U.S. patent application number 15/129988 was filed with the patent office on 2017-06-08 for filter materials and filters made therefrom.
The applicant listed for this patent is British American Tobacco (Investments) Limited. Invention is credited to Peter BRANTON, Rose GALATI, Gordon GRIERSON, John SAMPSON.
Application Number | 20170156393 15/129988 |
Document ID | / |
Family ID | 50737735 |
Filed Date | 2017-06-08 |
United States Patent
Application |
20170156393 |
Kind Code |
A1 |
BRANTON; Peter ; et
al. |
June 8, 2017 |
Filter materials and filters made therefrom
Abstract
The present invention relates to filter material for inclusion
in a smoking article, wherein the filter material is in the form of
a fibrous tow or a non-woven sheet comprising fine cellulose
acetate fibres having a mean diameter of from about 1 .mu.m to
about 15 um. The invention also relates to processes for preparing
filter material for inclusion in a smoking article, the filter
material comprising fine cellulose acetate fibres having a mean
diameter of from about 1 .mu.m to about 15 .mu.m. The invention
further relates to filters or filter elements comprising the filter
material, smoking articles comprising the same, and use of the
filter material in smoke filtration.
Inventors: |
BRANTON; Peter; (London,
GB) ; GALATI; Rose; (London, GB) ; GRIERSON;
Gordon; (London, GB) ; SAMPSON; John; (London,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
British American Tobacco (Investments) Limited |
London |
|
GB |
|
|
Family ID: |
50737735 |
Appl. No.: |
15/129988 |
Filed: |
March 27, 2015 |
PCT Filed: |
March 27, 2015 |
PCT NO: |
PCT/GB2015/050922 |
371 Date: |
September 28, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D01D 5/04 20130101; A24D
3/063 20130101; A24D 3/10 20130101 |
International
Class: |
A24D 3/06 20060101
A24D003/06; D01D 5/04 20060101 D01D005/04; A24D 3/10 20060101
A24D003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 31, 2014 |
GB |
1405757.4 |
Claims
1. A filter material for inclusion in a smoking article, wherein
the filter material is in the form of a fibrous tow comprising fine
cellulose acetate fibres having a mean diameter of from about 1
.mu.m to about 10 .mu.m.
2. A filter material as claimed in claim 1, wherein the tow is
formed from fibres and at least about 80% by weight of the fibres
are fine cellulose acetate fibres.
3. A filter material as claimed in claim 1, wherein the fine
cellulose acetate fibres have a diameter of no less than 0.3
.mu.m.
4. A filter material as claimed in claim 1, wherein the fine
cellulose acetate fibres comprise cellulose acetate and an
additive.
5. A filter material as claimed in claim 1, wherein filter material
further comprises a plasticizer which is one or more selected from
the group consisting of: triacetin; polyethylene glycol; triethyl
citrate; and triethylene glycol diacetate.
6. A filter material as claimed in claim 1, wherein the filter
material removes from about 50% to about 90% phenol from tobacco
smoke.
7. A filter material as claimed in claim 1, wherein the filter
material removes from about 50% to about 90% cresol from tobacco
smoke.
8. A process for preparing filter material for inclusion in a
smoking article, the filter material comprising fine cellulose
acetate fibres having a mean diameter of from about 1 .mu.m to
about 10 .mu.m, the process comprising electrospinning or
centrifugal spinning or melt spinning.
9. A process as claimed in claim 8, wherein a cellulose acetate
solution is spun, the solution having a cellulose acetate
concentration of from about 6% to about 30%.
10. A process as claimed in claim 8, wherein the fine cellulose
acetate fibres are produced by spinning through a spinneret using
centrifugal force, and the spinneret spins at a rate of from about
4500 to about 7500 rpm.
11. A process as claimed in claim 8, wherein the flow rate of the
cellulose acetate solution through the orifice(s) of the spinneret
is from about 5 to about 100 ml/min.
12. A process as claimed in claim 8, wherein the fine cellulose
acetate fibres are laid down as a non-woven sheet or non-woven web
directly following spinning.
13. A process as claimed in claim 12, wherein the fine cellulose
acetate fibres are drawn onto a base sheet upon which a non-woven
sheet or web is formed by a vacuum pull, by air flow or by
electrostatic charge.
14. A filter material obtained or obtainable by a process as
claimed in claim 8.
15. A filter element or filter for a smoking article, comprising a
filter material as claimed in claim 1, or comprising a filter
material obtained or obtainable by a process for preparing filter
material for inclusion in a smoking article, the filter material
comprising fine cellulose acetate fibres having a mean diameter of
from about 1 .mu.m to about 10 .mu.m, the process comprising
electrospinning or centrifugal spinning or melt spinning.
16. A filter as claimed in claim 15, wherein the filter has a
pressure drop of from about 60 to about 140 mmWG.
17. A filter as claimed in claim 15 comprising from about 30 to
about 90 mg of filter material in the form of a fibrous tow
comprising fine cellulose acetate fibres having a mean diameter of
from about 1 .mu.m to about 10 .mu.m.
18. A filter as claimed in claim 17, comprising from about 40 to
about 80 mg of said filter material.
19. A smoking article comprising a filter or filter element as
claimed in claim 15.
20. A filter material as claimed in claim 1 configured for
filtration of tobacco smoke.
Description
FIELD
[0001] The present invention relates to filter materials for use in
smoking articles. The invention also relates to filters or filter
elements comprising the filter materials, smoking articles
comprising the same, and use of the filter materials in smoke
filtration.
BACKGROUND
[0002] A wide variety of fibrous materials have been suggested as
filters for cigarette smoke. Cellulose acetate tow is the most
commonly used filter material and the fibres generally have a mean
diameter in the region of 20 .mu.m.
SUMMARY
[0003] According to a first aspect of the invention, a filter
material for inclusion in a smoking article is provided, wherein
the filter material is in the form of a fibrous tow or a non-woven
sheet comprising fine cellulose acetate fibres having a mean
diameter of from about 1 .mu..mu.m to about 15 .mu.m.
[0004] In some embodiments, the tow or non-woven sheet is formed
from fibres and at least about 80% by weight of the fibres are fine
cellulose acetate fibres.
[0005] In some embodiments, the fine cellulose acetate fibres have
a diameter of no less than 0.3 .mu.m.
[0006] In some embodiments, the fine cellulose acetate fibres
comprise cellulose acetate and an additive.
[0007] In some embodiments, the filter material further comprises a
plasticizer which is one or more selected from the group consisting
of: triacetin; polyethylene glycol; triethyl citrate; and
triethylene glycol diacetate.
[0008] In some embodiments, the filter material removes from about
50% to about 90% phenol from tobacco smoke.
[0009] In some embodiments, the filter material removes from about
50% to about 90% cresol from tobacco smoke.
[0010] According to a second aspect of the invention, a process for
preparing filter material for inclusion in a smoking article is
provided, the filter material comprising fine cellulose acetate
fibres having a mean diameter of from about 1 .mu.m to about 15
.mu.m, the process comprising electrospinning or centrifugal
spinning or melt spinning.
[0011] In some embodiments, a cellulose acetate solution is spun,
the solution having a cellulose acetate concentration of from about
6% to about 30%.
[0012] In some embodiments, the fine cellulose acetate fibres are
produced by spinning through a spinneret using centrifugal force,
and the spinneret spins at a rate of from about 4500 to about 7500
rpm.
[0013] In some embodiments, the flow rate of the cellulose acetate
solution through the orifice(s) of the spinneret is from about 5 to
about 100 ml/min.
[0014] In some embodiments, the fine cellulose acetate fibres are
laid down as a non-woven sheet or non-woven web directly following
spinning.
[0015] In some embodiments, the fine cellulose acetate fibres are
drawn onto a base sheet upon which a non-woven sheet or web is
formed by a vacuum pull, by air flow or by electrostatic
charge.
[0016] According to a third aspect of the invention, a filter
material is provided, obtained or obtainable by a process according
to the second aspect.
[0017] According to a fourth aspect of the invention, a filter
element or filter for a smoking article is provided, comprising a
filter material according to the first aspect, or comprising a
filter material obtained or obtainable by a process according to
the second aspect.
[0018] In some embodiments, the filter has a pressure drop of from
about 60 to about 140 mmWG.
[0019] In some embodiments, the filter comprises from about 30 to
about 90 mg of filter material in the form of a fibrous tow or a
non-woven sheet comprising fine cellulose acetate fibres having a
mean diameter of from about 1 .mu.m to about 15 .mu.m.
[0020] In some embodiments, the filter comprises from about 40 to
about 80 mg of said filter material.
[0021] According to a fifth aspect of the invention, smoking
article is provided comprising a filter or filter element according
to the fourth aspect.
[0022] According to a sixth aspect of the invention, there is
provided use of the filter material according to the first or third
aspect, in the filtration of tobacco smoke.
BRIEF DESCRIPTION OF THE FIGURES
[0023] In order that aspects of the invention may be more fully
understood, embodiments thereof are described, by way of
illustrative example, with reference to the accompanying drawing in
which:
[0024] FIG. 1 is a schematic side view of a smoking article
including a filter according to some embodiments.
DETAILED DESCRIPTION
[0025] Most commercial cigarette filters are made from cellulose
acetate (CA) fibres or "tow". This CA tow, which is used as
cigarette filter material in many commercially available filter
cigarettes, is referred to herein as "conventional" cellulose
acetate. Conventional CA typically has a degree of substitution of
less than 3.0, preferably in the range of 2.0 to 2.8, and most
preferably in the range of 2.3 to 2.5.
[0026] The filaments of conventional CA tow have a diameter of
approximately 20 .mu.m. The filaments of conventionally used CA tow
generally have a Y cross section, but it is known to make filaments
with other cross-sectional shapes, including crenulated, X, and I
(or "dog bone").
[0027] The amount of filter tow in the filter rod (associated with
a parameter called "tow weight") determines the density of the
filter rod. The firmness of the filter rod can be controlled by
adding a so-called "plasticizer", for example glycerol triacetate,
usually referred to as triacetin. The plasticizer actually acts as
a binder, binding adjacent fibres at their points of contact. This
results in an increase in the hardness or structural rigidity of
the rod formed from the tow.
[0028] Routinely measured filter parameters include pressure drop
and `tar` or NFDPM (nicotine-free dry particulate matter) and
nicotine filtration efficiency and these parameters are
related.
[0029] Pressure drop (also referred to as "draw resistance")
determines the amount of suction a smoker needs to apply to the
cigarette to draw smoke through the filter. The pressure drop of
the filter plus that of the tobacco column must be within a range
acceptable to consumers, which is typically in the range 80-160 mm
water gauge (WG). The pressure drop will be affected by the
physical properties of the filter material, such as fibre diameter
and cross-sectional shape. In addition, it will be affected by the
manner in which the filter material is incorporated into the
filter. For example, the packing is density of the filter material
within the filter will affect the pressure drop.
[0030] Filtration efficiency refers to the proportion of the
material retained by the filter compared with that entering it. The
filtration efficiency is affected by the smoke flow velocity and is
typically determined using a standard machine-smoking regime. The
main purpose of a cigarette filter is to reduce the particulate
smoke yield which is achieved by mechanical filtration of aerosol
particles.
[0031] Herein, the filtration efficiency is measured for smoking by
taking puffs of 35 ml volume and of a 2 second duration at 60
second intervals with the ventilation zone blocked.
[0032] Removal of specific constituents of the particulate phase is
generally in proportion to the "tar" filtration efficiency. Gas
phase smoke passes through cellulose acetate filters largely
unaffected. Some semi-volatile constituents, e.g. phenolic species,
can be selectively retained by conventional CA tow and this
selective retention may be further enhanced by certain
plasticizers. When used to filter cigarette smoke, conventional
cellulose acetate tow has been shown to selectively remove phenol,
cresol and pyridine.
[0033] The inventors have surprisingly found that the replacement
of conventional cellulose acetate tow with cellulose acetate fibres
having a smaller mean diameter results in greater than expected
selective reduction from tobacco smoke of selected phenol
compounds.
[0034] Therefore, in one aspect of the invention, a filter material
for inclusion in a smoking article is provided, the filter material
comprising cellulose acetate fibres having a mean diameter which is
smaller than that of the fibres making up conventional CA tow.
[0035] The filter material may be in the form of a fibrous tow or a
non-woven sheet, the tow or sheet comprising cellulose acetate
fibres having a mean diameter of from about 1 .mu.m to about 15
.mu.m. In some embodiments, the filter material is in the form of a
fibrous tow or a non-woven sheet comprising fine cellulose acetate
fibres.
[0036] As used herein, "fine fibres", "fine cellulose acetate
fibres" or "fine CA fibres" are cellulose acetate fibres having a
mean diameter of from about 1 .mu.m to about 15 .mu.m, or from
about 1 .mu.m to about 10 .mu.m, or from about 5 .mu.m to about 10
.mu.m, or from about 1 .mu.m to about 7 .mu.m.
[0037] In some embodiments, the mean is calculated based upon the
number of fibres. In other embodiments, the mean is calculated
based upon the mass of fibres.
[0038] In some embodiments, the filter material may preferably be
in the form of a fibrous tow, the tow having an analogous structure
to the conventional CA tow used in smoking article filters.
[0039] In some embodiments, the filter material is not a sheet
formed by melt blowing in which fibres of relatively short length
(for example, up to a maximum length of about 100 mm) are
melt-bonded to form a web.
[0040] In some embodiments, the filter material, i.e. the tow or
non-woven sheet, is formed from fibres and at least about 80%, at
least about 85%, at least about 90%, at least about 95%, at least
about 97%, at least about 98%, at least about 99%, at least about
99.5%, or at least about 99.8% by weight of the fibres are fine
cellulose acetate fibres.
[0041] Alternatively or in addition, in some embodiments, the
filter material may comprise at least about 80%, at least about
85%, at least about 90%, at least about 95%, at least about 97%, at
least about 98%, at least about 99%, at least about 99.5%, or at
least about 99.8% by volume fine fibres.
[0042] Alternatively or in addition, in some embodiments, the
filter material may comprise at least about 80%, at least about
85%, at least about 90%, at least about 95%, at least about 97%, at
least about 98%, at least about 99%, at least about 99.5%, or at
least about 99.8% by surface area fine cellulose acetate
fibres.
[0043] The tow or non-woven sheet may consist of the fine cellulose
acetate fibres or may consist essentially of the fine cellulose
acetate fibres.
[0044] In some embodiments, the tow or sheet is formed directly
using the fine cellulose acetate fibres, without the need to first
form the fine fibres into filaments, for example by spinning or a
similar process. Thus, the tow or non-woven sheet is made up of
individual fine fibres.
[0045] In some embodiments, individual fine fibres may have a
sufficiently large diameter so that they do not dissolve when in
use, for example when filtering tobacco smoke. In some embodiments,
the fine cellulose acetate fibres have a diameter of no less than
0.3 .mu.m.
[0046] Where the fine fibres are in the form of tow, the tow is
made directly from the fibres of cellulose acetate, rather than
being formed of filaments created from fine cellulose acetate
fibres.
[0047] The fine cellulose acetate fibres comprise or consist of
cellulose acetate. In some embodiments, the fibres comprise
cellulose acetate and any additives or the like used in their
manufacture and/or used in the manufacture of the filter material,
such as a tow or non-woven sheet.
[0048] For example, in some embodiments, the fibres are formed from
a cellulose acetate solution which may include an additive such as
polyethylene oxide (PEO) which may act as a lubricant and/or may
help to control the rate of evaporation of the solvent during the
formation of the fibres. Some PEO may be present in the fine fibres
produced in such as way. For the avoidance of doubt, PEO is an
oligomer or polymer of ethylene oxide with a molecular mass greater
than 20,000 g/mol or a molecular weight greater than 100,000.
[0049] In some embodiments, fine fibres include at least about
0.1%, at least about 0.5%, at least about 1%, at least about 2%, at
least about 5%, at least about 10%, or at least about 15% of an
additive by weight of the fine fibres. Additionally or
alternatively, in some embodiments, the fine fibres include up to
about 20%, up to about 15%, up to about 10%, up to about 5% or up
to about 2% of an additive by weight of the fine fibres.
[0050] In some embodiments, the filter material includes at least
about 0.1%, at least about 0.5%, at least about 1%, at least about
2%, at least about 5%, at least about 10%, or at least about 15% of
an additive by weight of the filter material. Additionally or
alternatively, in some embodiments, the filter material includes up
to about 20%, up to about 15%, up to about 10%, up to about 5% or
up to about 2% of an additive by weight of the filter material.
[0051] In some embodiments, the fine fibres may comprise at least
about 50%, at least about 60%, at least about 70%, at least about
75%, at least about 80%, at least about 85%, at least about 90%, at
least about 95%, at least about 97%, at least about 98%, at least
about 99% by weight cellulose acetate.
[0052] After manufacture of the fine fibres, the filter material
may be treated with other additives, such as plasticizers. Such
additives which are added to the fibres will generally not be
considered to form part of the fibres themselves.
[0053] In some embodiments, the plasticizer is one or more selected
from the group consisting of: triacetin; polyethylene glycol (PEG);
triethyl citrate (TEC); and triethylene glycol diacetate (TEGDA).
For the avoidance of doubt, PEG is an oligomer or polymer of
ethylene oxide with a molecular mass below than 20,000 g/mol or a
molecular weight below than 100,000.
[0054] In some embodiments, the filter material includes at least
about 0.1%, at least about 0.5%, at least about 1%, at least about
2%, at least about 5%, at least about 10%, or at least about 15%
plasticizer by weight of the filter material. Additionally or
alternatively, in some embodiments, the filter material includes up
to about 20%, up to about 15%, up to about 10%, up to about 5% or
up to about 2% plasticizer by weight of the filter material.
[0055] In some embodiments, the filter material may comprise at
least about 50%, at least about 60%, at least about 70%, at least
about 75%, at least about 80%, at least about 85%, at least about
90%, at least about 95%, at least about 97%, at least about 98%, at
least about 99% by weight cellulose acetate.
[0056] The filter material may have an acceptable and/or desirable
filtration efficiency. The filter material may have an acceptable
and/or desirable filtration efficiency for an aerosol such as
tobacco smoke.
[0057] It has been found that the filter material according to the
invention provides at least the same filtration efficiency per gram
of filter material as conventional cellulose acetate tow. Indeed,
in many embodiments, the filtration efficiency of the filter
material of the invention is greater per gram of filter material
than that of conventional cellulose acetate. This allows less
filter material to be used whilst achieving the same filtration
effect.
[0058] In some embodiments, an acceptable filtration efficiency for
the filtration of tobacco smoke may be the removal of at least
about 15%, at least about 20%, at least about 25%, at least about
30%, at least about 35%, at least about 40%, at least about 45%, or
at least about 50% nicotine-free dry particulate matter (NFDPM). In
some embodiments, an acceptable filtration efficiency for the
filtration of tobacco smoke may be the removal of at least about
15%, at least about 20%, at least about 25%, at least about 30%, at
least about 35%, at least about 40%, at least about 45%, or at
least about 50% nicotine.
[0059] In some embodiments, the filter material of the invention
removes at least about 60%, at least about 70%, at least about 75%
or at least about 80% of the NFDPM. In some embodiments, the filter
material of the invention removes at least about 60%, at least
about 70%, at least about 75% or at least about 80% of the
nicotine.
[0060] It has further been shown that the fine fibre cellulose
acetate filter material exhibits increased phenol selectivity
compared to conventional cellulose acetate tow.
[0061] In some embodiments, the filter material of the invention
removes from about 50% to about 90% phenol from tobacco smoke. In
some embodiments, the filter material of the invention removes from
about 50% to about 90% cresol from tobacco smoke.
[0062] Thus, the filter material of the invention exhibits greater
selectivity for phenol and cresol than conventional cellulose
acetate tow (as shown in the Examples below).
[0063] The experimental data show that, by decreasing the diameter
of the CA fibre, we get an improved filtration efficiency of the
smoke particulate phase and an above expected increase in
filtration efficiency of phenol and cresol.
Processes
[0064] In order to form fibres from cellulose acetate, the
cellulose acetate may be dissolved in acetone to produce a solution
which is then extruded by being forced out through one or more
orifices to form fibres. Frequently, it will be desirable to filter
the cellulose acetate solution before it is extruded.
[0065] Spinning is the basic technique used for forming fibres from
substances in solution, such as cellulose acetate. The solution is
generally forced through a cap or nozzle, called a spinneret. The
spinneret is perforated with small holes and a filament is extruded
through each one. A spinneret may have from one to several hundred
or even thousand holes. As the filaments emerge from the holes in
the spinneret, the liquid polymer is converted first to a rubbery
state and then solidified. This process of extrusion and
solidification of endless filaments is called spinning (however, it
should not be confused with the process used to combine multiple
fibres into a filament, which is also called spinning).
[0066] Solidification of the extruded polymer is achieved by
evaporating the solvent in a stream of warm air or inert gas.
[0067] While extruded fibres are solidifying, or in some cases even
after they have hardened, the filaments may be drawn to impart
strength. Drawing pulls the molecular chains together and orients
them along the fibre axis, creating considerably stronger fibres.
This can also reduce the diameter of the fibres.
[0068] Following the exiting of the cellulose acetate from the
spinneret, there may be rapid evaporation of the solvent from the
surface of the extruded filament. This leads to the formation of a
skin layer on the surface. As the solvent from within the body of
the filament subsequently evaporates, the skin layer on the surface
caves in, providing the fibre with a cross section having a
collapsed shape.
[0069] The filter material of the invention is made by a spinning
process. In such processes, various factors may be varied and/or
controlled, for example the cellulose acetate concentration of the
solution, the orifice size and/or the flow rate of the polymer
solution through the spinneret, to provide fibres having a mean
diameter of from about 1 .mu.m to about 15 .mu.m. In some
embodiments, the fine cellulose acetate fibres formed by a spinning
process have a mean diameter of from about 1 .mu.m to about 15
.mu.m, or from about 1 .mu.m to about 10 .mu.m, or from about 5
.mu.m to about 10 .mu.m, or from about 1 .mu.m to about 7 .mu.m. In
some embodiments, the fine cellulose acetate fibres formed by a
spinning process have a diameter of no less than 0.3 .mu.m.
[0070] In some embodiments, the spinning is controlled to provide
finer fibres than seen in conventional cellulose acetate tow. In
some embodiments, this may be as a result of utilising
electrostatic charge to draw out the fibres (electrospinning), or
utilising high velocity air flow to blow the fibres, or by
utilising centrifugal force to draw out the fibres from liquid feed
stock (so-called forcespinning), or by melt spinning.
[0071] In some embodiments, it may be preferable to form the fine
cellulose acetate fibres by a process comprising centrifugal
spinning.
[0072] In embodiments where the fibres of cellulose acetate are
produced by melt spinning, the cellulose acetate is heated to a
temperature at which it has a desired viscosity for the
process.
[0073] In some embodiments where the fibres of cellulose acetate
are produced by other spinning processes, the fibres are made from
a cellulose acetate solution. In some embodiments, the cellulose
acetate solution, formed from cellulose acetate in acetone, has a
cellulose acetate concentration of from about 6% to about 30%, from
about 7% to about 25% or from about 8% to about 20%.
[0074] In some embodiments, the feedstock may be heated during
spinning, for example to prevent gelling and the consequent
clogging of the orifices that can be observed with some cellulose
acetate solutions. For example, the temperature of the feedstock
being spun may be from about room temperature (for example
20.degree. C. or 25.degree. C.) to about 60.degree. C.
[0075] In embodiments where the fine fibre are produced by spinning
using centrifugal force, the spinneret may spin at a rate of from
about 4500 to about 7500 rpm, or from about 5000 to about 7000
rpm.
[0076] In some embodiments, the flow rate of the feedstock, i.e. of
the cellulose acetate solution, through the orifice(s) of the
spinneret is from about 5 to about 100 ml/min, or from about 10 to
about 50 ml/min. In some embodiments, these flow rates may be used
in combination with the spin rates mentioned above for centrifugal
force spinning.
[0077] In some embodiments, the fine fibres are laid down as a
non-woven sheet or non-woven web directly following spinning. In
some embodiments, the fibres are drawn to a base sheet upon which
the non-woven sheet is formed by a vacuum pull, by air flow or by
electrostatic charge.
[0078] In some embodiments, the non-woven sheets have a basis
weight or grammage of from about 5 to about 50 g/m.sup.2 (also
referred to as gsm), or from about 10 to about 40 g/m.sup.2, or
from about 15 to about 35 g/m.sup.2.
[0079] In some embodiments, the non-woven sheets have a caliper of
from about 100 to about 1500 .mu.m, or from about 250 to about 750
.mu.m.
[0080] In some embodiments, the fine cellulose acetate fibres of
the present invention are not formed by a melt blowing process.
[0081] In some embodiments, the process comprises forming fine
cellulose acetate fibres having a length of greater than 100 mm.
These fibres may be used to form a fibrous tow or a non-woven
sheet. In some embodiments the fibrous tow or non-woven sheet is
subsequently cut to a desired size for inclusion in a filter or
filter element.
Filters and Smoking Articles
[0082] The filter material may be incorporated into a smoking
article, or a part thereof. In some embodiments, a filter or filter
element containing the filter material is incorporated into a
smoking article. The filter material, filter or filter element may
be incorporated into a smoking article by any method known in the
art.
[0083] 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. In addition, in some embodiments, the term "smoking
article", as used herein, further encompasses aerosol generation
devices, such as e-cigarettes and other nicotine inhalers, as well
as inhalation devices such as so-called "heat-not-burn" devices in
which tobacco is heated but not combusted.
[0084] Referring to FIG. 1, a smoking article 1 according to an
embodiment of the invention comprises a filter 2 and a cylindrical
rod of smokeable material 3, such as tobacco, aligned with the
filter 2 such that one end of the smokeable material rod 3 abuts
the end of the filter 2. The filter 2 is wrapped in a plug wrap
(not shown) and the smokeable material rod 3 is joined to the
filter 2 by tipping paper in a conventional manner. The filter 2 is
substantially cylindrical and has a mouth end 4 and a smokeable
material end 5. The filter 2 comprises filter material 6 as
described herein.
[0085] Because of the enhanced filtration characteristics of the
fine CA fibres, it is possible to achieve an equivalent or improved
filtration compared to that of a conventional CA filter using less
filter material. This means that less filter material needs to be
used. In some embodiments, it may be desirable to make the filter
to the same dimensions as used in a conventional cigarette design,
namely having a target length of 144 mm and a target circumference
of 24.3 mm. In other embodiments, the filters may be for use in
smoking articles of other formats, such as so-called super-slim or
demi-slim, the filters will have different dimensions.
[0086] When incorporated into a filter or filter element, the
filter material may confer desirable physical properties. For
example, pressure drop across the filter or filter element may be
between 60 and 140 mmWG, which would be a desirable pressure drop
when the filter or filter element is incorporated into a smoking
article.
[0087] In some embodiments, a filter comprising the filter material
of the invention may have a pressure drop of from about 60 to about
140 mmWG, from about 70 to about 130 mmWG, from about 75 to about
120 mmWG, from about 80 to about 110 mmWG, from about 85 to about
100 mmWG, or from about 90 to about 95 mmWG.
[0088] In some embodiments, a filter comprising the filter material
of the invention may include filter material having a weight of
from about 30 to about 90 mg, or from about 40 to about 80 mg. This
is compared to a conventional cellulose acetate filter (of a
so-called king-size format) in which approximately 120 to 130 mg of
the cellulose acetate tow is included. For alternative filter
formats, for example in those for use in a super-slim or demi-slim
smoking article, the amount of filter material used would obviously
be reduced.
[0089] In embodiments where less filter material of the invention
is incorporated in a filter having conventional dimensions, this
may mean that the filter is less densely packed with the filter
material. In other embodiments, the filter may be designed so that
the filter material is present in only part of the filter rod, for
example in a central axial rod surrounded by a void or by other
material. In such embodiments it may be desirable to ensure that
the flow path of the mainstream smoke being drawn through the
filter rod is channelled through the filter material. In
alternative embodiments, the flow path may be variable. In an
alternative approach, the filter may have one or more cavities.
Such cavities may have essentially the same diameter as the filter
material plug. For example, such a cavity may be formed between two
plugs of filter material, or between one plug of filter material
and the rod of smokeable material. In some embodiments, the cavity
may house filter components such as adsorbent material, flavourants
or additive release components.
[0090] In some embodiments, the filter material has an acceptable
and/or desirable filtration efficiency and an acceptable and/or
desirable pressure drop when in use, for example when the filter
material is incorporated into a smoking article.
EXAMPLES
[0091] The fine fibre cellulose acetate filter materials used in
the experiments of the examples set out below were produced by
centrifugal spinning of a cellulose acetate solution. The
concentration and the spinning of the spinneret were adjusted to
obtain fibres of the desired mean diameter. The fibres were
deposited on substrate sheet and removed to provide non-woven
sheets of fine cellulose acetate fibres.
Example 1
[0092] Cellulose acetate tow was produced with an average fibre
diameter of 2 .mu.m. To test the filtration characteristics of a
filter consisting of this material, test cigarettes were
manufactured and compared to a control cigarette having a filter
with filter material consisting of conventional cellulose acetate
tow having a mean fibre diameter of about 20 .mu.m.
[0093] The control cigarettes used were commercial Lucky Strike
Blue cigarettes which had a filter made from cellulose acetate tow
with a 20 .mu.m mean fibre diameter and 7% triacetin as
plasticiser. To prepare the test cigarettes, the filters of the
Lucky Strike Blue cigarettes were removed and replaced with filter
material consisting of unplasticised cellulose acetate filter tip
having an average 2 .mu.m fibre diameter.
[0094] Any filter tip ventilation was completely blocked on both
cigarettes.
[0095] The filter of the test cigarettes was formed to provide a
pressure drop which is equivalent to that of the control
cigarettes.
[0096] As shown by the results set out in Table 1, at a matched
pressure drop, although significantly less of the smaller diameter
cellulose acetate filter material was used in the filters of the
control cigarettes (30 mg cellulose acetate in the test cigarette
compared to 124 mg in the control), the test cigarettes exhibited
greater filtration efficiency. When the results are normalised to
unit tar, there is enhanced reductions of phenol and cresol, even
with the test cigarette filter material including no plasticiser.
It is known that triacetin on cellulose acetate improves the
selective filtration efficiency for phenol and cresol. The
cigarettes were smoked under ISO smoking conditions.
TABLE-US-00001 TABLE 1 Filter Conventional CA 2 .mu.m CA fibres
Weight 124 mg 30 mg Pressure Drop 95 mmWG 90 mmWG Puff No. 6.1 5.9
NFDPM (mg/cig) 10 5.8 Nicotine 0.73 0.42 Water 5.5 1.2 CO 10.1 10.9
Hydroquinone 37.1 19.8 Resorcinol 3.1 1.9 Catechol 38.6 20.8 Phenol
11.5 4.1 m + p-Cresol 7.1 3.0 o-Cresol 3.0 1.1 NFDPM normalised
Hydroquinone 3.71 3.41 Resorcinol 0.31 0.33 Catechol 3.86 3.59
Phenol 1.15 0.71 m + p-Cresol 0.71 0.52 o-Cresol 0.30 0.19 %
Reduction Hydroquinone 8 Resorcinol -6 Catechol 7 Phenol 39 m +
p-Cresol 27 o-Cresol 37
[0097] A negative % reduction means an increase in yield, whilst a
positive % reduction means a decrease in yield.
Example 2
[0098] This experiment was carried out to investigate the effect of
different fibre diameters of the cellulose acetate filter
material.
[0099] To provide control cigarettes, filter tips were removed from
a Lucky Strike Blue cigarette and replaced with a standard
cellulose acetate filter tip with 20 .mu.m fibre diameter (labelled
CA 20 .mu.m below). For the test cigarettes, filter tips were
removed from a Lucky Strike Blue cigarette and replaced with: (i) a
cellulose acetate filter tip with filter material consisting of
fibre having an average diameter of 7 .mu.m; (ii) a cellulose
acetate filter tip with filter material consisting of fibre having
an average diameter of 2 .mu.m; and (iii) a cellulose acetate
filter tip with filter material consisting of fibre having an
average diameter of 0.8 .mu.m.
[0100] Because of the small amount of the small diameter cellulose
acetate required for filtration, this was incorporated into a
narrow bore filter tube to get a better "fill" value.
[0101] This time no plasticiser was used on any filter and there
was also no filter tip ventilation. The cigarettes were smoked
under ISO smoking conditions.
[0102] Filtration efficiencies for the smoke particulate matter
(NFDPM, nicotine, hydroquinone, resorcinol, catechol) are show in
Table 2. The results demonstrate that the filtration efficiency
increased using smaller diameter cellulose acetate fibres. Phenol
and cresol filtration efficiencies are increased by a greater
amount using the smaller diameter cellulose acetate fibres.
TABLE-US-00002 TABLE 2 Filter Empty 20 .mu.m CA 0.8 .mu.m CA 2
.mu.m CA 7 .mu.m CA tube fibres fibres fibres fibres Pressure Drop
95 90 93 97 mmWG mmWG mmWG mmWG CA Weight 124 11* 19* 46* (mg)
Format KS KS Narrow Narrow Narrow bore bore bore Puff No. 6.1 6.1
6.9 6.2 6 NFDPM 19.5 10.9 7.7 5.9 6.3 (mg/cig) Nicotine 1.24 0.79
0.46 0.43 0.46 Water 5.9 1.9 1.9 1.3 1 CO 11 10.7 10.7 10.6 11.1
Hydroquinone 64.5 38.9 28.7 21.7 23.8 Resorcinol 4.9 3.1 2.2 1.7
1.9 Catechol 77.3 46.9 30.2 23.5 26.7 Phenol 54.0 22.4 10.4 3.9 5.6
m + p-Cresol 26.9 12.7 6.0 2.9 3.8 o-Cresol 12.4 5.7 2.5 1.1 1.5
NFDPM normalised Hydroquinone 3.31 3.57 3.73 3.67 3.78 Resorcinol
0.25 0.29 0.29 0.28 0.30 Catechol 3.96 4.30 3.92 3.98 4.24 Phenol
2.77 2.05 1.35 0.66 0.88 m + p-Cresol 1.38 1.16 0.78 0.49 0.60
o-Cresol 0.64 0.52 0.32 0.19 0.24 Filtration Efficiency (%) NFDPM
44 61 70 68 Nicotine 36 63 65 63 Hydroquinone 40 55 66 63
Resorcinol 36 54 65 61 Catechol 39 61 70 65 Phenol 59 81 93 90 m +
p-Cresol 53 78 89 86 o-Cresol 54 80 91 88 Filtration Selectivity
Nicotine 0.88 1.05 0.86 0.86 Hydroquinone 0.93 0.87 0.88 0.86
Resorcinol 0.88 0.85 0.86 0.82 Catechol 0.92 1.00 1.00 0.91 Phenol
1.36 2.05 4.28 3.20 m + p-Cresol 1.19 1.77 2.73 2.28 o-Cresol 1.22
1.95 3.33 2.67 *excluding tube CA
[0103] The selectivity data provided in Table 2 emphasises how good
the fine fibres are at removing phenol. Selectivity is defined as
the ratio of NFDPM filtration efficiency to smoke analyte
filtration efficiency). A selectivity for a toxicant which is
greater than 1 is an indication of selectivity and the higher the
value, the greater the selectivity. Selectivity is desirable as it
indicates that more toxicant is removed from the smoke than
tar.
Example 3
[0104] The experiment was carried out to investigate the effect of
the plasticizer and of the reduced diameter.
[0105] Control cigarettes were commercial Lucky Strike Blue
cigarettes with filters comprising conventional plasticized
cellulose acetate tow with a fibre diameter of about 20 .mu.m
(labelled CA+Pz below). For the test cigarettes, the filter tips
were removed from a Lucky Strike Blue cigarette and replaced with:
(i) unplasticised cellulose acetate tow with a fibre diameter of
about 20 .mu.m (labelled CA no Pz); and (ii) unplasticised
cellulose acetate tow having an average fibre diameter of 9 .mu.m
(labelled 9 .mu.m).
[0106] Any filter tip ventilation was completely blocked on all
cigarettes. The Lucky Strike Blue control filter contained 7%
triacetin which is known to give improved phenol and cresol
reductions.
[0107] Filter tip pressure drops matched at approximately 85 mmWG.
The small diameter cellulose acetate fibre filter tip weight was 91
mg, compared to the standard cellulose acetate weight of 125 mg.
The cigarettes were smoked under ISO smoking conditions.
[0108] As before, for a matched pressure drop, less material with
smaller diameter fibres is required. This also gives a higher
filtration efficiency, as shown by the results set out in Table
3.
TABLE-US-00003 TABLE 3 Filter 20 .mu.m CA no Pz 9 .mu.m CA fibres
20 .mu.m CA + Pz Puff No. 6.1 6.3 6.1 NFDPM (mg/cig) 10.9 7.7 10.4
Nicotine 0.79 0.55 0.70 Water 1.9 1.2 2.5 CO 10.7 10.7 11.5
Hydroquinone 38.9 32.5 47.1 Resorcinol 3.1 2.2 3.6 Catechol 46.9
32.5 47.1 Phenol 22.4 10.2 11.7 m + p-Cresol 12.7 6.3 7.0 o-Cresol
5.7 2.7 2.9 NFDPM normalised Hydroquinone 3.57 4.22 4.52 Resorcinol
0.29 0.29 0.34 Catechol 4.30 4.22 4.53 Phenol 2.05 1.33 1.12 m +
p-Cresol 1.16 0.82 0.67 o-Cresol 0.52 0.35 0.28 % Difference in
unplasticised samples Hydroquinone -18 Resorcinol -1 Catechol 2
Phenol 35 m + p-Cresol 30 o-Cresol 34
[0109] It can be seen that triacetin has a large effect on phenol
and cresol filtration. However, for the unplasticised materials it
still appears that the smaller diameter fibres give an enhanced
phenol and cresol selectivity.
[0110] In order to address various issues and advance the art, the
entirety of this disclosure shows by way of illustration various
embodiments in which the claimed invention(s) may be practiced and
provide for superior filter materials. The advantages and features
of the disclosure are of a representative sample of embodiments
only, and are not exhaustive and/or exclusive. They are presented
only to assist in understanding and teach the claimed features. It
is to be understood that advantages, embodiments, examples,
functions, features, structures, and/or other aspects of the
disclosure are not to be considered limitations on the disclosure
as defined by the claims or limitations on equivalents to the
claims, and that other embodiments may be utilised and
modifications may be made without departing from the scope and/or
spirit of the disclosure. Various embodiments may suitably
comprise, consist of, or consist essentially of, various
combinations of the disclosed elements, components, features,
parts, steps, means, etc. In addition, the disclosure includes
other inventions not presently claimed, but which may be claimed in
future.
* * * * *