AEROSOL-FORMING SUBSTRATE WITH IMPROVED THERMAL CONDUCTIVITY

Abstract

An aerosol-forming substrate for a heatable aerosol-generating article is provided, the aerosol-forming substrate including an aerosol-forming material and between 0.1 and 15 weight percent carbon particles, the carbon particles having a volume mean particle size of greater than 10 microns, the carbon particles having a particle size distribution having a D10 particle size and a D90 particle size, and the D90 particle size being less than 20 times the D10 particle size. A method of forming the aerosol-forming substrate, and an aerosol-generating article including the aerosol-forming substrate, are also provided.

Claims

1.-15. (canceled)

16. An aerosol-forming substrate for a heatable aerosol-generating article, the aerosol-forming substrate comprising: an aerosol-forming material and between 0.1 and 15 weight percent carbon particles, wherein the carbon particles have a volume mean particle size of greater than 10 microns, wherein the carbon particles have a particle size distribution having a D10 particle size and a D90 particle size, and wherein the D90 particle size is less than 20 times the D10 particle size.

17. The aerosol-forming substrate according to claim 16, wherein the carbon particles consist of one or more of: graphite particles, expanded graphite particles, and graphene particles.

18. The aerosol-forming substrate according to claim 16, wherein the aerosol-forming material comprises an organic material, an aerosol-former, and a binder.

19. The aerosol-forming substrate according to claim 16, wherein the aerosol-forming material is in a form of one or more of: cut-filler, powder particles, granules, pellets, shreds, spaghettis, strips, or sheets, and wherein the carbon particles have a volume mean particle size of between 10 and 1,000 microns.

20. The aerosol-forming substrate according to claim 16, wherein the aerosol-forming material is in a form of a gathered sheet and the carbon particles have a volume mean particle size of between 10 microns and 200 microns.

21. The aerosol-forming substrate according to claim 20, wherein the carbon particles have a volume mean particle size of between 30 microns and 150 microns.

22. The aerosol-forming substrate according to claim 16, wherein the aerosol-forming substrate has a thermal conductivity of greater than 0.06 W/mK in at least one direction.

23. The aerosol-forming substrate according to claim 16, wherein the aerosol-forming substrate has a density of less than 1,000 kg/m.sup.3.

24. The aerosol-forming substrate according to claim 16, wherein the carbon particles consist of one or both of expanded graphite particles and graphene particles.

25. The aerosol-forming substrate according to claim 16, wherein the carbon particles have a volume mean particle size of between 10 microns and 75 microns.

26. The aerosol-forming substrate according to claim 16, wherein one or both of a volume mean particle size and a D50 particle size of the carbon particles is greater than or equal to 150 microns.

27. A method of forming an aerosol-forming substrate according to claim 16, the method comprising: forming a slurry comprising an organic material and carbon particles having a volume mean particle size of greater than 10 microns and a particle size distribution having a D10 particle size and a D90 particle size, wherein the D90 particle size is less than 20 times the D10 particle size; homogenising the slurry; and casting and drying the slurry to form the aerosol-forming substrate.

28. A method of forming an aerosol-forming substrate according to claim 16, the method comprising: providing an aerosol-forming material; and coating carbon particles having a volume mean particle size of greater than 10 microns onto the aerosol-forming material to form the aerosol-forming substrate.

29. An aerosol-generating article comprising an aerosol-forming substrate according to claim 16.

30. An aerosol-generating system comprising an aerosol-generating article according to claim 29 and an electrical aerosol-generating device configured to heat the aerosol-generating article so as to generate an aerosol.

Description

[0265] Examples will now be further described with reference to the figures in which:

[0266] FIG. 1 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating article;

[0267] FIG. 2 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating article;

[0268] FIG. 3 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating system;

[0269] FIG. 4 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating system; and

[0270] FIG. 5 shows a schematic cross-sectional view of a third embodiment of an aerosol-generating article.

[0271] FIG. 1 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating article 10. The aerosol-generating article 10 comprises a rod 12 of aerosol-forming substrate and a downstream section 14 at a location downstream of the rod 12 of aerosol-forming substrate. Further, the aerosol-generating article 10 comprises an upstream section 16 at a location upstream of the rod 12 of aerosol-forming substrate. Thus, the aerosol-generating article 10 extends from an upstream or distal end 18 to a downstream or proximal or mouth end 20.

[0272] The aerosol-generating article has an overall length of about 45 millimetres.

[0273] The downstream section 14 comprises a support element 22 located immediately downstream of the rod 12 of aerosol-forming substrate, the support element 22 being in longitudinal alignment with the rod 12. In the embodiment of FIG. 1, the upstream end of the support element 22 abuts the downstream end of the rod 12 of aerosol-generating substrate. In addition, the downstream section 14 comprises an aerosol-cooling element 24 located immediately downstream of the support element 22, the aerosol-cooling element 24 being in longitudinal alignment with the rod 12 and the support element 22. In the embodiment of FIG. 1, the upstream end of the aerosol-cooling element 24 abuts the downstream end of the support element 22.

[0274] As will become apparent from the following description, the support element 22 and the aerosol-cooling element 24 together define an intermediate hollow section 50 of the aerosol-generating article 10. As a whole, the intermediate hollow section 50 does not substantially contribute to the overall RTD of the aerosol-generating article. An RTD of the intermediate hollow section 26 as a whole is substantially 0 millimetres H.sub.2O.

[0275] The support element 22 comprises a first hollow tubular segment 26. The first hollow tubular segment 26 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular segment 26 defines an internal cavity 28 that extends all the way from an upstream end 30 of the first hollow tubular segment to a downstream end 32 of the first hollow tubular segment 20. The internal cavity 28 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 28. The first hollow tubular segment 26and, as a consequence, the support element 22does not substantially contribute to the overall RTD of the aerosol-generating article 10. In more detail, the RTD of the first hollow tubular segment 26 (which is essentially the RTD of the support element 22) is substantially 0 millimetres H.sub.2O.

[0276] The first hollow tubular segment 26 has a length of about 8 millimetres, an external diameter of about 7.25 millimetres, and an internal diameter (D.sub.FTS) of about 1.9 millimetres. Thus, a thickness of a peripheral wall of the first hollow tubular segment 26 is about 2.67 millimetres.

[0277] The aerosol-cooling element 24 comprises a second hollow tubular segment 34. The second hollow tubular segment 34 is provided in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular segment 34 defines an internal cavity 36 that extends all the way from an upstream end 38 of the second hollow tubular segment to a downstream end 40 of the second hollow tubular segment 34. The internal cavity 36 is substantially empty, and so substantially unrestricted airflow is enabled along the internal cavity 36. The second hollow tubular segment 28and, as a consequence, the aerosol-cooling element 24does not substantially contribute to the overall RTD of the aerosol-generating article 10. In more detail, the RTD of the second hollow tubular segment 34 (which is essentially the RTD of the aerosol-cooling element 24) is substantially 0 millimetres H.sub.2O.

[0278] The second hollow tubular segment 34 has a length of about 8 millimetres, an external diameter of about 7.25 millimetres, and an internal diameter (D.sub.STS) of about 3.25 millimetres. Thus, a thickness of a peripheral wall of the second hollow tubular segment 34 is about 2 millimetres. Thus, a ratio between the internal diameter (D.sub.FTS) of the first hollow tubular segment 26 and the internal diameter (D.sub.STS) of the second hollow tubular segment 34 is about 0.75.

[0279] The aerosol-generating article 10 comprises a ventilation zone 60 provided at a location along the second hollow tubular segment 34. In more detail, the ventilation zone is provided at about 2 millimetres from the upstream end of the second hollow tubular segment 34. In this embodiment, the ventilation zone 60 comprises a circumferential row of perforations through a paper wrapper 70 and a ventilation level of the aerosol-generating article 10 is about 25 percent.

[0280] In the embodiment of FIG. 1, the downstream section 14 further comprises a mouthpiece element 42 at a location downstream of the intermediate hollow section 50. In more detail, the mouthpiece element 42 is positioned immediately downstream of the aerosol-cooling element 24. As shown in the drawing of FIG. 1, an upstream end of the mouthpiece element 42 abuts the downstream end 40 of the aerosol-cooling element 24.

[0281] The mouthpiece element 42 is provided in the form of a cylindrical plug of low-density cellulose acetate.

[0282] The mouthpiece element 42 has a length of about 12 millimetres and an external diameter of about 7.25 millimetres. The RTD of the mouthpiece element 42 is about 12 millimetres H.sub.2O. The ratio of the length of the mouthpiece element 42 to the length of the intermediate hollow section 50 is approximately 0.6.

[0283] The rod 12 of aerosol-forming substrate has an external diameter of about 7.25 millimetres and a length of about 12 millimetres.

[0284] The upstream section 16 comprises an upstream element 46 located immediately upstream of the rod 12 of aerosol-forming substrate, the upstream element 46 being in longitudinal alignment with the rod 12. In the embodiment of FIG. 1, the downstream end of the upstream element 46 abuts the upstream end of the rod 12 of aerosol-forming substrate. The upstream element 46 is provided in the form of a cylindrical plug of cellulose acetate. The upstream element 46 has a length of about 5 millimetres. The RTD of the upstream element 46 is about 30 millimetres H.sub.2O.

[0285] The upstream element 46, rod 12 of aerosol-forming substrate, support element 22, aerosol-cooling element 24, and mouthpiece element 42 are circumscribed by the paper wrapper 70.

[0286] The rod 12 of aerosol-forming substrate comprises an aerosol-forming material and thermally conductive particles 44. The aerosol-forming material comprises a reconstituted and gathered sheet comprising tobacco material and glycerine. The thermally conductive particles 44 are carbon particles, specifically expanded graphite particles, having a particle size distribution with a D10 particle size of 6.6 microns, a D50 particle size of 20 microns, and a D90 particle size of 56 microns. Each of the expanded graphite particles has a particle size greater than 2 microns and less than 100 microns. The expanded graphite particles have a volume mean particle size of around 35 microns. Each of the expanded graphite particles is substantially spherical in shape. The expanded graphite particles have a density of less than 1000 kilograms per metre cubed. The aerosol-forming substrate, including the aerosol-forming material and the thermally conductive particles 44, have a combined density of around 760 kilograms per metre cubed. The expanded graphite particles make up approximately 5% of the aerosol-forming substrate by weight.

[0287] The rod 12 of aerosol-forming substrate is formed by a process including the following steps: [0288] pre-mixing a binder, guar gum, with an aerosol-former, glycerine, to form a first pre-mixture; [0289] pre-mixing finely shredded tobacco material and a powder consisting of the expanded graphite particles 44 and having a bulk density of around 0.065 grams per centimetre cubed, to form a second pre-mixture; [0290] mixing the first and second pre-mixtures with water to form a slurry; [0291] homogenising the slurry using a high-shear mixer; [0292] casting the slurry onto a conveyor belt; [0293] controlling a thickness of the slurry and drying the slurry to form a large sheet of aerosol-forming substrate; and [0294] gathering and cutting the large sheet of aerosol-forming substrate to form the rod 12 of aerosol-forming substrate.

[0295] After forming the rod 12 of aerosol-forming substrate, the aerosol-generating article 10 is assembled by positioning the various components of the article 10 and wrapping the components in the wrapper 70.

[0296] FIG. 2 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating article 11. This second embodiment is identical to the first embodiment of FIG. 1 except that the rod 12 of aerosol-forming substrate has been replaced by an alternative rod 13 of aerosol-forming substrate. Identical reference numerals have been used for identical components in the embodiments of FIGS. 1 and 2.

[0297] In the rod 13 of the second embodiment, the aerosol-forming substrate comprises an aerosol-forming material and thermally conductive particles 45. The aerosol-forming material comprises tobacco and glycerine and is in the form of cut-filler. The cut-filler comprises shreds of aerosol-forming material, the shreds having widths between 0.3 and 2 millimetres. The thermally conductive particles 45 are graphite particles, rather than expanded graphite particles, with a particle size distribution with a D10 particle size of 6 microns, a D50 particle size of 21 microns, and a D90 particle size of 55 microns. Each of the graphite particles has a particle size greater than 2 microns and less than 100 microns. The graphite particles have a volume mean particle size of around 35 microns. Each of the graphite particles is substantially spherical in shape. The graphite particles have a density of around 2200 kilograms per metre cubed. The aerosol-forming substrate, including the aerosol-forming material and the thermally conductive particles 45, have a combined density of around 960 kilograms per metre cubed. The graphite particles make up approximately 5% of the aerosol-forming substrate by weight.

[0298] The rod 13 of aerosol-forming substrate is formed by a process including the following steps: [0299] pre-mixing a binder, guar gum, with an aerosol-former, glycerine, to form a first pre-mixture; [0300] pre-mixing finely shredded tobacco material and water to form a second pre-mixture; [0301] mixing the first and second pre-mixtures to form a slurry; [0302] homogenising the slurry using a high-shear mixer; [0303] casting the slurry onto a conveyor belt; [0304] controlling a thickness of the slurry and drying the slurry to form a large sheet of reconstituted, substantially homogeneous, tobacco-containing, aerosol-forming material; [0305] shredding the large sheet of reconstituted and substantially homogeneous aerosol-forming material to form cut-filler; [0306] mixing a powder consisting of the graphite particles 45 having a bulk density of around 560 kilograms per metre cubed with the cut-filler, thereby coating the graphite particles 45 onto the cut-filler; [0307] adding flavourants to the cut-filler with graphite particles 45 coated thereon; and [0308] forming the cut-filler (with graphite particles 45 and flavourants) into a plug for use as the rod 13 of aerosol-forming substrate.

[0309] After forming the rod 13 of aerosol-forming substrate, the aerosol-generating article 11 is assembled by positioning the various components of the article 11 and wrapping the components in the wrapper 70.

[0310] FIG. 3 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating system 100. The system 100 comprises an aerosol-generating device 102 and the aerosol-generating article 10 of FIG. 1.

[0311] The aerosol-generating device 102 comprises a battery 104, a controller 106, a heating blade 108 coupled to the battery, and a puff-detection mechanism (not shown). The controller 106 is coupled to the battery 104, the heating blade 108 and the puff-detection mechanism.

[0312] The aerosol-generating device 102 further comprises a housing 110 defining a substantially cylindrical cavity for receiving a portion of the article 10. The heating blade 108 is positioned centrally within the cavity and extends longitudinally from a base of the cavity.

[0313] In this embodiment, the heating blade 108 comprises a substrate and an electrically resistive track located on the substrate. The battery 104 is coupled to the heating blade 108 so as to be able to pass a current through the electrically resistive track and heat the electrically resistive track and heating blade 108 to an operational temperature.

[0314] In use, a user inserts the article 10 into the cavity, causing the heating blade 108 to penetrate the upstream element 46 and rod 12 of aerosol-forming substrate of the article 10. FIG. 3 shows the article 10 inserted into the cavity of the device 102.

[0315] Then, the user puffs on the downstream end of the article 10. This causes air to flow through an air inlet (not shown) of the device 102, then through the article 10, from the upstream end 18 to the downstream end 20, and into the mouth of the user.

[0316] The user puffing on the article 10 causes air to flow through the air inlet of the device. The puff-detection mechanism detects that the air flow rate through the air inlet has increased to greater than a non-zero threshold flow rate. The puff-detection mechanism sends a signal to the controller 106 accordingly. The controller 106 then controls the battery 104 so as to pass a current through the electrically resistive track and heat up the heating blade 108. This heats up the rod 12 of aerosol-forming substrate, which is in contact with the heating blade 108.

[0317] The expanded graphite particles 44 have a significantly higher thermal conductivity than the surrounding aerosol-forming material. As such, these particles may act as local hot-spots and provide a more even temperature throughout the aerosol-forming substrate, particularly in a radial direction from the heating blade 108 where, with prior art substrates, there would be a significant temperature gradient. This may result in a greater proportion of the aerosol-forming substrate reaching a sufficiently high temperature to release volatile compounds, and thus a higher usage efficiency of the aerosol-forming substrate.

[0318] Heating of the aerosol-forming substrate cause the aerosol-forming substrate to release volatile compounds. These compounds are entrained by the air flowing from the upstream end 18 of the article 10 towards the downstream end 20 of the article 10. The compounds cool and condense to form an aerosol as they pass through the internal cavities 28, 36 of the support element and the aerosol-cooling element. The aerosol then passes through the mouthpiece element 42, which may filter out unwanted particles entrained in the air flow, and into the mouth of the user.

[0319] When the user stops inhaling on the article 10, the air flow rate through the air inlet of the device decreases to less than the non-zero threshold flow rate. This is detected by the puff-detection mechanism. The puff-detection mechanism sends a signal to the controller 106 accordingly. The controller 106 then controls the battery 104 so as to reduce the current being passed through the electrically resistive track to zero.

[0320] After a number of puffs on the article 10, the user may choose to replace the article 10 with a fresh article.

[0321] FIG. 4 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating system 200. The system 200 comprises an aerosol-generating device 202 and the aerosol-generating article 11 of FIG. 2.

[0322] The aerosol-generating device 202 comprises a battery 204, a controller 206, an inductor coil 208, and a puff-detection mechanism (not shown). The controller 206 is coupled to the battery 204, the inductor coil 208 and the puff-detection mechanism.

[0323] The aerosol-generating device 202 further comprises a housing 210 defining a substantially cylindrical cavity for receiving a portion of the article 11. The inductor coil 208 spirals around the cavity.

[0324] The battery 204 is coupled to the inductor coil 208 so as to be able to pass an alternating current through the inductor coil 208.

[0325] In use, a user inserts the article 11 into the cavity. FIG. 4 shows the article 11 inserted into the cavity of the device 202.

[0326] Then, the user puffs on the downstream end of the article 11. This causes air to flow through an air inlet (not shown) of the device 202, then through the article 11, from the upstream end 18 to the downstream end 20, and into the mouth of the user.

[0327] The user puffing on the article 11 causes air to flow through the air inlet of the device. The puff-detection mechanism detects that the air flow rate through the air inlet has increased to greater than a non-zero threshold flow rate. The puff-detection mechanism sends a signal to the controller 206 accordingly. The controller 206 then controls the battery 204 so as to pass an alternating current through the inductor coil 208. This causes the inductor coil 208 to generate a fluctuating electromagnetic field. The rod 13 of aerosol-forming substrate is located within this fluctuating electromagnetic field and graphite, the material of the particles 45, is a susceptor material. Thus, the fluctuating electromagnetic field causes eddy currents in the particles 45. This causes the particles 45 to heat up, thereby also heating nearby aerosol-forming material.

[0328] Heating of the aerosol-forming material cause the aerosol-forming material to release volatile compounds. These compounds are entrained by the air flowing from the upstream end 18 of the article 11 towards the downstream end 20 of the article 11. The compounds cool and condense to form an aerosol as they pass through the internal cavities 28, 36 of the support element and the aerosol-cooling element. The aerosol then passes through the mouthpiece element 42, which may filter out unwanted particles entrained in the air flow, and into the mouth of the user.

[0329] When the user stops inhaling on the article 11, the air flow rate through the air inlet of the device decreases to less than the non-zero threshold flow rate. This is detected by the puff-detection mechanism. The puff-detection mechanism sends a signal to the controller 206 accordingly. The controller 206 then controls the battery 204 so as to reduce the current being passed through the electrically resistive track to zero.

[0330] After a number of puffs on the article 11, the user may choose to replace the article 11 with a fresh article.

[0331] FIG. 5 shows a schematic cross-sectional view of a third embodiment of an aerosol-generating article 510. This third embodiment is identical to the first embodiment of FIG. 1 except that the rod 12 of aerosol-forming substrate has been replaced by an alternative rod 512 of aerosol-forming substrate. Identical reference numerals have been used for identical components in the embodiments of FIGS. 1 and 5.

[0332] The rod 512 of aerosol-forming substrate of the third embodiment of FIG. 5 is identical to the rod 12 of aerosol-forming substrate of the first embodiment of FIG. 1 except that the rod 512 of aerosol-forming substrate of the third embodiment of FIG. 5 additionally includes an elongate susceptor element 580.

[0333] The susceptor element 580 is arranged substantially longitudinally within the rod 512 of aerosol-forming substrate so as to be approximately parallel with a longitudinal axis of the rod 512 of aerosol-forming substrate. As shown in the drawing of FIG. 5, the susceptor element 580 is positioned in a radially central position within the rod and extends along the longitudinal axis of the rod 12.

[0334] The susceptor element 580 extends all the way from an upstream end to a downstream end of the rod 512 of aerosol-forming substrate. As such, the susceptor element 580 has substantially the same length as the rod 512 of aerosol-forming substrate.

[0335] In the embodiment of FIG. 5, the susceptor element 580 is provided in the form of a strip of a ferromagnetic steel and has a length of about 12 millimetres, a thickness of about 60 micrometres, and a width of about 4 millimetres.

[0336] The aerosol-generating article 510 of FIG. 5 may be used with the aerosol-generating device 202 of FIG. 4 in the same way as the aerosol-generating article 11 of FIG. 2. Notably, the inclusion of the susceptor element 580 means that the article 510 may be inductively heated regardless of whether the thermally conductive particles comprise a suitable susceptor material for inductive heating.

[0337] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term about. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein. In this context, therefore, a number A is understood as A?10% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.