WO2007093757A1

WO2007093757A1 - Improvements relating to smoking articles and filter therefor

Info

Publication number: WO2007093757A1
Application number: PCT/GB2007/000155
Authority: WO
Inventors: Edward Awty; Peter Rex White
Original assignee: British American Tobacco (Investments) Limited
Priority date: 2006-02-16
Filing date: 2007-01-19
Publication date: 2007-08-23
Also published as: KR20080094731A; JP2009526540A; GB0603126D0; BRPI0707756A2; RU2421110C2; CA2642521A1; UA91407C2; MX2008010505A; CN101384185B; ATE516716T1; PL1983852T3; ES2370008T3; ZA200806787B; EP1983852A1; MY159363A; TWI399181B; RU2008136759A; AR059453A1; AU2007216341B2; CN101384185A

Abstract

A filter for smoking articles includes two sections, a first section (2) comprising a longitudinally extending opening (4) surrounded by smoke impervious material (6) and a second section (8) comprising a core (10) having a high-pressure drop material, a circumscribing annulus (12) having a lower pressure drop filter material than the core. The first section (2) is generally adjacent to the tobacco section (18) of a cigarette (3) at a first end and is spaced from the second section (8). Moreover, the invention comprises ventilation holes (20) circumscribing the space or gap (14) between the first and second section or circumscribes the second section (8).

Description

Improvements relating to Smoking Articles and filters therefor i

The present invention relates to an improved filter for smoking articles and to smoking articles incorporating such a filter. More particularly, it relates to a filter for a cigarette.

For many years, cigarette manufacturers have attempted to reduce the amount of smoke constituents delivered to a smoker by means of filtration. Much effort has been made to provide a smoking article that, when smoked, has a reduced bandwidth and a puff profile with reduced variance between puffs. The bandwidth of a smoking article is a measurement ratio between the tar delivery of a cigarette smoked under testing conditions of the International Standards Organization (ISO) versus the tar delivery of the same cigarette smoked in other, usually more intense conditions.

Specifically, ISO testing conditions involve the smoking of a cigarette wherein the puff volume is 35 mL, the puff duration is two seconds, and the interval between puffs is 60 seconds. More intense smoking conditions may include an increase in puff volume, an increase in puff duration, a decrease in time between puffs, or some combination of these changes. A lower bandwidth corresponds to a decreased variance in the amount of smoke constituents delivered by a cigarette when smoked under ISO conditions and by the same cigarette smoked under more intense smoking conditions.

The puff profile of a cigarette is the delivery of smoke constituents per puff recorded against puff number. A puff profile having reduced variance between puffs, i.e., a relatively flat puff profile, is one in which the delivery of smoke constituents is more consistent in each puff during smoking.

Unfortunately, a flat puff profile does not usually result when conventional cigarettes are smoked. It has been known for some time in the tobacco industry that delivery of smoke particulate phase constituents, or "Total Particulate Matter" (TPM), is not uniform during smoking. Under ISO machine smoking conditions, the "strength" per puff — measured by the amount of smoke particulate phase constituents in each puff — increases significantly from the first puff to the last. This increase in particulate matter in later puffs is caused by a number of factors, including a decrease in filtration efficiency of the tobacco rod, a decreased level of ventilation of the tobacco rod through the cigarette paper — both of which result from the length of the tobacco rod being reduced during smoking — and an increased smoke particulate phase constituent potential of the tobacco rod due to the deposition of smoke particulate phase constituents from the earlier puffs onto the rod.

The ratio of smoke constituents between the first to last puffs in a cigarette varies based on a number of product design characteristics, including the total smoke constituent yield for that product. Typically, ratios of between 2 and 4 for "full flavor" products (having more thanlO mg TPM), between 3 and 5 for "lights" (5-10mg TPM), and between 4 and 6 for "ultra lights" (less than 5mg TPM) are achieved under ISO machine smoking conditions. The higher levels of ventilation used in the "light" and "ultra light" products cause the ratio to increase even as the products' smoke constituent yields decrease. This imbalance in the yield of smoke constituents between the first and last puffs in a cigarette can lead to consumer rejection of the product due to a perception that the cigarette is too "weak" in the first few puffs or too "strong" in the final few puffs. This problem is exacerbated for the products yielding a lower level of smoke constituents due to the much larger differences between the amount of smoke constituents in the first and last puffs. Accordingly, there is a desire to provide a cigarette with a flatter puff profile that is able to deliver a similar level of smoke constituents in both the first and last puffs.

Furthermore, it is known that the increased level of smoke constituents delivered in the final few puffs represents a significant proportion of the total amount of smoke constituents generated in all cigarette products. Consequently, by reducing the delivery of smoke constituents in the final few puffs, the amount of smoke constituents delivered in total will also be reduced.

Accordingly, it is an object of the present invention to provide a smoking article filter which efficiently and effectively reduces the delivery of smoke constituents delivered to a consumer in use.

It is a further object of the present invention to provide a smoking article filter which is capable of decreasing the bandwidth of a smoking article and/or which is capable of decreasing the variance of smoke constituent delivery between puffs.

The invention comprises a filter for smoking articles having at least two different sections. A first section comprises an inner area and a surrounding area, the inner area and the surrounding area comprising a smoke flow path and an area of relatively smoke impervious material. The relatively smoke impervious material has increased flow resistance when compared to the smoke flow resistance of the smoke flow path. In one embodiment, the smoke flow path and the relatively smoke impervious material are arranged in a core and annulus configuration, with the smoke flow path forming the core. In an alternative embodiment the smoke flow path forms the annulus and the relatively smoke impervious material forms the core of the first section.

The second section comprises a smoke impaction zone in axial alignment with the smoke flow path of the first section. The second section of the filter may comprise a core comprising high pressure drop filter material and an annulus comprising a lower pressure drop material than the core or vice versa.

In one embodiment of the filter of the present invention, the first and second sections are spaced apart from one another by means of an intervening gap.

In one embodiment of the invention, the filter is designed such that the smoke flow path of the first section is axially aligned with the core of the second section. In this embodiment, the core of the second section is made of high pressure drop filter material when compared to the filter material of the annulus of the second section. In use, smoke exits the smoke flow path of the first section such that a large portion of the smoke — especially the heavier smoke constituents — impact on the high pressure drop core of the second section. Alternatively in this embodiment, a plug of relatively smoke impervious material may be located in the second section in axial alignment with the exit of the smoke flow path of the first section such that a large portion of the smoke — especially the heavier smoke constituents — impact on the plug of relatively smoke impervious material on the second section. Impaction filtration occurs when smoke particles hit a material and are retained by it, thus in the embodiments described above, smoke components impacting on the smoke impaction zone of the second section will be retained thereby.

In another embodiment, the invention further comprises ventilation holes circumscribing the second section or circumscribing the space or gap between the first and second section. When the cigarette is smoked, the smoke flow path of the first section begins to fill with particulate smoke constituents that condense and are deposited in the smoke flow path, and the smoke flow through it begins to become restricted. This restriction leads to an increase in the pressure drop in the first section. As the pressure drop increases, more air is brought into the filter through the ventilation holes, thereby, as smoking proceeds in subsequent puffs, causing a decrease in the variance in the delivery of smoke constituents in subsequent puffs that would otherwise occur as smoking proceeds due to the known phenomenon of increasing smoke constituent delivery in the later puffs of a smoking article.

Ventilation may be provided by means known to the skilled artisan, such as laser or mechanical perforation.

The filter may further comprise additional sections. The additional filter sections may comprise conventional filtration material such as, for example, cellulose acetate, polypropylene or paper. The additional filter sections may alternatively or additionally comprise carbonaceous material for example, activated charcoal, resin material for example, amberlite, duolite or the like, and/or catalytic material.

The present invention further provides a smoking article comprising a rod of smokable material, a wrapper circumscribing the rod of smokable material, and a filter according to the present invention attached to the rod of smokable material.

The first section of the filter according to the invention is preferably adjacent to the rod of smokable material of the smoking article at a first end and is spaced from the second section of the filter at an opposed end.

The filter of the present invention and the rod of smokable material may be interattached by any means known in the art such as, for example, a tipping wrapper. As is commonly known, the tipping wrapper may circumscribe the filter along its length and overlap with the rod of smokable material. The tipping wrapper may be attached to the wrapper of the rod of smokable material by conventional means, for example, by adhesive.

In the smoking article of the invention, the filter and the rod of smokable material are preferably in co-axial alignment with one another.

In one embodiment of the smoking article according to the invention, the filter may comprise one or more additional filter segments. The additional filter segment(s) may be located between the rod of smokable material and the first filter section, and/or may be located at the mouth end of the second filter section.

The aspects and advantages of the present invention will be better understood when the detailed description of the preferred embodiment is taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a perspective view of a cigarette with selected portions shown in cut-away; and Fig. 2 is a cross-section of an embodiment of the cigarette shown in Fig. 1;

Fig. 3 is a cross-section of another embodiment of the cigarette shown in Fig. 1;

Fig. 4 is a perspective view of another embodiment of the cigarette shown in Fig.l ;

Fig. 5 is a perspective view of yet another embodiment of the cigarette shown in Fig. 1;

Fig. 6 is a graphical representation of the effectiveness of several embodiments of the invention in reducing total particulate matter, and

Fig. 7 is a graphical representation of the effectiveness of one embodiment of the invention in reducing bandwidth.

While this invention is capable of embodiments in many different forms, multiple embodiments are shown in the figures and will be herein described in detail. The present disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the broad aspects of the invention to the embodiments illustrated.

Referring now to Figure 1, the invention comprises a cigarette filter 1 and a cigarette 3 designed to reduce the delivery bandwidth of a cigarette in use. The cigarette 3 comprises a tobacco section 18 and a filter 1. The filter 1 comprises a first section 2 comprising an inner area 4 and a first surrounding area 6. In one embodiment, the first section 2 is on the end of the cigarette 3 nearest to the tobacco section 18. The diameter of the inner area 4 is preferably between 0.5 and 3.0 mm and between 5 and 10 mm in length. It will be understood that the length of the smoke flow path will be determined by the length of the filter; the length of the smoke flow path of the first section, however, will be equal to the length of the first section.

For the filter to function properly, the inner area 4 and the surrounding area 6 should comprise a smoke flow path and an area that is relatively impervious to smoke. In the preferred embodiment, the inner area 4 is the smoke flow path and the surrounding area 6 is impervious to smoke. In this embodiment, the smoke travels through the smoke flow path 4 and exits the cigarette at a high velocity. In another embodiment, however, the smoke flow path can be formed by the surrounding area 6 with the inner area 4 being formed of smoke impervious material.

The smoke flow path 4 can take on a number of different embodiments. For example, the smoke flow path 4 can comprise a tube 30, as shown in Fig. 2, or a lower pressure drop material 40 — such as cellulose acetate — than that of the surrounding area 6, as shown in Fig. 3.

Referring again to Fig. 1, the filter 1 further comprises an axially aligned second section 8 comprising a core 10 circumscribed by an aπnulus 12. The inner core 10 of the second section 8 is axially aligned with the inner area 4 of the first section 2. As can be more clearly seen in Figure 2, the filter 1 further comprises a space or gap 14 situated between the first section 2 and the second section 8. The gap 14 can be in the range of 0.0001 mm to 4 mm in length, but in various embodiments of the invention may be in the range of 0.1 - 3.8 mm, or in the range of 0.5 - 3.5 mm, or in the range of 1 - 3 mm, or in the range of 1.5 - 2.5 mm, and in one particular embodiment of the invention is about 2 mm. If the gap is too wide, the heavier smoke constituents will diffuse within the gap 14 between the first and second filter sections before impacting the second section 8, which would negatively impact the performance of the filter 1. Along with the rest of the filter 1, the gap 14 is wrapped in plug wrap and attached to the rest of the cigarette with conventional tipping paper.

Either the core 10 or the annulus 12 of the second section 8 must form an impaction zone of relatively smoke impervious material. If the smoke flow path in the first section is the inner area 4, then the impaction zone of the second section 8 will be in the region of the core 10. The smoke impaction section can extend along the whole length of the second section 8, as shown in Figs. 1-3, or as shown in Figure 4, it can be a small disc 32 of smoke impervious material attached to the end of a regular filter section 34. In the embodiment shown in Figure 4, smoke would diffuse behind the smoke impervious material, but the heavier smoke constituents would first be removed by their impaction on the small disc 32.

If the smoke flow path in the first section 2 is tiie surrounding area 6, then the impaction zone of the second section 8 will be in the region of the annulus 12. As shown in Figs. 1-3, this can be an annulus 12 of relatively impervious material along the whole length of the second section 8, or it could be an annular disc 36 of the same material affixed to the end of the regular filter section 34, as shown in Fig. 5.

When the core 10 acts as the impaction zone, the diameter of the outer annulus 12 is preferably 40% of the total diameter of the filter 1, but the filter will function properly, however, as long as the core 10 is wider than the exit diameter of the smoke flow path of the first section 2. Likewise, when the annulus 12 acts as the impaction zone, its width should be bigger than that of the smoke flow path formed by the surrounding area 6.

The length of the second section 8 can be any length to make up the desired total length of the filter 1, and it is usually about 5 to 50 mm. The second section 8 is generally the mouth end of the cigarette filter.

In one embodiment, the filter 1 further comprises ventilation holes 20, which can be positioned in either the second section 8 or the gap 14.

The filter 1 reduces the delivery bandwidth in two different ways. Firstly, when the cigarette is being smoked, the smoke passes through the smoke flow path of the first section 2 and enters the gap 14 at high velocity. Due to the short distance between the filter sections 2, 8 and the high velocity at which the smoke travels, most of the smoke particles do not disperse before impacting and sticking on the high pressure drop material of the second section 8 opposite the smoke flow path of the first section 2. The heavier smoke particles disperse less than the lighter particles, which leads to less total particulate matter leaving the cigarette. The harder the puff on the cigarette, the less dispersion of the smoke occurs, and the more filtering that takes place.

The second way that bandwidth is reduced involves the use of ventilation holes. As the cigarette is smoked, the tube 4 in the first section 2 progressively fills with particulate smoke constituents, which increases the resistance to smoke flowing through the tube 4. This increases the pressure drop through the first section 2, which causes more diluting air to be pulled through the ventilation holes 20 when the smoker inhales. The diluting air enters the gap 14 or the second section 8 through ventilation holes 20 circumscribing the second section 8 or the gap 14. This further concentrates the smoke in the middle of the gap 14, thereby causing most of the smoke to impact the core 10, which in the preferred embodiment comprises the impaction area of the second section 8.

While there have been described what are believed to be the preferred embodiments of the present invention, those skilled in the art will recognize that other and further changes and modifications may be made thereto without departing from the spirit of the invention, and it is intended to claim all such changes and modifications as fall within the true scope of the invention.

EXAMPLES

Four different embodiments of the invention were tested to determine the amount of nicotine-free total particulate matter in each puff and to determine whether the delivery changed as the number of puffs increased. In Examples A and B, the first and second sections were 11 and 14 mm in length, respectively, and there was a 2 mm gap between the sections. In Examples C and D, the first section was 11 mm long and the second section was 16 mm long, and the gap between the two sections was 0.001 mm. AU of Examples A, B, C, and D had a tube in the first section with an internal diameter of 2 mm. In Examples A and C, the annulus of the second section was made of high pressure drop material, whereas in Examples

B and D, the annulus of the second section was made of lower pressure drop material.

Table 1 below and Fig. 6 demonstrate the beneficial effect that the invention has on smoothing out the puff profile when compared with a "control" cigarette: TABLE I- Puff by Puff Delivery of Nicotine-Free Wet Particulate Matter (in mg)

Furthermore, Table 2 and Fig. 7 show the reduction in bandwidth that occurs when one embodiment of the invention — Example D — is smoked under various conditions. The more extreme the conditions, the better Example D performs compared to the control cigarette. At ISO conditions (puff volume of 35 mL, puff duration of 2 seconds, puff interval of 60 seconds), the difference between the amounts of particulate matter is relatively small. But as the overall intensity of the puffs increases, the effectiveness of the filter of the invention improves, as is demonstrated by the large difference in TPM between the control and Example D. TABLE 2 -Delivery of TPM at ISO and Other Conditions

The various embodiments of the invention have a measurable beneficial effect on decreasing the bandwidth, decreasing the TPM, and smoothing out the puff profile of a cigarette as it is smoked. It is apparent that the location of the high pressure drop material and the width of the gap will modify the performance of the invention while still using concepts of the present invention. Such variations are deemed to fall within the bounds of the present application.

Claims

1. A filter for smoking articles comprising: a first section comprising smoke impervious material having a longitudinally extending smoke flow path therethrough; a second section spaced from and axially aligned with said first section, said second section comprising a core portion circumscribed by an annulus portion; wherein one of said core portion and annulus portion comprises high pressure drop filter material and the other portion comprises lower pressure drop material; wherein said smoke flow path is longitudinally aligned with said annulus or core portion that comprises high pressure drop material.

2. The filter for smoking articles of claim 1, wherein said smoke flow path is an opening centrally disposed in said first section.

3. The filter for smoking articles of claim 2, wherein said smoke flow path includes a tube therein.

4. The filter for smoking articles of claim 1, wherein said smoke flow path comprises lower pressure drop material than said smoke impervious material.

5. The filter for smoking articles of claim 4, wherein said lower pressure drop material is centrally disposed in said first section.

6. The filter for smoking articles of claim 4, wherein said lower pressure drop material circumscribes said smoke impervious material in an annulus/core relationship.

7. The filter for smoking articles of claim 2 further comprising ventilation holes.

8. The filter for smoking articles of claim 7, wherein said ventilation holes circumscribe said second section.

9. The filter for smoking articles of claim 7, wherein said ventilation holes are located between said first section and said second section.

10. The filter for smoking articles of claim 7, wherein said ventilation holes allow outside air to enter said filter.

11. The filter for smoking articles of claim 10, wherein the amount of air pulled through said ventilation holes increases as said tube fills with tar.

12. The filter for smoking articles of claim 1 , wherein said smoke flow path is between 5 and 10 mm in length.

13. The filter for smoking articles of claim 1, wherein said smoke flow path is between 0.5 and 3 mm in diameter.

14. The filter for smoking articles of claim 1 , wherein the diameter of said core of said second section is approximately 60% of the diameter of said filter.

15. The filter for smoking articles of claim 1, wherein there is less than 4 mm between said first section and said second section.

16. A smoking article comprising a rod of smokable material; a wrapper circumscribing said rod of smokable material; and a filter comprising a first section and a second section; said first section having a first end and an opposed end, said first end being attached to said rod of smokable material, said first section comprising smoke impervious material having a centrally disposed longitudinally extending opening therethrough; and said second section spaced from and axially aligned with said opposed end of said first section, said second section comprising a core portion comprising high pressure drop filter material circumscribed by an annulus portion comprising a lower pressure drop filter material than said core portion.

17. The smoking article of claim 16, wherein said opening includes a tube therein.

18. The smoking article of claim 17 further comprising ventilation holes.

19. The smoking article of claim 18, wherein said ventilation holes circumscribe said second section.

20. The smoking article of claim 18, wherein said ventilation holes are located between said first section and said second section.

21. The smoking article of claim 18, wherein said ventilation holes allow outside air to enter the filter.

22. The smoking article of claim 21, wherein the amount of air pulled through said ventilation holes increases as said tube fills with tar.

23. The smoking article of claim 16, wherein said opening is between 5 and 10 mm in length.

24. The smoking article of claim 16, wherein said opening is between 0.5 and 3 mm in diameter.

25. The smoking article of claim 16, wherein the diameter of said core of said second section is approximately 60% of the diameter of said filter.

26. The smoking article of claim 16, wherein there is less than 4 mm between said first section and said second section.

27. A filter for smoking articles comprising: a first section comprising smoke impervious material having a longitudinally extending smoke flow path therethrough; a second section spaced from and axially aligned with said first section, wherein said second section comprises a mouth end and a gap end; a smoke impervious blocking patch attached to the gap end of said second section; wherein said smoke flow path is longitudinally aligned with said blocking patch.

28. The filter for smoking articles of claim 27, wherein said smoke flow path is an opening centrally disposed in said first section.

29. The filter for smoking articles of claim 28, wherein said smoke flow path includes a tube therein.

30. The filter for smoking articles of claim 27, wherein said smoke flow path comprises lower pressure drop material than said smoke impervious material.

31. The filter for smoking articles of claim 30, wherein said lower pressure drop material is centrally disposed in said first section.

32. The filter for smoking articles of claim 30, wherein said lower pressure drop material circumscribes said smoke impervious material in an annulus/core relationship.

33. The filter for smoking articles of claim 28 further comprising ventilation holes.

34. The filter for smoking articles of claim 33, wherein said ventilation holes circumscribe said second section.

35. The filter for smoking articles of claim 33, wherein said ventilation holes are located between said first section and said second section.

36. The filter for smoking articles of claim 33, wherein said ventilation holes allow outside air to enter the filter.

37. The filter for smoking articles of claim 36, wherein the amount of air pulled through said ventilation holes increases as said tube fills with tar.

38. The filter for smoking articles of claim 27, wherein said smoke flow path is between 5 and 10 mm in length.

39. The filter for smoking articles of claim 27, wherein said smoke flow path is between 0.5 and 3 mm in diameter.

40. The filter for smoking articles of claim 27, wherein there is less than 4 mm between said first section and said second section.

41. A filter for smoking articles substantially as hereinbefore described with reference to the accompanying drawings.

42. A smoking article substantially as hereinbefore described with reference to the accompanying drawings.