CA2829718C

CA2829718C - Smoking article with a filter

Info

Publication number: CA2829718C
Application number: CA2829718A
Authority: CA
Inventors: Richard Fiebelkorn
Original assignee: British American Tobacco Investments Ltd
Current assignee: British American Tobacco Investments Ltd
Priority date: 2011-03-22
Filing date: 2012-03-06
Publication date: 2015-11-24
Anticipated expiration: 2032-03-06
Also published as: WO2012126721A1; CL2013002677A1; CA2829718A1; KR20140020293A; GB201104788D0; MX2013010876A; AR085529A1; JP5918348B2; EP2688430A1; CN103501644B; BR112013024191A2; TW201302109A; AU2012230553A1; UA110516C2; EP2688430B1; JP2014511675A; RU2589437C2; AU2012230553B2; MY164045A; CN103501644A

Abstract

A smoking article comprising a filter section comprising a first region of filtration material for removing particulate matter from a smoke stream, wherein the rod the smoking article is arranged to enhance heat transfer towards the first region of filtration material is disclosed.

Description

Smoking Article with a Filter Field The invention relates to smoking articles and, in particular, to modifying smoke in smoking articles.
3 Background Smoking articles comprising smoke modifying agents are known in the art.
Examples include absorbents or adsorbents located in the filter section or tobacco rod of the smoking article. Particulate filters absorb smoke constituents residing in the particulate phase of a smoke stream. Adsorbents are often included and are known to adsorb smoke constituents travelling in the vapour phase of the smoke stream.
While such absorbents and adsorbents have removed smoke constituents from the smoke stream as it passes through the smoking article, the arrangement of the smoking article has not allowed the temperature profile of the smoke to be controlled. As such, smoke constituents are not removed when it is desirable that they be removed.
13 Summary An embodiment of the present invention provides a smoking article with a filter comprising: a first region of filtration material for removing particulate matter from a smoke stream, wherein the smoking article is arranged to enhance heat transfer towards the first region of filtration material, a second region of filtration material downstream of the first region and of lower filtration efficiency than the filtration efficiency of the first region of filtration material, and a configuration to cool the smoke stream downstream of the first region of filtration material prior to entry into the second region.
In one embodiment a rod of smokable material is provided wrapped by a wrapper and arranged to form a coal at one end thereof when lit, wherein the wrapper has heat conducting strips attached thereto to enhance heat transfer from the coal towards the first region of filtration material.

2 The rod of smokable material may have at least one channel extending therethrough to enhance heat transfer from the coal towards the first region of filtration material.
The at least one channel may comprise a plurality of channels disposed radially about the circumference of the rod of smokable material.
In one embodiment the configuration to cool the smoke comprises a cooling chamber. A
region of adsorbent material may be provided in or downstream of the cooling chamber.
Perforations for cooling the smoke may be included in a wrapper circumscribing the filter section.
The configuration to cool the smoke may include at least one gap in the wrapper circumscribing the filter section.
A diluent may be provided, for example adjacently downstream of the first region of filtration material.
The rod of smokable material may comprise a pelletised composite of tobacco and may further comprise carbon.
The filter may be configured to alter the composition of the smoke stream as the smoking article is smoked.
The first region of filtration material may form an annulus around a bore which becomes obstructed as the smoking article is smoked.
The filter may be arranged to channel the smoke stream onto the first region of filtration material.
The first region of filtration material may be wrapped by an insulating material.
The first region of filtration material may have a retention value greater than 30 percent or even greater than 70 percent.

2a The smoking article may be configured such that the first region of filtration material only removes matter with boiling points of or greater than a predetermined level.
The predetermined level may be one of about 250 C, 300 C, 350 C, 400 C, 450 C and 500 C.
Brief description of the drawings So that the present invention may be more fully understood several embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, in which:

3 Figure 1 is a side cross sectional view of a smoking article according to one embodiment of the present invention;
Figure 2 is a side cross sectional view of a smoking article according to an alternative embodiment of the present invention;
Figure 3 is a side cross sectional view of a smoking article according to an alternative embodiment of the present invention;
Figure 4 is a side cross sectional view of a smoking article according to an alternative embodiment of the present invention;
Figure 5 is a side cross sectional view of a smoking article according to another embodiment of the present invention; and Figure 6 is a side cross sectional view of a smoking article according to another embodiment of the present invention;
Figure 7 is an end view of a smoking article according to one embodiment of the present invention;
Figure 8 is a plan view of a tobacco rod wrapper according to an embodiment of the present invention; and Figure 9 is an end view of a smoking article in accordance with another embodiment of the present invention.
Detailed description Figure 1 shows a cylindrical cigarette 10 in accordance with one embodiment of the present invention. The cigarette 10 comprises a tobacco rod 15 and a filter section 20. The tobacco rod 15 and filter section 20 shown in Figure 1 are attached to each other by tipping paper 25 although other means for attaching tobacco rods to filter

4 sections that are known in the art may be employed in the alternative. The filter section 20 is wrapped in a length of tipping paper 25 which is longer than the filter section 20 and connects the tobacco rod 15 to the filter section 20 in a manner well known in the art.
The tobacco rod 15 shown in Figure 1 may be shorter than conventional tobacco rods that are well known in the art. The tobacco rod 15 may be formed from reconstituted or pelletised tobacco circumscribed by a wrapper 26. The wrapper may be formed from any paper suitable for wrapping tobacco rods that is known in the art. The wrapper 26 may have a natural permeability between 0 and 25 Coresta units (hereinafter denoted as CU) although preferably between 2 and 10 CU. A
higher permeability may be achieved using electrostatic perforation.
The tobacco rod may be 10 to 50 millimetres (hereinafter denoted as mm) in length, although 30 to 40 mm is a preferred length. The tobacco rod 15 may be between and 28 mm in circumference although 17 to 25 mm is a preferred circumference.
A binder may be added to the tobacco during manufacture of the tobacco rod 15 to make the tobacco easier to manipulate and form into rods. Carbon, in granular form e.g. activated carbon or any other carbon additive known in the art, may also be added to the tobacco which, as well as making the tobacco rod 15 easier to manipulate, facilitating combustion and increasing combustion heat, is also known to act as an adsorbent of certain smoke constituents.
The wrapper 26 which circumscribes the tobacco rod 15 is made from low permeability paper although wrapping materials other than paper that are known in the art may be used. The permeability or porosity of an object is known to affect its burn rate. As such, the low permeability of the wrapper 26 ensures that the tobacco rod 15 burns more slowly than a tobacco rod wrapped in a higher permeability wrapper would burn. Where the tobacco rod 15 is shorter than conventional tobacco rods that are known in the art the decreased burn rate increases the number of draws or puffs that a user may take from the cigarette 10 during use.

The filter section 20 of the cigarette 10 may be wrapped in a plugwrap 27 in addition to the tipping paper 25. The plugwrap 27 may have a permeability between 0 and 2000 Coresta units.

5 The filter section 20 comprises a region of high filtration efficiency (hereinafter FE) material 30. The region of high FE material 30 is located at the upstream end of the filter section 20 and is adjacent to the tobacco rod 15. The high FE material 30 may be heat resistant as it will be exposed to high temperatures and may be a Cambridge filter pad formed from fibre glass. The high FE material 30 may also contain materials, such as zeolites, which can selectively remove individual smoke constituents. The region of high FE material may be between 1 and 15 mm in length. The filtration efficiency and/or retention value of the high FE
material should be selected to achieve a high level of particulate filtration. The retention value according to embodiments of the invention is greater than 30% and preferably greater than 70% of particulate matter, although the invention is also effective with retention values greater than 40%, 50%, 60%, 80% and/or 90%.
Since the region of high FE material 30 is likely to become hot during use an insulating layer 31 may be provided between the high FE material 30 and the tipping paper 25 to reduce the risk of a user burning himself upon contact with the filter section 20.
A diluent holding material 35 or aerosol forming agent may be located within the region of high FE material 30. The diluent holding material 35 may contain glycerol although other diluents known in the art may equally be used. The diluent holding material 35 provides another means for modifying the contents of the smoke by introducing other constituents into and thereby diluting the smoke aerosol.
The diluent holding material 35 may alternatively be located inside a cooling chamber 40 downstream of the region of high FE material 30. Additional regions of diluent may be located further downstream the filter section 20. The cooling chamber 40 shown in Figure 1 provides a space for smoke to circulate and cool as it

6 travels downstream. The cooling chamber 40 may be between 10 and 30 mm in length.
Further downstream from the cooling chamber 40 is a region of low FE material 45.
The low FE material 45 may be formed from cellulose acetate threads although other filtration materials of low FE that are known in the art may be used.
The low FE material 45 may be formed into a plug which absorbs smoke constituents passing through. The region of low FE material 45 may be between 10 and 30 mm in length.
Located within the region of low FE material 45 there may be adsorbent material 50 which adsorbs smoke constituents. Examples of suitable adsorbent materials include activated carbon granules, carbon husks or any other material which is known in the art to adsorb smoke constituents.
A mouth end filter section 55 is located at the mouth end 60 of the smoking article 10. The mouth end filter section may be between 5 and 15 mm in length. The mouth end filter section 55 may be formed from a plug of low FE filtration material without adsorbent material located therein. The mouth end filter section 55 prevents the adsorbent material 50 from coming into contact with the users mouth.
Although not shown in Figure 1, flavourants may be included in the mouth end filter section 55. This can have the effect of counteracting any change to the taste that may be caused by the adsorbent material 50.
The tipping paper 25 is provided with a gap 65 along its length which allows air to permeate into the filter section 20 and some smoke constituents to permeate out of the filter section 20.
An alternative embodiment of the cigarette 10 is shown in Figure 2. The filter section 20 is substantially the same as the filter section 20 shown in Figure 1. A
bore 70 extends along the longitudinal axis of the tobacco rod 15. The bore 70 provides a passage for smoke to travel downstream from a burning coal 75 towards the region of high FE filtration material 30. The bore 70 may have a diameter of

7 between 1 and 3 mm. Multiple bores, substantially parallel to each other, may also be applied. The bore 70 assists in heat transfer towards the filter section 20.
Forming the tobacco rod 15 from an extruded or compressed composite of tobacco and carbon, as described above with reference to Figure 1, may also make forming the bore 70 easier since the composite material will aid in the retention of the bore shape and form. Addition of a binding agent such as guar gum or adhesive material to cut tobacco can also be used as an aid in retaining bore shape.
A cigarette 10 similar to that shown in Figure 2 but with a modified filter section 20 is shown in Figure 3. No gaps, such as the gaps 65 shown in Figure 2, are provided in the tipping paper 25. Air permeates through the tipping paper 25 and plugwrap 27 which are naturally porous. Similarly, some constituents of the smoke are able to permeate out of the filter section 20.
A cigarette 10 similar to that shown in Figure 1 comprising an alternative arrangement of the filter section 20 is shown in Figure 4. In this embodiment, the adsorbent material 50 has been included in the cooling chamber 40, for instance in granule form filling or substantially filling the cooling chamber cavity.
As the cigarette 10 shown in Figure 1 is lit by a user a coal 75 is formed where the tobacco rod 15 and the wrapper 26 circumscribing the tobacco rod 15 are combusted. A smoke stream is formed which moves towards the filter section 20 as a pressure differential is formed as a user draws through the mouth end filter section 55.
The smoke stream is formed from various constituents, each of which exist in a vapour phase and/or a particulate phase. The amount of each smoke constituent that exists in each phase depends on the temperature of the smoke. The proportion of a particular smoke constituent that exists in the vapour phase rises with rising temperature.

8 As the smoke moves downstream through the tobacco rod 15 towards the filter section 20 the temperature of the smoke falls as it moves further from the coal 75.
The fall in temperature of the smoke is reduced by factors such as changes in the downstream flow of the smoke. The flow is affected by using short, slim tobacco rods or via channels or bores of low flow resistance in the tobacco and the use of low permeability wrappers around the tobacco rod. Additional factors such as use of thermal conducting materials and reducing the thermal mass of the tobacco rod are also important factors.
As the smoke reaches the region of high FE material 30 a large proportion of those constituents travelling in the particulate phase will be removed from the smoke stream. The constituents in the particulate phase have higher boiling points than those constituents travelling in the vapour phase. A relatively small amount of the vapour phase constituents will inevitably be removed from the smoke stream by the high FE material 30. However, a proportion of these constituents may be eluted from the high FE filtration material 30 as more smoke is subsequently drawn through the filter section 20.
The smoke stream passes through the diluent holding material 35 which dilutes the smoke by adding further constituents to the smoke aerosol. As stated above, the diluent holding material 35 may be located either within the region of high FE

material 30 or inside the cooling chamber 40.
Inside the cooling chamber 40 the smoke cools to a lower temperature. As the smoke cools various constituents that were previously in the vapour phase condense into the particulate phase.
The rate at which the smoke cools will be affected by factors such as the positioning of any perforations such as gap 65 in the tipping paper 26 and the level of natural permeability of the tipping paper 25 and plugwrap 27 as the smoke is ventilated with ambient air. The gaps 65 may be between 1 and 30 mm in length.

9 It will be apparent to those skilled in the art that the choice of tipping paper 25 and plugwrap 27 is therefore important since it allows the cooling of the smoke, and the proportions of constituents residing in the vapour and particulate phases to be better controlled.
As smoke enters the region of low FE material 45 particulate phase constituents are removed. The amount of particulate material removed from the smoke stream at the region of low FE material 45 is lower than that removed at the region of high FE material 30 due to the lower filtration efficiency of the region 45 relative to the region 30.
Adsorbent material 50, such as activated carbon or any other adsorbent of smoke constituents that is known in the art, may be located within the region of low FE
material 45. The adsorbent material 50 removes smoke constituents mainly in the vapour phase.
Finally, the smoke stream is drawn through the mouth end filter section 55.
The mouth end filter section 55 comprises a plug of low FE material. The mouth end filter section 55 may be impregnated with flavourants of a type known in the art, particularly where carbon or other such adsorbents have been employed upstream.
Figure 5 shows an alternative filter arrangement. The filter section 20 comprises an annular region of high FE material 80 located where the tobacco rod 15 abuts the filter section 20. Downstream of the annular filter section 80 there is provided a region of medium FE material 85. The region of high FE material 80 and the region of medium FE material 85 may be wrapped in thermal conduction material 90, which in turn may be wrapped in insulating material 95.
Downstream of this medium FE material 85 there is provided a filter arrangement substantially similar to the arrangement described above with reference to Figure 1.
The FE of the region 85 is higher than the FE of the region 45 and lower than the FE of the region 80.

Before use, the centre of the annular region 80 forms a longitudinal bore 86 extending along the length of the annular region 80 which may be approximately 0.1 to 2 mm in width. During use, certain smoke constituents build up in the central bore 86, eventually at least partially blocking the bore 86 to smoke constituents.

Therefore, the pressure drop across the filter region 80 during the first few draws, for instance while the filter region 80 has yet to become hot and while the tobacco rod 15 is at its longest, will differ from that after later draws when the filter region 80 has become hot and when the tobacco rod 15 has been at least partially

10 combusted and is therefore shorter. Smoke that passes through the filter region 80 following the first few draws will therefore contain different proportions of certain smoke constituents than will smoke passing through the region 80 from later draws.
This is because some smoke that is drawn through the region 80 from the earliest draws will travel through the central bore 86 and will be substantially unfiltered by the region 80. However, smoke from later draws will be forced through the filtration material located in the outer annulus of the annular region 80.
Alternative configurations of filter region 80, differing in shape or composition, that will be apparent to those skilled in the art may be employed.
In the cigarette 10 shown in Figure 5 the region of low FE filtration material 45 may be wrapped in a plugwrap 96 of high porosity between the region 45 and the plugwrap 27 which may also be of similar porosity. The mouth end filter section 55 may be wrapped in a plugwrap 97 with a porosity lower than that of the plugwrap 96 which wraps the region of low FE filtration material 45.
Additional modifications can be made to the various components within the filter section 20 either in combination or separately. For example, the plugwrap 27 surrounding the cooling chamber 40 may be impregnated with an aerosol forming material such as glycerol or an additional lining layer of a material that can hold an aerosol forming material can be added.
Figure 6 shows a cigarette 10 according to yet another embodiment. The cigarette 10 is similar to that shown in Figure 1 however an annular washer 100 is located

11 upstream of the region of high FE material 30. The washer 100 focuses or channels the smoke stream to impinge on the region of high FE material 30 and maintains the velocity of the smoke stream so as to help minimise heat loss. The region of high FE material 30 and washer 100 may be wrapped in thermal conduction material 90 which, in turn, may be wrapped in an insulating material 95.
The washer 100 may be formed from a conducting material thereby further enhancing the transfer of heat to the filter section 20. The cooling chamber 40 may be shaped so to provide a pressure gradient to assist in aerosol formation.
Alternatively, the cooling chamber 40 may be at least partially filled with an adsorbent material such as carbon.
The wrapper 26, shown in Figures 1-6 may have additional heat conducting means extending along its length. Figures 7 and 8 show heat conducting strips 110.
The heat conducting strips can conduct heat from the coal 75 to the region of high FE
material 30, 80, shown in Figures 1-6, thus increasing the temperature of smoke at the point where it leaves the tobacco rod 15 and enters the filter section 20.
The heat conducting strips 110 may be metallic or comprise any other suitable conductive material.
As an alternative or in addition to the strips 110 shown in Figures 7 and 8, a liner inside the wrapper 26 or a laminate with the wrapper 26 may be included, both of which may be in the form of aluminised paper.
The heat conducting strips 110 shown in Figures 7 and 8 may alternatively allow heat conducting channels 115 to be formed along the length of the tobacco rod 15.
Smoke may be transferred from the coal 75 to the filter section 20 with reduced loss of heat along these channels 115. The strips may be formed from paper, reconstituted tobacco or any other suitable material that would be apparent to those skilled in the art. The strips may be applied to the wrapper 26 before or after the wrapper 26 is wrapped around the tobacco rod 15. Figure 8 shows a wrapper 26 with strips 110 applied thereto prior to being wrapped around a tobacco rod 15.
The strips 110 may extend along part of the length of the tobacco rod 15 or along

12 the entire length of the tobacco rod 15. Channels 115 may alternatively be formed by placing a corrugated inner wrapping material 120 between the wrapper 26 and the tobacco rod 15 as shown in Figure 9.
While Figures 7 and 9 show end views of cigarettes 10 without bores 70 present, such bores 70 may be present according to various embodiments of the present invention.
Modifications made to alter the temperature profile of smoke passing through the length of the cigarette 10 and the order of components within the cigarette 10 can be made without departing from the scope of the invention which is defined by the appended claims.
It should also be understood that while the foregoing description refers to cigarettes, the scope of the present invention may apply equally to other smoking articles known in the art.
Experimental Data The smoke profile of a cigarette similar to the cigarette 10 shown in Figure 1 was analysed. The cigarette differed from the cigarette 10 shown in Figure 1 in that the filter section did not contain diluents, adsorbents or ventilation gaps. Smoke constituents measured included particulate nicotine, particulate water, tar (NFDPM), benzo(a)pyrene (B(a)P) and catechol. Also shown in the table are the ratios of B(a)P to NFDPM and catechol to NFDPM as well as the number of puffs or draws from each cigarette. The cigarette according to the invention was compared with two control cigarettes and the results are set out in the following table. The cigarettes were investigated by analysing draws of 55 cubic centimetres (cc) of 2 seconds' duration and with a 30 second interval between draws.

13 Table 1 Invention Control 1 Control 2 example Tip ventilation NO YES NO
Total particulate mg/cigarette 19 20 45.8 matter (TPM) Nicotine mg/cigarette 0.7 1.5 2.11 Water mg/cigarette 8.7 3.8 19.2 Nicotine-Free Dry mg/cigarette 9.7 14.7 24.5 Particulate Matter (NFDPM) Puff Number 7.1 9.1 7 Benz o(a)pyrene ng/cigarette 5.2 14.8 17.7 (B(a)P) B(a)P/NFDPM x10-6 0.54 1.01 0.72 Catechol Ilg/cigarette 21.2 59.5 74.2 Catechol/NFDPM x10-3 2.19 4.05 3.03 Exemplary cigarettes according to the invention, together with Control 1 and Control 2 contained the same blend of tobacco, tobacco rod and filter length.
The cigarette labelled Control 1 had a conventional cellulose acetate filter with ventilation gaps so that the total particulate matter (TPM) matched that of the cigarette of the invention. The cigarette referred to as Control 2 was similar to the invention cigarette however the region of high FE filtration material 30 was replaced with a low efficiency cellulose acetate filter. In the invention cigarette the high FE material was made from glass fibre.
The results, as displayed in the above table, show that the ratios of B(a)P
and catechol to NFDPM are lower in the example of a cigarette in accordance with the invention than in either of the control cigarettes. B(a)P and catechol have relatively high boiling points and are therefore removed, in their particular phases, by the high FE filter portion.

14 Embodiments of the invention can therefore be arranged to control the levels of smoke constituents based on their relative boiling points. For instance, the high FE
filter region of embodiments of the invention can be used to selectively remove only smoke constituents having relatively high boiling points, for instance boiling points above a particular temperature, for instance above temperatures in the region of 250 C, 300 C, 350 C, 400 C, 450 C or 500 C. Such constituents would be in the particulate phase when passing through the high FE filter region 30, 80, 85.
By cooling the smoke in the cooling chamber 40, the low FE filter material 45 having the adsorbent material 50, according to certain embodiments of the invention, can selectively remove smoke constituents having relatively low boiling points for instance constituents having boiling points below about 300 C, 250 C, 200 C, 150 C or 100 C.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A smoking article with a filter comprising:
a first region of filtration material for removing particulate matter from a smoke stream, wherein the smoking article is arranged to enhance heat transfer towards the first region of filtration material, a second region of filtration material downstream of the first region and of lower filtration efficiency than the filtration efficiency of the first region of filtration material, and a configuration to cool the smoke stream downstream of the first region of filtration material prior to entry into the second region.

2. The smoking article according to claim 1, further comprising a rod of smokable material wrapped by a wrapper and arranged to form a coal at one end thereof when lit, wherein the wrapper has heat conducting strips attached thereto to enhance heat transfer from the coal towards the first region of filtration material.

3. The smoking article according to claim 2, wherein the rod of smokable material comprises at least one channel extending therethrough to enhance heat transfer from the coal towards the first region of filtration material.

4. The smoking article according to claim 3, wherein the at least one channel is a plurality of channels disposed radially about the circumference of the rod of smokable material.

5. The smoking article according to claim 1, wherein the configuration to cool the smoke comprises a cooling chamber.

6. The smoking article according to claim 5, further comprising a region of adsorbent material in or downstream of the cooling chamber.

7. The smoking article according to claim 1, wherein the configuration to cool the smoke include perforations in a wrapper circumscribing the filter section.

8. The smoking article according to claim 1, wherein the configuration to cool the smoke includes at least one gap in the wrapper circumscribing the filter section.

9. The smoking article according to any one of claims 1 to 8 further comprising a diluent .

10. The smoking article according to claim 9, wherein the diluent is adjacently downstream of the first region of filtration material.

11. The smoking article according to any one of claims 2 to 4, wherein the rod of smokable material comprises a pelletised composite of tobacco.

17. The smoking article according to any one of claims 2 to 4, wherein the rod of smokable material further comprises carbon.

13. The smoking article according to any one of claims 1 to 12, wherein the filter is configured to alter the composition of the smoke stream as the smoking article is smoked.

14. The smoking article according to claim 13, wherein the first region of filtration material forms an annulus around a bore which becomes obstructed as the smoking article is smoked.

15. The smoking article according to any one of claims 1 to 14, wherein the filter is arranged to channel the smoke stream onto the first region of filtration material.

16. The smoking article according to any one of claims 1 to 15, wherein the first region of filtration material is wrapped by an insulating material.

17. The smoking article according to any one of claims 1 to 16, wherein the first region of filtration material has a retention value greater than 30 percent.

18. The smoking article according to any one of claims 1 to 17, wherein the first region of filtration material has a retention value greater than 70 percent.

19. The smoking article according to any one of claims 1 to 18, wherein the smoking article is arranged such that the first region of filtration material only removes matter with boiling points of or greater than a predetermined level.

20. The smoking article according to claim 19, wherein the predetermined level is one of about 250°C, 300°C, 350°C, 400°C, 450°C and 500°C.