Gr
Shallow G
Cellulo
Acetat
Impermeab
CZ)
110
cc
-`1
NJ
CD
cc
BATCo document for Province of British Columbia 10
November 1999


- 13 -
GENERAL COMMENTS
From the various comments made by Filtrona during
the discussion, it
was evident that their development policy was to
produce novel filters
based on the following concepts:
(a) high filtration/low pressure drop;
(b) low filtration/high pressure drop;
W means of reducing carbon monoxide via
ventilation;
(d) means of separating diluting air and smoke.
This is very similar to some of the GR&DC
thinking, but this was not
disclosed to Filtrona. Their approach appeared to
be short term,
aimed at development of marketable products as
quickly as possible
whilst making maximum use of their existing
technology. All the filters
presented must have required very close
co-operation between laboratory
and production facilities. Recently, Filtrona have
moved their research
facilities to their factory site at Jarrow. There
was no evidence of
long term filter research such as modelling,
understanding smoke filtra-
tion or any work on selective filtration. In this
respect, their
approach differs from GR&DC.
Finally, it was apparent from our discussions that
Filtrona USA work
somewhat independently from Filtrona UK, since
there were difficulties
in obtaining information from Filtrona USA on the
PBF filter, which was
developed in the USA. A similar situation occurred
some time ago when
Filtrona UK offered small samples of another USA
development (the COO
filter) which we understood was not being pursued
unless required by
interested customers.
CZ>
c0
cz:)
c3
C3
BATCo document for Province of British Columbia 10
November 1999