ARTICLE WITH TUBULAR AEROSOL-FORMING SUBSTRATE

Abstract

An aerosol-generating article for producing an inhalable aerosol upon heating comprises a plurality of components including an aerosol-forming substrate. The aerosol-forming substrate is in the form of a hollow tubular segment defining a substrate cavity extending between an upstream end of the aerosol-forming substrate and a downstream end of the aerosol-forming substrate. The aerosol-forming substrate comprises a plurality of thermally conductive particles and an aerosol-former. The combination of tubular geometry and thermally conductive particles allows swifter time to first puff, improved efficiency of aerosol extraction and lighter weight of aerosol-generating article.

Claims

1. An aerosol-generating article for producing an inhalable aerosol upon heating, the aerosol-generating article comprising an aerosol-forming substrate, wherein: the aerosol-forming substrate is in the form of a hollow tubular segment defining a substrate cavity extending between an upstream end of the aerosol-forming substrate and a downstream end of the aerosol-forming substrate; the aerosol-forming substrate comprises a plurality of thermally conductive particles and an aerosol-former; and the hollow tubular segment is an extruded tube of aerosol-forming material.

2. The aerosol-generating article according to claim 1, wherein the aerosol-forming substrate comprises one or more organic materials such as tobacco.

3. The aerosol-generating article according to claim 1, wherein the aerosol-forming substrate is a tobacco-free aerosol-forming substrate.

4. The aerosol-generating article according to claim 1, wherein the aerosol-forming substrate has a length of between 5 and 20 mm.

5. The aerosol-generating article according to claim 1, wherein the aerosol-forming substrate is in the form of a tube having a width in a radial dimension and a length in a longitudinal dimension, in which the width is defined by an outer diameter of the tube, the outer diameter being between 3 mm and 20 mm.

6. The aerosol-generating article according to claim 1, wherein the aerosol-forming substrate is in the form of a tube having an outer diameter, an inner diameter, and a length, a wall thickness of the tube being defined by a difference between the outer diameter and the inner diameter, wherein the wall thickness is between 100 microns and 5 mm.

7. The aerosol-generating article according to claim 1, wherein the aerosol forming substrate is in the form of a tube having an outer diameter, an inner diameter, and a length, a wall thickness of the tube being defined by a difference between the outer diameter and the inner diameter, wherein the wall thickness is between 5 percent and 40 percent of the outer diameter.

8. The aerosol-generating article according to claim 1, wherein the article comprises one or more or all of: a front plug, a first hollow tube, a second hollow tube, a mouth plug filter, and a wrapper.

9. The aerosol-generating article according to claim 1, wherein the article comprises: a front plug, the aerosol-forming substrate arranged downstream of the front plug; a first hollow support tube arranged downstream of the aerosol-forming substrate; a second hollow support tube arranged downstream of the first hollow support tube; and a mouth plug filter arranged downstream of the second hollow tube.

10. The aerosol-generating article according to claim 9, wherein the aerosol-generating article comprises a wrapper, and wherein the front plug, the aerosol-forming substrate, the first hollow support tube, the second hollow support tube, and the mouth plug filter are circumscribed by the wrapper.

11. The aerosol-generating article according to claim 9, wherein one or more of: the front plug has a length of between 2 and 10 mm; the first hollow tube has a length of between 2 and 20 mm; the second hollow tube has a length of between 2 and 20 mm; and the mouth plug filter has a length of between 5 and 20 mm.

12. The aerosol-generating article according to claim 9, wherein the second hollow tube comprises one or more ventilation holes.

13. A method of forming a hollow tubular aerosol-forming substrate for an aerosol-generating article, the method comprising: forming a slurry comprising thermally conductive particles, an aerosol former, fibres, and a binder; extruding the slurry into the shape of the hollow tubular aerosol-forming substrate, and drying the extruded slurry into a hollow tube.

14. A method according to claim 13, wherein the method comprises a step of cutting the hollow tube to form the hollow tubular aerosol-forming substrate.

15. An aerosol-generating system comprising the aerosol-generating article according to claim 1 and an electrical aerosol-generating device.

Description

[0298] Examples will now be further described with reference to the figures in which:

[0299] FIG. 1 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating article;

[0300] FIG. 2 shows a schematic cross-sectional view of a first embodiment of an aerosol-generating system, comprising the article of FIG. 1;

[0301] FIG. 3 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating system, comprising the article of FIG. 1; and

[0302] FIG. 4 shows a schematic cross-sectional view of a third embodiment of an aerosol-generating system, comprising the article of FIG. 1.

[0303] FIG. 1 shows a schematic cross-sectional view of an exemplary aerosol-generating article 10 according to an embodiment of the invention. The aerosol-generating article 10 extends from an upstream or distal end 18 to a downstream or proximal or mouth end 20 and has an overall length of about 45 millimetres and a diameter of about 7.2 mm.

[0304] The aerosol-generating article 10 comprises a plurality of elements arranged coaxially and assembled within a wrapper 70. The plurality of elements forming the article are, from distal end to proximal end, a front plug 46, a tubular segment of thermally enhanced aerosol-forming substrate 12, a cardboard tube free flow filter 34, and a mouthpiece filter 42. The wrapper 70 is a cigarette paper.

[0305] The front plug 46, also referred to as an upstream element, is located immediately upstream of the tubular aerosol-forming substrate 12. The front plug 46 is provided in the form of a cylindrical plug of cellulose acetate. The front plug 46 has a diameter of about 7.2 mm and a length of about 5 millimetres. The RTD of the front plug 46 is about 30 millimetres H.sub.2O.

[0306] The tubular segment of aerosol-forming substrate 12 has an outer diameter of about 7.2 millimetres, an inner diameter of about 6.8 millimetres, and a length of about 12 millimetres. The aerosol-forming substrate 12 is formed from a rolled sheet of aerosol-forming material, comprising thermally conductive particles 44. The tubular aerosol forming substrate 12 is configured to form an aerosol when heated to a temperature of between 150 degrees Centigrade and 350 degrees Centigrade. Some specific examples of suitable aerosol-forming substrate compositions are provided below.

[0307] The cardboard tube 34 has a length of 16 mm and provides a free space within the article 10 within which volatile components generated by heating of the aerosol-forming substrate can cool and form an aerosol.

[0308] The mouthpiece element 42 is provided in the form of a cylindrical plug of low-density cellulose acetate. The mouthpiece element 42 has a length of about 12 millimetres and an external diameter of about 7.2 mm. The RTD of the mouthpiece element 42 is about 12 millimetres H.sub.2O.

[0309] It should be clear that the configuration of the aerosol-generating article 10 of FIG. 1 is intended to serve as an example only. The thermally enhanced, tubular, aerosol-forming substrate 12 could, for example, be employed in an aerosol generating article that is longer, for example 80 mm long, and thinner, for example 4.5 mm in diameter.

[0310] In a specific embodiment of an aerosol-generating article as illustrated in FIG. 1, the tubular segment 12 of aerosol-forming substrate comprises, on a dry weight basis, around 76.1 wt % thermally conductive particles 44. In this embodiment, the thermally conductive particles 44 are graphite particles, specifically FP 99.5 (>99.5% purity) graphite particles from Graphit Kropfml GmbH, AMG Graphite GK, though other particles or mixtures of particles could be used. Each thermally conductive particle has a thermal conductivity of around 6 W/(mK) in at least one direction at 25 degrees Celsius.

[0311] The tubular aerosol-forming substrate 12 comprises, on a dry weight basis, around 17.7 wt % of an aerosol former. In this embodiment, the aerosol former is glycerol, specifically ICOF Europe food grade (>99.5% purity) glycerol.

[0312] The tubular aerosol-forming substrate 12 comprises, on a dry weight basis, around 3.9 wt % of fibres. In this embodiment, the fibres are cellulose fibres, specifically Birch cellulose fibres from Stora Enso OYJ.

[0313] The tubular aerosol-forming substrate 12 comprises, on a dry weight basis, around 2.3 wt % of a binder. In this embodiment, the binder is a guar gum, specifically guar gum from Gumix International Inc.

[0314] The tubular aerosol-forming substrate comprises about 10 wt % water, when measured at 25 degrees Celsius.

[0315] In other embodiments, the tubular aerosol-forming substrate 12 further comprises one or more of nicotine, an acid such as fumaric acid, a botanical such as clove or rosmarinus, and a flavourant.

[0316] The tubular aerosol-forming substrate 12 has a thermal conductivity of at least 0.1 W/(mK) in at least one direction at 25 degrees Celsius. The aerosol-forming substrate 12 may have a thermal conductivity of 0.2, 0.5, 1, 1.5 or greater W/(mK) in at least one direction at 25 degrees Celsius

[0317] Each of the thermally conductive particles 44 is substantially spherical in shape. The thermally conductive particles 44 are substantially homogeneously distributed throughout the aerosol-forming substrate. The particle size distribution has a volume D10 particle size of around 6 microns, a volume D50 particle size of around 20 microns, and a volume D90 particle size of around 56 microns. Each of the thermally conductive particles 44 has a particle size greater than around 1 microns and less than around 300 microns.

[0318] The thermally conductive particles 44 have a density of around 2200 kilograms per metre cubed. The aerosol-forming substrate has a density of around 800 kilograms per metre cubed.

[0319] The aerosol-forming substrate is formed by the process set out below.

[0320] A slurry is formed using a lab disperser capable of mixing viscous liquids, dispersing powders through liquids, and removing gas from a mixture (for example by applying a vacuum or other suitably low pressure). In this embodiment, a commercially available lab disperser from PC Laborsystem was used.

[0321] To form the slurry, a first mixture is formed by adding to the lap disperser around 7.11 grams of the aerosol former, then around 157.5 grams of water, then around 1.57 grams of the fibres. Then, these first ingredients are mixed at 25 degrees Celsius for 5 minutes at 600-700 rpm to ensure a homogeneous mixture and to hydrate the fibres. Then, a second mixture is formed by manually mixing around 32.95 grams of the thermally conductive particles and around 0.92 grams of the binder. This mixing of the second mixture avoids the formation of lumps in the lab dispersion. Then, the second mixture is added to the first mixture to form a combined mixture. Then, the combined mixture is mixed at 5000 rpm for 4 minutes at 25 degrees Celsius and a first reduced pressure of around 200 mbar. The reduced pressure may help to ensure that the thermally conductive particles are homogeneously dispersed in the mixture and that there is little trapped air and few lumps in the combined mixture. Then, the combined mixture is mixed at 5000 rpm for 20 second minutes at 25 degrees Celsius and a second reduced pressure of around 100 mbar. This second reduced pressure may help to remove any remaining air bubbles. This forms a slurry for casting.

[0322] The slurry is then cast and dried using a suitable apparatus. In this embodiment, a commercially available Labcoater Mathis apparatus is used. This apparatus includes a stainless steel, flat support, and a coma blade for adjusting a thickness of slurry cast onto the flat support.

[0323] The slurry is cast onto the flat support and a gap between the coma blade and the flat support is set at 0.6 millimetres. This ensures that a thickness of the slurry is no more than 0.6 millimetres at any given point.

[0324] The slurry is then dried with hot air between 120 and 140 degrees Celsius for between 2 and 5 minutes. After this drying, a sheet of the aerosol-forming substrate is formed. This sheet has a thickness of around 300 microns, a grammage of around 250 grams per metre squared, and a density of around 0.79 kilograms per metre cubed.

[0325] The sheet is then rolled to form a tube. Adhesive is applied to an overlapping portion of the rolled sheet to affix the sheet in the form of a tube and the tube is then cut into 12 mm lengths to for the tubular aerosol-forming substrate 12.

[0326] After forming the tubular aerosol-forming substrate 12, the aerosol-generating article 10 is assembled by positioning the various components of the article 10 and wrapping the components in the wrapper 70.

[0327] Other embodiments may have the same structure as described above, but have an aerosol-forming substrate of a different composition. For example, in a further embodiment the aerosol-forming material comprises a tube of thermally enhanced homogenised tobacco comprising thermally conductive particles 44. 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.

[0328] The tube 12 of aerosol-forming substrate is formed by a process including the following steps: [0329] pre-mixing a binder, guar gum, with an aerosol-former, glycerine, to form a first pre-mixture; [0330] 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; [0331] mixing the first and second pre-mixtures with water to form a slurry; [0332] homogenising the slurry using a high-shear mixer; [0333] casting the slurry onto a conveyor belt; [0334] controlling a thickness of the slurry and drying the slurry to form a sheet of aerosol-forming substrate; and [0335] rolling the sheet of aerosol forming substrate into a tube and cutting the tube to form tubular segments of aerosol-forming substrate.

[0336] Aerosol-forming substrates formed with compositions including conductive particles according to the present invention have demonstrated improved aerosol delivery compared to reference substrates without thermally conductive particles.

[0337] FIG. 2 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.

[0338] 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.

[0339] 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.

[0340] 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.

[0341] In use, a user inserts the article 10 into the cavity, causing the heating blade 108 to penetrate the upstream element 46 and extend into the internal bore or cavity of the tubular of aerosol-forming substrate 12 of the article 10. FIG. 3 shows the article 10 inserted into the cavity of the device 102, and the heating blade extending into the internal bore of the tubular aerosol-forming substrate.

[0342] 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.

[0343] 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 tubular aerosol-forming substrate.

[0344] The thermally conductive 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. Further, because the aerosol-forming substrate is in the form of a tube, the temperature equalizes relatively quickly between the inner surface of the tube and the outer surface of the tube. The combination of a tubular structure for the aerosol forming substrate and the presence of thermally conductive particles in the aerosol-forming substrate allows a greater proportion of the aerosol-forming substrate to swiftly a sufficiently high temperature to release volatile compounds, and thus allows a higher usage efficiency of the aerosol-forming substrate.

[0345] Heating of the aerosol-forming substrate causes 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 cardboard tube 34. 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.

[0346] 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.

[0347] After a number of puffs on the article 10, the user may choose to replace the article 10 with a fresh article.

[0348] FIG. 3 shows a schematic cross-sectional view of a second embodiment of an aerosol-generating system 300. The system 300 comprises an aerosol-generating device 302 and the aerosol-generating article 10 of FIG. 1.

[0349] The aerosol-generating device 302 comprises a battery 304, a controller 306, an external resistance heater 308, and a puff-detection mechanism (not shown). The controller 306 is coupled to the battery 304, the resistance heater 308 and the puff-detection mechanism.

[0350] The aerosol-generating device 302 further comprises a housing 310 defining a substantially cylindrical cavity for receiving a portion of the article 10. The external heater 208 is located on an inner surface of the cavity.

[0351] Use of the system is similar to that described above in relation to the system of FIG. 2, with the difference that the tubular aerosol-forming substrate 12 is heated from the outside rather than by a heater located in an internal portion of the aerosol-forming substrate.

[0352] FIG. 4 shows a schematic cross-sectional view of a third embodiment of an aerosol-generating system 400. The system 400 comprises an aerosol-generating device 402 and the aerosol-generating article 10 of FIG. 1.

[0353] The aerosol-generating device 402 comprises a battery 404, a controller 406, an inductor coil 408, and a puff-detection mechanism (not shown). The controller 406 is coupled to the battery 404, the inductor coil 408 and the puff-detection mechanism.

[0354] The aerosol-generating device 402 further comprises a housing 410 defining a substantially cylindrical cavity for receiving a portion of the article 10. The inductor coil 408 spirals around the cavity.

[0355] The battery 404 is coupled to the inductor coil 408 so as to be able to pass an alternating current through the inductor coil 408.

[0356] In use, a user inserts the article 10 into the cavity. FIG. 4 shows the article 10 inserted into the cavity of the device 402. Airflow is detected and the device actuated as described above in relation to the system of FIG. 1. When a puff is detected, the controller 406 controls the battery 404 so as to pass an alternating current through the inductor coil 408. This causes the inductor coil 408 to generate a fluctuating electromagnetic field. The aerosol-forming substrate 12 is located within this fluctuating electromagnetic field. The materials of the particles 44, for example graphite or expanded graphite, are susceptor materials. Thus, the fluctuating electromagnetic field causes eddy currents in the particles 44. This causes the particles 44 to heat up, thereby also heating aerosol-forming material of the aerosol-forming substrate.

[0357] 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 A10% 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.