AEROSOL-GENERATING ARTICLE WITH AN INSULATED HEAT SOURCE

Abstract

An aerosol-generating article is provided, including: an aerosol-forming substrate; a combustible heat source; at least one layer of fibre-reinforced aerogel circumscribing at least a portion of a length of the combustible heat source; one or more airflow pathways configured such that air may be drawn along the one or more airflow pathways through the aerosol-generating article and for inhalation by a user; and one or more non-combustible, substantially air-impermeable, barriers disposed between the combustible heat source and the aerosol-forming substrate.

Claims

1.-15. (canceled)

16. An aerosol-generating article, comprising: an aerosol-forming substrate; a combustible heat source; at least one layer of fibre-reinforced aerogel circumscribing at least a portion of a length of the combustible heat source; one or more airflow pathways configured such that air may be drawn along the one or more airflow pathways through the aerosol-generating article and for inhalation by a user; and one or more non-combustible, substantially air-impermeable, barriers disposed between the combustible heat source and the aerosol-forming substrate.

17. The aerosol-generating article according to claim 16, wherein the at least one layer of fibre-reinforced aerogel is isolated from the one or more airflow pathways such that air drawn through the aerosol-generating article along the one or more airflow pathways does not directly contact the at least one layer of fibre-reinforced aerogel.

18. The aerosol-generating article according to claim 16, wherein the combustible heat source, the aerosol-forming substrate, and the at least one layer of fibre-reinforced aerogel are arranged such that a temperature of the aerosol-forming substrate does not exceed 375 C. during combustion of the combustible heat source.

19. The aerosol-generating article according to claim 16, wherein the fibre-reinforced aerogel comprises less than about 80 percent by weight of aerogel.

20. The aerosol-generating article according to claim 16, wherein the fibre-reinforced aerogel comprises at least about 20 percent by weight of fibrous material.

21. The aerosol-generating article according to claim 16, wherein the fibre-reinforced aerogel comprises between about 20 percent by weight and about 70 percent by weight of fibrous material.

22. The aerosol-generating article according to claim 16, wherein the fibre-reinforced aerogel comprises at least one material selected from a ceramic fibrous material and a glass fibrous material.

23. The aerosol-generating article according to claim 16, wherein the at least one layer of fibre-reinforced aerogel has a thickness of between about 0.5 millimetres and about 5 millimetres.

24. The aerosol-generating article according to claim 16, wherein the one or more non-combustible, substantially air-impermeable, barriers between the combustible heat source and the aerosol-forming substrate, and wherein the aerosol-generating article further comprises a first barrier that abuts one or both of a proximal end of the combustible heat source and a distal end of the aerosol-forming substrate.

25. The aerosol-generating article according claim 16, wherein the one or more airflow pathways comprise one or more air inlets arranged between a proximal end of the combustible heat source and a proximal end of the aerosol-generating article, and are further configured such that air may be drawn into the one or more airflow pathways of the aerosol-generating article though the one or more air inlets, without passing through the combustible heat source.

26. The aerosol-generating article according to claim 16, wherein the one or more airflow pathways comprise one or more airflow channels along the combustible heat source and the one or more non-combustible, substantially air-impermeable, barriers between the combustible heat source and the aerosol-forming substrate, and wherein the aerosol-generating article further comprises a second barrier disposed between the combustible heat source and the one or more airflow channels of the combustible heat source.

27. The aerosol-generating article according to claim 16, further comprising one or more additional layers circumscribing at least a proximal portion of the combustible heat source and a distal portion of the aerosol-forming substrate, the one or more additional layers comprising a heat-conducting element configured to transfer heat from the combustible heat source to the aerosol-forming substrate, and/or a layer of cigarette paper.

28. The aerosol-generating article according to claim 27, wherein the at least one layer of fibre-reinforced aerogel is a radially outer layer, overlying at least a portion of the one or more additional layers.

29. A method of forming an aerosol-generating article comprising an aerosol-forming substrate, a combustible heat source, at least one layer of fibre-reinforced aerogel circumscribing at least a portion of a length of the combustible heat source, one or more airflow pathways configured such that air may be drawn along the one or more airflow pathways through the aerosol-generating article and for inhalation by a user, and one or more non-combustible, substantially air-impermeable, barriers disposed between the combustible heat source and the aerosol-forming substrate, the method comprising: arranging the combustible heat source so as to heat the aerosol-forming substrate; providing the one or more airflow pathways along which the air may be drawn through the aerosol-generating article for inhalation by the user; isolating the combustible heat source from the one or more airflow pathways such that the air drawn through the aerosol-generating article along the one or more airflow pathways does not directly contact the combustible heat source; and circumscribing at least a portion of a length of the combustible heat source with the at least one layer of fibre-reinforced aerogel.

30. The method according to claim 29, wherein the circumscribing the at least a portion of the length of the combustible heat source with the at least one layer of fibre-reinforced aerogel comprises: providing a strip of fibre-reinforced aerogel having opposing ends; wrapping the strip around the combustible heat source such that the combustible heat source is circumscribed by the at least one layer of fibre-reinforced aerogel; overlapping the opposing ends of the strip; and securing together the overlapping ends to secure the at least one layer of fibre-reinforced aerogel to the combustible heat source.

Description

[0126] The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

[0127] FIG. 1 shows a schematic representation of a first embodiment of an aerosol-generating article according to the present invention comprising a blind combustible heat source;

[0128] FIG. 2 shows the temperature profile of the aerosol-generating article of FIG. 1 at a first position;

[0129] FIG. 3 shows the temperature profile of the aerosol-generating article of FIG. 1 at a second position;

[0130] FIG. 4 shows the temperature profile of the aerosol-generating article of FIG. 1 at a third position; and

[0131] FIG. 5 shows a schematic representation of a second embodiment of an aerosol-generating article according to the present invention comprising a non-blind combustible heat source.

[0132] FIG. 1 shows a schematic representation of an aerosol-generating article 2. The aerosol-generating article 2 comprises a combustible heat source 3. The combustible heat source 3 comprises a substantially circularly cylindrical body of carbonaceous material, having a length of about 10 millimetres. The combustible heat source 3 is a blind heat source. In other words, the combustible heat source 3 does not comprise any air channels extending therethrough.

[0133] The aerosol-generating article 2 further comprises an aerosol-forming substrate 4. The aerosol-forming substrate 4 is arranged at a proximal end of the combustible heat source 3. The aerosol-forming substrate 4 comprises a substantially circularly cylindrical plug of tobacco material 18 circumscribed by filter plug wrap 19.

[0134] A non-combustible, substantially air impermeable first barrier 6 is arranged between the proximal end of the combustible heat source 3 and a distal end of the aerosol-forming substrate 4. The first barrier 6 comprises a disc of aluminium foil. The first barrier 6 also forms a heat-conducting member between the combustible heat source 3 and the aerosol-forming substrate 4, for conducting heat from the proximal face of the combustible heat source 3 to the distal face of the aerosol-forming substrate 4.

[0135] A heat-conducting element 9 circumscribes a proximal portion of the combustible heat source 3 and a distal portion of the aerosol-forming substrate 4. The heat-conducting element 9 comprises a tube of aluminium foil. The heat-conducting element 9 is in direct contact with the proximal portion of the combustible heat source 3 and the filter plug wrap 19 of the aerosol-forming substrate 4.

[0136] The aerosol-generating article 2 further comprises various other components arranged proximal to the aerosol-forming substrate 4, including: a transfer element 11 arranged at the proximal end of the aerosol-forming substrate 4; an aerosol-cooling element 12 arranged at the proximal end of the transfer element 11; a spacer element 13 arranged at the proximal end of the aerosol-cooling element 11; and a mouthpiece 10 arranged at a proximal end of the spacer element 13.

[0137] The components of the aerosol-generating article 2 are wrapped in a layer of cigarette paper 7. The layer of cigarette paper 7 circumscribes the heat conducting element 9, but does not extend beyond the distal end of the heat conducting element 9, over the distal portion of the combustible heat source 3.

[0138] In accordance with the present invention, the aerosol-generating article 2 further comprises a layer of fibre-reinforced aerogel 5. The layer of fibre-reinforced aerogel 5 circumscribes substantially the length of the combustible heat source 3 and a distal portion of the layer of cigarette paper 7, the heat-conducting element 9 and the aerosol-forming substrate 4. In other words, the layer of fibre-reinforced aerogel 5 is the radially outer layer at the distal end of the aerosol-generating article 2.

[0139] The layer of fibre-reinforced aerogel 5 comprises a silica aerogel and a fibrous material comprising continuous filament glass fibres. The fibre-reinforced aerogel comprises about 35 percent by weight of synthetic amorphous silica, about 15 percent by weight of methylsilylated silica and about 45 percent by weight of continuous filament glass fibres.

[0140] A plurality of air inlets 8 are arranged at the aerosol-forming substrate 4 to allow ambient air to be drawn into the aerosol-generating article 2. The air inlets 8 comprise a plurality of perforations through the layer of cigarette paper 7 and the underlying layer of plug wrap 19 that circumscribes the aerosol-forming substrate 4. The air inlets 8 are arranged between the distal face and the proximal face of the aerosol-forming substrate 4.

[0141] When a user draws on the mouthpiece 10 of the aerosol-generating article 2, ambient air may be drawn into the aerosol-generating article 2 through the air inlets 8. The air drawn into the aerosol-generating article 2 may flow along an airflow pathway of the aerosol-generating article 2, from the air inlets 8, through the aerosol-forming substrate 4, the transfer element 11, the cooling element 12 and the spacer element 13 to the mouthpiece 10, and out of the mouthpiece 10 to the user for inhalation. The general direction of the airflow through the aerosol-generating article 2 is indicated by the arrows.

[0142] In use, a user may ignite the combustible heat source 3 by exposing the combustible heat source 3 to an external heat source, such as a lighter. The combustible heat source 3 may ignite and combust and heat may be transferred from the combustible heat source 3 to the aerosol-forming substrate 4, via conduction through the heat-conducting member 6 and the heat-conducting element 9. Volatile components of the heated aerosol-forming substrate 4 may be vaporised. A user may draw on the mouthpiece 10 of the aerosol-generating article 2, drawing ambient air into the airflow pathway of the aerosol-generating article 2, through the air inlets 8. The vapour from the heated aerosol-forming substrate 4 may be entrained in the air drawn through the aerosol-forming substrate 4 and may be drawn with the air towards the mouthpiece 10. As the vapour is drawn towards the mouthpiece 10, the vapour may cool to form an aerosol. The aerosol may be drawn out of the mouthpiece 10 and be delivered to the user for inhalation.

[0143] It will be appreciated that the substantially air-impermeable first barrier 6 inhibits air being drawn through the combustible heat source 3 and into the aerosol-forming substrate 4. As such, the first barrier 6 substantially isolates the airflow pathway of the aerosol-generating article 2 from the combustible heat source 3.

[0144] In this embodiment, the layer of fibre-reinforced aerogel 5 extends over a minor portion of the distal end of the aerosol-forming substrate 4. As such, the layer of fibre-reinforced aerogel 5 is spaced from the air inlets 8. This spacing substantially isolates the layer of fibre-reinforced aerogel 5 from the air inlets 8, such that air drawn through the airflow pathway of the aerosol-generating article 2 does not come into contact with the layer of fibre-reinforced aerogel 5.

[0145] It will be appreciated that in some embodiments, the layer of fibre-reinforced aerogel may be in close proximity to the air inlets. In these embodiments, portions of the layer of fibre-reinforced aerogel that are in close proximity to the air inlets may be coated in a material substantially impermeable to fibers and particles. This may substantially isolate the portions of the layer of fibre-reinforced aerogel that are in close proximity to the air inlets, such that air drawn through the airflow pathway of the aerosol-generating article does not come into contact with the layer of fibre-reinforced aerogel.

[0146] Experimental data was collected to determine the temperature of combustible heat sources and aerosol-forming substrates of various aerosol-generating articles similar to the aerosol-generating article 2 shown in FIG. 1 over the period of combustion of the combustible heat source. Each of the aerosol-generating articles tested comprised a different layer of material circumscribing substantially the length of the combustible heat source. In particular, experimental data was collected for aerosol-generating articles comprising a layer of non-reinforced aerogel (AeroZero produced by Blueshift International Materials, Inc.) circumscribing substantially the length of the combustible heat source, a layer of fibre-reinforced aerogel (Pyrogel XT-F produced by Aspen Aerogels, Inc.) circumscribing substantially the length of the combustible heat source and no layer of material circumscribing substantially the length of the combustible heat source.

[0147] FIGS. 2-4 show graphs of the experimental measurements of temperature over time at three different locations of the various aerosol-generating articles.

[0148] FIG. 2 shows the temperature measured at a position 2 millimetres from the distal end of the combustible heat source, which corresponds to position T.sub.1 shown in FIG. 1. In other words, FIG. 2 shows the temperature at the distal end of the combustible heat source.

[0149] FIG. 3 shows the temperature measured at a position 5 millimetres from the distal end of the combustible heat source, which corresponds to position T.sub.2 shown in FIG. 1. In other words, FIG. 3 shows the temperature approximately half way along the length of the combustible heat source.

[0150] FIG. 4 shows the temperature measured at a position 11 millimetres from the distal end of the combustible heat source, which corresponds to position T.sub.3 in FIG. 1. In other words, FIG. 4 shows the temperature at the distal end of the aerosol-forming substrate.

[0151] All of the temperature profiles were measured using electronic temperature probes that were inserted approximately 2 millimetres deep into the relevant components of the aerosol-generating articles.

[0152] In FIGS. 2, 3 and 4, the AeroZero line, labelled as 20, shows the temperature profile of the aerosol-generating article with a layer of non-reinforced aerogel circumscribing substantially the length of the combustible heat source.

[0153] In FIGS. 2, 3 and 4, the Pyrogel XTF line, labelled as 21, shows the temperature profile of the aerosol-generating article with a layer of fibre-reinforced aerogel circumscribing substantially the length of the combustible heat source, in accordance with the present invention.

[0154] In FIGS. 2, 3 and 4, the SMAR line, labelled as 22, shows the temperature profile of the aerosol-generating article with no layer of material circumscribing substantially the length of the combustible heat source.

[0155] It is desirable for the aerosol-generating articles having a layer of material circumscribing substantially the length of the aerosol-generating article to exhibit temperatures profiles substantially similar to or exceeding the temperature profile of the aerosol-generating article with no layer of material circumscribing substantially the length of the combustible heat source, labelled as 22. This indicates that the layer of material does not substantially inhibit combustion of the combustible heat source.

[0156] As shown in FIGS. 2, 3 and 4, the temperature 20 of the aerosol-generating article having the layer of non-reinforced aerogel circumscribing substantially the length of the combustible heat source is below the temperature 22 of the aerosol-generating article with no layer of material circumscribing substantially the length of the combustible heat source at all three locations of the aerosol-generating article for the entire combustion time of the combustible heat source.

[0157] Surprisingly, as shown in FIGS. 2, 3 and 4, the temperature 21 of the aerosol-generating article having the layer of fibre-reinforced aerogel circumscribing substantially the length of the combustible heat source is substantially similar to the temperature 22 of the aerosol-generating article with no layer of material circumscribing substantially the length of the combustible heat source at all three locations of the aerosol-generating article for the majority of the combustion time of the combustible heat source. Moreover, the temperature 21 of the aerosol-generating article having the layer of fibre-reinforced aerogel circumscribing substantially the length of the combustible heat source actually exceeds the temperature 22 of the aerosol-generating article with no layer of material circumscribing substantially the length of the combustible heat source at all three locations of the aerosol-generating article at the end of the aerosol-generating experience.

[0158] This surprising result indicates that providing at least one layer of fibre-reinforced aerogel circumscribing substantially the length of the combustible heat source advantageously does not substantially impede combustion of the combustible heat source. In fact, providing the layer of fibre-reinforced aerogel may increase the temperature of the combustible heat source towards the end of the combustion time of the combustible heat source, which may extend the length of time that aerosol is generated by the aerosol-generating article, and thereby extend the aerosol-generating experience for the user.

[0159] Aerosol-generating articles according to the invention were tested by observing their effect from placing them on Whatmann papers after the heat source was ignited. For example, the aerosol-generating articles were conditioned for 24 hours at about 23 C.3 C. and 55%5% relative humidity. The conditioned aerosol-generating articles were lit, using an electric lighter, and left to combust for a period of 3 minutes. After 3 minutes, the aerosol-generating articles were placed on a stack of Whatmann papers for a period of 8 minutes. After 8 minutes, the Whatmann papers were inspected. It was observed that the aerosol-generating article having the layer of fibre-reinforced aerogel circumscribing substantially the length of the combustible heat source did not produce a hole in any of the Whatmann papers and produced a small area of browning in the top paper. This result shows that having the layer of fibre-reinforced aerogel circumscribing substantially the length of the combustible heat source reduces the surface temperature proximate to the heat source.

[0160] A schematic representation of a second embodiment of an aerosol-generating article according to the present invention is shown in FIG. 5. The aerosol-generating article 102 is substantially similar to the aerosol-generating article 2 shown in FIG. 1. The aerosol-generating article 102 comprises a combustible heat source 103, an aerosol-forming substrate 104, a layer of fibre-reinforced aerogel 105 and a layer of cigarette paper 107 arranged similarly to the corresponding components of the aerosol-generating article 102 shown in FIG. 1. However, combustible heat source 103 is a non-blind heat source. The non-blind heat source 103 comprises an annular body 115 of carbonaceous material having a passage 116 extending between the distal end face and the proximal end face. The passage 116 forms part of the airflow pathway through the aerosol-generating article 102 and enables air to be drawn from the proximal end of the aerosol-generating article 102, through the combustible heat source 103, and to the aerosol-forming substrate 104. The layer of fibre-reinforced aerogel 105 is spaced from the airflow pathway through the aerosol-generating article 102 such that air drawn through the airflow pathway does not come into contact with the layer of fibre-reinforced aerogel 105.

[0161] A non-combustible, substantially air impermeable, first barrier 106 is arranged between the proximal end of the combustible heat source 103 and the distal end of the aerosol-forming substrate 104, similar to the first barrier 6 described above in relation to FIG. 1. However, unlike the first barrier 6 described above, the first barrier 106 includes an aperture 120, aligned with the passage 116, to enable air to pass from the passage 116 to the aerosol-forming substrate 104.

[0162] A non-combustible, substantially air impermeable, second barrier 117 is coated on the inner surface of the passage 116. The second barrier 117 isolates air passing through the passage 116 from the combustible heat source 103 and from the products of combustion of the combustible heat source.

[0163] Since the combustible heat source 103 is a non-blind heat source, the aerosol-generating article 102 does not comprise air inlets arranged at the aerosol-forming substrate 104. When a user draws on the mouthpiece of the aerosol-generating article 102, ambient air may be drawn into the aerosol-generating article 102 through the passage 116 through the heat source 103. The air drawn into the aerosol-generating article 102 may flow along an airflow pathway of the aerosol-generating article 102, through the passage 116, through the aerosol-forming substrate 104, the transfer element, the cooling element and the spacer element to the mouthpiece, and out of the mouthpiece to the user for inhalation. The general direction of the airflow through the aerosol-generating article 102 is indicated by the arrows.

[0164] It will be appreciated that in some embodiments other air inlets may also be provided in the aerosol-generating article, in addition to the air passage through the combustible heat source.

[0165] The specific embodiments described above are intended to illustrate the invention. However, other embodiments may be made without departing from the scope of the invention as defined in the claims, and it is understood that the specific embodiments described above are not intended to be limiting.