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 ceramic paper circumscribing at least a portion of a length of the combustible heat source; one or more airflow pathways along which air may be drawn through the aerosol-generating article for inhalation; and one or more non-combustible, substantially air impermeable barriers between the combustible heat source and the aerosol forming substrate.

Claims

1. An aerosol-generating article, comprising: an aerosol-forming substrate; a combustible heat source; 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 allows sufficient air through the layer such that combustion of the combustible heat source is substantially unimpeded; one or more airflow pathways along which air may be drawn through the aerosol-generating article for inhalation; and one or more non-combustible, substantially air impermeable barriers between the combustible heat source and the aerosol-forming substrate.

2. The aerosol-generating article according to claim 1, 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.

3. The aerosol-generating article according claim 1, 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.

4. The aerosol-generating article according to claim 1, wherein the ceramic paper comprises between about 50 percent by weight ceramic material and about 100 percent by weight ceramic material.

5. The aerosol-generating article according to claim 1, wherein the ceramic paper comprises silica fibres.

6. The aerosol-generating article according to claim 1, wherein the at least one layer of ceramic paper has a thickness of between about 0.5 mm and about 5 mm.

7. The aerosol-generating article according to claim 1, 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.

8. The aerosol-generating article according to claim 1, 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 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.

9. The aerosol-generating article according to claim 1, wherein the one or more airflow pathways comprise one or more airflow channels along the combustible heat source and the non-combustible, substantially air impermeable, barrier between the combustible heat source and the one or more airflow channels further comprises a second barrier between the combustible heat source and the one or more airflow channels of the combustible heat source.

10. The aerosol-generating article according to claim 1, wherein the aerosol-generating article further comprises 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 to transfer heat from the combustible heat source to the aerosol-forming substrate, or a layer of cigarette paper, or both of the heat-conducting element to transfer heat from the combustible heat source to the aerosol-forming substrate, and the layer of cigarette paper.

11. The aerosol-generating article according to claim 10, wherein the at least one layer of ceramic paper is a radially outer layer, overlying at least a portion of the one or more additional layers.

12. The aerosol-generating article according to claim 1, wherein the at least one layer of ceramic paper has a permeability to air of greater than about 4,000 cm.sup.3/(min*cm.sup.2).

13. The aerosol-generating article according to claim 1, wherein the at least one layer of ceramic paper has a thermal conductivity of between about 0.5 W/mK to 2 W/mK at a temperature of about 23° C.

14. The aerosol-generating article according to claim 1, wherein the at least one layer of ceramic paper circumscribes an upstream end of the combustible heat source.

15. The aerosol-generating article according to claim 1, wherein the at least one layer of ceramic paper is a wrapper.

16. The aerosol-generating article according to claim 1, wherein the at least one layer of ceramic paper is in direct contact with the combustible heat source.

Description

(1) The invention will be further described, by way of example only, with reference to the accompanying drawings in which:

(2) 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;

(3) FIG. 2 shows the temperature profile of the aerosol-generating article of FIG. 1 at a first position;

(4) FIG. 3 shows the temperature profile of the aerosol-generating article of FIG. 1 at a second position;

(5) FIG. 4 shows the temperature profile of the aerosol-generating article of FIG. 1 at a third position; and

(6) 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.

(7) 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.

(8) 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.

(9) 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.

(10) 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.

(11) 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.

(12) 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.

(13) 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.

(14) The layer of ceramic paper 5 comprises between about 60 percent by weight silica and about 70 percent by weight silica; 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 alumina and a binder material.

(15) 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.

(16) 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.

(17) 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.

(18) 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.

(19) 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.

(20) 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.

(21) 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 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.

(22) 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.

(23) 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.

(24) FIG. 4 shows the temperature measured at a position 11 millimetres from the distal end of the combustible heat source, which corresponds to position 13 in FIG. 1. In other words, FIG. 4 shows the temperature at the distal end of the aerosol-forming substrate.

(25) 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.

(26) 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.

(27) 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, in accordance with the present invention. 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.

(28) 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, in accordance with the present invention. 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.

(29) 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, in accordance with the present invention. 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.

(30) 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, in accordance with the present invention. The ceramic paper circumscribing substantially the length of the combustible heat source in the “glass paper” test was ceramic paper comprising glass fibres.

(31) 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.

(32) 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.

(33) 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.

(34) Aerosol-generating articles according to the invention were also 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.

(35) 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 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.

(36) 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. 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.

(37) 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.

(38) 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. The specific embodiments described above are intended to illustrate the invention.

(39) 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.