RADIALLY FIRM SMOKING ARTICLE FILTER

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 downstream end segment of the smoking article, the plug being surrounded by one or more filter wrappers. The hardness of the smoking article at the downstream end segment is at least about 90%, and the filtration material extends to the furthest downstream end of the filter.

Claims

1. 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; wherein the hardness of the smoking article at the filter is at least about 90%; wherein the one or more filter wrappers have a basis weight between about 50 grams per square meter and about 100 grams per square meter; and wherein the ovality of a furthest downstream end of the smoking article, after a 50% deformation of the furthest downstream end of the smoking article, is less than about 25%.

2. The smoking article according to claim 1, wherein the hardness of the smoking article at the filter is at least about 92%.

3. The smoking article according to claim 1, wherein the hardness of the smoking article at the filter is no more than about 94%.

4. The smoking article according to claim 1, wherein the ovality of the furthest downstream end of the smoking article, after a 50% deformation of the furthest downstream end of the smoking article, performed after the smoking article has been subjected to a smoking test, is less than about 25%.

5. The smoking article according to claim 1, 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.

6. The smoking article according to claim 1, wherein the one or more filter wrappers have a bending stiffness of at least about 0.08 N in a machine direction of the filter wrapper.

7. The smoking article according to claim 1, wherein the one or more filter wrappers have a bending stiffness of at least about 0.04 N in the cross direction of the filter wrapper.

8. The smoking article according to claim 1, wherein the filtration material comprises cellulose acetate.

9. The smoking article according to claim 1, wherein the filtration material has a denier per filament of between about 5.0 dpf and about 12.0 dpf.

10. The smoking article according to claim 1, wherein the filter provides a resistance to draw of between about 130 mm H.sub.2O and about 210 mm H.sub.2O.

11. The smoking article according to claim 1, wherein the filter includes an adhesive or plasticizer.

12. The smoking article according to claim 1, wherein the tipping material includes a ventilation zone at a location about the filter.

13. The smoking article according to claim 1, wherein the tipping material has a thickness between about 30 m and about 70 m.

14. The smoking article according to claim 1, wherein the filtration material extends to the furthest downstream end of the filter.

15. The smoking article according to claim 2, wherein the hardness of the smoking article at the filter is no more than about 94%.

16. The smoking article according to claim 6, wherein the one or more filter wrappers have a bending stiffness of at least about 0.04 N in the cross direction of the filter wrapper.

17. The smoking article according to claim 14, wherein the ovality of the furthest downstream end of the smoking article, after a 50% deformation of the furthest downstream end of the smoking article, performed after the smoking article has been subjected to a smoking test, is less than about 25%.

Description

[0072] The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

[0073] FIG. 1 illustrates the definition of hardness;

[0074] FIG. 2 illustrates the definition of ovality, using a perfect circle;

[0075] FIG. 3 illustrates the definition of ovality, using an oval;

[0076] FIG. 4 illustrates a perspective view of an apparatus for determining the hardness of a filter or a smoking article, in a first configuration;

[0077] FIG. 5 illustrates a side view of the apparatus of FIG. 4, in a first configuration;

[0078] FIG. 6 illustrates a side view of the apparatus of FIG. 4, in a second configuration;

[0079] FIG. 7 is a graph showing hardness (%) for six types of filter (within a smoking article), both smoked and unsmoked;

[0080] FIG. 8 is a graph showing hardness (%) for six types of filter (not within a smoking article),

[0081] FIG. 9 is a graph showing ovality (%) for three types of unsmoked filters; and

[0082] FIG. 10 is a graph showing ovality (%) for three types of smoked filters.

[0083] As discussed previously, the inventors of the present invention have noted that, in order for a consumer to be able to enjoy chewing the mouth end of the smoking article filter during the smoking experience, the mouth end must have a hardness of at least about 90%.

[0084] The hardness of various types of smoking article was tested using a known DD60A Densimeter (manufactured and made commercially available by Heinr. Borgwaldt GmbH, Germany) device, which was fitted with a measuring head for cigarettes and with a cigarette receptacle, as described above. The samples were tested by following the method which is recommended for the known DD60A Densimeter device (manufactured and made commercially available by Heinr. Borgwaldt GmbH, Germany). That is, a sample of smoking articles were held in parallel alignment, and subjected to an overall load of 2 kg, for a period of 20 seconds, and the diameters of the smoking articles before and after compression were recorded. The depression was used to determine the hardness (%) of each smoking article.

[0085] The apparatus for testing the hardness of the smoking articles filters is shown in FIGS. 4, 5 and 6, and the measured hardness values are shown in FIGS. 7 and 8.

[0086] FIG. 4 is a perspective view of an apparatus 4, such as a DD60A Densimeter device, for determining the hardness of a filter of a smoking article. The apparatus includes two parallel load applying rods 24 positioned over a support plate 30. The support plate 30 includes two parallel, spaced apart walls 12, with each wall 12 having ten equally spaced recesses. The recesses are arranged to prevent the smoking articles 10 from contacting one another during testing.

[0087] As can be seen in FIG. 4, ten identically designed smoking articles 10 are aligned parallel in a plane, and placed on underlying cylindrical rods 14. The smoking articles 10 extend between corresponding recesses in the walls 12 to hold the smoking articles in place. The underlying cylindrical rods 14 extend parallel to the walls 12. Each smoking article 10 contacts the underlying rods 14 at two points, making for twenty total points of contact between the smoking articles to be tested and the underlying rods 14.

[0088] To test the hardness of a smoking article's filter, the smoking articles should be positioned such that the portion of the filter to be tested is in contact with the underlying rods 14. If filter is too short and the portion of the filter to be tested either does not contact both rods or contacts the rods very close to the ends of the portion of the filter to be tested, then it would appreciated that this could be achieved by using twenty cigarettes in a back-to-back configuration, such as that shown in FIG. 5.

[0089] As shown, the concept of the DD60A Test is that the underlying cylindrical rods contact the sample material to be tested at twenty contact points. If the filter is sufficiently long to extend across the underlying rods, then the twenty contact points can be provided with ten samples (as shown in FIG. 4). If the filter is not sufficiently long, then the twenty contact points can be provided with twenty samples, as shown in FIG. 5.

[0090] As can be seen in FIG. 5, portions of the tobacco rods have been removed from each smoking article 10, and the filter portion of each smoking article 10 rests on a respective cylindrical rod 14. In the present case, the hardness of the mouth end segment is being tested, and therefore it is this portion of the filter which rests on the rod 14, and the mouth end segment is approximately centered on the rods 14. If necessary, the tips of the smoking articles extending away from the cylindrical rods 14 may be supported by an underlying supporting means to prevent pivoting of the smoking articles.

[0091] The apparatus is shown in FIG. 5 in a first configuration, in which the two load applying cylindrical rods 24 are raised above and out of contact from the smoking articles 10. To test the hardness of the smoking articles, the load applying cylindrical rods 24 are lowered to a second configuration, to come into contact with the smoking articles 10, as shown in FIG. 6. When in contact with the smoking articles 10, the load applying rods 24 impart an overall load of 2 kg across the twenty contact points of the smoking articles 10 for a duration of 20 seconds. After 20 seconds have elapsed (and with the load still being applied to the smoking articles), the depression in the load applying cylindrical rods 24 across the smoking articles is determined, and then used to calculate the hardness.

[0092] FIG. 7 is a graph showing hardness (%) for six types of smoking article filter, both smoked and unsmoked. In FIG. 7, each filter was incorporated into a smoking article and subjected to the DD60A Test described above, and illustrated by FIGS. 4 to 6.

[0093] The six types of smoking article filters tested (using the above described method and apparatus) were: [0094] Filter Type A: Cigarette filters having a basis weight of the filter wrapper of about 26 gm.sup.2 and a filter length of 21 mm, and cigarette filters having a basis weight of the filter wrapper of about 26 gm.sup.2 and a filter length of 27 mm. In both cases, the smoking article diameter is 7.84 mm, the filter wrapper thickness is 40 m and the tipping material thickness is 40 m. Both these sets of data are shown with white bars in FIG. 7, 21 mm filters on the left hand side of FIG. 7, 27 mm filters on the right hand side of FIG. 7. [0095] Filter Type B: Filters according to the invention, having a basis weight of the filter wrapper of about 78 gm.sup.2 and a filter length of 21 mm, and filters according to the invention, having a basis weight of the filter wrapper of about 78 gm.sup.2 and a filter length of 27 mm. In both cases, the smoking article diameter is 7.84 mm, the filter wrapper thickness is 100 m and the tipping material thickness is 40 m. Both these sets of data are shown with light grey bars in FIG. 7, 21 mm filters on the left hand side of FIG. 7, 27 mm filters on the right hand side of FIG. 7. [0096] Filter Type C: Cigarette filters having a basis weight of the filter wrapper of about 110 gm.sup.2 and a filter length of 21 mm, and cigarette filters having a basis weight of the filter wrapper of about 110 gm.sup.2 and a filter length of 27 mm. In both cases, the smoking article diameter is 7.84 mm, the filter wrapper thickness is 140 m and the tipping material thickness is 40 m. Both these sets of data are shown with dark grey bars in FIG. 7, 21 mm filters on the left hand side of FIG. 7, 27 mm filters on the right hand side of FIG. 7.

[0097] As can be seen from FIG. 7, there is little difference in hardness between the 21 mm filters and the 27 mm filters. In addition, as can be seen from FIG. 7, there is little difference in hardness between the smoked and unsmoked filters.

[0098] However, as can be seen from FIG. 7, the hardness of the smoking article filters tends to increase as the basis weight of the filter wrapper increases. The mean increase in hardness between the 26 gm.sup.2 basis weight filters and the 78 gm.sup.2 basis weight filters was found to be 6.50%, which represents an increase of 0.125% per gm.sup.2 increase in basis weight. However, the mean increase in hardness between the 78 gm.sup.2 basis weight filters and the 110 gm.sup.2 basis weight filters was found to be 1.91%, which represents an increase of only 0.060% per gm.sup.2 increase in basis weight.

[0099] Thus, the relationship between basis weight and hardness is not linear, and hardness tends to increase relatively more at lower basis weight levels. Thus, the inventors have appreciated that the use of a filter wrapper having a basis weight of about 78 gm.sup.2 sufficiently increases the hardness, while avoiding the need for a very stiff filter wrapper, which may make manufacture more difficult.

[0100] The hardness of various types of filter rods (when not incorporated into a smoking article) was also tested using a DD60A Densimeter (manufactured and made commercially available by Heinr. Borgwaldt GmbH, Germany) fitted with a measuring head for cigarettes and with a cigarette receptacle, as described above, and following the DD60A Test method described above.

[0101] FIG. 8 is a graph showing hardness (%) for six types of smoking article filter. In FIG. 8, each filter was not incorporated into a smoking article. The six types of smoking article filters tested (using the above described apparatus and methodology) were the same as in FIG. 7, that is: [0102] Filter Type A: Filters having a basis weight of the filter wrapper of about 26 gm.sup.2 and a filter length of 21 mm/27 mm. In both cases, the filter wrapper thickness is 40 m. Both these sets of data are shown with white bars in FIG. 8, 21 mm filters on the left hand side, 27 mm filters on the right hand side. [0103] Filter Type B: Filters according to the invention, having a basis weight of the filter wrapper of about 78 gm.sup.2 and a filter length of 21 mm/27 mm. In both cases, the filter wrapper thickness is 100 m. Both these sets of data are shown with light grey bars in FIG. 8, 21 mm filters on the left hand side, 27 mm filters on the right hand side. [0104] Filter Type C: Filters having a basis weight of the filter wrapper of about 110 gm.sup.2 and a filter length of 21 mm/27 mm. In both cases, the filter wrapper thickness is 140 m. Both these sets of data are shown with dark grey bars in FIG. 8, 21 mm filters on the left hand side, 27 mm filters on the right hand side.

[0105] Just as in FIG. 7, in FIG. 8, the hardness of the smoking article filters tends to increase as the basis weight of the filter wrapper increases, but the relationship between basis weight and hardness is not linear. Thus, the inventors have appreciated that the use of a filter wrapper having a basis weight of about 78 gm.sup.2 sufficiently increases the hardness, while avoiding the need for a very stiff filter wrapper, which may make manufacture more difficult.

[0106] As discussed previously, the inventors of the present invention have noted that, in order for a consumer to be able to enjoy the smoking experience after chewing the mouth end of the smoking article filter, it is preferable for the mouth end to have an ovality, after a 50% deformation of less than about 25%, both before and after smoking.

[0107] The ovality of various types of smoking article was tested using the method described above. That is, the smoking articles were subject to deformation and then the mouth ends of the smoking articles were recorded using a transparent stage. The process was repeated and averaged over ten smoking articles.

[0108] FIGS. 9 and 10 are graphs showing ovality (%) for three types of smoking article filter, both smoked and unsmoked.

[0109] Referring to FIGS. 9 and 10, compression denotes that the smoking article mouth end was deformed to 66.67% of its original diameter (i.e. compressed by one third) and then released, compression denotes that the smoking article mouth end was deformed to 50% of its original diameter (i.e. compressed by one half) and then released, and compression denotes that the smoking article mouth end was deformed to 33.33% of its original diameter (i.e. compressed by two thirds) and then released.

[0110] The three types of smoking article filters tested (using the above described apparatus) were: [0111] Filter Type A: Cigarette filters having a basis weight of the filter wrapper of about 26 gm.sup.2, a filter length of 27 mm, a smoking article diameter of 7.84 mm, a filter wrapper thickness of 40 m and a tipping material thickness of 40 m. Both these sets of data are shown with a black line, unsmoked filters in FIG. 9, smoked filters in FIG. 10. [0112] Filter Type B: Filters according to the invention, having a basis weight of the filter wrapper of about 78 gm.sup.2, a filter length of 27 mm, a smoking article diameter of 7.84 mm, a filter wrapper thickness of 100 m and a tipping material thickness of 40 m. Both these sets of data are shown with a dark grey line, unsmoked filters in FIG. 9, smoked filters in FIG. 10. [0113] Filter Type C: Cigarette filters having a basis weight of the filter wrapper of about 110 gm.sup.2, a filter length of 27 mm, a smoking article diameter of 7.84 mm, a filter wrapper thickness of 140 m and a tipping material thickness of 40 m. Both these sets of data are shown with a light grey line, unsmoked filters in FIG. 9, smoked filters in FIG. 10.

[0114] As can be seen from FIGS. 9 and 10, the ovality of the smoking article filters after compression tends to increase as the basis weight of the filter wrapper increases. Just as with the hardness, however, the relationship does not appear to be linear.

[0115] It would be preferable for the mouth end to return to a perfect circle (0% ovality) after deformation. The closest to this is Filter Type A cigarette filters (where the basis weight of the filter wrapper is about 26 gm.sup.2), which have the lowest ovality values overall in FIGS. 9 and 10. However, it can be seen from FIGS. 7 and 8 that such a filter wrapper does not have a high hardness value, and therefore does not provide enough resistance to deformation for the chewing experience to be enjoyable for a consumer. The inventors have appreciated that use of a filter wrapper having a basis weight of about 78 gm.sup.2 sufficiently increases the hardness, while limiting the increase in ovality after chewing.

[0116] Thus, the smoking articles and filters according to this embodiment of the invention provide for increased hardness in order for the chewing experience to be enjoyable, but decreased ovality after chewing in order for the smoking experience to be enjoyable, even after chewing. This provides an excellent balance between enjoyable chewing and smoking experiences.