SMOKING ARTICLE FILTER FOR EASY EXTINGUISHING

Abstract

There is provided a smoking article comprising a tobacco rod, a filter and tipping material attaching the tobacco rod and the filter. The filter comprises a plug of filtration material that defines a furthest downstream end of the smoking article, the plug being surrounded by one or more filter wrappers. The tipping material includes a ventilation zone. The tipping material and the filter wrapper or wrappers have a combined thickness (t) perpendicular to the longitudinal direction of the smoking article, and the smoking article, at a location about the plug of filtration material, has a diameter (D.sub.SA) perpendicular to the longitudinal direction of the smoking article. The diameter (D.sub.SA) to thickness (t) ratio is less than about 80 and the filtration material extends to the furthest downstream end of the smoking article.

Claims

1-15. (canceled)

16. A smoking article comprising: a tobacco rod; a filter comprising a plug of filtration material, the plug being surrounded by one or more filter wrappers; and tipping material attaching the tobacco rod and the filter, the tipping material including a ventilation zone; wherein the tipping material and the filter wrapper or wrappers have a combined thickness (t) perpendicular to the longitudinal direction of the smoking article; wherein the smoking article, at a location about the plug of filtration material, has a diameter (D.sub.SA) perpendicular to the longitudinal direction of the smoking article; wherein the diameter (D.sub.SA) to thickness (t) ratio is less than about 80; wherein the ventilation zone comprises perforations through the tipping material; and wherein the perforations extend through the one or more filter wrappers, and wherein the filter has a critical load from 30 Newtons to 80 Newtons.

17. A smoking article according to claim 16, wherein the ventilation zone provides between about 10% and about 80% ventilation of the mainstream smoke.

18. A smoking article according to claim 16, wherein the one or more filter wrappers have a porosity of less than about 500 Coresta units.

19. A smoking article according to claim 16, wherein the one or more filter wrappers have a basis weight between about 65 grams per square metre and about 85 grams per square metre.

20. A smoking article according to claim 16, wherein the diameter (D.sub.SA) to thickness (t) ratio is greater than about 50.

21. A smoking article according to claim 16, wherein the filter wrapper or wrappers have a thickness (t.sub.1) substantially perpendicular to the longitudinal direction of the smoking article, wherein t.sub.1/t is greater than about 0.65.

22. A smoking article according to claim 16, wherein the tipping material and the one or more filter wrappers have a combined thickness (t) of between about 100 μm and about 160 μm.

23. A smoking article according to claim 16, wherein the one or more filter wrappers have a combined thickness (t.sub.1) of between about 90 μm and about 120 μm.

24. A smoking article according to claim 16, wherein the thickness of the tipping material is between about 30 microns and about 70 microns.

25. A filter for a smoking article, the filter comprising: a plug of filtration material; one or more filter wrappers surrounding the plug of filtration material; wherein the one or more filter wrappers have a combined wrapper thickness (t.sub.1) perpendicular to the longitudinal direction of the filter; wherein the filter has a diameter (D.sub.F) perpendicular to the longitudinal direction of the filter; wherein the filter diameter (D.sub.F) to wrapper thickness (t.sub.1) ratio is less than about 135; wherein the filter comprises perforations extending through the one or more filter wrappers, and wherein the filter has a critical load from 30 Newtons to 80 Newtons

26. A filter according to claim 25, wherein the one or more filter wrappers have a porosity of less than about 1000 Coresta units.

27. A filter according to claim 25, wherein the one or more filter wrappers have a porosity of less than about 500 Coresta units.

28. A filter according to claim 25, wherein the one or more filter wrappers have a basis weight between about 65 grams per square metre and about 85 grams per square metre.

29. A filter according to claim 25, wherein the filter diameter (D.sub.F) to wrapper thickness (t.sub.1) ratio is greater than about 70.

30. A filter according to claim 25, wherein the combined thickness of the one or more filter wrappers is between 90 microns and 120 microns.

31. A method of reducing buckling during extinguishing of the smoking article, the method comprising providing a plug of filtration material, the plug being surrounded by one or more filter wrappers; and tipping material attaching the tobacco rod and the filter, the tipping material including a ventilation zone; wherein the tipping material and the filter wrapper or wrappers have a combined thickness (t) perpendicular to the longitudinal direction of the smoking article; wherein the smoking article, at a location about the plug of filtration material, has a diameter (DSA) perpendicular to the longitudinal direction of the smoking article; wherein the diameter (DSA) to thickness (t) ratio is less than 80; wherein the ventilation zone comprises perforations through the tipping material; wherein the perforations extend through the one or more filter wrappers; and wherein the filter has a critical load from 30 Newtons to 80 Newtons.

Description

[0070] The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

[0071] FIG. 1 illustrates a graph of compression force (N) against compression distance (mm) for five samples of four types of smoking article.

[0072] The inventors of the present invention have noted that, without ventilation, smoking article filters may not buckle. The filters may simply reduce in size steadily with increasing compression force. However, when ventilation is provided, the structure of the filter may be weakened. Unfortunately, this weakened filter structure may buckle during extinguishing. This may mean that the consumer's fingers come into contact with, or close to, the lit end of the cigarette or old ash remaining in the ashtray.

[0073] However, as discussed previously, the inventors of the present invention have observed that, for a given filter height, the buckling strength or critical load of the smoking article filter may be considerably increased by decreasing the ratio of D.sub.SA:t relative to standard filter cigarettes. This allows the smoking article to be extinguished by a consumer while considerably reducing the chance of the filter buckling under the compressive load.

[0074] The relationship between D.sub.SA:t and critical load was tested using a force gauge obtained from Alluris GmbH & Co KG, Freiburg, Germany. Unsmoked filters were tested by first removing the tobacco rod and upstream portion of the tipping paper surrounding the tobacco rod, and then applying the required force in Newtons (N) to compress the filter by a preselected distance in millimetres (mm) at a particular compression speed (mm min.sup.−1). Smoked filters were tested by first removing any unburnt tobacco and tipping paper upstream of the filter, and then applying the required force in Newtons (N) to compress the filter by a preselected distance in millimetres (mm) at a particular compression speed (mm min.sup.−1). The values of compression force and compression distance were recorded (in this case for a compression speed of 100 mm min.sup.−1).

[0075] FIG. 1 is a graph of compression force (N) against compression distance (mm) for five samples of four types of smoking article. The four types of (unsmoked) smoking article filters tested (using the above described apparatus) were: [0076] Filter Type A: Cigarette filters having a diameter (D.sub.SA) to thickness (t) ratio of about 98 (D.sub.SA=7.84 mm, t=80 μm (t.sub.1=40 μm, t.sub.2=40 μm)). The filter height (H) is 27 mm and the basis weight of the filter wrapper is about 26 gm.sup.−2. Data for these filters are shown in dotted lines. [0077] Filter Type B: Filters according to the invention, having a diameter (D.sub.SA) to thickness (t) ratio of about 56 (D.sub.SA=7.84 mm, t=140 μm (t.sub.1=100 μm, t.sub.2=40 μm)) and 80% ventilation. The filter height (H) is 27 mm and the basis weight of the filter wrapper is about 78 gm.sup.−2. Data for these filters are shown in thick solid lines. [0078] Filter Type C: Filters according to the invention, having a diameter (D.sub.SA) to thickness (t) ratio of about 56 (D.sub.SA=7.84 mm, t=140 μm (t.sub.1=100 μm, t.sub.2=40 μm)) and 10% ventilation. The filter height (H) is 27 mm and the basis weight of the filter wrapper is about 78 gm.sup.−2. Data for these filters are shown in thin solid lines. [0079] Filter Type D: Cigarette filters having a diameter (D.sub.SA) to thickness (t) ratio of about 44 (D.sub.SA=7.84 mm, t=180 μm (t.sub.1=140 μm, t.sub.2=40 μm)). The filter height (H) is 27 mm and the basis weight of the filter wrapper is about 110 gm.sup.−2. Data for these filters are shown in dashed lines.

[0080] As can be seen most clearly from the dashed lines for Filter Type D, as the compression distance increases, at a particular point, the required compression force drops suddenly. This is the moment of buckling. So, the maximum compression force reached at the point of buckling corresponds to the critical load.

[0081] For the five samples of Filter Type A (dotted lines), the mean critical load was found to be 22.46 N. For the five samples of the filters according to the invention, with 80% ventilation, (Filter Type B, thick solid lines), the mean critical load was found to be 45.94 N. For the five samples of the filters according to the invention, with 10% ventilation, (Filter Type C thin solid lines), the mean critical load was found to be 52.92 N. For the five samples of Filter Type D (dashed lines), the mean critical load was found to be 85.22 N. Thus, FIG. 1 shows that, as the D.sub.SA/t ratio decreases (from 98 to 56 to 44), the critical load of the filter increases. This in turn reduces the chances of buckling. The filters according to the invention represent a balance between a sufficiently high critical load, while still using filter wrappers which are relatively easy to handle.

[0082] Interestingly, it has also been noted by the inventors that the approximate value of the critical load for Filter Type C (a filter according to the invention, having a diameter (D.sub.SA) to thickness (t) ratio of about 56, with 10% ventilation) after smoking is of the order of 20 N or slightly greater. To simulate the smoking of a smoking article, the smoking article is subjected to a standard smoking test under ISO conditions (35 ml puffs lasting 2 seconds each, with puffs occurring once every 60 seconds) as set out in ISO 4387:2000. In the ISO test method, the smoking article is smoked with the ventilation zone fully uncovered. Such a value of critical load may be advantageous, since the force exerted by a consumer during the extinguishing process may be up to about this value. Thus, this may represent a particularly advantageous balance between a sufficiently high critical load, while still using filter wrappers which are relatively easy to handle.

[0083] FIG. 1 also shows that there is a difference in critical load depending on the level of ventilation. Two types of filter according to the invention were tested (using the above mentioned apparatus): one with 10% ventilation and the other with 80% ventilation. As already mentioned, for the filter according to the invention having 10% ventilation, the mean critical load was found to be 52.92 N. For the filter according to the invention having 80% ventilation, the mean critical load was found to be 45.94 N. Thus, the critical load decreases with increased levels of ventilation.

[0084] Thus, the smoking articles and filters according to the invention provide for: reduced chances of buckling during extinguishing; a filter plug wrap which has sufficiently high critical load but is also thin enough to be relatively easy to handle, and critical loads during extinguishing which may correspond to an upper limit of forces typically exerted by consumer during extinguishing.