AEROSOL-GENERATING ARTICLE FILTER HAVING NOVEL FILTRATION MATERIAL

Abstract

An aerosol-generating article is provided, including: an aerosol-generating substrate; and a filter in axial alignment with the aerosol-generating substrate, the filter including at least one filter segment of filtration material formed of a plurality of fibres including a polyhydroxyalkanoate compound, in which the fibres have a denier per filament (dpf) of between 1.5 dpf and 2.7 dpf, in which a total denier of the fibres is between 25,000 and 40,000, and in which the at least one filter segment includes at least 20 percent by weight of the polyhydroxyalkanoate compound. A filter for an aerosol-generating article is also provided.

Claims

1.-13. (canceled)

14. An aerosol-generating article, comprising: an aerosol-generating substrate; and a filter in axial alignment with the aerosol-generating substrate, the filter comprising at least one filter segment of filtration material formed of a plurality of fibres comprising a polyhydroxyalkanoate compound, wherein the fibres have a denier per filament (dpf) of between 1.5 dpf and 2.7 dpf, wherein a total denier of the fibres is between 25,000 and 40,000, and wherein the at least one filter segment comprises at least 20 percent by weight of the polyhydroxyalkanoate compound.

15. The aerosol-generating article according to claim 14, wherein the plurality of fibres have a round cross-sectional shape and provide a total external surface area within the at least one filter segment of between 0.15 square meters per gram and 0.3 square meters per gram.

16. The aerosol-generating article according to claim 14, wherein the plurality of fibres have a Y-shaped cross-sectional shape and provide a total external surface area within the at least one filter segment of between 0.3 square meters per gram and 0.55 square meters per gram.

17. The aerosol-generating article according to claim 14, wherein the filtration material further comprises a plurality of fibres of at least one additional, biodegradable polymer.

18. The aerosol-generating article according to claim 14, wherein a resistance to draw (RTD) of the at least one filter segment is between 150 millimetres H.sub.2O and about 250 millimetres H.sub.2O.

19. The aerosol-generating article according to claim 14, wherein the at least one filter segment has a biodegradability in an aqueous medium of at least 50 percent when tested according to ISO 14851.

20. The aerosol-generating article according to claim 14, wherein the at least one filter segment further comprises at least 5 percent by weight of polyethylene glycol.

21. The aerosol-generating article according to claim 14, wherein the at least one filter segment has an average radial hardness of at least 80 percent.

22. The aerosol-generating article according to claim 14, wherein the at least one filter segment is circumscribed by a wrapper having a basis weight of at least 100 grams per square metre (gsm).

23. The aerosol-generating article according to claim 14, wherein the at least one filter segment is in the form of a hollow tubular element.

24. The aerosol-generating article according to claim 14, wherein the aerosol-generating substrate is a rod of tobacco having a length of at least 30 millimetres.

25. A filter for an aerosol-generating article, the filter comprising: at least one filter segment of filtration material formed of a plurality of fibres comprising a polyhydroxyalkanoate compound, wherein the fibres have a denier per filament (dpf) of between 1.5 dpf and 2.7 dpf, wherein a total denier of the fibres is between 25,000 and 40,000, and wherein the at least one filter segment comprises at least 20 percent by weight of the polyhydroxyalkanoate compound.

Description

[0106] The invention will now be further described with reference to the figures in which:

[0107] FIG. 1 shows a schematic longitudinal cross-sectional view of an aerosol-generating article according to a first embodiment of the invention, for use with an aerosol-generating device comprising a heater element;

[0108] FIG. 2 shows a schematic longitudinal cross-sectional view of an aerosol-generating article according to a second embodiment of the invention, comprising an integral heat source; and

[0109] FIG. 3 shows a schematic longitudinal cross-sectional view of an aerosol-generating article according to a third embodiment of the invention; and

[0110] FIG. 4 shows a schematic longitudinal cross-sectional view of an aerosol-generating system comprising an electrically operated aerosol-generating device and the aerosol-generating article shown in FIG. 1.

[0111] The aerosol-generating article 10 shown in FIG. 1 comprises a rod of aerosol-generating substrate 12, a support element provided as a hollow tubular element 14, a cooling element 16, and a mouth end filter segment 18. These four elements are arranged sequentially and in coaxial alignment and are circumscribed by a substrate wrapper 20 to form the aerosol-generating article 10. The aerosol-generating article 10 has a mouth end 22 and a distal end 24 located at the opposite end of the article to the mouth end 22. The aerosol-generating article 10 shown in FIG. 1 is particularly suitable for use with an electrically operated aerosol-generating device comprising a heater for heating the rod of aerosol-generating substrate.

[0112] In use air is drawn through the aerosol-generating article by a user from the distal end 24 to the mouth end 22. The distal end 24 of the aerosol-generating article may also be described as the upstream end of the aerosol-generating article 10 and the mouth end 22 of the aerosol-generating article 10 may also be described as the downstream end of the aerosol-generating article 10. Elements of the aerosol-generating article 10 located between the mouth end 22 and the distal end 24 can be described as being upstream of the mouth end 22 or, alternatively, downstream of the distal end 24.

[0113] The aerosol-generating substrate 12 is located at the extreme distal or upstream end of the aerosol-generating article 10. In the embodiment illustrated in FIG. 1, the aerosol-generating substrate 12 comprises a gathered sheet of crimped homogenised tobacco material circumscribed by a wrapper. The crimped sheet of homogenised tobacco material comprises glycerin as an aerosol former.

[0114] The support element 14 is located immediately downstream of the aerosol-generating substrate 12 and abuts the aerosol-generating substrate 12. In the embodiment shown in FIG. 1, the support element is a hollow tube formed of a fibrous filtration material. The support element 14 locates the aerosol-generating substrate 12 at the extreme distal end 24 of the aerosol-generating article 10 so that it can be penetrated by a heating element of an aerosol-generating device. In effect, the support element 14 acts to prevent the aerosol-generating substrate 16 from being forced downstream within the aerosol-generating article 10 towards the aerosol-cooling element 16 when a heating element of an aerosol-generating device is inserted into the aerosol-generating substrate 12. The support element 14 also acts as a spacer to space the aerosol-cooling element 16 of the aerosol-generating article 10 from the aerosol-generating substrate 12.

[0115] The aerosol-cooling element 16 is located immediately downstream of the support element 14 and abuts the support element 16. In use, volatile substances released from the aerosol-generating substrate 12 pass along the aerosol-cooling element 16 towards the mouth end 22 of the aerosol-generating article 10. The volatile substances may cool within the aerosol-cooling element 16 to form an aerosol that is inhaled by the user. In the embodiment illustrated in FIG. 1, the aerosol-cooling element comprises a tubular element 20. The crimped and gathered sheet of polylactic acid defines a plurality of longitudinal channels that extend along the length of the aerosol-cooling element 40.

[0116] The filter segment 18 is located immediately downstream of the aerosol-cooling element 16 and abuts the aerosol-cooling element 16. In the embodiment illustrated in FIG. 1, the filter segment 18 comprises a single cylindrical plug of a fibrous filtration material formed of a plurality of PHA fibres having a denier per filament of approximately 3 and a total denier of approximately 27,000. The PHA fibres have a round cross-sectional shape and are substantially longitudinally aligned with each other along the length of the filter segment. The total external surface area of the PHA fibres corresponds to about 0.16 square metres per gram. The PHA fibres have been formed by a melt spinning process and are crimped. The plug of fibrous filtration material is circumscribed by a plug wrap (not shown).

[0117] The aerosol-generating article 100 shown in FIG. 2 comprises a combustible heat source 112, a rod of aerosol-generating substrate 114, a transfer element 116, an aerosol-cooling element, 118, a spacer element 120 and a mouthpiece filter segment 122. These elements are arranged sequentially and in coaxial alignment and are circumscribed by a substrate wrapper to form the aerosol-generating article 100.

[0118] The combustible heat source 112 comprises a substantially circularly cylindrical body of carbonaceous material, having a length of about 10 millimetres. The combustible heat source 112 is a blind heat source. In other words, the combustible heat source 112 does not comprise any air channels extending therethrough.

[0119] The rod of aerosol-generating substrate 114 is arranged at a proximal end of the combustible heat source 112. The aerosol-generating substrate 114 comprises a substantially circularly cylindrical plug of tobacco material 124 circumscribed by filter plug wrap 126.

[0120] A non-combustible, substantially air impermeable first barrier 128 is arranged between the proximal end of the combustible heat source 112 and a distal end of the aerosol-generating substrate 114. The first barrier 128 comprises a disc of aluminium foil. The first barrier 128 also forms a heat-conducting member between the combustible heat source 112 and the aerosol-generating substrate 114, for conducting heat from the proximal face of the combustible heat source 112 to the distal face of the aerosol-generating substrate 114.

[0121] A heat-conducting element 130 circumscribes a proximal portion of the combustible heat source 112 and a distal portion of the aerosol-forming substrate 114. The heat-conducting element 130 comprises a tube of aluminium foil. The heat-conducting element 130 is in direct contact with the proximal portion of the combustible heat source 112 and the filter plug wrap 126 of the aerosol-generating substrate 114.

[0122] The mouthpiece filter 122 comprises a single cylindrical plug 126 of a fibrous filtration material formed of a plurality of PHA fibres having a denier per filament of approximately 3 and a total denier of approximately 27,000. The PHA fibres have a round cross-sectional shape and are substantially longitudinally aligned with each other along the length of the filter segment. The total external surface area of the PHA fibres corresponds to about 0.16 square metres per gram. The PHA fibres have been formed by a melt spinning process and are crimped. The plug of fibrous filtration material is circumscribed by a plug wrap (not shown).

[0123] The aerosol-generating article 310 shown in FIG. 3 is a combustible smoking article comprising an aerosol-generating substrate 312 and a filter 314 arranged in coaxial alignment with each other. The aerosol-generating substrate 312 comprises a tobacco rod circumscribed by an outer wrapper (not shown). A tipping wrapper 316 circumscribes both the filter 314 and an end portion of the aerosol-generating substrate 312 and attaches the filter 314 to the aerosol-generating substrate 312.

[0124] The filter 314 comprises a single cylindrical plug 318 of a fibrous filtration material formed of PHA fibres having a denier per filament of approximately 3 and a total denier of approximately 27,000. The PHA fibres have a round cross-sectional shape and are substantially longitudinally aligned with each other along the length of the filter segment. The total exposed surface area of the PHA fibres corresponds to about 0.16 square metres per gram. The PHA fibres have been formed by a melt spinning process and are crimped. The plug of fibrous filtration material is circumscribed by a plug wrap (not shown).

[0125] FIG. 4 shows a portion of an electrically operated aerosol-generating system 200 that utilises a heater blade 210 to heat the rod of aerosol-generating substrate 12 of the aerosol-generating article 10 shown in FIG. 1. The heater blade 210 is mounted within an aerosol-generating article chamber within a housing of an electrically operated aerosol-generating device 212. The aerosol-generating device 212 defines a plurality of air holes 214 for allowing air to flow to the aerosol-generating article 10, as illustrated by the arrows in FIG. 4. The aerosol-generating device 212 comprises a power supply and electronics, which are not shown in FIG. 4.

COMPARATIVE EXAMPLE

[0126] A PHA filter segment according to the invention is prepared from PHA fibres, with the parameters shown in Table 1 below. The PHA fibres are formed using a melt spinning process, the fibres are then crimped and formed into a filter segment using standard filter making apparatus. For the purposes of comparison, a conventional cellulose acetate (CA) tow filter segment is prepared, with similar values of denier per filament (dpf) and total denier.

TABLE-US-00001 TABLE 1 parameters of PHA filter segment and cellulose acetate filter segment Parameter PHA filter segment CA filter segment Denier per filament 3.2 3 Total denier 27000 27000 Weight in filter segment (mg) 406.76 409.76 External surface area (m.sup.2/g) 0.161 0.329

[0127] In a first test, the water absorption by exposure to water of the PHA filter segment according to the invention and the CA filter segment are compared. For each filter segment, the plug wrap is removed and the filter segment is attached to the probe of a force tensiometer (KRUSS force tensiometer, Model K100). The filter segment is moved down by the probe towards a container of water and automatically stopped when the filter segment makes contact with the water. The filter segment is retained in contact with the water for 300 seconds so that the filter material can absorb water and then the filter segment is weighed in order to determine the amount of water absorbed during the test period. For each of the PHA filter segment and the CA filter segment, this test is repeated three times and an average value of water absorption was calculated, as shown below in Table 2:

TABLE-US-00002 TABLE 2 Water absorption of the PHA and CA filter segments after exposure to water PHA filter segment CA filter segment Water absorption in 300 0.51 1.37 sec (g)

[0128] The amount of water absorbed by the PHA filter segment according to the invention during the test was therefore less than 40 percent of the amount of water absorbed by the CA filter segment. This test therefore demonstrates the significantly reduced affinity of water of the PHA filter segment according to the invention compared to the conventional CA filter segment.

[0129] In a second test, the water absorption by exposure to moisture of the PHA filter segment according to the invention and the CA filter segment are compared. For each filter segment, the plug wrap is removed and the fibres forming the filter segment are placed in a petri dish and exposed to air at 22 degrees Celsius and 50 percent relative humidity for 70 hours. This is conducted in a vapour sorption analyser (ProUmid SPSx-1μ). For each filter segment, the weight of the fibres is measured at the start of the test and the change in weight over time due to the absorption of water vapour by the fibres is measured. For each of the PHA filter segment and the CA filter segment, a value of the percentage difference in mass of the sample (% dm) is calculated, which expresses the increase in the weight of the sample as a percentage of the original weight. The values of % dm for each of the samples at the end of the 70 hour test are shown below in Table 3:

TABLE-US-00003 TABLE 3 Water absorption of the PHA and CA filter segments after exposure to moisture PHA filter segment CA filter segment % Difference in mass after 0.0133 0.6784 70 hours (% dm)

[0130] The results demonstrate that the amount of water vapour absorbed by the cellulose acetate fibres during the 70 hour test was more than 50 times greater than the amount of water vapour absorbed by the PHA fibres. The PHA fibres absorbed very little water vapour during the test. This further demonstrates the significantly reduced affinity of water of the PHA filter segment according to the invention compared to the conventional CA filter segment.

[0131] In a third test, the absorption of water from the mainstream smoke by a PHA filter segment according to the present invention and a conventional CA filter segment are compared. For each of the filter segments, a conventional smoking article is prepared as described above with reference to FIG. 3, with a combustible tobacco rod and a single segment of the filtration material forming the filter. Each of the smoking articles is then smoked in a cigarette-smoking machine under ISO conditions as set out in ISO 3308:2000 (puff volume 35 ml; 2 second puff duration every 60 seconds) and an analysis of the resultant smoke is carried out. For each of the filter segments, the amount of water in the mainstream smoke collected during the smoking test is measured, as shown in Table 4:

TABLE-US-00004 TABLE 4 Water in mainstream smoke generated during smoking test under ISO conditions PHA filter segment CA filter segment Water (mg per smoking 0.82 0.68 article)

[0132] This demonstrates that when smoked under equivalent conditions, the smoking article incorporating the PHA filter segment produces a mainstream smoke having a water content that is approximately 20 percent higher than the water content of the mainstream smoke from the smoking article including the CA filter segment. This demonstrates that the PHA filter segment is absorbing less water from the mainstream smoke than the CA filter segment, thereby reducing the potential problem of dry smoke as described above.