Note: Descriptions are shown in the official language in which they were submitted.
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
Filters for smoking articles for less additive(s) loss
Field of the Invention
The present invention relates to improvements in filters for use in smoking
articles,
comprising randomly oriented discrete fibres. The improvements mainly relate
to the loss of
additive(s) in said filters and to the manufacture thereof.
Background to the Invention
In conventional filter cigarettes, the filter commonly consists of a single
segment of
filtration material, typically a continuous tow of filamentary cellulose
acetate plasticised with
triacetin, circumscribed by porous and/or non-porous plug wrap. The cellulose
acetate is
gathered together to form a rod which is cut to form individual filter
segments. The filter for a
smoking article may be made of one segment of filter rod, or may be made from
multiple
segments.
In the past it has been proposed to replace the continuous tow with randomly
oriented
discrete fibres of cellulose acetate. The advantages of using such kind of
fibres have been
reported and listed in several publications, like WO 2009/080368, WO
2009/093051, WO
2013/068337, WO 2013/164624 and WO 2013/164623. Filter manufacturing machines
specifically developed for making such kind of filters are also known, e.g.
Turmalin machine
made by Hauni Maschinenbau AG, Germany.
With randomly oriented discrete fibres, filters having higher additive
loadings can be
produced compared to filters using continuous tow. In addition to this, the
Turmalin machine
is reported as allowing said higher loadings without using any plasticizer
such as triacetin,
e.g. in WO 2013/164624 and WO 2013/164623.
However, all publications are silent on how to process filters having said
higher
additive loading. Indeed, the present inventors have found that as soon as
filters comprising
randomly oriented discrete fibres and high additive loading are cut in order
to form individual
filter segments or to be assembled in multiple segments filters, a very
significant amount of
the additive is lost.
Therefore, there is a need to provide filters comprising randomly oriented
discrete
fibres and a stable, long lasting high additive loading with good performance
of the additive,
as well as smoking articles with these filters.
1
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
Summary of the Invention
The inventors identified particulate additive, e.g. granule, loss during the
combining
process as a problem in terms of filter quality and machinability for the
usage of granulated
filters with high loadings of additives like granules and randomly oriented
fibres, e.g.
randomly oriented acetate (ROA) fibres. With regard to filter quality,
pressure drop in the filter
and filter burst are significantly affected by granule loss.
An exemplary filter has a circumference of 23.9 mm and a filter length of 120
mm,
and contains 2.2 mg/mm filter tow. 13mg/mm of charcoal granules are added as
additive.
This results in a target pressure drop (PD) of 318 mmWG/rod (mm water
gauge/rod; 3118
Pa/rod).
A 10 wt.% granule loss in the above exemplary filter results in a pressure
drop of 287
mmWG/rod, resulting in a 10% pressure drop loss compared to the target
pressure drop.
This is not acceptable with regard to cigarette design.
Similarly, a 5 wt.% granule loss results in a pressure drop of 303 mmWG/rod,
resulting in 5% PD loss. This could for example be seen as an upper limit with
regard to
cigarette design/quality.
In addition, loose granules can accumulate at the seam of the combiner plug
wrap
used to attach a plurality of filter segments. This may even prevent seam
formation as the
loose granules reduce the effective area for the adhesive that is typically
applied to form the
seam. As a result, the filter may burst open. The inventors have identified
that this problem
increases with increased loss of granules.
Furthermore, having regard to machinability, charcoal contamination around the
machine is a problem that can lead to machine stoppage. To mitigate this
problem special
protections have been installed to ensure that charcoal does not accumulate in
problematic
areas, such as the plug wrap gluing and guiding system, and frequent machine
cleaning is
necessary.
Therefore, a target for additive loss, e.g. granule loss, should be for
example less
than about 5%, based on the total weight of the additive, to keep a good
filter quality and
machinability.
2
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
The inventors found that an improvement in additive loss, i.e. decreased loss
of at
least one particulate additive, can be achieved by a filter for a smoking
article comprising a
certain amount of fibres and a certain amount of additive.
Thus, a first aspect of the invention provides a filter for a smoking article
comprising
randomly oriented discrete fibres and at least one particulate additive, the
additive being
dispersed within the filter, wherein the value obtained by dividing the volume
fraction of the
additive (cc/mm) by the volume fraction of the fibres (cc/mm) is less than
about 1100%.
Furthermore, the invention relates to a smoking article comprising the filter
of the
present invention.
Further preferred and exemplary embodiments of the invention are indicated in
the
dependent claims and the following detailed description, which, however, do
not restrict the
scope of the invention and only help to understand and explain the features of
the present
invention. Deviations and modifications on these particular features,
particular in regard to
other aspects of the invention, can be made without departing from the scope
of the
invention.
Description of Figures
The invention will be further described in detail in the following with
reference to the
figures and particular embodiments thereof, without being limited thereto.
In the figures the following is shown:
Figure 1 shows a graph of exemplary data taken from the Examples.
Description of embodiments of the invention
All ranges disclosed herein are to be considered to be supplemented by the
term
"about", unless clearly defined to the contrary or otherwise clear from the
context.
All numbers or percentages relating to amounts of a substance within this
application
are given in wt.%, unless clearly defined to the contrary or otherwise clear
from the context.
The term "randomly oriented discrete fibres" refers to a plurality of fibres
that can be
distinguished from each other and are physically separated, i.e. discrete
fibres. They are
3
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
randomly oriented in three directions, i.e. form a random 3-dimensional fibre
network wherein
the fibres are directed in any direction, without all fibres being directed in
the same direction.
The fibres can have different lengths or have the same lengths as well as the
same diameter
or different diameters, and can be uniform or non-uniform with regard to their
individual sizes
and shapes.
The term "smoking article" relates to all kinds of smokable products like
cigarettes,
cigars, cigarillos, etc. In these smoking articles, the kind of smokable
material used, e.g.
tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco, tobacco
substitutes,
non-burnable products, etc., as well as mixtures thereof, is not particularly
limited. These
smoking articles are provided with a filter according to the invention.
Smoking articles and their formats can be e.g. characterized according to the
cigarette length, with "regular" being in the range 68 -75 mm, e.g. from about
68 mm to about
72 mm, "short" or "mini" being 68 mm or less, "king-size" being in the range
75 ¨ 91 mm, e.g.
from about 79 mm to about 88 mm, "long" or "super-king" being in the range 91 -
105 mm,
e.g. from about 94 mm to about 101 mm, and "ultra-long" being in the range
from about 110
mm to about 121 mm.
They can also be characterized by the circumference of the smoking article,
e.g. a
cigarette, with "regular" having a circumference of about 23-25 mm, "wide"
having a
circumference of greater than 25 mm, "slim" having a circumference of about 22-
23 mm,
"demi-slim" having a circumference of about 19-22 mm, "super-slim" having a
circumference
of about 16-19 mm, and "micro-slim" having a circumference of less than about
16 mm.
Accordingly, a cigarette in a king-size, super-slim format will, for example,
have a
length of about 83 mm and a circumference of about 17 mm. Cigarettes in the
regular, king-
size format have e.g. a circumference of from 23 to 25 mm and an overall
length of from 75
to 91 mm.
Each format may be produced with filters of different lengths, smaller filters
being
generally used in formats of smaller lengths and circumferences. Typically the
filter length
will be from 15 mm to 30 mm. The tipping paper can have a greater length than
the filter, for
example from 3 to 10 mm longer.
4
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
A particulate additive is an additive that is present in the form of
particles, i.e.
particularly in solid form. The particulate additive(s) can be e.g. in powder
(particle diameter
of about 50 to 150 pm) and/or granular form (particle diameter of about 150 to
1000 pm).
According to one aspect, the present invention relates to a filter for a
smoking article
comprising randomly oriented discrete fibres and at least one particulate
additive, the
(particulate) additive being dispersed within the filter, wherein the value
obtained by dividing
the volume fraction of the (particulate) additive(s) (cc/mm) by the volume
fraction of the fibres
(cc/mm) is less than about 1100 %, for example less than about 1000 %, such as
less than
about 900 %, e.g. less than about 800 %.
The volume fraction herein is the ratio of a volume of a certain material,
e.g. the
particulate additive and/or the randomly oriented discrete fibres, to the
total available volume
in the filter. The volume of a certain material can thereby be calculated
using the bulk density
of the material and the weight thereof. The total volume of a filter can be
determined by
consideration of the shape of the filter, e.g. ¨ in case of a cylindrical
filter ¨ using the
diameter and length. Suitable measurement procedures for the bulk density of
the particulate
additive are known from ASTM D2854-2009 for granular activated carbon, ASTM
D1895 test
method A for fine granules and powders that can be poured readily through a
small funnel
(e.g. silica granule, hydrotalcite, paper granule, acetate flake, or coffee
granule), ASTM
D1895 test method B for coarse granular materials, including dice and pellets,
that either
cannot be poured or that are poured with difficulty through the funnel
described in ASTM
D1895 test method A (e.g. tobacco granule, sugar granule), and ASTM D1895 test
method C
for materials supplied in the form of coarse flakes, chips, cut fibres, or
strands (e.g. mint leaf,
tobacco leaf). A suitable measurement procedure for the bulk density of the
randomly
oriented discrete fibres is known from ASTM D3887-1995.
By keeping a certain ratio between the volume fraction of the additive(s) and
the
volume fraction of the fibres, it is possible to minimize the loss of
additive, e.g. resulting from
cutting during preparation of the filters, e.g. cutting the filters to a
certain desired length of
e.g. 3 to 20 mm, e.g. 6 to 12 mm, or e.g. 8 to 10 mm. Individual filter
segments, or segments
for multiple segments filters, can be formed by cutting. According to certain
embodiments,
the loss weight of the additive(s) ¨ particularly during cutting ¨ is less
than 5 %, e.g. less than
4.5 %, e.g. less than 4 %, e.g. less than 3 %, based on the total weight of
the additive(s). The
weight loss can be determined by weighing using usual procedures. One example
is to
determine the weight difference between the weight of a certain filter before
cutting and the
5
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
total combined weight of cut filter segments ¨ cut from this filter ¨ after
cutting. Especially,
according to certain embodiments, it should be ensured that no loss is
obtained due to
cutting in any other components of the filter, e.g. the randomly oriented
discrete fibres and/or
a wrapping material, which can be ensured by collecting losses of such other
components, if
occurring, weighing them and adding this weight to the combined weight of the
cut filter
segments, before this total combined weight is subtracted from the weight of
the filter before
cutting. According to certain embodiments, loss of other components, e.g.
filter tows, during
cutting is negligible. According to certain embodiments, the loss of additive
is substantially
due to the at least one particulate additive, e.g. due to the at least one
particulate additive.
Thus, the present invention also relates to a process of producing a filter
for a
smoking article according to the present invention, as described below.
The dispersion of the at least one particulate additive in the filter is not
particularly
limited and can be in any form. It can for example be a homogeneous or
heterogeneous
dispersion within the filter, e.g. the randomly oriented discrete fibres,
and/or also at other
locations between the randomly oriented discrete fibres and another material,
e.g. a filter
wrapping material.
The filter of the invention can contain one or more particulate additive(s)
which are
not particularly limited and can be those particulate additives normally used
in filters for
smoking articles. Examples of suitable particulate additives include
flavourants or sorbents -
e.g. activated carbon/charcoal, zeolite, ion exchange resin, magnesium
silicate like sepiolite,
silica gel, alumina, molecular sieves, carbonaceous polymer resins and
diatomaceous
earths, or combinations thereof. Also, other additives, such as humectants,
can be used.
According to certain aspects, the particulate additive comprises or is
charcoal/activated
carbon. According to certain embodiments, the at least one particulate
additive has a particle
size from 50 to 2000 pm, e.g. from 100 to 1000 pm, as determined e.g. using
sieve analysis.
The material of the randomly oriented discrete fibres, which can be comprised
in or
be the filter tow material, is not particularly limited and can include a
material that is typically
used in filters for smoking articles, e.g. cigarette filters. It can include
natural fibre materials
which can be e.g. produced from cellulose, herb materials like tobacco, or
synthetic materials
like polypropylene. For example, the material of the randomly oriented
discrete fibres can
comprise or be cellulose acetate or polypropylene. Also mixtures of two or
more fibre
materials are possible. According to certain aspects, the filter tow material
may have a
6
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
filament denier in the range of from 3.0 up to 12.0 D, e.g. of between 4.0 and
10.0 D, e.g. of
between 5.0 and 8.0 D, e.g. of about 6.0 D.
According to certain embodiments, the range of the combined loading amount of
the
additive and the fibre is between 2.4 mg/mm and 19 mg/mm for a filter of any
diameter, e.g.
having a diameter between the lower limit for a super-slim size and the upper
limit of a
regular size, i.e. between 16 and 25 mm. According to certain embodiments, the
range of the
combined loading amount of the additive and the fibre is between 3 mg/mm and
18 mg/mm,
e.g. between 8 mg/mm and 17 mg/mm. According to certain embodiments, the range
of the
combined loading amount of the additive and the fibre is between 8 mg/mm and
17 mg/mm,
particularly for a regular circumference filter, i.e. a circumference of 23 to
25 mm, e.g. 23,
23.9, 24 or 25 mm. According to further embodiments, the range of the combined
loading
amount of the additive and the fibres is 9 mg/mm to 16 mg/mm, e.g. 10 mg/ mm
to 14.5
mg/mm, e.g. 10.5 mg/mm to 14 mg/mm, e.g. 11 mg/mm to 13 mg/mm, particularly
for a
regular circumference filter, i.e. a circumference of 23 to 25 mm, e.g. 23,
23.9, 24 or 25 mm.
According to certain embodiments, the amount of the additive is between 1
mg/mm
and 13.5 mg/mm for a filter of any diameter, e.g. having a diameter between
the lower limit
for a super-slim size and the upper limit of a regular size, i.e. between 16
and 25 mm.
According to certain embodiments, the amount of the additive is between 6
mg/mm and 13
mg/mm. According to certain embodiments, the amount of the additive is in the
range
between 7 mg/mm and 12 mg/mm, e.g. in the range between 7.5 mg/mm and 11
mg/mm,
e.g. in the range of from 8 mg/mm up to 10 mg/mm, particularly for a regular
circumference
filter, i.e. a circumference of 23 to 25 mm, e.g. 23, 23.9, 24 or 25 mm.
According to certain embodiments, the amount of fibres is between 1.4 and 5.5
mg/mm for a filter of any diameter, e.g. having a diameter between the lower
limit for a
super-slim size and the upper limit of a regular size, i.e. between 16 and 25
mm. According
to certain embodiments, the amount of fibres is between 2.0 and 4.5 mg/mm,
e.g. between
2.0 and 4.0 mg/mm, e.g. between 2.2 mg/mm and 3.8 mg/mm, e.g. between greater
than 2.2
mg/mm and up to 3.7 mg/mm. According to certain embodiments, the fibre loading
amount is
in the range of from 2.5 mg/mm to 3.6 mg/mm, e.g. from 2.8 mg/mm to less than
3.6 mg/mm,
e.g. in the range from 3.0 mg/mm up to 3.5 mg/mm, particularly for a regular
circumference
filter, i.e. a circumference of 23 to 25 mm, e.g. 23, 23.9, 24 or 25 mm.
7
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
According to certain embodiments, the amount of the additive is between 6
mg/mm
and 13 mg/mm, and/or the amount of fibres is between 2.0 and 4.0 mg/mm, e.g.
between 2.2
mg/mm and 3.8 mg/mm, e.g. between greater than 2.2 mg/mm and up to 3.7 mg/mm,
particularly for a regular circumference filter, i.e. a circumference of 23 to
25 mm, e.g. 23,
23.9, 24 or 25 mm.
The filter of the invention can have any shape and is not particularly
limited, but is
preferably in a shape commonly used in smoking articles, e.g. in cylindrical
shape. According
to certain embodiments, the filter has a cylindrical shape with a
circumference of the cylinder
being equal to or smaller than 26 mm, preferably equal to or smaller than 23.9
mm.
Further, the filter of the invention may optionally include other materials,
for example
one or more liquid(s) (such as a flavourant, e.g. menthol solution).
In addition, the present filter is also not particularly limited regarding
other
components of the filter and can include components that are commonly used in
filters for
smoking articles. For example, the filter may be wrapped with a wrapper or
plug wrap, for
example a wrapper of paper, e.g. an air-permeable paper. Particulate additives
as discussed
above can also be applied to the wrapper or plug wrap surrounding the filter
material. The
material of the plug wrap is not particularly limited and can comprise paper
and/or plastic
materials like PE, PP, etc.
According to certain embodiments, the filter of the present invention does not
contain
a binder or a plasticizer, making processing and manufacturing of the filter
easier. A binder
may have the disadvantage that it solidifies after application, which leads to
contamination in
the process and a higher pressure drop. A plasticizer like triacetin can,
especially at high
loading, lead to melt holes in the filter, i.e. dissolve the filter tow,
causing defect in the
smoking article. Even without using a binder or a plasticizer, additive loss
in the present filter
can be reduced.
According to certain embodiments, the filter comprising randomly oriented
discrete
fibres and the additive is cut into desired lengths in order to form
individual filter segments or
to be assembled to multiple segments filters. In such a case - by determining
the weight
difference between the filter before and after cutting, resulting from the
loss of additive during
cutting, e.g. to a length of 6 mm - the loss weight of the additive can be
less than about 5 %,
8
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
e.g. less than about 4.5 %, e.g. less than about 4 %, e.g. less than about 3
%, based on the
total weight of the additive.
In a further aspect, the present invention relates to a smoking article
comprising the
filter of the present invention. The smoking article is not particularly
limited and can be e.g. a
cigarette, a cigar or a cigarillo in any size and shape. In such a smoking
article, also two or
more of the filters according to the invention can be used, and/or the present
filter can be
used in combination with another filter, e.g. in a segmented filter. Regarding
the further
composition, the smoking article of the invention is not limited. As a matter
of course, a
tobacco containing segment can be contained in the smoking article, wherein
the tobacco is
not limited, and the smoking article can e.g. be wrapped using usual material,
and can also
contain other components like a tipping paper.
In a further aspect, the present invention also relates to a method of
producing/manufacturing a filter for a smoking article, particularly according
to the present
invention, wherein at least one particulate additive and randomly oriented
fibres are provided
and added to a filter for a smoking article, wherein the at least one
particulate additive is
dispersed in the filter, wherein the value obtained by dividing the volume
fraction of the
additive (cc/mm) by the volume fraction of the fibres (cc/mm) is less than
about 1100 %.
The filter of the present invention may be manufactured by known methods,
using
common equipment, e.g. a Turmalin machine from Hauni, DE. The at least one
particulate
can be, for example added into the filter tow, i.e. the randomly oriented
discrete fibres, and
then the tow is shapes into e.g. a rod of any desirable circumference. The
e.g. cylindrical rod
formed to any desired size and shape may be wrapped in a plug wrap and sealed
with an
adhesive by means that are well-known in the prior art, e.g. using spiral
anchor glue.
Afterwards, the filter rod can further be cut into desired lengths using known
methods. Other
additives, if included, can be introduced at suitable times in the filter
production process.
Using the filter of the present invention, a smoking article can be produced,
e.g. by
combining one or more filters of the invention with a tobacco rod and
optionally other filters,
and wrapping the resultant, e.g. by methods known in the art.
Examples
The present invention will now be described with reference to examples
thereof,
without limiting the scope of the invention to these particular examples.
9
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
Example 1
In the following, different filters for cigarettes were produced with
different loadings of
additive and different loadings and sizes of randomly oriented discrete fibres
(hereinafter also
referred to as filter tow).
The controllable parameters were herein as follows:
Charcoal loading: 8-13 mg/mm
Filter tow loading: 2.0 ¨ 3.5 mg/mm
Filter tow cut length: 10 ¨ 20 mm
Furthermore, the following parameters were given for production. Cylindrical
base
filters were produced with a circumference of 23.9 mm and a length of 120 mm
length, which
were then wrapped with a non-porous plug wrap. After wrapping, the base filter
was cut 19
times to obtain equal cut filters, each with a final length of 6 mm. For
anchor glue application,
a spiral glue application was used.
Charcoal was supplied from JacobiCarbons (Sweden). It had a bulk density of
603 kg/m3, a CCI4 adsorption of 60 ¨ 70 %, and an ASTM Mesh size of 30 x 60
(595 pm x
250 pm). For the present charcoal, the bulk density was determined by ASTM
D2854-2009.
Filter tow, i.e. randomly oriented discrete fibres, was obtained from
Celanese. It had
the following properties: Denier per Filament (g/9000m) was 6.0 D, and total
Denier
(g/9000m) was 17000 D, with the cross Section being Y. The bulk density was
1255 kg/m3
measured according to ASTM D3887-1995.
As a plug wrap, a wrap from Delfort with a porosity (cm3/cm2/min) of 0 (i.e.
without
pores), a basis weight of 27 g/m2, and a thickness of 43 pm was used.
Base rod making of base filter rods was carried out with a Turmalin base rod
maker,
supplied by Hauni, DE, at a machine speed of 200 m/min, to obtain base filter
rods /base
filters with a length of 120 mm.
These base filters were then introduced into a combining process, using a
Solaris
(Combiner) from ITM working at a machine speed of 350 m/min.
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
The following additive loss test has been carried out:
1. Before entering into the combining process, selected base filter rods were
separately color-coded by colour application to the outside (using a coloured
pen), and
weighed.
2. The base filter rods were then introduced into the combining process and
processed, wherein the base filter rods were cut from the original length of
120 mm to a
target length of 6 mm.
3. After the combining process, the coloured & cut filters, i.e. filter tips,
were collected,
and cut filters with the same colour, i.e. coming from the same base filter
rod, were
combined.
4. These combined, cut filter rods were weighed, and the weight was compared
to the
weight of the base filter rod with the same colour, the weight difference
representing loss in
the combining process. It was confirmed visually that substantially no other
losses but
charcoal losses arose in the combining process, and further losses, if
occurring, were
negligible.
The results for several filters of comparative examples (Comp. Ex.) and
examples
(Ex.) with different charcoal and filter tow loading and different length of
the fibres, after
.. cutting the base filter rods, with regard to additive loss are given in
Table 1. Standard
deviations (STDEV) were calculated for 15 samples in each example,
respectively
comparative example, using the Excel function "stdev".
Table 1:
Example Product parameter Additive loss
Charcoal Filter tow (FT) FT cut length Average STDEV
mg/mm mg/mm mm % %
Comp. Ex 1-1 13 2.1 10 9.1 1.1
Comp. Ex 1-2 13 2.2 10 7.3 1.0
Ex. 1-1 10 3.0 10 2.7 1.5
Ex. 1-2 8 3.5 10 1.9 1.4
Comp. Ex 1-3 13 2.1 20 9.1 1.4
Comp. Ex 1-4 13 2.2 20 9.6 1.7
Ex. 1-3 10 3.0 20 2.7 1.4
Ex. 1-4 8 3.5 20 2.4 0.8
11
CA 03039585 2019-04-05
WO 2018/114395
PCT/EP2017/082022
Selected values from Table 1 are shown in FIG. 1, wherein the x-axis
represents the ratio of
the volume fraction of charcoal (Pc divided by the volume fraction of fibres
OF, and the y-axis
represents the charcoal loss L. Examples with a fibre length of 10 mm are
represented with
an empty circle, whereas examples with a fibre length of 20 mm are represented
with a
rhombus. As can be seen, a significant reduction in charcoal loss was observed
when
keeping the ratio szl)c/ OF below a certain value, e.g. less than about 1000 %
if the charcoal
loss is to be limited to about 5 % or less, based on the total weight of the
charcoal.
When comparing the results represented in FIG. 1, it was observed that
shortening fibre
length has a slight influence in additive loss reduction. It is expected that
by further reducing
fibre length, e.g. to 5 mm, additive loss will be limited to about 5 % or less
by keeping the
ratio (I)c/ OF below 1100 %.
With the present filter, a significant reduction in additive(s) can be
achieved, resulting in
cigarettes with improved pressure drop and a manufacturing process that
requires less
cleaning due to such losses.
12
