AEROSOL-GENERATING ARTICLE WITH AN INSULATED HEAT SOURCE

Abstract

An aerosol-generating article is provided, including an aerosol-forming substrate; a combustible heat source; and at least one layer of ceramic paper circumscribing at least a portion of a length of the combustible heat source. The at least one layer of ceramic paper includes a cellulose derivative binder and at least one of: biosoluble fibers, low biopersistent fibers, and fibers comprising at least one of: silicon dioxide, calcium oxide, and magnesium oxide. A method of forming an aerosol-generating article is also provided.

Claims

1.-13. (canceled)

14. An aerosol-generating article, comprising: an aerosol-forming substrate; a combustible heat source; and at least one layer of ceramic paper circumscribing at least a portion of a length of the combustible heat source, wherein the at least one layer of ceramic paper comprises a cellulose derivative binder, and at least one of: biosoluble fibers, low biopersistent fibers, and fibers comprising at least one of: silicon dioxide, calcium oxide, and magnesium oxide.

15. The aerosol-generating article according to claim 14, wherein the at least one layer of ceramic paper comprises less than or equal to about 40 weight percent of cellulose derivative binder.

16. The aerosol-generating article according to claim 14, wherein the at least one layer of ceramic paper comprises fibers comprising an alkaline earth silicate.

17. The aerosol-generating article according to claim 14, further comprising one or more airflow pathways configured such to allow air to be drawn along said pathways through the aerosol-generating article for inhalation by a user.

18. The aerosol-generating article according to claim 14, further comprising one or more non-combustible, substantially air impermeable, barriers between the combustible heat source and the aerosol forming substrate.

19. The aerosol-generating article according to claim 18, wherein the one or more non-combustible, substantially air impermeable, barriers between the combustible heat source and the aerosol-forming substrate 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.

20. The aerosol-generating article according to claim 17, wherein the at least one layer of ceramic paper 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 ceramic paper.

21. The aerosol-generating article according to claim 14, wherein the combustible heat source, the aerosol-forming substrate, and the at least one layer of ceramic paper are arranged such that a temperature of the aerosol-forming substrate does not exceed 375 C. during combustion of the combustible heat source.

22. The aerosol-generating article according to claim 14, wherein the at least one layer of ceramic paper comprises at least about 50 percent by weight of ceramic material.

23. The aerosol-generating article according to claim 14, wherein the at least one layer of ceramic paper has a thickness of between about 0.5 millimeters and about 5 millimeters.

24. A method of forming an aerosol-generating article according to claim 14, the method comprising: arranging a combustible heat source to heat an aerosol-forming substrate; and circumscribing at least a portion of a length of the combustible heat source with at least one layer of ceramic paper comprising a cellulose derivative binder.

25. The method of forming an aerosol-generating article according to claim 24, wherein the circumscribing at least the portion of the length of the combustible heat source with the at least one layer of ceramic paper comprises: providing a strip of ceramic paper comprising a cellulose derivative binder 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 ceramic paper, overlapping opposing ends of the strip, and securing together the overlapping opposing ends to secure the at least one layer of ceramic paper to the combustible heat source.

26. The method of forming an aerosol-generating article according to claim 24, wherein circumscribing at least a portion of the length of the combustible heat source with at least one layer of ceramic paper comprises: providing a strip ceramic paper comprising a cellulose derivative binder having opposing ends; applying an layer of adhesive to one side of the strip at least at each of the opposing ends; arranging the strip with the adhesive layer facing the combustible heat source; wrapping the strip around the combustible heat source such that the combustible heat source is circumscribed by the at least one layer of ceramic paper; abutting the opposing ends of the strip without overlapping the opposing ends; and securing the strip to the combustible heat source with the adhesive layer.

Description

[0154] The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

[0155] 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;

[0156] FIG. 2 shows the temperature profiles of aerosol-generating articles similar to that shown in FIG. 1 at a first position in the articles;

[0157] FIG. 3 shows the temperature profiles of aerosol-generating articles similar to that shown in FIG. 1 at a second position in the articles;

[0158] FIG. 4 shows the temperature profiles of the aerosol-generating articles similar to that shown in FIG. 1 at a third position in the articles;

[0159] FIG. 5 shows the temperature profiles of further aerosol-generating articles similar to that shown in FIG. 1 at the third position in the articles, one of the aerosol-generating articles comprising a ceramic paper having biosoluble alkaline earth silicate fibres and

[0160] FIG. 6 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] In accordance with the present invention, the aerosol-generating article 2 further comprises a layer of ceramic paper 5. The layer of ceramic paper 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 ceramic paper 5 is the radially outer layer at the distal end of the aerosol-generating article 2.

[0168] The layer of ceramic paper 5 comprises between about 60 percent by weight silicon dioxide and about 70 percent by weight silicon dioxide; between about 16 percent by weight calcium oxide and about 22 percent by weight calcium oxide and between about 12 percent by weight magnesium oxide and about 19 percent by weight magnesium oxide. The layer of ceramic paper 5 also comprises aluminium oxide. The layer of ceramic paper 5 also comprises a cellulose derivative binder. The cellulose derivative binder comprises CMC dispersed in water at a concentration of 8 weight percent.

[0169] 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.

[0170] 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.

[0171] 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 vapourised. 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.

[0172] 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.

[0173] In this embodiment, the layer of ceramic paper 5 extends over a minor portion of the distal end of the aerosol-forming substrate 4. As such, the layer of ceramic paper 5 is spaced from the air inlets 8. This spacing substantially isolates the layer of ceramic paper 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 ceramic paper 5.

[0174] It will be appreciated that in some embodiments, the layer of ceramic paper may be in close proximity to the air inlets. In these embodiments, portions of the layer of ceramic paper that are in close proximity to the air inlets may be coated in a material substantially impermeable to fibres and particles. This may substantially isolate the portions of the layer of ceramic paper 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 ceramic paper.

[0175] 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 the experiment, 2 mm deep holes were formed in the aerosol-generating articles; two of the holes were formed in the combustible heat source at positions T.sub.1 and T.sub.2 shown in FIG. 1, and one of the holes was formed in the aerosol-forming substrate at position T.sub.3 shown in FIG. 1. A thermocouple was inserted into each hole to enable the temperature at each position to be measured. In particular, experimental data was collected for aerosol-generating articles comprising a layer of ceramic paper circumscribing substantially the length of the combustible heat source and no layer of material circumscribing substantially the length of the combustible heat source. FIGS. 2-4 show graphs of the experimental measurements of temperature over time at three different locations of the various aerosol-generating articles.

[0176] 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.

[0177] 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.

[0178] 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.

[0179] 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.

[0180] In FIGS. 2, 3 and 4, the SMAR line, labelled as 20, shows the temperature profile of the aerosol-generating article with a naked combustible heat source. In other words, the SMAR line 22 shows the temperature profile of the aerosol-generating article with no layer of material circumscribing substantially the length of the combustible heat source.

[0181] In FIGS. 2, 3 and 4, the ceramic paper 1 line, labelled as 21, shows the temperature profile of the aerosol-generating article with a layer of ceramic paper circumscribing substantially the length of the combustible heat source. The ceramic paper circumscribing substantially the length of the combustible heat source in the ceramic paper 1 test was Superwool Plus Fibre available from Morgan Advanced Materials, plc.

[0182] In FIGS. 2, 3 and 4, the ceramic paper 2 line, labelled as 22, shows the temperature profile of the aerosol-generating article with a layer of ceramic paper circumscribing substantially the length of the combustible heat source. The ceramic paper circumscribing substantially the length of the combustible heat source in the ceramic paper 2 test was CFP Ceramic Fibre Paper available from Ningbo Firewheel Thermal Insulation & Sealing Co., Ltd.

[0183] In FIGS. 2, 3 and 4, the glass paper line, labelled as 23, shows the temperature profile of the aerosol-generating article with a layer of ceramic paper circumscribing substantially the length of the combustible heat source. The ceramic paper circumscribing substantially the length of the combustible heat source in the glass paper test was ceramic paper comprising glass fibres.

[0184] 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 20 of the aerosol-generating article with the naked combustible heat source, with no layer of material circumscribing substantially the length of the combustible heat source. Where the combustible heat source exhibits a similar or greater temperature than the naked combustible heat source, this indicates that the layer of material circumscribing substantially the length of the combustible heat source does not substantially inhibit combustion of the combustible heat source.

[0185] Surprisingly, as shown in FIGS. 2, 3 and 4, the temperature profiles 21, 22, 23 of the aerosol-generating article having a layer of ceramic paper circumscribing substantially the length of the combustible heat source are substantially similar to the temperature profile 20 of the aerosol-generating article with no layer of material circumscribing substantially the length of the combustible heat source at all three tested locations of the aerosol-generating article for the majority of the combustion time of the combustible heat source. Moreover, the temperature profiles 21 and 22 of the aerosol-generating article having a layer of ceramic paper circumscribing substantially the length of the combustible heat source actually exceeds the temperature profile 20 of the aerosol-generating article with no layer of material circumscribing substantially the length of the combustible heat source for some periods of time during the aerosol-generating experience.

[0186] This surprising result indicates that providing at least one layer of ceramic paper 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 ceramic paper may increase the temperature of the combustible heat source for periods of time during combustion of the combustible heat source.

[0187] FIG. 5 shows a graph of further experimental data collected as described above for three specific aerosol-generating articles. Similar to FIG. 4, FIG. 5 shows the temperature at the distal end of the aerosol-forming substrate, 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. The temperature profiles were again measured using electronic temperature probes that were inserted approximately 2 millimetres deep into the aerosol-forming substrate of the aerosol-generating articles.

[0188] In FIG. 5, the SMAR line, labelled as 30, shows the temperature profile of the aerosol-generating article with a naked combustible heat source. In other words, the SMAR line 22 shows the temperature profile of the aerosol-generating article with no layer of material circumscribing substantially the length of the combustible heat source.

[0189] In FIG. 5, the glass paper line, labelled as 31, shows the temperature profile of the aerosol-generating article with a layer of ceramic paper circumscribing substantially the length of the combustible heat source. The ceramic paper circumscribing substantially the length of the combustible heat source in the glass paper test was ceramic paper comprising glass fibres. The ceramic paper comprising glass fibres had a thickness of about 1 millimetre and a length of about 5.5 millimetres, extending from the distal end of the combustible heat source over the entire length of the combustible heat source and the distal end of the aerosol-forming substrate.

[0190] In FIG. 5, the biosoluble fibres line, labelled as 32, shows the temperature profile of the aerosol-generating article with a layer of ceramic paper circumscribing substantially the length of the combustible heat source. The ceramic paper circumscribing substantially the length of the combustible heat source in the biosoluble fibres test was Superwool Plus Fibre available from Morgan Advanced Materials, plc. Superwool Plus Fibre comprises biosoluble alkaline earth silicate fibres. The ceramic paper comprising biosoluble fibres had a thickness of about 0.5 millimetres and a length of about 5.5 millimetres, extending from the distal end of the combustible heat source over the entire length of the combustible heat source and the distal end of the aerosol-forming substrate.

[0191] Surprisingly, as shown in FIG. 5, the temperature profile 32 of the aerosol-generating article having the layer of ceramic paper comprising biosoluble alkaline earth silicate fibres has been found to be indicate a higher temperature after a time period of around 200 seconds than both the temperature profile 30 of the aerosol-generating article with no layer of material circumscribing substantially the length of the combustible heat source and the temperature profile 31 of the aerosol-generating article with a layer of ceramic paper comprising glass fibres after a period of 200 seconds.

[0192] This surprising result indicates that the smoking time may be increased by providing an aerosol-forming article with a layer of ceramic paper comprising biosoluble alkaline earth silicate fibres circumscribing substantially the length of the combustible heat source, even compared to articles having a layer of ceramic paper comprising glass fibres circumscribing substantially the length of the combustible heat source.

[0193] 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 2 minutes. After 2 minutes, the aerosol-generating articles were placed on a stack of Whatmann papers for a period of 10 minutes. After 10 minutes the Whatmann papers were inspected It was observed that the aerosol-generating article having the layer of ceramic paper 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 ceramic paper circumscribing substantially the length of the combustible heat source reduces the surface temperature proximate to the heat source.

[0194] A schematic representation of a second embodiment of an aerosol-generating article according to the present invention is shown in FIG. 6. 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 ceramic paper 105 and a layer of cigarette paper 107 arranged similarly to the corresponding components of the aerosol-generating article 2 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 and enables air to be drawn from the proximal end of the aerosol-generating article, through the combustible heat source 103, and to the aerosol-forming substrate 104. The layer of ceramic paper 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 ceramic paper 105.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] 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.

[0199] 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.